590,844 research outputs found
Confinement at Weak Coupling
The free energy of U(N) and SU(N) gauge theory was recently found to be of
order N^0 to all orders of a perturbative expansion about a center-symmetric
orbit of vanishing curvature. Here I consider extended models for which this
expansion is perturbatively stable. The extreme case of an SU(2) gauge theory
whose configuration space is restricted to center-symmetric orbits has recently
been investigated on the lattice hep-lat/0509156. In extension of my talk, a
discussion and possible interpretation of the observed finite temperature phase
transition is given. The transfer matrix of constrained SU(N) lattice gauge
theory is constructed for any finite temperature.Comment: 8 pages, no figures, updated talk given at LC2005 in Cairns,
Australi
Color superconductivity in weak coupling
We derive perturbatively the gap equations for a color-superconducting
condensate with total spin J=0 in dense QCD. At zero temperature, we confirm
the results of Son for the dependence of the condensate on the coupling
constant, and compute the prefactor to leading logarithmic accuracy. At nonzero
temperature, we find that to leading order in weak coupling, the temperature
dependence of the condensate is identical to that in BCS-like theories. The
condensates for total spin J=1 are classified; to leading logarithmic accuracy
these condensates are of the same order as those of spin J=0.Comment: 30 pages, 3 figures, RevTeX, epsf and psfig style files require
The Hagedorn temperature of AdS5/CFT4 at finite coupling via the Quantum Spectral Curve
Building on the recently established connection between the Hagedorn
temperature and integrability [Phys.Rev.Lett. 120 (2018) no.7, 071605], we show
how the Quantum Spectral Curve formalism can be used to calculate the Hagedorn
temperature of AdS5/CFT4 for any value of the 't Hooft coupling. We solve this
finite system of finite-difference equations perturbatively at weak coupling
and numerically at finite coupling. We confirm previous results at weak
coupling and obtain the previously unknown three-loop Hagedorn temperature. Our
finite-coupling results interpolate between weak and strong coupling and allow
us to extract the first perturbative order at strong coupling. Our results
indicate that the Hagedorn temperature for large 't Hooft coupling approaches
that of type IIB string theory in ten-dimensional Minkowski space.Comment: 7 page
Negative-coupling resonances in pump-coupled lasers
We consider coupled lasers, where the intensity deviations from the steady
state, modulate the pump of the other lasers. Most of our results are for two
lasers where the coupling constants are of opposite sign. This leads to a Hopf
bifurcation to periodic output for weak coupling. As the magnitude of the
coupling constants is increased (negatively) we observe novel amplitude effects
such as a weak coupling resonance peak and, strong coupling subharmonic
resonances and chaos. In the weak coupling regime the output is predicted by a
set of slow evolution amplitude equations. Pulsating solutions in the strong
coupling limit are described by discrete map derived from the original model.Comment: 29 pages with 8 figures Physica D, in pres
Tate Form and Weak Coupling Limits in F-theory
We consider the weak coupling limit of F-theory in the presence of
non-Abelian gauge groups implemented using the traditional ansatz coming from
Tate's algorithm. We classify the types of singularities that could appear in
the weak coupling limit and explain their resolution. In particular, the weak
coupling limit of SU(n) gauge groups leads to an orientifold theory which
suffers from conifold singulaties that do not admit a crepant resolution
compatible with the orientifold involution. We present a simple resolution to
this problem by introducing a new weak coupling regime that admits
singularities compatible with both a crepant resolution and an orientifold
symmetry. We also comment on possible applications of the new limit to model
building. We finally discuss other unexpected phenomena as for example the
existence of several non-equivalent directions to flow from strong to weak
coupling leading to different gauge groups.Comment: 34 page
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