2,141 research outputs found
Phases of \Nc= \infty QCD-like gauge theories on and nonperturbative orbifold-orientifold equivalences
We study the phase diagrams of \Nc= \infty vector-like, asymptotically free
gauge theories as a function of volume, on . The theories of
interest are the ones with fermions in two index representations [adjoint,
(anti)symmetric, and bifundamental abbreviated as QCD(adj), QCD(AS/S) and
QCD(BF)], and are interrelated via orbifold or orientifold projections. The
phase diagrams reveal interesting phenomena such as disentangled realizations
of chiral and center symmetry, confinement without chiral symmetry breaking,
zero temperature chiral transitions, and in some cases, exotic phases which
spontaneously break the discrete symmetries such as C, P, T as well as CPT. In
a regime where the theories are perturbative, the deconfinement temperature in
SYM, and QCD(AS/S/BF) coincide. The thermal phase diagrams of thermal orbifold
QCD(BF), orientifold QCD(AS/S), and SYM coincide, provided charge
conjugation symmetry for QCD(AS/S) and interchange symmetry of the
QCD(BF) are not broken in the phase continously connected to limit. When
the circle is endowed with periodic boundary conditions, the (nonthermal)
phase diagrams of orbifold and orientifold QCD are still the same, however,
both theories possess chirally symmetric phases which are absent in \None
SYM. The match and mismatch of the phase diagrams depending on the spin
structure of fermions along the circle is naturally explained in terms of
the necessary and sufficient symmetry realization conditions which determine
the validity of the nonperturbative orbifold orientifold equivalence.Comment: 60 pages, 6 figure
Continuity, Deconfinement, and (Super) Yang-Mills Theory
We study the phase diagram of SU(2) Yang-Mills theory with one adjoint Weyl
fermion on R^3xS^1 as a function of the fermion mass m and the compactification
scale L. This theory reduces to thermal pure gauge theory as m->infinity and to
circle-compactified (non-thermal) supersymmetric gluodynamics in the limit
m->0. In the m-L plane, there is a line of center symmetry changing phase
transitions. In the limit m->infinity, this transition takes place at
L_c=1/T_c, where T_c is the critical temperature of the deconfinement
transition in pure Yang-Mills theory. We show that near m=0, the critical
compactification scale L_c can be computed using semi-classical methods and
that the transition is of second order. This suggests that the deconfining
phase transition in pure Yang-Mills theory is continuously connected to a
transition that can be studied at weak coupling. The center symmetry changing
phase transition arises from the competition of perturbative contributions and
monopole-instantons that destabilize the center, and topological molecules
(neutral bions) that stabilize the center. The contribution of molecules can be
computed using supersymmetry in the limit m=0, and via the
Bogomolnyi--Zinn-Justin (BZJ) prescription in the non-supersymmetric gauge
theory. Finally, we also give a detailed discussion of an issue that has not
received proper attention in the context of N=1 theories---the non-cancellation
of nonzero-mode determinants around supersymmetric BPS and KK
monopole-instanton backgrounds on R^3xS^1. We explain why the non-cancellation
is required for consistency with holomorphy and supersymmetry and perform an
explicit calculation of the one-loop determinant ratio.Comment: A discussion of the non-cancellation of the nonzero mode determinants
around supersymmetric monopole-instantons in N=1 SYM on R^3xS^1 is added,
including an explicit calculation. The non-cancellation is, in fact, required
by supersymmetry and holomorphy in order for the affine-Toda superpotential
to be reproduced. References have also been adde
Inflation on an Open Racetrack
We present a variant of warped D-brane inflation by incorporating multiple
sets of holomorphically-embedded D7-branes involved in moduli stabilization
with extent into a warped throat. The resultant D3-brane motion depends on the
D7-brane configuration and the relative position of the D3-brane in these
backgrounds. The non-perturbative moduli stabilization superpotential takes the
racetrack form, but the additional D3-brane open string moduli dependence
provides more flexibilities in model building. For concreteness, we consider
D3-brane motion in the warped deformed conifold with the presence of multiple
D7-branes, and derive the scalar potential valid for the entire throat. By
explicit tuning of the microphysical parameters, we obtain inflationary
trajectories near an inflection point for various D7-brane configurations.
Moreover, the open racetrack potential admits approximate Minkowski vacua
before uplifting. We demonstrate with a concrete D-brane inflation model where
the Hubble scale during inflation can exceed the gravitino mass. Finally, the
multiple sets of D7-branes present in this open racetrack setup also provides a
mechanism to stabilize the D3-brane to metastable vacua in the intermediate
region of the warped throat.Comment: 29 pages, 15 figures, pre-print number and references adde
The soft supersymmetry breaking in D=5 supergravity compactified on S_1/Z_2 orbifolds
We study the origin of the supersymmetry breaking induced by the mediation of
gravity and the radion multiplet from the hidden to the visible brane in the
context of the N=2, D=5 supergravity compactified on S_1/Z_2 orbifolds. The
soft supersymmetry breaking terms for scalar masses, trilinear scalar couplings
and gaugino masses are calculated to leading order in the five dimensional
Newton's constant k_5^2 and the gravitino mass m_{3/2}. These are finite and
non-vanishing, with the scalar soft masses be non-tachyonic, and are all
expressed in terms of the gravitino mass and the length scale R of the fifth
dimension. The soft supersymmetry breaking parameters are thus correlated and
the phenomenological implications are discussed.Comment: 16 pages, 3 figures, 1 Table, final version to appear in Physics
Letters B, slightly shortened, comments added, typos correcte
Gauge unification, non-local breaking, open strings
The issue of non-local GUT symmetry breaking is addressed in the context of
open string model building. We study ZNxZM' orbifolds with all the GUT-breaking
orbifold elements acting freely, as rotations accompanied by translations in
the internal space.We consider open strings quantized on these backgrounds,
distinguishing whether the translational action is parallel or perpendicular to
the D-branes. GUT breaking is impossible in the purely perpendicular case,
non-local GUT breaking is instead allowed in the purely parallel case. In the
latter, the scale of breaking is set by the compactification moduli, and there
are no fixed points with reduced gauge symmetry, where dangerous explicit
GUT-breaking terms could be located. We investigate the mixed
parallel+perpendicular case in a Z2xZ2' example, having also a simplified field
theory realization.It is a new S1/Z2xZ2' orbifold-GUT model, with bulk gauge
symmetry SU(5)xSU(5) broken locally to the Standard Model gauge group. In spite
of the locality of the GUT symmetry breaking, there is no localized
contribution to the running of the coupling constants, and the unification
scale is completely set by the length of S1.Comment: 16 pages, 6 figure
Deconfinement on for all gauge groups and duality to double Coulomb Gas
I study finite-temperature super Yang-Mills for any gauge
group , compactified from four
dimensions on a torus, . I examine
in particular the low temperature regime , where is the
length of the spatial circle with periodic boundary conditions and with
anti-periodic boundary conditions for the adjoint gauginos along the thermal
cycle . For small such we are in a regime were semiclassical
calculations can be performed and a transition occurs at much smaller
than . The transition is mediated by the competition between
non-perturbative objects including 'exotic' topological molecules: neutral and
magnetic bions composed of BPS and KK monopole constituents, with
different charges in the co-root lattice of the gauge group , and the
perturbative electrically charged W-bosons (along with their wino
superpartners). I determine a duality to a double Coulomb gas of neutral and
magnetic bions of different charges of their constituent monopole-instantons,
and W-bosons of both scalar and electric charges. Aharanov-Bohm interactions
exist between magnetic bions and W-bosons, and scalar charges of W-bosons and
neutral bions attract like charges, as opposed to the magnetic and electric
charges where like charges repel. It is hoped in the future that lattice
studies of this Coulomb gas can be done as in [1] for all gauge groups. It is
hoped that a dual lattice 'affine' XY model with symmetry breaking
perturbations can also be found in future studies of general gauge group as
done in [1] for .Comment: 40 pages, 0 figure
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