1,664 research outputs found
Dimer statistics on the M\"obius strip and the Klein bottle
Closed-form expressions are obtained for the generating function of
close-packed dimers on a simple quartic lattice embedded on a
M\"obius strip and a Klein bottle. Finite-size corrections are also analyzed
and compared with those under cylindrical and free boundary conditions.
Particularly, it is found that, for large lattices of the same size and with a
square symmetry, the number of dimer configurations on a M\"obius strip is
70.2% of that on a cylinder. We also establish two identities relating dimer
generating functions for M\"obius strips and cylinders.Comment: 12 pages, 2 figs included, accepted by Phys. Lett.
Ising model on nonorientable surfaces: Exact solution for the Moebius strip and the Klein bottle
Closed-form expressions are obtained for the partition function of the Ising
model on an M x N simple-quartic lattice embedded on a Moebius strip and a
Klein bottle for finite M and N. The finite-size effects at criticality are
analyzed and compared with those under cylindrical and toroidal boundary
conditions. Our analysis confirms that the central charge is c=1/2.Comment: 8 pages, 3 eps figure
Stability of NLO Global Analysis and Implications for Hadron Collider Physics
The phenomenology of Standard Model and New Physics at hadron colliders
depends critically on results from global QCD analysis for parton distribution
functions (PDFs). The accuracy of the standard next-to-leading-order (NLO)
global analysis, nominally a few percent, is generally well matched to the
expected experimental precision. However, serious questions have been raised
recently about the stability of the NLO analysis with respect to certain
inputs, including the choice of kinematic cuts on the data sets and the
parametrization of the gluon distribution. In this paper, we investigate this
stability issue systematically within the CTEQ framework. We find that both the
PDFs and their physical predictions are stable, well within the few percent
level. Further, we have applied the Lagrange Multiplier method to explore the
stability of the predicted cross sections for W production at the Tevatron and
the LHC, since W production is often proposed as a standard candle for these
colliders. We find the NLO predictions on sigma_W to be stable well within
their previously-estimated uncertainty ranges.Comment: 24 pages, 11 figures. Minor changes in response to JHEP referee
repor
Ambient Isotopic Meshing of Implicit Algebraic Surface with Singularities
A complete method is proposed to compute a certified, or ambient isotopic,
meshing for an implicit algebraic surface with singularities. By certified, we
mean a meshing with correct topology and any given geometric precision. We
propose a symbolic-numeric method to compute a certified meshing for the
surface inside a box containing singularities and use a modified
Plantinga-Vegter marching cube method to compute a certified meshing for the
surface inside a box without singularities. Nontrivial examples are given to
show the effectiveness of the algorithm. To our knowledge, this is the first
method to compute a certified meshing for surfaces with singularities.Comment: 34 pages, 17 Postscript figure
Gauge Orbit Types for Theories with Classical Compact Gauge Group
We determine the orbit types of the action of the group of local gauge
transformations on the space of connections in a principal bundle with
structure group O(n), SO(n) or over a closed, simply connected manifold
of dimension 4. Complemented with earlier results on U(n) and SU(n) this
completes the classification of the orbit types for all classical compact gauge
groups over such space-time manifolds. On the way we derive the classification
of principal bundles with structure group SO(n) over these manifolds and the
Howe subgroups of SO(n).Comment: 57 page
The Strange Parton Distribution of the Nucleon: Global Analysis and Applications
The strangeness degrees of freedom in the parton structure of the nucleon are
explored in the global analysis framework, using the new CTEQ6.5 implementation
of the general mass perturbative QCD formalism of Collins. We systematically
determine the constraining power of available hard scattering experimental data
on the magnitude and shape of the strange quark and anti-quark parton
distributions. We find that current data favor a distinct shape of the strange
sea compared to the isoscalar non-strange sea. A new reference parton
distribution set, CTEQ6.5S0, and representative sets spanning the allowed
ranges of magnitude and shape of the strange distributions, are presented. Some
applications to physical processes of current interest in hadron collider
phenomenology are discussed.Comment: 19 pages; revised version submitted to JHE
Photonuclear reactions of actinides in the giant dipole resonance region
Photonuclear reactions at energies covering the giant dipole resonance (GDR)
region are analyzed with an approach based on nuclear photoabsorption followed
by the process of competition between light particle evaporation and fission
for the excited nucleus. The photoabsorption cross section at energies covering
the GDR region is contributed by both the Lorentz type GDR cross section and
the quasideuteron cross section. The evaporation-fission process of the
compound nucleus is simulated in a Monte-Carlo framework. Photofission reaction
cross sections are analyzed in a systematic manner in the energy range of
10-20 MeV for the actinides Th, U and Np.
Photonuclear cross sections for the medium-mass nuclei Cu and Zn,
for which there are no fission events, are also presented. The study reproduces
satisfactorily the available experimental data of photofission cross sections
at GDR energy region and the increasing trend of nuclear fissility with the
fissility parameter for the actinides.Comment: 4 pages including 2 tables and 1 figur
Magnetization distribution in the transverse Ising chain with energy flux
The zero-temperature transverse Ising chain carrying an energy flux j_E is
studied with the aim of determining the nonequilibrium distribution functions,
P(M_z) and P(M_x), of its transverse and longitudinal magnetizations,
respectively. An exact calculation reveals that P(M_z) is a Gaussian both at
j_E=0 and j_E not equal 0, and the width of the distribution decreases with
increasing energy flux. The distribution of the order-parameter fluctuations,
P(M_x), is evaluated numerically for spin-chains of up to 20 spins. For the
equilibrium case (j_E=0), we find the expected Gaussian fluctuations away from
the critical point while the critical order-parameter fluctuations are shown to
be non-gaussian with a scaling function Phi(x)=Phi(M_x/)=P(M_x)
strongly dependent on the boundary conditions. When j_E not equal 0, the system
displays long-range, oscillating correlations but P(M_x) is a Gaussian
nevertheless, and the width of the Gaussian decreases with increasing j_E. In
particular, we find that, at critical transverse field, the width has a
j_E^(-3/8) asymptotic in the j_E -> 0 limit.Comment: 8 pages, 5 ps figure
Structure of the Partition Function and Transfer Matrices for the Potts Model in a Magnetic Field on Lattice Strips
We determine the general structure of the partition function of the -state
Potts model in an external magnetic field, for arbitrary ,
temperature variable , and magnetic field variable , on cyclic, M\"obius,
and free strip graphs of the square (sq), triangular (tri), and honeycomb
(hc) lattices with width and arbitrarily great length . For the
cyclic case we prove that the partition function has the form ,
where denotes the lattice type, are specified
polynomials of degree in , is the corresponding
transfer matrix, and () for ,
respectively. An analogous formula is given for M\"obius strips, while only
appears for free strips. We exhibit a method for
calculating for arbitrary and give illustrative
examples. Explicit results for arbitrary are presented for
with and . We find very simple formulas
for the determinant . We also give results for
self-dual cyclic strips of the square lattice.Comment: Reference added to a relevant paper by F. Y. W
Transfer Matrices and Partition-Function Zeros for Antiferromagnetic Potts Models. V. Further Results for the Square-Lattice Chromatic Polynomial
We derive some new structural results for the transfer matrix of
square-lattice Potts models with free and cylindrical boundary conditions. In
particular, we obtain explicit closed-form expressions for the dominant (at
large |q|) diagonal entry in the transfer matrix, for arbitrary widths m, as
the solution of a special one-dimensional polymer model. We also obtain the
large-q expansion of the bulk and surface (resp. corner) free energies for the
zero-temperature antiferromagnet (= chromatic polynomial) through order q^{-47}
(resp. q^{-46}). Finally, we compute chromatic roots for strips of widths 9 <=
m <= 12 with free boundary conditions and locate roughly the limiting curves.Comment: 111 pages (LaTeX2e). Includes tex file, three sty files, and 19
Postscript figures. Also included are Mathematica files data_CYL.m and
data_FREE.m. Many changes from version 1: new material on series expansions
and their analysis, and several proofs of previously conjectured results.
Final version to be published in J. Stat. Phy
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