scholarly journals Braneworld in f(T) gravity theory with noncanonical scalar matter field

2018 ◽  
Vol 98 (8) ◽  
Author(s):  
Jian Wang ◽  
Wen-Di Guo ◽  
Zi-Chao Lin ◽  
Yu-Xiao Liu
Keyword(s):  
Matter Field ◽  
Gravity Theory ◽  
Scalar Matter

scholarly journals How a projectively flat geometry regulates F(R)-gravity theory?

2021 ◽  
Author(s):  
Tee-How Loo ◽  
Avik De ◽  
Sanjay Mandal ◽  
P. K. Sahoo
Keyword(s):  
Matter Field ◽  
Gravity Theory ◽  
Gravity Models ◽  
Spacetime Geometry ◽  
Projectively Flat ◽  
Expansion Scalar ◽  
Isotropic Pressure ◽  
Constant Energy Density ◽  
Projective Flatness

Abstract In the present paper we examine a projectively flat spacetime solution of F(R)-gravity theory. It is seen that once we deploy projective flatness in the geometry of the spacetime, the matter field has constant energy density and isotropic pressure. We then make the condition weaker and discuss the effects of projectively harmonic spacetime geometry in F(R)-gravity theory and show that the spacetime in this case reduces to a generalised Robertson-Walker spacetime with a shear, vorticity, acceleration free perfect fluid with a specific form of expansion scalar presented in terms of the scale factor. Role of conharmonic curvature tensor in the spacetime geometry is also briefly discussed. Some analysis of the obtained results are conducted in terms of couple of F(R)-gravity models.

scholarly journals The Casimir effect with quantized charged scalar matter in background magnetic field

2014 ◽  
Vol 29 (09) ◽  
pp. 1450052 ◽  
Author(s):  
Yu. A. Sitenko ◽  
S. A. Yushchenko
Keyword(s):  
Magnetic Field ◽  
Boundary Condition ◽  
Boundary Conditions ◽  
Casimir Force ◽  
Matter Field ◽  
Particle Energy ◽  
Parallel Plates ◽  
Charged Scalar ◽  
Scalar Matter ◽  
Background Magnetic Field

We study the influence of a background uniform magnetic field and boundary conditions on the vacuum of a quantized charged massive scalar matter field confined between two parallel plates; the magnetic field is directed orthogonally to the plates. The admissible set of boundary conditions at the plates is determined by the requirement that the operator of one-particle energy squared be self-adjoint and positive-definite. We show that, in the case of a weak magnetic field and a small separation of the plates, the Casimir force is either attractive or repulsive, depending on the choice of a boundary condition. In the case of a strong magnetic field and a large separation of the plates, the Casimir force is repulsive, being independent of the choice of a boundary condition, as well as of the distance between the plates.

scholarly journals On Gauge Invariant Cosmological Perturbations in UV-modified Hořava Gravity: A Brief Introduction

2018 ◽  
Vol 168 ◽  
pp. 08003 ◽  
Author(s):  
Mu-In Park
Keyword(s):  
Detailed Balance ◽  
Big Bang ◽  
Matter Field ◽  
Cosmological Perturbations ◽  
Scale Invariant ◽  
Gauge Invariant ◽  
Four Dimensions ◽  
Detailed Balance Condition ◽  
Scalar Matter ◽  
Horava Gravity

We revisit gauge invariant cosmological perturbations in UV-modified, z = 3 Hořava gravity with one scalar matter field, which has been proposed as a renormalizable gravity theory without the ghost problem in four dimensions. We confirm that there is no extra graviton modes and general relativity is recovered in IR, which achieves the consistency of the model. From the UV-modification terms which break the detailed balance condition in UV, we obtain scale-invariant power spectrums for non-inflationary backgrounds, like the power-law expansions, without knowing the details of early expansion history of Universe. This could provide a new framework for the Big Bang cosmology.

scholarly journals CASIMIR ENERGY AND FORCE INDUCED BY AN IMPENETRABLE FLUX TUBE OF FINITE RADIUS

2013 ◽  
Vol 28 (31) ◽  
pp. 1350161 ◽  
Author(s):  
VOLODYMYR M. GORKAVENKO ◽  
YURII A. SITENKO ◽  
OLEXANDER B. STEPANOV
Keyword(s):  
Magnetic Flux ◽  
Vacuum Polarization ◽  
Dirichlet Boundary ◽  
Topological Defect ◽  
Casimir Energy ◽  
Matter Field ◽  
Tube Radius ◽  
Finite Radius ◽  
Polarization Effects ◽  
Scalar Matter

A perfectly reflecting (Dirichlet) boundary condition at the edge of an impenetrable magnetic-flux-carrying tube of nonzero transverse size is imposed on the charged massive scalar matter field which is quantized outside the tube. We show that the vacuum polarization effects outside the tube give rise to a macroscopic force acting at the increase of the tube radius (if the magnetic flux is held steady). The Casimir energy and force are periodic in the value of the magnetic flux, being independent of the coupling to the space–time curvature scalar. We conclude that a topological defect of the vortex type can polarize the vacuum of only those quantum fields that have masses which are much less than a scale of the spontaneous symmetry breaking.

scholarly journals Induced vacuum current and magnetic field in the background of a vortex

2016 ◽  
Vol 31 (06) ◽  
pp. 1650017 ◽  
Author(s):  
Volodymyr M. Gorkavenko ◽  
Iryna V. Ivanchenko ◽  
Yurii A. Sitenko
Keyword(s):  
Magnetic Field ◽  
Side Surface ◽  
Matter Field ◽  
Transverse Size ◽  
Compton Wavelength ◽  
Charged Scalar ◽  
Quantum Matter ◽  
Scalar Matter ◽  
Bohm Effect ◽  
Aharonov Bohm

A topological defect in the form of the Abrikosov–Nielsen–Olesen vortex is considered as a gauge-flux-carrying tube that is impenetrable for quantum matter. Charged scalar matter field is quantized in the vortex background with the perfectly reflecting (Dirichlet) boundary condition imposed at the side surface of the vortex. We show that a current circulating around the vortex and a magnetic field directed along the vortex are induced in the vacuum, if the Compton wavelength of the matter field exceeds considerably the transverse size of the vortex. The vacuum current and magnetic field are periodic in the value of the gauge flux of the vortex, providing a quantum-field-theoretical manifestation of the Aharonov–Bohm effect. The total flux of the induced vacuum magnetic field attains notable finite values even for the Compton wavelength of the matter field exceeding the transverse size of the vortex by just three orders of magnitude.

scholarly journals TIME IN THE CHAOTIC INFLATION MODEL AND NUMERICAL CALCULATIONS

1995 ◽  
Vol 10 (16) ◽  
pp. 2317-2332
Author(s):  
YOSHIAKI OHKUWA ◽  
TETSURO KITAZOE ◽  
YOSHIHIKO MIZUMOTO
Keyword(s):  
Quantum Gravity ◽  
Perturbation Method ◽  
Orbital Motion ◽  
Semiclassical Approximation ◽  
Natural Extension ◽  
Matter Field ◽  
Time Variable ◽  
Inflation Model ◽  
Scalar Matter ◽  
Scalar Mass

The time variable is considered in the quantum gravity theory and calculated explicitly in the framework of the chaotic inflationary scenario where the scalar matter field has a contribution to the time variable in addition to the gravity field. The time formulated under the semiclassical approximation is a natural extension of that in the classical orbital motion. A perturbation method is introduced in terms of the scalar mass to obtain analytically solvable expressions for the time. The Wheeler-DeWitt equation is solved numerically to ensure that the semiclassical approximation is well justified. We examine the obtained time in detail and find that it is reasonable to consider it as time in the region where the semiclassical approximation is well justified.

Scalar matter field in a fixed-point compactified five-dimentional Kaluza-Klein theory

1987 ◽  
Vol 281 (3-4) ◽  
pp. 426-444 ◽  
Author(s):  
A. Heil ◽  
N.A. Papadopoulos ◽  
B. Reifenhäuser ◽  
F. Scheck
Keyword(s):  
Fixed Point ◽  
Matter Field ◽  
Scalar Matter ◽  
Klein Theory ◽  
Kaluza Klein

scholarly journals Preheating with fractional powers

2016 ◽  
Vol 31 (39) ◽  
pp. 1650217 ◽  
Author(s):  
Hossein Bazrafshan Moghaddam ◽  
Robert Brandenberger
Keyword(s):  
Parametric Resonance ◽  
Fractional Power ◽  
Matter Field ◽  
Fractional Powers ◽  
Inflaton Field ◽  
Floquet Exponent ◽  
Scalar Matter

We consider preheating in models in which the potential for the inflaton is given by a fractional power, as is the case in axion monodromy inflation. We assume a standard coupling between the inflaton field and a scalar matter field. We find that in spite of the fact that the oscillation of the inflaton about the field value which minimizes the potential is anharmonic, there is nevertheless a parametric resonance instability, and we determine the Floquet exponent which describes this instability as a function of the parameters of the inflaton potential.

scholarly journals Some specific wormhole solutions in f(R)-modified gravity theory

2021 ◽  
pp. 2150024
Author(s):  
Bikram Ghosh ◽  
Saugata Mitra ◽  
Subenoy Chakraborty
Keyword(s):  
Modified Gravity ◽  
Shape Function ◽  
Matter Field ◽  
Gravity Theory ◽  
Energy Conditions ◽  
Spherically Symmetric ◽  
Shape Functions ◽  
Matter Distribution ◽  
Anisotropic Matter ◽  
Modified Gravity Theory

The paper deals with the static spherically symmetric wormhole solutions in [Formula: see text]-modified gravity theory with anisotropic matter field and for some particular choices for the shape functions. This work may be considered as an extension of the general formalism in [S. Halder, S. Bhattacharya and S. Chakraborty, Phys. Lett. B 791, 270 (2019)] for finding wormhole solutions. For isotropic matter distribution it has been shown that wormhole solutions are possible for zero tidal force and it modifies the claim in [M. Cataldo, L. Leimpi and P. Rodriguez, Phys. Lett. B 757, 130 (2016)]. Finally, energy conditions are examined and it is found that all energy conditions are satisfied in a particular domain with a particular choice of the shape function.

scholarly journals VIOLATION OF STRONG ENERGY CONDITION IN EFFECTIVE LOOP QUANTUM COSMOLOGY

2007 ◽  
Vol 22 (18) ◽  
pp. 3137-3146 ◽  
Author(s):  
HUA-HUI XIONG ◽  
JIAN-YANG ZHU
Keyword(s):  
Quantum Cosmology ◽  
Small Volume ◽  
Energy Condition ◽  
Matter Field ◽  
Loop Quantum Cosmology ◽  
Quantum Geometry ◽  
Strong Energy Condition ◽  
Strong Energy ◽  
Scalar Matter ◽  
The Universe

In loop quantum cosmology nonperturbative modification to a scalar matter field at short scales implies inflation which also means a violation of the strong energy condition. In the framework of effective Hamiltonian we discuss the issue of violation of the strong energy condition in the presence of quantum geometry potential. It is shown that the appearance of quantum geometry potential strengthens the violation of the strong energy condition in small volume regions. In the small volume regions superinflation can easily happen. Furthermore, when the evolution of the universe approaches the bounce scale, this trend of violating the strong energy condition can be greatly amplified.

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