Solar flux and its variations

Data are presented on the solar irradiance as derived from a number of sources. An attempt was made to bring these data onto a uniform scale. Summation of fluxes at all wavelengths yields a figure of 1357.826 for the solar constant. Estimates are made of the solar flux variations due to flares, active regions (slowly varying component), 27-day period, and the 11-yr cycle. Solar activity does not produce a significant variation in the value of the solar constant. Variations in the X-ray and EUV portions of the solar flux may be several orders of magnitude during solar activity, especially at times of major flares. It is established that these short wavelength flux enhancements cause significant changes in the terrestrial ionosphere

Rotational Spectroscopy of PAHs: Acenaphthene, Acenaphthylene and Fluorene

Pure rotational spectra of three polycyclic aromatic hydrocarbons - acenaphthene, acenaphthylene and fluorene - have been obtained by Fourier transform microwave spectroscopy of a molecular beam and subsequently by millimeter wave absorption spectroscopy for acenaphthene and fluorene. The data presented here will be useful for deep radio astronomical searches for PAHs employing large radio telecopes.Comment: 2 pages, 1 figure (uses iaus.sty), to appear in IAU Symposium No. 231, Astrochemistry - Recent Successes and Current Challenges, eds. D. C. Lis, G. A. Blake & E. Herbst (Cambridge Univ. Press

Lattice QCD Production on Commodity Clusters at Fermilab

We describe the construction and results to date of Fermilab's three Myrinet-networked lattice QCD production clusters (an 80-node dual Pentium III cluster, a 48-node dual Xeon cluster, and a 128-node dual Xeon cluster). We examine a number of aspects of performance of the MILC lattice QCD code running on these clusters.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 6 pages, LaTeX, 8 eps figures. PSN TUIT00

Charmonia from Lattice QCD

Recent lattice QCD results on charmonium properties are reviewed. I comment on molecules and hybrid states as well as on future studies of states near strong decay thresholds.Comment: 8 pages, 5 figures, Invited talk presented at ``Charm 2006'', Beijing, 5-7 June 200

Pressure and non-linear susceptibilities in QCD at finite chemical potentials

When the free energy density of QCD is expanded in a series in the chemical potential, mu, the Taylor coefficients are the non-linear quark number susceptibilities. We show that these depend on the prescription for putting chemical potential on the lattice, making all extrapolations in chemical potential prescription dependent at finite lattice spacing. To put bounds on the prescription dependence, we investigate the magnitude of the non-linear susceptibilities over a range of temperature, T, in QCD with two degenerate flavours of light dynamical quarks at lattice spacing 1/4T. The prescription dependence is removed in quenched QCD through a continuum extrapolation, and the dependence of the pressure, P, on mu is obtained.Comment: 15 pages, 2 figures. Data on chi_uuuu added, discussion enhance

Physical Acoustics

Contains research objectives and reports on four research projects.U.S. Navy (Office of Naval Research) under Contract Nonr-1841(42)U.S. Air Force (Air Force Cambridge Research Center, Air Research and Development Command) under Contract AF 19(604)-205

Two-Flavor Staggered Fermion Thermodynamics at N_t = 12

We present results of an ongoing study of the nature of the high temperature crossover in QCD with two light fermion flavors. These results are obtained with the conventional staggered fermion action at the smallest lattice spacing to date---approximately 0.1 fm. Of particular interest are a study of the temperature of the crossover a determination of the induced baryon charge and baryon susceptibility, the scalar susceptibility, and the chiral order parameter, used to test models of critical behavior associated with chiral symmetry restoration. From our new data and published results for N_t = 4, 6, and 8, we determine the QCD magnetic equation of state from the chiral order parameter using O(4) and mean field critical exponents and compare it with the corresponding equation of state obtained from an O(4) spin model and mean field theory. We also present a scaling analysis of the Polyakov loop, suggesting a temperature dependent ``constituent quark free energy.''Comment: LaTeX 25 pages, 15 Postscript figure

New measure of electron correlation

We propose to quantify the "correlation" inherent in a many-electron (or many-fermion) wavefunction by comparing it to the unique uncorrelated state that has the same single-particle density operator as it does.Comment: Final version to appear in PR

The Traveling Salesman Problem: Low-Dimensionality Implies a Polynomial Time Approximation Scheme

The Traveling Salesman Problem (TSP) is among the most famous NP-hard optimization problems. We design for this problem a randomized polynomial-time algorithm that computes a (1+eps)-approximation to the optimal tour, for any fixed eps>0, in TSP instances that form an arbitrary metric space with bounded intrinsic dimension. The celebrated results of Arora (A-98) and Mitchell (M-99) prove that the above result holds in the special case of TSP in a fixed-dimensional Euclidean space. Thus, our algorithm demonstrates that the algorithmic tractability of metric TSP depends on the dimensionality of the space and not on its specific geometry. This result resolves a problem that has been open since the quasi-polynomial time algorithm of Talwar (T-04)