Browsing by Author "Tupper, Gary B"
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- ItemOpen AccessSpherically symmetric dark energy structures in the context of Chaplygin gas model(2006) Tekola, Abiy G; Tupper, Gary B; Viollier, Raoul DThis paper investigates the existence of spherically symmetrical dark energy structures under the context of Chaplygin gas. A scaling solution of the form r -2/3 is found for the density and then we calculated the corresponding rotational curve and it turns out to be unrealistic implying that such objects don't exist. Finally we modified the equation of state of the Chaplygin gas to an equation of state of the form P = (j 2 P - A and compared p with observational data to see to what physical extent this equation works and it isdetermined that it works as far as a couple of hundred Mpc while the physical length of galaxies is in Kpc. implying the modified Chaplygin equation fits the observed rotational curves.
- ItemOpen AccessA study in spherical accretion of self-gravitating fluids in a general relativistic framework(2010) Richter, M C; Viollier, Raoul D; Tupper, Gary BA new general framework for studying relativistic spherical accretion of a self-gravitating fluid onto a central black hole is introduced in stationary coordinates for an observer at infinity. The important feature of gravitational backreaction due to a self-gravitating fluid on the metric is included in the model. The model is solved numerically for the most simple case of a polytropic fluid and compared to analytical solutions, which the model approximates in the "test-fluid" limit. The model is then focused on the accretion of a relativistic Fermi gas and the implications this might have on the rapid growth of supermassive black holes from clouds of sterile neutrino dark matter in the early universe. The results give good agreement with a Newtonian model of supermassive black hole growth called the symbiotic scenario.