Eleven-dimensional massless superparticles and matrix theory spin-orbit couplings revisited

The classical probe dynamics of the eleven-dimensional massless superparticles in the background geometry produced by N source M-momenta is investigated in the framework of N-sector DLCQ supergravity. We expand the probe action up to the two fermion terms and find that the fermionic contributions are the spin-orbit couplings, which precisely agree with the matrix theory calculations. We comment on the lack of non-perturbative corrections in the one-loop matrix quantum mechanics effective action and its compatibility with the supergravity analysis.Comment: 11 pages, Latex, no figure

Two-pion-exchange parity-violating potential and n⃗p→dγ\vec{n} p \to d \gamma

We calculate the parity-violating nucleon-nucleon potential in heavy-baryon chiral perturbation theory up to the next-to-next-to-leading order. The one-pion exchange comes in the leading order and the next-to-next-to-leading order consists of two-pion-exchange and the two-nucleon contact terms. In order to investigate the effect of the higher order contributions, we calculate the parity-violating asymmetry in $\vec{n} p \to d \gamma$ at the threshold. The one-pion dominates the physical observable and the two-pion contribution is about or less than 10% of the one-pion contribution.Comment: 3 pages, contribution to the workshop PAVI06 held in Milos island, Greece, May 16-20, 200

The Environmental Consequences of Economic Growth Revisited

Although numerous studies on the economic growth-environment nexus exist, relatively little attention has been paid to model the effect of income on the environment, controlling for other relevant factors. The primary contribution of this paper is to examine the environmental consequences of economic growth for developed and developing countries in a dynamic cointegration framework by incorporating energy consumption and foreign direct investment (FDI). For this purpose, an autoregressive distributed lag (ARDL) approach to cointegration is applied to annual data for the period 1971-2005. Results show that economic growth improves environmental quality for developed countries in the long-run, but worsen the environment in developing economies. We also find that energy consumption has a detrimental long-run effect on environmental quality for both developed and developing countries. FDI, however, is found to have little long-run effect on the environment in both developed and developing countries. Finally, it is found that, in the short-run, income and energy play key roles in affecting the environment in developed and developing countries, but FDI does not.

Theoretical study of X-ray absorption of three-dimensional topological insulator Bi2Se3\mathrm{Bi}_2\mathrm{Se}_3

X-ray absorption edge singularity which is usually relevant for metals is studied for the prototype topological insulator $\mathrm{Bi}_2\mathrm{Se}_3$. The generalized integral equation of Nozi\`eres and Dominicis type for X-ray edge singularity is derived and solved. The spin texture of surfaces states causes a component of singularity dependent on the helicity of the spin texture. It also yields another component for which the singularity from excitonic processes is absent.Comment: RevTeX 4.1. 4 pages, no figur