Gravitational wave recoils in non-axisymmetric Robinson-Trautman spacetimes

We examine the gravitational wave recoil waves and the associated net kick velocities in non-axisymmetric Robinson-Trautman spacetimes. We use characteristic initial data for the dynamics corresponding to non-head-on collisions of black holes. We make a parameter study of the kick distributions, corresponding to an extended range of the incidence angle $\rho_0$ in the initial data. For the range of $\rho_0$ examined ($3^{\circ} \leq \rho_0 \leq 110^{\circ}$) the kick distributions as a function of the symmetric mass parameter $\eta$ satisfy a law obtained from an empirical modification of the Fitchett law, with a parameter $C$ that accounts for the non-zero net gravitational momentum wave fluxes for the equal mass case. The law fits accurately the kick distributions for the range of $\rho_0$ examined, with a rms normalized error of the order of $5 \%$. For the equal mass case the nonzero net gravitational wave momentum flux increases as $\rho_0$ increases, up to $\rho_0 \simeq 55^{\circ}$ beyond which it decreases. The maximum net kick velocity is about $190 {\rm km/s}$ for for the boost parameter considered. For $\rho_0 \geq 50^{\circ}$ the distribution is a monotonous function of $\eta$. The angular patterns of the gravitational waves emitted are examined. Our analysis includes the two polarization modes present in wave zone curvature.Comment: 10 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:1403.4581, arXiv:1202.1271, arXiv:1111.122

Anisotropy and percolation threshold in a multifractal support

Recently a multifractal object, $Q_{mf}$, was proposed to study percolation properties in a multifractal support. The area and the number of neighbors of the blocks of $Q_{mf}$ show a non-trivial behavior. The value of the probability of occupation at the percolation threshold, $p_{c}$, is a function of $\rho$, a parameter of $Q_{mf}$ which is related to its anisotropy. We investigate the relation between $p_{c}$ and the average number of neighbors of the blocks as well as the anisotropy of $Q_{mf}$

Nonclassical correlation in NMR quadrupolar systems

The existence of quantum correlation (as revealed by quantum discord), other than entanglement and its role in quantum-information processing (QIP), is a current subject for discussion. In particular, it has been suggested that this nonclassical correlation may provide computational speedup for some quantum algorithms. In this regard, bulk nuclear magnetic resonance (NMR) has been successfully used as a test bench for many QIP implementations, although it has also been continuously criticized for not presenting entanglement in most of the systems used so far. In this paper, we report a theoretical and experimental study on the dynamics of quantum and classical correlations in an NMR quadrupolar system. We present a method for computing the correlations from experimental NMR deviation-density matrices and show that, given the action of the nuclear-spin environment, the relaxation produces a monotonic time decay in the correlations. Although the experimental realizations were performed in a specific quadrupolar system, the main results presented here can be applied to whichever system uses a deviation-density matrix formalism.Comment: Published versio

Public attitudes towards the restoration and management of Lake Vela (Central Portugal)

Lake Vela local inhabitants' and visitors' environmental attitudes and opinions about ecological conditions of the area and future management strategies to be implemented were investigated. The facilities required and the proposal to promote tourism activities, to enhance economic development, have revealed public illiteracy about ecosystems functioning and carrying capacity. This lack of scientific knowledge was recognized by a great percentage of individuals (61%, n=175), who mentioned environmental education programs as one of the main activities to be developed in the area. To spend some hours in a calm and healthy environment (67.6%, n=194), to share some moments with friends (58.2%, n=167), picnics (49.5, n=49.5%), and wildlife observation (46.7%, n=134) were the main motives cited by respondents to visit Lake Vela. These activities do not need to be restricted in the management of the area, but only directed for specific areas and carefully monitored, since they are passive activities that yield few significant impacts. The study also proposed some social benefits that could be integrated in the management of the area, in order to increase the quality of visitors' experiences and, hence, to get public compliance and involvement in the preservation of that natural resources