11,500 research outputs found
The Euler-Heisenberg Lagrangian beyond one loop
We review what is presently known about higher loop corrections to the
Euler-Heisenberg Lagrangian and its Scalar QED analogue. The use of those
corrections as a tool for the study of the properties of the QED perturbation
series is outlined. As a further step in a long-term effort to prove or
disprove the convergence of the N photon amplitudes in the quenched
approximation, we present a parameter integral representation of the three-loop
Euler-Heisenberg Lagrangian in 1+1 dimensional QED, obtained in the worldline
formalism.Comment: 11 pages, 2 figures, talk given by Christian Schubert at QFEXT11,
Benasque, Spain, Sept. 18-24, 2011, to appear in the conference proceeding
The SCUBA Local Universe Galaxy Survey
The SCUBA local universe galaxy survey is the first systematic survey of the
local universe at submillimetre wavelengths. We have observed ~200 galaxies
from the IRAS bright galaxy catalogue and the CfA optical redshift survey. The
IRAS sample showed that our estimate of the luminosity function was potentially
biased if a cold population of galaxies existed which would not have appeared
in the IRAS BGS but would have been detected in a SCUBA blind survey. Here we
present preliminary results from the optically selected sample which suggest
that this is indeed the case.Comment: 2 pages, 2 figs, proceedings from Euro-conference on galaxy evolution
held in La Reunion, 200
Quantum Group Covariance and the Braided Structure of Deformed Oscillators
The connection between braided Hopf algebra structure and the quantum group
covariance of deformed oscillators is constructed explicitly. In this context
we provide deformations of the Hopf algebra of functions on SU(1,1). Quantum
subgroups and their representations are also discussed.Comment: 12 pages, to be published in JM
Balanced filters for the analysis of Al, Si, K, Ca, Fe, and Ni
Balanced filters evaluated for performance in X-ray fluorescence analysis of lunar and planetary surface material
Symmetry Aspects and Finite-Size Scaling of Quantum Hall Fluids
The exactness and universality observed in the quantum Hall effect suggests
the existence of a symmetry principle underlying Laughlin's theory. We review
the role played by the infinite and conformal algebras as
dynamical symmetries of incompressible quantum fluids and show how they predict
universal finite-size effects in the excitation spectrum.Comment: 15 pages, CERN-TH-6784/93, LateX fil
Exact computation of one-loop correction to energy of spinning folded string in AdS_5 x S^5
We consider the 1-loop correction to the energy of folded spinning string
solution in the AdS_3 part of AdS_5 x S^5. The classical string solution is
expressed in terms of elliptic functions so an explicit computation of the
corresponding fluctuation determinants for generic values of the spin appears
to be a non-trivial problem. We show how it can be solved exactly by using the
static gauge expression for the string partition function (which we demonstrate
to be equivalent to the conformal gauge one) and observing that all the
corresponding second order fluctuation operators can be put into the standard
(single-gap) Lam\'e form. We systematically derive the small spin and large
spin expansions of the resulting expression for the string energy and comment
on some of their applications.Comment: 52 pp, 12 figures; v3: footnote 9 adde
On the QED Effective Action in Time Dependent Electric Backgrounds
We apply the resolvent technique to the computation of the QED effective
action in time dependent electric field backgrounds. The effective action has
both real and imaginary parts, and the imaginary part is related to the pair
production probability in such a background. The resolvent technique has been
applied previously to spatially inhomogeneous magnetic backgrounds, for which
the effective action is real. We explain how dispersion relations connect these
two cases, the magnetic case which is essentially perturbative in nature, and
the electric case where the imaginary part is nonperturbative. Finally, we use
a uniform semiclassical approximation to find an expression for very general
time dependence for the background field. This expression is remarkably similar
in form to Schwinger's classic result for the constant electric background.Comment: 27 pages, no figures; reference adde
A Gauge-Gravity Relation in the One-loop Effective Action
We identify an unusual new gauge-gravity relation: the one-loop effective
action for a massive spinor in 2n dimensional AdS space is expressed in terms
of precisely the same function [a certain multiple gamma function] as the
one-loop effective action for a massive charged scalar in 4n dimensions in a
maximally symmetric background electromagnetic field [one for which the
eigenvalues of F_{\mu\nu} are maximally degenerate, corresponding in 4
dimensions to a self-dual field, equivalently to a field of definite helicity],
subject to the identification F^2 \Lambda, where \Lambda is the
gravitational curvature. Since these effective actions generate the low energy
limit of all one-loop multi-leg graviton or gauge amplitudes, this implies a
nontrivial gauge-gravity relation at the non-perturbative level and at the
amplitude level.Comment: 6 page
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