Collisional Energy Loss of Fast Charged Particles in Relativistic Plasmas

Following an argument by Kirzhnits we rederive an exact expression for the energy loss of a fast charged particle in a relativistic plasma using the quantum field theoretical language. We compare this result to perturbative calculations of the collisional energy loss of an energetic electron or muon in an electron-positron plasma and of an energetic parton in the quark-gluon plasma.Comment: 9 pages, LATEX, 2 PostScript figure

Quark Number Susceptibility in Hard Thermal Loop Approximation

We calculate the quark number susceptibility in the deconfined phase of QCD using the hard thermal loop (HTL) approximation for the quark propagator. This improved perturbation theory takes into account important medium effects such as thermal quark masses and Landau damping in the quark-gluon plasma. We explicitly show that the Landau damping part in the quark propagator for spacelike quark momenta does not contribute to the quark number susceptibility due to the quark number conservation. We find that the quark number susceptibility only due to the collective quark modes deviates from that of free one around the critical temperature but approaches free results at infinite temperature limit. The results are in conformity with recent lattice calculations

Damping Rate of a Hard Photon in a Relativistic Plasma

The damping rate of a hard photon in a hot relativistic QED and QCD plasma is calculated using the resummation technique by Braaten and Pisarski.Comment: 4 pages, REVTeX, 2 figures (not included), UGI-MT-94-0

Autowaves in a dc complex plasma confined behind a de Laval nozzle

Experiments to explore stability conditions and topology of a dense microparticle cloud supported against gravity by a gas flow were carried out. By using a nozzle shaped glass insert within the glass tube of a dc discharge plasma chamber a weakly ionized gas flow through a de Laval nozzle was produced. The experiments were performed using neon gas at a pressure of 100 Pa and melamine-formaldehyde particles with a diameter of 3.43 {\mu}m. The capturing and stable global confining of the particles behind the nozzle in the plasma were demonstrated. The particles inside the cloud behaved as a single convection cell inhomogeneously structured along the nozzle axis in a tube-like manner. The pulsed acceleration localized in the very head of the cloud mediated by collective plasma-particle interactions and the resulting wave pattern were studied in detail.Comment: 6 pages, 4 figure

Wakes in the quark-gluon plasma

Using the high temperature approximation we study, within the linear response theory, the wake in the quark-gluon plasma by a fast parton owing to dynamical screening in the space like region. When the parton moves with a speed less than the average speed of the plasmon, we find that the wake structure corresponds to a screening charge cloud traveling with the parton with one sign flip in the induced charge density resulting in a Lennard-Jones type potential in the outward flow with a short range repulsive and a long range attractive part. On the other hand if the parton moves with a speed higher than that of plasmon, the wake structure in the induced charge density is found to have alternate sign flips and the wake potential in the outward flow oscillates analogous to Cerenkov like wave generation with a Mach cone structure trailing the moving parton. The potential normal to the motion of the parton indicates a transverse flow in the system. We also calculate the potential due to a color dipole and discuss consequences of possible new bound states and $J/\psi$ suppression in the quark-gluon plasma.Comment: 20 pages, 14 figures (high resolution figures available with authors); version accepted for publication in Phys. Rev.

Field Theoretic Description of Ultrarelativistic Electron-Positron Plasmas

Ultrarelativistic electron-positron plasmas can be produced in high-intensity laser fields and play a role in various astrophysical situations. Their properties can be calculated using QED at finite temperature. Here we will use perturbative QED at finite temperature for calculating various important properties, such as the equation of state, dispersion relations of collective plasma modes of photons and electrons, Debye screening, damping rates, mean free paths, collision times, transport coefficients, and particle production rates, of ultrarelativistic electron-positron plasmas. In particular, we will focus on electron-positron plasmas produced with ultra-strong lasers.Comment: 13 pages, 7 figures, 1 table, published versio

Non-Perturbative Dilepton Production from a Quark-Gluon Plasma

The dilepton production rate from the quark-gluon plasma is calculated from the imaginary part of the photon self energy using a quark propagator that contains the gluon condensate. The low mass dilepton rate obtained in this way exhibits interesting structures (peaks and gaps), which might be observable at RHIC and LHC.Comment: 16 pages, REVTEX, 8 PostScript figure

First Results from Viper: Detection of Small-Scale Anisotropy at 40 GHZ

Results of a search for small-scale anisotropy in the cosmic microwave background (CMB) are presented. Observations were made at the South Pole using the Viper telescope, with a .26 degree (FWHM) beam and a passband centered at 40 GHz. Anisotropy band-power measurements in bands centered at l = 108, 173, 237, 263, 422 and 589 are reported. Statistically significant anisotropy is detected in all bands.Comment: 5 pages, 4 figures, uses emulateapj.sty, submitted to ApJ Letter