Special symmetries of the charged Kerr-AdS black hole of D=5 minimal gauged supergravity

In this note we prove that the Hamilton-Jacobi equation in the background of the recently discovered charged Kerr-AdS black hole of D=5 minimal gauged supergravity is separable, for arbitrary values of the two rotation parameters. This allows us to write down an irreducible Killing tensor for the spacetime. As a result we also show that the Klein-Gordon equation in this background is separable. We also consider the Dirac equation in this background in the special case of equal rotation parameters and show it has separable solutions. Finally we discuss the near-horizon geometry of the supersymmetric limit of the black hole.Comment: 7 pages, Latex. v2, two references added and discussion of near horizon limit corrected and expande

DDoS defense by offense

This article presents the design, implementation, analysis, and experimental evaluation of speak-up, a defense against application-level distributed denial-of-service (DDoS), in which attackers cripple a server by sending legitimate-looking requests that consume computational resources (e.g., CPU cycles, disk). With speak-up, a victimized server encourages all clients, resources permitting, to automatically send higher volumes of traffic. We suppose that attackers are already using most of their upload bandwidth so cannot react to the encouragement. Good clients, however, have spare upload bandwidth so can react to the encouragement with drastically higher volumes of traffic. The intended outcome of this traffic inflation is that the good clients crowd out the bad ones, thereby capturing a much larger fraction of the server's resources than before. We experiment under various conditions and find that speak-up causes the server to spend resources on a group of clients in rough proportion to their aggregate upload bandwidths, which is the intended result.National Science Foundation (U.S.) (NSF grant CNS-0225660)National Science Foundation (U.S.) (NSF grant CNS-0520241)United States. Dept. of Defense (National Security Science and Engineering Faculty Fellowship

“Regimes”, Regional cooperation organizations and the promise of “proto-regimes”. Indo-Russian relations in the 21st century and the challenge of Vladimir Putin´s “values” initiatives

The concept of ‘proto-regimes’ is a useful analytical tool in investigating various quasi multilateral organizations which have come up during the post-Cold War period. ‘Proto-regimes’, according to the scholar, have emerged as the post-1991 scenario in international affairs. We have witnessed activities where regional and trans-regional organizations, focused on cooperation between actors, have taken shape, and seek to impinge on sovereignty of states through common commitments but in a strongly qualified manner. At issue are also values initiatives of new Russia under the Putin presidency that privilege engagements within a sharply delimited cultural range – values that endow Russian policy with a degree of introversion or “nationalism”. The article analyses the evolving relations between India and Russia in recent decades in terms of greater multilateral involvement within the conceptual framework of proto-regimes. The concept of ‘proto-regimes’ is a useful analytical tool in investigating various quasi multilateral organizations which have come up during the post-Cold War period. ‘Proto-regimes’, according to the scholar, have emerged as the post-1991 scenario in international affairs. We have witnessed activities where regional and trans-regional organizations, focused on cooperation between actors, have taken shape, and seek to impinge on sovereignty of states through common commitments but in a strongly qualified manner. At issue are also values initiatives of new Russia under the Putin presidency that privilege engagements within a sharply delimited cultural range – values that endow Russian policy with a degree of introversion or “nationalism”. The article analyses the evolving relations between India and Russia in recent decades in terms of greater multilateral involvement within the conceptual framework of proto-regimes. Palabras Clave: Russia, India, Proto-regime, Regional, Europe

Rendering stiffer walls: a hybrid haptic system using continuous and discrete time feedback

Instability in conventional haptic rendering destroys the perception of rigid objects in virtual environments. Inherent limitations in the conventional haptic loop restrict the maximum stiffness that can be rendered. In this paper we present a method to render virtual walls that are much stiffer than those achieved by conventional techniques. By removing the conventional digital haptic loop and replacing it with a part-continuous and part-discrete time hybrid haptic loop, we were able to render stiffer walls. The control loop is implemented as a combinational logic circuit on an field-programmable gate array. We compared the performance of the conventional haptic loop and our hybrid haptic loop on the same haptic device, and present mathematical analysis to show the limit of stability of our device. Our hybrid method removes the computer-intensive haptic loop from the CPU-this can free a significant amount of resources that can be used for other purposes such as graphical rendering and physics modeling. It is our hope that, in the future, similar designs will lead to a haptics processing unit (HPU)