scholarly journals ON THE QUARTIC CURVATURE GRAVITY IN THE CONTEXT OF FRW COSMOLOGY

2008 ◽  
Vol 23 (14n15) ◽  
pp. 2153-2160 ◽  
Author(s):  
MASAO IIHOSHI ◽  
SERGEI V. KETOV
Keyword(s):  
Fourth Order ◽  
Quantum Corrections ◽  
Slope Parameter ◽  
Leading Order ◽  
Frw Cosmology ◽  
Friedmann Equations ◽  
Spacetime Singularity ◽  
Spacetime Curvature ◽  
Rule Out

We consider the purely gravitational fourth-order (in the spacetime curvature) quantum corrections to the Einstein-Hilbert gravity action, coming from superstrings in the leading order with respect to the Regge slope parameter, and study their impact on the evolution of the Hubble scale in the context of the FRW cosmology, in four spacetime dimensions. We propose the generalized Friedmann equations, and rule out the most naive (Bel-Robinson tensor squared) gravity. Our new cosmological equations have exact inflationary solutions without a spacetime singularity.

scholarly journals On the Superstrings-Induced Four-Dimensional Gravity and Its Applications to Cosmology

2008 ◽  
Vol 2008 ◽  
pp. 1-27 ◽  
Author(s):  
Masao Iihoshi ◽  
Sergei V. Ketov
Keyword(s):  
Effective Action ◽  
Leading Order ◽  
De Sitter ◽  
Frw Cosmology ◽  
Spacetime Singularity ◽  
Spacetime Curvature ◽  
The Status ◽  
Dimensional Gravity ◽  
Definition Of ◽  
M Theory

We review the status of the fourth-order (quartic in the spacetime curvature) terms induced by superstrings/M-theory (compactified on a warped torus) in the leading order with respect to the Regge slope parameter, and study their (nonperturbative) impact on the evolution of the Hubble scale in the context of the four-dimensional FRW cosmology. After taking into account the quantum ambiguities in the definition of the off-shell superstring effective action, we propose the generalized Friedmann equations, find the existence of their (de Sitter) exact inflationary solutions without a spacetime singularity, and constrain the ambiguities by demanding stability and the scale factor duality invariance of our solutions. The most naive (Bel-Robinson tensor squared) quartic terms are ruled out, thus giving the evidence for the necessity of extra quartic (Ricci tensor-dependent) terms in the off-shell gravitational effective action for superstrings. Our methods are generalizable to the higher orders in the spacetime curvature.

ONE-LOOP CORRECTION TO ENERGY OF SPINNING STRINGS IN AdS5×T1, 1

2012 ◽  
Vol 27 (03) ◽  
pp. 1250015
Author(s):  
HYOJOONG KIM ◽  
NAKWOO KIM ◽  
JUNG HUN LEE
Keyword(s):  
Field Theory ◽  
Mode Frequency ◽  
Harmonic Oscillators ◽  
Quantum Corrections ◽  
Gauge Field Theory ◽  
Leading Order ◽  
Loop Correction ◽  
Conformal Dimension ◽  
Normal Mode Frequency ◽  
The One

We consider circular spinning string solutions in AdS5×T1, 1 and calculate the quantum corrections to the energy at one-loop on worldsheet. The fluctuations are given as a set of harmonic oscillators and we calculate their normal mode frequency in closed form. The sum of frequency is equal to the one-loop string energy, which through AdS/CFT correspondence corresponds to the leading order correction of the conformal dimension for long operators in Klebanov–Witten conifold gauge field theory.

scholarly journals COSMOLOGY OF DILATONIC BRANE WORLD

2001 ◽  
Vol 16 (14) ◽  
pp. 937-945 ◽  
Author(s):  
DONAM YOUM
Keyword(s):  
Energy Density ◽  
Brane World ◽  
Leading Order ◽  
Correct Sign ◽  
Friedmann Equations ◽  
Cosmological Solutions ◽  
Matter Energy

We study cosmological solutions in the dilatonic brane world models. The effective four-dimensional equations on the brane are analyzed for the models with one positive tension brane and two branes with tensions of opposite signs. Just as in the non-dilatonic brane case, the conventional Friedmann equations of the four-dimensional universe are reproduced to the leading order in matter energy density for the model with one brane and the introduction of a radion potential is required in order to reproduce the Friedmann equations with the correct sign for the model with two branes.

scholarly journals FOURTH-ORDER GRAVITY AS THE INFLATIONARY MODEL REVISITED

2010 ◽  
Vol 25 (32) ◽  
pp. 2753-2762 ◽  
Author(s):  
SHO KANEDA ◽  
SERGEI V. KETOV ◽  
NATSUKI WATANABE
Keyword(s):  
Gravity Model ◽  
Fourth Order ◽  
Scalar Potential ◽  
Inflationary Model ◽  
Spectral Indices ◽  
Leading Order ◽  
Gravity Theories

We revisit the old (fourth-order or quadratically generated) gravity model of Starobinsky in four spacetime dimensions, and derive the (inflaton) scalar potential in the equivalent scalar–tensor gravity model. The inflaton scalar potential is used to compute the (CMB) observables of inflation, associated with curvature perturbations (namely, the scalar and tensor spectral indices, and the tensor-to-scalar ratio), including the new next-to-leading order terms with respect to the inverse number of e-foldings. The results are compared to the recent (WMAP5) experimental bounds. We confirm both mathematical and physical equivalence between f(R) gravity theories and the corresponding scalar–tensor gravity theories.

Leading order of quantum corrections to black hole entropy sum relations

2019 ◽  
Vol 34 (32) ◽  
pp. 1950216
Author(s):  
Tairan Liang ◽  
Wei Xu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quantum Physics ◽  
Black Hole Entropy ◽  
Flat Space ◽  
Quantum Corrections ◽  
Leading Order ◽  
Physics Of Black Holes ◽  
Mass Dependent ◽  
Modified Entropy

It has been found recently that the entropy relations of horizons have the universality of black hole mass-independence for many black holes. These universal entropy relations have some geometric and CFT understanding, which may provide further insight into the quantum physics of black holes. In this paper, we present the leading order of black hole entropy sum relations under the quantum corrections. It is found that the modified entropy sum becomes mass-dependent for some black holes in asymptotical (A)dS and flat space–times. We also give an example that the modified entropy sum of regular Bardeen AdS black holes is mass-independent, which may be quantized in the form of the electric charge and the cosmological constant.

scholarly journals Calculation of Acceleration Effects Using the Zubarev Density Operator

Particles ◽  
2020 ◽  
Vol 3 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Georgy Prokhorov ◽  
Oleg Teryaev ◽  
Valentin Zakharov
Keyword(s):  
Perturbation Theory ◽  
Fourth Order ◽  
Density Operator ◽  
Quantum Effects ◽  
Quantum Corrections ◽  
Unruh Effect ◽  
Relativistic Form ◽  
Perturbative Corrections

The relativistic form of the Zubarev density operator can be used to study quantum effects associated with acceleration of the medium. In particular, it was recently shown that the calculation of perturbative corrections in acceleration based on the Zubarev density operator makes it possible to show the existence of the Unruh effect. In this paper, we present the details of the calculation of quantum correlators arising in the fourth order of the perturbation theory needed to demonstrate the Unruh effect. Expressions for the quantum corrections for massive fermions are also obtained.

scholarly journals NLO critical exponents of O(N) λ ϕ4 scalar field theories in curved spacetime

2019 ◽  
Vol 28 (01) ◽  
pp. 1950024
Author(s):  
H. A. S. Costa ◽  
P. R. S. Carvalho
Keyword(s):  
Scalar Field ◽  
Critical Exponents ◽  
Conformal Symmetry ◽  
Field Theories ◽  
Quantum Corrections ◽  
Leading Order ◽  
Loop Order ◽  
Curved Spacetime ◽  
Flat Spacetime

In this paper, we investigate analytically the conformal symmetry influence on the next-to-leading order radiative quantum corrections to critical exponents for massless O([Formula: see text]) [Formula: see text] scalar field theories in curved spacetime. We renormalize the theory by applying the Bogoliubov–Parasyuk–Hepp–Zimmermann (BPHZ) method. We find that the critical exponents are the same as that of flat spacetime, at least at the loop order considered. We argue that this result agrees perfectly with the universality hypothesis.

scholarly journals Semiclassical Behavior of Uniform-Density Models for Cosmic Strings and Relativistic Stars

1997 ◽  
Vol 06 (06) ◽  
pp. 771-784
Author(s):  
Manuela Campanelli ◽  
Carlos O. Lousto
Keyword(s):  
Neutron Stars ◽  
Fourth Order ◽  
Cosmic Strings ◽  
Coupling Constants ◽  
Quantum Corrections ◽  
Uniform Density ◽  
Relativistic Stars ◽  
Classical Models ◽  
Consistent Solution

In this paper we show how quantum corrections, although perturbatively small, may play an important role in the analysis of the existence of some classical models. This, in fact, appears to be the case of static, uniform-density models of the interior metric of cosmic strings and neutron stars. We consider the fourth-order semiclassical equations and first look for perturbative solutions in the coupling constants α and β of the quadratic curvature terms in the effective gravitational Lagrangian. We find that there is not a consistent solution; neither for strings nor for spherical stars. We then look for nonperturbative solutions and find an explicit approximate metric for the case of straight cosmic strings. We then conclude that nonperturbative solutions are valuable for describing certain physical situations.

THE GAUSS-BONNET IDENTITY IN FOURTH ORDER GRAVITY

1993 ◽  
Vol 08 (21) ◽  
pp. 1977-1982 ◽  
Author(s):  
S.A. BRUNINI ◽  
M. GOMES
Keyword(s):  
Fourth Order ◽  
Dimensional Regularization ◽  
Quantum Corrections ◽  
Conformally Flat ◽  
Model Based ◽  
Conformally Flat Metrics

For a class of conformally flat metrics a model based in fourth order gravity is constructed to investigate the existence of quantum corrections to the Gauss-Bonnet identity. If dimensional regularization is employed we prove that anomalies spoil the quantum validity of this topological identity.

scholarly journals Squashing, mass, and holography for 3d sphere free energy

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Shai M. Chester ◽  
Rohit R. Kalloor ◽  
Adar Sharon
Keyword(s):  
Free Energy ◽  
Matrix Model ◽  
Fourth Order ◽  
Fermi Gas ◽  
Leading Order ◽  
Round Sphere ◽  
Dimensional Matrix ◽  
Fifth Order ◽  
M Theory ◽  
Derivatives Of

Abstract We consider the sphere free energy F(b; mI) in $$ \mathcal{N} $$ N = 6 ABJ(M) theory deformed by both three real masses mI and the squashing parameter b, which has been computed in terms of an N dimensional matrix model integral using supersymmetric localization. We show that setting $$ {m}_3=i\frac{b-{b}^{-1}}{2} $$ m 3 = i b − b − 1 2 relates F(b; mI) to the round sphere free energy, which implies infinite relations between mI and b derivatives of F(b; mI) evaluated at mI = 0 and b = 1. For $$ \mathcal{N} $$ N = 8 ABJ(M) theory, these relations fix all fourth order and some fifth order derivatives in terms of derivatives of m1, m2, which were previously computed to all orders in 1/N using the Fermi gas method. This allows us to compute $$ {\partial}_b^4F\left|{}_{b=1}\right. $$ ∂ b 4 F b = 1 and $$ {\partial}_b^5F\left|{}_{b=1}\right. $$ ∂ b 5 F b = 1 to all orders in 1/N, which we precisely match to a recent prediction to sub-leading order in 1/N from the holographically dual AdS4 bulk theory.

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