Solitons of axion-dilaton gravity

TL;DR

This paper employs soliton techniques to generate and analyze various non-trivial string backgrounds, including cosmological models, black holes, and wormholes, from flat space within axion-dilaton gravity, highlighting their relation to string dualities.

Contribution

It introduces a method to construct string backgrounds via soliton solutions characterized by integer parameters, linking these to known cosmological and black hole solutions and exploring their relation to string dualities.

Findings

Nappi-Witten universe as a (1,1) soliton for certain moduli

Black holes as (2,0) solitons in two dimensions

Euclidean wormholes as (0,2) solitons on flat space

Abstract

We use soliton techniques of the two-dimensional reduced beta-function equations to obtain non-trivial string backgrounds from flat space. These solutions are characterized by two integers (n, m) referring to the soliton numbers of the metric and axion-dilaton sectors respectively. We show that the Nappi-Witten universe associated with the SL(2) x SU(2) / SO(1, 1) x U(1) CFT coset arises as an (1, 1) soliton in this fashion for certain values of the moduli parameters, while for other values of the soliton moduli we arrive at the SL(2)/SO(1, 1) x SO(1, 1)^2 background. Ordinary 4-dim black-holes arise as 2-dim (2, 0) solitons, while the Euclidean worm-hole background is described as a (0, 2) soliton on flat space. The soliton transformations correspond to specific elements of the string Geroch group. These could be used as starting point for exploring the role of U-dualities in string compactifications to two dimensions.