A dynamical characterization of acylindrically hyperbolic groups

We give a dynamical characterization of acylindrically hyperbolic groups. As an application, we prove that non-elementary convergence groups are acylindrically hyperbolic

Cohomology of group theoretic Dehn fillings I: Cohen-Lyndon type theorems

This is the first paper of three papers in a row aiming to study cohomology of group theoretic Dehn fillings. In the present paper, we prove a particular free product structure, which is termed the Cohen-Lyndon property, of Dehn filling kernels. As an application, we describe the structure of relative relation modules of Dehn fillings.Comment: 30 pages, 5 figure

Note on DBI dynamics of Dbrane Near NS5-branes

In this note, we investigate the homogeneous radial dynamics of (Dp, NS5)-systems without and with one compactified transverse direction, in the framework of DBI effective action. During the homogeneous evolution, the electric field on the D-brane is always conserved and the radial motion could be reduced to an one-dimension dynamical system with an effective potential. When the Dp-brane energy is not high, the brane moves in a restricted region, with the orbits depending on the conserved energy, angular momentum through the form of the effective potential. When the Dp-brane energy is high enough, it can escape to the infinity. It turns out that the conserved angular momentum plays an interesting role in the dynamics. Moreover, we discuss the gauge dynamics around the tachyon vacuum and find that the dynamics is very reminiscent of the string fluid in the rolling tachyon case.Comment: 13 pages, 2 figures; typos corrected, discussions improved; gauge dynamics has been include

Assessing Time-Varying Oligopoly and Oligopsony Power in the U.S. Paper Industry

The U.S. paper industry has become increasingly concentrated and therefore been suspected of imperfect competition. In this study, the new empirical industrial organization approach is employed to measure the degree of oligopoly and oligopsony power in the U.S. paper industry simultaneously. The model is estimated by iterative three-stage least squares using annual data from 1955 to 2003. The results reveal that there has been significant oligopoly and oligopsony power in the U.S. paper industry, and the oligopoly power has been consistently lower than the oligopsony power.market power, NEIO, three-stage least squares, time-varying parameters, Agribusiness, Environmental Economics and Policy, Land Economics/Use, Production Economics, L13, Q23,