143 resultados para Relativity


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The Numerical INJection Analysis (NINJA) project is a collaborative effort between members of the numerical relativity and gravitational-wave (GW) astrophysics communities. The purpose of NINJA is to study the ability to detect GWs emitted from merging binary black holes (BBH) and recover their parameters with next-generation GW observatories. We report here on the results of the second NINJA project, NINJA-2, which employs 60 complete BBH hybrid waveforms consisting of a numerical portion modelling the late inspiral, merger, and ringdown stitched to a post-Newtonian portion modelling the early inspiral. In a 'blind injection challenge' similar to that conducted in recent Laser Interferometer Gravitational Wave Observatory (LIGO) and Virgo science runs, we added seven hybrid waveforms to two months of data recoloured to predictions of Advanced LIGO (aLIGO) and Advanced Virgo (AdV) sensitivity curves during their first observing runs. The resulting data was analysed by GW detection algorithms and 6 of the waveforms were recovered with false alarm rates smaller than 1 in a thousand years. Parameter-estimation algorithms were run on each of these waveforms to explore the ability to constrain the masses, component angular momenta and sky position of these waveforms. We find that the strong degeneracy between the mass ratio and the BHs' angular momenta will make it difficult to precisely estimate these parameters with aLIGO and AdV. We also perform a large-scale Monte Carlo study to assess the ability to recover each of the 60 hybrid waveforms with early aLIGO and AdV sensitivity curves. Our results predict that early aLIGO and AdV will have a volume-weighted average sensitive distance of 300 Mpc (1 Gpc) for 10M circle dot + 10M circle dot (50M circle dot + 50M circle dot) BBH coalescences. We demonstrate that neglecting the component angular momenta in the waveform models used in matched-filtering will result in a reduction in sensitivity for systems with large component angular momenta. This reduction is estimated to be up to similar to 15% for 50M circle dot + 50M circle dot BBH coalescences with almost maximal angular momenta aligned with the orbit when using early aLIGO and AdV sensitivity curves.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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This paper analyses how innovations and educational reforms affect curricular construction at public schools. It aims at reflecting if the Curricular Proposal for the state of São Paulo preserves the autonomy and identity of schools, if it respects their pedagogical political project, without attempting to homogenize them; how it changes every‐day school life, teacher’s practices, interpersonal relationships and power relations. We depart from the presupposition that this proposal adopts principles of the educational reforms started in the middle of the 90s, such as: adoption of national guidelines; introduction of market mechanisms, generating the fragility of teachers’ representation and their de‐ professionalization; relativity of the State’s role; stimuli to partnerships between public and private institutions in the fields of administration, allocation of financial resources for teaching    and implementation of external evaluating systems. At the same time, official discourse highlights decentralization, democratic administration, community participation. Some of these principles are recurrent in curriculum reforms: emphasis on the knowledge society, pedagogy of competencies and of learning to learn. In this way, we understand that the proposal aims at homogenizing school knowledge and curriculum practices, representing the notion of curriculum as product. We consider that the novelty and relevance of implemented measures demand further research, and that will be implemented by the author in 2010.

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Pós-graduação em Física - FEG

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Pós-graduação em Ciência e Tecnologia de Materiais - FC

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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The paper summarizes the parallel session C6 Q&A-everything you wanted to know about gravitational waves but were afraid to ask of the joint 10th Amaldi Conference on Gravitational Waves and 20th International Conference on General Relativity and Gravitation.

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In this paper, we will show the types of Lorentz transformations, from the most described in books, special Lorentz transformation that relates two inertial systems whose relative velocities are directed along an axis of the respective bases systems. However, we will see a peculiarity that goes unnoticed in this transformation, although they have reported in many books a parallel between the transformation inertial systems, due to the fact that the speed is parallel to an axis, it is actually a semi-parallel processing. The next transformation that we will see is one in which a system moves with a relative speed that has arbitrary direction with respect to a given system, we will show that this transformation may be appointed as non-rotational Lorentz transformation. Before obtain, the later type of transformation, the rotational Lorentz transformation, which is the interface between Special Relativity and General Relativity, we will describe the systems to be rotated, not just inertial systems, show what the characteristics are that define the non-rotational and rotational transformations. The in last topic of this chapter we will also show how the idea of Thoma’s theorythat uses this transformation to create what he defines as the proper coordinate axes of the particleused to obtain the factor 1/2 electron spin. In the last chapter we show how the Lorentz invariants are obtained, quantities measures that are also in different Lorentz reference, with the focus on mass that has erroneously been described in many books, that varies according to the agreement reference system

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The constancy of the speed of light appears to be an unbreakable barrier for future interstellar journeys, tending to infinite energy would be needed to achieve such speed. However in the general relativity one can circumvent this limit and get arbitrarily higher global speeds, without violating the constancy of the speed of light. The so-called “warp-drive metrics is a theoretical means to achieve global superluminal speeds. The Alcubierre metric is one case in which the science fiction inspired reality, from which was drawn the term “warp-drive. In the present work, a study of the theories of special and general relativity and of some works on solutions that allow superluminal speeds will be done

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The cosmological standard model needs a deep improvement when compared to recent observational data and also when contrasted with a broad theorical context. Al- ternative theories to General Relativity are possible candidates to reach the expectation Physics of Elementary Particles and Gravitation. Scalar-tensor theories seem to reappear from the ashes of the old work by Jordan corresponding appropriately low power limits of unifying theories. Being the Brans Dicke theory a scalar tensor is conducted a comprehensive study starting from its rst motivations to it s current one it is re flections

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The flow of Ricci is an analytical tool, and a similar equation for heat geometry, a diffusive process which acts on a variety of metrics Riemannian and thus can be used in mathematics to understand the topology of varieties and also in the study geometric theories. Thus, the Ricci curvature plays an important role in the General Theory of Relativity, characterized as a geometric theory, which is the dominant term in the Einstein field equations. The present work has as main objectives to develop and apply Ricci flow techniques to general relativity, in this case, a three-dimensional asymptotically flat Riemannian metric as a set of initial data for Einstein equations and establish relations and comparisons between them.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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This paper analyses the cosmological consequences of amodified theory of gravity whose action integral is built from a linear combination of the Ricci scalar R and a quadratic term in the covariant derivative of R. The resulting Friedmann equations are of the fifth-order in the Hubble function. These equations are solved numerically for a flat space section geometry and pressureless matter. The cosmological parameters of the higher-order model are fit using SN Ia data and X-ray gas mass fraction in galaxy clusters. The best-fit present-day t(0) values for the deceleration parameter, jerk and snap are given. The coupling constant beta of the model is not univocally determined by the data fit, but partially constrained by it. Density parameter Omega(m0) is also determined and shows weak correlation with the other parameters. The model allows for two possible future scenarios: there may be either an eternal expansion or a Rebouncing event depending on the set of values in the space of parameters. The analysis towards the past performed with the best-fit parameters shows that the model is not able to accommodate a matter-dominated stage required to the formation of structure.