870 research outputs found
Covariance of Time-Ordered Products Implies Local Commutativity of Fields
We formulate Lorentz covariance of a quantum field theory in terms of
covariance of time-ordered products (or other Green's functions). This
formulation of Lorentz covariance implies spacelike local commutativity or
anticommutativity of fields, sometimes called microscopic causality or
microcausality. With this formulation microcausality does not have to be taken
as a separate assumption.Comment: 6 pages, section on non-local theories removed, published versio
Junction conditions in General Relativity with spin sources
The junction conditions for General Relativity in the presence of domain
walls with intrinsic spin are derived in three and higher dimensions. A stress
tensor and a spin current can be defined just by requiring the existence of a
well defined volume element instead of an induced metric, so as to allow for
generic torsion sources. In general, when the torsion is localized on the
domain wall, it is necessary to relax the continuity of the tangential
components of the vielbein. In fact it is found that the spin current is
proportional to the jump in the vielbein and the stress-energy tensor is
proportional to the jump in the spin connection. The consistency of the
junction conditions implies a constraint between the direction of flow of
energy and the orientation of the spin. As an application, we derive the
circularly symmetric solutions for both the rotating string with tension and
the spinning dust string in three dimensions. The rotating string with tension
generates a rotating truncated cone outside and a flat space-time with
inevitable frame dragging inside. In the case of a string made of spinning
dust, in opposition to the previous case no frame dragging is present inside,
so that in this sense, the dragging effect can be "shielded" by considering
spinning instead of rotating sources. Both solutions are consistently lifted as
cylinders in the four-dimensional case.Comment: 24 pages, no figures, CECS style. References added and misprints
corrected. Published Versio
Lorentz and CPT Violating Chern-Simons Term in the Formulation of Functional Integral
We show that in the functional integral formalism the (finite) coefficient of
the induced, Lorentz- and CPT-violating Chern-Simons term, arising from the
Lorentz- and CPT-violating fermion sector, is undetermined.Comment: 5 pages, no figure, RevTe
Generalized Tomonaga-Schwinger equation from the Hadamard formula
A generalized Tomonaga--Schwinger equation, holding on the entire boundary of
a {\em finite} spacetime region, has recently been considered as a tool for
studying particle scattering amplitudes in background-independent quantum field
theory. The equation has been derived using lattice techniques under
assumptions on the existence of the continuum limit. Here I show that in the
context of continuous euclidean field theory the equation can be directly
derived from the functional integral formalism, using a technique based on
Hadamard's formula for the variation of the propagator.Comment: 11 pages, no figure
Extended de Sitter Theory of Two Dimensional Gravitational Forces
We present a simple unifying gauge theoretical formulation of gravitational
theories in two dimensional spacetime. This formulation includes the effects of
a novel matter-gravity coupling which leads to an extended de Sitter symmetry
algebra on which the gauge theory is based. Contractions of this theory
encompass previously studied cases.Comment: 19pp, no figs., CTP 2228, UCONN-93-
Anyons as quon particles
The momentum operator representation of nonrelativistic anyons is developed
in the Chern - Simons formulation of fractional statistics. The connection
between anyons and the q-deformed bosonic algebra is established.Comment: 10 pages,Late
Self-dual Vortices in the Generalized Abelian Higgs Model with Independent Chern-Simons Interaction
Self-dual vortex solutions are studied in detail in the generalized abelian
Higgs model with independent Chern-Simons interaction. For special choices of
couplings, it reduces to a Maxwell-Higgs model with two scalar fields, a
Chern-Simons-Higgs model with two scalar fields, or other new models. We
investigate the properties of the static solutions and perform detailed
numerical analyses. For the Chern-Simons-Higgs model with two scalar fields in
an asymmetric phase, we prove the existence of multisoliton solutions which can
be viewed as hybrids of Chern-Simons vortices and lumps. We also discuss
solutions in a symmetric phase with the help of the corresponding exact
solutions in its nonrelativistic limit. The model interpolating all three
models---Maxwell-Higgs, Chern-Simons-Higgs, and models--- is discussed
briefly. Finally we study the possibility of vortex solutions with half-integer
vorticity in the special case of the model. Numerical results are negative.Comment: 32 pages, LATEX, SNUTP 92-7
Supersymmetry and the Chiral Schwinger Model
We have constructed the N=1/2 supersymmetric general Abelian model with
asymmetric chiral couplings. This leads to a N=1/2 supersymmetrization of the
Schwinger model. We show that the supersymmetric general model is plagued with
problems of infrared divergence. Only the supersymmetric chiral Schwinger model
is free from such problems and is dynamically equivalent to the chiral
Schwinger model because of the peculiar structure of the N=1/2 multiplets.Comment: one 9 pages Latex file, one ps file with one figur
Solving simultaneously Dirac and Ricatti equations
We analyse the behaviour of the Dirac equation in with Lorentz scalar
potential. As the system is known to provide a physical realization of
supersymmetric quantum mechanics, we take advantage of the factorization method
in order to enlarge the restricted class of solvable problems. To be precise,
it suffices to integrate a Ricatti equation to construct one-parameter families
of solvable potentials. To illustrate the procedure in a simple but relevant
context, we resort to a model which has proved useful in showing the phenomenon
of fermion number fractionalization
Operator Ordering Problem of the Nonrelativistic Chern-Simons Theory
The operator ordering problem due to the quantization or regularization
ambiguity in the Chern-Simons theory exists. However, we show that this can be
avoided if we require Galilei covariance of the nonrelativistic Abelian
Chern-Simons theory even at the quantum level for the extended sources. The
covariance can be recovered only by choosing some particular operator orderings
for the generators of the Galilei group depending on the quantization
ambiguities of the commutation relation. We show that the
desired ordering for the unusual prescription is not the same as the well-known
normal ordering but still satisfies all the necessary conditions. Furthermore,
we show that the equations of motion can be expressed in a similar form
regardless of the regularization ambiguity. This suggests that the different
regularization prescriptions do not change the physics. On the other hand, for
the case of point sources the regularization prescription is uniquely
determined, and only the orderings, which are equivalent to the usual one, are
allowed.Comment: 18 page
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