Kerr-de Sitter Universe

It is now widely accepted that the universe as we understand it is accelerating in expansion and fits the de Sitter model rather well. As such, a realistic assumption of black holes must place them on a de Sitter background and not Minkowski as is typically done in General Relativity. The most astrophysically relevant black hole is the uncharged, rotating Kerr solution, a member of the more general Kerr-Newman metrics. A generalization of the rotating Kerr black hole to a solution of the Einstein's equation with a cosmological constant $\Lambda$ was discovered by Carter \cite{DWDW}. It is typically referred to as the Kerr-de Sitter spacetime. Here, we discuss the horizon structure of this spacetime and its dependence on $\Lambda$. We recall that in a \La>0 universe, the term `extremal black hole' refers to a black hole with angular momentum $J > M^2$. We obtain explicit numerical results for the black hole's maximal spin value and get a distribution of admissible Kerr holes in the ($\Lambda$, spin) parameter space. We look at the conformal structure of the extended spacetime and the embedding of the 3-geometry of the spatial hypersurfaces. In analogy with Reissner-Nordstr\"{o}m -de Sitter spacetime, in particular by considering the Kerr-de Sitter causal structure as a distortion of the Reissner-Nordstr\"{o}m-de Sitter one, we show that spatial sections of the extended spacetime are 3-spheres containing 2-dimensional topologically spherical sections of the horizons of Kerr holes at the poles. Depending on how a $t=$ constant 3-space is defined these holes may be seen as black or white holes (four possible combinations).Comment: 20 pages, 9 figure

Numerical computation of the EOB potential q using self-force results

The effective-one-body theory (EOB) describes the conservative dynamics of compact binary systems in terms of an effective Hamiltonian approach. The Hamiltonian for moderately eccentric motion of two non-spinning compact objects in the extreme mass-ratio limit is given in terms of three potentials: $a(v), \bar{d}(v), q(v)$. By generalizing the first law of mechanics for (non-spinning) black hole binaries to eccentric orbits, [\prd{\bf92}, 084021 (2015)] recently obtained new expressions for $\bar{d}(v)$ and $q(v)$ in terms of quantities that can be readily computed using the gravitational self-force approach. Using these expressions we present a new computation of the EOB potential $q(v)$ by combining results from two independent numerical self-force codes. We determine $q(v)$ for inverse binary separations in the range $1/1200 \le v \lesssim 1/6$. Our computation thus provides the first-ever strong-field results for $q(v)$. We also obtain $\bar{d}(v)$ in our entire domain to a fractional accuracy of $\gtrsim 10^{-8}$. We find to our results are compatible with the known post-Newtonian expansions for $\bar{d}(v)$ and $q(v)$ in the weak field, and agree with previous (less accurate) numerical results for $\bar{d}(v)$ in the strong field.Comment: 4 figures, numerical data at the end. Fixed the typos, added the journal referenc

To what extent are the mob languages responsible for the rise and success of ethnically based organized crime in the U.S. from late 19th century to early 20th century?

Mob language studies have seen various attempts at explaining the major effect of the use of this specific language and its contribution to the rise of Mafia in the USA. Different scholars, writers and researchers have variously emphasized the role of crime subcultures and their unique vernaculars in the U.S. In this paper, I would like to report on an even more ambitious claim that the rise organized crime in the U.S. would have not been possible were it not to the wielding of specific mob languages. The goal of the paper is to analyze the selection and use of special vocabulary to bind organized crime members together and avoid the governmental and judiciary control. This paper aims to show how mob languages developed as fusion languages resulting from the interaction of English with the experiences of different groups of people at different times. Crime usually results from socio-economic despair and dissatisfaction. We usually come across these two factors as an end product of immigrant stories and ostracism of different ethnic and socio-economic groups within a society. Out of this situation evolves many things: literature, songs, movies and arts related to this feeling of being the “outcasts”. However, lack of opportunities, feeling of alienation and despair also result in a tendency towards crime. When this situation of becoming the “outcast” occurs to any group, the group’s self-identification changes with its specific circumstances and gives rise to a specific language and culture that is self-evident in various cultural artifacts related to the group. When criminal tendencies permeate the group, this development of language and culture results in the development of a mob language that in return brings about many advantages for organized crime. As far as my research is concerned, my conclusion is that the creation of specific mob languages in the organized crime scene of U.S. has greatly shaped the successes of these criminal organizations

Kitaplar arasında:Tevfik Fikret'in değeri ve Sabiha Sertel'in eseri

Taha Toros Arşivi, Dosya No: 98/A Tevfik Fikretİstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033

Frequency-domain algorithm for the Lorenz-gauge gravitational self-force

State-of-the-art computations of the gravitational self-force (GSF) on massive particles in black hole spacetimes involve numerical evolution of the metric perturbation equations in the time-domain, which is computationally very costly. We present here a new strategy, based on a frequency-domain treatment of the perturbation equations, which offers considerable computational saving. The essential ingredients of our method are (i) a Fourier-harmonic decomposition of the Lorenz-gauge metric perturbation equations and a numerical solution of the resulting coupled set of ordinary equations with suitable boundary conditions; (ii) a generalized version of the method of extended homogeneous solutions [Phys. Rev. D {\bf 78}, 084021 (2008)] used to circumvent the Gibbs phenomenon that would otherwise hamper the convergence of the Fourier mode-sum at the particle's location; and (iii) standard mode-sum regularization, which finally yields the physical GSF as a sum over regularized modal contributions. We present a working code that implements this strategy to calculate the Lorenz-gauge GSF along eccentric geodesic orbits around a Schwarzschild black hole. The code is far more efficient than existing time-domain methods; the gain in computation speed (at a given precision) is about an order of magnitude at an eccentricity of 0.2, and up to three orders of magnitude for circular or nearly circular orbits. This increased efficiency was crucial in enabling the recently reported calculation of the long-term orbital evolution of an extreme mass ratio inspiral [Phys. Rev. D {\bf 85}, 061501(R) (2012)]. Here we provide full technical details of our method to complement the above report.Comment: 27 pages, 4 figure