3,321 research outputs found
Multi-particle Production and Thermalization in High-Energy QCD
We argue that multi-particle production in high energy hadron and nuclear
collisions can be considered as proceeding through the production of gluons in
the background classical field. In this approach we derive the gluon spectrum
immediately after the collision and find that at high energies it is
parametrically enhanced by ln(1/x) with respect to the quasi-classical result
(x is the Bjorken variable). We show that the produced gluon spectrum becomes
thermal (in three dimensions) with an effective temperature determined by the
saturation momentum Qs, T= c Qs/2pi during the time ~1/T; we estimate
c=sqrt{2pi}/2 ~ 1.2. Although this result by itself does not imply that the
gluon spectrum will remain thermal at later times, it has an interesting
applications to heavy ion collisions. In particular, we discuss the possibility
of Bose-Einstein condensation of the produced gluon pairs and estimate the
viscosity of the produced gluon system.Comment: 25 pages, 4 figures; typos fixed; discussions expanded; we added a
new section IV in which we argue that at high energies the production
mechanism discussed in the paper is parametrically enhanced by ln(1/x) with
respect to the quasi-classical resul
Spline Intersection Improvement
Rendering and simulation software needs many models of reality. Every human has hair and we need to visualize realistic hair. We can model hair with many spline curves. A typical task of the ray tracing method is finding an intersection of spline curves with a ray. We try to find a fast way to calculate the point where the ray intersects the curve
Generalized Euler Angle Paramterization for SU(N)
In a previous paper (math-ph/0202002) an Euler angle parameterization for
SU(4) was given. Here we present the derivation of a generalized Euler angle
parameterization for SU(N). The formula for the calculation of the Haar measure
for SU(N) as well as its relation to Marinov's volume formula for SU(N) will
also be derived. As an example of this parameterization's usefulness, the
density matrix parameterization and invariant volume element for a
qubit/qutrit, three qubit and two three-state systems, also known as two qutrit
systems, will also be given.Comment: 36 pages, no figures; added qubit/qutrit work, corrected minor
definition problems and clarified Haar measure derivation. To be published in
J. Phys. A: Math. and Ge
Pair production by boost-invariant fields in comoving coordinates
We derive the pair-production probability in a constant electric field in
Rindler coordinates in a quasi-classical approximation. Our result is different
from the pair-production probability in an inertial frame (Schwinger formula).
In particular, it exhibits non-trivial dependence on rapidity and deviation
from Gaussian behavior at small transverse momenta. Our results can be
important for analysis of particle production in heavy-ion collisions.Comment: 12 pages, 2 figures. Discussion added and typos fixe
Biodesulphurized subbituminous coal by different fungi and bacteria studied by reductive pyrolysis. Part 1: Initial coal
One of the perspective methods for clean solid fuels production is biodesulphurization. In order to increase the effect of this approach
it is necessary to apply the advantages of more informative analytical techniques. Atmospheric pressure temperature programming
reduction (AP-TPR) coupled with different detection systems gave us ground to attain more satisfactory explanation of the effects of
biodesulphurization on the treated solid products.
Subbituminous high sulphur coal from ââPirinâ basin (Bulgaria) was selected as a high sulphur containing sample. Different types of
microorganisms were chosen and maximal desulphurization of 26% was registered. Biodesulphurization treatments were performed with
three types of fungi: ââTrametes Versicolorâ â ATCC No. 200801, ââPhanerochaeta Chrysosporiumâ â ME446, Pleurotus Sajor-Caju and
one Mixed Culture of bacteria â ATCC No. 39327. A high degree of inorganic sulphur removal (79%) with Mixed Culture of bacteria
and consecutive reduction by 13% for organic sulphur (Sorg) decrease with ââPhanerochaeta Chrysosporiumâ and ââTrametes Versicolorâ
were achieved.
To follow the Sorg changes a set of different detection systems i.e. AP-TPR coupled ââon-lineâ with mass spectrometry (AP-TPR/MS),
on-line with potentiometry (AP-TPR/pot) and by the ââoff-lineâ AP-TPR/GC/MS analysis was used. The need of applying different
atmospheres in pyrolysis experiments was proved and their effects were discussed. In order to reach more precise total sulphur balance,
oxygen bomb combustion followed by ion chromatography was used
A Parametrization of Bipartite Systems Based on SU(4) Euler Angles
In this paper we give an explicit parametrization for all two qubit density
matrices. This is important for calculations involving entanglement and many
other types of quantum information processing. To accomplish this we present a
generalized Euler angle parametrization for SU(4) and all possible two qubit
density matrices. The important group-theoretical properties of such a
description are then manifest. We thus obtain the correct Haar (Hurwitz)
measure and volume element for SU(4) which follows from this parametrization.
In addition, we study the role of this parametrization in the Peres-Horodecki
criteria for separability and its corresponding usefulness in calculating
entangled two qubit states as represented through the parametrization.Comment: 23 pages, no figures; changed title and abstract and rewrote certain
areas in line with referee comments. To be published in J. Phys. A: Math. and
Ge
Intraoperative and postoperative complications during microlaryngeal surgery
Theoretical basis: Patients presenting for microlaryngeal surgery may have a variety of comorbidities contributing to their voice symptoms and affecting anesthetic management.Results: Many patients presenting for laryngeal surgery have a long history of heavy smoking and drinking. Many patients who present for laryngeal surgery are elderly and have cardiovascular disease. The rate of difficult endotracheal intubation may reach almost 16% among patients presenting for ear, nose, or throat cancer surgery, which is on average six times higher than among the general surgical patient population. Loss of the airway on induction, requiring emergent cricothyrotomy or tracheostomy, can be sudden, especially in patients with critical airway obstruction. Prospective trials identify the incidence of dental trauma after suspension laryngoscopy at 0% to 6.5%, depending on the operatorâs experience, methodology of the study, dental injury criteria, preexisting dentition status of the patient, and suspension technique used. Minor surgical complications, such as sore throat, mucosal injury (e.g., cuts, edema, hematoma), and cranial nerve dysfunction (e.g., lingual, glossopharyngeal, hypoglossal), are most commonly observed. The risk of postoperative airway compromise is significantly greater among the patients who underwent diagnostic laryngoscopy than those in the general surgical population.Conclusion: Patients presenting for microlaryngeal surgery may have a variety of intraoperative and postoperative complications
Semiempirical Shell Model Masses with Magic Number Z = 126 for Superheavy Elements
A semiempirical shell model mass equation applicable to superheavy elements
up to Z = 126 is presented and shown to have a high predictive power. The
equation is applied to the recently discovered superheavy nuclei Z = 118, A =
293 and Z = 114, A = 289 and their decay products.Comment: 7 pages, including 2 figures and 2 table
Realization of compact Lie algebras in K\"ahler manifolds
The Berezin quantization on a simply connected homogeneous K\"{a}hler
manifold, which is considered as a phase space for a dynamical system, enables
a description of the quantal system in a (finite-dimensional) Hilbert space of
holomorphic functions corresponding to generalized coherent states. The Lie
algebra associated with the manifold symmetry group is given in terms of
first-order differential operators. In the classical theory, the Lie algebra is
represented by the momentum maps which are functions on the manifold, and the
Lie product is the Poisson bracket given by the K\"{a}hler structure. The
K\"{a}hler potentials are constructed for the manifolds related to all compact
semi-simple Lie groups. The complex coordinates are introduced by means of the
Borel method. The K\"{a}hler structure is obtained explicitly for any unitary
group representation. The cocycle functions for the Lie algebra and the Killing
vector fields on the manifold are also obtained
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