Dynamics of spinning test particles in Kerr spacetime

We investigate the dynamics of relativistic spinning test particles in the spacetime of a rotating black hole using the Papapetrou equations. We use the method of Lyapunov exponents to determine whether the orbits exhibit sensitive dependence on initial conditions, a signature of chaos. In the case of maximally spinning equal-mass binaries (a limiting case that violates the test-particle approximation) we find unambiguous positive Lyapunov exponents that come in pairs ± lambda, a characteristic of Hamiltonian dynamical systems. We find no evidence for nonvanishing Lyapunov exponents for physically realistic spin parameters, which suggests that chaos may not manifest itself in the gravitational radiation of extreme mass-ratio binary black-hole inspirals (as detectable, for example, by LISA, the Laser Interferometer Space Antenna)

Philosophy and Hip-Hop: Ruminations on Postmodern Cultural Form

Book review of Philosophy and Hip-Hop: Ruminations on Postmodern Cultural Form. By Julius Bailey (2014)

Risk Assessment and Sustainable Development: Towards a Concept of Sustainable Risk

Dr. Mehta examines two dominant approaches for managing health and environmental risks and suggests that they would better serve if integrated

Public Perceptions of Food Safety: Assessing the Risks Posed by Genetic Modification, Irradiation, Pesticides, Microbiological Contamination and High Fat/High Calorie Foods

[Excerpt] In general, people in the developed world have access to a safe and varied supply of food. Instead of systemic hunger, many developed countries have problems with obesity and other kinds of eating disorders among their citizenry. It is within this context that some find public concerns about the safety of food both paradoxical and misplaced. Nevertheless, understanding how people perceive the risk associated with food is an important exercise in demonstrating accountability and in setting priorities for regulation. With the advent of technologies for producing genetically modified foods, and the development of fat blockers like Olestra, the public is increasingly being asked to judge the social acceptability of various kinds of food modifications. In addition to interpreting the risks and benefits associated with these newer innovations, the public is also balancing the risks and benefits of more familiar food interventions. Not only must consumers of food assess the merits of genetic modification and food irradiation, they still must consider exposure to pesticide residues and microbiological contaminants like Salmonella, Listeria, Escherichia coli, and Campylobacter. Additionally, with high rates of cardiovascular disease and elevated concerns about developing diseases like diabetes, many people seriously consider the fat and sugar content of the foods they consume. This exploratory study examines how the public perceives food risks by employing a ranking exercise, a scale for assessing food safety practices, a scale for combining elements from the psychometric paradigm (e.g., voluntary exposure, perceived benefit, and perceived risk) across five potential food hazards, and demographic variables (sex, age, and level of education) most commonly linked to the perception of food risks

A monopole solution in a Lorentz-violating field theory

I present a topological defect solution that arises in a theory where Lorentz symmetry is spontaneously broken by a rank-two antisymmetric tensor field, and I discuss its observational signatures.Comment: 4 pages, 1 figur