58 research outputs found
Hard Thermal Loops, Static Response and the Composite Effective Action
First, we investigate the static non-Abelian Kubo equation. We prove that it
does not possess finite energy solutions; thereby we establish that gauge
theories do not support hard thermal solitons. A similar argument shows that
"static" instantons are absent. In addition, we note that the static equations
reproduce the expected screening of the non-Abelian electric field by a gauge
invariant Debye mass m=gT sqrt((N+N_F/2)/3). Second, we derive the non-Abelian
Kubo equation from the composite effective action. This is achieved by showing
that the requirement of stationarity of the composite effective action is
equivalent, within a kinematical approximation scheme, to the condition of
gauge invariance for the generating functional of hard thermal loops.Comment: 17 pages, MIT preprint CTP#2261. An Appendix [including one
(appended) PS figure] presenting a numerical analysis of the static solutions
has been included. A note relating our approach to alternative ones has been
added. We have also added references and comments in Section II
A Simple Derivation of the Hard Thermal Loop Effective Action
We use the background field method along with a special gauge condition, to
derive the hard thermal loop effective action in a simple manner. The new point
in the paper is to relate the effective action explicitly to the S-matrix from
the onset.Comment: 11 pages, Latex; lost text after sect. 2 reinserte
Bosonic Description of Spinning Strings in Dimensions
We write down a general action principle for spinning strings in 2+1
dimensional space-time without introducing Grassmann variables. The action is
written solely in terms of coordinates taking values in the 2+1 Poincare group,
and it has the usual string symmetries, i.e. it is invariant under a)
diffeomorphisms of the world sheet and b) Poincare transformations. The system
can be generalized to an arbitrary number of space-time dimensions, and also to
spinning membranes and p-branes.Comment: Latex, 12 page
Classical Open String Models in 4-Dim Minkowski Spacetime
Classical bosonic open string models in fourdimensional Minkowski spacetime
are discussed. A special attention is paid to the choice of edge conditions,
which can follow consistently from the action principle. We consider
lagrangians that can depend on second order derivatives of worldsheet
coordinates. A revised interpretation of the variational problem for such
theories is given. We derive a general form of a boundary term that can be
added to the open string action to control edge conditions and modify
conservation laws. An extended boundary problem for minimal surfaces is
examined. Following the treatment of this model in the geometric approach, we
obtain that classical open string states correspond to solutions of a complex
Liouville equation. In contrast to the Nambu-Goto case, the Liouville potential
is finite and constant at worldsheet boundaries. The phase part of the
potential defines topological sectors of solutions.Comment: 25 pages, LaTeX, preprint TPJU-28-93 (the previous version was
truncated by ftp...
Classical Lattice Gauge Fields with Hard Thermal Loops
We propose a formulation of the long-distance dynamics of gauge theories at
finite temperature on a lattice in Minkowski space, including the effects of
hard thermal loops on the dynamics of the long wavelength modes. Our approach
is based on the dual classical limits of quantum fields as waves and particles
in the infrared and ultraviolet limits, respectively. It exhibits manifest
invariance under space-dependent lattice gauge transformations and conserves
Gauss' law.Comment: 11 pages, plain latex file, with major revisions to include details
on the algorith
Transport Theory of Massless Fields
Using the Schwinger-Keldysh technique we discuss how to derive the transport
equations for the system of massless quantum fields. We analyse the scalar
field models with quartic and cubic interaction terms. In the model
the massive quasiparticles appear due to the self-interaction of massless bare
fields. Therefore, the derivation of the transport equations strongly resembles
that one of the massive fields, but the subset of diagrams which provide the
quasiparticle mass has to be resummed. The kinetic equation for the finite
width quasiparticles is found, where, except the mean-field and collision
terms, there are terms which are absent in the standard Boltzmann equation. The
structure of these terms is discussed. In the massless model the
massive quasiparticles do not emerge and presumably there is no transport
theory corresponding to this model. It is not surprising since the
model is anyhow ill defined.Comment: 32 pages, no macro
Chern-Simons Theory and the Quark-Gluon Plasma
The generating functional for hard thermal loops in QCD is important in
setting up a resummed perturbation theory, so that all terms of a given order
in the coupling constant can be consistently taken into account. It is also the
functional which leads to a gauge invariant description of Debye screening and
plasma waves in the quark-gluon plasma. We have recently shown that this
functional is closely related to the eikonal for a Chern-Simons gauge theory.
In this paper, this relationship is explored and explained in more detail,
along with some generalizations.Comment: 28 pages (4 Feynman diagrams not included, available upon request
Effective QED Actions: Representations, Gauge Invariance, Anomalies and Mass Expansions
We analyze and give explicit representations for the effective abelian vector
gauge field actions generated by charged fermions with particular attention to
the thermal regime in odd dimensions, where spectral asymmetry can be present.
We show, through function regularization, that both small and large
gauge invariances are preserved at any temperature and for any number of
fermions at the usual price of anomalies: helicity/parity invariance will be
lost in even/odd dimensions, and in the latter even at zero mass. Gauge
invariance dictates a very general ``Fourier'' representation of the action in
terms of the holonomies that carry the novel, large gauge invariant,
information. We show that large (unlike small) transformations and hence their
Ward identities, are not perturbative order-preserving, and clarify the role of
(properly redefined) Chern-Simons terms in this context. From a powerful
representation of the action in terms of massless heat kernels, we are able to
obtain rigorous gauge invariant expansions, for both small and large fermion
masses, of its separate parity even and odd parts in arbitrary dimension. The
representation also displays both the nonperturbative origin of a finite
renormalization ambiguity, and its physical resolution by requiring decoupling
at infinite mass. Finally, we illustrate these general results by explicit
computation of the effective action for some physical examples of field
configurations in the three dimensional case, where our conclusions on finite
temperature effects may have physical relevance. Nonabelian results will be
presented separately.Comment: 36 pages, RevTeX, no figure
Lyapunov Exponent and Plasmon Damping Rate in Nonabelian Gauge Theories
We explain why the maximal positive Lyapunov exponent of classical SU()
gauge theory coincides with (twice) the damping rate of a plasmon at rest in
the leading order of thermal gauge theory. [This is a substantially revised and
expanded version of the manuscript.]Comment: 18 pages, one figure included as PostScript file, REVTeX, revised
version, DUKE-TH-94-7
The problem of nonlinear Landau damping in quark-gluon plasma
On the basis of the semiclassical equations for quark-gluon plasma (QGP) and
Yang-Mills equation, the generalized kinetic equation for waves with regard to
its interaction is obtained. The physical mechanisms defining nonlinear
scattering of a plasmon by QGP particles are analysed. The problem on a
connection of nonlinear Landau damping rate of longitudinal oscillation with
damping rate, obtained on the basis of hard thermal loops approximation, is
considered.Comment: 33 page
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