Related papers: Mildly sequestered supergravity models and their r…
It is generally believed that weak scale supersymmetry implies weak scale supergravity, in the sense that the masses of the gravitino and gravitationally coupled moduli have masses below 100 TeV. This paper presents a realistic framework…
In this dissertation, we study the generalized symmetries in supergravities and superconformal field theories from the string theory perspective. Part one is devoted to the study of string universality in high spacetime dimensions.…
We consider string phenomenological models based on 11D Horava-Witten M-theory with 5 branes in the bulk. If the 5-branes cluster close to the distant orbifold plane (d_n\equiv 1-z_n\simeq 0.1) and if the topological charges of the physical…
Compactifications of heterotic M-theory are shown to provide solutions to the weak- and axion-scale hierarchy problems as a consequence of warped large extra dimensions. They allow a description that is reminiscent of the so-called…
I argue that the ten dimensional non--supersymmetric tachyonic superstrings may serve as good starting points for the construction of viable phenomenological vacua. Thus, enlarging the space of possible solutions that may address some of…
We argue that once all theoretical and phenomenological constraints are imposed on the different versions of the Large Volume Scenario (LVS) compactifications of type IIB string theory, one particular version is favored. This is essentially…
We elaborate on a recent study of a model of supersymmetry breaking we proposed recently, in the presence of a tunable positive cosmological constant, based on a gauged shift symmetry of a string modulus, external to the Standard Model (SM)…
We study total and partial supersymmetry breaking by freely acting orbifolds, or equivalently by Scherk-Schwarz compactifications, in type I string theory. In particular, we describe a four-dimensional chiral compactification with…
In this paper we investigate the problem of spontaneous supersymmetry breaking without a cosmological term in $N=3$ supergravity with matter vector multiplets, scalar fields geometry being $SU(3,m)/SU(3)\otimes SU(m)\otimes U(1)$. At first,…
We present a framework for embedding scalar-tensor models of screened modifed gravity such as chameleons, symmetrons and environmental dilatons into global supersymmetry. This achieved by secluding the dark sector from both the observable…
In this thesis, we consider heterotic string vacua based on a warped product of a four-dimensional domain wall and a six-dimensional internal manifold preserving only two supercharges. Thus, they correspond to half-BPS states of heterotic…
In this thesis we focus on the construction of models in which a supersymmetry breaking hidden sector is located on one fixed point of an extra dimensional interval and the effects are gauge mediated across this interval to the other fixed…
We consider quintessence models within 4D effective descriptions of gravity coupled to two scalar fields. These theories are known to give rise to viable models of late-time cosmic acceleration without any need for flat potentials, and so…
We consider the contraction of some non linear sigma models which appear in effective supergravity theories. In particular we consider the contractions of maximally symmetric spaces corresponding to N=1 and N=2 theories, as they appear in…
Using E-strings, we can analyze not only six-dimensional superconformal field theories but also probe vacua of non-perturabative heterotic string. We study strings made of D3-branes wrapped on various two-cycles in the global F-theory…
We study how two moduli can be stabilized in a Minkowski/de Sitter vacuum for a wide class of string-inspired Supergravity models with an effective Fayet-like Supersymmetry breaking. It is shown under which conditions this mechanism can be…
I review the relations between mass scales in various string theories and in M-theory. I discuss physical motivations and possible consistent realizations of large volume compactifications and low string scale. Large longitudinal…
We give a general formulation of semi-direct gauge mediation of supersymmetry breaking where the messengers interact with the hidden sector only through a weakly gauged group. Using this general formulation, we provide an explicit proof…
We begin the study of a class of string-motivated effective supergravity theories in light of current data from the CERN Large Hadron Collider (LHC). The case of heterotic string theory, in which the dilaton is stabilized via…
Supersymmetry and supergravity extend the standard model by introducing a new symmetry between fermions and bosons. Experimental data imply that supergravity must be broken. Among several mechanisms of supersymmetry breaking, gravity…