329 research outputs found
Hagedorn transition, vortices and D0 branes: Lessons from 2+1 confining strings
We study the behaviour of Polyakov confining string in the Georgi-Glashow
model in three dimensions near confining-deconfining phase transition described
in hep-th/0010201. In the string language, the transition mechanism is the
decay of the confining string into D0 branes (charged W bosons of the
Georgi-Glashow model). In the world-sheet picture the world-lines of heavy D0
branes at finite temperature are represented as world-sheet vortices of a
certain type, and the transition corresponds to the condensation of these
vortices. We also show that the ``would be'' Hagedorn transition in the
confining string (which is not realized in our model) corresponds to the
monopole binding transition in the field theoretical language. The fact that
the decay into D0 branes occurs at lower than the Hagedorn temperature is
understood as the consequence of the large thickness of the confining string
and finite mass of the branes.Comment: 31 pages, Late
Deconfining Phase Transition in 2+1 D: the Georgi-Glashow Model
We analyze the finite temperature deconfining phase transition in 2+1
dimensional Georgi-Glashow model. We show explicitly that the transition is due
to the restoration of the magnetic symmetry and that it is in the Ising
universality class. We find that neglecting effects of the charged bosons
leads to incorrect predictions for the value of the critical temperature and
the universality class of the transition, as well as for various correlation
functions in the high temperature phase. We derive the effective action for the
Polyakov loop in the high temperature phase and calculate the correlation
functions of magnetic vortex operators.Comment: 26 pages, 1 figure, discussion about spatial Wilson loops added, to
appear in JHE
The two phases of topologically massive compact U(1) theory
The mean field like gauge invariant variational method formulated recently, is applied to a topologically massive QED in 3 dimensions. We find that the theory has a phase transition in the Chern Simons coefficient n. The phase transition is of the Berezinsky-Kosterlitz - Thouless type, and is triggered by the liberation of Polyakov monopoles, which for n>8 are tightly bound into pairs. In our Hamiltonian approach this is seen as a similar behaviour of the magnetic vortices, which are present in the ground state wave functional of the compact theory. For n>8, the low energy behavior of the theory is the same as in the noncompact case. For n<8 there are no propagating degrees of freedom on distance scales larger than the ultraviolet cutoff. The distinguishing property of the n<8 phase, is that the magnetic flux symmetry is spontaneoously broken
Magnetic Z(N) symmetry in 2+1 dimensions
This review describes the role of magnetic symmetry in 2+1 dimensional gauge
theories. In confining theories without matter fields in fundamental
representation the magnetic symmetry is spontaneously broken. Under some mild
assumptions, the low-energy dynamics is determined universally by this
spontaneous breaking phenomenon. The degrees of freedom in the effective theory
are magnetic vortices. Their role in confining dynamics is similar to that
played by pions and sigma in the chiral symmetry breaking dynamics.
I give an explicit derivation of the effective theory in (2+1)-dimensional
weakly coupled confining models and argue that it remains qualitatively the
same in strongly coupled (2+1)-dimensional gluodynamics. Confinement in this
effective theory is a very simple classical statement about the long range
interaction between topological solitons, which follows (as a result of a
simple direct classical calculation) from the structure of the effective
Lagrangian. I show that if fundamentally charged dynamical fields are present
the magnetic symmetry becomes local rather than global. The modifications to
the effective low energy description in the case of heavy dynamical fundamental
matter are discussed. This effective lagrangian naturally yields a bag like
description of baryonic excitations. I also discuss the fate of the magnetic
symmetry in gauge theories with the Chern-Simons term
Dense-Dilute Duality at work: dipoles of the target
We explore the properties of the QCD high energy evolution in the limit of a
dilute target. Using the recently established property of selfduality of the
evolution operator (hep-ph/0502119), we show how to properly define the target
gluon and dipole creation operators in terms of dual Wilson lines (dual eikonal
factors). We explain how to expand these operators in terms of the functional
derivatives of the color charge density, in the situation when they act on the
eikonal factors of the projectile partons. We explicitly calculate the
expansion of the high energy evolution operator to fourth order in the
functional derivatives. Our result is infrared and ultraviolet finite, but does
not coincide with the formula given in hep-ph/0501088. We resolve this
discrepancy by showing that the identification of the dipole creation and
annihilation operators used in hep-ph/0501088 is incomplete, and provide the
required corrections to these definitions. The use of the corrected operators
in the calculational framework of hep-ph/0501088 reproduces our result. We also
prove that there is no discrepancy between the expansion of the JIMWLK equation
and the dualization of the expansion of the weak field limit.Comment: 18 pages, Explanations added. Version to appear in PR
Monopoles, Vortices and Strings: Confinement and Deconfinement in 2+1 Dimensions at Weak Coupling
We consider, from several complementary perspectives, the physics of
confinement and deconfinement in the 2+1 dimensional Georgi-Glashow model.
Polyakov's monopole plasma and 't Hooft's vortex condensation are discussed
first. We then discuss the physics of confining strings at zero temperature. We
review the Hamiltonian variational approach and show how the linear confining
potential arises in this framework. The second part of this review is devoted
to study of the deconfining phase transition. We show that the mechanism of the
transition is the restoration of 't Hooft's magnetic symmetry in the deconfined
phase. The heavy charged bosons play a crucial role in the dynamics of the
transition, and we discuss the interplay between the charged plasma and the
binding of monopoles at high temperature. Finally we discuss the phase
transition from the point of view of confining strings. We show that from this
point of view the transition is not driven by the Hagedorn mechanism
(proliferation of arbitrarily long strings), but rather by the "disintegration"
of the string due to the proliferation of 0 branes.Comment: 72 pages, 6 figures, to be published in Handbook of QCD, Volume
From Color Fields to Quark Gluon Plasma
We discuss a model for the energy distribution and the early space-time
evolution of a heavy ion collision. We estimate the gluon field generated in
the wake of hard processes and through primordial fluctuations of the color
charges in the nuclei. Without specifying the dynamical mechanism of
thermalization we calculate the energy momentum tensor of the following plasma
phase. The results of this model can be used as initial conditions for a
further hydrodynamic evolution.Comment: Contribution to Quark Matter 2005; 4 pages, 4 figure
Treading on the cut: Semi inclusive observables at high energy
We develop the formalizm for calculating semi inclusive observables at high
energy in the JIMWLK/KLWMIJ approach. We consider several examples including
diffractive processes, elastic and inclusive over the target degrees of
freedom, scattering with fixed total transverse momentum transfer and inclusive
gluon production. We discuss evolution of these observables with respect to
various rapidity variables involved in their definitions (total rapidity,
rapidity gap, width of diffractive interval etc.). We also discuss the dipole
model limit of these observables and derive closed simple (as opposed to
functional) differential equations in this approximation. We point out that
there are some interesting differences between the full JIMWLK/KLWMIJ evolution
and the dipole model evolution of diffractive cross section. In particular we
show that in the dipole approximation the target does not diffract beyond the
valence rapidity interval, consistently with the intuition suggested by the
Pomeron fan diagramms. On the other hand such diffractive processes do exist in
the full JIMWLK/KLWMIJ approach, albeit suppressed by the factor 1/N_c^2.Comment: 37 pages, 3 figures. A few remarks added. To appear in PR
Relativistic Winds from Compact Gamma-Ray Sources: II. Pair Loading and Radiative Acceleration in Gamma-ray Bursts
We consider the effects of rapid pair creation by an intense pulse of
gamma-rays propagating ahead of a relativistic shock. Side-scattered photons
colliding with the main gamma-ray beam amplify the density of scattering
charges. The acceleration rate of the pair-loaded medium is calculated, and its
limiting bulk Lorentz factor related to the spectrum and compactness of the
photon source. One obtains, as a result, a definite prediction for the relative
inertia in baryons and pairs. The deceleration of a relativistic shock in the
moving medium, and the resulting synchrotron emissivity, are compared with
existing calculations for a static medium. The radiative efficiency is
increased dramatically by pair loading. When the initial ambient density
exceeds a critical value, the scattering depth traversed by the main gamma-ray
pulse rises above unity, and the pulse is broadened. These considerations place
significant constraints on burst progenitors: a pre-burst mass loss rate
exceeding 10^{-5} M_\odot per year is difficult to reconcile with individual
pulses narrower than 10 s, unless the radiative efficiency is low. An
anisotropic gamma-ray flux (on an angular scale \Gamma^{-1} or larger) drives a
large velocity shear that greatly increases the energy in the seed magnetic
field forward of the propagating shock.Comment: 19 pp., LaTeX (aaspp4.sty), revised 12/23/99, Ap. J. in press;
summary section added and several minor improvements in presentatio
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