702 research outputs found
Quantum Chaos in Compact Lattice QED
Complete eigenvalue spectra of the staggered Dirac operator in quenched
compact QED are studied on and lattices. We
investigate the behavior of the nearest-neighbor spacing distribution as
a measure of the fluctuation properties of the eigenvalues in the strong
coupling and the Coulomb phase. In both phases we find agreement with the
Wigner surmise of the unitary ensemble of random-matrix theory indicating
quantum chaos. Combining this with previous results on QCD, we conjecture that
quite generally the non-linear couplings of quantum field theories lead to a
chaotic behavior of the eigenvalues of the Dirac operator.Comment: 11 pages, 4 figure
Non-Hermitian Random Matrix Theory and Lattice QCD with Chemical Potential
In quantum chromodynamics (QCD) at nonzero chemical potential, the
eigenvalues of the Dirac operator are scattered in the complex plane. Can the
fluctuation properties of the Dirac spectrum be described by universal
predictions of non-Hermitian random matrix theory? We introduce an unfolding
procedure for complex eigenvalues and apply it to data from lattice QCD at
finite chemical potential to construct the nearest-neighbor spacing
distribution of adjacent eigenvalues in the complex plane. For intermediate
values of , we find agreement with predictions of the Ginibre ensemble of
random matrix theory, both in the confinement and in the deconfinement phase.Comment: 4 pages, 3 figures, to appear in Phys. Rev. Let
The QCD Phase Diagram at Non-zero Baryon and Isospin Chemical Potentials
In heavy ion collision experiments as well as in neutron stars, both baryon
and isospin chemical potentials are different from zero. In particular, the
regime of small isospin chemical potential is phenomenologically important.
Using a random matrix model, we find that the phase diagram at non-zero
temperature and baryon chemical potential is greatly altered by an arbitrarily
small isospin chemical potential: There are two first order phase transitions
at low temperature, two critical endpoints, and two crossovers at high
temperature. As a consequence, in the region of the phase diagram explored by
RHIC experiments, there are two crossovers that separate the hadronic phase
from the quark-gluon plasma phase at high temperature.Comment: 3 pages, 2 figures. Talk presented at Lattice2004(non-zero),
Fermilab, June 21 - 26, 200
The Fractal Geometry of Critical Systems
We investigate the geometry of a critical system undergoing a second order
thermal phase transition. Using a local description for the dynamics
characterizing the system at the critical point T=Tc, we reveal the formation
of clusters with fractal geometry, where the term cluster is used to describe
regions with a nonvanishing value of the order parameter. We show that,
treating the cluster as an open subsystem of the entire system, new
instanton-like configurations dominate the statistical mechanics of the
cluster. We study the dependence of the resulting fractal dimension on the
embedding dimension and the scaling properties (isothermal critical exponent)
of the system. Taking into account the finite size effects we are able to
calculate the size of the critical cluster in terms of the total size of the
system, the critical temperature and the effective coupling of the long
wavelength interaction at the critical point. We also show that the size of the
cluster has to be identified with the correlation length at criticality.
Finally, within the framework of the mean field approximation, we extend our
local considerations to obtain a global description of the system.Comment: 1 LaTeX file, 4 figures in ps-files. Accepted for publication in
Physical Review
The QCD Phase Diagram at Nonzero Temperature, Baryon and Isospin Chemical Potentials in Random Matrix Theory
We introduce a random matrix model with the symmetries of QCD at finite
temperature and chemical potentials for baryon number and isospin. We analyze
the phase diagram of this model in the chemical potential plane for different
temperatures and quark masses. We find a rich phase structure with five
different phases separated by both first and second order lines. The phases are
characterized by the pion condensate and the chiral condensate for each of the
flavors. In agreement with lattice simulations, we find that in the phase with
zero pion condensate the critical temperature depends in the same way on the
baryon number chemical potential and on the isospin chemical potential. At
nonzero quark mass, we remarkably find that the critical end point at nonzero
temperature and baryon chemical potential is split in two by an arbitrarily
small isospin chemical potential. As a consequence, there are two crossovers
that separate the hadronic phase from the quark-gluon plasma phase at high
temperature. Detailed analytical results are obtained at zero temperature and
in the chiral limit.Comment: 13 pages, 5 figures, REVTeX
Chiral thermodynamics of dense hadronic matter
We discuss phases of hot and dense hadronic matter using chiral Lagrangians.
A two-flavored parity doublet model constrained by the nuclear matter ground
state predicts chiral symmetry restoration. The model thermodynamics is shown
within the mean field approximation. A field-theoretical constraint on possible
phases from the anomaly matching is also discussed.Comment: 8 pages, 2 figures, to appear in the proceedings of 6th International
Workshop on Critical Point and Onset of Deconfinement (CPOD), 23-29 August
2010 at Joint Institute for Nuclear Research, Dubna, Russi
Chiral Symmetry Restoration and Realisation of the Goldstone Mechanism in the U(1) Gross-Neveu Model at Non-Zero Chemical Potential
We simulate the Gross-Neveu model in 2+1 dimensions at nonzero baryon density
(chemical potential mu =/= 0). It is possible to formulate this model with a
real action and therefore to perform standard hybrid Monte Carlo simulations
with mu =/= 0 in the functional measure. We compare the physical observables
from these simulations with simulations using the Glasgow method where the
value of mu in the functional measure is fixed at a value mu_upd. We find that
the observables are sensitive to the choice of mu_upd. We consider the
implications of our findings for Glasgow method QCD simulations at mu =/= 0. We
demonstrate that the realisation of the Goldstone mechanism in the Gross-Neveu
model is fundamentally different from that in QCD. We find that this difference
explains why there is an unphysical transition in QCD simulations at mu =/= 0
associated with the pion mass scale whereas the transition in the Gross-Neveu
model occurs at a larger mass scale and is therefore consistent with
theoretical predictions. We note classes of theories which are exceptions to
the Vafa-Witten theorem which permit the possibility of formation of baryon
number violating diquark condensates.Comment: 28 pages RevTe
Future aspects of renal transplantation
New and exciting advances in renal transplantation are continuously being made, and the horizons for organ transplantation are bright and open. This article reviews only a few of the newer advances that will allow renal transplantation to become even more widespread and successful. The important and exciting implications for extrarenal organ transplantation are immediately evident. © 1988 Springer-Verlag
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