KTH/Nordita/SU seminar in Theoretical Physics

Strings in magnetic fields in extra-dimensions and the Standard Model

by Paolo Di Vecchia (Nordita)



I will start discussing the ideas presently used for connecting string theory to particle phenomenology. They are based on the existence in string theory of non-perturbative objects called D branes. I will give a brief description of them. Then, in order to be able to describe chiral matter as leptons and quarks, I will introduce the magnetized D branes that have the property of having magnetic fields living on the compact extra dimensions. I will then determine the spectrum of open strings connected to D branes having different magnetizations and I will show that this spectrum reduces, in the field theory limit, to that of an electron in an external magnetic field. The degeneracy of the Landau levels corresponds to the different families of quarks and leptons. Finally, I will discuss the Kaluza-Klein reduction of the low-energy effective action living on a stack of D9 branes and I will show how to compute the parameters of the low-energy Lagrangian as the Kähler metrics and Yukawa couplings that enter in the determination of the masses of quarks and leptons.