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Articles de revues sur le sujet « Cosmology Mathematical models »

Auteur : Grafiati

Publié le 4 juin 2021

Mis à jour le 28 janvier 2023

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1

Christianto, Victor, and Yunita Umniyati. "Remark on ‘The future of mathematical Cosmology” and “100 years of mathematical cosmology: Models, theories and problems, Part B” by S. Cotsakis and A.P. Yefremov." Journal of Cosmology, Filaments and Astrobiology 2, no. 1 (2022): 38–41. http://dx.doi.org/10.54216/jcfa.020105.

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In this review article, allow us to offer a few remark on “the future of mathematical cosmology” “100 years of mathematical cosmology: Models, theories and problems, Part B” by Cotsakis and Yefremov, which seems to us very interesting piece of review on progress on the last 3 or 4 decades in theoretical cosmology development. In particular, we would emphasize on testability of cosmology models, which seem to us this criterion can only be achieved via correspondence between condensed mattersuperfluiditylow temperature physics and cosmology (cf. for instance, Kibble Pickett, 2008).

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2

Tzvi Langermann, Y. "Arabic Cosmology." Early Science and Medicine 2, no. 2 (1997): 185–213. http://dx.doi.org/10.1163/157338297x00113.

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AbstractRepresentations of the heavens in various levels of detail can be found in a number of branches of Arabic literature. One particular genre, the hay'a texts, has as its purpose a full though non-mathematical discussion of the arrangement of the celestial orbs; hay'a writers are particularly sensitive to the philosophical requirements which all systems must meet. The pivotal work in this genre, On the Configuration, was written by Ibn al-Haytham. Later writers continued to produce works in the spirit of On the Configuration. In the east, al-Tusi and his followers developed new models; in

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Elizaga Navascués, Beatriz, Mercedes Martín-Benito, and Guillermo A. Mena Marugán. "Hybrid models in loop quantum cosmology." International Journal of Modern Physics D 25, no. 08 (July 2016): 1642007. http://dx.doi.org/10.1142/s0218271816420074.

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In the framework of Loop Quantum Cosmology (LQC), inhomogeneous models are usually quantized by means of a hybrid approach that combines loop quantization techniques with standard quantum field theory methods. This approach is based on a splitting of the phase space in a homogeneous sector, formed by global, zero-modes and an inhomogeneous sector, formed by the remaining, infinite number of modes, that describe the local degrees of freedom. Then, the hybrid quantization is attained by adopting a loop representation for the homogeneous gravitational sector, while a Fock representation is used f

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DEL CAMPO, SERGIO, RAMÓN HERRERA, and JOEL SAAVEDRA. "CLOSED INFLATIONARY UNIVERSE MODELS IN BRANE WORLD COSMOLOGY." International Journal of Modern Physics D 14, no. 05 (May 2005): 861–72. http://dx.doi.org/10.1142/s0218271805007036.

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In this article we study closed inflationary universe models proposed by Linde in a brane world cosmological context. In this scenario we determine and characterize the existence of a closed universe, in presence of one self-interacting scalar field with an inflationary stage. We have found that our model, which takes into account a Brane World Cosmology, is less restrictive than the one that uses standard Einstein's General Relativity cosmology.

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COLEY, A. A. "BRANE-WORLD COSMOLOGY." International Journal of Modern Physics D 11, no. 10 (December 2002): 1609–14. http://dx.doi.org/10.1142/s0218271802002979.

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It is argued that typically the initial singularity is isotropic in brane world cosmological models. Consequently brane cosmology naturally gives rise to a set of initial data that provide the conditions for inflation to subsequently take place, leading to a self-consistent and viable cosmological scenario.

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SAHNI, VARUN, and YURI SHTANOV. "NEW VISTAS IN BRANEWORLD COSMOLOGY." International Journal of Modern Physics D 11, no. 10 (December 2002): 1515–21. http://dx.doi.org/10.1142/s0218271802002827.

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Traditionally, higher-dimensional cosmological models have sought to provide a description of the fundamental forces in terms of a unifying geometrical construction. In this essay we discuss how, in their present incarnation, higher-dimensional "braneworld" models might provide answers to a number of cosmological puzzles including the issue of dark energy and the nature of the big bang singularity.

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MACÍAS, ALFREDO, ECKEHARD W. MIELKE, and JOSÉ SOCORRO. "SUPERSYMMETRIC QUANTUM COSMOLOGY FOR BIANCHI CLASS A MODELS." International Journal of Modern Physics D 07, no. 05 (October 1998): 701–12. http://dx.doi.org/10.1142/s0218271898000462.

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The canonical theory of [Formula: see text] supergravity, with a matrix representation for the gravitino covector–spinor, is applied to the Bianchi class A spatially homogeneous cosmologies. The full Lorentz constraint and its implications for the wave function of the universe are analyzed in detail. We found that in this model no physical states other than the trivial "rest frame" type occur.

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Stornaiolo, Cosimo. "Tomographic analysis of quantum and classical de Sitter cosmological models." International Journal of Modern Physics D 28, no. 16 (October 15, 2019): 2040009. http://dx.doi.org/10.1142/s021827182040009x.

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In this work, we show the importance of introducing the quantum tomography formalism to analyze the properties of wave functions in quantum cosmology. In particular, we examine the initial conditions of the universe proposed by various authors in the context of de Sitter’s cosmology studying their classical limit and comparing it with the classical tomogram obtained from the Hamiltonian constraint in General Relativity. This comparison gives us the opportunity to find under which conditions there is a transition from the quantum universe to the classical one. A relevant result is that in these

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Jawad, Abdul, Shamaila Rani, Ines G. Salako, and Faiza Gulshan. "Pilgrim dark energy models in fractal universe." International Journal of Modern Physics D 26, no. 06 (November 22, 2016): 1750049. http://dx.doi.org/10.1142/s0218271817500493.

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We discuss the cosmological implications of interacting pilgrim dark energy (PDE) models (with Hubble, Granda–Oliveros and generalized ghost cutoffs) with cold dark matter ([Formula: see text]CDM) in fractal cosmology by assuming the flat universe. We observe that the Hubble parameter lies within observational suggested ranges while deceleration parameter represents the accelerated expansion behavior of the universe. The equation of state (EoS) parameter ([Formula: see text]) corresponds to the quintessence region and phantom region for different cases of [Formula: see text]. Further, we can s

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COTSAKIS, SPIROS. "STRUCTURE OF INFINITY IN COSMOLOGY." International Journal of Modern Physics D 22, no. 03 (March 2013): 1330003. http://dx.doi.org/10.1142/s0218271813300036.

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We discuss recent developments related to certain blow-up methods suitable for the analysis of cosmological singularities and asymptotics. We review results obtained in a variety of currently popular themes and describe ongoing research about universes with various kinds of extreme states, higher-order gravity and certain models of braneworlds.

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VAKILI, BABAK. "COSMOLOGY WITH MINIMAL LENGTH UNCERTAINTY RELATIONS." International Journal of Modern Physics D 18, no. 07 (July 2009): 1059–71. http://dx.doi.org/10.1142/s0218271809014935.

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We study the effects of the existence of a minimal observable length in the phase space of classical and quantum de Sitter (dS) and anti-de Sitter (AdS) cosmology. Since this length has been suggested in quantum gravity and string theory, its effects in the early universe might be expected. Adopting the existence of such a minimum length results in the generalized uncertainty principle (GUP), which is a deformed Heisenberg algebra between minisuperspace variables and their momenta operators. We extend these deformed commutating relations to the corresponding deformed Poisson algebra in the cla

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CAPOZZIELLO, SALVATORE, RUGGIERO DE RITIS, and PAOLO SCUDELLARO. "NÖTHER’S SYMMETRIES IN QUANTUM COSMOLOGY." International Journal of Modern Physics D 03, no. 03 (September 1994): 609–21. http://dx.doi.org/10.1142/s0218271894000745.

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We construct minisuperspace models for a class of theories of gravity nonminimally coupled with a scalar field. We show that when a Nöther symmetry exists, it is always possible to integrate the Wheeler-DeWitt equation and recover the semiclassical regime for the wave function of the universe. In this sense, we can interpret the Nöther symmetries as a selection rule in the philosophy of the so called Hartle criterion: when they exist, it is possible to select classical universes.

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Sadeghi, J., M. Khurshudyan, and H. Farahani. "Interacting ghost dark energy models in the higher dimensional cosmology." International Journal of Modern Physics D 25, no. 14 (December 2016): 1650108. http://dx.doi.org/10.1142/s021827181650108x.

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We investigate interacting ghost dark energy models in higher dimensional cosmology. We attempt to model dark matter within a barotropic fluid with [Formula: see text]. In this work, we consider four different models based on choosing equation of state (EoS) parameter and interaction term. We confirm that our models agree with observational data.

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Brevik, I., and A. V. Timoshkin. "Holographic cosmology with two coupled fluids in the presence of viscosity." International Journal of Geometric Methods in Modern Physics 18, no. 09 (June 11, 2021): 2150149. http://dx.doi.org/10.1142/s0219887821501498.

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We explore the cosmological models of the late-time universe based on the holographic principle, taking into account the properties of the viscosity of the dark fluid. We use the mathematical formalism of generalized infrared cutoff holographic dark energy, as presented by Nojiri and Odintsov [Covariant generalized holographic dark energy and accelerating universe, Eur. Phys. J. C 77 (2017) 528]. We consider the Little Rip, the Pseudo Rip, and a bounce exponential model, with two interacting fluids, namely dark energy and dark matter in a spatially-flat Friedmann–Robertson–Walker universe. Wit

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Akbarieh, Amin Rezaei, Hossein Motavalli, and Elham Nouri. "Non-canonical Chameleon cosmology." International Journal of Modern Physics D 30, no. 08 (May 12, 2021): 2150059. http://dx.doi.org/10.1142/s0218271821500590.

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One of the most important issues in modern cosmology is understanding the origin of the accelerated expansion of the universe, known as “dark energy”. The scalar–tensor model is one of the most interesting candidates for describing dark energy. In this paper, we investigate the non-canonical scalar model, which is written in the framework of Chameleon models. In this model, the scalar field is coupled to a mass density [Formula: see text] under an arbitrary [Formula: see text] coupling function. We study the cosmological aspect of this model according to its Chameleon state and we conclude tha

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Khlopov, Maxim Yu. "Removing the conspiracy of BSM physics and BSM cosmology." International Journal of Modern Physics D 28, no. 13 (October 2019): 1941012. http://dx.doi.org/10.1142/s0218271819410128.

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The standard model (SM) of elementary particles finds no contradictions in the experimental data, but appeals to extensions for solutions of its internal problems and physical basis of the modern cosmology. The latter is based on inflationary models with baryosynthesis and dark matter/energy that involves Physics beyond the standard model (BSM) of elementary particles. However, studies of the BSM physical basis of the modern cosmology inevitably reveals additional particle model-dependent cosmological consequences that go beyond the modern standard cosmological model. The mutual relationship o

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Díaz-Barrón, Luis Rey, Abraham Espinoza-García, S. Pérez-Payán, and J. Socorro. "Anisotropic chiral cosmology: Exact solutions." International Journal of Modern Physics D 30, no. 11 (July 8, 2021): 2150080. http://dx.doi.org/10.1142/s0218271821500802.

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In this work, we investigate the anisotropic Bianchi type I cosmological model in the chiral set-up in a twofold manner. Firstly, we consider a quintessence plus a [Formula: see text]-essence-like model, where two scalar fields but only one potential term is considered. Secondly, we look at a model where in addition to the two scalar fields the two potential terms are taken into account as well as the standard kinetic energy and the mixed term. Regarding this second model, it is shown that two possible cases can be studied: a quintom-like case and a quintessence-like case. In each of the model

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Jamal, Sameerah. "Multiscalar field models: Interaction potentials, wave functions and cosmological solutions." International Journal of Modern Physics D 29, no. 07 (May 2020): 2050046. http://dx.doi.org/10.1142/s0218271820500467.

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We consider a multiscalar tensor cosmology model described by Friedmann–Robertson–Walker (FRW) spacetime with zero spatial curvature. Three specific scalar interaction potentials that characterize the model are analyzed under a set of coordinate transformations. By implication, we solve for the wave function of the universe, reduce the dimension of the underlying Hamiltonian system and consequently, establish analytical solutions of the multiscalar model’s field equations.

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Banks, Tom, and W. Fischler. "The holographic spacetime model of cosmology." International Journal of Modern Physics D 27, no. 14 (October 2018): 1846005. http://dx.doi.org/10.1142/s0218271818460057.

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This essay outlines the Holographic Spacetime (HST) theory of cosmology and its relation to conventional theories of inflation. The predictions of the theory are compatible with observations, and one must hope for data on primordial gravitational waves or non-Gaussian fluctuations to distinguish it from conventional models. The model predicts an early era of structure formation, prior to the Big Bang. Understanding the fate of those structures requires complicated simulations that have not yet been done. The result of those calculations might falsify the model, or might provide a very economic

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COULE, D. H. "ENTROPIC ISSUES IN CONTEMPORARY COSMOLOGY." International Journal of Modern Physics D 12, no. 06 (July 2003): 963–76. http://dx.doi.org/10.1142/s0218271803003530.

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Penrose1 has emphasized how the initial big bang singularity requires a special low entropy state. We address how recent brane cosmological schemes address this problem and whether they offer any apparent resolution. Pushing the start time back to t = -∞, or utilizing maximally symmetric AdS spaces, simply exacerbates or transfers the problem. Since the entropy of de Sitter space is S ≤ 1/Λ, using the present acceleration of the universe as a low energy (Λ ~ 10-120) inflationary stage, as in cyclic ekpyrotic models, produces a gravitational heat death after one cycle. Only higher energy driven

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Wang, Deng. "Cosmology with Type II supernovae." International Journal of Modern Physics D 28, no. 08 (June 2019): 1950106. http://dx.doi.org/10.1142/s0218271819501062.

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With the recent progresses on the Type II supernovae, we attempt to investigate whether there does exist new physics beyond the standard cosmological paradigm, i.e. the cosmological constant [Formula: see text] plus cold dark matter ([Formula: see text]CDM). Constraining four alternative cosmological models with a data combination of currently available Type II supernovae calibrated by the standard color method, Type Ia supernovae, baryon acoustic oscillations (BAO), cosmic microwave background (CMB) and cosmic chronometers, at the [Formula: see text] confidence level, we find that (i) a spati

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KONSTANTINOV, M. YU, V. N. MELNIKOV, and M. NOVELLO. "NUMERICAL INVESTIGATION OF INTEGRABLE WEYL GEOMETRY IN MULTIDIMENSIONAL COSMOLOGY." International Journal of Modern Physics D 04, no. 03 (June 1995): 339–55. http://dx.doi.org/10.1142/s0218271895000260.

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The evolution of 4-dimensional and (4+D)-dimensional (D=1, 2) cosmological models based on the integrable Weyl geometry are considered numerically both for empty space-time and for scalar field with nonminimal coupling with gravity. In both cases nonsingular solutions exist only for the open exterior space and flat (with torus topology) interior space. It is shown that in the nonsingular case the scenario of dynamical dimension reduction is realized. Some characteristic features of the considered models and their possible generalizations are discussed.

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Ahmed, Nasr, Anirudh Pradhan, and F. Salama. "A new topological perspective of expanding space-times with applications to cosmology." International Journal of Geometric Methods in Modern Physics 18, no. 08 (May 12, 2021): 2150130. http://dx.doi.org/10.1142/s0219887821501309.

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We discuss the possible role of the Tietze extension theorem in providing a rigorous topological base to the expanding space-time in cosmology. A simple toy model has been introduced to show the analogy between the topological extension from a circle [Formula: see text] to the whole space [Formula: see text] and the cosmic expansion from a non-zero volume to the whole space-time in non-singular cosmological models. A topological analogy to the cosmic scale factor function has been suggested, the paper refers to the possible applications of the topological extension in mathematical physics.

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KIM, KYONG HEE, and YUN SOO MYUNG. "TEST OF PATCH COSMOLOGY WITH WMAP." International Journal of Modern Physics D 14, no. 10 (October 2005): 1813–29. http://dx.doi.org/10.1142/s0218271805007425.

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We calculate the power spectrum, spectral index, and running spectral index for inflationary patch cosmology arisen from Gauss–Bonnet braneworld scenario using the Mukhanov equation. This patch cosmology consists of Gauss–Bonnet (GB), Randall–Sundrum (RS-II), and four-dimensional (4D) cosmological models. There exist several modifications in higher order calculations. However, taking the power-law inflation by choosing different potentials depending on the model, there exist minor changes up to second order corrections. Since second order corrections are rather small in the slow-roll limit, we

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ANDRIANOV, ALEXANDER A., FRANCESCO CANNATA, ALEXANDER YU KAMENSHCHIK, and DANIELE REGOLI. "PHANTOM COSMOLOGY BASED ON PT SYMMETRY." International Journal of Modern Physics D 19, no. 01 (January 2010): 97–111. http://dx.doi.org/10.1142/s0218271810016269.

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We consider the PT-symmetric flat Friedmann model of two scalar fields with positive kinetic terms. While the potential of one "normal" field is taken real, that of the other field is complex. We study a complex classical solution of the system of the two Klein–Gordon equations together with the Friedmann equation. The solution for the normal field is real, while the solution for the second field is purely imaginary, realizing classically the "phantom" behavior. The energy density and pressure are real and the corresponding geometry is well defined. The Lagrangian for the linear perturbations

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KARAMI, K., S. ASADZADEH, M. MOUSIVAND, and Z. SAFARI. "QCD MODIFIED GHOST SCALAR FIELD DARK ENERGY MODELS." International Journal of Modern Physics D 22, no. 05 (April 2013): 1350018. http://dx.doi.org/10.1142/s0218271813500181.

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Within the framework of FRW cosmology, we study the QCD modified ghost scalar field models of dark energy (DE) in the presence of both interaction and viscosity. For a spatially nonflat FRW universe containing modified ghost dark energy (MGDE) and dark matter (DM), we obtain the equation of state of MGDE, the deceleration parameter as well as a differential equation governing the MGDE density parameter. We also investigate the growth of structure formation for our model in a linear perturbation regime. Furthermore, we reconstruct both the dynamics and potentials of the quintessence, tachyon, K

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Moniz, P. V. "Conserved Currents in Supersymmetric Quantum Cosmology?" International Journal of Modern Physics D 06, no. 05 (October 1997): 625–41. http://dx.doi.org/10.1142/s0218271897000388.

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In this paper we investigate whether conserved currents can be sensibly defined in super-symmetric minisuperspaces. Our analysis deals with k = +1 FRW and Bianchi class-A models. Supermatter in the form of scalar supermultiplets is included in the former. Moreover, we restrict ourselves to the first-order differential equations derived from the Lorentz and supersymmetry constraints. The "square-root" structure of N = 1 super-gravity was our motivation to contemplate this interesting research. We show that conserved currents cannot be adequately established except for some very simple scenarios

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BARCELÓ, CARLOS, STEFANO LIBERATI, and MATT VISSER. "ANALOGUE MODELS FOR FRW COSMOLOGIES." International Journal of Modern Physics D 12, no. 09 (October 2003): 1641–49. http://dx.doi.org/10.1142/s0218271803004092.

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It is by now well known that various condensed matter systems may be used to mimic many of the kinematic aspects of general relativity, and in particular of curved-spacetime quantum field theory. In this essay we will take a look at what would be needed to mimic a cosmological spacetime — to be precise a spatially flat FRW cosmology — in one of these analogue models. In order to do this one needs to build and control suitable time dependent systems. We discuss here two quite different ways to achieve this goal. One might rely on an explosion, physically mimicking the big bang by an outflow of

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GUNZIG, E., and ALBERTO SAA. "QUANTUM EFFECTS AND SUPERQUINTESSENCE IN THE NEW AGE OF PRECISION COSMOLOGY." International Journal of Modern Physics D 13, no. 10 (December 2004): 2255–59. http://dx.doi.org/10.1142/s0218271804006292.

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Recent observations of Type Ia supernova at high redshifts establish that the dark energy component of the universe has (a probably constant) ratio between pressure and energy density [Formula: see text]. The conventional quintessence models for dark energy are restricted to the range -1≤w<0, with the cosmological constant corresponding to w=-1. Conformally coupled quintessence models are the simplest ones compatible with the marginally allowed superaccelerated regime (w<-1). However, they are known to be plagued with anisotropic singularities. We argue here that the extension of the cla

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Benetti, Micol, Simony Santos da Costa, Salvatore Capozziello, Jailson S. Alcaniz, and Mariafelicia De Laurentis. "Observational constraints on Gauss–Bonnet cosmology." International Journal of Modern Physics D 27, no. 08 (May 30, 2018): 1850084. http://dx.doi.org/10.1142/s0218271818500840.

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We analyze a fully geometric approach to dark energy in the framework of [Formula: see text] theories of gravity, where [Formula: see text] is the Ricci curvature scalar and [Formula: see text] is the Gauss–Bonnet topological invariant. The latter invariant naturally exhausts, together with [Formula: see text], the whole curvature content related to curvature invariants coming from the Riemann tensor. In particular, we study a class of [Formula: see text] models with power law solutions and find that, depending on the value of the geometrical parameter, a shift in the anisotropy peaks position

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GALIAKHMETOV, A. M. "SPATIALLY FLAT FRW MODELS WITH A NONMINIMALLY COUPLED GHOST SCALAR FIELD AND PERFECT FLUID IN EINSTEIN–CARTAN THEORY." International Journal of Modern Physics D 21, no. 01 (January 2012): 1250001. http://dx.doi.org/10.1142/s0218271812500010.

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Exact general solutions to the Einstein–Cartan equations are obtained for spatially flat Friedmann cosmologies with a nonminimally coupled ghost scalar field and perfect fluid. It is shown that both singular and bouncing models are possible. An analogous problem is investigated in general relativity. Some effects of torsion are elucidated. The role of perfect fluid in the Einstein–Cartan cosmology is discussed.

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ALTSHULER, B. L., A. M. BOYARSKY, and A. YU NERONOV. "THE PROBLEM OF CLASSICAL LIMIT IN QUANTUM COSMOLOGY: THE EFFECTIVE ACTION LANGUAGE." International Journal of Modern Physics D 05, no. 06 (December 1996): 869–84. http://dx.doi.org/10.1142/s0218271896000527.

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The tool of functional averaging over some “large” diffeomorphisms is used to describe quantum systems with constraints, in particular quantum cosmology, in the language of quantum Effective. Action. Simple toy models demonstrate a supposedly general phenomenon: the presence of a constraint results in “quantum repel” from the classical mass shell.

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Mijić, Milan. "Quantum Squeezing and Late Time Classical Behavior of Massive Fields in Expanding Robertson–Walker Universe." International Journal of Modern Physics D 06, no. 04 (August 1997): 505–14. http://dx.doi.org/10.1142/s0218271897000303.

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A Schroedinger picture analysis of time dependent quantum oscillators, in a manner of Guth and Pi, clearly identifies two physical mechanisms for possible decoherence of vacuum fluctuations in the early universe: turning of quantum oscillators upside-down, and rapid squeezing of upside-right oscillators so that certain squeezing factor diverges. In inflationary cosmology the former mechanism explains the stochastic evolution of light inflatons and the classical nature of density perturbations in most of the inflationary models, while the later one is responsible for the classical evolution of

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ALLEMANDI, GIANLUCA, and MAURO FRANCAVIGLIA. "THE VARIATIONAL APPROACH TO ALTERNATIVE THEORIES OF GRAVITY." International Journal of Geometric Methods in Modern Physics 04, no. 01 (February 2007): 1–23. http://dx.doi.org/10.1142/s0219887807001965.

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This paper is based on lectures given in Ladek-Zdroj, Poland during the 42nd edition of the Karpac winter school on Theoretical Physics. The aim of these lectures was to give an introduction to a rigorous, mathematically well based, variational approach to alternative theories of Gravity, in view of their very interesting recent applications in the framework of Cosmology. We discuss alternative theories of Gravity both in the metric, purely affine and Palatini formalism, stressing differences and analogies both from a physical and mathematical viewpoint. Moreover we give and introduction to al

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El Hanafy, W., and G. G. L. Nashed. "Lorenz gauge fixing of f(T) teleparallel cosmology." International Journal of Modern Physics D 26, no. 14 (December 2017): 1750154. http://dx.doi.org/10.1142/s0218271817501541.

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In teleparallel gravity, we apply Lorenz type gauge fixing to cope with redundant degrees of freedom in the vierbein field. This condition is mainly to restore the Lorentz symmetry of the teleparallel torsion scalar. In cosmological application, this technique provides standard cosmology, turnaround, bounce or [Formula: see text]CDM as separate scenarios. We reconstruct the [Formula: see text] gravity which generates these models. We study the stability of the solutions by analyzing the corresponding phase portraits. Also, we investigate Lorenz gauge in the unimodular coordinates, it leads to

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ALVARENGA, F. G., A. B. BATISTA, and J. C. FABRIS. "DOES QUANTUM COSMOLOGY PREDICT A CONSTANT DILATONIC FIELD?" International Journal of Modern Physics D 14, no. 02 (February 2005): 291–307. http://dx.doi.org/10.1142/s0218271805005955.

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Quantum cosmology may permit to determine the initial conditions of the Universe. In particular, it may select a specific model between many possible classical models. In this work, we study a quantum cosmological model based on the string effective action coupled to matter. The Schutz's formalism is employed in the description of the fluid. A radiation fluid is considered. In this way, a time coordinate may be identified and the Wheeler–DeWitt equation reduces in the minisuperspace to a Schrödinger-like equation. It is shown that, under some quite natural assumptions, the expectation values i

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Chakraborty, Subenoy, and Arabinda Ghosh. "Brans–Dicke Cosmology—A Generalization in Four and Five Dimensional Space-time Models." Physica Scripta 68, no. 1 (January 1, 2003): 98–100. http://dx.doi.org/10.1238/physica.regular.068a00098.

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Zecca, Antonio. "Models of H-atom in Lemaitre Tolman Bondi cosmology from Dirac equation with `curved' Coulomb potential." Advanced Studies in Theoretical Physics 16, no. 3 (2022): 121–30. http://dx.doi.org/10.12988/astp.2022.91877.

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Rabha, Chayanika, and Sanjeev Kalita. "Cosmic expansion with curved dark energy cosmology: Inevitability of cosmic doomsday." International Journal of Modern Physics D 30, no. 07 (April 8, 2021): 2150048. http://dx.doi.org/10.1142/s0218271821500486.

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In this work, we have constructed deceleration–acceleration and future evolution of cosmic expansion with curved dynamical dark energy models. Closed and open spatial curvatures are calculated by assuming that dark energy density does not exceed 85% of the closure density and by obtaining lower bounds on the ratio of dark energy to matter density, in terms of equation of state of dark energy. The range of transition epoch [Formula: see text] realized for spatial curvature [Formula: see text] is consistent with model independent estimations coming from galactic ages, strong lensing, Type Ia sup

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Padilla, Luis E., Luis O. Tellez, Luis A. Escamilla, and Jose Alberto Vazquez. "Cosmological Parameter Inference with Bayesian Statistics." Universe 7, no. 7 (June 28, 2021): 213. http://dx.doi.org/10.3390/universe7070213.

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Bayesian statistics and Markov Chain Monte Carlo (MCMC) algorithms have found their place in the field of Cosmology. They have become important mathematical and numerical tools, especially in parameter estimation and model comparison. In this paper, we review some fundamental concepts to understand Bayesian statistics and then introduce MCMC algorithms and samplers that allow us to perform the parameter inference procedure. We also introduce a general description of the standard cosmological model, known as the ΛCDM model, along with several alternatives, and current datasets coming from astro

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Desgrange, Célia, Asta Heinesen, and Thomas Buchert. "Dynamical spatial curvature as a fit to Type Ia supernovae." International Journal of Modern Physics D 28, no. 11 (August 2019): 1950143. http://dx.doi.org/10.1142/s0218271819501438.

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Few statements in cosmology can be made without assuming a cosmological model within which to interpret data. Statements about cosmic acceleration are no exception to this rule, and the inferred positive volume acceleration of our universe often quoted in the literature is valid in the context of the standard Friedmann–Lemaître–Robertson–Walker (FLRW) class of spacetimes. Using the Joint Light-curve Analysis (JLA) catalogue of supernovae Type Ia (SNIa), we examine the fit of a class of exact scaling solutions with dynamical spatial curvature formulated in the framework of a scalar averaging sc

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SOURADEEP, TARUN. "COSMOLOGICAL QUESTS IN THE CMB SKY." International Journal of Modern Physics D 15, no. 10 (October 2006): 1725–42. http://dx.doi.org/10.1142/s0218271806009066.

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Observational cosmology has indeed made a very rapid progress in recent years. The ability to quantify the universe has largely improved due to observational constraints coming from structure formation measurements of CMB anisotropy and, more recently, polarization has played a very important role. Besides precise determination of various parameters of the "standard" cosmological model, observations have also established some important basic tenets that underlie models of cosmology and structure formation in the universe — "acausally" correlated initial perturbations in a flat, statistically i

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Momeni, Davood, та Ratbay Myrzakulov. "Cosmological reconstruction of f(T, 𝒯) gravity". International Journal of Geometric Methods in Modern Physics 11, № 08 (вересень 2014): 1450077. http://dx.doi.org/10.1142/s0219887814500777.

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Motivated by the newly proposal for gravity as the effect of the torsion scalar T and trace of the energy momentum tensor 𝒯, we investigate the cosmological reconstruction of different models of the Universe. Our aim here is to show that how this modified gravity model, f(T, 𝒯) is able to reproduce different epochs of the cosmological history. We explicitly show that f(T, 𝒯) can be reconstructed for ΛCDM as the most popular and consistent model. Also we study the mathematical reconstruction of f(T, 𝒯) for a flat cosmological background filled by two fluids mixture. Such model describes phantom

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KRASIŃSKI, ANDRZEJ, and KRZYSZTOF BOLEJKO. "EXACT INHOMOGENEOUS MODELS AND THE DRIFT OF LIGHT RAYS INDUCED BY NONSYMMETRIC FLOW OF THE COSMIC MEDIUM." International Journal of Modern Physics D 22, no. 06 (April 28, 2013): 1330013. http://dx.doi.org/10.1142/s0218271813300139.

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After introducing the Szekeres and Lemaître–Tolman cosmological models, the real-time cosmology program is briefly mentioned. Then, a few widespread misconceptions about the cosmological models are pointed out and corrected. Investigation of null geodesic equations in the Szekeres models shows that observers in favorable positions would see galaxies drift across the sky at a rate of up to 10-6 arc s per year. Such a drift would be possible to measure using devices that are under construction; the required time of monitoring would be ≈10 years. This effect is zero in the FLRW models, so it prov

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Schmidt, H. J. "BOOK REVIEW: Modern Mathematical Models of Time and Their Applications to Physics and Cosmology edited by W. Tifft and W. Cocke." General Relativity and Gravitation 33, no. 8 (August 2001): 1425. http://dx.doi.org/10.1023/a:1012017910820.

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Avetisyan, Zhirayr G. "A unified mode decomposition method for physical fields in homogeneous cosmology." Reviews in Mathematical Physics 26, no. 03 (April 2014): 1430001. http://dx.doi.org/10.1142/s0129055x14300015.

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The methods of mode decomposition and Fourier analysis of classical and quantum fields on curved spacetimes previously available mainly for the scalar field on Friedman–Robertson–Walker (FRW) spacetimes are extended to arbitrary vector bundle fields on general spatially homogeneous spacetimes. This is done by developing a rigorous unified framework which incorporates mode decomposition, harmonic analysis and Fourier analysis. The limits of applicability and uniqueness of mode decomposition by separation of the time variable in the field equation are found. It is shown how mode decomposition ca

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REN, JIE, and XIN-HE MENG. "TACHYON FIELD-INSPIRED DARK ENERGY AND SUPERNOVAE CONSTRAINTS." International Journal of Modern Physics D 17, no. 12 (November 2008): 2325–35. http://dx.doi.org/10.1142/s0218271808013893.

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The tachyon field in cosmology is studied in this paper by applying the generating function method to obtain exact solutions. The equation of state parameter of the tachyon field is [Formula: see text], which can be expressed as a function in terms of the redshift z. Based on these solutions, we propose some tachyon-inspired dark energy models to explore the properties of the corresponding cosmological evolution. The explicit relations between the Hubble parameter and redshift enable us to test the models with SNe Ia data sets easily. In this paper, we employ the SNe Ia data with the parameter

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Burde, Georgy I. "Cosmological models based on relativity with a privileged frame." International Journal of Modern Physics D 29, no. 06 (April 2020): 2050038. http://dx.doi.org/10.1142/s0218271820500388.

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Cosmological models, stemming from the extension of the “special relativity (SR) with a privileged frame” to general relativity (GR), are developed and fitted to the observational data. The framework termed “SR with a privileged frame” incorporates the privileged frame into SR while retaining the fundamental spacetime symmetry which, in the standard SR, manifests itself as Lorentz invariance. The correspondingly modified GR, like the standard GR, is based on the equivalence principle but with the properly modified spacetime local symmetry in which an invariant combination differs from the Mink

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Chetry, Binod, Jibitesh Dutta, and Wompherdeiki Khyllep. "Thermodynamics of scalar field models with kinetic corrections." International Journal of Modern Physics D 28, no. 15 (November 2019): 1950163. http://dx.doi.org/10.1142/s0218271819501633.

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In this work, we compare the thermodynamical viability of two types of noncanonical scalar field models with kinetic corrections: the square kinetic and square root kinetic corrections. In modern cosmology, the generalized second law of thermodynamics (GSLT) plays an important role in deciding thermodynamical compliance of a model as one cannot consider a model to be viable if it fails to respect GSLT. Hence, for comparing thermodynamical viability, we examine the validity of GSLT for these two models. For this purpose, by employing the Unified first law (UFL), we calculate the total entropy o

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Endress, Gerhard. "Averroes' De Caelo Ibn Rushd's Cosmology in his Commentaries on Aristotle's On the Heavens." Arabic Sciences and Philosophy 5, no. 1 (March 1995): 9–49. http://dx.doi.org/10.1017/s0957423900001934.

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Averroes defended philosophy by returning to the true Aristotle. For this purpose, Aristotle's book “On the Heaven,” in which he explained the eternity, uniqueness and movement of the universe, occupied a place of special importance. But the Aristotelian philosopher had a hard time holding his own in the face of contradictions within the book and with respect to Aristotle's later works. In his early Compendium, later Paraphrase, and final Long Commentary of De Caelo, Ibn Rushd continued the efforts of the Hellenistic commentators in order to integrate all the elements of his doctrine into a un

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