1. Origin of Abelian gauge symmetries in heterotic/Ftheory dualityMirjam Cvetič, Antonella Grassi, Denis Klevers, Peng Song, Maximilian Poretschkin, 2016, izvirni znanstveni članek Opis: We study aspects of heterotic/Ftheory duality for compactifications with Abelian gauge symmetries. We consider Ftheory on general CalabiYau manifolds with a rank one MordellWeil group of rational sections. By rigorously performing the stable degeneration limit in a class of toric models, we derive both the CalabiYau geometry as well as the spectral cover describing the vector bundle in the heterotic dual theory. We carefully investigate the spectral cover employing the group law on the elliptic curve in the heterotic theory. We find in explicit examples that there are three different classes of heterotic duals that have U(1) factors in their low energy effective theories: split spectral covers describing bundles with S(U(m) x U(1)) structure group, spectral covers containing torsional sections that seem to give rise to bundles with SU(m) X Z(k) structure group and bundles with purely nonAbelian structure groups having a centralizer in E8 containing a U(1) factor. In the former two cases, it is required that the elliptic fibration on the heterotic side has a nontrivial MordellWeil group. While the number of geometrically massless U(1)'s is determined entirely by geometry on the Ftheory side, on the heterotic side the correct number of U(1)'s is found by taking into account a Stiickelberg mechanism in the lowerdimensional effective theory. In geometry, this corresponds to the condition that sections in the two half K3 surfaces that arise in the stable degeneration limit of Ftheory can be glued together globally. Ključne besede: Ftheory, string duality, superstrings, heterotic strings, Mtheory Objavljeno: 27.06.2017; Ogledov: 349; Prenosov: 99 Celotno besedilo (1,15 MB) Gradivo ima več datotek! Več...

2. Type II string theory on CalabiYau manifolds with torsion and nonAbelian discrete gauge symmetriesVolker Braun, Mirjam Cvetič, Ron Donagi, Maximilian Poretschkin, 2017, izvirni znanstveni članek Opis: We provide the first explicit example of Type IIB string theory compactification on a globally defined CalabiYau threefold with torsion which results in a fourdimensional effective theory with a nonAbelian discrete gauge symmetry. Our example is based on a particular CalabiYau manifold, the quotient of a product of three elliptic curves by a fixed point free action of Z(2) x Z(2). Its cohomology contains torsion classes in various degrees. The main technical novelty is in determining the multiplicative structure of the (torsion part of) the cohomology ring, and in particular showing that the cup product of second cohomology torsion elements goes nontrivially to the fourth cohomology. This specifies a nonAbelian, Heisenbergtype discrete symmetry group of the fourdimensional theory. Ključne besede: string field theory, conformal field models, string theory, discrete symmetries Objavljeno: 08.03.2018; Ogledov: 352; Prenosov: 88 Celotno besedilo (355,78 KB) Gradivo ima več datotek! Več...

3. Discrete symmetries in Heterotic/Ftheory duality and mirror symmetryMirjam Cvetič, Antonella Grassi, Maximilian Poretschkin, 2017, izvirni znanstveni članek Opis: We study aspects of Heterotic/Ftheory duality for compactifications with Abelian discrete gauge symmetries. We consider Ftheory compactifications on genusone fibered CalabiYau manifolds with nsections, associated with the TateShafarevich group Z(n). Such models are obtained by studying first a specific toric setup whose associated Heterotic vector bundle has structure group Z(n). By employing a conjectured Heterotic/Ftheory mirror symmetry we construct dual geometries of these original toric models, where in the stable degeneration limit we obtain a discrete gauge symmetry of order two and three, for compactifications to six dimensions. We provide explicit constructions of mirrorpairs for symmetric examples with Z(2) and Z(3), in six dimensions. The Heterotic models with symmetric discrete symmetries are related in field theory to a Higgsing of Heterotic models with two symmetric abelian U(1) gauge factors, where due to the Stuckelberg mechanism only a diagonal U(1) factor remains massless, and thus after Higgsing only a diagonal discrete symmetry of order n is present in the Heterotic models and detected via Heterotic/Ftheory duality. These constructions also provide further evidence for the conjectured mirror symmetry in Heterotic/Ftheory at the level of fibrations with torsional sections and those with multisections. Ključne besede: discrete symmetries, Ftheory, string duality, superstrings, heterotic strings Objavljeno: 08.03.2018; Ogledov: 355; Prenosov: 85 Celotno besedilo (510,30 KB) Gradivo ima več datotek! Več...
