摘要: In [18] Nekrasov and Shatashvili pointed out that the N = 2 instanton partition function in
a special limit of the Ω-deformation parameters is characterized by certain thermodynamic
Bethe ansatz (TBA) like equations. In this work we present an explicit derivation of this fact
as well as generalizations to quiver gauge theories. To do so we combine various techniques
like the iterated Mayer expansion, the method of expansion by regions, and the path integral
tricks for non-perturbative summation. The TBA equations derived entirely within gauge
theory have been proposed to encode the spectrum of a large class of quantum integrable
systems. We hope that the derivation presented in this paper elucidates further this completely
new point of view on the origin, as well as on the structure, of TBA equations in
integrable models.