2,284 research outputs found
Improvement of the hot QCD pressure by the minimal sensitivity criterion
The principles of minimal sensitivity (PMS) criterion is applied to the
perturbative free energy density, or pressure, of hot QCD, which include the
and part of the terms. Applications are made
separately to the short- and long-distance parts of the pressure. Comparison
with the lattice results, at low temperatures, shows that the resultant ``
optimal'' approximants are substantially improved when compared to the
results. In particular, for the realistic case of three quark
flavors, the `` optimal'' approximants are comparable with the lattice results.Comment: 14 pages, 9 figures, LaTe
Ferromagnetism of two-flavor quark matter in chiral and/or color-superconducting phases at zero and finite temperatures
We study the phase structure of the unpolarized and polarized two-flavor
quark matters at zero and finite temperatures within the Nambu--Jona-Lasinio
(NJL) model. We focus on the region, which includes the coexisting phase of
quark-antiquark and diquark condensates. Generalizing the NJL model so as to
describe the polarized quark matter, we compute the thermodynamic potential as
a function of the quark chemical potential (), the temperature (), and
the polarization parameter. The result heavily depends on the ratio , where is the quark-antiquark coupling constant and is the
diquark coupling constant. We find that, for small , the
"ferromagnetic" phase is energetically favored over the "paramagnetic" phase.
On the other hand, for large , there appears the window in the
()-plane, in which the "paramagnetic" phase is favored.Comment: 25 pages, 10 figure
Numerical study of quantum percolation
We study the density of states and the optical conductivity of the classical
double-exchange model on a site percolated cluster.Comment: 2 pages, 2 figures, submitted to SCES 200
Photodarkening of amorphous selenium under high pressure
The photodarkening phenomena of amorphous Se have been studied by the optical absorption coefficient, sound velocity and attenuation measurements. The light illumination at low temperatures induces the photodarkening, and the photodarkened state is completely recovered by annealing near 306 K corresponding to the glass transition temperature. The photodarkening is enhanced by application of pressure. The sound velocity decreases and the sound attenuation increases by the illumination at low temperature. These suggest that a structural disorder increases in the photodarkened state. Three stages are observed for the recovery process of the photodarkened specimen. The photodarkening and the recovery process are discussed on the basis of VAP (valence alternative pair) model.<br /
Cancellation of energy-divergences and renormalizability in Coulomb gauge QCD within the Lagrangian formalism
In Coulomb gauge QCD in the Lagrangian formalism, energy divergences arise in
individual diagrams. We give a proof on cancellation of these divergences to
all orders of perturbation theory without obstructing the algebraic
renormalizability of the theory.Comment: 13 pages, 7 figure
N\'eel and singlet RVB orders in the t-J model
The N\'eel and the singlet RVB orders of the {\it t-J} model in a 2D square
lattice are studied in the slave-boson mean-field approximation. It is shown
that the N\'eel order parameter takes the maximum value at the finite
temperature and disappear at the lower temperature for a certain range of
doping. It is also shown that the N\'eel and the singlet RVB orders coexist at
low temperature. This suggests the possibility of the coexistence of the N\'eel
and the superconducting orders.Comment: RevTeX, 8 pages, 1 postscript figure. To appear in Physica C, Volume
257, issue 38
Split transplantation of the trachea: A new operative procedure for extended tracheal resection
AbstractBefore tracheal transplantation can be applied clinically, several problems must be solved: immunosuppression, blood supply to grafts, and reliable long-term preservation of grafts. We have conducted experiments on tracheal transplantation to solve these problems. In the present study, we tried a new operative procedure to accomplish reliable revascularization of transplanted tracheal grafts. It has been reported that transplantation of a 10-ring length of trachea is difficult even with omentopexy. Long tracheal allografts can be transplanted with use of direct revascularization, but this technique is extremely troublesome. Thus we developed a new operative procedure, “split tracheal transplantation,” in which grafts are divided at the midportion and covered with omentum, after demonstrating that the blood supply to tracheal grafts can be reestablished around the suture lines. Two groups of dogs were used. In group A (control, n = 4), a 10-ring length of trachea was autotransplanted. The anastomotic sites and grafts were covered with omental pedicles. In group B (split tracheal transplantation, n = 10), tracheal grafts 10 rings long were autotransplanted. These grafts were divided at the midportion, a piece of omentum was inserted between the two halves, and the midportion was sutured. Grafts were observed regularly by bronchoscopy and examined histopathologically after the animals died or were killed. In some animals, microangiography of the bronchial circulation was done. In the control group, necrosis, stenosis, or malacia of the grafts was observed in three of the four animals. In the split transplantation group, all animals survived for at least 2 months, all grafts were incorporated, and none showed ischemia, stenosis, or malacia. Microscopic examination and microangiography revealed that neovascularization of the graft was promoted by omentum inserted at the midportion of the graft. Split transplantation of the trachea is an easy and reliable way to extend tracheal resection. (J Thorac Cardiovasc Surg 1996;112:-8
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