544 research outputs found
Correlation lengths and E_8 mass spectrum of the dilute A_3 lattice model
The exact perturbation approach is used to derive the elementary correlation
lengths and related mass gaps of the two-dimensional dilute A_L
lattice model in regimes 1 and 2 for L odd from the Bethe Ansatz solution. In
regime 2 the A_3 model is the E_8 lattice realisation of the two-dimensional
Ising model in a magnetic field at T=T_c. The calculations for the A_3 model in
regime 2 start from the eight thermodynamically significant string types found
in previous numerical studies. These string types are seen to be consistent in
the ordered high field limit. The eight masses obtained reduce with the
approach to criticality to the E_8 masses predicted by Zamolodchikov, thus
providing a further direct lattice determination of the E_8 mass spectrum.Comment: 57 pages, Latex, Elsevier style file
Universal amplitude ratios and Coxeter geometry in the dilute A model
The leading excitations of the dilute model in regime 2 are considered
using analytic arguments. The model can be identified with the integrable
perturbation of the unitary minimal series . It is
demonstrated that the excitation spectrum of the transfer matrix satisfies the
same functional equations in terms of elliptic functions as the exact
S-matrices of the perturbation do in terms of trigonometric
functions. In particular, the bootstrap equation corresponding to a self-fusing
process is recovered. For the special cases corresponding to the
Ising model in a magnetic field, and the leading thermal perturbations of the
tricritical Ising and three-state Potts model, as well as for the unrestricted
model, , we relate the structure of the Bethe roots to the Lie
algebras and using Coxeter geometry. In these cases Coxeter
geometry also allows for a single formula in generic Lie algebraic terms
describing all four cases. For general we calculate the spectral gaps
associated with the leading excitation which allows us to compute universal
amplitude ratios characteristic of the universality class. The ratios are of
field theoretic importance as they enter the bulk vacuum expectation value of
the energy momentum tensor associated with the corresponding integrable quantum
field theories.Comment: 32 pages (tcilatex
Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering
We have measured the beam-normal single-spin asymmetry in elastic scattering
of transversely-polarized 3 GeV electrons from unpolarized protons at Q^2 =
0.15, 0.25 (GeV/c)^2. The results are inconsistent with calculations solely
using the elastic nucleon intermediate state, and generally agree with
calculations with significant inelastic hadronic intermediate state
contributions. A_n provides a direct probe of the imaginary component of the
2-gamma exchange amplitude, the complete description of which is important in
the interpretation of data from precision electron-scattering experiments.Comment: 5 pages, 3 figures, submitted to Physical Review Letters; shortened
to meet PRL length limit, clarified some text after referee's comment
Strange Quark Contributions to Parity-Violating Asymmetries in the Forward G0 Electron-Proton Scattering Experiment
We have measured parity-violating asymmetries in elastic electron-proton
scattering over the range of momentum transfers 0.12 < Q^2 < 1.0 GeV^2. These
asymmetries, arising from interference of the electromagnetic and neutral weak
interactions, are sensitive to strange quark contributions to the currents of
the proton. The measurements were made at JLab using a toroidal spectrometer to
detect the recoiling protons from a liquid hydrogen target. The results
indicate non-zero, Q^2 dependent, strange quark contributions and provide new
information beyond that obtained in previous experiments.Comment: 5 pages, 2 figure
Menus for Feeding Black Holes
Black holes are the ultimate prisons of the Universe, regions of spacetime
where the enormous gravity prohibits matter or even light to escape to
infinity. Yet, matter falling toward the black holes may shine spectacularly,
generating the strongest source of radiation. These sources provide us with
astrophysical laboratories of extreme physical conditions that cannot be
realized on Earth. This chapter offers a review of the basic menus for feeding
matter onto black holes and discusses their observational implications.Comment: 27 pages. Accepted for publication in Space Science Reviews. Also to
appear in hard cover in the Space Sciences Series of ISSI "The Physics of
Accretion onto Black Holes" (Springer Publisher
The G0 Experiment: Apparatus for Parity-Violating Electron Scattering Measurements at Forward and Backward Angles
In the G0 experiment, performed at Jefferson Lab, the parity-violating
elastic scattering of electrons from protons and quasi-elastic scattering from
deuterons is measured in order to determine the neutral weak currents of the
nucleon. Asymmetries as small as 1 part per million in the scattering of a
polarized electron beam are determined using a dedicated apparatus. It consists
of specialized beam-monitoring and control systems, a cryogenic hydrogen (or
deuterium) target, and a superconducting, toroidal magnetic spectrometer
equipped with plastic scintillation and aerogel Cerenkov detectors, as well as
fast readout electronics for the measurement of individual events. The overall
design and performance of this experimental system is discussed.Comment: Submitted to Nuclear Instruments and Method
Exact results for topological strings on resolved Y(p,q) singularities
We obtain exact results in \alpha' for open and closed A-model topological
string amplitudes on a large class of toric Calabi-Yau threefolds by using
their correspondence with five dimensional gauge theories. The toric
Calabi-Yau's that we analyze are obtained as minimal resolution of cones over
Y(p,q) manifolds and give rise via M-theory compactification to SU(p) gauge
theories on R^4 x S^1. As an application we present a detailed study of the
local F_2 case and compute open and closed genus zero Gromov-Witten invariants
of the C^3/Z_4 orbifold. We also display the modular structure of the
topological wave function and give predictions for higher genus amplitudes.The
mirror curve in this case is the spectral curve of the relativistic A_1 Toda
chain. Our results also indicate the existence of a wider class of relativistic
integrable systems associated to generic Y(p,q) geometries.Comment: 54 pages, 10 figures; typos corrected, new section added. Version
accepted for publication on Communications in Mathematical Physic
A theoretical framework and research agenda for studying team attributions in sport
The attributions made for group outcomes have attracted a great deal of interest in recent years. In this article we bring together much of the current research on attribution theory in sport and outline a new conceptual framework and research agenda for investigating the attributions of team members. The proposed framework draws on multiple conceptual approaches including models of attribution, group dynamics and stress responses to provide a detailed hypothetical description of athletes' physiological, cognitive and affective responses to group competition. In describing this model we outline important antecedents of team attributions before hypothesising how attributions can impact hormonal and cardiovascular responses of athletes, together with cognitive (goals, choices, expectations), affective (self-esteem, emotions), and behavioural (approach-avoidance actions) responses of groups and group members. We conclude by outlining important methodological considerations and implications for structured context specific attribution-based interventions
Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS
We present the results of a search for new, heavy particles that decay at a
significant distance from their production point into a final state containing
charged hadrons in association with a high-momentum muon. The search is
conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV
and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS
detector operating at the Large Hadron Collider. Production of such particles
is expected in various scenarios of physics beyond the standard model. We
observe no signal and place limits on the production cross-section of
supersymmetric particles in an R-parity-violating scenario as a function of the
neutralino lifetime. Limits are presented for different squark and neutralino
masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final
version to appear in Physics Letters
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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