Tachyon condensation in magnetic compactifications

by Dr Yoshiyuki Tatsuta (Scuola Normale Superiore)

Thursday 17 Dec 2020, 16:45 → 17:15 Europe/Rome

zoom meeting

PRIN Joint Seminar - "Supersymmetry breaking with fields, strings and branes"

Intersecting D-brane models and their T-dual magnetic
compactifications provide an attractive framework for particle
physics, allowing for chiral fermions and supersymmetry breaking.
Generically, magnetic compactifications have tachyons that are
usually removed by Wilson lines. However, quantum corrections prevent local minima for Wilson lines. 
We therefore study tachyon condensation in the simplest case,
the magnetic compactification of type I string theory on a torus to
eight dimensions. We find that tachyon condensation restores 
supersymmetry, which is broken by the magnetic flux, and we
compute the Kaluza-Klein mass spectrum.
The gauge group $\text{SO}(32)$ is broken to $\text{USp}(16)$.
We give arguments that the vacuum reached by tachyon  condensation corresponds to  the unique 8d superstring theory already known in the literature,  with discrete  $B_{ab}$ background or, in the T-dual version, the type IIB  orientifold with three $\text{O}7_-$-planes, one $\text{O}7_+$-plane and eight  D7-branes coincident with the  $\text{O}7_+$-plane.
The ground state after tachyon condensation is supersymmetric and has no chiral fermions.