Pantelis Manousselis

Non-Kähler string backgrounds and their five torsion classes

We discuss the mathematical properties of six-dimensional non-Kahler manifolds which occur in the context of N=1 supersymmetric heterotic and type IIA string compactifications with non-vanishing background H-field. The intrinsic torsion of the associated SU(3) structures falls into five different classes. For heterotic compactifications we present an explicit dictionary between the supersymmetry conditions and these five torsion classes. We show that the non-Ricci-flat Iwasawa manifold solves the supersymmetry conditions with non-zero H-field, so that it is a consistent heterotic supersymmetric groundstate.

Dimensional reduction over fuzzy coset spaces

We examine gauge theories on Minkowski space-time times fuzzy coset spaces. This means that the extra space dimensions instead of being a continuous coset space S/R are a corresponding finite matrix approximation. The gauge theory defined on this non-commutative setup is reduced to four dimensions and the rules of the corresponding dimensional reduction are established. We investigate in particular the case of the fuzzy sphere including the dimensional reduction of fermion fields.

Supersymmetric compactifications of heterotic strings with fluxes and condensates

Abstract We discuss supersymmetric compactifications of heterotic strings in the presence of H-flux and general condensates using the formalism of G -structures and intrinsic torsion. We revisit the examples based on nearly-Kahler coset spaces and show that supersymmetric solutions, where the Bianchi identity is satisfied, can be obtained when both gaugino and dilatino condensates are present.

Dimensional Reduction over Coset Spaces and Supersymmetry Breaking

We address the question of supersymmetry breaking of a higher dimensional supersymmetric theory due to coset space dimensional reduction. In particular we study a ten-dimensional supersymmetric E8 gauge theory which is reduced over all six-dimensional coset spaces. We find that the original supersymmetry is completely broken in the process of dimensional reduction when the coset spaces are symmetric. On the contrary softly broken four-dimensional supersymmetric theories result when the coset spaces are non-symmetric. From our analysis two promising cases are emerging which lead to interesting GUTs with three fermion families in four dimensions, one being non-supersymmetric and the other softly broken supersymmetric.

Dimensional reduction of ten-dimensional supersymmetric gauge theories in the = 1, D = 4 superfield formalism

A ten-dimensional supersymmetric gauge theory is written in terms of = 1, D = 4 superfields. The theory is dimensionally reduced over six-dimensional coset spaces. We find that the resulting four-dimensional theory is either a softly broken = 1 supersymmetric gauge theory or a non-supersymmetric gauge theory depending on whether the coset spaces used in the reduction are non-symmetric or symmetric. In both cases examples susceptible to yield realistic models are presented.

Can non-commutativity resolve the big-bang singularity?

Abstract.A possible way to resolve the singularities of general relativity is proposed based on the assumption that the description of space-time using commuting coordinates is not valid above a certain fundamental scale. Beyond that scale it is assumed that the space-time has non-commutative structure leading in turn to a resolution of the singularity. As a first attempt towards realizing the above programme a modification of the Kasner metric is constructed which is commutative only at large time scales. At small time scales, near the singularity, the commutation relations among the space coordinates diverge. We interpret this result as meaning that the singularity has been completely delocalized.

Supersymmetry breaking by dimensional reduction over coset spaces

Abstract We study the dimensional reduction of a ten-dimensional supersymmetric E 8 gauge theory over six-dimensional coset spaces. We find that the coset space dimensional reduction over a symmetric coset space leaves the four dimensional gauge theory without any track of the original supersymmetry. On the contrary the dimensional reduction over a non-symmetric coset space leads to a softly broken supersymmetric gauge theory in four dimensions. The SO 7 / SO 6 and G 2 / SU (3) are used as representative prototypes of symmetric and non symmetric coset spaces, respectively.

On the consistency of coset space dimensional reduction

Abstract In this Letter we consider higher-dimensional Yang–Mills theories and examine their consistent coset space dimensional reduction. Utilizing a suitable ansatz and imposing a simple set of constraints we determine the four-dimensional gauge theory obtained from the reduction of both the higher-dimensional Lagrangian and the corresponding equations of motion. The two reductions yield equivalent results and hence they constitute an example of a consistent truncation.

Soft supersymmetry breaking due to dimensional reduction over non-symmetric coset spaces

Abstract A ten-dimensional supersymmetric E 8 gauge theory is compactified over six-dimensional coset spaces, establishing further our earlier conjecture that the resulting four-dimensional theory is a softly broken supersymmetric gauge theory in the case that the used coset space is non-symmetric. The specific non-symmetric six-dimensional spaces examined in the present study are Sp (4)/( SU (2)× U (1)) non-max and SU (3)/ U (1)× U (1).

Coset Space Dimensional Reduction of Einstein--Yang--Mills theory

In the present contribution we extend our previous work by considering the coset space dimensional reduction of higher-dimensional Einstein–Yang–Mills theories including scalar fluctuations as well as Kaluza–Klein excitations of the compactification metric and we describe the gravity-modified rules for the reduction of non-abelian gauge theories.