Thermal quark production in pure glue and quark gluon plasmas

We calculate production rates for massless $(u,d)$ and massive $(s,c,b)$ quarks in pure glue and quark gluon plasmas to leading order in the strong coupling constant $g$. The leading contribution comes from gluon decay into $q\bar q$ pairs, using a thermal gluon propagator with finite thermal mass and damping rate. The rate behaves as $\alpha_S^2(\ln 1/\alpha_S)^2 T^4$ when $m, \alpha_S \rightarrow 0$ and depends linearly on the transverse gluon damping rate for all values of the quark mass $m$. The light quark ($u$, $d$, $s$) chemical equilibration time is approximately 10-100 $T^{-1}$ for $g=$2-3, so that quarks are likely to remain far from chemical equilibrium in ultrarelativistic nuclear collisions.Comment: 7 pages, 5 figures (available upon request), CERN preprint CERN-TH-6882/9

Geometric Aspects of Confining Strings

Confining strings in 4D are effective, thick strings describing the confinement phase of compact U(1) and, possibly, also non-Abelian gauge fields. We show that these strings are dual to the gauge fields, inasmuch as their perturbative regime corresponds to the strong coupling (large e) regime of the gauge theory. In this regime they describe smooth surfaces with long-range correlations and Hausdorff dimension two. For lower couplings e and monopole fugacities z, a phase transition takes place, beyond which the smooth string picture is lost. On the critical line intrinsic distances on the surface diverge and correlators vanish, indicating that world-sheets become fractal.Comment: 19 pages, 4 figures, harvma

A detailed assessment of snow accumulation in katabatic wind areas on the Ross Ice Shelf, Antarctica

This is the published version, also available here: http://dx.doi.org/10.1029/97JD02337.An investigation of time dependent snow accumulation and erosion dynamics in a wind-swept environment was undertaken at two automatic weather stations sites on the Ross Ice Shelf between January 1994 and November 1995 using newly developed instrumentation employing a technique which automatically disperses inert, colored (high albedo) glass microspheres onto the snow surface at fixed intervals throughout the year. The microspheres act as a time marker and tracer to allow the accumulation rate and wind erosion processes to be quantified with a high temporal resolution. Snow core and snow pit sampling was conducted twice during the study period to identify microsphere horizons in the annual snow accumulation profile, allowing the snow accumulation/erosion events to be reconstructed. The two sites chosen for this investigation have characteristically different mean wind speeds and therefore allow a comparative examination on the role of wind on ice sheet growth. Mass accumulation rate at the two sites for the 14-day integration periods available ranged from 0.0 to >2.0 kg m−2 d−1. The mean mass accumulation rate during the study period was greater at the site with stronger winds (0.69 kg m−2 d−1) than the site with lower mean wind speeds (0.61 kg m−2 d−1); however, the difference between the two means is not statistically significant. Accumulation rates derived from an ultrasonic snow depth gauge operated at one of the sites are compared to the actual tracer-derived accumulation rates and show the limitations of only having a measure of snow surface height with no instantaneous measurements of the snow density profile. Snow depth gauge derived accumulation rates were found to be greatly overestimated during high-accumulation periods and were greatly underestimated during low-accumulation periods

A Note on Quantum Liouville Theory via Quantum Group; an Approach to Strong Coupling Liouville Theory

Quantum Liouville theory is analyzed in terms of the infinite dimensional representations of $U_Qsl(2,C)$ with q a root of unity. Making full use of characteristic features of the representations, we show that vertex operators in this Liouville theory are factorized into `classical' vertex operators and those which are constructed from the finite dimensional representations of $U_qsl(2,C)$. We further show explicitly that fusion rules in this model also enjoys such a factorization. Upon the conjecture that the Liouville action effectively decouples into the classical Liouville action and that of a quantum theory, correlation functions and transition amplitudes are discussed, especially an intimate relation between our model and geometric quantization of the moduli space of Riemann surfaces is suggested. The most important result is that our Liouville theory is in the strong coupling region, i.e., the central charge c_L satisfies $1<c_L<25$. An interpretation of quantum space-time is also given within this formulation.Comment: 25 pages, Latex file, no figure

Economic Impact of North Dakota Laws that Permit Delayed or Partial Repayment of Agricultural Debt � July 1, 1986

Agricultural Finance,

Classical and Quantum Considerations of Two-dimensional Gravity

The two-dimensional theory of gravity describing a graviton-dilaton system is considered. The graviton-dilaton coupling can be fixed such that the quantum theory remains free of the conformal anomaly for any conformal dimension of the coupled matter system, even if the dilaton does not appear as Lagrange multiplier. Interaction terms are introduced and the system is analyzed and solutions are given at the classical level and at the quantum level by using canonical quantization.Comment: 18 page

Classical Liouville action on the sphere with three hyperbolic singularities

The classical solution to the Liouville equation in the case of three hyperbolic singularities of its energy-momentum tensor is derived and analyzed. The recently proposed classical Liouville action is explicitly calculated in this case. The result agrees with the classical limit of the three point function in the DOZZ solution of the quantum Liouville theory.Comment: 14 pages, 2 eps figure

Direct measurements of episodic snow accumulation on the Antarctic polar plateau

This is the published version, also available here: http://dx.doi.org/10.1029/2000JD900099.During a 1-year field experiment at a remote location on the Antarctic polar plateau (85.67°S, 46.38°W) influenced by moderate magnitude katabatic winds, snow accumulation was characterized at three different spatial and temporal scales using snow stakes, tracer material dispersed periodically on the snow surface, and an acoustic depth gauge. The spatial variability of snow accumulation was found to be large, on both annual and intra-annual timescales, and is attributed to the high frequency of moderate to strong winds at the site. Accumulation throughout the year was observed to be episodic in nature, with a small number of snow accumulation events producing the majority of the annual total accumulation for the site, averaging 0.174 m. In the intervals between observed accumulation events (up to several months), negative changes to snow surface height caused by sublimation and densification of the firn were quantified using an acoustic depth gauge. The rate of decrease in snow surface elevation was largest during the austral summer, as expected, and the overall change in snow surface elevation due to sublimation/densification during the year was estimated to be about −0.10 m. Using the precise timing of accumulation events provided by the acoustic depth gauge, meteorological surface observations, numerical model analyses, and satellite imagery were used to gain insights into whether the event was associated with precipitation or related exclusively to blowing snow and to diagnose the meteorological conditions producing the event. Meteorological conditions during the accumulation events were found to strongly support an association with precipitation events caused by mesoscale or synoptic-scale cyclones along the coastal margin. Dating of the accumulation profile using the dispersed tracer technique identified several other accumulation events that were not measured within the target area of the acoustic depth gauge, suggesting that snow accumulation data from a single acoustic depth gauge cannot be extrapolated over a broad area

Spectrum Generating Algebra and No-Ghost Theorem for Fermionic Massive String

The covariant operator quantization of the ordinary free spinning BDH string modified by adding the supersymmetric Liouville sector is analysed in the even target space dimensions $d=2,4,6,8$. The spectrum generating algebra for this model is constructed and a general version of the no-ghost theorem is proven. A counterpart of the GSO projection leads to a family of tachyon free unitary free string theories. One of these models is equivalent to the non-critical Rammond-Neveu-Schwarz spinning string truncated in the Neveu-Schwarz sector to the tachyon free eigenspace of the fermion parity operator.Comment: 17 page