327 research outputs found
Coulomb Gas Representation of the SU(2) WZW Correlators at Higher Genera
We express the correlation functions of the SU(2) WZW conformal field theory
on Riemann surfaces of genus >1 by finite dimensional integrals.Comment: 9 pages, late
Propagating Waves Transverse to the Magnetic Field in a Solar Prominence
We report an unusual set of observations of waves in a large prominence
pillar which consist of pulses propagating perpendicular to the prominence
magnetic field. We observe a huge quiescent prominence with the Solar Dynamics
Observatory (SDO) Atmospheric Imaging Assembly (AIA) in EUV on 2012 October 10
and only a part of it, the pillar, which is a foot or barb of the prominence,
with the Hinode Solar Optical Telescope (SOT) (in Ca II and H\alpha lines), Sac
Peak (in H\alpha, H\beta\ and Na-D lines), THEMIS ("T\'elescope
H\'eliographique pour l' Etude du Magn\'etisme et des Instabilit\'es Solaires")
with the MTR (MulTi-Raies) spectropolarimeter (in He D_3 line). The THEMIS/MTR
data indicates that the magnetic field in the pillar is essentially horizontal
and the observations in the optical domain show a large number of horizontally
aligned features on a much smaller scale than the pillar as a whole. The data
is consistent with a model of cool prominence plasma trapped in the dips of
horizontal field lines. The SOT and Sac Peak data over the 4 hour observing
period show vertical oscillations appearing as wave pulses. These pulses, which
include a Doppler signature, move vertically, perpendicular to the field
direction, along thin quasi-vertical columns in the much broader pillar. The
pulses have a velocity of propagation of about 10 km/s, a period about 300 sec,
and a wavelength around 2000 km. We interpret these waves in terms of fast
magneto-sonic waves and discuss possible wave drivers.Comment: Accepted for publication in The Astrophysical Journa
Supergravity dressing of beta-functions in N=1 and N=2 supersymmetric models
We discuss the dressing of one-loop sigma-model beta-functions by induced
supergravity, for both N=1 and N=2 supersymmetric theories. We obtain exact
results by a superconformal gauge argument, and verify them in the
semi-classical limit by explicit perturbative calculations in the light-cone
gauge. We find that for N=2 theories there is no dressing of the one-loop
beta-functions.Comment: 10 pages, latex, macros included, 2 figures in figures.u
On the mass spectrum of the two-dimensional O(3) sigma model with theta term
Form Factor Perturbation Theory is applied to study the spectrum of the O(3)
non--linear sigma model with the topological term in the vicinity of . Its effective action near this value is given by the non--integrable
double Sine--Gordon model. Using previous results by Affleck and the explicit
expressions of the Form Factors of the exponential operators , we show that the spectrum consists of a stable triplet
of massive particles for all values of and a singlet state of higher
mass. The singlet is a stable particle only in an interval of values of
close to whereas it becomes a resonance below a critical value
.Comment: 4 pages REVTEX4, 2 figures reference added,corrected typo
Renormalization of the Topological Charge in Yang-Mills Theory
The conditions leading to a nontrivial renormalization of the topological
charge in four--dimensional Yang--Mills theory are discussed. It is shown that
if the topological term is regarded as the limit of a certain nontopological
interaction, quantum effects due to the gauge bosons lead to a finite
multiplicative renormalization of the theta--parameter while fermions give rise
to an additional shift of theta. A truncated form of an exact renormalization
group equation is used to study the scale dependence of the theta--parameter.
Possible implications for the strong CP--problem of QCD are discussed.Comment: 31 pages, late
Area-preserving Structure and Anomalies in 1+1-dimensional Quantum Gravity
We investigate the gauge-independent Hamiltonian formulation and the
anomalous Ward identities of a matter-induced 1+1-dimensional gravity theory
invariant under Weyl transformations and area-preserving diffeomorphisms, and
compare the results to the ones for the conventional diffeomorphism-invariant
theory. We find that, in spite of several technical differences encountered in
the analysis, the two theories are essentially equivalent.Comment: 9 pages, LaTe
correction to free energy in hermitian two-matrix model
Using the loop equations we find an explicit expression for genus 1
correction in hermitian two-matrix model in terms of holomorphic objects
associated to spectral curve arising in large N limit. Our result generalises
known expression for in hermitian one-matrix model. We discuss the
relationship between , Bergmann tau-function on Hurwitz spaces, G-function
of Frobenius manifolds and determinant of Laplacian over spectral curve
The Crumpling Transition Revisited
The ``crumpling" transition, between rigid and crumpled surfaces, has been
object of much discussion over the past years. The common lore is that such
transition should be of second order. However, some lattice versions of the
rigidity term on fixed connectivity surfaces seem to suggest that the
transition is of higher order instead. While some models exhibit what appear to
be lattice artifacts, others are really indistiguishable from models where
second order transitions have been reported and yet appear to have third order
transitions.Comment: Contribution to Lattice 92. 4 pages. espcrc2.sty file included. 6
figures upon request. UB-ECM-92/30 and UAB-FT-29
Branched polymers, complex spins and the freezing transition
We show that by coupling complex three-state systems to branched-polymer like
ensembles we can obtain models with gamma-string different from one half. It is
also possible to study the interpolation between dynamical and crystalline
graphs for these models; we find that only when geometry fluctuations are
completely forbidden is there a crystalline phase.Comment: 14 pages plain LateX2e, 4 eps figures included using eps
Universality in Two Dimensional Gauge Theory.
We discuss two dimensional Yang -- Mills theories with massless fermions in
arbitrary representations of a gauge group . It is shown that the physics
(spectrum and interactions) of the massive states in such models is independent
of the detailed structure of the model, and only depends on the gauge group
and an integer measuring the total anomaly. The massless physics, which
does depend on the details of the model, decouples (almost) completely from
that of the massive one. As an example, we discuss the equivalence of QCD
coupled to fermions in the adjoint, and fundamental representations.Comment: 16 pages, harvma
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