Lowest Order Effective Field Theory for the weak ΛN\Lambda N interaction

The $|\Delta S|=1$ $\Lambda N$ interaction, responsible for the decay of hypernuclei, is studied by means of an Effective Field Theory where the long range physics is described by pion and kaon exchange mechanisms, and its short range counterpart is obtained from the most general non-derivative local four-fermion interaction. We show that, including the Lowest Order Parity Conserving contact terms, allows us to reproduce the total decay rates for $^5_\Lambda {\rm He}$, $^{11}_\Lambda {\rm B}$ and $^{12}_\Lambda {\rm C}$ with a reasonable value of ${\hat \chi^2}$, while in order to get a prediction for the Parity Violating (PV) asymmetry compatible with experiments, we have to include the Lowest Order PV contact pieces.Comment: 3 pages, no figures. Contribution to the 17th International IUPAP Conference on Few-body Problems in Physics, June 5-10, 2003 Durham, North Carolina, USA. Uses espcrc1.st

Neutrino Physics

The basic concepts of neutrino physics are presented at a level appropriate for integration into elementary courses on quantum mechanics and/or modern physics.Comment: Prepared for the American Journal of Physics; 50 pages; 11 figures (10 included); late

Extracting Electric Polarizabilities from Lattice QCD

Charged and neutral, pion and kaon electric polarizabilities are extracted from lattice QCD using an ensemble of anisotropic gauge configurations with dynamical clover fermions. We utilize classical background fields to access the polarizabilities from two-point correlation functions. Uniform background fields are achieved by quantizing the electric field strength with the proper treatment of boundary flux. These external fields, however, are implemented only in the valence quark sector. A novel method to extract charge particle polarizabilities is successfully demonstrated for the first time.Comment: 17 pages, 6 figures, a few clarifications added, published versio

Polaron self-trapping in a honeycomb net

Small polaron behavior in a two dimensional honeycomb net is studied by applying the strong coupling perturbative method to the Holstein molecular crystal model. We find that small optical polarons can be mobile also if the electrons are strongly coupled to the lattice. Before the polarons localize and become very heavy, there is infact a window of {\it e-ph} couplings in which the polarons are small and have masses of order $\simeq 5 - 50$ times the bare band mass according to the value of the adiabaticity parameter. The 2D honeycomb net favors the mobility of small optical polarons in comparison with the square lattice.Comment: 6 pages, 3 figures, to appear in J.Phys.:Condensed Matter {PACS: 63.10.+a, 63.20.Dj, 71.38.+i

Exotic Meson Decay Widths using Lattice QCD

A decay width calculation for a hybrid exotic meson h, with JPC=1-+, is presented for the channel h->pi+a1. This quenched lattice QCD simulation employs Luescher's finite box method. Operators coupling to the h and pi+a1 states are used at various levels of smearing and fuzzing, and at four quark masses. Eigenvalues of the corresponding correlation matrices yield energy spectra that determine scattering phase shifts for a discrete set of relative pi+a1 momenta. Although the phase shift data is sparse, fits to a Breit-Wigner model are attempted, resulting in a decay width of about 60 MeV when averaged over two lattice sizes.Comment: 9 pages, 8 figures, RevTex4, minor change to Fig.

Resonances in weak nonleptonic Omega^- decay

We examine the importance of J^P = 1/2^+, 1/2^- resonances for weak nonleptonic Omega^- decays within the framework of chiral perturbation theory. The spin-1/2 resonances are included into an effective theory and tree contributions to the Omega^- decays are calculated. We find significant contributions to the decay amplitudes and satisfactory agreement with experiment. This confirms and extends previous results wherein such spin-1/2 resonances were included in nonleptonic and radiative-nonleptonic hyperon decays.Comment: 12 pages, 2 figure

Resonances in radiative hyperon decays

The importance of resonances for the radiative hyperon decays is examined in the framework of chiral perturbation theory. Low lying baryon resonances are included into the effective theory and tree contributions to these decays are calculated. We find significant contributions to both the parity-conserving and parity-violating decay amplitudes and a large negative value for the asymmetry parameter in polarized Sigma^+ -> p gamma is found, in agreement with the experimental result alpha(p Sigma^+) = -0.76 +/- 0.08.Comment: 14 pages, 2 figure

On Quantum Groups in the Hubbard Model with Phonons

The correct Hamiltonian for an extended Hubbard model with quantum group symmetry as introduced by A. Montorsi and M. Rasetti is derived for a D-dimensional lattice. It is shown that the superconducting SUq(2) holds as a true quantum symmetry only for D = 1 and that terms of higher order in the fermionic operators in addition to phonons are required for a quantum symmetric hamiltonian. The condition for quantum symmetry is "half filling" and there is no local electron-phonon coupling. A discussion of Quantum symmetries in general is given in a formalism that should be readily accessible to non Hopf-algebraists.Comment: latex, 17 page