Solitary kinetic Alfven waves in a plasma with negative ions

Models of static wormholes within the f (R, T) extended theory of gravity are investigated and, in particular, the family f (R, T) = R + λT , with T = ρ + Pr + 2P l being the trace of the energymomentum tensor. Models corresponding to different relations for the pressure components (radial and lateral), and several equations of state (EoS), reflecting different matter content, are worked out explicitly. The solutions obtained for the shape functions of the generated wormholes obey the necessary metric conditions, as manifested in other studies in the literature. The respective energy conditions reveal the physical nature of the wormhole models thus constructed. It is found, in particular, that for each of those considered, the parameter space can be divided into different regions, in which the exact wormhole solutions fulfill the null (NEC) and the weak energy conditions (WEC), respectively, in terms of the lateral pressure. Moreover, the dominant energy condition (DEC) in terms of both pressures is also valid, while ρ + Pr + 2P l = 0. A similar solution for the theory Pr = ω1ρ + ω2ρ 2 is found numerically, where ω1 and ω2 are either constant or functions of r, leading to the result that the NEC in terms of the radial pressure is also valid. For non-constant ωi models, attention is focused on the behavior ωi ∝ r m . To finish, the question is addressed, how f (R) = R + αR 2 will affect the wormhole solutions corresponding to fluids of the form Pr = ω1ρ + ω2ρ 2 , in the three cases mentioned above. Issues concerning the nonconservation of the matter energy-momentum tensor, the stability of the solutions obtained, and the observational possibilities for testing these models are discussed in the last section.

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“…A similar situation has been observed also for the model given by Eq. (34), for which we have obtained…”

Section: Wormhole Models With R + αR 2 + 2f (T ) Gravitymentioning

confidence: 99%

Wormhole models in f(R,T) gravity

Elizalde

Khurshudyan

2019

Int. J. Mod. Phys. D

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“…Therefore, the investigation of homogeneous and anisotropic Bianchi universe models are considerable in general relativity and other gravitational theories [35]. In this context, Sahoo and Sivakumar [36] have studied f (R, T ) theory in LRS Bianchi type-I universe and they have presented the big rip singularity in this theory. Mishra et al [37] have investigated homogeneous and anisotropic Bianchi type-II universe for dark energy with/without a magnetic field in f (R, T ) gravitation theory.…”

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confidence: 99%

Magnetized strange quark matter in f ( R, T ) gravity with bilinear and special form of time varying deceleration parameter

2018

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In this paper, we have studied homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi type-I model with magnetized strange quark matter (MSQM) distribution and cosmological constant Λ in f (R, T ) gravity where R is the Ricci scalar and T the trace of matter source. The exact solutions of the field equations are obtained under bilinear and special form of time varying deceleration parameter (DP). Firstly, we have considered two specific forms of bilinear DP with a single parameter of the form: q = α(1−t) 1+t and q = − αt 1+t , which leads to the constant or linear nature of the function based on the constant α. Second one is the special form of the DP as q = −1 + β 1+a β . From the results obtained here, one can observe that in the early universe magnetic flux has more effects and it reduces gradually in the later stage. For t → ∞, we get p → −Bc and ρ → Bc. The behaviour of strange quark matter along with magnetic epoch gives an idea of accelerated expansion of the universe as per the observations of the type Ia Supernovae.The theoretical arguments for the late-time cosmic acceleration are being a major issue among cosmologist of the twentieth century. The idea of this accelerated expansion of universe was discovered nearly 20 years ago by observations through Supernovae Ia [1-5], CMB [6,7], baryon acoustic oscillation (BAO) in galaxy clustering [8][9][10] and WMAP [11] etc. To investigate the nature of the universe, modern cosmology continues to test the above predictions, which leads to the refinement of cosmological models. The nature and behaviour of some unknown mechanism of the universe are responsible for this accelerated expansion, commonly referred as dark energy and contains more energy budget of the universe along with negative pressure. It triggers one of the important issue to study the current acceleration of the universe.Instead of resorting the mysterious concept of dark energy, there is an alternative way to reproduce the dynamics of the expanding universe through modified theories of gravity which is an extension of general relativity. These modifications can occur in several ways such as: one can use a base as the torsional formulation of general relativity called the teleparallel gravity equivalent to general relativity [12] e.g. f (T ) gravity, where T is the torsion scalar. On the other hand one can start the curvature formulation of general relativity in Einstein-Hilbert action by replacing the Ricci scalar with its arbitrary functions or even more complicated curvature invariants such as: f (R), f (R, G) gravity, and the latest f (R, T ) gravity proposed by Harko et al. [13]. The matter Lagrangian of f (R, T ) gravity coupled with Ricci scalar R and trace of energy-momentum tensor T . Such Lagrangian with matter content will differ from the Einstein's one. It has much significance to study late-time cosmic acceleration as well as dark energy and dark matter problem [14][15][16][17]. Hypothetically matter plays more fundamental role in the description of gravitational eff...

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“…55 In particular, the LRS BI model has been studied for inflation 55 and in Brans-Dicke theory. 56 It was also analysed in f (R, T ) gravity models, 57,58 for which T is the trace of the energymomentum tensor.…”

Section: Cosmological Formulation Of Bianchi I Phantom Energy Universmentioning

confidence: 99%

Phantom energy-dominated universe as a transient stage in f(R) cosmology

Moraes

Sahoo

Taori

2019

Int. J. Mod. Phys. D

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The f (R) theories of gravity are the most popular, simple and well succeeded extension of Einstein's General Relativity. They can account for some observational issues of standard cosmology with no need for evoking the dark sector of the universe. In the present article we will investigate LRS Bianchi type-I space-time in f (R) gravity theory within the phantom energy dominated era. We show that in this formalism the phantom energy dominated universe is a transient stage and in the further stage of the universe dynamics, it is dominated, once again, by dark energy. Such an important feature is obtained from the model, rather than imposed to it, and may have a relation to loop quantum cosmology.

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Solitary kinetic Alfven waves in a plasma with negative ions

Cited by 11 publications

References 19 publications

Wormhole models in f(R,T) gravity

Wormhole models in f(R,T) gravity

Magnetized strange quark matter in f ( R, T ) gravity with bilinear and special form of time varying deceleration parameter

Phantom energy-dominated universe as a transient stage in f(R) cosmology

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