119 research outputs found
Path integrals in curved space and the worldline formalism
We describe how to construct and compute unambiguously path integrals for
particles moving in a curved space, and how these path integrals can be used to
calculate Feynman graphs and effective actions for various quantum field
theories with external gravity in the framework of the worldline formalism. In
particular, we review a recent application of this worldline approach and
discuss vector and antisymmetric tensor fields coupled to gravity. This
requires the construction of a path integral for the N=2 spinning particle,
which is used to compute the first three Seeley-DeWitt coefficients for all
p-form gauge fields in all dimensions and to derive exact duality relations.Comment: 16 pages, to appear in the proceedings of "Path Integrals 2005: from
Quantum Information to Cosmology" (Prague, June 6-10, 2005), references adde
On a New Method for Computing Trace Anomalies
I describe a new method for computing trace anomalies in quantum field
theories which makes use of path-integrals for particles moving in curved
spaces. After presenting the main ideas of the method, I discuss how it is
connected to the first quantized approach of particle theory and to heat kernel
techniques. (Talk given at Journees Relativistes '93).Comment: 4 pages, LaTeX, USITP-93-1
A note on 2D chiral gravity and chiral bosons
Quantization of two dimensional chiral matter coupled to gravity induces an
effective action for the zweibein field which is both Weyl and Lorentz
anomalous. Recently, the quantization of this induced action has been analyzed
in the light-cone gauge as well as in the conformal gauge. An apparent mismatch
between the results obtained in the two gauges is analyzed and resolved by
properly treating the Lorentz field as a chiral boson.Comment: 7 pages, plain TeX, USITP-92-09 (minor correction in the list of
references
A Locally Supersymmetric Action for the Bosonic String
Recently Berkovits and Vafa have shown that the bosonic string can be viewed
as the fermionic string propagating in a particular background. Such a
background is described by a somewhat unusual superconformal system. By
coupling it to supergravity I construct a local supersymmetric action for
the bosonic string.Comment: 7 pages, NBI-93-6
One loop photon-graviton mixing in an electromagnetic field: Part 1
Photon-graviton mixing in an electromagnetic field is a process of potential
interest for cosmology and astrophysics. At the tree level it has been studied
by many authors. We consider the one-loop contribution to this amplitude
involving a charged spin 0 or spin 1/2 particle in the loop and an arbitrary
constant field. In the first part of this article, the worldline formalism is
used to obtain a compact two-parameter integral representation for this
amplitude, valid for arbitrary photon energies and background field strengths.
The calculation is manifestly covariant througout.Comment: 27 pages, final published version (minor corrections
On the trace anomaly of a Weyl fermion
We calculate the trace anomaly of a Weyl fermion coupled to gravity by using
Fujikawa's method supplemented by the choice of a consistent regulator. The
latter is constructed out of Pauli-Villars regulating fields. The motivation
for presenting such a calculation stems from recent studies that suggest that
the trace anomaly of chiral fermions in four dimensions might contain an
imaginary part proportional to the Pontryagin density. We find that the trace
anomaly of a Weyl fermion is given by half the trace anomaly of a Dirac
fermion, so that no imaginary part proportional to the Pontryagin density is
seen to arise.Comment: 25 pages, added references and acknowledgment
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