492 research outputs found
Low Energy Effective Action in N=2 Yang-Mills as an Integrated Anomaly
Based on chiral ring relations and anomalies, as described by Cachazo,
Douglas, Seiberg and Witten, we argue that the holomorphic effective action in
N=2 Yang-Mills theory can be understood as an integrated U(1) anomaly from a
purely field theory point of view. In particular, we show that the periods of
the Riemann surface arising from the generalized Konishi anomaly can be given a
physical interpretation without referring to special geometry. We also discuss
consequences for the multi-instanton calculus in N=2 Yang-Mills theory.Comment: 25 pages, 2 figures ; v2: reference adde
Slow-light enhanced light-matter interactions with applications to gas sensing
Optical gas detection in microsystems is limited by the short micron scale
optical path length available. Recently, the concept of slow-light enhanced
absorption has been proposed as a route to compensate for the short path length
in miniaturized absorption cells. We extend the previous perturbation theory to
the case of a Bragg stack infiltrated by a spectrally strongly dispersive gas
with a narrow and distinct absorption peak. We show that considerable signal
enhancement is possible. As an example, we consider a Bragg stack consisting of
PMMA infiltrated by O2. Here, the required optical path length for visible to
near-infrared detection (~760 nm) can be reduced by at least a factor of 10^2,
making a path length of 1 mm feasible. By using this technique, optical gas
detection can potentially be made possible in microsystems
Multiloop Superstring Amplitudes from Non-Minimal Pure Spinor Formalism
Using the non-minimal version of the pure spinor formalism, manifestly
super-Poincare covariant superstring scattering amplitudes can be computed as
in topological string theory without the need of picture-changing operators.
The only subtlety comes from regularizing the functional integral over the pure
spinor ghosts. In this paper, it is shown how to regularize this functional
integral in a BRST-invariant manner, allowing the computation of arbitrary
multiloop amplitudes. The regularization method simplifies for scattering
amplitudes which contribute to ten-dimensional F-terms, i.e. terms in the
ten-dimensional superspace action which do not involve integration over the
maximum number of 's.Comment: 23 pages harvmac, added acknowledgemen
Disorder driven quantum critical behavior in CuGeO3 doped with magnetic impurity
For the CuGeO3 doped with 1% of Fe the quantum critical behavior in a wide
temperature range 1-40 K is reported. The critical exponents for susceptibility
along different crystallographic axes are determined: a=0.34 (B//a and B//c)
and a=0.31 (B//b). New effect of the frequency dependence of the critical
exponent is discussed.Comment: Submitted to SCES0
Prepotential and Instanton Corrections in N=2 Supersymmetric SU(N_1)xSU(N_2) Yang Mills Theories
In this paper we analyse the non-hyperelliptic Seiberg-Witten curves derived
from M-theory that encode the low energy solution of N=2 supersymmetric
theories with product gauge groups. We consider the case of a SU(N_1)xSU(N_2)
gauge theory with a hypermultiplet in the bifundamental representation together
with matter in the fundamental representations of SU(N_1) and SU(N_2). By means
of the Riemann bilinear relations that hold on the Riemann surface defined by
the Seiberg--Witten curve, we compute the logarithmic derivative of the
prepotential with respect to the quantum scales of both gauge groups. As an
application we develop a method to compute recursively the instanton
corrections to the prepotential in a straightforward way. We present explicit
formulas for up to third order on both quantum scales. Furthermore, we extend
those results to SU(N) gauge theories with a matter hypermultiplet in the
symmetric and antisymmetric representation. We also present some non-trivial
checks of our results.Comment: 21 pages, 2 figures, minor changes and references adde
The Curve of Compactified 6D Gauge Theories and Integrable Systems
We analyze the Seiberg-Witten curve of the six-dimensional N=(1,1) gauge
theory compactified on a torus to four dimensions. The effective theory in four
dimensions is a deformation of the N=2* theory. The curve is naturally
holomorphically embedding in a slanted four-torus--actually an abelian
surface--a set-up that is natural in Witten's M-theory construction of N=2
theories. We then show that the curve can be interpreted as the spectral curve
of an integrable system which generalizes the N-body elliptic Calogero-Moser
and Ruijsenaars-Schneider systems in that both the positions and momenta take
values in compact spaces. It turns out that the resulting system is not simply
doubly elliptic, rather the positions and momenta, as two-vectors, take values
in the ambient abelian surface. We analyze the two-body system in some detail.
The system we uncover provides a concrete realization of a Beauville-Mukai
system based on an abelian surface rather than a K3 surface.Comment: 22 pages, JHEP3, 4 figures, improved readility of figures, added
reference
Critical equation of state of randomly dilute Ising systems
We determine the critical equation of state of three-dimensional randomly
dilute Ising systems, i.e. of the random-exchange Ising universality class. We
first consider the small-magnetization expansion of the Helmholtz free energy
in the high-temperature phase. Then, we apply a systematic approximation scheme
of the equation of state in the whole critical regime, that is based on
polynomial parametric representations matching the small-magnetization of the
Helmholtz free energy and satisfying a global stationarity condition. These
results allow us to estimate several universal amplitude ratios, such as the
ratio A^+/A^- of the specific-heat amplitudes. Our best estimate A^+/A^-=1.6(3)
is in good agreement with experimental results on dilute uniaxial
antiferromagnets.Comment: 21 pages, 1 figure, refs adde
Is cosmology consistent?
We perform a detailed analysis of the latest CMB measurements (including
BOOMERaNG, DASI, Maxima and CBI), both alone and jointly with other
cosmological data sets involving, e.g., galaxy clustering and the Lyman Alpha
Forest. We first address the question of whether the CMB data are internally
consistent once calibration and beam uncertainties are taken into account,
performing a series of statistical tests. With a few minor caveats, our answer
is yes, and we compress all data into a single set of 24 bandpowers with
associated covariance matrix and window functions. We then compute joint
constraints on the 11 parameters of the ``standard'' adiabatic inflationary
cosmological model. Out best fit model passes a series of physical consistency
checks and agrees with essentially all currently available cosmological data.
In addition to sharp constraints on the cosmic matter budget in good agreement
with those of the BOOMERaNG, DASI and Maxima teams, we obtain a heaviest
neutrino mass range 0.04-4.2 eV and the sharpest constraints to date on gravity
waves which (together with preference for a slight red-tilt) favors
``small-field'' inflation models.Comment: Replaced to match accepted PRD version. 14 pages, 12 figs. Tiny
changes due to smaller DASI & Maxima calibration errors. Expanded neutrino
and tensor discussion, added refs, typos fixed. Combined CMB data, window and
covariance matrix at http://www.hep.upenn.edu/~max/consistent.html or from
[email protected]
Matrix Models, Geometric Engineering and Elliptic Genera
We compute the prepotential of N=2 supersymmetric gauge theories in four
dimensions obtained by toroidal compactifications of gauge theories from 6
dimensions, as a function of Kahler and complex moduli of T^2. We use three
different methods to obtain this: matrix models, geometric engineering and
instanton calculus. Matrix model approach involves summing up planar diagrams
of an associated gauge theory on T^2. Geometric engineering involves
considering F-theory on elliptic threefolds, and using topological vertex to
sum up worldsheet instantons. Instanton calculus involves computation of
elliptic genera of instanton moduli spaces on R^4. We study the
compactifications of N=2* theory in detail and establish equivalence of all
these three approaches in this case. As a byproduct we geometrically engineer
theories with massive adjoint fields. As one application, we show that the
moduli space of mass deformed M5-branes wrapped on T^2 combines the Kahler and
complex moduli of T^2 and the mass parameter into the period matrix of a genus
2 curve.Comment: 90 pages, Late
Adjoint "quarks" on coarse anisotropic lattices: Implications for string breaking in full QCD
A detailed study is made of four dimensional SU(2) gauge theory with static
adjoint ``quarks'' in the context of string breaking. A tadpole-improved action
is used to do simulations on lattices with coarse spatial spacings ,
allowing the static potential to be probed at large separations at a
dramatically reduced computational cost. Highly anisotropic lattices are used,
with fine temporal spacings , in order to assess the behavior of the
time-dependent effective potentials. The lattice spacings are determined from
the potentials for quarks in the fundamental representation. Simulations of the
Wilson loop in the adjoint representation are done, and the energies of
magnetic and electric ``gluelumps'' (adjoint quark-gluon bound states) are
calculated, which set the energy scale for string breaking. Correlators of
gauge-fixed static quark propagators, without a connecting string of spatial
links, are analyzed. Correlation functions of gluelump pairs are also
considered; similar correlators have recently been proposed for observing
string breaking in full QCD and other models. A thorough discussion of the
relevance of Wilson loops over other operators for studies of string breaking
is presented, using the simulation results presented here to support a number
of new arguments.Comment: 22 pages, 14 figure
- âŠ