In this pedagogical review we introduce systematic approaches to deforming integrable two-
dimensional sigma models. We use the integrable principal chiral model and the conformal …

This review provides an introduction to non-geometric backgrounds in string theory. Starting
from a discussion of T-duality, geometric and non-geometric torus-fibrations are reviewed …

We introduce a class of 2D sigma models which are parametrized by a function of one
variable. In addition to the physical field g, these models include an auxiliary field v α which …

We consider two integrable deformations of 2d sigma models on supercosets associated
with AdS n× S n. The first, the “η-deformation”(based on the Yang–Baxter sigma model), is a …

A bstract A general class of deformations of integrable sigma-models with symmetric space
F/G target-spaces are found. These deformations involve defining the non-abelian T dual of …

The S-matrix on the world-sheet theory of the string in AdS $ _ {5}\times {{S}^{5}} $ has
previously been shown to admit a deformation where the symmetry algebra is replaced by …

A bstract We study the integrable η and λ-deformations of supercoset string sigma models,
the basic example being the deformation of the AdS 5× S 5 superstring. We prove that the …

We show that the so-called λ deformed σ-model as well as the η deformed one belong to a
class of the E-models introduced in the context of the Poisson–Lie-T-duality. The λ and η …

We construct two-parameter families of integrable λ-deformations of two-dimensional field
theories. These interpolate between a CFT (a WZW/gauged WZW model) and the non …

A bstract The worldsheet theories that describe Poisson-Lie T-dualisable σ-models on group
manifolds as well as integrable η, λ and β-deformations provide examples of ℰ-models …