Integrability of the Minimal Strain Equations for the Lapse and Shift in 3+1 Numerical Relativity

Brady, Creighton and Thorne have argued that, in numerical relativity simulations of the inspiral of binary black holes, if one uses lapse and shift functions satisfying the ``minimal strain equations'' (MSE), then the coordinates might be kept co-rotating, the metric components would then evolve on the very slow inspiral timescale, and the computational demands would thus be far smaller than for more conventional slicing choices. In this paper, we derive simple, testable criteria for the MSE to be strongly elliptic, thereby guaranteeing the existence and uniqueness of the solution to the Dirichlet boundary value problem. We show that these criteria are satisfied in a test-bed metric for inspiraling binaries, and we argue that they should be satisfied quite generally for inspiraling binaries. If the local existence and uniqueness that we have proved holds globally, then, for appropriate boundary values, the solution of the MSE exhibited by Brady et. al. (which tracks the inspiral and keeps the metric evolving slowly) will be the unique solution and thus should be reproduced by (sufficiently accurate and stable) numerical integrations.Comment: 6 pages; RevTeX; submitted to Phys. Rev. D15. Technical issue of the uniqueness of the solution to the Dirichlet problem clarified. New subsection on the nature of the boundary dat

No-horizon theorem for spacetimes with spacelike G1 isometry groups

We consider four-dimensional spacetimes $(M,{\mathbf g})$ which obey the Einstein equations ${\mathbf G}={\mathbf T}$, and admit a global spacelike $G_{1}={\mathbb R}$ isometry group. By means of dimensional reduction and local analyis on the reduced (2+1) spacetime, we obtain a sufficient condition on ${\mathbf T}$ which guarantees that $(M,{\mathbf g})$ cannot contain apparent horizons. Given any (3+1) spacetime with spacelike translational isometry, the no-horizon condition can be readily tested without the need for dimensional reduction. This provides thus a useful and encompassing apparent horizon test for $G_{1}$-symmetric spacetimes. We argue that this adds further evidence towards the validity of the hoop conjecture, and signals possible violations of strong cosmic censorship.Comment: 8 pages, LaTeX, uses IOP package; published in Class. Quantum Gra

Enhancement of prompt photons in ultrarelativistic proton-proton collisions from nonlinear gluon evolution at small-xx

In this paper we estimate the influence of nonlinear gluon evolution in the production of prompt photons at the LHC pp collider. We assume the validity of collinear factorization and consider the EHKQS parton distributions, which are solutions of the GLR-MQ evolution equations and describe quite well the DESY $ep$ HERA data, as input in our calculations. We find that both single and double photon production are enhanced for low-$p_T$ photons and central rapidities, while this effect is absent for the high-$p_T$ photons. The implications of this effect for the Quark-Gluon Plasma searches and for the QCD background to Higgs are also discussed.Comment: 4 pages, 4 figures. Version to be published in Physical Review

Breakfast habits and knowledge: Study involving participants from Brazil and Portugal

Breakfast has been considered one of the most important meals of the day. While breakfast habits and their consequences on children’s health and performance are well documented, studies on the adult population are still lacking. The aim of this study is to observe the breakfast consumption habits of Portuguese and Brazilian adults to understand the importance attributed to this meal, which leads people to have breakfast or to skip it, and also what types of food are consumed. To achieve these objectives, a questionnaire survey was carried out in both countries, and the data were collected through the internet. A convenience sample consisting of 694 participants (380 from Brazil and 314 from Portugal) were used in this study, all were adults who gave informed consent to participate in the research. The results showed that the majority of participants consumed breakfast every day (74.4% in Brazil and 78.3% in Portugal), and they did it at home (94.4 and 94.3% for Brazilians and Portuguese, respectively). The results also showed that the reasons for consuming breakfast and skipping it are very similar in both countries. People say they do not have breakfast because they do not want to eat in the morning or they do not have time. The reasons to always have breakfast include providing energy, satiety from night fasting, preventing hunger until lunch, because they like it, or simply because it is a habit. The level of knowledge was slightly higher among Portuguese than Brazilian participants and was found to vary according to the habits of having breakfast or skipping it and also according to country, sex, BMI class, and school level. In conclusion, breakfast habits were found to be very similar in both countries’, but the knowledge was higher among the Portuguese than the Brazilian participants. Breakfast is linked to a healthy lifestyle, and individuals’ behaviours and beliefs must be taken into account to promote health and well-being, thus diminishing the burden of noncommunicable diseases related to improper eating habits and dietary patterns.info:eu-repo/semantics/publishedVersio

Avaliação de diferentes tipos de poda no desenvolvimento de frutos de pessegueiro.

foi objetivo do presente trabalho, avaliar o desenvolvimento de frutos de pessegueiros das cultivares BRS Kampai e BRS Rubimel, submetidas a diferentes tipos de poda, na região de Pelotas-RS.ENPOS

Produtividade de cultivares de morangueiro de dia neutro na região de Pelotas-RS.

O objetivo deste trabalho foi avaliar o desempenho e produtividade de seis cultivares de dia neutro de morangueiro no município de Pelotas-RS.ENPOS

Interfaces between wind energy aspects analysis and Weibull distribution: Evidences from a bibliometric study

This paper aims to address and understand the knowledge application of Weibull distribution to analyze wind energy aspects, which is related to technical, sustainable and economic assessment, along with wind characteristics. It is structured under bibliometric analysis and reveals a panorama of 177 papers from 2007 to 2017 that presents where and how these relationships between wind energy aspects and Weibull distribution occur. This study presents six different analyses to understand these possibilities: papers by year, wordlcoud, papers by author, papers by topic, papers by affiliation, papers by journal and its subjects. Main findings of this research show that the leading areas where these interfaces occur in academic research are energy, engineering and environment science. Another relevant result is that the intersection of wind energy and the Weibull distribution has been figured as a core research topic to individual or a group of researchers around the world. The main contribution of this paper to the academic community is the pioneering on presenting a view on the size and on the main characteristics of this interface through bibliometric analysis

Exact Foldy-Wouthuysen transformation for gravitational waves and magnetic field background

We consider an exact Foldy-Wouthuysen transformation for the Dirac spinor field on the combined background of a gravitational wave and constant uniform magnetic field. By taking the classical limit of the spinor field Hamiltonian we arrive at the equations of motion for the non-relativistic spinning particle. Two different kinds of the gravitational fields are considered and in both cases the effect of the gravitational wave on the spinor field and on the corresponding spinning particle may be enforced by the sufficiently strong magnetic field. This result can be relevant for the astrophysical applications and, in principle, useful for creating the gravitational wave detectors based on atomic physics and precise interferometry