Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solitons of axion-dilaton gravity   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.

21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con