Extremal Hairy Black Holes

We consider a gravitating system consisting of a scalar field minimally coupled to gravity with a self-interacting potential and an U(1) electromagnetic field. Solving the coupled Einstein-Maxwell-scalar system we find exact hairy charged black hole solutions with the scalar field regular everywhere. We go to the zero temperature limit and we study the effect of the scalar field on the near horizon geometry of an extremal black hole. We find that except a critical value of the charge of the black hole there is also a critical value of the charge of the scalar field beyond of which the extremal black hole is destabilized. We study the thermodynamics of these solutions and we find that if the space is flat then at low temperature the Reissner-Nordstr\"om black hole is thermodynamically preferred, while if the space is AdS the hairy charged black hole is thermodynamically preferred at low temperature.Comment: 17 pages. Match with the journal version accepted by JHEP. arXiv admin note: substantial text overlap with arXiv:1309.216

Scalar Perturbations of two-dimensional Horava-Lifshitz Black Holes

In this article, we study the stability of black hole solutions found in the context of dilatonic Horava-Lifshitz gravity in $1+1$ dimensions by means of the quasinormal modes approach. In order to find the corresponding quasinormal modes, we consider the perturbations of massive and massless scalar fields minimally coupled to gravity. In both cases, we found that the quasinormal modes have a discrete spectrum and are completely imaginary, which leads to damping modes. For a massive scalar field and a non-vanishing cosmological constant, our results suggest unstable behaviour for large values of the scalar field mass.Comment: 18 pages, 1 figure. Accepted version in EPJC. arXiv admin note: text overlap with arXiv:gr-qc/070109

A Selected Surveyo f Ocean Acidifcation\u27s Effect on Coccolithophore and other Marine Ecosystems

With it\u27s rapid rate of generation, the coccolithophore was expected to adapt to the altered pH levels relatively quickly. By analyzing several scientific studies concerning this algae\u27s interaction with various water qualities, the species\u27 response is clarified. These findings are compared to rudimentary data concerning pH levels taken along the coast of Malibu