2,361 research outputs found
Non-Central Heavy-Ion Collisions are the Place to Look for DCC
We give two reasons why we believe that non-central ultrarelativistic heavy
ion collisions are the place to look for the disoriented chiral condensates
(DCC). First, we argue that the most probable quench scenario for the formation
of DCC requires non-central collisions. Second, we show by numerical
simulations that strong electromagnetic fields of heavy ions can exert a
surprisingly large effect on the DCC domain formation through the chiral
anomaly. The effect again requires non-central collisions. Interestingly, the
result of simulations is consistent with the formation of correlated two
domains of the chiral condensate, which are aligned in space, perpendicular to
the scattering plane, but misaligned in isospin space.Comment: 4 pages (Latex), 3 embedded ps figures, espcrc1 style, talk given at
Quark Matter 97, December 97, Tsukuba, Japa
Secondary phi meson peak as an indicator of QCD phase transition in ultrarelativistic heavy ion collisions
In a previous paper, we have shown that a double phi peak structure appears
in the dilepton invariant mass spectrum if a first order QCD phase transition
occurs in ultrarelativistic heavy ion collisions. Furthermore, the transition
temperature can be determined from the transverse momentum distribution of the
low mass phi peak. In this work, we extend the study to the case that a smooth
crossover occurs in the quark-gluon plasma to the hadronic matter transition.
We find that the double phi peak structure still exists in the dilepton
spectrum and thus remains a viable signal for the formation of the quark-gluon
plasma in ultrarelativistic heavy ion collisions.Comment: 8 pages, 9 uuencoded postscript figures included, Latex, LBL-3572
Wilson-like real-space renormalization group and low-energy effective spectrum of the XXZ chain in the critical regime
We present a novel real-space renormalization group(RG) for the
one-dimensional XXZ model in the critical regime, reconsidering the role of the
cut-off parameter in Wilson's RG for the Kondo impurity problem. We then
demonstrate the RG calculation for the XXZ chain with the free boundary.
Comparing the hierarchical structure of the obtained low-energy spectrum with
the Bethe ansatz result, we find that the proper scaling dimension is
reproduced as a fixed point of the RG transformation.Comment: 4 pages, 6 figures, typos corrected, final versio
Boundary susceptibility in the spin-1/2 chain: Curie like behavior without magnetic impurities
We investigate the low-temperature thermodynamics of the spin-1/2 Heisenberg
chain with open ends. On the basis of boundary conformal field theory arguments
and numerical density matrix renormalization group calculations, it is
established that in the isotropic case the impurity susceptibility exhibits a
Curie-like divergent behavior as the temperature decreases, even in the absence
of magnetic impurities. A similar singular temperature dependence is also found
in the boundary contributions of the specific heat coefficient. In the
anisotropic case, for , these boundary quantities still show
singular temperature dependence obeying a power law with an anomalous
dimension. Experimental consequences will be discussed.Comment: 5 pages, 1 figure, final versio
Heavy Quark Interactions in Finite Temperature QCD
We study the free energy of a heavy quark-antiquark pair in a thermal medium.
We constuct a simple ansatz for the free energy for two quark flavors motivated
by the Debye-H\"uckel theory of screening.Comment: 4 pages, 4 figures, contribution to the proceedings of the
International Conference on Hard and Electromagnetic Probes of High Energy
Nuclear Collisions, Ericeira, Portugal, Nov. 4-10, 200
Open String Tachyon in Supergravity Solution
We study the tachyon condensation of the D-\bar{D}-brane system with a
constant tachyon vev in the context of classical solutions of the Type II
supergravity. We find that the general solution with the symmetry
ISO(1,p)xSO(9-p) (the three-parameter solution) includes the extremal black
p-brane solution as an appropriate limit of the solution with fixing one of the
three parameters (c_1). Furthermore, we compare the long distance behavior of
the solution with the massless modes of the closed strings from the boundary
state of the D-\bar{D}-brane system with a constant tachyon vev. We find that
we must fix c_1 to zero and the only two parameters are needed to express the
tachyon condensation of the D\={D}-brane system. This means that the parameter
does not correspond to the tachyon vev of the D\={D}-brane system.Comment: 20 pages, no figures, LaTeX2e, typos corrected, references added and
more general result presente
Interaction effects between impurities in low dimensional spin-1/2 antiferromagnets
We are considering the interplay between several non-magnetic impurities in
the spin-1/2 Heisenberg antiferromagnet in chains, ladders and planes by
introducing static vacancies in numerical quantum Monte Carlo simulations. The
effective potential between two and more impurities is accurately determined,
which gives a direct measure of the quantum correlations in the systems. Large
effective interaction potentials are an indication of strong quantum
correlations in the system and reflect the detailed nature of the valence bond
ground states. In two-dimensions (2D) the interactions are smaller, but can
still be analyzed in terms of valence bonds.Comment: 8 pages, 6 figures, accepted by Europhys. Lett. The latest pdf file
is available at http://www.physik.uni-kl.de/eggert/papers/interact2d.pd
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