Wormhole modeling in f(R,T) gravity with minimally-coupled massless scalar field

2020 ◽  
Vol 35 (29) ◽  
pp. 2050186
Author(s):  
Nisha Godani ◽  
Gauranga C. Samanta
Keyword(s):  
Scalar Field ◽  
Gravitational Lensing ◽  
Massless Scalar ◽  
Qualitative Behavior ◽  
Energy Tensor ◽  
Massless Scalar Field ◽  
Stress Energy Tensor ◽  
Shape Functions ◽  
Traversable Wormholes ◽  
Stress Energy

In this paper, the strong gravitational lensing is explored for traversable wormholes in [Formula: see text] theory of gravity with minimally-coupled massless scalar field. First, the effective wormhole solutions are obtained using the model [Formula: see text], where [Formula: see text] is constant, [Formula: see text] is scalar curvature and [Formula: see text] is the trace of stress-energy tensor. Furthermore, three different shape functions namely, [Formula: see text] (Ref. 36), [Formula: see text] (Refs. 35 and 37) and [Formula: see text], [Formula: see text] (Refs. 34, 35, 39, 73) are considered and studied their qualitative behavior for the construction of wormhole geometry respectively. Subsequently, gravitational lensing effect is implemented to detect the existence of photon spheres at or outside the throat of wormholes.

On several static cylindrically symmetric solutions of the Einstein equations

2016 ◽  
Vol 31 (11) ◽  
pp. 1650068
Author(s):  
Sergey Grigoryev ◽  
Arkadiy Leonov
Keyword(s):  
Einstein Equations ◽  
Massless Scalar ◽  
Energy Tensor ◽  
Massless Scalar Field ◽  
Stress Energy Tensor ◽  
Perfect Fluid Solution ◽  
Cylindrically Symmetric ◽  
Special Cases ◽  
Stress Energy ◽  
Barotropic Equation

We study the Einstein equations in the static cylindrically symmetric case with the stress–energy tensor of the form [Formula: see text], where [Formula: see text] is an unknown function and [Formula: see text], [Formula: see text], [Formula: see text] are arbitrary real constants ([Formula: see text] is assumed to be nonzero). The stress–energy tensor of this form includes as special cases several well-known solutions, such as the perfect fluid solution with the barotropic equation of state, the solution with the static electric field and the solution with the massless scalar field. We solve the Einstein equations with this stress–energy tensor and study some properties of the obtained metric.

scholarly journals The time traveler’s guide to the quantization of zero modes

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Ana Alonso-Serrano ◽  
Erickson Tjoa ◽  
Luis J. Garay ◽  
Eduardo Martín-Martínez
Keyword(s):  
Zero Mode ◽  
Massless Scalar ◽  
Energy Tensor ◽  
Massless Scalar Field ◽  
Stress Energy Tensor ◽  
Squeezed State ◽  
Time Machine ◽  
Zero Modes ◽  
Stress Energy ◽  
The Relationship

Abstract We study the relationship between the quantization of a massless scalar field on the two-dimensional Einstein cylinder and in a spacetime with a time machine. We find that the latter picks out a unique prescription for the state of the zero mode in the Einstein cylinder. We show how this choice arises from the computation of the vacuum Wightman function and the vacuum renormalized stress-energy tensor in the time-machine geometry. Finally, we relate the previously proposed regularization of the zero mode state as a squeezed state with the time-machine warp parameter, thus demonstrating that the quantization in the latter regularizes the quantization in an Einstein cylinder.

scholarly journals LIGHT-CONE FLUCTUATIONS AND THE RENORMALIZED STRESS TENSOR OF A MASSLESS SCALAR FIELD

2013 ◽  
Vol 28 (01) ◽  
pp. 1350001 ◽  
Author(s):  
V. A. DE LORENCI ◽  
G. MENEZES ◽  
N. F. SVAITER
Keyword(s):  
Scalar Field ◽  
Light Cone ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Flat Space ◽  
Massless Scalar ◽  
Energy Tensor ◽  
Massless Scalar Field ◽  
Expectation Value ◽  
Stress Energy

We investigate the effects of light-cone fluctuations over the renormalized vacuum expectation value of the stress–energy tensor of a real massless minimally coupled scalar field defined in a (d+1)-dimensional flat space–time with topology [Formula: see text]. For modeling the influence of light-cone fluctuations over the quantum field, we consider a random Klein–Gordon equation. We study the case of centered Gaussian processes. After taking into account all the realizations of the random processes, we present the correction caused by random fluctuations. The averaged renormalized vacuum expectation value of the stress–energy associated with the scalar field is presented.

scholarly journals Local zeta regularization and the scalar Casimir effect IV: The case of a rectangular box

2016 ◽  
Vol 31 (04n05) ◽  
pp. 1650003 ◽  
Author(s):  
Davide Fermi ◽  
Livio Pizzocchero
Keyword(s):  
Casimir Effect ◽  
Arbitrary Dimension ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Massless Scalar ◽  
Energy Tensor ◽  
Massless Scalar Field ◽  
Stress Energy Tensor ◽  
Expectation Value ◽  
Stress Energy

Applying the general framework for local zeta regularization proposed in Part I of this series of papers, we compute the renormalized vacuum expectation value of several observables (in particular, of the stress–energy tensor) for a massless scalar field confined within a rectangular box of arbitrary dimension.

Vacuum stress-energy tensor of a massive scalar field in a wormhole spacetime

2010 ◽  
Vol 81 (8) ◽  
Author(s):  
V. B. Bezerra ◽  
E. R. Bezerra de Mello ◽  
N. R. Khusnutdinov ◽  
S. V. Sushkov
Keyword(s):  
Scalar Field ◽  
Energy Tensor ◽  
Massive Scalar ◽  
Stress Energy Tensor ◽  
Massive Scalar Field ◽  
Stress Energy

scholarly journals EXACT SOLUTIONS OF BRANS–DICKE WORMHOLES IN THE PRESENCE OF MATTER

2011 ◽  
Vol 26 (40) ◽  
pp. 3067-3076 ◽  
Author(s):  
NADIEZHDA MONTELONGO GARCIA ◽  
FRANCISCO S. N. LOBO
Keyword(s):  
Scalar Field ◽  
Vacuum Solution ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Exotic Matter ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Normal Matter ◽  
Stress Energy

A fundamental ingredient in wormhole physics is the presence of exotic matter, which involves the violation of the null energy condition. Although a plethora of wormhole solutions have been explored in the literature, it is useful to find geometries that minimize the usage of exotic matter. In this work, we find exact wormhole solutions in Brans–Dicke theory where the normal matter threading the wormhole satisfies the null energy condition throughout the geometry. Thus, the latter implies that it is the effective stress–energy tensor containing the scalar field, that plays the role of exotic matter, that is responsible for sustaining the wormhole geometry. More specifically, we consider a zero redshift function and a particular choice for the scalar field and determine the remaining quantities, namely, the stress–energy tensor components and the shape function. The solution found is not asymptotically flat, so that this interior wormhole spacetime needs to be matched to an exterior vacuum solution.

scholarly journals Local zeta regularization and the scalar Casimir effect III. The case with a background harmonic potential

2015 ◽  
Vol 30 (35) ◽  
pp. 1550213 ◽  
Author(s):  
Davide Fermi ◽  
Livio Pizzocchero
Keyword(s):  
Scalar Field ◽  
General Framework ◽  
Casimir Effect ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Harmonic Potential ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Expectation Value ◽  
Stress Energy

Applying the general framework for local zeta regularization proposed in Part I of this series of papers, we renormalize the vacuum expectation value of the stress-energy tensor (and of the total energy) for a scalar field in presence of an external harmonic potential.

scholarly journals VACUUM QUANTUM EFFECTS OF NONCONFORMAL SCALAR FIELD IN A NONSINGULAR COSMOLOGICAL MODEL

1998 ◽  
Vol 07 (05) ◽  
pp. 779-792 ◽  
Author(s):  
M. NOVELLO ◽  
V. B. BEZERRA ◽  
V. M. MOSTEPANENKO
Keyword(s):  
Scalar Field ◽  
Energy Density ◽  
Negative Energy ◽  
Back Reaction ◽  
Energy Tensor ◽  
Stress Energy Tensor ◽  
Negative Energy Density ◽  
Stress Energy ◽  
Nonsingular Cosmological Model ◽  
Reaction Problem

The total vacuum stress-energy tensor of nonconformal scalar field is calculated in a nonsingular metric determined by some background matter with the effective negative energy density and pressure. The corrections due to the field nonconformity are shown to dominate the conformal contributions for some cases. The back reaction problem of vacuum stress-energy tensor upon the background metric is also discussed.

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