75 research outputs found
Superparticle actions from superfields
Gauge invariant complex covariant actions for superparticles are derived from
the field equations for the chiral superfields in a precise manner. The massive
and massless cases in four dimensions are treated both free and in interaction
with an external super Maxwell field. By means of a generalized BRST
quantization these complex actions are related to real actions with second
class constraints which are new in some cases.Comment: 23 pages, ITP-G\"{o}teborg 94-14, LATE
Extended observables in theories with constraints
In a classical Hamiltonian theory with second class constraints the phase
space functions on the constraint surface are observables. We give general
formulas for extended observables, which are expressions representing the
observables in the enveloping unconstrained phase space. These expressions
satisfy in the unconstrained phase space a Poisson algebra of the same form as
the Dirac bracket algebra of the observables on the constraint surface. The
general formulas involve new differential operators that differentiate the
Dirac bracket. Similar extended observables are also constructed for theories
with first class constraints which, however, are gauge dependent. For such
theories one may also construct gauge invariant extensions with similar
properties. Whenever extended observables exist the theory is expected to allow
for a covariant quantization. A mapping procedure is proposed for covariant
quantization of theories with second class constraints.Comment: 26 pages, Latexfile,Minor misprints on page 4 are correcte
Hamiltonian BRST Quantization of the Conformal String
We present a new formulation of the tensionless string () where the
space-time conformal symmetry is manifest. Using a Hamiltonian BRST scheme we
quantize this {\em Conformal String} and find that it has critical dimension
. This is in keeping with our classical result that the model describes
massless particles in this dimension. It is also consistent with our previous
results which indicate that quantized conformally symmetric tensionless strings
describe a topological phase away {}from . We reach our result by
demanding nilpotency of the BRST charge and consistency with the Jacobi
identities. The derivation is presented in two different ways: in operator
language and using mode expansions. Careful attention is payed to
regularization, a crucial ingredient in our calculations.Comment: 33pp (LaTeX), USITP-94-0
BRST quantization of anomalous gauge theories
It is shown how the BRST quantization can be applied to a gauge invariant
sector of theories with anomalously broken symmetries. This result is used to
show that shifting the anomalies to a classically trivial sector of fields
(Wess-Zumino mechanism) makes it possible to quantize the physical sector using
a standard BRST procedure, as for a non anomalous theory. The trivial sector
plays the role of a topological sector if the system is quantized without
shifting the anomalies.Comment: 16 pages, latex, revised and enlarged version to appear in Phys.Rev.
Time Variation of Fine Structure Constant and Proton-Electron Mass Ratio with Quintessence
Recent astrophysical observations of quasar absorption systems indicate that
the fine structure constant and the proton-electron mass ratio
may have evolved through the history of the universe. Motivated by these
observations, we consider the cosmological evolution of a quintessence-like
scalar field coupled to gauge fields and matter which leads to effective
modifications of the coupling constants and particle masses over time. We show
that a class of models where the scalar field potential and the
couplings to matter admit common extremum in naturally
explains constraints on variations of both the fine structure constant and the
proton-electron mass ratio.Comment: 9 pages, 4 figures, CosPA 2006 Proceeding. 9 pages, 4 figures, CosPA
2006 Proceeding will be published in the Mod. Phys. Lett.
A pedestrian approach to the high energy limits of branes and other gravitational systems
In this article we study limits of models that contain a dimensionful
parameter such as the mass of the relativistic point-particle. The limits are
analogous to the massless limit of the particle and may be thought of as high
energy limits. We present the ideas and work through several examples in a
(hopefully) pedagogical manner. Along the way we derive several new results.Comment: 19 pages, 1 figur
On the Minimal Model of Anyons
We present new geometric formulations for the fractional spin particle models
on the minimal phase spaces. New consistent couplings of the anyon to
background fields are constructed. The relationship between our approach and
previously developed anyon models is discussed.Comment: 17 pages, LaTex, no figure
Schwinger-Dyson equation for non-Lagrangian field theory
A method is proposed of constructing quantum correlators for a general gauge
system whose classical equations of motion do not necessarily follow from the
least action principle. The idea of the method is in assigning a certain BRST
operator to any classical equations of motion, Lagrangian or not.
The generating functional of Green's functions is defined by the equation
that is reduced to the standard Schwinger-Dyson equation
whenever the classical field equations are Lagrangian. The corresponding
probability amplitude of a field is defined by the same equation
although in another representation. When the
classical dynamics are Lagrangian, the solution for is reduced to
the Feynman amplitude , while in the non-Lagrangian case
this amplitude can be a more general distribution.Comment: 33 page
Pseudoclassical description of the massive Dirac particles in odd dimensions
A pseudoclassical model is proposed to describe massive Dirac (spin one-half)
particles in arbitrary odd dimensions. The quantization of the model reproduces
the minimal quantum theory of spinning particles in such dimensions. A
dimensional duality between the model proposed and the pseudoclassical
description of Weyl particles in even dimensions is discussed.Comment: 12 pages, LaTeX (RevTeX
Gauge Fixing and BFV Quantization
Nonsingularity conditions are established for the BFV gauge-fixing fermion
which are sufficient for it to lead to the correct path integral for a theory
with constraints canonically quantized in the BFV approach. The conditions
ensure that anticommutator of this fermion with the BRST charge regularises the
path integral by regularising the trace over non-physical states in each ghost
sector. The results are applied to the quantization of a system which has a
Gribov problem, using a non-standard form of the gauge-fixing fermion.Comment: 14 page
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