Tuning the generalized Hybrid Monte Carlo algorithm

We discuss the analytic computation of autocorrelation functions for the generalized Hybrid Monte Carlo algorithm applied to free field theory and compare the results with numerical results for the $O(4)$ spin model in two dimensions. We explain how the dynamical critical exponent $z$ for some operators may be reduced from two to one by tuning the amount of randomness introduced by the updating procedure, and why critical slowing down is not a problem for other operators.Comment: 4 pages, to be published in the Proceedings of Lattice 95, uuencoded PostScript fil

Towards the Theory of Cosmological Phase Transitions

We discuss recent progress (and controversies) in the theory of finite temperature phase transitions. This includes the structure of the effective potential at a finite temperature, the infrared problem in quantum statistics of gauge fields, the theory of formation of critical and subcritical bubbles and the theory of bubble wall propagation.Comment: 50 p

Influence of damping on the vanishing of the electro-optic effect in chiral isotropic media

Using first principles, it is demonstrated that radiative damping alone cannot lead to a nonvanishing electro-optic effect in a chiral isotropic medium. This conclusion is in contrast with that obtained by a calculation in which damping effects are included using the standard phenomenological model. We show that these predictions differ because the phenomenological damping equations are valid only in regions where the frequencies of the applied electromagnetic fields are nearly resonant with the atomic transitions. We also show that collisional damping can lead to a nonvanishing electrooptic effect, but with a strength sufficiently weak that it is unlikely to be observable under realistic laboratory conditions

Moringa oleifera leaf powder ameriorate neuronal degeneration in the entorhinal cortex of adolescent male alcoholic rats

Moringa oleifera is an important medicinal plant that has shown great promise in CNS conditions. However, the potential protective effect of M. oleifera in the entorhinal cortex (EC) of adolescent rats with Alcohol Use Disorder (AUD) is still unknown. The effect of M. oleifera was therefore assessed in an adolescent model of AUD.Two groups of rats were orogastrically fed thrice daily with 5 g/kg ethanol (25% w/v), and 5 g/kg ethanol (25% w/v) plus M. oleifera (10 mg/kg body weight) respectively in diluted nutritionally complete diet (50%v/v). A control group was fed a nutritionally complete diet (50%v/v) made isocaloric with glucose. Cytoarchitectural study of the entorhinal cortex was examined with H&E. The extent of damage was assessed biochemically by determination of tissue levels of lipid peroxidation and protein oxidation. After 4 days of binge alcohol treatment, histologic and biochemical indices of degeneration in EC were significantly reduced by M. oleifera supplementation compared with the non-supplemented rats. In conclusion, M. oleifera attenuates alcohol-induced entorhinal degeneration in the rats by alleviating oxidative stress and reducing the expression of degenerative changes in the EC.Key words: Alcoholism, Medicinal plant, Nutraceuticals, Neuroprotectio

Inuit Knowledge of Long-term Changes in a Population of Arctic Tundra Caribou

Indigenous peoples possess knowledge about wildlife that dates back many generations. Inuit observations of historical changes in a caribou population on southern Baffin Island, collected from 43 elders and active hunters during 1983-95, indicate that caribou were abundant and their distributions extensive in most coastal areas of southern Baffin Island from c.1900-25. Subsequently, caribou distributions contracted and abundance declined, probably reaching an overall low in the 1940s. Beginning in the mid-1950s, distributions and abundance increased gradually, at least until the mid-1980s. Changes in distribution occurred mainly during autumn, as caribou migrated to their wintering areas. Within most wintering areas, increases in caribou abundance followed a process of range expansion, range drift (i.e., expanding on one front while contracting on another), and finally range shift (i.e., mass emigration to a new winter range). During the population decline and low, the caribou often exhibited winter range volatility (i.e., frequent, unpredictable interannual range shifts). On the basis of Inuit descriptions of caribou abundance, we estimated that the population as a whole decreased an average of 9% annually from 1910 to 1940, and then increased about 8% annually from 1940 to 1980. This pattern was largely consistent across southern Baffin Island. As Inuit elders had predicted in 1985, the population essentially abandoned its highest-density wintering area on Foxe Peninsula during the late 1980s, apparently emigrating en masse to a new wintering area on Meta Incognita Peninsula, about 375 km to the southeast. Inuit knowledge suggested that caribou population fluctuations are cyclic, with each full cycle occurring over the lifetime of an elder. Both this study and historical records dating from 1860 support a periodicity of 60-80 years for fluctuations of the South Baffin caribou population. Inuit elders suggested that the abundance of caribou on wintering areas decreases several years after caribou occupy small coastal islands, a phenomenon currently occurring throughout southern Baffin Island, except on Cumberland Peninsula. The Inuit recognize two ecotypes of caribou: migratory upland-lowland caribou and resident mountain-plateau caribou. After migratory caribou from Foxe Peninsula shifted their winter range around 1990, Meta Incognita Peninsula was occupied by both ecotypes. The migratory caribou apparently occupy low elevations, while the resident caribou remain in the mountains, producing two seasonal migratory patterns. Inuit knowledge proved to be temporally and spatially more complete than the written record.Les peuples autochtones possèdent des connaissances sur la faune qui remontent à des générations. Les observations inuit sur les changements historiques survenus dans une population de caribous sur la partie méridionale de l'île de Baffin recueillies auprès de 44 anciens et chasseurs en activité entre 1983 et 1995 révèlent que, d'environ 1900 à 1925, le caribou était abondant et réparti sur une vaste superficie dans la plupart des zones côtières du sud de l'île de Baffin. Par la suite, le domaine du caribou s'est rétréci et l'animal a diminué en nombre, atteignant probablement son niveau le plus bas dans les années 1940. À partir du milieu des années 1950, la distribution et le nombre d'animaux ont augmenté graduellement, au moins jusqu'au milieu des années 1980. La distribution changeait surtout durant l'automne, quand le caribou migrait vers ses aires d'hivernage. Dans toute aire d'hivernage, l'augmentation du nombre de caribous suivait un processus d'expansion du territoire, de dérive du territoire (c.-à-d. expansion sur un front en même temps que contraction sur un autre), et finalement de déplacement du territoire (c.-à-d. émigration généralisée du caribou vers une nouvelle aire d'hivernage). Durant la baisse et le minimum de population, l'aire du caribou se révélait souvent instable (c-.à-d. que d'une année à l'autre, l'animal changeait fréquemment de territoire, et ce, d'une façon imprévisible). En se fondant sur les descriptions inuit de l'abondance du caribou, on a estimé que l'ensemble de la population a baissé en moyenne de 9 p. cent par an de 1910 à 1940, puis augmenté de près de 8 p. cent par an de 1940 à 1980. Ce schéma était à peu près identique dans toute la partie méridionale de l'île de Baffin. Comme les Inuit l'avaient prédit en 1985, la population a quasiment abandonné son aire d'hivernage à très forte densité sur la péninsule Foxe à la fin des années 1980, pour apparemment émigrer en masse vers une nouvelle aire d'hivernage sur la péninsule Meta Incognita située à environ 375 km au sud-est. Le savoir inuit suggérait que les fluctuations dans la population du caribou sont cycliques, chaque cycle complet couvrant la durée de vie d'un ancien. Cette étude, de même que les dossiers historiques datant de 1860, appuient une périodicité de 60 à 80 ans pour les fluctuations de la population du caribou du sud de Baffin. Les anciens inuit suggéraient que les sous-populations de caribou sur l'île principale diminuent plusieurs années après que l'animal a occupé les petites îles côtières, phénomène qui se passe actuellement dans toute la partie méridionale de l'île de Baffin, sauf dans la péninsule Cumberland. Les anciens inuit identifient deux écotypes de caribou: celui qui migre des hautes terres vers les basses terres et inversement et celui qui réside en permanence sur les montagnes et plateaux. Après que le caribou de la péninsule Foxe a changé d'aire d'hivernage vers 1990, la péninsule Meta Incognita a été occupée par les deux écotypes. Le caribou migrateur occupe apparemment les sites bas, tandis que le caribou sédentaire reste dans les montagnes, ce qui donne lieu à deux schémas migratoires saisonniers. Les connaissances des Inuit se sont avérées plus complètes que celles consignées dans les documents écrits, autant en ce qui concerne les données spatiales que temporelles

Inhomogeneous Neutrino Degeneracy and Big Bang Nucleosynthesis

We examine Big Bang nucleosynthesis (BBN) in the case of inhomogenous neutrino degeneracy, in the limit where the fluctuations are sufficiently small on large length scales that the present-day element abundances are homogeneous. We consider two representive cases: degeneracy of the electron neutrino alone, and equal chemical potentials for all three neutrinos. We use a linear programming method to constrain an arbitrary distribution of the chemical potentials. For the current set of (highly-restrictive) limits on the primordial element abundances, homogeneous neutrino degeneracy barely changes the allowed range of the baryon-to-photon ratio. Inhomogeneous degeneracy allows for little change in the lower bound on the baryon-to-photon ratio, but the upper bound in this case can be as large as 1.1 \times 10^{-8} (only electron neutrino degeneracy) or 1.0 \times 10^{-9} (equal degeneracies for all three neutrinos). For the case of inhomogeneous neutrino degeneracy, we show that there is no BBN upper bound on the neutrino energy density, which is bounded in this case only by limits from structure formation and the cosmic microwave background.Comment: 6 pages, no figure

On the Dynamics of Light Quarks in QCD

We describe recent results concerning the behavior of lattice QCD with light dynamical Wilson and Staggered quarks. We show that it is possible to reach regions of parameter space with light pions $m_\pi\approx 0.2/a$ using Wilson fermions. If the Hybrid Molecular Dynamics (HMD) algorithm is used with the same parameters it gives incorrect results. We also present preliminary results using a higher-order integration scheme.Comment: 4 pages (all in postscript), proceedings of LAT'9

Influence of radiative damping on the optical-frequency susceptibility

Motivated by recent discussions concerning the manner in which damping appears in the electric polarizability, we show that (a) there is a dependence of the nonresonant contribution on the damping and that (b) the damping enters according to the "opposite sign prescription." We also discuss the related question of how the damping rates in the polarizability are related to energy-level decay rates