Narrow Results

D6-branes intersecting at angles allow for phenomenologically appealing constructions of four-dimensional string theory vacua. While it is straightforward to obtain non-supersymmetric realizations of the standard model, supersymmetric and stable models with three generations and no exotic chiral matter require more involved orbifold constructions. The T⁶/(ℤ₄×ℤ₂×Ωℛ) case is discussed in detail. Other orbifolds including fractional D6-branes are treated briefly.

We revisit the integration of fields in 𝒩 = 1 Supergravity with the requirement that the effective theory has a reliable two-derivative supersymmetric description. In particular, we study, in a supersymmetric manifest way, the situation where the fields that are mapped out have masses comparable to the Supersymmetry breaking scale and masses of the remaining fields. We find that as long as one stands in regions of the field configuration space where the analytic continuation to superspace of the F-flatness conditions be reliable equations of motion for the fields that are being mapped out, and provided their solutions are stable regardless the dynamics of the remaining fields, such a two-derivative description is a reliable truncation of the full effective theory. The study is mainly focused to models with two chiral sectors, H and L, described by a Kähler invariant function with schematic dependencies of the form , which leads to a nearly decoupled theory that allows the previous requirements to be easily satisfied in a consistent way. Interestingly, enough for the matters of our study, this kind of models present a scenario that is as safe as the one presented in sequestered models. It is also possible to allow gauge symmetries as long as these appear also factorized in hidden and visible sectors. Then, the integration of the hidden vector superfields is compulsory and proceeds reliably through the D-flatness condition analytically continued to superspace.

All the models of elementary particles and their interactions derived from String Theory involve a compact six-dimensional internal space. Its volume and shape should be fixed or stabilized, since otherwise massless scalar fields (moduli) reflecting their deformations appear in our four-dimensional space–time, with sizable effects on known particles and fields. We propose a strategy toward stabilizing the compact space without fluxes of three-form fields from closed strings. Our main motivation and goal is to proceed insofar as possible within conventional string worldsheet theory. As we shall see, D-branes with magnetic flux ("magnetized D-branes") and the forces between them can be used to this end. We investigate here some necessary ingredients: open string one-loop vacuum amplitudes between magnetized D-branes, magnetized D-branes fixed at orbifold singularities, and potential energies among such D-branes in the compact space that result from tree-level closed string exchanges.

In this paper, we present a string realization of the hybrid inflationary scenario within type IIB effective string theory constructions and a geometric configuration of intersecting D7 branes. A metastable de Sitter minimum is ensured by perturbative logarithmic corrections and D-term contributions from abelian factors associated with the D7 branes. The inflaton is identified with the internal volume modulus whereas possible waterfall fields correspond to excitations of open strings attached to the magnetized D7 branes. By incorporating contributions of these fields in the scalar potential, inflation stops and the metastable vacuum settles to a minimum with the observed tunable value of the cosmological constant.

A microscopic construction of black holes from M-theory that break supersymmetry is presented, by introducing a twist in the boundary condition of the fields in the superconformal theory of an effective string. To illustrate the mechanism, a specific example based on the choice of a Calabi-Yau compactification where h_1,1 = h_1,2 = 1 is constructed^* (Based on the work JHEP 1506 (2015) 058, in collaboration with N. Gaddam, S. Vandoren and O. Varela.).

The stabilization of moduli is one of the main problems in string theory. In this talk I will discuss some stringy mechanisms based on non-geometrical compactifications to obtain four dimensional models with a reduced number of moduli.