This series consists of talks in the area of Superstring Theory.
I will discuss a solution generating technique that allows to generate
stationary axisymmetric solutions of five-dimensional gravity, starting
from static ones. This technique can be used to add angular momentum
to static configurations. It can also be used to add KK-monopole charge
to asymptotically flat five-dimensional solutions, thus generating geometries
that interpolate between five-dimensional and four-dimensional solutions.
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To realize massive pions, I propose a variation of the holographic model of massless QCD using the D4/D8/D8bar-brane configuration proposed by Sakai and Sugimoto. The deformation breaks the chiral symmetry explicitly and I compute the mass of the pions and vector mesons. The observed value of the pion mass can be obtained. I also argue a chiral perturbation corresponding to the deformation.
We discuss D-brane instantons in four-dimensional string compactifications with special emphasis on Eucliden D2-branes in Type IIA orientifolds with spacetime filling D6-branes. These can induce superpotential couplings among the open string fields which are forbidden at the perturbative level since they violate some of the global U(1) symmetries generically present in string theory.
After reviewing recent developments in the study of the AdS/CFT correspondence between the IR gauge theory living on a stack of D3-branes placed at a Calabi-Yau singularity and type IIB string theory on the near horizon geometry, we focus on the problem of counting chiral BPS operators in this class of CFTs and we match them with the dual string states in the general case of toric CY. Partition functions can be explicitly written in all sectors with fixed baryonic charge using localization over fixed points of the toric actions.