3,101 research outputs found
The Resurgence of the Cusp Anomalous Dimension
This work addresses the resurgent properties of the cusp anomalous
dimension's strong coupling expansion, obtained from the integral
Beisert-Eden-Staudacher (BES) equation. This expansion is factorially
divergent, and its first nonperturbative corrections are related to the mass
gap of the -model. The factorial divergence can also be analysed
from a resurgence perspective. Building on the work of Basso and Korchemsky, a
transseries ansatz for the cusp anomalous dimension is proposed and the
corresponding expected large-order behaviour studied. One finds
non-perturbative phenomena in both the positive and negative real coupling
directions, which need to be included to address the analyticity conditions
coming from the BES equation. After checking the resurgence structure of the
proposed transseries, it is shown that it naturally leads to an unambiguous
resummation procedure, furthermore allowing for a strong/weak coupling
interpolation.Comment: 12 pages, 5 figure
Digital equalization of time-delay array receivers on coherent laser communications
© [2017 Optical Society of America.]. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.Field conjugation arrays use adaptive combining techniques on multi-aperture receivers to improve the performance of coherent laser communication links by mitigating the consequences of atmospheric turbulence on the down-converted coherent power. However, this motivates the use of complex receivers as optical signals collected by different apertures need to be adaptively processed, co-phased, and scaled before they are combined. Here, we show that multiple apertures, coupled with optical delay lines, combine retarded versions of a signal at a single coherent receiver, which uses digital equalization to obtain diversity gain against atmospheric fading. We found in our analysis that, instead of field conjugation arrays, digital equalization of time-delay multi-aperture receivers is a simpler and more versatile approach to accomplish reduction of atmospheric fading.Peer ReviewedPostprint (author's final draft
Notes on Collective Field Theory of Matrix and Spin Calogero Models
Matrix models and related Spin-Calogero-Sutherland models are of major
relevance in a variety of subjects, ranging from condensed matter physics to
QCD and low dimensional string theory. They are characterized by integrability
and exact solvability. Their continuum, field theoretic representations are
likewise of definite interest. In this paper we describe various continuum,
field theoretic representations of these models based on bosonization and
collective field theory techniques. We compare various known representations
and describe some nontrivial applications.Comment: 36 pages, no figures v2: references added, a version to appear in the
special issue of JPhysA (edited by G Dunne, J Feinberg and P Dorey)
v3:comments changed, paper identical to v
Nonperturbative Ambiguities and the Reality of Resurgent Transseries
In a wide range of quantum theoretical settings -- from quantum mechanics to
quantum field theory, from gauge theory to string theory -- singularities in
the complex Borel plane, usually associated to instantons or renormalons,
render perturbation theory ill-defined as they give rise to nonperturbative
ambiguities. These ambiguities are associated to choices of an integration
contour in the resummation of perturbation theory, along (singular) Stokes
directions in the complex Borel plane (rendering perturbative expansions
non-Borel summable along any Stokes line). More recently, it has been shown
that the proper framework to address these issues is that of resurgent analysis
and transseries. In this context, the cancelation of all nonperturbative
ambiguities is shown to be a consequence of choosing the transseries median
resummation as the appropriate family of unambiguous real solutions along the
coupling-constant real axis. While the median resummation is easily implemented
for one-parameter transseries, once one considers more general multi-parameter
transseries the procedure becomes highly dependent upon properly understanding
Stokes transitions in the complex Borel plane. In particular, all Stokes
coefficients must now be known in order to explicitly implement multi-parameter
median resummations. In the cases where quantum-theoretical physical
observables are described by resurgent functions and transseries, the methods
described herein show how one may cancel nonperturbative ambiguities, and
define these observables nonperturbatively starting out from perturbation
theory. Along the way, structural results concerning resurgent transseries are
also obtained.Comment: 62 pages, 4 figures; v2: corrected typos, added small discussion on
topological sectors, two new figure
Poisson Structures of Calogero-Moser and Ruijsenaars-Schneider Models
We examine the Hamiltonian structures of some Calogero-Moser and
Ruijsenaars-Schneider N-body integrable models. We propose explicit
formulations of the bihamiltonian structures for the discrete models, and
field-theoretical realizations of these structures. We discuss the relevance of
these realizations as collective-field theory for the discrete models.Comment: 15 pages, no figures; v2 references added, typos correcte
Massless L\"uscher Terms and the Limitations of the AdS3 Asymptotic Bethe Ansatz
In AdS5/CFT4 integrability the Bethe ansatz gives the spectrum of long
strings, accurate up to exponentially small corrections. This is no longer true
in AdS3, as we demonstrate here by studying Luscher F-terms with a massless
particle running in the loop. We apply this to the classic test of Hernandez &
Lopez, in which the su(2) sector Bethe equations (including one-loop dressing
phase) should match the semiclassical string theory result for a circular
spinning string. These calculations did not agree in AdS3xS3xT4, and we show
that the sum of all massless Luscher F-terms can reproduce the difference.Comment: 15 pages, 1 figure; v2:references, typos and clarification
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