8,021 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
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
Braided Oscillators
The braided Hopf algebra structure of the generalized oscillator is
investigated. Using the solutions two types of braided Fibonacci oscillators
are introduced. This leads to two types of braided Biedenharn-Macfarlane
oscillators.Comment: 12 pages, latex, some references added, published versio
Analogies between self-duality and stealth matter source
We consider the problem of a self-interacting scalar field nonminimally
coupled to the three-dimensional BTZ metric such that its energy-momentum
tensor evaluated on the BTZ metric vanishes. We prove that this system is
equivalent to a self-dual system composed by a set of two first-order
equations. The self-dual point is achieved by fixing one of the coupling
constant of the potential in terms of the nonminimal coupling parameter. At the
self-dual point and up to some boundary terms, the matter action evaluated on
the BTZ metric is bounded below and above. These two bounds are saturated
simultaneously yielding to a vanishing action for configurations satisfying the
set of self-dual first-order equations.Comment: 6 pages. To be published in Jour. Phys.
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
Hopf instantons, Chern-Simons vortices, and Heisenberg ferromagnets
The dimensional reduction of the three-dimensional fermion-Chern-Simons model
(related to Hopf maps) of Adam et el. is shown to be equivalent to (i) either
the static, fixed--chirality sector of our non-relativistic spinor-Chern-Simons
model in 2+1 dimensions, (ii) or a particular Heisenberg ferromagnet in the
plane.Comment: 4 pages, Plain Tex, no figure
Symmetry Breaking in the Schr\"odinger Representation for Chern-Simons Theories
This paper discusses the phenomenon of spontaneous symmetry breaking in the
Schr\"odinger representation formulation of quantum field theory. The analysis
is presented for three-dimensional space-time abelian gauge theories with
either Maxwell, Maxwell-Chern-Simons, or pure Chern-Simons terms as the gauge
field contribution to the action, each of which leads to a different form of
mass generation for the gauge fields.Comment: 16pp, LaTeX , UCONN-94-
Emergent gauge dynamics of highly frustrated magnets
Condensed matter exhibits a wide variety of exotic emergent phenomena such as
the fractional quantum Hall effect and the low temperature cooperative behavior
of highly frustrated magnets. I consider the classical Hamiltonian dynamics of
spins of the latter phenomena using a method introduced by Dirac in the 1950s
by assuming they are constrained to their lowest energy configurations as a
simplifying measure. Focusing on the kagome antiferromagnet as an example, I
find it is a gauge system with topological dynamics and non-locally connected
edge states for certain open boundary conditions similar to doubled
Chern-Simons electrodynamics expected of a spin liquid. These dynamics
are also similar to electrons in the fractional quantum Hall effect. The
classical theory presented here is a first step towards a controlled
semi-classical description of the spin liquid phases of many pyrochlore and
kagome antiferromagnets and towards a description of the low energy classical
dynamics of the corresponding unconstrained Heisenberg models.Comment: Updated with some appendices moved to the main body of the paper and
some additional improvements. 21 pages, 5 figure
B2 and G2 Toda systems on compact surfaces: a variational approach
We consider the B2 and G2 Toda systems on compact surfaces. We attack the
problem using variational techniques. We get existence and multiplicity of
solutions under a topological assumption on the surface and some generic
conditions on the parameters. We also extend some of the results to the case of
general systems.Comment: 28 pages, accepted on Journal of Mathematical Physic
On the Yang-Mills two-loop effective action with wordline methods
We derive the two-loop effective action for covariantly constant field
strength of pure Yang-Mills theory in the presence of an infrared scale. The
computation is done in the framework of the worldline formalism, based on a
generalization procedure of constructing multiloop effective actions in terms
of the bosonic worldline path integral. The two-loop beta-function is correctly
reproduced. This is the first derivation in the worldline formulation, and
serves as a nontrivial check on the consistency of the multiloop generalization
procedure in the worldline formalism.Comment: 8 pages, 4 figure
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