978 research outputs found
On the Perturbative Nature of Color Superconductivity
Color superconductivity is a possible phase of high density QCD. We present a
systematic derivation of the transition temperature, T_C, from the QCD
Lagrangian through study of the di-quark proper vertex. With this approach, we
confirm the dependence of T_C on the coupling g, namely , previously obtained from the one-gluon exchange approximation
in the superconducting phase. The diagrammatic approach we employ allows us to
examine the perturbative expansion of the vertex and the propagators. We find
an additional O(1) contribution to the prefactor of the exponential from the
one-loop quark self energy and that the other one-loop radiative contributions
and the two gluon exchange vertex contribution are subleading.Comment: 13 pages, 3 figures, revtex, details and discussion expande
Conference Web Site Redesign
Sustainable Resources was a non-profit organization based out of Boulder, CO that, at the time of this project hosted yearly conferences to help find solutions to world poverty. Although, the previous web site had a professional appearance, it was not meeting their needs with regards to usability, extensibility, and maintainability, as they had been forced to rely heavily on a transient volunteer IT labor base. The aim of this project was to address their functional and maintenance problems. The application\u27s front-end was built in adherence to the Model -view-Controller (MVC) design pattern and implemented using the Jakarta Struts framework and consisted of, a JSP interface. Hibernate was used as the database persistence layer and the entire data model was completely replaced, as certain data fields were being duplicated in the former system. While giving Sustainable Resources the same functionality they had previously enjoyed, the new application enabled the site\u27s administrators to effectively maintain parts of the application without IT support and supplied them with the necessary documentation to assist future developers with upgrades
Numerical simulation of random paths with a curvature dependent action
We study an ensemble of closed random paths, embedded in R^3, with a
curvature dependent action. Previous analytical results indicate that there is
no crumpling transition for any finite value of the curvature coupling.
Nevertheless, in a high statistics numerical simulation, we observe two
different regimes for the specific heat separated by a rather smooth structure.
The analysis of this fact warns us about the difficulties in the interpretation
of numerical results obtained in cases where theoretical results are absent and
a high statistics simulation is unreachable. This may be the case of random
surfaces.Comment: 9 pages, LaTeX, 4 eps figures. Final version to appear in Mod. Phys.
Lett.
Gross-Witten-Wadia transition in a matrix model of deconfinement
We study the deconfining phase transition at nonzero temperature in a SU(N)
gauge theory, using a matrix model which was analyzed previously at small N. We
show that the model is soluble at infinite N, and exhibits a Gross-Witten-Wadia
transition. In some ways, the deconfining phase transition is of first order:
at a temperature , the Polyakov loop jumps discontinuously from 0 to1/2,
and there is a nonzero latent heat . In other ways, the transition is
of second order: e.g., the specific heat diverges as
when . Other critical exponents satisfy the usual scaling
relations of a second order phase transition. In the presence of a nonzero
background field for the Polyakov loop, there is a phase transition at the
temperature where the value of the loop =1/2, with . Since
as , this
transition is of third order.Comment: 7pages, 1 figure; discussion on matrix models is extended; references
are adde
Axial anomaly, vector meson dominance and at finite temperature
A thermal Finite Energy QCD Sum Rule is used to determine the temperature
behaviour of the strong coupling. This coupling decreases
with increasing and vanishes at the critical temperature, a likely signal
for quark deconfinement. This is then used in the Vector Meson Dominance (VMD)
expression for the amplitude, which is also found to
vanish at the critical temperature, as expected. This result supports the
validity of VMD at . However, if VMD would not hold at finite
temperature, then there is no prediction for the
amplitude.Comment: 8 pages, no figure
Debye screening and Meissner effect in a two-flavor color superconductor
I compute the gluon self-energy in a color superconductor with two flavors of
massless quarks, where condensation of Cooper pairs breaks SU(3)_c to SU(2)_c.
At zero temperature, there is neither Debye screening nor a Meissner effect for
the three gluons of the unbroken SU(2)_c subgroup. The remaining five gluons
attain an electric as well as a magnetic mass. For temperatures approaching the
critical temperature for the onset of color superconductivity, or for gluon
momenta much larger than the color-superconducting gap, the self-energy assumes
the form given by the standard hard-dense loop approximation. The gluon
self-energy determines the coefficient of the kinetic term in the effective
low-energy theory for the condensate fields.Comment: 29 pages, RevTe
Thermodynamics with Dynamical Clover Fermions
We investigate the finite temperature behavior of nonperturbatively improved
clover fermions on lattices with temporal extent N_t=4 and 6. Unfortunately in
the gauge coupling range, where the clover coefficient has been determined
nonperturbatively, the finite temperature crossover/transition occurs at heavy
pseudoscalar masses and large pseudoscalar to vector meson mass ratios.
However, on an N_t=6 lattice the thermal crossover for the improved fermions is
much smoother than for unimproved Wilson fermions and no strange metastable
behavior is observed.Comment: 8 pages, LaTeX, 5 postscript figure
Two-Loop Finiteness of Chern-Simons Field Theory in Background Field Method
We perform two-loop calculation of Chern-Simons in background field method
using the hybrid regularization of higher-covariant derivative and dimensional
regularization. It is explicitly shown that Chern-Simons field theory is finite
at the two-loop level. This finiteness plays an important role in the relation
of Chern-Simons theory with two-dimensional conformal field theory and the
description of link invariant.Comment: RevTex, 13 pages. The proof of the existence of the large topological
mass limit has been proved. Some typewritten mistakes have been correcte
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