arXiv subjects

D. W. Murray

Publications and source records attributed to D. W. Murray.

7 recordsLinked to original sources

arXiv1998

Enhancement factor for the electron electric dipole moment in francium and gold atoms

If electrons had an electric dipole moment (EDM) they would induce EDMs of atoms. The ratio of the atomic EDM to the electron EDM for a particular atom is called the enhancement factor, R. We calculate the enhancement factor for the francium and gold atoms, with the results 910 plus/minus 5% for Fr and 260 plus/minus 15% for Au. The large values of these enhancement factors make these atoms attractive for electron EDM measurements, and hence the search for time-reversal invariance violation.

physics.atom-ph↗

arXiv1998

Dyons as a source of CP and time invariance violation: electric dipole moments and K-meson decays

We consider a mechanism by which dyons (electrically charged magnetic monopoles) can produce both a T- and P-odd (i.e. time reversal invariance and parity violating) mixed polarizability beta [defined by Delta E = -beta E.B, where Delta E is the energy change when electric (E) and magnetic (B) fields are applied to a system] and a T- and P-odd interaction between two particles: psi_1-bar gamma_5 psi_1 psi_2-bar psi_2, where the psi_i are electron and quark spinors. The latter can create atomic and neutron electric dipole moments (EDMs). From experimental bounds on these we find limits on the properties of dyons. Our best limit, using the experimental limit for the EDM of the Tl atom, is M |Q g (Q^2 - g^2)|^(-1/4) > 6 GeV, where M is the dyon mass and Q is the electric and g the magnetic charge of the dyons. The contribution of dyons to CP violation in K-meson decays is also estimated.

hep-ph↗

arXiv1997

Time invariance violating nuclear electric octupole moments

The existence of a nuclear electric octupole moment (EOM) requires both parity and time invariance violation. The EOMs of odd $Z$ nuclei that are induced by a particular T- and P-odd interaction are calculated. We compare such octupole moments with the collective EOMs that can occur in nuclei having a static octupole deformation. A nuclear EOM can induce a parity and time invariance violating atomic electric dipole moment, and the magnitude of this effect is calculated. The contribution of a nuclear EOM to such a dipole moment is found, in most cases, to be smaller than that of other mechanisms of atomic electric dipole moment production.

nucl-th↗

arXiv1997

The anapole moment and nucleon weak interactions

From the recent measurement of parity nonconservation (PNC) in the Cs atom we have extracted the constant of the nuclear spin dependent electron-nucleon PNC interaction, $κ= 0.442 (63)$; the anapole moment constant, $κ_a = 0.364 (62)$; the strength of the PNC proton-nucleus potential, $g_p = 7.3 \pm 1.2 (exp.) \pm 1.5 (theor.)$; the $π$-meson-nucleon interaction constant, $f_π\equiv h_π^{1} = [9.5 \pm 2.1 (exp.) \pm 3.5 (theor.)] \times 10^{-7}$; and the strength of the neutron-nucleus potential, $g_n = -1.7 \pm 0.8 (exp.) \pm 1.3 (theor.)$.

nucl-th↗

arXiv1996

Limits on the monopole magnetic field from measurements of the electric dipole moments of atoms, molecules and the neutron

A radial magnetic field can induce a time invariance violating electric dipole moment (EDM) in quantum systems. The EDMs of the Tl, Cs, Xe and Hg atoms and the neutron that are produced by such a field are estimated. The contributions of such a field to the constants, $χ$ of the T,P-odd interactions $χ_e {\bf N} \cdot {\bf s}/s$ and $χ_N {\bf N} \cdot {\bf I}/I$ are also estimated for the TlF, HgF and YbF molecules (where ${\bf s}$ (${\bf I}$) is the electron (nuclear) spin and ${\bf N}$ is the molecular axis). The best limit on the contact monopole field can be obtained from the measured value of the Tl EDM. The possibility of such a field being produced from polarization of the vacuum of electrically charged magnetic monopoles (dyons) by a Coulomb field is discussed, as well as the limit on these dyons. An alternative mechanism involves chromomagnetic and chromoelectric fields in QCD.

atom-ph↗

arXiv1996

Quantum Monte Carlo study of the one-dimensional Holstein model of spinless fermions

The Holstein model of spinless fermions interacting with dispersionless phonons in one dimension is studied by a Green's function Monte Carlo technique. The ground state energy, first fermionic excited state, density wave correlations, and mean lattice displacement are calculated for lattices of up to 16 sites, for one fermion per two sites, i.e., a half-filled band. Results are obtained for values of the fermion hopping parameter of $t=0.1 ω$, $ω$, and $10 ω$ where $ω$ is the phonon frequency. At a finite fermion-phonon coupling $g$ there is a transition from a metallic phase to an insulating phase in which there is charge-density-wave order. Finite size scaling is found to hold in the metallic phase and is used to extract the coupling dependence of the Luttinger liquid parameters, $u_ρ$ and $K_ρ$, the velocity of charge excitations and the correlation exponent, respectively. For free fermions ($g=0$) and for strong coupling ($g^2 \gg t ω$) our results agree well with known analytic results. For $t=ω$ and $t=10ω$ our results are inconsistent with the metal-insulator transition being a Kosterlitz-Thouless transition.\\

cond-mat↗

arXiv1995

The incoherent part of the spin-wave polarization operator in the t-J model

A calculation of the spin-wave polarization operator is very important for the analysis of the magnetic structure of high temperature superconductors. We analyze the significance of the incoherent part of the spin-wave polarization operator within the framework of the t-J model. This part is calculated analytically for small doping with logarithmic accuracy. We conclude that the incoherent part of the spin-wave polarization operator is negligible in comparison with the coherent part.

cond-mat↗