Gluon Distribution Functions for Very Large Nuclei at Small Transverse Momentum

We show that the gluon distribution function for very large nuclei may be computed for small transverse momentum as correlation functions of an ultraviolet finite two dimensional Euclidean field theory. This computation is valid to all orders in the density of partons per unit area, but to lowest order in $\alpha_s$. The gluon distribution function is proportional to $1/x$, and the effect of the finite density of partons is to modify the dependence on transverse momentum for small transverse momentum.Comment: TPI--MINN--93--52/T, NUC--MINN--93--28/T, UMN--TH--1224/93, LaTex, 11 page

Back-reaction in a cylinder

A system is studied in which initially a strong classical electric field exists within an infinitely-long cylinder and no charges are present. Subsequently, within the cylinder, pairs of charged particles tunnel out from the vacuum and the current produced through their acceleration by the field acts back on the field, setting up plasma oscillations. This yields a rough model of phenomena that may occur in the pre-equilibrium formation phase of a quark-gluon plasma. In an infinite volume, this back-reaction has been studied in a field-theory description, and it has been found that the results of a full calculation of this sort are well represented in a much simpler transport formalism. It is the purpose here to explore that comparison for a situation involving a cylindrical volume of given radius.Comment: 19 pages plus 13 figure

The kinetic description of vacuum particle creation in the oscillator representation

The oscillator representation is used for the non-perturbative description of vacuum particle creation in a strong time-dependent electric field in the framework of scalar QED. It is shown that the method can be more effective for the derivation of the quantum kinetic equation (KE) in comparison with the Bogoliubov method of time-dependent canonical transformations. This KE is used for the investigation of vacuum creation in periodical linear and circular polarized electric fields and also in the case of the presence of a constant magnetic field, including the back reaction problem. In particular, these examples are applied for a model illustration of some features of vacuum creation of electron-positron plasma within the planned experiments on the X-ray free electron lasers.Comment: 17 pages, 3 figures, v2: a reference added; some changes in tex

Pair creation: back-reactions and damping

We solve the quantum Vlasov equation for fermions and bosons, incorporating spontaneous pair creation in the presence of back-reactions and collisions. Pair creation is initiated by an external impulse field and the source term is non-Markovian. A simultaneous solution of Maxwell's equation in the presence of feedback yields an internal current and electric field that exhibit plasma oscillations with a period tau_pl. Allowing for collisions, these oscillations are damped on a time-scale, tau_r, determined by the collision frequency. Plasma oscillations cannot affect the early stages of the formation of a quark-gluon plasma unless tau_r >> tau_pl and tau_pl approx. 1/Lambda_QCD approx 1 fm/c.Comment: 16 pages, 6 figure, REVTEX, epsfig.st

Schwinger Mechanism for Gluon Pair Production in the Presence of Arbitrary Time Dependent Chromo-Electric Field

We study Schwinger mechanism for gluon pair production in the presence of arbitrary time-dependent chromo-electric background field $E^a(t)$ with arbitrary color index $a$=1,2,...8 in SU(3) by directly evaluating the path integral. We obtain an exact expression for the probability of non-perturbative gluon pair production per unit time per unit volume and per unit transverse momentum $\frac{dW}{d^4x d^2p_T}$ from arbitrary $E^a(t)$. We show that the tadpole (or single gluon) effective action does not contribute to the non-perturbative gluon pair production rate $\frac{dW}{d^4x d^2p_T}$. We find that the exact result for non-perturbative gluon pair production is independent of all the time derivatives $\frac{d^nE^a(t)}{dt^n}$ where $n=1,2,....\infty$ and has the same functional dependence on two casimir invariants $[E^a(t)E^a(t)]$ and $[d_{abc}E^a(t)E^b(t)E^c(t)]^2$ as the constant chromo-electric field $E^a$ result with the replacement: $E^a \to E^a(t)$. This result may be relevant to study the production of a non-perturbative quark-gluon plasma at RHIC and LHC.Comment: 13 pages latex, Published in European Physical Journal

Dileptons from Disoriented Chiral Condensates

Disoriented chiral condensates or long wavelength pionic oscillations and their interaction with the thermal environment can be a significant source of dileptons. We calculate the yield of such dilepton production within the linear sigma model, both in a quantal mean-field treatment and in a semi-classical approximation. We then illustrate the basic features of the dilepton spectrum in a schematic model. We find that dilepton yield with invariant mass near and below $2m_{\pi}$ due to the soft pion modes can be up to two orders of magnitude larger than the corresponding equilibrium yield.Comment: 22 pages, 8 figures, uses epsf-styl

Tattoo complications in treated and non-treated psoriatic patients

Background Tattooing is a widespread phenomenon, with an estimated prevalence of 10-30% in Western populations. For psoriasis patients, current recommendations are to avoid having a tattoo if the disease is active and they are receiving immunosuppressive treatments. Although scientific data supporting these recommendations are lacking, dermatologists are often reluctant to advocate tattooing in psoriasis patients. Objective We aimed to evaluate the frequency of tattoo complications in patients with psoriasis and determine whether the occurrence of complications was associated with psoriasis status and treatments received at the time of tattooing. Methods We performed a multicentre cross-sectional study. Adults with psoriasis were consecutively included and classified as tattooed or non-tattooed. Prevalence of complications associated with tattoos was then evaluated according to psoriasis onset and treatments. The study was divided into three parts, in which data were collected through a series of questionnaires filled in by the dermatologist. Complications included pruritus, oedema, allergic reaction/eczema, infection/superinfection, granuloma, lichenification, photosensitivity, Koebner phenomenon and psoriasis flare after tattooing. Diagnosis of complications was made retrospectively. Results We included 2053 psoriatic patients, 20.2% had 894 tattoos. Amongst non-tattooed patients, 15.4% had wished to be tattooed, with psoriasis being stated as a reason for not having a tattoo by 44.0% and 5.7% indicating that they planned to have a tattoo in the future. Local complications, such as oedema, pruritus, allergy and Koebner phenomenon, were reported in tattoos in 6.6%, most frequently in patients with psoriasis requiring treatment at the time of tattooing (P <0.0001). No severe complications were reported. Conclusions The rate of tattoo complications in psoriasis patients was low. Although the risk of complications was highest amongst patients with psoriasis requiring treatment at the time of tattooing, all the complications observed were benign. These results can be helpful for practitioners to give objective information to patients.Peer reviewe

Aberrant right subclavian artery- suggested mechanism for esophageal foreign body impaction: Case report

Aberrant right subclavian artery (ARSA) is asymptomatic in most cases. This variant anatomy can cause dysphagia in elderly patients. Impaction of foreign body in the esophagus is rarely the presenting symptom of ARSA. We present an eighty four years old patient who first presented with esophageal foreign body impaction and was diagnosed with an aberrant right subclavian artery compressing the esophagus just below the site of impaction

Pilot Study on Improving Crash Data Accuracy in Kentucky through University Collaboration

Without high-quality crash data and robust interpretive/analytical tools to analyze these data, transportation agencies will struggle to develop evidence-based strategies for improving road safety. Crash narratives are one element of crash reports that pose especially acute interpretive challenges. These narratives supplement coded data and give an account of incidents authored by responding law enforcement officers. Despite their value, conducting manual reviews of the 150,000+ crash reports and narratives issued in Kentucky each year is not feasible. To address this challenge, reviewers examined approximately 8,000 crash narratives from calendar year 2020 using a proprietary web-based quality control tool to identify discrepancies between narratives and coded data. The most pronounced inconsistencies between coded data and narratives were found in questions related to aggressive driving, distracted driving, intersection and secondary crashes, and travel direction. Building on this exercise, researchers developed a machine learning algorithm that automatically classifies attributes in crash records based on the interpretation of unstructured narrative text. Although this model performed well, goodness-of-fit metrics showed that a Google AI Language model (Bidirectional Encoder Representations from Transformers [BERT]) was more accurate and precise as well as having better recall. Future crash data quality control efforts that incorporate machine learning applications should use BERT, however, the latest advances in AI technology need to be integrated into new applications and models as they are developed