62 research outputs found
Orbifolds versus smooth heterotic compactifications
Following the recent exploration of smooth heterotic compactifications with
unitary bundles, orbifold compactifications in six dimensions can be shown to
correspond in the blow-up to compactifications with U(1) gauge backgrounds. A
powerful tool is the comparison of anomaly polynomials. The presentation here
focuses on heterotic SO(32) compactifications in six dimensions including
five-branes. Four dimensional and E8 x E8 models are briefly commented on.Comment: Submitted for the SUSY07 proceedings, 4 pages, LaTe
Towards exact field theory results for the Standard Model on fractional D6-branes
Fractional D6-branes on toroidal orbifold backgrounds are known to be able to
accommodate the particle spectrum and gauge group of the Standard Model, but up
to now exact results for their low-energy effective action are missing. Here we
discuss how the conceptual ansatz of matching the string theoretic gauge
couplings at one-loop with the supergravity expressions is generalised from the
six-torus to orbifold backgrounds on which the Standard Model spectrum can be
realised on fractional D6-branes. The Kaehler metrics and perturbatively exact
holomorphic gauge kinetic functions can be classified in terms of the vanishing
of some intersection angle and the related beta function coefficients, which
potentially opens the possibility to extrapolate to smooth Calabi-Yau
backgrounds.Comment: 1+3 pages, 2 tables; proceedings of the EPS-HEP 2011 conference in
Grenoble 21-27 July 2011; v2: introduction and conclusion extended, published
versio
Mapping an Island in the Landscape
We provide a complete classification and statistical analysis of all type IIA
orientifold compactifications with intersecting D6-branes on the orbifold
T^6/Z'_6. The total number of four dimensional N=1 supersymmetric models is
found to be O(10^23). After a statistical analysis of the gauge sector
properties of all possible solutions, we study three subsets of configurations
which contain the chiral matter sector of the standard model, a Pati-Salam or
SU(5) GUT model, respectively. We find O(10^15) compactifications with an MSSM
and O(10^11) models with a Pati-Salam sector. Along the way we derive an
explicit algebraic formulation for the computation of the non-chiral matter
spectrum for all Z_N orbifolds.Comment: 46 pages, 10 figures; v2: typos corrected, new examples and expanded
study on chiral exotic
Discrete Abelian gauge symmetries and axions
We combine two popular extensions of beyond the Standard Model physics within
the framework of intersecting D6-brane models: discrete Zn symmetries and
Peccei-Quinn axions. The underlying natural connection between both extensions
is formed by the presence of massive U(1) gauge symmetries in D-brane model
building. Global intersecting D6-brane models on toroidal orbifolds of the type
T6/Z2N and T6/Z2xZ2M with discrete torsion offer excellent playgrounds for
realizing these extensions. A generation-dependent Z2 symmetry is identified in
a global Pati-Salam model, while global left-right symmetric models give rise
to supersymmetric realizations of the DFSZ axion model. In one class of the
latter models, the axion as well as Standard Model particles carry a
non-trivial Z3 charge.Comment: Contribution to the proceedings of DISCRETE2014; 13 page
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