WorldWideScience

Sample records for kantowski-sachs cosmological models

  1. Kantowski--Sachs cosmological models as big-bang models

    International Nuclear Information System (INIS)

    Weber, E.

    1985-01-01

    In the presence of a nonzero cosmological constant Λ, we classify the anisotropic cosmological models of the Kantowski--Sachs type by means of the quantities epsilon 2 0 , q 0 , summation 0 corresponding, respectively, to the relative root-mean-square deviation from isotropy, the deceleration parameter, and the density parameter of the perfect fluid at a given time t = t 0 . We obtain for Λ>0 a set of big-bang models of zero measure as well as a set of cosmological models of nonzero measure evolving toward the de Sitter solution

  2. Bianchi - I, II, VIII, IX and Kantowski-Sachs-like cosmological models with perfect fluid and electromagnetic fields with conductivity current

    International Nuclear Information System (INIS)

    Portugal, R.

    1984-01-01

    Three processes of solutions of the Einstein-Maxwell equations for Bianchi - I, II, VIII, IX and Kantowski-Sachs-like cosmological models with perfect fluid in magnetohydrolodynamical regimem are presented. Diagonal Bianchi-like models are considered with two anisotropy direction in the maximum. Solutions are found for Bianchi-II and IX-like models with energy conditions to be analyzed. Solutions are found for Bianchi-IX and Kantowski-Sachs-Like models with positive electric conductivity and satisfering to the predominant energy conditions. Solutions are formed for isotropic Kantowski-Sachs-Like models satisfering to the equation of state p=λρ, 0 0, admiting, in addition to the perfect fluid, electric field only. It is shown that a class of Bertotti-Robinson-like solutions is unstable by perturbations and it is carried in Kantowski-Sachs-like models with non-null electric conductivity. (L.C.) [pt

  3. Gravitational, shear and matter waves in Kantowski-Sachs cosmologies

    Energy Technology Data Exchange (ETDEWEB)

    Keresztes, Zoltán; Gergely, László Á. [Department of Theoretical Physics, University of Szeged, Tisza Lajos krt 84-86, Szeged 6720 (Hungary); Forsberg, Mats; Bradley, Michael [Department of Physics, UmeåUniversity (Sweden); Dunsby, Peter K.S., E-mail: zkeresztes@titan.physx.u-szeged.hu, E-mail: forsberg.mats.a.b@gmail.com, E-mail: michael.bradley@physics.umu.se, E-mail: peter.dunsby@uct.ac.za, E-mail: gergely@physx.u-szeged.hu [Astrophysics, Cosmology and Gravity Centre (ACGC), University of Cape Town, Rondebosch 7701, Cape Town (South Africa)

    2015-11-01

    A general treatment of vorticity-free, perfect fluid perturbations of Kantowski-Sachs models with a positive cosmological constant are considered within the framework of the 1+1+2 covariant decomposition of spacetime. The dynamics is encompassed in six evolution equations for six harmonic coefficients, describing gravito-magnetic, kinematic and matter perturbations, while a set of algebraic expressions determine the rest of the variables. The six equations further decouple into a set of four equations sourced by the perfect fluid, representing forced oscillations and two uncoupled damped oscillator equations. The two gravitational degrees of freedom are represented by pairs of gravito-magnetic perturbations. In contrast with the Friedmann case one of them is coupled to the matter density perturbations, becoming decoupled only in the geometrical optics limit. In this approximation, the even and odd tensorial perturbations of the Weyl tensor evolve as gravitational waves on the anisotropic Kantowski-Sachs background, while the modes describing the shear and the matter density gradient are out of phase dephased by π /2 and share the same speed of sound.

  4. Exact Kantowski-Sachs and Bianchi types I and III cosmological models with a conformally invariant scalar field

    International Nuclear Information System (INIS)

    Accioly, A.J.

    1985-01-01

    Exact solutions of the Einstein-Conformally Invariant Scalar Field Equations are obtained for Kantowski-Sachs and Bianchi types I and III cosmologies. The presence of the conformally invariant scalar field is responsible for some interesting features of the solutions. In particular it is found that the Bianchi I model is consistent with the big-bang theory of cosmology. (Author) [pt

  5. Phenomenological dynamics of loop quantum cosmology in Kantowski-Sachs spacetime

    International Nuclear Information System (INIS)

    Chiou, D.-W.

    2008-01-01

    The fundamental theory and the semiclassical description of loop quantum cosmology (LQC) have been studied in the Friedmann-Robertson-Walker and Bianchi I models. As an extension to include both anisotropy and intrinsic curvature, this paper investigates the cosmological model of Kantowski-Sachs spacetime with a free massless scalar field at the level of phenomenological dynamics with the LQC discreteness corrections. The LQC corrections are implemented in two different improved quantization schemes. In both schemes, the big bang and big crunch singularities of the classical solution are resolved and replaced by the big bounces when the area or volume scale factor approaches the critical values in the Planck regime measured by the reference of the scalar field momentum. Symmetries of scaling are also noted and suggest that the fundamental spatial scale (area gap) may give rise to a temporal scale. The bouncing scenarios are in an analogous fashion of the Bianchi I model, naturally extending the observations obtained previously.

  6. Kantowski-Sachs multidimensional cosmological models and dynamical dimensional reduction

    International Nuclear Information System (INIS)

    Demianski, M.; Rome Univ.; Golda, Z.A.; Heller, M.; Szydlowski, M.

    1988-01-01

    Einstein's field equations are solved for a multidimensional spacetime (KS) x Tsup(m), where (KS) is a four-dimensional Kantowski-Sachs spacetime and Tsup(m) is an m-dimensional torus. Among all possible vacuum solutions there is a large class of spacetimes in which the macroscopic space expands and the microscopic space contracts to a finite volume. We also consider a non-vacuum case and we explicitly solve the field equations for the matter satisfying the Zel'dovich equation of state. In non-vacuum models, with matter satisfying an equation of state p = γρ, O ≤ γ < 1, at a sufficiently late stage of evolution the microspace always expands and the dynamical dimensional reduction does not occur. (author)

  7. Quantum field theory of the universe in the Kantowski-Sachs space-time

    International Nuclear Information System (INIS)

    Shen, Y.; Tan, Z.

    1996-01-01

    In this paper, the quantum field theory of the universe in the Kantowski-Sachs space-time is studied. An analogue of proceedings in quantum field theory is applied in curved space-time to the Kantowski-Sachs space-time, obtaining the wave function of the universe satisfied the Wheeler-DeWitt equation. Regarding the wave function as a universe field in the minisuperspace, the authors can not only overcome the difficulty of the probabilistic interpretation in quantum cosmology, but also come to the conclusion that there is multiple production of universes. The average number of the produced universes from nothing is calculated. The distribution of created universe is given. It is the Planckian distribution

  8. Kantowski-Sachs Einstein-æther perfect fluid models

    Energy Technology Data Exchange (ETDEWEB)

    Latta, Joey [Department of Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia, B3H 3J5 (Canada); Leon, Genly [Instituto de Física, Pontificia Universidad de Católica de Valparaíso, Casilla 4950, Valparaíso (Chile); Paliathanasis, Andronikos, E-mail: lattaj@mathstat.dal.ca, E-mail: genly.leon@pucv.cl, E-mail: anpaliat@phys.uoa.gr [Instituto de Ciencias Físicas y Matemáticas, Universidad Austral de Chile, Valdivia (Chile)

    2016-11-01

    We investigate Kantowski-Sachs models in Einstein-æ ther theory with a perfect fluid source using the singularity analysis to prove the integrability of the field equations and dynamical system tools to study the evolution. We find an inflationary source at early times, and an inflationary sink at late times, for a wide region in the parameter space. The results by A.A. Coley, G. Leon, P. Sandin and J. Latta ( JCAP 12 (2015) 010), are then re-obtained as particular cases. Additionally, we select other values for the non-GR parameters which are consistent with current constraints, getting a very rich phenomenology. In particular, we find solutions with infinite shear, zero curvature, and infinite matter energy density in comparison with the Hubble scalar. We also have stiff-like future attractors, anisotropic late-time attractors, or both, in some special cases. Such results are developed analytically, and then verified by numerics. Finally, the physical interpretation of the new critical points is discussed.

  9. Relativistic cosmologies with closed, locally homogeneous space sections

    International Nuclear Information System (INIS)

    Fagundes, H.V.

    1985-01-01

    The homogeneous Bianchi and Kantowski-Sachs metrics of relativistic cosmology are investigated through their correspondence with recent geometrical results of Thurston. These allow a partial classification of the topologies for closed, locally homogeneous spaces according to Thurston's eight geometric types. Besides, which of the Bianchi-Kantowski-Sachs metrics can be imposed on closed space sections of cosmological models are learned. This is seen as a progress toward implementation of a postulate of the closure of space for both classical and quantum gravity. (Author) [pt

  10. Time-dependent automorphism-inducing diffeomorphisms, open algebras and the generality of the Kantowski-Sachs vacuum geometry

    Science.gov (United States)

    Christodoulakis, T.; Papadopoulos, G. O.

    2002-10-01

    Following the spirit of a previous work of ours, we investigate the group of those general coordinate transformations (GCTs) which preserve manifest spatial homogeneity. In contrast to the case of Bianchi type models, here we permit an isometry group of motions G4 = SO(3) ⊗ Tr, where Tr is the translations group, along the radial direction, while SO(3) acts multiply transitively on each hypersurface of simultaneity Σt. The basis 1-forms cannot be invariant under the action of the entire isometry group and hence produce an open Lie algebra. In order for these GCTs to exist and have a nontrivial, well-defined action, certain integrability conditions have to be satisfied; their solutions, exhibiting the maximum expected 'gauge' freedom, can be used to simplify the generic, spatially homogeneous, line element. In this way an alternative proof of the generality of the Kantowski-Sachs (KS) vacuum is given, while its most general, manifestly homogeneous, form is explicitly presented.

  11. Classification of Kantowski-Sachs and Bianchi Type III Space-Times According to Their Killing Vector Fields in Teleparallel Theory of Gravitation

    International Nuclear Information System (INIS)

    Shabbir, Ghulam; Khan, Suhail

    2010-01-01

    In this paper we classify Kantowski-Sachs and Bianchi type III space-times according to their teleparallel Killing vector fields using direct integration technique. It turns out that the dimension of the teleparallel Killing vector fields are 4 or 6, which are the same in numbers as in general relativity. In case of 4 the teleparallel Killing vector fields are multiple of the corresponding Killing vector fields in general relativity by some function of t. In the case of 6 Killing vector fields the metric functions become constants and the Killing vector fields in this case are exactly the same as in general relativity. Here we also discuss the Lie algebra in each case. (general)

  12. Self-similar cosmological solutions with dark energy. I. Formulation and asymptotic analysis

    International Nuclear Information System (INIS)

    Harada, Tomohiro; Maeda, Hideki; Carr, B. J.

    2008-01-01

    Based on the asymptotic analysis of ordinary differential equations, we classify all spherically symmetric self-similar solutions to the Einstein equations which are asymptotically Friedmann at large distances and contain a perfect fluid with equation of state p=(γ-1)μ with 0 1). However, in the latter case there is an additional parameter associated with the weak discontinuity at the sonic point and the solutions are only asymptotically 'quasi-Friedmann', in the sense that they exhibit an angle deficit at large distances. In the 0<γ<2/3 case, there is no sonic point and there exists a one-parameter family of solutions which are genuinely asymptotically Friedmann at large distances. We find eight classes of asymptotic behavior: Friedmann or quasi-Friedmann or quasistatic or constant-velocity at large distances, quasi-Friedmann or positive-mass singular or negative-mass singular at small distances, and quasi-Kantowski-Sachs at intermediate distances. The self-similar asymptotically quasistatic and quasi-Kantowski-Sachs solutions are analytically extendible and of great cosmological interest. We also investigate their conformal diagrams. The results of the present analysis are utilized in an accompanying paper to obtain and physically interpret numerical solutions

  13. Towards N = 2 SUSY homogeneous quantum cosmology; Einstein-Yang-Mills systems

    International Nuclear Information System (INIS)

    Donets, E.E.; Tentyukov, M.N.; Tsulaya, M.M.

    1998-01-01

    The application of N = 2 supersymmetric Quantum Mechanics for the quantization of homogeneous systems coupled with gravity is discussed. Starting with the superfield formulation of N = 2 SUSY sigma-model, Hermitian self-adjoint expressions for quantum Hamiltonians and Lagrangians for any signature of a sigma-model metric are obtained. This approach is then applied to coupled SU (2) Einstein-Yang-Mills (EYM) systems in axially-symmetric Bianchi - I,II,VIII, IX, Kantowski-Sachs and closed Friedmann-Robertson-Walker cosmological models. It is shown that all these models admit the embedding into N = 2 SUSY sigma-model with the explicit expressions for superpotentials, being direct sums of gravitational and Yang-Mills (YM) parts. In addition, YM parts of superpotentials exactly coincide with the corresponding Chern-Simons terms. The spontaneous SUSY breaking, caused by YM instantons in EYM systems is discussed in a number of examples

  14. Noncommutative black holes

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-DomInguez, J C [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico); Obregon, O [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico); RamIrez, C [Facultad de Ciencias FIsico Matematicas, Universidad Autonoma de Puebla, PO Box 1364, 72000 Puebla (Mexico); Sabido, M [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico)

    2007-11-15

    We study noncommutative black holes, by using a diffeomorphism between the Schwarzschild black hole and the Kantowski-Sachs cosmological model, which is generalized to noncommutative minisuperspace. Through the use of the Feynman-Hibbs procedure we are able to study the thermodynamics of the black hole, in particular, we calculate Hawking's temperature and entropy for the 'noncommutative' Schwarzschild black hole.

  15. Integrated Sachs-Wolfe effect versus redshift test for the cosmological parameters

    Science.gov (United States)

    Kantowski, R.; Chen, B.; Dai, X.

    2015-04-01

    We describe a method using the integrated Sachs-Wolfe (ISW) effect caused by individual inhomogeneities to determine the cosmological parameters H0, Ωm , and ΩΛ, etc. This ISW-redshift test requires detailed knowledge of the internal kinematics of a set of individual density perturbations, e.g., galaxy clusters and/or cosmic voids, in particular their density and velocity profiles, and their mass accretion rates. It assumes the density perturbations are isolated and embedded (equivalently compensated) and makes use of the newly found relation between the ISW temperature perturbation of the cosmic microwave background (CMB) and the Fermat potential of the lens. Given measurements of the amplitudes of the temperature variations in the CMB caused by such clusters or voids at various redshifts and estimates of their angular sizes or masses, one can constrain the cosmological parameters. More realistically, the converse is more likely, i.e., if the background cosmology is sufficiently constrained, measurement of ISW profiles of clusters and voids (e.g., hot and cold spots and rings) can constrain dynamical properties of the dark matter, including accretion, associated with such lenses and thus constrain the evolution of these objects with redshift.

  16. Anisotropic cosmological models and generalized scalar tensor theory

    Indian Academy of Sciences (India)

    Abstract. In this paper generalized scalar tensor theory has been considered in the background of anisotropic cosmological models, namely, axially symmetric Bianchi-I, Bianchi-III and Kortowski–. Sachs space-time. For bulk viscous fluid, both exponential and power-law solutions have been stud- ied and some assumptions ...

  17. Anisotropic cosmological models and generalized scalar tensor theory

    Indian Academy of Sciences (India)

    In this paper generalized scalar tensor theory has been considered in the background of anisotropic cosmological models, namely, axially symmetric Bianchi-I, Bianchi-III and Kortowski–Sachs space-time. For bulk viscous fluid, both exponential and power-law solutions have been studied and some assumptions among the ...

  18. Spherically symmetric Einstein-aether perfect fluid models

    Energy Technology Data Exchange (ETDEWEB)

    Coley, Alan A.; Latta, Joey [Department of Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia, B3H 3J5 (Canada); Leon, Genly [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4950, Valparaíso (Chile); Sandin, Patrik, E-mail: aac@mathstat.dal.ca, E-mail: genly.leon@ucv.cl, E-mail: patrik.sandin@aei.mpg.de, E-mail: lattaj@mathstat.dal.ca [Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut), Am Mühlenberg 1, D-14476 Potsdam (Germany)

    2015-12-01

    We investigate spherically symmetric cosmological models in Einstein-aether theory with a tilted (non-comoving) perfect fluid source. We use a 1+3 frame formalism and adopt the comoving aether gauge to derive the evolution equations, which form a well-posed system of first order partial differential equations in two variables. We then introduce normalized variables. The formalism is particularly well-suited for numerical computations and the study of the qualitative properties of the models, which are also solutions of Horava gravity. We study the local stability of the equilibrium points of the resulting dynamical system corresponding to physically realistic inhomogeneous cosmological models and astrophysical objects with values for the parameters which are consistent with current constraints. In particular, we consider dust models in (β−) normalized variables and derive a reduced (closed) evolution system and we obtain the general evolution equations for the spatially homogeneous Kantowski-Sachs models using appropriate bounded normalized variables. We then analyse these models, with special emphasis on the future asymptotic behaviour for different values of the parameters. Finally, we investigate static models for a mixture of a (necessarily non-tilted) perfect fluid with a barotropic equations of state and a scalar field.

  19. Integrated Sachs-Wolfe effect in a quintessence cosmological model: Including anisotropic stress of dark energy

    International Nuclear Information System (INIS)

    Wang, Y. T.; Xu, L. X.; Gui, Y. X.

    2010-01-01

    In this paper, we investigate the integrated Sachs-Wolfe effect in the quintessence cold dark matter model with constant equation of state and constant speed of sound in dark energy rest frame, including dark energy perturbation and its anisotropic stress. Comparing with the ΛCDM model, we find that the integrated Sachs-Wolfe (ISW)-power spectrums are affected by different background evolutions and dark energy perturbation. As we change the speed of sound from 1 to 0 in the quintessence cold dark matter model with given state parameters, it is found that the inclusion of dark energy anisotropic stress makes the variation of magnitude of the ISW source uncertain due to the anticorrelation between the speed of sound and the ratio of dark energy density perturbation contrast to dark matter density perturbation contrast in the ISW-source term. Thus, the magnitude of the ISW-source term is governed by the competition between the alterant multiple of (1+3/2xc-circumflex s 2 ) and that of δ de /δ m with the variation of c-circumflex s 2 .

  20. SAChES: Scalable Adaptive Chain-Ensemble Sampling.

    Energy Technology Data Exchange (ETDEWEB)

    Swiler, Laura Painton [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Ray, Jaideep [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Ebeida, Mohamed Salah [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Huang, Maoyi [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hou, Zhangshuan [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bao, Jie [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Ren, Huiying [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-08-01

    We present the development of a parallel Markov Chain Monte Carlo (MCMC) method called SAChES, Scalable Adaptive Chain-Ensemble Sampling. This capability is targed to Bayesian calibration of com- putationally expensive simulation models. SAChES involves a hybrid of two methods: Differential Evo- lution Monte Carlo followed by Adaptive Metropolis. Both methods involve parallel chains. Differential evolution allows one to explore high-dimensional parameter spaces using loosely coupled (i.e., largely asynchronous) chains. Loose coupling allows the use of large chain ensembles, with far more chains than the number of parameters to explore. This reduces per-chain sampling burden, enables high-dimensional inversions and the use of computationally expensive forward models. The large number of chains can also ameliorate the impact of silent-errors, which may affect only a few chains. The chain ensemble can also be sampled to provide an initial condition when an aberrant chain is re-spawned. Adaptive Metropolis takes the best points from the differential evolution and efficiently hones in on the poste- rior density. The multitude of chains in SAChES is leveraged to (1) enable efficient exploration of the parameter space; and (2) ensure robustness to silent errors which may be unavoidable in extreme-scale computational platforms of the future. This report outlines SAChES, describes four papers that are the result of the project, and discusses some additional results.

  1. An inducible mouse model of late onset Tay-Sachs disease.

    Science.gov (United States)

    Jeyakumar, Mylvaganam; Smith, David; Eliott-Smith, Elena; Cortina-Borja, Mario; Reinkensmeier, Gabriele; Butters, Terry D; Lemm, Thorsten; Sandhoff, Konrad; Perry, V Hugh; Dwek, Raymond A; Platt, Frances M

    2002-08-01

    Mouse models of the G(M2) gangliosidoses, Tay-Sachs and Sandhoff disease, are null for the hexosaminidase alpha and beta subunits respectively. The Sandhoff (Hexb-/-) mouse has severe neurological disease and mimics the human infantile onset variant. However, the Tay-Sachs (Hexa-/-) mouse model lacks an overt phenotype as mice can partially bypass the blocked catabolic pathway and escape disease. We have investigated whether a subset of Tay-Sachs mice develop late onset disease. We have found that approximately 65% of the mice develop one or more clinical signs of the disease within their natural life span (n = 52, P disease at an earlier age (n = 21, P Tay-Sachs mice confirmed that pregnancy induces late onset Tay-Sachs disease. Onset of symptoms correlated with reduced up-regulation of hexosaminidase B, a component of the bypass pathway.

  2. Quantum cosmology of a Bianchi III LRS geometry coupled to a source free electromagnetic field

    Science.gov (United States)

    Karagiorgos, A.; Pailas, T.; Dimakis, N.; Terzis, Petros A.; Christodoulakis, T.

    2018-03-01

    We consider a Bianchi type III axisymmetric geometry in the presence of an electromagnetic field. A first result at the classical level is that the symmetry of the geometry need not be applied on the electromagnetic tensor Fμν the algebraic restrictions, implied by the Einstein field equations to the stress energy tensor Tμν, suffice to reduce the general Fμν to the appropriate form. The classical solution thus found contains a time dependent electric and a constant magnetic charge. The solution is also reachable from the corresponding mini-superspace action, which is strikingly similar to the Reissner-Nordstr{öm one. This points to a connection between the black hole geometry and the cosmological solution here found, which is the analog of the known correlation between the Schwarzschild and the Kantowski-Sachs metrics. The configuration space is drastically modified by the presence of the magnetic charge from a 3D flat to a 3D pp wave geometry. We map the emerging linear and quadratic classical integrals of motion, to quantum observables. Along with the Wheeler-DeWitt equation these observables provide unique, up to constants, wave functions. The employment of a Bohmian interpretation of these quantum states results in deterministic (semi-classical) geometries most of which are singularity free.

  3. The theory of stochastic cosmological lensing

    Energy Technology Data Exchange (ETDEWEB)

    Fleury, Pierre; Uzan, Jean-Philippe [Institut d' Astrophysique de Paris, UMR 7095 du CNRS, 98 bis Bd Arago, 75014 Paris (France); Larena, Julien, E-mail: fleury@iap.fr, E-mail: j.larena@ru.ac.za, E-mail: uzan@iap.fr [Department of Mathematics, Rhodes University, Grahamstown 6140 (South Africa)

    2015-11-01

    On the scale of the light beams subtended by small sources, e.g. supernovae, matter cannot be accurately described as a fluid, which questions the applicability of standard cosmic lensing to those cases. In this article, we propose a new formalism to deal with small-scale lensing as a diffusion process: the Sachs and Jacobi equations governing the propagation of narrow light beams are treated as Langevin equations. We derive the associated Fokker-Planck-Kolmogorov equations, and use them to deduce general analytical results on the mean and dispersion of the angular distance. This formalism is applied to random Einstein-Straus Swiss-cheese models, allowing us to: (1) show an explicit example of the involved calculations; (2) check the validity of the method against both ray-tracing simulations and direct numerical integration of the Langevin equation. As a byproduct, we obtain a post-Kantowski-Dyer-Roeder approximation, accounting for the effect of tidal distortions on the angular distance, in excellent agreement with numerical results. Besides, the dispersion of the angular distance is correctly reproduced in some regimes.

  4. Recent results and perspectives on cosmology and fundamental physics from microwave surveys

    DEFF Research Database (Denmark)

    Burigana, Carlo; Battistelli, Elia Stefano; Benetti, Micol

    2016-01-01

    Recent cosmic microwave background (CMB) data in temperature and polarization have reached high precision in estimating all the parameters that describe the current so-called standard cosmological model. Recent results about the integrated Sachs-Wolfe (ISW) effect from CMB anisotropies, galaxy su...

  5. Tay-Sachs - resources

    Science.gov (United States)

    The following organizations provide information on Tay-Sachs disease : US National Library of Medicine -- ghr.nlm.nih.gov/condition/tay-sachs-disease March of Dimes -- www.marchofdimes.org/complications/tay-sachs- ...

  6. Emergence of the product of constant curvature spaces in loop quantum cosmology

    International Nuclear Information System (INIS)

    Dadhich, Naresh; Joe, Anton; Singh, Parampreet

    2015-01-01

    The loop quantum dynamics of Kantowski–Sachs spacetime and the interior of higher genus black hole spacetimes with a cosmological constant has some peculiar features not shared by various other spacetimes in loop quantum cosmology. As in the other cases, though the quantum geometric effects resolve the physical singularity and result in a non-singular bounce, after the bounce a spacetime with small spacetime curvature does not emerge in either the subsequent backward or the forward evolution. Rather, in the asymptotic limit the spacetime manifold is a product of two constant curvature spaces. Interestingly, though the spacetime curvature of these asymptotic spacetimes is very high, their effective metric is a solution to Einstein’s field equations. Analysis of the components of the Ricci tensor shows that after the singularity resolution, the Kantowski–Sachs spacetime leads to an effective metric which can be interpreted as the ‘charged’ Nariai, while the higher genus black hole interior can similarly be interpreted as an anti Bertotti–Robinson spacetime with a cosmological constant. These spacetimes are ‘charged’ in the sense that the energy–momentum tensor that satisfies Einstein’s field equations is formally the same as the one for the uniform electromagnetic field, albeit it has a purely quantum geometric origin. The asymptotic spacetimes also have an emergent cosmological constant which is different in magnitude, and sometimes even its sign, from the cosmological constant in the Kantowski–Sachs and the interior of higher genus black hole metrics. With a fine tuning of the latter cosmological constant, we show that ‘uncharged’ Nariai, and anti Bertotti–Robinson spacetimes with a vanishing emergent cosmological constant can also be obtained. (paper)

  7. Observable cosmology and cosmological models

    International Nuclear Information System (INIS)

    Kardashev, N.S.; Lukash, V.N.; Novikov, I.D.

    1987-01-01

    Modern state of observation cosmology is briefly discussed. Among other things, a problem, related to Hibble constant and slowdown constant determining is considered. Within ''pancake'' theory hot (neutrino) cosmological model explains well the large-scale structure of the Universe, but does not explain the galaxy formation. A cold cosmological model explains well light object formation, but contradicts data on large-scale structure

  8. Tay-Sachs Disease

    Science.gov (United States)

    Tay-Sachs disease is a rare, inherited disease. It is a type of lipid metabolism disorder. It causes too ... cells, causing mental and physical problems. . Infants with Tay-Sachs disease appear to develop normally for the first few ...

  9. Survey on serum acetylecholinesterase (SAChE activity in selected farming communities at risk of organophosphate exposure, Southern Ghana

    Directory of Open Access Journals (Sweden)

    Ato Kwamena Tetteh

    2017-12-01

    Material and Methods ― The study was cross-sectional, involving 963 participants who consented to being screened for serum acetylcholinesterase (SAChE activity, using the dry chemistry test strips. The SAChE activity was then categorized into normal, low or high risk of developing symptoms associated with OP poisoning. Results ― The total group included 54.5% females and 45.5% males. Majority were crop farmers (46.3% and students/pupils (30.8%. The remaining 22.9% consisted mainly of traders, teachers, fishermen/fish processors, drivers and dressmakers. Very low SAChE activity unit of 30 U/ml. By this, a significant majority had either low or high risk of developing OP poisoning (χ2=4.43, 95%CI: 4.12–4.65, p=0.014 compared with those with normal activity. Most of the participants were in the 10–19 years age group of which 15.6% were in the high risk category, while 13.6% had low risk of OP poisoning. Reduced SAChE activity was predominant among all age groups compared with those with normal activity of the enzyme. As well, 27.3% who were females had reduced SAChE activity rate <30 U/ml (high risk of OP poisoning. Similarly, 23.4% of males were also at high risk of OP poisoning. There was however no statistical significance between the sex with regards to the numbers at risk of OP poisoning (χ2=4.80, 95% CI: 4.25–4.75, p=0.160. Conclusion ― This study provides some evidence of exposure, deduced from reduced SAChE activity, which potentially puts participants at a high risk of developing symptoms associated with OP poisoning. A follow-up study might be able to suggest to physicians in Ghana considering diagnostics of OP poisoning, especially for clients from farming communities where pesticides are used extensively.

  10. Matter sources for a null big bang

    International Nuclear Information System (INIS)

    Bronnikov, K A; Zaslavskii, O B

    2008-01-01

    We consider the properties of stress-energy tensors compatible with a null big bang, i.e., cosmological evolution starting from a Killing horizon rather than a singularity. For Kantowski-Sachs cosmologies, it is shown that if matter satisfies the null energy condition, then (i) regular cosmological evolution can only start from a Killing horizon, (ii) matter is absent at the horizon and (iii) matter can only appear in the cosmological region due to interaction with vacuum. The latter is understood phenomenologically as a fluid whose stress tensor is insensitive to boosts in a particular direction. We also argue that matter is absent in a static region beyond the horizon. All this generalizes the observations recently obtained for a mixture of dust and a vacuum fluid. If, however, we admit the existence of phantom matter, its certain special kinds (with the parameter w ≤ -3) are consistent with a null big bang without interaction with vacuum (or without vacuum fluid at all). Then in the static region there is matter with w ≥ -1/3. Alternatively, the evolution can begin from a horizon in an infinitely remote past, leading to a scenario combining the features of a null big bang and an emergent universe

  11. Balancing anisotropic curvature with gauge fields in a class of shear-free cosmological models

    Science.gov (United States)

    Thorsrud, Mikjel

    2018-05-01

    We present a complete list of general relativistic shear-free solutions in a class of anisotropic, spatially homogeneous and orthogonal cosmological models containing a collection of n independent p-form gauge fields, where p\\in\\{0, 1, 2, 3\\} , in addition to standard ΛCDM matter fields modelled as perfect fluids. Here a (collection of) gauge field(s) balances anisotropic spatial curvature on the right-hand side of the shear propagation equation. The result is a class of solutions dynamically equivalent to standard FLRW cosmologies, with an effective curvature constant Keff that depends both on spatial curvature and the energy density of the gauge field(s). In the case of a single gauge field (n  =  1) we show that the only spacetimes that admit such solutions are the LRS Bianchi type III, Bianchi type VI0 and Kantowski–Sachs metric, which are dynamically equivalent to open (Keff0 ) FLRW models, respectively. With a collection of gauge fields (n  >  1) also Bianchi type II admits a shear-free solution (Keff>0 ). We identify the LRS Bianchi type III solution to be the unique shear-free solution with a gauge field Hamiltonian bounded from below in the entire class of models.

  12. Structural consequences of amino acid substitutions causing Tay-Sachs disease.

    Science.gov (United States)

    Ohno, Kazuki; Saito, Seiji; Sugawara, Kanako; Sakuraba, Hitoshi

    2008-08-01

    To determine the structural changes in the alpha-subunit of beta-hexosaminidase due to amino acid substitutions causing Tay-Sachs disease, we built structural models of mutant alpha-subunits resulting from 33 missense mutations (24 infantile and 9 late-onset), and analyzed the influence of each amino acid replacement on the structure by calculating the number of atoms affected and determining the solvent-accessible surface area of the corresponding amino acid residue in the wild-type alpha-subunit. In the infantile Tay-Sachs group, the number of atoms influenced by a mutation was generally larger than that in the late-onset Tay-Sachs group in both the main chain and the side chain, and residues associated with the mutations found in the infantile Tay-Sachs group tended to be less solvent-accessible than those in the late-onset Tay-Sachs group. Furthermore, color imaging determined the distribution and degree of the structural changes caused by representative amino acid substitutions, and that there were also differences between the infantile and late-onset Tay-Sachs disease groups. Structural study is useful for elucidating the basis of Tay-Sachs disease.

  13. Effective gene therapy in an authentic model of Tay-Sachs-related diseases.

    Science.gov (United States)

    Cachón-González, M Begoña; Wang, Susan Z; Lynch, Andrew; Ziegler, Robin; Cheng, Seng H; Cox, Timothy M

    2006-07-05

    Tay-Sachs disease is a prototypic neurodegenerative disease. Lysosomal storage of GM2 ganglioside in Tay-Sachs and the related disorder, Sandhoff disease, is caused by deficiency of beta-hexosaminidase A, a heterodimeric protein. Tay-Sachs-related diseases (GM2 gangliosidoses) are incurable, but gene therapy has the potential for widespread correction of the underlying lysosomal defect by means of the secretion-recapture cellular pathway for enzymatic complementation. Sandhoff mice, lacking the beta-subunit of hexosaminidase, manifest many signs of classical human Tay-Sachs disease and, with an acute course, die before 20 weeks of age. We treated Sandhoff mice by stereotaxic intracranial inoculation of recombinant adeno-associated viral vectors encoding the complementing human beta-hexosaminidase alpha and beta subunit genes and elements, including an HIV tat sequence, to enhance protein expression and distribution. Animals survived for >1 year with sustained, widespread, and abundant enzyme delivery in the nervous system. Onset of the disease was delayed with preservation of motor function; inflammation and GM2 ganglioside storage in the brain and spinal cord was reduced. Gene delivery of beta-hexosaminidase A by using adeno-associated viral vectors has realistic potential for treating the human Tay-Sachs-related diseases.

  14. The metabolism of Tay-Sachs ganglioside: catabolic studies with lysosomal enzymes from normal and Tay-Sachs brain tissue

    Science.gov (United States)

    Tallman, John F.; Johnson, William G.; Brady, Roscoe O.

    1972-01-01

    The catabolism of Tay-Sachs ganglioside, N-acetylgalactosaminyl- (N-acetylneuraminosyl) -galactosylglucosylceramide, has been studied in lysosomal preparations from normal human brain and brain obtained at biopsy from Tay-Sachs patients. Utilizing Tay-Sachs ganglioside labeled with 14C in the N-acetylgalactosaminyl portion or 3H in the N-acetylneuraminosyl portion, the catabolism of Tay-Sachs ganglioside may be initiated by either the removal of the molecule of N-acetylgalactosamine or N-acetylneuraminic acid. The activity of the N-acetylgalactosamine-cleaving enzyme (hexosaminidase) is drastically diminished in such preparations from Tay-Sachs brain whereas the activity of the N-acetylneuraminic acid-cleaving enzyme (neuraminidase) is at a normal level. Total hexosaminidase activity as measured with an artificial fluorogenic substrate is increased in tissues obtained from patients with the B variant form of Tay-Sachs disease and it is virtually absent in the O-variant patients. The addition of purified neuraminidase and various purified hexosaminidases exerted only a minimal synergistic effect on the hydrolysis of Tay-Sachs ganglioside in the lysosomal preparations from the control or patient with the O variant of Tay-Sachs disease. Images PMID:4639018

  15. Cosmological Models and Stability

    Science.gov (United States)

    Andersson, Lars

    Principles in the form of heuristic guidelines or generally accepted dogma play an important role in the development of physical theories. In particular, philosophical considerations and principles figure prominently in the work of Albert Einstein. As mentioned in the talk by Jiří Bičák at this conference, Einstein formulated the equivalence principle, an essential step on the road to general relativity, during his time in Prague 1911-1912. In this talk, I would like to discuss some aspects of cosmological models. As cosmology is an area of physics where "principles" such as the "cosmological principle" or the "Copernican principle" play a prominent role in motivating the class of models which form part of the current standard model, I will start by comparing the role of the equivalence principle to that of the principles used in cosmology. I will then briefly describe the standard model of cosmology to give a perspective on some mathematical problems and conjectures on cosmological models, which are discussed in the later part of this paper.

  16. Cosmological signatures of anisotropic spatial curvature

    International Nuclear Information System (INIS)

    Pereira, Thiago S.; Marugán, Guillermo A. Mena; Carneiro, Saulo

    2015-01-01

    If one is willing to give up the cherished hypothesis of spatial isotropy, many interesting cosmological models can be developed beyond the simple anisotropically expanding scenarios. One interesting possibility is presented by shear-free models in which the anisotropy emerges at the level of the curvature of the homogeneous spatial sections, whereas the expansion is dictated by a single scale factor. We show that such models represent viable alternatives to describe the large-scale structure of the inflationary universe, leading to a kinematically equivalent Sachs-Wolfe effect. Through the definition of a complete set of spatial eigenfunctions we compute the two-point correlation function of scalar perturbations in these models. In addition, we show how such scenarios would modify the spectrum of the CMB assuming that the observations take place in a small patch of a universe with anisotropic curvature

  17. Cosmological signatures of anisotropic spatial curvature

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Thiago S. [Departamento de Física, Universidade Estadual de Londrina, 86057-970, Londrina – PR (Brazil); Marugán, Guillermo A. Mena [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006, Madrid (Spain); Carneiro, Saulo, E-mail: tspereira@uel.br, E-mail: mena@iem.cfmac.csic.es, E-mail: saulo.carneiro@pq.cnpq.br [Instituto de Física, Universidade Federal da Bahia, 40210-340, Salvador – BA (Brazil)

    2015-07-01

    If one is willing to give up the cherished hypothesis of spatial isotropy, many interesting cosmological models can be developed beyond the simple anisotropically expanding scenarios. One interesting possibility is presented by shear-free models in which the anisotropy emerges at the level of the curvature of the homogeneous spatial sections, whereas the expansion is dictated by a single scale factor. We show that such models represent viable alternatives to describe the large-scale structure of the inflationary universe, leading to a kinematically equivalent Sachs-Wolfe effect. Through the definition of a complete set of spatial eigenfunctions we compute the two-point correlation function of scalar perturbations in these models. In addition, we show how such scenarios would modify the spectrum of the CMB assuming that the observations take place in a small patch of a universe with anisotropic curvature.

  18. Ethical Issues with Genetic Testing for Tay-Sachs.

    Science.gov (United States)

    Clayton, Tricia

    Several genetic disorders are specific to Jewish heritage; one of the most devastating is Tay-Sachs disease.Tay-Sachs is a fatal hereditary disease, causing progressive neurological problems for which there is no cure. Ethical issues surrounding genetic testing for Tay-Sachs within the Jewish community continue to be complex and multifaceted. A perspective of Tay-Sachs, using rights-based ethics and virtue ethics as a theoretical framework, is explored.

  19. Prenatal Diagnosis Of Tay-Sachs Disease

    Directory of Open Access Journals (Sweden)

    Özgür Özyüncü

    2010-04-01

    CONCLUSION: Tay-Sachs disease can be diagnosed prenatally by measuring hexosaminidase enzyme activity in fetal tissue samples with an acceptable complication rate. Prenatal diagnosis should be offered to families who have affected siblings with Tay-Sachs disease.

  20. Quantum cosmological models

    International Nuclear Information System (INIS)

    Coule, D H

    2005-01-01

    We contrast the initial condition requirements of various contemporary cosmological models including inflationary and bouncing cosmologies. Canonical quantization of general relativity is used, as a first approximation to full quantum gravity, to determine whether suitable initial conditions are present. Various proposals such as Hartle-Hawking's 'no boundary' or tunnelling boundary conditions are assessed on grounds of naturalness and fine tuning. Alternatively, a quiescent initial state or an initial closed timelike curve 'time machine' is considered. Possible extensions to brane models are also addressed. Further ideas about universe creation from a meta-universe are outlined. Semiclassical and time asymmetry requirements of cosmology are briefly discussed and contrasted with the black-hole final-state proposal. We compare the recent loop quantum cosmology of Bojowald and co-workers with these earlier schemes. A number of possible difficulties and limitations are outlined. (topical review)

  1. Energy in the Kantowski–Sachs space-time using teleparallel ...

    Indian Academy of Sciences (India)

    Energy in the Kantowski–Sachs space-time using teleparallel geometry ... Kantowski–Sachs metric; teleparallelism; gravitational energy. Abstract. The purpose of this paper is to examine the energy content of the inflationary Universe described by Kantowski–Sachs space-time in quasilocal approach of teleparallel gravity ...

  2. Midisuperspace-induced corrections to the Wheeler De Witt equation

    International Nuclear Information System (INIS)

    Mazzitelli, F.D.

    1992-04-01

    We consider the midisuperspace of four dimensional spherically symmetric metrics and the Kantowski-Sachs minisuperspace contained in it. We discuss the quantization of the midisuperspace using the fact that the dimensionally reduced Einstein Hilbert action becomes a scalar-tensor theory of gravity in two dimensions. We show that the covariant regularization procedure in the midisuperspace induces modifications into the minisuperspace Wheeler De Witt equation. (author). 8 refs

  3. Beyond the Standard Model of Cosmology

    International Nuclear Information System (INIS)

    Ellis, John; Nanopoulos, D. V.

    2004-01-01

    Recent cosmological observations of unprecented accuracy, by WMAP in particular, have established a 'Standard Model' of cosmology, just as LEP established the Standard Model of particle physics. Both Standard Models raise open questions whose answers are likely to be linked. The most fundamental problems in both particle physics and cosmology will be resolved only within a framework for Quantum Gravity, for which the only game in town is string theory. We discuss novel ways to model cosmological inflation and late acceleration in a non-critical string approach, and discuss possible astrophysical tests

  4. Cosmological evolution as squeezing: a toy model for group field cosmology

    Science.gov (United States)

    Adjei, Eugene; Gielen, Steffen; Wieland, Wolfgang

    2018-05-01

    We present a simple model of quantum cosmology based on the group field theory (GFT) approach to quantum gravity. The model is formulated on a subspace of the GFT Fock space for the quanta of geometry, with a fixed volume per quantum. In this Hilbert space, cosmological expansion corresponds to the generation of new quanta. Our main insight is that the evolution of a flat Friedmann–Lemaître–Robertson–Walker universe with a massless scalar field can be described on this Hilbert space as squeezing, familiar from quantum optics. As in GFT cosmology, we find that the three-volume satisfies an effective Friedmann equation similar to the one of loop quantum cosmology, connecting the classical contracting and expanding solutions by a quantum bounce. The only free parameter in the model is identified with Newton’s constant. We also comment on the possible topological interpretation of our squeezed states. This paper can serve as an introduction into the main ideas of GFT cosmology without requiring the full GFT formalism; our results can also motivate new developments in GFT and its cosmological application.

  5. Unified treatment of the luminosity distance in cosmology

    International Nuclear Information System (INIS)

    Yoo, Jaiyul; Scaccabarozzi, Fulvio

    2016-01-01

    Comparing the luminosity distance measurements to its theoretical predictions is one of the cornerstones in establishing the modern cosmology. However, as shown in Biern and Yoo, its theoretical predictions in literature are often plagued with infrared divergences and gauge-dependences. This trend calls into question the sanity of the methods used to derive the luminosity distance. Here we critically investigate four different methods—the geometric approach, the Sachs approach, the Jacobi mapping approach, and the geodesic light cone (GLC) approach to modeling the luminosity distance, and we present a unified treatment of such methods, facilitating the comparison among the methods and checking their sanity. All of these four methods, if exercised properly, can be used to reproduce the correct description of the luminosity distance.

  6. Unified treatment of the luminosity distance in cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Jaiyul; Scaccabarozzi, Fulvio, E-mail: jyoo@physik.uzh.ch, E-mail: fulvio@physik.uzh.ch [Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zürich, Zürich (Switzerland)

    2016-09-01

    Comparing the luminosity distance measurements to its theoretical predictions is one of the cornerstones in establishing the modern cosmology. However, as shown in Biern and Yoo, its theoretical predictions in literature are often plagued with infrared divergences and gauge-dependences. This trend calls into question the sanity of the methods used to derive the luminosity distance. Here we critically investigate four different methods—the geometric approach, the Sachs approach, the Jacobi mapping approach, and the geodesic light cone (GLC) approach to modeling the luminosity distance, and we present a unified treatment of such methods, facilitating the comparison among the methods and checking their sanity. All of these four methods, if exercised properly, can be used to reproduce the correct description of the luminosity distance.

  7. Cosmological models without singularities

    International Nuclear Information System (INIS)

    Petry, W.

    1981-01-01

    A previously studied theory of gravitation in flat space-time is applied to homogeneous and isotropic cosmological models. There exist two different classes of models without singularities: (i) ever-expanding models, (ii) oscillating models. The first class contains models with hot big bang. For these models there exist at the beginning of the universe-in contrast to Einstein's theory-very high but finite densities of matter and radiation with a big bang of very short duration. After short time these models pass into the homogeneous and isotropic models of Einstein's theory with spatial curvature equal to zero and cosmological constant ALPHA >= O. (author)

  8. The National Tay Sachs and Allied Diseases Association.

    Science.gov (United States)

    Zeitlin, Paula

    1986-01-01

    The National Tay-Sachs and Allied Diseases Association is involved in education, research, and prevention of Tay-Sachs, an inherited metabolic disorder which destroys the central nervous system, and over 30 related disorders. The group features a parent peer group network and a support group for carrier couples. (CL)

  9. National Tay-Sachs and Allied Diseases Association, Inc.

    Science.gov (United States)

    Exceptional Parent, 1977

    1977-01-01

    Reviewed are the history and organization, purpose and programs, and public services of the National Tay-Sachs and Allied Diseases Association, an organization geared toward eradicating Tay-Sachs disease (a hereditary disorder affecting primarily Jewish infants which generally leads to deterioration and death by the child's fifth year). (SBH)

  10. Standard cosmological evolution in the f(R) model to Kaluza-Klein cosmology

    International Nuclear Information System (INIS)

    Aghmohammadi, A; Abolhassani, M R; Saaidi, Kh; Vajdi, A

    2009-01-01

    In this paper, using f(R) theory of gravity we explicitly calculate cosmological evolution in the presence of a perfect fluid source in four- and five-dimensional space-time in which this cosmological evolution in self-creation is presented by Reddy et al (2009 Int. J. Theor. Phys. 48 10). An exact cosmological model is presented using a relation between Einstein's gravity field equation components due to a metric with the same component from f(R) theory of gravity. Some physics and kinematical properties of the model are also discussed.

  11. Embedded Lensing Time Delays, the Fermat Potential, and the Integrated Sachs-Wolfe Effect

    Science.gov (United States)

    Chen, Bin; Kantowski, Ronald; Dai, Xinyu

    2015-05-01

    We derive the Fermat potential for a spherically symmetric lens embedded in a Friedman-Lemaître-Robertson-Walker cosmology and use it to investigate the late-time integrated Sachs-Wolfe (ISW) effect, i.e., secondary temperature fluctuations in the cosmic microwave background (CMB) caused by individual large-scale clusters and voids. We present a simple analytical expression for the temperature fluctuation in the CMB across such a lens as a derivative of the lens’ Fermat potential. This formalism is applicable to both linear and nonlinear density evolution scenarios, to arbitrarily large density contrasts, and to all open and closed background cosmologies. It is much simpler to use and makes the same predictions as conventional approaches. In this approach the total temperature fluctuation can be split into a time-delay part and an evolutionary part. Both parts must be included for cosmic structures that evolve and both can be equally important. We present very simple ISW models for cosmic voids and galaxy clusters to illustrate the ease of use of our formalism. We use the Fermat potentials of simple cosmic void models to compare predicted ISW effects with those recently extracted from WMAP and Planck data by stacking large cosmic voids using the aperture photometry method. If voids in the local universe with large density contrasts are no longer evolving we find that the time delay contribution alone predicts values consistent with the measurements. However, we find that for voids still evolving linearly, the evolutionary contribution cancels a significant part of the time delay contribution and results in predicted signals that are much smaller than recently observed.

  12. [Tay-Sachs disease in non-Jewish infant in Israel].

    Science.gov (United States)

    Nadim, Nasser

    2012-01-01

    Tay-Sachs disease, also known as GM2 gangliosidosis or Hexosaminidase A deficiency is an autosomal recessive genetic fatal disorder. The disease is known to appear in East European Ashkenazi Jews, North African Jews, and Quebec French Canadians exclusively, but, with different frequency and type of mutation. Its most common variant is the infantile type Tay-Sachs disease. Juvenile and late-onset forms of the disease are infrequent and slowly progressive. At nearly 3 to 6 months old, a baby with Tay-Sachs progressively loses his motor skills and attentiveness. Startle responses and hyperreflexia become prominent, especially on eliciting deep patellar and Achilles reflexes, as a consequence of neurodegeneration of the upper motor neuron. Other systemic damage ensues gradually; seizures, blindness, spasticity of limbs, inability to swallow and breathe, and eventually the baby dies at 1-4 years of age. All Tay-Sachs patients have a "cherry red spot", easily seen in the macula area of the retina, using an ophthalmoscope. The "cherry red spot" is the only normal part of the retina in these sick babies. The case presented here emphasizes that Tay-Sachs disease is sometimes misdiagnosed at first visits even by an experienced clinician, because of his lack of awareness that this disease is not exclusively a Jewish disease.

  13. The effect of a combined glenoid and Hill-Sachs defect on glenohumeral stability: a biomechanical cadaveric study using 3-dimensional modeling of 142 patients.

    Science.gov (United States)

    Arciero, Robert A; Parrino, Anthony; Bernhardson, Andrew S; Diaz-Doran, Vilmaris; Obopilwe, Elifho; Cote, Mark P; Golijanin, Petr; Mazzocca, Augustus D; Provencher, Matthew T

    2015-06-01

    Bone loss in anterior glenohumeral instability occurs on both the glenoid and the humerus; however, existing biomechanical studies have evaluated glenoid and humeral head defects in isolation. Thus, little is known about the combined effect of these bony lesions in a clinically relevant model on glenohumeral stability. The purpose of this study was to determine the biomechanical efficacy of a Bankart repair in the setting of bipolar (glenoid and humeral head) bone defects determined via computer-generated 3-dimensional (3D) modeling of 142 patients with recurrent anterior shoulder instability. The null hypothesis was that adding a bipolar bone defect will have no effect on glenohumeral stability after soft tissue Bankart repair. Controlled laboratory study. A total of 142 consecutive patients with recurrent anterior instability were analyzed with 3D computed tomography scans. Two Hill-Sachs lesions were selected on the basis of volumetric size representing the 25th percentile (0.87 cm(3); small) and 50th percentile (1.47 cm(3); medium) and printed in plastic resin with a 3D printer. A total of 21 cadaveric shoulders were evaluated on a custom shoulder-testing device permitting 6 degrees of freedom, and the force required to translate the humeral head anteriorly 10 mm at a rate of 2.0 mm/s with a compressive load of 50 N was determined at 60° of glenohumeral abduction and 60° of external rotation. All Bankart lesions were made sharply from the 2- to 6-o'clock positions for a right shoulder. Subsequent Bankart repair with transosseous tunnels using high-strength suture was performed. Hill-Sachs lesions were made in the cadaver utilizing a plastic mold from the exact replica off the 3D printer. Testing was conducted in the following sequence for each specimen: (1) intact, (2) posterior capsulotomy, (3) Bankart lesion, (4) Bankart repair, (5) Bankart lesion with 2-mm glenoid defect, (6) Bankart repair, (7) Bankart lesion with 2-mm glenoid defect and Hill-Sachs lesion

  14. Homogenization and isotropization of an inflationary cosmological model

    International Nuclear Information System (INIS)

    Barrow, J.D.; Groen, Oe.; Oslo Univ.

    1986-01-01

    A member of the class of anisotropic and inhomogeneous cosmological models constructed by Wainwright and Goode is investigated. It is shown to describe a universe containing a scalar field which is minimally coupled to gravitation and a positive cosmological constant. It is shown that this cosmological model evolves exponentially rapidly towards the homogeneous and isotropic de Sitter universe model. (orig.)

  15. Fermat Potentials of Embedded Lensing, the Integrated Sachs-Wolfe Effect, and Weak-Lensing of CMB by Cosmic Voids

    Science.gov (United States)

    Chen, Bin; Kantowski, R.; Dai, X.

    2014-01-01

    We have developed an accurate gravitational lens theory for an inhomogeneity embedded in an otherwise homogeneous universe, which to the lowest order is applicable to any mass distribution. We derive the Fermat potential for a spherically symmetric lens embedded in a FLRW cosmology and use it to investigate the late-time integrated Sachs-Wolfe effect (ISW) caused by individual large scale inhomogeneities, in particular, cosmic voids. We present a simple analytical expression for the CMB temperature fluctuation across such a lens as the derivative of the lens Fermat potential. Our formalism is applicable to both linear and nonlinear density evolution scenarios, to arbitrarily large density contrasts, and to all open and closed background cosmologies. Our results are particularly useful for modeling ISW effects extracted through stacking large numbers of cosmic voids and clusters (that is, the aperture photometry method). For structures co-expanding with the background cosmology, i.e., for time-independent density contrasts, we find that the gravitational lensing time delay alone can produce fluctuations of the order of seen in recent observations by WMAP and Planck. We revisit the possibility of explaining the non-Gaussian cold spot on the south hemisphere via the Rees-Sciama effect of a large cosmic void using constraints obtained from the most recent void catalogs and our new void-lensing formalism, and compare it with other explanations such as a collapsing cosmic texture. We also study the remapping of primordial CMB anisotropies, the weak-lensing shear, and magnification caused by void lensing.

  16. Conformal cosmological model and SNe Ia data

    International Nuclear Information System (INIS)

    Zakharov, A. F.; Pervushin, V. N.

    2012-01-01

    Now there is a huge scientific activity in astrophysical studies and cosmological ones in particular. Cosmology transforms from a pure theoretical branch of science into an observational one. All the cosmological models have to pass observational tests. The supernovae type Ia (SNe Ia) test is among the most important ones. If one applies the test to determine parameters of the standard Friedmann-Robertson-Walker cosmological model one can conclude that observations lead to the discovery of the dominance of the Λ term and as a result to an acceleration of the Universe. However, there are big mysteries connected with an origin and an essence of dark matter (DM) and the Λ term or dark energy (DE). Alternative theories of gravitation are treated as a possible solution of DM and DE puzzles. The conformal cosmological approach is one of possible alternatives to the standard ΛCDM model. As it was noted several years ago, in the framework of the conformal cosmological approach an introduction of a rigid matter can explain observational data without Λ term (or dark energy). We confirm the claim with much larger set of observational data.

  17. Dynamical system approach to running Λ cosmological models

    International Nuclear Information System (INIS)

    Stachowski, Aleksander; Szydlowski, Marek

    2016-01-01

    We study the dynamics of cosmological models with a time dependent cosmological term. We consider five classes of models; two with the non-covariant parametrization of the cosmological term Λ: Λ(H)CDM cosmologies, Λ(a)CDM cosmologies, and three with the covariant parametrization of Λ: Λ(R)CDM cosmologies, where R(t) is the Ricci scalar, Λ(φ)-cosmologies with diffusion, Λ(X)-cosmologies, where X = (1)/(2)g"α"β∇_α∇_βφ is a kinetic part of the density of the scalar field. We also consider the case of an emergent Λ(a) relation obtained from the behaviour of trajectories in a neighbourhood of an invariant submanifold. In the study of the dynamics we used dynamical system methods for investigating how an evolutionary scenario can depend on the choice of special initial conditions. We show that the methods of dynamical systems allow one to investigate all admissible solutions of a running Λ cosmology for all initial conditions. We interpret Alcaniz and Lima's approach as a scaling cosmology. We formulate the idea of an emergent cosmological term derived directly from an approximation of the exact dynamics. We show that some non-covariant parametrization of the cosmological term like Λ(a), Λ(H) gives rise to the non-physical behaviour of trajectories in the phase space. This behaviour disappears if the term Λ(a) is emergent from the covariant parametrization. (orig.)

  18. Rapid detection of fetal Mendelian disorders: Tay-Sachs disease.

    Science.gov (United States)

    Guetta, Esther; Peleg, Leah

    2008-01-01

    Tay-Sachs disease is an autosomal recessive storage disease caused by the impaired activity of the lysosomal enzyme hexosaminidase A. In this fatal disease, the sphingolipid GM2 ganglioside accumulates in the neurons. Due to high carrier rates and the severity of the disease, population screening and prenatal diagnosis of Tay-Sachs disease are routinely carried out in Israel. Laboratory diagnosis of Tay-Sachs is carried out with biochemical and DNA-based methods in peripheral and umbilical cord blood, amniotic fluid, and chorionic villi samples. The assay of hexosaminidase A (Hex A) activity is carried out with synthetic substrates, 4-methylumbelliferyl-6-sulfo-N-acetyl-beta-glucosaminide (4-MUGS) and 4-methylumbelliferil-N-acetyl-beta-glucosamine (4-MUG), and the DNA-based analysis involves testing for the presence of specific known mutations in the alpha-subunit gene of Hex A. Prenatal diagnosis of Tay-Sachs disease is accomplished within 24-48 h from sampling. The preferred strategy is to simultaneously carry out enzymatic analysis in the amniotic fluid supernatant or in chorionic villi and molecular DNA-based testing in an amniotic fluid cell-pellet or in chorionic villi.

  19. Cosmic numbers: A physical classification for cosmological models

    International Nuclear Information System (INIS)

    Avelino, P.P.; Martins, C.J.A.P.

    2003-01-01

    We introduce the notion of the cosmic numbers of a cosmological model, and discuss how they can be used to naturally classify models according to their ability to solve some of the problems of the standard cosmological model

  20. Tay-Sachs and Sandhoff Diseases

    Science.gov (United States)

    ... more common in these groups: Creole of northern Argentina Metis Indians in Saskatchewan, Canada Lebanese If you or your partner is part of these ethnic groups, or you have a family history of Tay-Sachs disease or Sandhoff disease, tell ...

  1. Enfermedad de Tay-Sachs

    Directory of Open Access Journals (Sweden)

    Albia Josefina Pozo Alonso

    Full Text Available La enfermedad de Tay-Sachs es un trastorno neurodegenerativo progresivo de herencia autosómica recesiva. Se debe a la deficiencia de la enzima β-hexosaminidasa A, que provoca una acumulación de gangliósidos GM2 en los lisosomas. Se incluye dentro de las esfingolipidosis. De las esfingolipidosis que presentan mancha rojo cereza en la mácula, la enfermedad de Tay-Sachs es la única en la que no se evidencia hepatoesplenomegalia. La variante más frecuente se inicia en la lactancia. Se presenta un lactante del sexo masculino al que se le realizó el diagnóstico de esta entidad a los 8 meses de edad. A partir de los 4 meses comenzó a presentar una reacción de sobresalto. A los 6 meses comenzó a perder habilidades previamente adquiridas y crisis epilépticas mioclónicas. Se constató una disminución de la actividad específica de la enzima hexosaminidasa A en leucocitos.

  2. Arbitrary scalar-field and quintessence cosmological models

    International Nuclear Information System (INIS)

    Harko, Tiberiu; Lobo, Francisco S.N.; Mak, M.K.

    2014-01-01

    The mechanism of the initial inflationary scenario of the Universe and of its late-time acceleration can be described by assuming the existence of some gravitationally coupled scalar fields φ, with the inflaton field generating inflation and the quintessence field being responsible for the late accelerated expansion. Various inflationary and late-time accelerated scenarios are distinguished by the choice of an effective self-interaction potential V(φ), which simulates a temporarily non-vanishing cosmological term. In this work, we present a new formalism for the analysis of scalar fields in flat isotropic and homogeneous cosmological models. The basic evolution equation of the models can be reduced to a first-order non-linear differential equation. Approximate solutions of this equation can be constructed in the limiting cases of the scalar-field kinetic energy and potential energy dominance, respectively, as well as in the intermediate regime. Moreover, we present several new accelerating and decelerating exact cosmological solutions, based on the exact integration of the basic evolution equation for scalar-field cosmologies. More specifically, exact solutions are obtained for exponential, generalized cosine hyperbolic, and power-law potentials, respectively. Cosmological models with power-law scalar field potentials are also analyzed in detail. (orig.)

  3. A Time-Dependent Λ and G Cosmological Model Consistent with Cosmological Constraints

    Directory of Open Access Journals (Sweden)

    L. Kantha

    2016-01-01

    Full Text Available The prevailing constant Λ-G cosmological model agrees with observational evidence including the observed red shift, Big Bang Nucleosynthesis (BBN, and the current rate of acceleration. It assumes that matter contributes 27% to the current density of the universe, with the rest (73% coming from dark energy represented by the Einstein cosmological parameter Λ in the governing Friedmann-Robertson-Walker equations, derived from Einstein’s equations of general relativity. However, the principal problem is the extremely small value of the cosmological parameter (~10−52 m2. Moreover, the dark energy density represented by Λ is presumed to have remained unchanged as the universe expanded by 26 orders of magnitude. Attempts to overcome this deficiency often invoke a variable Λ-G model. Cosmic constraints from action principles require that either both G and Λ remain time-invariant or both vary in time. Here, we propose a variable Λ-G cosmological model consistent with the latest red shift data, the current acceleration rate, and BBN, provided the split between matter and dark energy is 18% and 82%. Λ decreases (Λ~τ-2, where τ is the normalized cosmic time and G increases (G~τn with cosmic time. The model results depend only on the chosen value of Λ at present and in the far future and not directly on G.

  4. Self-similar cosmological models

    Energy Technology Data Exchange (ETDEWEB)

    Chao, W Z [Cambridge Univ. (UK). Dept. of Applied Mathematics and Theoretical Physics

    1981-07-01

    The kinematics and dynamics of self-similar cosmological models are discussed. The degrees of freedom of the solutions of Einstein's equations for different types of models are listed. The relation between kinematic quantities and the classifications of the self-similarity group is examined. All dust local rotational symmetry models have been found.

  5. Protogalaxy formation from inhomogeneities in cosmological models

    International Nuclear Information System (INIS)

    Rankin, J.R.

    1977-01-01

    Equations governing the growth of protogalaxies in general homogeneous cosmological models were derived. Both non-relativistic Newtonian theory and general relativistic theory were covered. For the Newtonian case, by means of the concept of comoving Fourier analysis, the perturbation equations became coupled first order ordinary differential equations and were then further simplified. Bonnor's equation of galaxy formation in isotropic Newtonian cosmologies was generalized to anisotropic cases. The growth equations were solved for various background Newtonian models and gravitationally unstable solutions were found. By an approach analogous to Bonnor's non-relativistic approach, a relativistic version of the galaxy growth equation for the homogeneous isotropic cosmologies was derived. Galaxy growth in the anisotropic homogeneous Bianchi type I cosmologies was also considered. The full set of Einstein equations in synchronous coordinates was perturbed then simplified. The resulting equation was discussed in special cases of dust, axial symmetry and Kasner backgrounds. Finally the tetrad equations for perturbations in steady state cosmologies was set up with a view to considering the effect of rotation

  6. Gravitational Waves from Isolated Systems: Surprising Consequences of a Positive Cosmological Constant.

    Science.gov (United States)

    Ashtekar, Abhay; Bonga, Béatrice; Kesavan, Aruna

    2016-02-05

    There is a deep tension between the well-developed theory of gravitational waves from isolated systems and the presence of a positive cosmological constant Λ, however tiny. In particular a generalization of Einstein's 1918 quadrupole formula that would allow a positive Λ is not yet available. We first explain the principal difficulties and then show that it is possible to overcome them in the weak field limit. These results also provide concrete hints for constructing the Λ>0 generalization of the Bondi-Sachs framework for full, nonlinear general relativity.

  7. Theoretical cosmology

    International Nuclear Information System (INIS)

    Raychaudhuri, A.K.

    1979-01-01

    The subject is covered in chapters, entitled; introduction; Newtonian gravitation and cosmology; general relativity and relativistic cosmology; analysis of observational data; relativistic models not obeying the cosmological principle; microwave radiation background; thermal history of the universe and nucleosynthesis; singularity of cosmological models; gravitational constant as a field variable; cosmological models based on Einstein-Cartan theory; cosmological singularity in two recent theories; fate of perturbations of isotropic universes; formation of galaxies; baryon symmetric cosmology; assorted topics (including extragalactic radio sources; Mach principle). (U.K.)

  8. Proton MR spectroscopy in three children with Tay-Sachs disease.

    Science.gov (United States)

    Aydin, Kubilay; Bakir, Baris; Tatli, Burak; Terzibasioglu, Ege; Ozmen, Meral

    2005-11-01

    Tay-Sachs disease is an inherited metabolic disease caused by the accumulation of GM(2) gangliosides in the central nervous system. Deficiency of hexosaminidase A leads to the accumulation of gangliosides in neurons, axons and glial cells. To present the cranial MRI and proton MR spectroscopy findings of children of Tay-Sachs disease. Three children aged 10, 20 and 21 months were examined. On T2-weighted MR images there were hyperintense signal changes in the basal ganglia and cerebral white matter. MR spectroscopy demonstrated an increase in myoinositol/creatine and choline/creatine ratios with a decrease in the N-acetyl aspartate/creatine ratio. The spectroscopy findings support demyelination, gliosis and neuronal loss in the neuropathological process of Tay-Sachs disease.

  9. Proton MR spectroscopy in three children with Tay-Sachs disease

    Energy Technology Data Exchange (ETDEWEB)

    Aydin, Kubilay; Bakir, Baris; Terzibasioglu, Ege [Istanbul University, Neuroradiology Division, Department of Radiology, Istanbul (Turkey); Tatli, Burak; Ozmen, Meral [Istanbul University, Department of Paediatric Neurology, Istanbul (Turkey)

    2005-11-01

    Tay-Sachs disease is an inherited metabolic disease caused by the accumulation of GM{sub 2} gangliosides in the central nervous system. Deficiency of hexosaminidase A leads to the accumulation of gangliosides in neurons, axons and glial cells. To present the cranial MRI and proton MR spectroscopy findings of children of Tay-Sachs disease. Three children aged 10, 20 and 21 months were examined. On T2-weighted MR images there were hyperintense signal changes in the basal ganglia and cerebral white matter. MR spectroscopy demonstrated an increase in myoinositol/creatine and choline/creatine ratios with a decrease in the N-acetyl aspartate/creatine ratio. The spectroscopy findings support demyelination, gliosis and neuronal loss in the neuropathological process of Tay-Sachs disease. (orig.)

  10. Proton MR spectroscopy in three children with Tay-Sachs disease

    International Nuclear Information System (INIS)

    Aydin, Kubilay; Bakir, Baris; Terzibasioglu, Ege; Tatli, Burak; Ozmen, Meral

    2005-01-01

    Tay-Sachs disease is an inherited metabolic disease caused by the accumulation of GM 2 gangliosides in the central nervous system. Deficiency of hexosaminidase A leads to the accumulation of gangliosides in neurons, axons and glial cells. To present the cranial MRI and proton MR spectroscopy findings of children of Tay-Sachs disease. Three children aged 10, 20 and 21 months were examined. On T2-weighted MR images there were hyperintense signal changes in the basal ganglia and cerebral white matter. MR spectroscopy demonstrated an increase in myoinositol/creatine and choline/creatine ratios with a decrease in the N-acetyl aspartate/creatine ratio. The spectroscopy findings support demyelination, gliosis and neuronal loss in the neuropathological process of Tay-Sachs disease. (orig.)

  11. A critique of Jeffrey D. Sachs's The end of poverty.

    Science.gov (United States)

    Henwood, Doug

    2006-01-01

    Jeffrey Sachs's The End of Poverty is a manifesto and how-to guide on ending extreme poverty around the world; it promotes the U.N. Millennium Development Goals. Sachs achieved fame with his policy package for the "stabilization" of Bolivia (which did nothing to relieve Bolivia's poverty), and became advisor to the Yeltsin government in Russia and to Poland, Slovenia, and Estonia as they began their transitions to capitalism (the last three mixed successes; Russia a thorough disaster). Sachs later became more prominent as a critic of development orthodoxy, and was economic advisor to the Jubilee 2000 movement. The End of Poverty is full of sharp critiques of Western imperialism, but his views on the rest of the development business are more conventional.

  12. Viscous cosmological models with a variable cosmological term ...

    African Journals Online (AJOL)

    Einstein's field equations for a Friedmann-Lamaitre Robertson-Walker universe filled with a dissipative fluid with a variable cosmological term L described by full Israel-Stewart theory are considered. General solutions to the field equations for the flat case have been obtained. The solution corresponds to the dust free model ...

  13. Sachês antimicrobianos em pós-colheita de manga

    Directory of Open Access Journals (Sweden)

    Eber Antonio Alves Medeiros

    2011-10-01

    Full Text Available Objetivou-se com este trabalho desenvolver sachês incorporados com óleos essenciais avaliando as propriedades físico-químicas e microbiológicas de mangas armazenadas em saco de papel contendo estes sachês em seu interior. Os óleos essenciais de orégano (Origanum vulgaris e capim-limão (Cymbopogon citratus foram incorporados em saches, e sua atividade antimicrobiana foi testada nos fungos Colletotrichum gloeosporides, Lasiodiplodia theobromae, Xanthomonas campestris pv. mangiferae indica, Alternaria alternata. Frutos de manga 'Tommy Atkins' foram acondicionados individualmente em sacos de papel contendo em seu interior um sachê antimicrobiano e mantidos a 25 °C ± 2 °C e UR 80% ± 5% por nove dias. Os parâmetros cor da epiderme, firmeza de polpa, sólidos solúveis, acidez titulável e pH sofreram pouca influência dos óleos essenciais de orégano e capim limão, indicando que a presença do óleo essencial não altera as características físico-químicas da polpa de manga. Os sachês ativos incorporados com óleos essenciais de orégano e capim limão apresentaram controle no crescimento dos microrganismos testados, sendo o capim-limão mais eficiente, reduzindo em aproximadamente 2 ciclos Log a contagem de mesófilos aeróbios e fungos filamentosos e leveduras em relação ao tratamento controle empregado.

  14. 'Cherry red spot' in a patient with Tay-Sachs disease: case report.

    Science.gov (United States)

    Aragão, Ricardo Evangelista Marrocos de; Ramos, Régia Maria Gondim; Pereira, Felipe Bezerra Alves; Bezerra, Andreya Ferreira Rodrigues; Fernandes, Daniel Nogueira

    2009-01-01

    Tay-Sachs disease is an autosomal recessive disorder of sphingolipid metabolism, caused by enzyme hexosaminidase A deficiency that leads to an accumulation of GM2 in neurocytes which results in progressive loss of neurological function. The accumulation of lipid in retinal ganglion cells that leads to a chalk-white appearance of the fundus called 'cherry red spot' is the hallmark of Tay-Sachs disease. It is also seen in others neurometabolic diseases as well as in central retinal artery occlusion. This case reports a child with Tay-Sachs disease in a family with four previous similar deaths without diagnostic.

  15. Spontaneous appearance of Tay-Sachs disease in an animal model.

    Science.gov (United States)

    Zeng, B J; Torres, P A; Viner, T C; Wang, Z H; Raghavan, S S; Alroy, J; Pastores, G M; Kolodny, E H

    2008-01-01

    Tay-Sachs disease (TSD) is a progressive neurodegenerative disorder due to an autosomal recessively inherited deficiency of beta-hexosaminidase A (Hex A). Deficiency of Hex A in TSD is caused by a defect of the alpha-subunit resulting from mutations of the HEXA gene. To date, there is no effective treatment for TSD. Animal models of genetic diseases, similar to those known to exist in humans, are valuable and essential research tools for the study of potentially effective therapies. However, there is no ideal animal model of TSD available for use in therapeutic trials. In the present study, we report an animal model (American flamingo; Phoenicopterus ruber) of TSD with Hex A deficiency occurring spontaneously in nature, with accumulation of G(M2)-ganglioside, deficiency of Hex A enzymatic activity, and a homozygous P469L mutation in exon 12 of the hexa gene. In addition, we have isolated the full-length cDNA sequence of the flamingo, which consists of 1581 nucleotides encoding a protein of 527 amino acids. Its coding sequence indicates approximately 71% identity at the nucleotide level and about 72.5% identity at the amino acid level with the encoding region of the human HEXA gene. This animal model, with many of the same features as TSD in humans, could represent a valuable resource for investigating therapy of TSD.

  16. Cosmological models with Gurzadyan-Xue dark energy

    International Nuclear Information System (INIS)

    Vereshchagin, G V; Yegorian, G

    2006-01-01

    The formula for dark energy density derived by Gurzadyan and Xue is the only formula which provides (without a free parameter) a value for dark energy density in remarkable agreement with current cosmological datasets, unlike numerous phenomenological scenarios where the corresponding value is postulated. This formula suggests the possibility of variation of physical constants such as the speed of light and the gravitational constant. Considering several cosmological models based on that formula and deriving the cosmological equations for each case, we show that in all models source terms appear in the continuity equation. So, on one hand, GX models make up a rich set covering a lot of currently proposed models of dark energy; on the other hand, they reveal hidden symmetries, with a particular role of the separatrix Ω m = 2/3, and link with the issue of the content of physical constants

  17. Simple inflationary models in Gauss–Bonnet brane-world cosmology

    International Nuclear Information System (INIS)

    Okada, Nobuchika; Okada, Satomi

    2016-01-01

    In light of the recent Planck 2015 results for the measurement of the cosmic microwave background (CMB) anisotropy, we study simple inflationary models in the context of the Gauss–Bonnet (GB) brane-world cosmology. The brane-world cosmological effect modifies the power spectra of scalar and tensor perturbations generated by inflation and causes a dramatic change for the inflationary predictions of the spectral index ( n s ) and the tensor-to-scalar ratio ( r ) from those obtained in the standard cosmology. In particular, the predicted r values in the inflationary models favored by the Planck 2015 results are suppressed due to the GB brane-world cosmological effect, which is in sharp contrast with inflationary scenario in the Randall–Sundrum brane-world cosmology, where the r values are enhanced. Hence, these two brane-world cosmological scenarios are distinguishable. With the dramatic change of the inflationary predictions, the inflationary scenario in the GB brane-world cosmology can be tested by more precise measurements of n s and future observations of the CMB B -mode polarization. (paper)

  18. Vacuum inhomogeneous cosmological models

    International Nuclear Information System (INIS)

    Hanquin, J.-L.

    1984-01-01

    The author presents some results concerning the vacuum cosmological models which admit a 2-dimensional Abelian group of isometries: classifications of these space-times based on the topological nature of their space-like hypersurfaces and on their time evolution, analysis of the asymptotical behaviours at spatial infinity for hyperbolical models as well as in the neighbourhood of the singularity for the models possessing a time singularity during their evolution. (Auth.)

  19. Scalar-tensor cosmology with cosmological constant

    International Nuclear Information System (INIS)

    Maslanka, K.

    1983-01-01

    The equations of scalar-tensor theory of gravitation with cosmological constant in the case of homogeneous and isotropic cosmological model can be reduced to dynamical system of three differential equations with unknown functions H=R/R, THETA=phi/phi, S=e/phi. When new variables are introduced the system becomes more symmetrical and cosmological solutions R(t), phi(t), e(t) are found. It is shown that when cosmological constant is introduced large class of solutions which depend also on Dicke-Brans parameter can be obtained. Investigations of these solutions give general limits for cosmological constant and mean density of matter in plane model. (author)

  20. The bystander effect model of Brenner and Sachs fitted to lung cancer data in 11 cohorts of underground miners, and equivalence of fit of a linear relative risk model with adjustment for attained age and age at exposure

    International Nuclear Information System (INIS)

    Little, M P

    2004-01-01

    Bystander effects following exposure to α-particles have been observed in many experimental systems, and imply that linearly extrapolating low dose risks from high dose data might materially underestimate risk. Brenner and Sachs (2002 Int. J. Radiat. Biol. 78 593-604; 2003 Health Phys. 85 103-8) have recently proposed a model of the bystander effect which they use to explain the inverse dose rate effect observed for lung cancer in underground miners exposed to radon daughters. In this paper we fit the model of the bystander effect proposed by Brenner and Sachs to 11 cohorts of underground miners, taking account of the covariance structure of the data and the period of latency between the development of the first pre-malignant cell and clinically overt cancer. We also fitted a simple linear relative risk model, with adjustment for age at exposure and attained age. The methods that we use for fitting both models are different from those used by Brenner and Sachs, in particular taking account of the covariance structure, which they did not, and omitting certain unjustifiable adjustments to the miner data. The fit of the original model of Brenner and Sachs (with 0 y period of latency) is generally poor, although it is much improved by assuming a 5 or 6 y period of latency from the first appearance of a pre-malignant cell to cancer. The fit of this latter model is equivalent to that of a linear relative risk model with adjustment for age at exposure and attained age. In particular, both models are capable of describing the observed inverse dose rate effect in this data set

  1. Starobinsky cosmological model in Palatini formalism

    Energy Technology Data Exchange (ETDEWEB)

    Stachowski, Aleksander [Jagiellonian University, Astronomical Observatory, Krakow (Poland); Szydlowski, Marek [Jagiellonian University, Astronomical Observatory, Krakow (Poland); Jagiellonian University, Mark Kac Complex Systems Research Centre, Krakow (Poland); Borowiec, Andrzej [Wroclaw University, Institute for Theoretical Physics, Wroclaw (Poland)

    2017-06-15

    We classify singularities in FRW cosmologies, which dynamics can be reduced to the dynamical system of the Newtonian type. This classification is performed in terms of the geometry of a potential function if it has poles. At the sewn singularity, which is of a finite scale factor type, the singularity in the past meets the singularity in the future. We show that such singularities appear in the Starobinsky model in f(R) = R + γR{sup 2} in the Palatini formalism, when dynamics is determined by the corresponding piecewise-smooth dynamical system. As an effect we obtain a degenerate singularity. Analytical calculations are given for the cosmological model with matter and the cosmological constant. The dynamics of model is also studied using dynamical system methods. From the phase portraits we find generic evolutionary scenarios of the evolution of the universe. For this model, the best fit value of Ω{sub γ} = 3γH{sub 0}{sup 2} is equal 9.70 x 10{sup -11}. We consider a model in both Jordan and Einstein frames. We show that after transition to the Einstein frame we obtain both the form of the potential of the scalar field and the decaying Lambda term. (orig.)

  2. Basic versus applied research: Julius Sachs (1832-1897) and the experimental physiology of plants.

    Science.gov (United States)

    Kutschera, Ulrich

    2015-01-01

    The German biologist Julius Sachs was the first to introduce controlled, accurate, quantitative experimentation into the botanical sciences, and is regarded as the founder of modern plant physiology. His seminal monograph Experimental-Physiologie der Pflanzen (Experimental Physiology of Plants) was published 150 y ago (1865), when Sachs was employed as a lecturer at the Agricultural Academy in Poppelsdorf/Bonn (now part of the University). This book marks the beginning of a new era of basic and applied plant science. In this contribution, I summarize the achievements of Sachs and outline his lasting legacy. In addition, I show that Sachs was one of the first biologists who integrated bacteria, which he considered to be descendants of fungi, into the botanical sciences and discussed their interaction with land plants (degradation of wood etc.). This "plant-microbe-view" of green organisms was extended and elaborated by the laboratory botanist Wilhelm Pfeffer (1845-1920), so that the term "Sachs-Pfeffer-Principle of Experimental Plant Research" appears to be appropriate to characterize this novel way of performing scientific studies on green, photoautotrophic organisms (embryophytes, algae, cyanobacteria).

  3. Cosmology

    International Nuclear Information System (INIS)

    Novikov, I.D.

    1979-01-01

    Progress made by this Commission over the period 1976-1978 is reviewed. Topics include the Hubble constant, deceleration parameter, large-scale distribution of matter in the universe, radio astronomy and cosmology, space astronomy and cosmology, formation of galaxies, physics near the cosmological singularity, and unconventional cosmological models. (C.F.)

  4. Introduction to particle cosmology the standard model of cosmology and its open problems

    CERN Document Server

    Bambi, Cosimo

    2016-01-01

    This book introduces the basic concepts of particle cosmology and covers all the main aspects of the Big Bang Model (expansion of the Universe, Big Bang Nucleosynthesis, Cosmic Microwave Background, large scale structures) and the search for new physics (inflation, baryogenesis, dark matter, dark energy). It also includes the majority of recent discoveries, such as the precise determination of cosmological parameters using experiments like WMAP and Planck, the discovery of the Higgs boson at LHC, the non-discovery to date of supersymmetric particles, and the search for the imprint of gravitational waves on the CMB polarization by Planck and BICEP.   This textbook is based on the authors’ courses on Cosmology, and aims at introducing Particle Cosmology to senior undergraduate and graduate students. It has been especially written to be accessible even for those students who do not have a strong background in General Relativity and quantum field theory. The content of this book is organized in an easy-to-use ...

  5. Updated tomographic analysis of the integrated Sachs-Wolfe effect and implications for dark energy

    Science.gov (United States)

    Stölzner, Benjamin; Cuoco, Alessandro; Lesgourgues, Julien; Bilicki, Maciej

    2018-03-01

    We derive updated constraints on the integrated Sachs-Wolfe (ISW) effect through cross-correlation of the cosmic microwave background with galaxy surveys. We improve with respect to similar previous analyses in several ways. First, we use the most recent versions of extragalactic object catalogs, SDSS DR12 photometric redshift (photo-z ) and 2MASS Photo-z data sets, as well as those employed earlier for ISW, SDSS QSO photo-z and NVSS samples. Second, we use for the first time the WISE × SuperCOSMOS catalog, which allows us to perform an all-sky analysis of the ISW up to z ˜0.4 . Third, thanks to the use of photo-z s , we separate each data set into different redshift bins, deriving the cross-correlation in each bin. This last step leads to a significant improvement in sensitivity. We remove cross-correlation between catalogs using masks which mutually exclude common regions of the sky. We use two methods to quantify the significance of the ISW effect. In the first one, we fix the cosmological model, derive linear galaxy biases of the catalogs, and then evaluate the significance of the ISW using a single parameter. In the second approach we perform a global fit of the ISW and of the galaxy biases varying the cosmological model. We find significances of the ISW in the range 4.7 - 5.0 σ thus reaching, for the first time in such an analysis, the threshold of 5 σ . Without the redshift tomography we find a significance of ˜4.0 σ , which shows the importance of the binning method. Finally we use the ISW data to infer constraints on the dark energy redshift evolution and equation of state. We find that the redshift range covered by the catalogs is still not optimal to derive strong constraints, although this goal will be likely reached using future datasets such as from Euclid, LSST, and SKA.

  6. Mathematical cosmology

    International Nuclear Information System (INIS)

    Landsberg, P.T.; Evans, D.A.

    1977-01-01

    The subject is dealt with in chapters, entitled: cosmology -some fundamentals; Newtonian gravitation - some fundamentals; the cosmological differential equation - the particle model and the continuum model; some simple Friedmann models; the classification of the Friedmann models; the steady-state model; universe with pressure; optical effects of the expansion according to various theories of light; optical observations and cosmological models. (U.K.)

  7. Cosmological models in globally geodesic coordinates. II. Near-field approximation

    International Nuclear Information System (INIS)

    Liu Hongya

    1987-01-01

    A near-field approximation dealing with the cosmological field near a typical freely falling observer is developed within the framework established in the preceding paper [J. Math. Phys. 28, xxxx(1987)]. It is found that for the matter-dominated era the standard cosmological model of general relativity contains the Newtonian cosmological model, proposed by Zel'dovich, as its near-field approximation in the observer's globally geodesic coordinate system

  8. Testing and selecting cosmological models with ultra-compact radio quasars

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaolei [Beijing Normal University, Department of Astronomy, Beijing (China); University of Michigan, Department of Physics, Ann Arbor, MI (United States); Cao, Shuo; Qi, Jingzhao; Zhu, Zong-Hong [Beijing Normal University, Department of Astronomy, Beijing (China); Zheng, Xiaogang; Biesiada, Marek [Beijing Normal University, Department of Astronomy, Beijing (China); University of Silesia, Department of Astrophysics and Cosmology, Institute of Phyisics, Katowice (Poland)

    2017-10-15

    In this paper, we place constraints on four alternative cosmological models under the assumption of the spatial flatness of the Universe: CPL, EDE, GCG and MPC. A new compilation of 120 compact radio quasars observed by very-long-baseline interferometry, which represents a type of new cosmological standard rulers, are used to test these cosmological models. Our results show that the fits on CPL obtained from the quasar sample are well consistent with those obtained from BAO. For other cosmological models considered, quasars provide constraints in agreement with those derived with other standard probes at 1σ confidence level. Moreover, the results obtained from other statistical methods including figure of merit, Om(z) and statefinder diagnostics indicate that: (1) Radio quasar standard ruler could provide better statistical constraints than BAO for all cosmological models considered, which suggests its potential to act as a powerful complementary probe to BAO and galaxy clusters. (2) Turning to Om(z) diagnostics, CPL, GCG and EDE models cannot be distinguished from each other at the present epoch. (3) In the framework of statefinder diagnostics, MPC and EDE will deviate from the ΛCDM model in the near future, while GCG model cannot be distinguished from the ΛCDM model unless much higher precision observations are available. (orig.)

  9. "Cherry red spot" in a patient with Tay-Sachs disease: case report "Mácula em cereja" em paciente com doença de Tay-Sachs: relato de caso

    Directory of Open Access Journals (Sweden)

    Ricardo Evangelista Marrocos de Aragão

    2009-08-01

    Full Text Available Tay-Sachs disease is an autosomal recessive disorder of sphingolipid metabolism, caused by enzime hexosaminidase A deficiency that leads to an accumulation of GM2 in neurocytes which results in progressive loss of neurological function. The accumulation of lipid in retinal ganglion cells that leads to a chalk-white appearance of the fundus called "cherry red spot" is the hallmark of Tay-Sachs disease. It is also seen in others neurometabolic diseases as well as in central retinal artery occlusion. This case reports a child with Tay-Sachs disease in a family with four previous similar deaths without diagnostic.Tay-Sachs é uma doença autossômica recessiva, caracterizada pela deficiência da enzima hexosaminidase A levando ao acúmulo de esfingolipídios (GM2 em células neuronais que resulta em uma perda progressiva da função neurológica. O acúmulo de lipídios em células ganglionais da retina leva a uma aparência de mácula em cereja, característica do fundo de olho de pessoas acometidas. "Mácula em cereja" também pode ser vista em outras doenças neurometabólicas e em oclusão da artéria central da retina. Este trabalho relata o caso de um paciente com doença de Tay-Sachs em uma família com história de quatro óbitos por causas semelhantes sem diagnóstico.

  10. Late onset Tay-Sachs disease in mice with targeted disruption of the Hexa gene: behavioral changes and pathology of the central nervous system.

    Science.gov (United States)

    Miklyaeva, Elena I; Dong, Weijia; Bureau, Alexandre; Fattahie, Roya; Xu, Yongqin; Su, Meng; Fick, Gordon H; Huang, Jing-Qi; Igdoura, Suleiman; Hanai, Nobuo; Gravel, Roy A

    2004-03-19

    Tay-Sachs disease is an autosomal recessive neurodegenerative disease resulting from a block in the hydrolysis of GM2 ganglioside, an intermediate in ganglioside catabolism. The mouse model of Tay-Sachs disease (Hexa -/-) has been described as behaviorally indistinguishable from wild type until at least 1 year of age due to a sialidase-mediated bypass of the metabolic defect that reduces the rate of GM2 ganglioside accumulation. In this study, we have followed our mouse model to over 2 years of age and have documented a significant disease phenotype that is reminiscent of the late onset, chronic form of human Tay-Sachs disease. Onset occurs at 11-12 months of age and progresses slowly, in parallel with increasing storage of GM2 ganglioside. The disease is characterized by hind limb spasticity, weight loss, tremors, abnormal posture with lordosis, possible visual impairment, and, late in the disease, muscle weakness, clasping of the limbs, and myoclonic twitches of the head. Immunodetection of GM2 ganglioside showed that storage varies widely in different regions, but is most intense in pyriform cortex, hippocampus (CA3 field, subiculum), amygdala, hypothalamus (paraventricular supraoptic, ventromedial and arcuate nuclei, and mammilary body), and the somatosensory cortex (layer V) in 1- to 2-year-old mutant mice. We suggest that the Tay-Sachs mouse model is a phenotypically valid model of disease and may provide for a reliable indicator of the impact of therapeutic strategies, in particular geared to the late onset, chronic form of human Tay-Sachs disease.

  11. Cosmological model-independent Gamma-ray bursts calibration and its cosmological constraint to dark energy

    International Nuclear Information System (INIS)

    Xu, Lixin

    2012-01-01

    As so far, the redshift of Gamma-ray bursts (GRBs) can extend to z ∼ 8 which makes it as a complementary probe of dark energy to supernova Ia (SN Ia). However, the calibration of GRBs is still a big challenge when they are used to constrain cosmological models. Though, the absolute magnitude of GRBs is still unknown, the slopes of GRBs correlations can be used as a useful constraint to dark energy in a completely cosmological model independent way. In this paper, we follow Wang's model-independent distance measurement method and calculate their values by using 109 GRBs events via the so-called Amati relation. Then, we use the obtained model-independent distances to constrain ΛCDM model as an example

  12. Modern Cosmology

    CERN Document Server

    Zhang Yuan Zhong

    2002-01-01

    This book is one of a series in the areas of high-energy physics, cosmology and gravitation published by the Institute of Physics. It includes courses given at a doctoral school on 'Relativistic Cosmology: Theory and Observation' held in Spring 2000 at the Centre for Scientific Culture 'Alessandro Volta', Italy, sponsored by SIGRAV-Societa Italiana di Relativita e Gravitazione (Italian Society of Relativity and Gravitation) and the University of Insubria. This book collects 15 review reports given by a number of outstanding scientists. They touch upon the main aspects of modern cosmology from observational matters to theoretical models, such as cosmological models, the early universe, dark matter and dark energy, modern observational cosmology, cosmic microwave background, gravitational lensing, and numerical simulations in cosmology. In particular, the introduction to the basics of cosmology includes the basic equations, covariant and tetrad descriptions, Friedmann models, observation and horizons, etc. The ...

  13. CMB anisotropies at all orders: the non-linear Sachs-Wolfe formula

    OpenAIRE

    Roldan, Omar

    2017-01-01

    We obtain the non-linear generalization of the Sachs-Wolfe + integrated Sachs-Wolfe (ISW) formula describing the CMB temperature anisotropies. Our formula is valid at all orders in perturbation theory, is also valid in all gauges and includes scalar, vector and tensor modes. A direct consequence of our results is that the maps of the logarithmic temperature anisotropies are much cleaner than the usual CMB maps, because they automatically remove many secondary anisotropies. This can for instan...

  14. Tay-Sach disease with "cherry-red spot"--first reported case in Malaysia.

    Science.gov (United States)

    Chan, L Y; Balasubramaniam, S; Sunder, R; Jamalia, R; Karunakar, T V N; Alagaratnam, J

    2011-12-01

    We present a rare case of Tay-Sachs disease with retinal 'cherry-red spots' in a 19-month-old Malay child. Molecular genetic studies confirmed the diagnosis. The case highlights that 'cherry-red spot' is a useful clinical clue in Tay-Sachs disease and several other lysosomal storage disorders. It serves as an ideal illustration of the eye as a window to inborn error of metabolism.

  15. Stability of the Einstein static universe in open cosmological models

    International Nuclear Information System (INIS)

    Canonico, Rosangela; Parisi, Luca

    2010-01-01

    The stability properties of the Einstein static solution of general relativity are altered when corrective terms arising from modification of the underlying gravitational theory appear in the cosmological equations. In this paper the existence and stability of static solutions are considered in the framework of two recently proposed quantum gravity models. The previously known analysis of the Einstein static solutions in the semiclassical regime of loop quantum cosmology with modifications to the gravitational sector is extended to open cosmological models where a static neutrally stable solution is found. A similar analysis is also performed in the framework of Horava-Lifshitz gravity under detailed balance and projectability conditions. In the case of open cosmological models the two solutions found can be either unstable or neutrally stable according to the admitted values of the parameters.

  16. Probing the integrated Sachs-Wolfe effect using embedded lens models

    Science.gov (United States)

    Chen, B.; Kantowski, R.

    2015-04-01

    The photometry profile of the integrated Sachs-Wolfe (ISW) effect, recently obtained by the Planck consortium by stacking patches of cosmic microwave background (CMB) sky maps around a large number of cosmic voids, contains a cold ring at about half the void's effective radius surrounded by a hot ring near the void's boundary. The source of the temperature structure is assumed to be the ISW effect but the exact cause of the ringed structure is not currently well understood, particularly the outer hot ring. Numerical simulations have suggested that hot/cold ring structures can be produced by motions associated with nonlinear growths of cosmic structures whose gravitational potentials produce the ISW effect. We have recently developed the embedded lens theory and the Fermat potential formalism which can be used to model the ISW effect caused by intervening individual lens inhomogeneities evolving arbitrarily. This theory only requires knowledge of the void's projected mass profile as a function of the passing CMB photons' impact radius and the rate of change of that mass distribution at passage. We present two simple embedded void lens models with evolving mass densities and investigate the ISW effect caused by these lenses. Both models possess expanding mass shells which produce hot rings around central cold regions, consistent with the recent observations. By adding a small overdensity at the void's center we can produce the slight positive temperature excess hinted at in Planck's photometric results. We conclude that the embedded lens theory and the Fermat potential formalism is well suited for modeling the ISW effect.

  17. Eigenvalue treatment of cosmological models

    International Nuclear Information System (INIS)

    Novello, M.; Soares, D.

    1976-08-01

    From the decomposition of Weyl tensor into its electric and magnetic parts, it is formulated the eigenvalue problem for cosmological models, and is used quasi-maxwellian form of Einstein's equation to propagate it along a time-like congruence. Three related theorems are presented

  18. Tay Sachs and Related Storage Diseases: Family Planning

    Science.gov (United States)

    Schneiderman, Gerald; And Others

    1978-01-01

    Based on interviews with 24 families, the article discusses family planning and the choices available to those families in which a child has previously died from Tay-Sachs or related lipid storage diseases. (IM)

  19. Modeling the citation network by network cosmology.

    Science.gov (United States)

    Xie, Zheng; Ouyang, Zhenzheng; Zhang, Pengyuan; Yi, Dongyun; Kong, Dexing

    2015-01-01

    Citation between papers can be treated as a causal relationship. In addition, some citation networks have a number of similarities to the causal networks in network cosmology, e.g., the similar in-and out-degree distributions. Hence, it is possible to model the citation network using network cosmology. The casual network models built on homogenous spacetimes have some restrictions when describing some phenomena in citation networks, e.g., the hot papers receive more citations than other simultaneously published papers. We propose an inhomogenous causal network model to model the citation network, the connection mechanism of which well expresses some features of citation. The node growth trend and degree distributions of the generated networks also fit those of some citation networks well.

  20. Modern Cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yuanzhong

    2002-06-21

    This book is one of a series in the areas of high-energy physics, cosmology and gravitation published by the Institute of Physics. It includes courses given at a doctoral school on 'Relativistic Cosmology: Theory and Observation' held in Spring 2000 at the Centre for Scientific Culture 'Alessandro Volta', Italy, sponsored by SIGRAV-Societa Italiana di Relativita e Gravitazione (Italian Society of Relativity and Gravitation) and the University of Insubria. This book collects 15 review reports given by a number of outstanding scientists. They touch upon the main aspects of modern cosmology from observational matters to theoretical models, such as cosmological models, the early universe, dark matter and dark energy, modern observational cosmology, cosmic microwave background, gravitational lensing, and numerical simulations in cosmology. In particular, the introduction to the basics of cosmology includes the basic equations, covariant and tetrad descriptions, Friedmann models, observation and horizons, etc. The chapters on the early universe involve inflationary theories, particle physics in the early universe, and the creation of matter in the universe. The chapters on dark matter (DM) deal with experimental evidence of DM, neutrino oscillations, DM candidates in supersymmetry models and supergravity, structure formation in the universe, dark-matter search with innovative techniques, and dark energy (cosmological constant), etc. The chapters about structure in the universe consist of the basis for structure formation, quantifying large-scale structure, cosmic background fluctuation, galaxy space distribution, and the clustering of galaxies. In the field of modern observational cosmology, galaxy surveys and cluster surveys are given. The chapter on gravitational lensing describes the lens basics and models, galactic microlensing and galaxy clusters as lenses. The last chapter, 'Numerical simulations in cosmology', deals with spatial and

  1. Modelling non-dust fluids in cosmology

    International Nuclear Information System (INIS)

    Christopherson, Adam J.; Hidalgo, Juan Carlos; Malik, Karim A.

    2013-01-01

    Currently, most of the numerical simulations of structure formation use Newtonian gravity. When modelling pressureless dark matter, or 'dust', this approach gives the correct results for scales much smaller than the cosmological horizon, but for scenarios in which the fluid has pressure this is no longer the case. In this article, we present the correspondence of perturbations in Newtonian and cosmological perturbation theory, showing exact mathematical equivalence for pressureless matter, and giving the relativistic corrections for matter with pressure. As an example, we study the case of scalar field dark matter which features non-zero pressure perturbations. We discuss some problems which may arise when evolving the perturbations in this model with Newtonian numerical simulations and with CMB Boltzmann codes

  2. Quantum cosmological relational model of shape and scale in 1D

    International Nuclear Information System (INIS)

    Anderson, Edward

    2011-01-01

    Relational particle models are useful toy models for quantum cosmology and the problem of time in quantum general relativity. This paper shows how to extend existing work on concrete examples of relational particle models in 1D to include a notion of scale. This is useful as regards forming a tight analogy with quantum cosmology and the emergent semiclassical time and hidden time approaches to the problem of time. This paper shows furthermore that the correspondence between relational particle models and classical and quantum cosmology can be strengthened using judicious choices of the mechanical potential. This gives relational particle mechanics models with analogues of spatial curvature, cosmological constant, dust and radiation terms. A number of these models are then tractable at the quantum level. These models can be used to study important issues (1) in canonical quantum gravity: the problem of time, the semiclassical approach to it and timeless approaches to it (such as the naive Schroedinger interpretation and records theory) and (2) in quantum cosmology, such as in the investigation of uniform states, robustness and the qualitative understanding of the origin of structure formation.

  3. Segregation of Tay-Sachs and Sandhoff alleles in a non-Jewish family.

    OpenAIRE

    Lane, A B; Young, E; Jenkins, T

    1980-01-01

    A non-Jewish family is presented in which the genes for Tay-Sachs disease and Sandhoff disease are segregating. Individuals heterozygous for both alleles have low serum and white cell total hexosaminidase levels together with a proportion of heat-labile hexosaminidase A (HEX A) which falls in the normal range. The individuals would not be detected as carriers of Tay-Sachs disease or Sandhoff disease in a population screening program.

  4. Distribution of a pseudodeficiency allele among Tay-Sachs carriers

    Energy Technology Data Exchange (ETDEWEB)

    Tomczak, J.; Grebner, E.E. (Thomas Jefferson Univ., Philadelphia, PA (United States)); Boogen, C. (Univ. of Essen Medical School (Germany))

    1993-08-01

    Recently Triggs-Raine et al. (1992) identified a new mutation in the gene coding for the [alpha]-subunit of [beta]-hexosaminidase A (hex A), the enzyme whose deficiency causes Tay-Sachs disease. This mutation, a C[sub 739]-to-T transition in exon 7, results in an altered enzyme that is active (albeit at reduced levels) in cells but that has essentially no activity in serum. This so-called pseudodeficient allele was first detected in compound heterozygotes who also carried a Tay-Sachs disease allele and therefore had no detectable hex A in their serum but who were in good health. Carriers of this apparently benign mutation are generally indistinguishable from carriers of a lethal mutation by means of routine enzyme-based screening tests, because the product of the pseudodeficient allele is not detectable in serum and has decreased activity in cells. This suggests that some individuals who have been classified as Tay-Sachs carriers are actually carriers of the pseudodeficient allele and are not at risk to have a child affected with Tay-Sachs disease. The pseudodeficient allele may also be responsible for some inconclusive diagnoses, where leukocyte values fall below the normal range but are still above the carrier range. The fact that there are now two mutant alleles (the psuedodeficient and the adult) that are indistinguishable from the lethal infantile mutations by means of enzyme assay yet that are phenotypically very different and that together may account for as much as 12% of enzyme-defined carriers on the basis of the data here suggests that DNA analysis should be part of a comprehensive screening program. It will be particularly useful to identify the mutations in couples at risk, before they undergo prenatal diagnosis. DNA analysis will also resolve some inconclusive diagnoses.

  5. An introduction to cosmology

    CERN Document Server

    Narlikar, Jayant Vishnu

    2002-01-01

    The third edition of this successful textbook is fully updated and includes important recent developments in cosmology. It begins with an introduction to cosmology and general relativity, and goes on to cover the mathematical models of standard cosmology. The physical aspects of cosmology, including primordial nucleosynthesis, the astroparticle physics of inflation, and the current ideas on structure formation are discussed. Alternative models of cosmology are reviewed, including the model of Quasi-Steady State Cosmology, which has recently been proposed as an alternative to Big Bang Cosmology.

  6. A Monte Carlo Simulation Framework for Testing Cosmological Models

    Directory of Open Access Journals (Sweden)

    Heymann Y.

    2014-10-01

    Full Text Available We tested alternative cosmologies using Monte Carlo simulations based on the sam- pling method of the zCosmos galactic survey. The survey encompasses a collection of observable galaxies with respective redshifts that have been obtained for a given spec- troscopic area of the sky. Using a cosmological model, we can convert the redshifts into light-travel times and, by slicing the survey into small redshift buckets, compute a curve of galactic density over time. Because foreground galaxies obstruct the images of more distant galaxies, we simulated the theoretical galactic density curve using an average galactic radius. By comparing the galactic density curves of the simulations with that of the survey, we could assess the cosmologies. We applied the test to the expanding-universe cosmology of de Sitter and to a dichotomous cosmology.

  7. Deparametrization and path integral quantization of cosmological models

    CERN Document Server

    Simeone, Claudio

    2001-01-01

    The problem of time is a central feature of quantum cosmology: differing from ordinary quantum mechanics, in cosmology there is nothing "outside" the system which plays the role of clock, and this makes difficult the obtention of a consistent quantization. A possible solution is to assume that a subset of the variables describing the state of the universe can be a clock for the remaining of the system. Following this line, in this book a new proposal consisting in the previous identification of time by means of gauge fixation is applied to the quantization of homogeneous cosmological models. B

  8. Outcomes of arthroscopic "Remplissage": capsulotenodesis of the engaging large Hill-Sachs lesion

    Directory of Open Access Journals (Sweden)

    Mayo Lee

    2011-06-01

    Full Text Available Abstract Background A Hill-Sachs lesion of the humeral head after a shoulder dislocation is clinically insignificant in most cases. However, a sizable defect will engage with the anterior rim of the glenoid and cause instability even after anterior glenoid reconstruction. The purpose of this study was to evaluate the outcome of arthroscopic capsulotenodesis of the posterior capsule and infraspinatus tendon ("remplissage" to seal a large engaging Hill-Sachs lesion in an unstable shoulder. Methods This was a prospective follow-up study of patients who underwent arthroscopic surgery for recurrent shoulder instability with a large engaging Hill-Sachs lesion from 2007 to 2009. The clinical results were measured preoperatively and postoperatively with the Simple Shoulder test (SST and the Rowe score for instability. Results Eleven patients met the inclusion criteria of this study. The mean follow-up time was 30 months (range 24 to 35 months. At the last follow-up, significant improvement was observed in both scores with no recurrent dislocations. The mean SST improved from 6.6 to 11 (p Conclusions Arthroscopic remplissage for shoulder instability is an effective soft tissue technique to seal a large engaging Hill-Sachs lesion with respect to recurrence rate, range of motion and shoulder function.

  9. Dark-energy cosmological models in f(G) gravity

    Energy Technology Data Exchange (ETDEWEB)

    Shamir, M. F., E-mail: farasat.shamir@nu.edu.pk [National University of Computer and Emerging Sciences Lahore Campus, Department of Sciences and Humanities (Pakistan)

    2016-10-15

    We discuss dark-energy cosmological models in f(G) gravity. For this purpose, a locally rotationally symmetric Bianchi type I cosmological model is considered. First, exact solutions with a well-known form of the f(G) model are explored. One general solution is discussed using a power-law f(G) gravity model and physical quantities are calculated. In particular, Kasner’s universe is recovered and the corresponding f(G) gravity models are reported. Second, the energy conditions for the model under consideration are discussed using graphical analysis. It is concluded that solutions with f(G) = G{sup 5/6} support expansion of universe while those with f(G) = G{sup 1/2} do not favor the current expansion.

  10. Segregation of Tay-Sachs and Sandhoff alleles in a non-Jewish family.

    Science.gov (United States)

    Lane, A B; Young, E; Jenkins, T

    1980-01-01

    A non-Jewish family is presented in which the genes for Tay-Sachs disease and Sandhoff disease are segregating. Individuals heterozygous for both alleles have low serum and white cell total hexosaminidase levels together with a proportion of heat-labile hexosaminidase A (HEX A) which falls in the normal range. The individuals would not be detected as carriers of Tay-Sachs disease or Sandhoff disease in a population screening program. PMID:7446530

  11. The frequency of Tay-Sachs disease causing mutations in the Brazilian Jewish population justifies a carrier screening program.

    Science.gov (United States)

    Rozenberg, R; Pereira, L da V

    2001-07-05

    Tay-Sachs disease is an autosomal recessive disease characterized by progressive neurologic degeneration, fatal in early childhood. In the Ashkenazi Jewish population the disease incidence is about 1 in every 3,500 newborns and the carrier frequency is 1 in every 29 individuals. Carrier screening programs for Tay-Sachs disease have reduced disease incidence by 90% in high-risk populations in several countries. The Brazilian Jewish population is estimated at 90,000 individuals. Currently, there is no screening program for Tay-Sachs disease in this population. To evaluate the importance of a Tay-Sachs disease carrier screening program in the Brazilian Jewish population by determining the frequency of heterozygotes and the acceptance of the program by the community. Laboratory of Molecular Genetics--Institute of Biosciences--Universidade de São Paulo. 581 senior students from selected Jewish high schools. Molecular analysis of Tay-Sachs disease causing mutations by PCR amplification of genomic DNA, followed by restriction enzyme digestion. Among 581 students that attended educational classes, 404 (70%) elected to be tested for Tay-Sachs disease mutations. Of these, approximately 65% were of Ashkenazi Jewish origin. Eight carriers were detected corresponding to a carrier frequency of 1 in every 33 individuals in the Ashkenazi Jewish fraction of the sample. The frequency of Tay-Sachs disease carriers among the Ashkenazi Jewish population of Brazil is similar to that of other countries where carrier screening programs have led to a significant decrease in disease incidence. Therefore, it is justifiable to implement a Tay-Sachs disease carrier screening program for the Brazilian Jewish population.

  12. Substrate reduction therapy in the infantile form of Tay-Sachs disease.

    Science.gov (United States)

    Bembi, B; Marchetti, F; Guerci, V I; Ciana, G; Addobbati, R; Grasso, D; Barone, R; Cariati, R; Fernandez-Guillen, L; Butters, T; Pittis, M G

    2006-01-24

    Substrate reduction therapy (SRT) with miglustat has been proposed for treatment of some lysosomal storage disorders. Based on the positive experience in Gaucher disease and experimental data in Tay-Sachs (TSD) and Sandhoff animal models, the authors investigated the clinical efficacy of SRT in two patients with infantile TSD. SRT could not arrest the patients' neurologic deterioration. However, a significant drug concentration in CSF as well as macrocephaly prevention were observed.

  13. Cosmological models in general relativity

    Indian Academy of Sciences (India)

    Cosmological models in general relativity. B B PAUL. Department of Physics, Nowgong College, Nagaon, Assam, India. MS received 4 October 2002; revised 6 March 2003; accepted 21 May 2003. Abstract. LRS Bianchi type-I space-time filled with perfect fluid is considered here with deceler- ation parameter as variable.

  14. Cosmological constraints on spontaneous R-symmetry breaking models

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, Yuta; Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research and Dept. of Physics

    2012-11-15

    We study general constraints on spontaneous R-symmetry breaking models coming from the cosmological effects of the pseudo Nambu-Goldstone bosons, R-axions. They are substantially produced in the early Universe and may cause several cosmological problems. We focus on relatively long-lived R-axions and find that in a wide range of parameter space, models are severely constrained. In particular, R-axions with mass less than 1 MeV are generally ruled out for relatively high reheating temperature, T{sub R}>10 GeV.

  15. Cosmological models in the generalized Einstein action

    International Nuclear Information System (INIS)

    Arbab, A.I.

    2007-12-01

    We have studied the evolution of the Universe in the generalized Einstein action of the form R + β R 2 , where R is the scalar curvature and β = const. We have found exact cosmological solutions that predict the present cosmic acceleration. These models predict an inflationary de-Sitter era occurring in the early Universe. The cosmological constant (Λ) is found to decay with the Hubble constant (H) as, Λ ∝ H 4 . In this scenario the cosmological constant varies quadratically with the energy density (ρ), i.e., Λ ∝ ρ 2 . Such a variation is found to describe a two-component cosmic fluid in the Universe. One of the components accelerated the Universe in the early era, and the other in the present era. The scale factor of the Universe varies as a ∼ t n = 1/2 in the radiation era. The cosmological constant vanishes when n = 4/3 and n =1/2. We have found that the inclusion of the term R 2 mimics a cosmic matter that could substitute the ordinary matter. (author)

  16. Exacerbating the Cosmological Constant Problem with Interacting Dark Energy Models.

    Science.gov (United States)

    Marsh, M C David

    2017-01-06

    Future cosmological surveys will probe the expansion history of the Universe and constrain phenomenological models of dark energy. Such models do not address the fine-tuning problem of the vacuum energy, i.e., the cosmological constant problem (CCP), but can make it spectacularly worse. We show that this is the case for "interacting dark energy" models in which the masses of the dark matter states depend on the dark energy sector. If realized in nature, these models have far-reaching implications for proposed solutions to the CCP that require the number of vacua to exceed the fine-tuning of the vacuum energy density. We show that current estimates of the number of flux vacua in string theory, N_{vac}∼O(10^{272 000}), are far too small to realize certain simple models of interacting dark energy and solve the cosmological constant problem anthropically. These models admit distinctive observational signatures that can be targeted by future gamma-ray observatories, hence making it possible to observationally rule out the anthropic solution to the cosmological constant problem in theories with a finite number of vacua.

  17. The white matter of the human cerebrum: Part I The occipital lobe by Heinrich Sachs

    Science.gov (United States)

    Forkel, Stephanie J.; Mahmood, Sajedha; Vergani, Francesco; Catani, Marco

    2015-01-01

    This is the first complete translation of Heinrich Sachs' outstanding white matter atlas dedicated to the occipital lobe. This work is accompanied by a prologue by Prof Carl Wernicke who for many years was Sachs' mentor in Breslau and enthusiastically supported his work. PMID:25527430

  18. Impact of gene patents and licensing practices on access to genetic testing and carrier screening for Tay-Sachs and Canavan disease.

    Science.gov (United States)

    Colaianni, Alessandra; Chandrasekharan, Subhashini; Cook-Deegan, Robert

    2010-04-01

    Genetic testing for Tay-Sachs and Canavan disease is particularly important for Ashkenazi Jews, because both conditions are more frequent in that population. This comparative case study was possible because of different patenting and licensing practices. The role of DNA testing differs between Tay-Sachs and Canavan diseases. The first-line screening test for Tay-Sachs remains an enzyme activity test rather than genotyping. Genotyping is used for preimplantation diagnosis and confirmatory testing. In contrast, DNA-based testing is the basis for Canavan screening and diagnosis. The HEXA gene for Tay-Sachs was cloned at the National Institutes of Health, and the gene was patented but has not been licensed. The ASPA gene for Canavan disease was cloned and patented by Miami Children's Hospital. Miami Children's Hospital did not inform family members and patient groups that had contributed to the gene discovery that it was applying for a patent, and pursued restrictive licensing practices when a patent issued in 1997. This led to intense controversy, litigation, and a sealed, nonpublic 2003 settlement that apparently allowed for nonexclusive licensing. A survey of laboratories revealed a possible price premium for ASPA testing, with per-unit costs higher than for other genetic tests in the Secretary's Advisory Committee on Genetics, Health, and Society case studies. The main conclusion from comparing genetic testing for Tay-Sachs and Canavan diseases, however, is that patenting and licensing conducted without communication with patients and advocates cause mistrust and can lead to controversy and litigation, a negative model to contrast with the positive model of patenting and licensing for genetic testing of cystic fibrosis.

  19. Dimensional cosmological principles

    International Nuclear Information System (INIS)

    Chi, L.K.

    1985-01-01

    The dimensional cosmological principles proposed by Wesson require that the density, pressure, and mass of cosmological models be functions of the dimensionless variables which are themselves combinations of the gravitational constant, the speed of light, and the spacetime coordinates. The space coordinate is not the comoving coordinate. In this paper, the dimensional cosmological principle and the dimensional perfect cosmological principle are reformulated by using the comoving coordinate. The dimensional perfect cosmological principle is further modified to allow the possibility that mass creation may occur. Self-similar spacetimes are found to be models obeying the new dimensional cosmological principle

  20. Three-dimensional computed tomography measurement accuracy of varying Hill-Sachs lesion size.

    Science.gov (United States)

    Ho, Anthony; Kurdziel, Michael D; Koueiter, Denise M; Wiater, J Michael

    2018-02-01

    The glenoid track concept has been proposed to correlate shoulder stability with bone loss. Accurate assessment of Hill-Sachs lesion size preoperatively may affect surgical planning and postoperative outcomes; however, no measurement method has been universally accepted. This study aimed to assess the accuracy and reliability of measuring Hill-Sachs lesion sizes using 3-dimensional (3D) computed tomography (CT). Nine polyurethane humerus bone substitutes were used to create Hill-Sachs lesions of varying sizes with a combination of lesion depth (shallow, intermediate, and deep) and width (small, medium, and large). Specimens were scanned with a clinical CT scanner for size measurements and a micro-CT scanner for measurement of true lesion size. Six evaluators repeated measurements twice in a 2-week interval. Scans were measured by use of 3D CT reconstructions for length, width, and Hill-Sachs interval and with use of 2D CT for depth. The interclass correlation coefficient evaluated interobserver and intraobserver variability and percentage error, and Student t-tests assessed measurement accuracy. Interclass correlation coefficient reliability demonstrated strong agreement for all variables measured (0.856-0.975). Percentage error between measured length and measured depth and the true measurement significantly varied with respect to both lesion depth (P = .003 and P = .005, respectively) and lesion size (P = .049 and P = .004, respectively). The 3D CT imaging is effective and reproducible in determining lesion size. Determination of Hill-Sachs interval width is also reliable when it is applied to the glenoid track concept. Measured values on 3D and 2-dimensional imaging using a conventional CT scanner may slightly underestimate true measurements. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  1. [Sandhoff's and Tay-Sachs disease--based on our own cases].

    Science.gov (United States)

    Kokot, Witold; Raczyńska, Krystyna; Krajka-Lauer, Jarosława; Iwaszkiewicz-Bilikiewicz, Barbara; Wierzba, Jolanta

    2004-01-01

    The authors described two infant with Sandhoff's and Tay-Sachs disease. Tay-Sachs disease is well-known inherited disease leading to an accumulation of gangliosides in the brain and retina. Sandhoffs disease (GM2 gangliosidosis type 0) was diagnosed in an infant, in whom a progressive neurological disorder and cherry-red foveal spots were developed. In addition, to the general clinical examination, indirect ophthalnoscopy, blood white cells enzymatic examination are used to make definitive diagnosis. In this cases, the early eye fundus examination allowed us to make the proper diagnosis. The fundus change is characterized by the "cherry-red spot" in the central area.

  2. The frequency of Tay-Sachs disease causing mutations in the Brazilian Jewish population justifies a carrier screening program

    Directory of Open Access Journals (Sweden)

    Roberto Rozenberg

    Full Text Available CONTEXT: Tay-Sachs disease is an autosomal recessive disease characterized by progressive neurologic degeneration, fatal in early childhood. In the Ashkenazi Jewish population the disease incidence is about 1 in every 3,500 newborns and the carrier frequency is 1 in every 29 individuals. Carrier screening programs for Tay-Sachs disease have reduced disease incidence by 90% in high-risk populations in several countries. The Brazilian Jewish population is estimated at 90,000 individuals. Currently, there is no screening program for Tay-Sachs disease in this population. OBJECTIVE: To evaluate the importance of a Tay-Sachs disease carrier screening program in the Brazilian Jewish population by determining the frequency of heterozygotes and the acceptance of the program by the community. SETTING: Laboratory of Molecular Genetics - Institute of Biosciences - Universidade de São Paulo. PARTICIPANTS: 581 senior students from selected Jewish high schools. PROCEDURE: Molecular analysis of Tay-Sachs disease causing mutations by PCR amplification of genomic DNA, followed by restriction enzyme digestion. RESULTS: Among 581 students that attended educational classes, 404 (70% elected to be tested for Tay-Sachs disease mutations. Of these, approximately 65% were of Ashkenazi Jewish origin. Eight carriers were detected corresponding to a carrier frequency of 1 in every 33 individuals in the Ashkenazi Jewish fraction of the sample. CONCLUSION: The frequency of Tay-Sachs disease carriers among the Ashkenazi Jewish population of Brazil is similar to that of other countries where carrier screening programs have led to a significant decrease in disease incidence. Therefore, it is justifiable to implement a Tay-Sachs disease carrier screening program for the Brazilian Jewish population.

  3. Evolution of perturbations in distinct classes of canonical scalar field models of dark energy

    International Nuclear Information System (INIS)

    Jassal, H. K.

    2010-01-01

    Dark energy must cluster in order to be consistent with the equivalence principle. The background evolution can be effectively modeled by either a scalar field or by a barotropic fluid. The fluid model can be used to emulate perturbations in a scalar field model of dark energy, though this model breaks down at large scales. In this paper we study evolution of dark energy perturbations in canonical scalar field models: the classes of thawing and freezing models. The dark energy equation of state evolves differently in these classes. In freezing models, the equation of state deviates from that of a cosmological constant at early times. For thawing models, the dark energy equation of state remains near that of the cosmological constant at early times and begins to deviate from it only at late times. Since the dark energy equation of state evolves differently in these classes, the dark energy perturbations too evolve differently. In freezing models, since the equation of state deviates from that of a cosmological constant at early times, there is a significant difference in evolution of matter perturbations from those in the cosmological constant model. In comparison, matter perturbations in thawing models differ from the cosmological constant only at late times. This difference provides an additional handle to distinguish between these classes of models and this difference should manifest itself in the integrated Sachs-Wolfe effect.

  4. Tilted Bianchi type I dust fluid cosmological model in general relativity

    Indian Academy of Sciences (India)

    Tilted Bianchi type I dust fluid cosmological model in general relativity ... In this paper, we have investigated a tilted Bianchi type I cosmological model filled with dust of perfect fluid in general relativity. ... Pramana – Journal of Physics | News ...

  5. Cosmological aspects of superstring models

    International Nuclear Information System (INIS)

    Binetruy, P.

    1986-10-01

    I consider more specifically the cosmological aspects of supersymmetry breaking in ''superstring models'' (grand unified models which are believed to describe the effective theory obtained by compactification of superstring theories). The most interesting aspects are related to the presence of flat directions in the scalar potential (vacuum degeneracies). These flat directions are discussed both in the hidden sector of these models (do they give rise to inflation) and in the observable sector of quarks, leptons and Higgs particles, in connection with baryogenesis

  6. Top ten accelerating cosmological models

    International Nuclear Information System (INIS)

    Szydlowski, Marek; Kurek, Aleksandra; Krawiec, Adam

    2006-01-01

    Recent astronomical observations indicate that the Universe is presently almost flat and undergoing a period of accelerated expansion. Basing on Einstein's general relativity all these observations can be explained by the hypothesis of a dark energy component in addition to cold dark matter (CDM). Because the nature of this dark energy is unknown, it was proposed some alternative scenario to explain the current accelerating Universe. The key point of this scenario is to modify the standard FRW equation instead of mysterious dark energy component. The standard approach to constrain model parameters, based on the likelihood method, gives a best-fit model and confidence ranges for those parameters. We always arbitrary choose the set of parameters which define a model which we compare with observational data. Because in the generic case, the introducing of new parameters improves a fit to the data set, there appears the problem of elimination of model parameters which can play an insufficient role. The Bayesian information criteria of model selection (BIC) is dedicated to promotion a set of parameters which should be incorporated to the model. We divide class of all accelerating cosmological models into two groups according to the two types of explanation acceleration of the Universe. Then the Bayesian framework of model selection is used to determine the set of parameters which gives preferred fit to the SNIa data. We find a few of flat cosmological models which can be recommend by the Bayes factor. We show that models with dark energy as a new fluid are favoured over models featuring a modified FRW equation

  7. Introduction to cosmology

    CERN Document Server

    Roos, Matts

    2015-01-01

    The Fourth Edition of Introduction to Cosmology provides a concise, authoritative study of cosmology at an introductory level. Starting from elementary principles and the early history of cosmology, the text carefully guides the student on to curved spacetimes, special and general relativity, gravitational lensing, the thermal history of the Universe, and cosmological models, including extended gravity models, black holes and Hawking's recent conjectures on the not-so-black holes.

  8. Higher-dimensional cosmological model with variable gravitational ...

    Indian Academy of Sciences (India)

    We have studied five-dimensional homogeneous cosmological models with variable and bulk viscosity in Lyra geometry. Exact solutions for the field equations have been obtained and physical properties of the models are discussed. It has been observed that the results of new models are well within the observational ...

  9. Classification of cosmology with arbitrary matter in the Horava-Lifshitz model

    International Nuclear Information System (INIS)

    Minamitsuji, Masato

    2010-01-01

    In this work, we discuss the cosmological evolutions in the nonrelativistic and possibly renormalizable gravitational theory, called the Horava-Lifshitz (HL) theory. We consider the original HL model (type I), and the modified version obtained by an analytic continuation of parameters (type II). We classify the possible cosmological evolutions with arbitrary matter. We will find a variety of cosmology.

  10. A pseudodeficiency allele common in non-Jewish Tay-Sachs carriers: Implications for carrier screening

    Energy Technology Data Exchange (ETDEWEB)

    Triggs-Raine, B.L.; Akerman, B.R.; Gravel, R.A. (McGill Univ.-Montreal Children' s Hospital Research Institute, Montreal, Quebec (Canada)); Mules, E.H.; Thomas, G.H.; Dowling, C.E. (Johns Hopkins School of Medicine, Baltimore, MD (United States)); Kaback, M.M.; Lim-Steele, J.S.T. (Univ. of California, San Diego, CA (United States)); Natowicz, M.R. (Eunice Kennedy Shriver Center for Mental Retardation, Waltham, MA (United States)); Grebner, E.E. (Thomas Jefferson Univ., Philadelphia, PA (United States)); Navon, R.R. (Tel-Aviv Univ., Kfar-Sava (Israel)); Welch, J.P. (Dalhousie Univ., Halifax, Nova, Scotia (Canada)); Greenberg, C.R. (Univ. of Manitoba, Winnipeg (Canada))

    1992-10-01

    Deficiency of [beta]-hexosaminidase A (Hex A) activity typically results in Tay-Sachs disease. However, healthy subjects found to be deficient in Hex A activity (i.e., pseudodeficient) by means of in vitro biochemical tests have been described. The authors analyzed the HEXA gene of one pseudodeficient subject and identified both a C[sub 739]-to-T substitution that changes Arg[sub 247][yields]Trp on one allele and a previously identified Tay-Sachs disease mutation of the second allele. Six additional pseudodeficient subjects were found to have the C[sub 739]-to-T but for none of 36 Jewish enzyme-defined carries who did not have one of three known mutations common to this group. The C[sub 739]-to-T allele, together with a [open quotes]true[close quotes] Tay-Sachs disease allele, causes Hex A pseudodeficiency. Given both the large proportion of non-Jewish carriers with this allele and that standard biochemical screening cannot differentiate between heterozygotes for the C[sub 739]-to-T mutations and Tay-Sachs disease carriers, DNA testing for this mutation in at-risk couples is essential. This could prevent unnecessary or incorrect prenatal diagnoses. 40 refs., 3 figs., 4 tabs.

  11. Rapid identification of HEXA mutations in Tay-Sachs patients.

    Science.gov (United States)

    Giraud, Carole; Dussau, Jeanne; Azouguene, Emilie; Feillet, François; Puech, Jean-Philippe; Caillaud, Catherine

    2010-02-19

    Tay-Sachs disease (TSD) is a recessively inherited neurodegenerative disorder due to mutations in the HEXA gene resulting in a beta-hexosaminidase A (Hex A) deficiency. The purpose of this study was to characterize the molecular abnormalities in patients with infantile or later-onset forms of the disease. The complete sequencing of the 14 exons and flanking regions of the HEXA gene was performed with a unique technical condition in 10 unrelated TSD patients. Eleven mutations were identified, including five splice mutations, one insertion, two deletions and three single-base substitutions. Four mutations were novel: two splice mutations (IVS8+5G>A, IVS2+4delAGTA), one missense mutation in exon 6 (c.621T>G (p.D207E)) and one small deletion (c.1211-1212delTG) in exon 11 resulting in a premature stop codon at residue 429. The c.621T>G missense mutation was found in a patient presenting an infantile form. Its putative role in the pathogenesis of TSD is suspected as residue 207 is highly conserved in human, mouse and rat. Moreover, structural modelling predicted changes likely to affect substrate binding and catalytic activity of the enzyme. The time-saving procedure reported here could be useful for the characterization of Tay-Sachs-causing mutations, in particular in non-Ashkenazi patients mainly exhibiting rare mutations. Copyright (c) 2010 Elsevier Inc. All rights reserved.

  12. The white matter of the human cerebrum: part I The occipital lobe by Heinrich Sachs.

    Science.gov (United States)

    Forkel, Stephanie J; Mahmood, Sajedha; Vergani, Francesco; Catani, Marco

    2015-01-01

    This is the first complete translation of Heinrich Sachs' outstanding white matter atlas dedicated to the occipital lobe. This work is accompanied by a prologue by Prof Carl Wernicke who for many years was Sachs' mentor in Breslau and enthusiastically supported his work. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  13. Planck CMB Anomalies: Astrophysical and Cosmological Secondary Effects and the Curse of Masking

    Science.gov (United States)

    Rassat, Anais

    2016-07-01

    Large-scale anomalies have been reported in CMB data with both WMAP and Planck data. These could be due to foreground residuals and or systematic effects, though their confirmation with Planck data suggests they are not due to a problem in the WMAP or Planck pipelines. If these anomalies are in fact primordial, then understanding their origin is fundamental to either validate the standard model of cosmology or to explore new physics. We investigate three other possible issues: 1) the trade-off between minimising systematics due to foreground contamination (with a conservative mask) and minimising systematics due to masking, 2) astrophysical secondary effects (the kinetic Doppler quadrupole and kinetic Sunyaev-Zel'dovich effect), and 3) secondary cosmological signals (the integrated Sachs-Wolfe effect). We address the masking issue by considering new procedures that use both WMAP and Planck to produce higher quality full-sky maps using the sparsity methodology (LGMCA maps). We show the impact of masking is dominant over that of residual foregrounds, and the LGMCA full-sky maps can be used without further processing to study anomalies. We consider four official Planck PR1 and two LGMCA CMB maps. Analysis of the observed CMB maps shows that only the low quadrupole and quadrupole-octopole alignment seem significant, but that the planar octopole, Axis of Evil, mirror parity and cold spot are not significant in nearly all maps considered. After subtraction of astrophysical and cosmological secondary effects, only the low quadrupole may still be considered anomalous, meaning the significance of only one anomaly is affected by secondary effect subtraction out of six anomalies considered. In the spirit of reproducible research all reconstructed maps and codes are available online.

  14. Implications of a decay law for the cosmological constant in higher dimensional cosmology and cosmological wormholes

    International Nuclear Information System (INIS)

    Rami, El-Nabulsi Ahmad

    2009-01-01

    Higher dimensional cosmological implications of a decay law for the cosmological constant term are analyzed. Three independent cosmological models are explored mainly: 1) In the first model, the effective cosmological constant was chosen to decay with times like Δ effective = Ca -2 + D(b/a I ) 2 where a I is an arbitrary scale factor characterizing the isotropic epoch which proceeds the graceful exit period. Further, the extra-dimensional scale factor decays classically like b(t) approx. a x (t), x is a real negative number. 2) In the second model, we adopt in addition to Δ effective = Ca -2 + D(b/a I ) 2 the phenomenological law b(t) = a(t)exp( -Qt) as we expect that at the origin of time, there is no distinction between the visible and extra dimensions; Q is a real number. 3) In the third model, we study a Δ - decaying extra-dimensional cosmology with a static traversable wormhole in which the four-dimensional Friedmann-Robertson-Walker spacetime is subject to the conventional perfect fluid while the extra-dimensional part is endowed by an exotic fluid violating strong energy condition and where the cosmological constant in (3+n+1) is assumed to decays like Δ(a) = 3Ca -2 . The three models are discussed and explored in some details where many interesting points are revealed. (author)

  15. The Dirac-Milne cosmology

    Science.gov (United States)

    Benoit-Lévy, Aurélien; Chardin, Gabriel

    2014-05-01

    We study an unconventional cosmology, in which we investigate the consequences that antigravity would pose to cosmology. We present the main characteristics of the Dirac-Milne Universe, a cosmological model where antimatter has a negative active gravitational mass. In this non-standard Universe, separate domains of matter and antimatter coexist at our epoch without annihilation, separated by a gravitationally induced depletion zone. We show that this cosmology does not require a priori the Dark Matter and Dark Energy components of the standard model of cosmology. Additionally, inflation becomes an unnecessary ingredient. Investigating this model, we show that the classical cosmological tests such as primordial nucleosynthesis, Type Ia supernovæ and Cosmic Microwave Background are surprisingly concordant.

  16. Murine Sialidase Neu3 facilitates GM2 degradation and bypass in mouse model of Tay-Sachs disease.

    Science.gov (United States)

    Seyrantepe, Volkan; Demir, Secil Akyildiz; Timur, Zehra Kevser; Von Gerichten, Johanna; Marsching, Christian; Erdemli, Esra; Oztas, Emin; Takahashi, Kohta; Yamaguchi, Kazunori; Ates, Nurselin; Dönmez Demir, Buket; Dalkara, Turgay; Erich, Katrin; Hopf, Carsten; Sandhoff, Roger; Miyagi, Taeko

    2018-01-01

    Tay-Sachs disease is a severe lysosomal storage disorder caused by mutations in Hexa, the gene that encodes for the α subunit of lysosomal β-hexosaminidase A (HEXA), which converts GM2 to GM3 ganglioside. Unexpectedly, Hexa -/- mice have a normal lifespan and show no obvious neurological impairment until at least one year of age. These mice catabolize stored GM2 ganglioside using sialidase(s) to remove sialic acid and form the glycolipid GA2, which is further processed by β-hexosaminidase B. Therefore, the presence of the sialidase (s) allows the consequences of the Hexa defect to be bypassed. To determine if the sialidase NEU3 contributes to GM2 ganglioside degradation, we generated a mouse model with combined deficiencies of HEXA and NEU3. The Hexa -/- Neu3 -/- mice were healthy at birth, but died at 1.5 to 4.5months of age. Thin-layer chromatography and mass spectrometric analysis of the brains of Hexa -/- Neu3 -/- mice revealed the abnormal accumulation of GM2 ganglioside. Histological and immunohistochemical analysis demonstrated cytoplasmic vacuolation in the neurons. Electron microscopic examination of the brain, kidneys and testes revealed pleomorphic inclusions of many small vesicles and complex lamellar structures. The Hexa -/- Neu3 -/- mice exhibited progressive neurodegeneration with neuronal loss, Purkinje cell depletion, and astrogliosis. Slow movement, ataxia, and tremors were the prominent neurological abnormalities observed in these mice. Furthermore, radiographs revealed abnormalities in the skeletal bones of the Hexa -/- Neu3 -/- mice. Thus, the Hexa -/- Neu3 -/- mice mimic the neuropathological and clinical abnormalities of the classical early-onset Tay-Sachs patients, and provide a suitable model for the future pre-clinical testing of potential treatments for this condition. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. The Cosmological Standard Model and Its Implications for Beyond the Standard Model of Particle Physics

    CERN Multimedia

    CERN. Geneva

    2011-01-01

    While the cosmological standard model has many notable successes, it assumes 95% of the mass-energy density of the universe is dark and of unknown nature, and there was an early stage of inflationary expansion driven by physics far beyond the range of the particle physics standard model. In the colloquium I will discuss potential particle-physics implications of the standard cosmological model.

  18. Cosmological observables in the quasi-spherical Szekeres model

    Science.gov (United States)

    Buckley, Robert G.

    2014-10-01

    The standard model of cosmology presents a homogeneous universe, and we interpret cosmological data through this framework. However, structure growth creates nonlinear inhomogeneities that may affect observations, and even larger structures may be hidden by our limited vantage point and small number of independent observations. As we determine the universe's parameters with increasing precision, the accuracy is contingent on our understanding of the effects of such structures. For instance, giant void models can explain some observations without dark energy. Because perturbation theory cannot adequately describe nonlinear inhomogeneities, exact solutions to the equations of general relativity are important for these questions. The most general known solution capable of describing inhomogeneous matter distributions is the Szekeres class of models. In this work, we study the quasi-spherical subclass of these models, using numerical simulations to calculate the inhomogeneities' effects on observations. We calculate the large-angle CMB in giant void models and compare with simpler, symmetric void models that have previously been found inadequate to matchobservations. We extend this by considering models with early-time inhomogeneities as well. Then, we study distance observations, including selection effects, in models which are homogeneous on scales around 100 Mpc---consistent with standard cosmology---but inhomogeneous on smaller scales. Finally, we consider photon polarizations, and show that they are not directly affected by inhomogeneities. Overall, we find that while Szekeres models have some advantages over simpler models, they are still seriously limited in their ability to alter our parameter estimation while remaining within the bounds of current observations.

  19. Spherical collapse model in time varying vacuum cosmologies

    International Nuclear Information System (INIS)

    Basilakos, Spyros; Plionis, Manolis; Sola, Joan

    2010-01-01

    We investigate the virialization of cosmic structures in the framework of flat Friedmann-Lemaitre-Robertson-Walker cosmological models, in which the vacuum energy density evolves with time. In particular, our analysis focuses on the study of spherical matter perturbations, as they decouple from the background expansion, 'turn around', and finally collapse. We generalize the spherical collapse model in the case when the vacuum energy is a running function of the Hubble rate, Λ=Λ(H). A particularly well-motivated model of this type is the so-called quantum field vacuum, in which Λ(H) is a quadratic function, Λ(H)=n 0 +n 2 H 2 , with n 0 ≠0. This model was previously studied by our team using the latest high quality cosmological data to constrain its free parameters, as well as the predicted cluster formation rate. It turns out that the corresponding Hubble expansion history resembles that of the traditional ΛCDM cosmology. We use this Λ(t)CDM framework to illustrate the fact that the properties of the spherical collapse model (virial density, collapse factor, etc.) depend on the choice of the considered vacuum energy (homogeneous or clustered). In particular, if the distribution of the vacuum energy is clustered, then, under specific conditions, we can produce more concentrated structures with respect to the homogeneous vacuum energy case.

  20. Tilted Bianchi type I dust fluid cosmological model in general relativity

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 3. Tilted Bianchi type I dust fluid cosmological model in general ... In this paper, we have investigated a tilted Bianchi type I cosmological model filled with dust of perfect fluid in general relativity. To get a determinate solution, we have assumed a condition  ...

  1. Planck 2015 results: XXI. The integrated Sachs-Wolfe effect

    DEFF Research Database (Denmark)

    Ade, P. A R; Aghanim, N.; Arnaud, M.

    2016-01-01

    This paper presents a study of the integrated Sachs-Wolfe (ISW) effect from the Planck 2015 temperature and polarization data release. This secondary cosmic microwave background (CMB) anisotropy caused by the large-scale time-evolving gravitational potential is probed from different perspectives....

  2. The Weinberg-Salam model and early cosmology

    International Nuclear Information System (INIS)

    Steinhardt, P.J.

    1981-01-01

    The consequences for cosmology of the phase transition in which SU(2) x U(1) symmetry is broken in the Weinberg-Salam model are discussed. The qualitative arguments concerning the effect of the phase transition on the baryon-to-entropy ratio that were recently posed by Witten for the case of a Coleman-Weinberg light Higgs boson are confirmed through exact numerical computations, but some quantitative disagreement is found. The computations are extended to the case in which the light Higgs boson is not of the Coleman-Weinberg type and the nature of the phase transition is discussed. Other cosmological effects are considered. (orig.)

  3. Qualitative cosmology

    International Nuclear Information System (INIS)

    Khalatnikov, I.M.; Belinskij, V.A.

    1984-01-01

    Application of the qualitative theory of dynamic systems to analysis of homogeneous cosmological models is described. Together with the well-known cases, requiring ideal liquid, the properties of cosmological evolution of matter with dissipative processes due to viscosity are considered. New cosmological effects occur, when viscosity terms being one and the same order with the rest terms in the equations of gravitation or even exceeding them. In these cases the description of the dissipative process by means of only two viscosity coefficients (volume and shift) may become inapplicable because all the rest decomposition terms of dissipative addition to the energy-momentum in velocity gradient can be large application of equations with hydrodynamic viscosty should be considered as a model of dissipative effects in cosmology

  4. CMB anisotropies at all orders: the non-linear Sachs-Wolfe formula

    International Nuclear Information System (INIS)

    Roldan, Omar

    2017-01-01

    We obtain the non-linear generalization of the Sachs-Wolfe + integrated Sachs-Wolfe (ISW) formula describing the CMB temperature anisotropies. Our formula is valid at all orders in perturbation theory, is also valid in all gauges and includes scalar, vector and tensor modes. A direct consequence of our results is that the maps of the logarithmic temperature anisotropies are much cleaner than the usual CMB maps, because they automatically remove many secondary anisotropies. This can for instance, facilitate the search for primordial non-Gaussianity in future works. It also disentangles the non-linear ISW from other effects. Finally, we provide a method which can iteratively be used to obtain the lensing solution at the desired order.

  5. CMB anisotropies at all orders: the non-linear Sachs-Wolfe formula

    Energy Technology Data Exchange (ETDEWEB)

    Roldan, Omar, E-mail: oaroldan@if.ufrj.br [Instituto de Física, Universidade Federal do Rio de Janeiro, 21941-972, Rio de Janeiro, RJ (Brazil)

    2017-08-01

    We obtain the non-linear generalization of the Sachs-Wolfe + integrated Sachs-Wolfe (ISW) formula describing the CMB temperature anisotropies. Our formula is valid at all orders in perturbation theory, is also valid in all gauges and includes scalar, vector and tensor modes. A direct consequence of our results is that the maps of the logarithmic temperature anisotropies are much cleaner than the usual CMB maps, because they automatically remove many secondary anisotropies. This can for instance, facilitate the search for primordial non-Gaussianity in future works. It also disentangles the non-linear ISW from other effects. Finally, we provide a method which can iteratively be used to obtain the lensing solution at the desired order.

  6. Supernova cosmology

    International Nuclear Information System (INIS)

    Leibundgut, B.

    2005-01-01

    Supernovae have developed into a versatile tool for cosmology. Their impact on the cosmological model has been profound and led to the discovery of the accelerated expansion. The current status of the cosmological model as perceived through supernova observations will be presented. Supernovae are currently the only astrophysical objects that can measure the dynamics of the cosmic expansion during the past eight billion years. Ongoing experiments are trying to determine the characteristics of the accelerated expansion and give insight into what might be the physical explanation for the acceleration. (author)

  7. Einstein and cosmology

    International Nuclear Information System (INIS)

    Gekman, O.

    1982-01-01

    The brief essay of the development of the main ideas of relativistic cosmology is presented. The Einstein's cosmological work about the Universe - ''Cosmological considerations in connection with the general relativity theory'' - gave the basis to all further treatments in this field. In 1922 A. Friedman's work appeared, in which the first expanding Universe model was proposed as a solution of the Einstein field equations. The model was spherically closed, but its curvature radius was a function of time. About 1955 the searches for anisotropic homogeneous solutions to Einstein field equation began. It turned out that isotropic cosmological models are unstable in general. The predominant part of them transform to anisotropic at insignificant breaking of isotropy. The discovery of isotropic background cosmic radiation in 1965, along with the Hubble low of the Universe expansion, served as the direct confirmation of cosmology based on the Einstein theory

  8. Lyso-GM2 ganglioside: a possible biomarker of Tay-Sachs disease and Sandhoff disease.

    Science.gov (United States)

    Kodama, Takashi; Togawa, Tadayasu; Tsukimura, Takahiro; Kawashima, Ikuo; Matsuoka, Kazuhiko; Kitakaze, Keisuke; Tsuji, Daisuke; Itoh, Kohji; Ishida, Yo-Ichi; Suzuki, Minoru; Suzuki, Toshihiro; Sakuraba, Hitoshi

    2011-01-01

    To find a new biomarker of Tay-Sachs disease and Sandhoff disease. The lyso-GM2 ganglioside (lyso-GM2) levels in the brain and plasma in Sandhoff mice were measured by means of high performance liquid chromatography and the effect of a modified hexosaminidase (Hex) B exhibiting Hex A-like activity was examined. Then, the lyso-GM2 concentrations in human plasma samples were determined. The lyso-GM2 levels in the brain and plasma in Sandhoff mice were apparently increased compared with those in wild-type mice, and they decreased on intracerebroventricular administration of the modified Hex B. The lyso-GM2 levels in plasma of patients with Tay-Sachs disease and Sandhoff disease were increased, and the increase in lyso-GM2 was associated with a decrease in Hex A activity. Lyso-GM2 is expected to be a potential biomarker of Tay-Sachs disease and Sandhoff disease.

  9. Precision Cosmology

    Science.gov (United States)

    Jones, Bernard J. T.

    2017-04-01

    Preface; Notation and conventions; Part I. 100 Years of Cosmology: 1. Emerging cosmology; 2. The cosmic expansion; 3. The cosmic microwave background; 4. Recent cosmology; Part II. Newtonian Cosmology: 5. Newtonian cosmology; 6. Dark energy cosmological models; 7. The early universe; 8. The inhomogeneous universe; 9. The inflationary universe; Part III. Relativistic Cosmology: 10. Minkowski space; 11. The energy momentum tensor; 12. General relativity; 13. Space-time geometry and calculus; 14. The Einstein field equations; 15. Solutions of the Einstein equations; 16. The Robertson-Walker solution; 17. Congruences, curvature and Raychaudhuri; 18. Observing and measuring the universe; Part IV. The Physics of Matter and Radiation: 19. Physics of the CMB radiation; 20. Recombination of the primeval plasma; 21. CMB polarisation; 22. CMB anisotropy; Part V. Precision Tools for Precision Cosmology: 23. Likelihood; 24. Frequentist hypothesis testing; 25. Statistical inference: Bayesian; 26. CMB data processing; 27. Parametrising the universe; 28. Precision cosmology; 29. Epilogue; Appendix A. SI, CGS and Planck units; Appendix B. Magnitudes and distances; Appendix C. Representing vectors and tensors; Appendix D. The electromagnetic field; Appendix E. Statistical distributions; Appendix F. Functions on a sphere; Appendix G. Acknowledgements; References; Index.

  10. Tay Sachs disease: an autopsy case report.

    Science.gov (United States)

    Jadhav, Meenal Vitthal; Landge, Meenal P; Sawaimoon, Satyakam K; Harke, Arun B; Deshmukh, Sanjay D

    2005-10-01

    This report describes a case report of a postmortem performed on a 5-year old patient of Tay-Sachs disease, presenting with failure to thrive, muscular flaccidity, and cherry-red spots on macula on fundoscopy. There was no history of similarly affected sibling or any other family member. The diagnosis was confirmed by enzyme studies. At postmortem, there was no organomegaly. The brain, on microscopy, showed vacuolated swollen neurons.

  11. Cosmological models in energy-momentum-squared gravity

    Science.gov (United States)

    Board, Charles V. R.; Barrow, John D.

    2017-12-01

    We study the cosmological effects of adding terms of higher order in the usual energy-momentum tensor to the matter Lagrangian of general relativity. This is in contrast to most studies of higher-order gravity which focus on generalizing the Einstein-Hilbert curvature contribution to the Lagrangian. The resulting cosmological theories give rise to field equations of similar form to several particular theories with different fundamental bases, including bulk viscous cosmology, loop quantum gravity, k -essence, and brane-world cosmologies. We find a range of exact solutions for isotropic universes, discuss their behaviors with reference to the early- and late-time evolution, accelerated expansion, and the occurrence or avoidance of singularities. We briefly discuss extensions to anisotropic cosmologies and delineate the situations where the higher-order matter terms will dominate over anisotropies on approach to cosmological singularities.

  12. A summary view of the symmetric cosmological model

    International Nuclear Information System (INIS)

    Aldrovandi, R.

    1975-01-01

    A brief analysis of cosmological models is done, beginning with the standard model and following with the symmetric model of Omnes. Some attempts have been made for the phase transition in thermal radiation at high temperatures, to the annihilation period and to coalescence. One model with equal amounts of matter and antimatter seems to be reasonable [pt

  13. Planck CMB anomalies: astrophysical and cosmological secondary effects and the curse of masking

    International Nuclear Information System (INIS)

    Rassat, A.; Starck, J.-L.; Paykari, P.; Sureau, F.; Bobin, J.

    2014-01-01

    Large-scale anomalies have been reported in CMB data with both WMAP and Planck data. These could be due to foreground residuals and or systematic effects, though their confirmation with Planck data suggests they are not due to a problem in the WMAP or Planck pipelines. If these anomalies are in fact primordial, then understanding their origin is fundamental to either validate the standard model of cosmology or to explore new physics. We investigate three other possible issues: 1) the trade-off between minimising systematics due to foreground contamination (with a conservative mask) and minimising systematics due to masking, 2) astrophysical secondary effects (the kinetic Doppler quadrupole and kinetic Sunyaev-Zel'dovich effect), and 3) secondary cosmological signals (the integrated Sachs-Wolfe effect). We address the masking issue by considering new procedures that use both WMAP and Planck to produce higher quality full-sky maps using the sparsity methodology (LGMCA maps). We show the impact of masking is dominant over that of residual foregrounds, and the LGMCA full-sky maps can be used without further processing to study anomalies. We consider four official Planck PR1 and two LGMCA CMB maps. Analysis of the observed CMB maps shows that only the low quadrupole and quadrupole-octopole alignment seem significant, but that the planar octopole, Axis of Evil, mirror parity and cold spot are not significant in nearly all maps considered. After subtraction of astrophysical and cosmological secondary effects, only the low quadrupole may still be considered anomalous, meaning the significance of only one anomaly is affected by secondary effect subtraction out of six anomalies considered. In the spirit of reproducible research all reconstructed maps and codes will be made available for download here http://www.cosmostat.org/anomaliesCMB.html

  14. Planck CMB anomalies: astrophysical and cosmological secondary effects and the curse of masking

    Energy Technology Data Exchange (ETDEWEB)

    Rassat, A. [Laboratoire d' Astrophysique (LASTRO), École Polytechnique Fédérale de Lausanne (EPFL), 51 Chemin des Maillettes, Observatoire de Sauverny, Versoix, CH-1290 (Switzerland); Starck, J.-L.; Paykari, P.; Sureau, F.; Bobin, J., E-mail: anais.rassat@epfl.ch, E-mail: jstarck@cea.fr, E-mail: paniez.paykari@cea.fr, E-mail: florent.sureau@cea.fr, E-mail: jbobin@cea.fr [Laboratoire AIM, UMR CEA-CNRS-Paris, Irfu, SAp, CEA Saclay, Gif-Sur-Yvette Cedex, F-91191 France (France)

    2014-08-01

    Large-scale anomalies have been reported in CMB data with both WMAP and Planck data. These could be due to foreground residuals and or systematic effects, though their confirmation with Planck data suggests they are not due to a problem in the WMAP or Planck pipelines. If these anomalies are in fact primordial, then understanding their origin is fundamental to either validate the standard model of cosmology or to explore new physics. We investigate three other possible issues: 1) the trade-off between minimising systematics due to foreground contamination (with a conservative mask) and minimising systematics due to masking, 2) astrophysical secondary effects (the kinetic Doppler quadrupole and kinetic Sunyaev-Zel'dovich effect), and 3) secondary cosmological signals (the integrated Sachs-Wolfe effect). We address the masking issue by considering new procedures that use both WMAP and Planck to produce higher quality full-sky maps using the sparsity methodology (LGMCA maps). We show the impact of masking is dominant over that of residual foregrounds, and the LGMCA full-sky maps can be used without further processing to study anomalies. We consider four official Planck PR1 and two LGMCA CMB maps. Analysis of the observed CMB maps shows that only the low quadrupole and quadrupole-octopole alignment seem significant, but that the planar octopole, Axis of Evil, mirror parity and cold spot are not significant in nearly all maps considered. After subtraction of astrophysical and cosmological secondary effects, only the low quadrupole may still be considered anomalous, meaning the significance of only one anomaly is affected by secondary effect subtraction out of six anomalies considered. In the spirit of reproducible research all reconstructed maps and codes will be made available for download here http://www.cosmostat.org/anomaliesCMB.html.

  15. Exact solution in the cosmological chaotic inflation model with induced gravity

    International Nuclear Information System (INIS)

    Wang Wenfu

    2004-01-01

    We present a new, exact solution in the cosmological chaotic inflation model with induced gravity. The spectral index of the scalar density fluctuations, n s , is computed, and is consistent with the analyses of BOOMERANG data. The effective cosmological constant Λ eff tends to zero when inflation ends

  16. Lyso-GM2 ganglioside: a possible biomarker of Tay-Sachs disease and Sandhoff disease.

    Directory of Open Access Journals (Sweden)

    Takashi Kodama

    Full Text Available To find a new biomarker of Tay-Sachs disease and Sandhoff disease. The lyso-GM2 ganglioside (lyso-GM2 levels in the brain and plasma in Sandhoff mice were measured by means of high performance liquid chromatography and the effect of a modified hexosaminidase (Hex B exhibiting Hex A-like activity was examined. Then, the lyso-GM2 concentrations in human plasma samples were determined. The lyso-GM2 levels in the brain and plasma in Sandhoff mice were apparently increased compared with those in wild-type mice, and they decreased on intracerebroventricular administration of the modified Hex B. The lyso-GM2 levels in plasma of patients with Tay-Sachs disease and Sandhoff disease were increased, and the increase in lyso-GM2 was associated with a decrease in Hex A activity. Lyso-GM2 is expected to be a potential biomarker of Tay-Sachs disease and Sandhoff disease.

  17. Approximate Bayesian computation for forward modeling in cosmology

    International Nuclear Information System (INIS)

    Akeret, Joël; Refregier, Alexandre; Amara, Adam; Seehars, Sebastian; Hasner, Caspar

    2015-01-01

    Bayesian inference is often used in cosmology and astrophysics to derive constraints on model parameters from observations. This approach relies on the ability to compute the likelihood of the data given a choice of model parameters. In many practical situations, the likelihood function may however be unavailable or intractable due to non-gaussian errors, non-linear measurements processes, or complex data formats such as catalogs and maps. In these cases, the simulation of mock data sets can often be made through forward modeling. We discuss how Approximate Bayesian Computation (ABC) can be used in these cases to derive an approximation to the posterior constraints using simulated data sets. This technique relies on the sampling of the parameter set, a distance metric to quantify the difference between the observation and the simulations and summary statistics to compress the information in the data. We first review the principles of ABC and discuss its implementation using a Population Monte-Carlo (PMC) algorithm and the Mahalanobis distance metric. We test the performance of the implementation using a Gaussian toy model. We then apply the ABC technique to the practical case of the calibration of image simulations for wide field cosmological surveys. We find that the ABC analysis is able to provide reliable parameter constraints for this problem and is therefore a promising technique for other applications in cosmology and astrophysics. Our implementation of the ABC PMC method is made available via a public code release

  18. Inflation and late-time acceleration in braneworld cosmological models with varying brane tension

    International Nuclear Information System (INIS)

    Wong, K.C.; Cheng, K.S.; Harko, T.

    2010-01-01

    Braneworld models with variable brane tension λ introduce a new degree of freedom that allows for evolving gravitational and cosmological constants, the latter being a natural candidate for dark energy. We consider a thermodynamic interpretation of the varying brane tension models, by showing that the field equations with variable λ can be interpreted as describing matter creation in a cosmological framework. The particle creation rate is determined by the variation rate of the brane tension, as well as by the brane-bulk energy-matter transfer rate. We investigate the effect of a variable brane tension on the cosmological evolution of the Universe, in the framework of a particular model in which the brane tension is an exponentially dependent function of the scale factor. The resulting cosmology shows the presence of an initial inflationary expansion, followed by a decelerating phase, and by a smooth transition towards a late accelerated de Sitter type expansion. The varying brane tension is also responsible for the generation of the matter in the Universe (reheating period). The physical constraints on the model parameters, resulting from the observational cosmological data, are also investigated. (orig.)

  19. Inflation in the standard cosmological model

    Science.gov (United States)

    Uzan, Jean-Philippe

    2015-12-01

    The inflationary paradigm is now part of the standard cosmological model as a description of its primordial phase. While its original motivation was to solve the standard problems of the hot big bang model, it was soon understood that it offers a natural theory for the origin of the large-scale structure of the universe. Most models rely on a slow-rolling scalar field and enjoy very generic predictions. Besides, all the matter of the universe is produced by the decay of the inflaton field at the end of inflation during a phase of reheating. These predictions can be (and are) tested from their imprint of the large-scale structure and in particular the cosmic microwave background. Inflation stands as a window in physics where both general relativity and quantum field theory are at work and which can be observationally studied. It connects cosmology with high-energy physics. Today most models are constructed within extensions of the standard model, such as supersymmetry or string theory. Inflation also disrupts our vision of the universe, in particular with the ideas of chaotic inflation and eternal inflation that tend to promote the image of a very inhomogeneous universe with fractal structure on a large scale. This idea is also at the heart of further speculations, such as the multiverse. This introduction summarizes the connections between inflation and the hot big bang model and details the basics of its dynamics and predictions. xml:lang="fr"

  20. Cosmological Reflection of Particle Symmetry

    Directory of Open Access Journals (Sweden)

    Maxim Khlopov

    2016-08-01

    Full Text Available The standard model involves particle symmetry and the mechanism of its breaking. Modern cosmology is based on inflationary models with baryosynthesis and dark matter/energy, which involves physics beyond the standard model. Studies of the physical basis of modern cosmology combine direct searches for new physics at accelerators with its indirect non-accelerator probes, in which cosmological consequences of particle models play an important role. The cosmological reflection of particle symmetry and the mechanisms of its breaking are the subject of the present review.

  1. Quantum cosmology - science of Genesis

    International Nuclear Information System (INIS)

    Padmanabhan, Thanu

    1987-01-01

    Quantum cosmology, the marriage between the theories of the microscopic and macroscopic Universe, is examined in an attempt to explain the birth of the Universe in the 'big bang'. A quantum cosmological model of the Universe does not exist, but a rough approximation, or 'poor man's' version of quantum cosmology has been developed. The idea is to combine the theory of quantum mechanics with the classical cosmological solutions to obtain a quantum mechanical version of cosmology. Such a model of quantum cosmology is described -here the quantum universe behaves like a hydrogen atom with the Planck length replacing the Bohr radius. Properties of quantum cosmologies and the significance of the Planck length are both discussed. (UK)

  2. A varying-α brane world cosmology

    International Nuclear Information System (INIS)

    Youm, Donam

    2001-08-01

    We study the brane world cosmology in the RS2 model where the electric charge varies with time in the manner described by the varying fine-structure constant theory of Bekenstein. We map such varying electric charge cosmology to the dual variable-speed-of-light cosmology by changing system of units. We comment on cosmological implications for such cosmological models. (author)

  3. Energy in the Kantowski–Sachs space-time using teleparallel ...

    Indian Academy of Sciences (India)

    Inflation is again considered to be one of the early phases of the Universe [10]. For testing gravitational energy–momentum tensor of the teleparallel theory in quasilocal approach and also in the. Hamiltonian structure of TEGR, it is intended to calculate the total energy of inflationary. Kantowski–Sachs-type Universe. Again ...

  4. A Review on the Cosmology of the de Sitter Horndeski Models

    Directory of Open Access Journals (Sweden)

    Nelson J. Nunes

    2017-03-01

    Full Text Available We review the most general scalar-tensor cosmological models with up to second-order derivatives in the field equations that have a fixed spatially flat de Sitter critical point independent of the material content or vacuum energy. This subclass of the Horndeski Lagrangian is capable of dynamically adjusting any value of the vacuum energy of the matter fields at the critical point. We present the cosmological evolution of the linear models and the non-linear models with shift symmetry. We come to the conclusion that the shift symmetric non-linear models can deliver a viable background compatible with current observations.

  5. Cosmological viability conditions for f(T) dark energy models

    Energy Technology Data Exchange (ETDEWEB)

    Setare, M.R.; Mohammadipour, N., E-mail: rezakord@ipm.ir, E-mail: N.Mohammadipour@uok.ac.ir [Department of Science, University of Kurdistan, Sanandaj (Iran, Islamic Republic of)

    2012-11-01

    Recently f(T) modified teleparallel gravity where T is the torsion scalar has been proposed as the natural gravitational alternative for dark energy. We perform a detailed dynamical analysis of these models and find conditions for the cosmological viability of f(T) dark energy models as geometrical constraints on the derivatives of these models. We show that in the phase space exists two cosmologically viable trajectory which (i) The universe would start from an unstable radiation point, then pass a saddle standard matter point which is followed by accelerated expansion de sitter point. (ii) The universe starts from a saddle radiation epoch, then falls onto the stable matter era and the system can not evolve to the dark energy dominated epoch. Finally, for a number of f(T) dark energy models were proposed in the more literature, the viability conditions are investigated.

  6. Characterization of inducible models of Tay-Sachs and related disease.

    Science.gov (United States)

    Sargeant, Timothy J; Drage, Deborah J; Wang, Susan; Apostolakis, Apostolos A; Cox, Timothy M; Cachón-González, M Begoña

    2012-09-01

    Tay-Sachs and Sandhoff diseases are lethal inborn errors of acid β-N-acetylhexosaminidase activity, characterized by lysosomal storage of GM2 ganglioside and related glycoconjugates in the nervous system. The molecular events that lead to irreversible neuronal injury accompanied by gliosis are unknown; but gene transfer, when undertaken before neurological signs are manifest, effectively rescues the acute neurodegenerative illness in Hexb-/- (Sandhoff) mice that lack β-hexosaminidases A and B. To define determinants of therapeutic efficacy and establish a dynamic experimental platform to systematically investigate cellular pathogenesis of GM2 gangliosidosis, we generated two inducible experimental models. Reversible transgenic expression of β-hexosaminidase directed by two promoters, mouse Hexb and human Synapsin 1 promoters, permitted progression of GM2 gangliosidosis in Sandhoff mice to be modified at pre-defined ages. A single auto-regulatory tetracycline-sensitive expression cassette controlled expression of transgenic Hexb in the brain of Hexb-/- mice and provided long-term rescue from the acute neuronopathic disorder, as well as the accompanying pathological storage of glycoconjugates and gliosis in most parts of the brain. Ultimately, late-onset brainstem and ventral spinal cord pathology occurred and was associated with increased tone in the limbs. Silencing transgenic Hexb expression in five-week-old mice induced stereotypic signs and progression of Sandhoff disease, including tremor, bradykinesia, and hind-limb paralysis. As in germline Hexb-/- mice, these neurodegenerative manifestations advanced rapidly, indicating that the pathogenesis and progression of GM2 gangliosidosis is not influenced by developmental events in the maturing nervous system.

  7. Characterization of inducible models of Tay-Sachs and related disease.

    Directory of Open Access Journals (Sweden)

    Timothy J Sargeant

    2012-09-01

    Full Text Available Tay-Sachs and Sandhoff diseases are lethal inborn errors of acid β-N-acetylhexosaminidase activity, characterized by lysosomal storage of GM2 ganglioside and related glycoconjugates in the nervous system. The molecular events that lead to irreversible neuronal injury accompanied by gliosis are unknown; but gene transfer, when undertaken before neurological signs are manifest, effectively rescues the acute neurodegenerative illness in Hexb-/- (Sandhoff mice that lack β-hexosaminidases A and B. To define determinants of therapeutic efficacy and establish a dynamic experimental platform to systematically investigate cellular pathogenesis of GM2 gangliosidosis, we generated two inducible experimental models. Reversible transgenic expression of β-hexosaminidase directed by two promoters, mouse Hexb and human Synapsin 1 promoters, permitted progression of GM2 gangliosidosis in Sandhoff mice to be modified at pre-defined ages. A single auto-regulatory tetracycline-sensitive expression cassette controlled expression of transgenic Hexb in the brain of Hexb-/- mice and provided long-term rescue from the acute neuronopathic disorder, as well as the accompanying pathological storage of glycoconjugates and gliosis in most parts of the brain. Ultimately, late-onset brainstem and ventral spinal cord pathology occurred and was associated with increased tone in the limbs. Silencing transgenic Hexb expression in five-week-old mice induced stereotypic signs and progression of Sandhoff disease, including tremor, bradykinesia, and hind-limb paralysis. As in germline Hexb-/- mice, these neurodegenerative manifestations advanced rapidly, indicating that the pathogenesis and progression of GM2 gangliosidosis is not influenced by developmental events in the maturing nervous system.

  8. Introduction to cosmology

    CERN Document Server

    Roos, Matts

    2003-01-01

    The Third Edition of the hugely successful Introduction to Cosmology provides a concise, authoritative study of cosmology at an introductory level. Starting from elementary principles and the history of cosmology, the text carefully guides the student on to curved spacetimes, general relativity, black holes, cosmological models, particles and symmetries, and phase transitions. Extensively revised, this latest edition includes broader and updated coverage of distance measures, gravitational lensing and waves, dark energy and quintessence, the thermal history of the Universe, inflation,

  9. Anisotropic cosmological models with bulk viscosity and particle ...

    Indian Academy of Sciences (India)

    ... equations in two types of cosmologies, one with power-law expansion and the other with exponential expansion. ... a Big-Bang singularity at time t = 0 , whereas the model with exponential expansion has no finite singularity. ... Current Issue

  10. Cosmology

    CERN Document Server

    Vittorio, Nicola

    2018-01-01

    Modern cosmology has changed significantly over the years, from the discovery to the precision measurement era. The data now available provide a wealth of information, mostly consistent with a model where dark matter and dark energy are in a rough proportion of 3:7. The time is right for a fresh new textbook which captures the state-of-the art in cosmology. Written by one of the world's leading cosmologists, this brand new, thoroughly class-tested textbook provides graduate and undergraduate students with coverage of the very latest developments and experimental results in the field. Prof. Nicola Vittorio shows what is meant by precision cosmology, from both theoretical and observational perspectives.

  11. Correlation of augmented startle reflex with brainstem electrophysiological responses in Tay-Sachs disease.

    Science.gov (United States)

    Nakamura, Sadao; Saito, Yoshiaki; Ishiyama, Akihiko; Sugai, Kenji; Iso, Takashi; Inagaki, Masumi; Sasaki, Masayuki

    2015-01-01

    To clarify the evolution of an augmented startle reflex in Tay-Sachs disease and compare the temporal relationship between this reflex and brainstem evoked potentials. Clinical and electrophysiological data from 3 patients with Tay-Sachs disease were retrospectively collected. The augmented startle reflex appeared between the age of 3 and 17 months and disappeared between the age of 4 and 6 years. Analysis of brainstem auditory evoked potentials revealed that poor segregation of peak I, but not peak III, coincided with the disappearance of the augmented startle reflex. A blink reflex with markedly high amplitude was observed in a patient with an augmented startle reflex. The correlation between the augmented startle reflex and the preservation of peak I but not peak III supports the theory that the superior olivary nucleus is dispensable for this reflex. The blink reflex with high amplitudes may represent augmented excitability of reticular formation at the pontine tegmentum in Tay-Sachs disease, where the pattern generators for the augmented startle and blink reflexes may functionally overlap. Copyright © 2014 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

  12. An introduction to cosmology

    CERN Document Server

    Kunze, Kerstin E.

    2016-12-20

    Cosmology is becoming an important tool to test particle physics models. We provide an overview of the standard model of cosmology with an emphasis on the observations relevant for testing fundamental physics.

  13. Friedmann cosmology with a cosmological 'constant' in the scale covariant theory

    International Nuclear Information System (INIS)

    Beesham, A.

    1986-01-01

    Homogeneous isotropic cosmologies in the presence of a cosmological 'constant' are studied in the scale covariant theory. A class of solutions is obtained for kappa = 0 for models filled with dust, radiation or stiff matter. For kappa not= 0, solutions are presented for the radiation models. (author)

  14. Is the cosmological singularity compulsory

    International Nuclear Information System (INIS)

    Bekenstein, J.D.; Meisels, A.

    1980-01-01

    The cosmological singularity is inherent in all conventional general relativistic cosmological models. There can be no question that it is an unphysical feature; yet there does not seem to be any convervative way of eliminating it. Here we present singularity-free isotropic cosmological models which are indistinguishable from general relativistic ones at late times. They are based on the general theory of variable rest masses that we developed recently. Outside cosmology this theory simulates general relativity well. Thus it provides a framework incorporating those features which have made geneal relativity so sucessful while providing a way out of singularity dilemma. The cosmological models can be made to incorporate Dirac's large numbers hypothesis. G(now)/G(0)approx.10 -38

  15. A new possibility of cosmological model construction in Kaluza-Klein theories

    International Nuclear Information System (INIS)

    Berezin, V.A.; Kuzmin, V.A.; AN SSSR, Moscow. Inst. Yadernykh Issledovanij)

    1987-12-01

    We studied the dimensional reduction of the 5-dimensional Schwarzschild-deSitter solution and found that the Friedmann-Robertson-Walker cosmological model may be obtained by the dimensional reduction along the Killing vector in the T-region of the 5-manifold. For the Appelquist-Chodos reduction we observed the universal behaviour of the scale factor near the 4-dimensional singularity and found a possibility of cosmological model constructing with induced singularity like the Big Bang from non-singular 5-dimensional solution. (orig.)

  16. A taste of cosmology

    International Nuclear Information System (INIS)

    Verde, L.

    2011-01-01

    This is the summary of two lectures that aim to give an overview of cosmology. I will not try to be toa rigorous in derivations, nor to give a full historical overview. The idea is to provide a 'taste' of cosmology and some of the interesting topics it covers. The standard cosmological model is presented and I highlight the successes of cosmology over the past decade or so. Keys to the development of the standard cosmological model are observations of the cosmic microwave background and of large-scale structure, which are introduced. Inflation and dark energy and the outlook for the future are also discussed. Slides from the lectures are available from the school web site: physicschool.web.cern.ch/PhysicSchool/CLASHEP/CLASHEP2011/. (author)

  17. A Taste of Cosmology

    CERN Document Server

    Verde, L.

    2013-06-27

    This is the summary of two lectures that aim to give an overview of cosmology. I will not try to be too rigorous in derivations, nor to give a full historical overview. The idea is to provide a "taste" of cosmology and some of the interesting topics it covers. The standard cosmological model is presented and I highlight the successes of cosmology over the past decade or so. Keys to the development of the standard cosmological model are observations of the cosmic microwave background and of large-scale structure, which are introduced. Inflation and dark energy and the outlook for the future are also discussed. Slides from the lectures are available from the school website: physicschool.web.cern.ch/PhysicSchool/CLASHEP/CLASHEP2011/.

  18. Phase-space dynamics of Bianchi IX cosmological models

    International Nuclear Information System (INIS)

    Soares, I.D.

    1985-01-01

    The complex phase-space dynamical behaviour of a class of Biachi IX cosmological models is discussed, as the chaotic gravitational collapse due Poincare's homoclinic phenomena, and the n-furcation of periodic orbits and tori in the phase space of the models. Poincare maps which show this behaviour are constructed merically and applications are discussed. (Author) [pt

  19. A cosmological model with particle creation

    International Nuclear Information System (INIS)

    Chatterjee, Sujit

    2001-01-01

    A higher dimensional cosmological model is proposed where an expanding universe evolves from the vacuum fluctuation and matter creation takes place out of the gravitational energy. Choosing a particular form of the matter creation function N(t) as an initial conditions it can be shown that starting from an inflationary era the cosmos enters the higher dimensional Friedmann-like phase after a time scale when the matter creation stops

  20. Cosmology

    CERN Document Server

    García-Bellido, J

    2015-01-01

    In these lectures I review the present status of the so-called Standard Cosmological Model, based on the hot Big Bang Theory and the Inflationary Paradigm. I will make special emphasis on the recent developments in observational cosmology, mainly the acceleration of the universe, the precise measurements of the microwave background anisotropies, and the formation of structure like galaxies and clusters of galaxies from tiny primordial fluctuations generated during inflation.

  1. Cosmology and time

    Directory of Open Access Journals (Sweden)

    Balbi Amedeo

    2013-09-01

    Full Text Available Time has always played a crucial role in cosmology. I review some of the aspects of the present cosmological model which are more directly related to time, such as: the definition of a cosmic time; the existence of typical timescales and epochs in an expanding universe; the problem of the initial singularity and the origin of time; the cosmological arrow of time.

  2. Hidden past of dark energy cosmological models

    International Nuclear Information System (INIS)

    Fernandez-Jambrina, L.

    2007-01-01

    In this Letter we analyse the possibility of having homogeneous isotropic cosmological models with observers reaching t=∞ in finite proper time. It is shown that just observationally-suggested dark energy models with w element of (-5/3,-1) show this feature and that they are endowed with an exotic curvature singularity. Furthermore, it is shown that non-accelerated observers in these models may experience a duration of the universe as short as desired by increasing their linear momentum. A subdivision of phantom models in two families according to this behavior is suggested

  3. Cosmological models - in which universe do we live

    International Nuclear Information System (INIS)

    Hartvigsen, Y.

    1976-01-01

    A general discussion of the present state of cosmological models is introduced with a brief presentation of the expanding universe theory, the red shift and Hubble's Law. Hubble's Constant lies between 30 and 105 km/sec/Mpc, and a value of 55 km/sec/Mpc is assumed in this article. The arguments for the big bang and steady state theories are presented and the reasons for the present acceptance of the former given. Friedmann models are briefly discussed and 'universe density', rho, and 'space curvature',k, and the 'cosmological constant', Λ, are presented. These are shown on the Stabell-Refsdal diagram and the density parameter, sigma 0 , and the retardation parameter, q 0 , are related to Hubble's Constant. These parameters are then discussed and their values restricted such that the part of the Stabell-Refsdal diagram which is of interest may be defined. (JIW)

  4. Dissipative Boltzmann-Robertson-Walker cosmologies

    International Nuclear Information System (INIS)

    Hiscock, W.A.; Salmonson, J.

    1991-01-01

    The equations governing a flat Robertson-Walker cosmological model containing a dissipative Boltzmann gas are integrated numerically. The bulk viscous stress is modeled using the Eckart and Israel-Stewart theories of dissipative relativistic fluids; the resulting cosmologies are compared and contrasted. The Eckart models are shown to always differ in a significant quantitative way from the Israel-Stewart models. It thus appears inappropriate to use the pathological (nonhyperbolic) Eckart theory for cosmological applications. For large bulk viscosities, both cosmological models approach asymptotic nonequilibrium states; in the Eckart model the total pressure is negative, while in the Israel-Stewart model the total pressure is asymptotically zero. The Eckart model also expands more rapidly than the Israel-Stewart models. These results suggest that ''bulk-viscous'' inflation may be an artifact of using a pathological fluid theory such as the Eckart theory

  5. On estimating cosmology-dependent covariance matrices

    International Nuclear Information System (INIS)

    Morrison, Christopher B.; Schneider, Michael D.

    2013-01-01

    We describe a statistical model to estimate the covariance matrix of matter tracer two-point correlation functions with cosmological simulations. Assuming a fixed number of cosmological simulation runs, we describe how to build a 'statistical emulator' of the two-point function covariance over a specified range of input cosmological parameters. Because the simulation runs with different cosmological models help to constrain the form of the covariance, we predict that the cosmology-dependent covariance may be estimated with a comparable number of simulations as would be needed to estimate the covariance for fixed cosmology. Our framework is a necessary first step in planning a simulations campaign for analyzing the next generation of cosmological surveys

  6. Equivalence of Einstein and Jordan frames in quantized anisotropic cosmological models

    Science.gov (United States)

    Pandey, Sachin; Pal, Sridip; Banerjee, Narayan

    2018-06-01

    The present work shows that the mathematical equivalence of the Jordan frame and its conformally transformed version, the Einstein frame, so as far as Brans-Dicke theory is concerned, survives a quantization of cosmological models, arising as solutions to the Brans-Dicke theory. We work with the Wheeler-deWitt quantization scheme and take up quite a few anisotropic cosmological models as examples. We effectively show that the transformation from the Jordan to the Einstein frame is a canonical one and hence two frames furnish equivalent description of same physical scenario.

  7. Targeted disruption of the Hexa gene results in mice with biochemical and pathologic features of Tay-Sachs disease

    Energy Technology Data Exchange (ETDEWEB)

    Proia, R.L.; Yamanaka, S.; Johnson, M.D. [and others

    1994-09-01

    Tay-Sachs disease, the prototype of the G{sub M2} gangliosidoses, is a catastrophic neurodegenerative disorder of infancy. The disease is caused by mutations in the HEXA gene resulting in an absence of the lysosomal enzyme, {beta}-hexosaminidase A. As consequence of the enzyme deficiency, G{sub M2} ganglioside accumulates progressively, beginning early in fetal life, to excessive amounts in the central nervous system (CNS). Rapid mental and motor deterioration starting in the first year of life leads to death by 2 to 4 years of age. Through the targeted disruption of the Hexa gene in embryonic stem cells, we have produced mice with biochemical and neuropathologic features of Tay-Sachs disease. The mutant mice exhibited less than 1% of normal {beta}-hexosaminidase A activity and accumulated G{sub M2} ganglioside in their CNS in an age-dependent manner. The accumulated ganglioside was stored in neurons as membranous cytoplasmic bodies characteristically found in the neurons of Tay-Sachs disease patients. At three to five months of age the mutant mice showed no apparent defects in motor or memory function. These {beta}-hexosaminidase A deficient mice should be useful for devising strategies to introduce functional enzymes and genes into the CNS. This model may also be valuable for studying the biochemical and pathologic changes occurring during the course of the disease.

  8. New Cosmological Model and Its Implications on Observational Data Interpretation

    Directory of Open Access Journals (Sweden)

    Vlahovic Branislav

    2013-09-01

    Full Text Available The paradigm of ΛCDM cosmology works impressively well and with the concept of inflation it explains the universe after the time of decoupling. However there are still a few concerns; after much effort there is no detection of dark matter and there are significant problems in the theoretical description of dark energy. We will consider a variant of the cosmological spherical shell model, within FRW formalism and will compare it with the standard ΛCDM model. We will show that our new topological model satisfies cosmological principles and is consistent with all observable data, but that it may require new interpretation for some data. Considered will be constraints imposed on the model, as for instance the range for the size and allowed thickness of the shell, by the supernovae luminosity distance and CMB data. In this model propagation of the light is confined along the shell, which has as a consequence that observed CMB originated from one point or a limited space region. It allows to interpret the uniformity of the CMB without inflation scenario. In addition this removes any constraints on the uniformity of the universe at the early stage and opens a possibility that the universe was not uniform and that creation of galaxies and large structures is due to the inhomogeneities that originated in the Big Bang.

  9. Galileon cosmology

    International Nuclear Information System (INIS)

    Chow, Nathan; Khoury, Justin

    2009-01-01

    We study the cosmology of a galileon scalar-tensor theory, obtained by covariantizing the decoupling Lagrangian of the Dvali-Gabadadze-Poratti (DGP) model. Despite being local in 3+1 dimensions, the resulting cosmological evolution is remarkably similar to that of the full 4+1-dimensional DGP framework, both for the expansion history and the evolution of density perturbations. As in the DGP model, the covariant galileon theory yields two branches of solutions, depending on the sign of the galileon velocity. Perturbations are stable on one branch and ghostlike on the other. An interesting effect uncovered in our analysis is a cosmological version of the Vainshtein screening mechanism: at early times, the galileon dynamics are dominated by self-interaction terms, resulting in its energy density being suppressed compared to matter or radiation; once the matter density has redshifted sufficiently, the galileon becomes an important component of the energy density and contributes to dark energy. We estimate conservatively that the resulting expansion history is consistent with the observed late-time cosmology, provided that the scale of modification satisfies r c > or approx. 15 Gpc.

  10. Neurocognitive testing in late-onset Tay-Sachs disease: a pilot study.

    Science.gov (United States)

    Elstein, D; Doniger, G M; Simon, E; Korn-Lubetzki, I; Navon, R; Zimran, A

    2008-08-01

    To test neurocognitive function in patients with late-onset Tay-Sachs disease (LOTS) using a computerized system to assess whether cognition is a clinically relevant outcome measure of possible therapeutic intervention in LOTS. Ten adults with Tay-Sachs disease were administered at least one battery of the Mindstreams Neurotrax system for evaluation of cognitive function. Six sub-scores and a Global Cognitive Score (GCS) were tabulated. A disease specific severity score was also devised with six domains. Despite identical genotypes, all patients but the two oldest had > or = 3/6 sub-scores one standard deviation below normal mean (100); verbal and executive functions were most affected. The severity score measured other functions. Because of provocative findings on re-testing in patients exposed to miglustat, and despite the very small cohort, cognitive function may be an appropriate and clinically relevant outcome measure for future therapeutic interventions in LOTS.

  11. Simple inhomogeneous cosmological (toy) models

    International Nuclear Information System (INIS)

    Isidro, Eddy G. Chirinos; Zimdahl, Winfried; Vargas, Cristofher Zuñiga

    2016-01-01

    Based on the Lemaître-Tolman-Bondi (LTB) metric we consider two flat inhomogeneous big-bang models. We aim at clarifying, as far as possible analytically, basic features of the dynamics of the simplest inhomogeneous models and to point out the potential usefulness of exact inhomogeneous solutions as generalizations of the homogeneous configurations of the cosmological standard model. We discuss explicitly partial successes but also potential pitfalls of these simplest models. Although primarily seen as toy models, the relevant free parameters are fixed by best-fit values using the Joint Light-curve Analysis (JLA)-sample data. On the basis of a likelihood analysis we find that a local hump with an extension of almost 2 Gpc provides a better description of the observations than a local void for which we obtain a best-fit scale of about 30 Mpc. Future redshift-drift measurements are discussed as a promising tool to discriminate between inhomogeneous configurations and the ΛCDM model.

  12. Tay-Sachs disease with conspicuous cranial computerized tomographic appearances

    International Nuclear Information System (INIS)

    Watanabe, Kishichiro; Mukawa, Akio; Muto, Kazuhiko; Nishikawa, Jiro; Takahashi, Shigeko.

    1985-01-01

    An autopsy case of a 3-year-old female infant with Tay-Sachs disease was presented. A cherry red spot in the fundus and a deficiency of N-acetyl-β-hexosaminidase A in the white blood cells were revealed soon after admission at the age of one year. Her parents and sister were found to be healthy carriers. The patient showed a typical clinical course with marked cranial swelling. In addition to the marked ballooning of neurons on light microscope, membranous cytoplasmic body (MCB) on electron microscope and abnormal accumulation of GM 2 ganglioside in the cerebral cortex by thin layer chromatography were confirmed in the autopsy specimens. In the late stage of her clinical course, the cranial computerized tomography (CT) demonstrated symmetric and deep-wavy hyperdense cerebral cortical zones, diffuse hypodensity and diminished volume of cerebral white matter, mild to moderate ventricular dilatation, and a small cerebellum and brainstem. These conspicuous appearances of the cranial CT seem to be characteristic of Tay-Sachs disease in the late stage, and they are derived from abnormal accumulation of GM 2 ganglioside in the cerebral cortex, and diffuse intense demyelination (dysmyelinating demyelination) of the cerebral white matter. (author)

  13. Constraining viscous dark energy models with the latest cosmological data

    Science.gov (United States)

    Wang, Deng; Yan, Yang-Jie; Meng, Xin-He

    2017-10-01

    Based on the assumption that the dark energy possessing bulk viscosity is homogeneously and isotropically permeated in the universe, we propose three new viscous dark energy (VDE) models to characterize the accelerating universe. By constraining these three models with the latest cosmological observations, we find that they just deviate very slightly from the standard cosmological model and can alleviate effectively the current H_0 tension between the local observation by the Hubble Space Telescope and the global measurement by the Planck Satellite. Interestingly, we conclude that a spatially flat universe in our VDE model with cosmic curvature is still supported by current data, and the scale invariant primordial power spectrum is strongly excluded at least at the 5.5σ confidence level in the three VDE models as the Planck result. We also give the 95% upper limits of the typical bulk viscosity parameter η in the three VDE scenarios.

  14. Anisotropic Bianchi II cosmological models with matter and electromagnetic fields

    International Nuclear Information System (INIS)

    Soares, D.

    1978-01-01

    A class of solutions of Einstein-Maxwell equations is presented, which corresponds to anisotropic Bianchi II spatially homogeneous cosmological models with perfect fluid and electromagnetic field. A particular model is examined and shown to be unstable for perturbations of the electromagnetic field strength parameter about a particular value. This value defines a limiar unstable case in which the ratio epsilon, of the fluid density to the e.m. energy density is monotonically increasing with a minimum finite value at the singularity. Beyond this limiar, the model has a matter dominated singularity, and a characteristic stage appears where epsilon has a minimum, at a finite time from the singularity. For large times, the models tend to an exact solution for zero electromagnetic field and fluid with p = (1/5)p. Some cosmological features of the models are calculated, as the effect of anisotropy on matter density and expansion time scale factors, as compared to the corresponding Friedmann model [pt

  15. Choroidal Coloboma in a Case of Tay-Sachs Disease

    OpenAIRE

    Ahmed, Nasreen Raees; Tripathy, Koushik; Kumar, Vivek; Gogia, Varun

    2014-01-01

    Coloboma as an ocular finding has been documented in various syndromes. Here we have a case of infantile Tay-Sachs disease associated with unilateral choroidal coloboma. To the best of our knowledge, such an association has not been documented in the literature. Whether such an association is a matter of chance or signifies the involvement of ganglioside metabolism in ocular embryogenesis remains to be elucidated.

  16. Choroidal coloboma in a case of tay-sachs disease.

    Science.gov (United States)

    Ahmed, Nasreen Raees; Tripathy, Koushik; Kumar, Vivek; Gogia, Varun

    2014-01-01

    Coloboma as an ocular finding has been documented in various syndromes. Here we have a case of infantile Tay-Sachs disease associated with unilateral choroidal coloboma. To the best of our knowledge, such an association has not been documented in the literature. Whether such an association is a matter of chance or signifies the involvement of ganglioside metabolism in ocular embryogenesis remains to be elucidated.

  17. Phantom cosmologies and fermions

    International Nuclear Information System (INIS)

    Chimento, Luis P; Forte, Monica; Devecchi, Fernando P; Kremer, Gilberto M

    2008-01-01

    Form invariance transformations can be used for constructing phantom cosmologies starting with conventional cosmological models. In this work we reconsider the scalar field case and extend the discussion to fermionic fields, where the 'phantomization' process exhibits a new class of possible accelerated regimes. As an application we analyze the cosmological constant group for a fermionic seed fluid

  18. Deconstructing cosmology

    CERN Document Server

    Sanders, Robert H

    2016-01-01

    The advent of sensitive high-resolution observations of the cosmic microwave background radiation and their successful interpretation in terms of the standard cosmological model has led to great confidence in this model's reality. The prevailing attitude is that we now understand the Universe and need only work out the details. In this book, Sanders traces the development and successes of Lambda-CDM, and argues that this triumphalism may be premature. The model's two major components, dark energy and dark matter, have the character of the pre-twentieth-century luminiferous aether. While there is astronomical evidence for these hypothetical fluids, their enigmatic properties call into question our assumptions of the universality of locally determined physical law. Sanders explains how modified Newtonian dynamics (MOND) is a significant challenge for cold dark matter. Overall, the message is hopeful: the field of cosmology has not become frozen, and there is much fundamental work ahead for tomorrow's cosmologis...

  19. Tay-Sachs and Sandhoff diseases: enzymatic diagnosis in dried blood spots on filter paper: retrospective diagnoses in newborn-screening cards.

    Science.gov (United States)

    Chamoles, Néstor A; Blanco, Mariana; Gaggioli, Daniela; Casentini, Carina

    2002-04-01

    Tay-Sachs disease (TSD), Sandhoff disease (SD) and variants are caused by deficient activity of the lysosomal enzymes hexosaminidase A (HA) and total hexosaminidase (TH) (hexosaminidase A plus B), respectively. For diagnosis, these enzymes are usually measured in plasma or extracts of leukocytes. We describe methods for the assay of hexosaminidase A and total hexosaminidase activities in dried blood spots (DBSs) on filter paper. We studied 163 healthy controls, 9 Tay-Sachs patients, 4 Sandhoff patients, 18 obligate carriers and the newborn-screening cards from two patients with Tay-Sachs and one patient with Sandhoff disease. To tubes containing a 3-mm-diameter blood spot, we added elution liquid and substrate solution. After incubation at 37 degrees C, the amount of hydrolyzed product was compared with a calibrator to allow the quantification of enzyme activity. The described methodology is useful to distinguish patients with Tay-Sachs disease or Sandhoff disease from carriers and controls using samples that are sufficiently stable to be transported to the testing laboratory by mail. The diagnosis of both diseases from a newborn-screening card (NSC) was clearly demonstrated, even after storage for up to 38 months at room temperature. The newborn-screening card has been added to the biological materials that allow the identification of patients with Tay-Sachs disease and Sandhoff disease.

  20. A cosmological model with compact space sections and low mass density

    International Nuclear Information System (INIS)

    Fagundes, H.V.

    1982-01-01

    A general relativistic cosmological model is presented, which has closed space sections and mass density below a critical density similar to that of Friedmann's models. The model may predict double images of cosmic sources. (Author) [pt

  1. Preconception risk assessment for thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease.

    Science.gov (United States)

    Hussein, Norita; Weng, Stephen F; Kai, Joe; Kleijnen, Jos; Qureshi, Nadeem

    2018-03-14

    Globally, about five per cent of children are born with congenital or genetic disorders. The most common autosomal recessive conditions are thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease, with higher carrier rates in specific patient populations. Identifying and counselling couples at genetic risk of the conditions before pregnancy enables them to make fully informed reproductive decisions, with some of these choices not being available if genetic counselling is only offered in an antenatal setting. This is an update of a previously published review. To assess the effectiveness of systematic preconception genetic risk assessment to improve reproductive outcomes in women and their partners who are identified as carriers of thalassaemia, sickle cell disease, cystic fibrosis and Tay-Sachs disease in healthcare settings when compared to usual care. We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Trials Registers. In addition, we searched for all relevant trials from 1970 (or the date at which the database was first available if after 1970) to date using electronic databases (MEDLINE, Embase, CINAHL, PsycINFO), clinical trial databases (National Institutes of Health, Clinical Trials Search portal of the World Health Organization, metaRegister of controlled clinical trials), and hand searching of key journals and conference abstract books from 1998 to date (European Journal of Human Genetics, Genetics in Medicine, Journal of Community Genetics). We also searched the reference lists of relevant articles, reviews and guidelines and also contacted subject experts in the field to request any unpublished or other published trials.Date of latest search of the registers: 20 June 2017.Date of latest search of all other sources: 16 November 2017. Any randomised or quasi-randomised controlled trials (published or unpublished) comparing reproductive outcomes of systematic preconception genetic risk assessment for thalassaemia, sickle

  2. İki Kardeşte Görülen Tay-Sachs Hastalığı

    OpenAIRE

    KÜÇÜKÖDÜK, Ş.

    2010-01-01

    In view of two cases of autosomal recessive Tay-Sachs disease which affected two siblings, genetic consultation has been once more emphasized. The clinical features of this entity has been reviewed under the information obtained from recent literature. Otozomal resesif geçiş gösteren ve iki kardeşide etkiliyen Tay-Sachs hastalığında, genetik danışmanın önemi bir kez daha vurgulandı. Bu hastalığın klinik özellikleri literatür bilgilerinin ışığı altında gözden geçirildi....

  3. Tay-Sachs disease: high gene frequency in a non-Jewish population.

    Science.gov (United States)

    Kelly, T E; Chase, G A; Kaback, M M; Kumor, K; McKusick, V A

    1975-01-01

    A non-Amish "Pennsylvania Dutch" semi-isolate was found to have a high frequency of Tay-Sachs gene. This high frequency could be ascribed to founder effect and may represent, in microcosm, how this mechanism could have produced the high gene frequency among Ashkenazi Jews. PMID:803011

  4. 78 FR 24447 - Goldman Sachs Trust, et al.; Notice of Application

    Science.gov (United States)

    2013-04-25

    ... SECURITIES AND EXCHANGE COMMISSION [Investment Company Act Release No. 30471; 812-14075] Goldman Sachs Trust, et al.; Notice of Application April 19, 2013. AGENCY: Securities and Exchange Commission..., or cause more than 10% of the acquired company's voting stock to be owned by investment companies and...

  5. Testing general relativity at cosmological scales: Implementation and parameter correlations

    International Nuclear Information System (INIS)

    Dossett, Jason N.; Ishak, Mustapha; Moldenhauer, Jacob

    2011-01-01

    The testing of general relativity at cosmological scales has become a possible and timely endeavor that is not only motivated by the pressing question of cosmic acceleration but also by the proposals of some extensions to general relativity that would manifest themselves at large scales of distance. We analyze here correlations between modified gravity growth parameters and some core cosmological parameters using the latest cosmological data sets including the refined Cosmic Evolution Survey 3D weak lensing. We provide the parametrized modified growth equations and their evolution. We implement known functional and binning approaches, and propose a new hybrid approach to evolve the modified gravity parameters in redshift (time) and scale. The hybrid parametrization combines a binned redshift dependence and a smooth evolution in scale avoiding a jump in the matter power spectrum. The formalism developed to test the consistency of current and future data with general relativity is implemented in a package that we make publicly available and call ISiTGR (Integrated Software in Testing General Relativity), an integrated set of modified modules for the publicly available packages CosmoMC and CAMB, including a modified version of the integrated Sachs-Wolfe-galaxy cross correlation module of Ho et al. and a new weak-lensing likelihood module for the refined Hubble Space Telescope Cosmic Evolution Survey weak gravitational lensing tomography data. We obtain parameter constraints and correlation coefficients finding that modified gravity parameters are significantly correlated with σ 8 and mildly correlated with Ω m , for all evolution methods. The degeneracies between σ 8 and modified gravity parameters are found to be substantial for the functional form and also for some specific bins in the hybrid and binned methods indicating that these degeneracies will need to be taken into consideration when using future high precision data.

  6. Higher dimensional loop quantum cosmology

    International Nuclear Information System (INIS)

    Zhang, Xiangdong

    2016-01-01

    Loop quantum cosmology (LQC) is the symmetric sector of loop quantum gravity. In this paper, we generalize the structure of loop quantum cosmology to the theories with arbitrary spacetime dimensions. The isotropic and homogeneous cosmological model in n + 1 dimensions is quantized by the loop quantization method. Interestingly, we find that the underlying quantum theories are divided into two qualitatively different sectors according to spacetime dimensions. The effective Hamiltonian and modified dynamical equations of n + 1 dimensional LQC are obtained. Moreover, our results indicate that the classical big bang singularity is resolved in arbitrary spacetime dimensions by a quantum bounce. We also briefly discuss the similarities and differences between the n + 1 dimensional model and the 3 + 1 dimensional one. Our model serves as a first example of higher dimensional loop quantum cosmology and offers the possibility to investigate quantum gravity effects in higher dimensional cosmology. (orig.)

  7. Neutrino cosmology

    CERN Document Server

    Lesgourgues, Julien; Miele, Gennaro; Pastor, Sergio

    2013-01-01

    The role that neutrinos have played in the evolution of the Universe is the focus of one of the most fascinating research areas that has stemmed from the interplay between cosmology, astrophysics and particle physics. In this self-contained book, the authors bring together all aspects of the role of neutrinos in cosmology, spanning from leptogenesis to primordial nucleosynthesis, their role in CMB and structure formation, to the problem of their direct detection. The book starts by guiding the reader through aspects of fundamental neutrino physics, such as the standard cosmological model and the statistical mechanics in the expanding Universe, before discussing the history of neutrinos in chronological order from the very early stages until today. This timely book will interest graduate students and researchers in astrophysics, cosmology and particle physics, who work with either a theoretical or experimental focus.

  8. Building analytical three-field cosmological models

    Energy Technology Data Exchange (ETDEWEB)

    Santos, J.R.L. [Universidade de Federal de Campina Grande, Unidade Academica de Fisica, Campina Grande, PB (Brazil); Moraes, P.H.R.S. [ITA-Instituto Tecnologico de Aeronautica, Sao Jose dos Campos, SP (Brazil); Ferreira, D.A. [Universidade de Federal de Campina Grande, Unidade Academica de Fisica, Campina Grande, PB (Brazil); Universidade Federal da Paraiba, Departamento de Fisica, Joao Pessoa, PB (Brazil); Neta, D.C.V. [Universidade de Federal de Campina Grande, Unidade Academica de Fisica, Campina Grande, PB (Brazil); Universidade Estadual da Paraiba, Departamento de Fisica, Campina Grande, PB (Brazil)

    2018-02-15

    A difficult task to deal with is the analytical treatment of models composed of three real scalar fields, as their equations of motion are in general coupled and hard to integrate. In order to overcome this problem we introduce a methodology to construct three-field models based on the so-called ''extension method''. The fundamental idea of the procedure is to combine three one-field systems in a non-trivial way, to construct an effective three scalar field model. An interesting scenario where the method can be implemented is with inflationary models, where the Einstein-Hilbert Lagrangian is coupled with the scalar field Lagrangian. We exemplify how a new model constructed from our method can lead to non-trivial behaviors for cosmological parameters. (orig.)

  9. Cosmological Probes for Supersymmetry

    Directory of Open Access Journals (Sweden)

    Maxim Khlopov

    2015-05-01

    Full Text Available The multi-parameter character of supersymmetric dark-matter models implies the combination of their experimental studies with astrophysical and cosmological probes. The physics of the early Universe provides nontrivial effects of non-equilibrium particles and primordial cosmological structures. Primordial black holes (PBHs are a profound signature of such structures that may arise as a cosmological consequence of supersymmetric (SUSY models. SUSY-based mechanisms of baryosynthesis can lead to the possibility of antimatter domains in a baryon asymmetric Universe. In the context of cosmoparticle physics, which studies the fundamental relationship of the micro- and macro-worlds, the development of SUSY illustrates the main principles of this approach, as the physical basis of the modern cosmology provides cross-disciplinary tests in physical and astronomical studies.

  10. Higgs cosmology

    Science.gov (United States)

    Rajantie, Arttu

    2018-01-01

    The discovery of the Higgs boson in 2012 and other results from the Large Hadron Collider have confirmed the standard model of particle physics as the correct theory of elementary particles and their interactions up to energies of several TeV. Remarkably, the theory may even remain valid all the way to the Planck scale of quantum gravity, and therefore it provides a solid theoretical basis for describing the early Universe. Furthermore, the Higgs field itself has unique properties that may have allowed it to play a central role in the evolution of the Universe, from inflation to cosmological phase transitions and the origin of both baryonic and dark matter, and possibly to determine its ultimate fate through the electroweak vacuum instability. These connections between particle physics and cosmology have given rise to a new and growing field of Higgs cosmology, which promises to shed new light on some of the most puzzling questions about the Universe as new data from particle physics experiments and cosmological observations become available. This article is part of the Theo Murphy meeting issue `Higgs cosmology'.

  11. Constraining viscous dark energy models with the latest cosmological data

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Deng [Nankai University, Theoretical Physics Division, Chern Institute of Mathematics, Tianjin (China); Yan, Yang-Jie; Meng, Xin-He [Nankai University, Department of Physics, Tianjin (China)

    2017-10-15

    Based on the assumption that the dark energy possessing bulk viscosity is homogeneously and isotropically permeated in the universe, we propose three new viscous dark energy (VDE) models to characterize the accelerating universe. By constraining these three models with the latest cosmological observations, we find that they just deviate very slightly from the standard cosmological model and can alleviate effectively the current H{sub 0} tension between the local observation by the Hubble Space Telescope and the global measurement by the Planck Satellite. Interestingly, we conclude that a spatially flat universe in our VDE model with cosmic curvature is still supported by current data, and the scale invariant primordial power spectrum is strongly excluded at least at the 5.5σ confidence level in the three VDE models as the Planck result. We also give the 95% upper limits of the typical bulk viscosity parameter η in the three VDE scenarios. (orig.)

  12. What does cosmology tell us about particle physics beyond the Standard Model?

    Science.gov (United States)

    Komatsu, Eiichiro

    2012-07-01

    Cosmology demands particle physics beyond the Standard Model: we need to explain the nature of dark matter and dark energy, and the physics of cosmic inflation. Cosmology also provides the tightest upper bound on the sum of neutrino masses, and it seems only a matter of time before we measure the absolute mass of neutrinos, unveiling the neutrino mass hierarchy. It also provides a measurement of the number of relativistic species at the photon decoupling epoch (at which the temperature of the universe is 3000 K). Astronomy and Astrophysics Decadal Survey conducted by USA's National Academy of Sciences has identified these four topics (dark matter, dark energy, inflation and neutrinos) as the most important subjects to study in cosmology over the next decade. In this contribution, we review the current status on these topics, in light of the recent cosmological constraints.

  13. Quantum cosmology and late-time singularities

    International Nuclear Information System (INIS)

    Kamenshchik, A Yu

    2013-01-01

    The development of dark energy models has stimulated interest to cosmological singularities, which differ from the traditional Big Bang and Big Crunch singularities. We review a broad class of phenomena connected with soft cosmological singularities in classical and quantum cosmology. We discuss the classification of singularities from the geometrical point of view and from the point of view of the behavior of finite size objects, crossing such singularities. We discuss in some detail quantum and classical cosmology of models based on perfect fluids (anti-Chaplygin gas and anti-Chaplygin gas plus dust), of models based on the Born–Infeld-type fields and of the model of a scalar field with a potential inversely proportional to the field itself. We dwell also on the phenomenon of the phantom divide line crossing in the scalar field models with cusped potentials. Then we discuss the Friedmann equations modified by quantum corrections to the effective action of the models under considerations and the influence of such modification on the nature and the existence of soft singularities. We review also quantum cosmology of models, where the initial quantum state of the universe is presented by the density matrix (mixed state). Finally, we discuss the exotic singularities arising in the braneworld cosmological models. (topical review)

  14. Diagnosis and molecular characterization of non-classic forms of Tay-Sachs disease in Brazil.

    Science.gov (United States)

    Rozenberg, R; Kok, F; Burin, M G; Sá Miranda, M C; Vasques, C; Henriques-Souza, A M M; Giugliani, R; Vainzof, Mariz; Pereira, L V

    2006-06-01

    Molecular analysis of five Brazilian families, including eight patients presenting with nonclassic Tay-Sachs disease, was performed to identify frequent causative mutations and their correlation with clinical course. Three patients were affected by the B1 subacute variant and were shown to carry the R178H mutation (the DN allele), which is also common among Portuguese patients. Two of them were compound heterozygotes, whereas the third presented with the mutation in both alleles. Since Brazil was a Portuguese colony for over two centuries, common ancestry might be the probable explanation. The fourth patient presented with a juvenile phenotype and carries the R499H mutation, which has been reported only once worldwide and is associated with residual enzyme activity, responsible for a slower clinical course. The fifth family, of an Ashkenazi Jewish background, showed an extensive intrafamilial clinical variability among three affected sibs presenting with muscle atrophy, ataxia, and psychiatric symptoms. They were first diagnosed as having atypical spinal muscular atrophy and, subsequently, spinocerebellar ataxia, but, recently, the diagnosis of late-onset Tay-Sachs disease was confirmed based on reduced plasma hexosaminidase A activity and the G269S/InsTATC1278 genotype. It is therefore highly recommended to test patients with a similar clinical history for Tay-Sachs disease. In the same family, one first cousin committed suicide at the age of 24 years, presenting with a clinical phenotype that suggested an undiagnosed case and highlighting the effect of the intrafamilial clinical variability in delaying a prompt diagnosis. It is now recognized that his parents are, in fact, a carrier couple. Additionally, another relative had been previously identified as a heterozygote in a Tay-Sachs disease screening program, but the information was not shared among the family. Since this information might anticipate diagnosis and genetic counseling, it is advisable that

  15. Constraints on cosmological parameters in power-law cosmology

    International Nuclear Information System (INIS)

    Rani, Sarita; Singh, J.K.; Altaibayeva, A.; Myrzakulov, R.; Shahalam, M.

    2015-01-01

    In this paper, we examine observational constraints on the power law cosmology; essentially dependent on two parameters H 0 (Hubble constant) and q (deceleration parameter). We investigate the constraints on these parameters using the latest 28 points of H(z) data and 580 points of Union2.1 compilation data and, compare the results with the results of ΛCDM . We also forecast constraints using a simulated data set for the future JDEM, supernovae survey. Our studies give better insight into power law cosmology than the earlier done analysis by Kumar [arXiv:1109.6924] indicating it tuning well with Union2.1 compilation data but not with H(z) data. However, the constraints obtained on and i.e. H 0 average and q average using the simulated data set for the future JDEM, supernovae survey are found to be inconsistent with the values obtained from the H(z) and Union2.1 compilation data. We also perform the statefinder analysis and find that the power-law cosmological models approach the standard ΛCDM model as q → −1. Finally, we observe that although the power law cosmology explains several prominent features of evolution of the Universe, it fails in details

  16. Dynamic of exact perturbations in Bianchi IX type cosmological models

    International Nuclear Information System (INIS)

    Mello Neto, J.R.T. de.

    1985-01-01

    The dynamic of Bianchi IX type cosmological models is studied, after reducing Einstein equations to Hamiltonian system. Using the Melnikov method, the existence of chaos in the dynamic of these models is proved, and some numerical experiments are carried out. (M.C.K.) [pt

  17. Loop quantum cosmology of k=1 FRW models

    International Nuclear Information System (INIS)

    Ashtekar, Abhay; Pawlowski, Tomasz; Singh, Parampreet; Vandersloot, Kevin

    2007-01-01

    The closed, k=1, FRW model coupled to a massless scalar field is investigated in the framework of loop quantum cosmology using analytical and numerical methods. As in the k=0 case, the scalar field can be again used as emergent time to construct the physical Hilbert space and introduce Dirac observables. The resulting framework is then used to address a major challenge of quantum cosmology: resolving the big-bang singularity while retaining agreement with general relativity at large scales. It is shown that the framework fulfills this task. In particular, for states which are semiclassical at some late time, the big bang is replaced by a quantum bounce and a recollapse occurs at the value of the scale factor predicted by classical general relativity. Thus, the ''difficulties'' pointed out by Green and Unruh in the k=1 case do not arise in a more systematic treatment. As in k=0 models, quantum dynamics is deterministic across the deep Planck regime. However, because it also retains the classical recollapse, in contrast to the k=0 case one is now led to a cyclic model. Finally, we clarify some issues raised by Laguna's recent work addressed to computational physicists

  18. Choroidal Coloboma in a Case of Tay-Sachs Disease

    Directory of Open Access Journals (Sweden)

    Nasreen Raees Ahmed

    2014-01-01

    Full Text Available Coloboma as an ocular finding has been documented in various syndromes. Here we have a case of infantile Tay-Sachs disease associated with unilateral choroidal coloboma. To the best of our knowledge, such an association has not been documented in the literature. Whether such an association is a matter of chance or signifies the involvement of ganglioside metabolism in ocular embryogenesis remains to be elucidated.

  19. The cosmological model with a wormhole and Hawking temperature near apparent horizon

    Science.gov (United States)

    Kim, Sung-Won

    2018-05-01

    In this paper, a cosmological model with an isotropic form of the Morris-Thorne type wormhole was derived in a similar way to the McVittie solution to the black hole in the expanding universe. By solving Einstein's field equation with plausible matter distribution, we found the exact solution of the wormhole embedded in Friedmann-Lemaître-Robertson-Walker universe. We also found the apparent cosmological horizons from the redefined metric and analyzed the geometric natures, including causal and dynamic structures. The Hawking temperature for thermal radiation was obtained by the WKB approximation using the Hamilton-Jacobi equation and Hamilton's equation, near the apparent cosmological horizon.

  20. Possible evolution of a bouncing universe in cosmological models with non-minimally coupled scalar fields

    International Nuclear Information System (INIS)

    Pozdeeva, Ekaterina O.; Vernov, Sergey Yu.; Skugoreva, Maria A.; Toporensky, Alexey V.

    2016-01-01

    We explore dynamics of cosmological models with bounce solutions evolving on a spatially flat Friedmann-Lemaître-Robertson-Walker background. We consider cosmological models that contain the Hilbert-Einstein curvature term, the induced gravity term with a negative coupled constant, and even polynomial potentials of the scalar field. Bounce solutions with non-monotonic Hubble parameters have been obtained and analyzed. The case when the scalar field has the conformal coupling and the Higgs-like potential with an opposite sign is studied in detail. In this model the evolution of the Hubble parameter of the bounce solution essentially depends on the sign of the cosmological constant.

  1. KiDS-450: testing extensions to the standard cosmological model

    Science.gov (United States)

    Joudaki, Shahab; Mead, Alexander; Blake, Chris; Choi, Ami; de Jong, Jelte; Erben, Thomas; Fenech Conti, Ian; Herbonnet, Ricardo; Heymans, Catherine; Hildebrandt, Hendrik; Hoekstra, Henk; Joachimi, Benjamin; Klaes, Dominik; Köhlinger, Fabian; Kuijken, Konrad; McFarland, John; Miller, Lance; Schneider, Peter; Viola, Massimo

    2017-10-01

    We test extensions to the standard cosmological model with weak gravitational lensing tomography using 450 deg2 of imaging data from the Kilo Degree Survey (KiDS). In these extended cosmologies, which include massive neutrinos, non-zero curvature, evolving dark energy, modified gravity and running of the scalar spectral index, we also examine the discordance between KiDS and cosmic microwave background (CMB) measurements from Planck. The discordance between the two data sets is largely unaffected by a more conservative treatment of the lensing systematics and the removal of angular scales most sensitive to non-linear physics. The only extended cosmology that simultaneously alleviates the discordance with Planck and is at least moderately favoured by the data includes evolving dark energy with a time-dependent equation of state (in the form of the w0 - wa parametrization). In this model, the respective S_8=σ _8√{Ω m/0.3} constraints agree at the 1σ level, and there is 'substantial concordance' between the KiDS and Planck data sets when accounting for the full parameter space. Moreover, the Planck constraint on the Hubble constant is wider than in Λ cold dark matter (ΛCDM) and in agreement with the Riess et al. (2016) direct measurement of H0. The dark energy model is moderately favoured as compared to ΛCDM when combining the KiDS and Planck measurements, and marginalized constraints in the w0-wa plane are discrepant with a cosmological constant at the 3σ level. KiDS further constrains the sum of neutrino masses to 4.0 eV (95% CL), finds no preference for time or scale-dependent modifications to the metric potentials, and is consistent with flatness and no running of the spectral index.

  2. Cosmological model with viscosity media (dark fluid) described by an effective equation of state

    International Nuclear Information System (INIS)

    Ren Jie; Meng Xinhe

    2006-01-01

    A generally parameterized equation of state (EOS) is investigated in the cosmological evolution with bulk viscosity media modelled as dark fluid, which can be regarded as a unification of dark energy and dark matter. Compared with the case of the perfect fluid, this EOS has possessed four additional parameters, which can be interpreted as the case of the non-perfect fluid with time-dependent viscosity or the model with variable cosmological constant. From this general EOS, a completely integrable dynamical equation to the scale factor is obtained with its solution explicitly given out. (i) In this parameterized model of cosmology, for a special choice of the parameters we can explain the late-time accelerating expansion universe in a new view. The early inflation, the median (relatively late time) deceleration, and the recently cosmic acceleration may be unified in a single equation. (ii) A generalized relation of the Hubble parameter scaling with the redshift is obtained for some cosmology interests. (iii) By using the SNe Ia data to fit the effective viscosity model we show that the case of matter described by p=0 plus with effective viscosity contributions can fit the observational gold data in an acceptable level

  3. Splice junction mutation in some Ashkenazi Jews with Tay-Sachs disease: Evidence against a single defect within this ethnic group

    International Nuclear Information System (INIS)

    Myerowitz, R.

    1988-01-01

    Tay-Sachs disease is an inherited disorder in which the α chain of the lysosomal enzyme β-N-acetylhexosaminidase A bears the mutation. Ashkenazi Jews are found to be carriers for a severe type of Tay-Sachs disease, the classic form, 10 times more frequently than the general population. Ashkenazi Jewish patients with classic Tay-Sachs disease have appeared to be clinically and biochemically identical, and the usual assumption has been that they harbor the same α-chain mutation. The author has isolated the α-chain gene from an Ashkenazi Jewish patient, GM2968, with classic Tay-Sachs disease and compared its nucleotide sequences with that of the normal α-chain gene in the promoter region, exon and splice junction regions, and polyadenylylation signal area. Only one difference was observed between these sequences. The alteration is presumed to be functionally significant and to result in aberrant mRNA splicing. Utilizing the polymerase chain reaction to amplify the region encompassing the mutation, the author developed an assay to screen patients and heterozygote carriers for this mutation. Surprisingly, in each of two Ashkenazi patients, only one α-chain allele harbored the splice junction mutation. Only one parent of each of these patients was positive for the defect. Another Ashkenazi patient did not bear this mutation at all nor did either of the subject's parents. The data are consistent with the presence of more than one mutation underlying the classic form of Tay-Sachs disease in the Ashkenazi Jewish population

  4. A comparison of cosmological models using time delay lenses

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Jun-Jie; Wu, Xue-Feng; Melia, Fulvio, E-mail: jjwei@pmo.ac.cn, E-mail: xfwu@pmo.ac.cn, E-mail: fmelia@email.arizona.edu [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

    2014-06-20

    The use of time-delay gravitational lenses to examine the cosmological expansion introduces a new standard ruler with which to test theoretical models. The sample suitable for this kind of work now includes 12 lens systems, which have thus far been used solely for optimizing the parameters of ΛCDM. In this paper, we broaden the base of support for this new, important cosmic probe by using these observations to carry out a one-on-one comparison between competing models. The currently available sample indicates a likelihood of ∼70%-80% that the R {sub h} = ct universe is the correct cosmology versus ∼20%-30% for the standard model. This possibly interesting result reinforces the need to greatly expand the sample of time-delay lenses, e.g., with the successful implementation of the Dark Energy Survey, the VST ATLAS survey, and the Large Synoptic Survey Telescope. In anticipation of a greatly expanded catalog of time-delay lenses identified with these surveys, we have produced synthetic samples to estimate how large they would have to be in order to rule out either model at a ∼99.7% confidence level. We find that if the real cosmology is ΛCDM, a sample of ∼150 time-delay lenses would be sufficient to rule out R {sub h} = ct at this level of accuracy, while ∼1000 time-delay lenses would be required to rule out ΛCDM if the real universe is instead R {sub h} = ct. This difference in required sample size reflects the greater number of free parameters available to fit the data with ΛCDM.

  5. A comparison of cosmological models using time delay lenses

    International Nuclear Information System (INIS)

    Wei, Jun-Jie; Wu, Xue-Feng; Melia, Fulvio

    2014-01-01

    The use of time-delay gravitational lenses to examine the cosmological expansion introduces a new standard ruler with which to test theoretical models. The sample suitable for this kind of work now includes 12 lens systems, which have thus far been used solely for optimizing the parameters of ΛCDM. In this paper, we broaden the base of support for this new, important cosmic probe by using these observations to carry out a one-on-one comparison between competing models. The currently available sample indicates a likelihood of ∼70%-80% that the R h = ct universe is the correct cosmology versus ∼20%-30% for the standard model. This possibly interesting result reinforces the need to greatly expand the sample of time-delay lenses, e.g., with the successful implementation of the Dark Energy Survey, the VST ATLAS survey, and the Large Synoptic Survey Telescope. In anticipation of a greatly expanded catalog of time-delay lenses identified with these surveys, we have produced synthetic samples to estimate how large they would have to be in order to rule out either model at a ∼99.7% confidence level. We find that if the real cosmology is ΛCDM, a sample of ∼150 time-delay lenses would be sufficient to rule out R h = ct at this level of accuracy, while ∼1000 time-delay lenses would be required to rule out ΛCDM if the real universe is instead R h = ct. This difference in required sample size reflects the greater number of free parameters available to fit the data with ΛCDM.

  6. The cosmological term and a modified Brans-Dicke cosmology

    International Nuclear Information System (INIS)

    Endo, M.; Fukui, T.

    1977-01-01

    Adding the cosmological term Λ, which is assumed to be variable in this paper, to the Brans-Dicke Lagrangian, an attempt is made to understand the meaning of the term and to relate it to the mass of the universe. The Dirac large-number hypothesis is considered, applying the results obtained from the application of the present theory to a uniform cosmological model. (author)

  7. Friedmann-like cosmological models without singularity

    International Nuclear Information System (INIS)

    Kuchowicz, B.

    1978-01-01

    The Einstein-Cartan theory of gravitation ('general relativity with spin') provides a specific spin-spin contact interaction of matter, in addition to the usual long-range gravity. This new interaction enables us to prevent singularities in cosmological models. it is shown how this mechanism works in the case when the standard Einstein-Cartan equations are valid at a micro-physical level, and some spin-spin terms remain from the averaging procedure for randomly distributed spins. In contrast with the case of aligned spin distributions, it is possible to take over the isotropic and spatially homogeneous (i.e., Friedmannian) models into the Einstein-Cartan theory. These models can be made free from singularity, thanks to the self-interaction of spinning fluid. (author)

  8. Quantum Gravity and Cosmology: an intimate interplay

    Science.gov (United States)

    Sakellariadou, Mairi

    2017-08-01

    I will briefly discuss three cosmological models built upon three distinct quantum gravity proposals. I will first highlight the cosmological rôle of a vector field in the framework of a string/brane cosmological model. I will then present the resolution of the big bang singularity and the occurrence of an early era of accelerated expansion of a geometric origin, in the framework of group field theory condensate cosmology. I will then summarise results from an extended gravitational model based on non-commutative spectral geometry, a model that offers a purely geometric explanation for the standard model of particle physics.

  9. Improved standard cosmology: Comparison with observation

    International Nuclear Information System (INIS)

    Wesson, P.S.

    1982-01-01

    A cosmological model describing inhomogeneous clusters of galaxies embedded in a homogeneous background is compared to observation. In this model, a cluster is described as a spherically symmetric distribution of matter with an inverse-square density law and an isothermal equation of state, while the background universe is essentially the Einstein/de Sitter one of standard cosmology, but with a small pressure. The model is found to be in overall good agreement with observation, and its adjustable parameters are assigned numerical values. The equation of state for a cluster and the finite cosmological pressure are properties of the model which can in principle be investigated by carrying out observations. Subject headings: cosmology: galaxies: clusters of: relativity

  10. Kinematic tests of exotic flat cosmological models

    International Nuclear Information System (INIS)

    Charlton, J.C.; Turner, M.S.; NASA/Fermilab Astrophysics Center, Batavia, IL)

    1987-01-01

    Theoretical prejudice and inflationary models of the very early universe strongly favor the flat, Einstein-de Sitter model of the universe. At present the observational data conflict with this prejudice. This conflict can be resolved by considering flat models of the universe which posses a smooth component of energy density. The kinematics of such models, where the smooth component is relativistic particles, a cosmological term, a network of light strings, or fast-moving, light strings is studied in detail. The observational tests which can be used to discriminate between these models are also discussed. These tests include the magnitude-redshift, lookback time-redshift, angular size-redshift, and comoving volume-redshift diagrams and the growth of density fluctuations. 58 references

  11. Kinematic tests of exotic flat cosmological models

    International Nuclear Information System (INIS)

    Charlton, J.C.; Turner, M.S.

    1986-05-01

    Theoretical prejudice and inflationary models of the very early Universe strongly favor the flat, Einstein-deSitter model of the Universe. At present the observational data conflict with this prejudice. This conflict can be resolved by considering flat models of the Universe which possess a smooth component by energy density. We study in detail the kinematics of such models, where the smooth component is relativistic particles, a cosmological term, a network of light strings, or fast-moving, light strings. We also discuss the observational tests which can be used to discriminate between these models. These tests include the magnitude-redshift, lookback time-redshift, angular size-redshift, and comoving volume-redshift diagrams and the growth of density fluctuations

  12. Kinematic tests of exotic flat cosmological models

    Energy Technology Data Exchange (ETDEWEB)

    Charlton, J.C.; Turner, M.S.

    1986-05-01

    Theoretical prejudice and inflationary models of the very early Universe strongly favor the flat, Einstein-deSitter model of the Universe. At present the observational data conflict with this prejudice. This conflict can be resolved by considering flat models of the Universe which possess a smooth component by energy density. We study in detail the kinematics of such models, where the smooth component is relativistic particles, a cosmological term, a network of light strings, or fast-moving, light strings. We also discuss the observational tests which can be used to discriminate between these models. These tests include the magnitude-redshift, lookback time-redshift, angular size-redshift, and comoving volume-redshift diagrams and the growth of density fluctuations.

  13. Spectral action for Bianchi type-IX cosmological models

    International Nuclear Information System (INIS)

    Fan, Wentao; Fathizadeh, Farzad; Marcolli, Matilde

    2015-01-01

    A rationality result previously proved for Robertson-Walker metrics is extended to a homogeneous anisotropic cosmological model, namely the Bianchi type-IX minisuperspace. It is shown that the Seeley-de Witt coefficients appearing in the expansion of the spectral action for the Bianchi type-IX geometry are expressed in terms of polynomials with rational coefficients in the cosmic evolution factors w_1(t),w_2(t),w_3(t), and their higher derivates with respect to time. We begin with the computation of the Dirac operator of this geometry and calculate the coefficients a_0,a_2,a_4 of the spectral action by using heat kernel methods and parametric pseudodifferential calculus. An efficient method is devised for computing the Seeley-de Witt coefficients of a geometry by making use of Wodzicki’s noncommutative residue, and it is confirmed that the method checks out for the cosmological model studied in this article. The advantages of the new method are discussed, which combined with symmetries of the Bianchi type-IX metric, yield an elegant proof of the rationality result.

  14. Classical and quantum Big Brake cosmology for scalar field and tachyonic models

    Energy Technology Data Exchange (ETDEWEB)

    Kamenshchik, A. Yu. [Dipartimento di Fisica e Astronomia and INFN, Via Irnerio 46, 40126 Bologna (Italy) and L.D. Landau Institute for Theoretical Physics of the Russian Academy of Sciences, Kosygin str. 2, 119334 Moscow (Russian Federation); Manti, S. [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy)

    2013-02-21

    We study a relation between the cosmological singularities in classical and quantum theory, comparing the classical and quantum dynamics in some models possessing the Big Brake singularity - the model based on a scalar field and two models based on a tachyon-pseudo-tachyon field . It is shown that the effect of quantum avoidance is absent for the soft singularities of the Big Brake type while it is present for the Big Bang and Big Crunch singularities. Thus, there is some kind of a classical - quantum correspondence, because soft singularities are traversable in classical cosmology, while the strong Big Bang and Big Crunch singularities are not traversable.

  15. Classical and quantum Big Brake cosmology for scalar field and tachyonic models

    International Nuclear Information System (INIS)

    Kamenshchik, A. Yu.; Manti, S.

    2013-01-01

    We study a relation between the cosmological singularities in classical and quantum theory, comparing the classical and quantum dynamics in some models possessing the Big Brake singularity - the model based on a scalar field and two models based on a tachyon-pseudo-tachyon field . It is shown that the effect of quantum avoidance is absent for the soft singularities of the Big Brake type while it is present for the Big Bang and Big Crunch singularities. Thus, there is some kind of a classical - quantum correspondence, because soft singularities are traversable in classical cosmology, while the strong Big Bang and Big Crunch singularities are not traversable.

  16. General exact solution for homogeneous time-dependent self-gravitating perfect fluids

    International Nuclear Information System (INIS)

    Gaete, P.; Hojman, R.

    1988-01-01

    A procedure to obtain the general exact solution of Einstein equations for a self-gravitating spherically-symmetric static perfect fluid obeying an arbitrary equation of state, is applied to time-dependent Kantowsky-Sachs line elements (with spherical, planar and hyperbolic symmetry). As in the static case, the solution is generated by an arbitrary function of the independent variable and its first derivative. To illustrate the results, the whole family of (plane-symmetric) solutions with a ''gamma-law'' equation of state is explicity obtained in terms of simple known functions. It is also shown that, while in the static plane-symmtric line elements, every metric is in one to one correspondence with a ''partner-metric'' (both originated from the same generatrix function), in this case every generatrix function univocally determines one metric. (author) [pt

  17. Higgs cosmology.

    Science.gov (United States)

    Rajantie, Arttu

    2018-03-06

    The discovery of the Higgs boson in 2012 and other results from the Large Hadron Collider have confirmed the standard model of particle physics as the correct theory of elementary particles and their interactions up to energies of several TeV. Remarkably, the theory may even remain valid all the way to the Planck scale of quantum gravity, and therefore it provides a solid theoretical basis for describing the early Universe. Furthermore, the Higgs field itself has unique properties that may have allowed it to play a central role in the evolution of the Universe, from inflation to cosmological phase transitions and the origin of both baryonic and dark matter, and possibly to determine its ultimate fate through the electroweak vacuum instability. These connections between particle physics and cosmology have given rise to a new and growing field of Higgs cosmology, which promises to shed new light on some of the most puzzling questions about the Universe as new data from particle physics experiments and cosmological observations become available.This article is part of the Theo Murphy meeting issue 'Higgs cosmology'. © 2018 The Author(s).

  18. Cosmological effects of a class of fluid dark energy models

    International Nuclear Information System (INIS)

    Carturan, Daniela; Finelli, Fabio

    2003-01-01

    We study the impact of a generalized Chaplygin gas as a candidate for dark energy on density perturbations and on cosmic microwave background (CMB) anisotropies. The generalized Chaplygin gas is a fluid component with an exotic equation of state p=-A/ρ α (a polytropic gas with negative constant and exponent). Such a component interpolates in time between dust and a cosmological constant, with an intermediate behavior as p=A 1/(1+α) +αρ. Perturbations of this fluid are stable on small scales but behave in a very different way with respect to standard quintessence. Moreover, a generalized Chaplygin gas could also represent an archetypal example of the phenomenological unified models of dark energy and dark matter. The results presented here show how CMB anisotropies and density perturbations in this class of models differ from those of a cold dark matter model with a cosmological constant

  19. On globally static and stationary cosmologies with or without a cosmological constant and the dark energy problem

    International Nuclear Information System (INIS)

    Buchert, Thomas

    2006-01-01

    In the framework of spatially averaged inhomogeneous cosmologies in classical general relativity, effective Einstein equations govern the regional and the global dynamics of averaged scalar variables of cosmological models. A particular solution may be characterized by a cosmic equation of state. In this paper, it is pointed out that a globally static averaged dust model is conceivable without employing a compensating cosmological constant. Much in the spirit of Einstein's original model we discuss consequences for the global, but also for the regional properties of this cosmology. We then consider the wider class of globally stationary cosmologies that are conceivable in the presented framework. All these models are based on exact solutions of the averaged Einstein equations and provide examples of cosmologies in an out-of-equilibrium state, which we characterize by an information-theoretical measure. It is shown that such cosmologies preserve high-magnitude kinematical fluctuations and so tend to maintain their global properties. The same is true for a Λ-driven cosmos in such a state despite exponential expansion. We outline relations to inflationary scenarios and put the dark energy problem into perspective. Here, it is argued, on the grounds of the discussed cosmologies, that a classical explanation of dark energy through backreaction effects is theoretically conceivable, if the matter-dominated universe emerged from a non-perturbative state in the vicinity of the stationary solution. We also discuss a number of caveats that furnish strong counter arguments in the framework of structure formation in a perturbed Friedmannian model

  20. Parameterized post-Newtonian cosmology

    International Nuclear Information System (INIS)

    Sanghai, Viraj A A; Clifton, Timothy

    2017-01-01

    Einstein’s theory of gravity has been extensively tested on solar system scales, and for isolated astrophysical systems, using the perturbative framework known as the parameterized post-Newtonian (PPN) formalism. This framework is designed for use in the weak-field and slow-motion limit of gravity, and can be used to constrain a large class of metric theories of gravity with data collected from the aforementioned systems. Given the potential of future surveys to probe cosmological scales to high precision, it is a topic of much contemporary interest to construct a similar framework to link Einstein’s theory of gravity and its alternatives to observations on cosmological scales. Our approach to this problem is to adapt and extend the existing PPN formalism for use in cosmology. We derive a set of equations that use the same parameters to consistently model both weak fields and cosmology. This allows us to parameterize a large class of modified theories of gravity and dark energy models on cosmological scales, using just four functions of time. These four functions can be directly linked to the background expansion of the universe, first-order cosmological perturbations, and the weak-field limit of the theory. They also reduce to the standard PPN parameters on solar system scales. We illustrate how dark energy models and scalar-tensor and vector-tensor theories of gravity fit into this framework, which we refer to as ‘parameterized post-Newtonian cosmology’ (PPNC). (paper)

  1. Parameterized post-Newtonian cosmology

    Science.gov (United States)

    Sanghai, Viraj A. A.; Clifton, Timothy

    2017-03-01

    Einstein’s theory of gravity has been extensively tested on solar system scales, and for isolated astrophysical systems, using the perturbative framework known as the parameterized post-Newtonian (PPN) formalism. This framework is designed for use in the weak-field and slow-motion limit of gravity, and can be used to constrain a large class of metric theories of gravity with data collected from the aforementioned systems. Given the potential of future surveys to probe cosmological scales to high precision, it is a topic of much contemporary interest to construct a similar framework to link Einstein’s theory of gravity and its alternatives to observations on cosmological scales. Our approach to this problem is to adapt and extend the existing PPN formalism for use in cosmology. We derive a set of equations that use the same parameters to consistently model both weak fields and cosmology. This allows us to parameterize a large class of modified theories of gravity and dark energy models on cosmological scales, using just four functions of time. These four functions can be directly linked to the background expansion of the universe, first-order cosmological perturbations, and the weak-field limit of the theory. They also reduce to the standard PPN parameters on solar system scales. We illustrate how dark energy models and scalar-tensor and vector-tensor theories of gravity fit into this framework, which we refer to as ‘parameterized post-Newtonian cosmology’ (PPNC).

  2. Physical and Relativistic Numerical Cosmology.

    Science.gov (United States)

    Anninos, Peter

    1998-01-01

    In order to account for the observable Universe, any comprehensive theory or model of cosmology must draw from many disciplines of physics, including gauge theories of strong and weak interactions, the hydrodynamics and microphysics of baryonic matter, electromagnetic fields, and spacetime curvature, for example. Although it is difficult to incorporate all these physical elements into a single complete model of our Universe, advances in computing methods and technologies have contributed significantly towards our understanding of cosmological models, the Universe, and astrophysical processes within them. A sample of numerical calculations addressing specific issues in cosmology are reviewed in this article: from the Big Bang singularity dynamics to the fundamental interactions of gravitational waves; from the quark-hadron phase transition to the large scale structure of the Universe. The emphasis, although not exclusively, is on those calculations designed to test different models of cosmology against the observed Universe.

  3. Physical and Relativistic Numerical Cosmology

    Directory of Open Access Journals (Sweden)

    Peter Anninos

    1998-01-01

    Full Text Available In order to account for the observable Universe, any comprehensive theory or model of cosmology must draw from many disciplines of physics, including gauge theories of strong and weak interactions, the hydrodynamics and microphysics of baryonic matter, electromagnetic fields, and spacetime curvature, for example. Although it is difficult to incorporate all these physical elements into a single complete model of our Universe, advances in computing methods and technologies have contributed significantly towards our understanding of cosmological models, the Universe, and astrophysical processes within them. A sample of numerical calculations addressing specific issues in cosmology are reviewed in this article: from the Big Bang singularity dynamics to the fundamental interactions of gravitational waves; from the quark--hadron phase transition to the large scale structure of the Universe. The emphasis, although not exclusively, is on those calculations designed to test different models of cosmology against the observed Universe.

  4. Projective relativity, cosmology and gravitation

    International Nuclear Information System (INIS)

    Arcidiacono, G.

    1986-01-01

    This book describes the latest applications of projective geometry to cosmology and gravitation. The contents of the book are; the Poincare group and Special Relativity, the thermodynamics and electromagnetism, general relativity, gravitation and cosmology, group theory and models of universe, the special projective relativity, the Fantappie group and Big-Bang cosmology, a new cosmological projective mechanics, the plasma physics and cosmology, the projective magnetohydrodynamics field, projective relativity and waves propagation, the generalizations of the gravitational field, the general projective relativity, the projective gravitational field, the De Sitter Universe and quantum physics, the conformal relativity and Newton gravitation

  5. Observational cosmology

    International Nuclear Information System (INIS)

    Partridge, R.B.

    1977-01-01

    Some sixty years after the development of relativistic cosmology by Einstein and his colleagues, observations are finally beginning to have an important impact on our views of the Universe. The available evidence seems to support one of the simplest cosmological models, the hot Big Bang model. The aim of this paper is to assess the observational support for certain assumptions underlying the hot Big Bang model. These are that the Universe is isobaric and homogeneous on a large scale; that it is expanding from an initial state of high density and temperature; and that the proper theory to describe the dynamics of the Universe is unmodified General Relativity. The properties of the cosmic microwave background radiation and recent observations of the abundance of light elements, in particular, support these assumptions. Also examined here are the data bearing on the related questions of the geometry and the future of the Universe (is it ever-expanding, or fated to recollapse). Finally, some difficulties and faults of the standard model are discussed, particularly various aspects of the 'initial condition' problem. It appears that the simplest Big Bang cosmological model calls for a highly specific set of initial conditions to produce the presently observed properties of the Universe. (Auth.)

  6. Experimentally testing the standard cosmological model

    Energy Technology Data Exchange (ETDEWEB)

    Schramm, D.N. (Chicago Univ., IL (USA) Fermi National Accelerator Lab., Batavia, IL (USA))

    1990-11-01

    The standard model of cosmology, the big bang, is now being tested and confirmed to remarkable accuracy. Recent high precision measurements relate to the microwave background; and big bang nucleosynthesis. This paper focuses on the latter since that relates more directly to high energy experiments. In particular, the recent LEP (and SLC) results on the number of neutrinos are discussed as a positive laboratory test of the standard cosmology scenario. Discussion is presented on the improved light element observational data as well as the improved neutron lifetime data. alternate nucleosynthesis scenarios of decaying matter or of quark-hadron induced inhomogeneities are discussed. It is shown that when these scenarios are made to fit the observed abundances accurately, the resulting conclusions on the baryonic density relative to the critical density, {Omega}{sub b}, remain approximately the same as in the standard homogeneous case, thus, adding to the robustness of the standard model conclusion that {Omega}{sub b} {approximately} 0.06. This latter point is the deriving force behind the need for non-baryonic dark matter (assuming {Omega}{sub total} = 1) and the need for dark baryonic matter, since {Omega}{sub visible} < {Omega}{sub b}. Recent accelerator constraints on non-baryonic matter are discussed, showing that any massive cold dark matter candidate must now have a mass M{sub x} {approx gt} 20 GeV and an interaction weaker than the Z{sup 0} coupling to a neutrino. It is also noted that recent hints regarding the solar neutrino experiments coupled with the see-saw model for {nu}-masses may imply that the {nu}{sub {tau}} is a good hot dark matter candidate. 73 refs., 5 figs.

  7. Experimentally testing the standard cosmological model

    International Nuclear Information System (INIS)

    Schramm, D.N.

    1990-11-01

    The standard model of cosmology, the big bang, is now being tested and confirmed to remarkable accuracy. Recent high precision measurements relate to the microwave background; and big bang nucleosynthesis. This paper focuses on the latter since that relates more directly to high energy experiments. In particular, the recent LEP (and SLC) results on the number of neutrinos are discussed as a positive laboratory test of the standard cosmology scenario. Discussion is presented on the improved light element observational data as well as the improved neutron lifetime data. alternate nucleosynthesis scenarios of decaying matter or of quark-hadron induced inhomogeneities are discussed. It is shown that when these scenarios are made to fit the observed abundances accurately, the resulting conclusions on the baryonic density relative to the critical density, Ω b , remain approximately the same as in the standard homogeneous case, thus, adding to the robustness of the standard model conclusion that Ω b ∼ 0.06. This latter point is the deriving force behind the need for non-baryonic dark matter (assuming Ω total = 1) and the need for dark baryonic matter, since Ω visible b . Recent accelerator constraints on non-baryonic matter are discussed, showing that any massive cold dark matter candidate must now have a mass M x approx-gt 20 GeV and an interaction weaker than the Z 0 coupling to a neutrino. It is also noted that recent hints regarding the solar neutrino experiments coupled with the see-saw model for ν-masses may imply that the ν τ is a good hot dark matter candidate. 73 refs., 5 figs

  8. Cosmological dynamical systems

    CERN Document Server

    Leon, Genly

    2011-01-01

    In this book are studied, from the perspective of the dynamical systems, several Universe models. In chapter 1 we give a bird's eye view on cosmology and cosmological problems. Chapter 2 is devoted to a brief review on some results and useful tools from the qualitative theory of dynamical systems. They provide the theoretical basis for the qualitative study of concrete cosmological models. Chapters 1 and 2 are a review of well-known results. Chapters 3, 4, 5 and 6 are devoted to our main results. In these chapters are extended and settled in a substantially different, more strict mathematical language, several results obtained by one of us in arXiv:0812.1013 [gr-qc]; arXiv:1009.0689 [gr-qc]; arXiv:0904.1577[gr-qc]; and arXiv:0909.3571 [hep-th]. In chapter 6, we provide a different approach to the subject discussed in astro-ph/0503478. Additionally, we perform a Poincar\\'e compactification process allowing to construct a global phase space containing all the cosmological information in both finite and infinite...

  9. Dynamics and phenomenology of higher order gravity cosmological models

    Science.gov (United States)

    Moldenhauer, Jacob Andrew

    2010-10-01

    I present here some new results about a systematic approach to higher-order gravity (HOG) cosmological models. The HOG models are derived from curvature invariants that are more general than the Einstein-Hilbert action. Some of the models exhibit late-time cosmic acceleration without the need for dark energy and fit some current observations. The open question is that there are an infinite number of invariants that one could select, and many of the published papers have stressed the need to find a systematic approach that will allow one to study methodically the various possibilities. We explore a new connection that we made between theorems from the theory of invariants in general relativity and these cosmological models. In summary, the theorems demonstrate that curvature invariants are not all independent from each other and that for a given Ricci Segre type and Petrov type (symmetry classification) of the space-time, there exists a complete minimal set of independent invariants (a basis) in terms of which all the other invariants can be expressed. As an immediate consequence of the proposed approach, the number of invariants to consider is dramatically reduced from infinity to four invariants in the worst case and to only two invariants in the cases of interest, including all Friedmann-Lemaitre-Robertson-Walker metrics. We derive models that pass stability and physical acceptability conditions. We derive dynamical equations and phase portrait analyses that show the promise of the systematic approach. We consider observational constraints from magnitude-redshift Supernovae Type Ia data, distance to the last scattering surface of the Cosmic Microwave Background radiation, and Baryon Acoustic Oscillations. We put observational constraints on general HOG models. We constrain different forms of the Gauss-Bonnet, f(G), modified gravity models with these observations. We show some of these models pass solar system tests. We seek to find models that pass physical and

  10. Relic gravitons and viscous cosmologies

    International Nuclear Information System (INIS)

    Cataldo, Mauricio; Mella, Patricio

    2006-01-01

    Previously it was shown that there exists a class of viscous cosmological models which violate the dominant energy condition for a limited amount of time after which they are smoothly connected to the ordinary radiation era (which preserves the dominant energy conditions). This violation of the dominant energy condition at an early cosmological epoch may influence the slopes of energy spectra of relic gravitons that might be of experimental relevance. However, the bulk viscosity coefficient of these cosmologies became negative during the ordinary radiation era, and then the entropy of the sources driving the geometry decreases with time. We show that in the presence of viscous sources with a linear barotropic equation of state p=γρ we get viscous cosmological models with positive bulk viscous stress during all their evolution, and hence the matter entropy increases with the expansion time. In other words, in the framework of viscous cosmologies, there exist isotropic models compatible with the standard second law of thermodynamics which also may influence the slopes of energy spectra of relic gravitons

  11. The Bright Universe Cosmology

    International Nuclear Information System (INIS)

    Surdin, M.

    1980-01-01

    It is shown that viewed from the 'outside', our universe is a black hole. Hence the 'inside' cosmology considered is termed as the Bright Universe Cosmology. The model proposed avoids the singularities of cosmologies of the Big Bang variety, it gives a good account of the redshifts, the cosmic background radiation, the number counts; it also gives a satisfactory explanation of the 'large numbers coincidence' and of the variation in time of fundamental constants. (Auth.)

  12. Splice junction mutation in some Ashkenazi Jews with Tay-Sachs disease: Evidence against a single defect within this ethnic group

    Energy Technology Data Exchange (ETDEWEB)

    Myerowitz, R. (National Institute of Diabetes, Digestive and Kidney Diseases, Bethesda, MD (USA))

    1988-06-01

    Tay-Sachs disease is an inherited disorder in which the {alpha} chain of the lysosomal enzyme {beta}-N-acetylhexosaminidase A bears the mutation. Ashkenazi Jews are found to be carriers for a severe type of Tay-Sachs disease, the classic form, 10 times more frequently than the general population. Ashkenazi Jewish patients with classic Tay-Sachs disease have appeared to be clinically and biochemically identical, and the usual assumption has been that they harbor the same {alpha}-chain mutation. The author has isolated the {alpha}-chain gene from an Ashkenazi Jewish patient, GM2968, with classic Tay-Sachs disease and compared its nucleotide sequences with that of the normal {alpha}-chain gene in the promoter region, exon and splice junction regions, and polyadenylylation signal area. Only one difference was observed between these sequences. The alteration is presumed to be functionally significant and to result in aberrant mRNA splicing. Utilizing the polymerase chain reaction to amplify the region encompassing the mutation, the author developed an assay to screen patients and heterozygote carriers for this mutation. Surprisingly, in each of two Ashkenazi patients, only one {alpha}-chain allele harbored the splice junction mutation. Only one parent of each of these patients was positive for the defect. Another Ashkenazi patient did not bear this mutation at all nor did either of the subject's parents. The data are consistent with the presence of more than one mutation underlying the classic form of Tay-Sachs disease in the Ashkenazi Jewish population.

  13. Role of the physician in screening for carriers of Tay-Sachs disease.

    Science.gov (United States)

    Lowden, J. A.

    1978-01-01

    A screening test for carriers of Tay-Sachs disease has been available in Toronto for more than 6 years. In that time more than 11 000 Jewish residents have been tested. Most had requested testing after hearing about the screening program from friends or the media; few had been advised by their physicians to be tested. To sample the attitudes of physicians in Toronto towards carrier screening, we studied questionnaire responses of 42 physicians whose practices were composed largely of Jewish patients. Only 31% regularly advised their young adult Jewish patients to have a carrier screening test but 76% said they had patients who asked if they should be tested. Of the 14 (33%) who had had one or more patients with Tay-Sachs disease 6 did not advise carrier testing. There was a positive correlation between specialty training and support for the screening program. Methods for increasing physician advocacy of these programs are discussed. PMID:709448

  14. Cosmology and the early universe

    CERN Document Server

    Di Bari, Pasquale

    2018-01-01

    This book discusses cosmology from both an observational and a strong theoretical perspective. The first part focuses on gravitation, notably the expansion of the universe and determination of cosmological parameters, before moving onto the main emphasis of the book, the physics of the early universe, and the connections between cosmological models and particle physics. Readers will gain a comprehensive account of cosmology and the latest observational results, without requiring prior knowledge of relativistic theories, making the text ideal for students.

  15. Cosmological tests of modified gravity.

    Science.gov (United States)

    Koyama, Kazuya

    2016-04-01

    We review recent progress in the construction of modified gravity models as alternatives to dark energy as well as the development of cosmological tests of gravity. Einstein's theory of general relativity (GR) has been tested accurately within the local universe i.e. the Solar System, but this leaves the possibility open that it is not a good description of gravity at the largest scales in the Universe. This being said, the standard model of cosmology assumes GR on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. In this review, we first give an overview of recent developments in modified gravity theories including f(R) gravity, braneworld gravity, Horndeski theory and massive/bigravity theory. We then focus on common properties these models share, such as screening mechanisms they use to evade the stringent Solar System tests. Once armed with a theoretical knowledge of modified gravity models, we move on to discuss how we can test modifications of gravity on cosmological scales. We present tests of gravity using linear cosmological perturbations and review the latest constraints on deviations from the standard [Formula: see text]CDM model. Since screening mechanisms leave distinct signatures in the non-linear structure formation, we also review novel astrophysical tests of gravity using clusters, dwarf galaxies and stars. The last decade has seen a number of new constraints placed on gravity from astrophysical to cosmological scales. Thanks to on-going and future surveys, cosmological tests of gravity will enjoy another, possibly even more, exciting ten years.

  16. Model-independent cosmological constraints from growth and expansion

    Science.gov (United States)

    L'Huillier, Benjamin; Shafieloo, Arman; Kim, Hyungjin

    2018-05-01

    Reconstructing the expansion history of the Universe from Type Ia supernovae data, we fit the growth rate measurements and put model-independent constraints on some key cosmological parameters, namely, Ωm, γ, and σ8. The constraints are consistent with those from the concordance model within the framework of general relativity, but the current quality of the data is not sufficient to rule out modified gravity models. Adding the condition that dark energy density should be positive at all redshifts, independently of its equation of state, further constrains the parameters and interestingly supports the concordance model.

  17. Anisotropic, nonsingular early universe model leading to a realistic cosmology

    International Nuclear Information System (INIS)

    Dechant, Pierre-Philippe; Lasenby, Anthony N.; Hobson, Michael P.

    2009-01-01

    We present a novel cosmological model in which scalar field matter in a biaxial Bianchi IX geometry leads to a nonsingular 'pancaking' solution: the hypersurface volume goes to zero instantaneously at the 'big bang', but all physical quantities, such as curvature invariants and the matter energy density remain finite, and continue smoothly through the big bang. We demonstrate that there exist geodesics extending through the big bang, but that there are also incomplete geodesics that spiral infinitely around a topologically closed spatial dimension at the big bang, rendering it, at worst, a quasiregular singularity. The model is thus reminiscent of the Taub-NUT vacuum solution in that it has biaxial Bianchi IX geometry and its evolution exhibits a dimensionality reduction at a quasiregular singularity; the two models are, however, rather different, as we will show in a future work. Here we concentrate on the cosmological implications of our model and show how the scalar field drives both isotropization and inflation, thus raising the question of whether structure on the largest scales was laid down at a time when the universe was still oblate (as also suggested by [T. S. Pereira, C. Pitrou, and J.-P. Uzan, J. Cosmol. Astropart. Phys. 9 (2007) 6.][C. Pitrou, T. S. Pereira, and J.-P. Uzan, J. Cosmol. Astropart. Phys. 4 (2008) 4.][A. Guemruekcueoglu, C. Contaldi, and M. Peloso, J. Cosmol. Astropart. Phys. 11 (2007) 005.]). We also discuss the stability of our model to small perturbations around biaxiality and draw an analogy with cosmological perturbations. We conclude by presenting a separate, bouncing solution, which generalizes the known bouncing solution in closed FRW universes.

  18. Instabilities in dark coupled models and constraints from cosmological data

    CERN Document Server

    Honorez, L Lopez

    2010-01-01

    Coupled dark matter-dark energy systems can suffer from non-adiabatic instabilities at early times and large scales. In these proceedings, we consider two parameterizations of the dark sector interaction. In the first one the energy-momentum transfer 4-vector is parallel to the dark matter 4-velocity and in the second one to the dark energy 4-velocity. In these cases, coupled models which suffer from non-adiabatic instabilities can be identified as a function of a generic coupling Q and of the dark energy equation of state. In our analysis, we do not refer to any particular cosmic field. We confront then a viable class of models in which the interaction is directly proportional to the dark energy density and to the Hubble rate parameter to recent cosmological data. In that framework, we show that correlations between the dark coupling and several cosmological parameters allow for a larger neutrino mass than in uncoupled models.

  19. Crucial test of the Dirac cosmologies

    International Nuclear Information System (INIS)

    Steigman, G.

    1978-01-01

    In a cosmology consistent with the Cosmological Principle (large scale, statistical isotropy and homogeneity of the universe), a Planck spectrum is not preserved as the universe evolves unless the number of photons in a comoving volume is conserved. It is shown that a large class of cosmological models based on Dirac's Large Numbers Hypothesis (LNH) violate this constraint. The observed isotropy and spectral distribution of the microwave background radiation thus provide a crucial test of such cosmologies. After reviewing the LNH, the general evolution of radiation spectra in cosmologies consistent with the cosmological principle is outlined. It is shown that the predicted deviations from a Planck spectrum for Dirac cosmologies (as well as for ''tired-light'' cosmologies) are enormous. The Planckian (or near-Planckian) spectral form for the microwave radiation provides a crucial test, failed by such cosmologies

  20. Axions in inflationary cosmology

    International Nuclear Information System (INIS)

    Linde, A.

    1991-01-01

    The problem of the cosmological constraints on the axion mass is re-examined. It is argued that in the context of inflationary cosmology the constraint m a > or approx.10 -5 eV can be avoided even when the axion perturbations produced during inflation are taken into account. It is shown also that in most axion models the effective parameter f a rapidly changes during inflation. This modifies some earlier statements concerning isothermal perturbations in the axion cosmology. A hybrid inflation scenario is proposed which combines some advantages of chaotic inflation with specific features of new and/or extended inflation. Its implications for the axion cosmology are discussed. (orig.)

  1. Solitons in relativistic cosmologies

    International Nuclear Information System (INIS)

    Pullin, J.

    1988-08-01

    The application to the construction of solitonic cosmologies in General Relativity of the Inverse Scattering Technique of Belinskii an Zakharov is analyzed. Three improvements to the mentioned technique are proposed: the inclusion of higher order poles in the scattering matrix, a new renormalization technique for diagonal metrics and the extension of the technique to include backgrounds with material content by means of a Kaluza-Klein formalism. As a consequence of these improvements, three new aspects can be analyzed: a) The construction of anisotropic and inhomogeneous cosmological models which can mimic the formation of halos and voids, due to the presence of a material content. The new renormalization technique allows to construct an exact perturbation theory. b) The analysis of the dynamics of models with cosmological constant (inflationary models) and their perturbations. c) The study of interaction of gravitational solitonic waves on material backgrounds. Moreover, some additional works, connected with the existance of 'Crack of doom' type singularities in Kaluza-Klein cosmologies, stochastic perturbations in inflationary universes and inflationary phase transitions in rotating universes are described. (Author) [es

  2. Black Hole Entropy from Bondi-Metzner-Sachs Symmetry at the Horizon.

    Science.gov (United States)

    Carlip, S

    2018-03-09

    Near the horizon, the obvious symmetries of a black hole spacetime-the horizon-preserving diffeomorphisms-are enhanced to a larger symmetry group with a three-dimensional Bondi-Metzner-Sachs algebra. Using dimensional reduction and covariant phase space techniques, I investigate this augmented symmetry and show that it is strong enough to determine the black hole entropy in any dimension.

  3. Cosmological constant--the weight of the vacuum

    International Nuclear Information System (INIS)

    Padmanabhan, T.

    2003-01-01

    Recent cosmological observations suggest the existence of a positive cosmological constant Λ with the magnitude Λ(Gℎ/c 3 )∼10 -123 . This review discusses several aspects of the cosmological constant both from the cosmological (Sections 1-6) and field theoretical (Sections 7-11) perspectives. After a brief introduction to the key issues related to cosmological constant and a historical overview, a summary of the kinematics and dynamics of the standard Friedmann model of the universe is provided. The observational evidence for cosmological constant, especially from the supernova results, and the constraints from the age of the universe, structure formation, Cosmic Microwave Background Radiation (CMBR) anisotropies and a few others are described in detail, followed by a discussion of the theoretical models (quintessence, tachyonic scalar field, ...) from different perspectives. The latter part of the review (Sections 7-11) concentrates on more conceptual and fundamental aspects of the cosmological constant like some alternative interpretations of the cosmological constant, relaxation mechanisms to reduce the cosmological constant to the currently observed value, the geometrical structure of the de Sitter spacetime, thermodynamics of the de Sitter universe and the role of string theory in the cosmological constant problem

  4. Particle cosmology

    CERN Multimedia

    CERN. Geneva

    2007-01-01

    The understanding of the Universe at the largest and smallest scales traditionally has been the subject of cosmology and particle physics, respectively. Studying the evolution of the Universe connects today's large scales with the tiny scales in the very early Universe and provides the link between the physics of particles and of the cosmos. This series of five lectures aims at a modern and critical presentation of the basic ideas, methods, models and observations in today's particle cosmology.

  5. Inextendibility of expanding cosmological models with symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Dafermos, Mihalis [University of Cambridge, Department of Pure Mathematics and Mathematical Statistics, Wilberforce Road, Cambridge CB3 0WB (United Kingdom); Rendall, Alan D [Max Planck Institute for Gravitational Physics, Albert Einstein Institute, Am Muehlenberg 1, D-14476 Golm (Germany)

    2005-12-07

    A new criterion for inextendibility of expanding cosmological models with symmetry is presented. It is applied to derive a number of new results and to simplify the proofs of existing ones. In particular, it shows that the solutions of the Einstein-Vlasov system with T{sup 2} symmetry, including the vacuum solutions, are inextendible in the future. The technique introduced adds a qualitatively new element to the available tool-kit for studying strong cosmic censorship. (letter to the editor)

  6. The Case for a Hierarchical Cosmology

    Science.gov (United States)

    Vaucouleurs, G. de

    1970-01-01

    The development of modern theoretical cosmology is presented and some questionable assumptions of orthodox cosmology are pointed out. Suggests that recent observations indicate that hierarchical clustering is a basic factor in cosmology. The implications of hierarchical models of the universe are considered. Bibliography. (LC)

  7. Spectral action for Bianchi type-IX cosmological models

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Wentao; Fathizadeh, Farzad; Marcolli, Matilde [Division of Physics, Mathematics and Astronomy, California Institute of Technology,1200 E. California Blvd., Pasadena, CA 91125 (United States)

    2015-10-13

    A rationality result previously proved for Robertson-Walker metrics is extended to a homogeneous anisotropic cosmological model, namely the Bianchi type-IX minisuperspace. It is shown that the Seeley-de Witt coefficients appearing in the expansion of the spectral action for the Bianchi type-IX geometry are expressed in terms of polynomials with rational coefficients in the cosmic evolution factors w{sub 1}(t),w{sub 2}(t),w{sub 3}(t), and their higher derivates with respect to time. We begin with the computation of the Dirac operator of this geometry and calculate the coefficients a{sub 0},a{sub 2},a{sub 4} of the spectral action by using heat kernel methods and parametric pseudodifferential calculus. An efficient method is devised for computing the Seeley-de Witt coefficients of a geometry by making use of Wodzicki’s noncommutative residue, and it is confirmed that the method checks out for the cosmological model studied in this article. The advantages of the new method are discussed, which combined with symmetries of the Bianchi type-IX metric, yield an elegant proof of the rationality result.

  8. Bianchi type-V cosmological models with perfect fluid and heat flow ...

    Indian Academy of Sciences (India)

    In the cosmology with the power-law, the solutions correspond to a cos- mological model .... where ρ is the energy density, p is the thermodynamic pressure, uµ is the four- velocity of the fluid and ..... In the first category of models, the. Universe ...

  9. Late-onset Tay-Sachs disease: adverse effects of medications and implications for treatment.

    Science.gov (United States)

    Shapiro, B E; Hatters-Friedman, S; Fernandes-Filho, J A; Anthony, K; Natowicz, M R

    2006-09-12

    The authors conducted a retrospective and brief prospective study of adverse effects of approximately 350 medications in 44 adults with late-onset Tay-Sachs disease (LOTS). Some medications were relatively safe, whereas others, particularly haloperidol, risperidone, and chlorpromazine, were associated with neurologic worsening.

  10. Cosmological backreaction within the Szekeres model and emergence of spatial curvature

    Energy Technology Data Exchange (ETDEWEB)

    Bolejko, Krzysztof, E-mail: krzysztof.bolejko@sydney.edu.au [Sydney Institute for Astronomy, School of Physics A28, The University of Sydney, Sydney, NSW, 2006 (Australia)

    2017-06-01

    This paper discusses the phenomenon of backreaction within the Szekeres model. Cosmological backreaction describes how the mean global evolution of the Universe deviates from the Friedmannian evolution. The analysis is based on models of a single cosmological environment and the global ensemble of the Szekeres models (of the Swiss-Cheese-type and Styrofoam-type). The obtained results show that non-linear growth of cosmic structures is associated with the growth of the spatial curvature Ω{sub R} (in the FLRW limit Ω{sub R} → Ω {sub k} ). If averaged over global scales the result depends on the assumed global model of the Universe. Within the Swiss-Cheese model, which does have a fixed background, the volume average follows the evolution of the background, and the global spatial curvature averages out to zero (the background model is the ΛCDM model, which is spatially flat). In the Styrofoam-type model, which does not have a fixed background, the mean evolution deviates from the spatially flat ΛCDM model, and the mean spatial curvature evolves from Ω{sub R} =0 at the CMB to Ω{sub R} ∼ 0.1 at 0 z =. If the Styrofoam-type model correctly captures evolutionary features of the real Universe then one should expect that in our Universe, the spatial curvature should build up (local growth of cosmic structures) and its mean global average should deviate from zero (backreaction). As a result, this paper predicts that the low-redshift Universe should not be spatially flat (i.e. Ω {sub k} ≠ 0, even if in the early Universe Ω {sub k} = 0) and therefore when analysing low- z cosmological data one should keep Ω {sub k} as a free parameter and independent from the CMB constraints.

  11. Renormalization group approach to causal bulk viscous cosmological models

    International Nuclear Information System (INIS)

    Belinchon, J A; Harko, T; Mak, M K

    2002-01-01

    The renormalization group method is applied to the study of homogeneous and flat Friedmann-Robertson-Walker type universes, filled with a causal bulk viscous cosmological fluid. The starting point of the study is the consideration of the scaling properties of the gravitational field equations, the causal evolution equation of the bulk viscous pressure and the equations of state. The requirement of scale invariance imposes strong constraints on the temporal evolution of the bulk viscosity coefficient, temperature and relaxation time, thus leading to the possibility of obtaining the bulk viscosity coefficient-energy density dependence. For a cosmological model with bulk viscosity coefficient proportional to the Hubble parameter, we perform the analysis of the renormalization group flow around the scale-invariant fixed point, thereby obtaining the long-time behaviour of the scale factor

  12. A new cosmological paradigm: the cosmological constant and dark matter

    International Nuclear Information System (INIS)

    Krauss, L.M.

    1998-01-01

    The Standard Cosmological Model of the 1980 close-quote s is no more. I describe the definitive evidence that the density of matter is insufficient to result in a flat universe, as well as the mounting evidence that the cosmological constant is not zero. I finally discuss the implications of these results for particle physics and direct searches for non-baryonic dark matter. copyright 1998 American Institute of Physics

  13. Cosmological-model-parameter determination from satellite-acquired type Ia and IIP Supernova Data

    International Nuclear Information System (INIS)

    Podariu, Silviu; Nugent, Peter; Ratra, Bharat

    2000-01-01

    We examine the constraints that satellite-acquired Type Ia and IIP supernova apparent magnitude versus redshift data will place on cosmological model parameters in models with and without a constant or time-variable cosmological constant lambda. High-quality data which could be acquired in the near future will result in tight constraints on these parameters. For example, if all other parameters of a spatially-flat model with a constant lambda are known, the supernova data should constrain the non-relativistic matter density parameter omega to better than 1 (2, 0.5) at 1 sigma with neutral (worst case, best case) assumptions about data quality

  14. Simple cosmological model with inflation and late times acceleration

    Science.gov (United States)

    Szydłowski, Marek; Stachowski, Aleksander

    2018-03-01

    In the framework of polynomial Palatini cosmology, we investigate a simple cosmological homogeneous and isotropic model with matter in the Einstein frame. We show that in this model during cosmic evolution, early inflation appears and the accelerating phase of the expansion for the late times. In this frame we obtain the Friedmann equation with matter and dark energy in the form of a scalar field with a potential whose form is determined in a covariant way by the Ricci scalar of the FRW metric. The energy density of matter and dark energy are also parameterized through the Ricci scalar. Early inflation is obtained only for an infinitesimally small fraction of energy density of matter. Between the matter and dark energy, there exists an interaction because the dark energy is decaying. For the characterization of inflation we calculate the slow roll parameters and the constant roll parameter in terms of the Ricci scalar. We have found a characteristic behavior of the time dependence of density of dark energy on the cosmic time following the logistic-like curve which interpolates two almost constant value phases. From the required numbers of N-folds we have found a bound on the model parameter.

  15. Temporary Efficacy of Pyrimethamine in Juvenile-Onset Tay-Sachs Disease Caused by 2 Unreported HEXA Mutations in the Indian Population.

    Science.gov (United States)

    Udwadia-Hegde, Anaita; Hajirnis, Omkar

    2017-01-01

    Juvenile Tay-Sachs disease is rarer than other forms of Tay-Sachs disease and is usually seen in children between the age of 2 and 10 years. Pyrimethamine as a pharmacological chaperone was used to increase β-hexosaminidase A activity in this patient. We describe a patient with Tay-Sachs disease from the Indian population, a juvenile case who presented with developmental regression starting at the age of three, initially with motor followed by language regression. She is currently incapacitated with severe behavioral issues. This brief communication gives an insight into the efficacy of pharmacological chaperones. It also describes two unreported mutations in hexosaminidase A gene from the Indian population. After commencing Pyrimethamine, though initial benefits with increase in levels corresponded with briefly halting the motor regression, the observed increase was only transient and not associated with discernible beneficial neurological or psychiatric effects.

  16. Exact cosmological solutions of Einstein-Maxwell equations as perturbations of the Bertotti-Robinson model

    International Nuclear Information System (INIS)

    Portugal, R.; Soares, I.D.

    1985-01-01

    Two new classes of spatially homogeneous cosmological solutions of Einstein-Maxwell equations are obtained by considering a class of exact perturbations of the static Bertotti-Robinson (BR) model. The BR solution is shown to be unstable under these perturbations, being perturbed into exact cosmological solutions with perfect fluid (equations of state p = lambda rho, O [pt

  17. Exact string theory model of closed timelike curves and cosmological singularities

    International Nuclear Information System (INIS)

    Johnson, Clifford V.; Svendsen, Harald G.

    2004-01-01

    We study an exact model of string theory propagating in a space-time containing regions with closed timelike curves (CTCs) separated from a finite cosmological region bounded by a big bang and a big crunch. The model is an nontrivial embedding of the Taub-NUT geometry into heterotic string theory with a full conformal field theory (CFT) definition, discovered over a decade ago as a heterotic coset model. Having a CFT definition makes this an excellent laboratory for the study of the stringy fate of CTCs, the Taub cosmology, and the Milne/Misner-type chronology horizon which separates them. In an effort to uncover the role of stringy corrections to such geometries, we calculate the complete set of α ' corrections to the geometry. We observe that the key features of Taub-NUT persist in the exact theory, together with the emergence of a region of space with Euclidean signature bounded by timelike curvature singularities. Although such remarks are premature, their persistence in the exact geometry is suggestive that string theory is able to make physical sense of the Milne/Misner singularities and the CTCs, despite their pathological character in general relativity. This may also support the possibility that CTCs may be viable in some physical situations, and may be a natural ingredient in pre-big bang cosmological scenarios

  18. Adeno-Associated Virus Gene Therapy in a Sheep Model of Tay-Sachs Disease.

    Science.gov (United States)

    Gray-Edwards, Heather L; Randle, Ashley N; Maitland, Stacy A; Benatti, Hector R; Hubbard, Spencer M; Canning, Peter F; Vogel, Matthew B; Brunson, Brandon L; Hwang, Misako; Ellis, Lauren E; Bradbury, Allison M; Gentry, Atoska S; Taylor, Amanda R; Wooldridge, Anne A; Wilhite, Dewey R; Winter, Randolph L; Whitlock, Brian K; Johnson, Jacob A; Holland, Merilee; Salibi, Nouha; Beyers, Ronald J; Sartin, James L; Denney, Thomas S; Cox, Nancy R; Sena-Esteves, Miguel; Martin, Douglas R

    2018-03-01

    Tay-Sachs disease (TSD) is a fatal neurodegenerative disorder caused by a deficiency of the enzyme hexosaminidase A (HexA). TSD also occurs in sheep, the only experimental model of TSD that has clinical signs of disease. The natural history of sheep TSD was characterized using serial neurological evaluations, 7 Tesla magnetic resonance imaging, echocardiograms, electrodiagnostics, and cerebrospinal fluid biomarkers. Intracranial gene therapy was also tested using AAVrh8 monocistronic vectors encoding the α-subunit of Hex (TSD α) or a mixture of two vectors encoding both the α and β subunits separately (TSD α + β) injected at high (1.3 × 10 13 vector genomes) or low (4.2 × 10 12 vector genomes) dose. Delay of symptom onset and/or reduction of acquired symptoms were noted in all adeno-associated virus-treated sheep. Postmortem evaluation showed superior HexA and vector genome distribution in the brain of TSD α + β sheep compared to TSD α sheep, but spinal cord distribution was low in all groups. Isozyme analysis showed superior HexA formation after treatment with both vectors (TSD α + β), and ganglioside clearance was most widespread in the TSD α + β high-dose sheep. Microglial activation and proliferation in TSD sheep-most prominent in the cerebrum-were attenuated after gene therapy. This report demonstrates therapeutic efficacy for TSD in the sheep brain, which is on the same order of magnitude as a child's brain.

  19. Neutrino properties from cosmology

    CERN Multimedia

    CERN. Geneva

    2013-01-01

    Future, massive large-scale structure survey have been presented and approved.On the theory side, a significant effort has bene devoted to achieve better modeling of small scale clustering that is of cosmological non-linearities. As a result it has become clear that forthcoming cosmological data have enough statitsical power to detect the effect of non-zero neutrino mass (even at the lower mass scale limit imposed by oscillations) and to constrain the absolute neutrino mass scale.Cosmological data can also constrain the numb...

  20. Tay-Sachs disease: current perspectives from Australia

    Directory of Open Access Journals (Sweden)

    Lew RM

    2015-01-01

    Full Text Available Raelia M Lew,1,7 Leslie Burnett,2,3,4 Anné L Proos,2 Martin B Delatycki5,6 1Department of Obstetrics and Gynecology, QEII Research Institute for Mothers and Infants, The University of Sydney, Australia; 2NSW Health Pathology North, Royal North Shore Hospital, St Leonards, Australia; 3SEALS, Prince of Wales Hospital, Randwick, Australia; 4Sydney Medical School-Northern, Royal North Shore Hospital E25, University of Sydney, Sydney, Australia; 5Department of Clinical Genetics, Austin Health, Heidelberg, Australia; 6Bruce Lefroy Centre for Genetic Health Research, Murdoch Childrens Research Institute, Parkville, Australia; 7Department of Obstetrics and Gynaecology, Dentistry and Health Sciences, Faculty of Medicine, The University of Melbourne, Melbourne, Australia Abstract: Tay-Sachs disease (TSD is a fatal, recessively inherited neurodegenerative condition of infancy and early childhood. Although rare in most other populations, the carrier frequency is one in 25 in Ashkenazi Jews. Australian high-school-based TSD preconception genetic screening programs aim to screen, educate, and optimize reproductive choice for participants. These programs have demonstrated high uptake, low psychological morbidity, and have been shown to result in fewer than expected Jewish TSD-affected births over 18 years of operation. The majority of Jewish individuals of reproductive age outside of the high school screening program setting in Australia have not accessed screening. Recent recommendations advocate supplementing the community high school screening programs with general practitioner- and obstetrician-led genetic screening of Ashkenazi Jewish individuals for TSD and other severe recessive diseases for which this group is at risk. Massively parallel DNA sequencing is expected to become the testing modality of choice over the coming years. Keywords: Tay-Sachs disease, genetic screening, Australia

  1. Classical and quantum cosmology

    CERN Document Server

    Calcagni, Gianluca

    2017-01-01

    This comprehensive textbook is devoted to classical and quantum cosmology, with particular emphasis on modern approaches to quantum gravity and string theory and on their observational imprint. It covers major challenges in theoretical physics such as the big bang and the cosmological constant problem. An extensive review of standard cosmology, the cosmic microwave background, inflation and dark energy sets the scene for the phenomenological application of all the main quantum-gravity and string-theory models of cosmology. Born of the author's teaching experience and commitment to bridging the gap between cosmologists and theoreticians working beyond the established laws of particle physics and general relativity, this is a unique text where quantum-gravity approaches and string theory are treated on an equal footing. As well as introducing cosmology to undergraduate and graduate students with its pedagogical presentation and the help of 45 solved exercises, this book, which includes an ambitious bibliography...

  2. Modified geodetic brane cosmology

    International Nuclear Information System (INIS)

    Cordero, Rubén; Cruz, Miguel; Molgado, Alberto; Rojas, Efraín

    2012-01-01

    We explore the cosmological implications provided by the geodetic brane gravity action corrected by an extrinsic curvature brane term, describing a codimension-1 brane embedded in a 5D fixed Minkowski spacetime. In the geodetic brane gravity action, we accommodate the correction term through a linear term in the extrinsic curvature swept out by the brane. We study the resulting geodetic-type equation of motion. Within a Friedmann–Robertson–Walker metric, we obtain a generalized Friedmann equation describing the associated cosmological evolution. We observe that, when the radiation-like energy contribution from the extra dimension is vanishing, this effective model leads to a self-(non-self)-accelerated expansion of the brane-like universe in dependence on the nature of the concomitant parameter β associated with the correction, which resembles an analogous behaviour in the DGP brane cosmology. Several possibilities in the description for the cosmic evolution of this model are embodied and characterized by the involved density parameters related in turn to the cosmological constant, the geometry characterizing the model, the introduced β parameter as well as the dark-like energy and the matter content on the brane. (paper)

  3. Cosmological parameter estimation using Particle Swarm Optimization

    Science.gov (United States)

    Prasad, J.; Souradeep, T.

    2014-03-01

    Constraining parameters of a theoretical model from observational data is an important exercise in cosmology. There are many theoretically motivated models, which demand greater number of cosmological parameters than the standard model of cosmology uses, and make the problem of parameter estimation challenging. It is a common practice to employ Bayesian formalism for parameter estimation for which, in general, likelihood surface is probed. For the standard cosmological model with six parameters, likelihood surface is quite smooth and does not have local maxima, and sampling based methods like Markov Chain Monte Carlo (MCMC) method are quite successful. However, when there are a large number of parameters or the likelihood surface is not smooth, other methods may be more effective. In this paper, we have demonstrated application of another method inspired from artificial intelligence, called Particle Swarm Optimization (PSO) for estimating cosmological parameters from Cosmic Microwave Background (CMB) data taken from the WMAP satellite.

  4. Cosmological parameter estimation using Particle Swarm Optimization

    International Nuclear Information System (INIS)

    Prasad, J; Souradeep, T

    2014-01-01

    Constraining parameters of a theoretical model from observational data is an important exercise in cosmology. There are many theoretically motivated models, which demand greater number of cosmological parameters than the standard model of cosmology uses, and make the problem of parameter estimation challenging. It is a common practice to employ Bayesian formalism for parameter estimation for which, in general, likelihood surface is probed. For the standard cosmological model with six parameters, likelihood surface is quite smooth and does not have local maxima, and sampling based methods like Markov Chain Monte Carlo (MCMC) method are quite successful. However, when there are a large number of parameters or the likelihood surface is not smooth, other methods may be more effective. In this paper, we have demonstrated application of another method inspired from artificial intelligence, called Particle Swarm Optimization (PSO) for estimating cosmological parameters from Cosmic Microwave Background (CMB) data taken from the WMAP satellite

  5. Magnification-temperature correlation: The dark side of integrated Sachs-Wolfe measurements

    International Nuclear Information System (INIS)

    LoVerde, Marilena; Hui, Lam; Gaztanaga, Enrique

    2007-01-01

    Integrated Sachs-Wolfe (ISW) measurements, which involve cross-correlating the microwave background anisotropies with the foreground large-scale structure (e.g. traced by galaxies/quasars), have proven to be an interesting probe of dark energy. We show that magnification bias, which is the inevitable modulation of the foreground number counts by gravitational lensing, alters both the scale dependence and amplitude of the observed ISW signal. This is true especially at high redshifts because (1) the intrinsic galaxy-temperature signal diminishes greatly back in the matter-dominated era, (2) the lensing efficiency increases with redshift and (3) the number count slope generally steepens with redshift in a magnitude limited sample. At z > or approx. 2, the magnification-temperature correlation dominates over the intrinsic galaxy-temperature correlation and causes the observed ISW signal to increase with redshift, despite dark energy subdominance--a result of the fact that magnification probes structures all the way from the observer to the sources. Ignoring magnification bias therefore can lead to (significantly) erroneous conclusions about dark energy. While the lensing modulation opens up an interesting high z window for ISW measurements, high redshift measurements are not expected to add much new information to low redshift ones if dark energy is indeed the cosmological constant. This is because lensing introduces significant covariance across redshifts. The most compelling reasons for pursuing high redshift ISW measurements are to look for potential surprises such as early dark energy domination or signatures of modified gravity. We conclude with a discussion of existing measurements, the highest redshift of which is at the margin of being sensitive to the magnification effect. We also develop a formalism which might be of more general interest: to predict biases in estimating parameters when certain physical effects are ignored in interpreting observations

  6. Kinematic Cosmology & a new ``Steady State'' Model of Continued Creation

    Science.gov (United States)

    Wegener, Mogens

    2006-03-01

    Only a new "steady state" model justifies the observations of fully mature galaxies at ever increasing distances. The basic idea behind the world model presented here, which is a synthesis of the cosmologies of Parmenides and Herakleitos, is that the invariant structure of the infinite contents of a universe in flux may be depicted as a finite hyperbolic pseudo-sphere.

  7. The cosmological constant in theories with finite spacetime

    International Nuclear Information System (INIS)

    Kummer, Janis

    2014-08-01

    We study the role of the cosmological constant in different theories with finite spacetime. The cosmological constant appears both as an initial condition and as a constant of integration. In the context of the cosmological constant problem a new model will be presented. This modification of general relativity generates a small, non-vanishing cosmological constant, which is radiatively stable. The dynamics of the expansion of the universe in this model will be analyzed. Eventually, we try to solve the emergent problems concerning the generation of accelerated expansion using a quintessence model of dark energy.

  8. DGP cosmological model with generalized Ricci dark energy

    Energy Technology Data Exchange (ETDEWEB)

    Aguilera, Yeremy [Universidad de Santiago, Departamento de Matematicas y Ciencia de la Computacion, Santiago (Chile); Avelino, Arturo [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Cruz, Norman [Universidad de Santiago, Departamento de Fisica, Facultad de Ciencia, Santiago (Chile); Lepe, Samuel [Pontificia Universidad Catolica de Valparaiso, Facultad de Ciencias, Instituto de Fisica, Valparaiso (Chile); Pena, Francisco [Universidad de La Frontera, Departamento de Ciencias Fisicas, Facultad de Ingenieria y Ciencias, Temuco (Chile)

    2014-11-15

    The brane-world model proposed by Dvali, Gabadadze and Porrati (DGP) leads to an accelerated universe without cosmological constant or other form of dark energy for the positive branch (element of = +1). For the negative branch (element of = -1) we have investigated the behavior of a model with an holographic Ricci-like dark energy and dark matter, where the IR cutoff takes the form αH{sup 2} + βH, H being the Hubble parameter and α, β positive constants of the model. We perform an analytical study of the model in the late-time dark energy dominated epoch, where we obtain a solution for r{sub c}H(z), where r{sub c} is the leakage scale of gravity into the bulk, and conditions for the negative branch on the holographic parameters α and β, in order to hold the conditions of weak energy and accelerated universe. On the other hand, we compare the model versus the late-time cosmological data using the latest type Ia supernova sample of the Joint Light-curve Analysis (JLA), in order to constrain the holographic parameters in the negative branch, as well as r{sub c}H{sub 0} in the positive branch, where H{sub 0} is the Hubble constant. We find that the model has a good fit to the data and that the most likely values for (r{sub c}H{sub 0}, α, β) lie in the permitted region found from an analytical solution in a dark energy dominated universe. We give a justification to use a holographic cutoff in 4D for the dark energy in the 5-dimensional DGP model. Finally, using the Bayesian Information Criterion we find that this model is disfavored compared with the flat ΛCDM model. (orig.)

  9. Late-onset Tay-Sachs disease.

    Science.gov (United States)

    Barritt, Andrew W; Anderson, Stuart J; Leigh, P Nigel; Ridha, Basil H

    2017-10-01

    We discuss the assessment and differential diagnoses of a young adult Hungarian man with a 1-year history of a progressive and symmetric amyotrophic lateral sclerosis-like syndrome, along with irregular action tremor and stimulus-sensitive myoclonus of the arms. MR scan of the brain showed isolated cerebellar atrophy and formal neuropsychometric testing identified significant subclinical deficits in attention, processing speed and memory. We suspected a form of GM 2 gangliosidosis, and white cell enzyme analysis showed markedly reduced enzymatic activity of β-hexosaminidase A. Genetic testing subsequently revealed two heterozygous pathogenic mutations in the HEXA gene (c.1499delT p.(Leu500fs) and c.805G>A p.(Gly269Ser)), confirming the very rare diagnosis of adult-onset Tay-Sachs disease. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  10. Expressions for linearized perturbations in ideal-fluid cosmological models

    International Nuclear Information System (INIS)

    Ratra, B.

    1988-01-01

    We present closed-form solutions of the relativistic linear perturbation equations (in synchronous gauge) that govern the evolution of inhomogeneities in homogeneous, spatially flat, ideal-fluid, cosmological models. These expressions, which are valid for irregularities on any scale, allow one to analytically interpolate between the known approximate solutions which are valid at early times and at late times

  11. Cosmology and particle physics

    Energy Technology Data Exchange (ETDEWEB)

    Steigman, G [California Univ., Santa Barbara (USA). Inst. for Theoretical Physics; Bartol Research Foundation, Newark, Delaware (USA))

    1982-01-29

    The cosmic connections between physics on the very largest and very smallest scales are reviewed with an emphasis on the symbiotic relation between elementary particle physics and cosmology. After a review of the early Universe as a cosmic accelerator, various cosmological and astrophysical constraints on models of particle physics are outlined. To illustrate this approach to particle physics via cosmology, reference is made to several areas of current research: baryon non-conservation and baryon asymmetry; free quarks, heavy hadrons and other exotic relics; primordial nucleosynthesis and neutrino masses.

  12. Multi-dimensional cosmology and GUP

    International Nuclear Information System (INIS)

    Zeynali, K.; Motavalli, H.; Darabi, F.

    2012-01-01

    We consider a multidimensional cosmological model with FRW type metric having 4-dimensional space-time and d-dimensional Ricci-flat internal space sectors with a higher dimensional cosmological constant. We study the classical cosmology in commutative and GUP cases and obtain the corresponding exact solutions for negative and positive cosmological constants. It is shown that for negative cosmological constant, the commutative and GUP cases result in finite size universes with smaller size and longer ages, and larger size and shorter age, respectively. For positive cosmological constant, the commutative and GUP cases result in infinite size universes having late time accelerating behavior in good agreement with current observations. The accelerating phase starts in the GUP case sooner than the commutative case. In both commutative and GUP cases, and for both negative and positive cosmological constants, the internal space is stabilized to the sub-Planck size, at least within the present age of the universe. Then, we study the quantum cosmology by deriving the Wheeler-DeWitt equation, and obtain the exact solutions in the commutative case and the perturbative solutions in GUP case, to first order in the GUP small parameter, for both negative and positive cosmological constants. It is shown that good correspondence exists between the classical and quantum solutions

  13. Multi-dimensional cosmology and GUP

    Energy Technology Data Exchange (ETDEWEB)

    Zeynali, K.; Motavalli, H. [Department of Theoretical Physics and Astrophysics, University of Tabriz, 51666-16471, Tabriz (Iran, Islamic Republic of); Darabi, F., E-mail: k.zeinali@arums.ac.ir, E-mail: f.darabi@azaruniv.edu, E-mail: motavalli@tabrizu.ac.ir [Department of Physics, Azarbaijan Shahid Madani University, 53714-161, Tabriz (Iran, Islamic Republic of)

    2012-12-01

    We consider a multidimensional cosmological model with FRW type metric having 4-dimensional space-time and d-dimensional Ricci-flat internal space sectors with a higher dimensional cosmological constant. We study the classical cosmology in commutative and GUP cases and obtain the corresponding exact solutions for negative and positive cosmological constants. It is shown that for negative cosmological constant, the commutative and GUP cases result in finite size universes with smaller size and longer ages, and larger size and shorter age, respectively. For positive cosmological constant, the commutative and GUP cases result in infinite size universes having late time accelerating behavior in good agreement with current observations. The accelerating phase starts in the GUP case sooner than the commutative case. In both commutative and GUP cases, and for both negative and positive cosmological constants, the internal space is stabilized to the sub-Planck size, at least within the present age of the universe. Then, we study the quantum cosmology by deriving the Wheeler-DeWitt equation, and obtain the exact solutions in the commutative case and the perturbative solutions in GUP case, to first order in the GUP small parameter, for both negative and positive cosmological constants. It is shown that good correspondence exists between the classical and quantum solutions.

  14. Crystal Structure of Human [Beta]-Hexosaminidase B: Understanding the Molecular Basis of Sandhoff and Tay-Sachs Disease

    Energy Technology Data Exchange (ETDEWEB)

    Mark, Brian L.; Mahuran, Don J.; Cherney, Maia M.; Zhao, Dalian; Knapp, Spencer; James, Michael N.G.

    2010-12-01

    In humans, two major {beta}-hexosaminidase isoenzymes exist: Hex A and Hex B. Hex A is a heterodimer of subunits {alpha} and {beta} (60% identity), whereas Hex B is a homodimer of {beta}-subunits. Interest in human {beta}-hexosaminidase stems from its association with Tay-Sachs and Sandhoff disease; these are prototypical lysosomal storage disorders resulting from the abnormal accumulation of G{sub M2}-ganglioside (G{sub M2}). Hex A degrades G{sub M2} by removing a terminal N-acetyl-D-galactosamine ({beta}-GalNAc) residue, and this activity requires the G{sub M2}-activator, a protein which solubilizes the ganglioside for presentation to Hex A. We present here the crystal structure of human Hex B, alone (2.4 {angstrom}) and in complex with the mechanistic inhibitors GalNAc-isofagomine (2.2 {angstrom}) or NAG-thiazoline (2.5 {angstrom}). From these, and the known X-ray structure of the G{sub M2}-activator, we have modeled Hex A in complex with the activator and ganglioside. Together, our crystallographic and modeling data demonstrate how {alpha} and {beta}-subunits dimerize to form either Hex A or Hex B, how these isoenzymes hydrolyze diverse substrates, and how many documented point mutations cause Sandhoff disease ({beta}-subunit mutations) and Tay-Sachs disease ({alpha}-subunit mutations).

  15. Cosmological D-instantons and cyclic universes

    NARCIS (Netherlands)

    Bergshoeff, EA; Collinucci, A; Roest, D; Russo, JG; Townsend, PK

    2005-01-01

    For models of gravity coupled to hyperbolic sigma models, such as the metric-scalar sector of IIB supergravity, we show how smooth trajectories in the 'augmented target space' connect FLRW cosmologies to non-extremal D-instantons through a cosmological singularity. In particular, we find closed

  16. Temporary Efficacy of Pyrimethamine in Juvenile-Onset Tay-Sachs Disease Caused by 2 Unreported HEXA Mutations in the Indian Population

    Directory of Open Access Journals (Sweden)

    Anaita Udwadia-Hegde MD, DCH, MRCPCH

    2017-01-01

    Full Text Available Background: Juvenile Tay-Sachs disease is rarer than other forms of Tay-Sachs disease and is usually seen in children between the age of 2 and 10 years. Pyrimethamine as a pharmacological chaperone was used to increase β-hexosaminidase A activity in this patient. Patient: We describe a patient with Tay-Sachs disease from the Indian population, a juvenile case who presented with developmental regression starting at the age of three, initially with motor followed by language regression. She is currently incapacitated with severe behavioral issues. Conclusion: This brief communication gives an insight into the efficacy of pharmacological chaperones. It also describes two unreported mutations in hexosaminidase A gene from the Indian population. After commencing Pyrimethamine, though initial benefits with increase in levels corresponded with briefly halting the motor regression, the observed increase was only transient and not associated with discernible beneficial neurological or psychiatric effects.

  17. Self-accelerating universe in Galileon cosmology

    International Nuclear Information System (INIS)

    Silva, Fabio P.; Koyama, Kazuya

    2009-01-01

    We present a cosmological model with a solution that self-accelerates at late times without signs of ghost instabilities on small scales. The model is a natural extension of the Brans-Dicke (BD) theory including a nonlinear derivative interaction, which appears in a theory with the Galilean shift symmetry. The existence of the self-accelerating universe requires a negative BD parameter but, thanks to the nonlinear term, small fluctuations around the solution are stable on small scales. General relativity is recovered at early times and on small scales by this nonlinear interaction via the Vainshtein mechanism. At late time, gravity is strongly modified and the background cosmology shows a phantomlike behavior and the growth rate of structure formation is enhanced. Thus this model leaves distinct signatures in cosmological observations and it can be distinguished from standard LCDM cosmology.

  18. The Coyote Universe II: Cosmological Models and Precision Emulation of the Nonlinear Matter Power Spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Heitmann, Katrin [Los Alamos National Laboratory; Habib, Salman [Los Alamos National Laboratory; Higdon, David [Los Alamos National Laboratory; Williams, Brian J [Los Alamos National Laboratory; White, Martin [Los Alamos National Laboratory; Wagner, Christian [Los Alamos National Laboratory

    2008-01-01

    The power spectrum of density fluctuations is a foundational source of cosmological information. Precision cosmological probes targeted primarily at investigations of dark energy require accurate theoretical determinations of the power spectrum in the nonlinear regime. To exploit the observational power of future cosmological surveys, accuracy demands on the theory are at the one percent level or better. Numerical simulations are currently the only way to produce sufficiently error-controlled predictions for the power spectrum. The very high computational cost of (precision) N-body simulations is a major obstacle to obtaining predictions in the nonlinear regime, while scanning over cosmological parameters. Near-future observations, however, are likely to provide a meaningful constraint only on constant dark energy equation of state 'wCDM' cosmologies. In this paper we demonstrate that a limited set of only 37 cosmological models -- the 'Coyote Universe' suite -- can be used to predict the nonlinear matter power spectrum at the required accuracy over a prior parameter range set by cosmic microwave background observations. This paper is the second in a series of three, with the final aim to provide a high-accuracy prediction scheme for the nonlinear matter power spectrum for wCDM cosmologies.

  19. Einstein and modern cosmology

    International Nuclear Information System (INIS)

    Stabell, R.

    1979-01-01

    Einstein applied his gravitation theory to a universe model with positively curved space in 1917. In order to maintain a static universe he introduced the cosmological constant, which in the light of later nonstatic universe models, he described as his life's greatest mistake. The best known such model is the Einstein-de Sitter model, which is here discussed in some detail. The 'big bang' theory is also discussed leading to the cosmic background radiation. The early phase of the 'big bang' cosmology, the first ten seconds, and the first minutes are discussed, leading to the transparent stage. (JIW)

  20. Modified General Relativity and Cosmology

    Science.gov (United States)

    Abdel-Rahman, A.-M. M.

    1997-10-01

    Aspects of the modified general relativity theory of Rastall, Al-Rawaf and Taha are discussed in both the radiation- and matter-dominated flat cosmological models. A nucleosynthesis constraint on the theory's free parameter is obtained and the implication for the age of the Universe is discussed. The consistency of the modified matter- dominated model with the neoclassical cosmological tests is demonstrated.

  1. Second viscosity effects in cosmology

    International Nuclear Information System (INIS)

    Potupa, A.S.

    1978-01-01

    The object of the investigation is to draw attention to two important aspects in the choice of a substance model, namely an allowance for the viscosity and behaviour of the metrics at the later stages of cosmological evolution. It is shown that in homogeneous cosmological models taking into account the viscosity there are solutions which realize interpolation between the Fridman and steady-state regimes. In a closed model a solution is obtained which corresponds to the ''curvature compensation'' regime with an unboundedly increasing radius. The problem of compensation of singularity at t → o is discussed as well as the choice of the equations of state for the early (hadron) stages of cosmological evolution in connection with the hydrodynamic theory of multiple hadron production

  2. Modeling Supermassive Black Holes in Cosmological Simulations

    Science.gov (United States)

    Tremmel, Michael

    My thesis work has focused on improving the implementation of supermassive black hole (SMBH) physics in cosmological hydrodynamic simulations. SMBHs are ubiquitous in mas- sive galaxies, as well as bulge-less galaxies and dwarfs, and are thought to be a critical component to massive galaxy evolution. Still, much is unknown about how SMBHs form, grow, and affect their host galaxies. Cosmological simulations are an invaluable tool for un- derstanding the formation of galaxies, self-consistently tracking their evolution with realistic merger and gas accretion histories. SMBHs are often modeled in these simulations (generally as a necessity to produce realistic massive galaxies), but their implementations are commonly simplified in ways that can limit what can be learned. Current and future observations are opening new windows into the lifecycle of SMBHs and their host galaxies, but require more detailed, physically motivated simulations. Within the novel framework I have developed, SMBHs 1) are seeded at early times without a priori assumptions of galaxy occupation, 2) grow in a way that accounts for the angular momentum of gas, and 3) experience realistic orbital evolution. I show how this model, properly tuned with a novel parameter optimiza- tion technique, results in realistic galaxies and SMBHs. Utilizing the unique ability of these simulations to capture the dynamical evolution of SMBHs, I present the first self-consistent prediction for the formation timescales of close SMBH pairs, precursors to SMBH binaries and merger events potentially detected by future gravitational wave experiments.

  3. Cosmology solved? Maybe

    International Nuclear Information System (INIS)

    Turner, Michael S.

    1999-01-01

    For two decades the hot big-bang model as been referred to as the standard cosmology - and for good reason. For just as long cosmologists have known that there are fundamental questions that are not answered by the standard cosmology and point to a grander theory. The best candidate for that grander theory is inflation + cold dark matter. It holds that the Universe is flat, that slowly moving elementary particles left over from the earliest moments provide the cosmic infrastructure, and that the primeval density inhomogeneities that seed all the structure arose from quantum fluctuations. There is now prima facie evidence that supports two basic tenets of this paradigm. An avalanche of high-quality cosmological observations will soon make this case stronger or will break it. Key questions remain to be answered; foremost among them are: identification and detection of the cold dark matter particles and elucidation of the dark-energy component. These are exciting times in cosmology!

  4. Cosmology solved? Maybe

    Energy Technology Data Exchange (ETDEWEB)

    Turner, Michael S

    1999-03-01

    For two decades the hot big-bang model as been referred to as the standard cosmology - and for good reason. For just as long cosmologists have known that there are fundamental questions that are not answered by the standard cosmology and point to a grander theory. The best candidate for that grander theory is inflation + cold dark matter. It holds that the Universe is flat, that slowly moving elementary particles left over from the earliest moments provide the cosmic infrastructure, and that the primeval density inhomogeneities that seed all the structure arose from quantum fluctuations. There is now prima facie evidence that supports two basic tenets of this paradigm. An avalanche of high-quality cosmological observations will soon make this case stronger or will break it. Key questions remain to be answered; foremost among them are: identification and detection of the cold dark matter particles and elucidation of the dark-energy component. These are exciting times in cosmology{exclamation_point}.

  5. Cosmological D-instantons and cyclic universes

    International Nuclear Information System (INIS)

    Bergshoeff, E A; Collinucci, A; Roest, D; Russo, J G; Townsend, P K

    2005-01-01

    For models of gravity coupled to hyperbolic sigma models, such as the metric-scalar sector of IIB supergravity, we show how smooth trajectories in the 'augmented target space' connect FLRW cosmologies to non-extremal D-instantons through a cosmological singularity. In particular, we find closed cyclic universes that undergo an endless sequence of big-bang to big-crunch cycles separated by instanton 'phases'. We also find 'big-bounce' universes in which a collapsing closed universe bounces off its cosmological singularity to become an open expanding universe

  6. Ekpyrotic and cyclic cosmology

    International Nuclear Information System (INIS)

    Lehners, Jean-Luc

    2008-01-01

    Ekpyrotic and cyclic cosmologies provide theories of the very early and of the very late universe. In these models, the big bang is described as a collision of branes - and thus the big bang is not the beginning of time. Before the big bang, there is an ekpyrotic phase with equation of state w=P/(ρ) >>1 (where P is the average pressure and ρ the average energy density) during which the universe slowly contracts. This phase resolves the standard cosmological puzzles and generates a nearly scale-invariant spectrum of cosmological perturbations containing a significant non-Gaussian component. At the same time it produces small-amplitude gravitational waves with a blue spectrum. The dark energy dominating the present-day cosmological evolution is reinterpreted as a small attractive force between our brane and a parallel one. This force eventually induces a new ekpyrotic phase and a new brane collision, leading to the idea of a cyclic universe. This review discusses the detailed properties of these models, their embedding in M-theory and their viability, with an emphasis on open issues and observational signatures

  7. From Mateev's baryogenesis ideas to contemporary cosmological constraints

    International Nuclear Information System (INIS)

    Kirilova, D.

    2011-01-01

    Mateev's ideas on baryogenesis and the possibility to constrain new physics on the basis of cosmological observations present the first impulse for the development of the physical cosmology and astroparticle physics in Bulgaria. Contemporary cosmological models of baryogenesis, leptogenesis, primordial nucleosynthesis and cosmological constraints on new physics are discussed

  8. Bianchi-IX string cosmological model in Lyra geometry

    Indian Academy of Sciences (India)

    field in Lyra's geometry will either include a creation field and be equal to Hoyle's cre- ation field cosmology or contain a special vacuum field which together with the gauge vector term may be considered as a cosmological term. Subsequent investigations were done by several authors in scalar–tensor theory and cos-.

  9. Models for the brane-bulk interaction: Toward understanding braneworld cosmological perturbations

    Science.gov (United States)

    Binétruy, Pierre; Bucher, Martin; Carvalho, Carla

    2004-08-01

    Using some simple toy models, we explore the nature of the brane-bulk interaction for cosmological models with a large extra dimension. We are in particular interested in understanding the role of the bulk gravitons, which from the point of view of an observer on the brane will appear to generate dissipation and nonlocality, effects that cannot be incorporated into an effective (3+1)-dimensional Lagrangian field theoretic description. We explicitly work out the dynamics of several discrete systems consisting of a finite number of degrees of freedom on the boundary coupled to a (1+1)-dimensional field theory subject to a variety of wave equations. Systems both with and without time translation invariance are considered and moving boundaries are discussed as well. The models considered contain all the qualitative features of quantized linearized cosmological perturbations for a Randall-Sundrum universe having an arbitrary expansion history, with the sole exception of gravitational gauge invariance, which will be treated in a later paper.

  10. Fourth-rank cosmology

    International Nuclear Information System (INIS)

    Marrakchi, A.E.L.; Tapia, V.

    1992-05-01

    Some cosmological implications of the recently proposed fourth-rank theory of gravitation are studied. The model exhibits the possibility of being free from the horizon and flatness problems at the price of introducing a negative pressure. The field equations we obtain are compatible with k obs =0 and Ω obs t clas approx. 10 20 t Planck approx. 10 -23 s. When interpreted at the light of General Relativity the treatment is shown to be almost equivalent to that of the standard model of cosmology combined with the inflationary scenario. Hence, an interpretation of the negative pressure hypothesis is provided. (author). 8 refs

  11. Expanding the spectrum of HEXA mutations in Indian patients with Tay-Sachs disease.

    Science.gov (United States)

    Sheth, Jayesh; Mistri, Mehul; Datar, Chaitanya; Kalane, Umesh; Patil, Shekhar; Kamate, Mahesh; Shah, Harshuti; Nampoothiri, Sheela; Gupta, Sarita; Sheth, Frenny

    2014-01-01

    Tay-Sachs disease is an autosomal recessive neurodegenerative disorder occurring due to impaired activity of β-hexosaminidase-A (EC 3.2.1.52), resulting from the mutation in HEXA gene. Very little is known about the molecular pathology of TSD in Indian children except for a few mutations identified by us. The present study is aimed to determine additional mutations leading to Tay-Sachs disease in nine patients confirmed by the deficiency of β-hexosaminidase-A (C (D175A) and c.805G>C (p.G269R) in one case; and one small 1 bp deletion c.426delT (p.F142LfsX57) and one splice site mutation c.459+4A>C in the other two cases respectively. None of these mutations were detected in 100 chromosomes from healthy individuals of the same ethnic group. Three previously reported missense mutations, (i) c.532C>T (p.R178C), (ii) c.964G>T (p.D322Y), and (iii) c.1385A>T (p.E462V); two nonsense mutations (i) c.709C>T (p.Q237X) and (ii) c.1528C>T (p.R510X), one 4 bp insertion c.1277_1278insTATC (p.Y427IfsX5) and one splice site mutation c.459+5G>A were also identified in six cases. We observe from this study that novel mutations are more frequently observed in Indian patients with Tay-Sachs disease with clustering of ~ 73% of disease causing mutations in exons 5 to 12. This database can be used for a carrier rate screening in the larger population of the country.

  12. Nonsingular bouncing cosmologies in light of BICEP2

    International Nuclear Information System (INIS)

    Cai, Yi-Fu; Quintin, Jerome; Saridakis, Emmanuel N.; Wilson-Ewing, Edward

    2014-01-01

    We confront various nonsingular bouncing cosmologies with the recently released BICEP2 data and investigate the observational constraints on their parameter space. In particular, within the context of the effective field approach, we analyze the constraints on the matter bounce curvaton scenario with a light scalar field, and the new matter bounce cosmology model in which the universe successively experiences a period of matter contraction and an ekpyrotic phase. Additionally, we consider three nonsingular bouncing cosmologies obtained in the framework of modified gravity theories, namely the Hořava-Lifshitz bounce model, the f(T) bounce model, and loop quantum cosmology

  13. Constraints on cosmological models from strong gravitational lensing systems

    International Nuclear Information System (INIS)

    Cao, Shuo; Pan, Yu; Zhu, Zong-Hong; Biesiada, Marek; Godlowski, Wlodzimierz

    2012-01-01

    Strong lensing has developed into an important astrophysical tool for probing both cosmology and galaxies (their structure, formation, and evolution). Using the gravitational lensing theory and cluster mass distribution model, we try to collect a relatively complete observational data concerning the Hubble constant independent ratio between two angular diameter distances D ds /D s from various large systematic gravitational lens surveys and lensing by galaxy clusters combined with X-ray observations, and check the possibility to use it in the future as complementary to other cosmological probes. On one hand, strongly gravitationally lensed quasar-galaxy systems create such a new opportunity by combining stellar kinematics (central velocity dispersion measurements) with lensing geometry (Einstein radius determination from position of images). We apply such a method to a combined gravitational lens data set including 70 data points from Sloan Lens ACS (SLACS) and Lens Structure and Dynamics survey (LSD). On the other hand, a new sample of 10 lensing galaxy clusters with redshifts ranging from 0.1 to 0.6 carefully selected from strong gravitational lensing systems with both X-ray satellite observations and optical giant luminous arcs, is also used to constrain three dark energy models (ΛCDM, constant w and CPL) under a flat universe assumption. For the full sample (n = 80) and the restricted sample (n = 46) including 36 two-image lenses and 10 strong lensing arcs, we obtain relatively good fitting values of basic cosmological parameters, which generally agree with the results already known in the literature. This results encourages further development of this method and its use on larger samples obtained in the future

  14. Constraints on cosmological models from strong gravitational lensing systems

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Shuo; Pan, Yu; Zhu, Zong-Hong [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Biesiada, Marek [Department of Astrophysics and Cosmology, Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Godlowski, Wlodzimierz, E-mail: baodingcaoshuo@163.com, E-mail: panyu@cqupt.edu.cn, E-mail: biesiada@us.edu.pl, E-mail: godlowski@uni.opole.pl, E-mail: zhuzh@bnu.edu.cn [Institute of Physics, Opole University, Oleska 48, 45-052 Opole (Poland)

    2012-03-01

    Strong lensing has developed into an important astrophysical tool for probing both cosmology and galaxies (their structure, formation, and evolution). Using the gravitational lensing theory and cluster mass distribution model, we try to collect a relatively complete observational data concerning the Hubble constant independent ratio between two angular diameter distances D{sub ds}/D{sub s} from various large systematic gravitational lens surveys and lensing by galaxy clusters combined with X-ray observations, and check the possibility to use it in the future as complementary to other cosmological probes. On one hand, strongly gravitationally lensed quasar-galaxy systems create such a new opportunity by combining stellar kinematics (central velocity dispersion measurements) with lensing geometry (Einstein radius determination from position of images). We apply such a method to a combined gravitational lens data set including 70 data points from Sloan Lens ACS (SLACS) and Lens Structure and Dynamics survey (LSD). On the other hand, a new sample of 10 lensing galaxy clusters with redshifts ranging from 0.1 to 0.6 carefully selected from strong gravitational lensing systems with both X-ray satellite observations and optical giant luminous arcs, is also used to constrain three dark energy models (ΛCDM, constant w and CPL) under a flat universe assumption. For the full sample (n = 80) and the restricted sample (n = 46) including 36 two-image lenses and 10 strong lensing arcs, we obtain relatively good fitting values of basic cosmological parameters, which generally agree with the results already known in the literature. This results encourages further development of this method and its use on larger samples obtained in the future.

  15. A modified Ozer-Taha type cosmological model

    Science.gov (United States)

    John, Moncy V.; Joseph, K. Babu

    1996-02-01

    A modified version of the Ozer and Taha nonsingular cosmological model is presented on the assumption that the universe's radius is complex if it is regarded as empty, but it contains matter when the radius is real. It also predicts the values: ΩM --- ρM/(ρC) ≈ 4/(3), ΩV --- ρV/(ρC) ≈ 2/(3) and Ω- --- ρ-/(ρC) ≪ 1 in the present nonrelativistic era, where ρM = matter density, ρV = vacuum energy density, ρ- = negative energy density and ρC = critical density.

  16. Particle physics and cosmology

    International Nuclear Information System (INIS)

    Ellis, J.; Nanopoulos, D.

    1983-01-01

    The authors describe the connection between cosmology and particle physics in an introductory way. In this connection the big bang theory and unified gauge models of strong, electromagnetic, and weak interactions are considered. Furthermore cosmological nucleosynthesis is discussed in this framework, and the problem of cosmic neutrinos is considered with special regards to its rest mass. (HSI).

  17. Quantum Gowdy model within the new loop quantum cosmology improved dynamics

    International Nuclear Information System (INIS)

    Martin-Benito, M; Garay, L J; Mena Marugan, G A

    2011-01-01

    The linearly polarized Gowdy T 3 model can be regarded as compact Bianchi I cosmologies with inhomogeneous modes allowed to travel in one direction. We study a hybrid quantization of this model that combines the loop quantization of the Bianchi I background, adopting the improved dynamics scheme put forward by Ashtekar and Wilson-Ewing, with a Fock quantization for the inhomogeneities. The Hamiltonian constraint operator provides a resolution of the cosmological singularity and superselects separable sectors. We analyze the complicated structure of these sectors. In any of them the Hamiltonian constraint provides an evolution equation with respect to the volume of the associated Bianchi I universe, with a well posed initial value problem. This fact allows us to construct the Hilbert space of physical states and to show that we recover the standard quantum field theory for the inhomogeneities.

  18. Ghost instabilities of cosmological models with vector fields nonminimally coupled to the curvature

    International Nuclear Information System (INIS)

    Himmetoglu, Burak; Peloso, Marco; Contaldi, Carlo R.

    2009-01-01

    We prove that many cosmological models characterized by vectors nonminimally coupled to the curvature (such as the Turner-Widrow mechanism for the production of magnetic fields during inflation, and models of vector inflation or vector curvaton) contain ghosts. The ghosts are associated with the longitudinal vector polarization present in these models and are found from studying the sign of the eigenvalues of the kinetic matrix for the physical perturbations. Ghosts introduce two main problems: (1) they make the theories ill defined at the quantum level in the high energy/subhorizon regime (and create serious problems for finding a well-behaved UV completion), and (2) they create an instability already at the linearized level. This happens because the eigenvalue corresponding to the ghost crosses zero during the cosmological evolution. At this point the linearized equations for the perturbations become singular (we show that this happens for all the models mentioned above). We explicitly solve the equations in the simplest cases of a vector without a vacuum expectation value in a Friedmann-Robertson-Walker geometry, and of a vector with a vacuum expectation value plus a cosmological constant, and we show that indeed the solutions of the linearized equations diverge when these equations become singular.

  19. Cosmological evidence for leptonic asymmetry after Planck

    Energy Technology Data Exchange (ETDEWEB)

    Caramete, A.; Popa, L.A., E-mail: acaramete@spacescience.ro, E-mail: lpopa@spacescience.ro [Institute of Space Science, 409 Atomistilor Street, Magurele, Ilfov 077125 (Romania)

    2014-02-01

    Recently, the PLANCK satellite found a larger and most precise value of the matter energy density, that impacts on the present values of other cosmological parameters such as the Hubble constant H{sub 0}, the present cluster abundances S{sub 8}, and the age of the Universe t{sub U}. The existing tension between PLANCK determination of these parameters in the frame of the base ΛCDM model and their determination from other measurements generated lively discussions, one possible interpretation being that some sources of systematic errors in cosmological measurements are not completely understood. An alternative interpretation is related to the fact that the CMB observations, that probe the high redshift Universe are interpreted in terms of cosmological parameters at present time by extrapolation within the base ΛCDM model that can be inadequate or incomplete. In this paper we quantify this tension by exploring several extensions of the base ΛCDM model that include the leptonic asymmetry. We set bounds on the radiation content of the Universe and neutrino properties by using the latest cosmological measurements, imposing also self-consistent BBN constraints on the primordial helium abundance. For all asymmetric cosmological models we find the preference of cosmological data for smaller values of active and sterile neutrino masses. This increases the tension between cosmological and short baseline neutrino oscillation data that favors a sterile neutrino with the mass of around 1 eV. For the case of degenerate massive neutrinos, we find that the discrepancies with the local determinations of H{sub 0}, and t{sub U} are alleviated at ∼ 1.3σ level while S{sub 8} is in agreement with its determination from CFHTLenS survey data at ∼ 1σ and with the prediction of cluster mass-observation relation at ∼ 0.5σ. We also find 2σ statistical preference of the cosmological data for the leptonic asymmetric models involving three massive neutrino species and neutrino direct

  20. Cosmology. A first course

    Science.gov (United States)

    Lachieze-Rey, Marc

    This book delivers a quantitative account of the science of cosmology, designed for a non-specialist audience. The basic principles are outlined using simple maths and physics, while still providing rigorous models of the Universe. It offers an ideal introduction to the key ideas in cosmology, without going into technical details. The approach used is based on the fundamental ideas of general relativity such as the spacetime interval, comoving coordinates, and spacetime curvature. It provides an up-to-date and thoughtful discussion of the big bang, and the crucial questions of structure and galaxy formation. Questions of method and philosophical approaches in cosmology are also briefly discussed. Advanced undergraduates in either physics or mathematics would benefit greatly from use either as a course text or as a supplementary guide to cosmology courses.

  1. FRW cosmological model inside an isolated Schwarzschild black hole

    OpenAIRE

    Ortiz, C.; Rosales, J. J.; Socorro, J.; Tkach, V. I.

    2004-01-01

    Using the canonical quantum theory of spherically symmetric pure gravitational systems, we present a direct correspondence between the Friedmann-Robertson-Walker (FRW) cosmological model in the interior of a Schwarzschild black hole and the nth energy eigenstate of a linear harmonic oscillator. Such type of universe has a quantized mass of the order of the Planck mass and harmonic oscillator wave functions

  2. Cosmological implications of a class of SO(10) models

    International Nuclear Information System (INIS)

    Mangano, G.; Rosa, L.

    1996-01-01

    The cosmological implications of a class of SO(10) models are discussed. In particular we show how a good prediction for neutrino masses is obtained in order to fit with the MSW mechanism to explain the solar neutrino flux deficit and with the predicted amount of the dark matter hot component. A possible scenario for baryogenesis is also considered. (orig.)

  3. Nonparametric test of consistency between cosmological models and multiband CMB measurements

    Energy Technology Data Exchange (ETDEWEB)

    Aghamousa, Amir [Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784 (Korea, Republic of); Shafieloo, Arman, E-mail: amir@apctp.org, E-mail: shafieloo@kasi.re.kr [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)

    2015-06-01

    We present a novel approach to test the consistency of the cosmological models with multiband CMB data using a nonparametric approach. In our analysis we calibrate the REACT (Risk Estimation and Adaptation after Coordinate Transformation) confidence levels associated with distances in function space (confidence distances) based on the Monte Carlo simulations in order to test the consistency of an assumed cosmological model with observation. To show the applicability of our algorithm, we confront Planck 2013 temperature data with concordance model of cosmology considering two different Planck spectra combination. In order to have an accurate quantitative statistical measure to compare between the data and the theoretical expectations, we calibrate REACT confidence distances and perform a bias control using many realizations of the data. Our results in this work using Planck 2013 temperature data put the best fit ΛCDM model at 95% (∼ 2σ) confidence distance from the center of the nonparametric confidence set while repeating the analysis excluding the Planck 217 × 217 GHz spectrum data, the best fit ΛCDM model shifts to 70% (∼ 1σ) confidence distance. The most prominent features in the data deviating from the best fit ΛCDM model seems to be at low multipoles  18 < ℓ < 26 at greater than 2σ, ℓ ∼ 750 at ∼1 to 2σ and ℓ ∼ 1800 at greater than 2σ level. Excluding the 217×217 GHz spectrum the feature at ℓ ∼ 1800 becomes substantially less significance at ∼1 to 2σ confidence level. Results of our analysis based on the new approach we propose in this work are in agreement with other analysis done using alternative methods.

  4. Cosmology for high energy physicists

    International Nuclear Information System (INIS)

    Albrecht, A.

    1987-11-01

    The standard big bang model of cosmology is presented. Although not perfect, its many successes make it a good starting point for most discussions of cosmology. Places are indicated where well understood laboratory physics is incorporated into the big bang, leading to successful predictions. Much less established aspects of high energy physics and some of the new ideas they have introduced into the field of cosmology are discussed, such as string theory, inflation and monopoles. 49 refs., 5 figs

  5. Perfect fluid Bianchi Type-I cosmological models with time varying G ...

    Indian Academy of Sciences (India)

    Abstract. Bianchi Type-I cosmological models containing perfect fluid with time vary- ing G and Λ have been presented. The solutions obtained represent an expansion scalar θ bearing a constant ratio to the anisotropy in the direction of space-like unit vector λi. Of the two models obtained, one has negative vacuum energy ...

  6. Future evolution in a backreaction model and the analogous scalar field cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Amna; Majumdar, A.S., E-mail: amnaalig@gmail.com, E-mail: archan@bose.res.in [S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700106 (India)

    2017-01-01

    We investigate the future evolution of the universe using the Buchert framework for averaged backreaction in the context of a two-domain partition of the universe. We show that this approach allows for the possibility of the global acceleration vanishing at a finite future time, provided that none of the subdomains accelerate individually. The model at large scales is analogously described in terms of a homogeneous scalar field emerging with a potential that is fixed and free from phenomenological parametrization. The dynamics of this scalar field is explored in the analogous FLRW cosmology. We use observational data from Type Ia Supernovae, Baryon Acoustic Oscillations, and Cosmic Microwave Background to constrain the parameters of the model for a viable cosmology, providing the corresponding likelihood contours.

  7. Propagator with positive cosmological constant in the 3D Euclidean quantum gravity toy model

    International Nuclear Information System (INIS)

    Bunting, William E; Rovelli, Carlo

    2014-01-01

    We study the propagator on a single tetrahedron in a three-dimensional toy model of quantum gravity with positive cosmological constant. The cosmological constant is included in the model via q-deformation of the spatial symmetry algebra, that is, we use the Turaev–Viro amplitude. The expected repulsive effect of dark energy is recovered in numerical and analytic calculations of the propagator at large scales comparable to the infrared cutoff. However, due to the simplicity of the model, we do not obtain the exact Newton limit of the propagator. This is a first step toward the similar calculation in the full 3+1 dimensional theory with larger numbers of simplicies. (paper)

  8. Observational constraints on Visser's cosmological model

    International Nuclear Information System (INIS)

    Alves, M. E. S.; Araujo, J. C. N. de; Miranda, O. D.; Wuensche, C. A.; Carvalho, F. C.; Santos, E. M.

    2010-01-01

    Theories of gravity for which gravitons can be treated as massive particles have presently been studied as realistic modifications of general relativity, and can be tested with cosmological observations. In this work, we study the ability of a recently proposed theory with massive gravitons, the so-called Visser theory, to explain the measurements of luminosity distance from the Union2 compilation, the most recent Type-Ia Supernovae (SNe Ia) data set, adopting the current ratio of the total density of nonrelativistic matter to the critical density (Ω m ) as a free parameter. We also combine the SNe Ia data with constraints from baryon acoustic oscillations (BAO) and cosmic microwave background (CMB) measurements. We find that, for the allowed interval of values for Ω m , a model based on Visser's theory can produce an accelerated expansion period without any dark energy component, but the combined analysis (SNe Ia+BAO+CMB) shows that the model is disfavored when compared with the ΛCDM model.

  9. Is there evidence for additional neutrino species from cosmology?

    CERN Document Server

    Feeney, Stephen M.; Verde, Licia

    2013-01-01

    It has been suggested that recent cosmological and flavor-oscillation data favor the existence of additional neutrino species beyond the three predicted by the Standard Model of particle physics. We apply Bayesian model selection to determine whether there is indeed any evidence from current cosmological datasets for the standard cosmological model to be extended to include additional neutrino flavors. The datasets employed include cosmic microwave background temperature, polarization and lensing power spectra, and measurements of the baryon acoustic oscillation scale and the Hubble constant. We also consider other extensions to the standard neutrino model, such as massive neutrinos, and possible degeneracies with other cosmological parameters. The Bayesian evidence indicates that current cosmological data do not require any non-standard neutrino properties.

  10. Observational constraints on cosmological future singularities

    International Nuclear Information System (INIS)

    Beltran Jimenez, Jose; Lazkoz, Ruth; Saez-Gomez, Diego; Salzano, Vincenzo

    2016-01-01

    In this work we consider a family of cosmological models featuring future singularities. This type of cosmological evolution is typical of dark energy models with an equation of state violating some of the standard energy conditions (e.g. the null energy condition). Such a kind of behavior, widely studied in the literature, may arise in cosmologies with phantom fields, theories of modified gravity or models with interacting dark matter/dark energy. We briefly review the physical consequences of these cosmological evolution regarding geodesic completeness and the divergence of tidal forces in order to emphasize under which circumstances the singularities in some cosmological quantities correspond to actual singular spacetimes. We then introduce several phenomenological parameterizations of the Hubble expansion rate to model different singularities existing in the literature and use SN Ia, BAO and H(z) data to constrain how far in the future the singularity needs to be (under some reasonable assumptions on the behavior of the Hubble factor). We show that, for our family of parameterizations, the lower bound for the singularity time cannot be smaller than about 1.2 times the age of the universe, what roughly speaking means ∝2.8 Gyrs from the present time. (orig.)

  11. Observational constraints on cosmological future singularities

    Energy Technology Data Exchange (ETDEWEB)

    Beltran Jimenez, Jose [Aix Marseille Univ, Universite de Toulon CNRS, CPT, Marseille (France); Lazkoz, Ruth [Euskal Herriko Unibertsitatea, Fisika Teorikoaren eta Zientziaren Historia Saila, Zientzia eta Teknologia Fakultatea, Bilbao (Spain); Saez-Gomez, Diego [Faculdade de Ciencias da Universidade de Lisboa, Departamento de Fisica, Instituto de Astrofisica e Ciencias do Espaco, Lisbon (Portugal); Salzano, Vincenzo [University of Szczecin, Institute of Physics, Szczecin (Poland)

    2016-11-15

    In this work we consider a family of cosmological models featuring future singularities. This type of cosmological evolution is typical of dark energy models with an equation of state violating some of the standard energy conditions (e.g. the null energy condition). Such a kind of behavior, widely studied in the literature, may arise in cosmologies with phantom fields, theories of modified gravity or models with interacting dark matter/dark energy. We briefly review the physical consequences of these cosmological evolution regarding geodesic completeness and the divergence of tidal forces in order to emphasize under which circumstances the singularities in some cosmological quantities correspond to actual singular spacetimes. We then introduce several phenomenological parameterizations of the Hubble expansion rate to model different singularities existing in the literature and use SN Ia, BAO and H(z) data to constrain how far in the future the singularity needs to be (under some reasonable assumptions on the behavior of the Hubble factor). We show that, for our family of parameterizations, the lower bound for the singularity time cannot be smaller than about 1.2 times the age of the universe, what roughly speaking means ∝2.8 Gyrs from the present time. (orig.)

  12. Cosmological implication of massive neutrinos in a horizontal model context

    International Nuclear Information System (INIS)

    Goldman, C.

    1985-04-01

    An extended version of the Glashow-Weinberg-Salam model for the eletroweak interactions is studied in detail. It has an extra global horizontal symmetry, which allows the appearance of neutrino mass terms. The constraints imposed by the standard cosmological model were used to determine the allowed range of variations of the free parameters of this model. As applications, the solar neutrinos problem and the formation of large scale structures in the universe is studied. (Author) [pt

  13. Topics in inflationary cosmologies

    International Nuclear Information System (INIS)

    Mahajan, S.

    1986-04-01

    Several aspects of inflationary cosmologies are discussed. An introduction to the standard hot big bang cosmological model is reviewed, and some of the problems associated with it are presented. A short review of the proposals for solving the cosmological conundrums of the big bang model is presented. Old and the new inflationary scenarios are discussed and shown to be unacceptable. Some alternative scenarios especially those using supersymmetry are reviewed briefly. A study is given of inflationary models where the same set of fields that breaks supersymmetry is also responsible for inflation. In these models, the scale of supersymmetry breaking is related to the slope of the potential near the origin and can thus be kept low. It is found that a supersymmetry breaking scale of the order of the weak breaking scale. The cosmology obtained from the simplest of such models is discussed in detail and it is shown that there are no particular problems except a low reheating temperature and a violation of the thermal constraint. A possible solution to the thermal constraint problem is given by introducing a second field, and the role played by this second field in the scenario is discussed. An alternative mechanism for the generation of baryon number within the framework of supergravity inflationary models is studied using the gravitational couplings of the heavy fields with the hidden sector (the sector which breaks supersymmetry). This mechanism is applied to two specific models - one with and one without supersymmetry breaking. The baryon to entropy ratio is found to be dependent on parameters which are model dependent. Finally, the effect of direct coupling between the two sectors on results is related, 88 refs., 6 figs

  14. The Effective Field Theory of nonsingular cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Yong [School of Physics, University of Chinese Academy of Sciences,Beijing 100049 (China); Wan, Youping [School of Physics, University of Chinese Academy of Sciences,Beijing 100049 (China); CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy,University of Science and Technology of China, Chinese Academy of Sciences,Hefei, Anhui 230026 (China); Li, Hai-Guang [School of Physics, University of Chinese Academy of Sciences,Beijing 100049 (China); Qiu, Taotao [Institute of Astrophysics, Central China Normal University,Wuhan 430079 (China); Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University,Wuhan 430079 (China); Piao, Yun-Song [School of Physics, University of Chinese Academy of Sciences,Beijing 100049 (China); Institute of Theoretical Physics, Chinese Academy of Sciences,P.O. Box 2735, Beijing 100190 (China)

    2017-01-20

    In this paper, we explore the nonsingular cosmology within the framework of the Effective Field Theory (EFT) of cosmological perturbations. Due to the recently proved no-go theorem, any nonsingular cosmological models based on the cubic Galileon suffer from pathologies. We show how the EFT could help us clarify the origin of the no-go theorem, and offer us solutions to break the no-go. Particularly, we point out that the gradient instability can be removed by using some spatial derivative operators in EFT. Based on the EFT description, we obtain a realistic healthy nonsingular cosmological model, and show the perturbation spectrum can be consistent with the observations.

  15. The Effective Field Theory of nonsingular cosmology

    International Nuclear Information System (INIS)

    Cai, Yong; Wan, Youping; Li, Hai-Guang; Qiu, Taotao; Piao, Yun-Song

    2017-01-01

    In this paper, we explore the nonsingular cosmology within the framework of the Effective Field Theory (EFT) of cosmological perturbations. Due to the recently proved no-go theorem, any nonsingular cosmological models based on the cubic Galileon suffer from pathologies. We show how the EFT could help us clarify the origin of the no-go theorem, and offer us solutions to break the no-go. Particularly, we point out that the gradient instability can be removed by using some spatial derivative operators in EFT. Based on the EFT description, we obtain a realistic healthy nonsingular cosmological model, and show the perturbation spectrum can be consistent with the observations.

  16. Cosmological viability of the bimetric theory of gravitation

    International Nuclear Information System (INIS)

    Krygier, B.; Krempec-Krygier, J.

    1983-01-01

    The approximate solutions of field equations for flat radiative cosmological models in the second version of bimetric gravitation theory are discussed. They indicate that these cosmological models are ever expanding. The apparent magnitude-redshift relations for flat dust cosmological models for different theories of gravitation are described and compared. One can reject Dirac's additive creation theory and the first version of Rosen's bimetric theory on the basis of this observational test. (author)

  17. No Evidence for Extensions to the Standard Cosmological Model

    Science.gov (United States)

    Heavens, Alan; Fantaye, Yabebal; Sellentin, Elena; Eggers, Hans; Hosenie, Zafiirah; Kroon, Steve; Mootoovaloo, Arrykrishna

    2017-09-01

    We compute the Bayesian evidence for models considered in the main analysis of Planck cosmic microwave background data. By utilizing carefully defined nearest-neighbor distances in parameter space, we reuse the Monte Carlo Markov chains already produced for parameter inference to compute Bayes factors B for many different model-data set combinations. The standard 6-parameter flat cold dark matter model with a cosmological constant (Λ CDM ) is favored over all other models considered, with curvature being mildly favored only when cosmic microwave background lensing is not included. Many alternative models are strongly disfavored by the data, including primordial correlated isocurvature models (ln B =-7.8 ), nonzero scalar-to-tensor ratio (ln B =-4.3 ), running of the spectral index (ln B =-4.7 ), curvature (ln B =-3.6 ), nonstandard numbers of neutrinos (ln B =-3.1 ), nonstandard neutrino masses (ln B =-3.2 ), nonstandard lensing potential (ln B =-4.6 ), evolving dark energy (ln B =-3.2 ), sterile neutrinos (ln B =-6.9 ), and extra sterile neutrinos with a nonzero scalar-to-tensor ratio (ln B =-10.8 ). Other models are less strongly disfavored with respect to flat Λ CDM . As with all analyses based on Bayesian evidence, the final numbers depend on the widths of the parameter priors. We adopt the priors used in the Planck analysis, while performing a prior sensitivity analysis. Our quantitative conclusion is that extensions beyond the standard cosmological model are disfavored by Planck data. Only when newer Hubble constant measurements are included does Λ CDM become disfavored, and only mildly, compared with a dynamical dark energy model (ln B ˜+2 ).

  18. Redshift structure of the big bang in inhomogeneous cosmological models. I. Spherical dust solutions

    International Nuclear Information System (INIS)

    Hellaby, C.; Lake, K.

    1984-01-01

    The redshift from the big bang in the standard model is always infinite, but in inhomogeneous cosmological models infinite blueshifts are also possible. To avoid such divergent energy fluxes, we require that all realistic cosmological models must not display infinite blueshifts. We apply this requirement to the Tolman model (spherically symmetric dust), using the geometrical optics approximation, and assuming that the geodesic tangent vectors may be expanded in power series. We conclude that the bang time must be simultaneous. The stronger requirement, that only infinite redshifts from the big bang may occur, does not lead to a stronger condition on the metric. Further consequences of simultaneity are that no decaying mode fluctuations are possible, and that the only acceptable model which is homogeneous at late times is the Robertson-Walker model

  19. Redshift structure of the big bang in inhomogeneous cosmological models. I. Spherical dust solutions

    Energy Technology Data Exchange (ETDEWEB)

    Hellaby, C.; Lake, K.

    1984-07-01

    The redshift from the big bang in the standard model is always infinite, but in inhomogeneous cosmological models infinite blueshifts are also possible. To avoid such divergent energy fluxes, we require that all realistic cosmological models must not display infinite blueshifts. We apply this requirement to the Tolman model (spherically symmetric dust), using the geometrical optics approximation, and assuming that the geodesic tangent vectors may be expanded in power series. We conclude that the bang time must be simultaneous. The stronger requirement, that only infinite redshifts from the big bang may occur, does not lead to a stronger condition on the metric. Further consequences of simultaneity are that no decaying mode fluctuations are possible, and that the only acceptable model which is homogeneous at late times is the Robertson-Walker model.

  20. Integrable scalar cosmologies

    International Nuclear Information System (INIS)

    Fré, P.; Sorin, A.S.; Trigiante, M.

    2014-01-01

    The question whether the integrable one-field cosmologies classified in a previous paper by Fré, Sagnotti and Sorin can be embedded as consistent one-field truncations into Extended Gauged Supergravity or in N=1 supergravity gauged by a superpotential without the use of D-terms is addressed in this paper. The answer is that such an embedding is very difficult and rare but not impossible. Indeed, we were able to find two examples of integrable models embedded in supergravity in this way. Both examples are fitted into N=1 supergravity by means of a very specific and interesting choice of the superpotential W(z). The question whether there are examples of such an embedding in Extended Gauged Supergravity remains open. In the present paper, relying on the embedding tensor formalism we classified all gaugings of the N=2 STU model, confirming, in the absence on hypermultiplets, the uniqueness of the stable de Sitter vacuum found several years ago by Fré, Trigiante and Van Proeyen and excluding the embedding of any integrable cosmological model. A detailed analysis of the space of exact solutions of the first supergravity-embedded integrable cosmological model revealed several new features worth an in-depth consideration. When the scalar potential has an extremum at a negative value, the Universe necessarily collapses into a Big Crunch notwithstanding its spatial flatness. The causal structure of these Universes is quite different from that of the closed, positive curved, Universe: indeed, in this case the particle and event horizons do not coincide and develop complicated patterns. The cosmological consequences of this unexpected mechanism deserve careful consideration

  1. Kaluza-Klein cosmological model in f(R, T) gravity with Λ(T)

    Science.gov (United States)

    Sahoo, P. K.; Mishra, B.; Tripathy, S. K.

    2016-04-01

    A class of Kaluza-Klein cosmological models in $f(R,T)$ theory of gravity have been investigated. In the work, we have considered the functional $f(R,T)$ to be in the form $f(R,T)=f(R)+f(T)$ with $f(R)=\\lambda R$ and $f(T)=\\lambda T$. Such a choice of the functional $f(R,T)$ leads to an evolving effective cosmological constant $\\Lambda$ which depends on the stress energy tensor. The source of the matter field is taken to be a perfect cosmic fluid. The exact solutions of the field equations are obtained by considering a constant deceleration parameter which leads two different aspects of the volumetric expansion namely a power law and an exponential volumetric expansion. Keeping an eye on the accelerating nature of the universe in the present epoch, the dynamics and physical behaviour of the models have been discussed. From statefinder diagnostic pair we found that the model with exponential volumetric expansion behaves more like a $\\Lambda$CDM model.

  2. Fractal cosmology

    International Nuclear Information System (INIS)

    Dickau, Jonathan J.

    2009-01-01

    The use of fractals and fractal-like forms to describe or model the universe has had a long and varied history, which begins long before the word fractal was actually coined. Since the introduction of mathematical rigor to the subject of fractals, by Mandelbrot and others, there have been numerous cosmological theories and analyses of astronomical observations which suggest that the universe exhibits fractality or is by nature fractal. In recent years, the term fractal cosmology has come into usage, as a description for those theories and methods of analysis whereby a fractal nature of the cosmos is shown.

  3. Evolution in bouncing quantum cosmology

    International Nuclear Information System (INIS)

    Mielczarek, Jakub; Piechocki, Włodzimierz

    2012-01-01

    We present the method of describing an evolution in quantum cosmology in the framework of the reduced phase space quantization of loop cosmology. We apply our method to the flat Friedmann-Robertson-Walker model coupled to a massless scalar field. We identify the physical quantum Hamiltonian that is positive-definite and generates globally a unitary evolution of the considered quantum system. We examine the properties of expectation values of physical observables in the process of the quantum big bounce transition. The dispersion of evolved observables is studied for the Gaussian state. Calculated relative fluctuations enable an examination of the semi-classicality conditions and possible occurrence of the cosmic forgetfulness. Preliminary estimations based on the cosmological data suggest that there was no cosmic amnesia. Presented results are analytical, and numerical computations are only used for the visualization purposes. Our method may be generalized to sophisticated cosmological models including the Bianchi-type universes. (paper)

  4. Is cosmology consistent?

    International Nuclear Information System (INIS)

    Wang Xiaomin; Tegmark, Max; Zaldarriaga, Matias

    2002-01-01

    We perform a detailed analysis of the latest cosmic microwave background (CMB) measurements (including BOOMERaNG, DASI, Maxima and CBI), both alone and jointly with other cosmological data sets involving, e.g., galaxy clustering and the Lyman Alpha Forest. We first address the question of whether the CMB data are internally consistent once calibration and beam uncertainties are taken into account, performing a series of statistical tests. With a few minor caveats, our answer is yes, and we compress all data into a single set of 24 bandpowers with associated covariance matrix and window functions. We then compute joint constraints on the 11 parameters of the 'standard' adiabatic inflationary cosmological model. Our best fit model passes a series of physical consistency checks and agrees with essentially all currently available cosmological data. In addition to sharp constraints on the cosmic matter budget in good agreement with those of the BOOMERaNG, DASI and Maxima teams, we obtain a heaviest neutrino mass range 0.04-4.2 eV and the sharpest constraints to date on gravity waves which (together with preference for a slight red-tilt) favor 'small-field' inflation models

  5. Quasars and cosmology

    International Nuclear Information System (INIS)

    Fliche, H.-H.; Souriau, J.-M.

    1978-03-01

    On the basis of colorimetric data a composite spectrum of quasars is established from the visible to the Lyman's limit. Its agreement with the spectrum of the quasar 3C273, obtained directly, confirms the homogeneity of these objects. The compatibility of the following hypotheses: negligible evolution of quasars, Friedmann type model of the universe with cosmological constant, is studied by means of two tests: a non-correlation test adopted to the observation conditions and the construction of diagrams (absolute magnitude, volume) using the K-correction deduced from the composite spectrum. This procedure happens to give relatively well-defined values of the parameters; the central values of the density parameter, the reduced curvature and the reduced cosmological constant are: Ω 0 =0.053, k 0 =0.245, lambda-zero=1.19, which correspond to a big bang model, eternally expanding, spatially finite, in which Hubble's parameter H is presently increasing. This model responds well to different cosmological tests: density of matter, diameter of radio sources, age of the universe. Its characteristics suggest various cosmogonic mechanisms, espacially mass formation by growth of empty spherical bubbles [fr

  6. Bianchi Type-I cosmological mesonic stiff fluid models in Lyra's ...

    Indian Academy of Sciences (India)

    Some physical and kinematical properties of the models are also discussed. Keywords. Cosmology; Bianchi-I ... Here ρ, p and ui are respectively the energy density, equilibrium pressure and four-velocity vector of the .... In order to obtain an explicit form of physical parameters, we consider here stiff fluid distribution given by ...

  7. Tensors, relativity, and cosmology

    CERN Document Server

    Dalarsson, Mirjana

    2015-01-01

    Tensors, Relativity, and Cosmology, Second Edition, combines relativity, astrophysics, and cosmology in a single volume, providing a simplified introduction to each subject that is followed by detailed mathematical derivations. The book includes a section on general relativity that gives the case for a curved space-time, presents the mathematical background (tensor calculus, Riemannian geometry), discusses the Einstein equation and its solutions (including black holes and Penrose processes), and considers the energy-momentum tensor for various solutions. In addition, a section on relativistic astrophysics discusses stellar contraction and collapse, neutron stars and their equations of state, black holes, and accretion onto collapsed objects, with a final section on cosmology discussing cosmological models, observational tests, and scenarios for the early universe. This fully revised and updated second edition includes new material on relativistic effects, such as the behavior of clocks and measuring rods in m...

  8. Characterization of two Turkish beta-hexosaminidase mutations causing Tay-Sachs disease.

    Science.gov (United States)

    Ozkara, Hatice Asuman; Sandhoff, Konrad

    2003-04-01

    Two homoallelic mutations have recently been identified in the alpha-subunit of hexosaminidase A (EC 3.2.1.52) causing the infantile form of Tay-Sachs disease in Turkish patients. Both of these mutations, a 12 bp deletion (1096-1107 or 1098-1108 or 1099-1109) in exon 10 and a point mutation (G1362 to A, Gly454 to Asp) in exon 12, are located in the catalytic domain of the hexosaminidase alpha-chain. In order to determine whether these mutations affect the function of the catalytic domain or result in an instable protein, both mutant cDNAs were overexpressed in COS-1 cells. As judged by Western blotting, transfections of wild-type cDNA produced pro-alpha-chain and mature alpha-chain in parallel with a fivefold increase in cellular hexosaminidase activity using the synthetic substrate 4-methylumbelliferyl beta-N-acetylglucosamine 6-sulfate (MUGS). However, both mutants produced only pro-alpha-chains, although no mature form or detectable hexosaminidase activity towards two different synthetic substrates was observed. These data are consistent with the biochemical phenotype of infantile Tay-Sachs disease. We conclude that the overexpressed mutant pro-alpha-chains were misfolded and could not undergo further proteolytic processing to the active form of the enzyme in the lysosome.

  9. The importance of local measurements for cosmology

    CERN Document Server

    Verde, Licia; Jimenez, Raul

    2013-01-01

    We explore how local, cosmology-independent measurements of the Hubble constant and the age of the Universe help to provide a powerful consistency check of the currently favored cosmological model (flat LambdaCDM) and model-independent constraints on cosmology. We use cosmic microwave background (CMB) data to define the model-dependent cosmological parameters, and add local measurements to assess consistency and determine whether extensions to the model are justified. At current precision, there is no significant tension between the locally measured Hubble constant and age of the Universe (with errors of 3% and 5% respectively) and the corresponding parameters derived from the CMB. However, if errors on the local measurements could be decreased by a factor of two, one could decisively conclude if there is tension or not. We also compare the local and CMB data assuming simple extensions of the flat, $\\Lambda$CDM model (including curvature, dark energy with a constant equation of state parameter not equal to -1...

  10. Plane symmetric cosmological model with thick domain walls in Brans-Dicke theory of gravitation

    International Nuclear Information System (INIS)

    Pawar, D.; Bayaskar, S.; Patil, V.

    2009-01-01

    We have investigated plane symmetric cosmological model in presence of thick domain walls in Brans-Dicke theory of gravitation, some geometrical and physical behavior of the model are discussed. (authors)

  11. How robust are inflation model and dark matter constraints from cosmological data?

    DEFF Research Database (Denmark)

    Hamann, Jan; Hannestad, Steen; Sloth, Martin Snoager

    2006-01-01

    the tensor-to-scalar ratio r and the neutrino mass prevents lambda phi^4 from being excluded by present data. Reversing the argument, if lambda phi^4 is the correct model of inflation, it predicts a sum of neutrino masses at 0.3-0.5 eV, a range compatible with present experimental limits and within the reach......High-precision data from observation of the cosmic microwave background and the large scale structure of the universe provide very tight constraints on the effective parameters that describe cosmological inflation. Indeed, within a constrained class of LambdaCDM models, the simple lambda phi^4...... chaotic inflation model already appears to be ruled out by cosmological data. In this paper, we compute constraints on inflationary parameters within a more general framework that includes other physically motivated parameters such as a nonzero neutrino mass. We find that a strong degeneracy between...

  12. Physically self-consistent basis for modern cosmology

    International Nuclear Information System (INIS)

    Khlopov, M.Yu.

    2000-01-01

    Cosmoparticle physics appeared as a natural result of internal development of cosmology seeking physical grounds for inflation, baryosynthesis, and nonbaryonic dark matter and of particle physics going outside the Standard Model of particle interactions. Its aim is to study the foundations of particle physics and cosmology and their fundamental relationship in the combination of respective indirect cosmological, astrophysical, and physical effects. The ideas on new particles and fields predicted by particle theory and on their cosmological impact are discussed, as well as the methods of cosmoparticle physics to probe these ideas, are considered with special analysis of physical mechanisms for inflation, baryosynthesis, and nonbaryonic dark matter. These mechanisms are shown to reflect the main principle of modern cosmology, putting, instead of formal parameters of cosmological models, physical processes governing the evolution of the big-bang universe. Their realization on the basis of particle theory induces additional model-dependent predictions, accessible to various methods of nonaccelerator particle physics. Probes for such predictions, with the use of astrophysical data, are the aim of cosmoarcheology studying astrophysical effects of new physics. The possibility of finding quantitatively definite relationships between cosmological and laboratory effects on the basis of cosmoparticle approach, as well as of obtaining a unique solution to the problem of physical candidates for inflation, mechanisms of baryogenesis, and multicomponent dark matter, is exemplified in terms of gauge model with broken family symmetry, underlying horizontal unification and possessing quantitatively definite physical grounds for inflation, baryosynthesis, and effectively multicomponent dark-matter scenarios

  13. Expanding the spectrum of HEXA mutations in Indian patients with Tay–Sachs disease

    Directory of Open Access Journals (Sweden)

    Jayesh Sheth

    2014-01-01

    Full Text Available Tay–Sachs disease is an autosomal recessive neurodegenerative disorder occurring due to impaired activity of β-hexosaminidase-A (EC 3.2.1.52, resulting from the mutation in HEXA gene. Very little is known about the molecular pathology of TSD in Indian children except for a few mutations identified by us. The present study is aimed to determine additional mutations leading to Tay–Sachs disease in nine patients confirmed by the deficiency of β-hexosaminidase-A (C (D175A and c.805G>C (p.G269R in one case; and one small 1 bp deletion c.426delT (p.F142LfsX57 and one splice site mutation c.459+4A>C in the other two cases respectively. None of these mutations were detected in 100 chromosomes from healthy individuals of the same ethnic group. Three previously reported missense mutations, (i c.532C>T (p.R178C, (ii c.964G>T (p.D322Y, and (iii c.1385A>T (p.E462V; two nonsense mutations (i c.709C>T (p.Q237X and (ii c.1528C>T (p.R510X, one 4 bp insertion c.1277_1278insTATC (p.Y427IfsX5 and one splice site mutation c.459+5G>A were also identified in six cases. We observe from this study that novel mutations are more frequently observed in Indian patients with Tay–Sachs disease with clustering of ~73% of disease causing mutations in exons 5 to 12. This database can be used for a carrier rate screening in the larger population of the country.

  14. The Atacama Cosmology Telescope: Cosmology from Galaxy Clusters Detected via the Sunyaev-Zeldovich Effect

    International Nuclear Information System (INIS)

    Sehgal, N.

    2011-01-01

    We present constraints on cosmological parameters based on a sample of Sunyaev-Zeldovich-selected galaxy clusters detected in a millimeter-wave survey by the Atacama Cosmology Telescope. The cluster sample used in this analysis consists of 9 optically-confirmed high-mass clusters comprising the high-significance end of the total cluster sample identified in 455 square degrees of sky surveyed during 2008 at 148GHz. We focus on the most massive systems to reduce the degeneracy between unknown cluster astrophysics and cosmology derived from SZ surveys. We describe the scaling relation between cluster mass and SZ signal with a 4-parameter fit. Marginalizing over the values of the parameters in this fit with conservative priors gives σ 8 = 0.851 ± 0.115 and w = -1.14 ± 0.35 for a spatially-flat wCDM cosmological model with WMAP 7-year priors on cosmological parameters. This gives a modest improvement in statistical uncertainty over WMAP 7-year constraints alone. Fixing the scaling relation between cluster mass and SZ signal to a fiducial relation obtained from numerical simulations and calibrated by X-ray observations, we find σ 8 = 0.821 ± 0.044 and w = -1.05 ± 0.20. These results are consistent with constraints from WMAP 7 plus baryon acoustic oscillations plus type Ia supernoava which give σ 8 = 0.802 ± 0.038 and w = -0.98 ± 0.053. A stacking analysis of the clusters in this sample compared to clusters simulated assuming the fiducial model also shows good agreement. These results suggest that, given the sample of clusters used here, both the astrophysics of massive clusters and the cosmological parameters derived from them are broadly consistent with current models.

  15. Current observations with a decaying cosmological constant allow for chaotic cyclic cosmology

    International Nuclear Information System (INIS)

    Ellis, George F.R.; Platts, Emma; Weltman, Amanda; Sloan, David

    2016-01-01

    We use the phase plane analysis technique of Madsen and Ellis [1] to consider a universe with a true cosmological constant as well as a cosmological 'constant' that is decaying. Time symmetric dynamics for the inflationary era allows eternally bouncing models to occur. Allowing for scalar field dynamic evolution, we find that if dark energy decays in the future, chaotic cyclic universes exist provided the spatial curvature is positive. This is particularly interesting in light of current observations which do not yet rule out either closed universes or possible evolution of the cosmological constant. We present only a proof of principle, with no definite claim on the physical mechanism required for the present dark energy to decay

  16. Integrated cosmological probes: concordance quantified

    Energy Technology Data Exchange (ETDEWEB)

    Nicola, Andrina; Amara, Adam; Refregier, Alexandre, E-mail: andrina.nicola@phys.ethz.ch, E-mail: adam.amara@phys.ethz.ch, E-mail: alexandre.refregier@phys.ethz.ch [Department of Physics, ETH Zürich, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich (Switzerland)

    2017-10-01

    Assessing the consistency of parameter constraints derived from different cosmological probes is an important way to test the validity of the underlying cosmological model. In an earlier work [1], we computed constraints on cosmological parameters for ΛCDM from an integrated analysis of CMB temperature anisotropies and CMB lensing from Planck, galaxy clustering and weak lensing from SDSS, weak lensing from DES SV as well as Type Ia supernovae and Hubble parameter measurements. In this work, we extend this analysis and quantify the concordance between the derived constraints and those derived by the Planck Collaboration as well as WMAP9, SPT and ACT. As a measure for consistency, we use the Surprise statistic [2], which is based on the relative entropy. In the framework of a flat ΛCDM cosmological model, we find all data sets to be consistent with one another at a level of less than 1σ. We highlight that the relative entropy is sensitive to inconsistencies in the models that are used in different parts of the analysis. In particular, inconsistent assumptions for the neutrino mass break its invariance on the parameter choice. When consistent model assumptions are used, the data sets considered in this work all agree with each other and ΛCDM, without evidence for tensions.

  17. Cosmological tests of coupled Galileons

    International Nuclear Information System (INIS)

    Brax, Philippe; Burrage, Clare; Davis, Anne-Christine; Gubitosi, Giulia

    2015-01-01

    We investigate the cosmological properties of Galileon models which admit Minkowski space as a stable solution in vacuum. This is motivated by stable, positive tension brane world constructions that give rise to Galileons. We include both conformal and disformal couplings to matter and focus on constraints on the theory that arise because of these couplings. The disformal coupling to baryonic matter is extremely constrained by astrophysical and particle physics effects. The disformal coupling to photons induces a cosmological variation of the speed of light and therefore distorsions of the Cosmic Microwave Background spectrum which are known to be very small. The conformal coupling to baryons leads to a variation of particle masses since Big Bang Nucleosynthesis which is also tightly constrained. We consider the background cosmology of Galileon models coupled to Cold Dark Matter (CDM), photons and baryons and impose that the speed of light and particle masses respect the observational bounds on cosmological time scales. We find that requiring that the equation of state for the Galileon models must be close to -1 now restricts severely their parameter space and can only be achieved with a combination of the conformal and disformal couplings. This leads to large variations of particle masses and the speed of light which are not compatible with observations. As a result, we find that cosmological Galileon models are viable dark energy theories coupled to dark matter but their couplings, both disformal and conformal, to baryons and photons must be heavily suppressed making them only sensitive to CDM

  18. No hair theorem for inhomogeneous cosmologies

    International Nuclear Information System (INIS)

    Jensen, L.G.; Stein-Schabes, J.A.

    1986-03-01

    We show that under very general conditions any inhomogeneous cosmological model with a positive cosmological constant, that can be described in a synchronous reference system will tend asymptotically in time towards the de Sitter solution. This is shown to be relevant in the context of inflationary models as it makes inflation very weakly dependent on initial conditions. 8 refs

  19. The Atacama Cosmology Telescope: Cosmological Parameters from the 2008 Power Spectrum

    Science.gov (United States)

    Dunkley, J.; Hlozek, R.; Sievers, J.; Acquaviva, V.; Ade, P. A. R.; Aguirre, P.; Amiri, M.; Appel, J. W.; Barrientos, L. F.; Battistelli, E. S.; hide

    2011-01-01

    We present cosmological parameters derived from the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz and 218 GHz over 296 deg(exp 2) with the Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations at scales 500 cosmological parameters from the less contaminated 148 GHz spectrum, marginalizing over SZ and source power. The ACDM cosmological model is a good fit to the data (chi square/dof = 29/46), and ACDM parameters estimated from ACT+Wilkinson Microwave Anisotropy Probe (WMAP) are consistent with the seven-year WMAP limits, with scale invariant n(sub s) = 1 excluded at 99.7% confidence level (CL) (3 sigma). A model with no CMB lensing is disfavored at 2.8 sigma. By measuring the third to seventh acoustic peaks, and probing the Silk damping regime, the ACT data improve limits on cosmological parameters that affect the small-scale CMB power. The ACT data combined with WMAP give a 6 sigma detection of primordial helium, with Y(sub p) = 0.313 +/- 0.044, and a 4 sigma detection of relativistic species, assumed to be neutrinos, with N(sub eff) = 5.3 +/- 1.3 (4.6 +/- 0.8 with BAO+H(sub 0) data). From the CMB alone the running of the spectral index is constrained to be d(sub s) / d ln k = -0,034 +/- 0,018, the limit on the tensor-to-scalar ratio is r < 0,25 (95% CL), and the possible contribution of Nambu cosmic strings to the power spectrum is constrained to string tension G(sub mu) < 1.6 x 10(exp -7) (95% CL),

  20. Cosmological effects of nonlinear electrodynamics

    International Nuclear Information System (INIS)

    Novello, M; Goulart, E; Salim, J M; Bergliaffa, S E Perez

    2007-01-01

    It will be shown that a given realization of nonlinear electrodynamics, used as a source of Einstein's equations, generates a cosmological model with interesting features, namely a phase of current cosmic acceleration, and the absence of an initial singularity, thus pointing to a way of solving two important problems in cosmology

  1. TCP, quantum gravity, the cosmological constant and all that .

    International Nuclear Information System (INIS)

    Banks, T.

    1985-01-01

    We study cosmology from the point of view of quantum gravity. Some light is thrown on the nature of time, and it is suggested that the cosmological arrow of time is generated by a spontaneous breakdown of TCP. Conventional cosmological models in which quantum fields interact with a time-dependent gravitational field are shown to describe an approximation to the quantum gravitational wave function which is valid in the long-wavelength limit. Two problems with initial conditions are resolved in models in which a negative bare cosmological constant is cancelled by the classical excitation of a Bose field eta with a very flat potential. These models can also give a natural explanation for the observed value of the cosmological constant. (orig.)

  2. The Atacama Cosmology Telescope: Cosmology from Galaxy Clusters Detected Via the Sunyaev-Zel'dovich Effect

    Science.gov (United States)

    Sehgal, Neelima; Trac, Hy; Acquaviva, Viviana; Ade, Peter A. R.; Aguirre, Paula; Amiri, Mandana; Appel, John W.; Barrientos, L. Felipe; Battistelli, Elia S.; Bond, J. Richard; hide

    2010-01-01

    We present constraints on cosmological parameters based on a sample of Sunyaev-Zel'dovich-selected galaxy clusters detected in a millimeter-wave survey by the Atacama Cosmology Telescope. The cluster sample used in this analysis consists of 9 optically-confirmed high-mass clusters comprising the high-significance end of the total cluster sample identified in 455 square degrees of sky surveyed during 2008 at 148 GHz. We focus on the most massive systems to reduce the degeneracy between unknown cluster astrophysics and cosmology derived from SZ surveys. We describe the scaling relation between cluster mass and SZ signal with a 4-parameter fit. Marginalizing over the values of the parameters in this fit with conservative priors gives (sigma)8 = 0.851 +/- 0.115 and w = -1.14 +/- 0.35 for a spatially-flat wCDM cosmological model with WMAP 7-year priors on cosmological parameters. This gives a modest improvement in statistical uncertainty over WMAP 7-year constraints alone. Fixing the scaling relation between cluster mass and SZ signal to a fiducial relation obtained from numerical simulations and calibrated by X-ray observations, we find (sigma)8 + 0.821 +/- 0.044 and w = -1.05 +/- 0.20. These results are consistent with constraints from WMAP 7 plus baryon acoustic oscillations plus type Ia supernova which give (sigma)8 = 0.802 +/- 0.038 and w = -0.98 +/- 0.053. A stacking analysis of the clusters in this sample compared to clusters simulated assuming the fiducial model also shows good agreement. These results suggest that, given the sample of clusters used here, both the astrophysics of massive clusters and the cosmological parameters derived from them are broadly consistent with current models.

  3. Cosmological Structure Formation: From Dawn till Dusk

    DEFF Research Database (Denmark)

    Heneka, Caroline Samantha

    Cosmology has entered an era where a plethora data is available on structure formation to constrain astrophysics and underlying cosmology. This thesis strives to both investigate new observables and modeling of the Epoch of Reionization, as well as to constrain dark energy phenomenology with mass......Cosmology has entered an era where a plethora data is available on structure formation to constrain astrophysics and underlying cosmology. This thesis strives to both investigate new observables and modeling of the Epoch of Reionization, as well as to constrain dark energy phenomenology...... with massive galaxy clusters, traveling from the dawn of structure formation, when the first galaxies appear, to its dusk, when a representative part of the mass in the Universe is settled in massive structures. This hunt for accurate constraints on cosmology is complemented with the demonstration of novel...... Bayesian statistical tools and kinematical constraints on dark energy. Starting at the dawn of structure formation, we study emission line fluctuations, employing semi-numerical simulations of cosmological volumes of their line emission, in order to cross-correlate fluctuations in brightness. This cross...

  4. Cosmology

    International Nuclear Information System (INIS)

    Contopoulos, G.; Kotsakis, D.

    1987-01-01

    An extensive first part on a wealth of observational results relevant to cosmology lays the foundation for the second and central part of the book; the chapters on general relativity, the various cosmological theories, and the early universe. The authors present in a complete and almost non-mathematical way the ideas and theoretical concepts of modern cosmology including the exciting impact of high-energy particle physics, e.g. in the concept of the ''inflationary universe''. The final part addresses the deeper implications of cosmology, the arrow of time, the universality of physical laws, inflation and causality, and the anthropic principle

  5. The Cosmological Dependence of Galaxy Cluster Morphologies

    Science.gov (United States)

    Crone, Mary Margaret

    1995-01-01

    Measuring the density of the universe has been a fundamental problem in cosmology ever since the "Big Bang" model was developed over sixty years ago. In this simple and successful model, the age and eventual fate of the universe are determined by its density, its rate of expansion, and the value of a universal "cosmological constant". Analytic models suggest that many properties of galaxy clusters are sensitive to cosmological parameters. In this thesis, I use N-body simulations to examine cluster density profiles, abundances, and degree of subclustering to test the feasibility of using them as cosmological tests. The dependence on both cosmology and initial density field is examined, using a grid of cosmologies and scale-free initial power spectra P(k)~ k n. Einstein-deSitter ( Omegao=1), open ( Omegao=0.2 and 0.1) and flat, low density (Omegao=0.2, lambdao=0.8) models are studied, with initial spectral indices n=-2, -1 and 0. Of particular interest are the results for cluster profiles and substructure. The average density profiles are well fit by a power law p(r)~ r ^{-alpha} for radii where the local density contrast is between 100 and 3000. There is a clear trend toward steeper slopes with both increasing n and decreasing Omegao, with profile slopes in the open models consistently higher than Omega=1 values for the range of n examined. The amount of substructure in each model is quantified and explained in terms of cluster merger histories and the behavior of substructure statistics. The statistic which best distinguishes models is a very simple measure of deviations from symmetry in the projected mass distribution --the "Center-of-Mass Shift" as a function of overdensity. Some statistics which are quite sensitive to substructure perform relatively poorly as cosmological indicators. Density profiles and the Center-of-Mass test are both well-suited for comparison with weak lensing data and galaxy distributions. Such data are currently being collected and should

  6. Stepping out of homogeneity in loop quantum cosmology

    International Nuclear Information System (INIS)

    Rovelli, Carlo; Vidotto, Francesca

    2008-01-01

    We explore the extension of quantum cosmology outside the homogeneous approximation using the formalism of loop quantum gravity. We introduce a model where some of the inhomogeneous degrees of freedom are present, providing a tool for describing general fluctuations of quantum geometry near the initial singularity. We show that the dynamical structure of the model reduces to that of loop quantum cosmology in the Born-Oppenheimer approximation. This result corroborates the assumptions that ground loop cosmology sheds some light on the physical and mathematical relation between loop cosmology and full loop quantum gravity, and on the nature of the cosmological approximation. Finally, we show that the non-graph-changing Hamiltonian constraint considered in the context of algebraic quantum gravity provides a viable effective dynamics within this approximation

  7. The expanding Universe a primer on relativistic cosmology

    CERN Document Server

    Heacox, William D

    2015-01-01

    Cosmology - the science of the Universe at large - has experienced a renaissance in the decades bracketing the turn of the twenty-first century. Exploring our emerging understanding of cosmology, this text takes two complementary points of view: the physical principles underlying theories of cosmology, and the observable consequences of models of Universal expansion. The book develops cosmological models based on fundamental physical principles, with mathematics limited to the minimum necessary to keep the material accessible for students of physics and astronomy at the advanced undergraduate level. A substantial review of general relativity leading up to the Einstein field equations is included, with derivations of explicit formulations connecting observable features of the Universe to models of its expansion. Self-contained and up to date in respect of modern observations, the text provides a solid theoretical grounding in modern cosmology while preparing readers for the changes that will inevitably come fr...

  8. ACOG committee opinion. Number 318, October 2005. Screening for Tay-Sachs disease.

    Science.gov (United States)

    2005-10-01

    Tay-Sachs disease (TSD) is a severe progressive neurologic disease that causes death in early childhood. Carrier screening, should be offered before pregnancy to individuals and couples at high-risk, including those of Ashkenazi Jewish, French-Canadian, or Cajun descent and those with a family history consistent with TSD. If both partners are determined to be carriers of TSD, genetic counseling and prenatal diagnosis should be offered.

  9. Exact Solution and Exotic Fluid in Cosmology

    Directory of Open Access Journals (Sweden)

    Phillial Oh

    2012-09-01

    Full Text Available We investigate cosmological consequences of nonlinear sigma model coupled with a cosmological fluid which satisfies the continuity equation. The target space action is of the de Sitter type and is composed of four scalar fields. The potential which is a function of only one of the scalar fields is also introduced. We perform a general analysis of the ensuing cosmological equations and give various critical points and their properties. Then, we show that the model exhibits an exact cosmological solution which yields a transition from matter domination into dark energy epoch and compare it with the Λ-CDM behavior. Especially, we calculate the age of the Universe and show that it is consistent with the observational value if the equation of the state ωf of the cosmological fluid is within the range of 0.13 < ωf < 0.22. Some implication of this result is also discussed.

  10. Smoot Group Cosmology

    Science.gov (United States)

    the Universe About Cosmology Planck Satellite Launched Cosmology Videos Professor George Smoot's group conducts research on the early universe (cosmology) using the Cosmic Microwave Background radiation (CMB science goals regarding cosmology. George Smoot named Director of Korean Cosmology Institute The GRB

  11. Mathematical cosmology

    International Nuclear Information System (INIS)

    Wainwright, J.

    1990-01-01

    The workshop on mathematical cosmology was devoted to four topics of current interest. This report contains a brief discussion of the historical background of each topic and a concise summary of the content of each talk. The topics were; the observational cosmology program, the cosmological perturbation program, isotropic singularities, and the evolution of Bianchi cosmologies. (author)

  12. Constraining holographic cosmology using Planck data

    Science.gov (United States)

    Afshordi, Niayesh; Gould, Elizabeth; Skenderis, Kostas

    2017-06-01

    Holographic cosmology offers a novel framework for describing the very early Universe in which cosmological predictions are expressed in terms of the observables of a three-dimensional quantum field theory (QFT). This framework includes conventional slow-roll inflation, which is described in terms of a strongly coupled QFT, but it also allows for qualitatively new models for the very early Universe, where the dual QFT may be weakly coupled. The new models describe a universe which is nongeometric at early times. While standard slow-roll inflation leads to a (near-) power-law primordial power spectrum, perturbative super-renormalizable QFTs yield a new holographic spectral shape. Here, we compare the two predictions against cosmological observations. We use CosmoMC to determine the best fit parameters, and MultiNest for Bayesian evidence, comparing the likelihoods. We find that the dual QFT should be nonperturbative at the very low multipoles (l ≲30 ), while for higher multipoles (l ≳30 ) the new holographic model, based on perturbative QFT, fits the data just as well as the standard power-law spectrum assumed in Λ CDM cosmology. This finding opens the door to applications of nonperturbative QFT techniques, such as lattice simulations, to observational cosmology on gigaparsec scales and beyond.

  13. Chaos, decoherence and quantum cosmology

    International Nuclear Information System (INIS)

    Calzetta, Esteban

    2012-01-01

    In this topical review we discuss the connections between chaos, decoherence and quantum cosmology. We understand chaos as classical chaos in systems with a finite number of degrees of freedom, decoherence as environment induced decoherence and quantum cosmology as the theory of the Wheeler-DeWitt equation or else the consistent history formulation thereof, first in mini super spaces and later through its extension to midi super spaces. The overall conclusion is that consideration of decoherence is necessary (and probably sufficient) to sustain an interpretation of quantum cosmology based on the wavefunction of the Universe adopting a Wentzel-Kramers-Brillouin form for large Universes, but a definitive account of the semiclassical transition in classically chaotic cosmological models is not available in the literature yet. (topical review)

  14. An Introduction to General Relativity and Cosmology

    International Nuclear Information System (INIS)

    Wainwright, John

    2007-01-01

    The present volume is an introduction to general relativity and cosmology, at a level suitable for beginning graduate students or advanced undergraduates. The book consists of two main parts, the first entitled 'Elements of differential geometry', and the second 'The theory of gravitation'. Chapters 2-7, part I, introduce the basic ideas of differential geometry in a general setting, and are based on previously unpublished notes by one of the authors. On the one hand, the treatment is modern in that it uses a 'top-down' approach, i.e. starting with general differentiable manifolds, and deferring the introduction of a metric tensor until after the notions of affine connection and curvature have been introduced. On the other hand, the treatment is classical in that it relies heavily, though not exclusively, on index notation. The general material, chapters 1-7, is then followed by four more specialized chapters dealing with matters of specific interest for general relativity. Part II deals with general relativity and cosmology. The basic assumptions of the theory and its application to spherically symmetric gravitational fields are discussed in two chapters, and there is some historical material and motivation for the basic assumptions at the beginning of the book. The final chapter contains a detailed discussion of the Kerr solution. But the main emphasis in part II is on relativistic cosmology, in particular the analysis of cosmological models more general than the familiar Friedmann-Lemaitre (FL) models. The material on cosmology begins with a discussion of relativistic hydrodynamics and thermodynamics. The kinematical quantities (rate of expansion, shear, etc, of a timelike congruence) are introduced and their evolution equations are derived. There follows a description of the fluid model of the Universe and optical observations in such a model, within the framework of a general spacetime geometry. The discussion is subsequently specialized to the Robertson

  15. Doença de Tay-Sachs em criança de raça negra Tay-Sachs disease in a Negro child

    Directory of Open Access Journals (Sweden)

    Sérgio Rosemberg

    1970-12-01

    Full Text Available É relatado um caso de doença de Tay-Sachs em criança da raça negra. O encontro desta entidade em indivíduos não judeus é bastante raro, sendo este o quinto caso descrito em criança negra. Os autores estudam alguns aspectos genéticos, chegando à conclusão de que o cálculo da freqüência do gene mutante é impossível devido ao pequeno número de casos e ao fato de que não há estimativas seguras quanto à taxa de nascimento de indivíduos negros na população, Em que pese o fato de o diagnóstico se assentar em bases puramente clínicas e anatômicas, prescindindo os autores de exames bioquímicos específicos, os dados apresentados são congruentes com os casos clássicos descritos na literatura.A case of Tay-Sachs diseases in a Negro child is reported. The occurrence of this disease in non-Jewish individuals is very rare and this is the fifth case of a Negro-child reported in the litterature. Some genetical aspects are studied and the authors conclude that the frequency calculation of the mutant gene is impossible due to the small number of cases and to the fact that there is reliable information regarding the rate of birth of Negro individuals in the general population. The diagnosis was based on ophtalmological and clinical data. No specific biochemical tests were performed but the data obtained are congruent with other cases reported in the litterature.

  16. Cosmology and a general scalar-tensor theory of gravity

    International Nuclear Information System (INIS)

    Bishop, N.T.

    1976-01-01

    The cosmological models resulting from a general scalar-tensor theory of gravity are discussed. Those models for which the scalar field varies as a power of the cosmological expansion factor (i.e. phi varies as Rsup(n)) are considered in detail, leading to a set of such models compatible with observation. This set includes models in which the scalar coupling parameter ω is negative. The models described here are similar to those of Newtonian cosmology obtained from an impotence principle. (author)

  17. The Hubble IR cutoff in holographic ellipsoidal cosmologies

    Energy Technology Data Exchange (ETDEWEB)

    Cataldo, Mauricio [Universidad del Bio-Bio, Departamento de Fisica, Facultad de Ciencias, Concepcion (Chile); Cruz, Norman [Grupo de Cosmologia y Gravitacion-UBB, Concepcion (Chile)

    2018-01-15

    It is well known that for spatially flat FRW cosmologies, the holographic dark energy disfavors the Hubble parameter as a candidate for the IR cutoff. For overcoming this problem, we explore the use of this cutoff in holographic ellipsoidal cosmological models, and derive the general ellipsoidal metric induced by a such holographic energy density. Despite the drawbacks that this cutoff presents in homogeneous and isotropic universes, based on this general metric, we developed a suitable ellipsoidal holographic cosmological model, filled with a dark matter and a dark energy components. At late time stages, the cosmic evolution is dominated by a holographic anisotropic dark energy with barotropic equations of state. The cosmologies expand in all directions in accelerated manner. Since the ellipsoidal cosmologies given here are not asymptotically FRW, the deviation from homogeneity and isotropy of the universe on large cosmological scales remains constant during all cosmic evolution. This feature allows the studied holographic ellipsoidal cosmologies to be ruled by an equation of state ω = p/ρ, whose range belongs to quintessence or even phantom matter. (orig.)

  18. Cosmological birefringence constraints from CMB and astrophysical polarization data

    Energy Technology Data Exchange (ETDEWEB)

    Galaverni, M. [Studio Teologico Interdiocesano, V.le Timavo 93, Reggio Emilia, 42121 Italy (Italy); Gubitosi, G. [Dipartimento di Fisica and sez. Roma1 INFN, Università di Roma ' La Sapienza' , P.le A. Moro 2, Rome, 00185 Italy (Italy); Paci, F. [SISSA, Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea 265, Trieste, 34136 Italy (Italy); Finelli, F., E-mail: matteo.galaverni@gmail.com, E-mail: giulia.gubitosi@imperial.ac.uk, E-mail: fpaci@sissa.it, E-mail: finelli@iasfbo.inaf.it [INAF-IASF Bologna, via Gobetti 101, Bologna, I-40129 Italy (Italy)

    2015-08-01

    Cosmological birefringence is a rotation of the polarization plane of photons coming from sources of astrophysical and cosmological origin. The rotation can also depend on the energy of the photons and not only on the distance of the source and on the cosmological evolution of the underlying theoretical model. In this work, we constrain few selected models for cosmological birefringence, combining CMB and astrophysical data at radio, optical, X and γ wavelengths, taking into account the specific energy and distance dependences.

  19. Unilaterally and rapidly progressing white matter lesion and elevated cytokines in a patient with Tay-Sachs disease.

    Science.gov (United States)

    Hayase, Tomomi; Shimizu, Jun; Goto, Tamako; Nozaki, Yasuyuki; Mori, Masato; Takahashi, Naoto; Namba, Eiji; Yamagata, Takanori; Momoi, Mariko Y

    2010-03-01

    We report the case of a girl with Tay-Sachs disease who had convulsions and deteriorated rapidly after an upper respiratory infection at the age of 11 months. At the age of 16 months, her seizures became intractable and magnetic resonance imaging of the brain showed high signal intensity on T2-weighted images and marked swelling in the white matter and basal nucelei of the right hemisphere. Her seizures and right hemisphere lesion improved with glycerol and dexamethasone treatment. When dexamethasone was discontinued, her symptoms worsened and lesions later appeared in the left hemisphere. Her cerebrospinal fluid showed elevated levels of the cytokines TNF-alpha and IL-5. It is considered that inflammation contributes to disease progression in Tay-Sachs disease.

  20. A philosophy for big-bang cosmology.

    Science.gov (United States)

    McCrea, W H

    1970-10-03

    According to recent developments in cosmology we seem bound to find a model universe like the observed universe, almost independently of how we suppose it started. Such ideas, if valid, provide fresh justification for the procedures of current cosmological theory.

  1. Singular perturbations of empty Robertson-Walker cosmologies

    International Nuclear Information System (INIS)

    Newman, R.P.A.C.

    1979-02-01

    An investigation is presented which concerns a class of cosmological models defined by McVittie (1931): the universe is envisaged as a set of galaxies, idealised as point particles, which provide singular perturbations of Robertson-Walker cosmologies. The perturbations are considered only to first order in the gravitational coupling constant (8πG)/c 2 . Attention will only be given to such perturbations of empty Robertson-Walker cosmologies. Chapter 1 summarises the observational support for the type of model employed and for the smallness of the quantities to be used as perturbation coefficients. Chapter 2 provides the prerequisite analysis of Robertson-Walker cosmologies. Perturbations of empty Robertson-Walker cosmologies of non-vanishing cosmical constant are considered in general in Chapter 3. The structure of McVittie's singularly perturbed Robertson-Walker cosmologies are considered in detail in Chapter 4. The remaining chapters seek to investigate them further by way of their optical properties. Chapter 5 provides the necessary theory of geometric optics with particular regard to the intensity and distortion of a beam of light, and Chapter 6 applies this theory to the McVittie cosmologies. Chapter 7 sees the definition of an averaging procedure which leads to expressions for the intensity and distortion of a typical beam of light from a point source. (author)

  2. Coupled oscillators as models of phantom and scalar field cosmologies

    International Nuclear Information System (INIS)

    Faraoni, Valerio

    2004-01-01

    We study a toy model for phantom cosmology recently introduced in the literature and consisting of two oscillators, one of which carries negative kinetic energy. The results are compared with the exact phase space picture obtained for similar dynamical systems describing, respectively, a massive canonical scalar field conformally coupled to the spacetime curvature and a conformally coupled massive phantom. Finally, the dynamical system describing exactly a minimally coupled phantom is studied and compared with the toy model

  3. HAWKING'S Theory of Quantum Cosmology

    Science.gov (United States)

    Zhi, Fang Li; Chao, Wu Zhong

    The most important problem in cosmology is the birth of the universe. Recently Hartle and Hawking put forward a ground state proposal for the quantum state of the universe which incorporates the idea that the universe must come from nothing. Many models have been discussed in quantum cosmology with this boundary condition. It has been shown that every model is a step towards to a realistic universe, i.e. a 4-dimensional isotropic universe with a long inflationary stage.

  4. Kerr metric in cosmological background

    Energy Technology Data Exchange (ETDEWEB)

    Vaidya, P C [Gujarat Univ., Ahmedabad (India). Dept. of Mathematics

    1977-06-01

    A metric satisfying Einstein's equation is given which in the vicinity of the source reduces to the well-known Kerr metric and which at large distances reduces to the Robertson-Walker metric of a nomogeneous cosmological model. The radius of the event horizon of the Kerr black hole in the cosmological background is found out.

  5. Anisotropic cosmological constant and the CMB quadrupole anomaly

    International Nuclear Information System (INIS)

    Rodrigues, Davi C.

    2008-01-01

    There are evidences that the cosmic microwave background (CMB) large-angle anomalies imply a departure from statistical isotropy and hence from the standard cosmological model. We propose a ΛCDM model extension whose dark energy component preserves its nondynamical character but wields anisotropic vacuum pressure. Exact solutions for the cosmological scale factors are presented, upper bounds for the deformation parameter are evaluated and its value is estimated considering the elliptical universe proposal to solve the quadrupole anomaly. This model can be constructed from a Bianchi I cosmology with a cosmological constant from two different ways: (i) a straightforward anisotropic modification of the vacuum pressure consistently with energy-momentum conservation; (ii) a Poisson structure deformation between canonical momenta such that the dynamics remain invariant under scale factors rescalings

  6. Weak lensing cosmology beyond ΛCDM

    International Nuclear Information System (INIS)

    Das, Sudeep; Linder, Eric V.; Nakajima, Reiko; Putter, Roland de

    2012-01-01

    Weak gravitational lensing is one of the key probes of the cosmological model, dark energy, and dark matter, providing insight into both the cosmic expansion history and large scale structure growth history. Taking into account a broad spectrum of physics affecting growth — dynamical dark energy, extended gravity, neutrino masses, and spatial curvature — we analyze the cosmological constraints. Similarly we consider the effects of a range of systematic uncertainties, in shear measurement, photometric redshifts, intrinsic alignments, and the nonlinear power spectrum, on cosmological parameter extraction. We also investigate, and provide fitting formulas for, the influence of survey parameters such as redshift depth, galaxy number densities, and sky area on the cosmological constraints in the beyond-ΛCDM parameter space. Finally, we examine the robustness of results for different fiducial cosmologies

  7. A CP violetion model of cosmological origin

    International Nuclear Information System (INIS)

    Truppel, W.L.

    1987-01-01

    It's presented a model of spontaneous violation of the CP symmetry whose mechanism of symmetry breaking is of cosmological nature. The main feature is the conformal coupling of the field of a λφ 4 theory with a background gravitational field. We show that, for the open Friedmann model of the universe, the reason of the critical temperaTure for the symmetry restoration to the equilibrium temperature of the universe rrmains constant, so that either the symmetry breaking never happened or, if happened, it can't be reverted by means of thermal effects. Upon coupling the boson to a fermion, this symmetry breaking id related to the CP non-conservation in two distinct ways: violating the P and T symmetries, and violating the C and T symmetries. (author) [pt

  8. Landscape predictions from cosmological vacuum selection

    Energy Technology Data Exchange (ETDEWEB)

    Bousso, Raphael; Bousso, Raphael; Yang, Sheng

    2007-04-23

    In Bousso-Polchinski models with hundreds of fluxes, we compute the effects of cosmological dynamics on the probability distribution of landscape vacua. Starting from generic initial conditions, we find that most fluxes are dynamically driven into a different and much narrower range of values than expected from landscape statistics alone. Hence, cosmological evolution will access only a tiny fraction of the vacua with small cosmological constant. This leads to a host of sharp predictions. Unlike other approaches to eternal inflation, the holographic measure employed here does not lead to staggering, an excessive spread of probabilities that would doom the string landscape as a solution to the cosmological constant problem.

  9. Landscape predictions from cosmological vacuum selection

    International Nuclear Information System (INIS)

    Bousso, Raphael; Yang, I-S.

    2007-01-01

    In Bousso-Polchinski models with hundreds of fluxes, we compute the effects of cosmological dynamics on the probability distribution of landscape vacua. Starting from generic initial conditions, we find that most fluxes are dynamically driven into a different and much narrower range of values than expected from landscape statistics alone. Hence, cosmological evolution will access only a tiny fraction of the vacua with small cosmological constant. This leads to a host of sharp predictions. Unlike other approaches to eternal inflation, the holographic measure employed here does not lead to staggering, an excessive spread of probabilities that would doom the string landscape as a solution to the cosmological constant problem

  10. Introduction to gravity and cosmology

    International Nuclear Information System (INIS)

    Jauneau, L.

    1988-09-01

    Relativity principles, equivalence principles, and the general covariance principle are introduced. Curved space analysis via tensor calculus and absolute differential calculus is outlined. Einstein's equations are presented. The Schwarzschild solution; tests of general relativity; and black holes are discussed. Application of general relativity to cosmology is considered. The Standard Model of cosmology and its extensions are reviewed

  11. Some five-dimensional Bianchi type-iii string cosmological models in general relativity

    International Nuclear Information System (INIS)

    Samanta, G.C.; Biswal, S.K.; Mohanty, G.; Rameswarpatna, Bhubaneswar

    2011-01-01

    In this paper we have constructed some five-dimensional Bianchi type-III cosmological models in general relativity when source of gravitational field is a massive string. We obtained different classes of solutions by considering different functional forms of metric potentials. It is also observed that one of the models is not physically acceptable and the other models possess big-bang singularity. The physical and kinematical behaviors of the models are discussed

  12. Cosmology and Particle Physics beyond Standard Models Ten Years of the SEENET-MTP Network

    CERN Document Server

    Álvarez-Gaumé, Luis; Stojkovic, Dejan

    2014-01-01

    This publication - "Cosmology and Particle Physics beyond Standard Models" - is dedicated to the celebration of the tenth anniversary of the Southeastern European Network in Mathematical and Theoretical Physics (SEENET-MTP). As a Theme Collection, rather than a Monograph or Proceedings, this volume presents a number of reports and overviews, a few research papers and a short note. However, some of them are excellent examples of a nowadays increasingly deep interplay between particle physics and cosmology. Contributions span a wide range of topics in cosmology, particle physics, but also gravity, including the interface of these fields. The presented work is of both theoretical and experimental/ observational nature. The contributions represent recent progress in their respective fields: inflation, dark matter, neutrino physics, supersymmetry, collider physics, string theory, quantum gravity, black hole physics and massive gravity.

  13. Cosmology and philosophy

    International Nuclear Information System (INIS)

    Ginzburg, V.L.

    1981-01-01

    The problem of establishing boundaries between cosmology and philosophy is discussed. It is stated that the theoretic knowledge and observation data do not contradict the selection of one of non-stationary homogenous and isotropic relativistic models, which are also called the Friedmann models. In this model (with a zero Λ - member) there is a critical value of the substance density which is 10 -29 g/cm 2 . The determination of the average density of the Universe substance relatively to this value enables to choose between a closed and an open Universe model. Nowadays, this problem is not yet solved. But some philosophic theses reject the closed cosmological model without any naturally scientific argumentation. Critical remarks about such an approach to the problem studied are presented. The conclusion is made that the problems of the Universe volume infinity of finity, laws of its evolution in time or the like are not philosophic and should be considered taking into account the data of astronomic observations and modern physics

  14. Neuro-ophthalmology of late-onset Tay-Sachs disease (LOTS).

    Science.gov (United States)

    Rucker, J C; Shapiro, B E; Han, Y H; Kumar, A N; Garbutt, S; Keller, E L; Leigh, R J

    2004-11-23

    Late-onset Tay-Sachs disease (LOTS) is an adult-onset, autosomal recessive, progressive variant of GM2 gangliosidosis, characterized by involvement of the cerebellum and anterior horn cells. To determine the range of visual and ocular motor abnormalities in LOTS, as a prelude to evaluating the effectiveness of novel therapies. Fourteen patients with biochemically confirmed LOTS (8 men; age range 24 to 53 years; disease duration 5 to 30 years) and 10 age-matched control subjects were studied. Snellen visual acuity, contrast sensitivity, color vision, stereopsis, and visual fields were measured, and optic fundi were photographed. Horizontal and vertical eye movements (search coil) were recorded, and saccades, pursuit, vestibulo-ocular reflex (VOR), vergence, and optokinetic (OK) responses were measured. All patients showed normal visual functions and optic fundi. The main eye movement abnormality concerned saccades, which were "multistep," consisting of a series of small saccades and larger movements that showed transient decelerations. Larger saccades ended earlier and more abruptly (greater peak deceleration) in LOTS patients than in control subjects; these changes can be attributed to premature termination of the saccadic pulse. Smooth-pursuit and slow-phase OK gains were reduced, but VOR, vergence, and gaze holding were normal. Patients with late-onset Tay-Sachs disease (LOTS) show characteristic abnormalities of saccades but normal afferent visual systems. Hypometria, transient decelerations, and premature termination of saccades suggest disruption of a "latch circuit" that normally inhibits pontine omnipause neurons, permitting burst neurons to discharge until the eye movement is completed. These measurable abnormalities of saccades provide a means to evaluate the effects of novel treatments for LOTS.

  15. A scalar-tensor bimetric brane world cosmology

    International Nuclear Information System (INIS)

    Youm, Donam

    2001-08-01

    We study a scalar-tensor bimetric cosmology in the Randall-Sundrum model with one positive tension brane, where the biscalar field is assumed to be confined on the brane. The effective Friedmann equations on the brane are obtained and analyzed. We comment on resolution of cosmological problems in this bimetric model. (author)

  16. Cosmology, inflation, and supersymmetry

    International Nuclear Information System (INIS)

    Albrecht, A.; Dimopoulos, S.; Fischler, W.; Kolb, E.W.; Raby, S.; Steinhardt, P.J.

    1982-01-01

    Cosmological consequences of supersymmetric grand unified models based on the Witten-O'Raifeartaigh potential are discussed. In particular we study the development of the phase transition in the spontaneous breaking of supersymmetry. We find that in realistic models where light fields feel supersymmetry breaking only through coupling to massive fields, e.g., the Geometric Hierarchy model, the universe does not inflate or reheat. Thus, the standard cosmological flatness, monopole, and horizon problems remain. In addition, we find that the transition is never completed, in the sense that the universe remains dominated by coherent Higgs field energy, resulting in an apparent matter dominated universe with Ω greater than or equal to 10 30

  17. String Gas Cosmology

    OpenAIRE

    Brandenberger, Robert H.

    2008-01-01

    String gas cosmology is a string theory-based approach to early universe cosmology which is based on making use of robust features of string theory such as the existence of new states and new symmetries. A first goal of string gas cosmology is to understand how string theory can effect the earliest moments of cosmology before the effective field theory approach which underlies standard and inflationary cosmology becomes valid. String gas cosmology may also provide an alternative to the curren...

  18. Cosmology on a cosmic ring

    International Nuclear Information System (INIS)

    Niedermann, Florian; Schneider, Robert

    2015-01-01

    We derive the modified Friedmann equations for a generalization of the Dvali-Gabadadze-Porrati (DGP) model in which the brane has one additional compact dimension. The main new feature is the emission of gravitational waves into the bulk. We study two classes of solutions: first, if the compact dimension is stabilized, the waves vanish and one exactly recovers DGP cosmology. However, a stabilization by means of physical matter is not possible for a tension-dominated brane, thus implying a late time modification of 4D cosmology different from DGP. Second, for a freely expanding compact direction, we find exact attractor solutions with zero 4D Hubble parameter despite the presence of a 4D cosmological constant. The model hence constitutes an explicit example of dynamical degravitation at the full nonlinear level. Without stabilization, however, there is no 4D regime and the model is ruled out observationally, as we demonstrate explicitly by comparing to supernova data

  19. A perturbative RS I cosmological phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Bunk, Don [Skidmore College, Department of Physics, Saratoga Springs, NY (United States); Hubisz, Jay [Syracuse University, Department of Physics, Syracuse, NY (United States); Jain, Bithika [Korea Institute for Advanced Study, School of Physics, Seoul (Korea, Republic of)

    2018-01-15

    We identify a class of Randall-Sundrum type models with a successful first order cosmological phase transition during which a 5D dual of approximate conformal symmetry is spontaneously broken. Our focus is on soft-wall models that naturally realize a light radion/dilaton and suppressed dynamical contribution to the cosmological constant. We discuss phenomenology of the phase transition after developing a theoretical and numerical analysis of these models both at zero and finite temperature. We demonstrate a model with a TeV-Planck hierarchy and with a successful cosmological phase transition where the UV value of the curvature corresponds, via AdS/CFT, to an N of 20, where 5D gravity is expected to be firmly in the perturbative regime. (orig.)

  20. Regional averaging and scaling in relativistic cosmology

    International Nuclear Information System (INIS)

    Buchert, Thomas; Carfora, Mauro

    2002-01-01

    Averaged inhomogeneous cosmologies lie at the forefront of interest, since cosmological parameters such as the rate of expansion or the mass density are to be considered as volume-averaged quantities and only these can be compared with observations. For this reason the relevant parameters are intrinsically scale-dependent and one wishes to control this dependence without restricting the cosmological model by unphysical assumptions. In the latter respect we contrast our way to approach the averaging problem in relativistic cosmology with shortcomings of averaged Newtonian models. Explicitly, we investigate the scale-dependence of Eulerian volume averages of scalar functions on Riemannian three-manifolds. We propose a complementary view of a Lagrangian smoothing of (tensorial) variables as opposed to their Eulerian averaging on spatial domains. This programme is realized with the help of a global Ricci deformation flow for the metric. We explain rigorously the origin of the Ricci flow which, on heuristic grounds, has already been suggested as a possible candidate for smoothing the initial dataset for cosmological spacetimes. The smoothing of geometry implies a renormalization of averaged spatial variables. We discuss the results in terms of effective cosmological parameters that would be assigned to the smoothed cosmological spacetime. In particular, we find that on the smoothed spatial domain B-bar evaluated cosmological parameters obey Ω-bar B-bar m + Ω-bar B-bar R + Ω-bar B-bar A + Ω-bar B-bar Q 1, where Ω-bar B-bar m , Ω-bar B-bar R and Ω-bar B-bar A correspond to the standard Friedmannian parameters, while Ω-bar B-bar Q is a remnant of cosmic variance of expansion and shear fluctuations on the averaging domain. All these parameters are 'dressed' after smoothing out the geometrical fluctuations, and we give the relations of the 'dressed' to the 'bare' parameters. While the former provide the framework of interpreting observations with a 'Friedmannian bias

  1. Microphysics, cosmology, and high energy astrophysics

    International Nuclear Information System (INIS)

    Hoyle, F.

    1974-01-01

    The discussion of microphysics, cosmology, and high energy astrophysics includes particle motion in an electromagnetic field, conformal transformations, conformally invariant theory of gravitation, particle orbits, Friedman models with k = 0, +-1, the history and present status of steady-state cosmology, and the nature of mass. (U.S.)

  2. Cosmology and convention

    Science.gov (United States)

    Merritt, David

    2017-02-01

    I argue that some important elements of the current cosmological model are 'conventionalist' in the sense defined by Karl Popper. These elements include dark matter and dark energy; both are auxiliary hypotheses that were invoked in response to observations that falsified the standard model as it existed at the time. The use of conventionalist stratagems in response to unexpected observations implies that the field of cosmology is in a state of 'degenerating problemshift' in the language of Imre Lakatos. I show that the 'concordance' argument, often put forward by cosmologists in support of the current paradigm, is weaker than the convergence arguments that were made in the past in support of the atomic theory of matter or the quantization of energy.

  3. Cosmological evolution of p-brane networks

    International Nuclear Information System (INIS)

    Sousa, L.; Avelino, P. P.

    2011-01-01

    In this paper we derive, directly from the Nambu-Goto action, the relevant components of the acceleration of cosmological featureless p-branes, extending previous analysis based on the field theory equations in the thin-brane limit. The component of the acceleration parallel to the velocity is at the core of the velocity-dependent one-scale model for the evolution of p-brane networks. We use this model to show that, in a decelerating expanding universe in which the p-branes are relevant cosmologically, interactions cannot lead to frustration, except for fine-tuned nonrelativistic networks with a dimensionless curvature parameter k<<1. We discuss the implications of our findings for the cosmological evolution of p-brane networks.

  4. Bianchi type II brane-world cosmologies (U≥0)

    International Nuclear Information System (INIS)

    Hoogen, R.J. van den; Ibanez, J.

    2003-01-01

    The asymptotic properties of the Bianchi type II cosmological model in the brane-world scenario are investigated. The matter content is assumed to be a combination of a perfect fluid and a minimally coupled scalar field that is restricted to the brane. The isotropic brane-world solution is determined to represent the initial singularity in all brane-world cosmologies. Additionally, it is shown that it is the kinetic energy of the scalar field which dominates the initial dynamics in these brane-world cosmologies. It is important to note that the dynamics of these brane-world cosmologies is not necessarily asymptotic to general relativistic cosmologies to the future in the case of a zero four-dimensional cosmological constant

  5. Chaos in non-diagonal spatially homogeneous cosmological models in spacetime dimensions <=10

    Science.gov (United States)

    Demaret, Jacques; de Rop, Yves; Henneaux, Marc

    1988-08-01

    It is shown that the chaotic oscillatory behaviour, absent in diagonal homogeneous cosmological models in spacetime dimensions between 5 and 10, can be reestablished when off-diagonal terms are included. Also at Centro de Estudios Cientificos de Santiago, Casilla 16443, Santiago 9, Chile

  6. Cosmological reconstruction and Om diagnostic analysis of Einstein-Aether theory

    Energy Technology Data Exchange (ETDEWEB)

    Pasqua, Antonio [Department of Physics, University of Trieste, Via Valerio 2, 34127 Trieste (Italy); Chattopadhyay, Surajit [Pailan College of Management and Technology, Bengal Pailan Park, Kolkata-700 104 (India); Momeni, Davood; Myrzakulov, Ratbay [Eurasian International Center for Theoretical Physics and Department of General and Theoretical Physics, Eurasian National University, Astana 010008 (Kazakhstan); Raza, Muhammad [Department of Mathematics, COMSATS Institute of Information Technology, Sahiwal 57000 (Pakistan); Faizal, Mir, E-mail: toto.pasqua@gmail.com, E-mail: surajcha@iucaa.ernet.in, E-mail: d.momeni@yahoo.com, E-mail: mraza@zju.edu.cn, E-mail: rmyrzakulov@gmail.com, E-mail: mirfaizalmir@gmail.com [Irving K. Barber School of Arts and Sciences, University of British Columbia—Okanagan, Kelowna, British Columbia V1V 1V7 (Canada)

    2017-04-01

    In this paper, we analyze the cosmological models in Einstein-Aether gravity, which is a modified theory of gravity in which a time-like vector field breaks the Lorentz symmetry. We use this formalism to analyse different cosmological models with different behavior of the scale factor. In this analysis, we use a certain functional dependence of the Dark Energy (DE) on the Hubble parameter H . It will be demonstrated that the Aether vector field has a non-trivial effect on these cosmological models. We also perform the Om diagnostic in Einstein-Aether gravity and we fit the parameters of the cosmological models using recent observational data.

  7. Atypical presentation of late-onset Tay-Sachs disease.

    Science.gov (United States)

    Deik, Andres; Saunders-Pullman, Rachel

    2014-05-01

    Late-onset Tay-Sachs disease (LOTS) is a lysosomal storage disease caused by deficient Beta-hexosaminidase A activity. We describe a 53-year-old woman who presented with adult-onset leg weakness, and whose initial diagnosis was progressive muscular atrophy without identifiable etiology. Development of cerebellar ataxia in mid-life prompted reassessment. Beta-hexosaminidase A quantification assay demonstrated absence of the isozyme. Genetic testing identified compound heterozygous mutations in the HEXA gene, confirming the diagnosis of LOTS. The phenotypic spectrum of LOTS includes motor neuronopathy, ataxia, choreoathetosis, neuropathy, and psychiatric symptoms in various combinations. This patient highlights the emergence of different clinical features over many years and emphasizes the need to consider LOTS in the differential diagnosis of progressive muscular atrophy. Copyright © 2013 Wiley Periodicals, Inc.

  8. Cosmological simulations of multicomponent cold dark matter.

    Science.gov (United States)

    Medvedev, Mikhail V

    2014-08-15

    The nature of dark matter is unknown. A number of dark matter candidates are quantum flavor-mixed particles but this property has never been accounted for in cosmology. Here we explore this possibility from the first principles via extensive N-body cosmological simulations and demonstrate that the two-component dark matter model agrees with observational data at all scales. Substantial reduction of substructure and flattening of density profiles in the centers of dark matter halos found in simulations can simultaneously resolve several outstanding puzzles of modern cosmology. The model shares the "why now?" fine-tuning caveat pertinent to all self-interacting models. Predictions for direct and indirect detection dark matter experiments are made.

  9. Halo Models of Large Scale Structure and Reliability of Cosmological N-Body Simulations

    Directory of Open Access Journals (Sweden)

    José Gaite

    2013-05-01

    Full Text Available Halo models of the large scale structure of the Universe are critically examined, focusing on the definition of halos as smooth distributions of cold dark matter. This definition is essentially based on the results of cosmological N-body simulations. By a careful analysis of the standard assumptions of halo models and N-body simulations and by taking into account previous studies of self-similarity of the cosmic web structure, we conclude that N-body cosmological simulations are not fully reliable in the range of scales where halos appear. Therefore, to have a consistent definition of halos is necessary either to define them as entities of arbitrary size with a grainy rather than smooth structure or to define their size in terms of small-scale baryonic physics.

  10. Bianchi type-VIh string cloud cosmological models with bulk viscosity

    Science.gov (United States)

    Tripathy, Sunil K.; Behera, Dipanjali

    2010-11-01

    String cloud cosmological models are studied using spatially homogeneous and anisotropic Bianchi type VIh metric in the frame work of general relativity. The field equations are solved for massive string cloud in presence of bulk viscosity. A general linear equation of state of the cosmic string tension density with the proper energy density of the universe is considered. The physical and kinematical properties of the models have been discussed in detail and the limits of the anisotropic parameter responsible for different phases of the universe are explored.

  11. Bianchi type-I magnetized cosmological models for the Einstein-Boltzmann equation with the cosmological constant

    International Nuclear Information System (INIS)

    Ayissi, Raoul Domingo; Noutchegueme, Norbert

    2015-01-01

    Global solutions regular for the Einstein-Boltzmann equation on a magnetized Bianchi type-I cosmological model with the cosmological constant are investigated. We suppose that the metric is locally rotationally symmetric. The Einstein-Boltzmann equation has been already considered by some authors. But, in general Bancel and Choquet-Bruhat [Ann. Henri Poincaré XVIII(3), 263 (1973); Commun. Math. Phys. 33, 83 (1973)], they proved only the local existence, and in the case of the nonrelativistic Boltzmann equation. Mucha [Global existence of solutions of the Einstein-Boltzmann equation in the spatially homogeneous case. Evolution equation, existence, regularity and singularities (Banach Center Publications, Institute of Mathematics, Polish Academy of Science, 2000), Vol. 52] obtained a global existence result, for the relativistic Boltzmann equation coupled with the Einstein equations and using the Yosida operator, but confusing unfortunately with the nonrelativistic case. Noutchegueme and Dongho [Classical Quantum Gravity 23, 2979 (2006)] and Noutchegueme, Dongho, and Takou [Gen. Relativ. Gravitation 37, 2047 (2005)], have obtained a global solution in time, but still using the Yosida operator and considering only the uncharged case. Noutchegueme and Ayissi [Adv. Stud. Theor. Phys. 4, 855 (2010)] also proved a global existence of solutions to the Maxwell-Boltzmann system using the characteristic method. In this paper, we obtain using a method totally different from those used in the works of Noutchegueme and Dongho [Classical Quantum Gravity 23, 2979 (2006)], Noutchegueme, Dongho, and Takou [Gen. Relativ. Gravitation 37, 2047 (2005)], Noutchegueme and Ayissi [Adv. Stud. Theor. Phys. 4, 855 (2010)], and Mucha [Global existence of solutions of the Einstein-Boltzmann equation in the spatially homogeneous case. Evolution equation, existence, regularity and singularities (Banach Center Publications, Institute of Mathematics, Polish Academy of Science, 2000), Vol. 52] the

  12. Cosmology of a charged universe

    International Nuclear Information System (INIS)

    Barnes, A.

    1979-01-01

    The Proca generalization of electrodynamics admits the possibility that the universe could possess a net electric charge uniformly distributed throughout space, while possessing no electric field. A charged intergalactic (and intragalactic) medium of this kind could contain enough energy to be of cosmological importance. A general-relativistic model of cosmological expansion dominated by such a charged background has been calculated, and is consistent with present observational limits on the Hubble constant, the decleration parameter, and the age of the universe. However, if this cosmology applied at the present epoch, the very early expansion of the universe would have been much more rapid than in conventional ''big bang'' cosmologies, too rapid for cosmological nucleosynthesis or thermalization of the background radiation to have occurred. Hence, domination of the present expansion by background charge appears to be incompatible with the 3 K background and big-bang production of light elements. If the present background charge density were sufficiently small (but not strictly zero), expansion from the epoch of nucleosynthesis would proceed according to the conventional scenario, but the energy due to the background charge would have dominated at some earlier epoch. This last possibility leads to equality of pressure and energy density in the primordial universe, a condition of special significance in certain cosmological theories

  13. The Atacama Cosmology Telescope: Cosmology from Galaxy Clusters Detected via the Sunyaev-Zel'dovich Effect

    Energy Technology Data Exchange (ETDEWEB)

    Sehgal, Neelima; Trac, Hy; Acquaviva, Viviana; Ade, Peter A.R.; Aguirre, Paula; Amiri, Mandana; Appel, John W.; Barrientos, L.Felipe; Battistelli, Elia S.; Bond, J.Richard; Brown, Ben; Burger, Bryce; Chervenak, Jay; Das, Sudeep; Devlin, Mark J.; Dicker, Simon R.; Doriese, W.Bertrand; Dunkley, Joanna; Dunner, Rolando; Essinger-Hileman, Thomas; Fisher, Ryan P.

    2011-08-18

    We present constraints on cosmological parameters based on a sample of Sunyaev-Zeldovich-selected galaxy clusters detected in a millimeter-wave survey by the Atacama Cosmology Telescope. The cluster sample used in this analysis consists of 9 optically-confirmed high-mass clusters comprising the high-significance end of the total cluster sample identified in 455 square degrees of sky surveyed during 2008 at 148GHz. We focus on the most massive systems to reduce the degeneracy between unknown cluster astrophysics and cosmology derived from SZ surveys. We describe the scaling relation between cluster mass and SZ signal with a 4-parameter fit. Marginalizing over the values of the parameters in this fit with conservative priors gives {sigma}{sub 8} = 0.851 {+-} 0.115 and w = -1.14 {+-} 0.35 for a spatially-flat wCDM cosmological model with WMAP 7-year priors on cosmological parameters. This gives a modest improvement in statistical uncertainty over WMAP 7-year constraints alone. Fixing the scaling relation between cluster mass and SZ signal to a fiducial relation obtained from numerical simulations and calibrated by X-ray observations, we find {sigma}{sub 8} = 0.821 {+-} 0.044 and w = -1.05 {+-} 0.20. These results are consistent with constraints from WMAP 7 plus baryon acoustic oscillations plus type Ia supernoava which give {sigma}{sub 8} = 0.802 {+-} 0.038 and w = -0.98 {+-} 0.053. A stacking analysis of the clusters in this sample compared to clusters simulated assuming the fiducial model also shows good agreement. These results suggest that, given the sample of clusters used here, both the astrophysics of massive clusters and the cosmological parameters derived from them are broadly consistent with current models.

  14. Generalized Bondi-Sachs equations for characteristic formalism of numerical relativity

    Science.gov (United States)

    Cao, Zhoujian; He, Xiaokai

    2013-11-01

    The Cauchy formalism of numerical relativity has been successfully applied to simulate various dynamical spacetimes without any symmetry assumption. But discovering how to set a mathematically consistent and physically realistic boundary condition is still an open problem for Cauchy formalism. In addition, the numerical truncation error and finite region ambiguity affect the accuracy of gravitational wave form calculation. As to the finite region ambiguity issue, the characteristic extraction method helps much. But it does not solve all of the above issues. Besides the above problems for Cauchy formalism, the computational efficiency is another problem. Although characteristic formalism of numerical relativity suffers the difficulty from caustics in the inner near zone, it has advantages in relation to all of the issues listed above. Cauchy-characteristic matching (CCM) is a possible way to take advantage of characteristic formalism regarding these issues and treat the inner caustics at the same time. CCM has difficulty treating the gauge difference between the Cauchy part and the characteristic part. We propose generalized Bondi-Sachs equations for characteristic formalism for the Cauchy-characteristic matching end. Our proposal gives out a possible same numerical evolution scheme for both the Cauchy part and the characteristic part. And our generalized Bondi-Sachs equations have one adjustable gauge freedom which can be used to relate the gauge used in the Cauchy part. Then these equations can make the Cauchy part and the characteristic part share a consistent gauge condition. So our proposal gives a possible new starting point for Cauchy-characteristic matching.

  15. Black hole versus cosmological horizon entropy

    International Nuclear Information System (INIS)

    Davis, Tamara M; Davies, P C W; Lineweaver, Charles H

    2003-01-01

    The generalized second law of thermodynamics states that entropy always increases when all event horizons are attributed with an entropy proportional to their area. We test the generalized second law by investigating the change in entropy when dust, radiation and black holes cross a cosmological event horizon. We generalize for flat, open and closed Friedmann-Robertson-Walker universes by using numerical calculations to determine the cosmological horizon evolution. In most cases, the loss of entropy from within the cosmological horizon is more than balanced by an increase in cosmological event horizon entropy, maintaining the validity of the generalized second law of thermodynamics. However, an intriguing set of open universe models shows an apparent entropy decrease when black holes disappear over the cosmological event horizon. We anticipate that this apparent violation of the generalized second law will disappear when solutions are available for black holes embedded in arbitrary backgrounds

  16. Supersymmetric GUTs and cosmology

    International Nuclear Information System (INIS)

    Lazarides, G.; Shafi, Q.

    1982-06-01

    By examining the behaviour of supersymmetric GUTs in the very early universe we find two classes of realistic models. In one of them supersymmetry is broken at or near the superheavy GUT scale. The cosmological implications of such models are expected to be similar to those of nonsupersymmetric GUTs. In the second class of models, the superheavy GUT scale is related to the supersymmetry breaking scale a la Witten. Two types of cosmological scenarios appear possible in this case, either with or without an intermediate (new) inflationary phase. They can be experimentally distinguished, since the former predicts an absence and the latter an observable number density of superheavy monopoles. A mechanism for generating baryon asymmetry in such models is pointed out. Further constraint on model building appears if global R invariance is employed to resolve the strong CP problem. (author)

  17. Generation of HEXA-deficient hiPSCs from fibroblasts of a Tay-Sachs disease patient

    Directory of Open Access Journals (Sweden)

    Zhong Liu

    2016-09-01

    Full Text Available Human iPSC line TSD-01-hiPSC was generated from fibroblasts of a patient with infantile Tay-Sachs disease (TSD. The patient is compound heterozygous at the HEXA gene by carrying a 1278insTATC allele and an IVS12+1G>C allele. STEMCCA lentivirus, which expresses OCT4, SOX2, KLF4, and c-MYC from a polycistronic transcript, were used for reprogramming. TSD-01-hiPSC express pluripotency markers such as OCT4, SOX2, NANOG, Tra-1-60, and alkaline phosphatase, and can differentiate into tissues from all the three embryonic germ layers. This TSD patient-derived hiPSC line may serve as a valuable in vitro tool for disease modeling and drug test.

  18. Cosmology and unstable nuclei

    International Nuclear Information System (INIS)

    Schramm, D.N.

    1995-01-01

    Primordial nucleosynthesis has established itself as one of the three pillars of Big Bang cosmology. Many of the Big Bang Nucleosynthesis reactions involve unstable nuclei. Hence there is a tight relationship hetween the subject of this conference and cosmology. The prime role of unstable nuclei in cosmology is related to lithium synthesis and the lack of cosmological synthesis of Be and B. These nuclei will thus be focused upon. Nucleosynthesis involves comparing calculated abundances with observed abundances. In general, abundance determinations are dominated by systematic rather than statistical errors, and work on bounding systematics is crucial. The quark-hadron inspired inhomogeneous calculations now unanimously agree that only relatively small variations in Ω b are possible vis-a-vis the homogeneous model; hence the robustness of Ω b ∼0.05 is now apparent. (These calculations depend critically on unstable nuclei.) The above argues that the bulk of the baryons in the universe are not producing visible light. A comparison with the ROSAT cluster data is also shown to be consistent with the standard BBN model. Ω b ∼1 seems to be definitely excluded, so if Ω TOTAL =1, as some recent observations may hint, then non-baryonic dark matter is required. The implications of the recently reported halo microlensing events are discussed. In summary, it is argued that the physics of unstable nuclei affects the fundamental dark matter argument. ((orig.))

  19. Cosmological reconstruction of realistic modified F(R) gravities

    International Nuclear Information System (INIS)

    Nojiri, Shin'ichi; Odintsov, Sergei D.; Saez-Gomez, Diego

    2009-01-01

    The cosmological reconstruction scheme for modified F(R) gravity is developed in terms of e-folding (or, redshift). It is demonstrated how any FRW cosmology may emerge from specific F(R) theory. The specific examples of well-known cosmological evolution are reconstructed, including ΛCDM cosmology, deceleration with transition to phantom superacceleration era which may develop singularity or be transient. The application of this scheme to viable F(R) gravities unifying inflation with dark energy era is proposed. The additional reconstruction of such models leads to non-leading gravitational correction mainly relevant at the early/late universe and helping to pass the cosmological bounds (if necessary). It is also shown how cosmological reconstruction scheme may be generalized in the presence of scalar field.

  20. Holographic dark energy with cosmological constant

    Science.gov (United States)

    Hu, Yazhou; Li, Miao; Li, Nan; Zhang, Zhenhui

    2015-08-01

    Inspired by the multiverse scenario, we study a heterotic dark energy model in which there are two parts, the first being the cosmological constant and the second being the holographic dark energy, thus this model is named the ΛHDE model. By studying the ΛHDE model theoretically, we find that the parameters d and Ωhde are divided into a few domains in which the fate of the universe is quite different. We investigate dynamical behaviors of this model, and especially the future evolution of the universe. We perform fitting analysis on the cosmological parameters in the ΛHDE model by using the recent observational data. We find the model yields χ2min=426.27 when constrained by Planck+SNLS3+BAO+HST, comparable to the results of the HDE model (428.20) and the concordant ΛCDM model (431.35). At 68.3% CL, we obtain -0.07<ΩΛ0<0.68 and correspondingly 0.04<Ωhde0<0.79, implying at present there is considerable degeneracy between the holographic dark energy and cosmological constant components in the ΛHDE model.

  1. Holographic dark energy with cosmological constant

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yazhou; Li, Nan; Zhang, Zhenhui [State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, 100190 (China); Li, Miao, E-mail: asiahu@itp.ac.cn, E-mail: mli@itp.ac.cn, E-mail: linan@itp.ac.cn, E-mail: zhangzhh@mail.ustc.edu.cn [School of Astronomy and Space Science, Sun Yat-Sen University, Guangzhou 510275 (China)

    2015-08-01

    Inspired by the multiverse scenario, we study a heterotic dark energy model in which there are two parts, the first being the cosmological constant and the second being the holographic dark energy, thus this model is named the ΛHDE model. By studying the ΛHDE model theoretically, we find that the parameters d and Ω{sub hde} are divided into a few domains in which the fate of the universe is quite different. We investigate dynamical behaviors of this model, and especially the future evolution of the universe. We perform fitting analysis on the cosmological parameters in the ΛHDE model by using the recent observational data. We find the model yields χ{sup 2}{sub min}=426.27 when constrained by Planck+SNLS3+BAO+HST, comparable to the results of the HDE model (428.20) and the concordant ΛCDM model (431.35). At 68.3% CL, we obtain −0.07<Ω{sub Λ0}<0.68 and correspondingly 0.04<Ω{sub hde0}<0.79, implying at present there is considerable degeneracy between the holographic dark energy and cosmological constant components in the ΛHDE model.

  2. Holographic dark energy with cosmological constant

    International Nuclear Information System (INIS)

    Hu, Yazhou; Li, Nan; Zhang, Zhenhui; Li, Miao

    2015-01-01

    Inspired by the multiverse scenario, we study a heterotic dark energy model in which there are two parts, the first being the cosmological constant and the second being the holographic dark energy, thus this model is named the ΛHDE model. By studying the ΛHDE model theoretically, we find that the parameters d and Ω hde are divided into a few domains in which the fate of the universe is quite different. We investigate dynamical behaviors of this model, and especially the future evolution of the universe. We perform fitting analysis on the cosmological parameters in the ΛHDE model by using the recent observational data. We find the model yields χ 2 min =426.27 when constrained by Planck+SNLS3+BAO+HST, comparable to the results of the HDE model (428.20) and the concordant ΛCDM model (431.35). At 68.3% CL, we obtain −0.07<Ω Λ0 <0.68 and correspondingly 0.04<Ω hde0 <0.79, implying at present there is considerable degeneracy between the holographic dark energy and cosmological constant components in the ΛHDE model

  3. Dynamics and constraints of the Dissipative Liouville Cosmology

    CERN Document Server

    Basilakos, Spyros; Mitsou, Vasiliki A; Plionis, Manolis

    2012-01-01

    In this article we investigate the properties of the FLRW flat cosmological models in which the cosmic expansion of the Universe is affected by a dilaton dark energy (Liouville scenario). In particular, we perform a detailed study of these models in the light of the latest cosmological data, which serves to illustrate the phenomenological viability of the new dark energy paradigm as a serious alternative to the traditional scalar field approaches. By performing a joint likelihood analysis of the recent supernovae type Ia data (SNIa), the differential ages of passively evolving galaxies, and the Baryonic Acoustic Oscillations (BAOs) traced by the Sloan Digital Sky Survey (SDSS), we put tight constraints on the main cosmological parameters. Furthermore, we study the linear matter fluctuation field of the above Liouville cosmological models. In this framework, we compare the observed growth rate of clustering measured from the optical galaxies with those predicted by the current Liouville models. Performing vari...

  4. Quantum cosmology on the worldsheet

    International Nuclear Information System (INIS)

    Cooper, A.R.; Susskind, L.; Thorlacius, L.

    1991-08-01

    Two-dimensional quantum gravity coupled to conformally invariant matter central c > 25 provides a toy model for quantum gravity in four dimensions. Two-dimensional quantum cosmology can thus be studied in terms of string theory in background fields. The large scale cosmological constant depends on non-linear dynamics in the string theory target space and does not appear to be suppressed by wormhole effects. 13 refs

  5. The cosmology/particle physics interface

    International Nuclear Information System (INIS)

    Olive, K.A.; Schramm, D.N.

    1985-01-01

    The paper reviews the interface between elementary particle physics and cosmology; and concentrates on inflation and the dark matter problem. Inflationary models of the Universe are examined, including phase transitions and supergravity. The three classes of dark matter problems discussed are: dynamical halos, galaxy formation and clustering, and the Ω=1 of inflation. Possible solutions to the cosmological dark matter problems are considered. (U.K.)

  6. Tay-Sachs disease in Jacob sheep.

    Science.gov (United States)

    Torres, Paola A; Zeng, Bai Jin; Porter, Brian F; Alroy, Joseph; Horak, Fred; Horak, Joan; Kolodny, Edwin H

    2010-12-01

    Autopsy studies of four Jacob sheep dying within their first 6-8 months of a progressive neurodegenerative disorder suggested the presence of a neuronal storage disease. Lysosomal enzyme studies of brain and liver from an affected animal revealed diminished activity of hexosaminidase A (Hex A) measured with an artificial substrate specific for this component of β-hexosaminidase. Absence of Hex A activity was confirmed by cellulose acetate electrophoresis. Brain lipid analyses demonstrated the presence of increased concentrations of G(M2)-ganglioside and asialo-G(M2)-ganglioside. The hexa cDNA of Jacob sheep was cloned and sequenced revealing an identical number of nucleotides and exons as in human HexA and 86% homology in nucleotide sequence. A missense mutation was found in the hexa cDNA of the affected sheep caused by a single nucleotide change at the end of exon 11 resulting in skipping of exon 11. Transfection of normal sheep hexa cDNA into COS1 cells and human Hex A-deficient cells led to expression of Hex S but no increase in Hex A indicating absence of cross-species dimerization of sheep Hex α-subunit with human Hex β-subunits. Using restriction site analysis, the heterozygote frequency of this mutation in Jacob sheep was determined in three geographically separate flocks to average 14%. This large naturally occurring animal model of Tay-Sachs disease is the first to offer promise as a means for trials of gene therapy applicable to human infants. Copyright © 2010 Elsevier Inc. All rights reserved.

  7. GM2-Gangliosidosis (Sandhoff and Tay Sachs disease): Diagnosis and Neuroimaging Findings (An Iranian Pediatric Case Series).

    Science.gov (United States)

    Karimzadeh, Parvaneh; Jafari, Narjes; Nejad Biglari, Habibeh; Jabbeh Dari, Sayena; Ahmad Abadi, Farzad; Alaee, Mohammad-Reza; Nemati, Hamid; Saket, Sasan; Tonekaboni, Seyed Hasan; Taghdiri, Mohammad-Mahdi; Ghofrani, Mohammad

    2014-01-01

    GM2-Gangliosidosis disease is a rare autosomal recessive genetic disorder that includes two disorders (Tay-Sachs and Sandhoff disease).These disorders cause a progressive deterioration of nerve cells and inherited deficiency in creating hexosaminidases A, B, and AB. Patients who were diagnosed withGM2-Gangliosidosis in the Neurology Department of Mofid Children's Hospital in Tehran, Iran from October 2009 to February 2014were included in our study. The disorder was confirmed by neurometabolic and enzyme level detection of hexosaminidases A, B, and AB in reference to Wagnester Laboratory in Germany. We assessed age, gender, past medical history, developmental status, clinical manifestations, and neuroimaging findings of 9 patients with Sandhoff disease and 9 with Tay Sachs disease. 83% of our patients were the offspring of consanguineous marriages. All of them had a developmental disorder as a chief complaint. 38%of patients had a history of developmental delay or regression and 22% had seizures. The patients with Sandhoff and Tay Sachs disease were followed for approximately 5 years and the follow-up showed all patients were bedridden or had expired due to refractory seizures, pneumonia aspiration, or swallowing disorders. Neuro-imaging findings included bilateral thalamic involvement, brain atrophy, and hypo myelination in near half of our patients (48%). According to the results of this study, we suggest that cherry-red spots, hyperacusis, refractory seizures, and relative parents in children with developmental delay and/or regression should be considered for assessment of GM2-Gangliosidosis disease.

  8. A natural cosmological constant from chameleons

    International Nuclear Information System (INIS)

    Nastase, Horatiu; Weltman, Amanda

    2015-01-01

    We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT)-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero) and the coincidence problem (why Λ is comparable to the matter density now)

  9. A natural cosmological constant from chameleons

    Directory of Open Access Journals (Sweden)

    Horatiu Nastase

    2015-07-01

    Full Text Available We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero and the coincidence problem (why Λ is comparable to the matter density now.

  10. A natural cosmological constant from chameleons

    Energy Technology Data Exchange (ETDEWEB)

    Nastase, Horatiu, E-mail: nastase@ift.unesp.br [Instituto de Física Teórica, UNESP-Universidade Estadual Paulista, R. Dr. Bento T. Ferraz 271, Bl. II, Sao Paulo 01140-070, SP (Brazil); Weltman, Amanda, E-mail: amanda.weltman@uct.ac.za [Astrophysics, Cosmology & Gravity Center, Department of Mathematics and Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7700 (South Africa)

    2015-07-30

    We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT)-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero) and the coincidence problem (why Λ is comparable to the matter density now)

  11. Entropy - Some Cosmological Questions Answered by Model of Expansive Nondecelerative Universe

    Directory of Open Access Journals (Sweden)

    Miroslav Sukenik

    2003-01-01

    Full Text Available Abstract: The paper summarizes the background of Expansive Nondecelerative Universe model and its potential to offer answers to some open cosmological questions related to entropy. Three problems are faced in more detail, namely that of Hawkings phenomenon of black holes evaporation, maximum entropy of the Universe during its evolution, and time evolution of specific entropy.

  12. The anisotropic cosmological models in f ( R , T ) gravity with Λ

    Indian Academy of Sciences (India)

    The general class of anisotropic Bianchi cosmological models in f ( R , T ) modified theories of gravity with Λ ( T ) has been considered. This paper deals with f ( R , T ) modified theories of gravity, where the gravitational Lagrangian is given by an arbitrary function of Ricci scalar R and the trace of the stress-energy tensor T ...

  13. The cosmological principle is not in the sky

    Science.gov (United States)

    Park, Chan-Gyung; Hyun, Hwasu; Noh, Hyerim; Hwang, Jai-chan

    2017-08-01

    The homogeneity of matter distribution at large scales, known as the cosmological principle, is a central assumption in the standard cosmological model. The case is testable though, thus no longer needs to be a principle. Here we perform a test for spatial homogeneity using the Sloan Digital Sky Survey Luminous Red Galaxies (LRG) sample by counting galaxies within a specified volume with the radius scale varying up to 300 h-1 Mpc. We directly confront the large-scale structure data with the definition of spatial homogeneity by comparing the averages and dispersions of galaxy number counts with allowed ranges of the random distribution with homogeneity. The LRG sample shows significantly larger dispersions of number counts than the random catalogues up to 300 h-1 Mpc scale, and even the average is located far outside the range allowed in the random distribution; the deviations are statistically impossible to be realized in the random distribution. This implies that the cosmological principle does not hold even at such large scales. The same analysis of mock galaxies derived from the N-body simulation, however, suggests that the LRG sample is consistent with the current paradigm of cosmology, thus the simulation is also not homogeneous in that scale. We conclude that the cosmological principle is neither in the observed sky nor demanded to be there by the standard cosmological world model. This reveals the nature of the cosmological principle adopted in the modern cosmology paradigm, and opens a new field of research in theoretical cosmology.

  14. The cosmological constant problem

    International Nuclear Information System (INIS)

    Dolgov, A.D.

    1989-05-01

    A review of the cosmological term problem is presented. Baby universe model and the compensating field model are discussed. The importance of more accurate data on the Hubble constant and the Universe age is stressed. 18 refs

  15. (Lack of) Cosmological evidence for dark radiation after Planck

    CERN Document Server

    Verde, Licia; Mortlock, Daniel J; Peiris, Hiranya V

    2013-01-01

    We use Bayesian model comparison to determine whether extensions to Standard-Model neutrino physics -- primarily additional effective numbers of neutrinos and/or massive neutrinos -- are merited by the latest cosmological data. Given the significant advances in cosmic microwave background (CMB) observations represented by the Planck data, we examine whether Planck temperature and CMB lensing data, in combination with lower redshift data, have strengthened (or weakened) the previous findings. We conclude that the state-of-the-art cosmological data do not show evidence for deviations from the standard cosmological model (which has three massless neutrino families). This does not mean that the model is necessarily correct -- in fact we know it is incomplete as neutrinos are not massless -- but it does imply that deviations from the standard model (e.g., non-zero neutrino mass) are too small compared to the current experimental uncertainties to be inferred from cosmological data alone.

  16. Cosmological dynamics of extended chameleons

    International Nuclear Information System (INIS)

    Tamanini, Nicola; Wright, Matthew

    2016-01-01

    We investigate the cosmological dynamics of the recently proposed extended chameleon models at both background and linear perturbation levels. Dynamical systems techniques are employed to fully characterize the evolution of the universe at the largest distances, while structure formation is analysed at sub-horizon scales within the quasi-static approximation. The late time dynamical transition from dark matter to dark energy domination can be well described by almost all extended chameleon models considered, with no deviations from ΛCDM results at both background and perturbation levels. The results obtained in this work confirm the cosmological viability of extended chameleons as alternative dark energy models.

  17. Cosmological dynamics of extended chameleons

    Energy Technology Data Exchange (ETDEWEB)

    Tamanini, Nicola [Institut de Physique Théorique, CEA-Saclay, CNRS UMR 3681, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France); Wright, Matthew, E-mail: nicola.tamanini@cea.fr, E-mail: matthew.wright.13@ucl.ac.uk [Department of Mathematics, University College London, Gower Street, London, WC1E 6BT (United Kingdom)

    2016-04-01

    We investigate the cosmological dynamics of the recently proposed extended chameleon models at both background and linear perturbation levels. Dynamical systems techniques are employed to fully characterize the evolution of the universe at the largest distances, while structure formation is analysed at sub-horizon scales within the quasi-static approximation. The late time dynamical transition from dark matter to dark energy domination can be well described by almost all extended chameleon models considered, with no deviations from ΛCDM results at both background and perturbation levels. The results obtained in this work confirm the cosmological viability of extended chameleons as alternative dark energy models.

  18. Topics in quantum field theory and cosmology

    International Nuclear Information System (INIS)

    Brandenberger, R.H.

    1983-01-01

    This thesis contains a study of topics in quantum field theory and cosmology in the context of the new inflationary universe scenario. It presents a review of the quantum field theory methods used in the new cosmological models. The following chapters are a detailed study of energy density fluctuations in the early universe. Hawking radiation is derived as the source of initial perturbations in two complementary ways. The following section presents a new gauge invariant framework to study the growth of fluctuations outside the horizon. This framework is applied to the new inflationary universe in the final chapter. The introduction gives a brief outline of the new cosmological models

  19. Quantum effects and regular cosmological models

    International Nuclear Information System (INIS)

    Gurovich, V.Ts.; Starobinskij, A.A.; AN SSSR, Moscow. Inst. Teoreticheskoj Fiziki)

    1979-01-01

    Allowance for the quantum nature of material fields and weak gravitational waves on the background of the classical metric of the cosmological model results in two basic effects: vacuum polarization and particle production. The first of the effects may be taken into account qualitatively by introducing into the lagrangian density of the gravitational field an additional term of the type A+BR 2 +CR 2 In|R/R 0 |; the second effect can be accounted for by prescribing a local rate of particle (graviton) production which is proportional to the square of the scalar curvature R 2 . It is shown that the taking into account of the combined effect of these phenomena on the evolution of a homogeneous anisotropic metric of the first Bianchi type removes the Einstein singularities. Asymptotic approach to the classical model, however, is attained only if additional assumptions are made. At the stage of compression the solution is close to the anisotropic vacuum Kasner solution; at the expansion stage it tends to the isotropic Friedman solution in which matter is produced by the gravitational field

  20. Fluid observers and tilting cosmology

    International Nuclear Information System (INIS)

    Coley, A A; Hervik, S; Lim, W C

    2006-01-01

    We study perfect fluid cosmological models with a constant equation of state parameter γ in which there are two naturally defined timelike congruences, a geometrically defined geodesic congruence and a non-geodesic fluid congruence. We establish an appropriate set of boost formulae relating the physical variables, and consequently the observed quantities, in the two frames. We study expanding spatially homogeneous tilted perfect fluid models, with an emphasis on future evolution with extreme tilt. We show that for ultra-radiative equations of state (i.e. γ > 4/3), generically the tilt becomes extreme at late times and the fluid observers will reach infinite expansion within a finite proper time and experience a singularity similar to that of the big rip. In addition, we show that for sub-radiative equations of state (i.e. γ < 4/3), the tilt can become extreme at late times and give rise to an effective quintessential equation of state. To establish the connection with phantom cosmology and quintessence, we calculate the effective equation of state in the models under consideration and we determine the future asymptotic behaviour of the tilting models in the fluid frame variables using the boost formulae. We also discuss spatially inhomogeneous models and tilting spatially homogeneous models with a cosmological constant

  1. Hubble Diagram Test of Expanding and Static Cosmological Models: The Case for a Slowly Expanding Flat Universe

    Directory of Open Access Journals (Sweden)

    Laszlo A. Marosi

    2013-01-01

    Full Text Available We present a new redshift (RS versus photon travel time ( test including 171 supernovae RS data points. We extended the Hubble diagram to a range of z = 0,0141–8.1 in the hope that at high RSs, the fitting of the calculated RS/ diagrams to the observed RS data would, as predicted by different cosmological models, set constraints on alternative cosmological models. The Lambda cold dark matter (ΛCDM, the static universe model, and the case for a slowly expanding flat universe (SEU are considered. We show that on the basis of the Hubble diagram test, the static and the slowly expanding models are favored.

  2. Shock absorption of below-knee prostheses : A comparison between the SACH and the Multiflex foot

    NARCIS (Netherlands)

    van Leeuwen, J. L.; Speth, L. A W M; Daanen, H. A M

    1990-01-01

    Shock waves were measured during walking on a treadmill on the metal tube of a below-knee KBM prosthesis, provided either with a SACH foot or with a Multiflex foot. Accelerations were measured in the axial direction and the dorso-ventral direction, about 160 mm proximal to the sole of the shoe. The

  3. A curious explanation of some cosmological phenomena

    International Nuclear Information System (INIS)

    Vishwakarma, Ram Gopal

    2013-01-01

    Although observational cosmology has shown tremendous growth over the last decade, deep mysteries continue to haunt our theoretical understanding of the ingredients of the concordance cosmological model, which are mainly ‘dark’. More than 95% of the content of the energy–stress tensor has to be in the form of the inflaton field, dark matter and dark energy, which do not have any non-gravitational or laboratory evidence and remain unidentified. Moreover, the dark energy poses a serious confrontation between fundamental physics and cosmology. This makes a strong case to discover alternative theories that do not require the dark sectors of the standard approach to explain the observations. In the present situation, it would be important to gain insight about the requirements of the ‘would-be’ final theory from all possible means. In this context, this paper highlights some, hitherto unnoticed, interesting coincidences that may prove useful to develop insight about the ‘holy grail’ of gravitation. It appears that the requirement of the speculative dark sectors by the energy–stress tensor is indicative of a possible way out of the present crisis appearing in the standard cosmology, in terms of a theory wherein the energy–stress tensor does not play a direct role in the dynamics. It is shown that various cosmological observations can be explained satisfactorily in the framework of one such theory—the Milne model, without requiring the dark sectors of the standard approach. Moreover, the model evades the horizon, flatness and the cosmological constant problems afflicting the standard cosmology. Although Milne's theory is an incomplete, phenomenological theory, and cannot be the final theory of gravitation, nevertheless, it would be worthwhile to study these coincidences, which may help us develop insight about the would-be final theory. (paper)

  4. A curious explanation of some cosmological phenomena

    Science.gov (United States)

    Gopal Vishwakarma, Ram

    2013-05-01

    Although observational cosmology has shown tremendous growth over the last decade, deep mysteries continue to haunt our theoretical understanding of the ingredients of the concordance cosmological model, which are mainly ‘dark’. More than 95% of the content of the energy-stress tensor has to be in the form of the inflaton field, dark matter and dark energy, which do not have any non-gravitational or laboratory evidence and remain unidentified. Moreover, the dark energy poses a serious confrontation between fundamental physics and cosmology. This makes a strong case to discover alternative theories that do not require the dark sectors of the standard approach to explain the observations. In the present situation, it would be important to gain insight about the requirements of the ‘would-be’ final theory from all possible means. In this context, this paper highlights some, hitherto unnoticed, interesting coincidences that may prove useful to develop insight about the ‘holy grail’ of gravitation. It appears that the requirement of the speculative dark sectors by the energy-stress tensor is indicative of a possible way out of the present crisis appearing in the standard cosmology, in terms of a theory wherein the energy-stress tensor does not play a direct role in the dynamics. It is shown that various cosmological observations can be explained satisfactorily in the framework of one such theory—the Milne model, without requiring the dark sectors of the standard approach. Moreover, the model evades the horizon, flatness and the cosmological constant problems afflicting the standard cosmology. Although Milne's theory is an incomplete, phenomenological theory, and cannot be the final theory of gravitation, nevertheless, it would be worthwhile to study these coincidences, which may help us develop insight about the would-be final theory.

  5. Cosmology with primordial black holes

    International Nuclear Information System (INIS)

    Lindley, D.

    1981-09-01

    Cosmologies containing a substantial amount of matter in the form of evaporating primordial black holes are investigated. A review of constraints on the numbers of such black holes, including an analysis of a new limit found by looking at the destruction of deuterium by high energy photons, shows that there must be a negligible population of small black holes from the era of cosmological nucleosynthesis onwards, but that there are no strong constraints before this time. The major part of the work is based on the construction of detailed, self-consistent cosmological models in which black holes are continually forming and evaporating The interest in these models centres on the question of baryon generation, which occurs via the asymmetric decay of a new type of particle which appears as a consequence of the recently developed Grand Unified Theories of elementary particles. Unfortunately, there is so much uncertainty in the models that firm conclusions are difficult to reach; however, it seems feasible in principle that primordial black holes could be responsible for a significant part of the present matter density of the Universe. (author)

  6. On defects of the volume and curvature of the Robertson-Walker metric and construction of cosmological models

    International Nuclear Information System (INIS)

    Gackstatter, F.

    1987-01-01

    For the Robertson-Walker metric (RWM) normal coordinates are constructed and the Riemann curvature tensor is determined. Then results on the defects of the volume and curvature, derived formerly, are applied to the RWM and to cosmological models. Finally cosmological models are constructed, they describe different states of the development of the cosmos: p ∼ 0, 1/3u, 2/3u, in a unified form. A Laurent expansion of the density of energy u and pressure p is used to solve the Friedmann equations. (author)

  7. Cosmology with a decaying vacuum energy parametrization derived from quantum mechanics

    International Nuclear Information System (INIS)

    Szydłowski, M; Stachowski, A; Urbanowski, K

    2015-01-01

    Within the quantum mechanical treatment of the decay problem one finds that at late times tthe survival probability of an unstable state cannot have the form of an exponentially decreasing function of time t but it has an inverse power-like form. This is a general property of unstable states following from basic principles of quantum theory. The consequence of this property is that in the case of false vacuum states the cosmological constant becomes dependent on time: Λ — Λ bare ≡ Λ(t) — Λ bare ∼ 1/t 2 . We construct the cosmological model with decaying vacuum energy density and matter for solving the cosmological constant problem and the coincidence problem. We show the equivalence of the proposed decaying false vacuum cosmology with the Λ(t) cosmologies (the Λ(t)CDM models). The cosmological implications of the model of decaying vacuum energy (dark energy) are discussed. We constrain the parameters of the model with decaying vacuum using astronomical data. For this aim we use the observation of distant supernovae of type Ia, measurements of H(z), BAO, CMB and others. The model analyzed is in good agreement with observation data and explain a small value of the cosmological constant today. (paper)

  8. Religion, theology and cosmology

    Directory of Open Access Journals (Sweden)

    John T. Fitzgerald

    2013-10-01

    Full Text Available Cosmology is one of the predominant research areas of the contemporary world. Advances in modern cosmology have prompted renewed interest in the intersections between religion, theology and cosmology. This article, which is intended as a brief introduction to the series of studies on theological cosmology in this journal, identifies three general areas of theological interest stemming from the modern scientific study of cosmology: contemporary theology and ethics; cosmology and world religions; and ancient cosmologies. These intersections raise important questions about the relationship of religion and cosmology, which has recently been addressed by William Scott Green and is the focus of the final portion of the article.

  9. Inflation and cosmological parameter estimation

    Energy Technology Data Exchange (ETDEWEB)

    Hamann, J.

    2007-05-15

    In this work, we focus on two aspects of cosmological data analysis: inference of parameter values and the search for new effects in the inflationary sector. Constraints on cosmological parameters are commonly derived under the assumption of a minimal model. We point out that this procedure systematically underestimates errors and possibly biases estimates, due to overly restrictive assumptions. In a more conservative approach, we analyse cosmological data using a more general eleven-parameter model. We find that regions of the parameter space that were previously thought ruled out are still compatible with the data; the bounds on individual parameters are relaxed by up to a factor of two, compared to the results for the minimal six-parameter model. Moreover, we analyse a class of inflation models, in which the slow roll conditions are briefly violated, due to a step in the potential. We show that the presence of a step generically leads to an oscillating spectrum and perform a fit to CMB and galaxy clustering data. We do not find conclusive evidence for a step in the potential and derive strong bounds on quantities that parameterise the step. (orig.)

  10. Quantum cosmology and baby universes

    International Nuclear Information System (INIS)

    Grishchuk, L.P.

    1990-01-01

    The contributed papers presented to the workshop on ''Quantum Cosmology and Baby Universes'' have demonstrated the great interest in, and rapid development of, the field of quantum cosmology. In my view, there are at least three areas of active research at present. The first area can be defined as that of practical calculations. Here researchers are dealing with the basic quantum cosmological equation, which is the Wheeler-DeWitt equation. They try to classify all possible solutions to the Wheeler-DeWitt equation or seek a specific integration contour in order to select one particular wave function or generalize the simple minisuperspace models to more complicated cases, including various inhomogeneities, anisotropies, etc. The second area of research deals with the interpretational issues of quantum cosmology. There are still many questions about how to extract the observational consequences from a given cosmological wave function, the role of time in quantum cosmology, and how to reformulate the rules of quantum mechanics in such a way that they could be applicable to the single system which is our Universe. The third area of research is concerned with the so-called ''third quantization'' of gravity. In this approach a wave function satisfying the Wheeler-DeWitt equation becomes an operator acting on a Wave Function of the many-universes system. Within this approach one operates with Euclidean worm-holes joining different Lorentzian universes. (author)

  11. Classical resolution of singularities in dilaton cosmologies

    NARCIS (Netherlands)

    Bergshoeff, EA; Collinucci, A; Roest, D; Russo, JG; Townsend, PK

    2005-01-01

    For models of dilaton gravity with a possible exponential potential, such as the tensor-scalar sector of ITA supergravity, we show how cosmological solutions correspond to trajectories in a 2D Milne space (parametrized by the dilaton and the scale factor). Cosmological singularities correspond to

  12. Molecular characterization of a novel HEXA mutation at the +3 position of intron 8 in a Tay-Sachs disease patient

    Energy Technology Data Exchange (ETDEWEB)

    Richard, M.; Triggs-Raine, B. [Univ. of Manitoba, Winnipeg (Canada); Natowicz, M. [E.K. Shriver Center, Waltham, MA (United States)

    1994-09-01

    Tay-Sachs disease is an autosomal recessive lysosomal storage disorder resulting from mutations in the HEXA gene that cause a deficiency in the activity of that enzyme {beta}-hexosaminidase A (Hex A). This deficiency leads to the build-up of G{sub M2} ganglioside, resulting in neurodegeneration and death. Biochemical analysis of a non-Jewish patient with a late-infantile form of Tay-Sachs disease revealed a substantial level of Hex A activity (38.4%) when 4-MUG was used as the substrate. However, when a substrate (4-MUGS) specific for the {alpha}-subunit of Hex A ({alpha}{beta}) was used, almost no activity was detected in the HEXA gene of the patient using SSCP analysis followed by sequencing. The first mutation, a G533A substitution in exon 5, is previously described and associated with the B1 form of Tay-Sachs disease. The second mutation is a novel a-to-g base change at the +3 position of intron 8. This was confirmed using the AIRS method, whereby a MaeIII site was created in the presence of the mutation. Normal and patient mRNA was reverse transcribed and exons 7 to 9 were PCR-amplified from the cDNA. An abnormally sized amplification product detected only in the patient cDNA was sequenced; exon 8 had been deleted and exons 7 and 9 were spliced together. A substantial level of normally-sized PCR product was also detected in the patient`s cDNA. Experiments are in progress to determine if this is produced from the allele harboring the G533A mutation. Given that previous mutations of this type have been associated with 97-100% abnormal splicing, this mutation is likely to be the cause, together with the G533A mutation, of Tay-Sachs disease in this patient.

  13. Mathematical cosmology

    CERN Document Server

    Ellis, G F R

    1993-01-01

    Many topics were covered in the submitted papers, showing much life in this subject at present. They ranged from conventional calculations in specific cosmological models to provocatively speculative work. Space and time restrictions required selecting from them, for summarisation here; the book of Abstracts should be consulted for a full overview.

  14. Lagrangian derivation of the two coupled field equations in the Janus cosmological model

    Science.gov (United States)

    Petit, Jean-Pierre; D'Agostini, G.

    2015-05-01

    After a review citing the results obtained in previous articles introducing the Janus Cosmological Model, consisting of a set of two coupled field equations, where one metrics refers to the positive masses and the other to the negative masses, which explains the observed cosmic acceleration and the nature of dark energy, we present the Lagrangian derivation of the model.

  15. Quantum cosmology. 18

    International Nuclear Information System (INIS)

    Padmanabhan, T.

    1989-01-01

    Quantum cosmology is to quantum gravity what the Bohr model is to the full quantum mechanical description of the hydrogen atom. In quantum cosmology one attempts to give a quantum-mechanical meaning to classical solutions of general relativity. This is discussed in this chapter. The approach is illustrated by quantizing only the conformal degree of freedom of the gravitational field, in particular the Friedmann-Robertson-Walker models. And, as in the hydrogen atom, the classical singularity of general relativity is avoided and one has analogous stationary states in the quantum Universe. The chapter ends with a model of the fundamental role that the Planck length may play as the universal cutoff in all field theories, thus ridding the theory of ultra-violet divergences. Two appendices introduce field theory in the Schroedinger representation and the Schroedinger equation for quantum gravity, namely the Wheeler-De Wit equation. (author). 38 refs.; 2 figs.; 1 tab

  16. Brane world cosmologies with varying speed of light

    International Nuclear Information System (INIS)

    Youm, Donam

    2001-02-01

    We study cosmologies in the Randall-Sundrum models, incorporating the possibility of time-varying speed of light and Newton's constant. The cosmologies with varying speed of light (VSL) were proposed by Moffat and by Albrecht and Magueijo as an alternative to inflation for solving the cosmological problems. We consider the case in which the speed of light varies with time after the radion or the scale of the extra dimension has been stabilized. We elaborate on the conditions under which the flatness problem and the cosmological constant problem can be resolved. Particularly, the VSL cosmologies may provide a possible mechanism for bringing the quantum corrections to the fine-tuned brane tensions after the SUSY breaking under control. (author)

  17. On the Tidal Evolution of the Earth-Moon System: A Cosmological Model

    Directory of Open Access Journals (Sweden)

    Arbab A. I.

    2009-01-01

    Full Text Available We have presented a cosmological model for the tidal evolution of the Earth-Moon system. We have found that the expansion of the universe has immense consequences on our local systems. The model can be compared with the present observational data. The close approach problem inflicting the known tidal theory is averted in this model. We have also shown that the astronomical and geological changes of our local systems are of the order of Hubble constant.

  18. Loop quantum cosmology and singularities.

    Science.gov (United States)

    Struyve, Ward

    2017-08-15

    Loop quantum gravity is believed to eliminate singularities such as the big bang and big crunch singularity. This belief is based on studies of so-called loop quantum cosmology which concerns symmetry-reduced models of quantum gravity. In this paper, the problem of singularities is analysed in the context of the Bohmian formulation of loop quantum cosmology. In this formulation there is an actual metric in addition to the wave function, which evolves stochastically (rather than deterministically as the case of the particle evolution in non-relativistic Bohmian mechanics). Thus a singularity occurs whenever this actual metric is singular. It is shown that in the loop quantum cosmology for a homogeneous and isotropic Friedmann-Lemaître-Robertson-Walker space-time with arbitrary constant spatial curvature and cosmological constant, coupled to a massless homogeneous scalar field, a big bang or big crunch singularity is never obtained. This should be contrasted with the fact that in the Bohmian formulation of the Wheeler-DeWitt theory singularities may exist.

  19. The order of chaos on a Bianch IX cosmological model

    Energy Technology Data Exchange (ETDEWEB)

    Bugalho, H; da Silva, A R; Ramos, J S

    1986-12-01

    The purpose of this paper is to analyze the chaotic behavior that can arise on a type-IX cosmological model using methods from dynamic systems theory and symbolic dynamics. Specifically, instead of the Belinski-Khalatnikov-Lifschitz model, we use the iterates of a monotonously increasing map of the circle with a discontinuity, and for the Hamiltonian dynamics of Misner's Mixmaster model we introduce the iterates of a noninvertible map. An equivalence between these two models can easily be brought upon by translating them in symbolic dynamical terms. The resulting symbolic orbits can be inserted in an ordered tree structure set, and so we can present an effective counting and referentation of all period orbits.

  20. Testing averaged cosmology with type Ia supernovae and BAO data

    Energy Technology Data Exchange (ETDEWEB)

    Santos, B.; Alcaniz, J.S. [Departamento de Astronomia, Observatório Nacional, 20921-400, Rio de Janeiro – RJ (Brazil); Coley, A.A. [Department of Mathematics and Statistics, Dalhousie University, Halifax, B3H 3J5 Canada (Canada); Devi, N. Chandrachani, E-mail: thoven@on.br, E-mail: aac@mathstat.dal.ca, E-mail: chandrachaniningombam@astro.unam.mx, E-mail: alcaniz@on.br [Instituto de Astronomía, Universidad Nacional Autónoma de México, Box 70-264, México City, México (Mexico)

    2017-02-01

    An important problem in precision cosmology is the determination of the effects of averaging and backreaction on observational predictions, particularly in view of the wealth of new observational data and improved statistical techniques. In this paper, we discuss the observational viability of a class of averaged cosmologies which consist of a simple parametrized phenomenological two-scale backreaction model with decoupled spatial curvature parameters. We perform a Bayesian model selection analysis and find that this class of averaged phenomenological cosmological models is favored with respect to the standard ΛCDM cosmological scenario when a joint analysis of current SNe Ia and BAO data is performed. In particular, the analysis provides observational evidence for non-trivial spatial curvature.

  1. Testing averaged cosmology with type Ia supernovae and BAO data

    International Nuclear Information System (INIS)

    Santos, B.; Alcaniz, J.S.; Coley, A.A.; Devi, N. Chandrachani

    2017-01-01

    An important problem in precision cosmology is the determination of the effects of averaging and backreaction on observational predictions, particularly in view of the wealth of new observational data and improved statistical techniques. In this paper, we discuss the observational viability of a class of averaged cosmologies which consist of a simple parametrized phenomenological two-scale backreaction model with decoupled spatial curvature parameters. We perform a Bayesian model selection analysis and find that this class of averaged phenomenological cosmological models is favored with respect to the standard ΛCDM cosmological scenario when a joint analysis of current SNe Ia and BAO data is performed. In particular, the analysis provides observational evidence for non-trivial spatial curvature.

  2. Quantum gravity and quantum cosmology

    CERN Document Server

    Papantonopoulos, Lefteris; Siopsis, George; Tsamis, Nikos

    2013-01-01

    Quantum gravity has developed into a fast-growing subject in physics and it is expected that probing the high-energy and high-curvature regimes of gravitating systems will shed some light on how to eventually achieve an ultraviolet complete quantum theory of gravity. Such a theory would provide the much needed information about fundamental problems of classical gravity, such as the initial big-bang singularity, the cosmological constant problem, Planck scale physics and the early-time inflationary evolution of our Universe.   While in the first part of this book concepts of quantum gravity are introduced and approached from different angles, the second part discusses these theories in connection with cosmological models and observations, thereby exploring which types of signatures of modern and mathematically rigorous frameworks can be detected by experiments. The third and final part briefly reviews the observational status of dark matter and dark energy, and introduces alternative cosmological models.   ...

  3. Averaging Robertson-Walker cosmologies

    International Nuclear Information System (INIS)

    Brown, Iain A.; Robbers, Georg; Behrend, Juliane

    2009-01-01

    The cosmological backreaction arises when one directly averages the Einstein equations to recover an effective Robertson-Walker cosmology, rather than assuming a background a priori. While usually discussed in the context of dark energy, strictly speaking any cosmological model should be recovered from such a procedure. We apply the scalar spatial averaging formalism for the first time to linear Robertson-Walker universes containing matter, radiation and dark energy. The formalism employed is general and incorporates systems of multiple fluids with ease, allowing us to consider quantitatively the universe from deep radiation domination up to the present day in a natural, unified manner. Employing modified Boltzmann codes we evaluate numerically the discrepancies between the assumed and the averaged behaviour arising from the quadratic terms, finding the largest deviations for an Einstein-de Sitter universe, increasing rapidly with Hubble rate to a 0.01% effect for h = 0.701. For the ΛCDM concordance model, the backreaction is of the order of Ω eff 0 ≈ 4 × 10 −6 , with those for dark energy models being within a factor of two or three. The impacts at recombination are of the order of 10 −8 and those in deep radiation domination asymptote to a constant value. While the effective equations of state of the backreactions in Einstein-de Sitter, concordance and quintessence models are generally dust-like, a backreaction with an equation of state w eff < −1/3 can be found for strongly phantom models

  4. BOOK REVIEW: Black Holes, Cosmology and Extra Dimensions Black Holes, Cosmology and Extra Dimensions

    Science.gov (United States)

    Frolov, Valeri P.

    2013-10-01

    The book Black holes, Cosmology and Extra Dimensions written by Kirill A Bronnikov and Sergey G Rubin has been published recently by World Scientific Publishing Company. The authors are well known experts in gravity and cosmology. The book is a monograph, a considerable part of which is based on the original work of the authors. Their original point of view on some of the problems makes the book quite interesting, covering a variety of important topics of the modern theory of gravity, astrophysics and cosmology. It consists of 11 chapters which are organized in three parts. The book starts with an introduction, where the authors briefly discuss the main ideas of General Relativity, giving some historical remarks on its development and application to cosmology, and mentioning some more recent subjects such as brane worlds, f(R)-theories and gravity in higher dimensions. Part I of the book is called 'Gravity'. Chapters two and three are devoted to the Einstein equations and their spherical symmetric black hole solutions. This material is quite standard and can be found in practically any book on General Relativity. A brief summary of the Kerr metric and black hole thermodynamics are given in chapter four. The main part of this chapter is devoted to spherically symmetric black holes in non-Einstein gravity (with scalar and phantom fields), black holes with regular interior, and black holes in brane worlds. Chapters five and six are mainly dedicated to wormholes and the problem of their stability. Part II (Cosmology) starts with discussion of the Friedmann-Robertson-Walker and de Sitter solutions of the Einstein equations and their properties. It follows by describing a `big picture' of the modern cosmology (inflation, post-inflationary reheating, the radiation-dominated and matter-dominated states, and modern stage of the (secondary) inflation). The authors explain how the inflation models allow one to solve many of the long-standing problems of cosmology, such as

  5. Mechanism of interrupted saccades in patients with late-onset Tay-Sachs disease.

    Science.gov (United States)

    Optican, Lance M; Rucker, Janet C; Keller, Edward L; Leigh, R John

    2008-01-01

    In late-onset Tay-Sachs disease (LOTS), saccades are interrupted by one or more transient decelerations. Some saccades reaccelerate and continue on before eye velocity reaches zero, even in darkness. Intervals between successive decelerations are not regularly spaced. Peak decelerations of horizontal and vertical components of oblique saccades in LOTS is more synchronous than those in control subjects. We hypothesize that these decelerations are caused by dysregulation of the fastigial nuclei (FN) of the cerebellum, which fire brain stem inhibitory burst neurons (IBNs).

  6. EDITORIAL: Non-linear and non-Gaussian cosmological perturbations Non-linear and non-Gaussian cosmological perturbations

    Science.gov (United States)

    Sasaki, Misao; Wands, David

    2010-06-01

    In recent years there has been a resurgence of interest in the study of non-linear perturbations of cosmological models. This has been the result of both theoretical developments and observational advances. New theoretical challenges arise at second and higher order due to mode coupling and the need to develop new gauge-invariant variables beyond first order. In particular, non-linear interactions lead to deviations from a Gaussian distribution of primordial perturbations even if initial vacuum fluctuations are exactly Gaussian. These non-Gaussianities provide an important probe of models for the origin of structure in the very early universe. We now have a detailed picture of the primordial distribution of matter from surveys of the cosmic microwave background, notably NASA's WMAP satellite. The situation will continue to improve with future data from the ESA Planck satellite launched in 2009. To fully exploit these data cosmologists need to extend non-linear cosmological perturbation theory beyond the linear theory that has previously been sufficient on cosmological scales. Another recent development has been the realization that large-scale structure, revealed in high-redshift galaxy surveys, could also be sensitive to non-linearities in the primordial curvature perturbation. This focus section brings together a collection of invited papers which explore several topical issues in this subject. We hope it will be of interest to theoretical physicists and astrophysicists alike interested in understanding and interpreting recent developments in cosmological perturbation theory and models of the early universe. Of course it is only an incomplete snapshot of a rapidly developing field and we hope the reader will be inspired to read further work on the subject and, perhaps, fill in some of the missing pieces. This focus section is dedicated to the memory of Lev Kofman (1957-2009), an enthusiastic pioneer of inflationary cosmology and non-Gaussian perturbations.

  7. Conformally invariant braneworld and the cosmological constant

    International Nuclear Information System (INIS)

    Guendelman, E.I.

    2004-01-01

    A six-dimensional braneworld scenario based on a model describing the interaction of gravity, gauge fields and 3+1 branes in a conformally invariant way is described. The action of the model is defined using a measure of integration built of degrees of freedom independent of the metric. There is no need to fine tune any bulk cosmological constant or the tension of the two (in the scenario described here) parallel branes to obtain zero cosmological constant, the only solutions are those with zero 4D cosmological constant. The two extra dimensions are compactified in a 'football' fashion and the branes lie on the two opposite poles of the compact 'football-shaped' sphere

  8. Cosmology and Dark Matter

    CERN Document Server

    Tkachev, Igor

    2017-01-01

    This lecture course covers cosmology from the particle physicist perspective. Therefore, the emphasis will be on the evidence for the new physics in cosmological and astrophysical data together with minimal theoretical frameworks needed to understand and appreciate the evidence. I review the case for non-baryonic dark matter and describe popular models which incorporate it. In parallel, the story of dark energy will be developed, which includes accelerated expansion of the Universe today, the Universe origin in the Big Bang, and support for the Inflationary theory in CMBR data.

  9. Primordial nucleosynthesis: A cosmological point of view

    International Nuclear Information System (INIS)

    Mathews, G. J.; Kajino, T.; Yamazaki, D.; Kusakabe, M.; Cheoun, M.-K.

    2014-01-01

    Primordial nucleosynthesis remains as one of the pillars of modern cosmology. It is the test-ing ground upon which all cosmological models must ultimately rest. It is our only probe of the universe during the first few minutes of cosmic expansion and in particular during the important radiation-dominated epoch. These lectures review the basic equations of space-time, cosmology, and big bang nucleosynthesis. We will then review the current state of observational constraints on primordial abundances along with the key nuclear reactions and their uncertainties. We summarize which nuclear measure-ments are most crucial during the big bang. We also review various cosmological models and their constraints. In particular, we summarize the constraints that big bang nucleosynthesis places upon the possible time variation of fundamental constants, along with constraints on the nature and origin of dark matter and dark energy, long-lived supersymmetric particles, gravity waves, and the primordial magnetic field

  10. Generation of HEXA-deficient hiPSCs from fibroblasts of a Tay-Sachs disease patient.

    Science.gov (United States)

    Liu, Zhong; Zhao, Rui

    2016-09-01

    Human iPSC line TSD-01-hiPSC was generated from fibroblasts of a patient with infantile Tay-Sachs disease (TSD). The patient is compound heterozygous at the HEXA gene by carrying a 1278insTATC allele and an IVS12+1G>C allele. STEMCCA lentivirus, which expresses OCT4, SOX2, KLF4, and c-MYC from a polycistronic transcript, were used for reprogramming. TSD-01-hiPSC express pluripotency markers such as OCT4, SOX2, NANOG, Tra-1-60, and alkaline phosphatase, and can differentiate into tissues from all the three embryonic germ layers. This TSD patient-derived hiPSC line may serve as a valuable in vitro tool for disease modeling and drug test. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  11. Searching for sterile neutrinos in dynamical dark energy cosmologies

    Science.gov (United States)

    Feng, Lu; Zhang, Jing-Fei; Zhang, Xin

    2018-05-01

    We investigate how the dark energy properties change the cosmological limits on sterile neutrino parameters by using recent cosmological observations. We consider the simplest dynamical dark energy models, the wCDM model and the holographic dark energy (HDE) model, to make an analysis. The cosmological observations used in this work include the Planck 2015 CMB temperature and polarization data, the baryon acoustic oscillation data, the type Ia supernova data, the Hubble constant direct measurement data, and the Planck CMB lensing data. We find that, m v,terile ff energy properties could significantly influence the constraint limits of sterile neutrino parameters.

  12. Tay-Sachs disease: current perspectives from Australia.

    Science.gov (United States)

    Lew, Raelia M; Burnett, Leslie; Proos, Anné L; Delatycki, Martin B

    2015-01-01

    Tay-Sachs disease (TSD) is a fatal, recessively inherited neurodegenerative condition of infancy and early childhood. Although rare in most other populations, the carrier frequency is one in 25 in Ashkenazi Jews. Australian high-school-based TSD preconception genetic screening programs aim to screen, educate, and optimize reproductive choice for participants. These programs have demonstrated high uptake, low psychological morbidity, and have been shown to result in fewer than expected Jewish TSD-affected births over 18 years of operation. The majority of Jewish individuals of reproductive age outside of the high school screening program setting in Australia have not accessed screening. Recent recommendations advocate supplementing the community high school screening programs with general practitioner- and obstetrician-led genetic screening of Ashkenazi Jewish individuals for TSD and other severe recessive diseases for which this group is at risk. Massively parallel DNA sequencing is expected to become the testing modality of choice over the coming years.

  13. Combination and interpretation of observables in Cosmology

    Directory of Open Access Journals (Sweden)

    Virey Jean-Marc

    2010-04-01

    Full Text Available The standard cosmological model has deep theoretical foundations but need the introduction of two major unknown components, dark matter and dark energy, to be in agreement with various observations. Dark matter describes a non-relativistic collisionless fluid of (non baryonic matter which amount to 25% of the total density of the universe. Dark energy is a new kind of fluid not of matter type, representing 70% of the total density which should explain the recent acceleration of the expansion of the universe. Alternatively, one can reject this idea of adding one or two new components but argue that the equations used to make the interpretation should be modified consmological scales. Instead of dark matter one can invoke a failure of Newton's laws. Instead of dark energy, two approaches are proposed : general relativity (in term of the Einstein equation should be modified, or the cosmological principle which fixes the metric used for cosmology should be abandonned. One of the main objective of the community is to find the path of the relevant interpretations thanks to the next generation of experiments which should provide large statistics of observationnal data. Unfortunately, cosmological in formations are difficult to pin down directly fromt he measurements, and it is mandatory to combine the various observables to get the cosmological parameters. This is not problematic from the statistical point of view, but assumptions and approximations made for the analysis may bias our interprettion of the data. Consequently, a strong attention should be paied to the statistical methods used to make parameters estimation and for model testing. After a review of the basics of cosmology where the cosmological parameters are introduced, we discuss the various cosmological probes and their associated observables used to extract cosmological informations. We present the results obtained from several statistical analyses combining data of diferent nature but

  14. Nonsingular cosmology with a scale-invariant spectrum of cosmological perturbations from Lee-Wick theory

    International Nuclear Information System (INIS)

    Cai Yifu; Qiu Taotao; Brandenberger, Robert; Zhang Xinmin

    2009-01-01

    We study the cosmology of a Lee-Wick type scalar field theory. First, we consider homogeneous and isotropic background solutions and find that they are nonsingular, leading to cosmological bounces. Next, we analyze the spectrum of cosmological perturbations which result from this model. Unless either the potential of the Lee-Wick theory or the initial conditions are finely tuned, it is impossible to obtain background solutions which have a sufficiently long period of inflation after the bounce. More interestingly, however, we find that in the generic noninflationary bouncing cosmology, perturbations created from quantum vacuum fluctuations in the contracting phase have the correct form to lead to a scale-invariant spectrum of metric inhomogeneities in the expanding phase. Since the background is nonsingular, the evolution of the fluctuations is defined unambiguously through the bounce. We also analyze the evolution of fluctuations which emerge from thermal initial conditions in the contracting phase. The spectrum of gravitational waves stemming from quantum vacuum fluctuations in the contracting phase is also scale-invariant, and the tensor to scalar ratio is not suppressed.

  15. Large Scale Cosmological Anomalies and Inhomogeneous Dark Energy

    Directory of Open Access Journals (Sweden)

    Leandros Perivolaropoulos

    2014-01-01

    Full Text Available A wide range of large scale observations hint towards possible modifications on the standard cosmological model which is based on a homogeneous and isotropic universe with a small cosmological constant and matter. These observations, also known as “cosmic anomalies” include unexpected Cosmic Microwave Background perturbations on large angular scales, large dipolar peculiar velocity flows of galaxies (“bulk flows”, the measurement of inhomogenous values of the fine structure constant on cosmological scales (“alpha dipole” and other effects. The presence of the observational anomalies could either be a large statistical fluctuation in the context of ΛCDM or it could indicate a non-trivial departure from the cosmological principle on Hubble scales. Such a departure is very much constrained by cosmological observations for matter. For dark energy however there are no significant observational constraints for Hubble scale inhomogeneities. In this brief review I discuss some of the theoretical models that can naturally lead to inhomogeneous dark energy, their observational constraints and their potential to explain the large scale cosmic anomalies.

  16. On the cosmological gravitational waves and cosmological distances

    Science.gov (United States)

    Belinski, V. A.; Vereshchagin, G. V.

    2018-03-01

    We show that solitonic cosmological gravitational waves propagated through the Friedmann universe and generated by the inhomogeneities of the gravitational field near the Big Bang can be responsible for increase of cosmological distances.

  17. Cosmological principle

    International Nuclear Information System (INIS)

    Wesson, P.S.

    1979-01-01

    The Cosmological Principle states: the universe looks the same to all observers regardless of where they are located. To most astronomers today the Cosmological Principle means the universe looks the same to all observers because density of the galaxies is the same in all places. A new Cosmological Principle is proposed. It is called the Dimensional Cosmological Principle. It uses the properties of matter in the universe: density (rho), pressure (p), and mass (m) within some region of space of length (l). The laws of physics require incorporation of constants for gravity (G) and the speed of light (C). After combining the six parameters into dimensionless numbers, the best choices are: 8πGl 2 rho/c 2 , 8πGl 2 rho/c 4 , and 2 Gm/c 2 l (the Schwarzchild factor). The Dimensional Cosmological Principal came about because old ideas conflicted with the rapidly-growing body of observational evidence indicating that galaxies in the universe have a clumpy rather than uniform distribution

  18. Cosmology and particle physics

    International Nuclear Information System (INIS)

    Turner, M.S.

    1985-01-01

    The author reviews the standard cosmology, focusing on primordial nucleosynthesis, and discusses how the standard cosmology has been used to place constraints on the properties of various particles. Baryogenesis is examined in which the B, C, CP violating interactions in GUTs provide a dynamical explanation for the predominance of matter over antimatter and the present baryon-to-baryon ratio. Monoposes, cosmology and astrophysics are reviewed. The author also discusses supersymmetry/supergravity and cosmology, superstrings and cosmology in extra dimensions, and axions, astrophics, and cosmology

  19. Variable-speed-of-light cosmology and second law of thermodynamics

    International Nuclear Information System (INIS)

    Youm, Donam

    2002-01-01

    We examine whether cosmologies with a varying speed of light (VSL) are compatible with the second law of thermodynamics. We find that the VSL cosmology with a varying fundamental constant is severely constrained by the second law of thermodynamics, whereas the bimetric cosmological models are less constrained

  20. Variable-speed-of-light cosmology and second law of thermodynamics

    International Nuclear Information System (INIS)

    Youm, Donam

    2002-03-01

    We examine whether the cosmologies with varying speed of light (VSL) are compatible with the second law of thermodynamics. We find that the VSL cosmology with varying fundamental constant is severely constrained by the second law of thermodynamics, whereas the bimetric cosmological models are less constrained. (author)

  1. New holographic reconstruction of scalar-field dark-energy models in the framework of chameleon Brans-Dicke cosmology

    International Nuclear Information System (INIS)

    Chattopadhyay, Surajit; Pasqua, Antonio; Khurshudyan, Martiros

    2014-01-01

    Motivated by the work of Yang et al. (Mod. Phys. Lett. A 26:191, 2011), we report on a study of the new holographic dark energy (NHDE) model with energy density given by ρ D = (3φ 2 )/(4ω)(μH 2 + νH) in the framework of chameleon Brans-Dicke cosmology. We have studied the correspondence between the quintessence, the DBI-essence, and the tachyon scalar-field models with the NHDE model in the framework of chameleon Brans-Dicke cosmology. Deriving an expression of the Hubble parameter H and, accordingly, ρ D in the context of chameleon Brans-Dicke chameleon cosmology, we have reconstructed the potentials and dynamics for these scalar-field models. Furthermore, we have examined the stability for the obtained solutions of the crossing of the phantom divide under a quantum correction of massless conformally invariant fields, and we have seen that the quantum correction could be small when the phantom crossing occurs and the obtained solutions of the phantom crossing could be stable under the quantum correction. It has also been noted that the potential increases as the matter. chameleon coupling gets stronger with the evolution of the universe. (orig.)

  2. New holographic reconstruction of scalar-field dark-energy models in the framework of chameleon Brans-Dicke cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Chattopadhyay, Surajit [Pailan College of Management and Technology, Kolkata (India); Pasqua, Antonio [University of Trieste, Department of Physics, Trieste (Italy); Khurshudyan, Martiros [Yerevan State University, Department of Theoretical Physics, Yerevan (Armenia); Potsdam-Golm Science Park, Max Planck Institute of Colloids and Interfaces, Potsdam (Germany)

    2014-09-15

    Motivated by the work of Yang et al. (Mod. Phys. Lett. A 26:191, 2011), we report on a study of the new holographic dark energy (NHDE) model with energy density given by ρ{sub D} = (3φ{sup 2})/(4ω)(μH{sup 2} + νH) in the framework of chameleon Brans-Dicke cosmology. We have studied the correspondence between the quintessence, the DBI-essence, and the tachyon scalar-field models with the NHDE model in the framework of chameleon Brans-Dicke cosmology. Deriving an expression of the Hubble parameter H and, accordingly, ρ{sub D} in the context of chameleon Brans-Dicke chameleon cosmology, we have reconstructed the potentials and dynamics for these scalar-field models. Furthermore, we have examined the stability for the obtained solutions of the crossing of the phantom divide under a quantum correction of massless conformally invariant fields, and we have seen that the quantum correction could be small when the phantom crossing occurs and the obtained solutions of the phantom crossing could be stable under the quantum correction. It has also been noted that the potential increases as the matter. chameleon coupling gets stronger with the evolution of the universe. (orig.)

  3. Cosmological solutions, p-branes, and the Wheeler-DeWitt equation

    International Nuclear Information System (INIS)

    Lue, H.; Maharana, J.; Maharana, J.; Mukherji, S.; Pope, C.N.; Pope, C.N.

    1998-01-01

    The low energy effective actions which arise from string theory or M-theory are considered in the cosmological context, where the graviton, dilaton and antisymmetric tensor field strengths depend only on time. We show that previous results can be extended to include cosmological solutions that are related to the E N Toda equations. The solutions of the Wheeler-DeWitt equation in minisuperspace are obtained for some of the simpler cosmological models by introducing intertwining operators that generate canonical transformations which map the theories into free theories. We study the cosmological properties of these solutions, and also briefly discuss generalized Brans-Dicke models in our framework. The cosmological models are closely related to p-brane solitons, which we discuss in the context of the E N Toda equations. We give the explicit solutions for extremal multi-charge (D-3)-branes in the truncated system described by the D 4 =O(4,4) Toda equations. copyright 1998 The American Physical Society

  4. The cosmology of the Fab-Four

    International Nuclear Information System (INIS)

    Copeland, Edmund J.; Padilla, Antonio; Saffin, Paul M.

    2012-01-01

    We have recently proposed a novel self tuning mechanism to alleviate the famous cosmological constant problem, based on the general scalar tensor theory proposed by Horndeski. The self-tuning model ends up consisting of four geometric terms in the action, with each term containing a free potential function of the scalar field; the four together being labeled as the Fab-Four. In this paper we begin the important task of deriving the cosmology associated with the Fab-Four Lagrangian. Performing a phase plane analysis of the system we are able to obtain a number of fixed points for the system, with some remarkable new solutions emerging from the trade-off between the various potentials. As well as obtaining inflationary solutions we also find conventional radiation/matter-like solutions, but in regimes where the energy density is dominated by a cosmological constant, and where we do not have any explicit forms of radiation or matter. Stability conditions for matter solutions are obtained and we show how it is possible for there to exist an extended period of 'matter domination' opening up the possibility that we can generate cosmological structures, and recover a consistent cosmology even in the presence of a large cosmological constant

  5. F(R) cosmology via Noether symmetry and Λ-Chaplygin Gas like model

    Science.gov (United States)

    Fazlollahi, H. R.

    2018-06-01

    In this work, we consider f (R) alternative theories of gravity with an eye to Noether symmetry through the gauge theorem. For non-vacuum models, one finds Λ like gravity with energy density of Chaplygin Gas. We also obtain the effective equation of state parameter for corresponding cosmology and scale factor behavior with respect to cosmic time which show that the model provides viable EoS and scale factor with respect to observational data.

  6. Experimental constraints on light scalar field models in cosmology and particle physics (SNLS and CMS experiments)

    International Nuclear Information System (INIS)

    Neveu, Jeremy

    2014-01-01

    The nature of dark energy and dark matter is still unknown today. Light scalar field models have been proposed to explain the late-time accelerated expansion of the Universe and the apparent abundance of non-baryonic matter. In the first part of this thesis, the Galileon theory, a well-posed modified gravity theory preserving the local gravitation thanks to the Vainshtein screening effect, is accurately tested against recent cosmological data. Observational constraints are derived on the model parameters using cosmological distance and growth rate of structure measurements. A good agreement is observed between data and theory predictions. The Galileon theory appears therefore as a promising alternative to the cosmological constant scenario. In the second part, the dark matter question is explored through an extra-dimension theory containing massive and stable scalar fields called Branons. Branon production is searched for in the proton-proton collisions that were collected by the Compact Muon Solenoid experiment in 2012 at the Large Hadron Collider. Events with a single photon and transverse missing energy are selected in this data set and compared to the Standard Model and instrumental background estimates. No signature of new physics is observed, so experimental limits on the Branon model parameters are derived. This thesis concludes with some ideas to reach an unified description of both models in the frame of extra-dimension theories. (author) [fr

  7. Hill-Sachs lesion location: does it play a role in engagement?

    Energy Technology Data Exchange (ETDEWEB)

    Gyftopoulos, Soterios; Wang, Annie; Babb, James [NYU Langone Medical Center, Department of Radiology, New York, NY (United States)

    2015-08-15

    To see if there is an association between engagement on physical examination (PE) and the location of the Hill-Sachs lesion (HSL) as assessed by the modified biceps angle. Sixty-two patients with a history of anterior shoulder dislocation, who underwent preoperative MRI and arthroscopy at our institution and were tested for engagement on PE, were collected. Two musculoskeletal radiologists reviewed the MR studies, noting the presence of an HSL and documenting the location of the HSL with the modified biceps angle. Statistical analysis included the Mann-Whitney (MW) test and ROC (receiver-operating characteristic) curve. Of 62 patients, there were 58 males and 4 females with a mean age of 30 (range 18-59 years). Twenty patients demonstrated engagement on PE, while 42 did not. All patients had evidence of an HSL on MRI and arthroscopy. The mean biceps angle for the engaging group was 151.5 ± 13.9 , and 142.4 ± 17.3 for the non-engaging group. The biceps angle was statistically significantly higher among patients who had engagement compared to those who did not (p = 0.027). Overall, diagnostic accuracy was highest for a biceps angle >149 , which resulted in a sensitivity of 70 % and specificity of 67 %. The modified biceps angle, as measured on MRI, was significantly higher in patients who demonstrated engagement on physical examination than in those who did not. This supports the theory that the location of the Hill-Sachs lesion may play a role in engagement and may be its most important characteristic when determining its significance. (orig.)

  8. Generation of a scale-invariant spectrum of adiabatic fluctuations in cosmological models with a contracting phase

    International Nuclear Information System (INIS)

    Finelli, Fabio; Brandenberger, Robert

    2002-01-01

    In pre-big-bang and in ekpyrotic cosmology, perturbations on cosmological scales today are generated from quantum vacuum fluctuations during a phase when the Universe is contracting (viewed in the Einstein frame). The backgrounds studied to date do not yield a scale-invariant spectrum of adiabatic fluctuations. Here, we present a new contracting background model (neither of pre-big-bang nor of the ekpyrotic form) involving a single scalar field coupled to gravity in which a scale-invariant spectrum of curvature fluctuations and gravitational waves results. The equation of state of this scalar field corresponds to cold matter. We demonstrate that if this contracting phase can be matched via a nonsingular bounce to an expanding Friedmann cosmology, the scale-invariance of the curvature fluctuations is maintained. We also find new background solutions for pre-big-bang and for ekpyrotic cosmology, which involve two scalar fields with exponential potentials with background values which are evolving in time. We comment on the difficulty of obtaining a scale-invariant spectrum of adiabatic fluctuations with background solutions which have been studied in the past

  9. Particles and cosmology

    International Nuclear Information System (INIS)

    Tkachev, Igor

    1993-01-01

    When the common ground between particle physics, astrophysics and cosmology started to become a developing area, the Institute for Nuclear Research (INR) of the Russian Academy of Sciences had the foresight in 1981 to institute the Baksan Schools on Particles and Cosmology. This now traditional event, held biannually in the Baksan Valley, has gone on to attract international participation. The site is close to the INR Baksan Neutrino Observatory with its underground and surface installations, including the SAGE gallium solar neutrino detector, the Underground Scintillation Telescope, and the 'Carpet' extensive air shower array. Participation is mainly from experimentalists working in non accelerator particle physics and particle astrophysics. The most recent School, held from April 21 to 28, began with an opening address by INR Director V. A. Matveev. J.Frieman reviewed standard big bang cosmology, emphasizing how the recent COBE results and the observations of large scale galaxy clustering fit into a standard cosmology framework. For inflationary cosmology, he showed how different models may be tested through their predictions for large-scale galactic structure and for cosmic microwave background anisotropy. A.Stebbins presented details of the large scale distribution of galaxies which, combined with velocity information and microwave background anisotropy data, provide strong constraints on theories of the origin of primordial inhomogeneities. Inflation requires, and theories of the large scale structure strongly favour the critical value for the cosmic mass density, while, as D.Seckel explained in his lecture on nucleosynthesis and abundances of the light elements, the baryon contribution to this density has to be tens of times smaller. A general review on the observational evidence for dark matter, dark matter particle candidates and the strategy of dark matter searches was given by I. Tkachev, who stressed the gravitational microlensing MACHO

  10. Towards an observational appraisal of string cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Mulryne, David J [Astronomy Unit, School of Mathematical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS (United Kingdom); Ward, John, E-mail: d.mulryne@qmul.ac.uk, E-mail: jwa@uvic.ca [Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1 (Canada)

    2011-10-21

    We review the current observational status of string cosmology when confronted with experimental datasets. We begin by defining common observational parameters and discuss how they are determined for a given model. Then we review the observable footprints of several string theoretic models, discussing the significance of various potential signals. Throughout we comment on present and future prospects of finding evidence for string theory in cosmology and on significant issues for the future.

  11. Towards an observational appraisal of string cosmology

    International Nuclear Information System (INIS)

    Mulryne, David J; Ward, John

    2011-01-01

    We review the current observational status of string cosmology when confronted with experimental datasets. We begin by defining common observational parameters and discuss how they are determined for a given model. Then we review the observable footprints of several string theoretic models, discussing the significance of various potential signals. Throughout we comment on present and future prospects of finding evidence for string theory in cosmology and on significant issues for the future.

  12. Is there a cosmological evidence for additional particles

    International Nuclear Information System (INIS)

    Kirilova, D.P.; Chizhov, M.V.

    1998-05-01

    An extended cosmological model of the early Universe with additional antisymmetric tensor particles is described. The cosmological effects of the additional particles, namely additional interactions of the early Universe plasma with the tensor particles, a shift of the early Universe temperature-time dependence and the total energy density increase are discussed. The efficiency of the tensor particles interactions with the early Universe plasma components and their corresponding cosmological time and temperature are determined. (author)

  13. Effective dynamics of the closed loop quantum cosmology

    International Nuclear Information System (INIS)

    Mielczarek, Jakub; Szydłowski, Marek; Hrycyna, Orest

    2009-01-01

    In this paper we study dynamics of the closed FRW model with holonomy corrections coming from loop quantum cosmology. We consider models with a scalar field and cosmological constant. In case of the models with cosmological constant and free scalar field, dynamics reduce to 2D system and analysis of solutions simplify. If only free scalar field is included then universe undergoes non-singular oscillations. For the model with cosmological constant, different behaviours are obtained depending on the value of Λ. If the value of Λ is sufficiently small, bouncing solutions with asymptotic de Sitter stages are obtained. However if the value of Λ exceeds critical value Λ c = 3 1/2 m Pl 2 /2πγ 3 ≅ 21m Pl 2 then solutions become oscillatory. Subsequently we study models with a massive scalar field. We find that this model possess generic inflationary attractors. In particular field, initially situated in the bottom of the potential, is driven up during the phase of quantum bounce. This subsequently leads to the phase of inflation. Finally we find that, comparing with the flat case, effects of curvature do not change qualitatively dynamics close to the phase of bounce. Possible effects of inverse volume corrections are also briefly discussed

  14. Deformation of the Engle-Livine-Pereira-Rovelli spin foam model by a cosmological constant

    Science.gov (United States)

    Bahr, Benjamin; Rabuffo, Giovanni

    2018-04-01

    In this article, we consider an ad hoc deformation of the Engle-Livine-Pereira-Rovelli model for quantum gravity by a cosmological constant term. This sort of deformation was first introduced by Han for the case of the 4-simplex. In this article, we generalize the deformation to the case of arbitrary vertices, and compute its large-j asymptotics. We show that, if the boundary data correspond to a four-dimensional polyhedron P , then the asymptotic formula gives the usual Regge action plus a cosmological constant term. We pay particular attention to the determinant of the Hessian matrix, and show that it can be related to that of the undeformed vertex.

  15. The Philosophy of Cosmology

    Science.gov (United States)

    Chamcham, Khalil; Silk, Joseph; Barrow, John D.; Saunders, Simon

    2017-04-01

    Part I. Issues in the Philosophy of Cosmology: 1. Cosmology, cosmologia and the testing of cosmological theories George F. R. Ellis; 2. Black holes, cosmology and the passage of time: three problems at the limits of science Bernard Carr; 3. Moving boundaries? - comments on the relationship between philosophy and cosmology Claus Beisbart; 4. On the question why there exists something rather than nothing Roderich Tumulka; Part II. Structures in the Universe and the Structure of Modern Cosmology: 5. Some generalities about generality John D. Barrow; 6. Emergent structures of effective field theories Jean-Philippe Uzan; 7. Cosmological structure formation Joel R. Primack; 8. Formation of galaxies Joseph Silk; Part III. Foundations of Cosmology: Gravity and the Quantum: 9. The observer strikes back James Hartle and Thomas Hertog; 10. Testing inflation Chris Smeenk; 11. Why Boltzmann brains do not fluctuate into existence from the de Sitter vacuum Kimberly K. Boddy, Sean M. Carroll and Jason Pollack; 12. Holographic inflation revised Tom Banks; 13. Progress and gravity: overcoming divisions between general relativity and particle physics and between physics and HPS J. Brian Pitts; Part IV. Quantum Foundations and Quantum Gravity: 14. Is time's arrow perspectival? Carlo Rovelli; 15. Relational quantum cosmology Francesca Vidotto; 16. Cosmological ontology and epistemology Don N. Page; 17. Quantum origin of cosmological structure and dynamical reduction theories Daniel Sudarsky; 18. Towards a novel approach to semi-classical gravity Ward Struyve; Part V. Methodological and Philosophical Issues: 19. Limits of time in cosmology Svend E. Rugh and Henrik Zinkernagel; 20. Self-locating priors and cosmological measures Cian Dorr and Frank Arntzenius; 21. On probability and cosmology: inference beyond data? Martin Sahlén; 22. Testing the multiverse: Bayes, fine-tuning and typicality Luke A. Barnes; 23. A new perspective on Einstein's philosophy of cosmology Cormac O

  16. Regular and Chaotic Regimes in Scalar Field Cosmology

    Directory of Open Access Journals (Sweden)

    Alexey V. Toporensky

    2006-03-01

    Full Text Available A transient chaos in a closed FRW cosmological model with a scalar field is studied. We describe two different chaotic regimes and show that the type of chaos in this model depends on the scalar field potential. We have found also that for sufficiently steep potentials or for potentials with large cosmological constant the chaotic behavior disappears.

  17. Inflation after COBE: Lectures on inflationary cosmology

    International Nuclear Information System (INIS)

    Turner, M.S.

    1992-01-01

    In these lectures I review the standard hot big-bang cosmology, emphasizing its successes, its shortcomings, and its major challenge-a detailed understanding of the formation of structure in the Universe. I then discuss the motivations for and the fundamentals of inflationary cosmology, particularly emphasizing the quantum origin of metric (density and gravity-wave) perturbations. Inflation addresses the shortcomings of the standard cosmology and provides the ''initial data'' for structure formation. I conclude by addressing the implications of inflation for structure formation, evaluating the various cold dark matter models in the light of the recent detection of temperature anisotropies in the cosmic background radiation by COBE. In the near term, the study of structure formation offers a powerful probe of inflation, as well as specific inflationary models

  18. Inflation after COBE: Lectures on inflationary cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Turner, M.S. [Chicago Univ., IL (United States). Enrico Fermi Inst.]|[Fermi National Accelerator Lab., Batavia, IL (United States)

    1992-12-31

    In these lectures I review the standard hot big-bang cosmology, emphasizing its successes, its shortcomings, and its major challenge-a detailed understanding of the formation of structure in the Universe. I then discuss the motivations for and the fundamentals of inflationary cosmology, particularly emphasizing the quantum origin of metric (density and gravity-wave) perturbations. Inflation addresses the shortcomings of the standard cosmology and provides the ``initial data`` for structure formation. I conclude by addressing the implications of inflation for structure formation, evaluating the various cold dark matter models in the light of the recent detection of temperature anisotropies in the cosmic background radiation by COBE. In the near term, the study of structure formation offers a powerful probe of inflation, as well as specific inflationary models.

  19. More on cosmological constraints on spontaneous R-symmetry breaking models

    International Nuclear Information System (INIS)

    Hamada, Yuta; Kobayashi, Tatsuo; Kamada, Kohei; Ecole Polytechnique Federale de Lausanne; Ookouchi, Yutaka

    2013-10-01

    We study the spontaneous R-symmetry breaking model and investigate the cosmological constraints on this model due to the pseudo Nambu-Goldstone boson, R-axion. We consider the R-axion which has relatively heavy mass in order to complement our previous work. In this regime, model parameters, R-axions mass and R-symmetry breaking scale, are constrained by Big Bang Nucleosynthesis and overproduction of the gravitino produced from R-axion decay and thermal plasma. We find that the allowed parameter space is very small for high reheating temperature. For low reheating temperature, the U(1) R breaking scale f a is constrained as f a 12-14 GeV regardless of the value of R-axion mass.

  20. Time variable cosmological constants from the age of universe

    International Nuclear Information System (INIS)

    Xu Lixin; Lu Jianbo; Li Wenbo

    2010-01-01

    In this Letter, time variable cosmological constant, dubbed age cosmological constant, is investigated motivated by the fact: any cosmological length scale and time scale can introduce a cosmological constant or vacuum energy density into Einstein's theory. The age cosmological constant takes the form ρ Λ =3c 2 M P 2 /t Λ 2 , where t Λ is the age or conformal age of our universe. The effective equation of state (EoS) of age cosmological constant are w Λ eff =-1+2/3 (√(Ω Λ ))/c and w Λ eff =-1+2/3 (√(Ω Λ ))/c (1+z) when the age and conformal age of universe are taken as the role of cosmological time scales respectively. The EoS are the same as the so-called agegraphic dark energy models. However, the evolution histories are different from the agegraphic ones for their different evolution equations.