Electroweak Sudakov effect on processes at TeV scale

In Next Linear Colliders at TeV scale, electroweak double logarithmic corrections, which come from the infrared behaviors of theory can not be neglected. It is well known that in QED and QCD, double logarithmic corrections are resummed to all orders, and these corrections can be exponentiated, resulting in the Sudakov form factor. However it is never trivial that double logarithmic corrections in electroweak theory can be exponentiated, because of the spontaneous breaking of symmetry and the pattern of that. We discuss the electroweak double logarithmic corrections at two loop level and explain the differences of ``Soft'' structure between the electroweak theory and QCD (the unbroken non-abelian gauge theory).Comment: 5 pages, 17 figures;Talk presented at Theory Meeting on Physics at Linear Colliders, March 15 - 17, 2001, KEK, Japa

"Randomization, Communication and Efficiency in Repeated Games with Imperfect Public Monitoring"

The present paper shows that the Folk Theorem under imperfect (public) information (Fudenberg, Levine and Maskin (1994)) can be obtained under much weaker set of assumptions, if we allow communication among players. Our results in particular show that for generic symmetric games with at least four players, we can drop the FLM condition on the number of actions and signals altogether and prove the folk theorem under the same condition as in the perfect monitoring case.

"Repeated Games, Entry in The New Palgrave Dictionary of Economics, 2nd Edition"

This entry shows why self-interested agents manage to cooperate in a long-term relationship. When agents interact only once, they often have an incentive to deviate from cooperation. In a repeated interaction, however, any mutually beneficial outcome can be sustained in an equilibrium. This fact, known as the folk theorem, is explained under various information structures. This entry also compares repeated games with other means to achieve efficiency and briefly discuss the scope for potential applications.

"Weakly Belief-Free Equilibria in Repeated Games with Private Monitoring"

Repeated games with imperfect private monitoring have a wide range of applications, but a complete characterization of all equilibria in this class of games has yet to be obtained. The existing literature has identified a relatively tractable subset of equilibria. The present paper introduces the notion of weakly belief-free equilibria for repeated games with imperfect private monitoring. This is a tractable class which subsumes, as a special case, a major part of the existing literature (the belief-free equilibria), and it is shown that this class can outperform the equilibria identified by the previous work.

"The Erosion and Sustainability of Norms and Morale"

The initially high performance of a socioeconomic organization is quite often subject to gradual erosion over time. We present a simple model which captures such a phenomenon. We assume that players are partly motivated by certain psychological factors, norms and morale, and they are willing to exert extra effort if others do so. This results in a "continuum" of equilibrium effort levels, whose minimum corresponds to the Nash equilibrium with respect to the material incentives. We show that repeated random shocks induce the erosion of equilibrium e ort levels, but they do not completely decay; in the long run a certain range of efforts are sustainable. Our model shows that different organizations typically enjoy diverse norms and morale, which persist for a long time, in the vicinity of the equilibrium determined by material incentives.

Boundary states in Gepner models

We extend the construction of the boundary states in Gepner models to the non-diagonal modular invariant theories, and derive the same supersymmetric conditions as the diagonal theories. We also investigate the relation between the microscopic charges of the boundary states and Ramond charges of the B-type D-branes on the Calabi-Yau threefolds with one K\"ahler modulus in the large volume limit.Comment: 15 pages, no figures, LaTeX, typos corrected, reference adde