Wick's theorem for q-deformed boson operators

In this paper combinatorial aspects of normal ordering arbitrary words in the creation and annihilation operators of the q-deformed boson are discussed. In particular, it is shown how by introducing appropriate q-weights for the associated ``Feynman diagrams'' the normally ordered form of a general expression in the creation and annihilation operators can be written as a sum over all q-weighted Feynman diagrams, representing Wick's theorem in the present context.Comment: 9 page

The Kondo lattice model with correlated conduction electrons

We investigate a Kondo lattice model with correlated conduction electrons. Within dynamical mean-field theory the model maps onto an impurity model where the host has to be determined self-consistently. This impurity model can be derived from an Anderson-Hubbard model both by equating the low-energy excitations of the impurity and by a canonical transformation. On the level of dynamical mean-field theory this establishes the connection of the two lattice models. The impurity model is studied numerically by an extension of the non-crossing approximation to a two-orbital impurity. We find that with decreasing temperature the conduction electrons first form quasiparticles unaffected by the presence of the lattice of localized spins. Then, reducing the temperature further, the particle-hole symmetric model turns into an insulator. The quasiparticle peak in the one-particle spectral density splits and a gap opens. The size of the gap increases when the correlations of the conduction electrons become stronger. These findings are similar to the behavior of the Anderson-Hubbard model within dynamical mean-field theory and are obtained with much less numerical effort.Comment: 7 pages RevTeX with 3 ps figures, accepted by PR

Magnetic impurity coupled to interacting conduction electrons

We consider a magnetic impurity which interacts by hybridization with a system of weakly correlated electrons and determine the energy of the ground state by means of an 1/N_f expansion. The correlations among the conduction electrons are described by a Hubbard Hamiltonian and are treated to lowest order in the interaction strength. We find that their effect on the Kondo temperature, T_K, in the Kondo limit is twofold: First, the position of the impurity level is shifted due to the reduction of charge fluctuations, which reduces T_K. Secondly, the bare Kondo exchange coupling is enhanced as spin fluctuations are enlarged. In total, T_K increases. Both corrections require intermediate states beyond the standard Varma-Yafet ansatz. This shows that the Hubbard interaction does not just provide quasiparticles, which hybridize with the impurity, but also renormalizes the Kondo coupling.Comment: ReVTeX 19 pages, 3 uuenconded postscript figure

Magnetic Impurity in a Metal with Correlated Conduction Electrons: An Infinite Dimensions Approach

We consider the Hubbard model with a magnetic Anderson impurity coupled to a lattice site. In the case of infinite dimensions, one-particle correlations of the impurity electron are described by the effective Hamiltonian of the two-impurity system. One of the impurities interacts with a bath of free electrons and represents the Hubbard lattice, and the other is coupled to the first impurity by the bare hybridization interaction. A study of the effective two-impurity Hamiltonian in the frame of the 1/N expansion and for the case of a weak conduction-electron interaction (small U) reveals an enhancement of the usual exponential Kondo scale. However, an intermediate interaction (U/D = 1 - 3), treated by the variational principle, leads to the loss of the exponential scale. The Kondo temperature T_K of the effective two-impurity system is calculated as a function of the hybridization parameter and it is shown that T_K decreases with an increase of U. The non-Fermi-liquid character of the Kondo effect in the intermediate regime at the half filling is discussed.Comment: 12 pages with 8 PS figures, RevTe

Familial transmission of alcohol use, III. Impact of imitation non-imitation of parent alcohol use (1960) on the sensible/problem drinking of their offspring (1977)

Imitation/non-imitation by adult offspring of alcohol-related parent behavior was examined in the context of the fall-off effect’ and of sensible/problem alcohol use, two processes which tend to constrain drinking. Evidence indicates there is more imitation by adult offspring of abstemious parents (both abstainer and low volume) than of high volume parents. Adult offspring drink significantly less, on the average, than their high volume parents, a phenomenon here termed‘fall-off effect’ for both men and women with respect to either their fathers or mothers. This fall-off among social drinkers appears when the mother approaches or the father consumes at or more than a typical daily drinking level (≥1 drink per day). More sensible drinking occurs among adult offspring when (I) the parent has no drinking problem-signs than when the parent has drinking problems (this pattern appears at all levels of offspring consumption), and (2) when parents drink at high volume and have no problems for those offspring who do not imitate parent volume. Drinking “sensibly’ appears to be associated directly with the level of parent alcohol use and offsprings’ own drinking levels (considered as imitation or non-imitation of parents), and indirectly with offspring recall of problematic intake by parents. Drinking sensibly is a medical, education and public health issue.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72393/1/j.1360-0443.1990.tb03439.x.pd

Ferron-like states in YBa_2Cu_3O_(6+x)

With the use of the Hubbard model bound hole states in YBa_2Cu_3O_(6+x) are studied. For the parameters of this crystal the exchange interaction between the spin-carrying chain ion O^- and Cu-O plane sites is shown to ensure the formation of a large ferromagnetically ordered clusters around holes in the plane.Comment: 8 pages, 2 figure

A Bayesian model for longitudinal count data with non-ignorable dropout

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73907/1/j.1467-9876.2008.00628.x.pd

Effects of fluoxetine on the oral environment of bulimics

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73809/1/j.1399-302X.1993.tb00545.x.pd