4,384 research outputs found
Phase-diagram of two-color lattice QCD in the chiral limit
We study thermodynamics of strongly coupled lattice QCD with two colors of
massless staggered fermions as a function of the baryon chemical potential
in 3+1 dimensions using a new cluster algorithm. We find evidence that
the model undergoes a weak first order phase transition at which
becomes second order at a finite . Symmetry considerations suggest that
the universality class of these phase transitions should be governed by an
field theory with collinear order, with N=3 at and
N=2 at . The universality class of the second order phase
transition at appears to be governed by the decoupled XY fixed
point present in the field theory. Finally we show that the
quantum (T=0) phase transition as a function of is a second order mean
field transition.Comment: 31 pages, 12 figure
TeV scale 5D unification and the fixed point anomaly cancellation with chiral split multiplets
A possibility of 5D gauge unification of in
is examined. The orbifold compactification allows fixed points where
representations can be assigned. We present a few
possibilities which give long proton lifetime, top-bottom mass hierarchy from
geometry, and reasonable neutrino masses. In general, these {\it chiral models}
can lead to fixed point anomalies. We can show easily, due to the simplicity of
the model, that these anomalies are cancelled by the relevant Chern-Simons
terms for all the models we consider. It is also shown that the fixed point
U(1)--graviton--graviton anomaly cancels without the help from the Chern-Simons
term. Hence, we conjecture that the fixed point anomalies can be cancelled if
the effective 4D theory is made anomaly free by locating chiral fermions at the
fixed points.Comment: LaTeX file of 19 pages with 1 figur
Supersymmetry, local horizontal unification, and a solution to the flavor puzzle
Supersymmetric gauge models with local horizontal symmetries are known to
generate large flavor changing neutral current effects induced by supersymmetry
breaking D-terms. We show how the presence of a U(1) gauge symmetry solves this
problem. We then construct a realistic gauge model with SU(2)_H x U(1)_H as the
local horizontal symmetry and suggest that the U(1)_H factor may be identified
with the anomalous U(1) induced by string compactification. This model explains
the observed hierarchies among the quark masses and mixing angles, accommodates
naturally the solar and atmospheric neutrino data, and provides simultaneously
a solution to the supersymmetric flavor problem. The model can be excluded if
the rare decay \mu --> e \gamma is not observed in the current round of
experiments.Comment: 10 pages in RevTe
Recommended from our members
Optical injection locking of a THz quantum-cascade VECSEL with an electronic source.
Optical injection locking of a metasurface quantum-cascade (QC) vertical-external-cavity surface-emitting laser (VECSEL) is demonstrated at 2.5 THz using a Schottky diode frequency multiplier chain as the injection source. The spectral properties of the source are transferred to the laser output with a locked linewidth of ∼1 Hz, as measured by a separate subharmonic diode mixer, and a locking bandwidth of ∼300 MHz is achieved. The large locking range is enabled by the microwatt power levels available from modern diode multipliers. The interplay between the injected signal and feedback from external reflections is studied and demonstrated to increase or decrease the locking bandwidth relative to the classic locking range depending on the phase of the feedback
Instabilities of bulk fields and anomalies on orbifolds
Bulk matter modes of higher dimensional models generically become unstable in
the presence of additional matter multiplets at the branes. This quantum
instability is driven by localized Fayet-Iliopoulos terms that attract the bulk
zero modes towards the boundary branes. We study this mechanism in the
framework of a 5 dimensional S^1/Z_2 orbifold and give conditions for the
various possibilities of localization of (chiral) zero modes. This mechanism is
quite relevant for realistic model building, as the standard model contains
U(1) hypercharge with potentially localized FI-terms. The analysis is closely
related to localized anomalies in higher dimensional gauge theories. Five
dimensional gauge invariance of the effective action determines the anomaly
constraints and fixes the normalization of Chern-Simons terms. The localization
of the bulk modes does not effect the anomaly cancellation globally, but the
additional heavy Kaluza-Klein modes of the bulk fields may cancel the
Chern-Simons terms. We discuss also the potential appearance of the parity
anomaly that might render the construction of some orbifold models
inconsistent.Comment: 29 pages, LaTeX, with figure
Birhythmicity, Synchronization, and Turbulence in an Oscillatory System with Nonlocal Inertial Coupling
We consider a model where a population of diffusively coupled limit-cycle
oscillators, described by the complex Ginzburg-Landau equation, interacts
nonlocally via an inertial field. For sufficiently high intensity of nonlocal
inertial coupling, the system exhibits birhythmicity with two oscillation modes
at largely different frequencies. Stability of uniform oscillations in the
birhythmic region is analyzed by means of the phase dynamics approximation.
Numerical simulations show that, depending on its parameters, the system has
irregular intermittent regimes with local bursts of synchronization or
desynchronization.Comment: 21 pages, many figures. Paper accepted on Physica
Dimensionless supersymmetry breaking couplings, flat directions, and the origin of intermediate mass scales
The effects of supersymmetry breaking are usually parameterized by soft
couplings of positive mass dimensions. However, realistic models also predict
the existence of suppressed, but non-vanishing, dimensionless
supersymmetry-breaking couplings. These couplings are technically hard, but do
not lead to disastrous quadratic divergences in scalar masses, and may be
crucial for understanding low-energy physics. In particular, analytic scalar
quartic couplings that break supersymmetry can lead to intermediate scale
vacuum expectation values along nearly-flat directions. I study the one-loop
effective potential for flat directions in the presence of dimensionless
supersymmetry-breaking terms, and discuss the corresponding renormalization
group equations. I discuss two applications: a minimal model of automatic
R-parity conservation, and an extension of this minimal model which provides a
solution to the \mu problem and an invisible axion.Comment: 28 pages, LaTeX with epsf and axodraw.st
Gauge-Fermion Unification and Flavour Symmetry
After we study the 6-dimensional supersymmetry breaking
and symmetry breaking on , we construct two supersymmetric models on where is
broken down to by orbifold projection. In Model I, three
families of the Standard Model fermions arise from the zero modes of bulk
vector multiplet, and the symmetry
can be considered as flavour symmetry. This may explain why there are three
families of fermions in the nature. In Model II, the first two families come
from the zero modes of bulk vector multiplet, and the flavour symmetry is
similar. In these models, the anomalies can be cancelled, and we have very good
fits to the SM fermion masses and mixings. We also comment on the supersymmetric models on and ,
SU(9) models on , and SU(8) models on orbifolds.Comment: Latex, 33 pages, minor change
Anomalies on orbifolds with gauge symmetry breaking
We embed two 4D chiral multiplets of opposite representations in the 5D N=2
gauge theory compactified on an orbifold .
There are two types of orbifold boundary conditions in the extra dimension to
obtain the 4D N=1 gauge theory from the bulk: in
Type I, one has the bulk gauge group at and the unbroken gauge group at
while in Type II, one has the unbroken gauge group at both fixed
points. In both types of orbifold boundary conditions, we consider the zero
mode(s) as coming from a bulk -plet and brane fields at the fixed
point(s) with the unbroken gauge group. We check the consistency of this
embedding of fields by the localized anomalies and the localized FI terms. We
show that the localized anomalies in Type I are cancelled exactly by the
introduction of a bulk Chern-Simons term. On the other hand, in some class of
Type II, the Chern-Simons term is not enough to cancel all localized anomalies
even if they are globally vanishing. We also find that for the consistent
embedding of brane fields, there appear only the localized log FI terms at the
fixed point(s) with a U(1) factor.Comment: LaTeX file of 19 pages with no figure, published versio
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