386,235 research outputs found
A Note on Circle Compactification of Tensile Ambitwistor String
We discuss a number of problems associated with the circle compactification
of the bosonic tensile ambitwistor string with the asymmetric vacuum choice. By
considering the spectrum and physical state conditions, we show that the circle
radius plays a role as a tuning parameter which determines the low energy
effective field theory. At the self dual point, we construct the current
operators and compute OPEs between them. While the final outcome remains as yet
inconclusive, several new results are obtained. Through the current algebra
analysis we show that there is a subsector of the massless states where the
gauge symmetry is enhanced to . Using the fact that the
one loop partition function is not modular invariant, we show that tensile
ambitwistor string partition function is exactly the same as a field theory
partition function. Our result proves that despite the existence of winding
modes, which is a typical characteristic of a string, the tensile ambitwistor
string behaves as a point particle theory.Comment: 31 pages, v2: minor corrections, reference added, published in
Nucl.Phys.
Formalism for the Subhalo Mass Function in the Tidal-limit Approximation
We present a theoretical formalism by which the global and the local mass
functions of dark matter substructures (dark subhalos) can be analytically
estimated. The global subhalo mass function is defined to give the total number
density of dark subhalos in the universe as a function of mass, while the local
subhalo mass function counts only those subhalos included in one individual
host halo. We develop our formalism by modifying the Press-Schechter theory to
incorporate the followings: (i) the internal structure of dark halos; (ii) the
correlations between the halos and the subhalos; (iii) the subhalo mass-loss
effect driven by the tidal forces. We find that the resulting (cumulative)
subhalo mass function is close to a power law with the slope of ~ -1, that the
subhalos contribute approximately 10 % of the total mass, and that the tidal
stripping effect changes the subhalo mass function self-similarly, all
consistent with recent numerical detections.Comment: revised version, accepted by ApJ Letters, estimate of the local
subhalo mass function included, 10 pages, 1 figur
Liquid-Gas Phase Transition in Nuclear Equation of State
A canonical ensemble model is used to describe a caloric curve of nuclear
liquid-gas phase transition. Allowing a discontinuity in the freeze out density
from one spinodal density to another for a given initial temperature, the
nuclear liquid-gas phase transition can be described as first order. Averaging
over various freeze out densities of all the possible initial temperatures for
a given total reaction energy, the first order characteristics of liquid-gas
phase transition is smeared out to a smooth transition. Two experiments, one at
low beam energy and one at high beam energy show different caloric behaviors
and are discussed.Comment: 12 pages in Revtex including two Postscript figure
Quantitative absorption and fluorescence studies of NO between 1060 and 2000 A
Synchrotron radiation in the 1060 to 2000 A region was used to measure the average absorption and fluorescence cross sections of NO and to determine approximate photodissociation quantum yields. Several vibrational levels of the D(2) sigma(+), E(2) sigma(+), and B(2) delta states have high fluorescence quantum yields. The C(2) and B(2) states do not fluoresce when the excitation energies are above the first dissociation limit, in accord with previous experiments. In general, the fluorescence yields decrease with increasing photon energy. The quantitative measurements are compared with spectroscopic observations and are found to be reasonably consistent
AUTOTEM - Automated geometry meshing and heat conduction calculation
Temperature distribution for an arbitrary irregular body is calculated by AUTOTEM, which generates required input data automatically by computer. Temperature distribution is calculated for a two-dimensional plane section in /x,y/ coordinates or for an axisymmetric irregular body in /r,z/ coordinates
Mechanism for Surface Waves in Vibrated Granular Material
We use molecular dynamics simulations to study the formation of surface waves
in vertically vibrated granular material. We find that horizontal movements of
particles, which are essential for the formation of the waves, consist of two
distinct processes. First, the movements sharply increase while the particles
are colliding with a bottom plate, where the duration of the collisions is very
short compared to the period of the vibration. Next, the movements gradually
decrease between the collisions, during which the particles move through the
material. We also find that the horizontal velocity field after the collisions
is strongly correlated to the surface profile before the collisions.Comment: 6 pages, 3 figures (included
Bayesian threshold selection for extremal models using measures of surprise
Statistical extreme value theory is concerned with the use of asymptotically
motivated models to describe the extreme values of a process. A number of
commonly used models are valid for observed data that exceed some high
threshold. However, in practice a suitable threshold is unknown and must be
determined for each analysis. While there are many threshold selection methods
for univariate extremes, there are relatively few that can be applied in the
multivariate setting. In addition, there are only a few Bayesian-based methods,
which are naturally attractive in the modelling of extremes due to data
scarcity. The use of Bayesian measures of surprise to determine suitable
thresholds for extreme value models is proposed. Such measures quantify the
level of support for the proposed extremal model and threshold, without the
need to specify any model alternatives. This approach is easily implemented for
both univariate and multivariate extremes.Comment: To appear in Computational Statistics and Data Analysi
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