The Extension Structure of 2D Massive Current Algebras

The extension structure of the 2-dimensional current algebra of non-linear sigma models is analysed by introducing Kostant Sternberg $(L,M)$ systems. It is found that the algebra obeys a two step extension by abelian ideals. The second step is a non-split extension of a representation of the quotient of the algebra by the first step of the extension. The cocycle which appears is analysed.Comment: 9 page

The Algebra of the Energy-Momentum Tensor and the Noether Currents in Classical Non-Linear Sigma Models

The recently derived current algebra of classical non-linear sigma models on arbitrary Riemannian manifolds is extended to include the energy-momentum tensor. It is found that in two dimensions the energy-momentum tensor $\theta_{\mu\nu}$, the Noether current $j_\mu$ associated with the global symmetry of the theory and the composite field $j$ appearing as the coefficient of the Schwinger term in the current algebra, together with the derivatives of $j_\mu$ and $j$, generate a closed algebra. The subalgebra generated by the light-cone components of the energy-momentum tensor consists of two commuting copies of the Virasoro algebra, with central charge $\, c\!=\!0$, reflecting the classical conformal invariance of the theory, but the current algebra part and the semidirect product structure are quite different from the usual Kac-Moody / Sugawara type construction.Comment: 10 pages, THEP 92/2

Current Algebra of Classical Non-Linear Sigma Models

The current algebra of classical non-linear sigma models on arbitrary Riemannian manifolds is analyzed. It is found that introducing, in addition to the Noether current $j_\mu$ associated with the global symmetry of the theory, a composite scalar field $j$, the algebra closes under Poisson brackets.Comment: 6 page

Daily exposure to a nonphotic stimulus can alter photoperiodic response to short days in hamsters.

The ability of mammals to measure seasonal changes in daylength depends upon a circadian clock and the phase-relationship between this clock and the light: dark cycle. Recently, a number of pharmacological and nonpharmacological stimuli have been shown to have pronounced effects on the phase of the circadian clock of rodents. The objective of the present study was to determine if a drug-induced change in the phase-relationship between a measurable circadian rhythm (i.e. wheel running behavior) and the light:dark cycle would alter the effects of the light cycle on the neuroendocrine-gonadal axis. Adult male hamsters with regressed testes due to exposure to an inhibitory 10:14-hr light:dark cycle were daily injected with vehicle or the short-acting benzodiazepine, triazolam, while remaining on short days, while a control group of hamsters was transferred to a photostimulatory 14:10-hr light:dark cycle. Two other groups of hamsters with regressed testes were blinded and daily injected with vehicle or triazolam. The injections were timed to occur about 4 hr before activity onset because previous studies had demonstrated that injections of triazolam at this time can lead to a phase advance in the activity rhythm. The circadian rhythm of wheel running behavior was measured in all the animals maintained on the 10:14-hr light:dark cycle in order to monitor circadian phase. While no testicular growth was observed after 25 days of vehicle injections, growth was observed in the triazolam-treated animals that was comparable to that observed in control animals transferred to long days. Testicular growth in triazolam-treated animals was associated with an earlier onset of locomotor activity, when compared with the vehicle-treated animals. Importantly, triazolam had no effect on the testicular size of blind animals. These results indicate that daily injections of triazolam can stimulate neuroendocrine-gonadal activity by altering the phase-relationship between the cycle and the circadian clock involved in photoperiodic time measurement, and that agents which can affect the clock may be useful in altering seasonal cycles.Journal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.SCOPUS: ar.jinfo:eu-repo/semantics/publishe