The Temperature Dependence of the QCD Running Coupling

We study the running of the QCD coupling with the momentum squared ($Q^2$) and the temperature scales in the high temperature limit ($T > T_{c}$), using a mass dependent renormalization scheme to build the Renormalization Group Equations. The approach used guaranty gauge invariance, through the use of the Hard Thermal Loop approximation, and independence of the vertex chosen to renormalize the coupling. In general, the dependence of the coupling with the temperature is not logarithmical, although in the region $Q^2 \sim T^2$ the logarithm approximation is reasonable. Finally, as known from Debye screening, color charge is screened in the coupling. The number of flavors, however, is anti-screened.Comment: 5 pages, 2 figure

New Approaches to Target Mass Corrections

We analyze different prescriptions for the inclusion of target mass effects in the extraction of parton distributions from the measured structure functions. As a main result, the problem of defining parton distributions in the presence of mass is an open problem.Comment: 4 pages. Presented at HiX2010, Jlab, October 201

Target mass corrections revisited

We propose a new implementation of target mass corrections to nucleon structure functions which, unlike existing treatments, has the correct kinematic threshold behavior at finite Q^2 in the x -> 1 limit. We illustrate the differences between the new approach and existing prescriptions by considering specific examples for the F_2 and F_L structure functions, and discuss the broader implications of our results, which call into question the notion of universal parton distribution at finite Q^2.Comment: 11 pages, 5 figure

Vibrational Aspects of the SU(2) Skyrmion

We treat the Skyrme model with the breathing mode in a situation involving two quartic terms. It is seen that there is a new limit for large $e$ due to the breathing mode not found in the usual rotating hedgehog.Comment: 15 pages, ADP-93-206/T12

On the Interpretation of the NA51 Experiment

We study the $p-n$ Drell-Yan asymmetry, recently measured by the NA51 collaboration, and conclude that the value quoted by their experiment only sets a lower limit on the asymmetry of the proton sea. In particular, we notice that charge symmetry breaking between the proton and the neutron may produce corrections which should be taken into account.Comment: To appear in Phys. Lett.

Local Duality and Charge Symmetry Violation in Quark Distributions

We use local quark-hadron duality to calculate the nucleon structure function as seen by neutrino and muon beams. Our result indicates a possible signal of charge symmetry violation at the parton level in the very large x region.Comment: 4 pages, 2 figures. Modified version to appear on PRD. A dicussion on the experimental errors of the form factors was adde

A Constraint on the x Dependence of the Light Antiquarks Ratio

We perform a careful study on the effect of the Pauli blocking to the light antiquark structure of the proton sea. We develop the formal expressions for the antiquark distributions, highlighting the role played by quark statistics and the vacuum structure. Ratios involving the antiquarks are calculated. In particular, it is found that $\Delta\bar{d}(x)/\Delta\bar{u}(x)$ should be negative and x independent

Heavy Quarks in Polarized Structure Functions

Quark mass effects are included in the calculation of polarized structure functions. In particular, the validity of fixed order perturbation theory and of massless evolution is studied in the framework of heavy quarks structure functions. The polarized version of the ACOT and MRRS interpolating schemes for the evolution of massive quarks distributions is also developed and studied. The different behaviours of the various approaches in $x$ and $Q^2$ are shown

Standard map in magnetized relativistic systems: fixed points and regular acceleration

We investigate the concept of a standard map for the interaction of relativistic particles and electrostatic waves of arbitrary amplitudes, under the action of external magnetic fields. The map is adequate for physical settings where waves and particles interact impulsively, and allows for a series of analytical result to be exactly obtained. Unlike the traditional form of the standard map, the present map is nonlinear in the wave amplitude and displays a series of peculiar properties. Among these properties we discuss the relation involving fixed points of the maps and accelerator regimes.Comment: Work to appear in Phys. Rev. E. 2 figure