Magnetic and pair correlations of the Hubbard model with next-nearest-neighbor hopping

A combination of analytical approaches and quantum Monte Carlo simulations is used to study both magnetic and pairing correlations for a version of the Hubbard model that includes second-neighbor hopping $t^{\prime }=-0.35t$ as a model for high-temperature superconductors. Magnetic properties are analyzed using the Two-Particle Self-Consistent approach. The maximum in magnetic susceptibility as a function of doping appears both at finite $$ and at $t^{\prime }=0$ but for two totally different physical reasons. When $t^{\prime }=0$, it is induced by antiferromagnetic correlations while at $t^{\prime }=-0.35t$ it is a band structure effect amplified by interactions. Finally, pairing fluctuations are compared with $$-matrix results to disentangle the effects of van Hove singularity and of nesting on superconducting correlations. The addition of antiferromagnetic fluctuations increases slightly the $d$-wave superconducting correlations despite the presence of a van Hove singularity which tends to decrease them in the repulsive model. Some aspects of the phase diagram and some subtleties of finite-size scaling in Monte Carlo simulations, such as inverted finite-size dependence, are also discussed.Comment: Revtex, 8 pages + 15 uuencoded postcript figure

SERUM LUTEINIZING HORMONE AND FOLLICLE STIMULATING HORMONE IN NORMAL CHILDREN AND PATIENTS WITH VARIOUS CLINICAL DISORDERS

Serum concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were determined in 329 normal children and 185 individuals with endocrinological abnormalities or variations of development. A significant increase of gonadotrophins is noted at the onset of puberty among the boys and at menarche for girls. The values are compared with serum concentrations of LH and FSH in children with abnormalities of sexual development, pituitary malfunction as well as other clinical abnormalities. Comparable levels for age and stage of development were found for premature thelarche, premature adrenarche, cryptorchidism, male pseudohermaphroditism and pubertal gynaecomastia. Hypogonadal individuals (Klinefelter's and Turner's syndrome, pure ovarian dysgenesis and testicular dysgenesis) have markedly elevated values while those with pituitary hypofunction had low values. Patients with sexual prococity tended to have elevated concentrations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73601/1/j.1365-2265.1973.tb00427.x.pd

Gibbons-Hawking Boundary Terms and Junction Conditions for Higher-Order Brane Gravity Models

We derive the most general junction conditions for the fourth-order brane gravity constructed of arbitrary functions of curvature invariants. We reduce these fourth-order theories to second order theories at the expense of introducing new scalar and tensor fields - the scalaron and the tensoron. In order to obtain junction conditions we apply the method of generalized Gibbons-Hawking boundary terms which are appended to the appropriate actions. After assuming the continuity of the scalaron and the tensoron on the brane, we recover junction conditions for such general brane universe models previously obtained by different methods. The derived junction conditions can serve studying the cosmological implications of the higher-order brane gravity models.Comment: REVTEX4, 6 pages, no figures, version to match a JCAP accepted pape

Scalin behavior of multifractal-moment distributions near criticality

Sample to sample fluctuations of the multifractal moments of percolating random-resistor networks are studied via Monte Carlo simulations. For systems of size $L$, these fluctuations depend on $\Delta p$, the deviation from the critical concentration, only through the scaled variable $\Delta pL^{1/\nu}$. At $\Delta p=0$, these fluctuations depend on $h$, the ratio of the good and bad conductances, only through $hL^{\phi}$. This is consistent with a previously proposed scaling ansatz for the joint probability distribution of multifractal moments. In the $\Delta p \neq 0$ direction, the relative fluctuations are largest when the bulk correlation length is of the order of $L$.On étudie ici par simulation Monte Carlo les fluctuations d'un échantillon à l'autre des moments multifractals de réseaux de résistances aléatoires près du seuil de percolation. Pour des systèmes de taille $L$, les fluctuations ne dépendent de $\Delta_p$ qu'à travers la variable d'échelle $\Delta pL^{1/\nu} .\, A \Delta p=0$, ce n'est qu'à travers la variable d'échelle $hL^{\phi}$ que ces fluctuations dépendent de $h$, le rapport entre les bonnes et les mauvaises résistances. Ces résultats sont en accord avec les prédictions d'une forme d'échelle précédemment proposée pour la distribution de probabilité conjointe des moments multifractals. Dans la direction $\Delta p \neq 0$, les fluctuations relatives sont maximales lorsque la longueur de corrélation du massif est de l'ordre de $L$