Role of trans-Planckian modes in cosmology

Motivated by the old trans-Planckian (TP) problem of inflationary cosmology, it has been conjectured that any consistent effective field theory should keep TP modes `hidden' behind the Hubble horizon, so as to prevent them from turning classical and thereby affecting macroscopic observations. In this paper we present two arguments against the Hubble horizon being a scale of singular significance as has been put forward in the TP Censorship Conjecture (TCC). First, refinements of TCC are presented that allow for the TP modes to grow beyond the horizon while still keeping the de-Sitter conjecture valid. Second, we show that TP modes can turn classical even well within the Hubble horizon, which, as such, negates this rationale behind keeping them from crossing it. The role of TP modes is known to be less of a problem in warm inflation, because fluctuations start out usually as classical. This allows warm inflation to be more resilient to the TP problem compared to cold inflation. To understand how robust this is, we identity limits where quantum modes can affect the primordial power spectrum in one specific case.Comment: 33 pages, comments welcome; v2: References updated, matches published versio

Machine Learning Line Bundle Cohomologies of Hypersurfaces in Toric Varieties

Different techniques from machine learning are applied to the problem of computing line bundle cohomologies of (hypersurfaces in) toric varieties. While a naive approach of training a neural network to reproduce the cohomologies fails in the general case, by inspecting the underlying functional form of the data we propose a second approach. The cohomologies depend in a piecewise polynomial way on the line bundle charges. We use unsupervised learning to separate the different polynomial phases. The result is an analytic formula for the cohomologies. This can be turned into an algorithm for computing analytic expressions for arbitrary (hypersurfaces in) toric varieties

Swampland Variations on a Theme by KKLT

The KKLT scenario in a warped throat, if consistent, provides a concrete counterexample to both the AdS scale separation and the dS swampland conjectures. First, we define and analyze the relevant effective field theory for the conifold modulus and the overall Kaehler modulus that both have exponentially small masses. The scalar potential still admits KKLT-like AdS and dS minima. Second, we critically analyze the reliability of the employed Wilsonian effective action by evaluating the masses of light modes localized in the warped throat. The resulting mass spectrum is discussed with respect to the swampland distance conjecture. We find the recently observed emergent nature of the latter not only at large distance points but also at the conifold point motivating a general extension of it. In this respect, KKLT and trans-Planckian field distance are on equal footing. It is pointed out that the reliability of the KKLT minimum will depend on how this emergent behavior is interpreted

The Refined Swampland Distance Conjecture in Calabi-Yau Moduli Spaces

The Swampland Distance Conjecture claims that effective theories derived from a consistent theory of quantum gravity only have a finite range of validity. This will imply drastic consequences for string theory model building. The refined version of this conjecture says that this range is of the order of the naturally built in scale, namely the Planck scale. It is investigated whether the Refined Swampland Distance Conjecture is consistent with proper field distances arising in the well understood moduli spaces of Calabi-Yau compactification. Investigating in particular the non-geometric phases of Kahler moduli spaces of dimension $h^{11}\in\{1,2,101\}$, we always found proper field distances that are smaller than the Planck-length

KKLT and the Swampland Conjectures

Recently, various swampland conjectures have been proposed that every UV complete effective field theory should satisfy. In particular, these deal with the properties of AdS and dS solutions arising in theories of quantum gravity. Mainly summarizing the results of our two previous articles href{https://arxiv.org/abs/1910.10185}{arXiv:1910.10185}, we confront the string theory based KKLT scenario with these conjectures and argue that if quantum vacua as in the KKLT construction indeed exist, some of the conjectures receive some log-corrections. Furthermore we point out some new aspects not contained in the aforementioned two papers