De Sitter space in gauge/gravity duality

Abstract

We investigate gauge/gravity duality for gauge theories in de Sitter space.More precisely, we study a five-dimensional consistent truncation of type IIB supergravity, which encompasses a wide variety of gravity duals of strongly coupled gauge theories, including the Maldacena-Nunez solution and its walking deformations. We find several solutions of the 5d theory with dS 4 spacetime and nontrivial profiles for (some of) the scalars along the fifth (radial) direction. In the process, we prove that one of the equations of motion becomes dependent on the others, for nontrivial warp factor. This dependence reduces the number of field equations and, thus, turns out to be crucial for the existence of solutions with (A)dS 4 spacetime. Finally, we comment on the implications of our dS 4 solutions for building gravity duals of Glueball Inflation.August 21, 2018 1 anguelova@inrne.bas.bgSince the astronomical observations of [1] indicated that the expansion of the Universe is accelerating at present, which is consistent with having a (small, but non-vanishing) positive cosmological constant, there has been a huge interest in understanding quantum field theory in de Sitter space [2], as well as in finding dS solutions in string compactifications with stabilized moduli [3]. However, despite recent progress in either topic, these are still rather difficult endeavors. This has motivated a search for alternative approaches in the vein of attempts to develop holographic descriptions of physics in de Sitter space via proposed dS/CFT [4] or dS/dS [5] correspondences. 4 4 In this "dS/dS" correspondence the relation is between a dS d space and a CFT on a dS d−1 space. 1The most promising direction, though, for studying nonperturbative effects in gauge theories living in de Sitter space is via extensions of the gauge/gravity duality, that arose from [6,7,8,9], with a curved 4d spacetime instead of a flat one. This kind of idea was explored in [10], where a solution of type IIB supergravity with a Wick rotated RR scalar was used. 5 The ten-dimensional metric of that solution has a 4d de Sitter part, that can be viewed as the spacetime for a certain gauge theory. The same truncation of type IIB, with Wick rotated RR scalar, was also utilized in [14] to study more involved 4d cosmological backgrounds. However, this solution is rather peculiar, due to its reliance on a Wick rotated 10d field.Our goal here will be to find solutions with a dS 4 spacetime within the framework of the five-dimensional consistent truncation of type IIB, established in [15], that describes the gravity duals of a broad class of confining gauge theories. In particular, this framework encompasses the Maldacena-Nunez [16] and Klebanov-Strassler [17] solutions, which provide gravitational duals to N = 1 SYM, as well as the more recently found solutions [18,19,20], which give duals to strongly coupled gauge theories with more than one dynamical scale.We will study the equations of motion of the effective 5d action relevant for the consistent truncation of [15]. We will...

Systematics of constant roll inflation

“…Indeed, the minimal value of the first term now is: 29) which is greater than V t2 = 3+c 3−c for any c ∈ (0, 1). To conclude, the requirement, that V (φ) is positive-definite, does not impose any further restrictions on the parameter space of our class of models.…”

Anisotropic constant-roll Inflation

“…Under the constant-roll condition, one can solve equations exactly [5]. Thus, one can systematically find a certain class of constant-roll inflationary models which are compatible with the observational data [5][6][7]. Moreover, one can extend an idea of constant-roll inflation to teleparallel f (T ) gravity where the inflaton is coupled to the f (T ) [8].…”

On Non-slow Roll Inflationary Regimes

“…Despite the stability issue, ultra-slow roll inflation has received considerable attention during the last several years in relation to the observed low-l anomaly of the CMB [2]. It was also understood recently how to construct a class of ultra-slow roll composite inflation models in the context of the gauge/gravity duality [3,4,5]. Much more importantly, [6] showed that a certain generalization of ultra-slow roll, called constant roll, can give a longlasting/stable expansion in addition to producing a scale invariant spectrum of scalar perturbations.…”