420 research outputs found
Massless Scalar QED with Non-minimal Chern Simons Coupling
2+1 dimensional massless scalar QED with scalar
self-coupling is modified by the addition of a non- minimal Chern-Simons term
that couples the dual of the electromagnetic field strength to the covariant
current of the complex scalar field. The theory is shown to be fully one- loop
renormalizable. The one loop effective potential for the scalar field gives
rise to spontaneous symmetry breaking which induces masses for both the scalar
and vector fields. At high temperature there is a symmetry restoring phase
transition.Comment: 18 pages, latex, preprint WIN-93-1
Dynamical mass generation of a two-component fermion in Maxwell-Chern-Simons QED_3: The lowest ladder approximation
Dynamical mass generation of a two-component fermion in with a
Chern-Simons term is investigated by solving the Schwinger-Dyson equation
formulated in the lowest ladder approximation. Dependence of the dynamical
fermion mass on a gauge-fixing parameter, a gauge coupling constant, and a
topological mass is examined by approximated analytical and also numerical
methods. The inclusion of the Chern-Simons term makes impossible to choose a
peculiar gauge in which a wave function renormalization is absent. The
numerical evaluation shows that the wave function renormalization is fairly
close to 1 in the Landau gauge. It means that this gauge is still a specific
gauge where the Ward-Takahashi identity is satisfied approximately. We also
find that the dynamical mass is almost constant if the topological mass is
larger than the coupling constant, while it decreases when the topological mass
is comparable to or smaller than the coupling constant and tends to the value
in without the Chern-Simons term.Comment: 22 pages, 9 figures, Version to appear in Phys. Rev.
Anyon in External Electromagnetic Field: Hamiltonian and Lagrangian Formulations
We propose a simple model for a free relativistic particle of fractional spin
in 2+1 dimensions which satisfies all the necessary conditions. The canonical
quantization of the system leads to the description of one- particle states of
the Poincare group with arbitrary spin. Using the Hamil- tonian formulation
with the set of constraints, we introduce the electro- magnetic interaction of
a charged anyon and obtain the Lagrangian. The Casimir operator of the extended
algebra, which is the first-class constraint, is obtained and gives the
equation of motion of the anyon. In particular, from the latter it follows that
the gyromagnetic ratio for a charged anyon is two due to the parallelness of
spin and momentum of the particle in 2+1 dimensions. The canonical quantization
is also considered in this case.Comment: 9 pages, Latex, HU-SEFT R 1993-1
Quantum fluctuations of the Chern-Simons theory and dynamical dimensional reduction
We consider a large-N Chern-Simons theory for the attractive bosonic matter
(Jackiw-Pi model) in the Hamiltonian collective-field approach based on the 1/N
expansion. We show that the dynamics of low-lying density excitations around
the ground-state vortex configuration is equivalent to that of the Sutherland
model. The relationship between the Chern-Simons coupling constant lambda and
the Calogero-Sutherland statistical parameter lambda_s signalizes some sort of
statistical transmutation accompanying the dimensional reduction of the initial
problem.Comment: 10 pages, 2 figure
Reconstruction of field theory from excitation spectra of defects
We show how to reconstruct a field theory from the spectrum of bound states
on a topological defect. We apply our recipe to the case of kinks in 1+1
dimensions with one or two bound states. Our recipe successfully yields the
sine-Gordon and field theories when suitable bound state
spectra are assumed. The recipe can also be used to globally reconstruct the
inflaton potential of inflationary cosmology if the inflaton produces a
topological defect. We discuss how defects can provide ``smoking gun'' evidence
for a class of inflationary models.Comment: 10 pages, 4 figures. Included proof (Appendix B) that wall
fluctuation potentials have supersymmetric form. Added reference
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
Stochastic collective dynamics of charged--particle beams in the stability regime
We introduce a description of the collective transverse dynamics of charged
(proton) beams in the stability regime by suitable classical stochastic
fluctuations. In this scheme, the collective beam dynamics is described by
time--reversal invariant diffusion processes deduced by stochastic variational
principles (Nelson processes). By general arguments, we show that the diffusion
coefficient, expressed in units of length, is given by ,
where is the number of particles in the beam and the Compton
wavelength of a single constituent. This diffusion coefficient represents an
effective unit of beam emittance. The hydrodynamic equations of the stochastic
dynamics can be easily recast in the form of a Schr\"odinger equation, with the
unit of emittance replacing the Planck action constant. This fact provides a
natural connection to the so--called ``quantum--like approaches'' to beam
dynamics. The transition probabilities associated to Nelson processes can be
exploited to model evolutions suitable to control the transverse beam dynamics.
In particular we show how to control, in the quadrupole approximation to the
beam--field interaction, both the focusing and the transverse oscillations of
the beam, either together or independently.Comment: 15 pages, 9 figure
Current Algebra in Three Dimensions
We study a three dimensional analogue of the Wess--Zumino--Witten model,
which describes the Goldstone bosons of three dimensional Quantum
Chromodynamics. The topologically non--trivial term of the action can also be
viewed as a nonlinear realization of Chern--Simons form. We obtain the current
algebra of this model by canonical methods. This is a three dimensional
generalization of the Kac--Moody algebra.Comment: 11 pages, UR-1266, ER40685-72
Three-dimensional N=4 supersymmetry in harmonic N=3 superspace
We consider the map of three-dimensional N=4 superfields to N=3 harmonic
superspace. The left and right representations of the N=4 superconformal group
are constructed on N=3 analytic superfields. These representations are
convenient for the description of N=4 superconformal couplings of the Abelian
gauge superfields with hypermultiplets. We analyze the N=4 invariance in the
non-Abelian N=3 Yang-Mills theory.Comment: Latex file, 22 pages; v2 two references adde
Higher Derivative CP(N) Model and Quantization of the Induced Chern-Simons Term
We consider higher derivative CP(N) model in 2+1 dimensions with the
Wess-Zumino-Witten term and the topological current density squared term. We
quantize the theory by using the auxiliary gauge field formulation in the path
integral method and prove that the extended model remains renormalizable in the
large N limit. We find that the Maxwell-Chern-Simons theory is dynamically
induced in the large N effective action at a nontrivial UV fixed point. The
quantization of the Chern-Simons term is also discussed.Comment: 8 pages, no figure, a minor change in abstract, added Comments on the
quantization of the Chern-Simons term whose coefficient is also corrected,
and some references are added. Some typos are corrected. Added a new
paragraph checking the equivalence between (3) and (5), and a related
referenc
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