Nonlinear perturbations of Reissner-Nordström black holes
We develop a nonlinear perturbation theory of Reissner-Nordstr\"om black holes. We show that, at each perturbation level, Einstein-Maxwell equations can be reduced to four inhomogeneous wave equations, two for polar and two for axial sector. Gravitational part of these equations is similar to Regge-Wheeler and Zerilli equations with source and additional coupling to the electromagnetic sector. We construct solutions to the inhomogeneous part of wave equations in terms of sources for Einstein-Maxwell equations. We discuss $\ell=0$ and $ \ell=1$ cases separately.
Weakly turbulent instability of anti-de Sitter spacetime.
We study the nonlinear evolution of a weakly perturbed anti-de Sitter (AdS) space by solving numerically the four-dimensional spherically symmetric Einstein-massless-scalar field equations with negative cosmological constant. Our results suggest that AdS space is unstable under arbitrarily small generic perturbations. We conjecture that this instability is triggered by a resonant mode mixing which gives rise to diffusion of energy from low to high frequencies.
Relationships Between Food Preferences and Food Acceptance Ratings
A study was conducted to assess relationships between food preference ratings and food acceptability ratings. Acceptability ratings for each of two discriminably different samples of nine food items were obtained using the 9-point hedonic scale. Regression analysis indicated that no linear relationship existed between these ratings and either hedonic or frequency preference ratings of the foods. In addition, the range of acceptability ratings was smaller than the range of corresponding’preference ratings. Panelists’expressed preferences had no effect on their assignment of differential acceptance ratings to different samples of the items. Correlations between preference ratings of laboratory panelists and military field panelists were good, in spite of higher absolute preference ratings assigned by the laboratory panel.