String-inspired infinite-derivative theories of gravity: A brief overview

Biswas, Tirthabir; Talaganis, Spyridon

doi:10.1142/s021773231540009x

Cited by 29 publications

(32 citation statements)

References 52 publications

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“…Then, if the bounce period is short so that the link between the contracting phase and the expanding phase is approximately instantaneous just as we have assumed, our analysis is also approximately valid. However, in some kinds of modified gravity theories, in which the perturbation equations are modified, especially when higher-order terms of gravity appear in the perturbation equations, e.g., [73], our analysis will no longer be robust and will need to be revisited.…”

Section: Discussionmentioning

confidence: 99%

Preinflationary primordial perturbations

2015

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The large-scale power deficit in the cosmic microwave background fluctuations might be relevant with the physics of pre-inflation, a bounce, or a superinflationary phase preceding slow-roll inflation, which can provide a singular-free realization of inflation. We investigate the primordial perturbations from such pre-inflationary evolutions, which generally may consist of multiple phases with different background dynamics, and give a universal formula for the power spectrum of primordial perturbations in terms of the recursive Bogoliubov coefficients. We also apply our formula to corresponding cases and show how the intensity of large-scale power suppression is affected by the pre-inflationary physics.

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Section: Discussionmentioning

confidence: 99%

Preinflationary primordial perturbations

2015

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“…4 For other forms of infinite-derivative gravity theories which contain an additional scalar degree of freedom, see [25,27].…”

Section: Infinite-derivative Gravitational Actionmentioning

confidence: 99%

“…Given the prospects of the BGKM model at resolving the classical singularities of GR, see [27] for an overview, here we are going to explore the possibility of formulating a quantum theory of BGKM, and the various challenges we need to overcome. For important works on slightly different approaches to quantizing gravity involving infinite-derivative interactions, see 1 [28,29,30,31,32,33].…”

Section: Introductionmentioning

confidence: 99%

Towards understanding the ultraviolet behavior of quantum loops in infinite-derivative theories of gravity

Talaganis

Biswas

Mazumdar

2015

Class. Quantum Grav.

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140

252

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In this paper we will consider quantum aspects of a non-local, infinitederivative scalar field theory -a toy model depiction of a covariant infinitederivative, non-local extension of Einstein's general relativity which has previously been shown to be free from ghosts around the Minkowski background. The graviton propagator in this theory gets an exponential suppression making it asymptotically free, thus providing strong prospects of resolving various classical and quantum divergences. In particular, we will find that at 1-loop, the 2-point function is still divergent, but once this amplitude is renormalized by adding appropriate counter terms, the ultraviolet (UV) behavior of all other 1-loop diagrams as well as the 2-loop, 2-point function remains well under control. We will go on to discuss how one may be able to generalize our computations and arguments to arbitrary loops.

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“…Refs. (Accioly et al, 2002;Bartoli et al, 1999;Biswas and Talaganis, 2015;Buchbinder et al, 1992)but its roots date back to seminal studies on quadratic corrections to the Einstein-Hilbert action (Stelle, 1977(Stelle, , 1978.…”

Section: The Propagator For Higher-curvature Etg's: Linearizatiomentioning

confidence: 99%

Higher-order theories of gravity: diagnosis, extraction and reformulation via non-metric extra degrees of freedom—a review

Belenchia¹,

Letizia²,

Liberati³

et al. 2018

Rep. Prog. Phys.

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Modifications of Einstein's theory of gravitation have been extensively considered in the past years, in connection to both cosmology and quantum gravity. Higher-curvature and higher-derivative gravity theories constitute the main examples of such modifications. These theories exhibit, in general, more degrees of freedom than those found in standard general relativity; counting, identifying, and retrieving the description/representation of such dynamical variables is currently an open problem, and a decidedly nontrivial one. In this work we review, via both formal arguments and custom-made examples, the most relevant methods to unveil the gravitational degrees of freedom of a given model, discussing the merits, subtleties and pitfalls of the various approaches.

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String-inspired infinite-derivative theories of gravity: A brief overview

Cited by 29 publications

References 52 publications

Preinflationary primordial perturbations

Preinflationary primordial perturbations

Towards understanding the ultraviolet behavior of quantum loops in infinite-derivative theories of gravity

Higher-order theories of gravity: diagnosis, extraction and reformulation via non-metric extra degrees of freedom—a review

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