Chiral gauge theories in two dimensions with (0,2) supersymmetry admit a
much broader, and more interesting, class of vacuum solutions than
their better studied (2,2) counterparts. In this talk, we will explore
some of the possibilities that are offered by this additional freedom by
including field-dependent theta-angles and FI parameters. The moduli
spaces that will result from this procedure correspond to heterotic
string backgrounds with non-trivial H-flux and NS-brane sources. Along
the way, a remarkable relationship between (0,2) gauge anomalies and
H-flux will emerge.
G_2 manifolds play
the analogous role in M-theory that Calabi-Yau manifolds play in string
theory. There has been work in the physics community on conjectural
"mirror symmetry" in this context, and it has also been observed that
singularities are necessary for a satisfactory theory. After a very
brief review of these physical developments (by a mathematician who
doesn't necessarily understand the physics), I will give a mathematical
introduction to G_2 conifolds. I will then proceed to give a detailed
survey of recent mathematical developments on G_2 conifolds, including
desingularization, deformation theory, and possible constructions of G_2
conifolds. This includes separate joint works of myself with Jason
Lotay and with Dominic Joyce.
