Energy Technology Data Exchange (ETDEWEB)
Setare, M R; Kamali, V, E-mail: rezakord@ipm.ir, E-mail: vkamali1362@gmail.com [Department of Science, Payame Noor University, Bijar (Iran, Islamic Republic of)
2011-11-07
We show that a BTZ black hole solution of cosmological topological massive gravity has a hidden conformal symmetry. In this regard, we consider the wave equation of a massless scalar field propagating in BTZ spacetime and find that the wave equation could be written in terms of the SL(2, R) quadratic Casimir. From the conformal coordinates, the temperatures of the dual conformal field theories (CFTs) could be read directly. Moreover, we compute the microscopic entropy of the dual CFT by the Cardy formula and find a perfect match to the Bekenstein-Hawking entropy of a BTZ black hole. Then, we consider Galilean conformal algebras (GCA), which arises as a contraction of relativistic conformal algebras (x {yields} {epsilon}x, t {yields} t, {epsilon} {yields} 0). We show that there is a correspondence between GCA{sub 2} on the boundary and contracted BTZ in the bulk. For this purpose we obtain the central charges and temperatures of GCA{sub 2}. Then, we compute the microscopic entropy of the GCA{sub 2} by the Cardy formula and find a perfect match to the Bekenstein-Hawking entropy of a BTZ black hole in a non-relativistic limit. The absorption cross section of a near-region scalar field also matches the microscopic absorption cross section of the dual GCA{sub 2}. So we find further evidence that shows correspondence between a contracted BTZ black hole and two-dimensional GCA.
Cosmological solutions with massive gravitons
Energy Technology Data Exchange (ETDEWEB)
Chamseddine, Ali H. [Physics Department, American University of Beirut (Lebanon); Laboratoire de Mathematiques et Physique Theorique CNRS-UMR 6083, Universite de Tours, Parc de Grandmont, 37200 Tours (France); LE STUDIUM, Loire Valley Institute for Advanced Studies, Tours and Orleans (France); I.H.E.S., F-91440 Bures-sur-Yvette (France); Volkov, Mikhail S., E-mail: volkov@lmpt.univ-tours.fr [Laboratoire de Mathematiques et Physique Theorique CNRS-UMR 6083, Universite de Tours, Parc de Grandmont, 37200 Tours (France)
2011-10-25
We present solutions describing spatially closed, open, or flat cosmologies in the massive gravity theory within the recently proposed tetrad formulation. We find that the effect of the graviton mass is equivalent to introducing to the Einstein equations a matter source that can consist of several different matter types - a cosmological term, quintessence, gas of cosmic strings, and non-relativistic cold matter.
Cosmological perturbations in massive bigravity
Energy Technology Data Exchange (ETDEWEB)
Lagos, Macarena; Ferreira, Pedro G., E-mail: m.lagos13@imperial.ac.uk, E-mail: p.ferreira1@physics.ox.ac.uk [Astrophysics, University of Oxford, DWB, Keble road, Oxford OX1 3RH (United Kingdom)
2014-12-01
We present a comprehensive analysis of classical scalar, vector and tensor cosmological perturbations in ghost-free massive bigravity. In particular, we find the full evolution equations and analytical solutions in a wide range of regimes. We show that there are viable cosmological backgrounds but, as has been found in the literature, these models generally have exponential instabilities in linear perturbation theory. However, it is possible to find stable scalar cosmological perturbations for a very particular choice of parameters. For this stable subclass of models we find that vector and tensor perturbations have growing solutions. We argue that special initial conditions are needed for tensor modes in order to have a viable model.
Free energy of topologically massive gravity and flat space holography
Grumiller, Daniel
2015-01-01
We calculate the free energy from the on-shell action for topologically massive gravity with negative and vanishing cosmological constant, thereby providing a first principles derivation of the free energy of BTZ black holes and flat space cosmologies. We summarize related recent checks of flat space holography.
Perturbations in Massive Gravity Cosmology
Crisostomi, Marco; Pilo, Luigi
2012-01-01
We study cosmological perturbations for a ghost free massive gravity theory formulated with a dynamical extra metric that is needed to massive deform GR. In this formulation FRW background solutions fall in two branches. In the dynamics of perturbations around the first branch solutions, no extra degree of freedom with respect to GR ispresent at linearized level, likewise what is found in the Stuckelberg formulation of massive gravity where the extra metric isflat and non dynamical. In the first branch, perturbations are probably strongly coupled. On the contrary, for perturbations around the second branch solutions all expected degrees of freedom propagate. While tensor and vector perturbations of the physical metric that couples with matter follow closely the ones of GR, scalars develop an exponential Jeans-like instability on sub-horizon scales. On the other hand, around a de Sitter background there is no instability. We argue that one could get rid of the instabilities by introducing a mirror dark matter ...
Cosmological attractors in massive gravity
Dubovsky, S; Tkachev, I I
2005-01-01
We study Lorentz-violating models of massive gravity which preserve rotations and are invariant under time-dependent shifts of the spatial coordinates. In the linear approximation the Newtonian potential in these models has an extra ``confining'' term proportional to the distance from the source. We argue that during cosmological expansion the Universe may be driven to an attractor point with larger symmetry which includes particular simultaneous dilatations of time and space coordinates. The confining term in the potential vanishes as one approaches the attractor. In the vicinity of the attractor the extra contribution is present in the Friedmann equation which, in a certain range of parameters, gives rise to the cosmic acceleration.
FRW Cosmological Perturbations in Massive Bigravity
Comelli, D; Pilo, L
2014-01-01
Cosmological perturbations of FRW solutions in ghost free massive bigravity, including also a second matter sector, are studied in detail. At early time, we find that sub horizon exponential instabilities are unavoidable and they lead to a premature departure from the perturbative regime of cosmological perturbations.
New Cosmological Solutions in Massive Gravity Theory
Pinho, S. S. A.; Pereira, S. H.; Mendonça, E. L.
2017-04-01
In this paper we present some new cosmological solutions in massive gravity theory. Some homogeneous and isotropic solutions correctly describe accelerated evolutions for the universe. The study was realized considering a specific form to the fiducial metric and found different functions and constant parameters of the theory that guarantee the conservation of the energy momentum tensor. Several accelerating cosmologies were found, all of them reproducing a cosmological constant term proportional to the graviton mass, with a de Sitter type solution for the scale factor. We have also verified that when the fiducial metric is close to the physical metric the solutions are absent, except for some specific open cases.
A Cosmological Study in Massive Gravity theory
Pan, Supriya
2015-01-01
A detailed study of the various cosmological aspects in massive gravity theory has been presented in the present work. For the homogeneous and isotropic FLRW model, the deceleration parameter has been evaluated, and, it has been examined whether there is any transition from deceleration to acceleration in recent past, or not. With the proper choice of the free parameters, it has been shown that the massive gravity theory is equivalent to Einstein gravity with a modified Newtonian gravitational constant together with a negative cosmological constant. Also, in this context, it has been examined whether the emergent scenario is possible, or not, in massive gravity theory. Finally, we have done a cosmographic analysis in massive gravity theory.
Topologically massive gravity and Ricci-Cotton flow
Energy Technology Data Exchange (ETDEWEB)
Lashkari, Nima; Maloney, Alexander, E-mail: lashkari@physics.mcgill.ca, E-mail: maloney@physics.mcgill.ca [McGill Physics Department, 3600 rue University, Montreal, QC H3A 2T8 (Canada)
2011-05-21
We consider topologically massive gravity (TMG), which is three-dimensional general relativity with a cosmological constant and a gravitational Chern-Simons term. When the cosmological constant is negative the theory has two potential vacuum solutions: anti-de Sitter space and warped anti-de Sitter space. The theory also contains a massive graviton state which renders these solutions unstable for certain values of the parameters and boundary conditions. We study the decay of these solutions due to the condensation of the massive graviton mode using Ricci-Cotton flow, which is the appropriate generalization of Ricci flow to TMG. When the Chern-Simons coupling is small the AdS solution flows to warped AdS by the condensation of the massive graviton mode. When the coupling is large the situation is reversed, and warped AdS flows to AdS. Minisuperspace models are constructed where these flows are studied explicitly.
FRW Cosmology in Ghost Free Massive Gravity
Comelli, D; Nesti, F; Pilo, L
2011-01-01
We study FRW homogeneous cosmological solutions in the recently found ghost free massive gravity. In previous works it was shown that when the additional extra metric, needed to generate the mass term, is taken as non-dynamical and flat, no homogeneous FRW cosmology exists. We show that, when the additional metric is a dynamical field, a perfectly safe FRW universe exists. FRW solutions fall in two branches. In the first branch the massive deformation is equivalent to an effectively generated cosmological constant whose scale is determined by the graviton mass. The second branch is quite rich: we have FRW cosmology in the presence of a "gravitational" fluid. The control parameter xi is the ratio of the two conformal factors. When xi is large, generically the cosmological evolution greatly differs from GR at the early time. In the small xi region, the evolution is similar to GR and the universe flows at late time toward an attractor represented by a dS phase.
Hamiltonian cosmology in bigravity and massive gravity
Soloviev, Vladimir O
2015-01-01
In the Hamiltonian language we provide a study of flat-space cosmology in bigravity and massive gravity constructed mostly with de Rham, Gabadadze, Tolley (dRGT) potential. It is demonstrated that the Hamiltonian methods are powerful not only in proving the absence of the Boulware-Deser ghost, but also in solving other problems. The purpose of this work is to give an introduction both to the Hamiltonian formalism and to the cosmology of bigravity. We sketch three roads to the Hamiltonian of bigravity with the dRGT potential: the metric, the tetrad and the minisuperspace approaches.
Cosmological Perturbations in Extended Massive Gravity
Gumrukcuoglu, A Emir; Lin, Chunshan; Mukohyama, Shinji; Trodden, Mark
2013-01-01
We study cosmological perturbations around self-accelerating solutions to two extensions of nonlinear massive gravity: the quasi-dilaton theory and the mass-varying theory. We examine stability of the cosmological solutions, and the extent to which the vanishing of the kinetic terms for scalar and vector perturbations of self-accelerating solutions in massive gravity is generic when the theory is extended. We find that these kinetic terms are in general non-vanishing in both extensions, though there are constraints on the parameters and background evolution from demanding that they have the correct sign. In particular, the self-accelerating solutions of the quasi-dilaton theory are always unstable to scalar perturbations with wavelength shorter than the Hubble length.
A massive graviton in topologically new massive gravity
Kim, Yong-Wan; Park, Young-Jai
2013-01-01
We investigate the topologically new massive gravity in three dimensions. It turns out that a single massive mode is propagating in the flat spacetime, comparing to the conformal Chern-Simons gravity which has no physically propagating degrees of freedom. Also we discuss the realization of the BMS/GCA correspondence.
Does massive gravity have viable cosmologies?
Solomon, Adam R; Akrami, Yashar; Koivisto, Tomi S; Könnig, Frank; Mörtsell, Edvard
2015-01-01
Massive gravity has a well-known no-go theorem forbidding flat FLRW solutions; other solutions are unstable, seemingly ruling out the possibility of homogeneous and isotropic massive cosmology. Recently, de Rham, Heisenberg, and Ribeiro showed that this can be overcome if matter is coupled to both the spacetime metric and the reference metric, reopening the possibilities for cosmology with a single, massive graviton. It is shown that this proof, however, relies crucially on the existence of a scalar field or some other nonstandard matter, while a universe filled with only dust or radiation faces the same no-go restriction as in the original theory. Unusually, the total density, pressure, and Einstein-frame Friedmann equation are completely determined in terms of the scale factor, independent of the matter content; the physical Hubble rate, however, does not have this property. In the presence of a scalar, these models possess pathological evolution at both early and late times, unless the scalar has a highly ...
A cosmological context for compact massive galaxies
Stringer, Martin; Vecchia, Claudio Dalla; Martinez-Valpuesta, Inma
2015-01-01
To provide a quantitative cosmological context to ongoing observational work on the formation histories and location of compact massive galaxies, we locate and study a sample of exceptionally compact systems in the Bolshoi simulation, using the dark matter structural parameters from a real, compact massive galaxy (NGC1277) as a basis for our working criteria. We find that over 80% of objects in this nominal compact category are substructures of more massive groups or clusters, and that the probability of a given massive substructure being this compact increases significantly with the mass of the host structure; rising to ~30% for the most massive clusters in the simulation. Tracking the main progenitors of this subsample back to z=2, we find them all to be distinct structures with scale radii and densities representative of the population as a whole at this epoch. What does characterise their histories, in addition to mostly becoming substructures, is that they have almost all experienced below-average mass a...
On the cosmology of massive gravity
De Felice, Antonio; Lin, Chunshan; Mukohyama, Shinji
2013-01-01
We present a review of cosmological solutions in non-linear massive gravity, focusing on the stability of perturbations. Although homogeneous and isotropic solutions have been found, these are now known to suffer from either Higuchi ghost or a new non-linear ghost instability. We discuss two approaches to alleviate this issue. By relaxing the symmetry of the background by e.g. breaking isotropy in the hidden sector, it is possible to accommodate a stable cosmological solution. Alternatively, extending the theory to allow for new dynamical degrees of freedom can also remove the conditions which lead to the instability. As examples for this case, we study the stability of self-accelerating solutions in the quasi-dilatonic extension and generic cosmological solutions in the varying mass extension. While the quasi-dilaton case turns out to be unstable, the varying mass case allows stable regimes of parameters. Viable self-accelerating solutions in the varying mass theory yet remain to be found.
Interaction Between Massive and Massless Gravitons by Perturbing Topological Field Theory
Institute of Scientific and Technical Information of China (English)
E. Koorambas
2012-01-01
We test the Wu gauge theory of gravity with massive gravitons in the perturbing topological field theory framework. We show that the computation of the correlation function between massive and massless gravitons is reported up to 4-loop and appears to be unaffected by radiative correction. This result ensures the stability of the linking number between massive and massless gravitons with respect to the local perturbation, a result with potential wider applications in cosmology.
Anisotropic cosmological solutions in massive vector theories
Heisenberg, Lavinia; Kase, Ryotaro; Tsujikawa, Shinji
2016-11-01
In beyond-generalized Proca theories including the extension to theories higher than second order, we study the role of a spatial component v of a massive vector field on the anisotropic cosmological background. We show that, as in the case of the isotropic cosmological background, there is no additional ghostly degrees of freedom associated with the Ostrogradski instability. In second-order generalized Proca theories we find the existence of anisotropic solutions on which the ratio between the anisotropic expansion rate Σ and the isotropic expansion rate H remains nearly constant in the radiation-dominated epoch. In the regime where Σ/H is constant, the spatial vector component v works as a dark radiation with the equation of state close to 1/3. During the matter era, the ratio Σ/H decreases with the decrease of v. As long as the conditions |Σ| ll H and v2 ll phi2 are satisfied around the onset of late-time cosmic acceleration, where phi is the temporal vector component, we find that the solutions approach the isotropic de Sitter fixed point (Σ = 0 = v) in accordance with the cosmic no-hair conjecture. In the presence of v and Σ the early evolution of the dark energy equation of state wDE in the radiation era is different from that in the isotropic case, but the approach to the isotropic value wDE(iso) typically occurs at redshifts z much larger than 1. Thus, apart from the existence of dark radiation, the anisotropic cosmological dynamics at low redshifts is similar to that in isotropic generalized Proca theories. In beyond-generalized Proca theories the only consistent solution to avoid the divergence of a determinant of the dynamical system corresponds to v = 0, so Σ always decreases in time.
Cosmology with coalescing massive black holes
Energy Technology Data Exchange (ETDEWEB)
Hughes, Scott A; Holz, Daniel E [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States)
2003-05-21
The gravitational waves generated in the coalescence of massive binary black holes will be measurable by LISA to enormous distances. Redshifts z {approx} 10 or larger (depending somewhat on the mass of the binary) can potentially be probed by such measurements, suggesting that binary coalescences can be made into cosmological tools. We discuss two particularly interesting types of probe. First, by combining gravitational-wave measurements with information about the cosmography of the universe, we can study the evolution of black-hole masses and merger rates as a function of redshift, providing information about the growth of structures at high redshift and possibly constraining hierarchical merger scenarios. Second, if it is possible to associate an 'electromagnetic' counterpart with a coalescence, it may be possible to measure both redshift and luminosity distance to an event with less than {approx}1% error. Such a measurement would constitute an amazingly precise cosmological standard candle. Unfortunately, gravitational lensing uncertainties will reduce the quality of this candle significantly. Though not as amazing as might have been hoped, such a candle would nonetheless very usefully complement other distance-redshift probes, in particular providing a valuable check on systematic effects in such measurements.
Anisotropic cosmological solutions in massive vector theories
Heisenberg, Lavinia; Tsujikawa, Shinji
2016-01-01
In beyond-generalized Proca theories including the extension to theories higher than second order, we study the role of a spatial component $v$ of a massive vector field on the anisotropic cosmological background. We show that, as in the case of the isotropic cosmological background, there is no additional ghostly degrees of freedom associated with the Ostrogradski instability. In second-order generalized Proca theories we find the existence of anisotropic solutions on which the ratio between the anisotropic expansion rate $\\Sigma$ and the isotropic expansion rate $H$ remains nearly constant in the radiation-dominated epoch. In the regime where $\\Sigma/H$ is constant, the spatial vector component $v$ works as a dark radiation with the equation of state close to $1/3$. During the matter era, the ratio $\\Sigma/H$ decreases with the decrease of $v$. As long as the conditions $|\\Sigma| \\ll H$ and $v^2 \\ll \\phi^2$ are satisfied around the onset of late-time cosmic acceleration, where $\\phi$ is the temporal vector ...
Measure, Topology and Probabilistic Reasoning in Cosmology
Curiel, Erik
2015-01-01
I explain the difficulty of making various concepts of and relating to probability precise, rigorous and physically significant when attempting to apply them in reasoning about objects (e.g., spacetimes) living in infinite-dimensional spaces, working through many examples from cosmology. I focus on the relation of topological to measure-theoretic notions of and relating to probability, how they diverge in unpleasant ways in the infinite-dimensional case, and are difficult to work with on their own as well in that context. Even in cases where an appropriate family of spacetimes is finite-dimensional, however, and so admits a measure of the relevant sort, it is always the case that the family is not a compact topological space, and so does not admit a physically significant, well behaved probability measure. Problems of a different but still deeply troubling sort plague arguments about likelihood in that context, which I also discuss. I conclude that most standard forms of argument used in cosmology to estimate...
Topologically Massive Gauge Theory: A Lorentzian Solution
Saygili, K
2006-01-01
We obtain a lorentzian solution for the topologically massive non-abelian gauge theory on AdS space by means of a SU(1, 1) gauge transformation of the previously found abelian solution. There exists a natural scale of length which is determined by the inverse topological mass. The topological mass is proportional to the square of the gauge coupling constant. In the topologically massive electrodynamics the field strength locally determines the gauge potential up to a closed 1-form via the (anti-)self-duality equation. We introduce a transformation of the gauge potential using the dual field strength which can be identified with an abelian gauge transformation. Then we present the map from the AdS space to the pseudo-sphere including the topological mass. This is the lorentzian analog of the Hopf map. This map yields a global decomposition of the AdS space as a trivial circle bundle over the upper portion of the pseudo-sphere which is the the Hyperboloid model for the Lobachevski geometry. This leads to a redu...
Holographically Viable Extensions of Topologically Massive and Minimal Massive Gravity?
Altas, Emel
2015-01-01
Recently, an extension of the topologically massive gravity (TMG) in $2+1$ dimensions, dubbed as minimal massive gravity (MMG), was found which is free of the bulk-boundary unitarity clash that inflicts the former theory and all the other known three dimensional theories. Field equations of MMG differ from those of TMG at quadratic terms in the curvature that do not come from the variation of an action depending on the metric alone. Here we show that MMG is a unique theory and there does not exist a deformation of TMG or MMG at the cubic and quartic order (and beyond) in the curvature that is consistent at the level of the field equations. The only extension of TMG with the desired bulk and boundary properties having a single massive degree of freedom is MMG.
Cosmology of the Galileon from Massive Gravity
de Rham, Claudia
2011-01-01
We covariantize the decoupling limit of massive gravity proposed in arXiv:1011.1232 and study the cosmology of this theory as a proxy, which embodies key features of the fully non-linear covariant theory. We first confirm that it exhibits a self-accelerating solution, similar to what has been found in arXiv:1010.1780, where the Hubble parameter corresponds to the graviton mass. For a certain range of parameters fluctuations relative to the self-accelerating background are stable and form an attractor solution. We also show that a degravitating solution can not be constructed in this covariantized proxy theory in a meaningful way. As for cosmic structure formation, we find that the helicity-0 mode of the graviton causes an enhancement relative to LCDM. For consistency we also compare proxy theories obtained starting from different frames in the decoupling limit and discuss the possibility of obtaining a non-representative proxy theory by choosing the wrong starting frame.
Cosmology of the Galileon from massive gravity
de Rham, Claudia; Heisenberg, Lavinia
2011-08-01
We covariantize the decoupling limit of massive gravity proposed in [de Rham, G. Gabadadze, and A. J. Tolley, Phys. Rev. Lett. 106, 231101 (2011).PRLTAO0031-900710.1103/PhysRevLett.106.231101] and study the cosmology of this theory as a proxy, which embodies key features of the fully nonlinear covariant theory. We first confirm that it exhibits a self-accelerating solution, similar to what has been found in [C. de Rham, G. Gabadadze, L. Heisenberg, and D. Pirtskhalava, Phys. Rev. DPRVDAQ1550-7998 83, 103516 (2011).10.1103/PhysRevD.83.103516], where the Hubble parameter corresponds to the graviton mass. For a certain range of parameters fluctuations relative to the self-accelerating background are stable and form an attractor solution. We also show that a degravitating solution can not be constructed in this covariantized proxy theory in a meaningful way. As for cosmic structure formation, we find that the helicity-0 mode of the graviton causes an enhancement relative to ΛCDM. For consistency we also compare proxy theories obtained starting from different frames in the decoupling limit and discuss the possibility of obtaining a nonrepresentative proxy theory by choosing the wrong starting frame.
Semi-Analytic Galaxy Formation in Massive Neutrinos Cosmologies
Fontanot, Fabio; Bianchi, Davide; Viel, Matteo
2014-01-01
The present constraints on neutrino masses led to the revision of their cosmological role, as the presence of a cosmological neutrino background is a clear prediction of the current standard cosmological models. In this paper, we extend the study of the impact of such background on the spatial distribution of both Dark Matter (DM) and galaxies in the Universe, by coupling N-body numerical simulations with semi-analytic models (SAMs) of galaxy formation. Starting from the same initial conditions, massive neutrino cosmologies predict a slower evolution of DM perturbations with respect to the corresponding LCDM cosmology and a suppression on the matter power spectrum on small and intermediate scales. The resulting statistical properties of model galaxies reflect the different growth of the Large Scale Structure, but we explicitly show that most of the deviations from a LCDM realisation are due to the different $\\sigma_8$ associated with the massive neutrino cosmologies. We thus conclude that an independent estim...
Topology and incompleteness for 2+1-dimensional cosmological spacetimes
Fajman, David
2016-12-01
We study the long-time behavior of the Einstein flow coupled to matter on 2-dimensional surfaces. We consider massless matter models such as collisionless matter composed of massless particles, massless scalar fields and radiation fluids and show that the maximal globally hyperbolic development of homogeneous and isotropic initial data on the 2-sphere is geodesically incomplete in both time directions, i.e. the spacetime recollapses. This behavior also holds for open sets of initial data. In particular, we construct classes of recollapsing 2+1-dimensional spacetimes with spherical spatial topology which provide evidence for a closed universe recollapse conjecture for massless matter models in 2+1 dimensions. Furthermore, we construct solutions with toroidal and higher genus topology for the massless matter fields, which in both cases are future complete. The spacetimes with toroidal topology are 2+1-dimensional analogies of the Einstein-de Sitter model. In addition, we point out a general relation between the energy-momentum tensor and the Kretschmann scalar in 2+1 dimensions and use it to infer strong cosmic censorship for all these models. In view of this relation, we also recall corresponding models containing massive particles, constructed in a previous work and determine the nature of their initial singularities. We conclude that the global structure of non-vacuum cosmological spacetimes in 2+1 dimensions is determined by the mass of particles and—in the homogeneous and isotropic setting studied here—verifies strong cosmic censorship.
Classical and quantum cosmology of minimal massive bigravity
Darabi, F.; Mousavi, M.
2016-10-01
In a Friedmann-Robertson-Walker (FRW) space-time background we study the classical cosmological models in the context of recently proposed theory of nonlinear minimal massive bigravity. We show that in the presence of perfect fluid the classical field equations acquire contribution from the massive graviton as a cosmological term which is positive or negative depending on the dynamical competition between two scale factors of bigravity metrics. We obtain the classical field equations for flat and open universes in the ordinary and Schutz representation of perfect fluid. Focusing on the Schutz representation for flat universe, we find classical solutions exhibiting singularities at early universe with vacuum equation of state. Then, in the Schutz representation, we study the quantum cosmology for flat universe and derive the Schrodinger-Wheeler-DeWitt equation. We find its exact and wave packet solutions and discuss on their properties to show that the initial singularity in the classical solutions can be avoided by quantum cosmology. Similar to the study of Hartle-Hawking no-boundary proposal in the quantum cosmology of de Rham, Gabadadze and Tolley (dRGT) massive gravity, it turns out that the mass of graviton predicted by quantum cosmology of the minimal massive bigravity is large at early universe. This is in agreement with the fact that at early universe the cosmological constant should be large.
Classical and quantum cosmology of minimal massive bigravity
Directory of Open Access Journals (Sweden)
F. Darabi
2016-10-01
Full Text Available In a Friedmann–Robertson–Walker (FRW space–time background we study the classical cosmological models in the context of recently proposed theory of nonlinear minimal massive bigravity. We show that in the presence of perfect fluid the classical field equations acquire contribution from the massive graviton as a cosmological term which is positive or negative depending on the dynamical competition between two scale factors of bigravity metrics. We obtain the classical field equations for flat and open universes in the ordinary and Schutz representation of perfect fluid. Focusing on the Schutz representation for flat universe, we find classical solutions exhibiting singularities at early universe with vacuum equation of state. Then, in the Schutz representation, we study the quantum cosmology for flat universe and derive the Schrodinger–Wheeler–DeWitt equation. We find its exact and wave packet solutions and discuss on their properties to show that the initial singularity in the classical solutions can be avoided by quantum cosmology. Similar to the study of Hartle–Hawking no-boundary proposal in the quantum cosmology of de Rham, Gabadadze and Tolley (dRGT massive gravity, it turns out that the mass of graviton predicted by quantum cosmology of the minimal massive bigravity is large at early universe. This is in agreement with the fact that at early universe the cosmological constant should be large.
Classical and quantum cosmology of minimal massive bigravity
Darabi, F
2015-01-01
In a Friedmann-Robertson-Walker (FRW) space-time background we study the classical cosmological models in the context of recently proposed theory of nonlinear minimal massive bigravity. We show that in the presence of perfect fluid the classical field equations acquire contribution from the massive graviton as a cosmological term which is positive or negative depending on the dynamical competition between two scale factors of bigravity metrics. We obtain the classical field equations for flat and open universes in the ordinary and Schutz's representations of perfect fluid and find the solutions. Moreover, we study the quantum cosmology using the canonical quantization procedure and derive the Schrodinger-Wheeler-DeWitt equation. We find its exact and wave packet solutions and discuss on their properties to show that the initial singularity in the classical solutions can be avoided by quantum cosmological considerations. Similar to the study of Hartle-Hawking no-boundary proposal in the quantum cosmology of de...
Witten-Nester energy in topologically massive gravity
Energy Technology Data Exchange (ETDEWEB)
Sezgin, Ergin [George and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Tanii, Yoshiaki, E-mail: sezgin@physics.tamu.ed, E-mail: tanii@phy.saitama-u.ac.j [Division of Material Science, Graduate School of Science and Engineering, Saitama University, Saitama 338-8570 (Japan)
2009-12-07
We formulate topologically massive supergravity with a cosmological constant in the first-order formalism and construct the Noether supercurrent and superpotential associated with its local supersymmetry. Using these results, we construct in ordinary topologically massive gravity the Witten-Nester integral for conserved charges containing spinors which satisfy a generalized version of the Witten equation on the initial value surface. We show that the Witten-Nester charge, represented as an integral over the boundary of the initial value surface, produces the Abbott-Deser-Tekin energy for asymptotically anti-de Sitter spacetimes. We consider all values of the Chern-Simons coupling constant, including the critical value known as the chiral point, and study the cases of standard Brown-Henneaux boundary conditions, as well as their weaker version that allows a slower fall-off. Studying the Witten-Nester energy as a bulk integral over the initial value surface instead, we find a bound on the energy, and through it the sufficient condition for the positivity of the energy. In particular, we find that spacetimes of Petrov type N that admit globally well-defined solutions of the generalized Witten equation have positive energy.
Cosmological solutions of massive gravity on de Sitter
Langlois, David
2012-01-01
In the framework of the recently proposed models of massive gravity, but defined with respect to a de Sitter reference metric, we obtain new homogeneous and isotropic solutions for arbitrary spatial curvature. These solutions can be classified into three branches. In the first two, the massive gravity terms behave like a cosmological constant. In the third branch, the massive gravity effects can be described by a time evolving effective fluid with rather remarkable features, including the property to behave as a cosmological constant at low energy, when the Hubble parameter decreases below a critical value.
New Cosmologies on the Horizon. Cosmology and Holography in bigravity and massive gravity
Energy Technology Data Exchange (ETDEWEB)
Tolley, Andrew James [Case Western Reserve Univ., Cleveland, OH (United States)
2013-03-31
The goal of this research program is to explore the cosmological dynamics, the nature of cosmological and black hole horizons, and the role of holography in a new class of infrared modified theories of gravity. This will capitalize of the considerable recent progress in our understanding of the dynamics of massive spin two fields on curved spacetimes, culminating in the formulation of the first fully consistent theories of massive gravity and bigravity/bimetric theories.
Cosmology in massive gravity with effective composite metric
Heisenberg, Lavinia
2016-01-01
This paper is dedicated to scrutinizing the cosmology in massive gravity. A matter field of the dark sector is coupled to an effective composite metric while a standard matter field couples to the dynamical metric in the usual way. For this purpose, we study the dynamical system of cosmological solutions by using phase analysis, which provides an overview of the class of cosmological solutions in this setup. This also permits us to study the critical points of the cosmological equations together with their stability. We show the presence of stable attractor de Sitter critical points relevant to the late-time cosmic acceleration. Furthermore, we study the tensor, vector and scalar perturbations in the presence of standard matter fields and obtain the conditions for the absence of ghost and gradient instabilities. Hence, massive gravity in the presence of the effective composite metric can accommodate interesting dark energy phenomenology, that can be observationally distinguished from the standard model accord...
Cosmological perturbations in massive gravity with doubly coupled matter
Gümrükçüoğlu, A Emir; Mukohyama, Shinji
2014-01-01
We investigate the cosmological perturbations around FLRW solutions to non- linear massive gravity with a new effective coupling to matter proposed recently. Unlike the case with minimal matter coupling, all five degrees of freedom in the gravity sector propagate on generic self-accelerating FLRW backgrounds. We study the stability of the cosmological solutions and put constraints on the parameters of the theory by demanding the correct sign for the kinetic terms for scalar, vector and tensor perturbations.
Cosmological perturbations in massive gravity with doubly coupled matter
Gümrükçüoğlu, A. Emir; Heisenberg, Lavinia; Mukohyama, Shinji
2015-02-01
We investigate the cosmological perturbations around FLRW solutions to non- linear massive gravity with a new effective coupling to matter proposed recently. Unlike the case with minimal matter coupling, all five degrees of freedom in the gravity sector propagate on generic self-accelerating FLRW backgrounds. We study the stability of the cosmological solutions and put constraints on the parameters of the theory by demanding the correct sign for the kinetic terms for scalar, vector and tensor perturbations.
Topologically Massive Gravity from the Heterotic String
Lu, H
2010-01-01
Topologically massive gravity (TMG) in three dimensions provides an interesting toy model for constructing a quantum theory of gravity. Although it can be thought of as standing as a theory in its own right, it is also of interest to see whether it can be described within the larger framework of string theory or M-theory. In this paper, we show that it can be embedded within the heterotic string, via a compactification on $S^3\\times T^4$. Since all solutions of TMG can now be lifted to ten dimensions, this allows us to give a string and brane interpretation to quantities such as the central charges in the conformal field theory on the boundary of TMG, and the entropy of the BTZ black hole solution.
Problems and Challenges for Cosmology involving Massive Neutrinos
Krauss, L M
1996-01-01
I review the challenges and problems facing the standard cosmological model, involving an $\\Omega=1$ Universe dominated by non-baryonic dark matter, which arise due to: age estimates of the universe, estimates of the baryon fraction of the universe, and structure formation. Certain of these problems are exacerbated, and certain of these are eased, by the inclusion of some component to the energy density of matter from massive neutrinos. I conclude with a comparison of the two favored current cosmological models, involving either a mixture of cold dark matter and hot dark matter, or the inclusion of a cosmological constant.
Dirac field in topologically massive gravity
Sert, Özcan; Adak, Muzaffer
2013-01-01
We consider a Dirac field coupled minimally to the Mielke-Baekler model of gravity and investigate cosmological solutions in three dimensions. We arrive at a family of solutions which exists even in the limit of vanishing cosmological constant.
Minimal N=4 topologically massive supergravity
Kuzenko, Sergei M.; Novak, Joseph; Sachs, Ivo
2017-03-01
Using the superconformal framework, we construct a new off-shell model for N=4 topologically massive supergravity which is minimal in the sense that it makes use of a single compensating vector multiplet and involves no free parameter. As such, it provides a counterexample to the common lore that two compensating multiplets are required within the conformal approach to supergravity with eight supercharges in diverse dimensions. This theory is an off-shell N=4 supersymmetric extension of chiral gravity. All of its solutions correspond to non-conformally flat superspaces. Its maximally supersymmetric solutions include the so-called critical (4,0) anti-de Sitter superspace introduced in [25], and well as warped critical (4,0) anti-de Sitter superspaces. We also propose a dual formulation for the theory in which the vector multiplet is replaced with an off-shell hypermultiplet. Upon elimination of the auxiliary fields belonging to the hypermultiplet and imposing certain gauge conditions, the dual action reduces to the one introduced in [20].
Minimal $\\cal N=4$ topologically massive supergravity
Kuzenko, Sergei M; Sachs, Ivo
2016-01-01
Using the superconformal framework, we construct a new off-shell model for topologically massive $\\cal N=4$ supergravity which is minimal in the sense that it makes use of a single compensating vector multiplet. Our theory provides a counterexample to the common lore that two compensating multiplets are required within the conformal approach to supergravity with eight supercharges in diverse dimensions. All solutions in this theory correspond to non-conformally flat superspaces. Its maximally supersymmetric solutions include the so-called critical (4,0) anti-de Sitter superspace introduced in arXiv:1205.4622. Other maximally supersymmetric solutions describe warped critical (4,0) anti-de Sitter superspaces. We also propose a dual formulation for the theory in which the vector multiplet is replaced with an off-shell hypermultiplet. Upon elimination of the auxiliary fields belonging to the hypermultiplet and imposing certain gauge conditions, the dual action reduces to the one introduced in arXiv:1605.00103.
Massive photons in cosmology: a thermodynamical approach
Cuzinatto, R R; Medeiros, L G; de Souza, C Naldoni; Pimentel, B M
2016-01-01
We investigate the influence of massive photons on the evolution of the expanding universe. The analysis is performed assuming that the only relevant component in the universe is radiation. Two particular models for generalized electrodynamics are considered, namely Proca field and Podolsky electrodynamics. We obtain the equation of state (EOS) $P=P(\\varepsilon)$ for each case using the dispersion relation derived from both theories. The EOS are inputted into the Friedmann equations of a homogeneous and isotropic space-time to determine the cosmic scale factor $a(t)$. It is shown that the photon non-null mass does not alter significantly the result $a\\propto t^{1/2}$ valid for a massless photon gas; this is true either in Proca's case (where the photon mass $m$ is extremely small) or in Podolsky field (for which $m$ is extremely large).
Cosmology in massive gravity with effective composite metric
Heisenberg, Lavinia; Refregier, Alexandre
2016-09-01
This paper is dedicated to scrutinizing the cosmology in massive gravity. A matter field of the dark sector is coupled to an effective composite metric while a standard matter field couples to the dynamical metric in the usual way. For this purpose, we study the dynamical system of cosmological solutions by using phase analysis, which provides an overview of the class of cosmological solutions in this setup. This also permits us to study the critical points of the cosmological equations together with their stability. We show the presence of stable attractor de Sitter critical points relevant to the late-time cosmic acceleration. Furthermore, we study the tensor, vector and scalar perturbations in the presence of standard matter fields and obtain the conditions for the absence of ghost and gradient instabilities. Hence, massive gravity in the presence of the effective composite metric can accommodate interesting dark energy phenomenology, that can be observationally distinguished from the standard model according to the expansion history and cosmic growth.
TWO-DIMENSIONAL TOPOLOGY OF COSMOLOGICAL REIONIZATION
Energy Technology Data Exchange (ETDEWEB)
Wang, Yougang; Xu, Yidong; Chen, Xuelei [Key Laboratory of Computational Astrophysics, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012 China (China); Park, Changbom [School of Physics, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of); Kim, Juhan, E-mail: wangyg@bao.ac.cn, E-mail: cbp@kias.re.kr [Center for Advanced Computation, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of)
2015-11-20
We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two-dimensional genus curve for the early, middle, and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometre Array.
Two dimensional topology of cosmological reionization
Wang, Yougang; Xu, Yidong; Chen, Xuelei; Kim, Juhan
2015-01-01
We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two dimensional genus curve for the early, middle and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometer Array.
Simulating nonlinear cosmological structure formation with massive neutrinos
Banerjee, Arka
2016-01-01
We present a new method for simulating cosmologies that contain massive particles with thermal free streaming motion, such as massive neutrinos or warm/hot dark matter. This method combines particle and fluid descriptions of the thermal species to eliminate the shot noise known to plague conventional N-body simulations. We describe this method in detail, along with results for a number of test cases to validate our method, and check its range of applicability. Using this method, we demonstrate that massive neutrinos can produce a significant scale-dependence in the large-scale biasing of deep voids in the matter field. We show that this scale-dependence may be quantitatively understood using an extremely simple spherical expansion model which reproduces the behavior of the void bias for different neutrino parameters.
Cosmology of the proxy theory to massive gravity
Heisenberg, Lavinia; Yamamoto, Kazuhiro
2014-01-01
In this paper, we scrutinize very closely the cosmology in the proxy theory to massive gravity obtained in Phys. Rev. D84 (2011) 043503. This proxy theory was constructed by covariantizing the decoupling limit Lagrangian of massive gravity and represents a subclass of Horndeski scalar-tensor theory. Thus, this covariantization unifies two important classes of modified gravity theories, namely massive gravity and Horndeski theories. We go beyond the regime which was studied in Phys. Rev. D84 (2011) 043503 and show that the theory does not admit any homogeneous and isotropic self-accelerated solutions. We illustrate that the only attractor solution is flat Minkowski solution, hence this theory is less appealing as a dark energy model. We also show that the absence of de Sitter solutions is tightly related to the presence of shift symmetry breaking interactions.
Cosmology of the proxy theory to massive gravity
Heisenberg, Lavinia; Kimura, Rampei; Yamamoto, Kazuhiro
2014-05-01
In this paper, we scrutinize very closely the cosmology in the proxy theory to massive gravity obtained in de Rham and Heisenberg [Phys. Rev. D 84, 043503 (2011)]. This proxy theory was constructed by covariantizing the decoupling limit Lagrangian of massive gravity, and it represents a subclass of Horndeski scalar-tensor theory. Thus, this covariantization unifies two important classes of modified gravity theories, namely, massive gravity and Horndeski theories. We go beyond the regime which was studied in de Rham and Heisenberg [Phys. Rev. D 84, 043503 (2011)] and show that the theory does not admit any homogeneous and isotropic self-accelerated solutions. We illustrate that the only attractor solution is the flat Minkowski solution; hence, this theory is less appealing as a dark energy model. We also show that the absence of de Sitter solutions is tightly related to the presence of shift symmetry breaking interactions.
Cosmological bounds on open FLRW solutions of massive gravity
Pereira, S H; S., A Pinho S; Jesus, J F
2015-01-01
In this work we have analysed some cosmological bounds concerning an open FLRW solution of massive gravity. The constraints with recent observational $H(z)$ data were found and the best fit values for the cosmological parameters are in agreement with the $\\Lambda$CDM model, and also point to a nearly open spatial curvature, as expected from the model. The graviton mass dependence with the constant parameters $\\alpha_3$ and $\\alpha_4$, related to the additional lagrangians terms of the model, are also analysed, and we have obtained a strong dependence with such parameters, although the condition $m_g\\simeq H_0^{-1}$ seems dominant for a long range of the parameters $\\alpha_3$ and $\\alpha_4$. The limit $\\alpha_2 \\to 0$ forbid one of the branches of accelerated solution, which indicates the necessity of the corresponding lagrangian term.
Nonlinear stability of cosmological solutions in massive gravity
De Felice, Antonio; Lin, Chunshan; Mukohyama, Shinji
2013-01-01
We investigate nonlinear stability of two classes of cosmological solutions in massive gravity: isotropic Friedmann-Lemaitre-Robertson-Walker (FLRW) solutions and anisotropic FLRW solutions. For this purpose we construct the linear cosmological perturbation theory around axisymmetric Bianchi type--I backgrounds. We then expand the background around the two classes of solutions, which are fixed points of the background evolution equation, and analyze linear perturbations on top of it. This provides a consistent truncation of nonlinear perturbations around these fixed point solutions and allows us to analyze nonlinear stability in a simple way. In particular, it is shown that isotropic FLRW solutions exhibit nonlinear ghost instability. On the other hand, anisotropic FLRW solutions are shown to be ghost-free for a range of parameters and initial conditions.
How Very Massive Metal Free Stars Start Cosmological Reionization
Wise, John H
2007-01-01
(Abridged) Using ab initio cosmological Eulerian adaptive mesh refinement radiation hydrodynamical calculations, we discuss how very massive stars start the process of cosmological reionization. The models include non-equilibrium primordial gas chemistry and cooling processes and accurate radiation transport in the Case B approximation using adaptively ray traced photon packages, retaining the time derivative in the transport equation. Supernova feedback is modeled by thermal explosions triggered at parsec scales. All calculations resolve the local Jeans length by at least 16 grid cells at all times and as such cover a spatial dynamic range of ~10^6. These first sources of reionization are highly intermittent and anisotropic and first photoionize the small scales voids surrounding the halos they form in, rather than the dense filaments they are embedded in. As the merging objects form larger, dwarf sized galaxies, the escape fraction of UV radiation decreases and the HII regions only break out on some sides o...
The topological susceptibility in finite temperature QCD and axion cosmology
Petreczky, Peter; Schadler, Hans-Peter; Sharma, Sayantan
2016-11-01
We study the topological susceptibility in 2 + 1 flavor QCD above the chiral crossover transition temperature using Highly Improved Staggered Quark action and several lattice spacings corresponding to temporal extent of the lattice, Nτ = 6 , 8 , 10 and 12. We observe very distinct temperature dependences of the topological susceptibility in the ranges above and below 250 MeV. While for temperatures above 250 MeV, the dependence is found to be consistent with dilute instanton gas approximation, at lower temperatures the fall-off of topological susceptibility is milder. We discuss the consequence of our results for cosmology wherein we estimate the bounds on the axion decay constant and the oscillation temperature if indeed the QCD axion is a possible dark matter candidate.
The topological susceptibility in finite temperature QCD and axion cosmology
Petreczky, Peter; Sharma, Sayantan
2016-01-01
We study the topological susceptibility in 2+1 flavor QCD above the chiral crossover transition temperature using Highly Improved Staggered Quark action and several lattice spacings, corresponding to temporal extent of the lattice, $N_\\tau=6,8,10$ and $12$. We observe very distinct temperature dependences of the topological susceptibility in the ranges above and below $250$ MeV. While for temperatures above $250$ MeV, the dependence is found to be consistent with dilute instanton gas approximation, at lower temperatures the fall-off of topological susceptibility is milder. We discuss the consequence of our results for cosmology wherein we estimate the bounds on the axion decay constant and the oscillation temperature if indeed the QCD axion is a possible dark matter candidate.
Adiabatic density perturbations in a cosmological model with massive neutrinos
Jaroszynski, M.
Lifshitz (1946) has investigated the gravitational instability of a Friedmann Universe model. He treated the matter content of the universe as a single perfect fluid. In other studies, a two fluid approach was used to represent neutrinos and other kinds of matter separately. A distribution function was used by Peebles and Yu (1970), and also by Silk and Wilson (1980) to describe photons of the black-body background during and after the recombination of the primeval plasma. The approach used in the present investigation is similar, except for two differences. No collisional term is used in the kinetic equation, and massive particles are considered. A detailed description is provided of the method used to investigate the gravitational instability of a cosmological model with massive neutrinos. It is pointed out that the obtained results are preliminary. The final spectrum of perturbations is similar to those of Peebles and Yu (1970), and Wilson and Silk (1981).
Massive Particle's Tunnelling from Black Hole with Topological Defect
Institute of Scientific and Technical Information of China (English)
HAN Yi-Wen
2007-01-01
We extend Zhang and Zhao's recent work to black hole with topological defect whose Arnowitt-Deser-Misner mass is no longer identical to its mass parameter. The behaviour of the tunnelling massive particles is investigated,and the emission rate at which massive particles tunnel across the event horizon of the black hole is calculated.The result is consistent with an underlying unitary theory, and takes the same functional form as that of mass-less particles.
Stable and unstable cosmological models in bimetric massive gravity
Könnig, Frank; Amendola, Luca; Motta, Mariele; Solomon, Adam R
2014-01-01
Nonlinear, ghost-free massive gravity has two tensor fields; when both are dynamical, the mass of the graviton can lead to cosmic acceleration that agrees with background data, even in the absence of a cosmological constant. Here the question of the stability of linear perturbations in this theory is examined. Instabilities are presented for several classes of models, and simple criteria for the cosmological stability of massive bigravity are derived. In this way, we identify a particular self-accelerating bigravity model, infinite-branch bigravity (IBB), which exhibits both viable background evolution and stable linear perturbations. We discuss the modified gravity parameters for IBB, which do not reduce to the standard $\\Lambda$CDM result at early times, and compute the combined likelihood from measured growth data and type Ia supernovae. IBB predicts a present matter density $\\Omega_{m0}=0.18$ and an equation of state $w(z)=-0.79+0.21z/(1+z)$. The growth rate of structure is well-approximated at late times...
How Very Massive Metal Free Stars Start Cosmological Reionization
Energy Technology Data Exchange (ETDEWEB)
Wise, John H.; Abel, Tom
2007-11-07
The initial conditions and relevant physics for the formation of the earliest galaxies are well specified in the concordance cosmology. Using ab initio cosmological Eulerian adaptive mesh refinement radiation hydrodynamical calculations, we discuss how very massive stars start the process of cosmological reionization. The models include non-equilibrium primordial gas chemistry and cooling processes and accurate radiation transport in the Case B approximation using adaptively ray traced photon packages, retaining the time derivative in the transport equation. Supernova feedback is modeled by thermal explosions triggered at parsec scales. All calculations resolve the local Jeans length by at least 16 grid cells at all times and as such cover a spatial dynamic range of {approx}10{sup 6}. These first sources of reionization are highly intermittent and anisotropic and first photoionize the small scales voids surrounding the halos they form in, rather than the dense filaments they are! embedded in. As the merging objects form larger, dwarf sized galaxies, the escape fraction of UV radiation decreases and the H II regions only break out on some sides of the galaxies making them even more anisotropic. In three cases, SN blast waves induce star formation in overdense regions that were formed earlier from ionization front instabilities. These stars form tens of parsecs away from the center of their parent DM halo. Approximately 5 ionizing photons are needed per sustained ionization when star formation in 10{sup 6} M{sub {circle_dot}} halos are dominant in the calculation. As the halos become larger than {approx}10{sup 7} M{sub {circle_dot}}, the ionizing photon escape fraction decreases, which in turn increases the number of photons per ionization to 15--50, in calculations with stellar feedback only. Supernova feedback in these more massive halos creates a more diffuse medium, allowing the stellar radiation to escape more easily and maintaining the ratio of 5 ionizing
Energy Density Bounds in Cubic Quasi-Topological Cosmology
dS, U Camara; Sotkov, G M
2013-01-01
We investigate the thermodynamical and causal consistency of cosmological models of the cubic Quasi-Topological Gravity (QTG) in four dimensions, as well as their phenomenological consequences. Specific restrictions on the maximal values of the matter densities are derived by requiring the apparent horizon's entropy to be a non-negative, non-decreasing function of time. The QTG counterpart of the Einstein-Hilbert (EH) gravity model of linear equation of state is studied in detail. An important feature of this particular QTG cosmological model is the new early-time acceleration period of the evolution of the Universe, together with the standard late-time acceleration present in the original EH model. The QTG correction to the causal diamond's volume is also calculated.
Galileons Coupled to Massive Gravity: General Analysis and Cosmological Solutions
Goon, Garrett; Hinterbichler, Kurt; Mukohyama, Shinji; Trodden, Mark
2014-01-01
We further develop the framework for coupling galileons and Dirac-Born-Infeld (DBI) scalar fields to a massive graviton while retaining both the non-linear symmetries of the scalars and ghost-freedom of the theory. The general construction is recast in terms of vielbeins which simplifies calculations and allows for compact expressions. Expressions for the general form of the action are derived, with special emphasis on those models which descend from maximally symmetric spaces. We demonstrate the existence of maximally symmetric solutions to the fully non-linear theory and analyze their spectrum of quadratic fluctuations. Finally, we consider self-accelerating cosmological solutions and study their perturbations, showing that the vector and scalar modes have vanishing kinetic terms.
Topological structure of the vacuum, cosmological constant and dark energy
Sidharth, B. G.; Das, A.; Das, C. R.; Laperashvili, L. V.; Nielsen, H. B.
2016-11-01
In this review, we present a theory of cosmological constant and dark energy (DE), based on the topological structure of the vacuum. The multiple point principle (MPP) is reviewed. It demonstrates the existence of the two vacua into the SM. The Froggatt-Nielsen’s prediction of the top-quark and Higgs masses is given in the assumption that there exist two degenerate vacua in the SM. This prediction was improved by the next-order calculations. We also considered Sidharth’s theory of cosmological constant based on the noncommutative geometry of the Planck scale space-time, what gives an extremely small DE density providing the accelerating expansion of the Universe. Theory of two degenerate vacua — the Planck scale phase and electroweak (EW) phase — is also reviewed, topological defects in these vacua are investigated, also the Compton wavelength phase suggested by Sidharth is discussed. A general theory of the phase transition and the problem of the vacuum stability in the SM is reviewed. Assuming the existence of a new scalar S bound state 6t + 6t¯, earlier predicted by Froggatt, Nielsen and Laperashvili, we try to provide the vacuum stability in the SM and exact accuracy of the MPP.
How Very Massive Metal-Free Stars Start Cosmological Reionization
Wise, John H.; Abel, Tom
2008-01-01
The initial conditions and relevant physics for the formation of the earliest galaxies are well specified in the concordance cosmology. Using ab initio cosmological Eulerian adaptive mesh refinement radiation hydrodynamical calculations, we discuss how very massive stars start the process of cosmological reionization. The models include nonequilibrium primordial gas chemistry and cooling processes and accurate radiation transport in the case B approximation using adaptively ray-traced photon packages, retaining the time derivative in the transport equation. Supernova feedback is modeled by thermal explosions triggered at parsec scales. All calculations resolve the local Jeans length by at least 16 grid cells at all times and as such cover a spatial dynamic range of approx.10(exp 6). These first sources of reionization are highly intermittent and anisotropic and first photoionize the small-scale voids surrounding the halos they form in, rather than the dense filaments they are embedded in. As the merging objects form larger, dwarf-sized galaxies, the escape fraction of UV radiation decreases and the H II regions only break out on some sides of the galaxies, making them even more anisotropic. In three cases, SN blast waves induce star formation in overdense regions that were formed earlier from ionization front instabilities. These stars form tens of parsecs away from the center of their parent DM halo. Approximately five ionizing photons are needed per sustained ionization when star formation in 10(exp 6) stellar Mass halos is dominant in the calculation. As the halos become larger than approx.10(exp 7) Stellar Mass, the ionizing photon escape fraction decreases, which in turn increases the number of photons per ionization to 15-50, in calculations with stellar feedback only. Radiative feedback decreases clumping factors by 25% when compared to simulations without star formation and increases the average temperature of ionized gas to values between 3000 and 10,000 K.
Topologically Massive Gauge Theory: Wu-Yang Type Solutions
Saygili, K
2006-01-01
We discuss euclidean topologically massive Wu-Yang type solutions of the Maxwell-Chern-Simons and the Yang-Mills-Chern-Simons theories. The most distinctive feature of these solutions is the existence of a natural scale of length which is determined by the topological mass. The topological mass is proportional to the square of the gauge coupling constant. We find the non-abelian solution by a SU(2) gauge transformation of the abelian magnetic monopole type solution. In the topologically massive electrodynamics the field strength locally determines the gauge potential modulo a closed term via the self-duality equation. We present the Hopf map including the topological mass. The Wu-Yang construction is based on patching up the local potentials by means of a gauge transformation which can be expressed in terms of the magnetic or the electric charges. We also discuss solutions with different first Chern numbers. There exists a fundamental scale of length over which the gauge function is single-valued and periodic...
Signatures of very massive stars: supercollapsars and their cosmological rate
Maio, Umberto
2014-01-01
We compute the rate of supercollapsars by using cosmological, N-body, hydro, chemistry simulations of structure formation, following detailed stellar evolution according to proper yields (for He, C, N, O, Si, S, Fe, Mg, Ca, Ne, etc.) and lifetimes for stars having different masses and metallicities, and for different stellar populations (population III and population II-I). We find that supercollapsars are usually associated to dense, collapsing gas with little metal pollution and with abundances dominated by oxygen. The resulting supercollapsar rate is about $10^{-2}\\,\\rm yr^{-1} sr^{-1}$ at redshift $z=0$, and their contribution to the total rate is $ < 0.1 $ per cent, which explains why they have never been detected so far. Expected rates at redshift $z\\simeq 6$ are of the order of $\\sim 10^{-3}\\,\\rm yr^{-1} sr^{-1}$ and decrease further at higher $z$. Because of the strong metal enrichment by massive, short-lived stars, only $\\sim 1$ supercollapsar generation is possible in the same star forming region...
Thermodynamics of the apparent horizon in massive cosmology
Li, Hui
2013-01-01
Applying Clausius relation with energy-supply defined by the unified first law of thermodynamics formalism to the apparent horizon of a massive cosmological model proposed lately, the corrected entropic formula of the apparent horizon is obtained with the help of the modified Friedmann equations. This entropy-area relation, together with the identified internal energy, verifies the first law of thermodynamics for the apparent horizon with a volume change term for consistency. On the other hand, by means of the corrected entropy-area formula and the Clausius relation $\\delta Q=T dS$, where the heat flow $\\delta Q$ is the energy-supply of pure matter projecting on the vector $\\xi$ tangent to the apparent horizon and should be looked on as the amount of energy crossing the apparent horizon during the time interval $dt$ and the temperature of the apparent horizon for energy crossing during the same interval is $1/(2\\pi \\widetilde{r}_A)$, the modified Friedmann equations governing the dynamical evolution of the un...
First law of entanglement entropy in topologically massive gravity
Cheng, Long; Hung, Ling-Yan; Liu, Si-Nong; Zhou, Hong-Zhe
2016-09-01
In this paper we explore the validity of the first law of entanglement entropy in the context of topologically massive gravity (TMG). We find that the variation of the holographic entanglement entropy under perturbation from the pure anti-de Sitter background satisfies the first law upon imposing the bulk equations of motion in a given time slice, despite the appearance of instabilities in the bulk for generic gravitational Chern-Simons coupling μ . The Noether-Wald entropy is different from the holographic entanglement entropy in a general boosted frame. However, this discrepancy does not affect the entanglement first law.
On hybrid (topologically) massive supergravity in three dimensions
Lü, H.; Pang, Yi
2011-03-01
A class of hybrid (topologically) massive off-shell supergravities coupled to an on-shell matter scalar multiplet was recently constructed. The auxiliary field in the off-shell multiplet is dynamical for generic values of the eight parameters. We find that by choosing the parameters appropriately, it remains non-dynamical. We perform linearized analysis around the supersymmetric AdS3 vacuum and its Minkowski limit. The ghost-free condition for the Minkowski vacuum is explored. For the AdS3 vacuum, we obtain the criticality condition and find that at the critical points, one of the two massive gravitons becomes pure gauge and decouples from the bulk physics, whilst the other has positive energy. We demonstrate that the mass of the BTZ black hole is non-negative at the critical points. We also investigate general BPS solutions. For certain parameter choices, we obtain exact solutions. In particular, we present the BPS string (domain-wall) solution that is dual to certain two-dimensional quantum field theory with an ultra-violet conformal fixed point.
On Hybrid (Topologically) Massive Supergravity in Three Dimensions
Lu, Hong
2010-01-01
A class of hybrid (topologically) massive off-shell supergravities coupled to an on-shell matter scalar multiplet was recently constructed. The auxiliary field in the off-shell multiplet is dynamical for generic values of the eight parameters. We find that by choosing the parameters appropriately, it remains non-dynamical. We perform linearized analysis around the supersymmetric AdS3 vacuum and its Minkowski limit. The ghost-free condition for the Minkowski vacuum is explored. For the AdS3 vacuum, we obtain the criticality condition and find that at the critical points, one of the two massive gravitons becomes pure gauge and decouples from the bulk physics, whilst the other has positive energy. We also investigate general BPS solutions. For certain parameter choices, we obtain exact solutions. In particular, we present the BPS string (domain-wall) solution that is dual to certain two-dimensional quantum field theory with an ultra-violet conformal fixed point.
Initial Conditions for Accurate N-Body Simulations of Massive Neutrino Cosmologies
Zennaro, Matteo; Villaescusa-Navarro, Francisco; Carbone, Carmelita; Sefusatti, Emiliano; Guzzo, Luigi
2016-01-01
The set-up of the initial conditions in cosmological N-body simulations is usually implemented by rescaling the desired low-redshift linear power spectrum to the required starting redshift consistently with the Newtonian evolution of the simulation. The implementation of this practical solution requires more care in the context of massive neutrino cosmologies, mainly because of the non-trivial scale-dependence of the linear growth that characterises these models. In this work we consider a simple two-fluid, Newtonian approximation for cold dark matter and massive neutrinos perturbations that can reproduce the cold matter linear evolution predicted by Boltzmann codes such as CAMB or CLASS with a 0.1% accuracy or below for all redshift relevant to nonlinear structure formation. We use this description, in the first place, to quantify the systematic errors induced by several approximations often assumed in numerical simulations, including the typical set-up of the initial conditions for massive neutrino cosmolog...
String vacua with massive boson-fermion degeneracy and non-singular cosmology
Florakis, Ioannis
2011-01-01
We discuss marginal deformations of string vacua with Massive boson-fermion Degeneracy Symmetry (MSDS), in connection to the cosmological evolution of the Universe from an early non-geometrical era. In particular, we discuss recent results on the stringy mechanism that resolves both Hagedorn divergences and the Initial Singularity problem. Based on a talk given at the Workshop on Cosmology & Strings, Corfu Institute, Greece, Sept 10, 2010.
Directory of Open Access Journals (Sweden)
S.H. Hendi
2017-06-01
Full Text Available Violation of Lorentz invariancy in the high energy quantum gravity motivates one to consider an energy dependent spacetime with massive deformation of standard general relativity. In this paper, we take into account an energy dependent metric in the context of a massive gravity model to obtain exact solutions. We investigate the geometry of black hole solutions and also calculate the conserved and thermodynamic quantities, which are fully reproduced by the analysis performed with the standard techniques. After examining the validity of the first law of thermodynamics, we conduct a study regarding the effects of different parameters on thermal stability of the solutions. In addition, we employ the relation between cosmological constant and thermodynamical pressure to study the possibility of phase transition. Interestingly, we will show that for the specific configuration considered in this paper, van der Waals like behavior is observed for different topology. In other words, for flat and hyperbolic horizons, similar to spherical horizon, a second order phase transition and van der Waals like behavior are observed. Furthermore, we use geometrical method to construct phase space and study phase transition and bound points for these black holes. Finally, we obtain critical values in extended phase space through the use of a new method.
Hendi, S. H.; Eslam Panah, B.; Panahiyan, S.
2017-06-01
Violation of Lorentz invariancy in the high energy quantum gravity motivates one to consider an energy dependent spacetime with massive deformation of standard general relativity. In this paper, we take into account an energy dependent metric in the context of a massive gravity model to obtain exact solutions. We investigate the geometry of black hole solutions and also calculate the conserved and thermodynamic quantities, which are fully reproduced by the analysis performed with the standard techniques. After examining the validity of the first law of thermodynamics, we conduct a study regarding the effects of different parameters on thermal stability of the solutions. In addition, we employ the relation between cosmological constant and thermodynamical pressure to study the possibility of phase transition. Interestingly, we will show that for the specific configuration considered in this paper, van der Waals like behavior is observed for different topology. In other words, for flat and hyperbolic horizons, similar to spherical horizon, a second order phase transition and van der Waals like behavior are observed. Furthermore, we use geometrical method to construct phase space and study phase transition and bound points for these black holes. Finally, we obtain critical values in extended phase space through the use of a new method.
Topological massive Dirac edge modes and long-range superconducting Hamiltonians
Viyuela, O.; Vodola, D.; Pupillo, G.; Martin-Delgado, M. A.
2016-09-01
We discover novel topological effects in the one-dimensional Kitaev chain modified by long-range Hamiltonian deformations in the hopping and pairing terms. This class of models display symmetry-protected topological order measured by the Berry/Zak phase of the lower-band eigenvector and the winding number of the Hamiltonians. For exponentially decaying hopping amplitudes, the topological sector can be significantly augmented as the penetration length increases, something experimentally achievable. For power-law decaying superconducting pairings, the massless Majorana modes at the edges get paired together into a massive nonlocal Dirac fermion localized at both edges of the chain: a new topological quasiparticle that we call topological massive Dirac fermion. This topological phase has fractional topological numbers as a consequence of the long-range couplings. Possible applications to current experimental setups and topological quantum computation are also discussed.
Gama, F S; Nascimento, J R; Petrov, A Yu; da Silva, A J
2015-01-01
We explicitly calculate the one-loop effective potential for the supersymmetric topologically massive gauge theory in four dimensions, where the chiral scalar superfield is directly coupled to the field strength for the gauge spinor superfield.
KPZ Formulas for Weyl-Invariant Induced Gravity and Topologically Massive Gravity
Amelino-Camelia, G.
1997-01-01
I discuss the applicability in Weyl-invariant induced gravity and topologically massive gravity of certain formulas originally derived by Knizhnik, Polyakov, and Zamolodchikov in the context of diffeomorphism-invariant induced gravity.
KPZ Formulas for Weyl-Invariant Induced Gravity and Topologically Massive Gravity
Amelino-Camelia, G.
1997-01-01
I discuss the applicability in Weyl-invariant induced gravity and topologically massive gravity of certain formulas originally derived by Knizhnik, Polyakov, and Zamolodchikov in the context of diffeomorphism-invariant induced gravity.
Energy Technology Data Exchange (ETDEWEB)
Kogan, Ya.I. (Superconducting Super Collider Lab., Dallas, TX (USA)); Polyubin, I.V. (Gosudarstvennyj Komitet po Ispol' zovaniyu Atomnoj Ehnergii SSSR, Moscow (USSR). Inst. Teoreticheskoj i Ehksperimental' noj Fiziki)
1990-06-01
The particles interaction in the 2 + 1 topologically massive gauge theories is given. It turns out, that contrary to the usual case, two equally charged particles (fermions or the non-Abelian topologically massive vector bosons) attract each other, not repulse. This attraction can lead in principle to vacuum instability, in which we will use some trial wave function techniques. Possible applications are briefly discussed. 12 refs., 9 figs.
EFTCAMB/EFTCosmoMC: massive neutrinos in dark cosmologies
Hu, Bin; Silvestri, Alessandra; Frusciante, Noemi
2014-01-01
We revisit the degeneracy between massive neutrinos and generalized theories of gravity in the framework of effective field theory of cosmic acceleration. In particular we consider f(R) theories and a class of non-minimally coupled models parametrized via a coupling to gravity which is linear in the scale factor. In the former case, we find a slightly lower degeneracy with respect to what found so far in the literature, due to the fact that we implement exact designer f(R) models and evolve the full linear dynamics of perturbations. As a consequence, our bounds are slightly tighter on the f(R) parameter but looser on the summed neutrino mass. We also set a new upper bound on the Compton wavelength parameter ${\\rm Log}_{10}B_0<-4.1$ at 95% C.L. with fixed summed neutrino mass ($\\sum m_{\
Initial conditions for accurate N-body simulations of massive neutrino cosmologies
Zennaro, M.; Bel, J.; Villaescusa-Navarro, F.; Carbone, C.; Sefusatti, E.; Guzzo, L.
2017-04-01
The set-up of the initial conditions in cosmological N-body simulations is usually implemented by rescaling the desired low-redshift linear power spectrum to the required starting redshift consistently with the Newtonian evolution of the simulation. The implementation of this practical solution requires more care in the context of massive neutrino cosmologies, mainly because of the non-trivial scale-dependence of the linear growth that characterizes these models. In this work, we consider a simple two-fluid, Newtonian approximation for cold dark matter and massive neutrinos perturbations that can reproduce the cold matter linear evolution predicted by Boltzmann codes such as CAMB or CLASS with a 0.1 per cent accuracy or below for all redshift relevant to non-linear structure formation. We use this description, in the first place, to quantify the systematic errors induced by several approximations often assumed in numerical simulations, including the typical set-up of the initial conditions for massive neutrino cosmologies adopted in previous works. We then take advantage of the flexibility of this approach to rescale the late-time linear power spectra to the simulation initial redshift, in order to be as consistent as possible with the dynamics of the N-body code and the approximations it assumes. We implement our method in a public code (REPS rescaled power spectra for initial conditions with massive neutrinos https://github.com/matteozennaro/reps) providing the initial displacements and velocities for cold dark matter and neutrino particles that will allow accurate, i.e. 1 per cent level, numerical simulations for this cosmological scenario.
Garbarz, Alan; Vásquez, Yerko
2008-01-01
We study exact solutions to Cosmological Topologically Massive Gravity (CTMG) coupled to Topologically Massive Electrodynamics (TME) at special values of the coupling constants. For the particular case of the so called chiral point l\\mu_G=1, vacuum solutions (with vanishing gauge field) are exhibited. These correspond to a one-parameter deformation of GR solutions, and are continuously connected to the extremal Banados-Teitelboim-Zanelli black hole (BTZ) with bare constants J=-lM. In CTMG this extremal BTZ turns out to be massless, and thus it can be regarded as a kind of ground state. For certain range of parameters, our solution exhibits an event horizon located at finite geodesic distance. Although the solution is not asymptotically AdS_3 in the sense of Brown-Henneaux boundary conditions, it does obey the weakened asymptotic recently proposed by Grumiller and Johansson. Consequently, we discuss the computation of the conserved chages in terms of the stress-tensor in the boundary, and we find that the sign...
Quantum effects of massive modes in a cosmological quantum space-time
Tavakoli, Yaser
2015-01-01
The quantum theory of a massive, minimally coupled scalar field on an isotropic cosmological quantum space-time is revisited. The interplay between the quantum background and the massive modes of the field, when disregarding their back-reaction effects, gives rise to a theory of quantum field on an effective, dressed space-time whose isotropy may be broken in the direction of the field propagation. On the resulting dressed geometry, evolution of the massive modes, by analyzing the solutions to the corresponding Klein-Gordon equation, is investigated. In particular, by computing the leading order contributions in adiabatic series, an approximate solution for the mode function is obtained. By using the adiabatic regularization, to the fourth order in expansion series, the renormalization of the stress-energy and Hamiltonian of the quantized field is studied. The problem of particle production is studied here in the light of the classical theory of wave propagation on the effective anisotropic background. To the...
Lee, Namhyung
Understanding the merger rate history of galaxies is critical to understanding the formation, structure, and evolution of galaxies. Moreover, the sensitivity of the galaxy merger rate to the cosmological environment enables mutual constraints to be formulated between these two major scientific quandaries. In this dissertation, we have modeled the connection between galaxy merger rates and topologically flat cosmologies with varying multi-component energy density parameters---matter (OM), radiation (OR), cosmic strings (O S) and dark energy (OX). We performed kinematic tests deriving look back times, scale factors, deceleration parameters, proper distances, luminosity distances, angular diameter distances and comoving volume elements as a function of redshift (z). We found that models with greater O X (less OS) and more negative values of the dark energy parameter (w or alpha) provide greater values of the cosmological age H oto in fixed OM. Moreover, we found that the models with greater Hoto provide greater cosmological distances and comoving volume elements. The merger rate is often expressed as a power law of the redshift z, where the exponent m varies from 2 to 7 according to many observational and theoretical studies. We model the merger rate in terms of the number of interacting galaxies N, the dark energy parameter w (or alpha), the merger rate exponent m, and other cosmological parameters---where a flat topology is assumed. We find that m and alpha (or w) mutually constrain one another with unique dependences on particular cosmologies. Consequences of these variations on the number of galaxy mergers are plotted on Normalized Three Dimensional (N3D) plots. Forthcoming observations of the Universe's expansion history will help to further constrain alpha (or w), m, and other parameters (OX, OS and O M) relating to the structure, content, and evolution of the Universe. The inclusion of the cosmic string component, OS, in our calculation lays the groundwork for
LRS Bianchi Type II Massive String Cosmological Models with Magnetic Field in Lyra's Geometry
Directory of Open Access Journals (Sweden)
Raj Bali
2013-01-01
Full Text Available Bianchi type II massive string cosmological models with magnetic field and time dependent gauge function ( in the frame work of Lyra's geometry are investigated. The magnetic field is in -plane. To get the deterministic solution, we have assumed that the shear ( is proportional to the expansion (. This leads to , where and are metric potentials and is a constant. We find that the models start with a big bang at initial singularity and expansion decreases due to lapse of time. The anisotropy is maintained throughout but the model isotropizes when . The physical and geometrical aspects of the model in the presence and absence of magnetic field are also discussed.
Institute of Scientific and Technical Information of China (English)
BALI Raj; PAREEK Umesh Kumar; PRADHAN Anirudh
2007-01-01
@@ Bianchi type-Ⅰ massive string cosmological model with magnetic field of barotropic perfect fluid distribution through the techniques used by Latelier and Stachel is investigated. To obtain the deterministic model of the universe, it is assumed that the universe is filled with barotropic perfect fluid distribution. The magnetic field is due to electric current produced along the x-axis with infinite electrical condúctivity. The behaviour of the model in the presence and absence of magnetic field together with other physical aspects is further discussed.
The Nonlinear cosmological matter power spectrum with massive neutrinos. 1. The Halo model
Energy Technology Data Exchange (ETDEWEB)
Abazajian, Kevork; /Los Alamos; Switzer, Eric R.; /Princeton U.; Dodelson, Scott; /Fermilab /Chicago U., Astron. Astrophys. Ctr.; Heitmann, Katrin; Habib, Salman; /Los
2004-11-01
Measurements of the linear power spectrum of galaxies have placed tight constraints on neutrino masses. We extend the framework of the halo model of cosmological nonlinear matter clustering to include the effect of massive neutrino infall into cold dark matter (CDM) halos. The magnitude of the effect of neutrino clustering for three degenerate mass neutrinos with m{sub v{sub 1}} = 0.9 eV is of order {approx}1%, within the potential sensitivity of upcoming weak lensing surveys. In order to use these measurements to further constrain--or eventually detect--neutrino masses, accurate theoretical predictions of the nonlinear power spectrum in the presence of massive neutrinos will be needed, likely only possible through high-resolution multiple particle (neutrino, CDM and baryon) simulations.
Topologically Massive Spin-1 Particles and Spin-Dependent Potentials
Ferreira, F A Gomes; Ospedal, L P R; Helayël-Neto, J A
2014-01-01
We investigate the role played by particular representations of an intermediate massive spin-1 boson in the context of spin-dependent potentials between fermionic sources in the limit of low momentum transfer. A comparison between the well-known Proca case and that of a rank-2 tensor gauge potential coupled to a 4-vector gauge field is investigated in order to extract spin- as well as velocity-dependent profiles of the interparticle potentials. Bounds on some of the coupling parameters are derived and we discuss possible applications.
Topological implications of the extrinsic curvature for the cosmological constant problem
Capistrano, Abraao J S
2014-01-01
The concept of smooth deformation of a Riemannian manifolds associated with the extrinsic curvature is explained and applied to FLRW cosmology. We show that such deformation can be derived from an Einstein-Hilbert-like dynamical principle producing an observable effect in the sense of Noether. The Gupta equations are used to address the problem of the cosmological constant to provide the expression of the function $b(t)$ which is a consequence of the effect of extrinsic curvature. When using such a modification, we notice on how the extrinsic curvature compensates both quantitative and qualitative difference between $ \\Lambda$ and $\\rho_{\\; vac}$ due to the topological characteristics of the extrinsic geometry. It is also shown that the coincidence problem can be alleviated in this framework.
Vortex driven phase transition in Topologically Massive QED
Hoshino, Yuichi
2016-01-01
There is chiral like symmetry for 4-component massless fermion in (2+1)-dimensional gauge theory.Since QED$_{3}$ with Chern-Simons term contains vortex solution for vector potential,one may expect vortex driven phase transition as Kosterlitz-Thouless type where chiral condensate is washed away at zero temperature.To study this possibility,we evaluate the fermion propagator by Dyson-Schwinger equation numerically and spectral function analytically in the Landau gauge.For quenched case we adopt Ball-Chiu vertex to keep gauge invariance of the results.The critical value of topological mass,above which chiral condensate washed away, turned out to be $O(10^{-2})e^{2}$ at least for weak coupling in both cases.
Topologically massive spin-1 particles and spin-dependent potentials
Energy Technology Data Exchange (ETDEWEB)
Ferreira, F.A.G.; Malta, P.C.; Ospedal, L.P.R.; Helayel-Neto, J.A. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro (Brazil)
2015-05-15
We investigate the role played by particular field representations of an intermediate massive spin-1 boson in the context of spin-dependent interparticle potentials between fermionic sources in the limit of low momentum transfer. The comparison between the well-known case of the Proca field and that of an exchanged spin-1 boson (with gauge-invariant mass) described by a 2-form potential mixed with a 4-vector gauge field is established in order to pursue an analysis of spin- as well as velocity-dependent profiles of the interparticle potentials. We discuss possible applications and derive an upper bound on the product of vector and pseudo-tensor coupling constants. (orig.)
Topological sectors and gauge invariance in massive vector-tensor theories in D $\\geq$ 4
Arias, P J
1996-01-01
A family of local equivalent models is considered. They can be taken as a generalization to d+1 dimensions of the Topological Massive and ``Self-dual'' model in 2+1 dimensions. The corresponding 3+1 models are analized in detail. It is shown that one model can be seen as a gauge fixed version of the other, and their space of classical solutions differs in a topological sector represented by the classical solutions of a pure BF model. The topological sector can be gauged out on cohomologically trivial base manifolds but on general settings it may be responsible of the difference in the long distance behaviour of the models. The presence of this topological sector appears explicitly in the partition function of the theories. The generalization of this models to higher dimensions is shown to be straightfoward.
Anomalies and Hawking fluxes from the black holes of topologically massive gravity
Porfyriadis, Achilleas P
2009-01-01
The anomaly cancelation method proposed by Wilczek et al. is applied to the black holes of topologically massive gravity (TMG) and topologically massive gravito-electrodynamics (TMGE). Thus the Hawking temperature and fluxes of the ACL and ACGL black holes are found. The Hawking temperatures obtained agree with the surface gravity formula. Both black holes are rotating and this gives rise to appropriate terms in the effective U(1) gauge field of the reduced (1+1)-dimensional theory. It is found that the terms in this U(1) gauge field correspond exactly to the correct angular velocities on the horizon of both black holes as well as the correct electrostatic potential of the ACGL black hole. So the results for the Hawking fluxes derived here from the anomaly cancelation method, are in complete agreement with the ones obtained from integrating the Planck distribution.
On the dual equivalence of the self-dual and topologically massive p-form models
Menezes, R; Ribeiro, R F; Wotzasek, C
2003-01-01
We study the duality symmetry in p-form models containing a generalized $B_q\\wedge F_{p+1}$ term in spacetime manifolds of arbitrary dimensions. The equivalence between the $B_q\\wedge F_{p+1}$ self-dual ($SD_{B\\wedge F}$) and the $B_q\\wedge F_{p+1}$ topologically massive ($TM_{B\\wedge F}$) models is established using a gauge embedding procedure, including the minimal coupling to conserved charged matter current. The minimal coupling adopted for both tensor fields in the self-dual representation is transformed into a non minimal magnetic like coupling in the topologically massive representation but with the currents swapped. It is known that to establish this equivalence a current-current interaction term is needed to render the matter sector unchanged. We show that both terms arise naturally from the embedding adopted. Comparison with Higgs/Julia-Toulouse duality is established.
Evaluation of the cosmological constant in inflation with a massive non-minimal scalar field
Huang, Jung-Jeng
2015-01-01
In Schroedinger picture we study the possible effects of trans-Planckian physics on the quantum evolution of massive non-minimally coupled scalar field in de Sitter space. For the nonlinear Corley-Jacobson type dispersion relations with quartic or sextic correction, we obtain the time evolution of the vacuum state wave functional during slow-roll inflation, and calculate explicitly the corresponding expectation value of vacuum energy density. We find that the vacuum energy density is finite. For the usual dispersion parameter choice, the vacuum energy density for quartic correction to the dispersion relation is larger than for sextic correction, while for some other parameter choices, the vacuum energy density for quartic correction is smaller than for sextic correction. We also use the backreaction to constrain the magnitude of parameters in nonlinear dispersion relation, and show how the cosmological constant depends on the parameters and the energy scale during the inflation at the grand unification phase ...
Perturbations of cosmological and black hole solutions in massive gravity and bi-gravity
Kobayashi, Tsutomu; Siino, Masaru; Yamaguchi, Masahide; Yoshida, Daisuke
2016-10-01
We investigate perturbations of a class of spherically symmetric solutions in massive gravity and bi-gravity. The background equations of motion for the particular class of solutions we are interested in reduce to a set of the Einstein equations with a cosmological constant. Thus, the solutions in this class include all the spherically symmetric solutions in general relativity, such as the Friedmann-Lemaître-Robertson-Walker solution and the Schwarzschild (-de Sitter) solution, though the one-parameter family of two parameters of the theory admits such a class of solutions. We find that the equations of motion for the perturbations of this class of solutions also reduce to the perturbed Einstein equations at first and second order. Therefore, the perturbative stability of the solutions coincides with that of the corresponding solutions in general relativity at least up to the second-order perturbations.
Constraints on non-flat cosmologies with massive neutrinos after Planck 2015
Chen, Yun; Biesiada, Marek; Li, Song; Zhu, Zong-Hong
2016-01-01
We investigate two dark energy cosmological models (i.e., the $\\Lambda$CDM and $\\phi$CDM models) with massive neutrinos in both the spatially flat and non-flat scenarios, where in the $\\phi$CDM model the scalar field possesses an inverse power-law potential, $V(\\phi)\\propto {\\phi}^{-\\alpha}$ ($\\alpha>0$). Cosmic microwave background data from Planck 2015, baryon acoustic oscillations data from 6dFGS, SDSS-MGS, BOSS-LOWZ and BOSS CMASS-DR11, the JLA compilation of Type Ia supernova apparent magnitude observations, and the Hubble Space Telescope $H_0$ prior, are jointly employed to constrain the model parameters. In the spatially flat (non-flat) $\\Lambda$CDM model, the sum of neutrino masses is bounded as $\\Sigma m_{\
Cosmological perturbations of self-accelerating universe in nonlinear massive gravity
Gumrukcuoglu, A Emir; Mukohyama, Shinji
2011-01-01
We study cosmological perturbations of self-accelerating universe solutions in the recently proposed nonlinear theory of massive gravity, with general matter content. While the broken diffeomorphism invariance implies that there generically are 2 tensor, 2 vector and 2 scalar degrees of freedom in the gravity sector, we find that the scalar and vector degrees have vanishing kinetic terms and nonzero mass terms. Depending on their nonlinear behavior, this indicates either nondynamical nature of these degrees or strong couplings. Assuming the former, we integrate out the 2 vector and 2 scalar degrees of freedom. We then find that in the scalar and vector sectors, gauge-invariant variables constructed from metric and matter perturbations have exactly the same quadratic action as in general relativity. The difference from general relativity arises only in the tensor sector, where the graviton mass modifies the dispersion relation of gravitational waves, with a time-dependent effective mass. This may lead to modif...
Evaluation of the Cosmological Constant in Inflation with a Massive Nonminimal Scalar Field
Directory of Open Access Journals (Sweden)
Jung-Jeng Huang
2015-01-01
Full Text Available In Schrödinger picture we study the possible effects of trans-Planckian physics on the quantum evolution of massive nonminimally coupled scalar field in de Sitter space. For the nonlinear Corley-Jacobson type dispersion relations with quartic or sextic correction, we obtain the time evolution of the vacuum state wave functional during slow-roll inflation and calculate explicitly the corresponding expectation value of vacuum energy density. We find that the vacuum energy density is finite. For the usual dispersion parameter choice, the vacuum energy density for quartic correction to the dispersion relation is larger than for sextic correction, while for some other parameter choices, the vacuum energy density for quartic correction is smaller than for sextic correction. We also use the backreaction to constrain the magnitude of parameters in nonlinear dispersion relation and show how the cosmological constant depends on the parameters and the energy scale during the inflation at the grand unification phase transition.
Super-Eddington accreting massive black holes as long-lived cosmological standards.
Wang, Jian-Min; Du, Pu; Valls-Gabaud, David; Hu, Chen; Netzer, Hagai
2013-02-22
Super-Eddington accreting massive black holes (SEAMBHs) reach saturated luminosities above a certain accretion rate due to photon trapping and advection in slim accretion disks. We show that these SEAMBHs could provide a new tool for estimating cosmological distances if they are properly identified by hard x-ray observations, in particular by the slope of their 2-10 keV continuum. To verify this idea we obtained black hole mass estimates and x-ray data for a sample of 60 narrow line Seyfert 1 galaxies that we consider to be the most promising SEAMBH candidates. We demonstrate that the distances derived by the new method for the objects in the sample get closer to the standard luminosity distances as the hard x-ray continuum gets steeper. The results allow us to analyze the requirements for using the method in future samples of active black holes and to demonstrate that the expected uncertainty, given large enough samples, can make them into a useful, new cosmological ruler.
Quasi-local conserved charges of spin-3 topologically massive gravity
Directory of Open Access Journals (Sweden)
M.R. Setare
2016-08-01
Full Text Available In this paper we obtain conserved charges of spin-3 topologically massive gravity by using a quasi-local formalism. We find a general formula to calculate conserved charge of the spin-3 topologically massive gravity which corresponds to a Killing vector field ξ. We show that this general formula reduces to the previous one for the ordinary spin-3 gravity presented in [18] when we take into account only transformation under diffeomorphism, without considering generalized Lorentz gauge transformation (i.e. λξ=0, and by taking 1μ→0. Then we obtain a general formula for the entropy of black hole solutions of the spin-3 topologically massive gravity. Finally we apply our formalism to calculate energy, angular momentum and entropy of a special black hole solution and we find that obtained results are consistent with previous results in the limiting cases. Moreover our results for energy, angular momentum and entropy are consistent with the first law of black hole mechanics.
Vacaru, Sergiu I
2015-01-01
We re-investigate how generic off-diagonal cosmological solutions depending, in general, on all spacetime coordinates can be constructed in massive and f-modified gravity using the anholonomic frame deformation method. There are constructed new classes of locally anisotropic and (in) homogeneous cosmological metrics with open and closed spatial geometries. By resorting such solutions, we show that they describe the late time acceleration due to effective cosmological terms induced by nonlinear off-diagonal interactions, possible modifications of the gravitational action and graviton mass. The cosmological metrics and related St\\" uckelberg fields are constructed in explicit form up to nonholonomic frame transforms of the Friedmann-Lama\\^{\\i}tre-Robertson-Walker (FLRW) coordinates. The solutions include matter, graviton mass and other effective sources modelling nonlinear gravitational and matter fields interactions with polarization of physical constants and deformations of metrics, which may explain dark ene...
Redshift-space distortions in massive neutrino and evolving dark energy cosmologies
Upadhye, Amol; Pope, Adrian; Heitmann, Katrin; Habib, Salman; Finkel, Hal; Frontiere, Nicholas
2015-01-01
Large-scale structure surveys in the coming years will measure the redshift-space power spectrum to unprecedented accuracy, allowing for powerful new tests of the LambdaCDM picture as well as measurements of particle physics parameters such as the neutrino masses. We extend the Time-RG perturbative framework to redshift space, computing the power spectrum P_s(k,mu) in massive neutrino cosmologies with time-dependent dark energy equations of state w(z). Time-RG is uniquely capable of incorporating scale-dependent growth into the P_s(k,mu) computation, which is important for massive neutrinos as well as modified gravity models. Although changes to w(z) and the neutrino mass fraction both affect the late-time scale-dependence of the non-linear power spectrum, we find that the two effects depend differently on the line-of-sight angle mu. Finally, we use the HACC N-body code to quantify errors in the perturbative calculations. For a LambdaCDM model at redshift z=1, our procedure predicts the monopole~(quadrupole) ...
Energy Technology Data Exchange (ETDEWEB)
Gelmini, Graciela B [Department of Physics and Astronomy, UCLA, 475 Portola Plaza, Los Angeles, CA 90095 (United States); Gondolo, Paolo, E-mail: gelmini@physics.ucla.edu, E-mail: paolo@physics.utah.edu [Department of Physics, University of Utah, 115 S 1400 E 201, Salt Lake City, UT 84112 (United States)
2008-10-15
Weakly interacting massive particles (WIMPs) constitute one of very few probes of cosmology before big bang nucleosynthesis (BBN). We point out that in scenarios in which the Universe evolves in a non-standard manner during and after WIMP kinetic decoupling, the horizon mass scale at decoupling can be smaller and the dark matter WIMPs can be colder than in standard cosmology. This would lead to much smaller first objects in hierarchical structure formation. In low reheating temperature scenarios the effect may be large enough to noticeably enhance indirect detection signals in GLAST and other detectors, by up to two orders of magnitude.
Tomaschitz, R
1994-01-01
We investigate scattering effects in open Robertson-Walker cosmologies whose spacelike slices are multiply connected hyperbolic manifolds. We work out an example in which the 3-space is infinite and has the topology of a solid torus. The world-lines in these cosmologies are unstable, and classical probability densities evolving under the horospherical geodesic flow show dispersion, as do the densities of scalar wave packets. The rate of dispersion depends crucially on the expansion factor, and we calculate the time evolution of their widths. We find that the cosmic expansion can confine dispersion: The diameter of the domain of chaoticity in the 3-manifold provides the natural, time-dependent length unit in an infinite, multiply connected universe. In a toroidal 3-space manifold this diameter is just the length of the limit cycle. On this scale we find that the densities take a finite limit width in the late stage of the expansion. In the early stage classical densities and conformally coupled fields approach...
Matyjasek, Jerzy
2016-10-01
In this paper, using the general Schwinger-DeWitt approach, we construct the approximate stress-energy tensor of the quantized massive scalar field with arbitrary curvature coupling in D =4 and D =5 classical spacetimes of the electrically charged static black holes with the cosmological constant. Depending on the sign of the cosmological constant we consider both spherically symmetric and topological spacetimes with the special emphasis put on the extremal and ultraextremal configurations. Moreover, we analyze the geometries of the closest vicinity of the degenerate horizons, which topologically are the product of the maximally symmetric subspaces. We solve the semiclassical Einstein field equations for such product spacetimes. Since the transformation k →-k and f''→-f'' leaves the equations unchanged, where k is the curvature of the (D -2 )-dimensional subspace and f'' is the second derivative of the metric potential at the degenerate horizon, it suffices to consider only the spherically symmetric case. It is shown that in four and five dimensions there are forbidden sectors of the parameter space.
Constraints on Non-flat Cosmologies with Massive Neutrinos after Planck 2015
Chen, Yun; Ratra, Bharat; Biesiada, Marek; Li, Song; Zhu, Zong-Hong
2016-10-01
We investigate two dark energy cosmological models (i.e., the ΛCDM and ϕCDM models) with massive neutrinos assuming two different neutrino mass hierarchies in both the spatially flat and non-flat scenarios, where in the ϕCDM model the scalar field possesses an inverse power-law potential, V(ϕ) ∝ ϕ -α (α > 0). Cosmic microwave background data from Planck 2015, baryon acoustic oscillation data from 6dFGS, SDSS-MGS, BOSS-LOWZ and BOSS CMASS-DR11, the joint light-curve analysis compilation of SNe Ia apparent magnitude observations, and the Hubble Space Telescope H 0 prior, are jointly employed to constrain the model parameters. We first determine constraints assuming three species of degenerate massive neutrinos. In the spatially flat (non-flat) ΛCDM model, the sum of neutrino masses is bounded as Σm ν level (CL). Correspondingly, in the flat (non-flat) ϕCDM model, we find Σm ν < 0.164(0.301) eV at 95% CL. The inclusion of spatial curvature as a free parameter results in a significant broadening of confidence regions for Σm ν and other parameters. In the scenario where the total neutrino mass is dominated by the heaviest neutrino mass eigenstate, we obtain similar conclusions to those obtained in the degenerate neutrino mass scenario. In addition, the results show that the bounds on Σm ν based on two different neutrino mass hierarchies have insignificant differences in the spatially flat case for both the ΛCDM and ϕCDM models; however, the corresponding differences are larger in the non-flat case.
Topological charges in 2d N=(2,2) theories and massive BPS states
Park, Daniel S
2015-01-01
We study how charges of global symmetries that are manifest in the ultra-violet definition of a theory are realized as topological charges in its infra-red effective theory for two-dimensional theories with $\\mathcal{N}=(2,2)$ supersymmetry. We focus on the charges that the states living on $S^1$ carry. The central charge---or BPS masses---of the supersymmetry algebra play a crucial role in making this correspondence precise. We study two examples: $U(1)$ gauge theories with chiral matter, and world-volume theories of "dynamical surface operators" of 4d $\\mathcal{N}=2$ gauge theories. In the former example, we show that the flavor charges of the theory are realized as topological winding numbers in the effective theory on the Coulomb branch. In the latter, we show that there is a one-to-one correspondence between topological charges of the effective theory of the dynamical surface operator and the electric, magnetic, and flavor charges of the 4d gauge theory. We also examine the topologically charged massive ...
Quasinormal modes of BTZ black hole in spin-3 topologically massive gravity
Myung, Yun Soo; Park, Young-Jai
2012-01-01
Using the operator approach, we obtain quasinormal modes (QNMs) of BTZ black hole in spin-3 topologically massive gravity by solving the first-order equation of motion with the transverse-traceless condition. It seems that these are different from those obtained when solving the second-order differential equation for the third-rank tensor of spin-3 field, which are imposed by the boundary conditions and have the sign ambiguity of mass. However, it is shown clearly that two approaches to the left-moving QNMs are identical, while the right-moving QNMs of solving the second-order equation are given by descendants of the operator approach.
Triality and Dual Equivalence Between Dirac Field and Topologically Massive Gauge Field
Institute of Scientific and Technical Information of China (English)
LIU Yu-Fen
2006-01-01
It is proved that there exists a vector representation of Dirac's spinor field andin one sense it is equivalent to biquaternion (i.e. complexified quaternion) representation. This can be considered as a generalization of Cartan's idea of triality to Dirac's spinors. In the vector representation the first-order Dirac Lagrangian is dual-equivalent to the two-order Lagrangian of topologically massive gauge field. The potential field which corresponds to the Dirac field is obtained by using master (or parent) action approach. The novel gauge field is self-dual and contains both anti-symmetric Lee and symmetric Jordan structure.
Duality equivalence between nonlinear self-dual and topologically massive models
Ilha, A; Ilha, Anderson; Wotzasek, Clovis
2001-01-01
In this report we study the dual equivalence between the generalized self-dual (SD) and topologically massive (TM) models. To this end we linearize the model using an auxiliary field and apply a gauge embedding procedure to construct a gauge equivalent model. We clearly show that, under the above conditions, a nonlinear SD model always has a duality equivalent TM action.The general result obtained is then particularized for a number of examples, including the Born-Infeld-Chern-Simons (BICS) model recently discussed in the literature.
Stability of warped AdS3 black holes in Topologically Massive Gravity under scalar perturbations
Ferreira, Hugo R C
2013-01-01
We demonstrate that the warped AdS3 black hole solutions of Topologically Massive Gravity are classically stable against massive scalar field perturbations by analysing the quasinormal and bound state modes of the scalar field. In particular, it is found that although classical superradiance is present it does not give rise to superradiant instabilities. The stability is shown to persist even when the black hole is enclosed by a stationary mirror with Dirichlet boundary conditions. This is a surprising result in view of the similarity between the causal structure of the warped AdS3 black hole and the Kerr spacetime in 3+1 dimensions. This work provides the foundations for the study of quantum field theory in this spacetime.
Rubakov, V A
2014-01-01
In these lectures we first concentrate on the cosmological problems which, hopefully, have to do with the new physics to be probed at the LHC: the nature and origin of dark matter and generation of matter-antimatter asymmetry. We give several examples showing the LHC cosmological potential. These are WIMPs as cold dark matter, gravitinos as warm dark matter, and electroweak baryogenesis as a mechanism for generating matter-antimatter asymmetry. In the remaining part of the lectures we discuss the cosmological perturbations as a tool for studying the epoch preceeding the conventional hot stage of the cosmological evolution.
Sesana, A; Madau, P; Volonteri, M; Sesana, Alberto; Haardt, Francesco; Madau, Piero; Volonteri, Marta
2004-01-01
We compute the expected gravitational wave signal from coalescing massive black hole (MBH) binaries at the center of galaxies in a hierarchical structure formation scenario in which seed holes of intermediate mass form far up in the dark halo merger tree. The merger history of DM halos and MBHs is followed from z=20 to the present in a LCDM cosmology. MBHs get incorporated through halo mergers into larger and larger structures, sink to the center owing to dynamical friction against the DM background, accrete cold material in the merger remnant, and form MBH binary systems. Stellar dynamical interactions cause the hardening of the binary at large separations, while gravitational wave emission takes over at small radii and leads to the final coalescence of the pair. The integrated emission from inspiraling MBH binaries results in a gravitational wave background (GWB). The characteristic strain spectrum has the standard h_c(f)\\propto f^{-2/3} behavior only in the range 1E-91E-6 Hz, the strain amplitude is shaped...
arXiv Failures of homogeneous and isotropic cosmologies in Extended Quasi-Dilaton Massive Gravity
Anselmi, Stefano; López Nacir, Diana; Starkman, Glenn D.
2017-10-03
We analyze the Extended Quasi-Dilaton Massive Gravity model around a Friedmann-Lema\\^itre-Robertson-Walker cosmological background. We present a careful stability analysis of asymptotic fixed points. We find that the traditional fixed point cannot be approached dynamically, except from a perfectly fine-tuned initial condition involving both the quasi-dilaton and the Hubble parameter. A less-well examined fixed-point solution, where the time derivative of the 0-th St\\"uckelberg field vanishes $\\dot\\phi^0=0$, encounters no such difficulty, and the fixed point is an attractor in some finite region of initial conditions. We examine the question of the presence of a Boulware-Deser ghost in the theory. We show that the additional constraint which generically allows for the elimination of the Boulware-Deser mode is only present under special initial conditions. We find that the only possibility corresponds to the traditional fixed point and the initial conditions are the same fine-tuned conditions that allow the fix...
The Cosmological Quark-Hadron Transition and Massive Compact Halo Objects
Banerjee, S; Ghosh, S; Raha, S; Sinha, B; Banerjee, Shibaji; Bhattacharyya, Abhijit; Ghosh, Sanjay K.; Raha, Sibaji; Sinha, Bikash
2000-01-01
One of the abiding mysteries in the so-called standard cosmological model is the nature of the dark matter. It is universally accepted that there is an abundance of matter in the universe which is non-luminous, due to their very weak interaction, if at all, with the other forms of matter, excepting of course the gravitational attraction. Speculations as to the nature of dark matter are numerous, often bordering on exotics, and searches for such exotic matter is a very active field of astroparticle physics at the dawn of the new century. Nevertheless, in recent years, there has been experimental evidence for at least one form of dark matter - the massive compact halo objects detected through gravitational microlensing effects proposed by Paczynski some years ago. To date, no clear consensus as to what these objects, referred to in the literature as well as in the following by the acronym MACHO, are made of; for a brief discussion of some of the suggestions, see below. In this work, we show that they find a nat...
Vacuum creation of massive vector bosons and its application to a conformal cosmological model
Blaschke, D B; Smolyansky, S A
2004-01-01
In the simple model of a massive vector field in flat space-time, we derive a kinetic equation of non-Markovian type, describing the vacuum pair creation under the action of external fields of different nature. We use for this aim the non-perturbative methods of kinetic theory in combination with a new element when the transition of the instantaneous quasiparticle representation is realized within the oscillator (holomorphic) representation. We study in detail the process of vacuum creation of vector bosons generated by a time-dependent boson mass in accordance with a conformal-invariant scalar-tensor gravitational theory and its cosmological application. It is indicated that the choice of the equation of state (EoS) of the Universe allows to obtain a number density of the vector bosons that is sufficient to explain the observed number density of photons in the cosmic microwave background radiation. It is shown that the vector boson gas created from the vacuum is in a strong non-equilibrium state and correspo...
Cosmological perturbations and observational constraints on non-local massive gravity
Nesseris, Savvas
2014-01-01
Non-local massive gravity can provide an interesting explanation for the late-time cosmic acceleration, with a dark energy equation of state $w_{\\rm DE}$ smaller than $-1$ in the past. We derive the equations of linear cosmological perturbations to confront such models with the observations of large-scale structures. The effective gravitational coupling to non-relativistic matter associated with galaxy clusterings is close to the Newton's gravitational constant $G$ for a mass scale $m$ slightly smaller than the today's Hubble parameter $H_0$. Taking into account the background expansion history as well as the evolution of matter perturbations $\\delta_m$, we test for these models with the Type Ia Supernovae (SnIa) from the Union 2.1, the Cosmic Microwave Background (CMB) measurements from Planck, a collection of baryon acoustic oscillations (BAO), and the growth rate data of $\\delta_m$. Using a higher value of $H_0$ derived from its direct measurement ($H_0 \\gtrsim 70$ km s$^{-1}$ Mpc$^{-1}$) the data strongly...
The Era of Massive Population III Stars: Cosmological Implications and Self-Termination
Yoshida, N; Hernquist, L; Yoshida, Naoki; Bromm, Volker; Hernquist, Lars
2004-01-01
The birth and death of the first generation of stars have important implications for the thermal state and chemical properties of the intergalactic medium (IGM) in the early universe. Sometime after recombination, the neutral, chemically pristine gas was reionized by ultraviolet photons emitted from the first stars, but also enriched with heavy elements when these stars ended their lives as energetic supernovae. Using the results from high-resolution cosmological simulations of early structure formation that include radiative transfer, we show that a significant volume fraction of the IGM can be metal-polluted, as well as ionized, by massive Population III stars formed in small-mass (10^6-10^7 Msun) halos early on. If most of the early generation stars die as pair-instability supernovae with energies up to 10^{53} ergs, the volume-averaged mean metallicity will quickly reach Z ~ 10^{-4}Zsun by a redshift of 15-20, possibly causing a prompt transition to the formation of a stellar population that is dominated ...
Swift coalescence of supermassive black holes in cosmological mergers of massive galaxies
Khan, Fazeel M; Mayer, Lucio; Berczik, Peter; Just, Andreas
2016-01-01
Supermassive black holes (SMBHs) are ubiquitous in galaxies with a sizable mass. It is expected that a pair of SMBHs originally in the nuclei of two merging galaxies would form a binary and eventually coalesce via a burst of gravitational waves. So far theoretical models and simulations have been unable to predict directly the SMBH merger timescale from ab-initio galaxy formation theory, focusing only on limited phases of the orbital decay of SMBHs under idealized conditions of the galaxy hosts. The predicted SMBH merger timescales are long, of order Gyrs, which could be problematic for future gravitational wave searches. Here we present the first multi-scale $\\Lambda$CDM cosmological simulation that follows the orbital decay of a pair of SMBHs in a merger of two typical massive galaxies at $z\\sim3$, all the way to the final coalescence driven by gravitational wave emission. The two SMBHs, with masses $\\sim10^{8}$ M$_{\\odot}$, settle quickly in the nucleus of the merger remnant. The remnant is triaxial and ex...
Beyer, F.; Escobar, L.; Frauendiener, J.
2016-02-01
In this paper we consider the single patch pseudospectral scheme for tensorial and spinorial evolution problems on the 2-sphere presented by Beyer et al. [Classical Quantum Gravity 32, 175013 (2015); Classical Quantum Gravity31, 075019 (2014)], which is based on the spin-weighted spherical harmonics transform. We apply and extend this method to Einstein's equations and certain classes of spherical cosmological spacetimes. More specifically, we use the hyperbolic reductions of Einstein's equations obtained in the generalized wave map gauge formalism combined with Geroch's symmetry reduction, and focus on cosmological spacetimes with spatial S3 -topologies and symmetry groups U(1) or U (1 )×U (1 ) . We discuss analytical and numerical issues related to our implementation. We test our code by reproducing the exact inhomogeneous cosmological solutions of the vacuum Einstein field equations obtained by Beyer and Hennig [Classical Quantum Gravity 31, 095010 (2014)].
Topological string in harmonic space and correlation functions in S{sup 3} stringy cosmology
Energy Technology Data Exchange (ETDEWEB)
Saidi, El Hassan [Lab/UFR-Physique des Hautes Energies, Faculte des Sciences de Rabat (Morocco) and GNPHE, Groupement National de Physique des Hautes Energies, Siege focal, FS Rabat (Morocco) and Virtual African Centre for Basic Science and Technology, VACBT, Focal point, LabUFR-PHE, Rabat (Morocco)]. E-mail: h-saidi@fsr.ac.ma; Sedra, Moulay Brahim [Lab/UFR-Physique des Hautes Energies, Faculte des Sciences de Rabat (Morocco) and Lab Physique de la Matiere et Rayonnement, Faculte des Sciences Kenitra (Morocco) and GNPHE, Groupement National de Physique des Hautes Energies, Siege focal, FS Rabat (Morocco) and Virtual African Centre for Basic Science and Technology, VACBT, Focal point, LabUFR-PHE, Rabat (Morocco)]. E-mail: sedra@ictp.it
2006-08-07
We develop the harmonic space method for conifold and use it to study local complex deformations of T*S{sup 3} preserving manifestly SL(2,C) isometry. We derive the perturbative manifestly SL(2,C) invariant partition function Z{sub top} of topological string B model on locally deformed conifold. Generic n momentum and winding modes of 2D c=1 noncritical theory are described by highest {upsilon}{sub (n,0)} and lowest components {upsilon}{sub (0,n)} of SL(2,C) spin s=n2 multiplets ({upsilon}{sub (n-k,k)}), 0=
On the Faddeev-Jackiw symplectic framework for topologically massive gravity
Energy Technology Data Exchange (ETDEWEB)
Escalante, Alberto [Benemerita Universidad Autonoma de Puebla, Instituto de Fisica, Puebla (Mexico); Rodriguez-Tzompantzi, Omar [Benemerita Universidad Autonoma de Puebla, Facultad de Ciencias Fisico Matematicas, Puebla (Mexico)
2016-10-15
The dynamical structure of topologically massive gravity in the context of the Faddeev-Jackiw symplectic approach is studied. It is shown that this method allows us to avoid some ambiguities arising in the study of the gauge structure via the Dirac formalism. In particular, the complete set of constraints and the generators of the gauge symmetry of the theory are obtained straightforwardly via the zero modes of the symplectic matrix. In order to obtain the generalized Faddeev-Jackiw brackets and calculate the local physical degrees of freedom of this model, an appropriate gauge-fixing procedure is introduced. Finally, the similarities and relative advantages between the Faddeev-Jackiw method and Dirac's formalism are briefly discussed. (orig.)
Ablinger, J; Blümlein, J; De Freitas, A; von Manteuffel, A; Schneider, C
2015-01-01
Three loop ladder and $V$-topology diagrams contributing to the massive operator matrix element $A_{Qg}$ are calculated. The corresponding objects can all be expressed in terms of nested sums and recurrences depending on the Mellin variable $N$ and the dimensional parameter $\\varepsilon$. Given these representations, the desired Laurent series expansions in $\\varepsilon$ can be obtained with the help of our computer algebra toolbox. Here we rely on generalized hypergeometric functions and Mellin-Barnes representations, on difference ring algorithms for symbolic summation, on an optimized version of the multivariate Almkvist-Zeilberger algorithm for symbolic integration, and on new methods to calculate Laurent series solutions of coupled systems of differential equations. The solutions can be computed for general coefficient matrices directly for any basis also performing the expansion in the dimensional parameter in case it is expressible in terms of indefinite nested product-sum expressions. This structural ...
On the Faddeev-Jackiw Symplectic Framework for Topologically Massive Gravity
Escalante, Alberto
2016-01-01
The dynamical structure of topologically massive gravity in the context of the Faddeev-Jackiw approach is studied. We present a detailed analysis of the constraints and we show that this formalism is equivalent and more economical than Dirac's method. In particular, we identify the complete set of constraints of the theory, from which the number of physical degrees of freedom is explicitly computed. Furthermore, in order to obtain all the generalized Faddeev-Jackiw brackets an appropriate gauge-fixing procedure is introduced and we prove that the generalized Faddeev-Jackiw brackets and the Dirac ones coincide to each other. Finally, the similarities and advantages between Faddeev-Jackiw method and Dirac's formalism are discussed.
Topological defects in alternative theories to cosmic inflation and string cosmology
Alexander, Stephon H. S.
The physics of the Early Universe is described in terms of the inflationary paradigm, which is based on a marriage between Einstein's general theory of relativity minimally coupled to quantum field theory. Inflation was posed to solve some of the outstanding problems of the Standard Big Bang Cosmology (SBB) such as the horizon, formation of structure and monopole problems. Despite its observational and theoretical successes, inflation is plagued with fine tuning and initial singularity problems. On the other hand, superstring/M theory, a theory of quantum gravity, possesses symmetries which naturally avoid space-time singularities. This thesis investigates alternative theories to cosmic inflation for solving the initial singularity, horizon and monopole problems, making use of topological defects. It was proposed by Dvali, Liu and Vaschaspati that the monopole problem can be solved without inflation if domain walls "sweep" up the monopoles in the early universe, thus reducing their number density significantly. Necessary for this mechanism to work is the presence of an attractive force between the monopole and the domain wall as well as a channel for the monopole's unwinding. We show numerically and analytically in two field theory models that for global defects the attraction is a universal result but the unwinding is model specific. The second part of this thesis investigates a string/M theory inspired model for solving the horizon problem. It was proposed by Moffat, Albrecht and Magueijo that the horizon problem is solved with a "phase transition" associated with a varying speed of light before the surface of last scattering. We provide a string/M theory mechanism based on assuming that our space-time is a D-3 brane probing a bulk supergravity black hole bulk background. This mechanism provides the necessary time variation of the velocity of light to solve the horizon problem. We suggest a mechanism which stablilizes the speed of light on the D-3 brane. We
Vittorio, Nicola
2017-01-01
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.
Ablinger, J.; Behring, A.; Blümlein, J.; De Freitas, A.; von Manteuffel, A.; Schneider, C.
2016-05-01
Three loop ladder and V-topology diagrams contributing to the massive operator matrix element AQg are calculated. The corresponding objects can all be expressed in terms of nested sums and recurrences depending on the Mellin variable N and the dimensional parameter ε. Given these representations, the desired Laurent series expansions in ε can be obtained with the help of our computer algebra toolbox. Here we rely on generalized hypergeometric functions and Mellin-Barnes representations, on difference ring algorithms for symbolic summation, on an optimized version of the multivariate Almkvist-Zeilberger algorithm for symbolic integration, and on new methods to calculate Laurent series solutions of coupled systems of differential equations. The solutions can be computed for general coefficient matrices directly for any basis also performing the expansion in the dimensional parameter in case it is expressible in terms of indefinite nested product-sum expressions. This structural result is based on new results of our difference ring theory. In the cases discussed we deal with iterative sum- and integral-solutions over general alphabets. The final results are expressed in terms of special sums, forming quasi-shuffle algebras, such as nested harmonic sums, generalized harmonic sums, and nested binomially weighted (cyclotomic) sums. Analytic continuations to complex values of N are possible through the recursion relations obeyed by these quantities and their analytic asymptotic expansions. The latter lead to a host of new constants beyond the multiple zeta values, the infinite generalized harmonic and cyclotomic sums in the case of V-topologies.
Indian Academy of Sciences (India)
S D Katore; R S Rane; K S Wankhade
2011-04-01
Bianchi type-I massive string cosmological model for perfect ﬂuid distribution in the presence of magnetic ﬁeld is investigated in Rosen’s [Gen. Relativ. Gravit. 4, 435 (1973)] bimetric theory of gravitation. To obtain the deterministic model in terms of cosmic time, we have used the condition $A = (B C)^n$, where n is a constant, between the metric potentials. The magnetic ﬁeld is due to the electric current produced along the -axis with inﬁnite electrical conductivity. Some physical and geometrical properties of the exhibited model are discussed and studied.
Topological charges in SL(2,R) covariant massive 11-dimensional and Type IIB SUGRA
Callister, Andrew K
2009-01-01
In this paper we construct closed expressions that correspond to the topological charges of the various 1/2-BPS states of the maximal 10 and 11-dimensional supergravity theories. These expressions are related to the structure of the SUSY algebras in curved spacetimes. We mainly focus on IIB SUGRA and 11-dimensional SUGRA in a double M9-brane background, with an emphasis on the SL(2,R) multiplet structure of the charges and how these map between theories. This includes the charges corresponding to the multiplets of 7- and 9-branes in IIB. We find that examining the possible multiplet structures of the charges provides another tool for exploring the spectrum of BPS states that appear in these theories. As a prerequisite to constructing the charges we determine the field equations and multiplet structure of the 11-dimensional gauge potentials, extending previous results on the subject. The massive gauge transformations of the fields are also discussed. We also demonstrate how these massive gauge transformations ...
Topological charges in SL(2,R) covariant massive 11-dimensional and type IIB supergravity
Callister, Andrew K.; Smith, Douglas J.
2009-12-01
In this paper we construct closed expressions that correspond to the topological charges of the various 1/2-BPS states of the maximal 10- and 11-dimensional supergravity theories. These expressions are related to the structure of the supersymmetry algebras in curved spacetimes. We mainly focus on IIB supergravity and 11-dimensional supergravity in a double M9-brane background, with an emphasis on the SL(2,R) multiplet structure of the charges and how these map between theories. This includes the charges corresponding to the multiplets of 7- and 9-branes in IIB. We find that examining the possible multiplet structures of the charges provides another tool for exploring the spectrum of BPS states that appear in these theories. As a prerequisite to constructing the charges we determine the field equations and multiplet structure of the 11-dimensional gauge potentials, extending previous results on the subject. The massive gauge transformations of the fields are also discussed. We also demonstrate how these massive gauge transformations are compatible with the construction of an SL(2,R) covariant kinetic term in the 11-dimensional Kaluza-Klein monopole worldvolume action.
Tipler, Frank J.
2001-10-01
Hawking has shown that if black holes were to exist in a universe that expands forever, black holes would completely evaporate, violating unitarity. Unitarity thus requires that the universe exist for only a finite future proper time. I develop this argument, showing that unitarity also requires the boundaries of all future sets to be Cauchy surfaces, and so no event horizons can exist. Thus, the null generators of the surfaces of astrophysical black holes must leave the surface in both time directions, allowing non-spherical topologies for black hole surfaces. Unitarity thus also requires the effective cosmological constant to be zero eventually, otherwise the universe would expand forever. .
Beyer, Florian; Frauendiener, Jörg
2015-01-01
We apply a single patch pseudo-spectral scheme based on integer spin-weighted spherical harmonics presented in [1, 2] to Einstein's equations. The particular hyperbolic reduction of Einstein's equations which we use is obtained by a covariant version of the generalized harmonic formalism and Geroch's symmetry reduction. In this paper we focus on spacetimes with a spatial S3-topology and symmetry group U(1). We discuss analytical and numerical issues related to our implementation. As a test, we reproduce numerically exact inhomogeneous cosmological solutions of the vacuum Einstein field equations obtained in [3].
Energy Technology Data Exchange (ETDEWEB)
Villaescusa-Navarro, Francisco; Viel, Matteo [INAF - Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34143, Trieste (Italy); Marulli, Federico [Dipartimento di Fisica e Astronomia - Università di Bologna, viale Berti Pichat 6/2, I-40127 Bologna (Italy); Branchini, Enzo [Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma (Italy); Castorina, Emanuele [SISSA - International School For Advanced Studies, Via Bonomea, 265 34136 Trieste (Italy); Sefusatti, Emiliano [The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151, Trieste (Italy); Saito, Shun, E-mail: villaescusa@oats.inaf.it, E-mail: federico.marulli3@unibo.it, E-mail: viel@oats.inaf.it, E-mail: branchin@fis.uniroma3.it, E-mail: ecastori@sissa.it, E-mail: esefusat@ictp.it, E-mail: shun.saito@ipmu.jp [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo, Chiba 277-8582 (Japan)
2014-03-01
By using a suite of large box-size N-body simulations that incorporate massive neutrinos as an extra set of particles, with total masses of 0.15, 0.30, and 0.60 eV, we investigate the impact of neutrino masses on the spatial distribution of dark matter haloes and on the distribution of galaxies within the haloes. We compute the bias between the spatial distribution of dark matter haloes and the overall matter and cold dark matter distributions using statistical tools such as the power spectrum and the two-point correlation function. Overall we find a scale-dependent bias on large scales for the cosmologies with massive neutrinos. In particular, we find that the bias decreases with the scale, being this effect more important for higher neutrino masses and at high redshift. However, our results indicate that the scale-dependence in the bias is reduced if the latter is computed with respect to the cold dark matter distribution only. We find that the value of the bias on large scales is reasonably well reproduced by the Tinker fitting formula once the linear cold dark matter power spectrum is used, instead of the total matter power spectrum. We also investigate whether scale-dependent bias really comes from purely neutrino's effect or from nonlinear gravitational collapse of haloes. For this purpose, we address the Ω{sub ν}-σ{sub 8} degeneracy and find that such degeneracy is not perfect, implying that neutrinos imprint a slight scale dependence on the large-scale bias. Finally, by using a simple halo occupation distribution (HOD) model, we investigate the impact of massive neutrinos on the distribution of galaxies within dark matter haloes. We use the main galaxy sample in the Sloan Digital Sky Survey (SDSS) II Data Release 7 to investigate if the small-scale galaxy clustering alone can be used to discriminate among different cosmological models with different neutrino masses. Our results suggest that different choices of the HOD parameters can reproduce the
Energy Technology Data Exchange (ETDEWEB)
Ablinger, J.; Schneider, C. [Johannes Kepler Univ., Linz (Austria). Research Inst. for Symbolic Computation; Behring, A.; Bluemlein, J.; Freitas, A. de [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Manteuffel, A. von [Mainz Univ. (Germany). Inst. fuer Physik
2015-09-15
Three loop ladder and V-topology diagrams contributing to the massive operator matrix element A{sub Qg} are calculated. The corresponding objects can all be expressed in terms of nested sums and recurrences depending on the Mellin variable N and the dimensional parameter ε. Given these representations, the desired Laurent series expansions in ε can be obtained with the help of our computer algebra toolbox. Here we rely on generalized hypergeometric functions and Mellin-Barnes representations, on difference ring algorithms for symbolic summation, on an optimized version of the multivariate Almkvist-Zeilberger algorithm for symbolic integration, and on new methods to calculate Laurent series solutions of coupled systems of differential equations. The solutions can be computed for general coefficient matrices directly for any basis also performing the expansion in the dimensional parameter in case it is expressible in terms of indefinite nested product-sum expressions. This structural result is based on new results of our difference ring theory. In the cases discussed we deal with iterative sum- and integral-solutions over general alphabets. The final results are expressed in terms of special sums, forming quasi-shuffle algebras, such as nested harmonic sums, generalized harmonic sums, and nested binomially weighted (cyclotomic) sums. Analytic continuations to complex values of N are possible through the recursion relations obeyed by these quantities and their analytic asymptotic expansions. The latter lead to a host of new constants beyond the multiple zeta values, the infinite generalized harmonic and cyclotomic sums in the case of V-topologies.
Parallel HOP: A Scalable Halo Finder for Massive Cosmological Data Sets
Skory, Stephen; Norman, Michael L; Coil, Alison L
2010-01-01
Modern N-body cosmological simulations contain billions ($10^9$) of dark matter particles. These simulations require hundreds to thousands of gigabytes of memory, and employ hundreds to tens of thousands of processing cores on many compute nodes. In order to study the distribution of dark matter in a cosmological simulation, the dark matter halos must be identified using a halo finder, which establishes the halo membership of every particle in the simulation. The resources required for halo finding are similar to the requirements for the simulation itself. In particular, simulations have become too extensive to use commonly-employed halo finders, such that the computational requirements to identify halos must now be spread across multiple nodes and cores. Here we present a scalable-parallel halo finding method called Parallel HOP for large-scale cosmological simulation data. Based on the halo finder HOP, it utilizes MPI and domain decomposition to distribute the halo finding workload across multiple compute n...
Nuclear Reaction Uncertainties, Massive Gravitino Decays and the Cosmological Lithium Problem
Cyburt, Richard H; Fields, Brian D; Luo, Feng; Olive, Keith A; Spanos, Vassilis C
2010-01-01
We consider the effects of uncertainties in nuclear reaction rates on the cosmological constraints on the decays of unstable particles during or after Big-Bang nucleosynthesis (BBN). We identify the nuclear reactions due to non-thermal hadrons that are the most important in perturbing standard BBN, then quantify the uncertainties in these reactions and in the resulting light-element abundances. These results also indicate the key nuclear processes for which improved cross section data would allow different light-element abundances to be determined more accurately, thereby making possible more precise probes of BBN and evaluations of the cosmological constraints on unstable particles. Applying this analysis to models with unstable gravitinos decaying into neutralinos, we calculate the likelihood function for the light-element abundances measured currently, taking into account the current experimental errors in the determinations of the relevant nuclear reaction rates. We find a region of the gravitino mass and...
Cosmological evolution and Solar System consistency of massive scalar-tensor gravity
de Pirey Saint Alby, Thibaut Arnoulx; Yunes, Nicolás
2017-09-01
The scalar-tensor theory of Damour and Esposito-Farèse recently gained some renewed interest because of its ability to suppress modifications to general relativity in the weak field, while introducing large corrections in the strong field of compact objects through a process called scalarization. A large sector of this theory that allows for scalarization, however, has been shown to be in conflict with Solar System observations when accounting for the cosmological evolution of the scalar field. We here study an extension of this theory by endowing the scalar field with a mass to determine whether this allows the theory to pass Solar System constraints upon cosmological evolution for a larger sector of coupling parameter space. We show that the cosmological scalar field goes first through a quiescent phase, similar to the behavior of a massless field, but then it enters an oscillatory phase, with an amplitude (and frequency) that decays (and grows) exponentially. We further show that after the field enters the oscillatory phase, its effective energy density and pressure are approximately those of dust, as expected from previous cosmological studies. Due to these oscillations, we show that the scalar field cannot be treated as static today on astrophysical scales, and so we use time-dependent perturbation theory to compute the scalar-field-induced modifications to Solar System observables. We find that these modifications are suppressed when the mass of the scalar field and the coupling parameter of the theory are in a wide range, allowing the theory to pass Solar System constraints, while in principle possibly still allowing for scalarization.
Institute of Scientific and Technical Information of China (English)
N. P. Gaikwad; M. S. Borkar; S. S. Charjan
2011-01-01
@@ We investigate the Bianchi type-I massive string magnetized barotropic perfect fluid cosmological model in Rosen's bimetric theory of gravitation with and without a magnetic field by applying the techniques used by Latelier(1979,1980) and Stachel(1983).To obtain a deterministic model of the universe, it is assumed that the universe is filled with barotropic perfect fluid distribution.The physical and geometrical significance of the model are discussed.By comparing our model with the model of Bali et al.(2007), it is realized that there are no big-bang and big-crunch singularities in our model and T＝0 is not the time of the big bang, whereas the model of Bali et al.starts with a big bang at T=0.Further, our model is in agreement with Bali et al.(2007) as time increases in the presence, as well as in the absence, of a magnetic field.
Cosmology in doubly coupled massive gravity: Constraints from SNIa, BAO and CMB
Heisenberg, Lavinia; Refregier, Alexandre
2016-11-01
Massive gravity in the presence of doubly coupled matter field via en effective composite metric yields an accelerated expansion of the universe. It has been recently shown that the model admits stable de Sitter attractor solutions and could be used as a dark energy model. In this work, we perform a first analysis of the constraints imposed by the SNIa, BAO and CMB data on the massive gravity model with the effective composite metric and show that all the background observations are mutually compatible at the one sigma level with the model.
Cosmology in doubly coupled massive gravity: constraints from SNIa, BAO and CMB
Heisenberg, Lavinia
2016-01-01
Massive gravity in the presence of doubly coupled matter field via en effective composite metric yields an accelerated expansion of the universe. It has been recently shown that the model admits stable de Sitter attractor solutions and could be used as a dark energy model. In this work, we perform a first analysis of the constraints imposed by the SNIa, BAO and CMB data on the massive gravity model with the effective composite metric and show that all the background observations are mutually compatible at the one sigma level with the model.
Menanteau, Felipe; Barrientos, L Felipe; Deshpande, Amruta J; Hilton, Matt; Infante, Leopoldo; Jimenez, Raul; Kosowsky, Arthur; Moodley, Kavilan; Spergel, David; Verde, Licia
2010-01-01
We present a catalog of 105 rich and massive ($M>3\\times10^{14}M_{\\sun}$) optically-selected clusters of galaxies extracted from 70 square-degrees of public archival griz imaging from the Blanco 4-m telescope acquired over 45 nights between 2005 and 2007. We use the clusters' optically-derived properties to estimate photometric redshifts, optical luminosities, richness, and masses. We complement the optical measurements with archival XMM-Newton and ROSAT X-ray data which provide additional luminosity and mass constraints on a modest fraction of the cluster sample. Two of our clusters show clear evidence for central lensing arcs; one of these has a spectacular large-diameter, nearly-complete Einstein Ring surrounding the brightest cluster galaxy. A strong motivation for this study is to identify the massive clusters that are expected to display prominent signals from the Sunyaev-Zeldovich Effect (SZE) and therefore be detected in the wide-area mm-band surveys being conducted by both the Atacama Cosmology Teles...
Feldmann, Robert
2014-01-01
Observations show a prevalence of high redshift galaxies with large stellar masses and predominantly passive stellar populations. A variety of processes have been suggested that could reduce the star formation in such galaxies to observed levels, including quasar mode feedback, virial shock heating, or galactic winds driven by stellar feedback. However, the main quenching mechanisms have yet to be identified. Here we study the origin of star formation quenching using Argo, a cosmological zoom-in simulation that follows the evolution of a massive galaxy at $z\\geq{}2$. This simulation adopts the same sub-grid recipes of the Eris simulations, which have been shown to form realistic disk galaxies, and, in one version, adopts also a mass and spatial resolution identical to Eris. The resulting galaxy has properties consistent with those of observed, massive (M_* ~ 1e11 M_sun) galaxies at z~2 and with abundance matching predictions. Our models do not include AGN feedback indicating that supermassive black holes like...
Topology in the S U (Nf) chiral symmetry restored phase of unquenched QCD and axion cosmology
Azcoiti, Vicente
2016-11-01
We investigate the topological properties of unquenched QCD on the basis of numerical results of simulations at fixed topological charge, recently reported by Borsanyi et al. We demonstrate that their results for the mean value of the chiral condensate at fixed topological charge are inconsistent with the analytical prediction of the large-volume expansion around the saddle point, and argue that the most plausible explanation for the failure of the saddle-point expansion is a vacuum energy density that is θ -independent at high temperatures, but surprisingly not too high (T ˜2 Tc), a result which would imply a vanishing topological susceptibility and the absence of all physical effects of the U (1 ) axial anomaly at these temperatures. We also show that under a general assumption concerning the high-temperature phase of QCD, where the S U (Nf)A symmetry is restored, the analytical prediction for the chiral condensate at fixed topological charge is in very good agreement with the numerical results of Borsanyi et al., all effects of the axial anomaly should disappear, the topological susceptibility and all the θ derivatives of the vacuum energy density vanish, and the theory becomes θ independent at any T >Tc in the infinite-volume limit.
Topology in the SU(Nf) chiral symmetry restored phase of unquenched QCD and axion cosmology
Azcoiti, Vicente
2016-01-01
We investigate the topological properties of unquenched QCD on the basis of numerical results of simulations at fixed topological charge, recently reported by Borsanyi et al., and analytical predictions of the dilute instanton gas approximation. We demonstrate that the mean value of the chiral condensate at fixed topological charge is, in both cases, inconsistent with the analytical prediction of the large volume expansion around the saddle point, and argue that the most plausible explanation for the failure of the saddle point expansion is a vacuum energy density theta-independent at high temperatures, but surprisingly not too high (T\\sim 2T_c), a result which would imply a vanishing topological susceptibility, and the absence of all physical effects of the U(1) axial anomaly at these temperatures. We also show that under a general assumption concerning the high temperature phase of QCD, where the SU(Nf)_A symmetry is restored, the analytical prediction for the chiral condensate at fixed topological charge i...
A multi-element cosmological model with a complex space-time topology
Kardashev, N. S.; Lipatova, L. N.; Novikov, I. D.; Shatskiy, A. A.
2015-02-01
Wormhole models with a complex topology having one entrance and two exits into the same space-time of another universe are considered, as well as models with two entrances from the same space-time and one exit to another universe. These models are used to build a model of a multi-sheeted universe (a multi-element model of the "Multiverse") with a complex topology. Spherical symmetry is assumed in all the models. A Reissner-Norström black-hole model having no singularity beyond the horizon is constructed. The strength of the central singularity of the black hole is analyzed.
Taming the cosmological constant in 2D causal quantum gravity with topology change
Loll, R.; Westra, W.; Zohren, S.
2006-01-01
As shown in previous work, there is a well-defined nonperturbative gravitational path integral including an explicit sum over topologies in the setting of Causal Dy- namical Triangulations in two dimensions. In this paper we derive a complete ana- lytical solution of the quantum continuum dynamics o
Taming the cosmological constant in 2D causal quantum gravity with topology change
Loll, R.; Westra, W.; Zohren, S.
2005-01-01
As shown in previous work, there is a well-defined nonperturbative gravitational path integral including an explicit sum over topologies in the setting of Causal Dy- namical Triangulations in two dimensions. In this paper we derive a complete ana- lytical solution of the quantum continuum dynamics o
Taming the cosmological constant in 2D causal quantum gravity with topology change
Loll, R.; Westra, W.; Zohren, S.
2005-01-01
As shown in previous work, there is a well-defined nonperturbative gravitational path integral including an explicit sum over topologies in the setting of Causal Dy- namical Triangulations in two dimensions. In this paper we derive a complete ana- lytical solution of the quantum continuum
Lefschetz, Solomon
1930-01-01
Lefschetz's Topology was written in the period in between the beginning of topology, by PoincarÃ©, and the establishment of algebraic topology as a well-formed subject, separate from point-set or geometric topology. At this time, Lefschetz had already proved his first fixed-point theorems. In some sense, the present book is a description of the broad subject of topology into which Lefschetz's theory of fixed points fits. Lefschetz takes the opportunity to describe some of the important applications of his theory, particularly in algebraic geometry, to problems such as counting intersections of
Hocking, John G
1988-01-01
""As textbook and reference work, this is a valuable addition to the topological literature."" - Mathematical ReviewsDesigned as a text for a one-year first course in topology, this authoritative volume offers an excellent general treatment of the main ideas of topology. It includes a large number and variety of topics from classical topology as well as newer areas of research activity.There are four set-theoretic chapters, followed by four primarily algebraic chapters. Chapter I covers the fundamentals of topological and metrical spaces, mappings, compactness, product spaces, the Tychonoff t
Kuratowski, Kazimierz
1966-01-01
Topology, Volume I deals with topology and covers topics ranging from operations in logic and set theory to Cartesian products, mappings, and orderings. Cardinal and ordinal numbers are also discussed, along with topological, metric, and complete spaces. Great use is made of closure algebra. Comprised of three chapters, this volume begins with a discussion on general topological spaces as well as their specialized aspects, including regular, completely regular, and normal spaces. Fundamental notions such as base, subbase, cover, and continuous mapping, are considered, together with operations
Kuratowski, Kazimierz
1968-01-01
Topology, Volume II deals with topology and covers topics ranging from compact spaces and connected spaces to locally connected spaces, retracts, and neighborhood retracts. Group theory and some cutting problems are also discussed, along with the topology of the plane. Comprised of seven chapters, this volume begins with a discussion on the compactness of a topological space, paying particular attention to Borel, Lebesgue, Riesz, Cantor, and Bolzano-Weierstrass conditions. Semi-continuity and topics in dimension theory are also considered. The reader is then introduced to the connecte
Yi, Meng; Chen, Qingkui; Xiong, Neal N
2016-11-03
This paper considers the distributed access and control problem of massive wireless sensor networks' data access center for the Internet of Things, which is an extension of wireless sensor networks and an element of its topology structure. In the context of the arrival of massive service access requests at a virtual data center, this paper designs a massive sensing data access and control mechanism to improve the access efficiency of service requests and makes full use of the available resources at the data access center for the Internet of things. Firstly, this paper proposes a synergistically distributed buffer access model, which separates the information of resource and location. Secondly, the paper divides the service access requests into multiple virtual groups based on their characteristics and locations using an optimized self-organizing feature map neural network. Furthermore, this paper designs an optimal scheduling algorithm of group migration based on the combination scheme between the artificial bee colony algorithm and chaos searching theory. Finally, the experimental results demonstrate that this mechanism outperforms the existing schemes in terms of enhancing the accessibility of service requests effectively, reducing network delay, and has higher load balancing capacity and higher resource utility rate.
Directory of Open Access Journals (Sweden)
Meng Yi
2016-11-01
Full Text Available This paper considers the distributed access and control problem of massive wireless sensor networks’ data access center for the Internet of Things, which is an extension of wireless sensor networks and an element of its topology structure. In the context of the arrival of massive service access requests at a virtual data center, this paper designs a massive sensing data access and control mechanism to improve the access efficiency of service requests and makes full use of the available resources at the data access center for the Internet of things. Firstly, this paper proposes a synergistically distributed buffer access model, which separates the information of resource and location. Secondly, the paper divides the service access requests into multiple virtual groups based on their characteristics and locations using an optimized self-organizing feature map neural network. Furthermore, this paper designs an optimal scheduling algorithm of group migration based on the combination scheme between the artificial bee colony algorithm and chaos searching theory. Finally, the experimental results demonstrate that this mechanism outperforms the existing schemes in terms of enhancing the accessibility of service requests effectively, reducing network delay, and has higher load balancing capacity and higher resource utility rate.
Manetti, Marco
2015-01-01
This is an introductory textbook on general and algebraic topology, aimed at anyone with a basic knowledge of calculus and linear algebra. It provides full proofs and includes many examples and exercises. The covered topics include: set theory and cardinal arithmetic; axiom of choice and Zorn's lemma; topological spaces and continuous functions; connectedness and compactness; Alexandrov compactification; quotient topologies; countability and separation axioms; prebasis and Alexander's theorem; the Tychonoff theorem and paracompactness; complete metric spaces and function spaces; Baire spaces; homotopy of maps; the fundamental group; the van Kampen theorem; covering spaces; Brouwer and Borsuk's theorems; free groups and free product of groups; and basic category theory. While it is very concrete at the beginning, abstract concepts are gradually introduced. It is suitable for anyone needing a basic, comprehensive introduction to general and algebraic topology and its applications.
Topological string in harmonic space and correlation functions in $S^3$ stringy cosmology
Saidi, E H; Saidi, El Hassan; Sedra, Moulay Brahim
2006-01-01
We develop the harmonic space method for conifold and use it to study local complex deformations of $T^{\\ast}S^{3}$ preserving manifestly $SL(2,C) $ isometry. We derive the perturbative manifestly $SL(2,C) $ invariant partition function $\\mathcal{Z}_{top}$ of topological string B model on locally deformed conifold. Generic $n$ momentum and winding modes of 2D $c=1$ non critical theory are described by highest $% \\upsilon _{(n,0)}$ and lowest components $\\upsilon_{(0,n)}$ of $SL(2,C) $ spin $s=\\frac{n}{2}$ multiplets $% (\\upsilon _{(n-k,k)}) $, $0\\leq k\\leq n$ and are shown to be naturally captured by harmonic monomials. Isodoublets ($n=1$) describe uncoupled units of momentum and winding modes and are exactly realized as the $SL(2,C) $ harmonic variables $U_{\\alpha}^{+}$ and $V_{\\alpha}^{-}$. We also derive a dictionary giving the passage from Laurent (Fourier) analysis on $T^{\\ast }S^{1}$ ($S^{1}$) to the harmonic method on $T^{\\ast}S^{3}$ ($S^{3}$). The manifestly $SU(2,C) $ covariant correlation functions ...
Claudia de Rham
2016-01-01
We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali-Gabadadze-Porrati model (DGP), cascading gravity, and ghost-free massive gravity. We then explore their theoretical and phenomenological consistency, proving the absence of Boulware-Deser ghosts and reviewing the Vainshtein mechanism and the cosmological solutions in these models. Finally, we present alt...
de Rham, Claudia
2014-01-01
We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali-Gabadadze-Porrati model (DGP), cascading gravity, and ghost-free massive gravity. We then explore their theoretical and phenomenological consistency, proving the absence of Boulware-Deser ghosts and reviewing the Vainshtein mechanism and the cosmological solutions in these models. Finally, we present alt...
2014-01-01
We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali–Gabadadze–Porrati model (DGP), cascading gravity, and ghost-free massive gravity. We then explore their theoretical and phenomenological consistency, proving the absence of Boulware–Deser ghosts and reviewing the Vainshtein mechanism and the cosmological solutions in these models. Finally, we present alt...
Boehringer, Hans
2015-01-01
Clusters of galaxies are important probes for the large-scale structure that allow us to test cosmological models. With the REFLEX II galaxy cluster survey we previously derived tight constraints on the cosmological parameters for the matter density, Omega_m, and the amplitude parameter of the matter density fluctuations, sigma_8. Whereas in these previous studies no effect of massive neutrinos was taken into account, we explore these effects in the present publication. We derive cosmological constraints for the sum of the neutrino masses of the conventional three neutrino families in the range 0 to 0.6 eV. The influence on the constraints of Omega_m and sigma_8 for the expected mass range is weak. Interesting constraints on the neutrino properties can be derived by comparing the cluster data with those from the Planck cosmic microwave background observations. The current tension between the Planck results and clusters can formally be resolved with neutrino masses of about M_nu = 0.45 (+- 0.28, 1-sigma) eV. W...
Confined Vortices in Topologically Massive U(1)$\\times$U(1) Theory
Anber, Mohamed M; Sabancilar, Eray; Shaposhnikov, Mikhail
2015-01-01
We report on a new topological vortex solution in U(1)$\\times$U(1) Maxwell-Chern-Simons theory. The existence of the vortex is envisaged by analytical means, and a numerical solution is obtained by integrating the equations of motion. These vortices have a long-range force because one of the U(1)s remains unbroken in the infrared, which is guarded by the Coleman-Hill theorem. The sum of the winding numbers of an ensemble of vortices has to vanish; otherwise the system would have a logarithmically divergent energy. In turn, these vortices exhibit classical confinement. We investigate the rich parameter space of the solutions, and show that one recovers the Abrikosov-Nielsen-Olesen, U(1) Maxwell-Chern-Simons, U(1) pure Chern-Simons and global vortices as various limiting cases. Unlike these limiting cases, the higher winding solutions of our vortices carry non-integer charges under the broken U(1). This is the first vortex solution exhibiting such behavior.
Axions : Theory and Cosmological Role
Kawasaki, Masahiro; Nakayama, Kazunori
2013-01-01
We review recent developments on axion cosmology. Topics include : axion cold dark matter, axions from topological defects, axion isocurvature perturbation and its non-Gaussianity and axino/saxion cosmology in supersymmetric axion model.
Menezes, R; Ribeiro, R F; Wotzasek, C
2002-01-01
We study the equivalence between the $B\\wedge F$ self-dual ($SD_{B\\wedge F}$) and the $B\\wedge F$ topologically massive ($TM_{B\\wedge F}$) models including the coupling to dynamical, U(1) charged fermionic matter. This is done through an iterative procedure of gauge embedding that produces the dual mapping. In the interactive cases, the minimal coupling adopted for both vector and tensor fields in the self-dual representation is transformed into a non minimal magnetic like coupling in the topologically massive representation but with the currents swapped. It is known that to establish this equivalence a current-current interaction term is needed to render the matter sector unchanged. We show that both terms arise naturally from the embedding procedure.
Tomaschitz, R
1991-01-01
Keywords: Robertson-Walker cosmology, relativistic chaos, mixing, Bernoulli property, time evolution, quantum fields, quantum chaos, bound states, energy functional, hyperbolic manifold, deformation space, Kleinian group, limit set, Hausdorff dimension, convex hull.
Matter coupling in 3D "Minimal Massive Gravity"
Arvanitakis, Alex S; Townsend, Paul K
2014-01-01
The "Minimal Massive Gravity" (MMG) model of massive gravity in three spacetime dimensions (which has the same anti-de Sitter (AdS) bulk properties as "Topologically Massive Gravity" but improved boundary properties) is coupled to matter. Consistency requires a particular matter source tensor, which is quadratic in the stress tensor. The consequences are explored for an ideal fluid in the context of asymptotically de-Sitter (dS) cosmological solutions, which bounce smoothly from contraction to expansion. Various vacuum solutions are also found, including warped-(A)dS, and (for special values of parameters) static black holes and an (A)dS2 x S1 vacuum.
Menanteau, Felipe; Hughes, John Pl; Baker, Andrew J.; Sifon, Cristobal; Gonzalez, Jorge; Infante, Leopoldo; Barrientos, L. Felipe; Hilton, Matt; Das, Sudeep; Spergel, David N.; Hincks, Adam D.; Page, Lyman A.; Staggs, Suzanne T.; Mardsen, Danica; Reese, Erik D.; Dunkley, Joanna; Kosowsky, Arthur; Marriage, Tobias A.; Moodley, Kavilan; Niemack, Michael D.; Sehgal, Neelima; Sievers, Jon
2011-01-01
We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CL J0102-4915 as the most significant Sunyaev-Zeldovich (SZ) decrement in a sky survey area of 755 square degrees. Our VLT/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, sigma(gal) +/- 1321 106 km s-1. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T(X) = 14:5 +/- 0:1 keV and 0.5 2.0 keV band luminosity of L(X) = (2:19 0:11) 1045 h(exp -2)70erg s-1. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y(X) , and integrated SZ distortion, we estimate a cluster mass of M(200) = (2:16 +/- 0:32) 10(exp 15) h(exp-1) 70M compared to the Sun. We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CL J0102-4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6:6 +/- 0:7 keV at the merging low-entropy, high-metallicity, cool core to a high of 22 +/- 6 keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other from which we estimate a merger speed of around 1300 km s(exp -1) for an assumed merger timescale of 1 Gyr. ACTCL J0102-4915 is possibly a high-redshift analog of the famous Bullet Cluster. Such a massive cluster at this redshift is rare, although consistent with the standard CDM cosmology in the lower part of its allowed mass range. Massive
Cosmological evolution of massive black holes at the center of galaxies%星系中心大黑洞的宇宙学演化
Institute of Scientific and Technical Information of China (English)
徐生年; 袁业飞
2012-01-01
In the cosmological model of the hierarchical structure formation of dark matter halos, the black holes residing at the center of galaxies continue merging and accreting, following the merging of the dark matter halos. Based on the extended Press-Schechter formalism, we have developed a Monte Carlo algorithm with the self-adaptive time step, which could be used to reconstruction the merging tree of dark matter halos. Having introduced the evolutionary history of massive black holes, especially the two kinds of accretion modes: the direct accretion modes which includes the standard thin accretion disk model and the magnetohydrodynamic accretion disk model and the chaotic accretion model, we investigate the cosmological evolution of the spin and masses of massive black holes. Comparing with the observed luminosity function of active galactic nuclei, it is found that the magnetohydrodynamic accretion disk model describe the growth of massive black holes better than the other accretion models. We have also study the evolution of the binaries of massive black holes, and find that the circum-disk of the black hole binaries significantly affect the distribution of their mass ratio.%在冷暗物质晕等级成团的宇宙学模型中,伴随着暗物质晕的并合,星系中心的黑洞也不断地并合和增长.基于扩展的Press-Schechter公式(EPS)我们编写了一套自适应时间步长的Monte Carlo程序,重构了表征暗物质晕等级成团的并合树.在成功地建立了黑洞和暗物质晕宇宙学演化模型后,我们通过引入直接吸积(包括标准薄盘吸积和磁流体力学吸积)和随机吸积两类黑洞吸积模式,讨论了黑洞的自旋和质量的宇宙学演化.通过与观测得到的AGN光度函数的比较,我们发现黑洞通过磁流体力学吸积模式增长,与观测符合得最好.基于以上的理论框架,我们还研究了双大质量黑洞的演化,发现双黑洞通过共转气体吸积盘吸积对双黑洞质量比的分布存在显著的影响.
Particle physics and cosmology
Energy Technology Data Exchange (ETDEWEB)
Kolb, E.W.
1986-10-01
This series of lectures is about the role of particle physics in physical processes that occurred in the very early stages of the bug gang. Of particular interest is the role of particle physics in determining the evolution of the early Universe, and the effect of particle physics on the present structure of the Universe. The use of the big bang as a laboratory for placing limits on new particle physics theories will also be discussed. Section 1 reviews the standard cosmology, including primordial nucleosynthesis. Section 2 reviews the decoupling of weakly interacting particles in the early Universe, and discusses neutrino cosmology and the resulting limits that may be placed on the mass and lifetime of massive neutrinos. Section 3 discusses the evolution of the vacuum through phase transitions in the early Universe and the formation of topological defects in the transitions. Section 4 covers recent work on the generation of the baryon asymmetry by baryon-number violating reactions in Grand Unified Theories, and mentions some recent work on baryon number violation effects at the electroweak transition. Section 5 is devoted to theories of cosmic inflation. Finally, Section 6 is a discussion of the role of extra spatial dimensions in the evolution of the early Universe. 78 refs., 32 figs., 6 tabs.
Gaete, Patricio
2016-01-01
By using the gauge-invariant but path-dependent, variables formalism, we consider a recently proposed topologically massive $U{\\left( 1 \\right)_{\\cal W}} \\times U{(1)_{\\cal Y}}$ Chern-Simons-Higgs theory in $2+1$ dimensions. In particular, we inspect the impact of a Chern-Simons mixing term between two Abelian gauge fields on physical observables. We pursue our investigation by analysing the model in two different situations. In the first case, where we integrate out the massive excitation and consider an effective model for the massless field, we show that the interaction energy contains a linear term leading to the confinement of static charge probes along with a screening contribution. The second situation, where the massless field can be exactly integrated over with its constraint duly taken into account, the interesting feature is that the resulting effective model describes a purely screening phase, without any trace of a confining regime.
Energy Technology Data Exchange (ETDEWEB)
Menanteau, Felipe; Hughes, John P.; Baker, Andrew J. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Rd, Piscataway, NJ 08854 (United States); Sifon, Cristobal; Gonzalez, Jorge; Infante, Leopoldo; Felipe Barrientos, L. [Departamento de Astronomia y Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Hilton, Matt [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Bond, John R.; Hajian, Amir; Nolta, Michael R. [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada); Das, Sudeep [Berkeley Center for Cosmological Physics, LBL and Department of Physics, University of California, Berkeley, CA 94720 (United States); Devlin, Mark J.; Marsden, Danica [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Dunkley, Joanna [Department of Astrophysics, Oxford University, Oxford, OX1 3RH (United Kingdom); Hincks, Adam D. [Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544 (United States); Kosowsky, Arthur [Physics and Astronomy Department, University of Pittsburgh, 100 Allen Hall, 3941 O' Hara Street, Pittsburgh, PA 15260 (United States); Marriage, Tobias A. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218-2686 (United States); Moodley, Kavilan [Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, University of KwaZulu-Natal, Durban 4041 (South Africa); Niemack, Michael D. [NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305 (United States); and others
2012-03-20
We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CL J0102-4915 as the most significant SZ decrement in a sky survey area of 755 deg{sup 2}. Our Very Large Telescope (VLT)/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, {sigma}{sub gal} = 1321 {+-} 106 km s{sup -1}. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T{sub X} = 14.5 {+-} 0.1 keV and 0.5-2.0 keV band luminosity of L{sub X} = (2.19 {+-} 0.11) Multiplication-Sign 10{sup 45} h{sup -2}{sub 70} erg s{sup -1}. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y{sub X}, and integrated SZ distortion, we estimate a cluster mass of M{sub 200a} = (2.16 {+-} 0.32) Multiplication-Sign 10{sup 15} h{sup -1}{sub 70} M{sub Sun }. We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CL J0102-4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6.6 {+-} 0.7 keV at the merging low-entropy, high-metallicity, cool core to a high of 22 {+-} 6 keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other. Archival radio data at 843 MHz reveal diffuse radio emission that, if associated with the cluster, indicates the presence of an intense double radio relic, hosted by the highest redshift cluster yet. ACT-CL J0102-4915 is possibly a high
Menanteau, Felipe; Hughes, John P.; Sifon, Cristobal; Hilton, Matt; Gonzalez, Jorge; Infante, Leopoldo; Barrientos, L. Felipe; Baker, Andrew J.; Bond, John R.; Das, Sudeep; Devlin, Mark J.; Dunkley, Joanna; Hajian, Amir; Hincks, Adam D.; Kosowsky, Arthur; Marsden, Danica; Marriage, Tobias A.; Moodley, Kavilan; Niemack, Michael D.; Nolta, Michael R.; Page, Lyman A.; Reese, Erik D.; Sehgal, Neelima; Seivers, Jon; Spergel, David N.; Staggs, Suzanne T.; Wollack, Edward
2012-01-01
We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CL J0102-4915 as the most significant Sunyaev-Zeldovich (SZ) decrement in a sky survey area of 755 square degrees. Our VLT/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, sigma(sub gal) = 1321+/-106 km s-1. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T(sub X) = 14.5+/-1.0 keV and 0.5-2.0 keV band luminosity of L(sub X) = (2.19+/-0.11)×10(sup 45) h(sup -2)(sub 70) erg s-1. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y(sub X), and integrated SZ distortion, we estimate a cluster mass of M(sub 200a) = (2.16+/-0.32)×1015 h(sup -1)(sub 70) solar mass. We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CL J0102-4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6.6+/-0.7 keV at the merging low-entropy, high-metallicity, cool core to a high of 22+/-6 keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other. Archival radio data at 843 MHz reveal diffuse radio emission that, if associated with the cluster, indicates the presence of an intense double radio relic, hosted by the highest redshift cluster yet. ACT-CL J0102-4915 is possibly a high-redshift analog of the famous Bullet Cluster. Such a massive cluster at this redshift
Tipler, Frank J.
1996-10-01
It is generally believed that it is not possible to rigorously analyze a homogeneous and isotropic cosmological model in Newtonian mechanics. I show on the contrary that if Newtonian gravity theory is rewritten in geometrical language in the manner outlined in 1923-1924 by Élie Cartan [Ann. Ecole Norm. Sup. 40, 325-412 (1923); 41, 1-25 (1924)], then Newtonian cosmology is as rigorous as Friedmann cosmology. In particular, I show that the equation of geodesic deviation in Newtonian cosmology is exactly the same as equation of geodesic deviation in the Friedmann universe, and that this equation can be integrated to yield a constraint equation formally identical to the Friedmann equation. However, Newtonian cosmology is more general than Friedmann cosmology: Ever-expanding and recollapsing universes are allowed in any noncompact homogeneous and isotropic spatial topology. I shall give a brief history of attempts to do cosmology in the framework of Newtonian mechanics.
Baxter, J Erik
2015-01-01
We investigate the phase space of topological black hole solutions of ${\\mathfrak {su}}(N)$ Einstein-Yang-Mills theory in anti-de Sitter space with a purely magnetic gauge potential. The gauge field is described by $N-1$ magnetic gauge field functions $\\omega _{j}$, $j=1,\\ldots , N-1$. For ${\\mathfrak {su}}(2)$ gauge group, the function $\\omega _{1}$ has no zeros. This is no longer the case when we consider a larger gauge group. The phase space of topological black holes is considerably simpler than for the corresponding spherically symmetric black holes, but for $N>2$ and a flat event horizon, there exist solutions where at least one of the $\\omega _{j}$ functions has one or more zeros. For most of the solutions, all the $\\omega _{j}$ functions have no zeros, and at least some of these are linearly stable.
Sifon, Cristobal; Hasselfield, Matthew; Marriage, Tobias A; Hughes, John P; Barrientos, L Felipe; Gonzalez, Jorge; Infante, Leopoldo; Addison, Graeme E; Baker, Andrew J; Battaglia, Nick; Bond, J Richard; Das, Sudeep; Devlin, Mark J; Dunkley, Joanna; Dunner, Rolando; Gralla, Megan B; Hajian, Amir; Hilton, Matt; Hincks, Adam D; Kosowsky, Arthur B; Marsden, Danica; Moodley, Kavilan; Niemack, Michael D; Nolta, Michael R; Page, Lyman A; Partridge, Bruce; Reese, Erik D; Sehgal, Neelima; Sievers, Jon; Spergel, David N; Staggs, Suzanne T; Thornton, Robert J; Trac, Hy; Wollack, Edward
2012-01-01
We present the first dynamical mass estimates and scaling relations for a sample of Sunyaev-Zel'dovich effect (SZE) selected galaxy clusters. The sample consists of 16 massive clusters detected with the Atacama Cosmology Telescope (ACT) over a 455 sq deg. area of the southern sky. Deep multi-object spectroscopic observations were taken to secure intermediate-resolution (R~700-800) spectra and redshifts for ~60 member galaxies on average per cluster. The dynamical masses M_200c of the clusters have been calculated using simulation-based scaling relations between velocity dispersion and mass. The sample has a median redshift z=0.50 and a median mass M_200c=11x10^14 Msun/h_70 with a lower limit M_200c ~ 5x10^14 Msun/h_70, consistent with the expectations for the ACT southern sky survey. These masses are compared to the ACT SZE properties of the sample, specifically, the central SZE amplitude y0, the Compton signal within a 0.5' pixel y_0.5', and the integrated Compton signal Y_200c, which we use to derive SZE-Ma...
Menanteau, Felipe; Sifon, Cristobal; Hilton, Matt; Gonzalez, Jorge; Infante, Leopoldo; Barrientos, L Felipe; Baker, Andrew J; Das, Sudeep; Devlin, Mark J; Dunkley, Joanna; Hincks, Adam D; Kosowsky, Arthur; Mardsen, Danica; Marriage, Tobias A; Moodley, Kavilan; Niemack, Michael D; Page, Lyman A; Reese, Erik D; Sehgal, Neelima; Sievers, Jon; Spergel, David N; Staggs, Suzanne T; Wollack, Edward
2011-01-01
We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich(SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope collaboration discovered it as the most significant SZ decrement in a sky survey area of 755 square degrees. Our VLT/FORS2 spectra of 89 member galaxies yield a cluster redshift, z=0.870, and velocity dispersion, sigma=1321+/-106 km/s. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of Tx=14.5+/-0.1 keV and 0.5-2.0 keV band luminosity of Lx=(2.19+/-0.11) x 10^45 h_70^-2 erg/s. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Yx, and integrated SZ distortion, we estimate a cluster mass of M_200=(2.16+/-0.32)x10^15 M_sun/h_70. The Chandra and VLT/FORS2 optical data also reveal that ACT...
Chronology violation and the Cosmological Argument
Romero, G E
2003-01-01
The Kalam Cosmological Argument is perhaps the most solid and widly discussed argument for a caused creation of the universe. The usual objections to the argument mainly focus on the second premise. In this paper we discuss the dependency of the first premise on the topological structure of the space-time manifold adopted for the underlying cosmological model. It is shown that in chronology-violating space-times the first premise is also violated. The chronology-violation, in turn, requires a massive violation of the so-called energy conditions which could have observational effects that are briefly discussed here. Hence, astronomical observations could be relevant for the validity of the metaphysical argument. In this sense, it is possible to talk of "observational theology".
Chen, C.-C.; Teague, M. L.; He, L.; Kou, X.; Lang, M.; Fan, W.; Woodward, N.; Wang, K.-L.; Yeh, N.-C.
2015-11-01
Proximity-induced magnetic effects on the surface Dirac spectra of topological insulators are investigated by scanning tunneling spectroscopic studies of bilayer structures consisting of undoped Bi2Se3 thin films on top of Cr-doped Bi2Se3 layers. For thickness of the top Bi2Se3 layer equal to or smaller than 3 quintuple layers, a spatially inhomogeneous surface spectral gap Δ opens up below a characteristic temperature {{T}{{c}}}2{{D}}, which is much higher than the bulk Curie temperature {{T}{{c}}}3{{D}} determined from the anomalous Hall resistance. The mean value and spatial homogeneity of the gap Δ generally increase with increasing c-axis magnetic field (H) and increasing Cr doping level (x), suggesting that the physical origin of this surface gap is associated with proximity-induced c-axis ferromagnetism. On the other hand, the temperature (T) dependence of Δ is non-monotonic, showing initial increase below {{T}{{c}}}2{{D}}, which is followed by a ‘dip’ and then rises again, reaching maximum at T ≪ {{T}{{c}}}3{{D}}. These phenomena may be attributed to proximity magnetism induced by two types of contributions with different temperature dependences: a three-dimensional contribution from the bulk magnetism that dominates at low T, and a two-dimensional contribution associated with the RKKY interactions mediated by surface Dirac fermions, which dominates at {{T}{{c}}}3{{D}} ≪ T term stability of these topologically protected two-level states may find potential applications to quantum information technology.
Menezes, R; Ribeiro, R F; Wotzasek, C
2002-01-01
We study the dual equivalence between the nonlinear generalization of the self-dual ($NSD_{B\\wedge F}$) and the topologically massive $B\\wedge F$ models with particular emphasis on the nonlinear electrodynamics proposed by Born and Infeld. This is done through a dynamical gauge embedding of the nonlinear self-dual model yielding to a gauge invariant and dynamically equivalent theory. We clearly show that nonpolinomial $NSD_{B\\wedge F}$ models can be mapped, through a properly defined duality transformation, into $TM_{B\\wedge F}$ actions. The general result obtained is then particularized for a number of examples, including the Born-Infeld-BF (BIBF) model that has experienced a revival in the recent literature.
Zentner, A R
2003-01-01
Improvements in observational techniques have transformed cosmology into a field inundated with ever-expanding, high-quality data sets and driven cosmology toward a standard model where the classic cosmological parameters are accurately measured. I briefly discuss some of the methods used to determine cosmological parameters, particularly primordial nucleosynthesis, the magnitude- redshift relation of supernovae, and cosmic microwave background anisotropy. I demonstrate how cosmological data can be used to complement particle physics and constrain extensions to the Standard Model. Specifically, I present bounds on light particle species and the properties of unstable, weakly-interacting, massive particles. Despite the myriad successes of the emerging standard cosmological model, unanswered questions linger. Numerical simulations of structure formation predict galactic central densities that are considerably higher than observed. They also reveal hundreds of satellites orbiting Milky Way-like galaxies while th...
Inhomogeneous anisotropic cosmology
Energy Technology Data Exchange (ETDEWEB)
Kleban, Matthew [Center for Cosmology and Particle Physics, New York University,4 Washington Place, New York, NY 10003 (United States); Senatore, Leonardo [Stanford Institute for Theoretical Physics and Department of Physics, Stanford University,382 Via Pueblo Mall, Stanford, CA 94306 (United States); Kavli Institute for Particle Astrophysics and Cosmology, Stanford University and SLAC,2575 Sand Hill Road, M/S 29, Menlo Park, CA 94025 (United States)
2016-10-12
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with “flat” (including toroidal) and “open” (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are “flat” or “open”. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with “flat” or “open” topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.
Inhomogeneous anisotropic cosmology
Kleban, Matthew; Senatore, Leonardo
2016-10-01
In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with ``flat'' (including toroidal) and ``open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are ``flat'' or ``open''. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with ``flat'' or ``open'' topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.
Patel, Ekta; Besla, Gurtina; Mandel, Kaisey
2017-07-01
In the era of high-precision astrometry, space observatories like the Hubble Space Telescope (HST) and Gaia are providing unprecedented 6D phase-space information of satellite galaxies. Such measurements can shed light on the structure and assembly history of the Local Group, but improved statistical methods are needed to use them efficiently. Here we illustrate such a method using analogues of the Local Group's two most massive satellite galaxies, the Large Magellanic Cloud (LMC) and Triangulum (M33), from the Illustris dark-matter-only cosmological simulation. We use a Bayesian inference scheme combining measurements of positions, velocities and specific orbital angular momenta (j) of the LMC/M33 with importance sampling of their simulated analogues to compute posterior estimates of the Milky Way (MW) and Andromeda's (M31) halo masses. We conclude that the resulting host halo mass is more susceptible to bias when using measurements of the current position and velocity of satellites, especially when satellites are at short-lived phases of their orbits (i.e. at pericentre). Instead, the j value of a satellite is well conserved over time and provides a more reliable constraint on host mass. The inferred virial mass of the MW (M31) using j of the LMC (M33) is {{M}}_{vir, MW} = 1.02^{+0.77}_{-0.55} × 10^{12} M⊙ ({{M}}_{vir, M31} = 1.37^{+1.39}_{-0.75} × 10^{12} M⊙). Choosing simulated analogues whose j values are consistent with the conventional picture of a previous (<3 Gyr ago), close encounter (<100 kpc) of M33 about M31 results in a very low virial mass for M31 (˜1012 M⊙). This supports the new scenario put forth in Patel, Besla & Sohn, wherein M33 is on its first passage about M31 or on a long-period orbit. We conclude that this Bayesian inference scheme, utilizing satellite j, is a promising method to reduce the current factor of 2 spread in the mass range of the MW and M31. This method is easily adaptable to include additional satellites as new 6D
Energy Technology Data Exchange (ETDEWEB)
Sifon, Cristobal; Barrientos, L. Felipe; Gonzalez, Jorge; Infante, Leopoldo; Duenner, Rolando [Departamento de Astronomia y Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Menanteau, Felipe; Hughes, John P.; Baker, Andrew J. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Hasselfield, Matthew [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z4 (Canada); Marriage, Tobias A.; Crichton, Devin; Gralla, Megan B. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218-2686 (United States); Addison, Graeme E.; Dunkley, Joanna [Sub-department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Battaglia, Nick; Bond, J. Richard; Hajian, Amir [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada); Das, Sudeep [Berkeley Center for Cosmological Physics, LBL and Department of Physics, University of California, Berkeley, CA 94720 (United States); Devlin, Mark J. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Hilton, Matt [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); and others
2013-07-20
We present the first dynamical mass estimates and scaling relations for a sample of Sunyaev-Zel'dovich effect (SZE) selected galaxy clusters. The sample consists of 16 massive clusters detected with the Atacama Cosmology Telescope (ACT) over a 455 deg{sup 2} area of the southern sky. Deep multi-object spectroscopic observations were taken to secure intermediate-resolution (R {approx} 700-800) spectra and redshifts for Almost-Equal-To 60 member galaxies on average per cluster. The dynamical masses M{sub 200c} of the clusters have been calculated using simulation-based scaling relations between velocity dispersion and mass. The sample has a median redshift z = 0.50 and a median mass M{sub 200c}{approx_equal}12 Multiplication-Sign 10{sup 14} h{sub 70}{sup -1} M{sub sun} with a lower limit M{sub 200c}{approx_equal}6 Multiplication-Sign 10{sup 14} h{sub 70}{sup -1} M{sub sun}, consistent with the expectations for the ACT southern sky survey. These masses are compared to the ACT SZE properties of the sample, specifically, the match-filtered central SZE amplitude y{sub 0}-tilde, the central Compton parameter y{sub 0}, and the integrated Compton signal Y{sub 200c}, which we use to derive SZE-mass scaling relations. All SZE estimators correlate with dynamical mass with low intrinsic scatter ({approx}< 20%), in agreement with numerical simulations. We explore the effects of various systematic effects on these scaling relations, including the correlation between observables and the influence of dynamically disturbed clusters. Using the three-dimensional information available, we divide the sample into relaxed and disturbed clusters and find that {approx}50% of the clusters are disturbed. There are hints that disturbed systems might bias the scaling relations, but given the current sample sizes, these differences are not significant; further studies including more clusters are required to assess the impact of these clusters on the scaling relations.
Cosmological Black Holes on Branes
Rogatko, Marek
2003-01-01
We examined analytically a cosmological black hole domain wall system. Using the C-metric construction we derived the metric for the spacetime describing an infinitely thin domain wall intersecting a cosmological black hole. We studied the behaviour of the scalar field describing a self-interacting cosmological domain wall and find the approximated solution valid for large distances. The thin wall approximation and the back raection problem were elaborated finding that the topological kink so...
Gravitational Instantons and Cosmological Constant
Cyriac, Josily
2015-01-01
The cosmological dynamics of an otherwise empty universe in the presence of vacuum fields is considered. Quantum fluctuations at the Planck scale leads to a dynamical topology of space-time at very small length scales, which is dominated by compact gravitational instantons. The Planck scale vacuum energy acts as a source for the curvature of the these compact gravitational instantons and decouples from the large scale energy momentum tensor of the universe, thus making the observable cosmological constant vanish. However, a Euclidean functional integral over all possible topologies of the gravitational instantons generates a small non-zero value for the large scale cosmological constant, which agrees with the present observations.
Thermodynamics and Geometrothermodynamics of Charged black holes in Massive Gravity
Suresh, Jishnu; Prabhakar, Geethu; Kuriakose, V C
2016-01-01
The objective of this paper is to study the thermodynamics and thermodynamic geometry of charged de-Sitter and charged anti de-Sitter black hole solutions in massive gravity. In this study, the presence of a negative cosmological constant is identified as a thermodynamic variable, the pressure. By incorporating this idea, we study the effect of curvature parameter as well as the mass of graviton in the thermodynamics of the black hole system. We further extend our studies to different topology of the space time and its effects on phase transition and thermodynamics. In addition, the phase transition structure of the black hole and its interactions are reproduced using geometrothermodynamics.
Neutrinos in particle physics, astronomy, and cosmology
Xing, Zhi-Zhong
2011-01-01
""Neutrinos in Particle Physics, Astronomy and Cosmology"" provides a comprehensive and up-to-date introduction to neutrino physics, neutrino astronomy and neutrino cosmology. The intrinsic properties and fundamental interactions of neutrinos are described, as is the phenomenology of lepton flavor mixing, seesaw mechanisms and neutrino oscillations. The cosmic neutrino background, stellar neutrinos, supernova neutrinos and ultrahigh-energy cosmic neutrinos, together with the cosmological matter-antimatter asymmetry and other roles of massive neutrinos in cosmology, are discussed in detail. Thi
Solomon, Adam R
2015-01-01
The accelerating expansion of the Universe poses a major challenge to our understanding of fundamental physics. One promising avenue is to modify general relativity and obtain a new description of the gravitational force. Because gravitation dominates the other forces mostly on large scales, cosmological probes provide an ideal testing ground for theories of gravity. In this thesis, we describe two complementary approaches to the problem of testing gravity using cosmology. In the first part, we discuss the cosmological solutions of massive gravity and its generalisation to a bimetric theory. These theories describe a graviton with a small mass, and can potentially explain the late-time acceleration in a technically-natural way. We describe these self-accelerating solutions and investigate the cosmological perturbations in depth, beginning with an investigation of their linear stability, followed by the construction of a method for solving these perturbations in the quasistatic limit. This allows the predictio...
Bergshoeff, Eric; Hohm, Olaf; Merbis, Wout; Routh, Alasdair J.; Townsend, Paul K.
2014-01-01
We present an alternative to topologically massive gravity (TMG) with the same 'minimal' bulk properties; i.e. a single local degree of freedom that is realized as a massive graviton in linearization about an anti-de Sitter (AdS) vacuum. However, in contrast to TMG, the new 'minimal massive gravity'
Magnetic brane solutions in Gauss-Bonnet-Maxwell massive gravity
Hendi, Seyed Hossein; Eslam Panah, Behzad; Panahiyan, Shahram; Momennia, Mehrab
2017-09-01
Magnetic branes of Gauss-Bonnet-Maxwell theory in the context of massive gravity is studied in detail. Exact solutions are obtained and their interesting geometrical properties are investigated. It is argued that although these horizonless solutions are free of curvature singularity, they enjoy a cone-like geometry with a conic singularity. In order to investigate the effects of various parameters on the geometry of conic singularity, its corresponding deficit angle is studied. It will be shown that despite the effects of Gauss-Bonnet gravity on the solutions, deficit angle is free of Gauss-Bonnet parameter. On the other hand, the effects of massive gravity, cosmological constant and electrical charge on the deficit angle will be explored. Also, a brief discussion related to possible geometrical phase transition of these topological objects is given.
Tartaglia, Angelo
2015-01-01
Starting from some relevant facts concerning the behaviour of the universe over large scale and time span, the analogy between the geometric approach of General Relativ- ity and the classical description of an elastic strained material continuum is discussed. Extending the elastic deformation approach to four dimensions it is shown that the accelerated expansion of the universe is recovered. The strain field of space-time repro- duces properties similar to the ones ascribed to the dark energy currently called in to explain the accelerated expansion. The strain field in the primordial universe behaves as radiation, but asymptotically it reproduces the cosmological constant. Subjecting the theory to a number of cosmological tests confirms the soundness of the approach and gives an optimal value for the one parameter of the model, i.e. the bulk modulus of the space-time continuum. Finally various aspects of the Strained State Cosmology (SSC) are discussed and contrasted with some non-linear massive gravity theor...
Sabirli, Kivanc; Romer, A. K.; Davidson, M.; Stanford, S. A.; Viana, P. T.; Hilton, M.; Collins, C. A.; Kay, S. T.; Liddle, A. R.; Mann, R. G.; Miller, C. J.; Nichol, R. C.; West, M. J.; Conselice, C. J.; Spinrad, H.; Stern, D.; XCS Collaboration
2006-06-01
We report the discovery of the hottest cluster known at z > 1. It was identified as an extended X-ray source in the XMM Cluster Survey (XCS, Romer et al., 2001) and optical spectroscopy shows that 6 galaxies within a 60 arcsec diameter region lie at z = 1.45 ± 0.01. Hence its redshift is the highest currently known for a spectroscopically-confirmed cluster. Analysis of the X-ray spectra yields kT = 7.9+2.8-1.8 keV (90% confidence) and suggests that it is relatively massive for such a high redshift cluster.We acknowledge financial support from NASA grant NAG-11634 (AKR, RCN, KS, MD, PTPV), The Royal Astronomical Society's Hosie Request (MD, KS), PPARC (ARL, STK, RGM), the NASA XMM program (KS), the Institute of Astronomy at the University of Edinburgh (MD), Liverpool John Moores University (MH), Carnegie Mellon University (KS, AKR), and NSF grant AST-0205960 (MJW).
Oda, Ichiro
2016-01-01
We propose a topological model of induced gravity (pregeometry) where both Newton's coupling constant and the cosmological constant appear as integration constants in solving field equations. The matter sector of a scalar field is also considered, and by solving field equations it is shown that various types of cosmological solutions in the FRW universe can be obtained. A detailed analysis is given of the meaning of the BRST transformations, which make the induced gravity be a topological field theory, by means of the canonical quantization analysis, and the physical reason why such BRST transformations are needed in the present formalism is clarified. Finally, we propose a dynamical mechanism for fixing the Lagrange multiplier fields by following the Higgs mechanism. The present study clearly indicates that the induced gravity can be constructed at the classical level without recourse to quantum fluctuations of matter and suggests an interesting relationship between the induced gravity and the topological qu...
Simulating cosmologies beyond $\\Lambda$CDM with PINOCCHIO
Rizzo, Luca Alberto; Monaco, Pierluigi; Munari, Emiliano; Borgani, Stefano; Castorina, Emanuele; Sefusatti, Emiliano
2016-01-01
We present a method that extends the capabilities of the PINpointing Orbit-Crossing Collapsed HIerarchical Objects (PINOCCHIO) code, allowing it to generate accurate dark matter halo mock catalogues in cosmological models where the linear growth factor and the growth rate depend on scale. Such cosmologies comprise, among others, models with massive neutrinos and some classes of modified gravity theories. We validate the code by comparing the halo properties from PINOCCHIO against N-body simulations, focusing on cosmologies with massive neutrinos: $\
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.
Higher dimensional nonlinear massive gravity
Do, Tuan Q
2016-01-01
Inspired by a recent ghost-free nonlinear massive gravity in four-dimensional spacetime, we study its higher dimensional scenarios. As a result, we are able to show the constant-like behavior of massive graviton terms for some well-known metrics such as the Friedmann-Lemaitre-Robertson-Walker, Bianchi type I, and Schwarzschild-Tangherlini-(A)dS metrics in a specific five-dimensional nonlinear massive gravity under an assumption that its fiducial metrics are compatible with physical ones. In addition, some simple cosmological solutions of the five-dimensional massive gravity will be figured out consistently.
Massive Gravity in Three Dimensions
Bergshoeff, Eric A.; Hohm, Olaf; Townsend, Paul K.
2009-01-01
A particular higher-derivative extension of the Einstein-Hilbert action in three spacetime dimensions is shown to be equivalent at the linearized level to the (unitary) Pauli-Fierz action for a massive spin-2 field. A more general model, which also includes "topologically-massive" gravity as a speci
Energy Technology Data Exchange (ETDEWEB)
Lin, Chunshan
2013-11-25
In this Letter, we propose a massive gravity theory with 5 degrees of freedom. The mass term is constructed by 3 Stückelberg scalar fields, which respects SO(3) symmetry in the fields' configuration. By the analysis on the linear cosmological perturbations, we found that such 5 d.o.f. are free from ghost instability, gradient instability, and tachyonic instability.
Sanders, RH; Papantonopoulos, E
2005-01-01
I discuss the classical cosmological tests, i.e., angular size-redshift, flux-redshift, and galaxy number counts, in the light of the cosmology prescribed by the interpretation of the CMB anisotropies. The discussion is somewhat of a primer for physicists, with emphasis upon the possible systematic
Brandenberger, R H; Brandenberger, Robert H.; Magueijo, Joao
1999-01-01
We review a few off-the-beaten-track ideas in cosmology. They solve a variety of fundamental problems; also they are fun. We start with a description of non-singular dilaton cosmology. In these scenarios gravity is modified so that the Universe does not have a singular birth. We then present a variety of ideas mixing string theory and cosmology. These solve the cosmological problems usually solved by inflation, and furthermore shed light upon the issue of the number of dimensions of our Universe. We finally review several aspects of the varying speed of light theory. We show how the horizon, flatness, and cosmological constant problems may be solved in this scenario. We finally present a possible experimental test for a realization of this theory: a test in which the Supernovae results are to be combined with recent evidence for redshift dependence in the fine structure constant.
Topological gravity on plumbed V-cobordisms
Efremov, Vladimir N.; Mitskievich, Nikolai V.; Magdaleno, Alfonso M. Hernandez; Bautista, Ramona Serrano
2005-01-01
An ensemble of cosmological models based on generalized BF-theory is constructed where the role of vacuum (zero-level) coupling constants is played by topologically invariant rational intersection forms (cosmological-constant matrices) of 4-dimensional plumbed V-cobordisms which are interpreted as Euclidean spacetime regions. For these regions describing topology changes, the rational and integer intersection matrices are calculated. A relation is found between the hierarchy of certain elemen...
Energy Technology Data Exchange (ETDEWEB)
Moura-Melo, Winder A.; Panza, N.; Helayel Neto, J.A. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)
1998-12-01
An Abelian gauge model, with vector and 2-form potential; fields linked by a topological mass term that mixes the two Abelian factors, is shown to exhibit Dirac-like magnetic monopoles in the presence of a matter background. In addition, considering a 'non-minimal coupling' between the fermions and the tensor fields, we obtain a generalized quantisation condition that involves, among others, the mass parameter. Also, it is explicitly shown that 1{sub loop} (finite) corrections do no shift the value of such a mass parameter. (author)
Ryan, M.
1972-01-01
The study of cosmological models by means of equations of motion in Hamiltonian form is considered. Hamiltonian methods applied to gravity seem to go back to Rosenfeld (1930), who constructed a quantum-mechanical Hamiltonian for linearized general relativity theory. The first to notice that cosmologies provided a simple model in which to demonstrate features of Hamiltonian formulation was DeWitt (1967). Applications of the ADM formalism to homogeneous cosmologies are discussed together with applications of the Hamiltonian formulation, giving attention also to Bianchi-type universes. Problems involving the concept of superspace and techniques of quantization are investigated.
Gill, S P D; Gibson, B K; Flynn, C; Ibata, R A; Lewis, G F; Gill, Stuart P.D.; Knebe, Alexander; Gibson, Brad K.; Flynn, Chris; Ibata, Rodrigo A.; Lewis, Geraint F.
2002-01-01
An adaptive multi grid approach to simulating the formation of structure from collisionless dark matter is described. MLAPM (Multi-Level Adaptive Particle Mesh) is one of the most efficient serial codes available on the cosmological 'market' today. As part of Swinburne University's role in the development of the Square Kilometer Array, we are implementing hydrodynamics, feedback, and radiative transfer within the MLAPM adaptive mesh, in order to simulate baryonic processes relevant to the interstellar and intergalactic media at high redshift. We will outline our progress to date in applying the existing MLAPM to a study of the decay of satellite galaxies within massive host potentials.
Belinski, V
2009-01-01
The talk at international conference in honor of Ya. B. Zeldovich 95th Anniversary, Minsk, Belarus, April 2009. The talk represents a review of the old results and contemporary development on the problem of cosmological singularity.
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.
Gods as Topological Invariants
Schoch, Daniel
2012-01-01
We show that the number of gods in a universe must equal the Euler characteristics of its underlying manifold. By incorporating the classical cosmological argument for creation, this result builds a bridge between theology and physics and makes theism a testable hypothesis. Theological implications are profound since the theorem gives us new insights in the topological structure of heavens and hells. Recent astronomical observations can not reject theism, but data are slightly in favor of atheism.
Energy Technology Data Exchange (ETDEWEB)
Wesson, P.S.
1979-10-01
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: 8..pi..Gl/sup 2/ rho/c/sup 2/, 8..pi..Gl/sup 2/ rho/c/sup 4/, and 2 Gm/c/sup 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. (SC)
Dereli, T.; Yetişmişoğlu, C.
2016-06-01
We derive the field equations for topologically massive gravity coupled with the most general quadratic curvature terms using the language of exterior differential forms and a first-order constrained variational principle. We find variational field equations both in the presence and absence of torsion. We then show that spaces of constant negative curvature (i.e. the anti de-Sitter space AdS 3) and constant torsion provide exact solutions.
Standard Model Background of the Cosmological Collider
Chen, Xingang; Xianyu, Zhong-Zhi
2016-01-01
The inflationary universe can be viewed as a "Cosmological Collider" with energy of Hubble scale, producing very massive particles and recording their characteristic signals in primordial non-Gaussianities. To utilize this collider to explore any new physics at very high scales, it is a prerequisite to understand the background signals from the particle physics Standard Model. In this paper we describe the Standard Model background of the Cosmological Collider.
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...
Narimani, Ali; Scott, Douglas
2011-01-01
Although it is possible that some fundamental physical constants could vary in time, it is important to only consider dimensionless combinations, such as the fine structure constant or the equivalent coupling constant for gravity. Once all such dimensionless numbers have been given, then we can be sure that our cosmological picture is governed by the same physical laws as that of another civilization with an entirely different set of units. An additional feature of the standard model of cosmology raises an extra complication, namely that the epoch at which we live is a crucial part of the model. This can be defined by giving the value of any one of the evolving cosmological parameters. It takes some care to avoid inconsistent results for constraints on variable constants, which could be caused by effectively fixing more than one parameter today. We show examples of this effect by considering in some detail the physics of Big Bang nucleosynthesis, recombination and microwave background anisotropies, being care...
Interacting galaxies and cosmological parameters
Reboul, H
2006-01-01
We propose a (physical)-geometrical method to measure the present rates of the density cosmological parameters for a Friedmann-Lemaitre universe. The distribution of linear separations between two interacting galaxies,when both of them undergo a first massive starburst, is used as a standard of length. Statistical properties of the linear separations of such pairs of ``interactivated'' galaxies are estimated from the data in the Two Degree Field Galaxy Redshift Survey. Synthetic samples of interactivated pairs are generated with random orientations and a likely distribution of redshifts. The resolution of the inverse problem provides the probability densities of the retrieved cosmological parameters. The accuracies that can be achieved by that method on matter and cosmological constant densities parameters are computed depending on the size of ongoing real samples. Observational prospects are investigated as the foreseeable surface densities on the sky and magnitudes of those objects.
Particle Creation in Bouncing Cosmologies
Celani, Diogo C F; Vitenti, Sandro D P
2016-01-01
We investigate scalar particle creation in a set of bouncing models where the bounce occurs due to quantum cosmological effects described by the Wheeler-DeWitt equation. The scalar field can be either conformally or minimally coupled to gravity, and it can be massive or massless, without self interaction. The analysis is made for models containing a single radiation fluid, and for the more realistic case of models containing the usual observed radiation and dust fluids, which can fit most of the observed features of our Universe, including an almost scale invariant power spectrum of scalar cosmological perturbations. In the conformal coupling case, the particle production is negligible. In the minimal coupling case, for massive particles, the results point to the same physical conclusion within observational constraints: particle production is most important at the bounce energy scale, and it is not sensitive neither to its mass nor whether there is dust in the background model. The only caveat is the case wh...
Noether Symmetry Approach in Gauss-Bonnet Cosmology
Capozziello, Salvatore; Odintsov, Sergei D
2014-01-01
We discuss the Noether Symmetry Approach in the framework of Gauss-Bonnet cosmology showing that the functional form of the $F(R, {\\cal G})$ function, where $R$ is the Ricci scalar and ${\\cal G}$ is the Gauss-Bonnet topological invariant, can be determined by the presence of symmetries. Besides, the method allows to find out exact solutions due to the reduction of cosmological dynamical system and the presence of conserved quantities. Some specific cosmological models are worked out
Kiselev, V V
2012-01-01
A huge value of cosmological constant characteristic for the particle physics and the inflation of early Universe are inherently related to each other: one can construct a fine-tuned superpotential, which produces a flat potential of inflaton with a constant density of energy V=\\Lambda^4 after taking into account for leading effects due to the supergravity, so that an introduction of small quantum loop-corrections to parameters of this superpotential naturally results in the dynamical instability relaxing the primary cosmological constant by means of inflationary regime. The model phenomenologically agrees with observational data on the large scale structure of Universe at \\Lambda~10^{16} GeV.
Cosmological solution moduli of bigravity
Energy Technology Data Exchange (ETDEWEB)
Yılmaz, Nejat Tevfik [Department of Electrical and Electronics Engineering, Yaşar University,Selçuk Yaşar Kampüsü, Üniversite Caddesi,No. 35-37, AğaçlıYol, 35100, Bornova, İzmir (Turkey)
2015-09-29
We construct the complete set of metric-configuration solutions of the ghost-free massive bigravity for the scenario in which the g−metric is the Friedmann-Lemaitre-Robertson-Walker (FLRW) one, and the interaction Lagrangian between the two metrics contributes an effective ideal fluid energy-momentum tensor to the g-metric equations. This set corresponds to the exact background cosmological solution space of the theory.
Isotropic cosmological singularities other matter models
Tod, K P
2003-01-01
Isotropic cosmological singularities are singularities which can be removed by rescaling the metric. In some cases already studied (gr-qc/9903008, gr-qc/9903009, gr-qc/9903018) existence and uniqueness of cosmological models with data at the singularity has been established. These were cosmologies with, as source, either perfect fluids with linear equations of state or massless, collisionless particles. In this article we consider how to extend these results to a variety of other matter models. These are scalar fields, massive collisionless matter, the Yang-Mills plasma of Choquet-Bruhat, or matter satisfying the Einstein-Boltzmann equation.
Plionis, M.
2004-07-01
The recent scientific efforts in Astrophysics & Cosmology have brought a revolution to our understanding of the Cosmos. Amazing results is the outcome of amazing experiments! The huge scientific, technological & financial effort that has gone into building the 10-m class telescopes as well as many space and balloon observatories, essential to observe the multitude of cosmic phenomena in their manifestations at different wavelengths, from gamma-rays to the millimetre and the radio, has given and is still giving its fruits of knowledge. These recent scientific achievements in Observational and Theoretical Cosmology were presented in the "Multiwavelength Cosmology" conference that took place on beautiful Mykonos island in the Aegean between 17 and 20 June 2003. More than 180 Cosmologists from all over the world gathered for a four-day intense meeting in which recent results from large ground based surveys (AAT/2-df, SLOAN) and space missions (WMAP, Chandra, XMM, ISO, HST) were presented and debated, providing a huge impetus to our knowledge of the Cosmos. The future of the subject (experiments, and directions of research) was also discussed. The conference was devoted mostly on the constraints on Cosmological models and galaxy formation theories that arise from the study of the high redshift Universe, from clusters of galaxies, and their evolution, from the cosmic microwave background, the large-scale structure and star-formation history. Link: http://www.wkap.nl/prod/b/1-4020-1971-8
Marsh, David J E
2015-01-01
Axions comprise a broad class of particles that can play a major role in explaining the unknown aspects of cosmology. They are also extraordinarily well-motivated within high energy physics, and so axion cosmology offers us a unique view onto these theories. I present a comprehensive and pedagogical view on the cosmology and astrophysics of axion-like particles, starting from inflation and progressing via the CMB and structure formation up to the present-day Universe. I briefly review the motivation and models for axions in particle physics and string theory. The primary focus is on the population of ultralight axions created via vacuum realignment, and its role as a dark matter (DM) candidate with distinctive phenomenology. Cosmological observations place robust constraints on the axion mass and relic density in this scenario, and I review where such constraints come from. I next cover aspects of galaxy formation with axion DM, and ways this can be used to further search for evidence of axions. An absolute l...
Bianchi-IX string cosmological model in Lyra geometry
Indian Academy of Sciences (India)
F Rahaman; S Chakraborty; N Begum; M Hossain; M Kalam
2003-06-01
A class of cosmological solutions of massive strings for the Bianchi-IX space-time are obtained within the framework of Lyra geometry. Various physical and kinematical properties of the models are discussed.
National Research Council Canada - National Science Library
de Rham, Claudia
2014-01-01
We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali–Gabadadze–Porrati model (DGP...
Bojowald, Martin
The universe, ultimately, is to be described by quantum theory. Quantum aspects of all there is, including space and time, may not be significant for many purposes, but are crucial for some. And so a quantum description of cosmology is required for a complete and consistent worldview. At any rate, even if we were not directly interested in regimes where quantum cosmology plays a role, a complete physical description could not stop at a stage before the whole universe is reached. Quantum theory is essential in the microphysics of particles, atoms, molecules, solids, white dwarfs and neutron stars. Why should one expect this ladder of scales to end at a certain size? If regimes are sufficiently violent and energetic, quantum effects are non-negligible even on scales of the whole cosmos; this is realized at least once in the history of the universe: at the big bang where the classical theory of general relativity would make energy densities diverge. 1.Lachieze-Rey, M., Luminet, J.P.: Phys. Rept. 254,135 (1995), gr-qc/9605010 2.BSDeWitt1967Phys. Rev.160511131967PhRv..160.1113D0158.4650410.1103/PhysRev.160.1113DeWitt, B.S.: Phys. Rev. 160(5), 1113 (1967) 3.Wiltshire, D.L.: In: Robson B., Visvanathan N., Woolcock W.S. (eds.) Cosmology: The Physics of the Universe, pp. 473-531. World Scientific, Singapore (1996). gr-qc/0101003 4.Isham C.J.: In: DeWitt, B.S., Stora, R. (eds.) Relativity, Groups and Topology II. Lectures Given at the 1983 Les Houches Summer School on Relativity, Groups and Topology, Elsevier Science Publishing Company (1986) 5.Klauder, J.: Int. J. Mod. Phys. D 12, 1769 (2003), gr-qc/0305067 6.Klauder, J.: Int. J. Geom. Meth. Mod. Phys. 3, 81 (2006), gr-qc/0507113 7.DGiulini1995Phys. Rev. D5110563013381161995PhRvD..51.5630G10.1103/PhysRevD.51.5630Giulini, D.: Phys. Rev. D 51(10), 5630 (1995) 8.Kiefer, C., Zeh, H.D.: Phys. Rev. D 51, 4145 (1995), gr-qc/9402036 9.WFBlythCJIsham1975Phys. Rev. D117684086991975PhRvD..11..768B10.1103/PhysRevD.11.768Blyth, W
Modern Gravitational Lens Cosmology for Introductory Physics and Astronomy Students
Huwe, Paul; Field, Scott
2015-01-01
Recent and exciting discoveries in astronomy and cosmology have inspired many high school students to learn about these fields. A particularly fascinating consequence of general relativity at the forefront of modern cosmology research is gravitational lensing, the bending of light rays that pass near massive objects. Gravitational lensing enables…
Cosmological tests of modified gravity
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 Λ 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.
Cosmological tests of modified gravity.
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.
Bothun, Greg
2011-10-01
Ever since Aristotle placed us, with certainty, in the Center of the Cosmos, Cosmological models have more or less operated from a position of known truths for some time. As early as 1963, for instance, it was ``known'' that the Universe had to be 15-17 billion years old due to the suspected ages of globular clusters. For many years, attempts to determine the expansion age of the Universe (the inverse of the Hubble constant) were done against this preconceived and biased notion. Not surprisingly when more precise observations indicated a Hubble expansion age of 11-13 billion years, stellar models suddenly changed to produce a new age for globular cluster stars, consistent with 11-13 billion years. Then in 1980, to solve a variety of standard big bang problems, inflation was introduced in a fairly ad hoc manner. Inflation makes the simple prediction that the net curvature of spacetime is zero (i.e. spacetime is flat). The consequence of introducing inflation is now the necessary existence of a dark matter dominated Universe since the known baryonic material could comprise no more than 1% of the necessary energy density to make spacetime flat. As a result of this new cosmological ``truth'' a significant world wide effort was launched to detect the dark matter (which obviously also has particle physics implications). To date, no such cosmological component has been detected. Moreover, all available dynamical inferences of the mass density of the Universe showed in to be about 20% of that required for closure. This again was inconsistent with the truth that the real density of the Universe was the closure density (e.g. Omega = 1), that the observations were biased, and that 99% of the mass density had to be in the form of dark matter. That is, we know the universe is two component -- baryons and dark matter. Another prevailing cosmological truth during this time was that all the baryonic matter was known to be in galaxies that populated our galaxy catalogs. Subsequent
Marsh, David J. E.
2016-07-01
Axions comprise a broad class of particles that can play a major role in explaining the unknown aspects of cosmology. They are also well-motivated within high energy physics, appearing in theories related to CP-violation in the standard model, supersymmetric theories, and theories with extra-dimensions, including string theory, and so axion cosmology offers us a unique view onto these theories. I review the motivation and models for axions in particle physics and string theory. I then present a comprehensive and pedagogical view on the cosmology and astrophysics of axion-like particles, starting from inflation and progressing via BBN, the CMB, reionization and structure formation, up to the present-day Universe. Topics covered include: axion dark matter (DM); direct and indirect detection of axions, reviewing existing and future experiments; axions as dark radiation; axions and the cosmological constant problem; decays of heavy axions; axions and stellar astrophysics; black hole superradiance; axions and astrophysical magnetic fields; axion inflation, and axion DM as an indirect probe of inflation. A major focus is on the population of ultralight axions created via vacuum realignment, and its role as a DM candidate with distinctive phenomenology. Cosmological observations place robust constraints on the axion mass and relic density in this scenario, and I review where such constraints come from. I next cover aspects of galaxy formation with axion DM, and ways this can be used to further search for evidence of axions. An absolute lower bound on DM particle mass is established. It is ma > 10-24eV from linear observables, extending to ma ≳ 10-22eV from non-linear observables, and has the potential to reach ma ≳ 10-18eV in the future. These bounds are weaker if the axion is not all of the DM, giving rise to limits on the relic density at low mass. This leads to the exciting possibility that the effects of axion DM on structure formation could one day be detected
GAMMA-RAY BURSTS, NEW COSMOLOGICAL BEACONS
Directory of Open Access Journals (Sweden)
V. Avila-Reese
2009-01-01
Full Text Available Long Gamma-Ray Bursts (GRBs are the brightest electromagnetic explosions in the Universe, associated to the death of massive stars. As such, GRBs are potential tracers of the evolution of the cosmic massive star formation, metallicity, and Initial Mass Function. GRBs also proved to be appealing cosmological distance indicators. This opens a unique opportunity to constrain the cosmic expansion history up to redshifts 5-6. A brief review on both subjects is presented here.
Gauge Invariance for the Massive Axion
Arias, P J; Arias, Pio Jose; Khoudeir, Adel
1997-01-01
A massive gauge invariant formulation for scalar ($\\phi$) and antisymmetric ($C_{mnp}$) fields with a topological coupling, which provides a mass for the axion field, is considered. The dual and local equivalence with the non-gauge invariant proposal is established, but on manifolds with non-trivial topological structure both formulations are not globally equivalent.
Neves, J C S
2015-01-01
In the Nietzschean philosophy, the concept of force from physics is important to build one of its main concepts: the will to power. The concept of force, which Nietzsche found out in the Classical Mechanics, almost disappears in the physics of the XX century with the Quantum Field Theory and General Relativity. Is the Nietzschean world as contending forces, a Dionysian cosmology, possible in the current science?
Alvarez, Enrique
1985-01-01
Some cosmological consequences of the assumption that superstrings are more fundamental objects than ordinary local quantum fields are examined. We study, in particular, the dependence of both the string tension and the temperature of the primordial string soup on cosmic time. A particular scenario is proposed in which the universe undergoes a contracting ``string phase'' before the ordinary ``big bang,'' which according to this picture is nothing but the outcome of the transition from nonlocal to local fundamental physics.
Grant, E.; Murdin, P.
2000-11-01
During the early Middle Ages (ca 500 to ca 1130) scholars with an interest in cosmology had little useful and dependable literature. They relied heavily on a partial Latin translation of PLATO's Timaeus by Chalcidius (4th century AD), and on a series of encyclopedic treatises associated with the names of Pliny the Elder (ca AD 23-79), Seneca (4 BC-AD 65), Macrobius (fl 5th century AD), Martianus ...
Brax, Philippe
2016-01-01
We investigate scalar-tensor theories where matter couples to the scalar field via a kinetically dependent conformal coupling. These models can be seen as the low-energy description of invariant field theories under a global Abelian symmetry. The scalar field is then identified with the Goldstone mode of the broken symmetry. It turns out that the properties of these models are very similar to the ones of ultralocal theories where the scalar-field value is directly determined by the local matter density. This leads to a complete screening of the fifth force in the Solar System and between compact objects, through the ultralocal screening mechanism. On the other hand, the fifth force can have large effects in extended structures with large-scale density gradients, such as galactic halos. Interestingly, it can either amplify or damp Newtonian gravity, depending on the model parameters. We also study the background cosmology and the linear cosmological perturbations. The background cosmology is hardly different f...
Minimal theory of massive gravity
De Felice, Antonio
2016-01-01
We propose a new theory of massive gravity with only two propagating degrees of freedom. After defining the theory in the unitary gauge in the vielbein language, we shall perform a Hamiltonian analysis to count the number of physical degrees of freedom, and then study some phenomenologies. While the homogeneous and isotropic background cosmology and the tensor linear perturbations around it are described by exactly the same equations as those in the de Rham - Gabadadze - Tolley (dRGT) massive gravity, the scalar and vector gravitational degrees of freedom are absent in the new theory at the fully nonlinear level. Hence the new theory provides a stable nonlinear completion of the self-accelerating cosmological solution that was originally found in the dRGT theory.
Causality in 3D Massive Gravity Theories
Edelstein, Jose D; Kilicarslan, Ercan; Leoni, Matias; Tekin, Bayram
2016-01-01
We study the constraints coming from local causality requirement in various 2+1 dimensional dynamical theories of gravity. In Topologically Massive Gravity, with a single parity noninvariant massive degree of freedom, and in New Massive Gravity, with two massive spin-$2$ degrees of freedom, causality and unitarity are compatible with each other and they both require the Newton's constant to be negative. In their extensions, such as the Born-Infeld gravity and the minimal massive gravity the situation is similar and quite different from their higher dimensional counterparts, such as quadratic (e.g., Einstein-Gauss-Bonnet) or cubic theories, where causality and unitarity are in conflict.
Nonlinear field space cosmology
Mielczarek, Jakub; Trześniewski, Tomasz
2017-08-01
We consider the FRW cosmological model in which the matter content of the Universe (playing the role of an inflaton or quintessence) is given by a novel generalization of the massive scalar field. The latter is a scalar version of the recently introduced nonlinear field space theory, where the physical phase space of a given field is assumed to be compactified at large energies. For our analysis, we choose the simple case of a field with the spherical phase space and endow it with the generalized Hamiltonian analogous to the XXZ Heisenberg model, normally describing a system of spins in condensed matter physics. Subsequently, we study both the homogenous cosmological sector and linear perturbations of such a test field. In the homogenous sector, we find that nonlinearity of the field phase space is becoming relevant for large volumes of the Universe and can lead to a recollapse, and possibly also at very high energies, leading to the phase of a bounce. Quantization of the field is performed in the limit where the nontrivial nature of its phase space can be neglected, while there is a nonvanishing contribution from the Lorentz symmetry breaking term of the Hamiltonian. As a result, in the leading order of the XXZ anisotropy parameter, we find that the inflationary spectral index remains unmodified with respect to the standard case but the total amplitude of perturbations is subject to a correction. The Bunch-Davies vacuum state also becomes appropriately corrected. The proposed new approach is bringing cosmology and condensed matter physics closer together, which may turn out to be beneficial for both disciplines.
Moffat, J W
2016-01-01
An alternative to the postulate of dark energy required to explain the accelerated expansion of the universe is to adopt an inhomogeneous cosmological model to explain the supernovae data without dark energy. We adopt a void cosmology model, based on the inhomogeneous Lema\\^{i}tre-Tolman-Bondi solution of Einstein's field equations. The model can resolve observational anomalies in the $\\Lambda CDM$ model, such as the discrepancy between the locally measured value of the Hubble constant, $H_0=73.24\\pm 1.74\\,{\\rm km}\\,{\\rm s}^{-1}\\,{\\rm Mpc}^{-1}$, and the $H_0=66.93\\pm 0.62\\,{\\rm km}\\,{\\rm s}^{-1}\\,{\\rm Mpc}^{-1}$ determined by the Planck satellite data and the $\\Lambda CDM$ model, and the lithium $^{7}{\\rm Li}$ problem, which is a $5\\sigma$ mismatch between the theoretical prediction for the $^{7}{\\rm Li}$ from big bang nucleosynthesis and the value that we observe locally today at $z=0$. The void model can also resolve the tension between the number of massive clusters derived from the Sunyaev-Zel'dovich eff...
Topological Defects in the Cosmos and Lab
Vachaspati, T
1998-01-01
Current theories of particle physics lead to the unavoidable conclusion that there must have been several phase transitions in the early universe. Further, in the context of these theories, it is possible that cosmological phase transitions would have produced topological defects that may be roaming our heavens today. A finding of these fossils from the early universe would provide a direct confirmation of the thermal history of the cosmos, insight into astrophysical phenomena, and, vital information about particle physics. The elimination of unobserved topological defects provides important constraints on particle physics and may also suggest novel cosmology. I describe some of the research on cosmic topological defects and recent efforts to address cosmological issues in condensed matter systems. (Invited article for publication in Contemporary Physics.)
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.
Boeyens, Jan CA
2010-01-01
The composition of the most remote objects brought into view by the Hubble telescope can no longer be reconciled with the nucleogenesis of standard cosmology and the alternative explanation, in terms of the LAMBDA-Cold-Dark-Matter model, has no recognizable chemical basis. A more rational scheme, based on the chemistry and periodicity of atomic matter, opens up an exciting new interpretation of the cosmos in terms of projective geometry and general relativity. The response of atomic structure to environmental pressure predicts non-Doppler cosmical redshifts and equilibrium nucleogenesis by alp
Bojowald, Martin
1999-01-01
A complete model of the universe needs at least three parts: (1) a complete set of physical variables and dynamical laws for them, (2) the correct solution of the dynamical laws, and (3) the connection with conscious experience. In quantum cosmology, item (2) is the quantum state of the cosmos. Hartle and Hawking have made the `no-boundary' proposal, that the wavefunction of the universe is given by a path integral over all compact Euclidean 4-dimensional geometries and matter fields that hav...
Fabris, J C; Rodrigues, D C; Batista, C E M; Daouda, M H
2012-01-01
We review the difficulties of the generalized Chaplygin gas model to fit observational data, due to the tension between background and perturbative tests. We argue that such issues may be circumvented by means of a self-interacting scalar field representation of the model. However, this proposal seems to be successful only if the self-interacting scalar field has a non-canonical form. The latter can be implemented in Rastall's theory of gravity, which is based on a modification of the usual matter conservation law. We show that, besides its application to the generalized Chaplygin gas model, other cosmological models based on Rastall's theory have many interesting and unexpected new features.
Cosmological experiments in superfluid helium?
Zurek, W. H.
1985-10-01
Symmetry breaking phase transitions occurring in the early Universe are expected to leave behind long-lived topologically stabel structures such as monopoles, strings or domain walls. The author discusses the analogy between cosmological strings and vortex lines in the superfluid, and suggests a cryogenic experiment which tests key elements of the cosmological scenario for string formation. In a superfluid obtained through a rapid pressure quench, the phase of the Bose condensate wavefunction - the 4He analogue of the broken symmetry of the field-theoretic vacuum - will be chosen randomly in domains of some characteristic size d. When the quench is performed in an annulus of circumference C the typical value of the phase mismatch around the loop will be ≡(C/d)1/2. The resulting phase gradient can be sufficiently large to cause the superfluid to flow with a measurable, randomly directed velocity.
Phantom stars and topology change
DeBenedictis, Andrew; Lobo, Francisco S N
2008-01-01
In this work, we consider time-dependent dark energy star models, with an evolving parameter $\\omega$ crossing the phantom divide, $\\omega=-1$. Once in the phantom regime, the null energy condition is violated, which physically implies that the negative radial pressure exceeds the energy density. Therefore, an enormous negative pressure in the center may, in principle, imply a topology change, consequently opening up a tunnel and converting the dark energy star into a wormhole. The criteria for this topology change are discussed, in particular, we consider the Morse Index analysis and a Casimir energy approach involving quasi-local energy difference calculations that may reflect or measure the occurrence of a topology change. We denote these exotic geometries consisting of dark energy stars (in the phantom regime) and phantom wormholes as phantom stars. The final product of this topological change, namely, phantom wormholes, have far-reaching physical and cosmological implications, as in addition to being use...
Livio, Mario; Villaver, Eva
2009-11-01
Participants; Preface Mario Livio and Eva Villaver; 1. High-mass star formation by gravitational collapse of massive cores M. R. Krumholz; 2. Observations of massive star formation N. A. Patel; 3. Massive star formation in the Galactic center D. F. Figer; 4. An X-ray tour of massive star-forming regions with Chandra L. K. Townsley; 5. Massive stars: feedback effects in the local universe M. S. Oey and C. J. Clarke; 6. The initial mass function in clusters B. G. Elmegreen; 7. Massive stars and star clusters in the Antennae galaxies B. C. Whitmore; 8. On the binarity of Eta Carinae T. R. Gull; 9. Parameters and winds of hot massive stars R. P. Kudritzki and M. A. Urbaneja; 10. Unraveling the Galaxy to find the first stars J. Tumlinson; 11. Optically observable zero-age main-sequence O stars N. R. Walborn; 12. Metallicity-dependent Wolf-Raynet winds P. A. Crowther; 13. Eruptive mass loss in very massive stars and Population III stars N. Smith; 14. From progenitor to afterlife R. A. Chevalier; 15. Pair-production supernovae: theory and observation E. Scannapieco; 16. Cosmic infrared background and Population III: an overview A. Kashlinsky.
Moving mesh cosmology: tracing cosmological gas accretion
Nelson, Dylan; Genel, Shy; Sijacki, Debora; Keres, Dusan; Springel, Volker; Hernquist, Lars; 10.1093/mnras/sts595
2013-01-01
We investigate the nature of gas accretion onto haloes and galaxies at z=2 using cosmological hydrodynamic simulations run with the moving mesh code AREPO. Implementing a Monte Carlo tracer particle scheme to determine the origin and thermodynamic history of accreting gas, we make quantitative comparisons to an otherwise identical simulation run with the smoothed particle hydrodynamics (SPH) code GADGET-3. Contrasting these two numerical approaches, we find significant physical differences in the thermodynamic history of accreted gas in haloes above 10^10.5 solar masses. In agreement with previous work, GADGET simulations show a cold fraction near unity for galaxies forming in massive haloes, implying that only a small percentage of accreted gas heats to an appreciable fraction of the virial temperature during accretion. The same galaxies in AREPO show a much lower cold fraction, <20% in haloes above 10^11 solar masses. This results from a hot gas accretion rate which, at this same halo mass, is an order o...
Coasting cosmologies with time dependent cosmological constant
Pimentel, L O; Pimentel, Luis O.
1999-01-01
The effect of a time dependent cosmological constant is considered in a family of scalar tensor theories. Friedmann-Robertson-Walker cosmological models for vacumm and perfect fluid matter are found. They have a linear expansion factor, the so called coasting cosmology, the gravitational "constant" decreace inversely with time; this model satisfy the Dirac hipotesis. The cosmological "constant" decreace inversely with the square of time, therefore we can have a very small value for it at present time.
2013-01-01
The chapter provides an introduction to the basic concepts of Algebraic Topology with an emphasis on motivation from applications in the physical sciences. It finishes with a brief review of computational work in algebraic topology, including persistent homology.
Hinterbichler, Kurt; Levy, Aaron; Matas, Andrew
2011-01-01
The symmetron is a scalar field associated with the dark sector whose coupling to matter depends on the ambient matter density. The symmetron is decoupled and screened in regions of high density, thereby satisfying local constraints from tests of gravity, but couples with gravitational strength in regions of low density, such as the cosmos. In this paper we derive the cosmological expansion history in the presence of a symmetron field, tracking the evolution through the inflationary, radiation- and matter-dominated epochs, using a combination of analytical approximations and numerical integration. For a broad range of initial conditions at the onset of inflation, the scalar field reaches its symmetry-breaking vacuum by the present epoch, as assumed in the local analysis of spherically-symmetric solutions and tests of gravity. For the simplest form of the potential, the energy scale is too small for the symmetron to act as dark energy, hence we must add a cosmological constant to drive late-time cosmic acceler...
Agarwal, Nishant; Khoury, Justin; Trodden, Mark
2009-01-01
We develop a fully covariant, well-posed 5D effective action for the 6D cascading gravity brane-world model, and use this to study cosmological solutions. We obtain this effective action through the 6D decoupling limit, in which an additional scalar degree mode, \\pi, called the brane-bending mode, determines the bulk-brane gravitational interaction. The 5D action obtained this way inherits from the sixth dimension an extra \\pi self-interaction kinetic term. We compute appropriate boundary terms, to supplement the 5D action, and hence derive fully covariant junction conditions and the 5D Einstein field equations. Using these, we derive the cosmological evolution induced on a 3-brane moving in a static bulk. We study the strong- and weak-coupling regimes analytically in this static ansatz, and perform a complete numerical analysis of our solution. Although the cascading model can generate an accelerating solution in which the \\pi field comes to dominate at late times, the presence of a critical singularity prev...
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Chimento, L P; Forte, M [Physics Department, UBA, 1428 Buenos Aires (Argentina); Devecchi, F P; Kremer, G M; Ribas, M O; Samojeden, L L, E-mail: kremer@fisica.ufpr.br, E-mail: devecchi@fisica.ufpr.br, E-mail: chimento@df.uba.ar [Physics Department, UFPR, 81531-990 Curitiba (Brazil)
2011-07-08
In this work we review if fermionic sources could be responsible for accelerated periods during the evolution of a FRW universe. In a first attempt, besides the fermionic source, a matter constituent would answer for the decelerated periods. The coupled differential equations that emerge from the field equations are integrated numerically. The self-interaction potential of the fermionic field is considered as a function of the scalar and pseudo-scalar invariants. It is shown that the fermionic field could behave like an inflaton field in the early universe, giving place to a transition to a matter dominated (decelerated) period. In a second formulation we turn our attention to analytical results, specifically using the idea of form-invariance transformations. These transformations can be used for obtaining accelerated cosmologies starting with conventional cosmological models. Here we reconsider the scalar field case and extend the discussion to fermionic fields. Finally we investigate the role of a Dirac field in a Brans-Dicke (BD) context. The results show that this source, in combination with the BD scalar, promote a final eternal accelerated era, after a matter dominated period.
Newtonian cosmology - Problems of cosmological didactics
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Skarzynski, E.
1983-03-01
The article presents different methods of model construction in Newtonian cosmology. Newtonian cosmology is very convenient for discussion of local problems, so the problems presented are of great didactic importance. The constant k receives a new interpretation in relativistic cosmology as the curvature of the space in consequence of the greater informational capacity of Riemann space in comparison to Euclidean space. 11 references.
Topological gravity on plumbed V-cobordisms
Efremov, V N; Magdaleno, A M H; Bautista, R S; Efremov, Vladimir N.; Mitskievich, Nikolai V.; Magdaleno, Alfonso M. Hernandez; Bautista, Ramona Serrano
2005-01-01
An ensemble of cosmological models based on generalized BF-theory is constructed where the role of vacuum (zero-level) coupling constants is played by topologically invariant rational intersection forms (cosmological-constant matrices) of 4-dimensional plumbed V-cobordisms which are interpreted as Euclidean spacetime regions. For these regions describing topology changes, the rational and integer intersection matrices are calculated. A relation is found between the hierarchy of certain elements of these matrices and the hierarchy of coupling constants of the universal (low-energy) interactions. PACS numbers: 0420G, 0240, 0460
Topological gravity on plumbed V-cobordisms
Energy Technology Data Exchange (ETDEWEB)
Efremov, Vladimir N [Mathematics Department, CUCEI, University of Guadalajara, Guadalajara (Mexico); Mitskievich, Nikolai V [Physics Department, CUCEI, University of Guadalajara, Guadalajara (Mexico); Magdaleno, Alfonso M Hernandez [Physics Department, CUCEI, University of Guadalajara, Guadalajara (Mexico); Bautista, Ramona Serrano [Mathematics Department, CUCEI, University of Guadalajara, Guadalajara (Mexico)
2005-09-07
An ensemble of cosmological models based on generalized BF-theory is constructed where the role of vacuum (zero-level) coupling constants is played by topologically invariant rational intersection forms (cosmological-constant matrices) of four-dimensional plumbed V-cobordisms which are interpreted as Euclidean spacetime regions. For these regions describing topology changes, the rational and integer intersection matrices are calculated. A relation is found between the hierarchy of certain elements of these matrices and the hierarchy of coupling constants of the universal (low-energy) interactions.
Shifted Riccati procedure: Application to conformal barotropic FRW cosmologies
Rosu, H C
2010-01-01
In the case of barotropic FRW cosmologies, the Hubble parameter is the solution of a simple Riccati equation of constant coefficients. We therefore consider these cosmologies in the framework of nonrelativistic supersymmetry that has been so effective in the area of supersymmetric quantum mechanics. Recalling that in 1999 Faraoni showed how to reduce the barotropic FRW system of differential equations to simple harmonic oscillator differential equations, we set the latter equations in the supersymmetric approach and divide their solutions into two classes of `bosonic' (nonsingular) and `fermionic' (singular) cosmological zero-mode solutions. The fermionic equations can be considered as representing cosmologies of Stephani type, i.e., of topology changing in the conformal time. We next apply the so-called shifted Riccati procedure by introducing a constant parameter, denoted by S, in the common Riccati solution of these supersymmetric partner cosmologies and obtain barotropic Stephani cosmologies with periodic...
Dubovsky, Sergei L.
2004-10-01
We systematically study the most general Lorentz-violating graviton mass invariant under three-dimensional Eucledian group. We find that at general values of mass parameters the massive graviton has six propagating degrees of freedom, and some of them are ghosts or lead to rapid classical instabilities. However, there is a number of different regions in the mass parameter space where massive gravity is described by a consistent low-energy effective theory with cutoff ~ (mMPl)1/2. This theory is free of rapid instabilities and vDVZ discontinuity. Each of these regions is characterized by certain fine-tuning relations between mass parameters, generalizing the Fierz Pauli condition. In some cases the required fine-tunings are consequences of the existence of the subgroups of the diffeomorphism group that are left unbroken by the graviton mass. We found two new cases, when the resulting theories have a property of UV insensitivity, i.e. remain well behaved after inclusion of arbitrary higher dimension operators without assuming any fine-tunings among the coefficients of these operators, besides those enforced by the symmetries. These theories can be thought of as generalizations of the ghost condensate model with a smaller residual symmetry group. We briefly discuss what kind of cosmology can one expect in massive gravity and argue that the allowed values of the graviton mass may be quite large, affecting growth of primordial perturbations, structure formation and, perhaps, enhancing the backreaction of inhomogeneities on the expansion rate of the Universe.
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.
Negative Energy Cosmology and the Cosmological Constant
Prokopec, Tomislav
2011-01-01
It is well known that string theories naturally compactify on anti-de Sitter spaces, and yet cosmological observations show no evidence of a negative cosmological constant in the early Universe's evolution. In this letter we present two simple nonlocal modifications of the standard Friedmann cosmology that can lead to observationally viable cosmologies with an initial (negative) cosmological constant. The nonlocal operators we include are toy models for the quantum cosmological backreaction. In Model I an initial quasiperiodic oscillatory epoch is followed by inflation and a late time matter era, representing a dark matter candidate. The backreaction in Model II quickly compensates the negative cosmological term such that the Ricci curvature scalar rapidly approaches zero, and the Universe ends up in a late time radiation era.
Boguna, Marian; Krioukov, Dmitri
2013-01-01
Networks often represent systems that do not have a long history of studies in traditional fields of physics, albeit there are some notable exceptions such as energy landscapes and quantum gravity. Here we consider networks that naturally arise in cosmology. Nodes in these networks are stationary observers uniformly distributed in an expanding open FLRW universe with any scale factor, and two observers are connected if one can causally influence the other. We show that these networks are growing Lorentz-invariant graphs with power-law distributions of node degrees. New links in these networks not only connect new nodes to existing ones, but also appear at a certain rate between existing nodes, as they do in many complex networks.
Topologically Induced Chaos in the Open Universe
Tomaschitz, R
1994-01-01
An elementary account on chaos, its origins, and its physical impact in an infinite and multiply connected space-time is given. The anisotropy of the microwave background and the violation of the space-reflection symmetry (parity) by topological self-interference are reviewed in this context. Keywords: Robertson-Walker cosmology, relativistic chaos, chaotic nucleus, center of the Universe, CP violation, self-interference, background radiation, anisotropy, particle creation, hyperbolic manifold, deformation space, topology change, Kleinian group, limit set, mixing, shadowing.
Quantum Corrections in Massive Gravity
de Rham, Claudia; Ribeiro, Raquel H
2013-01-01
We compute the one-loop quantum corrections to the potential of ghost-free massive gravity. We show how the mass of external matter fields contribute to the running of the cosmological constant, but do not change the ghost-free structure of the massive gravity potential at one-loop. When considering gravitons running in the loops, we show how the structure of the potential gets destabilized at the quantum level, but in a way which would never involve a ghost with a mass smaller than the Planck scale. This is done by explicitly computing the one-loop effective action and supplementing it with the Vainshtein mechanism. We conclude that to one-loop order the special mass structure of ghost-free massive gravity is technically natural.
Quantum corrections in massive gravity
de Rham, Claudia; Heisenberg, Lavinia; Ribeiro, Raquel H.
2013-10-01
We compute the one-loop quantum corrections to the potential of ghost-free massive gravity. We show how the mass of external matter fields contributes to the running of the cosmological constant, but does not change the ghost-free structure of the massive gravity potential at one-loop. When considering gravitons running in the loops, we show how the structure of the potential gets destabilized at the quantum level, but in a way which would never involve a ghost with a mass smaller than the Planck scale. This is done by explicitly computing the one-loop effective action and supplementing it with the Vainshtein mechanism. We conclude that to one-loop order the special mass structure of ghost-free massive gravity is technically natural.
Horizon Run 3: Topology as a Standard Ruler
Speare, Robert; Kim, Juhan; Park, Changbom
2013-01-01
We study the Physically Self Bound Cold Dark Matter Halo distribution which we associate with the massive galaxies within the Horizon Run 3 to estimate the accuracy in determination of the cosmological distance scale measured by the topology analysis. We apply the routine "Contour 3D" to 108 Mock Survey of $\\pi$ steradians out to redshift z = 0.6, which effectively correspond to the SDSS-III BOSS survey, and compare the topology with that of a Gaussian Random Phase Field. We find that given three separate smoothing lengths $\\lambda =$ 15, 21, and 34 $h^{-1}{\\rm Mpc}$, the least $\\chi^2$ fit genus per unit volume g yields a 1.7 % fractional uncertainty in smoothing length and angular diameter distance to $z = 0.6$. This is an improvement upon former calibrations of and presents a competitive error estimate with next BAO scale techniques. We also present three dimensional graphics of the Horizon Run 3 spherical mock survey to show a wealth of large-scale structures of the universe that are predicted in surveys ...
HORIZON RUN 3: TOPOLOGY AS A STANDARD RULER
Energy Technology Data Exchange (ETDEWEB)
Speare, Robert [New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi (United Arab Emirates); Gott, J. Richard [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544-1001 (United States); Kim, Juhan [Center for Advanced Computation, Korea Institute for Advanced Study, Heogiro 85, Seoul 130-722 (Korea, Republic of); Park, Changbom, E-mail: robert.speare@nyu.edu, E-mail: kjhan@kias.re.kr [School of Physics, Korea Institute for Advanced Study, Heogiro 85, Seoul 130-722 (Korea, Republic of)
2015-02-01
We study the physically self-bound cold dark matter halo distribution, which we associate with the massive galaxies within Horizon Run 3, to estimate the accuracy of the determination of the cosmological distance scale measured by the topology analysis. We apply the routine '''Contour 3D''' to the 108 Mock Survey of π steradians out to redshift z = 0.6, which effectively corresponds to the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) survey, and compare the topology with that of a Gaussian random phase field. We find that given three separate smoothing lengths λ = 15, 21, and 34 h {sup –1} Mpc, the least χ{sup 2} fit genus per unit volume (g) yields a 1.7% fractional uncertainty in smoothing length and angular diameter distance to z = 0.6. This is an improvement on former calibrations and presents an error estimate competitive with baryon acoustic oscillation scale techniques. We also present three-dimensional graphics of the Horizon Run 3 spherical mock survey to show a wealth of large-scale structures of the universe that are expected for surveys like BOSS.
Vankov, A
1998-01-01
The suggested alternative cosmology is based on the idea of barion symmetric universe, in which our home universe is a representative of multitude of typical matter and antimatter universes. This alternative concept gives a physically reasonable explanation of all major problems of the Standard Cosmological Model. Classification Code MSC: Cosmology 524.8 Key words: standard cosmological model, alternative cosmology, barionic symmetry, typical universe, quasars, cosmic rays.
Particle propagation in cosmological backgrounds
Arteaga, Daniel
2007-01-01
We study the quantum propagation of particles in cosmological backgrounds, by considering a doublet of massive scalar fields propagating in an expanding universe, possibly filled with radiation. We focus on the dissipative effects related to the expansion rate. At first order, we recover the expected result that the decay rate is determined by the local temperature. Beyond linear order, the decay rate has an additional contribution governed by the expansion parameter. This latter contribution is present even for stable particles in the vacuum. Finally, we analyze the long time behaviour of the propagator and briefly discuss applications to the trans-Planckian question.
SIMP (Strongly Interacting Massive Particle) Search
Teplitz, V L; Olness, F I; Stroynowski, R; Teplitz, Vigdor L.; Mohapatra, Rabindra N.; Olness, Fred; Stroynowski, Ryszard
2000-01-01
We consider laboratory experiments that can detect stable, neutral stronglyinteracting massive particles (SIMPs). We explore the SIMP annihilation crosssection from its minimum value (restricted by cosmological bounds) to the barnrange, and vary the mass values from a GeV to a TeV. We also consider the prospects and problems of detecting such particles at theTevatron.
Hamiltonian analysis of BHT massive gravity
Blagojević, M
2010-01-01
We study the Hamiltonian structure of the Bergshoeff-Hohm-Townsend (BHT) massive gravity with a cosmological constant. In the space of coupling constants $(\\Lambda_0,m^2)$, our canonical analysis reveals the special role of the condition $\\Lambda_0/m^2\
Topological insulators and topological superconductors
Bernevig, Andrei B
2013-01-01
This graduate-level textbook is the first pedagogical synthesis of the field of topological insulators and superconductors, one of the most exciting areas of research in condensed matter physics. Presenting the latest developments, while providing all the calculations necessary for a self-contained and complete description of the discipline, it is ideal for graduate students and researchers preparing to work in this area, and it will be an essential reference both within and outside the classroom. The book begins with simple concepts such as Berry phases, Dirac fermions, Hall conductance and its link to topology, and the Hofstadter problem of lattice electrons in a magnetic field. It moves on to explain topological phases of matter such as Chern insulators, two- and three-dimensional topological insulators, and Majorana p-wave wires. Additionally, the book covers zero modes on vortices in topological superconductors, time-reversal topological superconductors, and topological responses/field theory and topolo...
BRS structure of simple model of cosmological constant and cosmology
Mori, Taisaku; Nitta, Daisuke; Nojiri, Shin'ichi
2017-07-01
In Mod. Phys. Lett. A 31, 1650213 (2016, 10.1142/S0217732316502138), Nojiri proposed a simple model in order to solve one of the problems related to the cosmological constant. The model is induced from a topological field theory, and the model has an infinite number of BRS symmetries. The BRS symmetries are, in general, spontaneously broken, however. We investigate the BRS symmetry in detail and show that there is one and only one BRS symmetry which is not broken, and the unitarity can be guaranteed. In the model, the quantum problem of the vacuum energy, which may be identified with the cosmological constant, reduces to the classical problem of the initial condition. We investigate the cosmology given by the model and specify the region of the initial conditions, which could be consistent with the evolution of the Universe. We also show that there is a stable solution describing the de Sitter space-time, which may explain the accelerating expansion in the current Universe.
Topological Methods for Visualization
Energy Technology Data Exchange (ETDEWEB)
Berres, Anne Sabine [Los Alamos National Lab. (LANL), Los Alamos, NM (United Stat
2016-04-07
This slide presentation describes basic topological concepts, including topological spaces, homeomorphisms, homotopy, betti numbers. Scalar field topology explores finding topological features and scalar field visualization, and vector field topology explores finding topological features and vector field visualization.
Bell Violation in Primordial Cosmology
Directory of Open Access Journals (Sweden)
Sayantan Choudhury
2017-02-01
Full Text Available In this paper, we have worked on the possibility of setting up an Bell’s inequality violating experiment in the context of primordial cosmology following the fundamental principles of quantum mechanics. To set up this proposal, we have introduced a model-independent theoretical framework using which we have studied the creation of new massive particles for the scalar fluctuations in the presence of an additional time-dependent mass parameter. Next we explicitly computed the one-point and two-point correlation functions from this setup. Then, we comment on the measurement techniques of isospin breaking interactions of newly introduced massive particles and its further prospects. After that, we give an example of the string theory-originated axion monodromy model in this context. Finally, we provide a bound on the heavy particle mass parameter for any arbitrary spin field.
Nieto, Carlos M.; Rodríguez, Yeinzon
2016-06-01
Gauge-flation model at zeroth-order in cosmological perturbation theory offers an interesting scenario for realizing inflation within a particle physics context, allowing us to investigate interesting possible connections between inflation and the subsequent evolution of the Universe. Difficulties, however, arise at the perturbative level, thus motivating a modification of the original model. In order to agree with the latest Planck observations, we modify the model such that the new dynamics can produce a relation between the spectral index ns and the tensor-to-scalar ratio r allowed by the data. By including an identical mass term for each of the fields of the system, we find interesting dynamics leading to slow-roll inflation of the right length. The presence of the mass term has the potential to modify the ns versus r relation so as to agree with the data. As a first step, we study the model at zeroth-order in cosmological perturbation theory, finding the conditions required for slow-roll inflation and the number of e-foldings of inflation. Numerical solutions are used to explore the impact of the mass term. We conclude that the massive version of gauge-flation offers a viable inflationary model.
Degravitation of the Cosmological Constant in Bigravity
Platscher, Moritz
2016-01-01
In this article the phenomenon of degravitation of the cosmological constant is studied in the framework of bigravity. It is demonstrated that despite a sizable value of the cosmological constant its gravitational effect can be only mild. The bigravity framework is chosen for this demonstration as it leads to a consistent, ghost-free theory of massive gravity. We show that degravitation takes place in the limit where the physical graviton is dominantly a gauge invariant metric combination. We present and discuss several phenomenological consequences expected in this regime.
Goodman, Sue E
2009-01-01
Beginning Topology is designed to give undergraduate students a broad notion of the scope of topology in areas of point-set, geometric, combinatorial, differential, and algebraic topology, including an introduction to knot theory. A primary goal is to expose students to some recent research and to get them actively involved in learning. Exercises and open-ended projects are placed throughout the text, making it adaptable to seminar-style classes. The book starts with a chapter introducing the basic concepts of point-set topology, with examples chosen to captivate students' imaginations while i
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Weinstein, M
2003-11-19
This paper discusses the problem of inflation in the context of Friedmann-Robertson-Walker Cosmology. We show how, after a simple change of variables, one can quantize the problem in a way which parallels the classical discussion. The result is that two of the Einstein equations arise as exact equations of motion; one of the usual Einstein equations (suitably quantized) survives as a constraint equation to be imposed on the space of physical states. However, the Friedmann equation, which is also a constraint equation and which is the basis of the Wheeler-DeWitt equation, acquires a welcome quantum correction that becomes significant for small scale factors. We then discuss the extension of this result to a full quantum mechanical derivation of the anisotropy ({delta}{rho}/{rho}) in the cosmic microwave background radiation and the possibility that the extra term in the Friedmann equation could have observable consequences. Finally, we suggest interesting ways in which these techniques can be generalized to cast light on the question of chaotic or eternal inflation. In particular, we suggest that one can put an experimental bound on how far away a universe with a scale factor very different from our own must be, by looking at its effects on our CMB radiation.
Aref'eva, I. Ya.; Volovich, I. V.
2011-08-01
Classical versions of the Big Bang cosmological models of the universe contain a singularity at the start of time, hence the time variable in the field equations should run over a half-line. Nonlocal string field theory equations with infinite number of derivatives are considered and an important difference between nonlocal operators on the whole real line and on a half-line is pointed out. We use the heat equation method and show that on the half-line in addition to the usual initial data a new arbitrary function (external source) occurs that we call the daemon function. The daemon function governs the evolution of the universe similar to Maxwell's demon in thermodynamics. The universe and multiverse are open systems interacting with the daemon environment. In the simplest case the nonlocal scalar field reduces to the usual local scalar field coupled with an external source which is discussed in the stochastic approach to inflation. The daemon source can help to get the chaotic inflation scenario with a small scalar field.
Tipler, Frank J.
1996-09-01
I show that if Newtonian gravity is formulated in geometrical language, then Newtonian cosmology is as rigorous as relativistic cosmology. In homogeneous and isotropic universes, the geodesic deviation equation in Newtonian cosmology is proven to be exactly the same as the geodesic deviation equation in relativistic Friedmann cosmologies. This equation can be integrated to yield a constraint equation formally identical to the Friedmann equation. However, Newtonian cosmology is more general than Friedmann cosmology: by generalizing the flat-space Newtonian gravity force law to Riemannian metrics, I show that ever-expanding and recollapsing universes are allowed in any homogeneous and isotropic spatial geometry.
P-V criticality in the extended phase space of black holes in massive gravity
Xu, Jianfei; Hu, Ya-Peng
2015-01-01
We study the P-V criticality and phase transition in the extended phase space of charged anti-de Sitter black holes in canonical ensemble of ghost-free massive gravity, where the cosmological constant is viewed as a dynamical pressure of the black hole system. We give the generalized thermodynamic first law and the Smarr relation with massive gravity correction. We find that not only when the horizon topology is spherical but also in the Ricci flat or hyperbolic case, there appear the P-V criticality and phase transition up to the combination k+c02c2m2 in the four-dimensional case, where k characterizes the horizon curvature and c2m2 is the coefficient of the second term of massive potential associated with the graviton mass. The positivity of such combination indicate the van der Waals-like phase transition. When the spacetime dimension is larger then four, the Maxwell charge there seems unnecessary for the appearance of critical behavior, but a infinite repulsion effect needed, which can also be realized th...
Cosmology and astrophysics from relaxed galaxy clusters - II. Cosmological constraints
Mantz, A. B.; Allen, S. W.; Morris, R. G.; Rapetti, D. A.; Applegate, D. E.; Kelly, P. L.; von der Linden, A.; Schmidt, R. W.
2014-05-01
This is the second in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. The data set employed here consists of Chandra observations of 40 such clusters, identified in a comprehensive search of the Chandra archive for hot (kT ≳ 5 keV), massive, morphologically relaxed systems, as well as high-quality weak gravitational lensing data for a subset of these clusters. Here we present cosmological constraints from measurements of the gas mass fraction, fgas, for this cluster sample. By incorporating a robust gravitational lensing calibration of the X-ray mass estimates, and restricting our measurements to the most self-similar and accurately measured regions of clusters, we significantly reduce systematic uncertainties compared to previous work. Our data for the first time constrain the intrinsic scatter in fgas, 7.4 ± 2.3 per cent in a spherical shell at radii 0.8-1.2 r2500 (˜1/4 of the virial radius), consistent with the expected level of variation in gas depletion and non-thermal pressure for relaxed clusters. From the lowest redshift data in our sample, five clusters at z 1, we obtain consistent results for Ωm and interesting constraints on dark energy: Ω _{{Λ }}=0.65^{+0.17}_{-0.22}> for non-flat ΛCDM (cosmological constant) models, and w = -0.98 ± 0.26 for flat models with a constant dark energy equation of state. Our results are both competitive and consistent with those from recent cosmic microwave background, Type Ia supernova and baryon acoustic oscillation data. We present constraints on more complex models of evolving dark energy from the combination of fgas data with these external data sets, and comment on the possibilities for improved fgas constraints using current and next-generation X-ray observatories and lensing data.
Energy Technology Data Exchange (ETDEWEB)
Schramm, D.N.
1992-03-01
The cosmological dark matter problem is reviewed. The Big Bang Nucleosynthesis constraints on the baryon density are compared with the densities implied by visible matter, dark halos, dynamics of clusters, gravitational lenses, large-scale velocity flows, and the {Omega} = 1 flatness/inflation argument. It is shown that (1) the majority of baryons are dark; and (2) non-baryonic dark matter is probably required on large scales. It is also noted that halo dark matter could be either baryonic or non-baryonic. Descrimination between ``cold`` and ``hot`` non-baryonic candidates is shown to depend on the assumed ``seeds`` that stimulate structure formation. Gaussian density fluctuations, such as those induced by quantum fluctuations, favor cold dark matter, whereas topological defects such as strings, textures or domain walls may work equally or better with hot dark matter. A possible connection between cold dark matter, globular cluster ages and the Hubble constant is mentioned. Recent large-scale structure measurements, coupled with microwave anisotropy limits, are shown to raise some questions for the previously favored density fluctuation picture. Accelerator and underground limits on dark matter candidates are also reviewed.
Energy Technology Data Exchange (ETDEWEB)
Schramm, D.N.
1992-03-01
The cosmological dark matter problem is reviewed. The Big Bang Nucleosynthesis constraints on the baryon density are compared with the densities implied by visible matter, dark halos, dynamics of clusters, gravitational lenses, large-scale velocity flows, and the {Omega} = 1 flatness/inflation argument. It is shown that (1) the majority of baryons are dark; and (2) non-baryonic dark matter is probably required on large scales. It is also noted that halo dark matter could be either baryonic or non-baryonic. Descrimination between cold'' and hot'' non-baryonic candidates is shown to depend on the assumed seeds'' that stimulate structure formation. Gaussian density fluctuations, such as those induced by quantum fluctuations, favor cold dark matter, whereas topological defects such as strings, textures or domain walls may work equally or better with hot dark matter. A possible connection between cold dark matter, globular cluster ages and the Hubble constant is mentioned. Recent large-scale structure measurements, coupled with microwave anisotropy limits, are shown to raise some questions for the previously favored density fluctuation picture. Accelerator and underground limits on dark matter candidates are also reviewed.
Evolving extrinsic curvature and the cosmological constant problem
Capistrano, Abraão J. S.; Cabral, Luis A.
2016-10-01
The concept of smooth deformation of Riemannian manifolds associated with the extrinsic curvature is explained and applied to the Friedmann-Lemaître-Robertson-Walker cosmology. We show that such deformation can be derived from the Einstein-Hilbert-like dynamical principle may produce an observable effect in the sense of Noether. As a result, we show how the extrinsic curvature compensates both quantitative and qualitative differences between the cosmological constant Λ and the vacuum energy {ρ }{vac} obtaining the observed upper bound for the cosmological constant problem at electroweak scale. The topological characteristics of the extrinsic curvature are discussed showing that the produced extrinsic scalar curvature is an evolving dynamical quantity.
Nojiri, S; Oikonomou, V K
2016-01-01
We combine the unimodular gravity and mimetic gravity theories into a unified theoretical framework, which is proposed to solve the cosmological constant problem and the dark matter issue. After providing the formulation of the unimodular mimetic gravity and investigating all the new features that the vacuum unimodular gravity implies, by using the underlying reconstruction method, we realize some well known cosmological evolutions, with some of these being exotic for the ordinary Einstein-Hilbert gravity. Specifically we provide the vacuum unimodular mimetic gravity description of the de Sitter cosmology, of the perfect fluid with constant equation of state cosmology, of the Type IV singular cosmology and of the $R^2$ inflation cosmology. Moreover, we investigate how cosmologically viable cosmologies, which are compatible with the recent observational data, can be realized by the vacuum unimodular mimetic gravity. Since in some cases, the graceful exit from inflation problem might exist, we provide a qualita...
Kunze, Kerstin E
2016-01-01
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.
A general theory of linear cosmological perturbations: bimetric theories
Lagos, Macarena
2016-01-01
We implement the method developed in [1] to construct the most general parametrised action for linear cosmological perturbations of bimetric theories of gravity. Specifically, we consider perturbations around a homogeneous and isotropic background, and identify the complete form of the action invariant under diffeomorphism transformations, as well as the number of free parameters characterising this cosmological class of theories. We discuss, in detail, the case without derivative interactions, and compare our results with those found in massive bigravity.
Rainbow metric from quantum gravity: anisotropic cosmology
Assanioussi, Mehdi
2016-01-01
In this paper we present a construction of effective cosmological models which describe the propagation of a massive quantum scalar field on a quantum anisotropic cosmological spacetime. Each obtained effective model is represented by a rainbow metric in which particles of distinct momenta propagate on different classical geometries. Our analysis shows that upon certain assumptions and conditions on the parameters determining such anisotropic models, we surprisingly obtain a unique deformation parameter $\\beta$ in the modified dispersion relation of the modes. Hence inducing an isotropic deformation despite the general starting considerations. We then ensure the recovery of the dispersion relation realized in the isotropic case, studied in [arXiv:1412.6000], when some proper symmetry constraints are imposed, and we estimate the value of the deformation parameter for this case in loop quantum cosmology context.
Rainbow metric from quantum gravity: Anisotropic cosmology
Assanioussi, Mehdi; Dapor, Andrea
2017-03-01
In this paper we present a construction of effective cosmological models which describe the propagation of a massive quantum scalar field on a quantum anisotropic cosmological spacetime. Each obtained effective model is represented by a rainbow metric in which particles of distinct momenta propagate on different classical geometries. Our analysis shows that upon certain assumptions and conditions on the parameters determining such anisotropic models, we surprisingly obtain a unique deformation parameter β in the modified dispersion relation of the modes, hence, inducing an isotropic deformation despite the general starting considerations. We then ensure the recovery of the dispersion relation realized in the isotropic case, studied in [M. Assanioussi, A. Dapor, and J. Lewandowski, Phys. Lett. B 751, 302 (2015), 10.1016/j.physletb.2015.10.043], when some proper symmetry constraints are imposed, and we estimate the value of the deformation parameter for this case in loop quantum cosmology context.
Cosmological constraints on superconducting dark energy models
Keresztes, Zoltán; Harko, Tiberiu; Liang, Shi-Dong
2015-01-01
We consider cosmological tests of a scalar-vector-tensor gravitational model, in which the dark energy is included in the total action through a gauge invariant, electromagnetic type contribution. The ground state of dark energy, corresponding to a constant potential $V$ is a Bose-Einstein type condensate with spontaneously broken U(1) symmetry. In another words dark energy appears as a massive vector field emerging from a superposition of a massless vector and a scalar field, the latter corresponding to the Goldstone boson. Two particular cosmological models, corresponding to pure electric and pure magnetic type potentials, respectively are confronted with Type IA Supernovae and Hubble parameter data. In the electric case good fit is obtained along a narrow inclined stripe in the $\\Omega _{m}-\\Omega _{V}$ parameter plane, which includes the $\\Lambda $CDM limit. The other points on this admissible region represent superconducting dark energy as a sum of a cosmological constant and a time-evolving contribution...
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.
Gasperini, Maurizio
2011-03-01
Preface; Acknowledgements; Notation, units and conventions; 1. A short review of standard and inflationary cosmology; 2. The basic string cosmology equations; 3. Conformal invariance and string effective action; 4. Duality symmetries and cosmological solutions; 5. Inflationary kinematics; 6. The string phase; 7. The cosmic background of relic gravitational waves; 8. Scalar perturbations and the anisotropy of the CMB radiation; 9. Dilaton phenomenology; 10. Elements of brane cosmology; Index.
Strong cosmic censorship for T^2-symmetric cosmological spacetimes with collisionless matter
Dafermos, M; Dafermos, Mihalis; Rendall, Alan D.
2006-01-01
We prove strong cosmic censorship for T^2-symmetric cosmological spacetimes (with spatial topology T^3 and vanishing cosmological constant Lambda) with collisionless matter. Gowdy symmetric spacetimes constitute a special case. The formulation of the conjecture is in terms of generic C^2-inextendibility of the metric. Our argument exploits a rigidity property of Cauchy horizons, inherited from Killing fields.
Indian Academy of Sciences (India)
Tarun Sandeep
2004-10-01
Cosmology is passing through a golden phase of rapid advance. The cosmology workshop at ICGC-2004 attracted a large number of research contributions to diverse topics of cosmology. I attempt to classify and summarize the research work and results of the oral and poster presentations made at the meeting.
Disney, M J
2000-01-01
It is argued that some of the recent claims for cosmology are grossly overblown. Cosmology rests on a very small database: it suffers from many fundamental difficulties as a science (if it is a science at all) whilst observations of distant phenomena are difficult to make and harder to interpret. It is suggested that cosmological inferences should be tentatively made and sceptically received.
Chiral heterotic strings with positive cosmological constant
Florakis, Ioannis; Rizos, John
2016-12-01
We present explicit examples of semi-realistic heterotic models with spontaneously broken supersymmetry, which dynamically lead to breaking scales much smaller than MPlanck and exponentially small positive values for the cosmological constant. Contrary to field theoretic intuition, we find that the global structure of the effective potential is significantly affected by contributions of massive and non-level matched string states and we investigate the conditions that dynamically ensure a number of desired properties.
Chiral Heterotic Strings with Positive Cosmological Constant
Florakis, Ioannis
2016-01-01
We present explicit examples of semi-realistic heterotic models with spontaneously broken supersymmetry, which dynamically lead to breaking scales much smaller than $M_{\\rm Planck}$ and exponentially small positive values for the cosmological constant. Contrary to field theoretic intuition, we find that the global structure of the effective potential is significantly affected by contributions of massive and non-level matched string states and we investigate the conditions that dynamically ensure a number of desired properties.
Neutrino masses in astrophysics and cosmology
Energy Technology Data Exchange (ETDEWEB)
Raffelt, G.G. [Max-Planck-Institut fuer Physik, Muenchen (Germany)
1996-11-01
Astrophysical and cosmological arguments and observations give us the most restrictive constraints on neutrino masses, electromagnetic couplings, and other properties. Conversely, massive neutrinos would contribute to the cosmic dark-matter density and would play an important role for the formation of structure in the universe. Neutrino oscillations may well solve the solar neutrino problem, and can have a significant impact on supernova physics. (author) 14 figs., tabs., 33 refs.
Particle creation in bouncing cosmologies
Celani, Diogo C. F.; Pinto-Neto, Nelson; Vitenti, Sandro D. P.
2017-01-01
We investigate scalar particle creation in a set of bouncing models where the bounce occurs due to quantum cosmological effects described by the Wheeler-DeWitt equation. The scalar field can be either conformally or minimally coupled to gravity, and it can be massive or massless, without self-interaction. The analysis is made for models containing a single radiation fluid and for the more realistic case of models containing the usual observed radiation and dust fluids, which can fit most of the observed features of our universe, including an almost scale invariant power spectrum of scalar cosmological perturbations. In the conformal coupling case, the particle production is negligible. In the minimal coupling case, for massive particles, the results point to the same physical conclusion within observational constraints: particle production is most important at the bounce energy scale, and it is not sensitive either to its mass or to whether there is dust in the background model. The only caveat is the case where the particle mass is larger than the bounce energy scale. On the other hand, the energy density of produced massive particles depend on their masses and the energy scale of the bounce. For very large masses and deep bounces, this energy density may overcome that of the background. In the case of massless particles, the energy density of produced particles can become comparable to the background energy density only for bounces occurring at energy scales comparable to the Planck scale or above, which lies beyond the scope of this paper: we expect that the simple Wheeler-DeWitt approach we are using should be valid only at scales a few orders of magnitude below the Planck energy. Nevertheless, in the case in which dust is present, there is an infrared divergence, which becomes important only for scales much larger than today's Hubble radius.
Effective equations for isotropic quantum cosmology including matter
Bojowald, Martin; Skirzewski, Aureliano
2007-01-01
Effective equations often provide powerful tools to develop a systematic understanding of detailed properties of a quantum system. This is especially helpful in quantum cosmology where several conceptual and technical difficulties associated with the full quantum equations can be avoided in this way. Here, effective equations for Wheeler-DeWitt and loop quantizations of spatially flat, isotropic cosmological models sourced by a massive or interacting scalar are derived and studied. The resulting systems are remarkably different from that given for a free, massless scalar. This has implications for the coherence of evolving states and the realization of a bounce in loop quantum cosmology.
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
Buchstaber, Victor M
2015-01-01
This book is about toric topology, a new area of mathematics that emerged at the end of the 1990s on the border of equivariant topology, algebraic and symplectic geometry, combinatorics, and commutative algebra. It has quickly grown into a very active area with many links to other areas of mathematics, and continues to attract experts from different fields. The key players in toric topology are moment-angle manifolds, a class of manifolds with torus actions defined in combinatorial terms. Construction of moment-angle manifolds relates to combinatorial geometry and algebraic geometry of toric v
Directory of Open Access Journals (Sweden)
Pąk Karol
2015-02-01
Full Text Available Let us recall that a topological space M is a topological manifold if M is second-countable Hausdorff and locally Euclidean, i.e. each point has a neighborhood that is homeomorphic to an open ball of E n for some n. However, if we would like to consider a topological manifold with a boundary, we have to extend this definition. Therefore, we introduce here the concept of a locally Euclidean space that covers both cases (with and without a boundary, i.e. where each point has a neighborhood that is homeomorphic to a closed ball of En for some n.
Franz, Marcel
2013-01-01
Topological Insulators, volume six in the Contemporary Concepts of Condensed Matter Series, describes the recent revolution in condensed matter physics that occurred in our understanding of crystalline solids. The book chronicles the work done worldwide that led to these discoveries and provides the reader with a comprehensive overview of the field. Starting in 2004, theorists began to explore the effect of topology on the physics of band insulators, a field previously considered well understood. However, the inclusion of topology brings key new elements into this old field. Whereas it was
Warner, S
1989-01-01
Aimed at those acquainted with basic point-set topology and algebra, this text goes up to the frontiers of current research in topological fields (more precisely, topological rings that algebraically are fields).The reader is given enough background to tackle the current literature without undue additional preparation. Many results not in the text (and many illustrations by example of theorems in the text) are included among the exercises. Sufficient hints for the solution of the exercises are offered so that solving them does not become a major research effort for the reader. A comprehensive bibliography completes the volume.
Tseytlin, Arkady A
1992-01-01
Aspects of string cosmology for critical and non-critical strings are discussed emphasizing the necessity to account for the dilaton dynamics for a proper incorporation of ``large - small" duality. This drastically modifies the intuition one has with Einstein's gravity. For example winding modes, even though contribute to energy density, oppose expansion and if not annihilated will stop the expansion. Moreover we find that the radiation dominated era of the standard cosmology emerges quite naturally in string cosmology. Our analysis of non-critical string cosmology provides a reinterpretation of the (universal cover of the) recently studied two dimensional black hole solution as a conformal realization of cosmological solutions found previously by Mueller.
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.
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...
Mukherjee, Amiya
2015-01-01
This book presents a systematic and comprehensive account of the theory of differentiable manifolds and provides the necessary background for the use of fundamental differential topology tools. The text includes, in particular, the earlier works of Stephen Smale, for which he was awarded the Fields Medal. Explicitly, the topics covered are Thom transversality, Morse theory, theory of handle presentation, h-cobordism theorem, and the generalised Poincaré conjecture. The material is the outcome of lectures and seminars on various aspects of differentiable manifolds and differential topology given over the years at the Indian Statistical Institute in Calcutta, and at other universities throughout India. The book will appeal to graduate students and researchers interested in these topics. An elementary knowledge of linear algebra, general topology, multivariate calculus, analysis, and algebraic topology is recommended.
Tunelling with a negative cosmological constant
Gibbons, G W
1996-01-01
The point of this paper is see what light new results in hyperbolic geometry may throw on gravitational entropy and whether gravitational entropy is relevant for the quantum origin of the univeres. We introduce some new gravitational instantons which mediate the birth from nothing of closed universes containing wormholes and suggest that they may contribute to the density matrix of the universe. We also discuss the connection between their gravitational action and the topological and volumetric entropies introduced in hyperbolic geometry. These coincide for hyperbolic 4-manifolds, and increase with increasing topological complexity of the four manifold. We raise the questions of whether the action also increases with the topological complexity of the initial 3-geometry, measured either by its three volume or its Matveev complexity. We point out, in distinction to the non-supergravity case, that universes with domains of negative cosmological constant separated by supergravity domain walls cannot be born from ...
Condensed matter analogues of cosmology
Kibble, Tom; Srivastava, Ajit
2013-10-01
It is always exciting when developments in one branch of physics turn out to have relevance in a quite different branch. It would be hard to find two branches farther apart in terms of energy scales than early-universe cosmology and low-temperature condensed matter physics. Nevertheless ideas about the formation of topological defects during rapid phase transitions that originated in the context of the very early universe have proved remarkably fruitful when applied to a variety of condensed matter systems. The mathematical frameworks for describing these systems can be very similar. This interconnection has led to a deeper understanding of the phenomena in condensed matter systems utilizing ideas from cosmology. At the same time, one can view these condensed matter analogues as providing, at least in a limited sense, experimental access to the phenomena of the early universe for which no direct probe is possible. As this special issue well illustrates, this remains a dynamic and exciting field. The basic idea is that when a system goes through a rapid symmetry-breaking phase transition from a symmetric phase into one with spontaneously broken symmetry, the order parameter may make different choices in different regions, creating domains that when they meet can trap defects. The scale of those domains, and hence the density of defects, is constrained by the rate at which the system goes through the transition and the speed with which order parameter information propagates. This is what has come to be known as the Kibble-Zurek mechanism. The resultant scaling laws have now been tested in a considerable variety of different systems. The earliest experiments illustrating the analogy between cosmology and condensed matter were in liquid crystals, in particular on the isotropic-to-nematic transition, primarily because it is very easy to induce the phase transition (typically at room temperature) and to image precisely what is going on. This field remains one of the
A Topological Analysis of Large-Scale Structure, Studied Using the CMASS Sample of SDSS-III
Parihar, Prachi; Vogeley, Michael S.; Gott, J. Richard, III; Choi, Yun-Young; Kim, Juhan; Kim, Sungsoo S.; Speare, Robert; Brownstein, Joel R.; Brinkmann, J.
2014-12-01
We study the three-dimensional genus topology of large-scale structure using the northern region of the CMASS Data Release 10 (DR10) sample of the SDSS-III Baryon Oscillation Spectroscopic Survey. We select galaxies with redshift 0.452 z 1011.56 M ⊙. We study the topology at two smoothing lengths: R G = 21 h -1 Mpc and R G = 34 h -1 Mpc. The genus topology studied at the R G = 21 h -1 Mpc scale results in the highest genus amplitude observed to date. The CMASS sample yields a genus curve that is characteristic of one produced by Gaussian random phase initial conditions. The data thus support the standard model of inflation where random quantum fluctuations in the early universe produced Gaussian random phase initial conditions. Modest deviations in the observed genus from random phase are as expected from shot noise effects and the nonlinear evolution of structure. We suggest the use of a fitting formula motivated by perturbation theory to characterize the shift and asymmetries in the observed genus curve with a single parameter. We construct 54 mock SDSS CMASS surveys along the past light cone from the Horizon Run 3 (HR3) N-body simulations, where gravitationally bound dark matter subhalos are identified as the sites of galaxy formation. We study the genus topology of the HR3 mock surveys with the same geometry and sampling density as the observational sample and find the observed genus topology to be consistent with ΛCDM as simulated by the HR3 mock samples. We conclude that the topology of the large-scale structure in the SDSS CMASS sample is consistent with cosmological models having primordial Gaussian density fluctuations growing in accordance with general relativity to form galaxies in massive dark matter halos.
A topological analysis of large-scale structure, studied using the CMASS sample of SDSS-III
Energy Technology Data Exchange (ETDEWEB)
Parihar, Prachi; Gott, J. Richard III [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544-1001 (United States); Vogeley, Michael S. [Department of Physics, Drexel University, Philadelphia, PA 19104 (United States); Choi, Yun-Young [Department of Astronomy and Space Science, Kyung Hee University, Gyeonggi 446-701 (Korea, Republic of); Kim, Juhan [Center for Advanced Computation, Korea Institute for Advanced Study, Heogiro 85, Seoul 130-722 (Korea, Republic of); Kim, Sungsoo S. [School of Space Research, Kyung Hee University, Gyeonggi 446-701 (Korea, Republic of); Speare, Robert [New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi (United Arab Emirates); Brownstein, Joel R. [Department of Physics and Astronomy, University of Utah, 115 S 1400 E, Salt Lake City, UT 84112 (United States); Brinkmann, J., E-mail: pparihar@caltech.edu, E-mail: yy.choi@khu.ac.kr [Apache Point Observatory, Sunspot, NM 88349 (United States)
2014-12-01
We study the three-dimensional genus topology of large-scale structure using the northern region of the CMASS Data Release 10 (DR10) sample of the SDSS-III Baryon Oscillation Spectroscopic Survey. We select galaxies with redshift 0.452 < z < 0.625 and with a stellar mass M {sub stellar} > 10{sup 11.56} M {sub ☉}. We study the topology at two smoothing lengths: R {sub G} = 21 h {sup –1} Mpc and R {sub G} = 34 h {sup –1} Mpc. The genus topology studied at the R {sub G} = 21 h {sup –1} Mpc scale results in the highest genus amplitude observed to date. The CMASS sample yields a genus curve that is characteristic of one produced by Gaussian random phase initial conditions. The data thus support the standard model of inflation where random quantum fluctuations in the early universe produced Gaussian random phase initial conditions. Modest deviations in the observed genus from random phase are as expected from shot noise effects and the nonlinear evolution of structure. We suggest the use of a fitting formula motivated by perturbation theory to characterize the shift and asymmetries in the observed genus curve with a single parameter. We construct 54 mock SDSS CMASS surveys along the past light cone from the Horizon Run 3 (HR3) N-body simulations, where gravitationally bound dark matter subhalos are identified as the sites of galaxy formation. We study the genus topology of the HR3 mock surveys with the same geometry and sampling density as the observational sample and find the observed genus topology to be consistent with ΛCDM as simulated by the HR3 mock samples. We conclude that the topology of the large-scale structure in the SDSS CMASS sample is consistent with cosmological models having primordial Gaussian density fluctuations growing in accordance with general relativity to form galaxies in massive dark matter halos.
Modesto, Leonardo
2013-01-01
We present a general covariant action for massive gravity merging together a class of "non-polynomial" and super-renormalizable or finite theories of gravity with the non-local theory of gravity recently proposed by Jaccard, Maggiore and Mitsou (arXiv:1305.3034 [hep-th]). Our diffeomorphism invariant action gives rise to the equations of motion appearing in non-local massive massive gravity plus quadratic curvature terms. Not only the massive graviton propagator reduces smoothly to the massless one without a vDVZ discontinuity, but also our finite theory of gravity is unitary at tree level around the Minkowski background. We also show that, as long as the graviton mass $m$ is much smaller the today's Hubble parameter $H_0$, a late-time cosmic acceleration can be realized without a dark energy component due to the growth of a scalar degree of freedom. In the presence of the cosmological constant $\\Lambda$, the dominance of the non-local mass term leads to a kind of "degravitation" for $\\Lambda$ at the late cos...
Classical N-particle cosmology in 2+1 dimensions
Hooft, G. 't
1993-01-01
In 2+1 dimensional cosmology particles are topological defects in a universe that is nearly everywhere flat. The author uses a time dependent triangulation procedure of space to formulate the laws of evolution and to construct the phase space of this system. A theorem is derived from which it follow
Classical N-particle cosmology in 2+1 dimensions
Hooft, G. 't
1993-01-01
In 2+1 dimensional cosmology particles are topological defects in a universe that is nearly everywhere flat. The author uses a time dependent triangulation procedure of space to formulate the laws of evolution and to construct the phase space of this system. A theorem is derived from which it
Inflation in multidimensional quantum cosmology
Carugno, E; Occhionero, F; Pollifrone, G; Carugno, Enrico; Litterio, Marco; Occhionero, Franco; Pollifrone, Giuseppe
1996-01-01
We extend to multidimensional cosmology Vilenkin's prescription of tunnelling from nothing for the quantum origin of the observable Universe. Our model consists of a D+4-dimensional spacetime of topology {\\cal R}\\times {\\cal S}^3 \\times{\\cal S}^D, with a scalar field (``chaotic inflaton'') for the matter component. Einstein gravity and Casimir compactification are assumed. The resulting minisuperspace is 3--dimensional. Patchwise we find an approximate analytic solution of the Wheeler--DeWitt equation through which we discuss the tunnelling picture and the probability of nucleation of the classical Universe with compactifying extra dimensions. Our conclusion is that the most likely initial conditions, although they do not lead to the compactification of the internal space, still yield (power-law) inflation for the outer space. The scenario is physically acceptable because the inner space growth is limited to \\sim 10^{11} in 100 e-foldings of inflation, starting from the Planck scale.
Nonlocal Quantum Effects in Cosmology
Dumin, Yurii V
2014-01-01
Since it is commonly believed that the observed large-scale structure of the Universe is an imprint of quantum fluctuations existing at the very early stage of its evolution, it is reasonable to pose the question: Do the effects of quantum nonlocality, which are well established now by the laboratory studies, manifest themselves also in the early Universe? We try to answer this question by utilizing the results of a few experiments, namely, with the superconducting multi-Josephson-junction loops and the ultracold gases in periodic potentials. Employing a close analogy between the above-mentioned setups and the simplest one-dimensional Friedmann-Robertson-Walker cosmological model, we show that the specific nonlocal correlations revealed in the laboratory studies might be of considerable importance also in treating the strongly-nonequilibrium phase transitions of Higgs fields in the early Universe. Particularly, they should substantially reduce the number of topological defects (e.g., domain walls) expected du...
Cosmology in Conformally Flat Spacetime
Endean, Geoffrey
1997-04-01
A possible solution to cosmological age and redshift-distance difficulties has recently been proposed by applying the appropriate conformally flat spacetime (CFS) coordinates to the standard solution of the field equations in a standard dust model closed universe. Here it is shown that CFS time correctly measures the true age of the universe, thus answering a major theoretical objection to the proposal. It is also shown that the CFS interpretation leads to a strong Copernican principle and is in all other respects wholly self-consistent. The deceleration parameter q0 is related to t0, the present age of the universe divided by L, the scale length of its curvature (an absolute constant). The values of q0 and L are approximately 5/6 and 9.2 × 109 yr, respectively. It is shown that the universe started everywhere simultaneously, with no recession velocity until the effects of its closed topology became significant. Conclusions to the contrary in standard theory (the big bang) stem from a different definition of recession velocity. The theoretical present cosmological mass density is quantified as 4.4 × 10-27 kg m-3 approximately, thus greatly reducing, in a closed universe, the observational requirement to find hidden mass. It is also shown that the prediction of standard theory, for a closed universe, of collapse toward a big crunch termination, will not in fact take place.
Nonlinear interactions for massive spin-2 fields
Schmidt-May, Angnis
2016-01-01
We give a basic introduction to ghost-free nonlinear theories involving massive spin-2 fields, focussing on bimetric theory. After motivating the construction of such models from field theoretical considerations, we review the linear theories for massive and massless spin-2 fluctuations propagating on maximally symmetric backgrounds. The structure of general nonlinear spin-2 interactions is explained before we specialise to the ghost-free case. We review the maximally symmetric solutions of bimetric theory, its mass spectrum and the parameter limit which brings the theory close to general relativity. Finally we discuss applications of bimetric theory to cosmology with particular emphasis on the role of the general relativity limit.
Doubly coupled matter fields in massive bigravity
Gao, Xian
2016-01-01
In the context of massive (bi-)gravity non-minimal matter couplings have been proposed. These couplings are special in the sense that they are free of the Boulware-Deser ghost below the strong coupling scale and can be used consistently as an effective field theory. Furthermore, they enrich the phenomenology of massive gravity. We consider these couplings in the framework of bimetric gravity and study the cosmological implications for background and linear tensor, vector, and scalar perturbations. Previous works have investigated special branch of solutions. Here we perform a complete perturbation analysis for the general background equations of motion completing previous analysis.
Ignat'ev, Yurii
2016-01-01
On the basis of qualitative analysis of the system of differential equations of the standard cosmological model it is shown that in the case of zero cosmological constant this system has a stable center corresponding to zero values of potential and its derivative at infinity. Thus, the cosmological model based on single massive classical scalar field in infinite future would give a flat Universe. The carried out numerical simulation of the dynamic system corresponding to the system of Einstein - Klein - Gordon equations showed that at great times of the evolution the invariant cosmological acceleration has an oscillating character and changes from $-2$ (braking), to $+1$ (acceleration). Average value of the cosmological acceleration is negative and is equal to $-1/2$. Oscillations of the cosmological acceleration happen on the background of rapidly falling Hubble constant. In the case of nonzero value of the cosmological constant depending on its value there are possible three various qualitative behavior typ...
DEFF Research Database (Denmark)
A. Kristensen, Anders Schmidt; Damkilde, Lars
2007-01-01
. A way to solve the initial design problem namely finding a form can be solved by so-called topology optimization. The idea is to define a design region and an amount of material. The loads and supports are also fidefined, and the algorithm finds the optimal material distribution. The objective function...... dictates the form, and the designer can choose e.g. maximum stiness, maximum allowable stresses or maximum lowest eigenfrequency. The result of the topology optimization is a relatively coarse map of material layout. This design can be transferred to a CAD system and given the necessary geometrically...... refinements, and then remeshed and reanalysed in other to secure that the design requirements are met correctly. The output of standard topology optimization has seldom well-defined, sharp contours leaving the designer with a tedious interpretation, which often results in less optimal structures. In the paper...
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.
Search for WIMP dark matter in VBF- and monojet topologies with the ATLAS experiment at 13 TeV
Energy Technology Data Exchange (ETDEWEB)
Geisler, Manuel Patrice [Kirchhoff-Institut fuer Physik, Heidelberg (Germany)
2016-07-01
The cosmological evidence for Dark Matter is strong, however the nature of Dark Matter is still unknown and it has yet to be detected directly. The presented search with the ATLAS experiment at the LHC, CERN, focuses on WIMP (weakly interacting massive particles) Dark Matter candidates. Different kinds of final states are investigated: both so-called monojets and final states with at least two jets of high transverse momenta and a significant amount of missing transverse momentum. The inclusion of the two-jet selection criteria enhances the sensitivity of this search to vector boson fusion topologies. Furthermore, the selection criteria are optimized in order to suppress background processes that mimic the production of Dark Matter particles. In this talk, further techniques of the search are presented, and aspects of the analysis performed with the 2015 dataset of proton-proton collision at √(s)=13 TeV are covered.
Topological inflation with graceful exit
Marunović, Anja
2015-01-01
We investigate a class of models of topological inflation in which a super-Hubble-sized global monopole seeds inflation. These models are attractive since inflation starts from rather generic initial conditions, but their not so attractive feature is that, unless symmetry is again restored, inflation never ends. In this work we show that, in presence of another nonminimally coupled scalar field, that is both quadratically and quartically coupled to the Ricci scalar, inflation naturally ends, representing an elegant solution to the graceful exit problem of topological inflation. While the monopole core grows during inflation, the growth stops after inflation, such that the monopole eventually enters the Hubble radius, and shrinks to its Minkowski space size, rendering it immaterial for the subsequent Universe's dynamics. Furthermore, we find that our model can produce cosmological perturbations that source CMB temperature fluctuations and seed large scale structure statistically consistent (within one standard...
Warner, S
1993-01-01
This text brings the reader to the frontiers of current research in topological rings. The exercises illustrate many results and theorems while a comprehensive bibliography is also included. The book is aimed at those readers acquainted with some very basic point-set topology and algebra, as normally presented in semester courses at the beginning graduate level or even at the advanced undergraduate level. Familiarity with Hausdorff, metric, compact and locally compact spaces and basic properties of continuous functions, also with groups, rings, fields, vector spaces and modules, and with Zorn''s Lemma, is also expected.
Arnold, Vladimir; Zorich, Anton
1999-01-01
This volume offers an account of the present state of the art in pseudoperiodic topology-a young branch of mathematics, born at the boundary between the ergodic theory of dynamical systems, topology, and number theory. Related topics include the theory of algorithms, convex integer polyhedra, Morse inequalities, real algebraic geometry, statistical physics, and algebraic number theory. The book contains many new results. Most of the articles contain brief surveys on the topics, making the volume accessible to a broad audience. From the Preface by V.I. Arnold: "The authors … have done much to s
Milewski, Emil G
2013-01-01
REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Topology includes an overview of elementary set theory, relations and functions, ordinals and cardinals, topological spaces, continuous functions, metric spaces and normed spaces, co
López-Corredoira, M.
2009-08-01
Certain results of observational cosmology cast critical doubt on the foundations of standard cosmology but leave most cosmologists untroubled. Alternative cosmological models that differ from the Big Bang have been published and defended by heterodox scientists; however, most cosmologists do not heed these. This may be because standard theory is correct and all other ideas and criticisms are incorrect, but it is also to a great extent due to sociological phenomena such as the ``snowball effect'' or ``groupthink''. We might wonder whether cosmology, the study of the Universe as a whole, is a science like other branches of physics or just a dominant ideology.
Inhomogeneous Big Bang Cosmology
Wagh, S M
2002-01-01
In this letter, we outline an inhomogeneous model of the Big Bang cosmology. For the inhomogeneous spacetime used here, the universe originates in the infinite past as the one dominated by vacuum energy and ends in the infinite future as the one consisting of "hot and relativistic" matter. The spatial distribution of matter in the considered inhomogeneous spacetime is {\\em arbitrary}. Hence, observed structures can arise in this cosmology from suitable "initial" density contrast. Different problems of the standard model of Big Bang cosmology are also resolved in the present inhomogeneous model. This inhomogeneous model of the Big Bang Cosmology predicts "hot death" for the universe.
Cosmology with orthogonal nilpotent superfields
Ferrara, Sergio; Kallosh, Renata; Thaler, Jesse
2016-02-01
We study the application of a supersymmetric model with two constrained supermultiplets to inflationary cosmology. The first superfield S is a stabilizer chiral superfield satisfying a nilpotency condition of degree 2, S2=0 . The second superfield Φ is the inflaton chiral superfield, which can be combined into a real superfield B ≡1/2 i (Φ -Φ ¯ ) . The real superfield B is orthogonal to S , S B =0 , and satisfies a nilpotency condition of degree 3, B3=0 . We show that these constraints remove from the spectrum the complex scalar sgoldstino, the real scalar inflaton partner (i.e. the "sinflaton"), and the fermionic inflatino. The corresponding supergravity model with de Sitter vacua describes a graviton, a massive gravitino, and one real scalar inflaton, with both the goldstino and inflatino being absent in unitary gauge. We also discuss relaxed superfield constraints where S2=0 and S Φ ¯ is chiral, which removes the sgoldstino and inflatino, but leaves the sinflaton in the spectrum. The cosmological model building in both of these inflatino-less models offers some advantages over existing constructions.
Electromagnetic Radiation in Multiply Connected Robertson-Walker Cosmologies
Tomaschitz, R
1993-01-01
Maxwell's equations on a topologically nontrivial cosmological background are studied. The cosmology is locally determined by a Robertson-Walker line element, but the spacelike slices are open hyperbolic manifolds, whose topology and geometry may vary in time. In this context the spectral resolution of Maxwell's equations in terms of horospherical elementary waves generated at infinity of hyperbolic space is given. The wave fronts are orthogonal to bundles of unstable geodesic rays, and the eikonal of geometric optics appears just as the phase of the horospherical waves. This fact is used to attach to the unstable geodesic rays a quantum mechanical momentum. In doing so the quantized energy-momentum tensor of the radiation field is constructed in a geometrically and dynamically transparent way, without appealing to the intricacies of the second quantization. In particular Planck's radiation formula, and the bearing of the multiply connected topology on the fluctuations in the temperature of the background rad...
Non-decoupling of heavy scalars in cosmology
Hardeman, Sjoerd Reimer
2012-01-01
The theory describing physics at the highest energy scales likely contains extra dimensions, whose internal degrees of freedom result in many massive field and particles. At accelerator experiments these fields and particles generally decouple from the low energy physics. However, in cosmology gravi
Mergers and star formation in SPH cosmological simulations
Tissera, P B
1999-01-01
The star formation rate history of galactic objects in hydrodynamical cosmological simulations are analyzed in relation to their merger histories. The findings suggest that massive mergers produce more efficient starbursts and that, depending on the internal structure of the objects, double starbursts could also occur.
Nonlocal Quantum Effects in Cosmology
Directory of Open Access Journals (Sweden)
Yurii V. Dumin
2014-01-01
Full Text Available Since it is commonly believed that the observed large-scale structure of the universe is an imprint of quantum fluctuations existing at the very early stage of its evolution, it is reasonable to pose the question: do the effects of quantum nonlocality, which are well established now by the laboratory studies, manifest themselves also in the early universe? We try to answer this question by utilizing the results of a few experiments, namely, with the superconducting multi-Josephson-junction loops and the ultracold gases in periodic potentials. Employing a close analogy between the above-mentioned setups and the simplest one-dimensional Friedmann-Robertson-Walker cosmological model, we show that the specific nonlocal correlations revealed in the laboratory studies might be of considerable importance also in treating the strongly nonequilibrium phase transitions of Higgs fields in the early universe. Particularly, they should substantially reduce the number of topological defects (e.g., domain walls expected due to independent establishment of the new phases in the remote spatial regions. This gives us a hint on resolving a long-standing problem of the excessive concentration of topological defects, inconsistent with observational constraints. The same effect may be also relevant to the recent problem of the anomalous behavior of cosmic microwave background fluctuations at large angular scales.
Multidimensional Global Monopole and Nonsingular Cosmology
Bronnikov, K A; Bronnikov, Kirill A.; Meierovich, Boris E.
2003-01-01
We consider a spherically symmetric global monopole in general relativity in $(D=d+2)$-dimensional spacetime. The monopole is shown to be asymptotically flat up to a solid angle defect in case $\\gamma < d-1$, where $\\gamma$ is a parameter characterizing the gravitational field strength. In the range $d-1< \\gamma < 2d(d+1)/(d+2)$ the monopole space-time contains a cosmological horizon. Outside the horizon the metric corresponds to a cosmological model of Kantowski-Sachs type, where spatial sections have the topology ${\\R\\times \\S}^d$. In the important case when the horizon is far from the monopole core, the temporal evolution of the Kantowski-Sachs metric is described analytically. The Kantowski-Sachs space-time contains a subspace with a $(d+1)$-dimensional Friedmann-Robertson-Walker metric, and its possible cosmological application is discussed. Some numerical estimations in case $d=3$ are made showing that this class of nonsingular cosmologies can be viable. Other results, generalizing those known ...
Oliver, Bob; Pawałowski, Krzystof
1991-01-01
As part of the scientific activity in connection with the 70th birthday of the Adam Mickiewicz University in Poznan, an international conference on algebraic topology was held. In the resulting proceedings volume, the emphasis is on substantial survey papers, some presented at the conference, some written subsequently.
DEFF Research Database (Denmark)
Bendsøe, Martin P.; Sigmund, Ole
2007-01-01
Taking as a starting point a design case for a compliant mechanism (a force inverter), the fundamental elements of topology optimization are described. The basis for the developments is a FEM format for this design problem and emphasis is given to the parameterization of design as a raster image...
Frank-Kamenetskii, Maxim D.
2013-01-01
A new variety on non-coding RNA has been discovered by several groups: circular RNA (circRNA). This discovery raises intriguing questions about the possibility of the existence of knotted RNA molecules and the existence of a new class of enzymes changing RNA topology, RNA topoisomerases.
Quark-hadron phase transition in massive gravity
Atazadeh, K.
2016-11-01
We study the quark-hadron phase transition in the framework of massive gravity. We show that the modification of the FRW cosmological equations leads to the quark-hadron phase transition in the early massive Universe. Using numerical analysis, we consider that a phase transition based on the chiral symmetry breaking after the electroweak transition, occurred at approximately 10 μs after the Big Bang to convert a plasma of free quarks and gluons into hadrons.
Quark–hadron phase transition in massive gravity
Energy Technology Data Exchange (ETDEWEB)
Atazadeh, K., E-mail: atazadeh@azaruniv.ac.ir
2016-11-15
We study the quark–hadron phase transition in the framework of massive gravity. We show that the modification of the FRW cosmological equations leads to the quark–hadron phase transition in the early massive Universe. Using numerical analysis, we consider that a phase transition based on the chiral symmetry breaking after the electroweak transition, occurred at approximately 10 μs after the Big Bang to convert a plasma of free quarks and gluons into hadrons.
Phantom cosmologies and fermions
Chimento, Luis P; Forte, Monica; Kremer, Gilberto M
2007-01-01
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.
Energy Technology Data Exchange (ETDEWEB)
Vilenkin, Alexander, E-mail: vilenkin@cosmos.phy.tufts.ed [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)
2010-01-01
The 'new standard cosmology', based on the theory of inflation, has very impressive observational support. I review some outstanding problems of the new cosmology and the global view of the universe - the multiverse - that it suggests. I focus in particular on prospects for further observational tests of inflation and of the multiverse.
Energy Technology Data Exchange (ETDEWEB)
McAllister, Liam P.; Silverstein, Eva
2007-10-22
We give an overview of the status of string cosmology. We explain the motivation for the subject, outline the main problems, and assess some of the proposed solutions. Our focus is on those aspects of cosmology that benefit from the structure of an ultraviolet-complete theory.
Cosmological implications of Geometrothermodynamics
Luongo, Orlando
2013-01-01
We use the formalism of Geometrothermodynamics to derive a series of fundamental equations for thermodynamic systems. It is shown that all these fundamental equations can be used in the context of relativistic cosmology to derive diverse scenarios which include the standard cosmological model, a unified model for dark energy and dark matter, and an effective inflationary model.
Cosmological Implications of Geometrothermodynamics
Luongo, O.; Quevedo, H.
2015-01-01
We use the formalism of Geometrothermodynamics to derive a series of fundamental equations for thermodynamic systems. It is shown that all these fundamental equations can be used in the context of relativistic cosmology to derive diverse scenarios which include the standard cosmological model, a unified model for dark energy and dark matter, and an effective inflationary model.
Neutrino properties from cosmology
DEFF Research Database (Denmark)
Hannestad, S.
2013-01-01
In recent years precision cosmology has become an increasingly powerful probe of particle physics. Perhaps the prime example of this is the very stringent cosmological upper bound on the neutrino mass. However, other aspects of neutrino physics, such as their decoupling history and possible non-s...
Schulte-Ladbeck, Regina; Brinks, Elias; Kravtsov, Andrey
2010-01-01
Dwarf galaxies provide opportunities for drawing inferences about the processes in the early universe by observing our "cosmological backyard"-the Local Group and its vicinity. This special issue of the open-access journal Advances in Astronomy is a snapshot of the current state of the art of dwarf-galaxy cosmology.
Energy Technology Data Exchange (ETDEWEB)
Koivisto, Tomi S., E-mail: T.Koivisto@ThPhys.Uni-Heidelberg.d [Institute for Theoretical Physics, University of Heidelberg, 69120 (Germany); Nunes, Nelson J. [Institute for Theoretical Physics, University of Heidelberg, 69120 (Germany)
2010-03-01
Cosmology of self-interacting three-forms is investigated. The minimally coupled canonical theory can naturally generate a variety of isotropic background dynamics, including scaling, possibly transient acceleration and phantom crossing. An intuitive picture of the cosmological dynamics is presented employing an effective potential. Numerical solutions and analytical approximations are provided for scenarios which are potentially important for inflation or dark energy.
(Lack of) Cosmological evidence for dark radiation after Planck
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.
Sehgal, Neelima; 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; Dünner, Rolando; Essinger-Hileman, Thomas; Fisher, Ryan P; Fowler, Joseph W; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hernández-Monteagudo, Carlos; Hilton, Gene C; Hilton, Matt; Hincks, Adam D; Hlozek, Renée; Holtz, David; Huffenberger, Kevin M; Hughes, David H; Hughes, John P; Infante, Leopoldo; Irwin, Kent D; Jones, Andrew; Juin, Jean Baptiste; Klein, Jeff; Kosowsky, Arthur; Lau, Judy M; Limon, Michele; Lin, Yen-Ting; Lupton, Robert H; Marriage, Tobias A; Marsden, Danica; Martocci, Krista; Mauskopf, Phil; Menanteau, Felipe; Moodley, Kavilan; Moseley, Harvey; Netterfield, Calvin B; Niemack, Michael D; Nolta, Michael R; Page, Lyman A; Parker, Lucas; Partridge, Bruce; Reid, Beth; Sherwin, Blake D; Sievers, Jon; Spergel, David N; Staggs, Suzanne T; Swetz, Daniel S; Switzer, Eric R; Thornton, Robert; Tucker, Carole; Warne, Ryan; Wollack, Ed; Zhao, Yue
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 cluste...
Finite Canonical Measure for Nonsingular Cosmologies
Page, Don N
2011-01-01
The total canonical (Liouville-Henneaux-Gibbons-Hawking-Stewart) measure is finite for completely nonsingular Friedmann-Robertson-Walker classical universes with a minimally coupled massive scalar field and a positive cosmological constant. For a cosmological constant very small in units of the square of the scalar field mass, most of the measure is for nearly de Sitter solutions with no inflation at a much more rapid rate. However, if one restricts to solutions in which the scalar field energy density is ever more than twice the equivalent energy density of the cosmological constant, then the number of e-folds of rapid inflation must be large, and the fraction of the measure is low in which the spatial curvature is comparable to the cosmological constant at the time when it is comparable to the energy density of the scalar field. The measure for such classical FRW-Lambda-phi models with both a big bang and a big crunch is also finite. Only the solutions with a big bang that expand forever, or the time-revers...
Cosmology with three interacting spin-2 fields
Lüben, Marvin; Akrami, Yashar; Amendola, Luca; Solomon, Adam R.
2016-08-01
Theories of massive gravity with one or two dynamical metrics generically lack stable and observationally viable cosmological solutions that are distinguishable from Λ cold dark matter (CDM). We consider an extension to trimetric gravity, with three interacting spin-2 fields which are not plagued by the Boulware-Deser ghost. We systematically explore every combination with two free parameters in search of background cosmologies that are competitive with Λ CDM . For each case we determine whether the expansion history satisfies viability criteria, and whether or not it contains beyond-Λ CDM phenomenology. Among the many models we consider, there are only three cases that seem to be both viable and distinguishable from standard cosmology. One of the models has only one free parameter and displays a crossing from above to below the phantom divide. The other two provide scaling behavior, although they contain future singularities that need to be studied in more detail. These models possess interesting features that make them compelling targets for a full comparison to observations of both cosmological expansion history and structure formation.
Kehagias, Alex
2016-01-01
Symmetries play an interesting role in cosmology. They are useful in characterizing the cosmological perturbations generated during inflation and lead to consistency relations involving the soft limit of the statistical correlators of large-scale structure dark matter and galaxies overdensities. On the other hand, in observational cosmology the carriers of the information about these large-scale statistical distributions are light rays traveling on null geodesics. Motivated by this simple consideration, we study the structure of null infinity and the associated BMS symmetry in a cosmological setting. For decelerating Friedmann-Robertson-Walker backgrounds, for which future null infinity exists, we find that the BMS transformations which leaves the asymptotic metric invariant to leading order. Contrary to the asymptotic flat case, the BMS transformations in cosmology generate Goldstone modes corresponding to both scalar and tensor degrees of freedom which may exist at null infinity and perturb the asymptotic d...
Classical and quantum cosmology
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...
Cosmology and particle physics
Turner, Michael S.
1988-01-01
The interplay between cosmology and elementary particle physics is discussed. The standard cosmology is reviewed, concentrating on primordial nucleosynthesis and discussing how the standard cosmology has been used to place constraints on the properties of various particles. Baryogenesis is discussed, showing how a scenario in which the B-, C-, and CP-violating interactions in GUTs provide a dynamical explanation for the predominance of matter over antimatter and for the present baryon-to-photon ratio. It is shown how the very early dynamical evolution of a very weakly coupled scalar field which is initially displaced from the minimum of its potential may explain a handful of very fundamental cosmological facts which are not explained by the standard cosmology.
Testing loop quantum cosmology
Wilson-Ewing, Edward
2017-03-01
Loop quantum cosmology predicts that quantum gravity effects resolve the big-bang singularity and replace it by a cosmic bounce. Furthermore, loop quantum cosmology can also modify the form of primordial cosmological perturbations, for example by reducing power at large scales in inflationary models or by suppressing the tensor-to-scalar ratio in the matter bounce scenario; these two effects are potential observational tests for loop quantum cosmology. In this article, I review these predictions and others, and also briefly discuss three open problems in loop quantum cosmology: its relation to loop quantum gravity, the trans-Planckian problem, and a possible transition from a Lorentzian to a Euclidean space-time around the bounce point.
Ryden, Barbara
2002-01-01
Introduction to Cosmology provides a rare combination of a solid foundation of the core physical concepts of cosmology and the most recent astronomical observations. The book is designed for advanced undergraduates or beginning graduate students and assumes no prior knowledge of general relativity. An emphasis is placed on developing the readers' physical insight rather than losing them with complex math. An approachable writing style and wealth of fresh and imaginative analogies from "everyday" physics are used to make the concepts of cosmology more accessible. The book is unique in that it not only includes recent major developments in cosmology, like the cosmological constant and accelerating universe, but also anticipates key developments expected in the next few years, such as detailed results on the cosmic microwave background.
Zhao, Wen
2016-01-01
The foundation of modern cosmology relies on the so-called cosmological principle which states an homogeneous and isotropic distribution of matter in the universe on large scales. However, recent observations, such as the temperature anisotropy of the cosmic microwave background (CMB) radiation, the motion of galaxies in the universe, the polarization of quasars and the acceleration of the cosmic expansion, indicate preferred directions in the sky. If these directions have a cosmological origin, the cosmological principle would be violated, and modern cosmology should be reconsidered. In this paper, by considering the preferred axis in the CMB parity violation, we find that it coincides with the preferred axes in CMB quadrupole and CMB octopole, and they all align with the direction of the CMB kinematic dipole. In addition, the preferred directions in the velocity flows, quasar alignment, anisotropy of the cosmic acceleration, the handedness of spiral galaxies, and the angular distribution of the fine-structu...
Verde, L
2013-01-01
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/.
On the Expansions in Spin Foam Cosmology
Hellmann, Frank
2011-01-01
We discuss the expansions used in spin foam cosmology. We point out that already at the one vertex level arbitrarily complicated amplitudes contribute, and discuss the geometric asymptotics of the five simplest ones. We discuss what type of consistency conditions would be required to control the expan- sion. We show that the factorisation of the amplitude originally considered is best interpreted in topological terms. We then consider the next higher term in the graph expansion. We demonstrate the tension between the truncation to small graphs and going to the homogeneous sector, and conclude that it is necessary to truncate the dynamics as well.
Fomenko, Anatoly
2016-01-01
This classic text of the renowned Moscow mathematical school equips the aspiring mathematician with a solid grounding in the core of topology, from a homotopical perspective. Its comprehensiveness and depth of treatment are unmatched among topology textbooks: in addition to covering the basics—the fundamental notions and constructions of homotopy theory, covering spaces and the fundamental group, CW complexes, homology and cohomology, homological algebra—the book treats essential advanced topics, such as obstruction theory, characteristic classes, Steenrod squares, K-theory and cobordism theory, and, with distinctive thoroughness and lucidity, spectral sequences. The organization of the material around the major achievements of the golden era of topology—the Adams conjecture, Bott periodicity, the Hirzebruch–Riemann–Roch theorem, the Atiyah–Singer index theorem, to name a few—paints a clear picture of the canon of the subject. Grassmannians, loop spaces, and classical groups play a central role ...
Seeding Black Holes in Cosmological Simulations
Taylor, Philip
2014-01-01
We present a new model for the formation of black holes in cosmological simulations, motivated by the first star formation. Black holes form from high density peaks of primordial gas, and grow via both gas accretion and mergers. Massive black holes heat the surrounding material, suppressing star formation at the centres of galaxies, and driving galactic winds. We perform an investigation into the physical effects of the model parameters, and obtain a `best' set of these parameters by comparing the outcome of simulations to observations. With this best set, we successfully reproduce the cosmic star formation rate history, black hole mass -- velocity dispersion relation, and the size -- velocity dispersion relation of galaxies. The black hole seed mass is 10^3Msun, which is orders of magnitude smaller than has been used in previous cosmological simulations with active galactic nuclei, but suggests that the origin of the seed black holes is the death of Population III stars.
Energy Technology Data Exchange (ETDEWEB)
Kehagias, A. [Physics Division, National Technical University of Athens, 15780 Zografou Campus, Athens (Greece); Riotto, A. [Department of Theoretical Physics,24 quai E. Ansermet, CH-1211 Geneva 4 (Switzerland); Center for Astroparticle Physics (CAP),24 quai E. Ansermet, CH-1211 Geneva 4 (Switzerland)
2016-05-25
Symmetries play an interesting role in cosmology. They are useful in characterizing the cosmological perturbations generated during inflation and lead to consistency relations involving the soft limit of the statistical correlators of large-scale structure dark matter and galaxies overdensities. On the other hand, in observational cosmology the carriers of the information about these large-scale statistical distributions are light rays traveling on null geodesics. Motivated by this simple consideration, we study the structure of null infinity and the associated BMS symmetry in a cosmological setting. For decelerating Friedmann-Robertson-Walker backgrounds, for which future null infinity exists, we find that the BMS transformations which leaves the asymptotic metric invariant to leading order. Contrary to the asymptotic flat case, the BMS transformations in cosmology generate Goldstone modes corresponding to scalar, vector and tensor degrees of freedom which may exist at null infinity and perturb the asymptotic data. Therefore, BMS transformations generate physically inequivalent vacua as they populate the universe at null infinity with these physical degrees of freedom. We also discuss the gravitational memory effect when cosmological expansion is taken into account. In this case, there are extra contribution to the gravitational memory due to the tail of the retarded Green functions which are supported not only on the light-cone, but also in its interior. The gravitational memory effect can be understood also from an asymptotic point of view as a transition among cosmological BMS-related vacua.
Nojiri, S.; Odintsov, S. D.; Oikonomou, V. K.
2016-06-01
We combine the unimodular gravity and mimetic gravity theories into a unified theoretical framework, which is proposed to provide a suggestive proposal for a framework that may assist in the discussion and search for a solution to the cosmological constant problem and the dark matter issue. After providing the formulation of the unimodular mimetic gravity and investigating all the new features that the vacuum unimodular gravity implies, by using the underlying reconstruction method, we realize some well known cosmological evolutions, with some of these being exotic for the ordinary Einstein-Hilbert gravity. Specifically we provide the vacuum unimodular mimetic gravity description of the de Sitter cosmology and of the perfect fluid with constant equation of state cosmology. As we demonstrate, these cosmologies can be realized by vacuum mimetic unimodular gravity, without the existence of any matter fluid source. Moreover, we investigate how cosmologically viable cosmologies, which are compatible with the recent observational data, can be realized by the vacuum unimodular mimetic gravity. Since in some cases, a graceful exit from inflation problem might exist, we provide a qualitative description of the mechanism that can potentially generate the graceful exit from inflation in these theories, by searching for the unstable de Sitter solutions in the context of unimodular mimetic theories of gravity.
Kehagias, A.; Riotto, A.
2016-05-01
Symmetries play an interesting role in cosmology. They are useful in characterizing the cosmological perturbations generated during inflation and lead to consistency relations involving the soft limit of the statistical correlators of large-scale structure dark matter and galaxies overdensities. On the other hand, in observational cosmology the carriers of the information about these large-scale statistical distributions are light rays traveling on null geodesics. Motivated by this simple consideration, we study the structure of null infinity and the associated BMS symmetry in a cosmological setting. For decelerating Friedmann-Robertson-Walker backgrounds, for which future null infinity exists, we find that the BMS transformations which leaves the asymptotic metric invariant to leading order. Contrary to the asymptotic flat case, the BMS transformations in cosmology generate Goldstone modes corresponding to scalar, vector and tensor degrees of freedom which may exist at null infinity and perturb the asymptotic data. Therefore, BMS transformations generate physically inequivalent vacua as they populate the universe at null infinity with these physical degrees of freedom. We also discuss the gravitational memory effect when cosmological expansion is taken into account. In this case, there are extra contribution to the gravitational memory due to the tail of the retarded Green functions which are supported not only on the light-cone, but also in its interior. The gravitational memory effect can be understood also from an asymptotic point of view as a transition among cosmological BMS-related vacua.
Critique of Coleman's Theory of the Vanishing Cosmological Constant
Susskind, Leonard
In these lectures I would like to review some of the criticisms to the Coleman worm-hole theory of the vanishing cosmological constant. In particular, I would like to focus on the most fundamental assumption that the path integral over topologies defines a probability for the cosmological constant which has the form EXP(A) with A being the Baum-Hawking-Coleman saddle point. Coleman argues that the euclideam path integral over all geometries may be dominated by special configurations which consist of large smooth "spheres" connected by any number of narrow wormholes. Formally summing up such configurations gives a very divergent expression for the path integral…
Decaying Domain Walls in an Extended Gravity Model and Cosmology
Shiraishi, Kiyoshi
2013-01-01
We investigate cosmological consequences of an extended gravity model which belongs to the same class studied by Accetta and Steinhardt in an extended inflationary scenario. But we do not worry about inflation in our model; instead, we focus on a topological object formed during cosmological phase transitions. Although domain walls appear during first-order phase transitions such as QCD transition, they decay at the end of the phase transition. Therefore the "domain wall problem" does not exist in the suitable range of pameters and, on the contrary, the "fragments" of walls may become seeds of dark matter. A possible connection to "oscillating universe" model offered by Morikawa et al. is also discussed.
Magnetogenesis in bouncing cosmology
Qian, Peng; Easson, Damien A; Guo, Zong-Kuan
2016-01-01
We consider the process of magnetogenesis in the context of nonsingular bounce cosmology. We show that large primordial magnetic fields can be generated during contraction without encountering strong coupling and backreaction issues. The fields may seed large-scale magnetic fields with observationally interesting strengths. This result leads to a theoretical constraint on the relation of the energy scale of the bounce cosmology to the number of effective e-folding of the contracting phase in the case of scale invariance for the power spectrum of primordial magnetic fields. We show that this constraint can be satisfied in a sizable region of the parameter space for the nonsingular bounce cosmology.
Cosmology Theory and Observations
Dolgov, A D
1998-01-01
The comparison of the Standard Cosmological Model (SCM) with astronomical observations, i.e. theory versus experiment, and with the Minimal Standard Model (MSM) in particle physics, i.e. theory versus theory, is discussed. The main issue of this talk is whether cosmology indicates new physics beyond the standard $SU(3)\\times SU(2)\\times U(1)$ model with minimal particle content. The answer to this question is strongly and definitely "YES". New, yet unknown, physics exists and cosmology presents very weighty arguments in its favor.
Magnetogenesis in bouncing cosmology
Qian, Peng; Cai, Yi-Fu; Easson, Damien A.; Guo, Zong-Kuan
2016-10-01
We consider the process of magnetogenesis in the context of nonsingular bounce cosmology. We show that large primordial magnetic fields can be generated during contraction without encountering strong coupling and backreaction issues. The fields may seed large-scale magnetic fields with observationally interesting strengths. This result leads to a theoretical constraint on the relation of the energy scale of the bounce cosmology to the number of effective e -foldings of the contracting phase in the case of scale invariance for the power spectrum of primordial magnetic fields. We show that this constraint can be satisfied in a sizable region of the parameter space for the nonsingular bounce cosmology.
Cosmology, Epistemology and Chaos
Unno, Wasaburo
1992-03-01
We may consider the following three fundamental epistemological questions concerning cosmology. Can cosmology at last understand the origin of the universe? Can computers at last create? Can life be formed at last synthetically? These questions are in some sense related to the liar paradox containing the self-reference and, therefore, may not be answered by recursive processes in finite time. There are, however, various implications such that the chaos may break the trap of the self- reference paradox. In other words, Goedel's incompleteness theorem would not apply to chaos, even if the chaos can be generated by recursive processes. Internal relations among cosmology, epistemology and chaos must be investigated in greater detail
Stable massive particles at colliders
Energy Technology Data Exchange (ETDEWEB)
Fairbairn, M.; /Stockholm U.; Kraan, A.C.; /Pennsylvania U.; Milstead, D.A.; /Stockholm U.; Sjostrand, T.; /Lund U.; Skands, P.; /Fermilab; Sloan, T.; /Lancaster U.
2006-11-01
We review the theoretical motivations and experimental status of searches for stable massive particles (SMPs) which could be sufficiently long-lived as to be directly detected at collider experiments. The discovery of such particles would address a number of important questions in modern physics including the origin and composition of dark matter in the universe and the unification of the fundamental forces. This review describes the techniques used in SMP-searches at collider experiments and the limits so far obtained on the production of SMPs which possess various colour, electric and magnetic charge quantum numbers. We also describe theoretical scenarios which predict SMPs, the phenomenology needed to model their production at colliders and interactions with matter. In addition, the interplay between collider searches and open questions in cosmology such as dark matter composition are addressed.
Derivative couplings in massive bigravity
Gao, Xian
2016-01-01
In this work we study the cosmological perturbations in massive bigravity in the presence of non-minimal derivative couplings. For this purpose we consider a specific subclass of Horndeski scalar-tensor interactions that live on the unique composite effective metric. For the viability of the model both metrics have to be dynamical. Nevertheless, the number of allowed kinetic terms is crucial. We adapt to the restriction of having one single kinetic term. After deriving the full set of equations of motion for flat Friedmann-Lemaitre-Robertson-Walker background, we study linear perturbations on top of it. We show explicitly that only four tensor, two vector and two scalar degrees of freedom propagate, one of which being the Horndeski scalar, while the Boulware-Deser ghost can be integrated out.
Derivative couplings in massive bigravity
Gao, Xian; Heisenberg, Lavinia
2016-03-01
In this work we study the cosmological perturbations in massive bigravity in the presence of non-minimal derivative couplings. For this purpose we consider a specific subclass of Horndeski scalar-tensor interactions that live on the unique composite effective metric. For the viability of the model both metrics have to be dynamical. Nevertheless, the number of allowed kinetic terms is crucial. We adapt to the restriction of having one single kinetic term. After deriving the full set of equations of motion for flat Friedmann-Lemaitre-Robertson-Walker background, we study linear perturbations on top of it. We show explicitly that only four tensor, two vector and two scalar degrees of freedom propagate, one of which being the Horndeski scalar, while the Boulware-Deser ghost can be integrated out.
The quantum mechanics of cosmology.
Hartle, James B.
The following sections are included: * INTRODUCTION * POST-EVERETT QUANTUM MECHANICS * Probability * Probabilities in general * Probabilities in Quantum Mechanics * Decoherent Histories * Fine and Coarse Grained Histories * Decohering Sets of Coarse Grained Histories * No Moment by Moment Definition of Decoherence * Prediction, Retrodiction, and History * Prediction and Retrodiction * The Reconstruction of History * Branches (Illustrated by a Pure ρ) * Sets of Histories with the Same Probabilities * The Origins of Decoherence in Our Universe * On What Does Decoherence Depend? * Two Slit Model * The Caldeira-Leggett Oscillator Model * The Evolution of Reduced Density Matrices * Towards a Classical Domain * The Branch Dependence of Decoherence * Measurement * The Ideal Measurement Model and the Copenhagen Approximation to Quantum Mechanics * Approximate Probabilities Again * Complex Adaptive Systems * Open Questions * GENERALIZED QUANTUM MECHANICS * General Features * Hamiltonian Quantum Mechanics * Sum-Over-Histories Quantum Mechanics for Theories with a Time * Differences and Equivalences between Hamiltonian and Sum-Over-Histories Quantum Mechanics for Theories with a Time * Classical Physics and the Classical Limit of Quantum Mechanics * Generalizations of Hamiltonian Quantum Mechanics * TIME IN QUANTUM MECHANICS * Observables on Spacetime Regions * The Arrow of Time in Quantum Mechanics * Topology in Time * The Generality of Sum Over Histories Quantum Mechanics * THE QUANTUM MECHANICS OF SPACETIME * The Problem of Time * General Covariance and Time in Hamiltonian Quantum Mechanics * The "Marvelous Moment" * A Quantum Mechanics for Spacetime * What we Need * Sum-Over-Histories Quantum Mechanics for Theories Without a Time * Sum-Over-Spacetime-Histories Quantum Mechanics * Extensions and Contractions * The Construction of Sums Over Spacetime Histories * Some Open Questions * PRACTICAL QUANTUM COSMOLOGY * The Semiclassical Regime * The Semiclassical Approximation
Building Cosmological Frozen Stars
Kastor, David
2016-01-01
Janis-Newman-Winicour (JNW) spacetimes generalize the Schwarzschild solution to include a massless scalar field. Although suffering from naked singularities, they share the `frozen star' features of Schwarzschild black holes. Cosmological versions of the JNW spacetimes were discovered some time ago by Husain, Martinez and Nunez and by Fonarev. Unlike Schwarzschild-deSitter black holes, these solutions are dynamical, and the scarcity of exact solutions for dynamical black holes in cosmological backgrounds motivates their further study. Here we show how the cosmological JNW spacetimes can be built, starting from simpler, static, higher dimensional, vacuum `JNW brane' solutions via two different generalized dimensional reduction schemes that together cover the full range of JNW parameter space. Cosmological versions of a BPS limit of charged dilaton black holes are also known. JNW spacetimes represent a different limiting case of the charged, dilaton black hole family. We expect that understanding this second da...
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.
Cosmological Ontology and Epistemology
Page, Don N
2014-01-01
In cosmology, we would like to explain our observations and predict future observations from theories of the entire universe. Such cosmological theories make ontological assumptions of what entities exist and what their properties and relationships are. One must also make epistemological assumptions or metatheories of how one can test cosmological theories. Here I shall propose a Bayesian analysis in which the likelihood of a complete theory is given by the normalized measure it assigns to the observation used to test the theory. In this context, a discussion is given of the trade-off between prior probabilities and likelihoods, of the measure problem of cosmology, of the death of Born's rule, of the Boltzmann brain problem, of whether there is a better principle for prior probabilities than mathematical simplicity, and of an Optimal Argument for the Existence of God.
Holland, Jonathan
2014-01-01
A new approach to cosmology and space-time is developed, which emphasizes the description of the matter degrees of freedom of Einstein's theory of gravity by a family of K\\"ahler-Einstein Fano manifolds.
Cosmological Probes for Supersymmetry
Khlopov, Maxim
2015-01-01
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.
Tensors, relativity, and cosmology
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...
Quantum Cosmology: Effective Theory
Bojowald, Martin
2012-01-01
Quantum cosmology has traditionally been studied at the level of symmetry-reduced minisuperspace models, analyzing the behavior of wave functions. However, in the absence of a complete full setting of quantum gravity and detailed knowledge of specific properties of quantum states, it remained difficult to make testable predictions. For quantum cosmology to be part of empirical science, it must allow for a systematic framework in which corrections to well-tested classical equations can be derived, with any ambiguities and ignorance sufficiently parameterized. As in particle and condensed-matter physics, a successful viewpoint is one of effective theories, adapted to specific issues one encounters in quantum cosmology. This review presents such an effective framework of quantum cosmology, taking into account, among other things, space-time structures, covariance, the problem of time and the anomaly issue.
Testing Fractional Action Cosmology
Shchigolev, V K
2015-01-01
The present work deals with a combined test of the so-called Fractional Action Cosmology (FAC) on the example of a specific model obtained by the author earlier. In this model, the effective cosmological term is proportional to the Hubble parameter squared through the so-called kinematic induction. The reason of studying this cosmological model could be explained by its ability to describe two periods of accelerated expansion, that is in agreement with the recent observations and the cosmological inflation paradigm. First of all, we put our model through the theoretical tests that gives a general conception of the influence of the model parameters on its behavior. Then, we obtain some restrictions on the principal parameters of the model, including the fractional index, by means of the observational data. Finally, the cosmography parameters and the observational data compared to the theoretical predictions are presented both analytically and graphically.
Testing fractional action cosmology
Shchigolev, V. K.
2016-08-01
The present work deals with a combined test of the so-called Fractional Action Cosmology (FAC) on the example of a specific model obtained by the author earlier. In this model, the effective cosmological term is proportional to the Hubble parameter squared through the so-called kinematic induction. The reason of studying this cosmological model could be explained by its ability to describe two periods of accelerated expansion, that is in agreement with the recent observations and the cosmological inflation paradigm. First of all, we put our model through the theoretical tests, which gives a general conception of the influence of the model parameters on its behavior. Then, we obtain some restrictions on the principal parameters of the model, including the fractional index, by means of the observational data. Finally, the cosmography parameters and the observational data compared to the theoretical predictions are presented both analytically and graphically.
Cosmological diagrammatic rules
Giddings, Steven B
2010-01-01
A simple set of diagrammatic rules is formulated for perturbative evaluation of ``in-in" correlators, as is needed in cosmology and other nonequilibrium problems. These rules are both intuitive, and efficient for calculational purposes.
Cosmological diagrammatic rules
Energy Technology Data Exchange (ETDEWEB)
Giddings, Steven B. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Sloth, Martin S., E-mail: giddings@physics.ucsb.edu, E-mail: sloth@cern.ch [CERN, Physics Department, Theory Unit, CH-1211 Geneva 23 (Switzerland)
2010-07-01
A simple set of diagrammatic rules is formulated for perturbative evaluation of ''in-in'' correlators, as is needed in cosmology and other nonequilibrium problems. These rules are both intuitive, and efficient for calculational purposes.
Gibbons, Gary W
2013-01-01
In this paper we lay down the foundations for a purely Newtonian theory of cosmology, valid at scales small compared with the Hubble radius, using only Newtonian point particles acted on by gravity and a possible cosmological term. We describe the cosmological background which is given by an exact solution of the equations of motion in which the particles expand homothetically with their comoving positions constituting a central configuration. We point out, using previous work, that an important class of central configurations are homogeneous and isotropic, thus justifying the usual assumptions of elementary treatments. The scale factor is shown to satisfy the standard Raychaudhuri and Friedmann equations without making any fluid dynamic or continuum approximations. Since we make no commitment as to the identity of the point particles, our results are valid for cold dark matter, galaxies, or clusters of galaxies. In future publications we plan to discuss perturbations of our cosmological background from the p...
Ryden, Barbara
2017-01-01
This second edition of Introduction to Cosmology is an exciting update of an award-winning textbook. It is aimed primarily at advanced undergraduate students in physics and astronomy, but is also useful as a supplementary text at higher levels. It explains modern cosmological concepts, such as dark energy, in the context of the Big Bang theory. Its clear, lucid writing style, with a wealth of useful everyday analogies, makes it exceptionally engaging. Emphasis is placed on the links between theoretical concepts of cosmology and the observable properties of the universe, building deeper physical insights in the reader. The second edition includes recent observational results, fuller descriptions of special and general relativity, expanded discussions of dark energy, and a new chapter on baryonic matter that makes up stars and galaxies. It is an ideal textbook for the era of precision cosmology in the accelerating universe.
Energy Technology Data Exchange (ETDEWEB)
Townsend, Paul K [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Wohlfarth, Mattias N R [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)
2004-12-07
For gravity coupled to N scalar fields, with arbitrary potential V, it is shown that all flat (homogeneous and isotropic) cosmologies correspond to geodesics in an (N + 1)-dimensional 'augmented' target space of Lorentzian signature (1, N), timelike if V > 0, null if V = 0 and spacelike if V < 0. Accelerating cosmologies correspond to timelike geodesics that lie within an 'acceleration subcone' of the 'lightcone'. Non-flat (k = {+-}1) cosmologies are shown to evolve as projections of geodesic motion in a space of dimension N + 2, of signature (1, N + 1) for k = -1 and signature (2, N) for k = +1. This formalism is illustrated by cosmological solutions of models with an exponential potential, which are comprehensively analysed; the late-time behaviour for other potentials of current interest is deduced by comparison.
Guillemin, Victor
2010-01-01
Differential Topology provides an elementary and intuitive introduction to the study of smooth manifolds. In the years since its first publication, Guillemin and Pollack's book has become a standard text on the subject. It is a jewel of mathematical exposition, judiciously picking exactly the right mixture of detail and generality to display the richness within. The text is mostly self-contained, requiring only undergraduate analysis and linear algebra. By relying on a unifying idea-transversality-the authors are able to avoid the use of big machinery or ad hoc techniques to establish the main
Simulating cosmologies beyond ΛCDM with PINOCCHIO
Rizzo, Luca A.; Villaescusa-Navarro, Francisco; Monaco, Pierluigi; Munari, Emiliano; Borgani, Stefano; Castorina, Emanuele; Sefusatti, Emiliano
2017-01-01
We present a method that extends the capabilities of the PINpointing Orbit-Crossing Collapsed HIerarchical Objects (PINOCCHIO) code, allowing it to generate accurate dark matter halo mock catalogues in cosmological models where the linear growth factor and the growth rate depend on scale. Such cosmologies comprise, among others, models with massive neutrinos and some classes of modified gravity theories. We validate the code by comparing the halo properties from PINOCCHIO against N-body simulations, focusing on cosmologies with massive neutrinos: νΛCDM. We analyse the halo mass function, halo two-point correlation function and halo power spectrum, showing that PINOCCHIO reproduces the results from simulations with the same level of precision as the original code (~ 5–10%). We demonstrate that the abundance of halos in cosmologies with massless and massive neutrinos from PINOCCHIO matches very well the outcome of simulations, and point out that PINOCCHIO can reproduce the Ων–σ8 degeneracy that affects the halo mass function. We finally show that the clustering properties of the halos from PINOCCHIO matches accurately those from simulations both in real and redshift-space, in the latter case up to k = 0.3 h Mpc‑1. We emphasize that the computational time required by PINOCCHIO to generate mock halo catalogues is orders of magnitude lower than the one needed for N-body simulations. This makes this tool ideal for applications like covariance matrix studies within the standard ΛCDM model but also in cosmologies with massive neutrinos or some modified gravity theories.
Classification of cosmological milestones
Fernández-Jambrina, L
2006-01-01
In this paper causal geodesic completeness of FLRW cosmological models is analysed in terms of generalised power expansions of the scale factor in coordinate time. The strength of the found singularities is discussed following the usual definitions due to Tipler and Krolak. It is shown that while classical cosmological models are both timelike and lightlike geodesically incomplete, certain observationally alllowed models which have been proposed recently are lightlike geodesically complete.
Directory of Open Access Journals (Sweden)
Daywitt W. C.
2009-04-01
Full Text Available Both the big-bang and the quasi-steady-state cosmologies originate in some type of Planck state. This paper presents a new cosmological theory based on the Planck- vacuum negative-energy state, a state consisting of a degenerate collection of negative- energy Planck particles. A heuristic look at the Einstein field equation provides a con- vincing argument that such a vacuum state could provide a theoretical explanation for the visible universe.
Accelerating Cosmologies from Compactification
Townsend, P K; Townsend, Paul K.; Wohlfarth, Mattias N.R.
2003-01-01
A solution of the (4+n)-dimensional vacuum Einstein equations is found for which spacetime is compactified on a compact hyperbolic manifold of time-varying volume to a flat four-dimensional FLRW cosmology undergoing accelerated expansion in Einstein conformal frame. This shows that the `no-go' theorem forbidding acceleration in `standard' (time-independent) compactifications of string/M-theory does not apply to `cosmological' (time-dependent) hyperbolic compactifications.
Relativistic cosmological hydrodynamics
Hwang, J
1997-01-01
We investigate the relativistic cosmological hydrodynamic perturbations. We present the general large scale solutions of the perturbation variables valid for the general sign of three space curvature, the cosmological constant, and generally evolving background equation of state. The large scale evolution is characterized by a conserved gauge invariant quantity which is the same as a perturbed potential (or three-space curvature) in the comoving gauge.
Building cosmological frozen stars
Kastor, David; Traschen, Jennie
2017-02-01
Janis–Newman–Winicour (JNW) solutions generalize Schwarzschild to include a massless scalar field. While they share the familiar infinite redshift feature of Schwarzschild, they suffer from the presence of naked singularities. Cosmological versions of JNW spacetimes were discovered some years ago, in the most general case, by Fonarev. Fonarev solutions are also plagued by naked singularities, but have the virtue, unlike e.g. Schwarzschild–deSitter, of being dynamical. Given that exact dynamical cosmological black hole solutions are scarce, Fonarev solutions merit further study. We show how Fonarev solutions can be obtained via generalized dimensional reduction from simpler static vacuum solutions. These results may lead towards constructions of actual dynamical cosmological black holes. In particular, we note that cosmological versions of extremal charged dilaton black holes are known. JNW spacetimes represent a different limiting case of the family of charged dilaton black holes, which have been important in the context of string theory, and better understanding their cosmological versions of JNW spacetimes thus provides a second data point towards finding cosmological versions of the entire family.
Energy Technology Data Exchange (ETDEWEB)
Bag, Satadru; Sahni, Varun [Inter-University Centre for Astronomy and Astrophysics, Pune 411007 (India); Shtanov, Yuri [Bogolyubov Institute for Theoretical Physics, Kiev 03680 (Ukraine); Unnikrishnan, Sanil, E-mail: satadru@iucaa.ernet.in, E-mail: varun@iucaa.ernet.in, E-mail: shtanov@bitp.kiev.ua, E-mail: sanil@lnmiit.ac.in [Department of Physics, The LNM Institute of Information Technology, Jaipur 302031 (India)
2014-07-01
We explore the possibility of emergent cosmology using the effective potential formalism. We discover new models of emergent cosmology which satisfy the constraints posed by the cosmic microwave background (CMB). We demonstrate that, within the framework of modified gravity, the emergent scenario can arise in a universe which is spatially open/closed. By contrast, in general relativity (GR) emergent cosmology arises from a spatially closed past-eternal Einstein Static Universe (ESU). In GR the ESU is unstable, which creates fine tuning problems for emergent cosmology. However, modified gravity models including Braneworld models, Loop Quantum Cosmology (LQC) and Asymptotically Free Gravity result in a stable ESU. Consequently, in these models emergent cosmology arises from a larger class of initial conditions including those in which the universe eternally oscillates about the ESU fixed point. We demonstrate that such an oscillating universe is necessarily accompanied by graviton production. For a large region in parameter space graviton production is enhanced through a parametric resonance, casting serious doubts as to whether this emergent scenario can be past-eternal.
String cosmology versus standard and inflationary cosmology
Gasperini, M
2000-01-01
This paper presents a review of the basic, model-independent differences between the pre-big bang scenario, arising naturally in a string cosmology context, and the standard inflationary scenario. We use an unconventional approach in which the introduction of technical details is avoided as much as possible, trying to focus the reader's attention on the main conceptual aspects of both scenarios. The aim of the paper is not to conclude in favour either of one or of the other scenario, but to raise questions that are left to the reader's meditation. Warnings: the paper does not contain equations, and is not intended as a complete review of all aspects of string cosmology.
Cosmological perturbations in teleparallel Loop Quantum Cosmology
Haro, Jaime
2013-01-01
Cosmological perturbations in Loop Quantum Cosmology (LQC) could be studied from two totally different ways. The first one, called holonomy corrected LQC, is performed in the Hamiltonian framework, where the Asthekar connection is replaced by a suitable sinus function (holonomy correction), in order to have a well-defined quantum analogue. The alternative approach is based in the fact that isotropic LQC could be also obtained as a particular case of teleparallel $F(T)$ gravity (teleparallel LQC). Then, working in the Lagrangian framework and using the well-know perturbation equations in $F(T)$ gravity, we have obtained, in teleparallel LQC, the equations for scalar and tensor perturbations, and the corresponding Mukhanov-Sasaki equations. For scalar perturbations, our equation only differs from the one obtained by holonomy corrections in the velocity of sound, leading both formulations, essentially to the same scale invariant power spectrum when a matter-dominated universe is considered. However for tensor pe...
Geometry, topology and quantum field theory (fundamental theories of physics)
Bandyopadhyay, P.
2013-01-01
This monograph deals with the geometrical and topological aspects related to quantum field theory with special reference to the electroweak theory and skyrmions. This book is unique in its emphasis on the topological aspects of a fermion manifested through chiral anomaly which is responsible for the generation of mass. This has its relevance in electroweak theory where it is observed that weak interaction gauge bosons attain mass topologically. These geometrical and topological features help us to consider a massive fermion as a skyrmion and for a composite state we can realise the internal symmetry of hadrons from reflection group. Also, an overview of noncommutative geometry has been presented and it is observed that the manifold M 4 x Z2 has its relevance in the description of a massive fermion as skyrmion when the discrete space is considered as the internal space and the symmetry breaking gives rise to chiral anomaly leading to topological features.
Linear growth of structure in massive bigravity
Energy Technology Data Exchange (ETDEWEB)
Solomon, Adam R. [DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Rd., Cambridge CB3 0WA (United Kingdom); Akrami, Yashar [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo (Norway); Koivisto, Tomi S., E-mail: a.r.solomon@damtp.cam.ac.uk, E-mail: yashar.akrami@astro.uio.no, E-mail: tomi.koivisto@nordita.org [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)
2014-10-01
The ghost-free theory of massive gravity with two dynamical metrics has been shown to produce viable cosmological expansion, where the late-time acceleration of the Universe is due to the finite range of the gravitational interaction rather than a nonzero cosmological constant. Here the cosmological perturbations are studied in this theory. The full perturbation equations are presented in a general gauge and analyzed, focusing on subhorizon scales in the quasistatic limit during the matter-dominated era. An evolution equation for the matter inhomogeneities and the parameters quantifying the deviations from general relativistic structure formation are expressed in terms of five functions whose forms are determined directly by the coupling parameters in the theory. The evolution equation has a similar structure to Horndeski-type scalar-tensor theories, exhibiting a modified growth rate and scale-dependence at intermediate wavenumbers. Predictions of the theory are confronted with observational data on both background expansion and large-scale structure, although care must be taken to ensure a model is stable. It is found that while the stable models fit the data well, they feature deviations from the standard cosmology that could be detected or ruled out by near-future experiments.
Exploring Bouncing Cosmologies with Cosmological Surveys
Cai, Yi-Fu
2014-01-01
In light of the recent observational data coming from the sky we have two significant directions in the field of theoretical cosmology recently. First, we are now able to make use of present observations, such as the Planck and BICEP2 data, to examine theoretical predictions from the standard inflationary $\\Lambda$CDM which were made decades of years ago. Second, we can search for new cosmological signatures as a way to explore physics beyond the standard cosmic paradigm. In particular, a subset of early universe models admit a nonsingular bouncing solution that attempts to address the issue of the big bang singularity. These models have achieved a series of considerable developments in recent years, in particular in their perturbative frameworks, which made brand-new predictions of cosmological signatures that could be visible in current and forthcoming observations. In this article we present two representative paradigms of very early universe physics. The first is the so-called new matter (or matter-ekpyro...
BOOK REVIEW: Observational Cosmology Observational Cosmology
Howell, Dale Andrew
2013-04-01
Observational Cosmology by Stephen Serjeant fills a niche that was underserved in the textbook market: an up-to-date, thorough cosmology textbook focused on observations, aimed at advanced undergraduates. Not everything about the book is perfect - some subjects get short shrift, in some cases jargon dominates, and there are too few exercises. Still, on the whole, the book is a welcome addition. For decades, the classic textbooks of cosmology have focused on theory. But for every Sunyaev-Zel'dovich effect there is a Butcher-Oemler effect; there are as many cosmological phenomena established by observations, and only explained later by theory, as there were predicted by theory and confirmed by observations. In fact, in the last decade, there has been an explosion of new cosmological findings driven by observations. Some are so new that you won't find them mentioned in books just a few years old. So it is not just refreshing to see a book that reflects the new realities of cosmology, it is vital, if students are to truly stay up on a field that has widened in scope considerably. Observational Cosmology is filled with full-color images, and graphs from the latest experiments. How exciting it is that we live in an era where satellites and large experiments have gathered so much data to reveal astounding details about the origin of the universe and its evolution. To have all the latest data gathered together and explained in one book will be a revelation to students. In fact, at times it was to me. I've picked up modern cosmological knowledge through a patchwork of reading papers, going to colloquia, and serving on grant and telescope allocation panels. To go back and see them explained from square one, and summarized succinctly, filled in quite a few gaps in my own knowledge and corrected a few misconceptions I'd acquired along the way. To make room for all these graphs and observational details, a few things had to be left out. For one, there are few derivations
Entropy spectrum of charged BTZ black holes in massive gravity's rainbow
Panah, Behzad Eslam
2016-01-01
Regarding the significant interests in massive gravity's rainbow and also BTZ black holes, we apply the formalism introduced by Jiang and Han in order to investigate the quantization of the entropy of black holes. We show that the entropy of BTZ black holes in massive gravity's rainbow is quantized with equally spaced spectra and it depends on the value of the parameters of this black hole such as; massive parameters, electrical charge, the cosmological constant and also rainbow functions.
Brane Inflation, Solitons and Cosmological Solutions: I
Energy Technology Data Exchange (ETDEWEB)
Chen, P.
2005-01-25
In this paper we study various cosmological solutions for a D3/D7 system directly from M-theory with fluxes and M2-branes. In M-theory, these solutions exist only if we incorporate higher derivative corrections from the curvatures as well as G-fluxes. We take these corrections into account and study a number of toy cosmologies, including one with a novel background for the D3/D7 system whose supergravity solution can be completely determined. Our new background preserves all the good properties of the original model and opens up avenues to investigate cosmological effects from wrapped branes and brane-antibrane annihilation, to name a few. We also discuss in some detail semilocal defects with higher global symmetries, for example exceptional ones, that occur in a slightly different regime of our D3/D7 model. We show that the D3/D7 system does have the required ingredients to realize these configurations as non-topological solitons of the theory. These constructions also allow us to give a physical meaning to the existence of certain underlying homogeneous quaternionic Kahler manifolds.
Asorey, Manuel
2016-01-01
An old branch of mathematics, Topology, has opened the road to the discovery of new phases of matter. A hidden topology in the energy spectrum is the key for novel conducting/insulating properties of topological matter.
Noether symmetries in Gauss-Bonnet-teleparallel cosmology
Energy Technology Data Exchange (ETDEWEB)
Capozziello, Salvatore [Universita' di Napoli' ' Federico II' ' , Complesso Universitario di Monte S. Angelo, Dipartimento di Fisica ' ' E. Pancini' ' , Napoli (Italy); INFN Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Napoli (Italy); Gran Sasso Science Institute (INFN), L' Aquila (Italy); Tomsk State Pedagogical University, Tomsk (Russian Federation); De Laurentis, Mariafelicia [INFN Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Napoli (Italy); Tomsk State Pedagogical University, Tomsk (Russian Federation); Goethe University, Institute for Theoretical Physics, Frankfurt (Germany); Laboratory of Theoretical Cosmology, Tomsk State University of Control Systems and Radioelectronics (TUSUR), Tomsk (Russian Federation); Dialektopoulos, Konstantinos F. [Universita' di Napoli' ' Federico II' ' , Complesso Universitario di Monte S. Angelo, Dipartimento di Fisica ' ' E. Pancini' ' , Napoli (Italy); INFN Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Napoli (Italy)
2016-11-15
A generalized teleparallel cosmological model, f(T{sub G},T), containing the torsion scalar T and the teleparallel counterpart of the Gauss-Bonnet topological invariant T{sub G}, is studied in the framework of the Noether symmetry approach. As f(G, R) gravity, where G is the Gauss-Bonnet topological invariant and R is the Ricci curvature scalar, exhausts all the curvature information that one can construct from the Riemann tensor, in the same way, f(T{sub G},T) contains all the possible information directly related to the torsion tensor. In this paper, we discuss how the Noether symmetry approach allows one to fix the form of the function f(T{sub G},T) and to derive exact cosmological solutions. (orig.)
Noether symmetries in Gauss-Bonnet-teleparallel cosmology.
Capozziello, Salvatore; De Laurentis, Mariafelicia; Dialektopoulos, Konstantinos F
2016-01-01
A generalized teleparallel cosmological model, [Formula: see text], containing the torsion scalar T and the teleparallel counterpart of the Gauss-Bonnet topological invariant [Formula: see text], is studied in the framework of the Noether symmetry approach. As [Formula: see text] gravity, where [Formula: see text] is the Gauss-Bonnet topological invariant and R is the Ricci curvature scalar, exhausts all the curvature information that one can construct from the Riemann tensor, in the same way, [Formula: see text] contains all the possible information directly related to the torsion tensor. In this paper, we discuss how the Noether symmetry approach allows one to fix the form of the function [Formula: see text] and to derive exact cosmological solutions.
Noether symmetries in Gauss-Bonnet-teleparallel cosmology
Capozziello, Salvatore; De Laurentis, Mariafelicia; Dialektopoulos, Konstantinos F.
2016-11-01
A generalized teleparallel cosmological model, f(T_{G},T), containing the torsion scalar T and the teleparallel counterpart of the Gauss-Bonnet topological invariant T_{{G}}, is studied in the framework of the Noether symmetry approach. As f({G}, R) gravity, where {G} is the Gauss-Bonnet topological invariant and R is the Ricci curvature scalar, exhausts all the curvature information that one can construct from the Riemann tensor, in the same way, f(T_{G},T) contains all the possible information directly related to the torsion tensor. In this paper, we discuss how the Noether symmetry approach allows one to fix the form of the function f(T_{G},T) and to derive exact cosmological solutions.
Noether Symmetries in Gauss-Bonnet-teleparallel cosmology
Capozziello, Salvatore; Dialektopoulos, Konstantinos F
2016-01-01
A generalized teleparallel cosmological model, $f(T_\\mathcal{G},T)$, containing the torsion scalar $T$ and the teleparallel counterpart of the Gauss-Bonnet topological invariant $T_{\\mathcal{G}}$, is studied in the framework of the Noether Symmetry Approach. As $f(\\mathcal{G}, R)$ gravity, where $\\mathcal{G}$ is the Gauss-Bonnet topological invariant and $R$ is the Ricci curvature scalar, exhausts all the curvature information that one can construct from the Riemann tensor, in the same way, $f(T_\\mathcal{G},T)$ contains all the possible information directly related to the torsion tensor. In this paper, we discuss how the Noether Symmetry Approach allows to fix the form of the function $f(T_\\mathcal{G},T)$ and to derive exact cosmological solutions.
Modern Cosmology: Assumptions and Limits
Hwang, Jai-Chan
2012-06-01
Physical cosmology tries to understand the Universe at large with its origin and evolution. Observational and experimental situations in cosmology do not allow us to proceed purely based on the empirical means. We examine in which sense our cosmological assumptions in fact have shaped our current cosmological worldview with consequent inevitable limits. Cosmology, as other branches of science and knowledge, is a construct of human imagination reflecting the popular belief system of the era. The question at issue deserves further philosophic discussions. In Whitehead's words, ``philosophy, in one of its functions, is the critic of cosmologies.'' (Whitehead 1925).
Modern Cosmology: Assumptions and Limits
Hwang, Jai-chan
2012-01-01
Physical cosmology tries to understand the Universe at large with its origin and evolution. Observational and experimental situations in cosmology do not allow us to proceed purely based on the empirical means. We examine in which sense our cosmological assumptions in fact have shaped our current cosmological worldview with consequent inevitable limits. Cosmology, as other branches of science and knowledge, is a construct of human imagination reflecting the popular belief system of the era. The question at issue deserves further philosophic discussions. In Whitehead's words, "philosophy, in one of its functions, is the critic of cosmologies". (Whitehead 1925)
Margalef-Roig, J
1992-01-01
...there are reasons enough to warrant a coherent treatment of the main body of differential topology in the realm of Banach manifolds, which is at the same time correct and complete. This book fills the gap: whenever possible the manifolds treated are Banach manifolds with corners. Corners add to the complications and the authors have carefully fathomed the validity of all main results at corners. Even in finite dimensions some results at corners are more complete and better thought out here than elsewhere in the literature. The proofs are correct and with all details. I see this book as a reliable monograph of a well-defined subject; the possibility to fall back to it adds to the feeling of security when climbing in the more dangerous realms of infinite dimensional differential geometry. Peter W. Michor
Compact extra dimensions in cosmologies with f(T) structure
Fiorini, Franco; Vasquez, Yerko
2013-01-01
The presence of compact extra dimensions in cosmological scenarios in the context of f(T)-like gravities is discussed. For the case of toroidal compactifications, the analysis is performed in an arbitrary number of extra dimensions. Spherical topologies for the extra dimensions are then carefully studied in six and seven spacetime dimensions, where the proper vielbein fields responsible for the parallelization process are found.
Cosmological inflation in $F(R,\\mathcal{G})$ gravity
De Laurentis, Mariafelicia; Capozziello, Salvatore
2015-01-01
Cosmological inflation is discussed in the framework of $F(R,{\\cal G})$ gravity where $F$ is a generic function of the curvature scalar $R$ and the Gauss-Bonnet topological invariant $\\cal G$. The main feature that emerges in this analysis is the fact that this kind of theory can exhaust all the curvature budget related to curvature invariants without considering derivatives of $R,$ $R_{\\mu\
Statistical Issues in Galaxy Cluster Cosmology
Mantz, Adam
2013-01-01
The number and growth of massive galaxy clusters are sensitive probes of cosmological structure formation. Surveys at various wavelengths can detect clusters to high redshift, but the fact that cluster mass is not directly observable complicates matters, requiring us to simultaneously constrain scaling relations of observable signals with mass. The problem can be cast as one of regression, in which the data set is truncated, the (cosmology-dependent) underlying population must be modeled, and strong, complex correlations between measurements often exist. Simulations of cosmological structure formation provide a robust prediction for the number of clusters in the Universe as a function of mass and redshift (the mass function), but they cannot reliably predict the observables used to detect clusters in sky surveys (e.g. X-ray luminosity). Consequently, observers must constrain observable-mass scaling relations using additional data, and use the scaling relation model in conjunction with the mass function to predict the number of clusters as a function of redshift and luminosity.
The Future of Theoretical Physics and Cosmology
Gibbons, G. W.; Shellard, E. P. S.; Rankin, S. J.
2009-08-01
Preface; List of contributors; 1. Introduction; Part I. Popular Symposium: 2. Our complex cosmos and its future Martin J. Rees; 3. Theories of everything and Hawking's wave function of the Universe James B. Hartle; 4. The problem of space-time singularities: implications for quantum gravity? Roger Penrose; 5. Warping spacetime Kip Thorne; 6. 60 years in a nutshell Stephen W. Hawking; Part II. Spacetime Singularities: 7. Cosmological perturbations and singularities George F. R. Ellis; 8. The quantum physics of chronology protection Matt Visser; 9. Energy dominance and the Hawking-Ellis vacuum conservation theorem Brandon Carter; 10. On the instability of extra space dimensions Roger Penrose; Part III. Black Holes: 11. Black hole uniqueness and the inner horizon stability problem Werner Israel; 12. Black holes in the real universe and their prospects as probes of relativistic gravity Martin J. Rees; 13. Primordial black holes Bernard Carr; 14. Black hole pair creation Simon F. Ross; 15. Black holes as accelerators Steven Giddings; Part IV. Hawking Radiation: 16. Black holes and string theory Malcolm Perry; 17. M theory and black hole quantum mechanics Joe Polchinski; 18. Playing with black strings Gary Horowitz; 19. Twenty years of debate with Stephen Leonard Susskind; Part V. Quantum Gravity: 20. Euclidean quantum gravity: the view from 2002 Gary Gibbons; 21. Zeta functions, anomalies and stable branes Ian Moss; 22. Some reflections on the status of conventional quantum theory when applied to quantum gravity Chris Isham; 23. Quantum geometry and its ramifications Abhay Ashtekar; 24. Topology change in quantum gravity Fay Dowker; Part VI. M Theory and Beyond: 25. The past and future of string theory Edward Witten; 26. String theory David Gross; 27. A brief description of string theory Michael Green; 28. The story of M Paul Townsend; 29. Gauged supergravity and holographic field theory Nick Warner; 30. 57 varieties in a NUTshell Chris Pope; Part VII. de Sitter Space
Silk, Joseph
2008-11-01
The field of cosmology has been transformed since the glorious decades of the 1920's and 1930's when theory and observation converged to develop the current model of the expanding universe. It was a triumph of the theory of general relativity and astronomy. The first revolution came when the nuclear physicists entered the fray. This marked the debut of the hot big bang, in which the light elements were synthesized in the first three minutes. It was soon realised that elements like carbon and iron were synthesized in exploding stars. However helium, as well as deuterium and lithium, remain as George Gamow envisaged, the detritus of the big bang. The climax arrived with one of the most remarkable discoveries of the twentieth century, the cosmic microwave background radiation, in 1964. The fossil glow turned out to have the spectrum of an ideal black body. One could not imagine a stronger confirmation of the hot and dense origin of the universe. This discovery set the scene for the next major advance. It was now the turn of the particle physicists, who realized that the energies attained near the beginning of the universe, and unachievable in any conceivable terrestrial accelerator, provided a unique testing ground for theories of grand unification of the fundamental forces. This led Alan Guth and Andrei Linde in 1980 to propose the theory of inflation, which solved outstanding puzzles of the big bang. One could now understand why the universe is so large and homogeneous, and the origin of the seed fluctuations that gave rise to large-scale structure. A key prediction was that the universe should have Euclidean geometry, now verified to a precision of a few percent. Modern cosmology is firmly embedded in particle physics. It merits a text written by a particle physicist who can however appreciate the contributions of astronomy that provide the foundation and infrastructure for the theory of the expanding universe. There are now several such texts available. The most
Thermal Tachyacoustic Cosmology
Agarwal, Abhineet
2014-01-01
An intriguing possibility that can address pathologies in both early universe cosmology (i.e. the horizon problem) and quantum gravity (i.e. non-renormalizability), is that particles at very high energies and/or temperatures could propagate arbitrarily fast. A concrete realization of this possibility for the early universe is the Tachyacoustic (or Speedy Sound) cosmology, which could also produce a scale-invariant spectrum for scalar cosmological perturbations. Here, we study Thermal Tachyacoustic Cosmology (TTC), i.e. this scenario with thermal initial conditions. We find that a phase transition in the early universe, around the scale of Grand Unified Theories (GUT scale; $T\\sim 10^{15}$ GeV), during which the speed of sound drops by $25$ orders of magnitude within a Hubble time, can fit current CMB observations. We further discuss how production of primordial black holes constrains the cosmological acoustic history, while coupling TTC to Horava-Lifshitz gravity leads to a lower limit on the amplitude of ten...
Thermal tachyacoustic cosmology
Agarwal, Abhineet; Afshordi, Niayesh
2014-08-01
An intriguing possibility that can address pathologies in both early Universe cosmology (i.e. the horizon problem) and quantum gravity (i.e. nonrenormalizability), is that particles at very high energies and/or temperatures could propagate arbitrarily fast. A concrete realization of this possibility for the early Universe is the tachyacoustic (or speedy sound) cosmology, which could also produce a scale-invariant spectrum for scalar cosmological perturbations. Here, we study thermal tachyacoustic cosmology (TTC), i.e. this scenario with thermal initial conditions. We find that a phase transition in the early Universe, around the scale of the grand unified theory (GUT scale; T ˜1015 GeV), during which the speed of sound drops by 25 orders of magnitude within a Hubble time, can fit current CMB observations. We further discuss how production of primordial black holes constrains the cosmological acoustic history, while coupling TTC to Horava-Lifshitz gravity leads to a lower limit on the amplitude of tensor modes (r≳10-3), that are detectable by CMBpol (and might have already been seen by the BICEP-Keck Collaboration).
Conceptual Problems in Cosmology
Vieira, F J Amaral
2011-01-01
In this essay a critical review of present conceptual problems in current cosmology is provided from a more philosophical point of view. In essence, a digression on how could philosophy help cosmologists in what is strictly their fundamental endeavor is presented. We start by recalling some examples of enduring confrontations among philosophers and physicists on what could be contributed by the formers to the day-time striving of the second ones. Then, a short review of the standard model Friedmann-Lema\\^itre-Robertson-Walter (FLRW) of cosmology is given. It seems apparent that cosmology is living a golden age with the advent of observations of high precision. Nonetheless, a critical revisiting of the direction in which it should go on appears also needed, for misconcepts like "quantum backgrounds for cosmological classical settings" and "quantum gravity unification" have not been properly constructed up-to-date. Thus, knowledge-building in cosmology, more than in any other field, should begin with visions of...
Bonometto, S A; Musco, I; Mainini, R; Maccio', A V
2014-01-01
Models including an energy transfer from CDM to DE are widely considered in the literature, namely to allow DE a significant high-z density. Strongly Coupled cosmologies assume a much larger coupling between DE and CDM, together with the presence of an uncoupled warm DM component, as the role of CDM is mostly restricted to radiative eras. This allows us to preserve small scale fluctuations even if the warm particle, possibly a sterile neutrino, is quite light, O(100 eV). Linear theory and numerical simulations show that these cosmologies agree with LCDM on supergalactic scales; e.g., CMB spectra are substantially identical. Simultaneously, simulations show that they significantly ease problems related to the properties of MW satellites and cores in dwarfs. SC cosmologies also open new perspectives on early black hole formation, and possibly lead towards unificating DE and inflationary scalar fields.
Silk, Joseph; Barrow, John D; Saunders, Simon
2017-01-01
Following a long-term international collaboration between leaders in cosmology and the philosophy of science, this volume addresses foundational questions at the limit of science across these disciplines, questions raised by observational and theoretical progress in modern cosmology. Space missions have mapped the Universe up to its early instants, opening up questions on what came before the Big Bang, the nature of space and time, and the quantum origin of the Universe. As the foundational volume of an emerging academic discipline, experts from relevant fields lay out the fundamental problems of contemporary cosmology and explore the routes toward finding possible solutions. Written for graduates and researchers in physics and philosophy, particular efforts are made to inform academics from other fields, as well as the educated public, who wish to understand our modern vision of the Universe, related philosophical questions, and the significant impacts on scientific methodology.
Evolving Horava Cosmological Horizons
Fathi, Mohsen
2016-01-01
Several sets of radially propagating null congruence generators are exploited in order to form 3-dimensional marginally trapped surfaces, referred to as black hole and cosmological apparent horizons in a Horava universe. Based on this method, we deal with the characteristics of the 2-dimensional space-like spheres of symmetry and the peculiarities of having trapping horizons. Moreover, we apply this method in standard expanding and contracting FLRW cosmological models of a Horava universe to investigate the conditions under which the extra parameters of the theory may lead to trapped/anti-trapped surfaces both in the future and in the past. We also include the cases of negative time, referred to as the finite past, and discuss the formation of anti-trapped surfaces inside the cosmological apparent horizons.
Stornaiolo, C
2002-01-01
In this letter we propose the existence of low density black holes and discuss its compatibility with the cosmological observations. The origin of these black holes can be traced back to the collapse of long wavelength cosmological perturbations during the matter dominated era, when the densities are low enough to neglect any internal and thermal pressure. By introducing a threshold density $\\hat{\\rho}$ above which pressure and non-gravitational interactions become effective, we find the highest wavelength for the perturbations that can reach an equilibrium state instead of collapsing to a black hole. The low density black holes introduced here, if they exist, can be observed through weak and strong gravitational lensing effects. Finally we observe that we obtained here a cosmological model which is capable to explain in a qualitative way the void formation together with the value $\\Omega=1$. But we remark that it needs to be improved by considering non spherical symmetric black holes.
Cosmological Perturbations in Antigravity
Oltean, Marius
2014-01-01
We compute the evolution of cosmological perturbations in a recently proposed Weyl-symmetric theory of two scalar fields with oppositely-signed conformal couplings to Einstein gravity. It is motivated from the minimal conformal extension of the Standard Model, such that one of these scalar fields is the Higgs while the other is a new particle, the dilaton, introduced to make the Higgs mass conformally symmetric. At the background level, the theory admits novel geodesically-complete cyclic cosmological solutions characterized by a brief period of repulsive gravity, or "antigravity", during each successive transition from a Big Crunch to a Big Bang. We show that despite the necessarily wrong-signed kinetic term of the dilaton in the full action, its cosmological solutions are stable at the perturbative level.
Bojowald, Martin
2016-01-01
A cosmological model with two global internal times shows that time reparameterization invariance, and therefore covariance, is not guaranteed by deparameterization. In particular, it is impossible to derive proper-time effective equations from a single deparameterized model if quantum corrections from fluctuations and higher moments are included. The framework of effective constraints shows how proper-time evolution can consistently be defined in quantum cosmological systems, such that it is time reparameterization invariant when compared with other choices of coordinate time. At the same time, it allows transformations of moment corrections in different deparameterizations of the same model, indicating partial time reparameterization of internal-time evolution. However, in addition to corrections from moments such as quantum fluctuations, also factor ordering corrections may appear. The latter generically break covariance in internal-time formulations. Fluctuation effects in quantum cosmology are therefore ...
Townsend, P K; Townsend, Paul K.; Wohlfarth, Mattias N.R.
2004-01-01
For gravity coupled to N scalar fields with arbitrary potential V, it is shown that all flat (homogeneous and isotropic) cosmologies correspond to geodesics in an (N+1)-dimensional `extended target space' of Lorentzian signature (1,N), timelike if V>0 and spacelike if V<0. Accelerating cosmologies correspond to timelike geodesics that lie within an `acceleration subcone' of the `lightcone'. Non-flat (k=-1,+1) cosmologies are shown to evolve as projections of geodesic motion in a space of dimension N+2, of signature (1,N+1) for k=-1 and signature (2,N) for k=+1. We illustrate these results for various potentials of current interest, including exponential and inverse power potentials.
General relativity and cosmology
Bucher, Martin
2015-01-01
This year marks the hundredth anniversary of Einstein's 1915 landmark paper "Die Feldgleichungen der Gravitation" in which the field equations of general relativity were correctly formulated for the first time, thus rendering general relativity a complete theory. Over the subsequent hundred years physicists and astronomers have struggled with uncovering the consequences and applications of these equations. This contribution, which was written as an introduction to six chapters dealing with the connection between general relativity and cosmology that will appear in the two-volume book "One Hundred Years of General Relativity: From Genesis and Empirical Foundations to Gravitational Waves, Cosmology and Quantum Gravity," endeavors to provide a historical overview of the connection between general relativity and cosmology, two areas whose development has been closely intertwined.
Cosmology in generalized Proca theories
De Felice, Antonio; Heisenberg, Lavinia; Kase, Ryotaro; Mukohyama, Shinji; Tsujikawa, Shinji; Zhang, Ying-li
2016-06-01
We consider a massive vector field with derivative interactions that propagates only the 3 desired polarizations (besides two tensor polarizations from gravity) with second-order equations of motion in curved space-time. The cosmological implications of such generalized Proca theories are investigated for both the background and the linear perturbation by taking into account the Lagrangian up to quintic order. In the presence of a matter fluid with a temporal component of the vector field, we derive the background equations of motion and show the existence of de Sitter solutions relevant to the late-time cosmic acceleration. We also obtain conditions for the absence of ghosts and Laplacian instabilities of tensor, vector, and scalar perturbations in the small-scale limit. Our results are applied to concrete examples of the general functions in the theory, which encompass vector Galileons as a specific case. In such examples, we show that the de Sitter fixed point is always a stable attractor and study viable parameter spaces in which the no-ghost and stability conditions are satisfied during the cosmic expansion history.
Terapixel imaging of cosmological simulations
Feng, Yu; Di Matteo, Tiziana; Khandai, Nishikanta; Sargent, Randy; Nourbakhsh, Illah; Dille, Paul; Bartley, Chris; Springel, Volker; Jana, Anirban; Gardner, Jeffrey
2011-01-01
The increasing size of cosmological simulations has led to the need for new visualization techniques. We focus on Smoothed Particle Hydrodynamical (SPH) simulations run with the GADGET code and describe methods for visually accessing the entire simulation at full resolution. The simulation snapshots are rastered and processed on supercomputers into images that are ready to be accessed through a web interface (GigaPan). This allows any scientist with a web-browser to interactively explore simulation datasets in both in spatial and temporal dimensions, datasets which in their native format can be hundreds of terabytes in size or more. We present two examples, the first a static terapixel image of the MassiveBlack simulation, a P-GADGET SPH simulation with 65 billion particles, and the second an interactively zoomable animation of a different simulation with more than one thousand frames, each a gigapixel in size. Both are available for public access through the GigaPan web interface. We also make our imaging so...
Ivanov, Mikhail M.; Tokareva, Anna A.
2016-12-01
We study the creation and evolution of cosmological perturbations in renormalizable quadratic gravity with a Weyl term. We adopt a prescription that implies the stability of the vacuum at the price of introducing a massive spin-two ghost state, leading to the loss of unitarity. The theory may still be predictive regardless the interpretation of non-unitary processes provided that their rate is negligible compared to the Universe expansion rate. This implies that the ghost is effectively stable. In such a setup, there are two scalar degrees of freedom excited during inflation. The first one is the usual curvature perturbation whose power spectrum appears to coincide with that of single-field inflation. The second one is a scalar component of the ghost encoded in the shift vector of the metric in the uniform inflaton gauge. The amplitudes of primordial tensor and vector perturbations are strongly suppressed. After inflation the ghost field starts to oscillate and its energy density shortly becomes dominant in the Universe. For all ghost masses allowed by laboratory constraints ghosts should have ``overclosed'' the Universe at temperatures higher than that of primordial nucleosynthesis. Thus, the model with the light Weyl ghost is ruled out.
Ivanov, Mikhail M
2016-01-01
We study the creation and evolution of cosmological perturbations in renormalizable quadratic gravity with a Weyl term. We adopt a prescription that implies the stability of the vacuum at the price of introducing a massive spin-two ghost state, leading to the loss of unitarity. The theory may still be predictive regardless the interpretation of non-unitary processes provided that their rate is negligible compared to the Universe expansion rate. This implies that the ghost is effectively stable. In such a setup, there are two scalar degrees of freedom excited during inflation. The first one is the usual curvature perturbation whose power spectrum appears to coincide with that of single-filed inflation. The second one is a scalar component of the ghost encoded in the shift vector of the metric in the uniform inflaton gauge. The amplitudes of primordial tensor and vector perturbations are strongly suppressed. After inflation the ghost field starts to oscillate and its energy density shortly becomes dominant in t...
Cosmology with moving bimetric fluids
García-García, Carlos; Martín-Moruno, Prado
2016-01-01
We study cosmological implications of bigravity and massive gravity solutions with non-simultaneously diagonal metrics by considering the generalized Gordon and Kerr-Schild ansatzes. The scenario that we obtain is equivalent to that of General Relativity with additional non-comoving perfect fluids. We show that the most general ghost-free bimetric theory generates three kinds of effective fluids whose equations of state are fixed by a function of the ansatz. Different choices of such function allow to reproduce the behaviour of different dark fluids. In particular, the Gordon ansatz is suitable for the description of various kinds of slowly-moving fluids, whereas the Kerr-Schild one is shown to describe a null dark energy component. The motion of those dark fluids with respect to the CMB is shown to generate, in turn, a relative motion of baryonic matter with respect to radition which contributes to the CMB anisotropies. CMB dipole observations are able to set stringent limits on the dark sector described by ...
Wang, F Y; Liang, E W
2015-01-01
Gamma-ray bursts (GRBs) are the most luminous electromagnetic explosions in the Universe, which emit up to $8.8\\times10^{54}$ erg isotropic equivalent energy in the hard X-ray band. The high luminosity makes them detectable out to the largest distances yet explored in the Universe. GRBs, as bright beacons in the deep Universe, would be the ideal tool to probe the properties of high-redshift universe: including the cosmic expansion and dark energy, star formation rate, the reionization epoch and the metal enrichment history of the Universe. In this article, we review the luminosity correlations of GRBs, and implications for constraining the cosmological parameters and dark energy. Observations show that the progenitors of long GRBs are massive stars. So it is expected that long GRBs are tracers of star formation rate. We also review the high-redshift star formation rate derived from GRBs, and implications for the cosmic reionization history. The afterglows of GRBs generally have broken power-law spectra, so it...
Cosmology in generalized Proca theories
De Felice, Antonio; Kase, Ryotaro; Mukohyama, Shinji; Tsujikawa, Shinji; Zhang, Ying-li
2016-01-01
We consider a massive vector field with derivative interactions that propagates only the 3 desired polarizations (besides two tensor polarizations from gravity) with second-order equations of motion in curved space-time. The cosmological implications of such generalized Proca theories are investigated for both the background and the linear perturbation by taking into account the Lagrangian up to quintic order. In the presence of a matter fluid with a temporal component of the vector field, we derive the background equations of motion and show the existence of de Sitter solutions relevant to the late-time cosmic acceleration. We also obtain conditions for the absence of ghosts and Laplacian instabilities of tensor, vector, and scalar perturbations in the small-scale limit. Our results are applied to concrete examples of the general functions in the theory, which encompass vector Galileons as a specific case. In such examples, we show that the de Sitter fixed point is always a stable attractor and study viable ...
Cosmic Explosions, Life in the Universe, and the Cosmological Constant.
Piran, Tsvi; Jimenez, Raul; Cuesta, Antonio J; Simpson, Fergus; Verde, Licia
2016-02-26
Gamma-ray bursts (GRBs) are copious sources of gamma rays whose interaction with a planetary atmosphere can pose a threat to complex life. Using recent determinations of their rate and probability of causing massive extinction, we explore what types of universes are most likely to harbor advanced forms of life. We use cosmological N-body simulations to determine at what time and for what value of the cosmological constant (Λ) the chances of life being unaffected by cosmic explosions are maximized. Life survival to GRBs favors Lambda-dominated universes. Within a cold dark matter model with a cosmological constant, the likelihood of life survival to GRBs is governed by the value of Λ and the age of the Universe. We find that we seem to live in a favorable point in this parameter space that minimizes the exposure to cosmic explosions, yet maximizes the number of main sequence (hydrogen-burning) stars around which advanced life forms can exist.
Disappearing cosmological constant in f(R) gravity
Starobinsky, Alexei A
2007-01-01
For higher-derivative f(R) gravity where R is the Ricci scalar, a class of models is proposed which produce viable cosmology different from the LambdaCDM one at recent times and satisfy cosmological, Solar system and laboratory tests. These models have both flat and de Sitter space-times as particular solutions in the absence of matter. Thus, a cosmological constant is zero in flat space-time, but appears effectively in a curved one for sufficiently large R. A 'smoking gun' for these models would be small discrepancy in values of the slope of the primordial perturbation power spectrum determined from galaxy surveys and CMB fluctuations. On the other hand, a new problem for dark energy models based on f(R) gravity is pointed which is connected with possible overproduction of new massive scalar particles (scalarons) arising in this theory in the very early Universe.
Hamiltonian analysis of BHT massive gravity
Blagojević, M.; Cvetković, B.
2011-01-01
We study the Hamiltonian structure of the Bergshoeff-Hohm-Townsend (BHT) massive gravity with a cosmological constant. In the space of coupling constants ( Λ 0, m 2), our canonical analysis reveals the special role of the condition Λ 0/ m 2 ≠ -1. In this sector, the dimension of the physical phase space is found to be N ∗ = 4, which corresponds to two Lagrangian degree of freedom. When applied to the AdS asymptotic region, the canonical approach yields the conserved charges of the BTZ black hole, and central charges of the asymptotic symmetry algebra.
Towards Realistic Modeling of Massive Star Clusters
Gnedin, O.; Li, H.
2016-06-01
Cosmological simulations of galaxy formation are rapidly advancing towards smaller scales. Current models can now resolve giant molecular clouds in galaxies and predict basic properties of star clusters forming within them. I will describe new theoretical simulations of the formation of the Milky Way throughout cosmic time, with the adaptive mesh refinement code ART. However, many challenges - physical and numerical - still remain. I will discuss how observations of massive star clusters and star forming regions can help us overcome some of them. Video of the talk is available at https://goo.gl/ZoZOfX
Cosmological Reflection of Particle Symmetry
Maxim Khlopov
2016-01-01
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 symmetr...
Brane cosmology in teleparallel gravity
Atazadeh, K
2014-01-01
We consider cosmology of brane-world scenario in the frame work of teleparallel gravity in that way matter is localized on the brane. We show that the cosmology of such branes is different from the standard cosmology in teleparallelism. In particular, we obtain a class of new solutions with a constant five-dimensional radius and cosmologically evolving brane in the context of constant torsion $f(T)$ gravity.
The topology of geology 2: Topological uncertainty
Thiele, Samuel T.; Jessell, Mark W.; Lindsay, Mark; Wellmann, J. Florian; Pakyuz-Charrier, Evren
2016-10-01
Uncertainty is ubiquitous in geology, and efforts to characterise and communicate it are becoming increasingly important. Recent studies have quantified differences between perturbed geological models to gain insight into uncertainty. We build on this approach by quantifying differences in topology, a property that describes geological relationships in a model, introducing the concept of topological uncertainty. Data defining implicit geological models were perturbed to simulate data uncertainties, and the amount of topological variation in the resulting model suite measured to provide probabilistic assessments of specific topological hypotheses, sources of topological uncertainty and the classification of possible model realisations based on their topology. Overall, topology was found to be highly sensitive to small variations in model construction parameters in realistic models, with almost all of the several thousand realisations defining distinct topologies. In particular, uncertainty related to faults and unconformities was found to have profound topological implications. Finally, possible uses of topology as a geodiversity metric and validation filter are discussed, and methods of incorporating topological uncertainty into physical models are suggested.
The topology of geology 1: Topological analysis
Thiele, Samuel T.; Jessell, Mark W.; Lindsay, Mark; Ogarko, Vitaliy; Wellmann, J. Florian; Pakyuz-Charrier, Evren
2016-10-01
Topology has been used to characterise and quantify the properties of complex systems in a diverse range of scientific domains. This study explores the concept and applications of topological analysis in geology. We have developed an automatic system for extracting first order 2D topological information from geological maps, and 3D topological information from models built with the Noddy kinematic modelling system, and equivalent analyses should be possible for other implicit modelling systems. A method is presented for describing the spatial and temporal topology of geological models using a set of adjacency relationships that can be expressed as a topology network, thematic adjacency matrix or hive diagram. We define three types of spatial topology (cellular, structural and lithological) that allow us to analyse different aspects of the geology, and then apply them to investigate the geology of the Hamersley Basin, Western Australia.
Relativistic Cosmology Revisited
Directory of Open Access Journals (Sweden)
Crothers S. J.
2007-04-01
Full Text Available In a previous paper the writer treated of particular classes of cosmological solutions for certain Einstein spaces and claimed that no such solutions exist in relation thereto. In that paper the assumption that the proper radius is zero when the line-element is singular was generally applied. This general assumption is unjustified and must be dropped. Consequently, solutions do exist in relation to the aforementioned types, and are explored herein. The concept of the Big Bang cosmology is found to be inconsistent with General Relativity
Cervantes-Cota, Jorge L
2014-01-01
We review the role of fluids in cosmology by first introducing them in General Relativity and then applied to a FRW Universe's model. We describe how relativistic and non-relativistic components evolve in the background dynamics. We also introduce scalar fields to show that they are able to yield an inflationary dynamics at very early times (inflation) and late times (quintessence). Then, we proceed to study the thermodynamical properties of the fluids and, lastly, its perturbed kinematics. We make emphasis in the constrictions of parameters by recent cosmological probes.
Silk, Joseph
2011-01-01
Horizons of Cosmology: Exploring Worlds Seen and Unseen is the fourth title published in the Templeton Science and Religion Series, in which scientists from a wide range of fields distill their experience and knowledge into brief tours of their respective specialties. In this volume, highly esteemed astrophysicist Joseph Silk explores the vast mysteries and speculations of the field of cosmology in a way that balances an accessible style for the general reader and enough technical detail for advanced students and professionals. Indeed, while the p
The Cosmological Mass Function
Monaco, P
1997-01-01
This thesis aims to review the cosmological mass function problem, both from the theoretical and the observational point of view, and to present a new mass function theory, based on realistic approximations for the dynamics of gravitational collapse. Chapter 1 gives a general introduction on gravitational dynamics in cosmological models. Chapter 2 gives a complete review of the mass function theory. Chapters 3 and 4 present the ``dynamical'' mass function theory, based on truncated Lagrangian dynamics and on the excursion set approach. Chapter 5 reviews the observational state-of-the-art and the main applications of the mass function theories described before. Finally, Chapter 6 gives conclusions and future prospects.
2011-01-01
The twentieth century elevated our understanding of the Universe from its early stages to what it is today and what is to become of it. Cosmology is the weapon that utilizes all the scientific tools that we have created to feel less lost in the immensity of our Universe. The standard model is the theory that explains the best what we observe. Even with all the successes that this theory had, two main questions are still to be answered: What is the nature of dark matter and dark energy? This book attempts to understand these questions while giving some of the most promising advances in modern cosmology.
2012-01-01
This volume tells of the quest for cosmology as seen by some of the finest cosmologists in the world. It starts with "Galaxy Formation from Start to Finish" and ends with "The First Supermassive Black Holes in the Universe," exploring in between the grand themes of galaxies, the early universe, expansion of the universe, dark matter and dark energy. This up-to-date collection of review articles offers a general introduction to cosmology and is intended for all probing into the profound questions on where we came from and where we are going.
Optical image encryption topology.
Yong-Liang, Xiao; Xin, Zhou; Qiong-Hua, Wang; Sheng, Yuan; Yao-Yao, Chen
2009-10-15
Optical image encryption topology is proposed based on the principle of random-phase encoding. Various encryption topological units, involving peer-to-peer, ring, star, and tree topologies, can be realized by an optical 6f system. These topological units can be interconnected to constitute an optical image encryption network. The encryption and decryption can be performed in both digital and optical methods.
DEFF Research Database (Denmark)
Marcussen, Lars
2003-01-01
Rummets topologi, Historiens topologi: betragtninger om menneskets orientering til rum - fra hulen over beherskelse af flere akser til det flydende rum.......Rummets topologi, Historiens topologi: betragtninger om menneskets orientering til rum - fra hulen over beherskelse af flere akser til det flydende rum....
Tunnelling with a negative cosmological constant
Gibbons, G. W.
1996-02-01
The point of this paper is to see what light new results in hyperbolic geometry may throw on gravitational entropy and whether gravitational entropy is relevant for the quantum origin of the universe. We introduce some new gravitational instantons which mediate the birth from nothing of closed universes containing wormholes and suggest that they may contribute to the density matrix of the universe. We also discuss the connection between their gravitational action and the topological and volumetric entropies introduced in hyperbolic geometry. These coincide for hyperbolic 4-manifolds, and increase with increasing topological complexity of the 4-manifold. We raise the question of whether the action also increases with the topological complexity of the initial 3-geometry, measured either by its 3-volume or its Matveev complexity. We point out, in distinction to the non-supergravity case, that universes with domains of negative cosmological constant separated by supergravity domain walls cannot be born from nothing. Finally we point out that our wormholes provide examples of the type of Perpetual Motion machines envisaged by Frolov and Novikov.
Narici, Lawrence
2011-01-01
BackgroundTopology Valuation Theory Algebra Linear Functionals Hyperplanes Measure Theory Normed SpacesCommutative Topological GroupsElementary ConsiderationsSeparation and Compactness Bases at 0 for Group Topologies Subgroups and Products Quotients S-Topologies Metrizability CompletenessCompleteness Function Groups Total BoundednessCompactness and Total Boundedness Uniform Continuity Extension of Uniformly Continuous Maps CompletionTopological Vector SpacesAbsorbent and Balanced Sets Convexity-AlgebraicBasic PropertiesConvexity-Topological Generating Vector Topologies A Non-Locally Convex Spa
Cosmological simulations using a static scalar-tensor theory
Energy Technology Data Exchange (ETDEWEB)
RodrIguez-Meza, M A [Depto. de Fisica, Instituto Nacional de Investigaciones Nucleares, Col. Escandon, Apdo. Postal 18-1027, 11801 Mexico D.F (Mexico); Gonzalez-Morales, A X [Departamento Ingenierias, Universidad Iberoamericana, Prol. Paseo de la Reforma 880 Lomas de Santa Fe, Mexico D.F. Mexico (Mexico); Gabbasov, R F [Depto. de Fisica, Instituto Nacional de Investigaciones Nucleares, Col. Escandon, Apdo. Postal 18-1027, 11801 Mexico D.F (Mexico); Cervantes-Cota, Jorge L [Depto. de Fisica, Instituto Nacional de Investigaciones Nucleares, Col. Escandon, Apdo. Postal 18-1027, 11801 Mexico D.F (Mexico)
2007-11-15
We present {lambda}CDM N-body cosmological simulations in the framework of of a static general scalar-tensor theory of gravity. Due to the influence of the non-minimally coupled scalar field, the gravitational potential is modified by a Yukawa type term, yielding a new structure formation dynamics. We present some preliminary results and, in particular, we compute the density and velocity profiles of the most massive group.
Epidemiology of Massive Transfusion
DEFF Research Database (Denmark)
Halmin, Märit; Chiesa, Flaminia; Vasan, Senthil K;
2016-01-01
OBJECTIVE: There is an increasing focus on massive transfusion, but there is a paucity of comprehensive descriptions of the massively transfused patients and their outcomes. The objective of this study is to describe the incidence rate of massive transfusion, patient characteristics, and the mort...
Gilani, A H S
2004-01-01
It is claimed that only one gluon is massless and the other seven gluons are massive. Out of eight gluons, six are colored and two are neutral. Among neutral gluons, one is massless and other one is massive. Massive neutral gluon is heavier than the colored gluons. Gluons can only be predicted by set theory but not by SU(3).
Anti-de Sitter Space as Topological Insulator and Holography
Ho, Shih-Hao
2012-01-01
We argue that the Anti-de Sitter (AdS) space can be thought as a topological insulator with a co-dimensional one defect living at the UV boundary. Combining the bulk/edge correspondence for the topological insulators and the AdS/CFT correspondence, the fermionic topological phases for the dual conformal field theories (CFTs) can then be classified in the same way as classifying the topological phases of the massive free fermions in the co-dimensional one higher Minkowski spaces. The latter can then be obtained in Kitaev's framework of the K-theory analysis in classifying the topological insulators/superconductors. Our framework provides a way of classifying the symmetry-protected topologically ordered phases for the strongly interacting gapless systems, of which the classification is intractable in the context of strongly correlated condensed matters devised mainly for gapped systems.
A search for sterile neutrinos with the latest cosmological observations
Energy Technology Data Exchange (ETDEWEB)
Feng, Lu; Zhang, Jing-Fei [Northeastern University, Department of Physics, College of Sciences, Shenyang (China); Zhang, Xin [Northeastern University, Department of Physics, College of Sciences, Shenyang (China); Peking University, Center for High Energy Physics, Beijing (China)
2017-06-15
We report the result of a search for sterile neutrinos with the latest cosmological observations. Both cases of massless and massive sterile neutrinos are considered in the ΛCDM cosmology. The cosmological observations used in this work include the Planck 2015 temperature and polarization data, the baryon acoustic oscillation data, the Hubble constant direct measurement data, the Planck Sunyaev-Zeldovich cluster counts data, the Planck lensing data, and the cosmic shear data. We find that the current observational data give a hint of the existence of massless sterile neutrino (as dark radiation) at the 1.44σ level, and the consideration of an extra massless sterile neutrino can indeed relieve the tension between observations and improve the cosmological fit. For the case of massive sterile neutrino, the observations give a rather tight upper limit on the mass, which implies that actually a massless sterile neutrino is more favored. Our result is consistent with the recent result of neutrino oscillation experiment done by the Daya Bay and MINOS collaborations, as well as the recent result of cosmic ray experiment done by the IceCube collaboration. (orig.)
Gravitational wave signal from massive gravity
Gumrukcuoglu, A Emir; Lin, Chunshan; Mukohyama, Shinji; Tanahashi, Norihiro
2012-01-01
We discuss the detectability of gravitational waves with a time dependent mass contribution, by means of the stochastic gravitational wave observations. Such a mass term typically arises in the cosmological solutions of massive gravity theories. We conduct the analysis based on a general quadratic action, and thus the results apply universally to any massive gravity theories in which modification of general relativity appears primarily in the tensor modes. The primary manifestation of the modification in the gravitational wave spectrum is a sharp peak. The position and height of the peak carry information on the present value of the mass term, as well as the duration of the inflationary stage. We also discuss the detectability of such a gravitational wave signal using the future-planned gravitational wave observatories.
Nonlinear Properties of Vielbein Massive Gravity
Nibbelink, S G; Sexton, M; Nibbelink, Stefan Groot; Peloso, Marco; Sexton, Matthew
2006-01-01
We consider a special theory of massive gravity, which is obtained in a decoupling limit from a bi-gravity theory in the vielbein formulation, with only cosmological constant-like interactions between the two gravitational sectors. We investigate this theory using the Stueckelberg method, and construct a 't Hooft-Feynman gauge fixing in which the tensor, vector and scalar Stueckelberg fields are decoupled. We prove that this model has the softest possible ultraviolet behavior which can be expected from any generic (Lorentz invariant) theory of massive gravity, namely that it becomes strong only at the scale Lambda_3 = (m_g^2 M_P)^{1/3} . Finally, we confirm that also this model is plagued by a ghost instability, which, in the Stueckelberg formalism, arises from quartic scalar-vector and scalar-tensor interactions.
Topological superconductors: a review.
Sato, Masatoshi; Ando, Yoichi
2017-04-03
This review elaborates pedagogically on the fundamental concept, basic theory, expected properties, and materials realizations of topological superconductors. The relation between topological superconductivity and Majorana fermions are explained, and the difference between dispersive Majorana fermions and a localized Majorana zero mode is emphasized. A variety of routes to topological superconductivity are explained with an emphasis on the roles of spin-orbit coupling. Present experimental situations and possible signatures of topological superconductivity are summarized with an emphasis on intrinsic topological superconductors.
Strongly Correlated Topological Insulators
2016-02-03
Research Triangle Park , NC 27709-2211 Condensed Matter, Topological Phases of Matter REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT NUMBER(S...Strongly Correlated Topological Insulators In the past year, the grant was used for work in the field of topological phases, with emphasis on finding...surface of topological insulators. In the past 3 years, we have started a new direction, that of fractional topological insulators. These are materials
Relative Smooth Topological Spaces
Directory of Open Access Journals (Sweden)
B. Ghazanfari
2009-01-01
Full Text Available In 1992, Ramadan introduced the concept of a smooth topological space and relativeness between smooth topological space and fuzzy topological space in Chang's (1968 view points. In this paper we give a new definition of smooth topological space. This definition can be considered as a generalization of the smooth topological space which was given by Ramadan. Some general properties such as relative smooth continuity and relative smooth compactness are studied.
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.
Particle physics meets cosmology - The search for decaying neutrinos
Henry, R. C.
1982-01-01
The fundamental physical implications of the possible detection of massive neutrinos are discussed, with an emphasis on the Grand Unified Theories (GUTs) of matter. The Newtonian and general-relativistic pictures of the fundamental forces are compared, and the reduction of electromagnetic and weak forces to one force in the GUTs is explained. The cosmological consequences of the curved-spacetime gravitation concept are considered. Quarks, leptons, and neutrinos are characterized in a general treatment of elementary quantum mechanics. The universe is described in terms of quantized fields, the noninteractive 'particle' fields and the force fields, and cosmology becomes the study of the interaction of gravitation with the other fields, of the 'freezing out' of successive fields with the expansion and cooling of the universe. While the visible universe is the result of the clustering of the quark and electron fields, the distribution of the large number of quanta in neutrino field, like the mass of the neutrino, are unknown. Cosmological models which attribute anomalies in the observed motions of galaxies and stars to clusters or shells of massive neutrinos are shown to be consistent with a small but nonzero neutrino mass and a universe near the open/closed transition point, but direct detection of the presence of massive neutrinos by the UV emission of their decay is required to verify these hypotheses.
Ekpyrotic and Cyclic Cosmology
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/rho >> 1 (where P is the average pressure and rho 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, thei...
Quantum cosmological metroland model
Anderson, E.; Franzen, A.T.
2010-01-01
Relational particle mechanics is useful for modelling whole-universe issues such as quantum cosmology or the problem of time in quantum gravity, including some aspects outside the reach of comparably complex mini-superspace models. In this paper, we consider the mechanics of pure shape and not scale
Cosmological dynamical systems
Leon, Genly
2014-01-01
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...
Relativistic cosmology; Cosmologia Relativista
Energy Technology Data Exchange (ETDEWEB)
Bastero-Gil, M.
2015-07-01
Relativistic cosmology is nothing but the study of the evolution of our universe expanding from the General Theory of Relativity, which describes the gravitational interaction at any scale and given its character far-reaching is the force that dominate the evolution of the universe. (Author)
Ekpyrotic and cyclic cosmology
Energy Technology Data Exchange (ETDEWEB)
Lehners, Jean-Luc [Princeton Center for Theoretical Science, Jadwin Hall, Princeton University, Princeton NJ 08544 (United States)], E-mail: jlehners@princeton.edu
2008-09-15
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/({rho}) >>1 (where P is the average pressure and {rho} 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.
Energy Technology Data Exchange (ETDEWEB)
Sefusatti, Emiliano; /Fermilab /CCPP, New York; Crocce, Martin; Pueblas, Sebastian; Scoccimarro, Roman; /CCPP, New York
2006-04-01
The present spatial distribution of galaxies in the Universe is non-Gaussian, with 40% skewness in 50 h{sup -1} Mpc spheres, and remarkably little is known about the information encoded in it about cosmological parameters beyond the power spectrum. In this work they present an attempt to bridge this gap by studying the bispectrum, paying particular attention to a joint analysis with the power spectrum and their combination with CMB data. They address the covariance properties of the power spectrum and bispectrum including the effects of beat coupling that lead to interesting cross-correlations, and discuss how baryon acoustic oscillations break degeneracies. They show that the bispectrum has significant information on cosmological parameters well beyond its power in constraining galaxy bias, and when combined with the power spectrum is more complementary than combining power spectra of different samples of galaxies, since non-Gaussianity provides a somewhat different direction in parameter space. In the framework of flat cosmological models they show that most of the improvement of adding bispectrum information corresponds to parameters related to the amplitude and effective spectral index of perturbations, which can be improved by almost a factor of two. Moreover, they demonstrate that the expected statistical uncertainties in {sigma}s of a few percent are robust to relaxing the dark energy beyond a cosmological constant.
DEFF Research Database (Denmark)
Skaanes, Thea
2015-01-01
Abstract: This article concerns Hadza cosmology examined through objects, rituals and the Hadza concept of epeme. A brief background to the Hadza and the eldwork that informs this study is followed by a close analysis of three key objects that are central to the argument presented. The objects ar...
Indian Academy of Sciences (India)
B B Bhowmik; A Rajput
2004-06-01
Anisotropic Bianchi Type-I cosmological models have been studied on the basis of Lyra's geometry. Two types of models, one with constant deceleration parameter and the other with variable deceleration parameter have been derived by considering a time-dependent displacement field.
Phenomenology in minimal theory of massive gravity
Energy Technology Data Exchange (ETDEWEB)
Felice, Antonio De [Yukawa Institute for Theoretical Physics, Kyoto University,606-8502, Kyoto (Japan); Mukohyama, Shinji [Yukawa Institute for Theoretical Physics, Kyoto University,606-8502, Kyoto (Japan); Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo,277-8583, Chiba (Japan)
2016-04-15
We investigate the minimal theory of massive gravity (MTMG) recently introduced. After reviewing the original construction based on its Hamiltonian in the vielbein formalism, we reformulate it in terms of its Lagrangian in both the vielbein and the metric formalisms. It then becomes obvious that, unlike previous attempts in the literature of Lorentz-violating massive gravity, not only the potential but also the kinetic structure of the action is modified from the de Rham-Gabadadze-Tolley (dRGT) massive gravity theory. We confirm that the number of physical degrees of freedom in MTMG is two at fully nonlinear level. This proves the absence of various possible pathologies such as superluminality, acausality and strong coupling. Afterwards, we discuss the phenomenology of MTMG in the presence of a dust fluid. We find that on a flat homogeneous and isotropic background we have two branches. One of them (self-accelerating branch) naturally leads to acceleration without the genuine cosmological constant or dark energy. For this branch both the scalar and the vector modes behave exactly as in general relativity (GR). The phenomenology of this branch differs from GR in the tensor modes sector, as the tensor modes acquire a non-zero mass. Hence, MTMG serves as a stable nonlinear completion of the self-accelerating cosmological solution found originally in dRGT theory. The other branch (normal branch) has a dynamics which depends on the time-dependent fiducial metric. For the normal branch, the scalar mode sector, even though as in GR only one scalar mode is present (due to the dust fluid), differs from the one in GR, and, in general, structure formation will follow a different phenomenology. The tensor modes will be massive, whereas the vector modes, for both branches, will have the same phenomenology as in GR.
Some epistemic questions of cosmology
Grujic, Petar V
2007-01-01
We discuss a number of fundamental aspects of modern cosmological concepts, from the phenomenological, observational, theoretical and epistemic points of view. We argue that the modern cosmology, despite a great advent, in particular in the observational sector, is yet to solve important problems, posed already by the classical times. In particular the stress is put on discerning the scientific features of modern cosmological paradigms from the more speculative ones, with the latter immersed in some aspects deeply into mythological world picture. We finally discuss the principal paradigms, which are present in the modern cosmological studies and evaluate their epistemic merits. KEY WORDS: cosmology, epistemology, methodology, mythology, philosophy of science
The Maxwell-Chern-Simons gravity, and its cosmological implications
Haghani, Zahra; Harko, Tiberiu; Shahidi, Shahab
2017-08-01
We consider the cosmological implications of a gravitational theory containing two vector fields coupled via a generalized Chern-Simons term. One of the vector fields is the usual Maxwell field, while the other is a constrained vector field with constant norm included in the action via a Lagrange multiplier. The theory admits a de Sitter type solution, with healthy cosmological perturbations. We also show that there are seven degrees of freedom that propagate on top of de Sitter space-time, consisting of two tensor polarizations, four degrees of freedom related to the two vector fields, and a scalar degree of freedom that makes one of the vector fields massive. We investigate the cosmological evolution of Bianchi type I space-time, by assuming that the matter content of the Universe can be described by the stiff and dust. The cosmological evolution of the Bianchi type I Universe strongly depends on the initial conditions of the physical quantities, as well as on the model parameters. The mean anisotropy parameter, and the deceleration parameter, are also studied, and we show that independently of the matter equation of state the cosmological evolution of the Bianchi type I Universe always ends in an isotropic de Sitter type phase.
Can we distinguish early dark energy from a cosmological constant?
Shi, Difu; Baugh, Carlton M.
2016-07-01
Early dark energy (EDE) models are a class of quintessence dark energy with a dynamically evolving scalar field which display a small but non-negligible amount of dark energy at the epoch of matter-radiation equality. Compared with a cosmological constant, the presence of dark energy at early times changes the cosmic expansion history and consequently the shape of the linear theory power spectrum and potentially other observables. We constrain the cosmological parameters in the EDE cosmology using recent measurements of the cosmic microwave background and baryon acoustic oscillations. The best-fitting models favour no EDE; here we consider extreme examples which are in mild tension with current observations in order to explore the observational consequences of a maximally allowed amount of EDE. We study the non-linear evolution of cosmic structure in EDE cosmologies using large-volume N-body simulations. Many large-scale structure statistics are found to be very similar between the Λ cold dark matter (ΛCDM) and EDE models. We find that EDE cosmologies predict fewer massive haloes in comparison to ΛCDM, particularly at high redshifts. The most promising way to distinguish EDE from ΛCDM is to measure the power spectrum on large scales, where differences of up to 15 per cent are expected.
Self-interaction mechanism in Hagen's massive vector model
Arias, P J
2004-01-01
It is shown that the non-abelian vectorial model, proposed by C.R.Hagen is obtained using the self-interaction mechanism. The equivalence between this model and the non-abelian topologically massive one is studied showing that the existing equivalence between the abelian models is not sustained.
Espiro, J Lorca
2014-01-01
In this work we consider the effects of coupling characteristic classes to gravity by introducing appropriate operators in the Einstein--Hilbert action. As it is well known, this approach strays from the framework of General Relativity since it results in theories in which torsion can be present. An important point of our approach is that the solutions obtained explicitly carry topological information of the considered space-time manifold. We consider here all the characteristic classes that are consistent with a space-time manifold leading to the definition of an 'effective Cosmological Constant' that inherits topological information. We present analytical solutions for the contortion $1$-form that can be obtained under general conditions in various cases of interest. We show how to use these solutions to study cosmological scenarios that are obtained mainly by selecting a metric and an ideal fluid. We also discuss some of the consequences of these cosmological models over the topological and differential st...
Dipolar dark matter with massive bigravity
Energy Technology Data Exchange (ETDEWEB)
Blanchet, Luc [GRECO Institut d’Astrophysique de Paris - UMR 7095 du CNRS,Université Pierre & Marie Curie,98" b" i" s boulevard Arago, 75014 Paris (France); Heisenberg, Lavinia [Nordita, KTH Royal Institute of Technology and Stockholm University,Roslagstullsbacken 23, 10691 Stockholm (Sweden); Department of Physics & The Oskar Klein Centre, AlbaNova University Centre,Roslagstullsbacken 21, 10691 Stockholm (Sweden)
2015-12-14
Massive gravity theories have been developed as viable IR modifications of gravity motivated by dark energy and the problem of the cosmological constant. On the other hand, modified gravity and modified dark matter theories were developed with the aim of solving the problems of standard cold dark matter at galactic scales. Here we propose to adapt the framework of ghost-free massive bigravity theories to reformulate the problem of dark matter at galactic scales. We investigate a promising alternative to dark matter called dipolar dark matter (DDM) in which two different species of dark matter are separately coupled to the two metrics of bigravity and are linked together by an internal vector field. We show that this model successfully reproduces the phenomenology of dark matter at galactic scales (i.e. MOND) as a result of a mechanism of gravitational polarisation. The model is safe in the gravitational sector, but because of the particular couplings of the matter fields and vector field to the metrics, a ghost in the decoupling limit is present in the dark matter sector. However, it might be possible to push the mass of the ghost beyond the strong coupling scale by an appropriate choice of the parameters of the model. Crucial questions to address in future work are the exact mass of the ghost, and the cosmological implications of the model.
Dipolar dark matter with massive bigravity
Blanchet, Luc; Heisenberg, Lavinia
2015-12-01
Massive gravity theories have been developed as viable IR modifications of gravity motivated by dark energy and the problem of the cosmological constant. On the other hand, modified gravity and modified dark matter theories were developed with the aim of solving the problems of standard cold dark matter at galactic scales. Here we propose to adapt the framework of ghost-free massive bigravity theories to reformulate the problem of dark matter at galactic scales. We investigate a promising alternative to dark matter called dipolar dark matter (DDM) in which two different species of dark matter are separately coupled to the two metrics of bigravity and are linked together by an internal vector field. We show that this model successfully reproduces the phenomenology of dark matter at galactic scales (i.e. MOND) as a result of a mechanism of gravitational polarisation. The model is safe in the gravitational sector, but because of the particular couplings of the matter fields and vector field to the metrics, a ghost in the decoupling limit is present in the dark matter sector. However, it might be possible to push the mass of the ghost beyond the strong coupling scale by an appropriate choice of the parameters of the model. Crucial questions to address in future work are the exact mass of the ghost, and the cosmological implications of the model.
Topological inverse semigroups
Institute of Scientific and Technical Information of China (English)
ZHU Yongwen
2004-01-01
That the projective limit of any projective system of compact inverse semigroups is also a compact inverse semigroup,the injective limit of any injective system of inverse semigroups is also an inverse semigroup, and that a compact inverse semigroup is topologically isomorphic to a strict projective limit of compact metric inverse semigroups are proved. It is also demonstrated that Horn (S,T) is a topological inverse semigroup provided that S or T is a topological inverse semigroup with some other conditions. Being proved by means of the combination of topological semigroup theory with inverse semigroup theory,all these results generalize the corresponding ones related to topological semigroups or topological groups.
BRIGHT Lights, BIG City: Massive Galaxies, Giant Ly-A Nebulae, and Proto-Clusters
Energy Technology Data Exchange (ETDEWEB)
van Breugel, W; Reuland, M; de Vries, W; Stanford, A; Dey, A; Kurk, J; Venemans, B; Rottgering, H; Miley, G; De Breuck, C; Dopita, M; Sutherland, R; Bland-Hawthorn, J
2002-08-01
High redshift radio galaxies are great cosmological tools for pinpointing the most massive objects in the early Universe: massive forming galaxies, active super-massive black holes and proto-clusters. They report on deep narrow-band imaging and spectroscopic observations of several z > 2 radio galaxy fields to investigate the nature of giant Ly-{alpha} nebulae centered on the galaxies and to search for over-dense regions around them. They discuss the possible implications for our understanding of the formation and evolution of massive galaxies and galaxy clusters.
Loop Quantum Cosmology on a Torus
Lamon, Raphael
2009-01-01
In this paper we study the effect of a torus topology on Loop Quantum Cosmology. We first derive the Teichmueller space parametrizing all possible tori using Thurston's theorem and construct a Hamiltonian describing the dynamics of these torus universes. We then compute the Ashtekar variables for a slightly simplified torus such that the Gauss constraint can be solved easily. We perform a canonical transformation so that the holomies along the edges of the torus reduce to a product between almost and strictly periodic functions of the new variables. The drawback of this transformation is that the components of the densitized triad become complicated functions of these variables. Nevertheless we find two ways of quantizing these components, which in both cases leads surprisingly to a continuous spectrum.
Classical cosmologies from ten-dimensional supergravity
Energy Technology Data Exchange (ETDEWEB)
Gleiser, M.; Stein-Schabes, J.A.
1986-09-15
We study possible cosmological solutions to N = 1, D = 10 supergravity with the Yang-Mills field strength set to zero and show that the model accepts both power-law solutions and exponential solutions in the large-time limit. The stability of these solutions is investigated. It is found that a shrinking internal space is compatible with several field configurations. Using a stable power-law solution we analyze the conditions to obtain enough inflation in the physical space from the shrinking internal dimensions. We also show that for a flat topology a de Sitter phase is possible for late times. We used the consistency with the density perturbations to fix the inflationary parameter.
Low-Frequency Gravitational Radiation from Coalescing Massive Black Holes
Sesana, A; Madau, P; Volonteri, M
2005-01-01
We compute the expected low-frequency gravitational wave signal from coalescing massive black hole (MBH) binaries at the center of galaxies. We follow the merging history of halos and associated holes via cosmological Monte Carlo realizations of the merger hierarchy from early times to the present in a LCDM cosmology. MBHs get incorporated through a series of mergers into larger and larger halos, sink to the centre owing to dynamical friction, accrete a fraction of the gas in the merger remnant to become more massive, and form a binary system. Stellar dynamical processes dominates the orbital evolution of the binary at large separations, while gravitational wave emission takes over at small radii, causing the final coalescence of the system. We discuss the observability of inspiraling MBH binaries by a low-frequency gravitational wave experiment such as the planned Laser Interferometer Space Antenna (LISA), discriminating between resolvable sources and unresolved confusion noise. Over a 3-year observing perio...
Chiral gravity as a covariant formulation of massive gravity
Nibbelink, S G; Nibbelink, Stefan Groot; Peloso, Marco
2004-01-01
We present a covariant nonlinear completion of the Fierz-Pauli (FP) mass term for the graviton. The starting observation is that the FP mass is immediately obtained by expanding the cosmological constant term, i.e. the determinant of the vielbein, around Minkowski space to second order in the vielbein perturbations. Since this is an unstable expansion in the standard case, we consider an extended theory of gravity which describes two vielbeins that give rise to chiral spin--connections (consequently, fermions of a definite chirality only couple to one of the gravitational sectors). As for Einstein gravity with a cosmological constant, a single fine-tuning is needed to recover a Minkowski background; the two sectors then differ only by a constant conformal factor. The spectrum of this theory consists of a massless and a massive graviton, with FP mass term. The theory possesses interesting limits in which only the massive graviton is coupled to matter at the linearized level.
Einsteinian gravity from a topological action
Mielke, Eckehard W
2007-01-01
The curvature-squared model of gravity, in the affine form proposed by Weyl and Yang, is deduced from a topological action in 4D. More specifically, we start from the Pontrjagin (or Euler) invariant. Using the BRST antifield formalism with a double duality gauge fixing, we obtain a consistent quantization in spaces of double dual curvature as classical instanton type background. However, exact vacuum solutions with double duality properties exhibit a `vacuum degeneracy'. By modifying the duality via a scale breaking term, we demonstrate that only Einstein's equations with an induced cosmological constant emerge for the topology of the macroscopic background. This may have repercussions on the problem of `dark energy' as well as `dark matter' modeled by a torsion induced quintaxion.
Observing Dissipative Topological Defects with Coupled Lasers
Pal, Vishwa; Tradonsky, Chene; Chriki, Ronen; Friesem, Asher A.; Davidson, Nir
2017-07-01
Topological defects have been observed and studied in a wide range of systems, such as cosmology, spin systems, cold atoms, and optics, as they are quenched across a phase transition into an ordered state. These defects limit the coherence of the system and its ability to approach a fully ordered state, so revealing their origin and control is becoming an increasingly important field of research. We observe dissipative topological defects in a one-dimensional ring of phased-locked lasers, and show how their formation is related to the Kibble-Zurek mechanism and is governed in a universal manner by two competing time scales. The ratio between these two time scales depends on the system parameters, and thus offers the possibility of enabling the system to dissipate to a fully ordered, defect-free state that can be exploited for solving hard computational problems in various fields.
Domènech, Guillem
2016-01-01
From higher dimensional theories, e.g. string theory, one expects the presence of non-minimally coupled scalar fields. We review the notion of conformal frames in cosmology and emphasize their physical equivalence, which holds at least at a classical level. Furthermore, if there is a field, or fields, which dominates the universe, as it is often the case in cosmology, we can use such notion of frames to treat our system, matter and gravity, as two different sectors. On one hand, the gravity sector which describes the dynamics of the geometry and on the other hand the matter sector which has such geometry as a playground. We use this interpretation to build a model where the fact that a curvaton couples to a particular frame metric could leave an imprint in the CMB.
Relativistic Fractal Cosmologies
Ribeiro, Marcelo B
2009-01-01
This article reviews an approach for constructing a simple relativistic fractal cosmology whose main aim is to model the observed inhomogeneities of the distribution of galaxies by means of the Lemaitre-Tolman solution of Einstein's field equations for spherically symmetric dust in comoving coordinates. This model is based on earlier works developed by L. Pietronero and J.R. Wertz on Newtonian cosmology, whose main points are discussed. Observational relations in this spacetime are presented, together with a strategy for finding numerical solutions which approximate an averaged and smoothed out single fractal structure in the past light cone. Such fractal solutions are shown, with one of them being in agreement with some basic observational constraints, including the decay of the average density with the distance as a power law (the de Vaucouleurs' density power law) and the fractal dimension in the range 1 <= D <= 2. The spatially homogeneous Friedmann model is discussed as a special case of the Lemait...
Wormholes in viscous cosmology
Wang, Deng
2016-01-01
We study the wormhole spacetime configurations in bulk viscosity cosmology. Considering three classes of viscous models, i.e., bulk viscosity as a function of Hubble parameter $H$, temperature $T$ and dark energy density $\\rho$, respectively, we obtain nine wormhole solutions. Through the analysis for the anisotropic solutions, we conclude that, to some extent, these three classes of viscous models have very high degeneracy with each other. Subsequently, without the loss of generality, to investigate the traversabilities, energy conditions and stability for the wormhole solution, we study the wormhole solution of the constant redshift function of the viscous $\\omega$CDM model with a constant bulk viscosity coefficient. We obtain the following conclusions: the value of traversal velocity decreases for decreasing bulk viscosity, and the traversal velocity for a traveler depends on not only the wormhole geometry but also the effects of cosmological background evolution; the null energy condition will be violated...
Rich, James
2009-01-01
The book is aimed at astrophysics students and professional physicists who wish to understand the basics of cosmology and general relativity as well as the observational foundations of the LambdaCDM model of the Universe. The book provides a self-contained introduction to general relativity that is based on the homogeneity and isotropy of the local universe. The simplicity of this space allows general relativity to be presented in a very elementary manner while laying the foundation for the treatment of more complicated problems. The new edition presents the most recent observations, including those of CMB anisotropies by WMAP and of Baryon Acoustic Oscillations by SDSS. Future observational and theoretical challenges for the understanding of dark energy and dark matter are discussed. From 1st edition reviews: "The book provides a comprehensive and thorough explication of current cosmology at a level appropriate for a beginning graduate student or an advanced and motivated undergraduate. ... This is an extrem...
CERN. Geneva
2017-01-01
Extensions of Einstein’s theory of General Relativity are under investigation as a potential explanation of the accelerating expansion rate of the universe. I’ll present a cosmologist’s overview of attempts to test these ideas in an efficient and unbiased manner. I’ll start by introducing the bestiary of alternative gravity theories that have been put forwards. This proliferation of models motivates us to develop model-independent, agnostic tools for comparing the theory space to cosmological data. I’ll introduce the effective field theory for cosmological perturbations, a framework designed to unify modified gravity theories in terms of a manageable set of parameters. Having outlined the formalism, I’ll talk about the current constraints on this framework, and the improvements expected from the next generation of large galaxy clustering, weak lensing and intensity mapping experiments.
Integrable Cosmological Potentials
Sokolov, V V
2016-01-01
The problem of classification of the Einstein--Friedman cosmological Hamiltonians $H$ with a single scalar inflaton field $\\varphi$ that possess an additional integral of motion polynomial in momenta on the shell of the Friedman constraint $H=0$ is considered. Necessary and sufficient conditions for the existence of first, second, and third degree integrals are derived. These conditions have the form of ODEs for the cosmological potential $V(\\varphi)$. In the case of linear and quadratic integrals we find general solutions of the ODEs and construct the corresponding integrals explicitly. A new wide class of Hamiltonians that possess a cubic integral is derived. The corresponding potentials are represented in a parametric form in terms of the associated Legendre functions. Six families of special elementary solutions are described and sporadic superintegrable cases are discussed.
Tolish, Alexander; Wald, Robert M.
2016-08-01
The "memory effect" is the permanent change in the relative separation of test particles resulting from the passage of gravitational radiation. We investigate the memory effect for a general, spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) cosmology by considering the radiation associated with emission events involving particle-like sources. We find that if the resulting perturbation is decomposed into scalar, vector, and tensor parts, only the tensor part contributes to memory. Furthermore, the tensor contribution to memory depends only on the cosmological scale factor at the source and observation events, not on the detailed expansion history of the universe. In particular, for sources at the same luminosity distance, the memory effect in a spatially flat FLRW spacetime is enhanced over the Minkowski case by a factor of (1 +z ).
The Cosmological Memory Effect
Tolish, Alexander
2016-01-01
The "memory effect" is the permanent change in the relative separation of test particles resulting from the passage of gravitational radiation. We investigate the memory effect for a general, spatially flat FLRW cosmology by considering the radiation associated with emission events involving particle-like sources. We find that if the resulting perturbation is decomposed into scalar, vector, and tensor parts, only the tensor part contributes to memory. Furthermore, the tensor contribution to memory depends only on the cosmological scale factor at the source and observation events, not on the detailed expansion history of the universe. In particular, for sources at the same luminosity distance, the memory effect in a spatially flat FLRW spacetime is enhanced over the Minkowski case by a factor of $(1 + z)$.
Holography from quantum cosmology
Rashki, M
2014-01-01
The Weyl-Wigner-Groenewold-Moyal formalism of deformation quantization is applied to the closed Friedmann-Lema\\^itre-Robertson-Walker (FLRW) cosmological model. We show that the phase space average for the surface of the apparent horizon is quantized in units of the Planck's surface, and that the total entropy of the universe is also quantized. Taking into account these two concepts, it is shown that 't Hooft conjecture on the cosmological holographic principle (CHP) in radiation and dust dominated quantum universes is satisfied as a manifestation of quantization. This suggests that the entire universe (not only inside the apparent horizon) can be seen as a two-dimensional information structure encoded on the apparent horizon.
Steinhardt, Paul Joseph
1995-01-01
Observational tests during the next decade may determine if the evolution of the Universe can be understood from fundamental physical principles, or if special initial conditions, coincidences, and new, untestable physical laws must be invoked. The inflationary model of the Universe is an important example of a predictive cosmological theory based on physical principles. In this talk, we discuss the distinctive fingerprint that inflation leaves on the cosmic microwave background anisotropy. We then suggest a series of five milestone experimental tests of the microwave background which could determine the validity of the inflationary hypothesis within the next decade. The paper is a Review based on a Plenary talk given at the Snowmass Workshop on Particle Astrophysics and Cosmology, 1995 It will appear in the Proceedings edited by E. Kolb and R.Peccei. Software package for computing filter functions and band power estimates available thru world-wide-web at http://dept.physics.upenn.edu/~www/as tro-cosmo/ .