2,272 research outputs found
Excited D-branes and Supergravity Solutions
We investigate the general solution with the symmetry ISO(1,p)xSO(9-p) of
Type II supergravity (the three-parameter solution) from the viewpoint of the
superstring theory. We find that one of the three parameters (c_1) is closely
related to the ``dilaton charge'' and the appearance of the dilaton charge is a
consequence of deformations of the boundary condition from that of the boundary
state for BPS D-branes. We give three examples of the deformed D-branes by
considering the tachyon condensation from systems of D-\bar{D}p-branes,
unstable D9-branes and unstable D-instantons to the BPS saturated Dp-branes,
respectively. We argue that the deformed systems are generally regarded as
tachyonic and/or massive excitations of the open strings on Dp-\bar{D}p-brane
systems.Comment: 29 pages, 6 figures, LaTeX2e, typos corrected, references adde
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
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
Center Domains and their Phenomenological Consequences
We argue that the domain structure of deconfined QCD matter, which can be
inferred from the properties of the Polyakov loop, can simultaneously explain
the two most prominent experimentally verified features of the quark-gluon
plasma, namely its large opacity as well as its near ideal fluid properties
Possible Resolutions of the D-Paradox
We propose possible ways of explaining the net charge event-by-event
fluctuations in Au+Au collisions at the Relativistic Heavy Ion Collider within
a quark recombination model. We discuss various methods of estimating the
number of quarks at recombination and their implications for the predicted net
charge fluctuations. We also discuss the possibility of diquark and
quark-antiquark clustering above the deconfinement temperature.Comment: 5 pages, 2 figure
Baryon Number Fluctuation and the Quark-Gluon Plasma
We show that or , the squared baryon or
antibaryon number fluctuation per baryon or antibaryon, is a possible signature
for the quark-gluon plasma that is expected to be created in relativistic heavy
ion collisions, as it is a factor of three smaller than in an equilibrated
hadronic matter due to the fractional baryon number of quarks. Using kinetic
equations with exact baryon number conservation, we find that their values in
an equilibrated matter are half of those expected from a Poisson distribution.
Effects due to finite acceptance and non-zero net baryon number are also
studied.Comment: discussion and references added, version to appear in PR
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
The three-flavor chiral phase structure in hot and dense QCD matter
Chiral symmetry restoration at nonzero temperature and quark densities are
investigated in the framework of a linear sigma model with N_f=3 light quark
flavors. After the derivation of the grand potential in mean-field
approximation, the nonstrange and strange condensates, the in-medium masses of
the scalar and pseudoscalar nonets are analyzed in hot and dense medium. The
influence of the axial anomaly on the nonet masses and the isoscalar mixings on
the pseudoscalar \eta-\eta' and scalar \sigma(600)-f_0(1370) complex are
examined. The sensitivity of the chiral phase transition as well as the
existence and location of a critical end point in the phase diagram on the
value of the sigma mass is explored. The chiral critical surface with and
without the influence of the axial U(1)_A anomaly is elaborated as a function
of the pion and kaon masses for several values of the sigma mass.Comment: 19 pages, 12 figures, 2 tables, RevTex4; revised version, accepted
for publication in PR
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