1. Chiral fourdimensional Ftheory compactifications with SU(5) and multiple U(1)factorsMirjam Cvetič, Antonella Grassi, Denis Klevers, Hernan Piragua, 2014, izvirni znanstveni članek Opis: We develop geometric techniques to determine the spectrum and the chiral indices of matter multiplets for fourdimensional Ftheory compactifications on elliptic CalabiYau fourfolds with rank two MordellWeil group. The general elliptic fiber is the CalabiYau onefold in dP(2). We classify its resolved elliptic fibrations over a general base B. The study of singularities of these fibrations leads to explicit matter representations, that we determine both for U(1) xU(1) and SU(5) x U(1) x U(1) constructions. We determine for the first time certain matter curves and surfaces using techniques involving prime ideals. The vertical cohomology ring of these fourfolds is calculated for both cases and general formulas for the Euler numbers are derived. Explicit calculations are presented for a specific base B = P3. We determine the general G(4)flux that belongs to HV((2,2)) of the resolved CalabiYau fourfolds. As a byproduct, we derive for the first time all conditions on G(4)flux in general Ftheory compactifications with a nonholomorphic zero section. These conditions have to be formulated after a circle reduction in terms of ChernSimons terms on the 3D Coulomb branch and invoke Mtheory/Ftheory duality. New ChernSimons terms are generated by KaluzaKlein states of the circle compactification. We explicitly perform the relevant field theory computations, that yield nonvanishing results precisely for fourfolds with a nonholomorphic zero section. Taking into account the new ChernSimons terms, all 4D matter chiralities are determined via 3D Mtheory/Ftheory duality. We independently check these chiralities using the subset of matter surfaces we determined. The presented techniques are general and do not rely on toric data. Ključne besede: flux compactifications, Ftheory Objavljeno: 27.06.2017; Ogledov: 317; Prenosov: 347 Celotno besedilo (1,75 MB) Gradivo ima več datotek! Več...

2. 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: 520; Prenosov: 242 Celotno besedilo (1,15 MB) 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: 626; Prenosov: 232 Celotno besedilo (510,30 KB) Gradivo ima več datotek! Več...
