Search results for "theory [cosmology]"
showing 10 items of 973 documents
Constraint preserving boundary conditions for the Z4c formulation of general relativity
2010
We discuss high order absorbing constraint preserving boundary conditions for the Z4c formulation of general relativity coupled to the moving puncture family of gauges. We are primarily concerned with the constraint preservation and absorption properties of these conditions. In the frozen coefficient approximation, with an appropriate first order pseudo-differential reduction, we show that the constraint subsystem is boundary stable on a four dimensional compact manifold. We analyze the remainder of the initial boundary value problem for a spherical reduction of the Z4c formulation with a particular choice of the puncture gauge. Numerical evidence for the efficacy of the conditions is prese…
The initial boundary value problem for free-evolution formulations of General Relativity
2017
We consider the initial boundary value problem for free-evolution formulations of general relativity coupled to a parametrized family of coordinate conditions that includes both the moving puncture and harmonic gauges. We concentrate primarily on boundaries that are geometrically determined by the outermost normal observer to spacelike slices of the foliation. We present high-order-derivative boundary conditions for the gauge, constraint violating and gravitational wave degrees of freedom of the formulation. Second order derivative boundary conditions are presented in terms of the conformal variables used in numerical relativity simulations. Using Kreiss-Agranovich-Metivier theory we demons…
Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background
2018
The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually-unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generic…
Audiovisual speech perception in children with developmental language disorder in degraded listening conditions.
2013
Purpose The effect of the signal-to-noise ratio (SNR) on the perception of audiovisual speech in children with and without developmental language disorder (DLD) was investigated by varying the noise level and the sound intensity of acoustic speech. The main hypotheses were that the McGurk effect (in which incongruent visual speech alters the auditory speech percept) would be weaker for children with DLD than for controls and that it would get stronger with decreasing SNR in both groups. Method The participants were 8-year-old children with DLD and a sample of children with normal language development. In the McGurk stimuli, the consonant uttered by the voice differed from that articulated …
THE INFLUENCE OF SPATIAL COGNITION IN THEORY OF MIND AND CENTRAL COHERENCE TASKS: STUDY IN AUTISM
Autism Spectrum Disorder (ADS) is a severe developmental disability characterized by impairments in social interaction and communicative skills. Despite a growing research interest in the field, the causes of these impairments remain unknown. Two lines of research, Theory of Mind (ToM) and Central Coherence (CC), using experimental tasks such as visuo-spatial perspective Taking (VPT) and the local and global levels have suggested that visuo-spatial attention and spatial variables in the self-versus other recognition, may be the basis of the cognitive processes underlying social interaction. According to spatial attention, such as observed in the Unilateral spatial neglect (USN) may contribu…
Theory of Mind Profiles in Children With Autism Spectrum Disorder: Adaptive/Social Skills and Pragmatic Competence
2020
Theory of Mind (ToM) is one of the most relevant concepts in the field of social cognition, particularly in the case of Autism Spectrum Disorders (ASD). Literature showing that individuals with ASD display deficits in ToM is extensive and robust. However, some related issues deserve more research: the heterogeneous profile of ToM abilities in children with ASD and the association between different levels of ToM development and social, pragmatic, and adaptive behaviors in everyday life. The first objective of this study was to identify profiles of children with ASD without intellectual disability (ID), based on explicit and applied ToM knowledge, and compare these profiles with a group of ch…
Hans Kelsen, estado de exceção e Copa do Mundo no Brasil
2014
RESUMEN. Este trabajo presenta la situación de excepción económica creada en Brasil al hilo de la realización de los llamados “grandes eventos”, en particular la Copa del Mundo de 2014, que ha registrado la suspensión de diversos derechos y garantías fundamentales del derecho brasileño con objeto de garantizar la explotación económica monopólica del evento por la FIFA. El marco teórico del artículo se basa en la Teoría Pura del Derecho de Kelsen, que al ejemplificar una teoría del derecho de la normalidad, en la que la excepción no tiene espacio, sirve perfectamente de contra-paradigma para analizar el escenario político-legal autoritario que se ha introducido en Brasil, el cual se aborda b…
The pressure-induced ringwoodite to Mg-perovskite and periclase post-spinel phase transition: a Bader’s topological analysis of the ab initio electro…
2011
In order to characterize the pressure-induced decomposition of ringwoodite (c-Mg2SiO4), the topological analysis of the electron density q(r), based upon the theory of atoms in molecules (AIM) developed by Bader in the framework of the catastrophe theory, has been performed. Calculations have been carried out by means of the ab initio CRYSTAL09 code at the HF/DFT level, using Hamiltonians based on the Becke- LYP scheme containing hybrid Hartree– Fock/density functional exchange–correlation terms. The equation of state at 0 K has been constructed for the three phases involved in the post-spinel phase transition (ringwoodite -> Mg-perovskite + periclase) occurring at the transition zone–lower…
Entrepreneurship on Social Networking Sites: The Roles of Attitude and Perceived Usefulness
2023
Background: Social media platforms are a significant growth opportunity for enterprises, especially for microenterprises, due to the possibility of establishing direct contact with their customers. We investigate the psychological reasons that drive entrepreneurs towards the use of social networking sites (SNSs) for their business, following two important social psychology theories: the theory of planned behaviour and the technology acceptance model. We also tested for two personality traits: openness to experience and dominance. Methods: Data were acquired by examining 325 microentrepreneurs who decided to use either SNSs or traditional sales methods for their businesses. Results and concl…