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A Possible Explanation of Dark Matter and Dark Energy Involving a Vector Torsion Field. UNIVERSE 2022. [DOI: 10.3390/universe8060298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A simple gravitational model with torsion is studied, and it is suggested that it could explain the dark matter and dark energy in the universe. It can be reinterpreted as a model using the Einstein gravitational equations where spacetime has regions filled with a perfect fluid with negative energy (pressure) and positive mass density, other regions containing an anisotropic substance that in the rest frame (where the momentum is zero) has negative mass density and a uniaxial stress tensor, and possibly other “luminal” regions where there is no rest frame. The torsion vector field is inhomogeneous throughout spacetime, and possibly turbulent. Numerical simulations should reveal whether or not the equations are consistent with cosmological observations of dark matter and dark energy.
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Classical and Quantum f(R) Cosmology: The Big Rip, the Little Rip and the Little Sibling of the Big Rip. UNIVERSE 2021. [DOI: 10.3390/universe7080288] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The big rip, the little rip and the little sibling of the big rip are cosmological doomsdays predicted by some phantom dark-energy models that could describe the future evolution of our universe. When the universe evolves towards either of these future cosmic events, all bounded structures and, ultimately, space–time itself are ripped apart. Nevertheless, it is commonly believed that quantum gravity effects may smooth or even avoid these classically predicted singularities. In this review, we discuss the classical and quantum occurrence of these riplike events in the scheme of metric f(R) theories of gravity. The quantum analysis is performed in the framework of f(R) quantum geometrodynamics. In this context, we analyze the fulfilment of the DeWitt criterion for the avoidance of these singular fates. This review contains as well new unpublished work (the analysis of the equation of state for the phantom fluid and a new quantum treatment of the big rip and the little sibling of the big rip events).
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Reconstructed f(R) Gravity and Its Cosmological Consequences in theChameleon Scalar Field with a Scale Factor Describing the Pre-Bounce Ekpyrotic Contraction. Symmetry (Basel) 2020. [DOI: 10.3390/sym12091559] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The present study reports a reconstruction scheme for f(R) gravity with the scale factor a(t)∝(t*−t)2c2 describing the pre-bounce ekpyrotic contraction, where t* is the big crunch time. The reconstructed f(R) is used to derive expressions for density and pressure contributions, and the equation of state parameter resulting from this reconstruction is found to behave like “quintom”. It has also been observed that the reconstructed f(R) has satisfied a sufficient condition for a realistic model. In the subsequent phase, the reconstructed f(R) is applied to the model of the chameleon scalar field, and the scalar field ϕ and the potential V(ϕ) are tested for quasi-exponential expansion. It has been observed that although the reconstructed f(R) satisfies one of the sufficient conditions for realistic model, the quasi-exponential expansion is not available due to this reconstruction. Finally, the consequences of pre-bounce ekpyrotic inflation in f(R) gravity are compared to the background solution for f(R) matter bounce.
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Unified Inflation and Late-Time Accelerated Expansion with Exponential and R2 Corrections in Modified Gravity. Symmetry (Basel) 2020. [DOI: 10.3390/sym12050794] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Modified gravity models with and exponential function of curvature and R 2 corrections are proposed. At low curvature, the model explains the matter epoch and the late time accelerated expansion while at the inflation epoch the leading term is R 2 . At R → 0 the cosmological constant disappears, giving unified description of inflation and dark energy in pure geometrical context. The models satisfy the stability conditions, pass local tests and are viable in the ( r , m ) -plane, where the trajectories connect the saddle matter dominated critical point ( r = − 1 , m = 0 ) with the late time de Sitter attractor at r = − 2 and 0 < m ≤ 1 . Initial conditions were found, showing that the density parameters evolve in a way consistent with current cosmological observations, predicting late time behavior very close to the Λ CDM with future universe evolving towards the de Sitter attractor.
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Dark Energy and Dark Matter Interaction: Kernels of Volterra Type and Coincidence Problem. Symmetry (Basel) 2018. [DOI: 10.3390/sym10090411] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
We study a new exactly solvable model of coupling of the Dark Energy and Dark Matter, in the framework of which the kernel of non-gravitational interaction is presented by the integral Volterra-type operator well-known in the classical theory of fading memory. Exact solutions of this isotropic homogeneous cosmological model were classified with respect to the sign of the discriminant of the cubic characteristic polynomial associated with the key equation of the model. Energy-density scalars of the Dark Energy and Dark Matter, the Hubble function and acceleration parameter are presented explicitly; the scale factor is found in quadratures. Asymptotic analysis of the exact solutions has shown that the Big Rip, Little Rip, Pseudo Rip regimes can be realized with the specific choice of guiding parameters of the model. We show that the Coincidence problem can be solved if we consider the memory effect associated with the interactions in the Dark Sector of the universe.
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Granda LN, Jimenez DF. Dynamical analysis for a scalar-tensor model with Gauss-Bonnet and non-minimal couplings. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2017; 77:679. [PMID: 29081712 PMCID: PMC5640800 DOI: 10.1140/epjc/s10052-017-5262-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 09/26/2017] [Indexed: 06/07/2023]
Abstract
We study the autonomous system for a scalar-tensor model of dark energy with Gauss-Bonnet and non-minimal couplings. The critical points describe important stable asymptotic scenarios including quintessence, phantom and de Sitter attractor solutions. Two functional forms for the coupling functions and the scalar potential are considered: power-law and exponential functions of the scalar field. For the exponential functions the existence of stable quintessence, phantom or de Sitter solutions, allows for an asymptotic behavior where the effective Newtonian coupling becomes constant. The phantom solutions could be realized without appealing to ghost degrees of freedom. Transient inflationary and radiation-dominated phases can also be described.
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Affiliation(s)
- L. N. Granda
- Departamento de Fisica, Universidad del Valle, Cali, A.A. 25360 Colombia
| | - D. F. Jimenez
- Departamento de Fisica, Universidad del Valle, Cali, A.A. 25360 Colombia
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Sahni V, Shafieloo A, Starobinsky AA. MODEL-INDEPENDENT EVIDENCE FOR DARK ENERGY EVOLUTION FROM BARYON ACOUSTIC OSCILLATIONS. ACTA ACUST UNITED AC 2014. [DOI: 10.1088/2041-8205/793/2/l40] [Citation(s) in RCA: 166] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Arabsalmani M, Sahni V, Saini TD. Reconstructing the properties of dark energy using standard sirens. Int J Clin Exp Med 2013. [DOI: 10.1103/physrevd.87.083001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Aviles A, Bravetti A, Capozziello S, Luongo O. Cosmographic reconstruction off(T)cosmology. Int J Clin Exp Med 2013. [DOI: 10.1103/physrevd.87.064025] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Timashev SF, Solov’eva AB, Buslaeva EY, Gubin SP. Concerted processes in supercritical fluids. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2012. [DOI: 10.1134/s0036024413010305] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Lazkoz R, Montiel A, Salzano V. First cosmological constraints on the superfluid Chaplygin gas model. Int J Clin Exp Med 2012. [DOI: 10.1103/physrevd.86.103535] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Dzhunushaliev V, Folomeev V, Kleihaus B, Kunz J. Mixed neutron-star-plus-wormhole systems: Equilibrium configurations. Int J Clin Exp Med 2012. [DOI: 10.1103/physrevd.85.124028] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Folomeev V, Singleton D. Relativistic polytropic spheres embedded in a chameleon scalar field. Int J Clin Exp Med 2012. [DOI: 10.1103/physrevd.85.064045] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Saini TD, Sethi SK, Sahni V. Possible use of self-calibration to reduce systematic uncertainties in determining distance-redshift relation via gravitational radiation from merging binaries. Int J Clin Exp Med 2010. [DOI: 10.1103/physrevd.81.103009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Jassal HK. Evolution of perturbations in distinct classes of canonical scalar field models of dark energy. Int J Clin Exp Med 2010. [DOI: 10.1103/physrevd.81.083513] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Libanov MV, Rubakov VA, Sazhina OS, Sazhin MV. CMB anisotropy induced by tachyonic perturbations of dark energy. Int J Clin Exp Med 2009. [DOI: 10.1103/physrevd.79.083521] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Abramo LR, Batista RC, Liberato L, Rosenfeld R. Physical approximations for the nonlinear evolution of perturbations in inhomogeneous dark energy scenarios. Int J Clin Exp Med 2009. [DOI: 10.1103/physrevd.79.023516] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Sussman RA. Quasilocal variables in spherical symmetry: Numerical applications to dark matter and dark energy sources. Int J Clin Exp Med 2009. [DOI: 10.1103/physrevd.79.025009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Unnikrishnan S, Jassal HK, Seshadri TR. Scalar field dark energy perturbations and their scale dependence. Int J Clin Exp Med 2008. [DOI: 10.1103/physrevd.78.123504] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Sheykhi A, Wang B, Riazi N. String inspired explanation for the superacceleration of our Universe. Int J Clin Exp Med 2007. [DOI: 10.1103/physrevd.75.123513] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Amendola L, Polarski D, Tsujikawa S. Are f(R) dark energy models cosmologically viable? PHYSICAL REVIEW LETTERS 2007; 98:131302. [PMID: 17501182 DOI: 10.1103/physrevd.75.083504] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Revised: 12/18/2006] [Indexed: 05/27/2023]
Abstract
All f(R) modified gravity theories are conformally identical to models of quintessence in which matter is coupled to dark energy with a strong coupling. This coupling induces a cosmological evolution radically different from standard cosmology. We find that, in all f(R) theories where a power of R is dominant at large or small R (which include most of those proposed so far in the literature), the scale factor during the matter phase grows as t(1/2) instead of the standard law t(2/3). This behavior is grossly inconsistent with cosmological observations (e.g., Wilkinson Microwave Anisotropy Probe), thereby ruling out these models even if they pass the supernovae test and can escape the local gravity constraints.
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Affiliation(s)
- Luca Amendola
- INAF/Oss. Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio Catone, Rome, Italy
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