35 research outputs found
Spinor-Vector Duality in Heterotic String Orbifolds
The three generation heterotic-string models in the free fermionic
formulation are among the most realistic string vacua constructed to date,
which motivated their detailed investigation. The classification of free
fermion heterotic string vacua has revealed a duality under the exchange of
spinor and vector representations of the SO(10) GUT symmetry over the space of
models. We demonstrate the existence of the spinor-vector duality using
orbifold techniques, and elaborate on the relation of these vacua to free
fermionic models.Comment: 20 pages. v2 minor corrections. Version to appear on JHEP. v3
misprints correcte
Heterotic T-folds with a small number of neutral moduli
We discuss non-geometric supersymmetric heterotic string models in D=4, in
the framework of the free fermionic construction. We perform a systematic scan
of models with four a priori left-right asymmetric Z_2 projections and shifts.
We analyze some 2^{20} models, identifying 18 inequivalent classes and
addressing variants generated by discrete torsions. They do not contain
geometrical or trivial neutral moduli, apart from the dilaton. However, we show
the existence of flat directions in the form of exactly marginal deformations
and identify patterns of symmetry breaking where product gauge groups, realized
at level one, are broken to their diagonal at higher level. We also describe an
"inverse Gepner map" from Heterotic to Type II models that could be used, in
certain non geometric settings, to define "effective" topological invariants.Comment: 37 page
Gauged Linear Sigma Models for toroidal orbifold resolutions
Toroidal orbifolds and their resolutions are described within the framework
of (2,2) Gauged Linear Sigma Models (GLSMs). Our procedure describes two-tori
as hypersurfaces in (weighted) projective spaces. The description is chosen
such that the orbifold singularities correspond to the zeros of their
homogeneous coordinates. The individual orbifold singularities are resolved
using a GLSM guise of non-compact toric resolutions, i.e. replacing discrete
orbifold actions by Abelian worldsheet gaugings. Given that we employ the same
global coordinates for both the toroidal orbifold and its resolutions, our GLSM
formalism confirms the gluing procedure on the level of divisors discussed by
Lust et al. Using our global GLSM description we can study the moduli space of
such toroidal orbifolds as a whole. In particular, changes in topology can be
described as phase transitions of the underlying GLSM. Finally, we argue that
certain partially resolvable GLSMs, in which a certain number of fixed points
can never be resolved, might be useful for the study of mini-landscape orbifold
MSSMs.Comment: 71 pages, 2 figure
A realistic intersecting D6-brane model after the first LHC run
With the Higgs boson mass around 125 GeV and the LHC supersymmetry search
constraints, we revisit a three-family Pati-Salam model from intersecting
D6-branes in Type IIA string theory on the
orientifold which has a realistic phenomenology. We systematically scan the
parameter space for , and find that the gravitino mass is
generically heavier than about 2 TeV for both cases due to the Higgs mass low
bound 123 GeV. In particular, we identify a region of parameter space with the
electroweak fine-tuning as small as 24-32 (3-4). In the
viable parameter space which is consistent with all the current constraints,
the mass ranges for gluino, the first two-generation squarks and sleptons are
respectively TeV, TeV, and TeV. For the
third-generation sfermions, the light stop satisfying WMAP bounds via
neutralino-stop coannihilation has mass from 0.5 to 1.2 TeV, and the light stau
can be as light as 800 GeV. We also show various coannihilation and resonance
scenarios through which the observed dark matter relic density is achieved.
Interestingly, the certain portions of parameter space has excellent
-- and - Yukawa coupling unification. Three regions of
parameter space are highlighted as well where the dominant component of the
lightest neutralino is a bino, wino or higgsino. We discuss various scenarios
in which such solutions may avoid recent astrophysical bounds in case if they
satisfy or above observed relic density bounds. Prospects of finding
higgsino-like neutralino in direct and indirect searches are also studied. And
we display six tables of benchmark points depicting various interesting
features of our model.Comment: 41 pages, 12 figures, 6 table