An alpha'-complete theory of cosmology and its tensionless limit

DIEGO MARQUES; OLAF HOHM; TOMAS CODINA

PHYSICAL REVIEW D

AMER PHYSICAL SOC

Lugar: New York; Año: 2023

1550-7998

We explore the exactly duality invariant higher-derivative extension of double field theory due to Hohm, Siegel and Zwiebach (HSZ) specialized to cosmological backgrounds. Despite featuring a finite number of derivatives in its original formulation, this theory encodes infinitely many α′ corrections for metric, B-field and dilaton, which are obtained upon integrating out certain extra fields. We perform a cosmological reduction with fields depending only on time and show consistency of this truncation. We compute the α′4 coefficients of the general cosmological classification. As a possible model for how to deal with all α′ corrections in string theory we give a two-derivative reformulation in which the extra fields are kept. The corresponding Friedmann equations are then ordinary second order differential equations that capture all α′ corrections. We explore the tensionless limit α′ → ∞, which features string frame de Sitter vacua, and we set up perturbation theory in 1/α′.