Related papers: On Realistic Brane Worlds from Type I Strings
Recently, a new framework for solving the hierarchy problem has been proposed which does not rely on low energy supersymmetry or technicolor. The gravitational and gauge interactions unite at the electroweak scale, and the observed weakness…
We study Type I string theory compactified on a T^6/Z_3 orientifold. The low-energy dynamics is most conveniently analyzed in terms of D3-branes. We show that a sector of the theory, which corresponds to placing an odd number of D3-branes…
The massless spectrum of the ten dimensional USp(32) type I string has an N=1 supergravity multiplet coupled to non-supersymmetric matter. This raises the question of the consistency of the gravitino interactions. We resolve this apparent…
We propose a unified framework within Type IIA string theory, based on a globally consistent intersecting D6-brane model compactified on a $T^6/(\mathbb{Z}_2 \times \mathbb{Z}_2)$ orientifold. The model realizes the MSSM-like spectrum…
We review some aspects of the dramatic consequences of supersymmetry breaking on string vacua. In particular, we focus on the issue of vacuum stability in ten-dimensional string models with broken, or without, supersymmetry, whose…
We study supersymmetry breaking by Scherk-Schwarz compactifications in type I string theory. While in the gravitational sector all mass splittings are proportional to a (large) compactification radius, supersymmetry remains unbroken for the…
I discuss in detail the construction of realistic superstring standard--like models in the four dimensional free fermionic formulation. The analysis results in a restricted class of models with unique characteristics: (i) Three and only…
These lectures present some topics of string phenomenology and contain two parts. In the first part, I review the possibility of lowering the string scale in the TeV region, that provides a theoretical framework for solving the mass…
We elaborate that general intersecting brane models on orbifolds are obtained from type I string compactifications and their T-duals. Symmetry breaking and restoration occur via recombination and parallel separation of branes, preserving…
We investigate viable scenarios with various axions in the context of supersymmetric field theory and in globally consistent D-brane models. The Peccei-Quinn symmetry is associated with an anomalous U(1) symmetry, which acquires mass at the…
We consider a generic scenario of spontaneous breaking of supersymmetry in the hidden sector within N=1 supersymmetric orientifold compactifications of type II string theories with D-branes that support semi-realistic chiral gauge theories.…
We investigate a D-brane system in which spontaneous gauge symmetry breaking occurs. The system consists of four D3-branes and three anti-D7-branes at C^3/Z_3 singularity. The singularity is blown up by vacuum expectation values of the…
Intersecting D-brane models in string theory can naturally support the gauge and matter content of left-right symmetric extensions of the Standard Model with gauge symmetry SU(3)_c x SU(2)_L x SU(2)_R x U(1)_{B-L}. Considering such models…
We revisit the construction of the $\mathcal{N}=1$ supersymmetric trinification models with gauge group $\mathrm{U}(3)_C\times \mathrm{U}(3)_L \times \mathrm{U}(3)_R$ in Type IIA string theory on $\mathbf{T^6/(\mathbb{Z}_2\times…
We study mediation of supersymmetry breaking in the bulk, in models with primordial supersymmetry breaking on D-branes at the string scale, in the TeV region. We compute the gravitino and scalar masses up to one-loop level, as well as the…
Notwithstanding the central role of D-branes in many recently proposed string dualities, several interesting type I vacua have been found without resorting directly to D-brane technology. In this talk, we analyze a three-generation…
We identify the 4D field theories living on the world volume of D4 branes in non-supersymmetric type IIA string theory constructions. They are softly broken N=2 SQCD with the breakings introduced through vevs of the auxilliary fields in the…
In brane world models of nature, supersymmetry breaking is often isolated on a distant brane in a higher dimensional space. The form of the Kahler potential in generic string and M-theory brane world backgrounds is shown to give rise to…
This thesis studies meta- and exactly stable supersymmetry breaking mechanisms in heterotic and type IIB string theories and constructs an F-theory Grand Unified Theory model for neutrino physics in which neutrino mass is determined by the…
We consider supersymmetric theories where the standard-model quark and lepton fields are localized on a "3-brane" in extra dimensions, while the gauge and Higgs fields propagate in the bulk. If supersymmetry is broken on another 3-brane,…