2,416 research outputs found
Lessons from Non-Abelian Plasma Instabilities in Two Spatial Dimensions
Plasma instabilities can play a fundamental role in quark-gluon plasma
equilibration in the high energy (weak coupling) limit. Early simulations of
the evolution of plasma instabilities in non-abelian gauge theory, performed in
one spatial dimension, found behavior qualitatively similar to traditional QED
plasmas. Later simulations of the fully three-dimensional theory found
different behavior, unlike traditional QED plasmas. To shed light on the origin
of this difference, we study the intermediate case of two spatial dimensions.
Depending on how the "two-dimensional'' theory is formulated, we can obtain
either behavior.Comment: 15 pages, 10 figure
Dielectric photonic crystal as medium with negative electric permittivity and magnetic permeability
We show that a two-dimensional photonic crystal (PC) made from a non-magnetic
dielectric is a left-handed material in the sense defined by Veselago. Namely,
it has negative values of both the electric permittivity and the
magnetic permeability in some frequency range. This follows from a
recently proven general theorem. The negative values of and
are found by a numerical simulation. Using these values we demonstrate the
Veselago lens, a unique optical device predicted by Veselago. An approximate
analytical theory is proposed to calculate the values of and
from the PC band structure. It gives the results that are close to those
obtained by the numerical simulation. The theory explains how a non-zero
magnetization arises in a non-magnetic PC.Comment: 11 pages 4 figure
The Abelianization of QCD Plasma Instabilities
QCD plasma instabilities appear to play an important role in the
equilibration of quark-gluon plasmas in heavy-ion collisions in the theoretical
limit of weak coupling (i.e. asymptotically high energy). It is important to
understand what non-linear physics eventually stops the exponential growth of
unstable modes. It is already known that the initial growth of plasma
instabilities in QCD closely parallels that in QED. However, once the unstable
modes of the gauge-fields grow large enough for non-Abelian interactions
between them to become important, one might guess that the dynamics of QCD
plasma instabilities and QED plasma instabilities become very different. In
this paper, we give suggestive arguments that non-Abelian self-interactions
between the unstable modes are ineffective at stopping instability growth, and
that the growing non-Abelian gauge fields become approximately Abelian after a
certain stage in their growth. This in turn suggests that understanding the
development of QCD plasma instabilities in the non-linear regime may have close
parallels to similar processes in traditional plasma physics. We conjecture
that the physics of collisionless plasma instabilities in SU(2) and SU(3) gauge
theory becomes equivalent, respectively, to (i) traditional plasma physics,
which is U(1) gauge theory, and (ii) plasma physics of U(1)x U(1) gauge theory.Comment: 36 pages; 15 figures [minor changes made to text, and new figure
added, to reflect published version
Color filamentation in ultrarelativistic heavy-ion collisions
We study color fluctuations in the quark-gluon plasma produced at the early
stage of nucleus-nucleus collision at RHIC or LHC. The fluctuating color
current, which flows along the beam, can be very {\it large} due to the strong
anisotropy of the parton momentum distribution. A specific fluctuation, which
splits the parton system into the current filaments parallel to the beam
direction, is argued to grow exponentially. The physical mechanism responsible
for the phenomenon, which is known as a filamentation instability, is
discussed.Comment: 4 pages, no macro
Correlations in noisy Landau-Zener transitions
We analyze the influence of classical Gaussian noise on Landau-Zener
transitions during a two-level crossing in a time-dependent regular external
field. Transition probabilities and coherence factors become random due to the
noise. We calculate their two-time correlation functions, which describe the
response of this two-level system to a weak external pulse signal. The spectrum
and intensity of the magnetic response are derived. Although fluctuations are
of the same order of magnitude as averages, the results is obtained in an
analytic form.Comment: 12 pages LaTex with 6 EPS figure
Thermal melting of density waves on the square lattice
We present the theory of the effect of thermal fluctuations on commensurate
"p x p" density wave ordering on the square lattice (p >= 3, integer). For the
case in which this order is lost by a second order transition, we argue that
the adjacent state is generically an incommensurate striped state, with
commensurate p-periodic long range order along one direction, and
incommensurate quasi-long-range order along the orthogonal direction. We also
present the routes by which the fully disordered high temperature state can be
reached. For p=4, and at special commensurate densities, the "4 x 4"
commensurate state can melt directly into the disordered state via a self-dual
critical point with non-universal exponents.Comment: 12 pages, 5 figure
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