3,271 research outputs found
Small coupling limit and multiple solutions to the Dirichlet Problem for Yang Mills connections in 4 dimensions - Part I
In this paper (Part I) and its sequels (Part II and Part III), we analyze the
structure of the space of solutions to the epsilon-Dirichlet problem for the
Yang-Mills equations on the 4-dimensional disk, for small values of the
coupling constant epsilon. These are in one-to-one correspondence with
solutions to the Dirichlet problem for the Yang Mills equations, for small
boundary data. We prove the existence of multiple solutions, and, in
particular, non minimal ones, and establish a Morse Theory for this non-compact
variational problem. In part I, we describe the problem, state the main
theorems and do the first part of the proof. This consists in transforming the
problem into a finite dimensional problem, by seeking solutions that are
approximated by the connected sum of a minimal solution with an instanton, plus
a correction term due to the boundary. An auxiliary equation is introduced that
allows us to solve the problem orthogonally to the tangent space to the space
of approximate solutions. In Part II, the finite dimensional problem is solved
via the Ljusternik-Schirelman theory, and the existence proofs are completed.
In Part III, we prove that the space of gauge equivalence classes of Sobolev
connections with prescribed boundary value is a smooth manifold, as well as
some technical lemmas used in Part I. The methods employed still work when the
4-dimensional disk is replaced by a more general compact manifold with
boundary, and SU(2) is replaced by any compact Lie group
Finite Temperature Effects in One-dimensional Mott-Hubbard Insulator: Angle-Resolved Photoemission Study of Na_{0.96}V_{2}O_{5}
We have made an angle-resolved photoemission study of a one-dimensional (1D)
Mott-Hubbard insulator Na_{0.96}V_{2}O_{5} and found that the spectra of the V
3d lower Hubbard band are strongly dependent on the temperature. We have
calculated the one-particle spectral function of the one-dimensional t-J model
at finite temperatures by exact diagonalization and compared them with the
experimental results. Good overall agreement is obtained between experiment and
theory. The strong finite temperature effects are discussed in terms of the
existence of the ``Fermi surface'' of the spinon band.Comment: 4 pages, 3 figure
A one dimensional model for the prediction of extraction yields in a two phases modified twin-screw extruder
Solid/liquid extraction is performed on raw plant substrate with a modified twin-screw extruder (TSE) used as a thermo-mecanochemical reactor. Visual observations and experimental residence time distributions (RTD) are used to develop a solid transport model based on classical chemical engineering method. Modeled and experimental residence times are compared. The transport model is then coupled with a reactive extraction model in order to predict extraction yields
An estimate of the cross-frontal transport at the shelf break of the East China Sea with the Finite Volume Coastal Ocean Model
Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): C03012, doi:10.1029/2005JC003290.The Finite Volume Coastal Ocean Model (FVCOM) is used to estimate the onshore cross-frontal transport at the shelf break of the East China Sea. Boundary conditions of FVCOM are provided by the Princeton Ocean Model simulating ocean currents in the Yellow Sea and East China Sea realistically. One advantage of this study is that the unstructured triangular cell grid of FVCOM resolves complex bottom topography that may trigger Kuroshio frontal waves. It is anticipated that these nonlinear frontal waves enhance the exchange of seawater between the Kuroshio and shelf regions. Kuroshio frontal waves in the model are excited around the location where the bottom slope changes abruptly, and have the phase speed and amplitude consistent with those observed in the East China Sea. In addition, the model reproduces the onshore transport associated with growing frontal waves in the upper and lower layers. On the basis of passive tracer experiments, the annually averaged onshore-transport integrated along the shelf break is estimated to be 0.85 × 106 m3/s.This study was carried out when A. I. stayed at WHOI with the grant of Overseas Advanced Educational Research Practice Support Program supported by the Ministry of Education, Science and Culture, Japan. In addition, the Japan Society for the Promotion of Science supported this study through Grant-in-Aid for Scientific Research
Effects of Velocity Correlation on Early Stage of Free Cooling Process of Inelastic Hard Sphere System
The free cooling process in the inelastic hard sphere system is studied by
analysing the data from large scale molecular dynamics simulations on a three
dimensional system. The initial energy decay, the velocity distribution
function, and the velocity correlation functions are calculated to be compared
with theoretical predictions. The energy decay rate in the homogeneous cooling
state is slightly but distinctively smaller than that expected from the
independent collision assumption. The form of the one particle velocity
distribution is found not to be stationary. These contradict to the predictions
of the kinetic theory based on the Enskog-Boltzmann equation and suggest that
the velocity correlation is already important in the early stage of homogeneous
cooling state. The energy decay rate is analysed in terms of the velocity
correlation.Comment: 9 pages (figures included). To be published in J. Phys. Soc. Jpn.
Vol. 73 No. 1 (2004) Added two references and removed one. Changed the name
of T_{L}. Added unit constants in Sec. 5 and
Hard-disk equation of state: First-order liquid-hexatic transition in two dimensions with three simulation methods
We report large-scale computer simulations of the hard-disk system at high
densities in the region of the melting transition. Our simulations reproduce
the equation of state, previously obtained using the event-chain Monte Carlo
algorithm, with a massively parallel implementation of the local Monte Carlo
method and with event-driven molecular dynamics. We analyze the relative
performance of these simulation methods to sample configuration space and
approach equilibrium. Our results confirm the first-order nature of the melting
phase transition in hard disks. Phase coexistence is visualized for individual
configurations via the orientational order parameter field. The analysis of
positional order confirms the existence of the hexatic phase.Comment: 9 pages, 8 figures, 2 table
Charge-ordering and optical transitions of LiV2O5 and NaV2O5
We present the measurements of the polarized optical spectra of NaV2O5 and
LiV2O5. In an energy range from 0.5 to 5.5 eV we observe similar peaks in the E
parallel a spectra of LiV2O5 and NaV2O5, which suggests similar electronic
structure along the a axis in both materials. On the other hand, we find an
almost complete suppression of the peaks in sigma_b of LiV2O5 around 1 and 5
eV. We attribute this suppression to the charge localization originating from
the existence of double-chain charge-ordering patterin in LiV2O5.Comment: 7 pages, 3 figures final version, to appear in PR
Optical properties of NaxV2O5
The optical properties of sodium-deficient NaxV2O5 (0.85 < x <1) single
crystals are analyzed in the wide energy range, from 0.012 to 4.5 eV, using
ellipsometry, infrared reflectivity, and Raman scattering techniques. The
material remains insulating up to the maximal achieved hole concentration of
about 15%. In sodium deficient samples the optical absorption peak associated
to the fundamental electronic gap develops at about 0.44 eV. It corresponds to
the transition between vanadium dxy and the impurity band, which forms in the
middle of the pure NaV2O5 gap. Raman spectra measured with incident photon
energy larger then 2 eV show strong resonant behavior, due to the presence of
the hole-doping activated optical transitions, peaked at 2.8 eV.Comment: 7 pages, 4 fugures, to be published in PR
Discovery of a bright transient ultraluminous X-ray source Suzaku J1305-4931 in NGC 4945
This paper reports the discovery of a bright X-ray transient source, Suzaku
J1305-4913, in the south-west arm of the nearby Seyfert II galaxy NGC 4945. It
was detected at a 0.5 -- 10 keV flux of erg cm
s during the Suzaku observation conducted on 2006 January 15 -- 17, but
was undetectable in a shorter observation on 2005 August 22 --23, with an upper
limit of erg cm s (90% confidence level).
At a distance of 3.7 Mpc, the bolometric luminosity of the source becomes
erg s, where and is the disk inclination. Therefore, the source is
classified into so-called ultraluminous X-ray sources (ULXs). The time-averaged
X-ray spectrum of the source is described by a multi-color disk model, with the
innermost accretion disk temperature of
keV. During the 2006 January observation, it varied by a factor of 2 in
intensity, following a clear correlation of .
It is inferred that the innermost disk radius stayed constant at
km, suggesting the presence of a
standard accretion disk. Relating with the last stable orbit
around a non-rotating black hole yields a rather low black hole mass, solar masses, which would imply that the source is shining at a
luminosity of times the Eddington limit. These results
can be better interpreted by invoking sub-Eddington emission from a rapidly
spinning black hole with a mass of 20 -- 130 solar masses.Comment: 21 pages, 10 figures, Accepted for PASJ 2nd Suzaku special issu
A Search for Active Galactic Nuclei in Sc Galaxies with H II Spectra
(Abridged) We have searched for nuclear radio emission from a statistically
complete sample of 40 Sc galaxies within 30 Mpc that are optically classified
as star-forming objects, in order to determine whether weak AGNs might be
present. Only three nuclear radio sources were detected, in NGC 864, NGC 4123,
and NGC 4535. These galaxies have peak 6-cm radio powers of 10^{20} W/Hz at
arcsecond resolution, while upper limits of the non-detected galaxies typically
range from 10^{18.4} to 10^{20} W/Hz. The three nuclear radio sources all are
resolved and appear to have diffuse morphologies, with linear sizes of ~300 pc.
This strongly indicates that circumnuclear star formation has been detected in
these three H II galaxies. Comparison with previous 20-cm VLA results for the
detected galaxies shows that the extended nuclear radio emission has a flat
spectrum in two objects, and almost certainly is generated by thermal emission
from gas ionized by young stars in the centers of those galaxies. The 6-cm
radio powers are comparable to predictions for thermal emission that are based
on the nuclear H-alpha luminosities, and imply nuclear star formation rates of
0.08-0.8 solar masses/yr, while the low-resolution NRAO VLA Sky Survey implies
galaxy-wide star formation rates of 0.3-1.0 solar masses/yr in stars above 5
solar masses. Although the presence of active nuclei powered by massive black
holes cannot be definitively ruled out, the present results suggest that they
are likely to be rare in these late-type galaxies with H II spectra.Comment: To appear in ApJ. 7 page
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