scholarly journals Scalar cosmological perturbations in M-theory with higher-derivative corrections

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Kazuho Hiraga ◽  
Yoshifumi Hyakutake
Keyword(s):  
Power Spectrum ◽  
Equations Of Motion ◽  
Cosmological Perturbations ◽  
Curvature Perturbation ◽  
Linearized Equations ◽  
Higher Derivative ◽  
Expansion Of The Universe ◽  
M Theory ◽  
The Universe ◽  
Scalar Perturbations

Abstract We investigate the inflationary expansion of the universe induced by higher-curvature corrections in M-theory. The inflationary evolution of the geometry is discussed in K. Hiraga and Y. Hyakutake, Prog. Theor. Exp. Phys. 2018, 113B03 (2018), which we follow to analyze metric perturbations around the background. We especially focus on scalar perturbations and analyze linearized equations of motion for the scalar perturbations. By solving these equations explicitly, we evaluate the power spectrum of the curvature perturbation. The scalar spectrum index is estimated under some assumptions, and we show that it becomes close to 1.

scholarly journals QUANTUM EFFECTS AND STABILITY OF CHAMELEON COSMOLOGY

2004 ◽  
Vol 19 (17) ◽  
pp. 1273-1280 ◽  
Author(s):  
SHIN'ICHI NOJIRI ◽  
SERGEI D. ODINTSOV
Keyword(s):  
Quantum Effects ◽  
Equation Of Motion ◽  
Matter Density ◽  
Accelerated Expansion ◽  
Conformal Anomaly ◽  
Tensor Theory ◽  
Higher Derivative ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Principal Possibility

One possibility to explain the current accelerated expansion of the universe may be related with the presence of cosmologically evolving scalar whose mass depends on the local matter density (chameleon cosmology). We point out that matter quantum effects in such scalar–tensor theory produce the chameleon scalar field dependent conformal anomaly. Such conformal anomaly adds higher derivative terms to chameleon field equation of motion. As a result, the principal possibility for instabilities appears. These instabilities seem to be irrelevant at small curvature but may become dangerous in the regions where gravitational field is strong.

scholarly journals INFLATION IN F(R, T) GRAVITATION WITH f-ESSENCE

2020 ◽  
Vol 5 (333) ◽  
pp. 106-112
Author(s):  
S.R. Myrzakul ◽  
◽  
Y.M. Myrzakulov ◽  
М. Arzimbetova ◽  
◽  
...  
Keyword(s):  
Equations Of Motion ◽  
Accelerated Expansion ◽  
Modified Theories Of Gravity ◽  
Fermion Field ◽  
Theory Of Relativity ◽  
Modern Physics ◽  
Expansion Of The Universe ◽  
Isotropic Cosmological Model ◽  
Theories Of Gravity ◽  
The Universe

. Modified theories of gravity have become a kind of paradigm in modern physics because they seem to solve several shortcomings of the standard General Theory of Relativity (GTR) related to cosmology, astrophysics and quantum field theory. The most famous modified theories of gravity are F(R) and F(T) theories of gravity. A generalization of these two modified theories and gravitations, which was first proposed by Myrzakulov Ratbay. In this paper, we study an inhomogeneous isotropic cosmological model with a fermion field f-essence whose action has the form , where R is the scalar of curvature, and T is the torsion scalar, and Lm is the Lagrangian f-essence. A particular case is studied in detail when parameters are obtained that describe the current accelerated expansion of the Universe. The type of Lagrangian f-essence of this model is determined. The presented results show that gravity with f-essence can describe inflation in the early evolution of the Universe. A modified F(R, T) gravity with f-essence is considered. Equations of motion were obtained and the inflationary period of the early Universe was considered. To describe the inflationary period, the form of the Hubble parameter and the slow-roll parameter were determined.

scholarly journals Higher-derivative supergravity, AdS4 holography, and black holes

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Nikolay Bobev ◽  
Anthony M. Charles ◽  
Kiril Hristov ◽  
Valentin Reys
Keyword(s):  
Black Holes ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Conformal Supergravity ◽  
Supergravity Theory ◽  
Higher Derivative ◽  
All Solutions ◽  
M Theory ◽  
Supergravity Action

Abstract We use conformal supergravity techniques to study four-derivative corrections in four-dimensional gauged supergravity. We show that the four-derivative Lagrangian for the propagating degrees of freedom of the $$ \mathcal{N} $$ N = 2 gravity multiplet is determined by two real dimensionless constants. We demonstrate that all solutions of the two-derivative equations of motion in the supergravity theory also solve the four-derivative equations of motion. These results are then applied to explicitly calculate the regularized on-shell action for any asymptotically locally AdS4 solution of the two-derivative equations of motion. The four-derivative terms in the supergravity Lagrangian modify the entropy and other thermodynamic observables for the black hole solutions of the theory. We calculate these corrections explicitly and demonstrate that the quantum statistical relation holds for general stationary black holes in the presence of the four-derivative corrections. Employing an embedding of this supergravity model in M-theory we show how to use supersymmetric localization results in the holographically dual three-dimensional SCFT to determine the unknown coefficients in the four-derivative supergravity action. This in turn leads to new detailed results for the first subleading $$ {N}^{\frac{1}{2}} $$ N 1 2 correction to the large N partition function of a class of three-dimensional SCFTs on compact Euclidean manifolds. In addition, we calculate explicitly the first subleading correction to the Bekenstein-Hawking entropy of asymptotically AdS4 black holes in M-theory. We also discuss how to add matter multiplets to the supergravity theory in the presence of four-derivative terms and to generalize some of these results to six- and higher-derivative supergravity.

BOUNCING AND QUANTUM THEORY

2011 ◽  
Vol 03 ◽  
pp. 183-194
Author(s):  
NELSON PINTO-NETO
Keyword(s):  
Wave Function ◽  
Quantum Theory ◽  
Power Spectrum ◽  
Quantum Cosmology ◽  
Cosmological Perturbations ◽  
Simple Equations ◽  
The Universe ◽  
Inflationary Models

In this contribution I will present a review about bouncing models arriving from quantum cosmology and show how one can describe the evolution of quantum cosmological perturbations on them. I will discuss the important role played by the choice of the precise quantum theory one selects to interpret the wave function of the Universe in order to obtain simple equations for the evolution of quantum perturbations on these quantum cosmological backgrounds. I will present the predictions of these models concerning the power spectrum of cosmological perturbations and how they can be compared with the usual results obtained from inflationary models. Finally, I will present the new implications of these results for quantum theory.

DELTA GRAVITY AND THE ACCELERATED EXPANSION OF THE UNIVERSE

2011 ◽  
Vol 20 (supp01) ◽  
pp. 65-72
Author(s):  
JORGE ALFARO
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Cosmological Constant ◽  
Equivalence Principle ◽  
Equations Of Motion ◽  
Accelerated Expansion ◽  
Symmetric Tensors ◽  
Test Particles ◽  
Expansion Of The Universe ◽  
The Universe

We study a model of the gravitational field based on two symmetric tensors. The equations of motion of test particles are derived. We explain how the Equivalence principle is recovered. Outside matter, the predictions of the model coincide exactly with General Relativity, so all classical tests are satisfied. In Cosmology, we get accelerated expansion without a cosmological constant.

scholarly journals On the value of the cosmical constant

1931 ◽  
Vol 133 (822) ◽  
pp. 605-615 ◽  
Keyword(s):  
Wave Equation ◽  
Equations Of Motion ◽  
Geometrical Interpretation ◽  
De Sitter ◽  
Astronomical Observations ◽  
Alternative Expression ◽  
Scattering Force ◽  
Expansion Of The Universe ◽  
The Universe

1. The cosmical constant λ occurs in Einstein’s law of gravitation G μv = λ g μv . In the resulting equations of motion the term containing λ represents a scattering force which tends to make all very remote bodies recede from one another; this phenomenon is the basis of the theories of de Sitter and Lemaître concerning the “expansion of the universe.” If the observed recession of the spiral nebulæ is a manifestation of this effect the value of λ can be found from the astronomical observations. In this paper I put forward a simple geometrical interpretation of the term in the wave equation which contains the mass m of an electron; this interpretation provides an alternative expression for the term. The new expression involves λ, and by equating it to the ordinary expression we find a theoretical value of λ, viz., 9⋅8.10 -55 cm. -2 . This agrees satisfactorily with the value found from the observed recession of the spiral nebulae (8).

scholarly journals TWO NONCOMMUTATIVE PARAMETERS AND REGULAR COSMOLOGICAL PHASE TRANSITION IN THE SEMICLASSICAL DILATON COSMOLOGY

2008 ◽  
Vol 23 (15) ◽  
pp. 1079-1091 ◽  
Author(s):  
WONTAE KIM ◽  
EDWIN J. SON
Keyword(s):  
Phase Transition ◽  
Equations Of Motion ◽  
Accelerated Expansion ◽  
Dilaton Gravity ◽  
Initial State ◽  
Future Singularity ◽  
Flat Spacetime ◽  
Modified Equations ◽  
Expansion Of The Universe ◽  
The Universe

We study cosmological phase transitions from modified equations of motion by introducing two noncommutative parameters in the Poisson brackets, which describes the initial- and future-singularity-free phase transition in the soluble semiclassical dilaton gravity with a nonvanishing cosmological constant. Accelerated expansion and decelerated expansion appear alternatively, where the model contains the second accelerated expansion. The final stage of the universe approaches the flat spacetime independent of the initial state of the curvature scalar as long as the product of the two noncommutative parameters is less than one. Finally, we show that the initial-singularity-free condition is related to the second accelerated expansion of the universe.

scholarly journals SELF-ACCELERATED UNIVERSE

2005 ◽  
Vol 20 (11) ◽  
pp. 2459-2464 ◽  
Author(s):  
B. P. KOSYAKOV
Keyword(s):  
Dirac Equation ◽  
Free Electron ◽  
Vacuum Energy ◽  
Alternative Explanation ◽  
Equations Of Motion ◽  
Accelerated Expansion ◽  
System Of Equations ◽  
Entire System ◽  
Expansion Of The Universe ◽  
The Universe

It is widely believed that the large redshifts for distant supernovae are due to the vacuum energy dominance, which is responsible for the anti-gravitation effect. A tacit assumption is that particles move along geodesics for the background metric. This is in the same spirit as the consensus regarding the uniform Galilean motion of a free electron. However, apart from the Galilean solution, there is a self-accelerated solution to the Lorentz–Dirac equation governing the behavior of a radiating electron. Likewise, a runaway solution to the entire system of equations, both gravitation and matter equations of motion including, may exist, which provides an alternative explanation for the accelerated expansion of the Universe.

scholarly journals R2-Corrections to Chaotic Inflation

2003 ◽  
Vol 18 (29) ◽  
pp. 2039-2049 ◽  
Author(s):  
Víctor H. Cárdenas ◽  
Sergio del Campo ◽  
Ramón Herrera
Keyword(s):  
Early Evolution ◽  
Inflationary Universe ◽  
Universe Model ◽  
Spectral Indices ◽  
Cosmological Perturbations ◽  
Evolution Of The Universe ◽  
Scalar Density ◽  
Higher Derivative ◽  
Derivative Term ◽  
The Universe

Scalar density cosmological perturbations, spectral indices and reheating in a chaotic inflationary universe model, in which a higher derivative term is added, are investigated. This term is supposed to play an important role in the early evolution of the Universe, specifically at times closer to the Planck era.

scholarly journals On Nash theory of gravity with matter contents

2021 ◽  
Vol 36 (02) ◽  
pp. 2150006
Author(s):  
Phongpichit Channuie ◽  
Davood Momeni ◽  
Mudhahir Al Ajmi
Keyword(s):  
Lagrangian Density ◽  
Equations Of Motion ◽  
Cosmological Parameters ◽  
Free Theory ◽  
Expansion Of The Universe ◽  
Theory Of Gravity ◽  
The Stability ◽  
The Universe ◽  
Matter Fields ◽  
Alternative Theories

One of the alternative theories to Einstein’s general theory, a divergence-free theory was proposed by J. Nash with Lagrangian density given by [Formula: see text]. Although it was proved that the Nash theory does not have classical Einstein limits, it has been proven to be formally divergent free and considered to be of interest in constructing theories of quantum gravity. The original Nash gravity without matter contents cannot explain the current acceleration expansion of the Universe. A possible extension of theory is by adding some matter contents to the model. In this work, we generalize Nash theory of gravity by adding the matter fields. In order to examine the effects of this generalization, we first derive the equations of motion in the flat FLRW space–time and examine the behaviors of the solutions by invoking specific forms of the Hubble parameter. We also classify the physical behaviors of the solutions by employing the stability analysis and check the consistency of the model by considering particular cosmological parameters.

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