We consider the superfield formulation of supersymmetric gauge and matter
field theories on a three-dimensional sphere with rigid N=2
supersymmetry, as well as with N>2. The construction is based on a
supercoset SU(2∣1)/U(1) containing S3 as the bosonic subspace. We derive
an explicit form of SU(2∣1)/U(1) supervielbein and covariant derivatives, and
use them to construct classical superfield actions for gauge and matter
supermultiplets in this superbackground. We then apply superfield methods for
computing one-loop partition functions of these theories and demonstrate how
the localization technique works directly in the superspace.Comment: 1+64 pages; v2: Section 4.2 and a reference are adde