Stable, nonsingular bouncing universe with only a scalar mode

Kumar, K. Sravan; Maheshwari, Shubham; Mazumdar, Anupam; Peng, Jun

doi:10.1103/physrevd.102.024080

Cited by 15 publications

(26 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Perturbations in non-local gravity have been studied around flat [106,107], dS/AdS [111,112], bouncing [143,[148][149][150] and inflationary backgrounds [144,[191][192][193][194]. The aim of this chapter is to study perturbations in UV non-local gravity at the quadratic level of the action around backgrounds that go beyond those usually studied in literature, viz.…”

Section: Perturbations Around Non-maximally Symmetric Backgroundsmentioning

confidence: 99%

“…Note that the kinetic term for ⇣ has the correct sign to avoid ghosts. Similarly, for the case of ⇤ < 0, the minimal choice for F(⇤) would be one without any zeros for Z(⇤) [149]…”

Section: An Isotropic and Homogeneous Bouncing Universementioning

confidence: 99%

“…(4.14), for F(⇤) given in Eq. (4.18), are captured by solutions of the local equation [149] (⇤ m 2 )⇣ = 0 (4.21)…”

Section: Isotropic and Homogeneous Bouncing Backgroundsmentioning

confidence: 99%

“…Setting a 0 = 1, r 1 = m 2 = M 2 s for the cosine hyperbolic bounce, the generic solution of Eq. (4.21) in Fourier space looks like [149]…”

Section: Isotropic and Homogeneous Bouncing Backgroundsmentioning

confidence: 99%

“…Non-local QFTs were studied in [128][129][130][131][132][133][134][135][136][137] and at finite temperature in [138][139][140][141][142]. Inflation was studied in [143][144][145], non-singular bouncing cosmology in [94,143,[146][147][148][149][150] and Hamiltonian analysis was performed in [151,152]. Non-local gravity also shares many similar results with models of gravity inspired from non-commutative spacetime [153,154].…”

mentioning

confidence: 99%

See 4 more Smart Citations

Aspects of Ultraviolet Non-local Gravity

Maheshwari

Self Cite

View full text Add to dashboard Cite

The objective of this thesis is to introduce ultraviolet (UV) non-local gravity and discuss some new results in it. Motivated from approaches to quantum gravity like string theory, this is a higher derivative modification of General Relativity (GR) which aims to provide a softer description of gravity at short distances, while simultaneously keeping at bay the typical illnesses that accompany higher derivative theories. The derivatives appearing in the action are of infinite order, making the theory 'non-local'. Moreover, it is 'UV' because the derivatives modify gravity at high energies, while recovering GR at low energies. We discuss how such theories 1) possess linearized solutions with nondivergent gravitational potentials and curvatures, 2) admit non-maximally symmetric backgrounds which are stable (free from ghosts/tachyons) under perturbations, 3) admit non-singular, isotropic and homogeneous bouncing cosmological solutions with stable perturbations and 4) admit non-singular, anisotropic and homogeneous bouncing cosmological solutions where, unlike in GR, there is no unstable growth of spacetime anisotropies during the contraction phase of the universe, and isotropy and homogeneity is recovered at late times during the expanding phase.

show abstract

Section: Perturbations Around Non-maximally Symmetric Backgroundsmentioning

confidence: 99%

“…Note that the kinetic term for ⇣ has the correct sign to avoid ghosts. Similarly, for the case of ⇤ < 0, the minimal choice for F(⇤) would be one without any zeros for Z(⇤) [149]…”

Section: An Isotropic and Homogeneous Bouncing Universementioning

confidence: 99%

“…(4.14), for F(⇤) given in Eq. (4.18), are captured by solutions of the local equation [149] (⇤ m 2 )⇣ = 0 (4.21)…”

Section: Isotropic and Homogeneous Bouncing Backgroundsmentioning

confidence: 99%

“…Setting a 0 = 1, r 1 = m 2 = M 2 s for the cosine hyperbolic bounce, the generic solution of Eq. (4.21) in Fourier space looks like [149]…”

Section: Isotropic and Homogeneous Bouncing Backgroundsmentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Aspects of Ultraviolet Non-local Gravity

Maheshwari

Self Cite

View full text Add to dashboard Cite

show abstract

Infinite-derivative linearized gravity in convolutional form

Heredia

Kolář

Llosa

et al. 2022

Class. Quantum Grav.

Self Cite

View full text Add to dashboard Cite

This article aims to transform the inﬁnite-order Lagrangian density for ghost-free inﬁnite-derivative linearized gravity into non-local. To achieve it, we use the theory of generalized functions and the Fourier transform in the space of tempered distributions S′. We show that the non-local operator domain is not deﬁned on the whole functional space but on a subset of it. Moreover, we prove that these functions and their derivatives are bounded in all ℝ3and, consequently, the Riemann tensor is regular and the scalar curvature invariants do not present any spacetime singularity. Finally, we explore what conditions we need to satisfy so that the solutions of the linearized equations of motion exist in S′.

show abstract

An anisotropic bouncing universe in non-local gravity

Kumar

Maheshwari

Mazumdar

et al. 2021

J. Cosmol. Astropart. Phys.

Self Cite

View full text Add to dashboard Cite

We show that it is possible to realize a cosmological bouncing solution in an anisotropic but homogeneous Bianchi-I background in a class of non-local, infinite derivative theories of gravity. We show that the anisotropic shear grows slower than in general relativity during the contraction phase, peaks to a finite value at the bounce point, and then decreases as the universe asymptotes towards isotropy and homogeneity, and ultimately to de Sitter. Along with a cosmological constant, the matter sector required to drive such a bounce is found to consist of three components — radiation, stiff matter and k-matter (whose energy density decays like the inverse square of the average scale factor). Generically, k-matter exerts anisotropic pressures. We will test the bouncing solution in local and non-local gravity and show that in the latter case it is possible to simultaneously satisfy positivity of energy density and, at least in the late time de Sitter phase, avoid the introduction of propagating ghost/tachyonic modes.

show abstract

Stable, nonsingular bouncing universe with only a scalar mode

Cited by 15 publications

References 38 publications

Aspects of Ultraviolet Non-local Gravity

Aspects of Ultraviolet Non-local Gravity

Infinite-derivative linearized gravity in convolutional form

An anisotropic bouncing universe in non-local gravity

Contact Info

Product

Resources

About