Teaching the Very Recent Past: "Miriam's Vision" and the London Bombings
Kitson, Alison; Thompson, Sarah
2015-01-01
"Miriam's Vision" is an educational project developed by the Miriam Hyman Memorial Trust, an organisation set up in memory of Miriam Hyman, one of the 52 victims of the London bombings of 2005. The project has developed a number of subject-based modules, including history, which are provided free to schools through the website…
Bianchi surfaces: integrability in an arbitrary parametrization
International Nuclear Information System (INIS)
Nieszporski, Maciej; Sym, Antoni
2009-01-01
We discuss integrability of normal field equations of arbitrarily parametrized Bianchi surfaces. A geometric definition of the Bianchi surfaces is presented as well as the Baecklund transformation for the normal field equations in an arbitrarily chosen surface parametrization.
Bianchi models and new inflation
International Nuclear Information System (INIS)
Turner, M.S.; Widrow, L.
1986-03-01
The promise of the inflationary Universe scenario is to free the present state of the Universe from extreme dependence on initial data. Paradoxically, inflation is usually analyzed in the context of the homogeneous and isotropic Robertson-Walker (RW) cosmological models. We show that all but a small subset of the homogeneous models (the Bianchi models) undergo inflation. Any initial anisotropy is so strongly damped that if sufficient inflation occurs to solve the flatness/horizon problems the Universe today would still be very isotropic. Some of the Bianchi models will eventually (in the exponentially distant future) become very anisotropic again. 15 refs
In memoriam : Miriam Dorothy (Posner) Finkel (1916-1999)
International Nuclear Information System (INIS)
Reilly, C.A.
2000-01-01
Miriam P. Finkel, pioneer radiobiologist, passed away on August 20, 1999, at her home in Tucson, AZ. She was born on January 22, 1916, in Chicago to Russian immigrants. She spent much of her youth in Davenport, IA. She returned to Chicago for her college education, and received a B.S. in zoology in 1938 from the University of Chicago. While continuing her formal education in zoology, Miriam served as a laboratory instructor at Wilson Junior College. She received her Ph.D. in 1944 from the University of Chicago. She began her scientific career at the dawning of the nuclear age and seized upon the scientific opportunity present in the new field of radiobiology to be a life-long contributor to the understanding of the biological effects of radiation. Her technical insights and discoveries helped form the foundation for many of the health standards (i.e. permissible levels of internal radionuclide exposure) in use today. She also made a significant contribution to the field of molecular biology. Her isolation of a murine osteogenic sarcoma virus, the Finkel-Biskis-Jenkins or FBJ virus, led to fundamental discoveries in viral-induced tumors and ultimately provided the now universally used molecular biological tool, the FOS gene.
Time-dependent, Bianchi II, rotating universe
International Nuclear Information System (INIS)
Reboucas, M.J.
1981-01-01
An exact cosmological solution of Einstein's equations which has time-dependent rotation is presented. The t-constant sections are of Bianchi type II. The source of this geometry is a fluid which has not been thermalized. (Author) [pt
The contracted Bianchi identities in Regge calculus
International Nuclear Information System (INIS)
Williams, Ruth M
2012-01-01
In this note, we show explicitly how the linearized contracted Bianchi identities at a vertex in four-dimensional Regge calculus are related to a sum of the equations of motion for all the edges meeting at that vertex. (note)
Bianchi identities in higher dimensions
International Nuclear Information System (INIS)
Pravda, V; Pravdova, A; Coley, A; Milson, R
2004-01-01
A higher dimensional frame formalism is developed in order to study implications of the Bianchi identities for the Weyl tensor in vacuum spacetimes of the algebraic types III and N in arbitrary dimension n. It follows that the principal null congruence is geodesic and expands isotropically in two dimensions and does not expand in n - 4 spacelike dimensions or does not expand at all. It is shown that the existence of such principal geodesic null congruence in vacuum (together with an additional condition on twist) implies an algebraically special spacetime. We also use the Myers-Perry metric as an explicit example of a vacuum type D spacetime to show that principal geodesic null congruences in vacuum type D spacetimes do not share this property
Higher-dimensional Bianchi type-VIh cosmologies
Lorenz-Petzold, D.
1985-09-01
The higher-dimensional perfect fluid equations of a generalization of the (1 + 3)-dimensional Bianchi type-VIh space-time are discussed. Bianchi type-V and Bianchi type-III space-times are also included as special cases. It is shown that the Chodos-Detweiler (1980) mechanism of cosmological dimensional-reduction is possible in these cases.
“Draw yourself out of it” : Miriam Katin’s graphic metamorphosis of trauma
Oostdijk, Diederik
2018-01-01
Miriam Katin's two graphic memoirs We Are on Our Own [(2006). Montreal: Drawn & Quarterly] and Letting It Go [(2013). Montreal: Drawn & Quarterly] both reflect on how the trauma of the Holocaust can be transformed through and in art. In the former Katin details how she and her mother narrowly escape
“Draw yourself out of it”: : Miriam Katin’s Graphic Metamorphosis of Trauma
Oostdijk, D.M.
2018-01-01
Miriam Katin's two graphic memoirs We Are on Our Own [(2006). Montreal: Drawn & Quarterly] and Letting It Go [(2013). Montreal: Drawn & Quarterly] both reflect on how the trauma of the Holocaust can be transformed through and in art. In the former Katin details how she and her mother narrowly escape
Compact invariant sets of the Bianchi VIII and Bianchi IX Hamiltonian systems
International Nuclear Information System (INIS)
Starkov, Konstantin E.
2011-01-01
In this Letter we prove that all compact invariant sets of the Bianchi VIII Hamiltonian system are contained in the set described by several simple linear equalities and inequalities. Moreover, we describe invariant domains in which the phase flow of this system has no recurrence property and show that there are no periodic orbits and neither homoclinic, nor heteroclinic orbits contained in the zero level set of its Hamiltonian. Similar results are obtained for the Bianchi IX Hamiltonian system. -- Highlights: → Zero level set of Hamiltonian of Bianchi VIII/IX systems contains no periodic orbits. → Similar conditions for homoclinic/heteroclinic orbits are given. → General nonexistence conditions of compact invariant sets are got.
Compact invariant sets of the Bianchi VIII and Bianchi IX Hamiltonian systems
Energy Technology Data Exchange (ETDEWEB)
Starkov, Konstantin E., E-mail: konst@citedi.mx [CITEDI-IPN, Av. del Parque 1310, Mesa de Otay, Tijuana, BC (Mexico)
2011-08-22
In this Letter we prove that all compact invariant sets of the Bianchi VIII Hamiltonian system are contained in the set described by several simple linear equalities and inequalities. Moreover, we describe invariant domains in which the phase flow of this system has no recurrence property and show that there are no periodic orbits and neither homoclinic, nor heteroclinic orbits contained in the zero level set of its Hamiltonian. Similar results are obtained for the Bianchi IX Hamiltonian system. -- Highlights: → Zero level set of Hamiltonian of Bianchi VIII/IX systems contains no periodic orbits. → Similar conditions for homoclinic/heteroclinic orbits are given. → General nonexistence conditions of compact invariant sets are got.
Inhomogeneous generalizations of Bianchi type VIh models with perfect fluid
Roy, S. R.; Prasad, A.
1991-07-01
Inhomogeneous universes admitting an Abelian G2 of isometry and filled with perfect fluid have been derived. These contain as special cases exact homogeneous universes of Bianchi type VIh. Many of these universes asymptotically tend to homogeneous Bianchi VIh universes. The models have been discussed for their physical and kinematical behaviors.
Bianchi Type-I Universe with wet dark fluid
Indian Academy of Sciences (India)
Bianchi-type Universe; wet dark fluid; cosmological parameters. Abstract. The Bianchi Type-I Universe filled with dark energy from a wet dark fluid has been considered. A new equation of ... Pramana – Journal of Physics | News. © 2017 Indian ...
Bianchi congruences of two-dimensional surfaces in E4
International Nuclear Information System (INIS)
Gor'kavyi, V A
2005-01-01
Pseudospherical Bianchi congruences in Euclidean 4-space E 4 are considered. The focal surfaces of such congruences are shown to have a constant negative Gaussian curvature. A geometric and an analytic description of special pseudo- spherical surfaces in E 4 admitting a Bianchi congruence are obtained.
Directory of Open Access Journals (Sweden)
Maria Luisa A. Valdez
2017-02-01
Full Text Available Gender inequality and the resulting discrimination of women are deeply rooted in history, culture and tradition. It is said to be detrimental to the mental health of women and persists as a debilitating stigma which lowers their dignity and sense of self-worth. Thus, this qualitative research was conducted to underscore the issue of gender equality and women empowerment as core topics in selected speeches of Senator Miriam Defensor Santiago. Findings of the analysis showed that the issue of gender gap in the Philippines was manifested and discussed forthrightly by the senator in her speeches in terms of educational attainment, health and survival, economic participation and opportunity, and political empowerment, all being effectively touched by the senator with the signature wit, eloquence, astuteness and passion she was widely known for; that gender equality and women empowerment were likewise gleaned in the selected speeches, all of which were delivered by Miriam Defensor Santiago with the motive of persuading her audience to espouse the same advocacy, and this she achieved through her unique and distinct style of utilizing the persuasive ability of literature; and, that the implications of the author's advocacy on gender equality and gender empowerment delegated the monumental task upon the shoulders of the Filipino youth, in ways that their thinking will be directly influenced by her advocacy and thus promote within them a sense of urgency to embrace and espouse the same advocacies in order for them to be able to contribute to nation building.
Directory of Open Access Journals (Sweden)
Allan A. Boesak
2017-07-01
Full Text Available This article examines the manner and method of resistance against patriarchal power and privilege. Two types of power are contrasted. One is the violent, war-like and hierarchical power of an empire, and the other is the faithful resistance of Israel’s prophets. A further distinction is made between violent male power and non-violent female power. It is argued that Miriam was a prophet of the people and her prophetic witness is an example of the power and outcome of non-violent resistance. Her theology explicitly and specifically praises God not as a warrior. Hers is not a muscular, masculine God whose power seeks to match the power of empire. Her God has a power that through radical love for a slave people and taking sides with the enslaved overcomes the power of the slaveholder. In her theology, Miriam recalls the God of the exodus, who begins the acts of liberation with the women, to whose faithfulness, courage and defiant obedience, the freedom of the people is entrusted. From a feminist perspective it is argued that this style of non-violent, faithful prophetic witness has a greater impact than violent resistance associated with an empire-like power. It is suggested that black liberation theology should adopt this paradigm in its witness of and resistance against oppression.
Loop quantum cosmology of Bianchi IX: effective dynamics
International Nuclear Information System (INIS)
Corichi, Alejandro; Montoya, Edison
2017-01-01
We study solutions to the effective equations for the Bianchi IX class of spacetimes within loop quantum cosmology (LQC). We consider Bianchi IX models whose matter content is a massless scalar field, by numerically solving the loop quantum cosmology effective equations, with and without inverse triad corrections. The solutions are classified using certain geometrically motivated classical observables. We show that both effective theories—with lapse N = V and N = 1—resolve the big bang singularity and reproduce the classical dynamics far from the bounce. Moreover, due to the positive spatial curvature, there is an infinite number of bounces and recollapses. We study the limit of large field momentum and show that both effective theories reproduce the same dynamics, thus recovering general relativity. We implement a procedure to identify amongst the Bianchi IX solutions, those that behave like k = 0,1 FLRW as well as Bianchi I, II, and VII 0 models. The effective solutions exhibit Bianchi I phases with Bianchi II transitions and also Bianchi VII 0 phases, which had not been studied before. We comment on the possible implications of these results for a quantum modification to the classical BKL behaviour. (paper)
Loop quantum cosmology of Bianchi IX: effective dynamics
Corichi, Alejandro; Montoya, Edison
2017-03-01
We study solutions to the effective equations for the Bianchi IX class of spacetimes within loop quantum cosmology (LQC). We consider Bianchi IX models whose matter content is a massless scalar field, by numerically solving the loop quantum cosmology effective equations, with and without inverse triad corrections. The solutions are classified using certain geometrically motivated classical observables. We show that both effective theories—with lapse N = V and N = 1—resolve the big bang singularity and reproduce the classical dynamics far from the bounce. Moreover, due to the positive spatial curvature, there is an infinite number of bounces and recollapses. We study the limit of large field momentum and show that both effective theories reproduce the same dynamics, thus recovering general relativity. We implement a procedure to identify amongst the Bianchi IX solutions, those that behave like k = 0,1 FLRW as well as Bianchi I, II, and VII0 models. The effective solutions exhibit Bianchi I phases with Bianchi II transitions and also Bianchi VII0 phases, which had not been studied before. We comment on the possible implications of these results for a quantum modification to the classical BKL behaviour.
An intrinsic and exterior form of the Bianchi identities
Do, Thoan; Prince, Geoff
2017-09-01
We give an elegant formulation of the structure equations (of Cartan) and the Bianchi identities in terms of exterior calculus without reference to a particular basis and without the exterior covariant derivative. This approach allows both structure equations and the Bianchi identities to be expressed in terms of forms of arbitrary degree. We demonstrate the relationship with both the conventional vector version of the Bianchi identities and to the exterior covariant derivative approach. Contact manifolds, codimension one foliations and the Cartan form of classical mechanics are studied as examples of its flexibility and utility.
Homothetic matter collineations of LRS Bianchi type I spacetimes
Hussain, Tahir; Rahim, Waqas
2017-12-01
A complete classification of locally rotationally symmetric (LRS) Bianchi type I spacetimes via homothetic matter collineations (HMCs) is presented. For non-degenerate energy-momentum tensor, a general form of the vector field generating HMCs is found, subject to some integrability conditions. Solving the integrability conditions in different cases, it is found that the LRS Bianchi type I spacetimes admit 6-, 7-, 8-, 10- or 11-dimensional Lie algebra of HMCs. When the energy-momentum tensor is degenerate, two cases give 6 and 11 HMCs, while the remaining cases produce infinite number of HMCs. Some LRS Bianchi type I metrics are provided admitting HMCs.
Anisotropy and inflation in Bianchi I braneworlds
International Nuclear Information System (INIS)
Aguirregabiria, Juan M; Chimento, Luis P; Lazkoz, Ruth
2004-01-01
After a more general assumption on the influence of the bulk on the brane, we extend some conclusions by Maartens et al (2001 Phys. Rev. D 63 063509) and Santos et al (2001 Phys. Rev. D 64 063506) on the asymptotic behaviour of Bianchi I braneworlds. As a consequence of the nonlocal anisotropic stresses induced by the bulk, in most of our models, the brane does not isotropize and the nonlocal energy does not vanish in the limit in which the mean radius goes to infinity. We have also found the intriguing possibility that the inflation due to the cosmological constant might be prevented by the interaction with the bulk. We show that the problem for the mean radius can be completely solved in our models, which include as particular cases those in the references above
Energy distributions of Bianchi type-VIh Universe in general relativity ...
Indian Academy of Sciences (India)
2017-03-16
Mar 16, 2017 ... butions in Bianchi type-VIh metric for different gravitation theories. ... Bianchi VIh Universe; general relativity; teleparallel gravity; energy–momentum distribution. ... In §3, we introduce energy–momentum definitions of Einstein,.
Stability conditions for the Bianchi type II anisotropically inflating universes
International Nuclear Information System (INIS)
Kao, W.F.; Lin, Ing-Chen
2009-01-01
Stability conditions for a class of anisotropically inflating solutions in the Bianchi type II background space are shown explicitly in this paper. These inflating solutions were known to break the cosmic no-hair theorem such that they do not approach the de Sitter universe at large times. It can be shown that unstable modes of the anisotropic perturbations always exist for this class of expanding solutions. As a result, we show that these set of anisotropically expanding solutions are unstable against anisotropic perturbations in the Bianchi type II space
Dynamic of exact perturbations in Bianchi IX type cosmological models
International Nuclear Information System (INIS)
Mello Neto, J.R.T. de.
1985-01-01
The dynamic of Bianchi IX type cosmological models is studied, after reducing Einstein equations to Hamiltonian system. Using the Melnikov method, the existence of chaos in the dynamic of these models is proved, and some numerical experiments are carried out. (M.C.K.) [pt
Anisotropic Bianchi-I universe with phantom field and cosmological ...
Indian Academy of Sciences (India)
India. *Corresponding author. E-mail: bcpaul@iucaa.ernet.in. MS received 23 May ... We study an anisotropic Bianchi-I universe in the presence of a phantom ... The phantom cosmology has been analysed adopting phase space analysis ... the second part we study the critical points corresponding to the set of autonomous.
Bianchi Type-I Universe with wet dark fluid
Indian Academy of Sciences (India)
Abstract. The Bianchi Type-I Universe filled with dark energy from a wet dark fluid has ... model is in the spirit of the generalized Chaplygin gas (GCG) [9], where a physically motivated .... From the mechanical point of view, eq. (2.28) can be ...
Characterization of the Lovelock gravity by Bianchi derivative
Indian Academy of Sciences (India)
We prove the theorem: The second-order quasilinear differential operator as a second-rank divergence-free tensor in the equation of motion for gravitation could always be derived from the trace of the Bianchi derivative of the fourth-rank tensor, which is a homogeneous polynomial in curvatures. The existence of such a ...
Characterization of the Lovelock gravity by Bianchi derivative
Indian Academy of Sciences (India)
Characterization of the Lovelock gravity by Bianchi derivative. NARESH DADHICH. Inter-University Centre for Astronomy & Astrophysics, Post Bag 4, Pune 411 007, India. E-mail: nkd@iucaa.ernet.in. MS received 30 November 2009; revised 15 February 2010; accepted 19 February 2010. Abstract. We prove the theorem: ...
Bianchi type I inflationary universe in general relativity
Indian Academy of Sciences (India)
In this paper, we have investigated Bianchi type I inﬂationary universe in the presence of massless scalar ﬁeld with a ﬂat potential. To get an inﬂationary solution, we have considered a ﬂat region in which potential is constant. The inﬂationary scenario of the model is discussed in detail.
Bianchi type I inflationary universe in general relativity
Indian Academy of Sciences (India)
In this paper, we have investigated Bianchi type I inflationary universe in the presence of massless scalar field with a flat potential. To get an inflationary solution, we have considered a flat region in which potentialV is constant. The inflationary scenario of the model is discussed in detail. Keywords. Inflationary universe ...
Anisotropic Bianchi-I universe with phantom field and cosmological ...
Indian Academy of Sciences (India)
We study an anisotropic Bianchi-I universe in the presence of a phantom field and a cosmological constant. Cosmological solutions are obtained when the kinetic energy of the phantom field is of the order of anisotropy and dominates over the potential energy of the field. The anisotropy of the universe decreases and the ...
The Bianchi classification of maximal D = 8 gauged supergravities
Bergshoeff, Eric; Gran, Ulf; Linares, Román; Nielsen, Mikkel; Ortín, Tomás; Roest, Diederik
2003-01-01
We perform the generalized dimensional reduction of D = 11 supergravity over three-dimensional group manifolds as classified by Bianchi. Thus, we construct 11 different maximal D = 8 gauged supergravities, two of which have an additional parameter. One class of group manifolds (class B) leads to
The Bianchi classification of maximal D=8 gauged supergravities
Bergshoeff, E; Gran, U; Linares, R; Nielsen, M; Ortin, T; Roest, D
2003-01-01
We perform the generalized dimensional reduction of D = 11 supergravity over three-dimensional group manifolds as classified by Bianchi. Thus, we construct 11 different maximal D = 8 gauged supergravities, two of which have an additional parameter. One class of group manifolds (class B) leads to
Bianchi-identities for supersymmetric gauge-theories
International Nuclear Information System (INIS)
Sohnius, M.F.
1978-01-01
The Bianchi-identities for gauge-theories in an extended flat superspace are evaluated. They permitbetter understanding of possible constraint equations, and can serve as a starting point for further constructions of gauge-theories with extended supersymmetry. (orig.) [de
Vacuum solutions of Bianchi cosmologies in quadratic gravity
International Nuclear Information System (INIS)
Deus, Juliano Alves de; Muller, Daniel
2011-01-01
Full text: In this work we solve numerically the vacuum solutions of field equations of Bianchi homogeneous universes in the context of Semiclassical theory. Our interest is to study the quadratic theory of gravity with regard in the cosmological description of our universe in periods of intense fields. Bianchi cosmologies are anisotropic homogeneous cosmological models, but can include the isotropic models as particular cases (Bianchi I, VII and IX include homogeneous and isotropic Friedmann models plane, hyperbolic and spherical, respectively). Homogeneous models are good cosmological representations of our universe. With focus in solutions for intense fields, like the early universe, where isotropy is not necessarily required, the adopted scenario is the vacuum solutions, where the geometry is dominant in determining the gravitation. Still following in this way, the Semiclassical theory, which considers quantum matter fields propagating in classical geometrical background, is addressed to give the field equations. This formalism leads to fourth-order ordinary differential equations, in contrast to second-order equations from General Relativity. The Lagrangian of the theory is quadratic in the Ricci scalar and in the Ricci tensor. The equations system is highly non-linear and can be only numerically solved, except perhaps for few particular cases. We obtained numerical solutions for Bianchi V II A evolving to Minkowski and to de Sitter solutions, and also to singularities. The both first and second solutions were obtained choosing initial conditions near from respective exact vacuum solutions from Einstein theory, which are also exact solutions of the quadratic theory. Other Bianchi types are still under study. (author)
Classical Bianchi Type I Cosmology in K-Essence Theory
International Nuclear Information System (INIS)
Pimentel, Luis O.; Socorro, J.; Espinoza-García, Abraham
2014-01-01
We use one of the simplest forms of the K-essence theory and we apply it to the classical anisotropic Bianchi type I cosmological model, with a barotropic perfect fluid (p=γρ) modeling the usual matter content and with cosmological constant Λ. Classical exact solutions for any γ≠1 and Λ=0 are found in closed form, whereas solutions for Λ≠0 are found for particular values in the barotropic parameter. We present the possible isotropization of the cosmological model Bianchi I using the ratio between the anisotropic parameters and the volume of the universe. We also include a qualitative analysis of the analog of the Friedmann equation.
Motives and periods in Bianchi IX gravity models
Fan, Wentao; Fathizadeh, Farzad; Marcolli, Matilde
2018-05-01
We show that, when considering the anisotropic scaling factors and their derivatives as affine variables, the coefficients of the heat-kernel expansion of the Dirac-Laplacian on SU(2) Bianchi IX metrics are algebro-geometric periods of motives of complements in affine spaces of unions of quadrics and hyperplanes. We show that the motives are mixed Tate and we provide an explicit computation of their Grothendieck classes.
Spectral action for Bianchi type-IX cosmological models
International Nuclear Information System (INIS)
Fan, Wentao; Fathizadeh, Farzad; Marcolli, Matilde
2015-01-01
A rationality result previously proved for Robertson-Walker metrics is extended to a homogeneous anisotropic cosmological model, namely the Bianchi type-IX minisuperspace. It is shown that the Seeley-de Witt coefficients appearing in the expansion of the spectral action for the Bianchi type-IX geometry are expressed in terms of polynomials with rational coefficients in the cosmic evolution factors w_1(t),w_2(t),w_3(t), and their higher derivates with respect to time. We begin with the computation of the Dirac operator of this geometry and calculate the coefficients a_0,a_2,a_4 of the spectral action by using heat kernel methods and parametric pseudodifferential calculus. An efficient method is devised for computing the Seeley-de Witt coefficients of a geometry by making use of Wodzicki’s noncommutative residue, and it is confirmed that the method checks out for the cosmological model studied in this article. The advantages of the new method are discussed, which combined with symmetries of the Bianchi type-IX metric, yield an elegant proof of the rationality result.
Spectral action for Bianchi type-IX cosmological models
Energy Technology Data Exchange (ETDEWEB)
Fan, Wentao; Fathizadeh, Farzad; Marcolli, Matilde [Division of Physics, Mathematics and Astronomy, California Institute of Technology,1200 E. California Blvd., Pasadena, CA 91125 (United States)
2015-10-13
A rationality result previously proved for Robertson-Walker metrics is extended to a homogeneous anisotropic cosmological model, namely the Bianchi type-IX minisuperspace. It is shown that the Seeley-de Witt coefficients appearing in the expansion of the spectral action for the Bianchi type-IX geometry are expressed in terms of polynomials with rational coefficients in the cosmic evolution factors w{sub 1}(t),w{sub 2}(t),w{sub 3}(t), and their higher derivates with respect to time. We begin with the computation of the Dirac operator of this geometry and calculate the coefficients a{sub 0},a{sub 2},a{sub 4} of the spectral action by using heat kernel methods and parametric pseudodifferential calculus. An efficient method is devised for computing the Seeley-de Witt coefficients of a geometry by making use of Wodzicki’s noncommutative residue, and it is confirmed that the method checks out for the cosmological model studied in this article. The advantages of the new method are discussed, which combined with symmetries of the Bianchi type-IX metric, yield an elegant proof of the rationality result.
Tilted Bianchi type I dust fluid cosmological model in general relativity
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 3. Tilted Bianchi type I dust ﬂuid cosmological model in general ... In this paper, we have investigated a tilted Bianchi type I cosmological model ﬁlled with dust of perfect ﬂuid in general relativity. To get a determinate solution, we have assumed a condition ...
Bianchi Type-I, V and VIo models in modified generalized scalar ...
Indian Academy of Sciences (India)
Keywords. Bianchi type; scalar–tensor theory; cosmological term; scalar field. ... We obtain exact solutions of the field equations in Bianchi Type-I, V and VIo space–times. The evolution of the scale factor ... Pramana – Journal of Physics | News.
Tilted Bianchi type I dust fluid cosmological model in general relativity
Indian Academy of Sciences (India)
Tilted Bianchi type I dust ﬂuid cosmological model in general relativity ... In this paper, we have investigated a tilted Bianchi type I cosmological model ﬁlled with dust of perfect ﬂuid in general relativity. ... Pramana – Journal of Physics | News ...
Nonlinear Spinor Fields in Bianchi type-I spacetime reexamined
Saha, Bijan
2013-01-01
The specific behavior of spinor field in curve space-time with the exception of FRW model almost always gives rise to non-trivial non-diagonal components of the energy-momentum tensor. This non-triviality of non-diagonal components of the energy-momentum tensor imposes some severe restrictions either on the spinor field or on the metric functions. In this paper within the scope of an anisotropic Bianchi type-I Universe we study the role of spinor field in the evolution of the Universe. It is ...
The Bianchi IX model in loop quantum cosmology
International Nuclear Information System (INIS)
Bojowald, Martin; Date, Ghanashyam; Hossain, Golam Mortuza
2004-01-01
The Bianchi IX model has been used often to investigate the structure close to singularities of general relativity. Its classical chaos is expected to have, via the BKL scenario, implications even for the approach to general inhomogeneous singularities. Thus, it is a popular model to test consequences of modifications to general relativity suggested by quantum theories of gravity. This paper presents a detailed proof that modifications coming from loop quantum gravity lead to a non-chaotic effective behaviour. The way this is realized, independently of quantization ambiguities, suggests a new look at initial and final singularities
Bianchi's Bäcklund transformation for higher dimensional quadrics
Dincă, Ion I.
2016-12-01
We provide a generalization of Bianchi's Bäcklund transformation from 2-dimensional quadrics to higher dimensional quadrics (which is also a generalization of Tenenblat-Terng's Bäcklund transformation of isometric deformations of Hn(R) in R 2 n - 1 to general quadrics). Our investigation is the higher dimensional version of Bianchi's main three theorems on the theory of isometric deformations of quadrics and Bianchi's treatment of the Bäcklund transformation for diagonal paraboloids via conjugate systems. It became the driving force which led to the flourishing of the classical differential geometry in the second half of the XIX th century and its profound study by illustrious geometers led to interesting results. Today it is still an open problem in its full generality, but basic familiar results like the Gauß-Bonnet fundamental theorem of surfaces and the Codazzi-Mainardi equations (independently discovered also by Peterson) were first communicated to the French Academy of Sciences. A list (most likely incomplete) of the winners of the prize includes Bianchi, Bonnet, Guichard, Weingarten.Up to 1899 isometric deformations of the (pseudo-)sphere and isotropic quadrics without center (from a metric point of view they can be considered as metrically degenerate quadrics without center) together with their Bäcklund transformation and the complementary transformation of isometric deformations of surfaces of revolution were investigated by geometers such as Bäcklund, Bianchi, Bonnet, Darboux, Goursat, Hazzidakis, Lie, Weingarten, etc.In 1899 Guichard discovered that when quadrics with(out) center and of revolution around the focal axis roll on their isometric deformations their foci describe constant mean curvature (minimal) surfaces (and Bianchi proved the converse: all constant mean curvature (minimal) surfaces can be realized in this way).With Guichard's result the race to find the isometric deformations of general quadrics was on; it ended with Bianchi
Loop quantum cosmology of the Bianchi I model: complete quantization
International Nuclear Information System (INIS)
Martín-Benito, M; Garay, L J; Mena Marugán, G A; Wilson-Ewing, E
2012-01-01
We complete the canonical quantization of the vacuum Bianchi I model within the improved dynamics scheme of loop quantum cosmology, characterizing the Hilbert structure of the physical states and providing a complete set of observables acting on them. In order to achieve this task, it has been essential to determine the structure of the separable superselection sectors that arise owing to the polymeric quantization, and to prove that the initial value problem obtained when regarding the Hamiltonian constraint as an evolution equation, interpreting the volume as the evolution parameter, is well-posed.
A global conformal extension theorem for perfect fluid Bianchi space-times
International Nuclear Information System (INIS)
Luebbe, Christian; Tod, Paul
2008-01-01
A global extension theorem is established for isotropic singularities in polytropic perfect fluid Bianchi space-times. When an extension is possible, the limiting behaviour of the physical space-time near the singularity is analysed
On the asserted clash between the Freud and the Bianchi identities
Antoci, S.
1995-09-01
Through a constructive method it is shown that the claim advanced in recent times about a clash that should occur between the Freud and the Bianchi identities in Einstein's general theory of relativity is based on a faulty argument.
A complete solution of the Bianchi identities in superspace with supergravity constraints
International Nuclear Information System (INIS)
Grimm, R.; Wess, J.; Zumino, B.
1979-01-01
A short discussion of the superspace formulation of supergravity is given and the Bianchi identities are derived. The supergravity constraints are imposed and the identities are solved in terms of superfields and their covariant derivatives. (Auth.)
Anisotropic Bianchi II cosmological models with matter and electromagnetic fields
International Nuclear Information System (INIS)
Soares, D.
1978-01-01
A class of solutions of Einstein-Maxwell equations is presented, which corresponds to anisotropic Bianchi II spatially homogeneous cosmological models with perfect fluid and electromagnetic field. A particular model is examined and shown to be unstable for perturbations of the electromagnetic field strength parameter about a particular value. This value defines a limiar unstable case in which the ratio epsilon, of the fluid density to the e.m. energy density is monotonically increasing with a minimum finite value at the singularity. Beyond this limiar, the model has a matter dominated singularity, and a characteristic stage appears where epsilon has a minimum, at a finite time from the singularity. For large times, the models tend to an exact solution for zero electromagnetic field and fluid with p = (1/5)p. Some cosmological features of the models are calculated, as the effect of anisotropy on matter density and expansion time scale factors, as compared to the corresponding Friedmann model [pt
Bianchi type II brane-world cosmologies (U≥0)
International Nuclear Information System (INIS)
Hoogen, R.J. van den; Ibanez, J.
2003-01-01
The asymptotic properties of the Bianchi type II cosmological model in the brane-world scenario are investigated. The matter content is assumed to be a combination of a perfect fluid and a minimally coupled scalar field that is restricted to the brane. The isotropic brane-world solution is determined to represent the initial singularity in all brane-world cosmologies. Additionally, it is shown that it is the kinetic energy of the scalar field which dominates the initial dynamics in these brane-world cosmologies. It is important to note that the dynamics of these brane-world cosmologies is not necessarily asymptotic to general relativistic cosmologies to the future in the case of a zero four-dimensional cosmological constant
Scalar-flat Kaehler metrics with conformal Bianchi V symmetry
Energy Technology Data Exchange (ETDEWEB)
Dunajski, Maciej [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Plansangkate, Prim, E-mail: M.Dunajski@damtp.cam.ac.uk, E-mail: plansang@CRM.UMontreal.ca [Centre de Recherches Mathematiques (CRM), Universite de Montreal, CP 6128, Montreal (Quebec) H3C 3J7 (Canada)
2011-06-21
We provide an affirmative answer to a question posed by Tod (1995, Twistor Theory (New York: Dekker)), and construct all four-dimensional Kaehler metrics with vanishing scalar curvature which are invariant under the conformal action of the Bianchi V group. The construction is based on the combination of twistor theory and the isomonodromic problem with two double poles. The resulting metrics are non-diagonal in the left-invariant basis and are explicitly given in terms of Bessel functions and their integrals. We also make a connection with the LeBrun ansatz, and characterize the associated solutions of the SU({infinity}) Toda equation by the existence a non-abelian two-dimensional group of point symmetries.
Bianchi VI0 and III models: self-similar approach
International Nuclear Information System (INIS)
Belinchon, Jose Antonio
2009-01-01
We study several cosmological models with Bianchi VI 0 and III symmetries under the self-similar approach. We find new solutions for the 'classical' perfect fluid model as well as for the vacuum model although they are really restrictive for the equation of state. We also study a perfect fluid model with time-varying constants, G and Λ. As in other studied models we find that the behaviour of G and Λ are related. If G behaves as a growing time function then Λ is a positive decreasing time function but if G is decreasing then Λ 0 is negative. We end by studying a massive cosmic string model, putting special emphasis in calculating the numerical values of the equations of state. We show that there is no SS solution for a string model with time-varying constants.
Bianchi-Baecklund transformations, conservation laws, and linearization of various field theories
International Nuclear Information System (INIS)
Chau Wang, L.L.
1980-01-01
The discussion includes: the Sine-Gordon equation, parametric Bianchi-Baecklund transformations and the derivation of local conservation laws; chiral fields, parametric Bianchi-Baecklund transformations, local and non-local conservation laws, and linearization; super chiral fields, a parallel development similar to the chiral field; and self-dual Yang-Mills fields in 4-dimensional Euclidean space; loop-cpace chiral equations, parallel development but with subtlety
Homoclinic chaos in axisymmetric Bianchi IX cosmologies reexamined
International Nuclear Information System (INIS)
Soares, I. Damiao; Stuchi, T.J.
2005-01-01
The dynamics of Bianchi IX models with two scale factors A(t) and B(t) is reexamined. The matter content of the model is assumed to be comoving dust plus a positive cosmological constant. We make a complete numerical construction of topological structures present in the phase space of the model, as the center manifold of periodic orbits and the stable and unstable cylinders of orbits that emerge from the center manifold, associated to a saddle-center critical point. We exhibit the homoclinic intersections of the unstable and stable cylinders that produce homoclinic chaos in the models. A=0 is not a singularity of the Hamiltonian dynamics and any truncation of the dynamics at A=0 is bound to a loss of information. We make an explicit construction of a set with a horseshoe structure in the A>0 region, of initial conditions corresponding to initially expanding universes. We show that the dynamics of this set is chaotic even if restricted to the region A>0 and has the Einstein universe configuration as a chaotic scatterer. The result however demands the information of the Hamiltonian dynamics in whole phase space, including the region A<0. This refutes recent claims that no homoclinic chaos is present in the dynamics of the model
A quantum gravitational inflationary scenario in Bianchi-I spacetime
International Nuclear Information System (INIS)
Gupt, Brajesh; Singh, Parampreet
2013-01-01
We investigate the ϕ 2 inflationary model in the Bianchi-I spacetime using the effective spacetime description of loop quantum cosmology to understand the issues of the resolution of initial singularity, isotropization, effect of anisotropies on the amount of inflation, and the phase-space attractors in the presence of non-perturbative quantum gravitational modifications. A comparative analysis with the classical theory by including more general initial conditions than the ones previously considered in the latter is also performed. We show that, in general, the classical singularity is replaced by a bounce of the mean scale factor in loop quantum cosmology. Due to the underlying quantum geometric effects, the energy density of the inflaton and the anisotropic shear remain bounded throughout the non-singular evolution. Starting from arbitrary anisotropic initial conditions, a loop quantum universe isotropizes either before or soon after the onset of slow-roll inflation. We find a double attractor behavior in the phase-space dynamics of loop quantum cosmology, similar to the one in classical theory, but with some additional subtle features. Quantum modifications to the dynamical equations are such that, unlike the classical theory, the amount of inflation does not monotonically depend on the initial anisotropy in loop quantum cosmology. Our results suggest that a viable non-singular inflationary model can be constructed from highly anisotropic initial conditions in the Planck regime. (paper)
Oscillating Bianchi IX universe in Horava-Lifshitz gravity
International Nuclear Information System (INIS)
Misonoh, Yosuke; Maeda, Kei-ichi; Kobayashi, Tsutomu
2011-01-01
We study a vacuum Bianchi IX universe in the context of Horava-Lifshitz gravity. In particular, we focus on the classical dynamics of the universe and analyze how anisotropy changes the history of the universe. For small anisotropy, we find an oscillating universe as well as a bounce universe just as the case of the Friedmann-Lemaitre-Robertson-Walker spacetime. However, if the initial anisotropy is large, we find the universe which ends up with a big crunch after oscillations if a cosmological constant Λ is zero or negative. For Λ>0, we find a variety of histories of the universe, that is a de Sitter expanding universe after oscillations in addition to the oscillating solution and the previous big crunch solution. This fate of the universe shows sensitive dependence of initial conditions, which is one of the typical properties of a chaotic system. If the initial anisotropy is near the upper bound, we find the universe starting from a big bang and ending up with a big crunch for Λ≤0, and a de Sitter expanding universe starting from a big bang for Λ>0.
International Nuclear Information System (INIS)
Iizuka, Norihiro; Ishibashi, Akihiro; Maeda, Kengo
2014-01-01
Bianchi black branes (black brane solutions with homogeneous but anisotropic horizons classified by the Bianchi type) provide a simple holographic setting with lattice structures taken into account. In the case of holographic superconductor, we have a persistent current with lattices. Accordingly, we expect that in the dual gravity side, a black brane should carry some momentum along a direction of lattice structure, where translational invariance is broken. Motivated by this expectation, we consider whether — and if possible, in what circumstances — a Bianchi black brane can have momentum along a direction of no-translational invariance. First, we show that this cannot be the case for a certain class of stationary Bianchi black brane solutions in the Einstein-Maxwell-dilation theory. Then we also show that this can be the case for some Bianchi VII_0 black branes by numerically constructing such a solution in the Einstein-Maxwell theory with an additional vector field having a source term. The horizon of this solution admits a translational invariance on the horizon and conveys momentum (and is “rotating” when compactified). However this translational invariance is broken just outside the horizon. This indicates the existence of a black brane solution which is regular but non-analytic at the horizon, thereby evading the black hole rigidity theorem.
International Nuclear Information System (INIS)
Accioly, A.J.
1985-01-01
Exact solutions of the Einstein-Conformally Invariant Scalar Field Equations are obtained for Kantowski-Sachs and Bianchi types I and III cosmologies. The presence of the conformally invariant scalar field is responsible for some interesting features of the solutions. In particular it is found that the Bianchi I model is consistent with the big-bang theory of cosmology. (Author) [pt
Locally rotationally symmetric Bianchi type I cosmology in f(R, T) gravity
Energy Technology Data Exchange (ETDEWEB)
Shamir, M.F. [National University of Computer and Emerging Sciences, Department of Sciences and Humanities, Lahore (Pakistan)
2015-08-15
This manuscript is devoted to the investigation of the Bianchi type I universe in the context of f(R, T) gravity. For this purpose, we explore the exact solutions of locally rotationally symmetric Bianchi type I spacetime. The modified field equations are solved by assuming an expansion scalar θ proportional to the shear scalar σ, which gives A = B{sup n}, where A, B are the metric coefficients and n is an arbitrary constant. In particular, three solutions have been found and physical quantities are calculated in each case. (orig.)
Anderson, Anne W.
2018-01-01
Standardized achievement testing of children began in the United States in the 1960s. Since then, the data produced from such tests has been extrapolated to measure schools, teachers, and principals. Today, testing and its corollaries consume much of the time and energy of teachers and students. Miriam Cohen's (2006/1980) "First Grade Takes a…
Imparting small vorticity to a Bianchi type-VIh empty spacetime
Batakis, Nikos A.
1981-04-01
We present and briefly discuss a Bianchi type-VIh empty spacetime. The field equations have been solved after being linearized with respect to a parameter which imparts vorticity to the model. The limit of zero vorticity is an already known solution.
Inhomogeneous generalizations of Bianchi Type VIh universes with stiff perfect fluid and radiation
Roy, S. R.; Prasad, A.
1995-03-01
Families of inhomogeneous models filled with a stiff perfect fluid and radiation have been derived in which there is no flow of total momentum. The models are generalizations of those of Bianchi Type VIh and are discussed for some particular forms of the arbitrary functions appearing in them.
Late-time behaviour of the tilted Bianchi type VIh models
Hervik, S.; van den Hoogen, R. J.; Lim, W. C.; Coley, A. A.
2007-08-01
We study tilted perfect fluid cosmological models with a constant equation of state parameter in spatially homogeneous models of Bianchi type VIh using dynamical systems methods and numerical experimentation, with an emphasis on their future asymptotic evolution. We determine all of the equilibrium points of the type VIh state space (which correspond to exact self-similar solutions of the Einstein equations, some of which are new), and their stability is investigated. We find that there are vacuum plane-wave solutions that act as future attractors. In the parameter space, a 'loophole' is shown to exist in which there are no stable equilibrium points. We then show that a Hopf-bifurcation can occur resulting in a stable closed orbit (which we refer to as the Mussel attractor) corresponding to points both inside the loophole and points just outside the loophole; in the former case the closed curves act as late-time attractors while in the latter case these attracting curves will co-exist with attracting equilibrium points. In the special Bianchi type III case, centre manifold theory is required to determine the future attractors. Comprehensive numerical experiments are carried out to complement and confirm the analytical results presented. We note that the Bianchi type VIh case is of particular interest in that it contains many different subcases which exhibit many of the different possible future asymptotic behaviours of Bianchi cosmological models.
Bianchi type A hyper-symplectic and hyper-Kaehler metrics in 4D
International Nuclear Information System (INIS)
De Andrés, L C; Fernández, M; Ivanov, S; Santisteban, J A; Ugarte, L; Vassilev, D
2012-01-01
We present a simple explicit construction of hyper-Kaehler and hyper-symplectic (also known as neutral hyper-Kaehler or hyper-para-Kaehler) metrics in 4D using the Bianchi type groups of class A. The construction underlies a correspondence between hyper-Kaehler and hyper-symplectic structures of dimension 4. (paper)
Bianchi type A hyper-symplectic and hyper-K\\"ahler metrics in 4D
de Andrés, Luis C.; Fernández, Marisa; Ivanov, Stefan; Santisteban, José A.; Ugarte, Luis; Vassilev, Dimiter
2011-01-01
We present a simple explicit construction of hyper-Kaehler and hyper-symplectic (also known as neutral hyper-Kaehler or hyper-parakaehler) metrics in 4D using the Bianchi type groups of class A. The construction underlies a correspondence between hyper-Kaehler and hyper-symplectic structures in dimension four.
Bianchi type-I massive string magnetized barotropic perfect ﬂuid
Indian Academy of Sciences (India)
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, ...
Bianchi type-I model with conformally invariant scalar and electromagnetic field
International Nuclear Information System (INIS)
Accioly, A.J.; Vaidya, A.N.; Som, M.M.
1983-01-01
A Bianchi type-I exact solution of the Einstein theory representing the homogeneous anisotropic models with the electromagnetic field and the conformally invariant scalar field is studied. The solution contains Kasner model, pure electromagnetic and pure scalar models as special cases. It is found that the models evolve from an initial Kasner type to a final open Friedmann type universe. (Author) [pt
Bianchi Type-V universe with a viscous fluid and Λ-term
Indian Academy of Sciences (India)
conclusion that the Big Bang singularity occurs in the infinite past. The solutions for open, closed and flat universes have been found by Santos et al [10] under the assumption that the bulk viscosity (ξ) is a power function of energy density (ρ). The nature of cosmological solutions for homogeneous Bianchi Type-I model was.
On Bianchi-I cosmic strings coupled with Maxwell ﬁelds in bimetric ...
Indian Academy of Sciences (India)
Axially symmetric Bianchi-I model is studied with source cosmic cloud strings coupled with electromagnetic ﬁeld in Rosen's bimetric theory of relativity and observed that there is no contribution from cosmic strings and Maxwell ﬁelds in this theory.
String cosmology in Bianchi type-VI 0 dusty Universe with ...
Indian Academy of Sciences (India)
In this paper, the effect of electromagnetic field in the string Bianchi type-VI0 Universe is investigated. Einstein's field equations have been solved exactly with suitable physical assumptions for two types of strings: (i) massive strings and (ii) Nambu strings. It is found that when the Universe is dominated by massive strings, ...
Quark matter coupled to domain walls in Bianchi types II, VIII and IX ...
Indian Academy of Sciences (India)
In this study of Bianchi types II, VIII and IX Universes, quark matter coupled to domain walls in the ... The self-bound state appears to be at ρ ... The observations suggest that the Hubble expansion of the Universe ... Taking motivation from.
Energy–momentum localization for Bianchi type-IV Universe in ...
Indian Academy of Sciences (India)
different energy–momentum complexes give same and reasonable results for a given ... He investigated the formulation of covariant conservation laws and calculated the tidal work using ... tetrad theory of gravity, have obtained total energy of the Universe in Bianchi type- ...... Principle and applications of general theory of.
Bianchi Type I Cosmological Models in Eddington-inspired Born–Infeld Gravity
Directory of Open Access Journals (Sweden)
Tiberiu Harko
2014-10-01
Full Text Available We consider the dynamics of a barotropic cosmological fluid in an anisotropic, Bianchi type I space-time in Eddington-inspired Born–Infeld (EiBI gravity. By assuming isotropic pressure distribution, we obtain the general solution of the field equations in an exact parametric form. The behavior of the geometric and thermodynamic parameters of the Bianchi type I Universe is studied, by using both analytical and numerical methods, for some classes of high density matter, described by the stiff causal, radiation, and pressureless fluid equations of state. In all cases the study of the models with different equations of state can be reduced to the integration of a highly nonlinear second order ordinary differential equation for the energy density. The time evolution of the anisotropic Bianchi type I Universe strongly depends on the initial values of the energy density and of the Hubble function. An important observational parameter, the mean anisotropy parameter, is also studied in detail, and we show that for the dust filled Universe the cosmological evolution always ends into isotropic phase, while for high density matter filled universes the isotropization of Bianchi type I universes is essentially determined by the initial conditions of the energy density.
Quark matter coupled to domain walls in Bianchi types II, VIII and IX ...
Indian Academy of Sciences (India)
In this study of Bianchi types II, VIII and IX Universes, quark matter coupled to domain walls in the context of general relativity are explored. To obtain deterministic solution of the Einstein's field equations, various techniques are adopted. The features of the obtained solution are discussed.
Chaos in long-term behavior of some Bianchi-type VIII models
Energy Technology Data Exchange (ETDEWEB)
Halpern, P
1987-01-01
The long-term behavior of Bianchi-type VIII models with three different types of stress-energy tensors are examined and compared. The vacuum model, a matter-filled model, and a model with an electromagnetic field are considered. In each case the existence of chaotic behavior and transitions to chaotic behavior are discussed.
Interacting dark sector and the coincidence problem within the scope of LRS Bianchi type I model
Muharlyamov, Ruslan K.; Pankratyeva, Tatiana N.
2018-05-01
It is shown that a suitable interaction between dark energy and dark matter in locally rotationally symmetric (LRS) Bianchi-I space-time can solve the coincidence problem and not contradict the accelerated expansion of present Universe. The interaction parameters are estimated from observational data.
Nonlinear Spinor Field in Non-Diagonal Bianchi Type Space-Time
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Saha Bijan
2018-01-01
Full Text Available Within the scope of the non-diagonal Bianchi cosmological models we have studied the role of the spinor field in the evolution of the Universe. In the non-diagonal Bianchi models the spinor field distribution along the main axis is anisotropic and does not vanish in the absence of the spinor field nonlinearity. Hence within these models perfect fluid, dark energy etc. cannot be simulated by the spinor field nonlinearity. The equation for volume scale V in the case of non-diagonal Bianchi models contains a term with first derivative of V explicitly and does not allow exact solution by quadratures. Like the diagonal models the non-diagonal Bianchi space-time becomes locally rotationally symmetric even in the presence of a spinor field. It was found that depending on the sign of the coupling constant the model allows either an open Universe that rapidly grows up or a close Universe that ends in a Big Crunch singularity.
Bianchi Type-I cosmological mesonic stiff fluid models in Lyra's ...
Indian Academy of Sciences (India)
Some physical and kinematical properties of the models are also discussed. Keywords. Cosmology; Bianchi-I ... Here ρ, p and ui are respectively the energy density, equilibrium pressure and four-velocity vector of the .... In order to obtain an explicit form of physical parameters, we consider here stiff fluid distribution given by ...
Locally-rotationally-symmetric Bianchi type-V cosmology with heat flow
Indian Academy of Sciences (India)
LRS) Bianchi type-V cosmological model with perfect fluid and heat flow. A general approach is introduced to solve Einstein's field equations using a law of variation for the mean Hubble parameter, which is related to average scale factor of the ...
Perfect fluid Bianchi Type-I cosmological models with time varying G ...
Indian Academy of Sciences (India)
Abstract. Bianchi Type-I cosmological models containing perfect fluid with time vary- ing G and Λ have been presented. The solutions obtained represent an expansion scalar θ bearing a constant ratio to the anisotropy in the direction of space-like unit vector λi. Of the two models obtained, one has negative vacuum energy ...
Venkateswarlu, R.; Sreenivas, K.
2014-06-01
The LRS Bianchi type-I and type-II string cosmological models are studied when the source for the energy momentum tensor is a bulk viscous stiff fluid containing one dimensional strings together with zero-mass scalar field. We have obtained the solutions of the field equations assuming a functional relationship between metric coefficients when the metric is Bianchi type-I and constant deceleration parameter in case of Bianchi type-II metric. The physical and kinematical properties of the models are discussed in each case. The effects of Viscosity on the physical and kinematical properties are also studied.
Interpolating from Bianchi attractors to Lifshitz and AdS spacetimes
International Nuclear Information System (INIS)
Kachru, Shamit; Kundu, Nilay; Saha, Arpan; Samanta, Rickmoy; Trivedi, Sandip P.
2014-01-01
We construct classes of smooth metrics which interpolate from Bianchi attractor geometries of Types II, III, VI and IX in the IR to Lifshitz or AdS 2 ×S 3 geometries in the UV. While we do not obtain these metrics as solutions of Einstein gravity coupled to a simple matter field theory, we show that the matter sector stress-energy required to support these geometries (via the Einstein equations) does satisfy the weak, and therefore also the null, energy condition. Since Lifshitz or AdS 2 ×S 3 geometries can in turn be connected to AdS 5 spacetime, our results show that there is no barrier, at least at the level of the energy conditions, for solutions to arise connecting these Bianchi attractor geometries to AdS 5 spacetime. The asymptotic AdS 5 spacetime has no non-normalizable metric deformation turned on, which suggests that furthermore, the Bianchi attractor geometries can be the IR geometries dual to field theories living in flat space, with the breaking of symmetries being either spontaneous or due to sources for other fields. Finally, we show that for a large class of flows which connect two Bianchi attractors, a C-function can be defined which is monotonically decreasing from the UV to the IR as long as the null energy condition is satisfied. However, except for special examples of Bianchi attractors (including AdS space), this function does not attain a finite and non-vanishing constant value at the end points
A note on tilted Bianchi type VIh models: the type III bifurcation
Coley, A. A.; Hervik, S.
2008-10-01
In this note we complete the analysis of Hervik, van den Hoogen, Lim and Coley (2007 Class. Quantum Grav. 24 3859) of the late-time behaviour of tilted perfect fluid Bianchi type III models. We consider models with dust, and perfect fluids stiffer than dust, and eludicate the late-time behaviour by studying the centre manifold which dominates the behaviour of the model at late times. In the dust case, this centre manifold is three-dimensional and can be considered a double bifurcation as the two parameters (h and γ) of the type VIh model are varied. We therefore complete the analysis of the late-time behaviour of tilted ever-expanding Bianchi models of types I VIII.
Directory of Open Access Journals (Sweden)
L. Toledo Sesma
2016-01-01
Full Text Available We construct an effective four-dimensional model by compactifying a ten-dimensional theory of gravity coupled with a real scalar dilaton field on a time-dependent torus. This approach is applied to anisotropic cosmological Bianchi type I model for which we study the classical coupling of the anisotropic scale factors with the two real scalar moduli produced by the compactification process. Under this approach, we present an isotropization mechanism for the Bianchi I cosmological model through the analysis of the ratio between the anisotropic parameters and the volume of the Universe which in general keeps constant or runs into zero for late times. We also find that the presence of extra dimensions in this model can accelerate the isotropization process depending on the momenta moduli values. Finally, we present some solutions to the corresponding Wheeler-DeWitt (WDW equation in the context of standard quantum cosmology.
Hořava–Lifshitz gravity inspired Bianchi-II cosmology and the mixmaster universe
International Nuclear Information System (INIS)
Giani, Leonardo; Kamenshchik, Alexander Y
2017-01-01
We study different aspects of the Hořava-Lifshitz inspired Bianchi-II cosmology and its relations with the mixmaster universe model. First, we present exact solutions for a toy model, where only the cubic in spatial curvature terms are present in the action; then we briefly discuss some exotic singularities, which can appear in this toy model. We study also the toy model where only the quadratic in spatial curvature terms are present in the action. We establish relations between our results and those obtained by using the Hamiltonian formalism. Finally, we apply the results obtained by studying Bianchi-II cosmology to describe the evolution of the mixmaster universe in terms of the Belinsky–Khalatnikov–Lifshitz formalism. Generally, our analysis gives some arguments in favour of the existence of the oscillatory approach to the singularity in a universe governed by the Hořava–Lifshitz type gravity. (paper)
New curvature-torsion relations through decomposition of the Bianchi identities
International Nuclear Information System (INIS)
Davies, J.B.
1988-01-01
The Bianchi Identities relating asymmetric curvature to torsion are obtained as a new set of equations governing second-order curvature tensors. The usual contribution of symmetric curvature to the gravitational field is found to be a subset of these identities though with an added contribution due to torsion gradients. The antisymmetric curvature two-tensor is shown to be related to the divergence of the torsion. Using a model of particle-antiparticle pair production, identification of certain torsion components with electroweak fields is proposed. These components obey equations, similar to Maxwell's that are subsets of these linear Bianchi identities. These results are shown to be consistent with gauge and other previous analyses
Revisitation of chaos in Bianchi IX Universe and in generalized scalar-tensor cosmologies
International Nuclear Information System (INIS)
Lehner, Thierry; Di Menza, Laurent
2003-01-01
We show that there is a threshold for the onset of chaos in cosmology for the Universe described as a dynamical system derived from the Einstein equations of general relativity (GR). In the case of the mixmaster model (homogeneous and anisotropic cosmology with a Bianchi IX metric) the chaos occurs precisely at the prescribed necessary value H vac =0 of the GR for the energy of the Universe while the system is found regular for H vac >0 and chaotic for H vac <0 with respect to its pure vacuum part. In the case of generalized scalar tensor theories within the Bianchi IX model we show using the ADM formalism and a conformal transformation that the energy of the dynamical system as compared to vacuum lies below the threshold thus the system is not exhibiting chaos and the conclusion still holds in the presence of ordinary matter as well. The suppression of chaos occurs in a similar way for stiff matter alone
Wheeler-DeWitt equation and Lie symmetries in Bianchi scalar-field cosmology
Energy Technology Data Exchange (ETDEWEB)
Paliathanasis, A. [Universidad Austral de Chile, Instituto de Ciencias Fisicas y Matematicas, Valdivia (Chile); Karpathopoulos, L. [University of Athens, Faculty of Physics, Department of Astronomy-Astrophysics-Mechanics, Athens (Greece); Wojnar, A. [Institute for Theoretical Physics, Wroclaw (Poland); Universita' di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Dipartimento di Fisica ' ' E. Pancini' ' , Naples (Italy); Complesso Universitario di Monte S. Angelo, Naples (Italy); Istituto Nazionale di Fisica Nucleare (INFN) Sez. di Napoli, Naples (Italy); Capozziello, S. [Universita' di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Dipartimento di Fisica ' ' E. Pancini' ' , Naples (Italy); Complesso Universitario di Monte S. Angelo, Naples (Italy); Gran Sasso Science Institute (INFN), L' Aquila (Italy); Istituto Nazionale di Fisica Nucleare (INFN) Sez. di Napoli, Naples (Italy)
2016-04-15
Lie symmetries are discussed for the Wheeler-De Witt equation in Bianchi Class A cosmologies. In particular, we consider general relativity, minimally coupled scalar-field gravity and hybrid gravity as paradigmatic examples of the approach. Several invariant solutions are determined and classified according to the form of the scalar-field potential. The approach gives rise to a suitable method to select classical solutions and it is based on the first principle of the existence of symmetries. (orig.)
Some five-dimensional Bianchi type-iii string cosmological models in general relativity
International Nuclear Information System (INIS)
Samanta, G.C.; Biswal, S.K.; Mohanty, G.; Rameswarpatna, Bhubaneswar
2011-01-01
In this paper we have constructed some five-dimensional Bianchi type-III cosmological models in general relativity when source of gravitational field is a massive string. We obtained different classes of solutions by considering different functional forms of metric potentials. It is also observed that one of the models is not physically acceptable and the other models possess big-bang singularity. The physical and kinematical behaviors of the models are discussed
Locally Rotationally Symmetric Bianchi Type-I Model with Time Varying Λ Term
International Nuclear Information System (INIS)
Tiwari, R. K.; Jha, Navin Kumar
2009-01-01
We investigate the locally rotationally symmetric (LRS) Bianchi type-I cosmological model for stiff matter and a vacuum solution with a cosmological term proportional to R −m (R is the scale factor and m is a positive constant). The cosmological term decreases with time. We obtain that for both the cases the present universe is accelerating with a large fraction of cosmological density in the form of a cosmological term
Bianchi Type-IX viscous fluid cosmological model in general relativity
Indian Academy of Sciences (India)
the de-Sitter universe, the Taub-NUT solutions etc. are of Bianchi Type-IX space- times. In these models, neutrino viscosity does not guarantee isotropy at the present ..... The model (2.11) starts with a big-bang at T = 0 where α > 0 and m < 2, and the expansion in the model decreases as time increases. The expansion in the ...
Bianchi type-I universe in f(R, T) modified gravity with quark matter and Λ
Ćaǧlar, Halife; Aygün, Sezgin
2017-02-01
In this study, we investigate homogeneous and anisotropic Bianchi type I universe in the presence of quark matter source in f(R, T) gravity (Harko et al. in Phys. Rev. D 84:024020, 2011) with cosmological constant Λ (where R is the Ricci scalar and T is the trace of the energy momentum tensor). For this aim we have used the anisotropy feature of Bianchi type I universe and equation of states (EoS) of quark matter. We explore the exact solution f(R,T)=R+2f(T) model for Bianchi type I universe model. When t→∞, we get very small cosmological constant value, this result agrees with recent observations.
Revisiting the two formulations of Bianchi identities and their implications on moduli stabilization
Energy Technology Data Exchange (ETDEWEB)
Shukla, Pramod [ICTP - International Centre for Theoretical Physics,Strada Costiera 11, Trieste 34151 (Italy)
2016-08-24
In the context of non-geometric type II orientifold compactifications, there have been two formulations for representing the various NS-NS Bianchi-identities. In the first formulation, the standard three-form flux (H{sub 3}), the geometric flux (ω) and the non-geometric fluxes (Q and R) are expressed by using the real six-dimensional indices (e.g. H{sub ijk},ω{sub ij}{sup k},Q{sub i}{sup jk} and R{sup ijk}), and this formulation has been heavily utilized for simplifying the scalar potentials in toroidal-orientifolds. On the other hand, relevant for the studies beyond toroidal backgrounds, a second formulation is utilized in which all flux components are written in terms of various involutively even/odd (2,1)- and (1,1)-cohomologies of the complex threefold. In the lights of recent model building interests and some observations made in http://dx.doi.org/10.1088/1126-6708/2007/08/043, http://dx.doi.org/10.1088/1126-6708/2007/12/058, in this article, we revisit two most commonly studied toroidal examples in detail to illustrate that the present forms of these two formulations are not completely equivalent. To demonstrate the same, we translate all the identities of the first formulation into cohomology ingredients, and after a tedious reshuffling of the subsequent constraints, interestingly we find that all the identities of the second formulation are embedded into the first formulation which has some additional constraints. In addition, we look for the possible solutions of these Bianchi identities in a detailed analysis, and we find that some solutions can reduce the size of scalar potential very significantly, and in some cases are too strong to break the no-scale structure completely. Finally, we also comment on the influence of imposing some of the solutions of Bianchi identities in studying moduli stabilization.
Bianchi type I universe in brane world scenario with non-zero Weyl tensor of the bulk
Energy Technology Data Exchange (ETDEWEB)
Chaudhuri, S. [University of Burdwan, Department of Physics, Burdwan (India)
2017-09-15
In the paper, we present exact solutions of gravitational field equations for an anisotropic brane with a Bianchi type I universe with perfect fluid having non-vanishing Weyl tensor of the bulk. It is assumed that the thermodynamic pressure bears a linear relation with the energy density. For a particular non-zero value of the pressure the solutions are obtained in an exact analytic form with and without the cosmological constant for a Bianchi type I universe. The relevant physical quantities associated with the evolution of the universe are also derived in the two cases. (orig.)
Evolution of Bianchi I magnetized cosmic strings in Brans–Dicke gravity
International Nuclear Information System (INIS)
Sharif, M; Waheed, Saira
2013-01-01
In this paper, we consider a locally rotationally symmetric Bianchi I universe filled with magnetized viscous string fluid in Brans–Dicke gravity. For the exact solutions, we use the law of variation of the Hubble parameter that leads to volumetric expansion laws and assume power law ansatz for the scalar field. We discuss the nature of the resulting models through different parameters and their graphs. It is concluded that the constructed universe models yield an accelerated expanding behavior with an isotropic nature for the final stages of the universe evolution, which is consistent with recent observations. (paper)
Bianchi type-VIh string cloud cosmological models with bulk viscosity
Tripathy, Sunil K.; Behera, Dipanjali
2010-11-01
String cloud cosmological models are studied using spatially homogeneous and anisotropic Bianchi type VIh metric in the frame work of general relativity. The field equations are solved for massive string cloud in presence of bulk viscosity. A general linear equation of state of the cosmic string tension density with the proper energy density of the universe is considered. The physical and kinematical properties of the models have been discussed in detail and the limits of the anisotropic parameter responsible for different phases of the universe are explored.
A dossier about the Lunigiana domus of the Bianchi of Moregnano (12th-13th Century
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Mario Nobili
2005-12-01
Full Text Available Nelle fonti toscane dei secoli XII-XIII secolo, il termine domus significa "gruppo parentale definito da una ascendenza comune", ma può indicare anche il complesso dei beni patrimoniali di quel gruppo parentale, o ancora l'insieme degli agenti (servi ministeriali e masnade e dei coloni di quel gruppo parentale. Quest'ultimo significato, più largo e comprensivo, prevale nella documentazione dei secoli XII-XIII relativa alla domus dei Bianchi da Moregnano in Lunigiana, vassalli prima degli Estensi e poi dei Malaspina.
LRS Bianchi Type II Massive String Cosmological Models with Magnetic Field in Lyra's Geometry
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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.
On the relation between the Einstein field equations and the Jacobi–Ricci–Bianchi system
International Nuclear Information System (INIS)
Van den Bergh, N
2013-01-01
The 1 + 3 covariant equations, embedded in an extended tetrad formalism and describing a spacetime with an arbitrary energy–momentum distribution, are reconsidered. It is shown that, provided the 1 + 3 splitting is performed with respect to a generic time-like congruence with a tangent vector u, the Einstein field equations can be regarded as the integrability conditions for the Jacobi and Bianchi equations together with the Ricci equations for u. The same conclusion holds for a generic null congruence in the Newman–Penrose framework. (paper)
New Features about Chaos in Bianchi I non-Abelian Born-Infeld cosmology
International Nuclear Information System (INIS)
Dyadichev, Vladimir V.; Gal'tsov, Dmitri V.; Moniz, Paulo Vargas
2006-01-01
When the action is replaced by the Born-Infeld-type non-Abelian action (NBI), a chaos-order transition is observed in the high energy region for a Bianchi I cosmology with the homogeneous SU(2) Yang-Mills field. This is interpreted as a smothering effect due to (non-perturbative in α') string corrections to the classical EYM action. We give a numerical evidence for the chaos-order transition and present an analytical proof of regularity of color oscillations in the limit of strong Born-Infeld non-linearity
Green's functions in Bianchi type-I spaces. Relation between Minkowski and Euclidean approaches
International Nuclear Information System (INIS)
Bukhbinder, I.L.; Kirillova, E.N.
1988-01-01
A theory is considered for a free scalar field with a conformal connection in a curved space-time with a Bianchi type-I metric. A representation is obtained for the Green's function G∼ in in in the form of an integral of a Schwinger-DeWitt kernel along a contour in a plane of complex-valued proper time. It is shown how as transition may be accomplished from Green's functions in space with the Euclidean signature to Green's functions in space with Minkowski signature and vice versa
Bianchi type I cyclic cosmology from Lie-algebraically deformed phase space
International Nuclear Information System (INIS)
Vakili, Babak; Khosravi, Nima
2010-01-01
We study the effects of noncommutativity, in the form of a Lie-algebraically deformed Poisson commutation relations, on the evolution of a Bianchi type I cosmological model with a positive cosmological constant. The phase space variables turn out to correspond to the scale factors of this model in x, y, and z directions. According to the conditions that the structure constants (deformation parameters) should satisfy, we argue that there are two types of noncommutative phase space with Lie-algebraic structure. The exact classical solutions in commutative and type I noncommutative cases are presented. In the framework of this type of deformed phase space, we investigate the possibility of building a Bianchi I model with cyclic scale factors in which the size of the Universe in each direction experiences an endless sequence of contractions and reexpansions. We also obtain some approximate solutions for the type II noncommutative structure by numerical methods and show that the cyclic behavior is repeated as well. These results are compared with the standard commutative case, and similarities and differences of these solutions are discussed.
Holographic fermions at strong translational symmetry breaking: a Bianchi-VII case study
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Bagrov, A. [Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, Nijmegen 6525 AJ (Netherlands); Kaplis, N.; Krikun, A.; Schalm, K.; Zaanen, J. [Institute Lorentz ITP, Leiden University, PO Box 9506, Leiden 2300 RA (Netherlands)
2016-11-09
It is presently unknown how strong lattice potentials influence the fermion spectral function of the holographic strange metals predicted by the AdS/CFT correspondence. This embodies a crucial test for the application of holography to condensed matter experiments. We show that for one particular momentum direction this spectrum can be computed for arbitrary strength of the effective translational symmetry breaking potential of the so-called Bianchi-VII geometry employing ordinary differential equations. Deep in the strange metal regime we find rather small changes to the single-fermion response computed by the emergent quantum critical IR, even when the potential becomes relevant in the infra-red. However, in the regime where holographic quasi-particles occur, defining a Fermi surface in the continuum, they acquire a finite lifetime at any finite potential strength. At the transition from irrelevancy to relevancy of the Bianchi potential in the deep infra-red the quasi-particle remnants disappear completely and the fermion spectrum exhibits a purely relaxational behaviour.
International Nuclear Information System (INIS)
Portugal, R.
1984-01-01
Three processes of solutions of the Einstein-Maxwell equations for Bianchi - I, II, VIII, IX and Kantowski-Sachs-like cosmological models with perfect fluid in magnetohydrolodynamical regimem are presented. Diagonal Bianchi-like models are considered with two anisotropy direction in the maximum. Solutions are found for Bianchi-II and IX-like models with energy conditions to be analyzed. Solutions are found for Bianchi-IX and Kantowski-Sachs-Like models with positive electric conductivity and satisfering to the predominant energy conditions. Solutions are formed for isotropic Kantowski-Sachs-Like models satisfering to the equation of state p=λρ, 0 0, admiting, in addition to the perfect fluid, electric field only. It is shown that a class of Bertotti-Robinson-like solutions is unstable by perturbations and it is carried in Kantowski-Sachs-like models with non-null electric conductivity. (L.C.) [pt
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Ribas, M O; Samojeden, L L; Devecchi, F P; Kremer, G M
2015-01-01
In this work we investigate a model for the early Universe in a Bianchi type-I metric, where the sources of the gravitational field are a fermionic and a bosonic field, interacting through a Yukawa potential, following the standard model of elementary particles. It is shown that the fermionic field has a negative pressure, while the boson has a small positive pressure. The fermionic field is the responsible for an accelerated regime at early times, but since the total pressure tends to zero for large times, a transition to a decelerated regime occurs. Here the Yukawa potential answers for the duration of the accelerated regime, since by decreasing the value of its coupling constant the transition accelerated–decelerated occurs in later times. The isotropization which occurs for late times is due to the presence of the fermionic field as one of the sources of the gravitational field. (paper)
Bianchi VI{sub 0} and III models: self-similar approach
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Belinchon, Jose Antonio, E-mail: abelcal@ciccp.e [Departamento de Fisica, ETS Arquitectura, UPM, Av. Juan de Herrera 4, Madrid 28040 (Spain)
2009-09-07
We study several cosmological models with Bianchi VI{sub 0} and III symmetries under the self-similar approach. We find new solutions for the 'classical' perfect fluid model as well as for the vacuum model although they are really restrictive for the equation of state. We also study a perfect fluid model with time-varying constants, G and LAMBDA. As in other studied models we find that the behaviour of G and LAMBDA are related. If G behaves as a growing time function then LAMBDA is a positive decreasing time function but if G is decreasing then LAMBDA{sub 0} is negative. We end by studying a massive cosmic string model, putting special emphasis in calculating the numerical values of the equations of state. We show that there is no SS solution for a string model with time-varying constants.
Lyra’s cosmology of hybrid universe in Bianchi-V space-time
Yadav, Anil Kumar; Bhardwaj, Vinod Kumar
2018-06-01
In this paper we have searched for the existence of Lyra’s cosmology in a hybrid universe with minimal interaction between dark energy and normal matter using Bianchi-V space-time. To derive the exact solution, the average scale factor is taken as a={({t}n{e}kt)}\\frac{1{m}} which describes the hybrid nature of the scale factor and generates a model of the transitioning universe from the early deceleration phase to the present acceleration phase. The quintessence model makes the matter content of the derived universe remarkably able to satisfy the null, dominant and strong energy condition. It has been found that the time varying displacement β(t) co-relates with the nature of cosmological constant Λ(t). We also discuss some physical and geometrical features of the universe.
Anisotropic Bianchi Type-III Bulk Viscous Fluid Universe in Lyra Geometry
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Priyanka Kumari
2013-01-01
Full Text Available An anisotropic Bianchi type-III cosmological model is investigated in the presence of a bulk viscous fluid within the framework of Lyra geometry with time-dependent displacement vector. It is shown that the field equations are solvable for any arbitrary function of a scale factor. To get the deterministic model of the universe, we have assumed that (i a simple power-law form of a scale factor and (ii the bulk viscosity coefficient are proportional to the energy density of the matter. The exact solutions of the Einstein’s field equations are obtained which represent an expanding, shearing, and decelerating model of the universe. Some physical and kinematical behaviors of the cosmological model are briefly discussed.
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Álvaro Menanteau Aravena
2017-12-01
Full Text Available This article consists of two sections. In the first part we review the musical trajectory of Vicente Bianchi Alarcon, in his varied dimensions as a pianist, arranger, orchestral conductor and composer. Most of the information contained was obtained from conversations with Vicente Bianchi, especially from an interview made in 2002. The second part contains a list of data and considerations regarding the obtaining of the National Prize for Musical Arts 2016.
International Nuclear Information System (INIS)
Hehl, F.W.; McCrea, J.D.
1986-01-01
Automatic conservation of energy-momentum and angular momentum is guaranteed in a gravitational theory if, via the field equations, the conservation laws for the material currents are reduced to the contracted Bianchi identities. We first execute an irreducible decomposition of the Bianchi identities in a Riemann-Cartan space-time. Then, starting from a Riemannian space-time with or without torsion, we determine those gravitational theories which have automatic conservation: general relativity and the Einstein-Cartan-Sciama-Kibble theory, both with cosmological constant, and the nonviable pseudoscalar model. The Poincare gauge theory of gravity, like gauge theories of internal groups, has no automatic conservation in the sense defined above. This does not lead to any difficulties in principle. Analogies to 3-dimensional continuum mechanics are stressed throughout the article
Hehl, Friedrich W.; McCrea, J. Dermott
1986-03-01
Automatic conservation of energy-momentum and angular momentum is guaranteed in a gravitational theory if, via the field equations, the conservation laws for the material currents are reduced to the contracted Bianchi identities. We first execute an irreducible decomposition of the Bianchi identities in a Riemann-Cartan space-time. Then, starting from a Riemannian space-time with or without torsion, we determine those gravitational theories which have automatic conservation: general relativity and the Einstein-Cartan-Sciama-Kibble theory, both with cosmological constant, and the nonviable pseudoscalar model. The Poincaré gauge theory of gravity, like gauge theories of internal groups, has no automatic conservation in the sense defined above. This does not lead to any difficulties in principle. Analogies to 3-dimensional continuum mechanics are stressed throughout the article.
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Narita, Makoto [Department of Mathematics, National Taiwan University, 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan (China)
2006-12-21
We discuss the strong cosmic censorship conjecture for cosmological spacetimes in the Einstein-Yang-Mills-dilaton system. Locally rotational symmetric Bianchi I spacetimes are considered. We show local and global existence theorems for the system. Asymptotic behaviour for the spacetimes is also investigated. The curvature invariant is blowup at the initial singularities and the spacetimes are future geodesic complete. Thus, the strong cosmic censorship conjecture for the spacetimes holds.
International Nuclear Information System (INIS)
Narita, Makoto
2006-01-01
We discuss the strong cosmic censorship conjecture for cosmological spacetimes in the Einstein-Yang-Mills-dilaton system. Locally rotational symmetric Bianchi I spacetimes are considered. We show local and global existence theorems for the system. Asymptotic behaviour for the spacetimes is also investigated. The curvature invariant is blowup at the initial singularities and the spacetimes are future geodesic complete. Thus, the strong cosmic censorship conjecture for the spacetimes holds
New scheme for color confinement and violation of the non-Abelian Bianchi identities
Suzuki, Tsuneo; Ishiguro, Katsuya; Bornyakov, Vitaly
2018-02-01
A new scheme for color confinement in QCD due to violation of the non-Abelian Bianchi identities is proposed. The violation of the non-Abelian Bianchi identities (VNABI) Jμ is equal to Abelian-like monopole currents kμ defined by the violation of the Abelian-like Bianchi identities. Although VNABI is an adjoint operator satisfying the covariant conservation law DμJμ=0 , it satisfies, at the same time, the Abelian-like conservation law ∂μJμ=0 . The Abelian-like conservation law ∂μJμ=0 is also gauge-covariant. There are N2-1 conserved magnetic charges in the case of color S U (N ). The charge of each component of VNABI is quantized à la Dirac. The color-invariant eigenvalues λμ of VNABI also satisfy the Abelian conservation law ∂μλμ=0 and the magnetic charges of the eigenvalues are also quantized à la Dirac. If the color invariant eigenvalues condense in the QCD vacuum, each color component of the non-Abelian electric field Ea is squeezed by the corresponding color component of the solenoidal current Jμa. Then only the color singlets alone can survive as a physical state and non-Abelian color confinement is realized. This confinement picture is completely new in comparison with the previously studied monopole confinement scenario based on an Abelian projection after some partial gauge-fixing, where Abelian neutral states can survive as physical. To check if the scenario is realized in nature, numerical studies are done in the framework of lattice field theory by adopting pure S U (2 ) gauge theory for simplicity. Considering Jμ(x )=kμ(x ) in the continuum formulation, we adopt an Abelian-like definition of a monopole following DeGrand-Toussaint as a lattice version of VNABI, since the Dirac quantization condition of the magnetic charge is satisfied on lattice partially. To reduce severe lattice artifacts, we introduce various techniques of smoothing the thermalized vacuum. Smooth gauge fixings such as the maximal center gauge (MCG), block
Bianchi IX dynamics in bouncing cosmologies: homoclinic chaos and the BKL conjecture
Maier, Rodrigo; Damião Soares, Ivano; Valentino Tonini, Eduardo
2015-12-01
We examine the dynamics of a Bianchi IX model with three scale factors on a 4-dim Lorentzian brane embedded in a 5-dim conformally flat empty bulk with a timelike extra dimension. The matter content is a pressureless perfect fluid restricted to the brane, with the embedding consistently satisfying the Gauss-Codazzi equations. The 4-dim Einstein equations on the brane reduce to a 6-dim Hamiltonian dynamical system with additional terms (due to the bulk-brane interaction) that avoid the singularity and implement nonsingular bounces in the model. We examine the complex Bianchi IX dynamics in its approach to the neighborhood of the bounce which replaces the cosmological singularity of general relativity. The phase space of the model presents (i) two critical points (a saddle-center-center and a center-center-center) in a finite region of phase space, (ii) two asymptotic de Sitter critical points at infinity, one acting as an attractor to late-time acceleration and (iii) a 2-dim invariant plane, which together organize the dynamics of the phase space. The saddle-center-center engenders in the phase space the topology of stable and unstable 4-dim cylinders R × S 3, where R is a saddle direction and S 3 is the center manifold of unstable periodic orbits, the latter being the nonlinear extension of the center-center sector. By a proper canonical transformation the degrees of freedom of the dynamics are separated into one degree connected with the expansion/contraction of the scales of the model, and two rotational degrees of freedom associated with the center manifold S 3. The typical dynamical flow is thus an oscillatory mode about the orbits of the invariant plane. The stable and unstable cylinders are spanned by oscillatory orbits about the separatrix towards the bounce, leading to the homoclinic transversal intersection of the cylinders, as shown numerically in two distinct simulations. The homoclinic intersection manifold has the topology of R × S 2 consisting of
Hořava-Lifshitz bouncing Bianchi IX universes: A dynamical system analysis
Maier, Rodrigo; Soares, Ivano Damião
2017-11-01
We examine the Hamiltonian dynamics of bouncing Bianchi IX cosmologies with three scale factors in Hořava-Lifshitz (HL) gravity. We assume a positive cosmological constant plus noninteracting dust and radiation as the matter content of the models. In this framework the modified field equations contain additional terms which turn the dynamics nonsingular. The six-dimensional phase space presents (i) two critical points in a finite region of the phase space, (ii) one asymptotic de Sitter attractor at infinity and (iii) a two-dimensional invariant plane containing the critical points; together they organize the dynamics of the phase space. We identify four distinct parameter domains A , B , C and D for which the pair of critical points engenders distinct features in the dynamics, connected to the presence of centers of multiplicity 2 and saddles of multiplicity 2. In the domain A the dynamics consists basically of periodic bouncing orbits, or oscillatory orbits with a finite number of bounces before escaping to the de Sitter attractor. The center with multiplicity 2 engenders in its neighborhood the topology of stable and unstable cylinders R ×S3 of orbits, where R is a saddle direction and S3 is the center manifold of unstable periodic orbits. We show that the stable and unstable cylinders coalesce, realizing a smooth homoclinic connection to the center manifold, a rare event of regular/nonchaotic dynamics in bouncing Bianchi IX cosmologies. The presence of a saddle of multiplicity 2 in the domain B engenders a high instability in the dynamics so that the cylinders emerging from the center manifold about P2 towards the bounce have four distinct attractors: the center manifold itself, the de Sitter attractor at infinity and two further momentum-dominated attractors with infinite anisotropy. In the domain C we examine the features of invariant manifolds of orbits about a saddle of multiplicity 2 P2. The presence of the saddle of multiplicity 2 engenders bifurcations
Bianchi I cosmology in the presence of a causally regularized viscous fluid
Energy Technology Data Exchange (ETDEWEB)
Montani, Giovanni [ENEA, FSN-FUSPHY-TSM, R.C. Frascati, Frascati (Italy); Universita degli Studi di Roma ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); Venanzi, Marta [Universita degli Studi di Roma ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); University of Southampton, Department of Physics and Astronomy, Southampton (United Kingdom)
2017-07-15
We analyze the dynamics of a Bianchi I cosmology in the presence of a viscous fluid, causally regularized according to the Lichnerowicz approach. We show how the effect induced by shear viscosity is still able to produce a matter creation phenomenon, meaning that also in the regularized theory we address, the Universe is emerging from a singularity with a vanishing energy density value. We discuss the structure of the singularity in the isotropic limit, when bulk viscosity is the only retained contribution. We see that, as far as viscosity is not a dominant effect, the dynamics of the isotropic Universe possesses the usual non-viscous power-law behaviour but in correspondence to an effective equation of state, depending on the bulk viscosity coefficient. Finally, we show that, in the limit of a strong non-thermodynamical equilibrium of the Universe mimicked by a dominant contribution of the effective viscous pressure, a power-law inflation behaviour of the Universe appears, the cosmological horizons are removed and a significant amount of entropy is produced. (orig.)
Propagators for a scalar field in some Bianchi-type I universe
International Nuclear Information System (INIS)
Nariai, Hidekazu.
1976-05-01
As a sequel to previous papers on bi-scalar propagators in the Friedmann universes and a special Kasner universe (whose underlying space-time is flat), their counterparts for a massless scalar field in some Bianchi-type I universe (which is intrinsically curved and anisotropic) are derived by means of Hadamard's procedure and ours, the latter of which becomes inevitable in the realm of quantized field. The retarded propagator thus obtained is applied to the generation of the scalar field from a point source and a spatially uniform distribution of sources, respectively. In the former case, the luminosity formula for a point source is derived, which is an anisotropic version of Robertson's formula in the Friedmann universes. In the latter case, it is shown that the scalar field may behave as either a perfect fluid obeying Zel'dovich's hardest equation of state or an imperfect fluid whose equation of state violates the energy condition. Implication of the above three works on the occasion of quantizing the scalar field is also touched upon. (auth.)
Flux algebra, Bianchi identities and Freed-Witten anomalies in F-theory compactifications
International Nuclear Information System (INIS)
Aldazabal, G.; Camara, P.G.; Rosabal, J.A.
2009-01-01
We discuss the structure of 4D gauged supergravity algebras corresponding to globally non-geometric compactifications of F-theory, admitting a local geometric description in terms of 10D supergravity. By starting with the well-known algebra of gauge generators associated to non-geometric type IIB fluxes, we derive a full algebra containing all, closed RR and NSNS, geometric and non-geometric dual fluxes. We achieve this generalization by a systematic application of SL(2,Z) duality transformations and by taking care of the spinorial structure of the fluxes. The resulting algebra encodes much information about the higher dimensional theory. In particular, tadpole equations and Bianchi identities are obtainable as Jacobi identities of the algebra. When a sector of magnetized (p,q) 7-branes is included, certain closed axions are gauged by the U(1) transformations on the branes. We indicate how the diagonal gauge generators of the branes can be incorporated into the full algebra, and show that Freed-Witten constraints and tadpole cancellation conditions for (p,q) 7-branes can be described as Jacobi identities satisfied by the algebra mixing bulk and brane gauge generators
Quantum cosmology of a Bianchi III LRS geometry coupled to a source free electromagnetic field
Karagiorgos, A.; Pailas, T.; Dimakis, N.; Terzis, Petros A.; Christodoulakis, T.
2018-03-01
We consider a Bianchi type III axisymmetric geometry in the presence of an electromagnetic field. A first result at the classical level is that the symmetry of the geometry need not be applied on the electromagnetic tensor Fμν the algebraic restrictions, implied by the Einstein field equations to the stress energy tensor Tμν, suffice to reduce the general Fμν to the appropriate form. The classical solution thus found contains a time dependent electric and a constant magnetic charge. The solution is also reachable from the corresponding mini-superspace action, which is strikingly similar to the Reissner-Nordstr{öm one. This points to a connection between the black hole geometry and the cosmological solution here found, which is the analog of the known correlation between the Schwarzschild and the Kantowski-Sachs metrics. The configuration space is drastically modified by the presence of the magnetic charge from a 3D flat to a 3D pp wave geometry. We map the emerging linear and quadratic classical integrals of motion, to quantum observables. Along with the Wheeler-DeWitt equation these observables provide unique, up to constants, wave functions. The employment of a Bohmian interpretation of these quantum states results in deterministic (semi-classical) geometries most of which are singularity free.
International Nuclear Information System (INIS)
Triyanta; Zen, F. P.; Supardi; Wardaya, A. Y.
2010-01-01
Gauge theory, under the framework of quantum field theory, has successfully described three fundamental interactions: electromagnetic, weak, and strong interactions. Problems of describing the gravitational interaction in a similar manner has not been satisfied yet until now. Teleparallel gravity (TG) is one proposal describing gravitational field as a gauge field. This theory is quite new and it is equivalent to Einstein's general relativity. But as gravitational field in TG is expressed by torsion, rather than curvature, it gives an alternative framework for solving problems on gravity. This paper will present solution of the dynamical equation of abelian vector fields under the framework of TG in the Bianchi type I spacetime.
International Nuclear Information System (INIS)
Alvarado, R.; Rybakov, Yu.P.; Shikin, G.N.; Saha, B.
1995-01-01
Self-consistent solutions to the system of spinor and scalar field equations in General Relativity are studied for the case of Bianchi type-I space-time. The absence of initial singularity should be emphasized for some types of solutions and also the isotropic mode of space-time expansion in some special cases. 3 refs
Bianchi Type-V Bulk Viscous Cosmic String in f(R,T Gravity with Time Varying Deceleration Parameter
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Bïnaya K. Bishi
2015-01-01
Full Text Available We study the Bianchi type-V string cosmological model with bulk viscosity in f(R,T theory of gravity by considering a special form and linearly varying deceleration parameter. This is an extension of the earlier work of Naidu et al., 2013, where they have constructed the model by considering a constant deceleration parameter. Here we find that the cosmic strings do not survive in both models. In addition we study some physical and kinematical properties of both models. We observe that in one of our models these properties are identical to the model obtained by Naidu et al., 2013, and in the other model the behavior of these parameters is different.
International Nuclear Information System (INIS)
Gaikwad, N. P.; Borkar, M. S.; Charjan, S. S.
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. (geophysics, astronomy, and astrophysics)
Directory of Open Access Journals (Sweden)
Siomara Moreira Vieira Borba
2015-06-01
Full Text Available http://dx.doi.org/10.5007/2175-795X.2015v33n1p429 Neste artigo, reivindica-se a possibilidade de desenvolvimento de pesquisas educacionais tendo por referência a contribuição metodológica de Miriam Limoeiro Cardoso, posição que envolve dois movimentos desta pesquisa. Inicialmente, são expostas as teses da distinção entre realidade e objeto científico e da teorização como processo inicial da construção do objeto de investigação, que sintetizam o exame que autora empreende a partir dos apontamentos metodológicos de Karl Marx em seu processo de elaboração de uma teoria geral do capitalismo. A possibilidade da fecundidade de suas contribuições resulta da constatação de problemas na relação entre teoria e empiria que é identificada através da sumarização de análises da pesquisa educacional brasileira até início deste século, possivelmente ainda atual. Real primacy in the construction of scientific knowledge and the primacy of theory in the construction of scientific research: methodological contributions from Miriam Limoeiro Cardoso Abstract In this article it is claimed the possibility of developing educational research bearing in mind Miriam Limon Cardoso´s reference to the methodological contribution , a position that involves two research movements. At first, it is exhibited the thesis of the distinction between reality and scientific object and of the theorization as the initial process of the research object construction, which synthesize the examination which the author undertake from Karl Marx´s methodological notes in his process of elaboration of a general capitalism theory. The possibility of fecundity of her contributions result from the verification of problems between theory and practice that is identified by summarizing the analysis of the Brazilian educational research up to the beginning of this century, which is still current. Keywords: Scientific knowledge. Miriam Limoeiro Cardoso
Suzuki, Tsuneo
2018-02-01
Blockspin transformation of topological defects is applied to the violation of the non-Abelian Bianchi identity (VNABI) on lattice defined as Abelian monopoles. To get rid of lattice artifacts, we introduce (1) smooth gauge fixings such as the maximal center gauge (MCG), (2) blockspin transformations and (3) the tadpole-improved gauge action. The effective action can be determined by adopting the inverse Monte Carlo method. The coupling constants F (i ) of the effective action depend on the coupling of the lattice action β and the number of the blocking step n . But it is found that F (i ) satisfies a beautiful scaling; that is, they are a function of the product b =n a (β ) alone for lattice coupling constants 3.0 ≤β ≤3.9 and the steps of blocking 1 ≤n ≤12 . The effective action showing the scaling behavior can be regarded as an almost perfect action corresponding to the continuum limit, since a →0 as n →∞ for fixed b . The infrared effective monopole action keeps the global color invariance when smooth gauges such as MCG keeping the invariance are adopted. The almost perfect action showing the scaling is found to be independent of the smooth gauges adopted here as naturally expected from the gauge invariance of the continuum theory. Then we compare the results with those obtained by the analytic blocking method of topological defects from the continuum, assuming local two-point interactions are dominant as the infrared effective action. The action is formulated in the continuum limit while the couplings of these actions can be derived from simple observables calculated numerically on lattices with a finite lattice spacing. When use is made of Berezinskii-Kosterlitz-Thouless (BKT) transformation, the infrared monopole action can be transformed into that of the string model. Since large b =n a (β ) corresponds to the strong-coupling region in the string model, the physical string tension and the lowest glueball mass can be evaluated analytically
International Nuclear Information System (INIS)
Ayissi, Raoul Domingo; Noutchegueme, Norbert
2015-01-01
Global solutions regular for the Einstein-Boltzmann equation on a magnetized Bianchi type-I cosmological model with the cosmological constant are investigated. We suppose that the metric is locally rotationally symmetric. The Einstein-Boltzmann equation has been already considered by some authors. But, in general Bancel and Choquet-Bruhat [Ann. Henri Poincaré XVIII(3), 263 (1973); Commun. Math. Phys. 33, 83 (1973)], they proved only the local existence, and in the case of the nonrelativistic Boltzmann equation. Mucha [Global existence of solutions of the Einstein-Boltzmann equation in the spatially homogeneous case. Evolution equation, existence, regularity and singularities (Banach Center Publications, Institute of Mathematics, Polish Academy of Science, 2000), Vol. 52] obtained a global existence result, for the relativistic Boltzmann equation coupled with the Einstein equations and using the Yosida operator, but confusing unfortunately with the nonrelativistic case. Noutchegueme and Dongho [Classical Quantum Gravity 23, 2979 (2006)] and Noutchegueme, Dongho, and Takou [Gen. Relativ. Gravitation 37, 2047 (2005)], have obtained a global solution in time, but still using the Yosida operator and considering only the uncharged case. Noutchegueme and Ayissi [Adv. Stud. Theor. Phys. 4, 855 (2010)] also proved a global existence of solutions to the Maxwell-Boltzmann system using the characteristic method. In this paper, we obtain using a method totally different from those used in the works of Noutchegueme and Dongho [Classical Quantum Gravity 23, 2979 (2006)], Noutchegueme, Dongho, and Takou [Gen. Relativ. Gravitation 37, 2047 (2005)], Noutchegueme and Ayissi [Adv. Stud. Theor. Phys. 4, 855 (2010)], and Mucha [Global existence of solutions of the Einstein-Boltzmann equation in the spatially homogeneous case. Evolution equation, existence, regularity and singularities (Banach Center Publications, Institute of Mathematics, Polish Academy of Science, 2000), Vol. 52] the
International Nuclear Information System (INIS)
Shabbir, Ghulam; Khan, Suhail
2010-01-01
In this paper we classify Kantowski-Sachs and Bianchi type III space-times according to their teleparallel Killing vector fields using direct integration technique. It turns out that the dimension of the teleparallel Killing vector fields are 4 or 6, which are the same in numbers as in general relativity. In case of 4 the teleparallel Killing vector fields are multiple of the corresponding Killing vector fields in general relativity by some function of t. In the case of 6 Killing vector fields the metric functions become constants and the Killing vector fields in this case are exactly the same as in general relativity. Here we also discuss the Lie algebra in each case. (general)
Jaiswal, Rekha; Zia, Rashid
2018-04-01
In this paper, we have proposed a cosmological model, which is consistent with the new findings of `The Supernova Cosmology project' headed by Saul Perlmutter, and the `High-Z Supernova Search team', headed by Brian Schimdt. According to these new findings, the universe is undergoing an expansion with an increasing rate, in contrast to the earlier belief that the rate of expansion is constant or the expansion is slowing down. We have considered spatially homogeneous and anisotropic Bianchi-V dark energy model in Brans-Dicke theory of gravitation. We have taken the scale factor a(t)=k t^α e^{β t} , which results into variable deceleration parameter (DP). The graph of DP shows a transition from positive to negative, which shows that universe has passed through the past decelerated expansion to the current accelerated expansion phase. In this context, we have also calculated and plotted various parameters and observed that these are in good agreement with physical and kinematic properties of the universe and are also consistent with recent observations.
Kunstitudeng müügiks / Miriam Dagan
Dagan, Miriam
2006-01-01
Saksamaa näitel eri riikides ilmneva tendentsi üle, kus üliõpilased hakkavad juba õpingute ajal galeriide kaudu oma loomingut müüma. Neo Rauchi, Daniel Richteri õpilastest. Galerist Sebastian Klemmi seisukohtadest
The riverbank, the seashore and the wilderness: Miriam, liberation ...
African Journals Online (AJOL)
2017-07-25
Jul 25, 2017 ... feminist perspective it is argued that this style of non-violent, faithful prophetic witness has a ..... now shared by Yahweh and the military leader, the king. For the first ...... increasingly autocratic, and increasingly unpopular, rule.
Bradas, James C.; Fennelly, Alphonsus J.; Smalley, Larry L.
1987-01-01
It is shown that a generalized (or 'power law') inflationary phase arises naturally and inevitably in a simple (Bianchi type-I) anisotropic cosmological model in the self-consistent Einstein-Cartan gravitation theory with the improved stress-energy-momentum tensor with the spin density of Ray and Smalley (1982, 1983). This is made explicit by an analytical solution of the field equations of motion of the fluid variables. The inflation is caused by the angular kinetic energy density due to spin. The model further elucidates the relationship between fluid vorticity, the angular velocity of the inertially dragged tetrads, and the precession of the principal axes of the shear ellipsoid. Shear is not effective in damping the inflation.
A green management framework for hotels : a case of two African countries / Miriam Mbasera
Mbasera, Miriam
2015-01-01
Currently, there are environmental issues the world is facing which include global climate change, ozone depletion, pollution, high consumption of resources and increasing amounts of solid waste. Tourism is one of the largest industries and it is an important economic tool. However, it also has many negative effects on the environment. Hotels as one of the tourism industry’s component parts have a significant impact on the environment. From an environmental perspective, hotels consume a large...
Barbarid, plastiliinijänes, Miriam ja Frank Muller / Annika Koppel
Koppel, Annika
2003-01-01
Nukufilm näitab 4 uut filmi : "Barbarid" (stsenaristid Andrus Kivirähk ja Hardi Volmer, režissöör H. Volmer), "Porgand" (stsenarist Peep Pedmanson, režissöör Pärtel Tall), "Miriami jõulupäkapikk" (stsenaristid Leelo Tungal ja Peep Pedmanson, režissöör Mait Laas), "Kuuvaatleja" (reklaamitreiler Frank Mulleri kellafirmale ; stsenarist, režissöör, kunstnik Mati Kütt)
Spering, Miriam; Carrasco, Marisa
2015-01-01
Visual perception and eye movements are considered to be tightly linked. Diverse fields, ranging from developmental psychology to computer science, utilize eye tracking to measure visual perception. However, this prevailing view has been challenged by recent behavioral studies. We review converging evidence revealing dissociations between the contents of perceptual awareness and different types of eye movements. Such dissociations reveal situations in which eye movements are sensitive to part...
Spering, Miriam; Carrasco, Marisa
2015-01-01
Visual perception and eye movements are considered to be tightly linked. Diverse fields, ranging from developmental psychology to computer science, utilize eye tracking to measure visual perception. However, this prevailing view has been challenged by recent behavioral studies. We review converging evidence revealing dissociations between the contents of perceptual awareness and different types of eye movements. Such dissociations reveal situations in which eye movements are sensitive to particular visual features that fail to modulate perceptual reports. We also discuss neurophysiological, neuroimaging and clinical studies supporting the role of subcortical pathways for visual processing without awareness. Our review links awareness to perceptual-eye movement dissociations and furthers our understanding of the brain pathways underlying vision and movement with and without awareness. PMID:25765322
On Kasner solution in Bianchi I f( T) cosmology
Skugoreva, Maria A.; Toporensky, Alexey V.
2018-05-01
Recently the cosmological dynamics of an anisotropic Universe in f( T) gravity became an area of intense investigations. Some earlier papers devoted to this issue contain contradictory claims about the nature and propertied of vacuum solutions in this theory. The goal of the present paper is to clarify this situation. We compare properties of f( T) and f( R) vacuum solutions and outline differences between them. The Kasner solution appears to be an exact solution for the T=0 branch, and an asymptotic solution for the T ≠ 0 branch. It is shown that the Kasner solution is a past attractor if Tpast and future attractor for the T>0 branch.
The general class of Bianchi cosmological models with dark energy ...
Indian Academy of Sciences (India)
MS received 15 July 2016; accepted 5 October 2016; published online 8 March 2017. Abstract. ... Among all the possible alternatives, the simplest and ..... while green curve (with circles) and blue curve (with ..... [62] A D Linde, Phys. Lett.
Phase-space dynamics of Bianchi IX cosmological models
International Nuclear Information System (INIS)
Soares, I.D.
1985-01-01
The complex phase-space dynamical behaviour of a class of Biachi IX cosmological models is discussed, as the chaotic gravitational collapse due Poincare's homoclinic phenomena, and the n-furcation of periodic orbits and tori in the phase space of the models. Poincare maps which show this behaviour are constructed merically and applications are discussed. (Author) [pt
Bianchi-IX string cosmological model in Lyra geometry
Indian Academy of Sciences (India)
field in Lyra's geometry will either include a creation field and be equal to Hoyle's cre- ation field cosmology or contain a special vacuum field which together with the gauge vector term may be considered as a cosmological term. Subsequent investigations were done by several authors in scalar–tensor theory and cos-.
Can the modified Tan–Bianchi circumumbilical approach be used ...
African Journals Online (AJOL)
skin incision procedure (Table 1). The indications for surgery are summarized in Table 2. The most frequent indication for exploration was intus- susception mostly in infants below the age of 1 year. All 27 wounds except one healed with excellent aesthetic appearance, which was well appreciated by the parents. (Fig. 2).
Bianchi type IX string cosmological model in general relativity
Indian Academy of Sciences (India)
Cosmic strings arise during phase transitions after the big-bang explosion as the temperature goes down below some critical temperature [1–3]. These strings have stress energy and couple in a simple way to the gravitational field. The general relativistic formalism of cosmic strings is due to Letelier [4,5]. Stachel [6] has ...
Bianchi Type-I bulk viscous fluid string dust magnetized ...
Indian Academy of Sciences (India)
It is interesting to note that magnetic field present in galactic and inter galactic spaces plays a significant role at cosmological scale. Melvin [3] in the cosmological solution for dust and electromagnetic field suggested that during the evolution of the universe, the matter was in highly ionized state and is smoothly coupled with.
Bianchi Type-II inflationary models with constant deceleration ...
Indian Academy of Sciences (India)
ginning of the 1980s, nowadays receives a great deal of attention. Guth [1] proposed inflationary model in the context of grand unified theory (GUT), which has been accepted soon as the ..... where m1(> 0) is a constant of integration and n = 3. .... interesting feature of the present solution is that it is possible to exit from expo-.
Qualitative and numerical study of Bianchi IX Models
International Nuclear Information System (INIS)
Francisco, G.; Matsas, G.E.A.
1987-01-01
The qualitative behaviour of trajectories in the Mixmaster universe is studied. The Lyapunov exponents computed directly from the differential equations and from the Poincare map are shown to be different. A detailed discussion of the role of these exponents in analysing the effect of chaos on trajectories is presented. (Author) [pt
Study of primitive universe in the Bianchi IX model
International Nuclear Information System (INIS)
Matsas, G.E.A.
1988-03-01
The theory of general relativity is used to study the homogeneous cosmological model Bianch IX with isometry group SO(3) near the cosmological singularity. The Bogoyavlenskii-Novikov formalism to explain the anusual behaviour of the Liapunov exponent associated with this chaotic system, is introduced. (author) [pt
Combinatorial differential geometry and ideal Bianchi-Ricci identities
Czech Academy of Sciences Publication Activity Database
Janyška, J.; Markl, Martin
2011-01-01
Roč. 11, č. 3 (2011), s. 509-540 ISSN 1615-715X R&D Projects: GA ČR GA201/08/0397 Institutional research plan: CEZ:AV0Z10190503 Keywords : Natural operator * linear connection * reduction theorem Subject RIV: BA - General Mathematics Impact factor: 0.338, year: 2011 http://www.degruyter.com/view/j/advg.2011.11.issue-3/advgeom.2011.017/advgeom.2011.017. xml
Nonlinear photons in the type-I Bianchi universe
International Nuclear Information System (INIS)
Svaiter, N.F.
1984-01-01
It is shown that there exist several anisotropic solutions for the non-minimal coupled electromagnetic and gravitational field equations. A solution to vacuum is firstly presented, and afterwards a solution with matter and electric field, where the photon acquires a 'mass' proportional to the square root of the curvature scalar. This solution presents a true singularity in τ=0. A Kasner-like solution is also presented, with matter to the Einstein equations, where appears an ultra-relativistic perfect fluid (p=p). These two models give a good description of the universe dynamics in the neighborhood of the singularity. In this model, near to the singularity, does not occur the phenomenon described by lifshitz of the 'vacuum stage' because the influence of the matter can not be disregarded in regions near to the singularity. (L.C.) [pt
Combinatorial differential geometry and ideal Bianchi-Ricci identities
Czech Academy of Sciences Publication Activity Database
Janyška, J.; Markl, Martin
2011-01-01
Roč. 11, č. 3 (2011), s. 509-540 ISSN 1615-715X R&D Projects: GA ČR GA201/08/0397 Institutional research plan: CEZ:AV0Z10190503 Keywords : Natural operator * linear connection * reduction theorem Subject RIV: BA - General Mathematics Impact factor: 0.338, year: 2011 http://www.degruyter.com/view/j/advg.2011.11.issue-3/advgeom.2011.017/advgeom.2011.017.xml
Bianchi-V string cosmological model with dark energy anisotropy
Mishra, B.; Tripathy, S. K.; Ray, Pratik P.
2018-05-01
The role of anisotropic components on the dark energy and the dynamics of the universe is investigated. An anisotropic dark energy fluid with different pressures along different spatial directions is assumed to incorporate the effect of anisotropy. One dimensional cosmic strings aligned along x-direction supplement some kind of anisotropy. Anisotropy in the dark energy pressure is found to evolve with cosmic expansion at least at late times. At an early phase, the anisotropic effect due to the cosmic strings substantially affect the dynamics of the accelerating universe.
Conformally flat tilted Bianchi Type-V cosmological models in ...
Indian Academy of Sciences (India)
the complete determination of these quantities, we assume two extra conditions. First we assume that the space-time is conformally flat which leads to. 1008 .... Discussions. The model starts expanding with a big-bang at М = 0 and the expansion in the model stops at М = ∞ and = -2(Т + 2)¬. The model in general represents.
Dagan, Miriam
2007-01-01
Ameerika kunstniku ja režissööri kunstnikufilmidest "Cremaster' tsükkel" (1994-2002). Viie tsükli põhisündmusest. Viienda filmi rekvisiitor oli Meeli Salumäe, Kostabi Maailma assistent New Yorgis
Directory of Open Access Journals (Sweden)
Mark Kenneth Camiling
2017-08-01
Full Text Available Technology has greatly shaped pedagogical practices over time. However scholars posit that the developing technology-aided, -based, and -oriented instructional practices still need scholarly and systematic studies to prove their effectiveness. An emerging teaching strategy that highlights technology tools and programs is Flipped Learning: a strategy where technology redirects learning from large groups to individuals. The research described here hypothesizes that there is a significant difference between the basic science process skills test score means of elementary students in a Flipped classroom and those in a traditional classroom. To test this hypothesis, an experimental design was used as the participants were divided the into two groups: experimental and control. An instructional design was crafted to simultaneously teach both control and experimental groups within a one (1 hour schedule. The experimental group was asked to watch at home researcher-made videos that teach the basic science process skills. In class, these participants deepened understanding of the skills through varied activities. The control group was taught using the traditional method operationalized as 5E Inquiry-Based Model.Both pre- and post-tests were administered to check the relative test scores. A Mann Whitney U test was conducted to evaluate the difference between the basic process skills test mean scores. It is concluded that there is a statistically significant difference (at α=0.05, r = 0.42 with a large effect size between the two variables.
Equilibrium points of the tilted perfect fluid Bianchi VIh state space
Apostolopoulos, Pantelis S.
2005-05-01
We present the full set of evolution equations for the spatially homogeneous cosmologies of type VIh filled with a tilted perfect fluid and we provide the corresponding equilibrium points of the resulting dynamical state space. It is found that only when the group parameter satisfies h > -1 a self-similar solution exists. In particular we show that for h > -{1/9} there exists a self-similar equilibrium point provided that γ ∈ ({2(3+sqrt{-h})/5+3sqrt{-h}},{3/2}) whereas for h VIh.
Bianchi Type-IX viscous fluid cosmological model in general relativity
Indian Academy of Sciences (India)
Pramana – Journal of Physics. Current Issue : Vol. 90, Issue 4. Current Issue Volume 90 | Issue 4. April 2018. Home · Volumes & Issues · Special Issues · Forthcoming Articles · Search · Editorial Board · Information for Authors · Subscription ...
Perfect fluid Bianchi Type-I cosmological models with time varying G ...
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 70; Issue 4 ... Research Articles Volume 70 Issue 4 April 2008 pp 565-574 ... Department of Mathematical Sciences, A.P.S. University, Rewa 486 003, India; Department of Mathematics, Govt. ... Proceedings of the International Workshop/Conference on Computational ...
Bianchi-type II spacetime and anisotropic brane-world cosmology
International Nuclear Information System (INIS)
Sevinc, O.
2010-01-01
Anisotropic generalization of Randall and Sundrum brane-world model is considered. I studied a bulk with an anisotropic space of motion of the brane, depending on both time and extra coordinate. Then I discussed possibility of obtaining the fine-tuning condition of Randall and Sundrum following the method of Andrei V. Frolov (Phys. Lett. B, 514,213).
Bianchi type I expanding universe in Weyl-invariant gravity with a quartic interaction term
Energy Technology Data Exchange (ETDEWEB)
Kao, W.F.; Lin, Ing-Chen [National Chiao Tung University, Institute of Physics, Hsinchu (China)
2017-11-15
We will focus on the effect of a Weyl-invariant model with a quadratic interaction term and a free scalar field ψ. A set of analytic solutions will be obtained for this model. This model provides a dynamical alternative to the standard ΛCDM model. In particular, we will show that the quartic Weyl-invariant model prediction is consistent with the Hubble diagram observations. (orig.)
String cosmology in LRS Bianchi type-II dusty Universe with time ...
Indian Academy of Sciences (India)
The vacuum strings may generate sufficient density fluctuations to explain ... general theory of relativity some sort of dark energy, constant or which varies only ... ever, in the presence of interactions with matter or radiation, a solution of Einstein.
String cosmology in Bianchi type-VI0 dusty Universe with ...
Indian Academy of Sciences (India)
-VI0 Universe is investigated. Einstein's field equations have been solved exactly with suitable physical assump- tions for two types of strings: (i) massive strings and (ii) Nambu strings. It is found that when the. Universe is dominated by massive ...
A higher-dimensional Bianchi type-I inflationary Universe in general ...
Indian Academy of Sciences (India)
Inflation, the stage of accelerated expansion of the Universe, first proposed ... ary model in the context of grand unified theory (GUT), which has been ... The role of self-interacting scalar fields in inflationary cosmology in four-dimensional.
Bianchi Type-V model with a perfect fluid and Λ-term
Indian Academy of Sciences (India)
A self-consistent system of gravitational field with a binary mixture of perfect ... a form of quintessence, may explain the coincidence, adding a new motivation for .... hand, with the expansion of the universe, i.e., with the increase of V , the ...
Dynamics of Bianchi type-VI0 holographic dark energy models in ...
Indian Academy of Sciences (India)
2017-01-05
Jan 5, 2017 ... of the first attempts was made by Weyl [7] who pro- posed a ... the accelerated expansion of the Universe and is con- ..... range is in good agreement with large scale structure data. The EoS parameter of the HDE behaves like.
Bianchi type-V cosmological models with perfect fluid and heat flow ...
Indian Academy of Sciences (India)
In the cosmology with the power-law, the solutions correspond to a cos- mological model .... where ρ is the energy density, p is the thermodynamic pressure, uµ is the four- velocity of the fluid and ..... In the first category of models, the. Universe ...
Combinatorial differential geometry and ideal Bianchi-Ricci identities II - the torsion case
Czech Academy of Sciences Publication Activity Database
Janyška, J.; Markl, Martin
2012-01-01
Roč. 48, č. 1 (2012), s. 61-80 ISSN 0044-8753 R&D Projects: GA ČR GA201/08/0397 Institutional support: RVO:67985840 Keywords : natural operator * linear connection * torsion Subject RIV: BA - General Mathematics http://www.dml.cz/handle/10338.dmlcz/142092
Bianchi like classification of cosmologies in conformally flat space-times
International Nuclear Information System (INIS)
Tauber, G.E.
1989-01-01
Solutions of Killing's equations for a conformally flat line element have been found, which are seen to correspond to the conformal group of transformations consisting of the pure conformal group, the Lorentz group, translation and dilation. A classification of the line element has been carried out, singly and combining several of them. Upon comparison with expanding universes it has been found that the Friedmann universes are a subclass with other cosmologies resulting in wider subclasses. (orig.)
Palatini–Lovelock–Cartan gravity—Bianchi identities for stringy fluxes
Blumenhagen, R.; Deser, A.; Plauschinn, E.; Rennecke, F.
2012-01-01
A Palatini-type action for Einstein and Gauss–Bonnet gravity with non-trivial torsion is proposed. A three-form flux is incorporated via a deformation of the Riemann tensor, and consistency of the Palatini variational principle requires the flux to be covariantly constant and to satisfy a Jacobi
Reference: 352 [Arabidopsis Phenome Database[Archive
Lifescience Database Archive (English)
Full Text Available |Holtkamp Volker|Issakidis-Bourguet Emmanuelle|Kandlbinder Andrea|Lamkemeyer Petra|Laxa Miriam|Li Wenxue|Miginiac-Maslow Myroslawa|Schöttler Mark A|Tognetti Vanesa B|Weis Engelbert
Radio-Sensitizing Effects of Novel Histone De-Acetylase Inhibitors in Prostate Cancer
2005-09-01
14-16 A ppendices ....................................................................................... 16-17 I INTRODUCTION...Jr., He, L. Z., Richon, V., Calleja, E., and Pandolfi, P. P. Therapeutic targeting of transcription in acute promyelocytic leukemia by use of an
Defending the Amazon: Conservation, Development and Security in Brazil
2009-03-01
Globo, August 6, 2008, http://oglobo.globo.com/ economia /miriam/post.asp?t=rota_das_drogas&cod_Post=118173&a=496 (accessed February 24, 2009). 193...oglobo.globo.com/ economia /miriam/post.asp?t=rota_das_drogas&cod_Post =118173&a=496 (accessed February 24, 2009). Levitsky, Melvyn (U.S. Ambassador
Four of the south americans working at CERN
Laurent Guiraud
1999-01-01
Peruvian Jose Lamas Valverde (at back), and Brazilians (clockwise from right) Miriam Gandelman, Erica Polycarpo and Leandro de Paula Le peruvien Jose Lamas Valverde (au fond) et (dans le sens des aiguilles d'une montre, a partir du centre) les bresiliens Miriam Gandelman, Erica Polycarpo et Leandro de Paula
Sadhana | Indian Academy of Sciences
Indian Academy of Sciences (India)
Author Affiliations. Miriam Petitti1 Antonello A Barresi1 Daniele L Marchisio1. Dipartimento di Scienza Applicata e Tecnologia, Istituto di Ing. Chimica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italia ...
Reference: 712 [Arabidopsis Phenome Database[Archive
Lifescience Database Archive (English)
Full Text Available t cell Delledonne Massimo|Dietz Karl-Josef|Finkemeier Iris|Jones Alex M E|Laxa Miriam|Mattè Alessandro|Perazzolli Michele|Romero-Puertas Maria C|Vandelle Elodie|Zaninotto Federica
Cellular and molecular biology of filamentous fungi
National Research Council Canada - National Science Library
Borkovich, Katherine A; Ebbole, Daniel J
2010-01-01
... AND EXPRESSION OF THE GENETIC CODE / 61 6 Mitotic Cell Cycle Control / 63 COLIN P. C. DE SOUZA AND STEPHEN A. OSMANI 7 Meiosis / 81 CLAIRE BURNS, PATRICIA J. PUKKILA, AND MIRIAM E. ZOLAN 8 DNA Repa...
77 FR 61755 - Performance Review Board Members
2012-10-11
... JULIET COHEN GARY CONNOR SUZI COX VIRGINIA DANIEL KATHERINE DEL VECCHIO PAOLO DELPHIN-RITTMON MIRIAM DEVOSS ELIZABETH DICKINSON ELIZABETH ERNEY JOAN GABRIEL EDWARD GOLDHABER BEN GOTTLICH VICKI HENDERSON...
Anisotropic cosmological models and generalized scalar tensor theory
Indian Academy of Sciences (India)
Abstract. In this paper generalized scalar tensor theory has been considered in the background of anisotropic cosmological models, namely, axially symmetric Bianchi-I, Bianchi-III and Kortowski–. Sachs space-time. For bulk viscous fluid, both exponential and power-law solutions have been stud- ied and some assumptions ...
Anisotropic cosmological models and generalized scalar tensor theory
Indian Academy of Sciences (India)
In this paper generalized scalar tensor theory has been considered in the background of anisotropic cosmological models, namely, axially symmetric Bianchi-I, Bianchi-III and Kortowski–Sachs space-time. For bulk viscous ﬂuid, both exponential and power-law solutions have been studied and some assumptions among the ...
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics. Raj Bali. Articles written in Pramana – Journal of Physics. Volume 56 Issue 4 April 2001 pp 513-518 Research Articles. Bianchi type IX string cosmological model in general relativity · Raj Bali Shuchi Dave · More Details Abstract Fulltext PDF. We have investigated Bianchi type ...
Diagrams for certain quotients of PSL(2,Z[i])
Indian Academy of Sciences (India)
in their action on the complex plane. PSL(2, Z) is a Fuchsian group, 1 is discontinuous in C and therefore has no Fuchsian subgroups [2] of finite index. As with PSL (2, Z) and the other Euclidean Bianchi groups, many properties of 1 depends on its decomposition as a non-trivial amalgam. Real interest in Picard and Bianchi ...
Summary the race to reinvent energy and stop global warming
2013-01-01
Complete summary of Fred Krupp and Miriam Horn's book: ""Earth: The Sequel: The Race to Reinvent Energy and Stop Global Warming"". This summary of the ideas from Fred Krupp and Miriam Horn's book ""Earth: The Sequel"" explains how capitalism, as the most powerful economic force in the world, is the only engine of change that has the strength to stop global warming. In their book, the authors demonstrate how this can be achieved by installing a cap-and-trade initiative, providing genuine economic incentives for companies and reducing their carbon footprint. This summary explains their theory in
Polarization of photons in matter–antimatter annihilation
Energy Technology Data Exchange (ETDEWEB)
Moskaliuk, S.S. [Bogolyubov Institute for Theoretical Physics, Metrolohichna Street, 14-b, Kyiv-143, Ukraine, UA-03143 e-mail: mss@bitp.kiev.ua (Ukraine)
2015-03-10
In this work we demonstrate the possibility of generation of linear polarization of the electromagnetic field (EMF) due to the quantum effects in matter-antimatter annihilation process for anisotropic space of the I type according to Bianchi. We study the dynamics of this process to estimate the degree of polarisation of the EMF in the external gravitational field of the anisotropic Bianchi I model. It has been established that the quantum effects in matter-antimatter annihilation process in the external gravitational field of the anisotropic Bianchi I model provide contribution to the degree of polarisation of the EMF in quadrupole harmonics.
Steeling and Resilience in Art Education
Heise, Donalyn
2014-01-01
Steel is an incredibly strong alloy of iron and carbon. Due to its incredible strength and durability, this resilient material is commonly used for constructing buildings. The transitive verb "steeling" is defined in Miriam-Webster dictionary as "to fill with resolution or determination, as in, she 'steeled herself to face the…
Sadhana | Indian Academy of Sciences
Indian Academy of Sciences (India)
Home; Journals; Sadhana. Antonello A Barresi. Articles written in Sadhana. Volume 38 Issue 6 December 2013 pp 1219-1239. CFD modelling of condensers for freeze-drying processes · Miriam Petitti Antonello A Barresi Daniele L Marchisio · More Details Abstract Fulltext PDF. The aim of the present research is the ...
Sadhana | Indian Academy of Sciences
Indian Academy of Sciences (India)
Home; Journals; Sadhana. Daniele L Marchisio. Articles written in Sadhana. Volume 38 Issue 6 December 2013 pp 1219-1239. CFD modelling of condensers for freeze-drying processes · Miriam Petitti Antonello A Barresi Daniele L Marchisio · More Details Abstract Fulltext PDF. The aim of the present research is the ...
Indian Academy of Sciences (India)
Miriam
MIRIAM NAVLANI-GARCÍA,a PRIYANKA VERMA,a KOHSUKE MORI,*a,b,c YASUTAKA ... Colloid with Pd nanocrystals with various shapes. Figure ... Le Bars J, Specht U, Bradley J S and Blackmond D G 1999 Catalytic probe of the surface of ...
Collection Development: Relaxation & Meditation, September 1, 2010
Lettus, Dodi
2010-01-01
One of the first books to document the relationship between stress and physical and emotional health was "The Relaxation Response" by Herbert Benson, M.D., with Miriam Z. Klipper. Originally published in 1975, the book grew out of Benson's observations as a cardiologist and his research as a fellow at Harvard Medical School. Benson's study of…
EDITORIAL PSYCHIATRIC ILLNESS AMONG JUVENILES AND ...
African Journals Online (AJOL)
Kateee
2003-06-01
Jun 1, 2003 ... Bickel, R. and Campbell, A. Mental health of adolescents in custody: ... aged 8 to 18 years classified as criminal offenders, group I (60), and those for protection ... with poor socio-economic support (15). ..... Chief Residents' Office, The Miriam Hospital, 164 Summit Ave., Main Bldg, Room 344 Providence, RI.
African Journals Online (AJOL)
hond
2007-04-07
Apr 7, 2007 ... I can't help giggling to myself at the thought of the final showdown in heaven between the two ... After I placed my order I decided to walk to the .... Miriam Tlali's Amandla (1980) and Mongane Serote's To Every Birth its Blood (1979). Ride on the ... hatred, low self-esteem, and inferiority complexes. Sepamla ...
Ergonomics SA - Vol 28, No 2 (2016)
African Journals Online (AJOL)
Comparing fatigue responses between healthy individuals and asymptomatic low back pain sufferers - implications for return-to-work: a pilot study · EMAIL FULL TEXT EMAIL FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Miriam C. Mattison, Natalie A. Ross, 2-18. http://dx.doi.org/10.4314/esa.v28i2.2 ...
2011-08-01
... meetings, and solicits comments on the DEIS. DATES: Comments on the DEIS must be received no later than... public meetings. FOR FURTHER INFORMATION CONTACT: Miriam Valentine, Park Planner, Denali National Park... Memorial Day and a week after Labor Day. As tourism in Alaska has increased, so have demands for visits...
Indian Academy of Sciences (India)
Priyanka Verma
PRIYANKA VERMA,a MIRIAM NAVLANI-GARCÍA,a YASUTAKA KUWAHARA,a,b KOHSUKE MORI,a,b,c and HIROMI YAMASHITA*a,b. aDivision of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Japan. bUnit of Elements Strategy Initiative for Catalysts ...
Mentoring the modern African surgeon: A call to arms!
African Journals Online (AJOL)
2011-01-16
Jan 16, 2011 ... Hospital, Nairobi, 2-University of Nairobi, Kenya, 3-King Khalid University, UAE. Correspondence: Dr. Miriam Mutebi, Aga Khan. University Hospital. P.O. Bx 30270 .... Galukande M, Kijjambu S, Luboga S Improving recruitment of surgical trainees and training of surgeons in Uganda. East. Cent Afr J Surg.
African Journals Online (AJOL)
Items 451 - 500 of 592 ... Vol 15, No 1 (2013), Safe injections and waste management at a Sub-Saharan regional hospital: a quantitative descriptive study, Abstract PDF. Elisabeth Darj, Josefine Nilsson, Andrea Barnabas Pembe, Miriam Urasa. Vol 7, No 3 (2005), Sampling mosquitoes with CDC light trap in rice field and ...
Digital Repository Service at National Institute of Oceanography (India)
Sahoo, G.; Khandeparker, L.
associated with barnacle, Balanus amphitrite, shell and their role in gregarious settlement of cypris larvae. Journal of Experimental Marine Biology and Ecology, 413, 7- 12. Bavestrello, G., C. Bianchi, B. Calcinai, R. Cattaneo-Vietti, C. Cerrano, C. Morri...
Indian Academy of Sciences (India)
A higher-dimensional Bianchi type-I inflationary Universe in general relativity ... confinement as parent in the variationally improved perturbation theory. Bhaskar Jyoti .... quantum well under hydrostatic pressure and electric field. S Panda.
Novaes, Marcos Carneiro; Bispo, Pitágoras DA Conceição; Gonçalves, Maísa DE Carvalho
2016-12-14
Specimens of Perlidae (Plecoptera) from Espírito Santo State in southeastern Brazil were studied. A new species, Anacroneuria ruschii n. sp. is described. Brief remarks on A. debilis (Pictet) and Kempnyia neotropica (Jacobson & Bianchi) are also presented.
R2 inflation in anisotropic universes
International Nuclear Information System (INIS)
Berkin, A.L.
1990-01-01
The evolution of Bianchi type-I and type-IX universes for a theory of gravity with an εR 2 term added to the usual Lagrangian is considered. As in the spatially flat Robertson-Walker case considered previously by others, inflation is found to occur. For any amount of initial anisotropy, the anisotropy decays quickly relative to the length of the inflationary epoch, and the amount of expansion is enhanced by the anisotropy. The exceptions are Bianchi type-IX universes near or at isotropy. In these cases a wide range of initial parameters causes the universe to recollapse, thus reducing the phase space in which inflation can occur. The diagonal metric is shown to be the most general form in the R 2 theory for both Bianchi type-I universes with a perfect fluid and vacuum Bianchi type-IX models
Toward a gauge field theory of gravity.
Yilmaz, H.
Joint use of two differential identities (Bianchi and Freud) permits a gauge field theory of gravity in which the gravitational energy is localizable. The theory is compatible with quantum mechanics and is experimentally viable.
On the behaviour of test matter in the neighbourhood of caustics of homogeneous cosmological models
International Nuclear Information System (INIS)
Paul, H.G.
1983-01-01
Using power asymptotes for the metric of the BIANCHI types I, V, VII 0 , VIII and IX the intensity of geodesic focused scalar test matter is calculated in the neighbourhood of the caustic singularity of these space-time models. In all considered BIANCHI types there is a caustic diffraction with a diffraction field bounded by regions of extinction depending on the structure of the gravitational lense. (author)
Late time acceleration of the universe in f(R) gravity model
International Nuclear Information System (INIS)
Mukherjee, Ankan
2014-01-01
In this work, a new way to look at the nature of late time dynamics of the universe for f(R) gravity models using the contracted Bianchi Identity has been proposed. As the Einstein field equations contain derivatives of the curvature scalar R, the contracted Bianchi identity yields a second order nonlinear differential equation in H, the Hubble parameter. This equation is studied for two particular forms of f(R), and the late time behaviour of the model is discussed. (author)
Torsion and curvature in higher dimensional supergravity theories
International Nuclear Information System (INIS)
Smith, A.W.; Pontificia Univ. Catolica do Rio de Janeiro
1983-01-01
This work is an extension of Dragon's theorems to higher dimensional space-time. It is shown that the first set of Bianchi identities allow us to express the curvature components in terms of torsion components and its covariant derivatives. It is also shown that the second set of Bianchi identities does not give any new information which is not already contained in the first one. (Author) [pt
Hamiltonian dynamics of spatially-homogeneous Vlasov-Einstein systems
International Nuclear Information System (INIS)
Okabe, Takahide; Morrison, P. J.; Friedrichsen, J. E. III; Shepley, L. C.
2011-01-01
We introduce a new matter action principle, with a wide range of applicability, for the Vlasov equation in terms of a conjugate pair of functions. Here we apply this action principle to the study of matter in Bianchi cosmological models in general relativity. The Bianchi models are spatially-homogeneous solutions to the Einstein field equations, classified by the three-dimensional Lie algebra that describes the symmetry group of the model. The Einstein equations for these models reduce to a set of coupled ordinary differential equations. The class A Bianchi models admit a Hamiltonian formulation in which the components of the metric tensor and their time derivatives yield the canonical coordinates. The evolution of anisotropy in the vacuum Bianchi models is determined by a potential due to the curvature of the model, according to its symmetry. For illustrative purposes, we examine the evolution of anisotropy in models with Vlasov matter. The Vlasov content is further simplified by the assumption of cold, counter-streaming matter, a kind of matter that is far from thermal equilibrium and is not describable by an ordinary fluid model nor other more simplistic matter models. Qualitative differences and similarities are found in the dynamics of certain vacuum class A Bianchi models and Bianchi type I models with cold, counter-streaming Vlasov-matter potentials analogous to the curvature potentials of corresponding vacuum models.
Journal of Genetics | Indian Academy of Sciences
Indian Academy of Sciences (India)
Home; Journals; Journal of Genetics. Horacio Rivera. Articles written in Journal of Genetics. Volume 91 Issue 2 August 2012 pp 241-244 Research Note. De novo inv(17)(p11.2q21.3) in an intellectually disabled girl: appraisal of 21 inv(17) constitutional instances · Miriam Partida-Pérez María G. Domínguez Vivian Alejandra ...
Quantum Phases at the Nanoscale
2002-07-20
Sapienza" Roma. (Ital)y and Consejo perpendicular magnetic field, independent Nacional de Investigaciones Cientificas y electrons occupy Landau levels...Electromodulation of charge transfer and Departamento de Fisica Teorica de la the breathing mode of C60 on graphite Materia Condensada, Spain Miriam del...Instituto de Ciencia de Materiales de Madrid- epitaxial ferromagnetic metal [4], exhibiting CSIC. Spain coherent dynamics that persist over time scales
Formalising Living Labs to achieve organisational objectives in emerging economies
CSIR Research Space (South Africa)
Smit, D
2011-05-01
Full Text Available Conference Proceedings Paul Cunningham and Miriam Cunningham (Eds) IIMC International Information Management Corporation, 2011 ISBN: 978-1-905824-24-3 Formalising Living Labs to Achieve Organisational Objectives in Emerging Economies Danie SMIT1... organisation, a university) in the innovation process. In contrast to closed- innovation where firms only use internal sources, open-innovation suggests the companies use both external and internal sources. This shift in innovation paradigm becomes more...
McFarlane, Rosalind Nicole
2017-01-01
Poetry written by diasporic Asian groups in Australia has been gaining increasing attention, especially with the 2013 release of Contemporary Asian Australian Poets edited by Adam Aitken, Kim Cheng Boey and Michelle Cahill, the first anthology of this kind of work. This thesis aims to be the first instance of sustained critical attention paid to many of the poets included in this anthology, including Adam Aitken, Ivy Alvarez, Lachlan Brown, Lily Chan, Bella Li, Debbie Lim, Miriam Wei Wei Lo, ...
Janssen, Inger M.; Gerhardus,Ansgar; von Gersdorff,Gero; Schaller,Mathias; Barth,Claudia; Scheibler,Fueloep; Baldamus,Conrad
2015-01-01
Inger Miriam Janssen,1 Ansgar Gerhardus,2,3 Gero D von Gersdorff,4 Conrad August Baldamus,4 Mathias Schaller,4 Claudia Barth,5 Fueloep Scheibler6 1Department of Epidemiology and International Public Health, Bielefeld University, Bielefeld, Germany; 2Department for Health Services Research, University of Bremen, Bremen, Germany; 3Health Sciences Bremen, University of Bremen, Bremen, Germany; 4Department of Internal Medicine II, University Hospital of Cologne, Cologne, Germany; 5KfH K...
Where Corporate Culture and Local Markets Meet. Music and Film Majors in the Netherlands, 1990-2005
Kamp, Miriam
2009-01-01
textabstractSince the 1980s, media and entertainment companies have developed into large cross-media multinationals. Their international structure, strategy and operation have been investigated extensively. However, these majors operate globally by having local offices in various markets. So far, little attention has been paid to this aspect. In Where Corporate Culture and Local Markets Meet, Miriam van de Kamp addresses the local operation of international music and film corporations in the ...
Intelligent fractions learning system: implementation
CSIR Research Space (South Africa)
Smith, Andrew C
2011-05-01
Full Text Available Conference Proceedings Paul Cunningham and Miriam Cunningham (Eds) IIMC International Information Management Corporation, 2011 ISBN: 978-1-905824-24-3 An Intelligent Fractions Learning System: Implementation Andrew Cyrus SMITH1, Teemu H. LAINE2 1CSIR... to fractions. Our aim with the current research project is to extend the existing UFractions learning system to incorporate automatic data capturing. ?Intelligent UFractions? allows a teacher to remotely monitor the children?s progress during...
Poisson equation for weak gravitational lensing
International Nuclear Information System (INIS)
Kling, Thomas P.; Campbell, Bryan
2008-01-01
Using the Newman and Penrose [E. T. Newman and R. Penrose, J. Math. Phys. (N.Y.) 3, 566 (1962).] spin-coefficient formalism, we examine the full Bianchi identities of general relativity in the context of gravitational lensing, where the matter and space-time curvature are projected into a lens plane perpendicular to the line of sight. From one component of the Bianchi identity, we provide a rigorous, new derivation of a Poisson equation for the projected matter density where the source term involves second derivatives of the observed weak gravitational lensing shear. We also show that the other components of the Bianchi identity reveal no new results. Numerical integration of the Poisson equation in test cases shows an accurate mass map can be constructed from the combination of a ground-based, wide-field image and a Hubble Space Telescope image of the same system
On non-BPS effective actions of string theory
Hatefi, Ehsan
2018-05-01
We discuss some physical prospective of the non-BPS effective actions of type IIA and IIB superstring theories. By dealing with all complete three and four point functions, including a closed Ramond-Ramond string (in terms of both its field strength and its potential), gauge (scalar) fields as well as a real tachyon and under symmetry structures, we find various restricted world volume and bulk Bianchi identities. The complete forms of the non-BPS scattering amplitudes including their Chan-Paton factors are elaborated. All the singularity structures of the non-BPS amplitudes, their all order α ' higher-derivative corrections, their contact terms and various modified Bianchi identities are derived. Finally, we show that scattering amplitudes computed in different super-ghost pictures are compatible when suitable Bianchi identities are imposed on the Ramond-Ramond fields. Moreover, we argue that the higher-derivative expansion in powers of the momenta of the tachyon is universal.
Quantum Gowdy model within the new loop quantum cosmology improved dynamics
International Nuclear Information System (INIS)
Martin-Benito, M; Garay, L J; Mena Marugan, G A
2011-01-01
The linearly polarized Gowdy T 3 model can be regarded as compact Bianchi I cosmologies with inhomogeneous modes allowed to travel in one direction. We study a hybrid quantization of this model that combines the loop quantization of the Bianchi I background, adopting the improved dynamics scheme put forward by Ashtekar and Wilson-Ewing, with a Fock quantization for the inhomogeneities. The Hamiltonian constraint operator provides a resolution of the cosmological singularity and superselects separable sectors. We analyze the complicated structure of these sectors. In any of them the Hamiltonian constraint provides an evolution equation with respect to the volume of the associated Bianchi I universe, with a well posed initial value problem. This fact allows us to construct the Hilbert space of physical states and to show that we recover the standard quantum field theory for the inhomogeneities.
Thermodynamics and general relativity could determine the symmetry of the universe
International Nuclear Information System (INIS)
Bayin, S.S.
1986-01-01
Behavior of black hole parameters (area, surface gravity, and so on), like certain thermodynamic quantities (entropy, temperature, and so on), motivated Bekenstein to conjecture the existence of black hole thermodynamics. Later, the discovery of black hole radiation by Hawking established the physical link between these parameters and their thermodynamic counterparts. However, despite the success of black hole thermodynamics, the relation between general relativity and thermodynamics remains to be established for more general metrics. In this paper, in order to explore this relation the author considers the possibility of the Bianchi symmetry of a Friedmann model changing as the universe evolves. The suggestive model he uses is the one in which the radius of curvature of the three-dimensional space is treated like the inverse of the temperature and where rho(P,T) plays the role of the Gibbs potential energy density. He shows that for the transitions between Bianchi I and V and Bianchi I and IX symmetric Friedmann models, there is only one Gibbs function and the transformation is of second order. For the transformations between Bianchi V and Bianchi IV symmetric models, he has two distinct Gibbs functions and in general this leads us to first order phase transitions. These conclusions are obtained independently of the details of the local equation of state. He also discusses two specific cases to demonstrate some of the properties of the model. One of these properties is that this model gives us a new way of determining the symmetry of the universe. By using a well-known equation of state (P = αrho), he shows that with respect to the thermodynamics he has defined, it is advantageous for the universe to be open (Bianchi V symmetric)
Curvature tensors and unified field equations on SEX/sub n/
International Nuclear Information System (INIS)
Chung, K.T.; Lee, I.L.
1988-01-01
We study the curvature tensors and field equations in the n-dimensional SE manifold SEX/sub n/. We obtain several basic properties of the vectors S/subλ/ and U/sub λ/ and then of the SE curvature tensor and its contractions, such as a generalized Ricci identity, a generalized Bianchi identity, and two variations of the Bianchi identity satisfied by the SE Einstein tensor. Finally, a system of field equations is discussed in SEX/sub n/ an done of its particular solutions is constructed and displayed
Torsional heterotic geometries
International Nuclear Information System (INIS)
Becker, Katrin; Sethi, Savdeep
2009-01-01
We construct new examples of torsional heterotic backgrounds using duality with orientifold flux compactifications. We explain how duality provides a perturbative solution to the type I/heterotic string Bianchi identity. The choice of connection used in the Bianchi identity plays an important role in the construction. We propose the existence of a much larger landscape of compact torsional geometries using string duality. Finally, we present some quantum exact metrics that correspond to NS5-branes placed on an elliptic space. These metrics describe how torus isometries are broken by NS flux.
Mixmaster cosmological model in theories of gravity with a quadratic Lagrangian
International Nuclear Information System (INIS)
Barrow, J.D.; Sirousse-Zia, H.
1989-01-01
We use the method of matched asymptotic expansions to examine the behavior of the vacuum Bianchi type-IX mixmaster universe in a gravity theory derived from a purely quadratic gravitational Lagrangian. The chaotic behavior characteristic of the general-relativistic mixmaster model disappears and the asymptotic behavior is of the monotonic, nonchaotic form found in the exactly soluble Bianchi type-I models of the quadratic theory. The asymptotic behavior far from the singularity is also found to be of monotonic nonchaotic type
International Nuclear Information System (INIS)
Barrow, John D; Hervik, Sigbjorn
2002-01-01
We investigate brane-worlds with a pure magnetic field and a perfect fluid. We extend earlier work to brane-worlds and find new properties of the Bianchi type I brane-world. We find new asymptotic behaviours on approach to singularity and classify the critical points of the dynamical phase space. It is known that the Einstein equations for the magnetic Bianchi type I models are in general oscillatory and are believed to be chaotic, but in the brane-world model this chaotic behaviour does not seem to be possible
2009-06-01
Bianchi. MISC MISC MISC 1498 Sergeant McCain: Yeah, this is Sergeant Gaber from the 178th Op. I’d like to go secure. TIE TIE TIE 1499 Male Speaker...Sergeant Bianchi: Okay. MISC MISC MISC 1502 Sergeant Gaber : Northeast Air Defense Sector, this is Sergeant McCain, MISC MISC MISC may...Terrorist Team. TKS TKS TKS We need to get a BPR so the plane can land in Boston. TSOG TSOG TSOG 1504 Sergeant Gaber : Counter terrorist team
Loop groups, Kaluza-Klein reduction and M-theory
International Nuclear Information System (INIS)
Bergman, Aaron; Varadarajan, Uday
2005-01-01
We show that the data of a principal G-bundle over a principal circle bundle is equivalent to that of a LG-circumflex (def)/= U(1) x LG-bundle over the base of the circle bundle. We apply this to the Kaluza-Klein reduction of M-theory to IIA and show that certain generalized characteristic classes of the loop group bundle encode the Bianchi identities of the antisymmetric tensor fields of IIA supergravity. We further show that the low dimensional characteristic classes of the central extension of the loop group encode the Bianchi identities of massive IIA, thereby adding support to the conjectures given elsewhere
Relativistic cosmologies with closed, locally homogeneous space sections
International Nuclear Information System (INIS)
Fagundes, H.V.
1985-01-01
The homogeneous Bianchi and Kantowski-Sachs metrics of relativistic cosmology are investigated through their correspondence with recent geometrical results of Thurston. These allow a partial classification of the topologies for closed, locally homogeneous spaces according to Thurston's eight geometric types. Besides, which of the Bianchi-Kantowski-Sachs metrics can be imposed on closed space sections of cosmological models are learned. This is seen as a progress toward implementation of a postulate of the closure of space for both classical and quantum gravity. (Author) [pt
Properties of kinematic singularities
Energy Technology Data Exchange (ETDEWEB)
Coley, A A [Department of Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia B3H 3J5 (Canada); Hervik, S [Department of Mathematics and Natural Sciences, University of Stavanger, N-4036 Stavanger (Norway); Lim, W C [Albert-Einstein-Institut, Am Muehlenberg 1, D-14476 Potsdam (Germany); MacCallum, M A H, E-mail: aac@mathstat.dal.c, E-mail: sigbjorn.hervik@uis.n, E-mail: wclim@aei.mpg.d, E-mail: m.a.h.maccallum@qmul.ac.u [School of Mathematical Sciences, Queen Mary University of London, E1 4NS (United Kingdom)
2009-11-07
The locally rotationally symmetric tilted perfect fluid Bianchi type V cosmological model provides examples of future geodesically complete spacetimes that admit a 'kinematic singularity' at which the fluid congruence is inextendible but all frame components of the Weyl and Ricci tensors remain bounded. We show that for any positive integer n there are examples of Bianchi type V spacetimes admitting a kinematic singularity such that the covariant derivatives of the Weyl and Ricci tensors up to the nth order also stay bounded. We briefly discuss singularities in classical spacetimes.
Cosmic anisotropy with reduced relativistic gas
Energy Technology Data Exchange (ETDEWEB)
Castardelli dos Reis, Simpliciano [Universidade Federal de Juiz de Fora, Departamento de Fisica, ICE, Juiz de Fora, MG (Brazil); Shapiro, Ilya L. [Universidade Federal de Juiz de Fora, Departamento de Fisica, ICE, Juiz de Fora, MG (Brazil); Tomsk State Pedagogical University, Tomsk (Russian Federation); Tomsk State University, Tomsk (Russian Federation)
2018-02-15
The dynamics of cosmological anisotropies is investigated for Bianchi type I universe filled by a relativistic matter represented by the reduced relativistic gas model (RRG), with equation of state interpolating between radiation and matter. Previously it was shown that the interpolation is observed in the background cosmological solutions for homogeneous and isotropic universe and also for the linear cosmological perturbations. We extend the application of RRG to the Bianchi type I anisotropic model and find that the solutions evolve to the isotropic universe with the pressureless matter contents. (orig.)
Ambiguities on electric and magnetic fields for an extended gauge model
International Nuclear Information System (INIS)
Colatto, L.P.; Doria, R.M.
1990-01-01
Generalized electric and magnetic fields in a system containing N-potential fields in the same U (1) - group are obtained. Bianchi identities, equations of motions, conserved charges and Lorentz forces are developed in association to each of these fields. Such facts confirm that the same parameter α (x) is able to organize the presence of distinct fields. The physics generated from the minimal action principle is independent of the initial definition for the electric (magnetic) field. Nevertheless, such a choice reveals differences in the Bianchi identity context. (author)
Duality in superspace and anomaly free supergravity: Some remarks
International Nuclear Information System (INIS)
D'Auria, R.; Fre, P.
1988-01-01
The authors show that the superspace formulation of anomaly free supergravity based on the 2-form B/sup (2)/ and the 6-form B/sup (6)/ are asymmetrical. B/sup (6)/ is the electric potential while B/sup (2)/ is the magnetic one. As a consequence, the Bianchi-identity associated with the B/sup (2)/ formulation is the in homogeneous Maxwell equation which provides a full account of the dynamics. The Bianchi identity associated with B/sup (6)/ is the homogeneous Maxwell equation: a mere identity which yields no information on the dynamics. It admits a universal ''offshell'' solution
Between Two Empires. Histoire des deux Indes And Modern Colonialism
Directory of Open Access Journals (Sweden)
Alessandro Pandolfi
2013-07-01
Full Text Available The article critically analyses the late eighteenth century process of crisis and transformation of the concept of empire. By considering Raynal’s Histoire des deux Indes and the Enlightenment’s critique of the different imperial models, Pandolfi reconstructs the transit from classic colonialism – built around the relations between settlers, savages and slaves – to another phase characterized by the indirect exploitation of the labour force. The text underlines the ambivalence of Enlightenment towards the question of the empire by demonstrating how Raynal’s work reflects the constitutive tension of the second half of the 1700s. Therefore, through Diderot’s analysis, the author demonstrates how the moral advancement of humanity is the product of a constant interaction between the colonial rhetoric of commerce and those revolutions, which, – in different moments and places – have crossed the colonial space.
Fracture and Fragmentation of Simplicial Finite Elements Meshes using Graphs
Energy Technology Data Exchange (ETDEWEB)
Mota, A; Knap, J; Ortiz, M
2006-10-18
An approach for the topological representation of simplicial finite element meshes as graphs is presented. It is shown that by using a graph, the topological changes induced by fracture reduce to a few, local kernel operations. The performance of the graph representation is demonstrated and analyzed, using as reference the 3D fracture algorithm by Pandolfi and Ortiz [22]. It is shown that the graph representation initializes in O(N{sub E}{sup 1.1}) time and fractures in O(N{sub I}{sup 1.0}) time, while the reference implementation requires O(N{sub E}{sup 2.1}) time to initialize and O(N{sub I}{sup 1.9}) time to fracture, where NE is the number of elements in the mesh and N{sub I} is the number of interfaces to fracture.
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 68; Issue 5. Issue front cover thumbnail. Volume 68, Issue 5. May 2007, pages 707-880. pp 707-720 Research Articles. Bianchi Type-II inﬂationary models with constant deceleration parameter in general relativity · C P Singh S Kumar · More Details Abstract Fulltext ...
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 69; Issue 2. Issue front cover thumbnail. Volume 69, Issue 2. August 2007, pages 159-316. pp 159-166 Research Articles. Bianchi Type-I, V and VIo models in modified generalized scalar–tensor theory · T Singh R Chaubey · More Details Abstract Fulltext PDF.
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
A spatially homogeneous locally-rotationally-symmetric (LRS) Bianchi type-V cosmological model is considered with a perfect fluid in general relativity. We present two types of cosmologies (power-law and exponential forms) by using a law of variation for the mean Hubble parameter that yields a constant value for the ...
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
We have investigated Bianchi type IX string cosmological models in general relativity. To get a determinate solution, we have assumed a condition ρ= i.e. rest energy density for a cloud of strings is equal to the string tension density. The various physical and geometrical aspects of the models are also discussed.
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
A ﬁve-dimensional Bianchi type-I inﬂationary Universe is investigated in the presence of massless scalar ﬁeld with a ﬂat potential. To get an inﬂationary Universe, a ﬂat region in which the potential is constant is considered. Some physical and kinematical properties of the Universe are also discussed.
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
Bianchi Type-I magnetized bulk viscous fluid string dust cosmological model is investigated. To get a determinate model, we have assumed the conditions and = constant where is the shear, the expansion in the model and the coefficient of bulk viscosity. The behaviour of the model in the presence and ...
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
Bianchi type-V string cosmological models in general relativity are investigated. To get the exact solution of Einstein's ﬁeld equations, we have taken some scale transformations used by Camci et al [Astrophys. Space Sci. 275, 391 (2001)]. It is shown that Einstein's ﬁeld equations are solvable for any arbitrary cosmic scale ...
A sketch to the geometrical N=2-d=5 Yang-Mills theory over a supersymmetric group-manifold - I
International Nuclear Information System (INIS)
Borges, M.; Turin Univ.; Pio, G.
1983-03-01
This work concerns the search and the construction of a geometrical structure for a supersymmetric N=2-d=5 Yang-Mills theory on the group manifold. From criteria established throughout this paper, we build up an ansatz for the curvatures of our theory and then solve the Bianchi identities, whose solution is fundamental for the construction of the geometrical action. (author)
Collineations of the curvature tensor in general relativity
Indian Academy of Sciences (India)
Curvature collineations for the curvature tensor, constructed from a fundamental Bianchi Type-V metric, are studied. We are concerned with a symmetry property of space-time which is called curvature collineation, and we briefly discuss the physical and kinematical properties of the models.
Cosmic no-hair conjecture in scalar–tensor theories
Indian Academy of Sciences (India)
We have shown that, within the context of scalar–tensor theories, the anisotropic Bianchi-type cosmological models evolve towards de Sitter Universe. A similar result holds in the case of cosmology in Lyra manifold. Thus the analogue of cosmic no-hair theorem of Wald [1] hold in both the cases. In fact, during inflation there ...
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
hair conjecture in scalar–tensor theories · T Singh R Chaubey ... universe has been studied. Volume 69 Issue 2 August 2007 pp 159-166 Research Articles. Bianchi Type-I, V and VIo models in modified generalized scalar–tensor theory.
CERN PhotoLab
1980-01-01
The Radiobiology Group carries out experiments to study the effect of radiation on living cells. The photo shows the apparatus for growing broad beans which have been irradiated by 250 GeV protons. The roots are immersed in a tank of running water (CERN Weekly Bulletin 26 January 1981 and Annual Report 1980 p. 160). Karen Panman, Marilena Streit-Bianchi, Roger Paris.
Energy Technology Data Exchange (ETDEWEB)
Rajpoot, Subhash [California State University, Long Beach, CA (United States); Vacaru, Sergiu I. [Quantum Gravity Research, Topanga, CA (United States); University ' ' Al.I. Cuza' ' , Project IDEI, Iasi (Romania)
2017-05-15
Applying the anholonomic frame deformation method, we construct various classes of cosmological solutions for effective Einstein-Yang-Mills-Higgs, and two measure theories. The types of models considered are Freedman-Lemaitre-Robertson-Walker, Bianchi, Kasner and models with attractor configurations. The various regimes pertaining to plateau-type inflation, quadratic inflation, Starobinsky type and Higgs type inflation are presented. (orig.)
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
The general class of Bianchi cosmological models with dark energy in the form of modified Chaplygin gas with variable Λ and G and bulk viscosity have been considered. We discuss three types of average scalefactor by using a special law for deceleration parameter which is linear in time with negative slope. The exact ...
The fundamental theorem of linearised Regge calculus
International Nuclear Information System (INIS)
Barrett, J.W.
1987-01-01
In linearised Regge calculus in a topologically trivial region, the space of linearised deviations of the edge lengths from a flat configuration, divided by the subspace of deformations due to translations of the vertices, is equivalent to the space of the linearised curvatures which satisfy the Bianchi identities. (orig.)
Note on 3-dimensional Regge calculus
International Nuclear Information System (INIS)
Soda, Jiro
1991-01-01
We shall study 3-dimensional Regge calculus with concentrating the role of the Bianchi identity. As a result, the number of the physical variables is determined to be 12g - 12(g > 1). The reason why Rocek and Williams derived the exact result of Deser, Jackiw and 'tHooft is clarified. (author)
On the stability of the Lp -norm of the Riemannian curvature tensor
Indian Academy of Sciences (India)
Department of Mathematics, Indian Institute of Science, Bangalore 560 012, India .... the differential Bianchi identity simplifies the expression for the gradient of R2. ... it is a strict local minimizer for Rp. Applying Hölder inequality one can prove ...
De steenvlieg Protonemura risi nieuw voor Nederland (Plecoptera: Nemouridae).
Hoek, van den T.-H.
2006-01-01
The stonefly Protonemura risi new for the Netherlands (Plecoptera: Nemouridae) During a survey in the southernmost part of the province Limburg a stonefly new to the Netherlands was recorded: Protonemura risi (Jacobson & Bianchi, 1905). The species was observed in two spring brooks in June 2005.
Kakskümmend üheksa / Juhapekka Tukiainen
Tukiainen, Juhapekka
2013-01-01
TMi test: 29tollised maastikurattad, hinnaklass 1500 eurot. Bianchi Jab 29.2; Canyon Grand Canyon 8.9 AL 29; Corratec Superbow Team 29; Cube LTD SL 29; Felt Nine 30; Kona Kahuna DL; KTM Ultra Race 29; Merida Big Nine TFS XT Edition
New Models for Initial Teacher Education in Scotland
Kibble, Bob
2012-01-01
In this article, the author responds to the recent article by Lynne Bianchi commenting on the Donaldson report, "Teaching Scotland's future" (Donaldson, 2011). He agrees that the Donaldson report has indeed been a catalyst to drive change across the entire landscape of initial teacher education (ITE) in Scotland. In fact, not only ITE:…
Homoclinic phenomena in the gravitational collapse
International Nuclear Information System (INIS)
Koiller, J.; Mello Neto, J.R.T. de; Soares, I.D.
1984-01-01
A class of Bianchi IX cosmological models is shown to have chaotic gravitational collapse, due to Poincare's homoclinic phenomena. Such models can be programmed so that for any given positive integer N (N=infinity included) the universe undergoes N non-periodic oscillations (each oscillation requiring a long time) before collapsing. For N=infinity the universe undergoes periodic oscillations. (Author) [pt
International Nuclear Information System (INIS)
Wainwright, J.
1990-01-01
The workshop on mathematical cosmology was devoted to four topics of current interest. This report contains a brief discussion of the historical background of each topic and a concise summary of the content of each talk. The topics were; the observational cosmology program, the cosmological perturbation program, isotropic singularities, and the evolution of Bianchi cosmologies. (author)
Balancing anisotropic curvature with gauge fields in a class of shear-free cosmological models
Thorsrud, Mikjel
2018-05-01
We present a complete list of general relativistic shear-free solutions in a class of anisotropic, spatially homogeneous and orthogonal cosmological models containing a collection of n independent p-form gauge fields, where p\\in\\{0, 1, 2, 3\\} , in addition to standard ΛCDM matter fields modelled as perfect fluids. Here a (collection of) gauge field(s) balances anisotropic spatial curvature on the right-hand side of the shear propagation equation. The result is a class of solutions dynamically equivalent to standard FLRW cosmologies, with an effective curvature constant Keff that depends both on spatial curvature and the energy density of the gauge field(s). In the case of a single gauge field (n = 1) we show that the only spacetimes that admit such solutions are the LRS Bianchi type III, Bianchi type VI0 and Kantowski–Sachs metric, which are dynamically equivalent to open (Keff0 ) FLRW models, respectively. With a collection of gauge fields (n > 1) also Bianchi type II admits a shear-free solution (Keff>0 ). We identify the LRS Bianchi type III solution to be the unique shear-free solution with a gauge field Hamiltonian bounded from below in the entire class of models.
Time Frequency Analysis and Spatial Filtering in the Evaluation of Beta ERS After Finger Movement
2001-10-25
Italy. 5IRCCS Fondazione Santa Lucia , via Ardeatina 306, Roma, Italy Fig. 1 Scheme of the Wavelet Packet decomposition. The gray boxes represent...surface splines. J. Aircraft, 1972, 9: 189-191. [8]Maceri, B., Magnone, S., Bianchi, A., Cerutti, S. Studio della decomposizione wavelet dei segnali
A new interpretation of zero Lyapunov exponents in BKL time for Mixmaster cosmology
International Nuclear Information System (INIS)
Wu Xin
2010-01-01
A global relationship between cosmological time and Belinskii-Khalatnikov-Lifshitz (BKL) time during the entire evolution of the Mixmaster Bianchi IX universe is used to explain why all the Lyapunov exponents are zero at the BKL time. The actual reason is that the domain of the cosmological time is finite as the BKL time runs from minus infinity to infinity.
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
pp 1007-1014 Research Articles. Conformally flat tilted Bianchi Type-V cosmological models in general relativity · Raj Bali B L Meena · More Details Fulltext PDF. pp 1015-1028 Research Articles. Brownian motion in a classical ideal gas: A microscopic approach to Langevin's equation · Rangan Lahiri Arvind Anirban Sain.
African Journals Online (AJOL)
abp
18 mai 2017 ... J Bone Joint Surg. 1934; 16(3): 631-. 9. PubMed | Google Scholar. 7. Abdelwahab I F, Bianchi S, Martinoli C, Klein M, Hermann G. Atypical extraspinal musculoskeletal tuberculosis in immunocompetent patients : Part II, Tuberculous myositis, tuberculous bursitis, and tuberculous tenosynovitis. Can Assoc.
Indian Academy of Sciences (India)
Oza A T. Non-equilibrium and band tailing in organic conductors. 535. Pal Dipali. The extent of strangeness equilibration in quark gluon plasma. 1083. Pal S see Bhattacharya P. 1017. Pandey B P. Thermal condensation mode in a dusty plasma. 491. Pant D N. Bianchi type I string cosmologies. 433. Parhi S see Pandey B P.
Indian Academy of Sciences (India)
447–458. Anisotropic Bianchi-I universe with phantom field and cosmological con- stant ... Bifurcation methods of dynamical systems for generalized Kadomtsov–. Petviashvili– .... Dynamic instability at the origin of oxygen ion conduction in solid oxides ..... Effect of Solar features and interplanetary parameters on geomagne-.
Bianchi, Lynne
2015-01-01
In this article, Lynne Bianchi shares a project that has proved successful with helping schools to discover and overcome their barriers. "Deep Dives" was a pilot project supported by the Primary Science Teaching Trust (PSTT), initially piloted in Sheffield, and now forms part of the continuing professional development toolkit offered by…
Changing Families, Changing Workplaces
Bianchi, Suzanne M.
2011-01-01
American families and workplaces have both changed dramatically over the past half-century. Paid work by women has increased sharply, as has family instability. Education-related inequality in work hours and income has grown. These changes, says Suzanne Bianchi, pose differing work-life issues for parents at different points along the income…
New explicit spike solutions-non-local component of the generalized Mixmaster attractor
International Nuclear Information System (INIS)
Lim, Woei Chet
2008-01-01
By applying a standard solution-generating transformation to an arbitrary vacuum Bianchi type II solution, one generates a new solution with spikes commonly observed in numerical simulations. It is conjectured that the spike solutions are part of the generalized Mixmaster attractor
On the propagation of Einstein's equations with quasi-Maxwellian equations of gravity
International Nuclear Information System (INIS)
Novello, M.; Salim, J.M.
1985-01-01
It is proved that an affirmation proposed in a recent paper of Lesche and Som in which they argue about the non equivalence in the use of Weyl conformal tensor instead of the fuel curvature tensor in Bianchi identities regarded as the equation of evolution is wrong. (L.C.) [pt
The anisotropic cosmological models in f ( R , T ) gravity with Λ
Indian Academy of Sciences (India)
The general class of anisotropic Bianchi cosmological models in f ( R , T ) modified theories of gravity with Λ ( T ) has been considered. This paper deals with f ( R , T ) modified theories of gravity, where the gravitational Lagrangian is given by an arbitrary function of Ricci scalar R and the trace of the stress-energy tensor T ...
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics. Bikash Chandra Paul. Articles written in Pramana – Journal of Physics. Volume 71 Issue 6 December 2008 pp 1247-1257 Research Articles. Anisotropic Bianchi-I universe with phantom field and cosmological constant · Bikash Chandra Paul Dilip Paul · More Details Abstract ...
Genetics Home Reference: Griscelli syndrome
... Tezcan I, Ersoy F, Houdusse A, Fischer A, de Saint Basile G. Griscelli syndrome restricted to hypopigmentation results from a melanophilin defect ( ... N, Bianchi D, Fischer A, Le Deist F, de Saint Basile G. Mutations in RAB27A ... syndrome associated with haemophagocytic syndrome. Nat Genet. 2000 Jun; ...
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
In this paper, we study anisotropic Bianchi-V Universe with magnetic field and bulk viscous fluid in string cosmology. Exact solutions of the field equations are obtained by using the equation of state (EoS) for a cloud of strings, and a relationship between bulk viscous coefficient and scalar expansion. The bulk viscous ...
The Gibbs entropy production in general relativity
International Nuclear Information System (INIS)
Henneaux, M.
1983-01-01
The entropy production is analyzed in the case of homogeneous cosmological models of the Bianchi type. It is shown to vanish for class-A models and to be undefined for class-B ones, because of an ambiguity in the measure on the space of the true gravitational degrees of freedom. How this results extend to the full Einstein theory is discussed
Gibbs entropy production in general relativity
International Nuclear Information System (INIS)
Henneaux, M.
1983-01-01
The entropy production is analyzed in the case of homogeneous cosmological models of the Bianchi type. It is shown to vanish for class-A models and to be undefined for class-B ones, because of an ambiguity in the measure on the space of the true gravitational degrees of freedom. How this results extends to the full Einstein theory is discussed
Primary Science Interview: Science Sparks
Bianchi, Lynne
2016-01-01
In this "Primary Science" interview, Lynne Bianchi talks with Emma Vanstone about "Science Sparks," which is a website full of creative, fun, and exciting science activity ideas for children of primary-school age. "Science Sparks" started with the aim of inspiring more parents to do science at home with their…
Pramana – Journal of Physics | Indian Academy of Sciences
Indian Academy of Sciences (India)
Einstein's ﬁeld equations are considered for a locally rotationally symmetric Bianchi Type-II space–time in the presence of a massless scalar ﬁeld with a scalar potential. Exact solutions of scale factors and other physical parameters are obtained by using a special law of variation for Hubble's parameter that yields a constant ...
Indian Academy of Sciences (India)
see Reddy N Parvathala. 1065. Ahmad Irfan see Khan Ziauddin. 1011. Akhlaghi Parisa. The measurements of thermal neutron flux distribution in a paraffin phantom. 873. Amirhashchi Hassan. String cosmology in Bianchi type-VI0 dusty. Universe with electromagnetic field. 723. Aref Morteza see Feghhi Seyed Amir Hossein.
Cosmological models in general relativity
Indian Academy of Sciences (India)
Cosmological models in general relativity. B B PAUL. Department of Physics, Nowgong College, Nagaon, Assam, India. MS received 4 October 2002; revised 6 March 2003; accepted 21 May 2003. Abstract. LRS Bianchi type-I space-time filled with perfect fluid is considered here with deceler- ation parameter as variable.
Cosmological models in general relativity
Indian Academy of Sciences (India)
LRS Bianchi type-I space-time ﬁlled with perfect ﬂuid is considered here with deceleration parameter as variable. The metric potentials and are functions of as well as . Assuming '/=(), where prime denotes differentiation with respect to , it was found that =('/) and =(), where =() and is the ...
Indian Academy of Sciences (India)
... B 74, 182 (1983) has been utilized to solve the field equations. Some physical and kinematical properties of the models are also discussed. Volume 88 Issue 2 February 2017 pp 30 Regular. Dynamics of Bianchi type-VI 0 holographic dark energy models in general relativity and Lyra's geometry · S D KATORE D V KAPSE.
BioModels.net Web Services, a free and integrated toolkit for computational modelling software.
Li, Chen; Courtot, Mélanie; Le Novère, Nicolas; Laibe, Camille
2010-05-01
Exchanging and sharing scientific results are essential for researchers in the field of computational modelling. BioModels.net defines agreed-upon standards for model curation. A fundamental one, MIRIAM (Minimum Information Requested in the Annotation of Models), standardises the annotation and curation process of quantitative models in biology. To support this standard, MIRIAM Resources maintains a set of standard data types for annotating models, and provides services for manipulating these annotations. Furthermore, BioModels.net creates controlled vocabularies, such as SBO (Systems Biology Ontology) which strictly indexes, defines and links terms used in Systems Biology. Finally, BioModels Database provides a free, centralised, publicly accessible database for storing, searching and retrieving curated and annotated computational models. Each resource provides a web interface to submit, search, retrieve and display its data. In addition, the BioModels.net team provides a set of Web Services which allows the community to programmatically access the resources. A user is then able to perform remote queries, such as retrieving a model and resolving all its MIRIAM Annotations, as well as getting the details about the associated SBO terms. These web services use established standards. Communications rely on SOAP (Simple Object Access Protocol) messages and the available queries are described in a WSDL (Web Services Description Language) file. Several libraries are provided in order to simplify the development of client software. BioModels.net Web Services make one step further for the researchers to simulate and understand the entirety of a biological system, by allowing them to retrieve biological models in their own tool, combine queries in workflows and efficiently analyse models.
Ultraviolet imaging of planetary nebulae with GALEX
Bianchi, Luciana; Thilker, David
2018-05-01
Over four hundred Galactic Planetary Nebulae (PNe) have been imaged by GALEX in two ultraviolet (UV) bands, far-UV (FUV, 1344-1786 Å, λ _{eff}= 1528 Å) and near-NUV (NUV, 1771-2831 Å, λ _{eff} = 2271 Å). We present examples of extended PNe, for which UV spectroscopy is also available, to illustrate the variety in UV morphology and color, which reflects ionization conditions. The depth of the GALEX imaging varies from flux ≈ 0.4/5× 10 ^{-18} ergs cm^{-2} s^{-1} Å^{-1} \\square ^'' -1} (FUV/NUV) for exposures of the order of ˜ 100 seconds, typical of the survey with the largest area coverage, to ˜ 0.3/8.3× 10^{-19} ergs cm^{-2} s^{-1} Å^{-1} \\square ^'' -1} (FUV/NUV) for ˜ 1500 sec exposures, typical of the second largest survey (see Bianchi in Astrophys. Space Sci. 320:11, 2009; Bianchi et al. in Adv. Space Res. 53:900, 2014). GALEX broad-band FUV and NUV fluxes include nebular emission lines and in some cases nebular continuum emission. The sensitivity of the GALEX instrument and the low sky background, especially in FUV, enable detection and mapping of very faint ionization regions and fronts, including outermost wisps and bow shocks. The FUV-NUV color of the central star provides a good indication of its T_{eff}, because the GALEX FUV-NUV color is almost reddening-free for Milky Way type dust (Bianchi et al. in Astrophys. J. Suppl. Ser. 230:24, 2017; Bianchi in Astrophys. Space Sci. 335:51, 2011, Bianchi in Astrophys. Space Sci. 354:103, 2014) and it is more sensitive to hot temperatures than optical colors.
Fankhauser, Miriam
2016-01-01
Im folgenden Bericht geht es um das Projekt «Weiterentwicklung Gruppenleiter/innen-Kurs – Ein Pro- jekt in der Freiwilligenarbeit des CVJM/CVJF Regionalverband Basels». Dieses Projekt wurde von der Studentin Miriam Fankhauser im Rahmen der Praxisausbildung an der Hochschule Luzern für Soziale Arbeit durchgeführt. In Auftrag gegeben wurde das Projekt vom CVJM/CVJF Regionalverband Basel. Beim eben genannten Projekt ging es darum, den Gruppenleiter/innen-Kurs weiterzuentwickeln. Der Kurs rich...
Directory of Open Access Journals (Sweden)
Autori Vari
2012-10-01
Full Text Available Adriano Ardovino, Raccogliere il mondo. Per una fenomenologia della rete [Angela Maiello] • Clive Bell, L’Arte [Filippo Focosi] • Alessandro Bertinetto, Il pensiero dei suoni. Temi di filosofia della musica [Domenica Lentini] • Terrence Deacon, Incomplete Nature. How Mind Emerged From Matter [Mariagrazia Portera] • Roger Scruton, La bellezza. Ragione ed esperienza estetica [Filippo Focosi] • Miriam Bratu Hansen, Cinema and Experience. Sigfried Kracauer, Walter Benjamin and Theoder W. Adorno [Domenico Spinosa] • Lawrence Barsalou, scritti sulla “Grounded Cognition” [Gialuca Consoli] • Dis-forme, Università degli Studi di Palermo, 28-29 maggio 2012 [Michele Bertolini e Pietro Conte
Neuropsychological effects and attitudes in patients following electroconvulsive therapy
Edwards, Christopher
2008-01-01
Miriam Feliu1,2, Christopher L Edwards1,2,3, Shiv Sudhakar4, Camela McDougald1, Renee Raynor5, Stephanie Johnson6, Goldie Byrd7, Keith Whitfield8, Charles Jonassaint8, Heather Romero1, Lekisha Edwards1, Chante’ Wellington1, LaBarron K Hill9, James Sollers, III9, Patrick E Logue11Department of Psychiatry and Behavioral Sciences; 2Duke Pain and Palliative Care Center; 3Department of Medicine, Division of Hematology; 4Drexel University Medical School; 5Brain Tumor Center, Duke Universi...
m-Living Labs, A framework for collaborative community advancement
CSIR Research Space (South Africa)
Buitendag, A
2012-05-01
Full Text Available that will allow any HTML5 content to be used easily on any platform without the need to convert it for the hardware it is to run on. This means that the user of a desktop application may use the same application while mobile without the need to get a modified... Conference Proceedings Paul Cunningham and Miriam Cunningham (Eds) IIMC International Information Management Corporation, 2012 ISBN: 978-1-905824-34-2 Copyright ? 2012 The authors www.IST-Africa.org/Conference2012 Page 1 of 10 m-Living Labs...
Surveillance of Travel-Related Mosquito-borne Illness in Rhode Island.
Alang, Neha; Glavis-Bloom, Justin; Alexander-Scott, Nicole; Mermel, Leonard A; Mileno, Maria D
2016-07-01
Malaria and Dengue are some of the common infections occurring in persons traveling to countries endemic for these infections. Chinkungunya virus infection is another illness that can occur in people who have travelled to areas endemic for chikungunya virus infection. Herein we report cases of malaria, dengue, and chikungunya in Newport Hospital, The Miriam Hospital and Rhode Island Hospital between January 1, 2010 and December 31, 2014. [Full article available at http://rimed.org/rimedicaljournal-2016-07.asp, free with no login].
Systematic integration of experimental data and models in systems biology.
Li, Peter; Dada, Joseph O; Jameson, Daniel; Spasic, Irena; Swainston, Neil; Carroll, Kathleen; Dunn, Warwick; Khan, Farid; Malys, Naglis; Messiha, Hanan L; Simeonidis, Evangelos; Weichart, Dieter; Winder, Catherine; Wishart, Jill; Broomhead, David S; Goble, Carole A; Gaskell, Simon J; Kell, Douglas B; Westerhoff, Hans V; Mendes, Pedro; Paton, Norman W
2010-11-29
The behaviour of biological systems can be deduced from their mathematical models. However, multiple sources of data in diverse forms are required in the construction of a model in order to define its components and their biochemical reactions, and corresponding parameters. Automating the assembly and use of systems biology models is dependent upon data integration processes involving the interoperation of data and analytical resources. Taverna workflows have been developed for the automated assembly of quantitative parameterised metabolic networks in the Systems Biology Markup Language (SBML). A SBML model is built in a systematic fashion by the workflows which starts with the construction of a qualitative network using data from a MIRIAM-compliant genome-scale model of yeast metabolism. This is followed by parameterisation of the SBML model with experimental data from two repositories, the SABIO-RK enzyme kinetics database and a database of quantitative experimental results. The models are then calibrated and simulated in workflows that call out to COPASIWS, the web service interface to the COPASI software application for analysing biochemical networks. These systems biology workflows were evaluated for their ability to construct a parameterised model of yeast glycolysis. Distributed information about metabolic reactions that have been described to MIRIAM standards enables the automated assembly of quantitative systems biology models of metabolic networks based on user-defined criteria. Such data integration processes can be implemented as Taverna workflows to provide a rapid overview of the components and their relationships within a biochemical system.
Staff Association
2016-01-01
The Elementary Particles of Painting Alfonso Fratteggiani Bianchi and Ermanno Imbergamo From September 26 to October 7, 2016 CERN Meyrin, Main Building With intentions similar to those of CERN physicists, the artist Alfonso Fratteggiani Bianchi investigates the color pigment, studying its interaction with light and with the support on which it is deposited. He creates monochrome paintings by spreading the color pigment in the pure state on stones, without using glue or any other type of adhesive. With intentions similar to artists, the physicist Ermanno Imbergamo investigates the use of luminescent wavelength shifters, materials commonly used in Particle Physics, for art. He creates other monochrome artworks, which disclose further aspects of interaction among light, color pigments and support. For more information: staff.association@cern.ch | Tel: 022 767 28 19
Phenomenological dynamics of loop quantum cosmology in Kantowski-Sachs spacetime
International Nuclear Information System (INIS)
Chiou, D.-W.
2008-01-01
The fundamental theory and the semiclassical description of loop quantum cosmology (LQC) have been studied in the Friedmann-Robertson-Walker and Bianchi I models. As an extension to include both anisotropy and intrinsic curvature, this paper investigates the cosmological model of Kantowski-Sachs spacetime with a free massless scalar field at the level of phenomenological dynamics with the LQC discreteness corrections. The LQC corrections are implemented in two different improved quantization schemes. In both schemes, the big bang and big crunch singularities of the classical solution are resolved and replaced by the big bounces when the area or volume scale factor approaches the critical values in the Planck regime measured by the reference of the scalar field momentum. Symmetries of scaling are also noted and suggest that the fundamental spatial scale (area gap) may give rise to a temporal scale. The bouncing scenarios are in an analogous fashion of the Bianchi I model, naturally extending the observations obtained previously.
Conference: Diversity in the Workplace - How to Capitalise on Differences to Foster Innovation
2012-01-01
Diversity in the Workplace: How to Capitalise on Differences to Foster Innovation, by Cristina Bianchi. Tuesday 19 June 2012 – 12 noon to 2 p.m. Brasserie Restaurant 2 Diversity Lunch : Lunchtime conference organised by the CERN Diversity Programme. Diversity is an acknowledged source of creativity and innovation that can improve performance and ultimately create a definite advantage for the Organization. However, if not managed well both at team and individual level, it can become a source of misunderstanding, interpersonal tensions and conflict. The speaker will share concrete strategies and approaches to capitalise on a diverse workforce and create the right environment where differences become an asset that leads to creativity, idea generation and, ultimately, innovation. Cristina Bianchi is specialised in conflict management, cross-cultural relations and effective communication and has acquired valuable experience working in sensitive areas such as Palestine and Kosovo. Her se...
Global dynamics of asymptotically locally AdS spacetimes with negative mass
Dold, Dominic
2018-05-01
The Einstein vacuum equations in 5D with negative cosmological constant are studied in biaxial Bianchi IX symmetry. We show that if initial data of Eguchi–Hanson type, modelled after the 4D Riemannian Eguchi–Hanson space, have negative mass, the future maximal development does not contain horizons, i. e. the complement of the causal past of null infinity is empty. In particular, perturbations of Eguchi–Hanson–AdS spacetimes within the biaxial Bianchi IX symmetry class cannot form horizons, suggesting that such spacetimes are potential candidates for a naked singularity to form. The proof relies on an extension principle proven for this system and a priori estimates following from the monotonicity of the Hawking mass.
University of Ferrara strengthens partnership with CERN
2006-01-01
Professor Patrizio Bianchi, Head of the University of Ferrara, and Robert Aymar, CERN Director-General, signing an agreement to support the Doctoral Student Programme. The Head of the University of Ferrara, in Italy, Professor Patrizio Bianchi, visited CERN on 6 June. After a visit of the LHCb experiment, he met the Director-General, Robert Aymar, and signed an administrative agreement aiming to enhance the participation of doctoral students from the University of Ferrara in the CERN Doctoral Student Programme. Under this agreement, Ferrara students who are selected for the CERN Doctoral Programme will receive significant financial support from their home institution. Following the signature of the agreement, the Head of Ferrara University and the Secretary-General attented a lunch with representatives of the CERN Management, the LHCb experiment and the Italian Ministry for Research. The lunch was followed by a visit of the ATLAS experiment in the afternoon.
Arthur Schnitzler: immaginare il femminile. Esempi letterari e cinematografici
Saletta, Ester
2014-01-01
Short stories like Doktor Gräsler Badearzt, Casanova Heimfahrt, Traumnovelle, Spiel im Morgengrauen and cinematographic adaptations like the ones by Roberto Faenza (1990), Edouard Niermans (1992), Mario Bianchi (1989) and Götz Spielmann (2001) show various examples of female and male imaginative sexual/gender identity: strong emancipated women, weak and subordinated men and ambiguous beings like the chameleon couple Leopoldine/Willi Kasda. In these contexts literature and film no longer defi...
Relative-observer definition of the Simon tensor
Bini, Donato; Geralico, Andrea
2018-05-01
The definition of the Simon tensor, originally given only in Kerr spacetime and associated with the static family of observers, is generalized to any spacetime and to any possible observer family. Such generalization is obtained by a standard ‘3 + 1’ splitting of the Bianchi identities, which are rewritten here as a ‘balance equation’ between various spatial fields, associated with the kinematical properties of the observer congruence and representing the spacetime curvature.
On the energy-momentum tensors for field theories in spaces with affine connection and metric
International Nuclear Information System (INIS)
Manoff, S.
1991-01-01
Generalized covariant Bianchi type identities are obtained and investigated for Lagrangian densities, depending on co- and contravariant tensor fields and their first and second covariant derivatives in spaces with affine connection and metric (L n -space). The notions of canonical, generalized canonical, symmetric and variational energy-momentum tensor are introduced and necessary and sufficient conditions for the existence of the symmetric energy-momentum tensor as a local conserved quantity are obtained. 19 refs.; 1 tab
On Nonconvex Decentralized Gradient Descent
2016-08-01
and J. Bolte, On the convergence of the proximal algorithm for nonsmooth functions involving analytic features, Math . Program., 116: 5-16, 2009. [2] H...splitting, and regularized Gauss-Seidel methods, Math . Pro- gram., Ser. A, 137: 91-129, 2013. [3] P. Bianchi and J. Jakubowicz, Convergence of a multi-agent...subgradient method under random communication topologies , IEEE J. Sel. Top. Signal Process., 5:754-771, 2011. [11] A. Nedic and A. Ozdaglar, Distributed
Generalized Friedmann-Robertson-Walker metric and redundancy in the generalized Einstein equations
International Nuclear Information System (INIS)
Kao, W.F.; Pen, U.
1991-01-01
A nontrivial redundancy relation, due to the differential structure of the gravitational Bianchi identity as well as the symmetry of the Friedmann-Robertson-Walker metric, in the gravitational field equation is clarified. A generalized Friedmann-Robertson-Walker metric is introduced in order to properly define a one-dimensional reduced problem which offers an alternative approach to obtain the gravitational field equations on Friedmann-Robertson-Walker spaces
Andrade Filho, J D; Aguiar, G M; Dias, E S; Falcão, A L
1999-01-01
A new sand fly species is described based on males collected in Bananal, municipality of Mariana and the female from Sabará city, State of Minas Gerais, Brazil. Taxonomic remarks, geographic distribution and the description of new species are presented. The name Lutzomyia (Pintomyia) bianchigalatiae is in honour of Dr Eunice Aparecida Bianchi Galati, friend and researcher at the Faculdade de Saúde Pública, Universidade de São Paulo.
Clinical predictors of central sleep apnea evoked by positive airway pressure titration
Bianchi, Matt; Gannon,Karen; Lovell,Kathy; Merlino,Margaret; Mojica,James; Moro,Marilyn
2016-01-01
Marilyn Moro,1 Karen Gannon,1 Kathy Lovell,1 Margaret Merlino,1 James Mojica,2 Matt T Bianchi,1,3 1Neurology Department, 2Pulmonary and Critical Care Medicine, Massachusetts General Hospital, Boston, MA, USA; 3Division of Sleep Medicine, Harvard Medical School, Boston, MA, USA Purpose: Treatment-emergent central sleep apnea (TECSA), also called complex apnea, occurs in 5%–15% of sleep apnea patients during positive airway pressure (PAP) therapy, but the clinical predictors are not w...
The dimensional reduction in a multi-dimensional cosmology
International Nuclear Information System (INIS)
Demianski, M.; Golda, Z.A.; Heller, M.; Szydlowski, M.
1986-01-01
Einstein's field equations are solved for the case of the eleven-dimensional vacuum spacetime which is the product R x Bianchi V x T 7 , where T 7 is a seven-dimensional torus. Among all possible solutions, the authors identify those in which the macroscopic space expands and the microscopic space contracts to a finite size. The solutions with this property are 'typical' within the considered class. They implement the idea of a purely dynamical dimensional reduction. (author)
Canonical quantum theory of gravitational field with higher derivatives, 2
International Nuclear Information System (INIS)
Kawasaki, Shoichiro; Kimura, Tadahiko
1982-01-01
The asymptotic fields in a canonically quantized graviational field with higher derivatives are analyzed. A possible mechanism of the recovery of the physical S-matrix unitarity is discussed. The constraint nabla sub(μ)(B sup(μν) + (Beta /α)g sup(μν)B) = 0 due to the Bianchi identity on R sub(μν) is treated by Dirac's method. (author)
Consumer sleep monitors: is there a baby in the bathwater?
Bianchi, Matt; Russo,Kathryn; Goparaju,Balaji
2015-01-01
Kathryn Russo,1 Balaji Goparaju,1 Matt T Bianchi1,2 1Department of Neurology, Massachusetts General Hospital, 2Division of Sleep Medicine, Harvard Medical School, Boston, MA, USA Abstract: The rapid expansion of consumer sleep devices is outpacing the validation data necessary to assess the potential use of these devices in clinical and research settings. Common sleep monitoring devices utilize a variety of sensors to track movement as well as cardiac and respiratory physiology. The variety ...
Relabeling symmetries in hydrodynamics and magnetohydrodynamics
International Nuclear Information System (INIS)
Padhye, N.; Morrison, P.J.
1996-04-01
Lagrangian symmetries and concomitant generalized Bianchi identities associated with the relabeling of fluid elements are found for hydrodynamics and magnetohydrodynamics (MHD). In hydrodynamics relabeling results in Ertel's theorem of conservation of potential vorticity, while in MHD it yields the conservation of cross helicity. The symmetries of the reduction from Lagrangian (material) to Eulerian variables are used to construct the Casimir invariants of the Hamiltonian formalism
The structure of spectral problems and geometry: hyperbolic surfaces in E sup 3
Cieslinski, J L
2003-01-01
Working in the framework of Sym's soliton surfaces approach we point out that some simple assumptions about the structure of linear (spectral) problems of the theory of solitons lead uniquely to the geometry of some special immersions. In this paper we consider general su(2) spectral problems. Under some very weak assumptions they turn out to be associated with hyperbolic surfaces (surfaces of negative Gaussian curvature) immersed in three-dimensional Euclidean space, and especially with the so-called Bianchi surfaces.
A reciprocal Wald theorem for varying gravitational function
International Nuclear Information System (INIS)
Fay, Stephane
2004-01-01
We study when a cosmological constant is a natural issue if it is mimicked by the potential of a massive Hyperextended Scalar Tensor theory with a perfect fluid for Bianchi type I and V models. We then deduce a reciprocal Wald theorem giving the conditions such that the potential tends to a non vanishing constant when the gravitational function varies. We also get the conditions allowing the potential to vanish or diverge. (orig.)
African Journal of Marine Science - Vol 38, No 1 (2016)
African Journals Online (AJOL)
Spatial characterisation of the Benguela ecosystem for ecosystem-based management · EMAIL FULL TEXT EMAIL FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. S.P. Kirkman, L Blamey, T Lamont, J.G. Field, G Bianchi, J.A. Huggett, L Hutchings, J Jackson-Veitch, A Jarre, C Lett, M.R. Lipiński, S.W. Mafwila ...
Epilepsy: The Role of the Super Family of Voltage Gated Ion Channels
2011-02-22
Zara ...and F. Zara . 2006. Familial occurrence of febrile seizures and epilepsy in severe myoclonic epilepsy of...Bianchi, and F. Zara . 2003. Spectrum of SCN1A mutations in severe myoclonic epilepsy of
[Intestinal lengthening techniques: an experimental model in dogs].
Garibay González, Francisco; Díaz Martínez, Daniel Alberto; Valencia Flores, Alejandro; González Hernández, Miguel Angel
2005-01-01
To compare two intestinal lengthening procedures in an experimental dog model. Intestinal lengthening is one of the methods for gastrointestinal reconstruction used for treatment of short bowel syndrome. The modification to the Bianchi's technique is an alternative. The modified technique decreases the number of anastomoses to a single one, thus reducing the risk of leaks and strictures. To our knowledge there is not any clinical or experimental report that studied both techniques, so we realized the present report. Twelve creole dogs were operated with the Bianchi technique for intestinal lengthening (group A) and other 12 creole dogs from the same race and weight were operated by the modified technique (Group B). Both groups were compared in relation to operating time, difficulties in technique, cost, intestinal lengthening and anastomoses diameter. There were no statistical difference in the anastomoses diameter (A = 9.0 mm vs. B = 8.5 mm, p = 0.3846). Operating time (142 min vs. 63 min) cost and technique difficulties were lower in group B (p anastomoses (of Group B) and intestinal segments had good blood supply and were patent along their full length. Bianchi technique and the modified technique offer two good reliable alternatives for the treatment of short bowel syndrome. The modified technique improved operating time, cost and technical issues.
Quantization ambiguities and bounds on geometric scalars in anisotropic loop quantum cosmology
International Nuclear Information System (INIS)
Singh, Parampreet; Wilson-Ewing, Edward
2014-01-01
We study quantization ambiguities in loop quantum cosmology that arise for space-times with non-zero spatial curvature and anisotropies. Motivated by lessons from different possible loop quantizations of the closed Friedmann–Lemaître–Robertson–Walker cosmology, we find that using open holonomies of the extrinsic curvature, which due to gauge-fixing can be treated as a connection, leads to the same quantum geometry effects that are found in spatially flat cosmologies. More specifically, in contrast to the quantization based on open holonomies of the Ashtekar–Barbero connection, the expansion and shear scalars in the effective theories of the Bianchi type II and Bianchi type IX models have upper bounds, and these are in exact agreement with the bounds found in the effective theories of the Friedmann–Lemaître–Robertson–Walker and Bianchi type I models in loop quantum cosmology. We also comment on some ambiguities present in the definition of inverse triad operators and their role. (paper)
The Maxwell-Chern-Simons gravity, and its cosmological implications
Energy Technology Data Exchange (ETDEWEB)
Haghani, Zahra; Shahidi, Shahab [Damghan University, School of Physics, Damghan (Iran, Islamic Republic of); Harko, Tiberiu [Babes-Bolyai University, Department of Physics, Cluj-Napoca (Romania); University College London, Department of Mathematics, London (United Kingdom)
2017-08-15
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. (orig.)
Quantization ambiguities and bounds on geometric scalars in anisotropic loop quantum cosmology
Singh, Parampreet; Wilson-Ewing, Edward
2014-02-01
We study quantization ambiguities in loop quantum cosmology that arise for space-times with non-zero spatial curvature and anisotropies. Motivated by lessons from different possible loop quantizations of the closed Friedmann-Lemaître-Robertson-Walker cosmology, we find that using open holonomies of the extrinsic curvature, which due to gauge-fixing can be treated as a connection, leads to the same quantum geometry effects that are found in spatially flat cosmologies. More specifically, in contrast to the quantization based on open holonomies of the Ashtekar-Barbero connection, the expansion and shear scalars in the effective theories of the Bianchi type II and Bianchi type IX models have upper bounds, and these are in exact agreement with the bounds found in the effective theories of the Friedmann-Lemaître-Robertson-Walker and Bianchi type I models in loop quantum cosmology. We also comment on some ambiguities present in the definition of inverse triad operators and their role.
Through the big bang: Continuing Einstein's equations beyond a cosmological singularity
Koslowski, Tim A.; Mercati, Flavio; Sloan, David
2018-03-01
All measurements are comparisons. The only physically accessible degrees of freedom (DOFs) are dimensionless ratios. The objective description of the universe as a whole thus predicts only how these ratios change collectively as one of them is changed. Here we develop a description for classical Bianchi IX cosmology implementing these relational principles. The objective evolution decouples from the volume and its expansion degree of freedom. We use the relational description to investigate both vacuum dominated and quiescent Bianchi IX cosmologies. In the vacuum dominated case the relational dynamical system predicts an infinite amount of change of the relational DOFs, in accordance with the well known chaotic behaviour of Bianchi IX. In the quiescent case the relational dynamical system evolves uniquely though the point where the decoupled scale DOFs predict the big bang/crunch. This is a non-trivial prediction of the relational description; the big bang/crunch is not the end of physics - it is instead a regular point of the relational evolution. Describing our solutions as spacetimes that satisfy Einstein's equations, we find that the relational dynamical system predicts two singular solutions of GR that are connected at the hypersurface of the singularity such that relational DOFs are continuous and the orientation of the spatial frame is inverted.
Energy Technology Data Exchange (ETDEWEB)
Lombardo, Davide M. [Dipartimento di Fisica, Università di Roma “La Sapienza”,Piazzale Aldo Moro 2, 00185 Roma (Italy); Riccioni, Fabio [INFN - Sezione di Roma, Dipartimento di Fisica, Università di Roma “La Sapienza”,Piazzale Aldo Moro 2, 00185 Roma (Italy); Risoli, Stefano [Dipartimento di Fisica, Università di Roma “La Sapienza”,Piazzale Aldo Moro 2, 00185 Roma (Italy); INFN - Sezione di Roma, Dipartimento di Fisica, Università di Roma “La Sapienza”,Piazzale Aldo Moro 2, 00185 Roma (Italy)
2016-12-21
We consider the N=1 superpotential generated in type-II orientifold models by non-geometric fluxes. In particular, we focus on the family of P fluxes, that are related by T-duality transformations to the S-dual of the Q flux. We determine the general rule that transforms a given flux in this family under a single T-duality transformation. This rule allows to derive a complete expression for the superpotential for both the IIA and the IIB theory for the particular case of a T{sup 6}/[ℤ{sub 2}×ℤ{sub 2}] orientifold. We then consider how these fluxes modify the generalised Bianchi identities. In particular, we derive a fully consistent set of quadratic constraints coming from the NS-NS Bianchi identities. On the other hand, the P flux Bianchi identities induce tadpoles, and we determine a set of exotic branes that can be consistently included in order to cancel them. This is achieved by determining a universal transformation rule under T-duality satisfied by all the branes in string theory.
International Nuclear Information System (INIS)
Lombardo, Davide M.; Riccioni, Fabio; Risoli, Stefano
2016-01-01
We consider the N=1 superpotential generated in type-II orientifold models by non-geometric fluxes. In particular, we focus on the family of P fluxes, that are related by T-duality transformations to the S-dual of the Q flux. We determine the general rule that transforms a given flux in this family under a single T-duality transformation. This rule allows to derive a complete expression for the superpotential for both the IIA and the IIB theory for the particular case of a T 6 /[ℤ 2 ×ℤ 2 ] orientifold. We then consider how these fluxes modify the generalised Bianchi identities. In particular, we derive a fully consistent set of quadratic constraints coming from the NS-NS Bianchi identities. On the other hand, the P flux Bianchi identities induce tadpoles, and we determine a set of exotic branes that can be consistently included in order to cancel them. This is achieved by determining a universal transformation rule under T-duality satisfied by all the branes in string theory.
A multiscale model of distributed fracture and permeability in solids in all-round compression
De Bellis, Maria Laura; Della Vecchia, Gabriele; Ortiz, Michael; Pandolfi, Anna
2017-07-01
We present a microstructural model of permeability in fractured solids, where the fractures are described in terms of recursive families of parallel, equidistant cohesive faults. Faults originate upon the attainment of tensile or shear strength in the undamaged material. Secondary faults may form in a hierarchical organization, creating a complex network of connected fractures that modify the permeability of the solid. The undamaged solid may possess initial porosity and permeability. The particular geometry of the superposed micro-faults lends itself to an explicit analytical quantification of the porosity and permeability of the damaged material. The model is the finite kinematics version of a recently proposed porous material model, applied with success to the simulation of laboratory tests and excavation problems [De Bellis, M. L., Della Vecchia, G., Ortiz, M., Pandolfi, A., 2016. A linearized porous brittle damage material model with distributed frictional-cohesive faults. Engineering Geology 215, 10-24. Cited By 0. 10.1016/j.enggeo.2016.10.010]. The extension adds over and above the linearized kinematics version for problems characterized by large deformations localized in narrow zones, while the remainder of the solid undergoes small deformations, as typically observed in soil and rock mechanics problems. The approach is particularly appealing as a means of modeling a wide scope of engineering problems, ranging from the prevention of water or gas outburst into underground mines, to the prediction of the integrity of reservoirs for CO2 sequestration or hazardous waste storage, to hydraulic fracturing processes.
Stress free configuration of the human eye.
Elsheikh, Ahmed; Whitford, Charles; Hamarashid, Rosti; Kassem, Wael; Joda, Akram; Büchler, Philippe
2013-02-01
Numerical simulations of eye globes often rely on topographies that have been measured in vivo using devices such as the Pentacam or OCT. The topographies, which represent the form of the already stressed eye under the existing intraocular pressure, introduce approximations in the analysis. The accuracy of the simulations could be improved if either the stress state of the eye under the effect of intraocular pressure is determined, or the stress-free form of the eye estimated prior to conducting the analysis. This study reviews earlier attempts to address this problem and assesses the performance of an iterative technique proposed by Pandolfi and Holzapfel [1], which is both simple to implement and promises high accuracy in estimating the eye's stress-free form. A parametric study has been conducted and demonstrated reliance of the error level on the level of flexibility of the eye model, especially in the cornea region. However, in all cases considered 3-4 analysis iterations were sufficient to produce a stress-free form with average errors in node location <10(-6)mm and a maximal error <10(-4)mm. This error level, which is similar to what has been achieved with other methods and orders of magnitude lower than the accuracy of current clinical topography systems, justifies the use of the technique as a pre-processing step in ocular numerical simulations. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.
Planck 2015 results. XVIII. Background geometry and topology of the Universe
Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Basak, S.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bucher, M.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Feeney, S.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; McEwen, J. D.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Peiris, H. V.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pogosyan, D.; Pointecouteau, E.; Polenta, G.; Popa, L.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, F.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.
2016-09-01
Maps of cosmic microwave background (CMB) temperature and polarization from the 2015 release of Planck data provide the highestquality full-sky view of the surface of last scattering available to date. This enables us to detect possible departures from a globally isotropic cosmology. We present the first searches using CMB polarization for correlations induced by a possible non-trivial topology with a fundamental domain that intersects, or nearly intersects, the last-scattering surface (at comoving distance χrec), both via a direct scan for matched circular patterns at the intersections and by an optimal likelihood calculation for specific topologies. We specialize to flat spaces with cubic toroidal (T3) and slab (T1) topologies, finding that explicit searches for the latter are sensitive to other topologies with antipodal symmetry. These searches yield no detection of a compact topology with a scale below the diameter of the last-scattering surface. The limits on the radius ℛI of the largest sphere inscribed in the fundamental domain (at log-likelihood ratio Δlnℒ > -5 relative to a simply-connected flat Planck best-fit model) are: ℛI > 0.97 χrec for the T3 cubic torus; and ℛI > 0.56 χrec for the T1 slab. The limit for the T3 cubic torus from the matched-circles search is numerically equivalent, ℛI > 0.97 χrec at 99% confidence level from polarization data alone. We also perform a Bayesian search for an anisotropic global Bianchi VIIh geometry. In the non-physical setting, where the Bianchi cosmology is decoupled from the standard cosmology, Planck temperature data favour the inclusion of a Bianchi component with a Bayes factor of at least 2.3 units of log-evidence. However, the cosmological parameters that generate this pattern are in strong disagreement with those found from CMB anisotropy data alone. Fitting the induced polarization pattern for this model to the Planck data requires an amplitude of -0.10 ± 0.04 compared to the value of + 1 if the
Bianchi, Luciana
2018-01-01
Rest-frame UV, uniquely sensitive to luminous, short-lived hot massive stars, trace and age-date star formation across galaxies, and is very sensitive to dust, whose properties and presence are closely connected to star formation.With wide f-o-v and deep sensitivity in two broad filters,FUV and NUV,GALEX delivered the first comprehensive UV view of large nearby galaxies, and of the universe to z~2 (e.g.,Bianchi 2014 ApSS 354,103), detected star formation at the lowest rates, in environments where it was not seen before and not expected (e.g. Bianchi 2011 ApSS 335,51; Thilker+2009 Nature 457,990;2007 ApJS 173,538), triggering a new era of investigations with HST and large ground-based telescopes. New instrument technology and modeling capabilities make it now possible and compelling to solve standing issues. The scant UV filters available (esp. FUV) and the wide gap in resolution and f-o-v between GALEX and HST leaves old and new questions open. A chief limitation is degeneracies between physical parameters of stellar populations (age/SFR) and hot stars, and dust (e.g. Bianchi+ 2014 JASR 53,928).We show sample model simulations for filter optimization to provide critical measurements for the science objectives. We also demonstrate how adequate FUV+NUV filters, and resolution, allow us to move from speculative interpretation of UV data to unbiased physical characterization of young stellar populations and dust, using new data from UVIT, which, though smaller than CETUS, has better resolution and filter coverage than GALEX.Also, our understanding of galaxy chemical enrichment is limited by critical gaps in stellar evolution; GALEX surveys enabled the first unbiased census of the Milky Way hot-WD population (Bianchi+2011 MNRAS, 411,2770), which we complement with SDSS, Pan-STARRS, and Gaia data to fill such gaps (Bianchi et al.2018, ApSS). Such objects in CETUS fields (deeper exposures, more filters, and the first UV MOS) will be much better characterized, enabling
Planck 2015 results: XVIII. Background geometry and topology of the Universe
International Nuclear Information System (INIS)
Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.
2016-01-01
We report that maps of cosmic microwave background (CMB) temperature and polarization from the 2015 release of Planck data provide the highestquality full-sky view of the surface of last scattering available to date. This enables us to detect possible departures from a globally isotropic cosmology. We present the first searches using CMB polarization for correlations induced by a possible non-trivial topology with a fundamental domain that intersects, or nearly intersects, the last-scattering surface (at comoving distance χ rec ), both via a direct scan for matched circular patterns at the intersections and by an optimal likelihood calculation for specific topologies. We specialize to flat spaces with cubic toroidal (T3) and slab (T1) topologies, finding that explicit searches for the latter are sensitive to other topologies with antipodal symmetry. These searches yield no detection of a compact topology with a scale below the diameter of the last-scattering surface. The limits on the radius R i of the largest sphere inscribed in the fundamental domain (at log-likelihood ratio ΔlnL > -5 relative to a simply-connected flat Planck best-fit model) are: R i > 0.97 χ rec for the T3 cubic torus; and R i > 0.56 χ rec for the T1 slab. The limit for the T3 cubic torus from the matched-circles search is numerically equivalent, R i > 0.97 χ rec at 99% confidence level from polarization data alone. We also perform a Bayesian search for an anisotropic global Bianchi VII h geometry. In the non-physical setting, where the Bianchi cosmology is decoupled from the standard cosmology, Planck temperature data favour the inclusion of a Bianchi component with a Bayes factor of at least 2.3 units of log-evidence. However, the cosmological parameters that generate this pattern are in strong disagreement with those found from CMB anisotropy data alone. Fitting the induced polarization pattern for this model to the Planck data requires an amplitude of -0.10 ± 0.04 compared to the
Spinor Field Nonlinearity and Space-Time Geometry
Saha, Bijan
2018-03-01
Within the scope of Bianchi type VI,VI0,V, III, I, LRSBI and FRW cosmological models we have studied the role of nonlinear spinor field on the evolution of the Universe and the spinor field itself. It was found that due to the presence of non-trivial non-diagonal components of the energy-momentum tensor of the spinor field in the anisotropic space-time, there occur some severe restrictions both on the metric functions and on the components of the spinor field. In this report we have considered a polynomial nonlinearity which is a function of invariants constructed from the bilinear spinor forms. It is found that in case of a Bianchi type-VI space-time, depending of the sign of self-coupling constants, the model allows either late time acceleration or oscillatory mode of evolution. In case of a Bianchi VI 0 type space-time due to the specific behavior of the spinor field we have two different scenarios. In one case the invariants constructed from bilinear spinor forms become trivial, thus giving rise to a massless and linear spinor field Lagrangian. This case is equivalent to the vacuum solution of the Bianchi VI 0 type space-time. The second case allows non-vanishing massive and nonlinear terms and depending on the sign of coupling constants gives rise to accelerating mode of expansion or the one that after obtaining some maximum value contracts and ends in big crunch, consequently generating space-time singularity. In case of a Bianchi type-V model there occur two possibilities. In one case we found that the metric functions are similar to each other. In this case the Universe expands with acceleration if the self-coupling constant is taken to be a positive one, whereas a negative coupling constant gives rise to a cyclic or periodic solution. In the second case the spinor mass and the spinor field nonlinearity vanish and the Universe expands linearly in time. In case of a Bianchi type-III model the space-time remains locally rotationally symmetric all the time
Steni muinasjutuvõistluse võitjad selgunud / Ants Roos, Ann Roos
Roos, Ants
2008-01-01
Steni XVI muinasjutuvõistluse žüriisse kuulusid: Ann Roos, Ants Roos, Leelo Tungal, Krista Kumberg, Leida Olszak, Ülle Väljataga. Tulemused: I koht Siim Niinelaid, II koht Julius Air Kull, III koht Mihkel Rammu. Žürii eriauhinnad: Anna Kristin Peterson, Elis Ruus, Rain Hallikas, Mariliis Peterson, Marjaliisa Palu, Karl Kirsimäe, Margaret Pulk. Ergutusauhinnad: Karmel Klaus, Martti Kaljuste, Kristina Korell, Mirjam Võsaste, Mihkel Põder, Iirys Kalde, Miriam Jamul, Mari-Ann Mägi, Ketlin Saar, Liisbeth Kirss. Muud eriauhinnad said: Allan Läll, Berle Mees, Anett Kuuse, Karl Erik Kübarsepp, Grete Tamm, Siim Niinelaid, Kaisa Marie Sipelgas, Ellen Anett Põldmaa, Evelin Laul, Karl Laas, Karl Stamm, Kerli Retter
Treating disorganized attachment in the Group Attachment-Based Intervention (GABI©): A case study.
Knafo, Hannah; Murphy, Anne; Steele, Howard; Steele, Miriam
2018-05-24
This paper describes the treatment of a mother and child who demonstrated disorganized attachment behaviors in their interactions with one another. The mother, who was diagnosed with Borderline Personality Disorder, felt incapable of managing her aggressive toddler and his emotional needs. The dyad was referred for therapy due to concerns about his developmental progress, evident delays having been mainly attributed to the problems observed within the parent-child relationship. The primary intervention applied to working with the dyad was the Group Attachment-Based Intervention (GABI©), developed by Anne Murphy in collaboration with Miriam Steele and Howard Steele. The mother also received individual psychotherapy as a supplement to the dyadic and group work of GABI©. The process and outcome of this comprehensive approach to treating a vulnerable dyad is explored in this case study. © 2018 Wiley Periodicals, Inc.
López, Jorge Julio; Vénere, Virginia; Cardoso, Miriam; Toschi, Damián; Gil Lavedra, Ricardo; Bergman, Miriam; Yanzón, Rodolfo; Derotier de Cobacho, Sara; Eloy, Nilda; Mosquera, Alejandro; Ragendorfer, Alejandro; Vedio, Marta
2006-01-01
Con motivo de cumplirse el primer mes de la búsqueda y reclamo de aparición de Jorge Julio López, se emite un programa especial del ciclo Por la radio, programa periodístico de la segunda mañana de Radio Universidad, conducido por Virginia Vénere, Damián Toschi y Miriam Cardoso, con producción periodística de Virginia Ilariucci. Se realizan entrevistas y se reproducen testimonios en torno a la desaparición del testigo del juicio por crímenes de lesa humanidad contra el ex jefe de la Policía B...
Planck 2013 results. XXVI. Background geometry and topology of the Universe
Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bridges, M.; Bucher, M.; Burigana, C.; Butler, R. C.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Fabre, O.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leahy, J. P.; Leonardi, R.; Leroy, C.; Lesgourgues, J.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McEwen, J. D.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Peiris, H. V.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pogosyan, D.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Riazuelo, A.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Varis, J.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Yvon, D.; Zacchei, A.; Zonca, A.
2014-11-01
.0χrec for the truncated cube; and ℛi> 0.89χrec for the octahedral space. The limit for a wider class of topologies, i.e., those predicting matching pairs of back-to-back circles, among them tori and the three spherical cases listed above, coming from the matched-circles search, is ℛi> 0.94χrec at 99% confidence level. Similar limits apply to a wide, although not exhaustive, range of topologies. We also perform a Bayesian search for an anisotropic global Bianchi VIIh geometry. In the non-physical setting where the Bianchi cosmology is decoupled from the standard cosmology, Planck data favour the inclusion of a Bianchi component with a Bayes factor of at least 1.5 units of log-evidence. Indeed, the Bianchi pattern is quite efficient at accounting for some of the large-scale anomalies found in Planck data. However, the cosmological parameters that generate this pattern are in strong disagreement with those found from CMB anisotropy data alone. In the physically motivated setting where the Bianchi parameters are coupled and fitted simultaneously with the standard cosmological parameters, we find no evidence for a Bianchi VIIh cosmology and constrain the vorticity of such models to (ω/H)0< 8.1 × 10-10 (95% confidence level).
International Nuclear Information System (INIS)
Chau, L.L.
1983-01-01
Integrable properties, i.e., existence of linear systems, infinite number of conservation laws, Reimann-Hilbert transforms, affine Lie algebra of Kac-Moody, and Bianchi-Baecklund transformation, are discussed for the constraint equations of the supersymmetric Yang-Mills fields. For N greater than or equal to 3 these constraint equations give equations of motion of the fields. These equations of motion reduce to the ordinary Yang-Mills equations as the spinor and scalar fields are eliminated. These understandings provide a possible method to solve the full Yang-Mills equations. Connections with other non-linear systems are also discussed. 53 references
Arthur Schnitzler: immaginare il femminile. Esempi letterari e cinematografici
Directory of Open Access Journals (Sweden)
Ester Saletta
2014-05-01
Full Text Available Short stories like Doktor Gräsler Badearzt, Casanova Heimfahrt, Traumnovelle, Spiel im Morgengrauen and cinematographic adaptations like the ones by Roberto Faenza (1990, Edouard Niermans (1992, Mario Bianchi (1989 and Götz Spielmann (2001 show various examples of female and male imaginative sexual/gender identity: strong emancipated women, weak and subordinated men and ambiguous beings like the chameleon couple Leopoldine/Willi Kasda. In these contexts literature and film no longer define the female imaginative construction as a product of male imagination, but rather as a progressive female effort to become independent from traditional male stereotypes.
International Nuclear Information System (INIS)
Klusoň, Josef; Nojiri, Shin'ichi; Odintsov, Sergei D.
2013-01-01
We propose new version of massive F(R) gravity which is natural generalization of convenient massive ghost-free gravity. Its Hamiltonian formulation in scalar-tensor frame is developed. We show that such F(R) theory is ghost-free. The cosmological evolution of such theory is investigated. Despite the strong Bianchi identity constraint the possibility of cosmic acceleration (especially, in the presence of cold dark matter) is established. Ghost-free massive F(R,T) gravity is also proposed
Non-commutative gauge Gravity: Second- order Correction and Scalar Particles Creation
International Nuclear Information System (INIS)
Zaim, S.
2009-01-01
A noncommutative gauge theory for a charged scalar field is constructed. The invariance of this model under local Poincare and general coordinate transformations is verified. Using the general modified field equation, a general Klein-Gordon equation up to the second order of the noncommu- tativity parameter is derived. As an application, we choose the Bianchi I universe. Using the Seiberg-Witten maps, the deformed noncommutative metric is obtained and a particle production process is studied. It is shown that the noncommutativity plays the same role as an electric field, gravity and chemical potential.
Geometry of Quantum Principal Bundles. Pt. 1
International Nuclear Information System (INIS)
Durdevic, M.
1996-01-01
A theory of principal bundles possessing quantum structure groups and classical base manifolds is presented. Structural analysis of such quantum principal bundles is performed. A differential calculus is constructed, combining differential forms on the base manifold with an appropriate differential calculus on the structure quantum group. Relations between the calculus on the group and the calculus on the bundle are investigated. A concept of (pseudo)tensoriality is formulated. The formalism of connections is developed. In particular, operators of horizontal projection, covariant derivative and curvature are constructed and analyzed. Generalizations of the first Structure Equation and of the Bianchi identity are found. Illustrative examples are presented. (orig.)
Coleman-Weinberg symmetry breaking in an anisotropic spacetime
International Nuclear Information System (INIS)
Futamase, T.
1984-01-01
The Coleman-Weinberg mechanism of symmetry breaking in a Bianchi type-I universe is investigated. The one-loop effective potential for a phi 4 theory and for scalar electrodynamics is calculated by the zeta-function method. The result indicates that the symmetry of the theory will be restored in the highly anisotropic, cold, early universe, irrespective of the coupling between the scalar field and the spacetime curvature scalar. This mechanism of the phase transition explains the isotropy of our universe
Classification of supersymmetric spacetimes in eleven dimensions
International Nuclear Information System (INIS)
Cariglia, Marco; Mac Conamhna, Oisin A.P.
2005-01-01
We derive, for spacetimes admitting a Spin(7) structure, the general local bosonic solution of the Killing spinor equation of 11-dimensional supergravity. The metric, four-form, and Killing spinors are determined explicitly, up to an arbitrary eight-manifold of Spin(7) holonomy. It is sufficient to impose the Bianchi identity and one particular component of the four-form field equation to ensure that the solution of the Killing spinor equation also satisfies all the field equations, and we give these conditions explicitly
An approach to anisotropic cosmologies. 6
International Nuclear Information System (INIS)
Raychaudhuri, A.K.
1989-01-01
In this paper the motivation for the study of anisotropic cosmological models is set out. Then the mathematical basis for the study of such models as well as the description of some of the exact solutions of this genre are given. Killing vectors that spell out spacetime symmetries, are defined and the Bianchi classification of spacetimes based on the structure of the Killing vectors described. After a consideration of the kinematics of matter flow some of the known solutions are presented and their properties described. (author)
Edholm, James; Conroy, Aindriú
2017-12-01
We derive the conditions whereby null rays "defocus" within infinite derivative gravity for perturbations around an (A)dS background, and show that it is therefore possible to avoid singularities within this framework. This is in contrast to Einstein's theory of general relativity, where singularities are generated unless the null energy condition is violated. We further extend this to an (A)dS-Bianchi I background metric, and also give an example of a specific perturbation where defocusing is possible given certain conditions.
A continuous time formulation of the Regge calculus
International Nuclear Information System (INIS)
Brewin, Leo
1988-01-01
A complete continuous time formulation of the Regge calculus is presented by developing the associated continuous time Regge action. It is shown that the time constraint is, by way of the Bianchi identities conserved by the evolution equations. This analysis leads to an explicit first integral for each of the evolution equations. The dynamical equations of the theory are therefore reduced to a set of first-order differential equations. In this formalism the time constraints reduce to a simple sum of the integration constants. This result is unique to the Regge calculus-there does not appear to be a complete set of first integrals available for the vacuum Einstein equations. (author)
Cosmological models with a hybrid scale factor in an extended gravity theory
Mishra, B.; Tripathy, S. K.; Tarai, Sankarsan
2018-03-01
A general formalism to investigate Bianchi type V Ih universes is developed in an extended theory of gravity. A minimally coupled geometry and matter field is considered with a rescaled function of f(R,T) substituted in place of the Ricci scalar R in the geometrical action. Dynamical aspects of the models are discussed by using a hybrid scale factor (HSF) that behaves as power law in an initial epoch and as an exponential form at late epoch. The power law behavior and the exponential behavior appear as two extreme cases of the present model.
International Nuclear Information System (INIS)
Nariai, Hidekazu
1981-01-01
As a sequel to previous works on the definition of a positive frequency part of a quantized scalar field near an initial stage of several Robertson-Walker universes with flat, open or closed 3-space and the associated pair-creation of those particles, an attempt is made to seek for the same concept in several Bianchi-type I anisotropic universes. It is shown that, if the positive frequency part is introduced, the pair-creation of scalar particles and their spectral law are uniquely determined, as in the case of isotropic universes. (author)
COVARIANT INTEGRAL QUANTIZATIONS AND THEIR APPLICATIONS TO QUANTUM COSMOLOGY
Directory of Open Access Journals (Sweden)
Jean-Pierre Gazeau
2016-06-01
Full Text Available We present a general formalism for giving a measure space paired with a separable Hilbert space a quantum version based on a normalized positive operator-valued measure. The latter are built from families of density operators labeled by points of the measure space. We especially focus on group representation and probabilistic aspects of these constructions. Simple phase space examples illustrate the procedure: plane (Weyl-Heisenberg symmetry, half-plane (affine symmetry. Interesting applications to quantum cosmology (“smooth bouncing” for Friedmann-Robertson-Walker metric are presented and those for Bianchi I and IX models are mentioned.
New torsion black hole solutions in Poincaré gauge theory
Energy Technology Data Exchange (ETDEWEB)
Cembranos, Jose A.R.; Valcarcel, Jorge Gigante, E-mail: cembra@fis.ucm.es, E-mail: jorgegigante@ucm.es [Departamento de Física Teórica I, Universidad Complutense de Madrid, Av. Complutense s/n, E-28040 Madrid (Spain)
2017-01-01
We derive a new exact static and spherically symmetric vacuum solution in the framework of the Poincaré gauge field theory with dynamical massless torsion. This theory is built in such a form that allows to recover General Relativity when the first Bianchi identity of the model is fulfilled by the total curvature. The solution shows a Reissner-Nordström type geometry with a Coulomb-like curvature provided by the torsion field. It is also shown the existence of a generalized Reissner-Nordström-de Sitter solution when additional electromagnetic fields and/or a cosmological constant are coupled to gravity.
Towards the entropy of gravity time-dependent models via the Cardy-Verlinde formula
International Nuclear Information System (INIS)
Obregon, Octavio; Patino, Leonardo; Quevedo, Hernando
2003-01-01
For models with several time-dependent components, generalized entropies can be defined. This is shown for the Bianchi type IX model. We first derive the Cardy-Verlinde formula under the assumption that the first law of thermodynamics is valid. This leads to an explicit expression of the total entropy associated with this type of universe. Assuming the validity of the Cardy entropy formula, we obtain expressions for the corresponding Bekenstein, Bekenstein-Hawking and Hubble entropies. We discuss the validity of the Cardy-Verlinde formula and possible extensions of the outlined procedure to other time-dependent models
Cosmic no-hair in Brans-Dicke theory
International Nuclear Information System (INIS)
Guzman, E.; Alam, S.
1993-08-01
In this short note we report our finding that within the context of alternative version of the Brans-Dicke theory (for ω ≥ -3/2, where ω is the Brans-Dicke parameter) the anisotropic Bianchi type cosmological models evolve towards the de Sitter isotropic universe. In short it is shown that during inflation there is no difference between the Brans-Dicke theory and General Relativity. Our result can thus be viewed as a generalization of the Wald's theorem for General Relativity. (author). 5 refs
Exact Solutions in Three-Dimensional Gravity
García-Díaz, Alberto A.
2017-09-01
Preface; 1. Introduction; 2. Point particles; 3. Dust solutions; 4. AdS cyclic symmetric stationary solutions; 5. Perfect fluid static stars; 6. Static perfect fluid stars with Λ; 7. Hydrodynamic equilibrium; 8. Stationary perfect fluid with Λ; 9. Friedmann–Robertson–Walker cosmologies; 10. Dilaton-inflaton FRW cosmologies; 11. Einstein–Maxwell solutions; 12. Nonlinear electrodynamics black hole; 13. Dilaton minimally coupled to gravity; 14. Dilaton non-minimally coupled to gravity; 15. Low energy 2+1 string gravity; 16. Topologically massive gravity; 17. Bianchi type spacetimes in TMG; 18. Petrov type N wave metrics; 19. Kundt spacetimes in TMG; 20. Cotton tensor in Riemannian spacetimes; References; Index.
Generalized frame of reference with null congruence
International Nuclear Information System (INIS)
Ferrarese, G.; Antonelli, R.
2000-01-01
The paper derives the main properties of a generalized frame of reference with a null congruence (light flux), by means of adapted non-holonomic techniques; then it studies the geometry of the space-time in terms of non-orthogonal projection: longitudinal and transverse covariant derivatives and corresponding commutation formulae, decomposition of the Riemann and gravitational tensors, lie derivatives of the Ricci rotation coefficients, transverse Bianchi identity. Application to the (absolute and relative) light flux: kinematical characteristics and screen, Sachs theorems etc. are also given
Kasner asymptotics of mixmaster Horava-Witten and pre-big-bang cosmologies
International Nuclear Information System (INIS)
Dabrowski, Mariusz P.
2001-01-01
We discuss various superstring effective actions and, in particular, their common sector which leads to the so-called pre-big-bang cosmology (cosmology in a weak coupling limit of heterotic superstring theory. Using the conformal relationship between these two theories we present Kasner asymptotic solutions of Bianchi type IX geometries within these theories and make predictions about possible emergence of chaos. Finally, we present a possible method of generating Horava-Witten cosmological solutions out of the well-known general relativistic or pre-big-bang solutions
Numerical Simulation of Antennae by Discrete Exterior Calculus
International Nuclear Information System (INIS)
Xie Zheng; Ye Zheng; Ma Yujie
2009-01-01
Numerical simulation of antennae is a topic in computational electromagnetism, which is concerned with the numerical study of Maxwell equations. By discrete exterior calculus and the lattice gauge theory with coefficient R, we obtain the Bianchi identity on prism lattice. By defining an inner product of discrete differential forms, we derive the source equation and continuity equation. Those equations compose the discrete Maxwell equations in vacuum case on discrete manifold, which are implemented on Java development platform to simulate the Gaussian pulse radiation on antennaes. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)
A deep-sea bacterium with unique nitrifying property
Digital Repository Service at National Institute of Oceanography (India)
Ram, A.; LokaBharathi, P.A.; Nair, S.; Chandramohan, D.
assay (chemical assay). Bianchi et al . 10 had shown that the a c tivity determined by chemical assay was comparable to 15 N method. For the present study we used only the chemical assay. The activity in terms of ammonia and nitrite conversion... s tributed in the marine environment, the number of nitrif i ers mediating this process has rarely been deter - mined. N i trification is generally carried out by known nitrifiers which either oxidize ammonia to nit rite (Phase I) or nitrite to nitrate...
Energy Technology Data Exchange (ETDEWEB)
Montesinos, M. [CINVESTAV-IPN, 07360 Mexico D.F. (Mexico); Flores, E. [Facultad de Fisica e Inteligencia Artificial, Universidad Veracruzana, 91000 Xalapa, Veracruz (Mexico)]. E-mail: merced@fis.cinvestav.mx
2006-07-01
The symmetric and gauge-invariant energy-momentum tensors for source-free Maxwell and Yang-Mills theories are obtained by means of translations in spacetime via a systematic implementation of Noether's theorem. For the source-free neutral Proca field, the same procedure yields also the symmetric energy-momentum tensor. In all cases, the key point to get the right expressions for the energy-momentum tensors is the appropriate handling of their equations of motion and the Bianchi identities. It must be stressed that these results are obtained without using Belinfante's symmetrization techniques which are usually employed to this end. (Author)
International Nuclear Information System (INIS)
Montesinos, M.; Flores, E.
2006-01-01
The symmetric and gauge-invariant energy-momentum tensors for source-free Maxwell and Yang-Mills theories are obtained by means of translations in spacetime via a systematic implementation of Noether's theorem. For the source-free neutral Proca field, the same procedure yields also the symmetric energy-momentum tensor. In all cases, the key point to get the right expressions for the energy-momentum tensors is the appropriate handling of their equations of motion and the Bianchi identities. It must be stressed that these results are obtained without using Belinfante's symmetrization techniques which are usually employed to this end. (Author)
Mach's principle and rotating universes
International Nuclear Information System (INIS)
King, D.H.
1990-01-01
It is shown that the Bianchi 9 model universe satisfies the Mach principle. These closed rotating universes were previously thought to be counter-examples to the principle. The Mach principle is satisfied because the angular momentum of the rotating matter is compensated by the effective angular momentum of gravitational waves. A new formulation of the Mach principle is given that is based on the field theory interpretation of general relativity. Every closed universe with 3-sphere topology is shown to satisfy this formulation of the Mach principle. It is shown that the total angular momentum of the matter and gravitational waves in a closed 3-sphere topology universe is zero
Conversion of Goldstone bosons into gravitons in anisotropic cosmology
International Nuclear Information System (INIS)
Harari, D.D.; Mazzitelli, F.D.
1990-01-01
The gravitational chiral anomaly makes possible the conversion of a Goldstone boson into a graviton in a background gravitational field. We show that the interaction Lagrangian for this process does not vanish if and only if the background metric has a nonvanishing Weyl tensor, i.e., if it is not conformally flat. No conversion takes place in an isotropic expanding universe. We evaluate the probability for the conversion of Goldstone bosons into gravitons in Bianchi type-I background metrics, the simplest anisotropic cosmological backgrounds
How Isotropic is the Universe?
Saadeh, Daniela; Feeney, Stephen M; Pontzen, Andrew; Peiris, Hiranya V; McEwen, Jason D
2016-09-23
A fundamental assumption in the standard model of cosmology is that the Universe is isotropic on large scales. Breaking this assumption leads to a set of solutions to Einstein's field equations, known as Bianchi cosmologies, only a subset of which have ever been tested against data. For the first time, we consider all degrees of freedom in these solutions to conduct a general test of isotropy using cosmic microwave background temperature and polarization data from Planck. For the vector mode (associated with vorticity), we obtain a limit on the anisotropic expansion of (σ_{V}/H)_{0}Universe is strongly disfavored, with odds of 121 000:1 against.
Spinning fluids in general relativity
Ray, J. R.; Smalley, L. L.
1982-01-01
General relativity field equations are employed to examine a continuous medium with internal spin. A variational principle formerly applied in the special relativity case is extended to the general relativity case, using a tetrad to express the spin density and the four-velocity of the fluid. An energy-momentum tensor is subsequently defined for a spinning fluid. The equations of motion of the fluid are suggested to be useful in analytical studies of galaxies, for anisotropic Bianchi universes, and for turbulent eddies.
Cosmic no-hair theorem with a varying cosmological constant on brane scenario
Chakraborty, S
2002-01-01
In this work, we have studied cosmic no-hair theorem for homogeneous anisotropic Bianchi models with a varying cosmological constant (LAMBDA) in Randall-Sundrum braneworld-type scenarios. The matter fields are confined over the 3-brane onto which the five-dimensional Weyl tensor has a non-vanishing projection. The variation of LAMBDA is taken to be the recently proposed form of Vishwakarma and its generalization. In the first case, the universe will isotropize after power-law inflation while there is exponential expansion in the second case.
Residual supersymmetry of compactified d = 10 supergravity
International Nuclear Information System (INIS)
Wit, B. de; Smit, D.J.; Hari Dass, N.D.
1986-05-01
The conditions for residual supersymmetry in compactified ten-dimensional supergravity theories are investigated, including the effect of a non-constant 'warp factor'. The analysis is based on on-shell transformation laws which implies that certain linear combinations of classical field equations must be satisfied. The conditions for superysymmetry are, in general, not very restrictive. When, in addition, one assumes the validity of Bianchi identities, two independent contractions of the Einstein equation are implied. These equations exclude d=4 de Sitter space; for compactifications to d=4 Minkowski space they only allow purely metric Ricci-flat field configurations with constant warp factor. (Auth.)
International Nuclear Information System (INIS)
Chimento, Luis P.
2002-01-01
We find the group of symmetry transformations under which the Einstein equations for the spatially flat Friedmann-Robertson-Walker universe are form invariant. They relate the energy density and the pressure of the fluid to the expansion rate. We show that inflation can be obtained from nonaccelerated scenarios by a symmetry transformation. We derive the transformation rule for the spectrum and spectral index of the curvature perturbations. Finally, the group is extended to investigate inflation in the anisotropic Bianchi type-I spacetime and the brane-world cosmology
Off shell N=1 supergravity theory in six dimensions
International Nuclear Information System (INIS)
Smith, A.W.
1983-01-01
The off shell N=1 supergravity theory in six dimensions shows beneath the extreme simplicity of theories in higher dimensions useful properties for the study of a unification of normal gauge theories with the supergravity theory via dimensional reduction and yields a geometrical interpretation for the quantum numbers of internal symmtries of the reduced theory. Furthermore this theory permits a better understanding of ultraviolet divergences than a theory in four dimensions. This six-dimensional supergravity theory is constructed here in the corresponding superspace the importance of which was clained otherwise because a precisely defined mathematical formalism for this exists: Differential geometry in the superspace. We establish constraining conditions for the torsion components and give a complete solution of the Bianchi identities. In the formulation of the conditions for the torsions exists a certain freedom, because different conditions lead to the same solution. Therefore only the analysis of the Bianchi identities will show wether the conditions are too restrictive or not. Furthermore the dimensional reduction of D=6 to the four-dimensional space-time is performed. We show here that the reduced theory yields the conformal N=2 supergravity theory. In the last part of this thesis a Langrangian is presented by which the supergravity is coupled to a matter multiplet. In the analysis of the supersymmetry transformations of the component fields we see that the matter multiplet cannot be consistently brought to vanish. That means that a pure supergravity theory cannot be written manifestly Lorentz covariant. (orig.) [de
Loop quantum cosmology of the k=1 FRW: A tale of two bounces
International Nuclear Information System (INIS)
Corichi, Alejandro; Karami, Asieh
2011-01-01
We consider the k=1 Friedman-Robertson-Walker (FRW) model within loop quantum cosmology, paying special attention to the existence of an ambiguity in the quantization process. In spatially nonflat anisotropic models such as Bianchi II and IX, the standard method of defining the curvature through closed holonomies is not admissible. Instead, one has to implement the quantum constraints by approximating the connection via open holonomies. In the case of flat k=0 FRW and Bianchi I models, these two quantization methods coincide, but in the case of the closed k=1 FRW model they might yield different quantum theories. In this manuscript we explore these two quantizations and the different effective descriptions they provide of the bouncing cyclic universe. In particular, as we show in detail, the most dramatic difference is that in the theory defined by the new quantization method, there is not one, but two different bounces through which the cyclic universe alternates. We show that for a 'large' universe, these two bounces are very similar and, therefore, practically indistinguishable, approaching the dynamics of the 'curvature-based' quantum theory.
Generalized quantum theory of recollapsing homogeneous cosmologies
International Nuclear Information System (INIS)
Craig, David; Hartle, James B.
2004-01-01
A sum-over-histories generalized quantum theory is developed for homogeneous minisuperspace type A Bianchi cosmological models, focusing on the particular example of the classically recollapsing Bianchi type-IX universe. The decoherence functional for such universes is exhibited. We show how the probabilities of decoherent sets of alternative, coarse-grained histories of these model universes can be calculated. We consider in particular the probabilities for classical evolution defined by a suitable coarse graining. For a restricted class of initial conditions and coarse grainings we exhibit the approximate decoherence of alternative histories in which the universe behaves classically and those in which it does not. For these situations we show that the probability is near unity for the universe to recontract classically if it expands classically. We also determine the relative probabilities of quasiclassical trajectories for initial states of WKB form, recovering for such states a precise form of the familiar heuristic 'J·dΣ' rule of quantum cosmology, as well as a generalization of this rule to generic initial states
Terracotas de Calés en el Museo Arqueológico Nacional de Madrid
Directory of Open Access Journals (Sweden)
J. M. BLÁZQUEZ
2009-10-01
Full Text Available El Museo Arqueológico Nacional de Madrid exhibe entre sus magníficas colecciones una compuesta de numerosas terracotas traídas de Calés en el siglo pasado por el Marqués de Salamanca que nos hemos propuesto estudiar y a la que hemos dedicado varios trabajos ya. Colecciones similares se conservan en los museos de Lecce, Capua, Louvre, Leide, British Museum, Palazzo dei Conservatori, Villa Giulia, Nacionale Romano, Ny Carbsberg Glyptothek, Museo Universitario de Zurich, Museum für antike Kleinkunst de Munich, y Vaticano, en su mayoría inéditas. Todas estas terracotas plantean sugestivos y fundamentales problemas a los estudiosos del arte antiguo, que han sido señalados por Bianchi-Bandinelli con motivo del estudio y publicación de una terracota del Museo de Berlín. Bianchi-Bandinelli ha indicado alguna de las principales características del arte itálico de este momento, cual es su gusto moderno, su impresionismo e ilusionismo. En Italia en el periodo helenístico o época a la que pertenecen todas estas terracotas, existía una gran Koiné artística que abrazaba por lo menos Lacio, Campania y Etruria. Otros investigadores han estudiado algunas de estas terracotas,como G. Kaschnitz-Weinberg, Pesce, Mingazzini, Vessberg, R. Mengarelli, etc.
Geometric perspective on singularity resolution and uniqueness in loop quantum cosmology
International Nuclear Information System (INIS)
Corichi, Alejandro; Singh, Parampreet
2009-01-01
We reexamine the issue of singularity resolution in homogeneous loop quantum cosmology from the perspective of geometrical entities such as expansion rate and the shear scalar. These quantities are very reliable measures of the properties of spacetime and can be defined not only at the classical and effective level, but also at an operator level in the quantum theory. From their behavior in the effective constraint surface and in the effective loop quantum spacetime, we show that one can severely restrict the ambiguities in regularization of the quantum constraint and rule out unphysical choices. We analyze this in the flat isotropic model and the Bianchi-I spacetimes. In the former case we show that the expansion rate is absolutely bounded only for the so-called improved quantization, a result which synergizes with uniqueness of this quantization as proved earlier. Surprisingly, for the Bianchi-I spacetime, we show that out of the available choices, the expansion rate and shear are bounded for only one regularization of the quantum constraint. It turns out that only for this choice, the theory exhibits quantum gravity corrections at a unique scale, and is physically viable.
Changing families, changing workplaces.
Bianchi, Suzanne M
2011-01-01
American families and workplaces have both changed dramatically over the past half-century. Paid work by women has increased sharply, as has family instability. Education-related inequality in work hours and income has grown. These changes, says Suzanne Bianchi, pose differing work-life issues for parents at different points along the income distribution. Between 1975 and 2009, the labor force rate of mothers with children under age eighteen increased from 47.4 percent to 71.6 percent. Mothers today also return to work much sooner after the birth of a child than did mothers half a century ago. High divorce rates and a sharp rise in the share of births to unmarried mothers mean that more children are being raised by a single parent, usually their mother. Workplaces too have changed, observes Bianchi. Today's employees increasingly work nonstandard hours. The well-being of highly skilled workers and less-skilled workers has been diverging. For the former, work hours may be long, but income has soared. For lower-skill workers, the lack of "good jobs" disconnects fathers from family obligations. Men who cannot find work or have low earnings potential are much less likely to marry. For low-income women, many of whom are single parents, the work-family dilemma is how to care adequately for children and work enough hours to support them financially. Jobs for working-class and lower middle-class workers are relatively stable, except in economic downturns, but pay is low, and both parents must work full time to make ends meet. Family income is too high to qualify for government subsidized child care, but too low to afford high-quality care in the private market. These families struggle to have a reasonable family life and provide for their family's economic well-being. Bianchi concludes that the "work and family" problem has no one solution because it is not one problem. Some workers need more work and more money. Some need to take time off around the birth of a child
The effect of optical substrates on micro-FTIR analysis of single mammalian cells.
Wehbe, Katia; Filik, Jacob; Frogley, Mark D; Cinque, Gianfelice
2013-02-01
The study of individual cells with infrared (IR) microspectroscopy often requires living cells to be cultured directly onto a suitable substrate. The surface effect of the specific substrates on the cell growth-viability and associated biochemistry-as well as on the IR analysis-spectral interference and optical artifacts-is all too often ignored. Using the IR beamline, MIRIAM (Diamond Light Source, UK), we show the importance of the substrate used for IR absorption spectroscopy by analyzing two different cell lines cultured on a range of seven optical substrates in both transmission and reflection modes. First, cell viability measurements are made to determine the preferable substrates for normal cell growth. Successively, synchrotron radiation IR microspectroscopy is performed on the two cell lines to determine any genuine biochemically induced changes or optical effect in the spectra due to the different substrates. Multivariate analysis of spectral data is applied on each cell line to visualize the spectral changes. The results confirm the advantage of transmission measurements over reflection due to the absence of a strong optical standing wave artifact which amplifies the absorbance spectrum in the high wavenumber regions with respect to low wavenumbers in the mid-IR range. The transmission spectra reveal interference from a more subtle but significant optical artifact related to the reflection losses of the different substrate materials. This means that, for comparative studies of cell biochemistry by IR microspectroscopy, it is crucial that all samples are measured on the same substrate type.
Directory of Open Access Journals (Sweden)
Leandro Cisneros
2013-03-01
Full Text Available http://dx.doi.org/10.5007/2178-4582.2012v46n2p499 O presente trabalho é o resultado de um exercício de prática etnográfica proposto na disciplina de Métodos Antropológicos, coordenada por Miriam Grossi, Carmen Rial, Tânia Welter e Mônica Suarez,oferecida para estudantes de doutorado do Programa de Pós-Graduação Interdisciplinar em Ciências Humanas. Propusemo-nos a pesquisar um dos campos fechados da Antropologia, o da prostituição, na região urbana de Florianópolis/SC. Nossa contribuiçãoà reflexão sobre a interdisciplinaridade se faz presente na construção teórico-metodológica do campo de pesquisa, a partir das nossas trajetórias profissionais e percursos de estudo feitos em três áreas, orientações e instituições diferentes.
KEGGtranslator: visualizing and converting the KEGG PATHWAY database to various formats.
Wrzodek, Clemens; Dräger, Andreas; Zell, Andreas
2011-08-15
The KEGG PATHWAY database provides a widely used service for metabolic and nonmetabolic pathways. It contains manually drawn pathway maps with information about the genes, reactions and relations contained therein. To store these pathways, KEGG uses KGML, a proprietary XML-format. Parsers and translators are needed to process the pathway maps for usage in other applications and algorithms. We have developed KEGGtranslator, an easy-to-use stand-alone application that can visualize and convert KGML formatted XML-files into multiple output formats. Unlike other translators, KEGGtranslator supports a plethora of output formats, is able to augment the information in translated documents (e.g. MIRIAM annotations) beyond the scope of the KGML document, and amends missing components to fragmentary reactions within the pathway to allow simulations on those. KEGGtranslator is freely available as a Java(™) Web Start application and for download at http://www.cogsys.cs.uni-tuebingen.de/software/KEGGtranslator/. KGML files can be downloaded from within the application. clemens.wrzodek@uni-tuebingen.de Supplementary data are available at Bioinformatics online.
International Nuclear Information System (INIS)
Schwender, J.
1995-01-01
The biosynthesis of several prenyllipids (isoprenoid lipids) of the green alga Scendesmus obliquus was investigated. The aim was to verify, whether the biosynthesis of isopentenyl diphosphate (IPP) in Scenedesmus proceeds according to the classical acetate mevalonate pathway or to an alternative pathway. An alternative pathway for IPP formation has recently been detected in some eubacteria by the group of Prof. M. Rohmer. Some inhibition tests were performed with mevinolin, a specific inhibitor of HMG-CoA reductase which yields mevalonic acid. Mevinolin should block the biosynthesis of such isoprenoids which are formed via the acetate mevalonate pathway. Scenedesmus was grown heterotrophically on 13 C-labelled glucose or acetate. After isolation and purification of 13 C-labelled phytol (side chains of chlorophylls), β-carotene, lutein, plastoquinone-9 and three sterol compounds, the enrichment of 13 C at different carbon-positions of the labelled compounds was determined. This was achieved by the 13 C-NMR technique in cooperation with Miriam Seemann of the group of Prof. M. Rohmer in Mullhouse/France. (orig.) [de
Cine-Club
2011-01-01
Thursday 27 October 2011 at 20:30 CERN Council Chamber Private By: Saverio Costanzo (Italy, 2004) 90 min With: Mohammed Bakri, Lior Miller, Hend Ayoub A Palestinian family with five children lives outside town, near Israeli settlements. Samia, the wife, wants to leave; so does one teen son. Mohammad, the patriarch, is adamant that he is staying. Two of his adolescent children want to fight. His is the passive aggression of non-violent witness. Israeli soldiers burst into the home, taking over the second floor. At night, the family is locked in the living room. We see the effects of the occupation on the children and on the marriage. Through the eyes of Miriam, the older daughter, we watch the soldiers from her hiding place. Jamal, the eldest son, sets a trap with a grenade. Characters call upon Allah. Chaos and death are close. Original version arabic / english / hebrew; english subtitles Entrance: 2 CHF Projection from DVD http://cineclub.web.cern.ch/Cineclub/ Thursday 3 November 2011 a...
Non-climacteric ripening and sorbitol homeostasis in plum fruits.
Kim, Ho-Youn; Farcuh, Macarena; Cohen, Yuval; Crisosto, Carlos; Sadka, Avi; Blumwald, Eduardo
2015-02-01
During ripening fruits undergo several physiological and biochemical modifications that influence quality-related properties, such as texture, color, aroma and taste. We studied the differences in ethylene and sugar metabolism between two genetically related Japanese plum cultivars with contrasting ripening behaviors. 'Santa Rosa' (SR) behaved as a typical climacteric fruit, while the bud sport mutant 'Sweet Miriam' (SM) displayed a non-climacteric ripening pattern. SM fruit displayed a delayed ripening that lasted 120 days longer than that of the climacteric fruit. At the full-ripe stage, both cultivars reached similar final size and weight but the non-climacteric fruits were firmer than the climacteric fruits. Fully ripe non-climacteric plum fruits, showed an accumulation of sorbitol that was 2.5 times higher than that of climacteric fruits, and the increase in sorbitol were also paralleled to an increase in sucrose catabolism. These changes were highly correlated with decreased activity and expression of NAD(+)-dependent sorbitol dehydrogenase and sorbitol oxidase and increased sorbitol-6-phosphate dehydrogenase activity, suggesting an enhanced sorbitol synthesis in non-climacteric fruits. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.
β-glycosphingolipids ameliorated non-alcoholic steatohepatitis in the Psammomys obesus model
Directory of Open Access Journals (Sweden)
Zigmond E
2014-10-01
Full Text Available Ehud Zigmond,1,* Oshrat Tayer-Shifman,1,* Gadi Lalazar,1 Ami Ben Ya'acov,1 Sarah Weksler-Zangen,2 David Shasha,1 Miriam Sklair-Levy,3 Lidya Zolotarov,1 Zvi Shalev,1 Rony Kalman,2 Ehud Ziv,2 Itamar Raz,2 Yaron Ilan1 1Liver Unit, 2Diabetes Unit, 3Department of Radiology, Hebrew University-Hadassah Medical Center, Jerusalem, Israel *These authors contributed equally to this workAbstract: Liver steatosis is a common characteristic of obesity and type 2 diabetes, and fatty liver disease is increasingly recognized as a major health burden. Accumulating evidence suggests that β-glycosphingolipids play an important role in insulin sensitivity and thus could affect hepatic steatosis. To determine the effect associated with β-glycosphingolipid-mediated amelioration of liver injury, seven groups of Psammomys obesus on a high-energy diet were studied. Animals were treated with daily injections of β-glucosylceramide, β-lactosylceramide, or a combination of both. β-glycosphingolipids ameliorated the hepatic injury manifested by decreased liver enzymes, liver weight, and hepatic fat, and improved liver histology. Administration of both β-glucosylceramide and β-lactosylceramide also decreased interferon (IFN-γ serum levels. These effects were associated with improved serum cholesterol and triglyceride levels. These data suggest that β-glycosphingolipids ameliorate liver injury in an animal model of nonalcoholic steatohepatitis.Keywords: NAFLD, glycolipids, STAT, NASH, insulin resistance, diabetes
Fictionalization, conscientization and the trope of exile in Amandla and Third Generation
Directory of Open Access Journals (Sweden)
J. Geertsema
1993-05-01
Full Text Available The purpose of this article is to examine Amandla (by Miriam TIali and Third Generation (by Sipho Sepamla as anti-apartheid novels of resistance which are faced by a number of serious contradictions. The article is an attempt to analyse the ways in which these texts seek to cope, on the one hand, with what seems to be a lost cause, a struggle without an end, and on the other hand with their own status as fictional texts which attempt to change precisely that which seems to deny all possibilities of subversion. Both texts attempt to make sense of a reality which is perceived to be so horrifyingly real as to be fictional (in the sense of the fictive, unreal, ethereal. On the one hand the power of the apartheid state is seen to be insurmountable, and on the other hand, that stale has to be subverted and destroyed. The resulting dialectic, posited in the texts, of the state of affairs in reality and the state of affairs that is desired, can only be solved by the use of the trope of exile as an imaginary resolution to a very real contradiction in order to achieve at least some measure of conscientization in the readership.
Stafoggia, Massimo; Zauli-Sajani, Stefano; Pey, Jorge; Samoli, Evangelia; Alessandrini, Ester; Basagaña, Xavier; Cernigliaro, Achille; Chiusolo, Monica; Demaria, Moreno; Díaz, Julio; Faustini, Annunziata; Katsouyanni, Klea; Kelessis, Apostolos G.; Linares, Cristina; Marchesi, Stefano; Medina, Sylvia; Pandolfi, Paolo; Pérez, Noemí; Querol, Xavier; Randi, Giorgia; Ranzi, Andrea; Tobias, Aurelio; Forastiere, Francesco
2015-01-01
, Katsouyanni K, Kelessis AG, Linares C, Marchesi S, Medina S, Pandolfi P, Pérez N, Querol X, Randi G, Ranzi A, Tobias A, Forastiere F, MED-PARTICLES Study Group. 2016. Desert dust outbreaks in Southern Europe: contribution to daily PM10 concentrations and short-term associations with mortality and hospital admissions. Environ Health Perspect 124:413–419; http://dx.doi.org/10.1289/ehp.1409164 PMID:26219103
Stafoggia, Massimo; Zauli-Sajani, Stefano; Pey, Jorge; Samoli, Evangelia; Alessandrini, Ester; Basagaña, Xavier; Cernigliaro, Achille; Chiusolo, Monica; Demaria, Moreno; Díaz, Julio; Faustini, Annunziata; Katsouyanni, Klea; Kelessis, Apostolos G; Linares, Cristina; Marchesi, Stefano; Medina, Sylvia; Pandolfi, Paolo; Pérez, Noemí; Querol, Xavier; Randi, Giorgia; Ranzi, Andrea; Tobias, Aurelio; Forastiere, Francesco
2016-04-01
Evidence on the association between short-term exposure to desert dust and health outcomes is controversial. We aimed to estimate the short-term effects of particulate matter ≤ 10 μm (PM10) on mortality and hospital admissions in 13 Southern European cities, distinguishing between PM10 originating from the desert and from other sources. We identified desert dust advection days in multiple Mediterranean areas for 2001-2010 by combining modeling tools, back-trajectories, and satellite data. For each advection day, we estimated PM10 concentrations originating from desert, and computed PM10 from other sources by difference. We fitted city-specific Poisson regression models to estimate the association between PM from different sources (desert and non-desert) and daily mortality and emergency hospitalizations. Finally, we pooled city-specific results in a random-effects meta-analysis. On average, 15% of days were affected by desert dust at ground level (desert PM10 > 0 μg/m3). Most episodes occurred in spring-summer, with increasing gradient of both frequency and intensity north-south and west-east of the Mediterranean basin. We found significant associations of both PM10 concentrations with mortality. Increases of 10 μg/m3 in non-desert and desert PM10 (lag 0-1 days) were associated with increases in natural mortality of 0.55% (95% CI: 0.24, 0.87%) and 0.65% (95% CI: 0.24, 1.06%), respectively. Similar associations were estimated for cardio-respiratory mortality and hospital admissions. PM10 originating from the desert was positively associated with mortality and hospitalizations in Southern Europe. Policy measures should aim at reducing population exposure to anthropogenic airborne particles even in areas with large contribution from desert dust advections. Stafoggia M, Zauli-Sajani S, Pey J, Samoli E, Alessandrini E, Basagaña X, Cernigliaro A, Chiusolo M, Demaria M, Díaz J, Faustini A, Katsouyanni K, Kelessis AG, Linares C, Marchesi S, Medina S, Pandolfi P, P
Amato, F.; Pandolfi, M.; Escrig, A.; Querol, X.; Alastuey, A.; Pey, J.; Perez, N.; Hopke, P. K.
Atmospheric PM pollution from traffic comprises not only direct emissions but also non-exhaust emissions because resuspension of road dust that can produce high human exposure to heavy metals, metalloids, and mineral matter. A key task for establishing mitigation or preventive measures is estimating the contribution of road dust resuspension to the atmospheric PM mixture. Several source apportionment studies, applying receptor modeling at urban background sites, have shown the difficulty in identifying a road dust source separately from other mineral sources or vehicular exhausts. The Multilinear Engine (ME-2) is a computer program that can solve the Positive Matrix Factorization (PMF) problem. ME-2 uses a programming language permitting the solution to be guided toward some possible targets that can be derived from a priori knowledge of sources (chemical profile, ratios, etc.). This feature makes it especially suitable for source apportionment studies where partial knowledge of the sources is available. In the present study ME-2 was applied to data from an urban background site of Barcelona (Spain) to quantify the contribution of road dust resuspension to PM 10 and PM 2.5 concentrations. Given that recently the emission profile of local resuspended road dust was obtained (Amato, F., Pandolfi, M., Viana, M., Querol, X., Alastuey, A., Moreno, T., 2009. Spatial and chemical patterns of PM 10 in road dust deposited in urban environment. Atmospheric Environment 43 (9), 1650-1659), such a priori information was introduced in the model as auxiliary terms of the object function to be minimized by the implementation of the so-called "pulling equations". ME-2 permitted to enhance the basic PMF solution (obtained by PMF2) identifying, beside the seven sources of PMF2, the road dust source which accounted for 6.9 μg m -3 (17%) in PM 10, 2.2 μg m -3 (8%) of PM 2.5 and 0.3 μg m -3 (2%) of PM 1. This reveals that resuspension was responsible of the 37%, 15% and 3% of total
Dynamics of an Anisotropic Universe in f(R,T) Theory
International Nuclear Information System (INIS)
Mishra, B.; Tarai, Sankarsan; Tripathy, S. K.
2016-01-01
Dynamics of an anisotropic universe is studied in f(R,T) gravity using a rescaled functional f(R,T), where R is the Ricci Scalar and T is the trace of energy-momentum tensor. Three models have been constructed assuming a power law expansion of the universe. Physical features of the models are discussed. The model parameters are constrained from a dimensional analysis. It is found from the work that the anisotropic Bianchi type VI_h (BVI_h) model in the modified gravity generally favours a quintessence phase when the parameter h is either -1 or 0. We may not get viable models in conformity with the present day observation for h=1.
Factors influencing choice of chemotherapy in metastatic colorectal cancer (mCRC
Directory of Open Access Journals (Sweden)
Rossi L
2013-11-01
Full Text Available Luigi Rossi, Foteini Vakiarou, Federica Zoratto, Loredana Bianchi, Anselmo Papa, Enrico Basso, Monica Verrico, Giuseppe Lo Russo, Salvatore Evangelista, Guilia Rinaldi, Francesca Perrone-Congedi, Gian Paolo Spinelli, Valeria Stati, Davide Caruso, Alessandra Prete, Silverio TomaoDepartment of Medico-Surgical Sciences and Biotechnologies, "Sapienza" University of Rome, Rome, Italy; Oncology Unit, ICOT, Latina, ItalyAbstract: Management of metastatic colorectal cancer requires a multimodal approach and must be performed by an experienced, multidisciplinary expert team. The optimal choice of the individual treatment modality, according to disease localization and extent, tumor biology, and patient clinical characteristics, will be one that can maintain quality of life and long-term survival, and even cure selected patients. This review is an overview of the different therapeutic approaches available in metastatic colorectal cancer, for the purpose of defining personalized therapeutic algorithms according to tumor biology and patient clinical features.Keywords: metastatic colorectal cancer, patient clinical features, tumor biology, multidisciplinary approach
International Nuclear Information System (INIS)
D'Auria, R.; Fre, P.; Townsend, P.K.; van Nieuwenhuizen, P.
1984-01-01
A new definition of rheonomy is proposed based on Bianchi identifies instead of field equations. For theories with auxiliary fields, the transformation rules are obtained in a completely geometrical way and invariance of the action is equilivalent to d'L = 0, which means surface-independence of the action integral. For theories without auxiliary fields, the transformation rules are found by requiring that the action be invariant, just as in the component approach. Previous methods of obtaining the transformation rules which start from rhenomy of field equations and use certain recipes to find the off-shell extensions of the rules are abandoned. New minimal supergravity is worked out in detail; it is the gauge theory based on a free differential algebra which includes the auxiliary fields
An exotic k-essence interpretation of interactive cosmological models
Energy Technology Data Exchange (ETDEWEB)
Forte, Monica [Universidad de Buenos Aires, Departamento de Fisica, Facultad de ciencias Exactas y Naturales, Buenos Aires (Argentina)
2016-01-15
We define a generalization of scalar fields with non-canonical kinetic term which we call exotic k-essence or, briefly, exotik. These fields are generated by the global description of cosmological models with two interactive fluids in the dark sector and under certain conditions they correspond to usual k-essences. The formalism is applied to the cases of constant potential and of inverse square potential and also we develop the purely exotik version for the modified holographic Ricci type (MHR) of dark energy, where the equations of state are not constant. With the kinetic function F = 1 + mx and the inverse square potential we recover, through the interaction term, the identification between k-essences and quintessences of an exponential potential, already known for Friedmann-Robertson-Walker and Bianchi type I geometries. Worked examples are shown that include the self-interacting MHR and also models with crossing of the phantom divide line (PDL). (orig.)
Stability of anisotropic stellar filaments
Bhatti, M. Zaeem-ul-Haq; Yousaf, Z.
2017-12-01
The study of perturbation of self-gravitating celestial cylindrical object have been carried out in this paper. We have designed a framework to construct the collapse equation by formulating the modified field equations with the background of f(R , T) theory as well as dynamical equations from the contracted form of Bianchi identities with anisotropic matter configuration. We have encapsulated the radial perturbations on metric and material variables of the geometry with some known static profile at Newtonian and post-Newtonian regimes. We examined a strong dependence of unstable regions on stiffness parameter which measures the rigidity of the fluid. Also, the static profile and matter variables with f(R , T) dark source terms control the instability of compact cylindrical system.
Cosmic recall and the scattering picture of loop quantum cosmology
International Nuclear Information System (INIS)
Kaminski, Wojciech; Pawlowski, Tomasz
2010-01-01
The global dynamics of a homogeneous Universe in loop quantum cosmology is viewed as a scattering process of its geometrodynamical equivalent. This picture is applied to build a flexible (easy to generalize) and not restricted just to exactly solvable models method of verifying the preservation of the semiclassicality through the bounce. The devised method is next applied to two simple examples: (i) the isotropic Friedmann-Robertson-Walker universe, and (ii) the isotropic sector of the Bianchi I model. For both of them we show that the dispersions in the logarithm of the volume ln(v) and scalar field momentum ln(p φ ) in the distant future and past are related via strong triangle inequalities. This implies, in particular, a strict preservation of the semiclassicality (in considered degrees of freedom) in both the cases (i) and (ii). Derived inequalities are general: valid for all the physical states within the considered models.
Stress among nurses working in an acute hospital in Ireland.
LENUS (Irish Health Repository)
Donnelly, Teresa
2014-01-01
Stress among nurses leads to absenteeism, reduced efficiency, long-term health problems and a decrease in the quality of patient care delivered. A quantitative cross-sectional study was conducted. The study\\'s aim was to identify perceived stressors and influencing factors among nurses working in the critical and non-critical care practice areas. A convenience sample of 200 nurses were invited to complete the Bianchi Stress Questionnaire. Information was collected on demographics and daily nursing practice. Findings indicated that perceived stressors were similar in both groups. The most severe stressors included redeployment to work in other areas and staffing levels. Results from this study suggest that age, job title, professional experience and formal post-registration qualifications had no influence on stress perception. These results will increase awareness of nurses\\' occupational stress in Ireland.
Levels of occupational stress and stressful activities for nurses working in emergency
Directory of Open Access Journals (Sweden)
José Ricardo Ferreira da Fonseca
2014-12-01
Full Text Available The study aimed to identify stress levels, areas and their activities identified as stressful by nurses working in the emergence in Manaus, AM, Brazil. It is an epidemiological, cross-sectional design, with 36 emergency nurses from December 2010 to January 2011. The Bianchi Stress Scale with 57 questions was used. The nurses were at risk for high levels of stress. The most stressful areas were the operation of the unit, conditions of work and personnel administration, and the most stressful activity was the request for equipment review and repair. The difference by Friedman test between the areas was significant (p <0.05, Dunn post-test significant (p <0.05 when compared by peers. The accumulation of management activities with the assistance activities can generate higher levels of stress, it is necessary to invest in improving the work environment and management support to minimize the stress experienced at work.
Two-point correlation functions in inhomogeneous and anisotropic cosmologies
International Nuclear Information System (INIS)
Marcori, Oton H.; Pereira, Thiago S.
2017-01-01
Two-point correlation functions are ubiquitous tools of modern cosmology, appearing in disparate topics ranging from cosmological inflation to late-time astrophysics. When the background spacetime is maximally symmetric, invariance arguments can be used to fix the functional dependence of this function as the invariant distance between any two points. In this paper we introduce a novel formalism which fixes this functional dependence directly from the isometries of the background metric, thus allowing one to quickly assess the overall features of Gaussian correlators without resorting to the full machinery of perturbation theory. As an application we construct the CMB temperature correlation function in one inhomogeneous (namely, an off-center LTB model) and two spatially flat and anisotropic (Bianchi) universes, and derive their covariance matrices in the limit of almost Friedmannian symmetry. We show how the method can be extended to arbitrary N -point correlation functions and illustrate its use by constructing three-point correlation functions in some simple geometries.
Dark-energy cosmological models in f(G) gravity
Energy Technology Data Exchange (ETDEWEB)
Shamir, M. F., E-mail: farasat.shamir@nu.edu.pk [National University of Computer and Emerging Sciences Lahore Campus, Department of Sciences and Humanities (Pakistan)
2016-10-15
We discuss dark-energy cosmological models in f(G) gravity. For this purpose, a locally rotationally symmetric Bianchi type I cosmological model is considered. First, exact solutions with a well-known form of the f(G) model are explored. One general solution is discussed using a power-law f(G) gravity model and physical quantities are calculated. In particular, Kasner’s universe is recovered and the corresponding f(G) gravity models are reported. Second, the energy conditions for the model under consideration are discussed using graphical analysis. It is concluded that solutions with f(G) = G{sup 5/6} support expansion of universe while those with f(G) = G{sup 1/2} do not favor the current expansion.
Boundary conditions for the gravitational field
International Nuclear Information System (INIS)
Winicour, Jeffrey
2012-01-01
A review of the treatment of boundaries in general relativity is presented with the emphasis on application to the formulations of Einstein's equations used in numerical relativity. At present, it is known how to treat boundaries in the harmonic formulation of Einstein's equations and a tetrad formulation of the Einstein-Bianchi system. However, a universal approach valid for other formulations is not in hand. In particular, there is no satisfactory boundary theory for the 3+1 formulations which have been highly successful in binary black hole simulation. I discuss the underlying problems that make the initial-boundary-value problem much more complicated than the Cauchy problem. I review the progress that has been made and the important open questions that remain. Science is a differential equation. Religion is a boundary condition. (Alan Turing, quoted in J D Barrow, 'Theories of Everything') (topical review)
Anisotropic Bulk Viscous String Cosmological Model in a Scalar-Tensor Theory of Gravitation
Directory of Open Access Journals (Sweden)
D. R. K. Reddy
2013-01-01
Full Text Available Spatially homogeneous, anisotropic, and tilted Bianchi type-VI0 model is investigated in a new scalar-tensor theory of gravitation proposed by Saez and Ballester (1986 when the source for energy momentum tensor is a bulk viscous fluid containing one-dimensional cosmic strings. Exact solution of the highly nonlinear field equations is obtained using the following plausible physical conditions: (i scalar expansion of the space-time which is proportional to the shear scalar, (ii the barotropic equations of state for pressure and energy density, and (iii a special law of variation for Hubble’s parameter proposed by Berman (1983. Some physical and kinematical properties of the model are also discussed.
Anisotropic cosmological constant and the CMB quadrupole anomaly
International Nuclear Information System (INIS)
Rodrigues, Davi C.
2008-01-01
There are evidences that the cosmic microwave background (CMB) large-angle anomalies imply a departure from statistical isotropy and hence from the standard cosmological model. We propose a ΛCDM model extension whose dark energy component preserves its nondynamical character but wields anisotropic vacuum pressure. Exact solutions for the cosmological scale factors are presented, upper bounds for the deformation parameter are evaluated and its value is estimated considering the elliptical universe proposal to solve the quadrupole anomaly. This model can be constructed from a Bianchi I cosmology with a cosmological constant from two different ways: (i) a straightforward anisotropic modification of the vacuum pressure consistently with energy-momentum conservation; (ii) a Poisson structure deformation between canonical momenta such that the dynamics remain invariant under scale factors rescalings
COMPOSITION OF THE JOINT ADVISORY APPEALS BOARDS 2000/2001 EXERCISE
Human Resources Division
2001-01-01
Appointed by the Director-General Appointed by the Staff Association Members Fréderick Bordry /sl Irene Seis/it 1st deputies Christian Fabjan/ep Jean-Claude Carlier/tis 2nd deputies Sue Foffano Morna Robillard/hr Mr Bordry and Mrs Seis have drawn up the following list of staff members from among whom the Chairman of the Board may be chosen when required: Christophe Delamare/est Guy Maurin/ep Maria Dimou/it Mats Moller/as Tobias Dobers/est Alasdair smith/ep Luc Durieu/ps Marilena Streit-Bianchi/tis Lennart Jirden/spl John Poole/sl Mediators [see Administrative Circular N° 6 (Rev. 1) entitled 'Review procedure'] will also be selected from this list of ten staff members.
Independent variables in 3 + 1 Regge calculus
International Nuclear Information System (INIS)
Tuckey, P.A.
1989-01-01
The space of metrics in 3+1 Regge calculus is discussed, and the problems of counting its dimensions, and of finding independent variables to parametrise the space, are addressed. The most general natural class of metrics is considered first, and bounds on its dimension are obtained, although no good parametrisations are found. The relationship between these metrics and those used in canonical Regge calculus is shown, and this leads to an interesting result via the Bianchi identities. A restricted class of metrics is then considered and independent variables, which parametrise these metrics and which may be computationally convenient, are given. The dimension of this space of metrics gives an improved lower bound for the dimension of the general space. (author)
A Kirchhoff-like conservation law in Regge calculus
International Nuclear Information System (INIS)
Gentle, Adrian P; Kheyfets, Arkady; McDonald, Jonathan R; Miller, Warner A
2009-01-01
Simplicial lattices provide an elegant framework for discrete spacetimes. The inherent orthogonality between a simplicial lattice and its circumcentric dual yields an austere representation of spacetime which provides a conceptually simple form of Einstein's geometric theory of gravitation. A sufficient understanding of simplicial spacetimes has been demonstrated in the literature for spacetimes devoid of all non-gravitational sources. However, this understanding has not been adequately extended to non-vacuum spacetime models. Consequently, a deep understanding of the diffeomorphic structure of the discrete theory is lacking. Conservation laws and symmetry properties are attractive starting points for coupling matter with the lattice. We present a simplicial form of the contracted Bianchi identity which is based on the E Cartan moment of rotation operator. This identity manifests itself in the conceptually simple form of a Kirchhoff-like conservation law. This conservation law enables one to extend Regge calculus to non-vacuum spacetimes and provides a deeper understanding of the simplicial diffeomorphism group.
GRG computer algebra system in gravitation and general relativity theory
International Nuclear Information System (INIS)
Zhitnikov, V.V.; Obukhova, I.G.
1985-01-01
The main concepts and capabilities of the GRG specialized computer agebra system intended for performing calculations in the gravitation theory are described. The GRG system is written in the STANDARD LISP language. The program consists of two parts: the first one - for setting initial data, the second one - for specifying a consequence of calculations. The system can function in three formalisms: a coordinate, a tetradic with the Lorentz basis and a spinor ones. The major capabilities of the GRG system are the following: calculation of connectivity and curvature according to the specified metrics, tetrad and torsion; metric type determination according to Petrov; calculation of the Bianchi indentities; operation with an electromagnetic field; tetradic rotations; coordinate conversions
Homoclinic chaos and energy condition violation
International Nuclear Information System (INIS)
Heinzle, J. Mark; Roehr, Niklas; Uggla, Claes
2006-01-01
In this letter we discuss the connection between so-called homoclinic chaos and the violation of energy conditions in locally rotationally symmetric Bianchi type IX models, where the matter is assumed to be nontilted dust and a positive cosmological constant. We show that homoclinic chaos in these models is an artifact of unphysical assumptions: it requires that there exist solutions with positive matter energy density ρ>0 that evolve through the singularity and beyond as solutions with negative matter energy density ρ<0. Homoclinic chaos is absent when it is assumed that the dust particles always retain their positive mass. In addition, we discuss more general models: for solutions that are not locally rotationally symmetric we demonstrate that the construction of extensions through the singularity, which is required for homoclinic chaos, is not possible in general
Occupational stressors among nurses working in urgent and emergency care units
Directory of Open Access Journals (Sweden)
Denyson Santana PEREIRA
Full Text Available The study aimed to assess occupational stressors among nurses working in urgent and emergency care facilities. It is a descriptive research developed in two public hospitals of different complexity degrees, with 49 nurses. Data were collected from June to September 2011. The Bianchi's Stress Scale, which is composed of six domains: Relationship, Unit functioning, Staff management, Nursing care, Unit coordination, and Work conditions was used to assess occupational stressors based on the regular activities performed by nurses. Data were analyzed by using descriptive statistics and Mann Whitney-U test. For the nurses working in the high complexity healthcare facility - hospital A the most stressful domain was Nursing care, while for those professionals working in the medium complexity healthcare facility - hospital B, Staff management was the most stressful domain. The nurses from hospital A perceived care-related activities as more stressful, while for those in hospital B administrative activities were considered more stressful.
The Simon and Simon-Mars tensors for stationary Einstein-Maxwell fields
International Nuclear Information System (INIS)
Bini, Donato; Cherubini, Christian; Jantzen, Robert T; Miniutti, Giovanni
2004-01-01
Modulo conventional scale factors, the Simon and Simon-Mars tensors are defined for stationary vacuum spacetimes so that their equality follows from the Bianchi identities of the second kind. In the nonvacuum case one can absorb additional source terms into a redefinition of the Simon tensor so that this equality is maintained. Among the electrovacuum class of solutions of the Einstein-Maxwell equations, the expression for the Simon tensor in the Kerr-Newman-Taub-NUT spacetime in terms of the Ernst potential is formally the same as in the vacuum case (modulo a scale factor), and its vanishing guarantees the simultaneous alignment of the principal null directions of the Weyl tensor, the Papapetrou field associated with the timelike Killing vector field, the electromagnetic field of the spacetime and even the Killing-Yano tensor
Energy Technology Data Exchange (ETDEWEB)
Heller, Marc Andre [Particle Theory and Cosmology Group, Department of Physics,Graduate School of Science, Tohoku University,Aoba-ku, Sendai 980-8578 (Japan); Ikeda, Noriaki [Department of Mathematical Sciences, Ritsumeikan University,Kusatsu, Shiga 525-8577 (Japan); Watamura, Satoshi [Particle Theory and Cosmology Group, Department of Physics,Graduate School of Science, Tohoku University,Aoba-ku, Sendai 980-8578 (Japan)
2017-02-15
We give a systematic derivation of the local expressions of the NS H-flux, geometric F- as well as non-geometric Q- and R-fluxes in terms of bivector β- and two-form B-potentials including vielbeins. They are obtained using a supergeometric method on QP-manifolds by twist of the standard Courant algebroid on the generalized tangent space without flux. Bianchi identities of the fluxes are easily deduced. We extend the discussion to the case of the double space and present a formulation of T-duality in terms of canonical transformations between graded symplectic manifolds. Thus, we find a unified description of geometric as well as non-geometric fluxes and T-duality transformations in double field theory. Finally, the construction is compared to the formerly introduced Poisson Courant algebroid, a Courant algebroid on a Poisson manifold, as a model for R-flux.
Entropy in the classical and quantum polymer black hole models
International Nuclear Information System (INIS)
Livine, Etera R; Terno, Daniel R
2012-01-01
We investigate the entropy counting for black hole horizons in loop quantum gravity (LQG). We argue that the space of 3D closed polyhedra is the classical counterpart of the space of SU(2) intertwiners at the quantum level. Then computing the entropy for the boundary horizon amounts to calculating the density of polyhedra or the number of intertwiners at fixed total area. Following the previous work (Bianchi 2011 Class. Quantum Grav. 28 114006) we dub these the classical and quantum polymer models for isolated horizons in LQG. We provide exact micro-canonical calculations for both models and we show that the classical counting of polyhedra accounts for most of the features of the intertwiner counting (leading order entropy and log-correction), thus providing us with a simpler model to further investigate correlations and dynamics. To illustrate this, we also produce an exact formula for the dimension of the intertwiner space as a density of ‘almost-closed polyhedra’. (paper)
Cosmological coevolution of Yang-Mills fields and perfect fluids
International Nuclear Information System (INIS)
Barrow, John D.; Jin, Yoshida; Maeda, Kei-ichi
2005-01-01
We study the coevolution of Yang-Mills fields and perfect fluids in Bianchi type I universes. We investigate numerically the evolution of the universe and the Yang-Mills fields during the radiation and dust eras of a universe that is almost isotropic. The Yang-Mills field undergoes small amplitude chaotic oscillations, as do the three expansion scale factors which are also displayed by the expansion scale factors of the universe. The results of the numerical simulations are interpreted analytically and compared with past studies of the cosmological evolution of magnetic fields in radiation and dust universes. We find that, whereas magnetic universes are strongly constrained by the microwave background anisotropy, Yang-Mills universes are principally constrained by primordial nucleosynthesis but the bound is comparatively weak with Ω YM rad
Dynamics of anisotropic power-law f(R) cosmology
International Nuclear Information System (INIS)
Shamir, M. F.
2016-01-01
Modified theories of gravity have attracted much attention of the researchers in the recent years. In particular, the f(R) theory has been investigated extensively due to important f(R) gravity models in cosmological contexts. This paper is devoted to exploring an anisotropic universe in metric f(R) gravity. A locally rotationally symmetric Bianchi type I cosmological model is considered for this purpose. Exact solutions of modified field equations are obtained for a well-known f(R) gravity model. The energy conditions are also discussed for the model under consideration. The viability of the model is investigated via graphical analysis using the present-day values of cosmological parameters. The model satisfies null energy, weak energy, and dominant energy conditions for a particular range of the anisotropy parameter while the strong energy condition is violated, which shows that the anisotropic universe in f(R) gravity supports the crucial issue of accelerated expansion of the universe.
Dynamics of anisotropic power-law f(R) cosmology
Energy Technology Data Exchange (ETDEWEB)
Shamir, M. F., E-mail: farasat.shamir@nu.edu.pk [National University of Computer and Emerging Sciences, Lahore Campus, Department of Sciences and Humanities (Pakistan)
2016-12-15
Modified theories of gravity have attracted much attention of the researchers in the recent years. In particular, the f(R) theory has been investigated extensively due to important f(R) gravity models in cosmological contexts. This paper is devoted to exploring an anisotropic universe in metric f(R) gravity. A locally rotationally symmetric Bianchi type I cosmological model is considered for this purpose. Exact solutions of modified field equations are obtained for a well-known f(R) gravity model. The energy conditions are also discussed for the model under consideration. The viability of the model is investigated via graphical analysis using the present-day values of cosmological parameters. The model satisfies null energy, weak energy, and dominant energy conditions for a particular range of the anisotropy parameter while the strong energy condition is violated, which shows that the anisotropic universe in f(R) gravity supports the crucial issue of accelerated expansion of the universe.
Cartan's equations define a topological field theory of the BF type
International Nuclear Information System (INIS)
Cuesta, Vladimir; Montesinos, Merced
2007-01-01
Cartan's first and second structure equations together with first and second Bianchi identities can be interpreted as equations of motion for the tetrad, the connection and a set of two-form fields T I and R J I . From this viewpoint, these equations define by themselves a field theory. Restricting the analysis to four-dimensional spacetimes (keeping gravity in mind), it is possible to give an action principle of the BF type from which these equations of motion are obtained. The action turns out to be equivalent to a linear combination of the Nieh-Yan, Pontrjagin, and Euler classes, and so the field theory defined by the action is topological. Once Einstein's equations are added, the resulting theory is general relativity. Therefore, the current results show that the relationship between general relativity and topological field theories of the BF type is also present in the first-order formalism for general relativity
Warm anisotropic inflationary universe model
International Nuclear Information System (INIS)
Sharif, M.; Saleem, Rabia
2014-01-01
This paper is devoted to the study of warm inflation using vector fields in the background of a locally rotationally symmetric Bianchi type I model of the universe. We formulate the field equations, and slow-roll and perturbation parameters (scalar and tensor power spectra as well as their spectral indices) in the slow-roll approximation. We evaluate all these parameters in terms of the directional Hubble parameter during the intermediate and logamediate inflationary regimes by taking the dissipation factor as a function of the scalar field as well as a constant. In each case, we calculate the observational parameter of interest, i.e., the tensor-scalar ratio in terms of the inflaton. The graphical behavior of these parameters shows that the anisotropic model is also compatible with WMAP7 and the Planck observational data. (orig.)
Warm anisotropic inflationary universe model
Energy Technology Data Exchange (ETDEWEB)
Sharif, M.; Saleem, Rabia [University of the Punjab, Department of Mathematics, Lahore (Pakistan)
2014-02-15
This paper is devoted to the study of warm inflation using vector fields in the background of a locally rotationally symmetric Bianchi type I model of the universe. We formulate the field equations, and slow-roll and perturbation parameters (scalar and tensor power spectra as well as their spectral indices) in the slow-roll approximation. We evaluate all these parameters in terms of the directional Hubble parameter during the intermediate and logamediate inflationary regimes by taking the dissipation factor as a function of the scalar field as well as a constant. In each case, we calculate the observational parameter of interest, i.e., the tensor-scalar ratio in terms of the inflaton. The graphical behavior of these parameters shows that the anisotropic model is also compatible with WMAP7 and the Planck observational data. (orig.)
Wireless Networks under a Backoff Attack: A Game Theoretical Perspective.
Parras, Juan; Zazo, Santiago
2018-01-30
We study a wireless sensor network using CSMA/CA in the MAC layer under a backoff attack: some of the sensors of the network are malicious and deviate from the defined contention mechanism. We use Bianchi's network model to study the impact of the malicious sensors on the total network throughput, showing that it causes the throughput to be unfairly distributed among sensors. We model this conflict using game theory tools, where each sensor is a player. We obtain analytical solutions and propose an algorithm, based on Regret Matching, to learn the equilibrium of the game with an arbitrary number of players. Our approach is validated via simulations, showing that our theoretical predictions adjust to reality.
New counterterms induced by trans-Planckian physics in semiclassical gravity
International Nuclear Information System (INIS)
Nacir, D. Lopez; Mazzitelli, F. D.
2008-01-01
We consider free and self-interacting quantum scalar fields satisfying modified dispersion relations in the framework of Einstein-Aether theory. Using adiabatic regularization, we study the renormalization of the equation for the mean value of the field in the self-interacting case, and the renormalization of the semiclassical Einstein-Aether equations for free fields. In both cases we consider Bianchi type I background spacetimes. Contrary to what happens for free fields in flat Robertson-Walker spacetimes, the self-interaction and/or the anisotropy produce nonpurely geometric terms in the adiabatic expansion, i.e. terms that involve both the metric g μν and the aether field u μ . We argue that, in a general spacetime, the renormalization of the theory would involve new counterterms constructed with g μν and u μ , generating a fine-tuning problem for the Einstein-Aether theory.
El grupo editor de la revista Nosotros visto desde dentro. Argentina, 1907-1920
Directory of Open Access Journals (Sweden)
Miranda Lida
2015-12-01
Full Text Available The cultural magazine Nosotros, founded in Buenos Aires by Alfredo Bianchi and Roberto Giusti, occupied an undisputed place in Argentine culture during the first half of the 20th century. This article offers a reconstruction of its editorial group in the period between 1907 and 1920, from a perspective of social and intellectual history. It suggests that the institutionalization of the editorial group around a Cooperative Society was decisive in its growth as a magazine and publishing house, as was its management by the poet Rafael Obligado, since Nosotros would soon become a prolific publishing label. Under the influence of World War I and the Russian Revolution, the magazine went through intense political and ideological debates that undermined the cohesion of the editorial group and threatened its continuity. The history of the magazine is reconstructed here on the basis of a wide variety of sources (correspondence, a complete collection of the magazine, and memoirs from the period.
Electromagnetic Gowdy universe
International Nuclear Information System (INIS)
Charach, C.
1979-01-01
Following Gowdy and Berger we construct an inhomogeneous closed electromagnetic universe with three-torus topology. This model is obtained as a result of the homogeneity breaking in the electromagnetic Bianchi type-I universe and contains interacting gravitational and electromagnetic waves. This cosmological solution provides an exactly solvable model for the study of the nonlinear fully relativistic regime of coupled electromagnetic and gravitational fields in the early universe. The asymptotic behavior is considered (i) in the vicinity of the initial singularity and (ii) in the high-frequency limit. It is shown that the effects of coupling between electromagnetic and gravitational waves cause an evolution which is significantly different from that of the vacuum model. The influence of the primordial homogeneous electromagnetic field on the dynamics of the model is also discussed
Geometric flows in Horava-Lifshitz gravity
Bakas, Ioannis; Lust, Dieter; Petropoulos, Marios
2010-01-01
We consider instanton solutions of Euclidean Horava-Lifshitz gravity in four dimensions satisfying the detailed balance condition. They are described by geometric flows in three dimensions driven by certain combinations of the Cotton and Ricci tensors as well as the cosmological-constant term. The deformation curvature terms can have competing behavior leading to a variety of fixed points. The instantons interpolate between any two fixed points, which are vacua of topologically massive gravity with Lambda > 0, and their action is finite. Special emphasis is placed on configurations with SU(2) isometry associated with homogeneous but generally non-isotropic Bianchi IX model geometries. In this case, the combined Ricci-Cotton flow reduces to an autonomous system of ordinary differential equations whose properties are studied in detail for different couplings. The occurrence and stability of isotropic and anisotropic fixed points are investigated analytically and some exact solutions are obtained. The correspond...
International Nuclear Information System (INIS)
Unge, Rikard von
2002-01-01
We extend the path-integral formalism for Poisson-Lie T-duality to include the case of Drinfeld doubles which can be decomposed into bi-algebras in more than one way. We give the correct shift of the dilaton, correcting a mistake in the literature. We then use the fact that the six dimensional Drinfeld doubles have been classified to write down all possible conformal Poisson-Lie T-duals of three dimensional space times and we explicitly work out two duals to the constant dilaton and zero anti-symmetric tensor Bianchi type V space time and show that they satisfy the string equations of motion. This space-time was previously thought to have no duals because of the tracefulness of the structure constants. (author)
Gravitational collapse of a magnetized fermion gas with finite temperature
Energy Technology Data Exchange (ETDEWEB)
Delgado Gaspar, I. [Instituto de Geofisica y Astronomia (IGA), La Habana (Cuba); Perez Martinez, A. [Instituto de Cibernetica, Matematica y Fisica (ICIMAF), La Habana (Cuba); Sussman, Roberto A. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (ICN-UNAM), Mexico (Mexico); Ulacia Rey, A. [Instituto de Cibernetica, Matematica y Fisica (ICIMAF), La Habana (Cuba); Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (ICN-UNAM), Mexico (Mexico)
2013-07-15
We examine the dynamics of a self-gravitating magnetized fermion gas at finite temperature near the collapsing singularity of a Bianchi-I spacetime. Considering a general set of appropriate and physically motivated initial conditions, we transform Einstein-Maxwell field equations into a complete and self-consistent dynamical system amenable for numerical work. The resulting numerical solutions reveal the gas collapsing into both, isotropic (''point-like'') and anisotropic (''cigar-like''), singularities, depending on the initial intensity of the magnetic field. We provide a thorough study of the near collapse behavior and interplay of all relevant state and kinematic variables: temperature, expansion scalar, shear scalar, magnetic field, magnetization, and energy density. A significant qualitative difference in the behavior of the gas emerges in the temperature range T/m{sub f} {proportional_to} 10{sup -6} and T/m{sub f} {proportional_to} 10{sup -3}. (orig.)
On Semi-classical Degravitation and the Cosmological Constant Problems
Patil, Subodh P
2010-01-01
In this report, we discuss a candidate mechanism through which one might address the various cosmological constant problems. We first observe that the renormalization of gravitational couplings (induced by integrating out various matter fields) manifests non-local modifications to Einstein's equations as quantum corrected equations of motion. That is, at the loop level, matter sources curvature through a gravitational coupling that is a non-local function of the covariant d'Alembertian. If the functional form of the resulting Newton's `constant' is such that it annihilates very long wavelength sources, but reduces to $1/M^2_{pl}$ ($M_{pl}$ being the 4d Planck mass) for all sources with cosmologically observable wavelengths, we would have a complimentary realization of the degravitation paradigm-- a realization through which its non-linear completion and the corresponding modified Bianchi identities are readily understood. We proceed to consider various theories whose coupling to gravity may a priori induce no...
On a new approach for constructing wormholes in Einstein-Born-Infeld gravity
Energy Technology Data Exchange (ETDEWEB)
Kim, Jin Young [Kunsan National University, Department of Physics, Kunsan (Korea, Republic of); Park, Mu-In [Sogang University, Research Institute for Basic Science, Seoul (Korea, Republic of)
2016-11-15
We study a new approach for the wormhole construction in Einstein-Born-Infeld gravity, which does not require exotic matters in the Einstein equation. The Born-Infeld field equation is not modified by coordinate independent conditions of continuous metric tensor and its derivatives, even though the Born-Infeld fields have discontinuities in their derivatives at the throat in general. We study the relation of the newly introduced conditions with the usual continuity equation for the energy-momentum tensor and the gravitational Bianchi identity. We find that there is no violation of energy conditions for the Born-Infeld fields contrary to the usual approaches. The exoticity of the energy-momentum tensor is not essential for sustaining wormholes. Some open problems are discussed. (orig.)
Las lógicas de acción emergentes en los nuevos modelos productivos
Directory of Open Access Journals (Sweden)
Francisco Pucci
2014-07-01
Full Text Available Este trabajo forma parte del Proyecto «La negociación de los umbrales aceptables de riesgo en la industria de la construcción uruguaya.», aprobado por la Comisión Sectorial de Investigación Científica (CSIC de la Universidad de la República Oriental del Uruguay. En el mismo trabajan. además de los autores. los Profs. Rodolfo Levin y Carlos Bianchi.Contenido: Introducción. La acción racional estratégica. La gestión de la incertidumbre en los nuevos modelos productivos. Las nuevas lógicas de acción. Conclusiones
An exotic k-essence interpretation of interactive cosmological models
International Nuclear Information System (INIS)
Forte, Monica
2016-01-01
We define a generalization of scalar fields with non-canonical kinetic term which we call exotic k-essence or, briefly, exotik. These fields are generated by the global description of cosmological models with two interactive fluids in the dark sector and under certain conditions they correspond to usual k-essences. The formalism is applied to the cases of constant potential and of inverse square potential and also we develop the purely exotik version for the modified holographic Ricci type (MHR) of dark energy, where the equations of state are not constant. With the kinetic function F = 1 + mx and the inverse square potential we recover, through the interaction term, the identification between k-essences and quintessences of an exponential potential, already known for Friedmann-Robertson-Walker and Bianchi type I geometries. Worked examples are shown that include the self-interacting MHR and also models with crossing of the phantom divide line (PDL). (orig.)
Evolution in bouncing quantum cosmology
International Nuclear Information System (INIS)
Mielczarek, Jakub; Piechocki, Włodzimierz
2012-01-01
We present the method of describing an evolution in quantum cosmology in the framework of the reduced phase space quantization of loop cosmology. We apply our method to the flat Friedmann-Robertson-Walker model coupled to a massless scalar field. We identify the physical quantum Hamiltonian that is positive-definite and generates globally a unitary evolution of the considered quantum system. We examine the properties of expectation values of physical observables in the process of the quantum big bounce transition. The dispersion of evolved observables is studied for the Gaussian state. Calculated relative fluctuations enable an examination of the semi-classicality conditions and possible occurrence of the cosmic forgetfulness. Preliminary estimations based on the cosmological data suggest that there was no cosmic amnesia. Presented results are analytical, and numerical computations are only used for the visualization purposes. Our method may be generalized to sophisticated cosmological models including the Bianchi-type universes. (paper)
The de Sitter spacetime as an attractor solution in fourth-order gravity
International Nuclear Information System (INIS)
Schmidt, H.-J.
1988-01-01
We investigate the general vacuum solution of fourth-order gravity, and include the Bach tensor. For L 2 = 1.3μR 2 + 1/2αC 2 the expanding de Sitter spacetime is an attractor in the set of axially symmetric Bianchi type-I models if and only if αμ ≤ 0 or α > 4μ holds. It will be argued that this result holds true for a large class of inhomogeneous models. As a byproduct, a new closed-form cosmological solution, is obtained. It is also shown that the de Sitter spacetime is an attractor for the Bach-Einstein gravity with a minimally coupled scalar field φ. Specialised to Einstein gravity (i.e. α = 0 above) this conformal equivalence remains a non-trivial one. (author)
International Nuclear Information System (INIS)
Thierry-Mieg, Jean
2006-01-01
In Yang-Mills theory, the charges of the left and right massless Fermions are independent of each other. We propose a new paradigm where we remove this freedom and densify the algebraic structure of Yang-Mills theory by integrating the scalar Higgs field into a new gauge-chiral 1-form which connects Fermions of opposite chiralities. Using the Bianchi identity, we prove that the corresponding covariant differential is associative if and only if we gauge a Lie-Kac super-algebra. In this model, spontaneous symmetry breakdown naturally occurs along an odd generator of the super-algebra and induces a representation of the Connes-Lott non commutative differential geometry of the 2-point finite space
Generalized isothermic lattices
International Nuclear Information System (INIS)
Doliwa, Adam
2007-01-01
We study multi-dimensional quadrilateral lattices satisfying simultaneously two integrable constraints: a quadratic constraint and the projective Moutard constraint. When the lattice is two dimensional and the quadric under consideration is the Moebius sphere one obtains, after the stereographic projection, the discrete isothermic surfaces defined by Bobenko and Pinkall by an algebraic constraint imposed on the (complex) cross-ratio of the circular lattice. We derive the analogous condition for our generalized isothermic lattices using Steiner's projective structure of conics, and we present basic geometric constructions which encode integrability of the lattice. In particular, we introduce the Darboux transformation of the generalized isothermic lattice and we derive the corresponding Bianchi permutability principle. Finally, we study two-dimensional generalized isothermic lattices, in particular geometry of their initial boundary value problem
The Raychaudhuri equation in homogeneous cosmologies
International Nuclear Information System (INIS)
Albareti, F.D.; Cembranos, J.A.R.; Cruz-Dombriz, A. de la; Dobado, A.
2014-01-01
In this work we address the issue of studying the conditions required to guarantee the Focusing Theorem for both null and timelike geodesic congruences by using the Raychaudhuri equation. In particular we study the case of Friedmann-Robertson-Walker as well as more general Bianchi Type I spacetimes. The fulfillment of the Focusing Theorem is mandatory in small scales since it accounts for the attractive character of gravity. However, the Focusing Theorem is not satisfied at cosmological scales due to the measured negative deceleration parameter. The study of the conditions needed for congruences convergence is not only relevant at the fundamental level but also to derive the viability conditions to be imposed on extended theories of gravity describing the different expansion regimes of the universe. We illustrate this idea for f(R) gravity theories
On a supersymmetric completion of the R4 term in IIB supergravity
International Nuclear Information System (INIS)
Haro, Sebastian de; Sinkovics, Annamaria; Skenderis, Kostas
2003-01-01
We analyze the possibility of constructing a supersymmetric invariant that contains the R 4 term among its components as a superpotential term in type IIB on-shell superspace. We consider a scalar superpotential, i.e. an arbitrary holomorphic function of a chiral scalar superfield. In general, type IIB superspace does not allow for the existence of chiral superfields, but the obstruction vanishes for a specific superfield, the dilaton superfield. This superfield contains all fields of type IIB supergravity among its components, and its existence is implied by the solution of the Bianchi identities. The construction requires the existence of an appropriate chiral measure, and we find an obstruction to the existence of such a measure. The obstruction is closely related to the obstruction for the existence of chiral superfields and is non-linear in the fields. These results imply that the type IIB superinvariant related to the R 4 term is not associated with a scalar chiral superpotential
The complete Brans–Dicke theories
International Nuclear Information System (INIS)
Kofinas, Georgios
2017-01-01
Given that the simple wave equation of Brans–Dicke theory for the scalar field is preserved, we have investigated, through exhaustively analyzing the Bianchi identities, the consistent theories which violate the exact energy conservation equation. It is found that only three theories exist which are unambiguously determined from consistency, without imposing arbitrary functions by hand. Each of these theories possesses a specific interaction term which controls the energy exchange between the scalar field and ordinary matter. The theories contain new parameters (integration constants from the integration procedure) and when these are switched-off, Brans–Dicke theory emerges. As usually, the vacuum theories can be defined from the complete Brans–Dicke theories when the matter energy–momentum tensor vanishes.
Anisotropy dissipation in quantum cosmology
International Nuclear Information System (INIS)
Calzetta, E.; Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires, Argentina)
1991-01-01
We study the issue of decoherence and dissipation in the wave function of the Universe for a Bianchi type-I universe with classical and quantum matter. We obtain a coarse-grained description by tracing over the matter degrees of freedom. Provided that for small universes the wave function of the universe is concentrated on a neighborhood of the isotropic configuration, then the coarse-grained density matrix of the universe will show an even more marked peak around isotropy for large universes. In this sense we can say that, while decoherence makes the reduced density matrix of the universe diagonal, dissipation causes the universe to be isotropic with a high probability for large radii
A new class of spatially homogeneous 4D string backgrounds
Batakis, N A
1995-01-01
A new class of spatially homogeneous 4D string backgrounds, the X(d\\rightarrow) according to a recent classification, is presented and shown to contain only five generic types. In contrast to the case of X(d\\uparrow) (which contains as a subclass all possible FRW backgrounds), exact SO(3) isotropy is always broken in the X(d\\rightarrow) class. This is due to the H-field, whose dual is necessarily along a principal direction of anisotropy. Nevertheless, FRW symmetry can be attained asymptotically for Bianchi-types I and VII_0 in a rather appealing physical context. Other aspects of the solutions found for types X=I,II,III,VI_{-1}, and of the VII_0 case are briefly discussed.
Magnetized Anisotropic Dark Energy Models in Barber’s Second Self-Creation Theory
Directory of Open Access Journals (Sweden)
D. D. Pawar
2014-01-01
Full Text Available The present paper deals with Bianchi type IX cosmological model with magnetized anisotropic dark energy by using Barber’s self-creation theory. The energy momentum tensor consists of anisotropic fluid with EoS parameter ω and a uniform magnetic field of energy density ρB. In order to obtain the exact solution we have assumed that dark energy components and the components of magnetic field interact minimally and obey the law of conservation of energy momentum tensors. We have also used the special law of variation for the mean generalized Hubble parameter and power law relation between scalar field and scale factor. Some physical and kinematical properties of the models have been discussed.
Effects of Low Anisotropy on Generalized Ghost Dark Energy in Galileon Gravity
Hossienkhani, H.; Fayaz, V.; Jafari, A.; Yousefi, H.
2018-04-01
The definition of the Galileon gravity form is extended to the Brans-Dicke theory. Given, the framework of the Galileon theory, the generalized ghost dark energy model in an anisotropic universe is investigated. We study the cosmological implications of this model. In particular, we obtain the equation of state and the deceleration parameters and a differential equation governing the evolution of this dark energy in Bianchi type I model. We also probe observational constraints by using the latest observational data on the generalized ghost dark energy models as the unification of dark matter and dark energy. In order to do so, we focus on observational determinations of the Hubble expansion rate (namely, the expansion history) H(z). As a result, we show the influence of the anisotropy (although low) on the evolution of the universe in the statefinder diagrams for Galileon gravity.
AdS strings with torsion: Noncomplex heterotic compactifications
International Nuclear Information System (INIS)
Frey, Andrew R.; Lippert, Matthew
2005-01-01
Combining the effects of fluxes and gaugino condensation in heterotic supergravity, we use a ten-dimensional approach to find a new class of four-dimensional supersymmetric AdS 4 compactifications on almost-Hermitian manifolds of SU(3) structure. Computation of the torsion allows a classification of the internal geometry, which for a particular combination of fluxes and condensate, is nearly Kaehler. We argue that all moduli are fixed, and we show that the Kaehler potential and superpotential proposed in the literature yield the correct AdS 4 radius. In the nearly Kaehler case, we are able to solve the H Bianchi identity using a nonstandard embedding. Finally, we point out subtleties in deriving the effective superpotential and understanding the heterotic supergravity in the presence of a gaugino condensate
On the viability of the truncated Israel–Stewart theory in cosmology
International Nuclear Information System (INIS)
Shogin, Dmitry; Amundsen, Per Amund; Hervik, Sigbjørn
2015-01-01
We apply the causal Israel–Stewart theory of irreversible thermodynamics to model the matter content of the Universe as a dissipative fluid with bulk and shear viscosity. Along with the full transport equations we consider their widely used truncated version. By implementing a dynamical systems approach to Bianchi type IV and V cosmological models with and without cosmological constant, we determine the future asymptotic states of such Universes and show that the truncated Israel–Stewart theory leads to solutions essentially different from the full theory. The solutions of the truncated theory may also manifest unphysical properties. Finally, we find that in the full theory shear viscosity can give a substantial rise to dissipative fluxes, driving the fluid extremely far from equilibrium, where the linear Israel–Stewart theory ceases to be valid. (paper)
Phase space analysis for anisotropic universe with nonlinear bulk viscosity
Sharif, M.; Mumtaz, Saadia
2018-06-01
In this paper, we discuss phase space analysis of locally rotationally symmetric Bianchi type I universe model by taking a noninteracting mixture of dust like and viscous radiation like fluid whose viscous pressure satisfies a nonlinear version of the Israel-Stewart transport equation. An autonomous system of equations is established by defining normalized dimensionless variables. In order to investigate stability of the system, we evaluate corresponding critical points for different values of the parameters. We also compute power-law scale factor whose behavior indicates different phases of the universe model. It is found that our analysis does not provide a complete immune from fine-tuning because the exponentially expanding solution occurs only for a particular range of parameters. We conclude that stable solutions exist in the presence of nonlinear model for bulk viscosity with different choices of the constant parameter m for anisotropic universe.
Energy Technology Data Exchange (ETDEWEB)
Cederwall, Martin [Division for Theoretical Physics, Department of Physics, Chalmers University of Technology,SE 412 96 Gothenburg (Sweden)
2016-06-27
A geometry of superspace corresponding to double field theory is developed, with type I I supergravity in D=10 as the main example. The formalism is based on an orthosymplectic extension OSp(d,d|2s) of the continuous T-duality group. Covariance under generalised super-diffeomorphisms is manifest. Ordinary superspace is obtained as a solution of the orthosymplectic section condition. A systematic study of curved superspace Bianchi identities is performed, and a relation to a double pure spinor superfield cohomology is established. A Ramond-Ramond superfield is constructed as an infinite-dimensional orthosymplectic spinor. Such objects in minimal orbits under the OSp supergroup (“pure spinors”) define super-sections.
Two-point correlation functions in inhomogeneous and anisotropic cosmologies
Energy Technology Data Exchange (ETDEWEB)
Marcori, Oton H.; Pereira, Thiago S., E-mail: otonhm@hotmail.com, E-mail: tspereira@uel.br [Departamento de Física, Universidade Estadual de Londrina, 86057-970, Londrina PR (Brazil)
2017-02-01
Two-point correlation functions are ubiquitous tools of modern cosmology, appearing in disparate topics ranging from cosmological inflation to late-time astrophysics. When the background spacetime is maximally symmetric, invariance arguments can be used to fix the functional dependence of this function as the invariant distance between any two points. In this paper we introduce a novel formalism which fixes this functional dependence directly from the isometries of the background metric, thus allowing one to quickly assess the overall features of Gaussian correlators without resorting to the full machinery of perturbation theory. As an application we construct the CMB temperature correlation function in one inhomogeneous (namely, an off-center LTB model) and two spatially flat and anisotropic (Bianchi) universes, and derive their covariance matrices in the limit of almost Friedmannian symmetry. We show how the method can be extended to arbitrary N -point correlation functions and illustrate its use by constructing three-point correlation functions in some simple geometries.
Energy Technology Data Exchange (ETDEWEB)
Houndjo, M.J.S. [Faculte des Sciences et Techniques de Natitingou, Natitingou (Benin); Institut de Mathematiques et de Sciences Physiques, Porto-Novo (Benin)
2017-09-15
In this paper we study a modified version of unimodular general relativity in the context of f(G), G denoting the Gauss-Bonnet invariant. We focus on Bianchi-type I and Friendmann-Robertson-Walker universes and search for unimodular f(G) models according to the de Sitter and power-law solutions. Assuming unimodular f(G) gravity as a perfect fluid and making use of the slow-roll parameters, the inflationary model has been reconstructed in concordance with the Planck observational data. Moreover, we investigate the realization of the bounce and loop quantum cosmological ekpyrotic paradigms. Assuming suitable and appropriate scale factors, unimodular f(G) models able to reproduce superbounce and ekpyrotic scenarios have been reconstructed. (orig.)
Towards N = 2 SUSY homogeneous quantum cosmology; Einstein-Yang-Mills systems
International Nuclear Information System (INIS)
Donets, E.E.; Tentyukov, M.N.; Tsulaya, M.M.
1998-01-01
The application of N = 2 supersymmetric Quantum Mechanics for the quantization of homogeneous systems coupled with gravity is discussed. Starting with the superfield formulation of N = 2 SUSY sigma-model, Hermitian self-adjoint expressions for quantum Hamiltonians and Lagrangians for any signature of a sigma-model metric are obtained. This approach is then applied to coupled SU (2) Einstein-Yang-Mills (EYM) systems in axially-symmetric Bianchi - I,II,VIII, IX, Kantowski-Sachs and closed Friedmann-Robertson-Walker cosmological models. It is shown that all these models admit the embedding into N = 2 SUSY sigma-model with the explicit expressions for superpotentials, being direct sums of gravitational and Yang-Mills (YM) parts. In addition, YM parts of superpotentials exactly coincide with the corresponding Chern-Simons terms. The spontaneous SUSY breaking, caused by YM instantons in EYM systems is discussed in a number of examples
The group theory of oxidation II: cosets of non-split groups
International Nuclear Information System (INIS)
Keurentjes, Arjan
2003-01-01
The oxidation program given in the first article of this series (see preceding article in this issue) is extended to cover oxidation of 3d sigma model theories on a coset G/H, with G non-compact (but not necessarily split), and H the maximal compact subgroup. We recover the matter content, the equations of motion and Bianchi identities from group lattice and Cartan involution. Satake diagrams provide an elegant tool for the computations, the maximal oxidation dimension, and group disintegration chains can be directly read off. We give a complete list of theories that can be recovered from oxidation of a 3-dimensional coset sigma model on G/H, where G is a simple non-compact group
Christodoulakis, T.; Papadopoulos, G. O.
2002-10-01
Following the spirit of a previous work of ours, we investigate the group of those general coordinate transformations (GCTs) which preserve manifest spatial homogeneity. In contrast to the case of Bianchi type models, here we permit an isometry group of motions G4 = SO(3) ⊗ Tr, where Tr is the translations group, along the radial direction, while SO(3) acts multiply transitively on each hypersurface of simultaneity Σt. The basis 1-forms cannot be invariant under the action of the entire isometry group and hence produce an open Lie algebra. In order for these GCTs to exist and have a nontrivial, well-defined action, certain integrability conditions have to be satisfied; their solutions, exhibiting the maximum expected 'gauge' freedom, can be used to simplify the generic, spatially homogeneous, line element. In this way an alternative proof of the generality of the Kantowski-Sachs (KS) vacuum is given, while its most general, manifestly homogeneous, form is explicitly presented.
On Lovelock analogs of the Riemann tensor
Camanho, Xián O.; Dadhich, Naresh
2016-03-01
It is possible to define an analog of the Riemann tensor for Nth order Lovelock gravity, its characterizing property being that the trace of its Bianchi derivative yields the corresponding analog of the Einstein tensor. Interestingly there exist two parallel but distinct such analogs and the main purpose of this note is to reconcile both formulations. In addition we will introduce a simple tensor identity and use it to show that any pure Lovelock vacuum in odd d=2N+1 dimensions is Lovelock flat, i.e. any vacuum solution of the theory has vanishing Lovelock-Riemann tensor. Further, in the presence of cosmological constant it is the Lovelock-Weyl tensor that vanishes.
Field Equations for Lovelock Gravity: An Alternative Route
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Sumanta Chakraborty
2018-01-01
Full Text Available We present an alternative derivation of the gravitational field equations for Lovelock gravity starting from Newton’s law, which is closer in spirit to the thermodynamic description of gravity. As a warm up exercise, we have explicitly demonstrated that, projecting the Riemann curvature tensor appropriately and taking a cue from Poisson’s equation, Einstein’s equations immediately follow. The above derivation naturally generalizes to Lovelock gravity theories where an appropriate curvature tensor satisfying the symmetries as well as the Bianchi derivative properties of the Riemann tensor has to be used. Interestingly, in the above derivation, the thermodynamic route to gravitational field equations, suited for null hypersurfaces, emerges quiet naturally.
Magnetoelasticity as a gauge field
International Nuclear Information System (INIS)
Zorawski, Marek
1987-01-01
The goal of the paper is to formulate such a system in such a metric space that the geodesics of the space give the movement equations with the influence of electromagnetic forces. Local fields (stress) should be, of course, also included in the movement equations. For the geometrical structure of energy-momentum tensor, the known Einstein equation is adopted. It is also supposed that the Bianchi identities hold. Then in Riemannian space a non-holonomic system of reference is introduced, and the anholonomity object is associated to the electromagnetic field, as a gauge field. The considered theory is the classical one, it is not difficult to extend it to quantum field theory. (Auth.)
International Nuclear Information System (INIS)
Heinzle, J Mark; Uggla, Claes
2009-01-01
We consider the dynamics towards the initial singularity of Bianchi type IX vacuum and orthogonal perfect fluid models with a linear equation of state. Surprisingly few facts are known about the 'Mixmaster' dynamics of these models, while at the same time most of the commonly held beliefs are rather vague. In this paper, we use Mixmaster facts as a base to build an infrastructure that makes it possible to sharpen the main Mixmaster beliefs. We formulate explicit conjectures concerning (i) the past asymptotic states of type IX solutions and (ii) the relevance of the Mixmaster/Kasner map for generic past asymptotic dynamics. The evidence for the conjectures is based on a study of the stochastic properties of this map in conjunction with dynamical systems techniques. We use a dynamical systems formulation, since this approach has so far been the only successful path to obtain theorems, but we also make comparisons with the 'metric' and Hamiltonian 'billiard' approaches.
On asymptotic behavior of anisotropic branes with induced gravity inspired by L(R) term
International Nuclear Information System (INIS)
Heydari-Fard, Malihe
2010-01-01
The DGP brane-world scenario provides the accelerated expansion of the universe at late-time by large-distance modification of general relativity without any need for dark energy. Using the method in reference [33], we investigate the asymptotic behavior of homogeneous and anisotropic cosmologies on a generalization of DGP scenario where the effective theory of gravity induced on the brane is given by a L(R) term. We show that for a constant induced curvature term on the brane all Bianchi models except type IX isotropize, like general relativity, if the effective energy density and E ab term satisfy some energy conditions. Finally, we compare the result of the model with the result of anisotropic DGP branes and general relativity
Multi-year GNSS monitoring of atmospheric IWV over Central and South America for climate studies
Mendoza, Luciano; Bianchi, Clara; Fernández, Laura; Natali, María Paula; Meza, Amalia; Moirano, Juan
2017-04-01
Atmospheric water vapour has been acknowledged as an essential climate variable. Weather prediction and hazard assessment systems benefit from real-time observations, whereas long-term records contribute to climate studies. Nowadays, ground-based GNSS products have become widely employed, complementing satellite observations over the oceans. Although the past decade has seen a significant development of the GNSS infrastructure in Central and South America, its potential for atmospheric water vapour monitoring has not been fully exploited. With this in mind, we have performed a regional, seven-year long and homogeneous analysis, comprising 136 GNSS tracking stations, obtaining high-rate and continuous observations of column integrated water vapour and troposphere zenith total delay (Bianchi et al. 2016). As preliminary application for this data set, we have estimated local water vapour trends, their significance, and their relation with specific climate regimes. We have found evidence of drying at temperate regions in South America, at a rate of about 2% per decade, while a slow moistening of the troposphere over tropical regions is also weakly suggested by our results. Furthermore, we have assessed the regional performance of the empirical model GPT2w to blindly estimate troposphere delays. The model fairly reproduces the observed mean delays, including their annual and semi-annual variations. Nevertheless, a long-term evaluation has shown systematical biases, up to 20 mm, probably inherited form the underling atmospheric reanalysis. Additionally, the complete data set has been made openly available at a scientific repository (doi:10.1594/PANGAEA.858234). References: C. Bianchi, L. Mendoza, L. Fernandez, M. P. Natali, A. Meza, J. F. Moirano, Multi-year GNSS monitoring of atmospheric IWV over Central and South America for climate studies, Ann. Geophys., ISSN 0992-7689, eISSN 1432-0576, 34 (7), 623-639 (doi:10.5194/angeo-34-623-2016).
Anisotropic, nonsingular early universe model leading to a realistic cosmology
International Nuclear Information System (INIS)
Dechant, Pierre-Philippe; Lasenby, Anthony N.; Hobson, Michael P.
2009-01-01
We present a novel cosmological model in which scalar field matter in a biaxial Bianchi IX geometry leads to a nonsingular 'pancaking' solution: the hypersurface volume goes to zero instantaneously at the 'big bang', but all physical quantities, such as curvature invariants and the matter energy density remain finite, and continue smoothly through the big bang. We demonstrate that there exist geodesics extending through the big bang, but that there are also incomplete geodesics that spiral infinitely around a topologically closed spatial dimension at the big bang, rendering it, at worst, a quasiregular singularity. The model is thus reminiscent of the Taub-NUT vacuum solution in that it has biaxial Bianchi IX geometry and its evolution exhibits a dimensionality reduction at a quasiregular singularity; the two models are, however, rather different, as we will show in a future work. Here we concentrate on the cosmological implications of our model and show how the scalar field drives both isotropization and inflation, thus raising the question of whether structure on the largest scales was laid down at a time when the universe was still oblate (as also suggested by [T. S. Pereira, C. Pitrou, and J.-P. Uzan, J. Cosmol. Astropart. Phys. 9 (2007) 6.][C. Pitrou, T. S. Pereira, and J.-P. Uzan, J. Cosmol. Astropart. Phys. 4 (2008) 4.][A. Guemruekcueoglu, C. Contaldi, and M. Peloso, J. Cosmol. Astropart. Phys. 11 (2007) 005.]). We also discuss the stability of our model to small perturbations around biaxiality and draw an analogy with cosmological perturbations. We conclude by presenting a separate, bouncing solution, which generalizes the known bouncing solution in closed FRW universes.
Dynamics of plane-symmetric thin walls in general relativity
International Nuclear Information System (INIS)
Wang, A.
1992-01-01
Plane walls (including plane domain walls) without reflection symmetry are studied in the framework of Einstein's general relativity. Using the distribution theory, all the Einstein field equations and Bianchi identities are split into two groups: one holding in the regions outside of the wall and the other holding at the wall. The Einstein field equations at the wall are found to take a very simple form, and given explicitly in terms of the discontinuities of the metric coefficients and their derivatives. The Bianchi identities at the wall are also given explicitly. Using the latter, the interaction of a plane wall with gravitational waves and some specific matter fields is studied. In particular, it is found that, when a gravitational plane wave passes through a wall, if the wall has no reflection symmetry, the phenomena, such as reflection, stimulation, or absorption, in general, occur. It is also found that, unlike for gravitational waves, a massless scalar wave or an electromagnetic wave continuously passes through a wall without any reflection. The repulsion and attraction of a plane wall are also studied. It is found that the acceleration of an observer who is at rest relative to the wall usually consists of three parts: one is due to the force produced by the wall, the second is due to the force produced by the space-time curvature, which is zero if the wall has reflection symmetry, and the last is due to the accelerated motion of the wall. As a result, a repulsive (attractive) plane wall may not be repulsive (attractive) at all. Finally, the collision and interaction among the walls are studied
Directory of Open Access Journals (Sweden)
Zuleide Hissano Tazima
2010-03-01
Full Text Available Na implantação dos pomares cítricos, é importante o uso de cultivares adaptadas às condições locais, de forma a assegurar boa produtividade. A laranjeira-'Pera' [Citrus sinensis (L. Osbeck] é a cultivar mais importante da citricultura brasileira. O objetivo deste trabalho foi avaliar três clones de laranjeira-'Pera' do Banco Ativo de Germoplasma de Citros (BAG-Citros do Instituto Agronômico do Paraná - IAPAR (acessos I-58 'Pera Vacinada 3', I-59 'Pera Vacinada 4' e I-89 'Pera Bianchi' enxertados sobre o limoeiro-'Cravo' (Citrus limonia Osbeck, nas condições edafoclimáticas de Londrina-PR. As plantas cultivadas no espaçamento 7,0 m x 6,0 m foram conduzidas sem irrigação e avaliadas em relação à produção por planta e às características físico-químicas dos frutos. Os clones de laranjeira I-58 'Pera Vacinada 3', I-59 'Pera Vacinada 4' e I-89 'Pera Bianchi' apresentaram em nove safras, produção média anual por planta de 164,10 kg, 133,96 kg e 131,03 kg, respectivamente. Não houve diferença estatística entre os clones para as variáveis estudadas nas 14 safras. A qualidade dos frutos foi a seguinte: para I-58 'Pera Vacinada 3' e I-59 'Pêra Vacinada 4' e I-89 'Pera Bianchi', respectivamente: 159,6 g, 149,9 g e 150,9 g para massa de fruto; sólidos solúveis de 11,16 ºBrix, 10,98 ºBrix e 10,65 ºBrix; acidez titulável de 1,07%, 1,12% e 0,99%; teor de suco de 50,8%, 52,9% e 49,7%; ratio de 10,6; 10,0 e 10,9 e índice tecnológico de 2,31; 2,34 e 2,15 kg de sólidos solúveis por caixa.The use of adapted cultivars to the local conditions is important when establishing citrus orchards to ensure good yield. The sweet orange 'Pêra' [Citrus sinensis (L. Osbeck] is the most important cultivar to the Brazilian citriculture. The aim of this study was to evaluate three clones of 'Pêra' orange trees from the Citrus Active Germplasm Bank of the Instituto Agronômico do Paraná - IAPAR ('Pêra Vacinada 3' accession I-58, 'Pêra
Ranked retrieval of Computational Biology models.
Henkel, Ron; Endler, Lukas; Peters, Andre; Le Novère, Nicolas; Waltemath, Dagmar
2010-08-11
The study of biological systems demands computational support. If targeting a biological problem, the reuse of existing computational models can save time and effort. Deciding for potentially suitable models, however, becomes more challenging with the increasing number of computational models available, and even more when considering the models' growing complexity. Firstly, among a set of potential model candidates it is difficult to decide for the model that best suits ones needs. Secondly, it is hard to grasp the nature of an unknown model listed in a search result set, and to judge how well it fits for the particular problem one has in mind. Here we present an improved search approach for computational models of biological processes. It is based on existing retrieval and ranking methods from Information Retrieval. The approach incorporates annotations suggested by MIRIAM, and additional meta-information. It is now part of the search engine of BioModels Database, a standard repository for computational models. The introduced concept and implementation are, to our knowledge, the first application of Information Retrieval techniques on model search in Computational Systems Biology. Using the example of BioModels Database, it was shown that the approach is feasible and extends the current possibilities to search for relevant models. The advantages of our system over existing solutions are that we incorporate a rich set of meta-information, and that we provide the user with a relevance ranking of the models found for a query. Better search capabilities in model databases are expected to have a positive effect on the reuse of existing models.
Fernandez I Marti, Angel; Saski, Christopher A; Manganaris, George A; Gasic, Ksenija; Crisosto, Carlos H
2018-01-01
It has recently been described that the Japanese plum "Santa Rosa" bud sport series contains variations in ripening pattern: climacteric, suppressed-climacteric and non-climacteric types. This provides an interesting model to study the role of ethylene and other key mechanisms governing fruit ripening, softening and senescence. The aim of the current study was to investigate such differences at the genomic level, using this series of plum bud sports, with special reference to genes involved in ethylene biosynthesis, signal transduction, and sugar metabolism. Genomic DNA, isolated from leaf samples of six Japanese plum cultivars ("Santa Rosa", "July Santa Rosa", "Late Santa Rosa", "Sweet Miriam", "Roysum", and "Casselman"), was used to construct paired-end standard Illumina libraries. Sequences were aligned to the Prunus persica genome, and genomic variations (SNPs, INDELS, and CNV's) were investigated. Results determined 12 potential candidate genes with significant copy number variation (CNV), being associated with ethylene perception and signal transduction components. Additionally, the Maximum Likelihood (ML) phylogenetic tree showed two sorbitol dehydrogenase genes grouping into a distinct clade, indicating that this natural group is well-defined and presents high sequence identity among its members. In contrast, the ethylene group, which includes ACO1, ACS1, ACS4, ACS5, CTR1, ERF1, ERF3, and ethylene-receptor genes, was widely distributed and clustered into 10 different groups. Thus, ACS, ERF, and sorbitol dehydrogenase proteins potentially share a common ancestor for different plant genomes, while the expansion rate may be related to ancestral expansion rather than species-specific events. Based on the distribution of the clades, we suggest that gene function diversification for the ripening pathway occurred prior to family extension. We herein report all the frameshift mutations in genes involved in sugar transport and ethylene biosynthesis detected as well
Directory of Open Access Journals (Sweden)
Abdalla A
2017-03-01
Full Text Available Abuelmagd Abdalla, Niamh Byrne, Richard Conway, Thomas Walsh, Geraldine Mannion, Michael Hanly, Miriam O’Sullivan, Ann Maria Curran, John J Carey Department of Rheumatology, Galway University Hospitals, Galway, Ireland Purpose: To evaluate the efficacy and safety of the biosimilar infliximab in adult patients with inflammatory arthritis switched from reference product in our center. Patients and methods: In April 2014, patients attending our rheumatology service for infliximab infusions were switched from reference product to the biosimilar infliximab following consent and hospital approval. Results: Around 34 patients with inflammatory arthritis were switched from reference product to biosimilar infliximab in 2014: 50% female, mean age 55 years (standard deviation=12.9, mean disease duration 14.79 years (9.7, median duration on infliximab 57 months, and two-thirds on oral disease-modifying antirheumatic drugs. There was no difference in efficacy or safety in the first 6 months of therapy. By the end of 2015, the mean follow-up on biosimilar infliximab was 15.8 (standard deviation=6.3 months. Our results showed no significant difference in Health Assessment Questionnaire score, patient global assessment of disease activity, number of disease flares, or the medication dose between the originator and the biosimilar infliximab. However, reported pain and C-reactive protein values were significantly higher during the longer follow-up period (p=0.043, 0.001 respectively. There was no significant difference in the number of adverse events or infusion reactions during follow-up periods. Only five (14.7% patients discontinued the biosimilar infliximab. Conclusion: Our patients experienced similar efficacy and safety for managing their arthritis with the biosimilar infliximab as the reference product infliximab, but at a much lower cost. Keywords: biologic therapy, rheumatic diseases, biosimilar exchange, infliximab, adult
Multiple sclerosis: patients’ information sources and needs on disease symptoms and management
Directory of Open Access Journals (Sweden)
Albert I Matti
2010-06-01
Full Text Available Albert I Matti1, Helen McCarl2, Pamela Klaer2, Miriam C Keane1, Celia S Chen11Department of Ophthalmology, Flinders Medical Centre and Flinders University, Bedford Park, SA, Australia; 2The Multiple Sclerosis Society of South Australia and Northern Territory, Klemzig, SA, AustraliaObjective: To investigate the current information sources of patients with multiple sclerosis (MS in the early stages of their disease and to identify patients’ preferred source of information. The relative amounts of information from the different sources were also compared.Methods: Participants at a newly diagnosed information session organized by the Multiple Sclerosis Society of South Australia were invited to complete a questionnaire. Participants were asked to rate on a visual analog scale how much information they had received about MS and optic neuritis from different information sources and how much information they would like to receive from each of the sources.Results: A close to ideal amount of information is being provided by the MS society and MS specialist nurses. There is a clear deficit between what information patients are currently receiving and the amount of information they actually want from various sources. Patients wish to receive significantly more information from treating general practitioners, eye specialists, neurologists, and education sessions. Patients have identified less than adequate information received on optic neuritis from all sources.Conclusion: This study noted a clear information deficit regarding MS from all sources. This information deficit is more pronounced in relation to optic neuritis and needs to be addressed in the future.Practice implications: More patient information and counselling needs to be provided to MS patients even at early stages of their disease, especially in relation to management of disease relapse.Keywords: information sources, information needs, MS patients, optic neuritis
Ashford, Miriam T; Olander, Ellinor K; Rowe, Heather; Fisher, Jane Rw; Ayers, Susan
2018-04-20
Postpartum anxiety can have adverse effects on the mother and child if left untreated. Time constraints and stigma are common barriers to postpartum treatment. Web-based treatments offer potential flexibility and anonymity. What Am I Worried About (WaWa) is a self-guided treatment based on cognitive-behavioral and mindfulness principles for women experiencing postpartum anxiety. WaWa was developed in Australia and consists of 9 modules with optional weekly telephone support. WaWa was adapted to a Web-based version for use in England (Internet-based What Am I Worried About, iWaWa). This study aimed to investigate the feasibility (engagement and usability) and acceptability (usefulness, satisfaction, and helpfulness) of iWaWa among English postpartum women with anxiety. Postpartum (parenting styles. Despite interest in iWaWa, the results suggest that both the study and iWaWa were not feasible in the current format. However, this first trial provides useful evidence about treatment format and content preferences that can inform iWaWa's future development, as well as research and development of Web-based postpartum anxiety treatments, in general, to optimize adherence. ClinicalTrials.gov NCT02434406; https://clinicaltrials.gov/ct2/show/NCT02434406 (Archived by WebCite at http://www.webcitation.org/6xTq7Bwmd). ©Miriam T Ashford, Ellinor K Olander, Heather Rowe, Jane RW Fisher, Susan Ayers. Originally published in JMIR Mental Health (http://mental.jmir.org), 20.04.2018.
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Christopher L Edwards
2007-01-01
Full Text Available Christopher L Edwards1, Renee Dunn Raynor1, Miriam Feliu1, Camela McDougald1, Stephanie Johnson2, Donald Schmechel3, Mary Wood1, Gary G Bennett4, Patrick Saurona5, Melanie Bonner1, Chante’ Wellington1, Laura M DeCastro6, Elaine Whitworth6, Mary Abrams6, Patrick Logue1, Lekisha Edwards1, Salutario Martinez7, Keith E Whitfield81Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC, USA; 2American Psychological Association, Science Directorate, Washington, DC, USA; 3Department of Medicine, Division of Neurology, Duke University Medical Center, Durham, NC, USA; 4Department of Society, Human Development, and Health, Harvard School of Public Health, Boston, MA, USA; 5Taub Institute For Research on Alzheimer’s Disease and The Aging Brain, Columbia University, New York, NY, USA; 6Department of Medicine, Division of Hematology, Duke University Medical Center, Durham, NC, USA; 7Department of Radiology, Duke University Medical Center, Durham, NC, USA; 8Duke University, Durham, NC, USAAbstract: Traditionally, neuropsychological deficits due to Sickle Cell Disease (SCD have been understudied in adults. We have begun to suspect, however, that symptomatic and asymptomatic Cerebrovascular Events (CVE may account for an alarming number of deficits in this population. In the current brief review, we critically evaluated the pediatric and adult literatures on the neurocognitive effects of SCD. We highlighted the studies that have been published on this topic and posit that early detection of CVE via neurocognitive testing, neuropsychiatric evaluations, and neuroimaging may significantly reduce adult cognitive and functional morbidities.Keywords: cerebral vascular event, neuropsychological assessment, sickle cell disease, neuroimaging
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Deborah L Jones
2010-05-01
Full Text Available Deborah L Jones1, Olga Villar-Loubet1, Chipepo Kankasa2, Ndashi Chitalu2, Miriam Mumbi2, Stephen M Weiss11Department of Psychiatry and Behavioral Sciences, University of Miami Miller School of Medicine, Miami, FL, USA; 2Department of Paediatrics, University of Zambia School of Medicine, Lusaka, ZambiaAbstract: With the advent of antiretroviral therapy, remarkable progress has been made in the reduction of morbidity and mortality associated with the human immunodeficiency virus (HIV. As a result, in both the developed and developing world, reproductive decision-making and family planning has re-emerged as an important health issue among HIV-seroconcordant and -serodiscordant couples. This study sought to explore contraceptive attitudes and practices among HIV-seropositive and -serodiscordant couples in the US and Zambia and to compare contraceptive decision-making between seroconcordant and discordant couples. Study results suggest that while most participants expressed a willingness to use protection to prevent pregnancy, the majority were not using protection consistently. Similarly, among seropositive younger men in both the US and Zambia, more men expressed a desire to have children than women of either serostatus group. Study outcomes also suggest that male and female condom use to reduce HIV transmission within couples is limited. Thus, as males are largely the sexual decision makers regarding condom use, women’s attitudes or plans regarding child bearing may be eclipsed by those of their male partners, and recent reductions in provision of female condoms in the developing world may further reduce women’s options to protect themselves and prevent pregnancy. Education and counseling on vertical and horizontal transmission of HIV among both seropositive and serodiscordant couples should be an element of family planning efforts. Conversely, family planning should be a critical element of HIV counseling and testing strategies to
Directory of Open Access Journals (Sweden)
Allahverdiyev AM
2011-11-01
Full Text Available Adil M Allahverdiyev1, Emrah Sefik Abamor1, Malahat Bagirova1, Cem B Ustundag2, Cengiz Kaya2, Figen Kaya2, Miriam Rafailovich3 1Department of Bioengineering; 2Department of Metallurgical and Materials Engineering, Yildiz Technical University, Esenler, Istanbul, Turkey; 3Department of Materials Science and Engineering, Stony Brook University, Stony Brook, NY, USA Abstract: Leishmaniasis is a protozoan vector-borne disease and is one of the biggest health problems of the world. Antileishmanial drugs have disadvantages such as toxicity and the recent development of resistance. One of the best-known mechanisms of the antibacterial effects of silver nanoparticles (Ag-NPs is the production of reactive oxygen species to which Leishmania parasites are very sensitive. So far no information about the effects of Ag-NPs on Leishmania tropica parasites, the causative agent of leishmaniasis, exists in the literature. The aim of this study was to investigate the effects of Ag-NPs on biological parameters of L. tropica such as morphology, metabolic activity, proliferation, infectivity, and survival in host cells, in vitro. Consequently, parasite morphology and infectivity were impaired in comparison with the control. Also, enhanced effects of Ag-NPs were demonstrated on the morphology and infectivity of parasites under ultraviolet (UV light. Ag-NPs demonstrated significant antileishmanial effects by inhibiting the proliferation and metabolic activity of promastigotes by 1.5- to threefold, respectively, in the dark, and 2- to 6.5-fold, respectively, under UV light. Of note, Ag-NPs inhibited the survival of amastigotes in host cells, and this effect was more significant in the presence of UV light. Thus, for the first time the antileishmanial effects of Ag-NPs on L. tropica parasites were demonstrated along with the enhanced antimicrobial activity of Ag-NPs under UV light. Determination of the antileishmanial effects of Ag-NPs is very important for the further
Directory of Open Access Journals (Sweden)
Hartman SJ
2011-08-01
Full Text Available Sheri J Hartman1, Shira I Dunsiger1, Paul B Jacobsen21Centers for Behavioral and Preventive Medicine, The Miriam Hospital and W Alpert Medical School of Brown University, Providence, RI; 2Department of Health Outcomes and Behavior, H Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USAAbstract: This study examined the relationship of psychosocial factors to health-promoting behaviors in sisters of breast cancer patients. One hundred and twenty sisters of breast cancer patients completed questionnaires assessing response efficacy of mammography screenings, physical activity, and fruit and vegetable consumption on decreasing breast cancer risk, breast cancer worry, involvement in their sister’s cancer care, mammography screenings, physical activity, and fruit and vegetable consumption. Results indicate that greater perceived effectiveness for mammograms was associated with a 67% increase in odds of yearly mammograms. Greater involvement in the patient’s care was associated with a 7% decrease in odds of yearly mammograms. Greater perceived effectiveness for physical activity was significantly related to greater physical activity. There was a trend for greater perceived effectiveness for fruits and vegetables to be associated with consuming more fruits and vegetables. Breast cancer worry was not significantly associated with the outcomes. While perceived effectiveness for a specific health behavior in reducing breast cancer risk was consistently related to engaging in that health behavior, women reported significantly lower perceived effectiveness for physical activity and fruits and vegetables than for mammograms. Making women aware of the health benefits of these behaviors may be important in promoting changes.Keywords: breast cancer risk, mammograms, physical activity, diet, perceived effectiveness
Salmoirago-Blotcher, Elena; DeCosta, Julie; Harris, Kristie; Breault, Christopher; Dunsiger, Shira; Santos, Claudia; Snyder, Peter
2018-05-01
Despite increasing evidence that aerobic exercise and cognitive training improve cognitive function among patients with cognitive impairment and dementia, few studies have focused on the effect of a combination of these approaches. This study will explore whether combining aerobic training (AT) with mindfulness training (MT), an intervention promoting the moment-to-moment awareness of physical sensations, affective states, and thoughts, improves cognitive function in individuals at risk of dementia. The primary objective is to determine the feasibility and acceptability of the intervention(s). The secondary objective is to obtain estimates of effect sizes on cognitive function and on possible mediators. Forty participants with at least 2 risk factors for dementia will be randomized (2 × 2 factorial design) to either AT (3 sessions/week for 12 weeks), MT (1 session/week for 8 weeks), both, or usual care. Assessments of cognitive function (attention, executive function, episodic, and working memory); physical activity (accelerometry), aerobic capacity (6-minute walk test), waist-to-hip ratio, blood pressure, social support (Multidimensional Scale of Perceived Social Support), depression (Hospital Anxiety and Depression Scale), and mindfulness (Five Facets of Mindfulness) will be conducted at baseline, end of treatment, and 6-months postbaseline. Rates of retention, attendance, and program satisfaction will be calculated for each of the 4 groups to determine the feasibility and acceptability of each intervention. This study has full ethical approval by The Miriam Hospital Institutional Review Board and adheres to the Standard Protocol Items: Recommendations for Interventional Trials reporting recommendations. If results from this exploratory, proof-of-concept study support our hypotheses, we will conduct a large randomized controlled trial (RCT) to determine the efficacy of combined MT and AT in improving cognitive function in individuals at risk of dementia
Drug use trajectory patterns among older drug users
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Tyndall B
2011-05-01
Full Text Available Miriam Boeri, Thor Whalen, Benjamin Tyndall, Ellen BallardKennesaw State University, Department of Sociology and Criminal Justice, Kennesaw GA, USAAbstract: To better understand patterns of drug use trajectories over time, it is essential to have standard measures of change. Our goal here is to introduce measures we developed to quantify change in drug use behaviors. A secondary goal is to provide effective visualizations of these trajectories for applied use. We analyzed data from a sample of 92 older drug users (ages 45 to 65 to identify transition patterns in drug use trajectories across the life course. Data were collected for every year since birth using a mixed methods design. The community-drawn sample of active and former users were 40% female, 50% African American, and 60% reporting some college or greater. Their life histories provided retrospective longitudinal data on the diversity of paths taken throughout the life course and changes in drug use patterns that occurred over time. Bayesian analysis was used to model drug trajectories displayed by innovative computer graphics. The mathematical techniques and visualizations presented here provide the foundation for future models using Bayesian analysis. In this paper we introduce the concepts of transition counts, transition rates and relapse/remission rates, and we describe how these measures can help us better understand drug use trajectories. Depicted through these visual tools, measurements of discontinuous patterns provide a succinct view of individual drug use trajectories. The measures we use on drug use data will be further developed to incorporate contextual influences on the drug trajectory and build predictive models that inform rehabilitation efforts for drug users. Although the measures developed here were conceived to better examine drug use trajectories, the applications of these measures can be used with other longitudinal datasets.Keywords: drug use, trajectory patterns
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Feder D
2017-10-01
Full Text Available David Feder,1 Miriam Eva Koch,1 Beniamino Palmieri,2 Fernando Luiz Affonso Fonseca,1 Alzira Alves de Siqueira Carvalho3 1Pharmacology Department, Faculdade de Medicina do ABC, Santo André, São Paulo, Brazil; 2Department of General Surgery and Surgical Specialties, University of Modena and Reggio Emilia Medical School, Surgical Clinic, Modena, Italy; 3Neuroscience Department, Faculdade de Medicina do ABC, Santo André, São Paulo, Brazil Abstract: Duchenne muscular dystrophy is the most frequent lethal genetic disease. Several clinical trials have established both the beneficial effect of steroids in Duchenne muscular dystrophy and the well-known risk of side effects associated with their daily use. For many years it has been known that steroids associated with ambulation loss lead to obesity and also damage the bone structure resulting in the bone density reduction and increased incidence of bone fractures and fat embolism syndrome, an underdiagnosed complication after fractures. Fat embolism syndrome is characterized by consciousness disturbance, respiratory failure and skin rashes. The use of steroids in Duchenne muscular dystrophy may result in vertebral fractures, even without previous trauma. Approximately 25% of patients with Duchenne muscular dystrophy have a long bone fracture, and 1% to 22% of fractures have a chance to develop fat embolism syndrome. As the patients with Duchenne muscular dystrophy have progressive cardiac and respiratory muscle dysfunction, the fat embolism may be unnoticed clinically and may result in increased risk of death and major complications. Different treatments and prevention measures of fat embolism have been proposed; however, so far, there is no efficient therapy. The prevention, early diagnosis and adequate symptomatic treatment are of paramount importance. The fat embolism syndrome should always be considered in patients with Duchenne muscular dystrophy presenting with fractures, or an unexplained and
Generic Argillite/Shale Disposal Reference Case
Energy Technology Data Exchange (ETDEWEB)
Zheng, Liange; Colon, Carlos Jové; Bianchi, Marco; Birkholzer, Jens
2014-08-08
Radioactive waste disposal in a deep subsurface repository hosted in clay/shale/argillite is a subject of widespread interest given the desirable isolation properties, geochemically reduced conditions, and widespread geologic occurrence of this rock type (Hansen 2010; Bianchi et al. 2013). Bianchi et al. (2013) provides a description of diffusion in a clay-hosted repository based on single-phase flow and full saturation using parametric data from documented studies in Europe (e.g., ANDRA 2005). The predominance of diffusive transport and sorption phenomena in this clay media are key attributes to impede radionuclide mobility making clay rock formations target sites for disposal of high-level radioactive waste. The reports by Hansen et al. (2010) and those from numerous studies in clay-hosted underground research laboratories (URLs) in Belgium, France and Switzerland outline the extensive scientific knowledge obtained to assess long-term clay/shale/argillite repository isolation performance of nuclear waste. In the past several years under the UFDC, various kinds of models have been developed for argillite repository to demonstrate the model capability, understand the spatial and temporal alteration of the repository, and evaluate different scenarios. These models include the coupled Thermal-Hydrological-Mechanical (THM) and Thermal-Hydrological-Mechanical-Chemical (THMC) models (e.g. Liu et al. 2013; Rutqvist et al. 2014a, Zheng et al. 2014a) that focus on THMC processes in the Engineered Barrier System (EBS) bentonite and argillite host hock, the large scale hydrogeologic model (Bianchi et al. 2014) that investigates the hydraulic connection between an emplacement drift and surrounding hydrogeological units, and Disposal Systems Evaluation Framework (DSEF) models (Greenberg et al. 2013) that evaluate thermal evolution in the host rock approximated as a thermal conduction process to facilitate the analysis of design options. However, the assumptions and the
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Gelena Lucinéia Gomes da Silva Versa
2012-06-01
Full Text Available Estudo descritivo, transversal, que teve como objetivo avaliar o nível de estresse de enfermeiros intensivistas do período noturno. Aplicou-se a Escala Bianchi de Stress em 26 (100% enfermeiros de cinco hospitais. Na análise dos dados, utilizou-se o teste Qui-quadrado de Pearson e constatou-se que o estresse entre enfermeiros da instituição pública (3,36 pontos e privada (3,02 pontos se classificou em nível mediano e que não houve relevância estatística (p=0,90 à sua ocorrência, conforme o tipo de instituição. Os domínios que mais contribuíram ao acontecimento de estresse foram: condições de trabalho (labor noturno, setor crítico e fechado, gravidade do paciente e atividades gerenciais associadas à assistência direta. Concluiu-se que o ambiente laboral se associou positivamente ao estresse em enfermeiros do turno noturno e que o seu aparecimento e efeitos podem ser minimizados por meio de melhorias na estrutura e na organização dos locais onde atuam.Estudio descriptivo, transversal, tuvo como objetivo evaluar el nivel de estrés de los enfermeros intensivistas, del período nocturno. Se aplicó escala de estrés Bianchi en 26 (100% enfermeros de cinco hospitales. Para análisis de datos, se utilizó el Chi-cuadrado de Pearson y resultó: estrés entre enfermeros de institución pública (3,36 puntos y privada (3,02 puntos se clasificó a nivel medio y no hubo significación estadística (p = 0,90 para el estrés en función del tipo de institución. Las áreas que más contribuyeron al acontecimiento de estrés fueron: condiciones de trabajo (nocturno, sector crítico y cerrado; gravedad del paciente; actividades de gestión asociadas a la atención. Se concluyó que el lugar de trabajo se asoció positivamente al estrés en los enfermeros que trabajan en el período nocturno y que, su aparición y efectos pueden ser minimizados por medio de mejoras en la estructura y organización de los locales donde act
New particle formation in the free troposphere: from the Alps to the Everest Base Camp.
Bianchi, F.; Junninen, H.; Kontkanen, J.; Marinoni, A.; Bonasoni, P.; Sellegri, K.; Laj, P.; Dommen, J.; Worsnop, D. R.; Baltensperger, U.
2016-12-01
Atmospheric aerosols can affect the climate by absorbing or scattering incoming radiation and also by acting as cloud condensation nuclei (CCN). A recent study estimates that the major fraction of CCN comes from gas to particle conversion (Merikanto et al., 2009). During the last decade, several nucleation studies have been published based on field observations mainly in the planetary boundary layer. Therefore, we have only little information about the free tropospheric case. The aim of these studies is to understand what species contribute to new particle formation at high altitude. In order to characterize NPF processes, advanced instrumentation was deployed at the Swiss station Jungfraujoch (3580 m asl - Bianchi et al., 2016) and at the Himalayan Nepal Climate Observatory Pyramid site, not far from Everest base camp (5079 m asl). Previous studies have already showed that at both of these locations NPF takes place frequently. However, no chemical information of the vapours was retrieved. At the Nepal Observatory, we deployed an atmospheric pressure interface time-of-flight mass spectrometer (APi-TOF), a particle size magnifier (PSM) and a neutral cluster and air ion spectrometer (NAIS). The APi-TOF measured the chemical composition of either the positive or negative ions during the nucleation events and when equipped with a chemical ionization source it provided information on the chemical composition of the neutral species. Figure 1 shows the first APi-TOF mass spectrum running in negative mode recorded above 5000 m asl during a nucleation event. The main ions that have been identified so far are all deprotonated acids: sulfuric acid, nitric acid, malonic acid, methanesulfonic acid and iodic acid. Larger ions are formed by different combinations of these acids (i.e. H2SO4°HSO4-, CH3SO3H°HSO4-, etc.). We will present a detailed analysis of the particle evolution during NPF and also the chemical composition of the small clusters measured with these advanced mass
Central Stars of Planetary Nebulae in the SMC
Bianchi, Luciana
2004-01-01
In FUSE cycle 3's program C056 we studied four Central Stars of Planetary Nebulae (CSPN) in the Small Magellanic Could. All FUSE observations have been successfully completed and have been reduced and analyzed. The observation of one object (SMP SMC 5) appeared to be off-target and no useful stellar flux was gathered. For another observation (SMP SMC 1) the voltage problems resulted in the loss of data from one of the SiC detectors, but we were still able to analyze the remaining data. The analysis and the results are summarized below. The FUSE data were reduced using the latest available version of the FUSE calibration pipeline (CALFUSE v2.4). The flux of these SMC post-AGB objects is at the threshold of FUSE S sensitivity, and the targets required many orbit-long exposures, each of which typically had low (target) count-rates. The background subtraction required special care during the reduction, and was done in a similar manner to our FUSE cycle 2 BOO1 objects. The resulting calibrated data from the different channels were compared in the overlapping regions for consistency. The final combined, extracted spectra of each target was then modeled to determine the stellar and nebular parameters. The FUSE spectra, combined with archival HST spectra, have been analyzed using stellar atmospheres codes such as TLUSTY and CMFGEN to derive photospheric and wind parameters of the central stars, and with ISM models to determine the amount and temperature of the surrounding atomic and molecular hydrogen. We have combined these results with those of our cycle 4 (D034) program (CSPN of the LMC) in Herald & Bianchi 2004a (paper in preparation, will be submitted to ApJ in June 2004). Two of the three SMC objects analyzed were found to have significantly lower stellar temperatures than had been predicted using nebular photoionization models, indicating either a hotter ionizing companion or the existence of strong shocks in the nebular environment. The analysis also revealed that
The cosmological constant, branes and non-geometry
International Nuclear Information System (INIS)
Gautason, Fridhrik Freyr
2014-01-01
In this thesis we derive an equation for the classical cosmological constant in general string compactifications by employing scaling symmetries present in string theory. We find that in heterotic string theory, a perturbatively small, but non-vanishing, cosmological constant is impossible unless non-perturbative and/or string loop corrections are taken into account. In type II string theory we show that the classical cosmological constant is given by a sum of two terms, the source actions evaluated on-shell, and a certain combination of non-vanishing fluxes integrated over spacetime. In many cases we can express the classical cosmological constant in terms of only the source contributions by exploiting two scaling symmetries. This result can be used in two ways. First one can simply predict the classical cosmological constant in a given setup without solving all equations of motion. A second application is to give constraints on the near brane behavior of supergravity fields when the cosmological constant is known. In particular we motivate that energy densities of some fields diverge in the well-known KKLT scenario for de Sitter solutions in type IIB string theory. More precisely, we show, using our results and minimal assumptions, that energy densities of the three-form fluxes diverge in the near-source region of internal space. This divergence is unusual, since these fields do not directly couple to the source, and has been interpreted as a hint of instability of the solution. In the last chapter of the thesis we discuss the worldvolume actions of exotic five-branes. Using a specific chain of T- and S-dualities in a spacetime with two circular isometries, we derive the DBI and WZ actions of the so-called 5 2 2 - and 5 2 3 -brane. These actions describe the dynamics of the branes as well as their couplings to the ten-dimensional gauge potentials. We propose a modified Bianchi identity for the non-geometric Q-flux due to one of the branes. Q-flux often appears
Effect of peritoneal dialysis fluid containing osmo-metabolic agents on human endothelial cells
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Bonomini M
2016-11-01
Full Text Available Mario Bonomini,1,2 Sara Di Silvestre,3,4 Pamela Di Tomo,3,4 Natalia Di Pietro,2,4 Domitilla Mandatori,3,4 Lorenzo Di Liberato,1 Vittorio Sirolli,1,2 Francesco Chiarelli,2,4 Cesare Indiveri,5 Assunta Pandolfi,3,4 Arduino Arduini6 1Unit of Nephrology and Dialysis, 2Department of Medicine and Aging Sciences, 3Department of Medical, Oral and Biotechnological Sciences, 4Aging Research Center and Translational Medicine, CeSI-MeT, University “G. d’Annunzio”, Chieti-Pescara, 5Department DiBEST (Biologia, Ecologia, Scienze della Terra, Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende CS, Italy; 6CoreQuest, Manno, Switzerland Background: The use of glucose as the only osmotic agent in peritoneal dialysis (PD solutions (PDSs is believed to exert local (peritoneal and systemic detrimental actions, particularly in diabetic PD patients. To improve peritoneal biocompatibility, we have developed more biocompatible PDSs containing xylitol and carnitine along with significantly less amounts of glucose and have tested them in cultured Human Vein Endothelial Cells (HUVECs obtained from the umbilical cords of healthy (C and gestational diabetic (GD mothers. Methods: Primary C- and GD-HUVECs were treated for 72 hours with our PDSs (xylitol 0.7% and 1.5%, whereas carnitine and glucose were fixed at 0.02% and 0.5%, respectively and two glucose-based PDSs (glucose 1.36% or 2.27%. We examined their effects on endothelial cell proliferation (cell count, viability (3-(4,5-dimethylthiazolyl-2-2,5-diphenyltetrazolium bromide assay, intracellular nitro-oxidative stress (peroxynitrite levels, Vascular Cell Adhesion Molecule-1 and Intercellular Adhesion Molecule-1 membrane exposure (flow cytometry, and HUVEC-monocyte interactions (U937 adhesion assay. Results: Compared to glucose-based PDSs, our in vitro studies demonstrated that the tested PDSs did not change the proliferative potential both in C- and GD-HUVECs. Moreover, our
Reche, Cristina; Moreno, Teresa; Viana, Mar; Querol, Xavier; Alastuey, Andrés.; Jimenez, Jose L.; Pandolfi, Marco; Amato, Fulvio; Pérez, Noemí; Moreno, Natalia
2010-05-01
The 2009 DAURE Aerosol Campaign (23-February-2009 to 27-March-2009 and 1-July to 31-July) (see Presentation: Pandolfi et al., section AS3.2) had the objective of characterising the main sources and chemical processes controlling atmospheric pollution due to particulate matter in the Mediterranean site of Barcelona (Spain). An urban and a rural background site were selected in order to describe both kinds of pollution setting. Several parameters were taken into consideration, including the variability of mass concentration in the coarse and fine fractions, particle number, amount of black carbon and the concentration of gaseous pollutants (SO2, H2S, NO, NO2, CO, O3) present. Comparisons between the chemical composition of ambient atmospheric particles during day versus night were made using twelve-hour PM samples. The data shown here are focused on results obtained for the urban site where two main atmospheric settings were distinguishable in winter, namely Atlantic advection versus local air mass recirculation. During the warmer months Saharan dust intrusions added a third important influence on PM background. The data demonstrate that superimposed upon these background influences on city air quality are important local contributions from road traffic, construction-demolition works and shipping. There is also a major local contribution of secondary aerosols, with elevated number of particles occurring at midday (and especially in summer) when nucleation processes are favoured by photochemistry. Concentrations of SO2 peak at different times to the other gaseous pollutants due to regular daytime onshore south-easterly breezes bringing harbour emissions into the city. Road traffic in Barcelona also has a great impact on air quality, as demonstrated by daily and weekly cycles of gaseous pollutants, black carbon and the finer fraction of PM, with peaks being coincident with traffic rush-hours (8-10h and 20-22h), levels of pollution increasing from Monday to Friday, and
Evolution of cyclic mixmaster universes with noncomoving radiation
Ganguly, Chandrima; Barrow, John D.
2017-12-01
We study a model of a cyclic, spatially homogeneous, anisotropic, "mixmaster" universe of Bianchi type IX, containing a radiation field with noncomoving ("tilted" with respect to the tetrad frame of reference) velocities and vorticity. We employ a combination of numerical and approximate analytic methods to investigate the consequences of the second law of thermodynamics on the evolution. We model a smooth cycle-to-cycle evolution of the mixmaster universe, bouncing at a finite minimum, by the device of adding a comoving "ghost" field with negative energy density. In the absence of a cosmological constant, an increase in entropy, injected at the start of each cycle, causes an increase in the volume maxima, increasing approach to flatness, falling velocities and vorticities, and growing anisotropy at the expansion maxima of successive cycles. We find that the velocities oscillate rapidly as they evolve and change logarithmically in time relative to the expansion volume. When the conservation of momentum and angular momentum constraints are imposed, the spatial components of these velocities fall to smaller values when the entropy density increases, and vice versa. Isotropization is found to occur when a positive cosmological constant is added because the sequence of oscillations ends and the dynamics expand forever, evolving towards a quasi-de Sitter asymptote with constant velocity amplitudes. The case of a single cycle of evolution with a negative cosmological constant added is also studied.
Stability of the Kasner universe in f (T ) gravity
Paliathanasis, Andronikos; Said, Jackson Levi; Barrow, John D.
2018-02-01
f (T ) gravity theory offers an alternative context in which to consider gravitational interactions where torsion, rather than curvature, is the mechanism by which gravitation is communicated. We investigate the stability of the Kasner solution with several forms of the arbitrary Lagrangian function examined within the f (T ) context. This is a Bianchi type-I vacuum solution with anisotropic expansion factors. In the f (T ) gravity setting, the solution must conform to a set of conditions in order to continue to be a vacuum solution of the generalized field equations. With this solution in hand, the perturbed field equations are determined for power-law and exponential forms of the f (T ) function. We find that the point which describes the Kasner solution is a saddle point which means that the singular solution is unstable. However, we find the de Sitter universe is a late-time attractor. In general relativity, the cosmological constant drives the isotropization of the spacetime while in this setting the extra f (T ) contributions now provide this impetus.
International Nuclear Information System (INIS)
Mueller, Daniel; Vitenti, Sandro D. P.
2006-01-01
It is believed that soon after the Planck era, space-time should have a semiclassical nature. According to this, the escape from the general relativity theory is unavoidable. Two geometric counterterms are needed to regularize the divergences which come from the expected value. These counterterms are responsible for a higher derivative metric gravitation. Starobinsky's idea was that these higher derivatives could mimic a cosmological constant. In this work numerical solutions are considered for general Bianchi I anisotropic space-times in this higher derivative theory. The approach is 'experimental' in the sense that there is no attempt for an analytical investigation of the results. It is shown that for zero cosmological constant Λ=0, there are sets of initial conditions which form basins of attraction that asymptote Minkowski space. The complement of this set of initial conditions form basins which are attracted to some singular solutions. It is also shown, for a cosmological constant Λ>0, that there are basins of attraction to a specific de Sitter solution. This result is consistent with Starobinsky's initial idea. The complement of this set also forms basins that are attracted to some type of singular solution. Because the singularity is characterized by curvature scalars, it must be stressed that the basin structure obtained is a topological invariant, i.e., coordinate independent
Field theoretic approach to structure formation in an anisotropic medium
International Nuclear Information System (INIS)
Joy, Minu; Kuriakose, V.C.
2003-01-01
Considering a real scalar field distribution which is assumed to be locally anisotropic and coupled to a Bianchi type-I background spacetime, the energy density and pressure associated with the anisotropic matter field distribution are evaluated. The vanishing of the expectation values of the nondiagonal components of T μν allows us to treat the scalar field in complete analogy with the distribution of fluid. The primeval density perturbations produced by the vacuum fluctuations of the scalar field are considered and the Jeans criterion for structure formation is obtained. The metric and matter field perturbations are considered and it is found that for the present anisotropic case the perturbations of the pressure in the radial and tangential directions are different. The Jeans instability is discussed and the Jeans wave number for the present case is evaluated. It is found that for the anisotropic case the Jeans length depends on the velocity of the fluctuations in the radial and transverse directions and thus on the direction of propagation of the perturbations
On SYM theory and all order bulk singularity structures of BPS strings in type II theory
Hatefi, Ehsan
2018-06-01
The complete forms of the S-matrix elements of a transverse scalar field, two world volume gauge fields, and a Potential Cn-1 Ramond-Ramond (RR) form field are investigated. In order to find an infinite number of t , s , (t + s + u)-channel bulk singularity structures of this particular mixed open-closed amplitude, we employ all the conformal field theory techniques to , exploring all the entire correlation functions and all order α‧ contact interactions to these supersymmetric Yang-Mills (SYM) couplings. Singularity and contact term comparisons with the other symmetric analysis, and are also carried out in detail. Various couplings from pull-Back of branes, Myers terms and several generalized Bianchi identities should be taken into account to be able to reconstruct all order α‧ bulk singularities of type IIB (IIA) superstring theory. Finally, we make a comment on how to derive without any ambiguity all order α‧ contact terms of this S-matrix which carry momentum of RR in transverse directions.
Superspace de Rham complex and relative cohomology
Energy Technology Data Exchange (ETDEWEB)
III, William D. Linch; Randall, Stephen [Center for String and Particle Theory,Department of Physics, University of Maryland at College Park,College Park, MD 20742-4111 (United States)
2015-09-28
We investigate the super-de Rham complex of five-dimensional superforms with N=1 supersymmetry. By introducing a free supercommutative algebra of auxiliary variables, we show that this complex is equivalent to the Chevalley-Eilenberg complex of the translation supergroup with values in superfields. Each cocycle of this complex is defined by a Lorentz- and iso-spin-irreducible superfield subject to a set of constraints. Restricting to constant coefficients results in a subcomplex in which components of the cocycles are coboundaries while the constraints on the defining superfields span the cohomology. This reduces the computation of all of the superspace Bianchi identities to a single linear algebra problem the solution of which implies new features not present in the standard four-dimensional, N=1 complex. These include splitting/joining in the complex and the existence of cocycles that do not correspond to irreducible supermultiplets of closed differential forms. Interpreting the five-dimensional de Rham complex as arising from dimensional reduction from the six-dimensional complex, we find a second five-dimensional complex associated to the relative de Rham complex of the embedding of the latter in the former. This gives rise to a second source of closed differential forms previously attributed to the phenomenon called “Weyl triviality”.
Effective dynamics of the hybrid quantization of the Gowdy T3 universe
International Nuclear Information System (INIS)
Brizuela, David; Mena Marugan, Guillermo A.; Pawlowski, Tomasz
2011-01-01
The quantum dynamics of the linearly polarized Gowdy T 3 model (compact inhomogeneous universes admitting linearly polarized gravitational waves) is analyzed within loop quantum cosmology by means of an effective dynamics. The analysis, performed via analytical and numerical methods, proves that the behavior found in the evolution of vacuum (homogeneous) Bianchi I universes is preserved qualitatively also in the presence of inhomogeneities. More precisely, the initial singularity is replaced by a big bounce which joins deterministically two large classical universes. In addition, we show that the size of the universe at the bounce is at least of the same order of magnitude (roughly speaking) as the size of the corresponding homogeneous universe obtained in the absence of gravitational waves. In particular, a precise lower bound for the ratio of these two sizes is found. Finally, the comparison of the amplitudes of the gravitational wave modes in the distant future and past shows that, statistically (i.e., for large samples of universes), the difference in amplitude is enhanced for nearly homogeneous universes, whereas this difference vanishes in inhomogeneity-dominated cases. The presented analysis constitutes the first systematic effective study of an inhomogeneous system within loop quantum cosmology, and it proves the robustness of the results obtained for homogeneous cosmologies in this context.
AdS solutions through transgression
International Nuclear Information System (INIS)
Donos, Aristomenis; Gauntlett, Jerome P.; Kim, Nakwoo
2008-01-01
We present new classes of explicit supersymmetric AdS 3 solutions of type IIB supergravity with non-vanishing five-form flux and AdS 2 solutions of D = 11 supergravity with electric four-form flux. The former are dual to two-dimensional SCFTs with (0,2) supersymmetry and the latter to supersymmetric quantum mechanics with two supercharges. We also investigate more general classes of AdS 3 solutions of type IIB supergravity and AdS 2 solutions of D = 11 supergravity which in addition have non-vanishing three-form flux and magnetic four-form flux, respectively. The construction of these more general solutions makes essential use of the Chern-Simons or 'transgression' terms in the Bianchi identity or the equation of motion of the field strengths in the supergravity theories. We construct infinite new classes of explicit examples and for some of the type IIB solutions determine the central charge of the dual SCFTs. The type IIB solutions with non-vanishing three-form flux that we construct include a two-torus, and after two T-dualities and an S-duality, we obtain new AdS 3 solutions with only the NS fields being non-trivial.
On the creation of scalar particles in some anisotropic universe
International Nuclear Information System (INIS)
Nariai, Hidekazu.
1978-01-01
Because of an importance of the particle creation (especially, its possible fulfilment of the black-body law with a definite temperature) in an early universe to various other cosmological problems we study how the creation of scalar particles occurs in the Bianchi-type I anisotropic universe adopted in our previous works on the quantized scalar field. It is shown that, as in a special isotropic case dealt with in recent papers, the creation may occur at the sacrifice of the requirement that the quantization procedure should reproduce the usual theory for a free field in the limit when the anisotropic universe changes into the Minkowski space-time. It is further shown that the creation occurs in accordance with the black-body law only in a 2-dimensional hyper-surface relating to the anisotropic cosmic expansion, provided that we fix two arbitrary constants appearing in a general expression for the Feynman propagator in terms of a procedure similar to that in the isotropic case. A speculation on the isotropization of our model-universe is also made from the standpoint of seeking for how the thermal equilibrium in the whole universe is attained. (auth.)
Meromorphic flux compactification
Energy Technology Data Exchange (ETDEWEB)
Damian, Cesar [Departamento de Ingeniería Mecánica, Universidad de Guanajuato,Carretera Salamanca-Valle de Santiago Km 3.5+1.8 Comunidad de Palo Blanco,Salamanca (Mexico); Loaiza-Brito, Oscar [Departamento de Física, Universidad de Guanajuato,Loma del Bosque No. 103 Col. Lomas del Campestre C.P 37150 León, Guanajuato (Mexico)
2017-04-26
We present exact solutions of four-dimensional Einstein’s equations related to Minkoswki vacuum constructed from Type IIB string theory with non-trivial fluxes. Following https://www.doi.org/10.1007/JHEP02(2015)187; https://www.doi.org/10.1007/JHEP02(2015)188 we study a non-trivial flux compactification on a fibered product by a four-dimensional torus and a two-dimensional sphere punctured by 5- and 7-branes. By considering only 3-form fluxes and the dilaton, as functions on the internal sphere coordinates, we show that these solutions correspond to a family of supersymmetric solutions constructed by the use of G-theory. Meromorphicity on functions constructed in terms of fluxes and warping factors guarantees that flux and 5-brane contributions to the scalar curvature vanish while fulfilling stringent constraints as tadpole cancelation and Bianchi identities. Different Einstein’s solutions are shown to be related by U-dualities. We present three supersymmetric non-trivial Minkowski vacuum solutions and compute the corresponding soft terms. We also construct a non-supersymmetric solution and study its stability.
Bossard, Guillaume; Kleinschmidt, Axel; Palmkvist, Jakob; Pope, Christopher N.; Sezgin, Ergin
2017-05-01
We study the non-linear realisation of E 11 originally proposed by West with particular emphasis on the issue of linearised gauge invariance. Our analysis shows even at low levels that the conjectured equations can only be invariant under local gauge transformations if a certain section condition that has appeared in a different context in the E 11 literature is satisfied. This section condition also generalises the one known from exceptional field theory. Even with the section condition, the E 11 duality equation for gravity is known to miss the trace component of the spin connection. We propose an extended scheme based on an infinite-dimensional Lie superalgebra, called the tensor hierarchy algebra, that incorporates the section condition and resolves the above issue. The tensor hierarchy algebra defines a generalised differential complex, which provides a systematic description of gauge invariance and Bianchi identities. It furthermore provides an E 11 representation for the field strengths, for which we define a twisted first order self-duality equation underlying the dynamics.
Avoidance of singularities in asymptotically safe Quantum Einstein Gravity
Energy Technology Data Exchange (ETDEWEB)
Kofinas, Georgios [Research Group of Geometry, Dynamical Systems and Cosmology, Department of Information and Communication Systems Engineering, University of the Aegean, Karlovassi 83200, Samos (Greece); Zarikas, Vasilios, E-mail: gkofinas@aegean.gr, E-mail: vzarikas@teilam.gr [Department of Electrical Engineering, Theory Division, ATEI of Central Greece, 35100 Lamia (Greece)
2015-10-01
New general spherically symmetric solutions have been derived with a cosmological ''constant'' Λ as a source. This Λ term is not constant but it satisfies the properties of the asymptotically safe gravity at the ultraviolet fixed point. The importance of these solutions comes from the fact that they may describe the near to the centre region of black hole spacetimes as this is modified by the Renormalization Group scaling behaviour of the fields. The consistent set of field equations which respect the Bianchi identities is derived and solved. One of the solutions (with conventional sign of temporal-radial metric components) is timelike geodesically complete, and although there is still a curvature divergent origin, this is never approachable by an infalling massive particle which is reflected at a finite distance due to the repulsive origin. Another family of solutions (of both signatures) range from a finite radius outwards, they cannot be extended to the centre of spherical symmetry, and the curvature invariants are finite at the minimum radius.
Avoidance of singularities in asymptotically safe Quantum Einstein Gravity
Energy Technology Data Exchange (ETDEWEB)
Kofinas, Georgios [Research Group of Geometry, Dynamical Systems and Cosmology,Department of Information and Communication Systems Engineering,University of the Aegean, Karlovassi 83200, Samos (Greece); Zarikas, Vasilios [Department of Electrical Engineering, Theory Division, ATEI of Central Greece,35100 Lamia (Greece); Department of Physics, Aristotle University of Thessaloniki,54124 Thessaloniki (Greece)
2015-10-30
New general spherically symmetric solutions have been derived with a cosmological “constant” Λ as a source. This Λ term is not constant but it satisfies the properties of the asymptotically safe gravity at the ultraviolet fixed point. The importance of these solutions comes from the fact that they may describe the near to the centre region of black hole spacetimes as this is modified by the Renormalization Group scaling behaviour of the fields. The consistent set of field equations which respect the Bianchi identities is derived and solved. One of the solutions (with conventional sign of temporal-radial metric components) is timelike geodesically complete, and although there is still a curvature divergent origin, this is never approachable by an infalling massive particle which is reflected at a finite distance due to the repulsive origin. Another family of solutions (of both signatures) range from a finite radius outwards, they cannot be extended to the centre of spherical symmetry, and the curvature invariants are finite at the minimum radius.
Protogalaxy formation from inhomogeneities in cosmological models
International Nuclear Information System (INIS)
Rankin, J.R.
1977-01-01
Equations governing the growth of protogalaxies in general homogeneous cosmological models were derived. Both non-relativistic Newtonian theory and general relativistic theory were covered. For the Newtonian case, by means of the concept of comoving Fourier analysis, the perturbation equations became coupled first order ordinary differential equations and were then further simplified. Bonnor's equation of galaxy formation in isotropic Newtonian cosmologies was generalized to anisotropic cases. The growth equations were solved for various background Newtonian models and gravitationally unstable solutions were found. By an approach analogous to Bonnor's non-relativistic approach, a relativistic version of the galaxy growth equation for the homogeneous isotropic cosmologies was derived. Galaxy growth in the anisotropic homogeneous Bianchi type I cosmologies was also considered. The full set of Einstein equations in synchronous coordinates was perturbed then simplified. The resulting equation was discussed in special cases of dust, axial symmetry and Kasner backgrounds. Finally the tetrad equations for perturbations in steady state cosmologies was set up with a view to considering the effect of rotation
Meromorphic flux compactification
International Nuclear Information System (INIS)
Damian, Cesar; Loaiza-Brito, Oscar
2017-01-01
We present exact solutions of four-dimensional Einstein’s equations related to Minkoswki vacuum constructed from Type IIB string theory with non-trivial fluxes. Following https://www.doi.org/10.1007/JHEP02(2015)187; https://www.doi.org/10.1007/JHEP02(2015)188 we study a non-trivial flux compactification on a fibered product by a four-dimensional torus and a two-dimensional sphere punctured by 5- and 7-branes. By considering only 3-form fluxes and the dilaton, as functions on the internal sphere coordinates, we show that these solutions correspond to a family of supersymmetric solutions constructed by the use of G-theory. Meromorphicity on functions constructed in terms of fluxes and warping factors guarantees that flux and 5-brane contributions to the scalar curvature vanish while fulfilling stringent constraints as tadpole cancelation and Bianchi identities. Different Einstein’s solutions are shown to be related by U-dualities. We present three supersymmetric non-trivial Minkowski vacuum solutions and compute the corresponding soft terms. We also construct a non-supersymmetric solution and study its stability.
Positive Cosmological Constant and Quantum Theory
Directory of Open Access Journals (Sweden)
Felix M. Lev
2010-11-01
Full Text Available We argue that quantum theory should proceed not from a spacetime background but from a Lie algebra, which is treated as a symmetry algebra. Then the fact that the cosmological constant is positive means not that the spacetime background is curved but that the de Sitter (dS algebra as the symmetry algebra is more relevant than the Poincare or anti de Sitter ones. The physical interpretation of irreducible representations (IRs of the dS algebra is considerably different from that for the other two algebras. One IR of the dS algebra splits into independent IRs for a particle and its antiparticle only when Poincare approximation works with a high accuracy. Only in this case additive quantum numbers such as electric, baryon and lepton charges are conserved, while at early stages of the Universe they could not be conserved. Another property of IRs of the dS algebra is that only fermions can be elementary and there can be no neutral elementary particles. The cosmological repulsion is a simple kinematical consequence of dS symmetry on quantum level when quasiclassical approximation is valid. Therefore the cosmological constant problem does not exist and there is no need to involve dark energy or other fields for explaining this phenomenon (in agreement with a similar conclusion by Bianchi and Rovelli.
COMPOSITION OF THE JOINT ADVISORY APPEALS BOARD & DISCIPLINARY BOARD 1999-2000 EXERCISE
Division des ressources humaines
2000-01-01
Appointed by the Director-GeneralAppointed by the Staff AssociationMembersBertrand Frammery / PSDaniel Boimond/ PS1st deputiesSue Foffano / ASJean-Claude Carlier / TIS2nd deputiesWolfgangvon Rüden / ITPoul Frandsen / LHCMessrs. Frammery and Boimond have drawn up the following list of staff members from among whom the Chairman of the Board may be chosen when required:Jean-Luc Baldy / STGuy Maurin / EPJean-Paul Fabre / EPMichel Rabany / LHCSverre Jarp / ITJean-Pierre Riunaud / PSLennart Jirden / SPLRoberto Saban / ACRobin Lauckner / SLMarilena Streit-Bianchi /TISMediators [see Administrative Circular N¡ 6 (Rev. 1) entitled 'Review procedure'] will also be selected from this list of ten staff members.COMPOSITION OF THE JOINT ADVISORY DISCIPLINARY BOARD1999-2000 Exercise Appointed by the Director-GeneralAppointed by the Staff AssociationMembersAchille Petrilli / ASMichel Bonnet / EP1st deputiesWisla Carena / EPIrene Seis / IT2nd deputiesRoland Garoby / PSJuan Diaz-Montoya / AC...
International Nuclear Information System (INIS)
Fennelly, A.J.
1978-01-01
Investigations of several problems of gravitation are discussed. The question of the existence of black holes is considered. While black holes like those in Einstein's theory may not exist in other gravity theories, trapped surfaces implying such black holes certainly do. The theories include those of Brans-Dicke, Lightman-Lee, Rosen, and Yang. A similar two-tensor theory of Yilmaz is investigated and found inconsistent and nonviable. The Newman-Penrose formalism for Riemannian geometries is adapted to general gravity theories and used to implement a search for twisting solutions of the gravity theories for empty and nonempty spaces. The method can be used to find the gravitational fields for all viable gravity theories. The rotating solutions are of particular importance for strong field interpretation of the Stanford/Marshall gyroscope experiment. Inhomogeneous cosmologies are examined in Einstein's theory as generalizations of homogeneous ones by raising the dimension of the invariance groups by one more parameter. The nine Bianchi classifications are extended to Rosen's theory of gravity for homogeneous cosmological models
Murányi, Dávid; Gamboa, Maribet; Vera, Alejandro
2016-12-01
Types of five of the six Plecoptera species described by Émile Blanchard and the holotype of the single stonefly described by Jules François Mabille were discovered in the National Museum Prague, Czech Republic. The identity of P. myrmidon Mabille, 1891 and P. pictetii Blanchard, 1854 are confirmed as Potamoperla myrmidon and Pictetoperla gayi (Pictet, 1841), respectively. Perla virescentipennis Blanchard, 1851 is considered as Diamphipnopsis virescentipennis comb. n., with Diamphipnosis samali Illies, 1960 syn. n. as a junior subjective synonym, and Diamphipnoa chillanae nom. n. is proposed for D. virescentipennis sensu Illies 1960. Lectotypes are designated for three species: Nemoura rufescens Blanchard, 1851 is redescribed as Austronemoura rufescens (Blanchard, 1851) comb. n., with Perla infuscata Blanchard, 1851 syn. n. and Perla blanchardi Jakobson & Bianchi, 1905 syn. n. designated as junior subjective synonyms, whereas Perla stictica Blanchard, 1851 is treated as Neonemura stictica (Blanchard, 1851) comb. n., nomen dubium. Paralectotypes of these three species belong to further four taxa. Due to the missing syntypes, Perla lineatocollis Blanchard, 1851 is treated as a nomen dubium of uncertain suborder assignment. Specimens of the Blanchard collections that cannot regarded as types are enumerated belonging to six species. Recent collections of 15 species from Chile are also reported.
The Nature of the Cosmological Constant Problem
Maia, M. D.; Capistrano, A. J. S.; Monte, E. M.
General relativity postulates the Minkowski space-time as the standard (flat) geometry against which we compare all curved space-times and also as the gravitational ground state where particles, quantum fields and their vacua are defined. On the other hand, experimental evidences tell that there exists a non-zero cosmological constant, which implies in a deSitter ground state, which not compatible with the assumed Minkowski structure. Such inconsistency is an evidence of the missing standard of curvature in Riemann's geometry, which in general relativity manifests itself in the form of the cosmological constant problem. We show how the lack of a curvature standard in Riemann's geometry can be fixed by Nash's theorem on metric perturbations. The resulting higher dimensional gravitational theory is more general than general relativity, similar to brane-world gravity, but where the propagation of the gravitational field along the extra dimensions is a mathematical necessity, rather than a postulate. After a brief introduction to Nash's theorem, we show that the vacuum energy density must remain confined to four-dimensional space-times, but the cosmological constant resulting from the contracted Bianchi identity represents a gravitational term which is not confined. In this case, the comparison between the vacuum energy and the cosmological constant in general relativity does not make sense. Instead, the geometrical fix provided by Nash's theorem suggests that the vacuum energy density contributes to the perturbations of the gravitational field.
Large-scale tides in general relativity
Energy Technology Data Exchange (ETDEWEB)
Ip, Hiu Yan; Schmidt, Fabian, E-mail: iphys@mpa-garching.mpg.de, E-mail: fabians@mpa-garching.mpg.de [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching (Germany)
2017-02-01
Density perturbations in cosmology, i.e. spherically symmetric adiabatic perturbations of a Friedmann-Lemaȋtre-Robertson-Walker (FLRW) spacetime, are locally exactly equivalent to a different FLRW solution, as long as their wavelength is much larger than the sound horizon of all fluid components. This fact is known as the 'separate universe' paradigm. However, no such relation is known for anisotropic adiabatic perturbations, which correspond to an FLRW spacetime with large-scale tidal fields. Here, we provide a closed, fully relativistic set of evolutionary equations for the nonlinear evolution of such modes, based on the conformal Fermi (CFC) frame. We show explicitly that the tidal effects are encoded by the Weyl tensor, and are hence entirely different from an anisotropic Bianchi I spacetime, where the anisotropy is sourced by the Ricci tensor. In order to close the system, certain higher derivative terms have to be dropped. We show that this approximation is equivalent to the local tidal approximation of Hui and Bertschinger [1]. We also show that this very simple set of equations matches the exact evolution of the density field at second order, but fails at third and higher order. This provides a useful, easy-to-use framework for computing the fully relativistic growth of structure at second order.
Geometry of extended null supersymmetry in M theory
International Nuclear Information System (INIS)
Conamhna, Oisin A.P. Mac
2006-01-01
For supersymmetric spacetimes in 11 dimensions admitting a null Killing spinor, a set of explicit necessary and sufficient conditions for the existence of any number of arbitrary additional Killing spinors is derived. The necessary and sufficient conditions are comprised of algebraic relationships, linear in the spinorial components, between the spinorial components and their first derivatives, and the components of the spin connection and four-form. The integrability conditions for the Killing spinor equation are also analyzed in detail, to determine which components of the field equations are implied by arbitrary additional supersymmetries and the four-form Bianchi identity. This provides a complete formalism for the systematic and exhaustive investigation of all spacetimes with extended null supersymmetry in 11 dimensions. The formalism is employed to show that the general bosonic solution of 11 dimensional supergravity admitting a G 2 structure defined by four Killing spinors is either locally the direct product of R 1,3 with a seven-manifold of G 2 holonomy, or locally the Freund-Rubin direct product of AdS 4 with a seven-manifold of weak G 2 holonomy. In addition, all supersymmetric spacetimes admitting a (G 2 xR 7 )xR 2 structure are classified
All Chern-Simons invariants of 4D, N=1 gauged superform hierarchies
Energy Technology Data Exchange (ETDEWEB)
Becker, Katrin; Becker, Melanie; III, William D. Linch [George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy,Texas A& M University,College Station, TX 77843-4242 (United States); Randall, Stephen [Department of Physics, University of California,Berkeley, CA 94720-7300 (United States); Robbins, Daniel [Department of Physics, University at Albany,Albany, NY 12222 (United States)
2017-04-19
We give a geometric description of supersymmetric gravity/(non-)abelian p-form hierarchies in superspaces with 4D, N=1 super-Poincaré invariance. These hierarchies give rise to Chern-Simons-like invariants, such as those of the 5D, N=1 graviphoton and the eleven-dimensional 3-form but also generalizations such as Green-Schwarz-like/BF-type couplings. Previous constructions based on prepotential superfields are reinterpreted in terms of p-forms in superspace thereby elucidating the underlying geometry. This vastly simplifies the calculations of superspace field-strengths, Bianchi identities, and Chern-Simons invariants. Using this, we prove the validity of a recursive formula for the conditions defining these actions for any such tensor hierarchy. Solving it at quadratic and cubic orders, we recover the known results for the BF-type and cubic Chern-Simons actions. As an application, we compute the quartic invariant ∼AdAdAdA+… relevant, for example, to seven-dimensional supergravity compactifications.
Some properties of spatially homogeneous spacetimes
International Nuclear Information System (INIS)
Coomer, G.C.
1979-01-01
This paper discusses two features of the universe which are influenced in a fundamental way by the spacetime geometry of the universe. The first is the growth of density fluctuations in the early stages of the evolution of the universe. The second is the propagation of electromagnetic radiation in the universe. A spatially homogeneous universe is assumed in both discussions. The gravitational instability theory of galaxy formation is investigated for a viscous fluid and for a charged, conducting fluid with a magnetic field added as a perturbation. It is found that the growth rate of density perturbations in both cases is lower than in the perfect fluid case. Spatially homogeneous but nonisotropic spacetimes are investigated next. Two perfect fluid solutions of Einstein's field equations are found which have spacelike hypersurfaces with Bianchi type II geometry. An expression for the spectrum of the cosmic microwave background radiation in a spatially homogeneous but nonisotropic universe is found. The expression is then used to determine the angular distribution of the intensity of the radiation in the simpler of the two solutions. When accepted values of the matter density and decoupling temperature are inserted into this solution, values for the age of the universe and the time of decoupling are obtained which agree reasonably well with the values of the standard model of the universe
Analytic self-gravitating Skyrmions, cosmological bounces and AdS wormholes
Directory of Open Access Journals (Sweden)
Eloy Ayón-Beato
2016-01-01
Full Text Available We present a self-gravitating, analytic and globally regular Skyrmion solution of the Einstein–Skyrme system with winding number w=±1, in presence of a cosmological constant. The static spacetime metric is the direct product R×S3 and the Skyrmion is the self-gravitating generalization of the static hedgehog solution of Manton and Ruback with unit topological charge. This solution can be promoted to a dynamical one in which the spacetime is a cosmology of the Bianchi type-IX with time-dependent scale and squashing coefficients. Remarkably, the Skyrme equations are still identically satisfied for all values of these parameters. Thus, the complete set of field equations for the Einstein–Skyrme–Λ system in the topological sector reduces to a pair of coupled, autonomous, nonlinear differential equations for the scale factor and a squashing coefficient. These equations admit analytic bouncing cosmological solutions in which the universe contracts to a minimum non-vanishing size, and then expands. A non-trivial byproduct of this solution is that a minor modification of the construction gives rise to a family of stationary, regular configurations in General Relativity with negative cosmological constant supported by an SU(2 nonlinear sigma model. These solutions represent traversable AdS wormholes with NUT parameter in which the only “exotic matter” required for their construction is a negative cosmological constant.
International Nuclear Information System (INIS)
Amsterdamski, P.
1986-01-01
The standard cosmological model is reviewed and shown not to be self-sufficient in that it requires initial conditions most likely to be supplied by quantum cosmology. The possible approaches to the issue of initial conditions for cosmology are then discussed. In this thesis, the author considers three separate problems related to this issue. First, the possibility of inflation is investigated in detail by analyzing the evolution of metric perturbations and fluctuations in the expectation value of a scalar field prior to a phase transition; finite temperature effects are also included. Since the inhomogeneities were damped well before the onset of a phase transition. It is concluded that an inflation was possible. Next, the effective action of neutrino and photon fields is calculated for homogeneous spacetimes with small anisotropy; it is shown that quantum corrections to the action due to these fields influence the evolution of an early Universe in the Same way as do the analogous correction terms arising from a conformally invariant scalar which has been previously studied. Finally, the question of an early anisotropy is also discussed in a framework of Hartle-Hawking wave function of the Universe. A wave function of a Bianchi IX type Universe is calculated in a semiclassical approximation
Hochadel, Oliver
2007-06-01
While it is a commonplace in the historiography of electricity that itinerant lecturers and instrument makers were `somehow' part of the `electrical flare' of the 18th century, very little is actually known about them, about their background, their careers and their self-understanding. Yet, research focusing on these practitioners of experimental physics outside the established institutions can contribute immensely to our understanding of the scientific culture of the Enlightenment. The development of electrical machines, the supply for increasing demand for instruments and instruction, the creation of interest in electricity through public demonstrations, relied heavily on these men. Furthermore, these `scientific salesmen' offered a perfect contrast, a foil for the natural philosophers from whom to distinguish themselves. Natural philosophers tried to discredit their extra-academic competitors, thereby forging their own image as serious, honest, truth-seeking, independent researchers. This essay focuses on this situation in the German Empire, tracing the steps of the itinerant lecturer Jakob von Bianchy on his way from court to college, from the workshop to the theatre, from Lake Como, to Vienna and Paris.
Thermodynamics of quantum spacetime histories
Smolin, Lee
2017-11-01
We show that the simplicity constraints, which define the dynamics of spin foam models, imply, and are implied by, the first law of thermodynamics, when the latter is applied to causal diamonds in the quantum spacetime. This result reveals an intimate connection between the holographic nature of gravity, as reflected by the Bekenstein entropy, and the fact that general relativity and other gravitational theories can be understood as constrained topological field theories. To state and derive this correspondence we describe causal diamonds in the causal structure of spin foam histories and generalize arguments given for the near horizon region of black holes by Frodden, Gosh and Perez [Phys. Rev. D 87, 121503 (2013); , 10.1103/PhysRevD.87.121503Phys. Rev. D 89, 084069 (2014); , 10.1103/PhysRevD.89.084069Phys. Rev. Lett. 107, 241301 (2011); , 10.1103/PhysRevLett.107.241301Phys. Rev. Lett.108, 169901(E) (2012)., 10.1103/PhysRevLett.108.169901] and Bianchi [arXiv:1204.5122.]. This allows us to apply a recent argument of Jacobson [Phys. Rev. Lett. 116, 201101 (2016).10.1103/PhysRevLett.116.201101] to show that if a spin foam history has a semiclassical limit described in terms of a smooth metric geometry, that geometry satisfies the Einstein equations. These results suggest also a proposal for a quantum equivalence principle.
Partial Differential Equations in General Relativity
International Nuclear Information System (INIS)
Choquet-Bruhat, Yvonne
2008-01-01
General relativity is a physical theory basic in the modeling of the universe at the large and small scales. Its mathematical formulation, the Einstein partial differential equations, are geometrically simple, but intricate for the analyst, involving both hyperbolic and elliptic PDE, with local and global problems. Many problems remain open though remarkable progress has been made recently towards their solutions. Alan Rendall's book states, in a down-to-earth form, fundamental results used to solve different types of equations. In each case he gives applications to special models as well as to general properties of Einsteinian spacetimes. A chapter on ODE contains, in particular, a detailed discussion of Bianchi spacetimes. A chapter entitled 'Elliptic systems' treats the Einstein constraints. A chapter entitled 'Hyperbolic systems' is followed by a chapter on the Cauchy problem and a chapter 'Global results' which contains recently proved theorems. A chapter is dedicated to the Einstein-Vlasov system, of which the author is a specialist. On the whole, the book surveys, in a concise though precise way, many essential results of recent interest in mathematical general relativity, and it is very clearly written. Each chapter is followed by an up to date bibliography. In conclusion, this book will be a valuable asset to relativists who wish to learn clearly-stated mathematical results and to mathematicians who want to penetrate into the subtleties of general relativity, as a mathematical and physical theory. (book review)
How universe evolves with cosmological and gravitational constants
Directory of Open Access Journals (Sweden)
She-Sheng Xue
2015-08-01
Full Text Available With a basic varying space–time cutoff ℓ˜, we study a regularized and quantized Einstein–Cartan gravitational field theory and its domains of ultraviolet-unstable fixed point gir≳0 and ultraviolet-stable fixed point guv≈4/3 of the gravitational gauge coupling g=(4/3G/GNewton. Because the fundamental operators of quantum gravitational field theory are dimension-2 area operators, the cosmological constant is inversely proportional to the squared correlation length Λ∝ξ−2. The correlation length ξ characterizes an infrared size of a causally correlate patch of the universe. The cosmological constant Λ and the gravitational constant G are related by a generalized Bianchi identity. As the basic space–time cutoff ℓ˜ decreases and approaches to the Planck length ℓpl, the universe undergoes inflation in the domain of the ultraviolet-unstable fixed point gir, then evolves to the low-redshift universe in the domain of ultraviolet-stable fixed point guv. We give the quantitative description of the low-redshift universe in the scaling-invariant domain of the ultraviolet-stable fixed point guv, and its deviation from the ΛCDM can be examined by low-redshift (z≲1 cosmological observations, such as supernova Type Ia.
Noether symmetry analysis of anisotropic universe in modified gravity
Energy Technology Data Exchange (ETDEWEB)
Shamir, M.F.; Kanwal, Fiza [National University of Computer and Emerging Sciences, Department of Sciences and Humanities, Lahore (Pakistan)
2017-05-15
In this paper we study the anisotropic universe using Noether symmetries in modified gravity. In particular, we choose a locally rotationally symmetric Bianchi type-I universe for the analysis in f(R, G) gravity, where R is the Ricci scalar and G is the Gauss-Bonnet invariant. Firstly, a model f(R, G) = f{sub 0}R{sup l} + f{sub 1}G{sup n} is proposed and the corresponding Noether symmetries are investigated. We have also recovered the Noether symmetries for f(R) and f(G) theories of gravity. Secondly, some important cosmological solutions are reconstructed. Exponential and power-law solutions are reported for a well-known f(R, G) model, i.e., f(R, G) = f{sub 0}R{sup n}G{sup 1-n}. Especially, Kasner's solution is recovered and it is anticipated that the familiar de Sitter spacetime giving ΛCDM cosmology may be reconstructed for some suitable value of n. (orig.)
Efficacy of ingenol mebutate gel for actinic keratosis in patients treated by thiazide diuretics
Directory of Open Access Journals (Sweden)
Campione E
2016-11-01
Full Text Available Elena Campione,1 Monia Di Prete,1 Laura Diluvio,1 Luca Bianchi,1 Augusto Orlandi2 1Department of Dermatology, 2Department of Pathology, University of Rome Tor Vergata, Rome, Italy Abstract: Actinic keratosis (AK is considered as superficial squamous cell carcinoma. Chronic sun exposure plays a central role in its pathogenesis. In particular, ultraviolet B radiation causes direct damage to the DNA, producing pyrimidine dimers that suppress the protective role of p53. Other risk factors include advanced age, male sex, and fair skin type. Even some drugs used for treating blood hypertension, such as thiazide diuretics, can increase the risk of developing AK. Their photosensitizing action seems to be connected with reactive oxygen species production. We report our experience on ten patients affected by multiple AK, in therapy with thiazide diuretics, treated by ingenol mebutate gel. AK was clinically and dermoscopically evaluated at baseline and after 30 days from the beginning of the treatment. Moreover, patients were screened for vitamin D3 values and reported a general hypovitaminosis status. To our knowledge, we report for the first time the efficacy of ingenol mebutate gel in this group of patients, particularly at risk of developing AK. Keywords: anticancer agents, antitumor activity, cancer cells, skin precancerous lesion
International Nuclear Information System (INIS)
Akbar, M.M.; D'Eath, P.D.
2003-01-01
The classical boundary-value problem of the Einstein field equations is studied with an arbitrary cosmological constant, in the case of a compact (S 3 ) boundary given a biaxial Bianchi-IX positive-definite three-metric, specified by two radii (a,b). For the simplest, four-ball, topology of the manifold with this boundary, the regular classical solutions are found within the family of Taub-NUT-(anti)de Sitter metrics with self-dual Weyl curvature. For arbitrary choice of positive radii (a,b), we find that there are three solutions for the infilling geometry of this type. We obtain exact solutions for them and for their Euclidean actions. The case of negative cosmological constant is investigated further. For reasonable squashing of the three-sphere, all three infilling solutions have real-valued actions which possess a 'cusp catastrophe' structure with a non-self-intersecting 'catastrophe manifold' implying that the dominant contribution comes from the unique real positive-definite solution on the ball. The positive-definite solution exists even for larger deformations of the three-sphere, as long as a certain inequality between a and b holds. The action of this solution is proportional to -a 3 for large a (∼b) and hence larger radii are favoured. The same boundary-value problem with more complicated interior topology containing a 'bolt' is investigated in a forthcoming paper
Energy Technology Data Exchange (ETDEWEB)
Bossard, Guillaume [Centre de Physique Théorique, Ecole Polytechnique, CNRS,Université Paris-Saclay 91128 Palaiseau cedex (France); Kleinschmidt, Axel [Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut),Am Mühlenberg 1, DE-14476 Potsdam (Germany); International Solvay Institutes,ULB-Campus Plaine CP231, BE-1050 Brussels (Belgium); Palmkvist, Jakob; Pope, Christopher N.; Sezgin, Ergin [Mitchell Institute for Fundamental Physics and Astronomy,Texas A& M University, College Station, TX 77843 (United States)
2017-05-03
We study the non-linear realisation of E{sub 11} originally proposed by West with particular emphasis on the issue of linearised gauge invariance. Our analysis shows even at low levels that the conjectured equations can only be invariant under local gauge transformations if a certain section condition that has appeared in a different context in the E{sub 11} literature is satisfied. This section condition also generalises the one known from exceptional field theory. Even with the section condition, the E{sub 11} duality equation for gravity is known to miss the trace component of the spin connection. We propose an extended scheme based on an infinite-dimensional Lie superalgebra, called the tensor hierarchy algebra, that incorporates the section condition and resolves the above issue. The tensor hierarchy algebra defines a generalised differential complex, which provides a systematic description of gauge invariance and Bianchi identities. It furthermore provides an E{sub 11} representation for the field strengths, for which we define a twisted first order self-duality equation underlying the dynamics.
Quantum effects and regular cosmological models
International Nuclear Information System (INIS)
Gurovich, V.Ts.; Starobinskij, A.A.; AN SSSR, Moscow. Inst. Teoreticheskoj Fiziki)
1979-01-01
Allowance for the quantum nature of material fields and weak gravitational waves on the background of the classical metric of the cosmological model results in two basic effects: vacuum polarization and particle production. The first of the effects may be taken into account qualitatively by introducing into the lagrangian density of the gravitational field an additional term of the type A+BR 2 +CR 2 In|R/R 0 |; the second effect can be accounted for by prescribing a local rate of particle (graviton) production which is proportional to the square of the scalar curvature R 2 . It is shown that the taking into account of the combined effect of these phenomena on the evolution of a homogeneous anisotropic metric of the first Bianchi type removes the Einstein singularities. Asymptotic approach to the classical model, however, is attained only if additional assumptions are made. At the stage of compression the solution is close to the anisotropic vacuum Kasner solution; at the expansion stage it tends to the isotropic Friedman solution in which matter is produced by the gravitational field
CERN and the 10,000th application of the WorldFIP protocol
2001-01-01
On 24 April, CERN received an award for the 10,000th application of the WorldFIP industrial communication network protocol. The award was presented to Juan Antonio Rubio, Head of CERN's ETT Division, by Marc Desjardins, President of the WorldFIP association, which groups together 430 industrial partners with the aim of promoting the WorldFIP concept. Marc Desjardins, President of the WorldFIP association, presenting the award for the 10,000th application to CERN ETT Division Leader Juan Antonio Rubio. From left to right: Guy Baribaud (CERN), Ercole Gallacio (WF), Noël Fayard (WF), Gérard Demars (WF), Dario Fantoni (WF), Marc Desjardins (WF), Raymond Brun (CERN), Jean-Pierre Hauet (WF), Juan Antonio Rubio (CERN), Bernard Jouga (WF), Raymond Rausch (CERN), Jean-Pierre Froidevaux (WF), Marilena Streit-Bianchi (CERN), Michel Rabany (CERN), Patrick Chatelet (WF), Nicolas Cravoisy (WF), Jean Bergeal (WF). Communication networks, also known as fieldbuses, provide for digital comunication betwe...
Generalized dynamics of moving dislocations in quasicrystals
International Nuclear Information System (INIS)
Agiasofitou, Eleni; Lazar, Markus; Kirchner, Helmut
2010-01-01
A theoretical framework for dislocation dynamics in quasicrystals is provided according to the continuum theory of dislocations. Firstly, we present the fundamental theory for moving dislocations in quasicrystals giving the dislocation density tensors and introducing the dislocation current tensors for the phonon and phason fields, including the Bianchi identities. Next, we give the equations of motion for the incompatible elastodynamics as well as for the incompatible elasto-hydrodynamics of quasicrystals. We continue with the derivation of the balance law of pseudomomentum thereby obtaining the generalized forms of the Eshelby stress tensor, the pseudomomentum vector, the dynamical Peach-Koehler force density and the Cherepanov force density for quasicrystals. The form of the dynamical Peach-Koehler force for a straight dislocation is obtained as well. Moreover, we deduce the balance law of energy that gives rise to the generalized forms of the field intensity vector and the elastic power density of quasicrystals. The above balance laws are produced for both models. The differences between the two models and their consequences are revealed. The influences of the phason fields as well as of the dynamical terms are also discussed.
On the creation of scalar particles in some anisotropic universe
International Nuclear Information System (INIS)
Nariai, Hidekazu
1978-01-01
Because of an importance of the particle creation (especially, its possible fulfilment of the black-body law with a definite temperature) in an early universe to various other cosmological problems, we study how the creation of scalar particles occurs in the Bianchi-type I anisotropic universe adopted in our previous works on the quantized scalar field. It is shown that, as in a special isotropic case dealt with in recent papers, the creation may occur at the sacrifice of the requirement that the quantization procedure should reproduce the usual theory for a free field in the limit when the anisotropic universe changes into the Minkowski space-time. It is further shown that the creation occurs in accordance with the black-body law only in a 2-dimensional hyper-surface relating to the anisotropic cosmic expansion, provided that we fix two arbitrary constants appearing in a general expression for the Feynman propagator in terms of a procedure similar to that in the isotropic case. A speculation on the isotropization of our model-universe is also made from the standpoint of seeking the attainment of the thermal equilibrium in the whole universe. (author)
On whole Abelian model dynamics
Energy Technology Data Exchange (ETDEWEB)
Chauca, J.; Doria, R. [CBPF, Rio de Janeiro (Brazil); Aprendanet, Petropolis, 25600 (Brazil)
2012-09-24
Physics challenge is to determine the objects dynamics. However, there are two ways for deciphering the part. The first one is to search for the ultimate constituents; the second one is to understand its behaviour in whole terms. Therefore, the parts can be defined either from elementary constituents or as whole functions. Historically, science has been moving through the first aspect, however, quarks confinement and complexity are interrupting this usual approach. These relevant facts are supporting for a systemic vision be introduced. Our effort here is to study on the whole meaning through gauge theory. Consider a systemic dynamics oriented through the U(1) - systemic gauge parameter which function is to collect a fields set {l_brace}A{sub {mu}I}{r_brace}. Derive the corresponding whole gauge invariant Lagrangian, equations of motion, Bianchi identities, Noether relationships, charges and Ward-Takahashi equations. Whole Lorentz force and BRST symmetry are also studied. These expressions bring new interpretations further than the usual abelian model. They are generating a systemic system governed by 2N+ 10 classical equations plus Ward-Takahashi identities. A whole dynamics based on the notions of directive and circumstance is producing a set determinism where the parts dynamics are inserted in the whole evolution. A dynamics based on state, collective and individual equations with a systemic interdependence.
2007 2008 ACADEMIC TRAINING PROGRAMME
2008-01-01
LECTURE SERIES 27, 28 & 29 May 2008 11:00 -12:00 – Main Auditorium, bldg. 500-1 The biological effects of ionizing radiation M. STREIT-BIANCHI, CERN, Geneva, CH Since the discovery of X-rays the practical use of ionizing radiation and its damaging effects have been a source of concern for occupational health and radiation protection. This led to the introduction of dose limits and strict controls associated with the use of radiation for civil uses. This Academic Training lecture series will discuss the effects of radiation on humans with special emphasis on the health effects of low doses. Radiation risks as assessed from Hiroshima and Nagasaki, Chernobyl as well as others accidental and occupational exposures will be presented and discussed. 2, 3, 4, 5, 6 June 2008 11:00 -12:00 – Main Auditorium, bldg. 500-1 Technology and applications of high field accelerator magnets Dr. G. AMBROSIO, Fermi National Accelerator Laboratory, USA Superconducting magnets are an enabling technology for high ene...
Resolutions of Cn/Zn orbifolds, their U(1) bundles, and applications to string model building
International Nuclear Information System (INIS)
Nibbelink, Stefan Groot; Trapletti, Michele; Walter, Martin G.A.
2007-01-01
We describe blowups of C n /Z n orbifolds as complex line bundles over CP n-1 . We construct some gauge bundles on these resolutions. Apart from the standard embedding, we describe U(1) bundles and an SU(n-1) bundle. Both blowups and their gauge bundles are given explicitly. We investigate ten dimensional SO(32) super Yang-Mills theory coupled to supergravity on these backgrounds. The integrated Bianchi identity implies that there are only a finite number of U(1) bundle models. We describe how the orbifold gauge shift vector can be read off from the gauge background. In this way we can assert that in the blow down limit these models correspond to heterotic C 2 /Z 2 and C 3 /Z 3 orbifold models. (Only the Z 3 model with unbroken gauge group SO(32) cannot be reconstructed in blowup without torsion.) This is confirmed by computing the charged chiral spectra on the resolutions. The construction of these blowup models implies that the mismatch between type-I and heterotic models on T 6 /Z 3 does not signal a complication of S-duality, but rather a problem of type-I model building itself: The standard type-I orbifold model building only allows for a single model on this orbifold, while the blowup models give five different models in blow down
On bulk singularity structures and all order α′ contact terms of BPS string amplitudes
Directory of Open Access Journals (Sweden)
Ehsan Hatefi
2016-10-01
Full Text Available The entire form of the amplitude of three SYM (involving two transverse scalar fields, a gauge field and a potential Cn−1 Ramond–Ramond (RR form field is found out. We first derive and then start constructing an infinite number of t,s channel bulk singularity structures by means of all order α′ corrections to pull-back of brane in an Effective Field Theory (EFT. Due to presence of the complete form of S-matrix, several new contact interactions as well as new couplings are explored. It is also shown that these couplings can be verified at the level of EFT by either the combinations of Myers terms, pull-back, Taylor expanded of scalar fields or the mixed combination of the couplings of this paper as well as employed Bianchi identities. For the first time, we also derive the algebraic and the complete form of the integrations for some arbitrary combinations of Mandelstam variables and for the most general case ∫d2z|1−z|a|z|b(z−z¯c(z+z¯3 on upper half plane as well.
Dual vector multiplet coupled to dual N=1 supergravity in 10D
International Nuclear Information System (INIS)
Nishino, Hitoshi; Rajpoot, Subhash
2005-01-01
We couple in superspace a dual vector multiplet (C m 1 ...m 7 ,λ α ) to the dual version of N=1 supergravity (e m a ,ψ m α ,M m 1 ...m 6 ,χ α ,Φ) in ten dimensions. The 7-form field C has its 8-form field strength H dual to the 2-form field strength F of the conventional vector multiplet. To simplify the computation, we use so-called beta-function-favored superspace constraints for dual supergravity developed for β-function computations. As in a more conventional constraint set, the H-Bianchi identity must have the form N and F, where N is the 7-form field strength in dual supergravity. The potential anomaly for the dual vector multiplet can be cancelled for the particular gauge group U(1) 496 by the Green-Schwarz mechanism. As a by-product, we also give the globally supersymmetric Abelian Dirac-Born-Infeld interactions for the dual vector multiplet for the first time
De Sitter universe described by a binary mixture with a variable cosmological constant λ
Biswal, S. K.
2018-04-01
We have constructed a self-consistent system of Bianchi Type VI0 cosmology, and mingling of perfect fluid and dark energy in five dimensions. The usual equation of state p = γ ρ with γ \\in [0, 1] is chosen by the perfect fluid. The dark energy assumed to be chosen is taken into consideration to be either the quintessence or Chaplygin gas. The same solutions pertaining to the corresponding the field equations of Einstein are obtained as a quadrature. State parameter's equations for dark energy ω is found to be consistent enough with the recent observations of SNe Ia data (SNe Ia data with CMBR anisotropy) and galaxy clustering statistics. Here our models predict that the rate of expansion of Universe would increase with passage of time. The cosmological constant Λ is traced as a declining function of time and it gets nearer to a small positive value later on which is supported by the results from the current supernovae Ia observations. Also a detail discussion is made on the physical and geometrical aspects of the models.
Gravitational F-terms through anomaly equations and deformed chiral rings
International Nuclear Information System (INIS)
Alday, Luis F.; Gava, Edi; Cirafici, Michele; David, Justin R.; Narain, K.S.
2003-05-01
We study effective gravitational F-terms, obtained by integrating an U(N) adjoint chiral superfield Φ coupled to the N = 1 gauge chiral superfield W α and supergravity, to arbitrary orders in the gravitational background. The latter includes in addition to the N = 1 Weyl superfield G αβγ , the self-dual graviphoton field strength F αβ of the parent, broken N = 2 theory. We first study the chiral ring relations resulting from the above non-standard gravitational background and find agreement, for gauge invariant operators, with those obtained from the dual closed string side via Bianchi identities for N = 2 supergravity coupled to vector multiplets. We then derive generalized anomaly equations for connected correlators on the gauge theory side, which allow us to solve for the basic one-point function 2 /(z - Φ)> to all orders in F 2 . By generalizing the matrix model loop equation to the generating functional of connected correlators of resolvents, we prove that the gauge theory result coincides with the genus expansion of the associated matrix model, after identifying the expansion parameters on the two sides. (author)
An Exact Homogeneous Stiff Cosmology that Reduces to the Kasner Solution
Directory of Open Access Journals (Sweden)
Fabio D. Lora
2007-01-01
Full Text Available Se presenta una familia de soluciones exactas sencillas de las ecua- ciones de Einstein homogéneas sobre el plano para las cosmologías rígidas. El método para obtener la solución se basa en la introducción de funciones auxiliares, a fin de emitir las ecuaciones de Einstein de tal manera que puedan ser integradas explícitamente. La solución obtenida se expresa en términos de funciones simples de las coordenadas utilizadas. Se analizan las propiedades geométricas y cinemáticas de la solución; los parámetros están restringidas a fin de tener un comportamiento aceptable físicamente. Las soluciones son del tipo Petrov I, y presentan una singularidad de big-bang. Ahora bien, para un cierto valor de uno de los parámetros la solución es una solución de vacío de tipo Bianchi I, que se reduce a la solución de Kasner.
Partial Differential Equations in General Relativity
Energy Technology Data Exchange (ETDEWEB)
Choquet-Bruhat, Yvonne
2008-09-07
General relativity is a physical theory basic in the modeling of the universe at the large and small scales. Its mathematical formulation, the Einstein partial differential equations, are geometrically simple, but intricate for the analyst, involving both hyperbolic and elliptic PDE, with local and global problems. Many problems remain open though remarkable progress has been made recently towards their solutions. Alan Rendall's book states, in a down-to-earth form, fundamental results used to solve different types of equations. In each case he gives applications to special models as well as to general properties of Einsteinian spacetimes. A chapter on ODE contains, in particular, a detailed discussion of Bianchi spacetimes. A chapter entitled 'Elliptic systems' treats the Einstein constraints. A chapter entitled 'Hyperbolic systems' is followed by a chapter on the Cauchy problem and a chapter 'Global results' which contains recently proved theorems. A chapter is dedicated to the Einstein-Vlasov system, of which the author is a specialist. On the whole, the book surveys, in a concise though precise way, many essential results of recent interest in mathematical general relativity, and it is very clearly written. Each chapter is followed by an up to date bibliography. In conclusion, this book will be a valuable asset to relativists who wish to learn clearly-stated mathematical results and to mathematicians who want to penetrate into the subtleties of general relativity, as a mathematical and physical theory. (book review)
Gravitational radiation from nearly Newtonian systems
International Nuclear Information System (INIS)
Kirk, E.M.
1989-09-01
A method of examining gravitational radiation from nearly Newtonian systems is presented. Using the Cartan formulation of Newtonian gravity, a one parameter family of space-times which have a strict Newtonian limit is constructed. An expression for the initial null data in terms of the Newtonian potential is obtained in the Newtonian limit. Using this, the problem is formulated as a series in the Newtonian parameter. The series expansions for the sources of the Bianchi identities are obtained to third order in both the vacuum and non-vacuum cases. A simple technique is presented for determining whether a particular source term gives rise to asymptotically flat null data. The far field quadrupole formula is derived in a leading approximation and a method for obtaining error bounds is discussed. Additionally, a method for solving Einstein's equations is shown. This involves expressing the Ricci identities as a matrix, Riccati equation and a system of linear matrix equations. A comparison of the formalisms of Bondi and Newman Penrose is presented and explicit correspondences between the supersurface constrain equations and the Ricci identities are shown. (author)