743 research outputs found
Bogomol'nyi equations for solitons in Maxwell-Chern-Simons gauge theories with the magnetic moment interaction term
Without assuming rotational invariance, we derive Bogomol'nyi equations for
the solitons in the abelian Chern-Simons gauge theories with the anomalous
magnetic moment interaction. We also evaluate the number of zero modes around a
static soliton configuration.Comment: 9 pages, Revtex, SNUTP-94/6
Transport Properties of the Quark-Gluon Plasma -- A Lattice QCD Perspective
Transport properties of a thermal medium determine how its conserved charge
densities (for instance the electric charge, energy or momentum) evolve as a
function of time and eventually relax back to their equilibrium values. Here
the transport properties of the quark-gluon plasma are reviewed from a
theoretical perspective. The latter play a key role in the description of
heavy-ion collisions, and are an important ingredient in constraining particle
production processes in the early universe. We place particular emphasis on
lattice QCD calculations of conserved current correlators. These Euclidean
correlators are related by an integral transform to spectral functions, whose
small-frequency form determines the transport properties via Kubo formulae. The
universal hydrodynamic predictions for the small-frequency pole structure of
spectral functions are summarized. The viability of a quasiparticle description
implies the presence of additional characteristic features in the spectral
functions. These features are in stark contrast with the functional form that
is found in strongly coupled plasmas via the gauge/gravity duality. A central
goal is therefore to determine which of these dynamical regimes the quark-gluon
plasma is qualitatively closer to as a function of temperature. We review the
analysis of lattice correlators in relation to transport properties, and
tentatively estimate what computational effort is required to make decisive
progress in this field.Comment: 54 pages, 37 figures, review written for EPJA and APPN; one parag.
added end of section 3.4, and one at the end of section 3.2.2; some Refs.
added, and some other minor change
Gravitating Chern-Simons vortices
The construction of self-dual vortex solutions to the Chern-Simons-Higgs
model (with a suitable eighth-order potential) coupled to Einstein gravity in
(2 + 1) dimensions is reconsidered. We show that the self-duality condition may
be derived from the sole assumption . Next, we derive a family of
exact, doubly self-dual vortex solutions, which interpolate between the
symmetrical and asymmetrical vacua. The corresponding spacetimes have two
regions at spatial infinity. The eighth-order Higgs potential is positive
definite, and closed timelike curves are absent, if the gravitational constant
is chosen to be negative.Comment: 11 pages, LaTe
Confront Holographic QCD with Regge Trajectories of vectors and axial-vectors
We derive the general 5-dimension metric structure of the system in
type II superstring theory, and demonstrate the physical meaning of the
parameters characterizing the 5-dimension metric structure of the
\textit{holographic} QCD model by relating them to the parameters describing
Regge trajectories. By matching the spectra of vector mesons with
deformed soft-wall model, we find that the spectra of vector mesons
can be described very well in the soft-wall model, i.e,
soft-wall model. We then investigate how well the soft-wall
model can describe the Regge trajectory of axial-vector mesons . We find
that the constant component of the 5-dimension mass square of axial-vector
mesons plays an efficient role to realize the chiral symmetry breaking in the
vacuum, and a small negative correction in the 5-dimension mass square is
helpful to realize the chiral symmetry restoration in high excitation states.Comment: 9 pages, 3 figure and 3 tables, one section adde
The Pomeron and Gauge/String Duality
The traditional description of high-energy small-angle scattering in QCD has
two components -- a soft Pomeron Regge pole for the tensor glueball, and a hard
BFKL Pomeron in leading order at weak coupling. On the basis of gauge/string
duality, we present a coherent treatment of the Pomeron. In large-N QCD-like
theories, we use curved-space string-theory to describe simultaneously both the
BFKL regime and the classic Regge regime. The problem reduces to finding the
spectrum of a single j-plane Schrodinger operator. For ultraviolet-conformal
theories, the spectrum exhibits a set of Regge trajectories at positive t, and
a leading j-plane cut for negative t, the cross-over point being
model-dependent. For theories with logarithmically-running couplings, one
instead finds a discrete spectrum of poles at all t, where the Regge
trajectories at positive t continuously become a set of slowly-varying and
closely-spaced poles at negative t. Our results agree with expectations for the
BFKL Pomeron at negative t, and with the expected glueball spectrum at positive
t, but provide a framework in which they are unified. Effects beyond the single
Pomeron exchange are briefly discussed.Comment: 68 pages, uses JHEP3.cls, utphys.bst; references added, typos
corrected, and clarifying remarks adde
Abnormal number of Nambu-Goldstone bosons in the color-asymmetric 2SC phase of an NJL-type model
We consider an extended Nambu--Jona-Lasinio model including both (q \bar q)-
and (qq)-interactions with two light-quark flavors in the presence of a single
(quark density) chemical potential. In the color superconducting phase of the
quark matter the color SU(3) symmetry is spontaneously broken down to SU(2). If
the usual counting of Goldstone bosons would apply, five Nambu-Goldstone (NG)
bosons corresponding to the five broken color generators should appear in the
mass spectrum. Unlike that expectation, we find only three gapless diquark
excitations of quark matter. One of them is an SU(2)-singlet, the remaining two
form an SU(2)-(anti)doublet and have a quadratic dispersion law in the small
momentum limit. These results are in agreement with the Nielsen-Chadha theorem,
according to which NG-bosons in Lorentz-noninvariant systems, having a
quadratic dispersion law, must be counted differently. The origin of the
abnormal number of NG-bosons is shown to be related to a nonvanishing
expectation value of the color charge operator Q_8 reflecting the lack of color
neutrality of the ground state. Finally, by requiring color neutrality, two
massive diquarks are argued to become massless, resulting in a normal number of
five NG-bosons with usual linear dispersion laws.Comment: 13 pages, 4 figures, revtex
Non-Abelian Vortices in Supersymmetric Gauge Field Theory via Direct Methods
Vortices in supersymmetric gauge field theory are important constructs in a
basic conceptual phenomenon commonly referred to as the dual Meissner effect
which is responsible for color confinement. Based on a direct minimization
approach, we present a series of sharp existence and uniqueness theorems for
the solutions of some non-Abelian vortex equations governing color-charged
multiply distributed flux tubes, which provide an essential mechanism for
linear confinement. Over a doubly periodic domain, existence results are
obtained under explicitly stated necessary and sufficient conditions that
relate the size of the domain, the vortex numbers, and the underlying physical
coupling parameters of the models. Over the full plane, existence results are
valid for arbitrary vortex numbers and coupling parameters. In all cases,
solutions are unique.Comment: 38 pages, late
Proof of the Julia-Zee Theorem
It is a well accepted principle that finite-energy static solutions in the
classical relativistic gauge field theory over the -dimensional
Minkowski spacetime must be electrically neutral. We call such a statement the
Julia--Zee theorem. In this paper, we present a mathematical proof of this
fundamental structural property
First and Second Order Vortex Dynamics
The low energy dynamics of vortices in selfdual Abelian Higgs theory is of
second order in vortex velocity and characterized by the moduli space metric.
When Chern-Simons term with small coefficient is added to the theory, we show
that a term linear in vortex velocity appears and can be consistently added to
the second order expression. We provides an additional check of the first and
second order terms by studying the angular momentum in the field theory. We
briefly explore other first order term due to small background electric charge
density and also the harmonic potential well for vortices given by the moment
of inertia.Comment: a rev tex file, 22 pages, no figur
Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits
The WWgamma triple gauge boson coupling parameters are studied using p-pbar
-> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were
collected with the DO detector from an integrated luminosity of 162 pb^{-1}
delivered by the Fermilab Tevatron Collider. The cross section times branching
fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV
and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum)
pb. The one-dimensional 95% confidence level limits on anomalous couplings are
-0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication
- …