Cosmological constraints on superconducting dark energy models (original) (raw)
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Physical Review D, 2015
Based on the analogy with superconductor physics we consider a scalar-vector-tensor gravitational model, in which the dark energy action is described by a gauge invariant electromagnetic type functional. By assuming that the ground state of the dark energy is in a form of a condensate with the U(1) symmetry spontaneously broken, the gauge invariant electromagnetic dark energy can be described in terms of the combination of a vector and of a scalar field (corresponding to the Goldstone boson), respectively. The gravitational field equations are obtained by also assuming the possibility of a non-minimal coupling between the cosmological mass current and the superconducting dark energy. The cosmological implications of the dark energy model are investigated for a Friedmann-Robertson-Walker homogeneous and isotropic geometry for two particular choices of the electromagnetic type potential, corresponding to a pure electric type field, and to a pure magnetic field, respectively. The time evolutions of the scale factor, matter energy density and deceleration parameter are obtained for both cases, and it is shown that in the presence of the superconducting dark energy the Universe ends its evolution in an exponentially accelerating vacuum de Sitter state. By using the formalism of the irreversible thermodynamic processes for open systems we interpret the generalized conservation equations in the superconducting dark energy model as describing matter creation. The particle production rates, the creation pressure and the entropy evolution are explicitly obtained.
Theory of superconductivity of gravitation and the dark matter enigma
In this article, the question of the nature of cold dark matter is approached from a new angle. By invoking the Cauchy problem of relativity it is shown how, under very precise astrophysical conditions, the Einstein general theory of relativity is formally equivalent to the Ginzburg-Landau theory of superconductivity. This fact lead us to suspect that the superconductivity of gravitation ought to be a real physical process occurring in the outskirts of galaxies. It is found that quantum mechanically gravity can achieve a type-II superconductor state characterised by the Gizburg-Landau parameter kappa=1.5\kappa=1.5kappa=1.5, and it is suggested that a probability flux of Cooper pairs (quantum gravitational geons charged with vacuum energy) are directly responsible for the flatness exhibited by the rotation curves in spiral galaxies, as well as the exotic behaviour observed in galactic cluster collisions. If this hypothesis proves correct, the whole phenomenon of dark matter may count, after all, as ...
New solution to the cosmological constant problem and cosmological model with superconductivity
Application of a quantum theory of superconductivity to the formation of the primary dark energy at the Planck scale allows us to solve the cosmological constant problem and to obtain the observed value of the dark energy density, corresponding to PLANK results. It is offered the new model of exponential expansion and the hot stage of the Universe. It is followed that the modern evolution of the universe can be viewed as a process of phase transition, and the physical time is an indicator of this transition. Keywords: dark energy theory, physics of the early universe, cosmological phase transitions, cosmological constant, vacuum energy density, cosmology.
Further analysis of a cosmological model with quintessence and scalar dark matter
Physical Review D, 2001
We present the complete solution to a 95% scalar field cosmological model in which the dark matter is modeled by a scalar field ⌽ with the scalar potential V(⌽)ϭV 0 ͓cosh(ͱ 0 ⌽)Ϫ1͔ and the dark energy is modeled by a scalar field ⌿, endowed with the scalar potential Ṽ (⌿)ϭṼ 0 ͓sinh(␣ͱ 0 ⌿)͔ . This model has only two free parameters, and the equation of state ⌿. With these potentials, the fine-tuning and cosmic coincidence problems are ameliorated for both dark matter and dark energy and the model agrees with astronomical observations. For the scalar dark matter, we clarify the meaning of a scalar Jeans length and then the model predicts a suppression of the mass power spectrum for small scales having a wave number kϾk min,⌽ , where k min,⌽ Ӎ4.5h Mpc Ϫ1 for Ӎ20.28. This last fact could help to explain the death of dwarf galaxies and the smoothness of galaxy core halos. From this, all parameters of the scalar dark matter potential are completely determined. The dark matter consists of an ultralight particle, whose mass is m ⌽ Ӎ1.1ϫ10 Ϫ23 eV and all the success of the standard cold dark matter model is recovered. This implies that a scalar field could also be a good candidate the dark matter of the Universe.
arXiv (Cornell University), 2024
It is well known that the cosmological constant term in the Einstein field equations can be interpreted as a stress tensor for dark energy. This stress tensor is formally analogous to an elastic constitutive equation in continuum mechanics. As a result, the cosmological constant leads to a "shear modulus" and "bulk modulus" affecting all gravitational fields in the universe. The form of the constitutive equation is also analogous to the London constitutive equation for a superconductor. Treating dark energy as a type of superconducting medium for gravitational waves leads to a Yukawa-like gravitational potential and a massive graviton within standard General Relativity. We discuss a number of resulting phenomenological aspects such as a screening length scale that can also be used to describe the effects generally attributed to dark matter. In addition, we find a gravitational wave plasma frequency, index of refraction, and impedance. The expansion of the universe is interpreted as a Meissner-like effect as dark energy causes an outward "expulsion" of space-time similar to a superconductor expelling a magnetic field. The fundamental cause of these effects is interpreted as a type of spontaneous symmetry breaking of a scalar field. There is an associated chemical potential, critical temperature, and an Unruh-Hawking effect associated with the formulation.
Constraints on scalar-tensor models of dark energy from observational and local gravity tests
Physical Review D, 2008
We construct a family of viable scalar-tensor models of dark energy (DE) which possess a phase of late-time acceleration preceded by a standard matter era, while at the same time satisfying the local gravity constraints (LGC). The coupling Q between the scalar field and the non-relativistic matter in the Einstein frame is assumed to be constant in our scenario, which is a generalization of f (R) gravity theories corresponding to the coupling Q = −1/ √ 6. We find that these models can be made compatible with local gravity constraints even when |Q| is of the order of unity through a chameleon mechanism, if the scalar-field potential is chosen to have a sufficiently large mass in the high-curvature regions. We show that these models generally lead to the divergence of the equation of state of DE, which occur at smaller redshifts as the deviation from the ΛCDM model become more significant. We also study the evolution of matter density perturbations and employ them to place bounds on the coupling |Q| as well as model parameters of the field potential from observations of the matter power spectrum and the CMB anisotropies. We find that, as long as |Q| is smaller than the order of unity, there exist allowed parameter regions that are consistent with both observational and local gravity constraints.
Supernovae constraints on models of dark energy reexamined
Physical Review D, 2005
We use the Type Ia Supernova gold sample data of Riess et al in order to constrain three models of dark energy. We study the Cardassian model, the Dvali-Turner gravity modified model, and the generalized Chaplygin gas model of dark energy-dark matter unification. In our best-fit analysis for these three dark energy proposals we consider the flat model and the nonflat model priors. We also discuss the degeneracy of the models with the XCDM model through the computation of the so-called jerk parameter.
N ov 2 01 8 Current Constraints on Anisotropic and Isotropic Dark Energy Models
2018
We use Gaussian processes in combination with MCMC method to place constraints on cosmological parameters of three dark energy models including flat and curved FRW and Bianchi type I spacetimes. To do so, we use recently compiled 36 measurements of the Hubble parameter H(z) in the redshifts intermediate 0.07 6 z 6 2.36. Moreover, we use these models to estimate the redshift of the deceleration-acceleration transition. We consider two Gaussian priors for current value of the Hubble constant i.e H0 = 73 ± 1.74(68 ± 2.8) km/s/Mpc to investigate the effect of the assumed H0 on our parameters estimations. For statistical analysis we use NUTS sampler which is an extension of Hamiltonian Monte Carlo algorithm to generate MCMC chains for parameters of dark energy models. To compare the considered cosmologies, we perform Akaike information criterion (AIC) and Bayes factor (Ψ). In general, when we compared our results with 9 years WMAP as well as Planck 2015 Collaboration, we found that Bianc...
BBN And CMB Constraints On Dark Energy
Phys Rev D, 2002
Current observational data favor cosmological models which differ from the standard model due to the presence of some form of dark energy and, perhaps, by additional contributions to the more familiar dark matter. Primordial nucleosynthesis provides a window on the very early evolution of the universe and constraints from Big Bang Nucleosynthesis (BBN) can bound the parameters of models for dark matter/energy at redshifts of order ten billion. The spectrum of temperature fluctuations imprinted on the Cosmic Microwave Background (CMB) radiation opens a completely different window on the universe at epochs from redshifts of order ten thousand to nearly the present. The CMB anisotropy spectrum provides constraints on new physics which are independent of, and complementary to those from BBN. Here we consider three classes of models for the dark matter/energy: extra particles which were relativistic during the early evolution of the universe (X); Quintessence models involving a minimally-coupled scalar field (Q); models with a non-minimally coupled scalar field which modify the strength of gravity during the early evolution of the universe (G). We constrain the parameters of these models using data from BBN and the CMB and identify the allowed regions in their parameter spaces consistent with the more demanding joint BBN and CMB constraints. For X and Q such consistency is relatively easy to find; it is more difficult for the G models with an inverse power law potential for the scalar field.
Supernovae constraints on dark energy and modified gravity models
Journal of Physics: Conference Series, 2006
We use the Type Ia Supernova gold sample to constrain the parameters of dark energy models namelly the Cardassian, Dvali-Turner (DT) and generalized Chaplygin gas (GCG) models. In our best fit analysis for these dark energy proposals we consider flat and the non-flat priors. For all models, we find that relaxing the flatness condition implies that data favors a positive curvature; moreover, the GCG model is nearly flat, as required by Cosmic Microwave Background (CMB) observations.