Anupam Mazumdar, Saleh Qutub, and Ken’ichi Saikawa Consortium for Fundamental Physics, Physics Department, Lancaster University, Lancaster LA1 4YB, United Kingdom Kapteyn Astronomical Institute, University of Groningen, 9700 AV Groningen, Netherlands Department of Astronomy, King Abdulaziz University, Jeddah 21589, Saudi Arabia Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hambu...

We show that the spectral and radial distribution of the nonthermal emission of massive, M & 10M⊙, galaxy clusters may be approximately described by simple analytic expressions, which depend on the cluster thermal X-ray properties and on two model parameter, βcore and ηe. βcore is the ratio of the cosmic-ray (CR) energy density (within a logarithmic CR energy interval) and the thermal energy de...

Liberati, Rothman and Sonego have recently showed that objects collapsing into extremal Reissner-Nordström black holes do not behave as thermal objects at any time in their history. In particular, a temperature, and hence thermodynamic entropy, are undefined for them. I demonstrate that the analysis goes through essentially unchanged for bodies collapsing into extremal Kerr black holes. PACS: 0...

We examine particle production from spherical bodies collapsing into extremal Reissner-Nordström black holes. Kruskal coordinates become ill-defined in the extremal case, but we are able to find a simple generalization of them that is good in this limit. The extension allows us to calculate the late-time worldline of the center of the collapsing star, thus establishing a correspondence with a u...