Nikolaos Prezas

The Partition Function of the Two-Dimensional Black Hole Conformal Field Theory

We compute the partition function of the conformal field theory on the two-dimensional euclidean black hole background using path-integral techniques. We show that the resulting spectrum is consistent with the algebraic expectations for the SL(2,)/U(1) coset conformal field theory construction. In particular, we find confirmation for the bound on the spin of the discrete representations and we determine the density of the continuous representations. We point out the relevance of the partition function to all string theory backgrounds that include an SL(2,)/U(1) coset factor.

Gauged supergravities from twisted doubled tori and non-geometric string backgrounds

Abstract We propose a universal geometric formulation of gauged supergravity in terms of a twisted doubled torus. We focus on string theory (M-theory) reductions with generalized Scherk–Schwarz twists residing in the O ( n , n ) (E7(7)) duality group. The set of doubled geometric fluxes, associated with the duality twists and identified naturally with the embedding tensor of gauged supergravity, captures all known fluxes, i.e. physical form fluxes, ordinary geometric fluxes, as well as their non-geometric counterparts. Furthermore, we propose a prescription for obtaining the effective geometry embedded in the string theory twisted doubled torus or in the M-theory megatorus and apply it for several models of geometric and non-geometric flux compactifications.

N = 1 geometries for M theory and type IIA strings with fluxes

We derive a set of necessary and sufficient conditions for obtaining

Scherk-Schwarz reduction of M-theory on G2-manifolds with fluxes

\mathcal{N}=1

Boundary superstring field theory

backgrounds of M theory and type IIA strings in the presence of fluxes. Our metrics are warped products of four-dimensional Minkowski space-time with a curved internal manifold. We classify the different solutions for irreducible internal manifolds as well as for manifolds with

BMN Operators for Script N = 1 superconformal Yang-Mills theories and associated string backgrounds

{S}^{1}

Supersymmetric compactifications of heterotic strings with fluxes and condensates

isometries by employing the formalism of group structures and intrinsic torsion. We provide examples within these various classes along with general techniques for their construction. In particular, we generalize the Hitchin flow equations so that one can explicitly build irreducible 7-manifolds with a 4-form flux. We also show how several of the examples found in the literature fit in our framework and suggest possible generalizations.

D-branes and extended characters in SL(2,R)/U(1)

We analyse the 4-dimensional effective supergravity theories obtained from the Scherk-Schwarz reduction of M-theory on twisted 7-tori in the presence of 4-form fluxes. We implement the appropriate orbifold projection that preserves a G2-structure on the internal 7-manifold and truncates the effective field theory to an N = 1, D = 4 supergravity. We provide a detailed account of the effective supergravity with explicit expressions for the Kahler potential and the superpotential in terms of the fluxes and of the geometrical data of the internal manifold. Subsequently, we explore the landscape of vacua of M-theory compactifications on twisted tori, where we emphasize the role of geometric fluxes and discuss the validity of the bottom-up approach. Finally, by reducing along isometries of the internal 7-manifold, we obtain superpotentials for the corresponding type IIA backgrounds.

Axionic symmetry gaugings in N = 4 supergravities and their higher-dimensional origin

Abstract Using the Batalin–Vilkovisky formalism we provide a detailed analysis of the NS sector of boundary superstring field theory. We construct explicitly the relevant BV structure and derive the master action. Furthermore, we show that this action is exactly equal to the superdisk worldsheet partition function as was recently conjectured.

D-branes and SQCD in non-critical superstring theory

We study a class of near-BPS operators for a complex 2-parameter family of = 1 superconformal Yang-Mills theories that can be obtained by a Leigh-Strassler deformation of = 4 SYM theory. We identify these operators in the large-N and large R-charge limit and compute their exact scaling dimensions using = 1 superspace methods. From these scaling dimensions we attempt to reverse-engineer the light-cone worldsheet theory that describes string propagation on the Penrose limit of the dual geometry.