Whittaker Modules for the twisted Heisenberg-Virasoro Algebra

We define Whittaker modules for the twisted Heisenberg-Virasoro algebra and obtain analogues to several results from the classical setting, including a classification of simple Whittaker modules by central characters.Comment: Latex, 18 pag

Improving Stochastic Estimator Techniques for Disconnected Diagrams

Disconnected diagrams are expected to be sensitive to the inclusion of dynamical fermions. We present a feasibility study for the observation of such effects on the nucleonic matrix elements of the axial vector current, using SESAM full QCD vacuum configurations with Wilson fermions on $16^3\times 32$ lattices, at $\beta =5.6$. Starting from the standard methods developed by the Kentucky and Tsukuba groups, we investigate the improvement from various refinements thereof.Comment: One author added. Contribution to Lattice 1997, 3 pages LaTex, to appear in Nucl. Phys. B (Proc. Suppl.

Photon-radion conversion cross-sections in external electromagnetic field

An attempt is made to present some experimental predictions of the Randall-Sundrum model, where compactification radius of the extra dimension is stabilized by the radion, which is a scalar field lighter than the graviton Kaluza-Klein states. We calculate the conversion cross-sections of the photons into the radions in the external electromagnetic fields, namely, in the static fields and in a periodic field of the wave guide. Numerical evaluations of the total cross-sections are also given. Our result shows that the conversion cross-section in the static electric field is quite small. But, in the static magnetic and periodic fields, the radion productions are much enhanced.Comment: 17 pages, 6 figures, Version published in JHE

On time-inhomogeneous controlled diffusion processes in domains

Time-inhomogeneous controlled diffusion processes in both cylindrical and noncylindrical domains are considered. Bellman's principle and its applications to proving the continuity of value functions are investigated.Comment: Published at http://dx.doi.org/10.1214/009117906000000395 in the Annals of Probability (http://www.imstat.org/aop/) by the Institute of Mathematical Statistics (http://www.imstat.org

On Representations of Conformal Field Theories and the Construction of Orbifolds

We consider representations of meromorphic bosonic chiral conformal field theories, and demonstrate that such a representation is completely specified by a state within the theory. The necessary and sufficient conditions upon this state are derived, and, because of their form, we show that we may extend the representation to a representation of a suitable larger conformal field theory. In particular, we apply this procedure to the lattice (FKS) conformal field theories, and deduce that Dong's proof of the uniqueness of the twisted representation for the reflection-twisted projection of the Leech lattice conformal field theory generalises to an arbitrary even (self-dual) lattice. As a consequence, we see that the reflection-twisted lattice theories of Dolan et al are truly self-dual, extending the analogies with the theories of lattices and codes which were being pursued. Some comments are also made on the general concept of the definition of an orbifold of a conformal field theory in relation to this point of view.Comment: 11 pages, LaTeX. Updated references and added preprint n

A simple model of gauged lepton and baryon charges

We argue that simpler fermionic contents, responsible for the extension of the standard model with gauged lepton and baryon charges, can be constructed by assuming existence of so-called leptoquarks (j,k) with exotic electric charges q_j=1/2, q_k=-1/2. Some new features in our model are that (i) as the natural consequences of anomaly cancelation the right-handed neutrinos exist, and the number of the observed fermion families is equal to the number of the fundamental colors; (ii) although the lepton and baryon charges are conserved, the neutrinos can obtain small masses through the type I seesaw mechanism in similarity to the standard context, and the baryogenesis can be generated in several cases. They all are natural results due to the spontaneous breaking of these charges. Some constraints on the new physics via flavor changing and related phenomenologies such as the stable scalar with anomalous electric charge and interested processes at colliders are also discussed.Comment: 13 pages, revised versio

Magnetic properties of Mn-doped Ge46 and Ba8Ge46 clathrates

We present a detailed study of the magnetic properties of unique cluster assembled solids namely Mn doped Ge46 and Ba8Ge46 clathrates using density functional theory. We find that ferromagnetic (FM) ground states may be realized in both the compounds when doped with Mn. In Mn2Ge44, ferromagnetism is driven by hybridization induced negative exchange splitting, a generic mechanism operating in many diluted magnetic semiconductors. However, for Mn-doped Ba8Ge46 clathrates incorporation of conduction electrons via Ba encapsulation results in RKKY-like magnetic interactions between the Mn ions. We show that our results are consistent with the major experimental observations for this system.Comment: 6 pages, 4 figure