In this first seminar I will review the situation of confronting string theory with experiments. Then I
will describe the explicit string models that are used to find string extensions of the Standard Model and that are based on intersecting and their T-dual magnetized D branes. The open strings, called twisted open strings, attached to those D branes contain chiral fermions and are therefore suitable to describe the quarks and
leptons
of the Standard Model. I will solve the equations of motion of an open string
on a torus interacting with two different and constant
magnetic fields located at its two end-points and I will find their quantum spectrum.
This provides a string extension of a particle interacting with a constant magnetic field on a torus. In
the second part of this first seminar I will discuss instantons in string theory.

Slides for this talk: see link above to the more advanced seminar.