Solution of the size and horizon problems from classical string geometry

We recently introduced a T-duality covariant mechanism to compute all-order higher-derivative interactions in the heterotic string. Here we extend the formalism to account for a two-parameter family of corrections that also include the bosonic string and HSZ theory. We use our result to compute the full second order Double Field Theory (DFT) for generic values of the parameters, including the generalized Green-Schwarz transformation and its invariant action.

Section: Jhep01(2021)171 5 Summary and Outlookmentioning

confidence: 73%

The generalized Bergshoeff-de Roo identification. Part II

Baron

Marqués

2021

“…After including matter in the form of a perfect fluid energy-momentum tensor in the framework [74], solutions to the equations of motion were studied in [75] and a model sourced by a string gas was introduced in [76]. This model has a short TCC compatible phase of accelerated (super-exponential) expansion that last long enough to solve the hori-JHEP04(2021)037 zon problem of standard cosmology [77], depicting the phenomenological relevance of this class of backgrounds.…”

Section: Non-perturbative Backgrounds and α -Cosmologymentioning

confidence: 99%

Crisis on infinite earths: short-lived de Sitter vacua in the string theory landscape

Bernardo

Brahma

Dasgupta

et al. 2021

Self Cite

We construct purely non-perturbative anti-de Sitter vacua in string theory which, on uplifting to a de Sitter (dS) one, have a decay time many orders of magnitude smaller than those of standard constructions, such as the KKLT and LVS scenarios. By virtue of being constructed purely from non-perturbative terms, these vacua avoids certain obstructions plaguing other constructions of dS in string theory. This results in a new class of phenomenological dS vacua in string theory with novel distinctive characteristics such as having two maxima. After examining whether these uplifted dS vacua obey the TCC, we revisit some old problems of realization of dS space as a vacuum. We find that not only is it phenomenologically hard to construct TCC-compatible vacua, but also inherent temporal dependences of the degrees of freedom generically arise in such constructions, amongst other issues. This reinforces the idea that dS, if it exists in string theory, should be a Glauber-Sudarshan state and not a vacuum.

“…Zwiebach [42,43] (generalizing [44]), who found the form of the most general action for the metric, the dilaton and the b-field when these fields only depend on time, which is invariant under O(d, d) transformations and which includes α corrections to all orders. The inclusion of coupling to other matter fields was then first explored in [45], and applications to string cosmology have been explored in a few studies so far [42,43,[45][46][47][48][49][50], often discovering new potential solutions, such as de Sitter-like or loitering backgrounds, which are otherwise often difficult to find in string cosmology (see, e.g., [51][52][53][54]). The current paper's aim is to go beyond these recent works on string-cosmology backgrounds to all orders in α .…”

Section: Jhep07(2021)149mentioning

confidence: 99%

“…8 The present paper shall not be concerned though with the construction of full cosmological scenarios. This has been first explored in, e.g., [48,49] and deserves to be extended in future work.…”

Section: The High-energy Limitmentioning

confidence: 99%

Cosmology at the top of the α′ tower

Quintin

Bernardo

Franzmann

2021

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The cosmology of the fully α′-corrected duality-invariant action for the Neveu-Schwarz sector of string theory is revisited, with special emphasis on its coupling to matter sources. The role of the duality covariant pressure and dilatonic charge of the matter sector is explored in various contexts, from the low-curvature regime to non-perturbative solutions in α′. We comment on how an infinite tower of α′ corrections allows for fixed-dilaton de Sitter solutions, even in vacuum. We further investigate the necessary conditions for accelerated expansion in the Einstein frame, as well as for non-singular bounces that could resolve the big bang singularity. In particular, explicit examples are constructed, which show that the tower of α′ corrections may support an Einstein-frame non-singular cosmological bouncing background, even when the matter sector respects the null energy condition.