Abstract
We study the de Sitter (dS) swampland conjecture in the Dirac-Born-Infeld (DBI) inflation model. We obtain the dS swampland bound for the relativistic regime using Bousso's entropy bound argument and proper distance. It restricts $m_{\rm Pl}\nabla V/V$ by some positive constant depending on warping and the field range. In the specific case of the DBI model driven by the quadratic potential, the model-dependent backreaction argument is interpreted as a natural bound for the slow-roll parameter. This shows that quasi-dS spacetime in the DBI model is a result of tuning.
Highlights
Various criteria for the low-energy effective field theory (EFT) admitting a consistent UV completion in quantum gravity have been proposed
Discussions so far show that in the DBI model Bousso’s entropy bound argument provides the bound for ðcVγÞ1=2= gYM ≃ mPl∇V=V as Eq (15) but it does not coincide with the mPl∇V=V bound in the nonrelativistic regime
The model-dependent backreaction argument is interpreted as the cV bound in the case of quadratic potential
Summary
Various criteria for the low-energy effective field theory (EFT) admitting a consistent UV completion in quantum gravity have been proposed (for a review, see Ref. [1]). Sufficiently large number of e-folds, these constraints are written as conjectured bounds for slow-roll parameters, εH They measure deviation of the spacetime geometry from dS, reflecting the instability of dS isometries under dynamics of scalar fields. [3] in the context of the DBI inflation model in which a more generic form of the dS swampland conjecture in terms of Eq (2) Masses of open string fluctuations and Kaluza-Klein (KK) modes are proportional to the modulus, realizing the situation similar to what the distance conjecture states This enables us to find the dS swampland bound through the arguments in Ref. [16], reduction of the model-independent backreaction effect through nonrenormalizable terms or interaction with bulk fields is regarded as a tuning similar to the attempt to solve the η problem It is another way to reveal difficulty in quasi-dS spacetime construction. We obtain the upper limit of the dS swampland bound value
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