Nucleation in a Fermi liquid at negative pressure

Experimental investigation of cavitation in liquid helium 3 has revealed a singular behaviour in the degenerate region at low temperature. As the temperature decreases below 80 mK, the cavitation pressure becomes significantly more negative. To investigate this, we have extrapolated the Fermi parameters in the negative pressure region. This allowed us to calculate the zero sound velocity, which we found to remain finite at the spinodal limit where the first sound velocity vanishes. We discuss the impact on the nucleation of the gas phase in terms of a quantum stiffness of the Fermi liquid. As a result we predict a cavitation pressure which is nearer to the spinodal line than previously thought.Comment: 6 pages, 2 figures. To be published in Journal of Low Temperature Physics, Proceedings of the International Symposium on Quantum Fluids and Solids QFS200

Logic system aids in evaluation of project readiness

Measurement Operational Readiness Requirements /MORR/ assignments logic is used for determining the readiness of a complex project to go forward as planned. The system used logic network which assigns qualities to all important criteria in a project and establishes a logical sequence of measurements to determine what the conditions are

Structure of A = 7 - 8 nuclei with two- plus three-nucleon interactions from chiral effective field theory

We solve the ab initio no-core shell model (NCSM) in the complete Nmax = 8 basis for A = 7 and A = 8 nuclei with two-nucleon and three-nucleon interactions derived within chiral effective field theory (EFT). We find that including the chiral EFT three-nucleon interaction in the Hamiltonian improves overall good agreement with experimental binding energies, excitation spectra, transitions and electromagnetic moments. We predict states that exhibit sensitivity to including the chiral EFT three-nucleon interaction but are not yet known experimentally.Comment: 10 pages, 6 figures, updated references and corrected a typ

Chirally symmetric quark description of low energy \pi-\pi scattering

Weinberg's theorem for \pi-\pi scattering, including the Adler zero at threshold in the chiral limit, is analytically proved for microscopic quark models that preserve chiral symmetry. Implementing Ward-Takahashi identities, the isospin 0 and 2 scattering lengths are derived in exact agreement with Weinberg's low energy results. Our proof applies to alternative quark formulations including the Hamiltonian and Euclidean space Dyson-Schwinger approaches. Finally, the threshold \pi-\pi scattering amplitudes are calculated using the Dyson-Schwinger equations in the rainbow-ladder truncation, confirming the formal derivation.Comment: 10 pages, 7 figures, Revtex

12^{12}C properties with evolved chiral three-nucleon interactions

We investigate selected static and transition properties of $^{12}$C using ab initio No-Core Shell Model (NCSM) methods with chiral two- and three-nucleon interactions. We adopt the Similarity Renormalization Group (SRG) to assist convergence including up to three-nucleon (3N) contributions. We examine the dependences of the $^{12}$C observables on the SRG evolution scale and on the model-space parameters. We obtain nearly converged low-lying excitation spectra. We compare results of the full NCSM with the Importance Truncated NCSM in large model spaces for benchmarking purposes. We highlight the effects of the chiral 3N interaction on several spectroscopic observables. The agreement of some observables with experiment is improved significantly by the inclusion of 3N interactions, e.g., the B(M1) from the first $J^\pi T = 1^+ 1$ state to the ground state. However, in some cases the agreement deteriorates, e.g., for the excitation energy of the first $1^+ 0$ state, leaving room for improved next-generation chiral Hamiltonians.Comment: 11 pages, 9 figure

Studying pion effects in the quark propagator

Within the framework of Schwinger-Dyson and Bethe-Salpeter equations we investigate the importance of pions for the quark-gluon interaction. To this end we choose a truncation for the quark-gluon vertex that includes intermediate pion degrees of freedom and adjust the interaction such that unquenched lattice results for various current quark masses are reproduced. The corresponding Bethe-Salpeter kernel is constructed from constraints by chiral symmetry. After extrapolation to the physical point we find a considerable contribution of the pion back reaction to the quark mass function as well as to the chiral condensate. The quark wave function is less affected.Comment: Talk given at 11th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU 2007), Julich, Germany, 10-14 Sep 200

K_{l3} transition form factors

The rainbow truncation of the quark Dyson-Schwinger equation is combined with the ladder Bethe-Salpeter equation for the meson bound state amplitudes and the dressed quark-W vertex in a manifestly covariant calculation of the K_{l3} transition form factors and decay width in impulse approximation. With model gluon parameters previously fixed by the chiral condensate, the pion mass and decay constant, and the kaon mass, our results for the K_{l3} form factors and the kaon semileptonic decay width are in good agreement with the experimental data.Comment: 8 pages, 3 figures, Revte