Jeremy W. Holt

Crystallographic space groups in geometric algebra

We present a complete formulation of the two-dimensional and three-dimensional crystallographic space groups in the conformal geometric algebra of Euclidean space. This enables a simple new representation of translational and orthogonal symmetries in a multiplicative group of versors. The generators of each group are constructed directly from a basis of lattice vectors that define its crystal class. A new system of space group symbols enables one to unambiguously write down all generators of a given space group directly from its symbol.

Shell Model Description of the {sup 14}C Dating {beta} Decay with Brown-Rho-Scaled NN Interactions

We present shell model calculations for the beta decay of 14C to the 14N ground state, treating the states of the A=14 multiplet as two 0p holes in an 16O core. We employ low-momentum nucleon-nucleon (NN) interactions derived from the realistic Bonn-B potential and find that the Gamow-Teller (GT) matrix element is too large to describe the known lifetime. By using a modified version of this potential that incorporates the effects of Brown-Rho scaling medium modifications, we find that the GT matrix element vanishes for a nuclear density around 85% that of nuclear matter. We find that the splitting between the (J(pi),T)=(1(+),0) and (J(pi),T)=(0(+),1) states in 14N is improved using the medium-modified Bonn-B potential and that the transition strengths from excited states of 14C to the 14N ground state are compatible with recent experiments.

Nuclear matter with Brown–Rho-scaled Fermi liquid interactions

Abstract We present a description of symmetric nuclear matter within the framework of Landau Fermi liquid theory. The low momentum nucleon–nucleon interaction V low - k is used to calculate the effective interaction between quasiparticles on the Fermi surface, from which we extract the quasiparticle effective mass, the nuclear compression modulus, the symmetry energy, and the anomalous orbital gyromagnetic ratio. The exchange of density, spin, and isospin collective excitations is included through the Babu–Brown induced interaction, and it is found that in the absence of three-body forces the self-consistent solution to the Babu–Brown equations is in poor agreement with the empirical values for the nuclear observables. This is improved by lowering the nucleon and meson masses according to Brown–Rho scaling, essentially by including a scalar tadpole contribution to the meson and nucleon masses, as well as by scaling g A . We suggest that modifying the masses of the exchanged mesons is equivalent to introducing a short-range three-body force, and the net result is that the Brown–Rho double decimation [G.E. Brown, M. Rho, Phys. Rep. 396 (2004) 1] is accomplished all at once.

Low-momentum NN interactions and all-order summation of ring diagrams of symmetric nuclear matter

We study the equation of state for symmetric nuclear matter using a ring-diagram approach in which the particle-particle hole-hole (pphh) ring diagrams within a momentum model space of decimation scale \ensuremath{\Lambda} are summed to all orders. The calculation is carried out using the renormalized low-momentum nucleon-nucleon (

Divergence of the isospin-asymmetry expansion of the nuclear equation of state in many-body perturbation theory

\mathit{NN}

Nuclear pairing from microscopic forces: singlet channels and higher-partial waves

) interaction

Thermodynamics of isospin-asymmetric nuclear matter from chiral effective field theory

{V}_{\mathrm{low}\text{\ensuremath{-}}k}

Structure of neutron star crusts from new Skyrme effective interactions constrained by chiral effective field theory

, which is obtained from a bare

Microscopically constrained mean field models from chiral nuclear thermodynamics

\mathit{NN}

Charged-current reactions in the supernova neutrino-sphere

potential by integrating out the high-momentum components beyond \ensuremath{\Lambda}. The bare