1,138 research outputs found
Finite-Size Effect of Hadron Masses with Kogut-Susskind Quarks
We present numerical results and their analyses of finite-size effects of
hadron masses for both quenched and full QCD calculations. We show that they
are much larger for full QCD due to dynamical sea quarks and the associated
breaking of symmetry. We also argue that finite-size effects are
non-negligible even for the largest lattice size simulation currently being
made for a very small quark mass. (talk at lattice93)Comment: 4 pages, compressed, uuencoded PostScript file(name:lat93.ps.Z
Two-Flavor Chiral Phase Transition in Lattice QCD with the Kogut-Susskind Quark Action
A summary is presented of a scaling study of the finite-temperature chiral
phase transition of two-flavor QCD with the Kogut-Susskind quark action based
on simulations on (=8, 12 and 16) lattices at the quark mass of
and 0.01. We find a phase transition to be absent for
, and also quite likely at . The quark mass dependence
of susceptibilities is consistent with a second-order transition at .
The exponents, however, deviate from the O(2) and O(4) values theoretically
expected.Comment: 3 pages, Latex(espcrc2,epsf), 3 ps figures, Poster presented at
Lattice 9
Charmonium spectroscopy with heavy Kogut-Susskind quarks
Charmonium spectroscopy with Kogut-Susskind valence quarks are carried out
for quenched QCD at and for two-flavor full QCD at .
Results for 1P--1S mass splitting and estimates of
are reported. Problems associated with
flavor breaking effects and finite size effects of states are discussed.Comment: 3 pages, contribution to the Lattice '94 conference, uuencoded
compressed ps-fil
Sea Quark Effects on the Strong Coupling Constant
We present results showing that the strong coupling constant measured in
two-flavor full QCD with dynamical Kogut-Susskind quarks at exhibit
a 15\% increase due to sea quarks over that for quenched QCD at the scale
GeV . (talk at lattice93)Comment: 3 pages, compressed, uuencoded PostScript file(name:lat93ch.ps.Z
I=2 Pion Scattering Length with Wilson Fermions
We present results for I=2 pion scattering length with the Wilson fermions in
the quenched approximation. The finite size method presented by L\"uscher is
employed, and calculations are carried out at , 6.1, and 6.3. In the
continuum limit, we obtain a result in reasonable agreement with the
experimental value.Comment: LATTICE99(matrixelement), 3 pages, 4 eps figure
Unusually Large Fluctuations in the Statistics of Galaxy Formation at High Redshift
We show that various milestones of high-redshift galaxy formation, such as
the formation of the first stars or the complete reionization of the
intergalactic medium, occurred at different times in different regions of the
universe. The predicted spread in redshift, caused by large-scale fluctuations
in the number density of galaxies, is at least an order of magnitude larger
than previous expectations that argued for a sharp end to reionization. This
cosmic scatter in the abundance of galaxies introduces new features that affect
the nature of reionization and the expectations for future probes of
reionization, and may help explain the present properties of dwarf galaxies in
different environments. The predictions can be tested by future numerical
simulations and may be verified by upcoming observations. Current simulations,
limited to relatively small volumes and periodic boundary conditions, largely
omit cosmic scatter and its consequences. In particular, they artificially
produce a sudden end to reionization, and they underestimate the number of
galaxies by up to an order of magnitude at redshift 20.Comment: 8 ApJ pages, 4 figures, ApJ. Minor changes in revised version.
Originally first submitted for publication on Aug. 29, 200
Galaxy types in the Sloan Digital Sky Survey using supervised artificial neural networks
Supervised artificial neural networks are used to predict useful properties of galaxies in the Sloan Digital Sky Survey, in this instance morphological classifications, spectral types and redshifts. By giving the trained networks unseen data, it is found that correlations between predicted and actual properties are around 0.9 with rms errors of order ten per cent. Thus, given a representative training set, these properties may be reliably estimated for galaxies in the survey for which there are no spectra and without human intervention
Detecting z > 10 objects through carbon, nitrogen and oxygen emission lines
By redshift of 10, star formation in the first objects should have produced
considerable amounts of Carbon, Nitrogen and Oxygen. The submillimeter lines of
C, N and O redshift into the millimeter and centimeter bands (0.5 mm -- 1.2
cm), where they may be detectable. High spectral resolution observations could
potentially detect inhomogeneities in C, N and O emission, and see the first
objects forming at high redshift. We calculate expected intensity fluctuations
and discuss frequency and angular resolution required to detect them. For CII
emission, we estimate the intensity using two independent methods: the line
emission coefficient argument and the luminosity density argument. We find they
are in good agreement. At 1+z \sim 10, the typical protogalaxy has a velocity
dispersion of 30 km s^{-1} and angular size of 1 arcsecond. If CII is the
dominant coolant, then we estimate a characteristic line strength of \sim 0.1 K
km s^{-1}. We also discuss other atomic lines and estimate their signal.
Observations with angular resolution of 10^{-3} can detect moderately nonlinear
fluctuations of amplitude 2 \cdot 10^{-5} times the microwave background. If
the intensity fluctuations are detected, they will probe matter density
inhomogeneity, chemical evolution and ionization history at high redshifts.Comment: 15 pages, 1 postscript figures included; Uses aaspp4.sty (AASTeX
v4.0); Submitted to The Astrophysical Journa
Metal Abundance in the Solar Interior
It is shown that the metal abundance in the solar interior is constrained
from the current solar neutrino experiment, even if one allows neutrino
conversion in the sun due to neutrino oscillation. The result shows that the
metal abundance in the interior should be within the range 0.4 - 1.4 times that
in the surface, supporting the idea that the sun formed by a contraction of a
gas cloud with an almost homogeneous composition.Comment: 7 pages including 4 postscript figures, uses AAS LaTex v4.0, entire
ps file and html file with embedded figures available at
http://www.sns.ias.edu/~hata/papers/metal
- …