Topic
Deceleration parameter
About: Deceleration parameter is a research topic. Over the lifetime, 1776 publications have been published within this topic receiving 89440 citations.
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TL;DR: In this article, the scalar curvature of the brane metric contributes to brane action and the curvature term arises generically on account of one-loop effects induced by matter fields residing on a brane.
Abstract: We explore a new class of braneworld models in which the scalar curvature of the (induced) brane metric contributes to the brane action. The scalar curvature term arises generically on account of one-loop effects induced by matter fields residing on the brane. Spatially flat braneworld models can enter into a regime of accelerated expansion at late times. This is true even if the brane tension and the bulk cosmological constant are tuned to satisfy the Randall--Sundrum constraint on the brane. Braneworld models admit a wider range of possibilities for dark energy than standard LCDM. In these models the luminosity distance can be both smaller and larger than the luminosity distance in LCDM. Whereas models with $d_L \leq d_L(\rm LCDM)$ imply $w = p/\rho \geq -1$ and have frequently been discussed in the literature, models with $d_L > d_L(\rm LCDM)$ have traditionally been ignored, perhaps because within the general-relativistic framework, the luminosity distance has this property {\em only if} the equation of state of matter is strongly negative ($w < -1$). Matter with $w < -1$ is beset with a host of undesirable properties, which makes this model of dark energy unattractive within the conventional framework. Braneworld models, on the other hand, have the capacity to endow dark energy with exciting new possibilities without suffering from the problems faced by models with $w < -1$. For a subclass of parameter values, braneworld dark energy and the acceleration of the universe are {\em transient} phenomena. In these models, the universe, after the current period of acceleration, re-enters the matter dominated regime so that the deceleration parameter $q(t) \to 0.5$ when $t \gg t_0$, where $t_0$ is the present epoch. Such models could help reconcile an accelerating universe with the requirements of string/M-theory.
36 citations
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TL;DR: In this paper, a spatially homogeneous and anisotropic Bianchi type-I space-time filled with perfect fluid is investigated within the framework of a scalar-tensor theory proposed by Saez and Ballester.
Abstract: In this paper, a spatially homogeneous and anisotropic Bianchi type-I space-time filled with perfect fluid is investigated within the framework of a scalar-tensor theory proposed by Saez and Ballester. Two different physically viable models of the universe are obtained by using a special law of variation for Hubble’s parameter that yields a constant value of deceleration parameter. One of the models is found to generalize a model recently investigated by Reddy et al. (Astrophys. Space Sci. 306:171, 2006). The Einstein’s field equations are solved exactly and the solutions are found to be consistent with the recent observations of type Ia supernovae. A detailed study of physical and kinematical properties of the models is carried out.
36 citations
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TL;DR: By considering the time-varying deceleration parameter (DP), this article investigated Tsallis holographic dark energy (THDE), infrared cut-off with the Hubble horizon proposed by Tavayef, et al. in the framework of Friedmann Robertson Walker universe.
36 citations
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TL;DR: In this article, the authors reconstruct a suitable model in $f(R,T)$ gravity, where $R$ is the Ricci scalar and $T is the trace of the energy momentum tensor, which depict the current cosmic picture in more consistent way.
Abstract: In this paper, we reconstruct a suitable model in $f(R,T)$
gravity, (where $R$
is the Ricci scalar and $T$
is the trace of the energy momentum tensor) which depict the current cosmic picture in more consistent way. The dynamical field equations are solved for generic anisotropic space-time. The solution of field equations helps us to determine the future cosmic evolution for both physical and kinematical quantities. We explore the nature of deceleration parameter, NEC and energy density for three different cases representing Bianchi type I, III and Kantowski-Sachs universe model. We find that this study favors the phantom cosmic evolution in all cases.
36 citations
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TL;DR: In this article, a model for the present accelerating universe is presented, where different important physical variables involved in the model under the phenomenological assumption Λ∝Hcffff 2 with a prescription for equation of state parameter in the form $\omega(t)=\omega 0+\frac{\omega_{1}\tau}{t^{2}}$�⌉(t), where ωcffff 0 and ω�� 1 are two constants and τ is a parameter having dimension of time tcffff 2.
Abstract: We present a model for the present accelerating Universe and focus on the different important physical variables involved in the model under the phenomenological assumption Λ∝H
2 with a prescription for equation of state parameter in the form $\omega(t)=\omega_{0}+\frac{\omega_{1}\tau}{t^{2}}$
, where ω
0 and ω
1 are two constants and τ is a parameter having dimension of time t
2. General expressions for the density parameter Ω and deceleration parameter q are obtained which under specific bound reproduce some of the previous results. We explore physical features of these parameters which (i) provide the scenario of complete evolution of the cosmos with ω(t) and (ii) agree mostly with the observational status of the present phase of the accelerating Universe.
36 citations