Structure Functions and Pair Correlations of the Quark-Gluon Plasma

Recent experiments at RHIC and theoretical considerations indicate that the quark-gluon plasma, present in the fireball of relativistic heavy-ion collisions, might be in a liquid phase. The liquid state can be identified by characteristic correlation and structure functions. Here definitions of the structure functions and pair correlations of the quark-gluon plasma are presented as well as perturbative results. These definitions might be useful for verifying the quark-gluon-plasma liquid in QCD lattice calculations.Comment: 9 pages, 1 figure, revised version (new remark on the coupling parameter on page 2), to be published in Phys. Rev.

Modeling Near Surface, Gas-Induced Seafloor Deformation Using Thin Plate Mechanics in the Thunder Horse Oil Field, Gulf of Mexico and Ninilchik Field, Cook Inlet Basin, Alaska

Seabed topographic expressions such as pockmarks and domes caused by the vertical migration and accumulation of methane are found in muddy, cohesive sea beds around the world. These surface features range from 10-1000 m in diameter and 1-20 m in relief (Judd and Hovland, 2007). The mechanics of soft, cohesive sediment deformation due to overpressure from rising gas is not well understood or quantitatively defined despite the hazards they present to offshore drilling. Shallow gas pockets and overpressured sediments formed by the migration of subsurface gas to the seafloor can cause drilling blowouts, resulting in the release of large amounts of methane into the atmosphere that may contribute to climate warming. Barry et al., (2012) took initial steps to quantitatively define the sediment deformation caused by the upward pressure of rising gas against an impermeable sediment layer. They observed that the deformation to clay-bearing, cohesive sediments could be characterized by elastic thin plate mechanics up to sediment failure. Thin plate theory, also, could be used to predict the pressures responsible for known sea domes around the world. In this study, shallow gas and associated subsequent deformation to the sediments around them were identified in two study areas: the Ninilchik field along the eastern shore of the Cook Inlet in Alaska and the Thunder Horse Field in the Mississippi Canyon Protraction area of the Gulf of Mexico. Each observable upward doming feature was measured for radius, deflection, and thickness. This information is used in an elastic thin plate equation for calculating pressure (Barry et al., 2012). In the Ninilchik field, all measurements were done by interpretation of 3D seismic data in Petrel® 2011. In the Thunder Horse Oil Field, measurements of the sediment response at the seafloor were collected using a 3D three meter-binned bathymetry survey in Schlumberger’s Petrel® 2011. Nine Gulf of Mexico and three Alaskan gas accumulations were identified and analyzed in this study. In addition, numerous other gas-related features were observed in the Gulf of Mexico study area including pockmarks, interpreted gas hydrates/outcrops, and subsurface gas that did not affect seafloor surface. By applying Barry et al. (2012) laboratory-derived method for predicting pressures, a range of predictive pressures for twelve gas domes was calculated using two equations based on the amount of observed deflection. Calculated pressures for individual domes ranged from 499-17,696 Pa in the Gulf of Mexico and 261-15,640 Pa in the Cook Inlet. The majority of observed domes displayed a deflection to thickness ratio (w/h) greater than 0.3 suggesting plate stretching during deformation and “flexible” plate behavior. Plate stretching equation best predicts the pressures for these 5 “flexible” domes, compensating for the added stresses created by their large deflections while still predicting comparable pressures (+/- 6%) for “stiff” domes (w/h\u3c0.3) compared to non-plate stretching equation. Domes with the smallest Young’s Modulus (low-end calculations) provided pressures most similar to Barry et al. (2012) and a range of lower pressure values more likely recreated in the subsurface than high-end values. Domes in the Gulf of Mexico were better suited for the application of elastic plate theory due to their more circular plate shape and clay-rich lithology, thus producing more reliable pressure results than the Cook Inlet domes

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

Conserved Density Fluctuation and Temporal Correlation Function in HTL Perturbation Theory

Considering recently developed Hard Thermal Loop perturbation theory that takes into account the effect of the variation of the external field through the fluctuations of a conserved quantity we calculate the temporal component of the Euclidian correlation function in the vector channel. The results are found to be in good agreement with the very recent results obtained within the quenched approximation of QCD and small values of the quark mass ($\sim 0.1T$) on improved lattices of size $128^3\times N_\tau$ at ($N_\tau=40, \ T=1.2T_C$), ($N_\tau=48, \ T=1.45T_C$), and ($N_\tau=16, \ T=2.98T_C$), where $N_\tau$ is the temporal extent of the lattice. This suggests that the results from lattice QCD and Hard Thermal Loop perturbation theory are in close proximity for a quantity associated with the conserved density fluctuation.Comment: 16 pages, 4 figures; One para added in introduction, Fig 1 modified; Accepted in Phys. Rev.

Cherenkov radiation by particles traversing the background radiatio n

High energy particles traversing the Universe through the cosmic microwave backgroung radiation can, in principle, emit Cherenkov radiation. It is shown that the energy threshold for this radiation is extremely high and its intensity would be too low due to the low density of the "relic photons gas" and very weak interaction of two photons.Comment: 6 pages, LATEX, no Figs.; to be published in JETP Lett. 75 (N4) (2002

Photon-Photon Interaction in a Photon Gas

Using the effective Lagrangian for the low energy photon-photon interaction the lowest order photon self energy at finite temperature and in non-equilibrium is calculated within the real time formalism. The Debye mass, the dispersion relation, the dielectric tensor, and the velocity of light following from the photon self energy are discussed. As an application we consider the interaction of photons with the cosmic microwave background radiation.Comment: REVTEX, 7 pages, 1 PostSrcipt figur

Low Mass Dilepton Rate from the Deconfined Phase

We discuss low mass dilepton rates ($\le 1$ GeV) from the deconfined phase of QCD using both perturbative and non-perturbative models and compare with those from lattice gauge theory and in-medium hadron gas. Our analysis suggests that the rate at very low invariant mass ($M\le 200$ MeV) using the nonperturbative gluon condensate in a semiempirical way within the Green function dominates over the Born-rate and independent of any uncertainty associated with the choice of the strong coupling in perturbation theory. On the other hand the rate from $\rho-q$ interaction in the deconfined phase is important between 200 MeV $\le M \le 1 GeV as it is almost of same order of the Born-rate as well as in-medium hadron gas rate. Also the higher order perturbative rate, leaving aside its various uncertainties, from HTL approximation becomes reliable at$M\ge 200$MeV and also becomes comparable with the Born-rate and the lattice-rate for$M\ge 500$ MeV, constraining on the broad resonance structures in the dilepton rate at large invariant mass. We also discuss the lattice constraints on the low mass dilepton rate. Furthermore, we discuss a more realistic way to advocate the quark-hadron duality hypothesis based on the dilepton rates from QGP and hadron gas than it is done in the literature.Comment: 24 pages, 9 figures; Discussion added, Accepted in Phys. Rev.

Photoproduction of η\eta mesons off neutrons from a deuteron target

A formalism is developed for the partial wave analysis of data on meson photoproduction off deuterons and applied to photoproduction of $\eta$ and $\pi^0$ mesons. Different interpretations of a dip-bump structure of the $\eta$ photoproduction cross section in the 1670 MeV region are presented and discussed. Helicity amplitudes for two low-mass $S_{11}$ states are determined.Comment: 11 pages, 13 figure

Jet quenching in thin plasmas

We investigate the energy loss of quarks and gluons produced in hard processes resulting from final state rescatterings in a finite quark-gluon plasma. The angular distribution of the soft gluon bremsstrahlung induced by n_s=1 rescatterings in the plasma is computed in the Gyulassy-Wang model. Special focus is on how the interference between the initial hard radiation amplitude, the multiple induced Gunion-Bertsch radiation amplitudes, and gluon rescattering amplitudes modifies the classical parton cascade results.Comment: 4 pages in Latex and 3 EPS figures, Proceedings of the Quark Matter'99 Conference, 10-15 May, 1999, Torin

Chromodynamic Fluctuations in Quark-Gluon Plasma

Fluctuations of chromodynamic fields in the collisionless quark-gluon plasma are found as a solution of the initial value linearized problem. The plasma initial state is on average colorless, stationary and homogeneous. When the state is stable, the initial fluctuations decay exponentially and in the long-time limit a stationary spectrum of fluctuations is established. For the equilibrium plasma it reproduces the spectrum which is provided by the fluctuation-dissipation relation. Fluctuations in the unstable plasma, where the memory of initial fluctuations is not lost, are also discussed.Comment: 19 pages, numerous but minor corrections, to appear in Phys. Rev.