arXiv subjects

Falk Rohsiepe

Publications and source records attributed to Falk Rohsiepe.

3 recordsLinked to original sources

arXiv2005

Fibration structures in toric Calabi-Yau Fourfolds

In the context of string dualities, fibration structures of Calabi-Yau manifolds play a prominent role. In particular, elliptic and K3 fibered Calabi-Yau fourfolds are important for dualities between string compactifications with four flat space-time dimensions. A natural framework for studying explicit examples of such fibrations is given by Calabi-Yau hypersurfaces in toric varieties, because this class of varieties is sufficiently large to provide examples with very different features while still allowing a large degree of explicit control. In this paper, many examples for elliptic K3 fibered Calabi-Yau fourfolds are found (not constructed) by searching for reflexive subpolyhedra of reflexive polyhedra corresponding to hypersurfaces in weighted projective spaces. Subpolyhedra not always give rise to fibrations and the obstructions are studied. In addition, perturbative gauge algebras for dual heterotic string theories are determined. In order to do so, all elliptically fibered toric K3 surfaces are determined. Then, the corresponding gauge algebras are calculated without specialization to particular polyhedra for the elliptic fibers. Finally, the perturbative gauge algebras for the fourfold fibrations are extracted from the generic fibers and monodromy.

hep-th↗

arXiv2004

Lattice polarized toric K3 surfaces

When studying mirror symmetry in the context of K3 surfaces, the hyperkaehler structure of K3 makes the notion of exchanging Kaehler and complex moduli ambiguous. On the other hand, the metric is not renormalized due to the higher amount of supersymmetry of the underlying superconformal field theory. Thus one can define a natural mapping from the classical K3 moduli space to the moduli space of conformal field theories. Apart from the generalization of mirror constructions for Calabi-Yau threefolds, there is a formulation of mirror symmetry in terms of orthogonal lattices and global moduli space arguments. In many cases both approaches agree perfectly - with a long outstanding exception: Batyrev's mirror construction for K3 hypersurfaces in toric varieties does not fit into the lattice picture whenever the Picard group of the K3 surface is not generated by the pullbacks of the equivariant divisors of the ambient toric variety. In this case, not even the ranks of the corresponding Picard lattices add up as expected. In this paper the connection is clarified by refining the lattice picture. We show (by explicit calculation with a computer) mirror symmetry for all families of toric K3 hypersurfaces corresponding to dual reflexive polyhedra, including the formerly problematic cases.

hep-th↗

arXiv1996

On Reducible but Indecomposable Representations of the Virasoro Algebra

Motivated by the necessity to include so-called logarithmic operators in conformal field theories (Gurarie, 1993) at values of the central charge belonging to the logarithmic series c_{1,p}=1-6(p-1)^2/p, reducible but indecomposable representations of the Virasoro algebra are investigated, where L_0 possesses a nontrivial Jordan decomposition. After studying `Jordan lowest weight modules', where L_0 acts as a Jordan block on the lowest weight space (we focus on the rank two case), we turn to the more general case of extensions of a lowest weight module by another one, where again L_0 cannot be diagonalized. The moduli space of such `staggered' modules is determined. Using the structure of the moduli space, very restrictive conditions on submodules of `Jordan Verma modules' (the generalization of the usual Verma modules) are derived. Furthermore, for any given lowest weight of a Jordan Verma module its `maximal preserving submodule' (the maximal submodule, such that the quotient module still is a Jordan lowest weight module) is determined. Finally, the representations of the W-algebra W(2,3^3) at central charge c=-2 are investigated yielding a rational logarithmic model.

hep-th↗