Improving LLR Tests of Gravitational Theory

Accurate analysis of precision ranges to the Moon has provided several tests of gravitational theory including the Equivalence Principle, geodetic precession, parameterized post-Newtonian (PPN) parameters $\gamma$ and $\beta$, and the constancy of the gravitational constant {\it G}. Since the beginning of the experiment in 1969, the uncertainties of these tests have decreased considerably as data accuracies have improved and data time span has lengthened. We are exploring the modeling improvements necessary to proceed from cm to mm range accuracies enabled by the new Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) currently under development in New Mexico. This facility will be able to make a significant contribution to the solar system tests of fundamental and gravitational physics. In particular, the Weak and Strong Equivalence Principle tests would have a sensitivity approaching 10$^{-14}$, yielding sensitivity for the SEP violation parameter $\eta$ of $\sim 3\times 10^{-5}$, $v^2/c^2$ general relativistic effects would be tested to better than 0.1%, and measurements of the relative change in the gravitational constant, $\dot{G}/G$, would be $\sim0.1$% the inverse age of the universe. Having this expected accuracy in mind, we discusses the current techniques, methods and existing physical models used to process the LLR data. We also identify the challenges for modeling and data analysis that the LLR community faces today in order to take full advantage of the new APOLLO ranging station.Comment: 15 pages, 3 figures, talk presented at 2003 NASA/JPL Workshop on Fundamental Physics in Space, April 14-16, 2003, Oxnard, C

The Chemical Nature of Ti₄O₁₀^-: Vibrational Predissociation Spectroscopy Combined with Global Structure Optimization

The gas-phase infrared spectrum of Ti4O10- is studied in the spectral range from 400 cm–1 to 1250 cm–1 using cryogenic ion trap vibrational spectroscopy, in combination with density functional theory (DFT). The infrared photodissociation (IRPD) spectrum of D2-tagged Ti4O10- provides evidence for a structure of lower symmetry that contains a superoxo group (1121 cm–1) and two terminal Ti=O moieties. DFT combined with a genetic algorithm for global structure optimization predicts two isomers which feature a superoxo group: the Cs symmetric global minimum-energy structure and a similar isomer (C1) that is slightly higher in energy. Coupled cluster calculations confirm the relative stability. Comparison of the harmonic DFT spectra (different functionals) with the IRPD spectrum suggests that both of these isomers contribute. Earlier assignments to the adamantane-like C3v isomer with three terminal Ti–O• – groups in a quartet state are not confirmed. They were based on the infrared multiple photon photodissociation (IRMPD) spectrum of bare Ti4O10- and local DFT structure optimizations

Optical conductivity of a metal-insulator transition for the Anderson-Hubbard model in 3 dimensions away from 1/2 filling

We have completed a numerical investigation of the Anderson-Hubbard model for three-dimensional simple cubic lattices using a real-space self-consistent Hartree-Fock decoupling approximation for the Hubbard interaction. In this formulation we treat the spatial disorder exactly, and therefore we account for effects arising from localization physics. We have examined the model for electronic densities well away 1/2 filling, thereby avoiding the physics of a Mott insulator. Several recent studies have made clear that the combined effects of electronic interactions and spatial disorder can give rise to a suppression of the electronic density of states, and a subsequent metal-insulator transition can occur. We augment such studies by calculating the ac conductivity for such systems. Our numerical results show that weak interactions enhance the density of states at the Fermi level and the low-frequency conductivity, there are no local magnetic moments, and the ac conductivity is Drude-like. However, with a large enough disorder strength and larger interactions the density of states at the Fermi level and the low-frequency conductivity are both suppressed, the conductivity becomes non-Drude-like, and these phenomena are accompanied by the presence of local magnetic moments. The low-frequency conductivity changes from a sigma-sigma_dc omega^{1/2} behaviour in the metallic phase, to a sigma omega^2 behaviour in the nonmetallic regime. Our numerical results show that the formation of magnetic moments is essential to the suppression of the density of states at the Fermi level, and therefore essential to the metal-insulator transition

Parton Equilibration in Relativistic Heavy Ion Collisions

We investigate the processes leading to phase-space equilibration of parton distributions in nuclear interactions at collider energies. We derive a set of rate equations describing the chemical equilibration of gluons and quarks including medium effects on the relevant QCD transport coefficients, and discuss their consequences for parton equilibration in heavy ion collisions.Comment: 18 pages, 6 Figures appended as uuencoded PostScript files, (no changes in the previously submitted manuscript), DUKE-TH-93-4

All bicovariant differential calculi on Glq(3,C) and SLq(3,C)

All bicovariant first order differential calculi on the quantum group GLq(3,C) are determined. There are two distinct one-parameter families of calculi. In terms of a suitable basis of 1-forms the commutation relations can be expressed with the help of the R-matrix of GLq(3,C). Some calculi induce bicovariant differential calculi on SLq(3,C) and on real forms of GLq(3,C). For generic deformation parameter q there are six calculi on SLq(3,C), on SUq(3) there are only two. The classical limit q-->1 of bicovariant calculi on SLq(3,C) is not the ordinary calculus on SL(3,C). One obtains a deformation of it which involves the Cartan-Killing metric.Comment: 24 pages, LaTe

Quark-Meson Coupling Model for a Nucleon

The quark-meson coupling model for a nucleon is considered. The model describes a nucleon as an MIT bag, in which quarks are coupled to scalar and vector mesons. A set of coupled equations for the quark and the meson fields are obtained and are solved in a self-consistent way. It is shown that the mass of a nucleon as a dressed MIT bag interacting with sigma- and omega-meson fields significantly differs from the mass of a free MIT bag. A few sets of model parameters are obtained so that the mass of a dressed MIT bag becomes the nucleon mass. The results of our calculations imply that the self-energy of the bag in the quark-meson coupling model is significant and needs to be considered in doing the nuclear matter calculations.Comment: 3 figure

Coupling Of The B1g Phonon To The Anti-Nodal Electronic States of Bi2Sr2Ca0.92Y0.08Cu2O(8+delta)

Angle-resolved photoemission spectroscopy (ARPES) on optimally doped Bi2Sr2Ca0.92Y0.08Cu2O(8+delta) uncovers a coupling of the electronic bands to a 40 meV mode in an extended k-space region away from the nodal direction, leading to a new interpretation of the strong renormalization of the electronic structure seen in Bi2212. Phenomenological agreements with neutron and Raman experiments suggest that this mode is the B1g oxygen bond-buckling phonon. A theoretical calculation based on this assignment reproduces the electronic renormalization seen in the data.Comment: 4 Pages, 4 Figures Updated Figures and Tex

Charm Correlation as a Diagnostic Probe of Quark Matter

The use of correlation between two open-charm mesons is suggested to give information about the nature of the medium created in heavy-ion collisions. Insensitivity to the charm production rate is achieved by measuring normalized cumulant. The acollinearity of the D momenta in the transverse plane is a measure of the medium effect. Its dependence on nuclear size or E_T provides a signature for the formation of quark matter.Comment: 12 pages, no figure