Bounds for axially symmetric linear perturbations for the extreme Kerr black hole

We obtain remarkably simple integral bounds for axially symmetric linear perturbations for the extreme Kerr black hole in terms of conserved energies. From these estimates we deduce pointwise bounds for the perturbations outside the horizon.Comment: 15 page

On the linear stability of the extreme Kerr black hole under axially symmetric perturbations

We prove that for axially symmetric linear gravitational perturbations of the extreme Kerr black hole there exists a positive definite and conserved energy. This provides a basic criteria for linear stability in axial symmetry. In the particular case of Minkowski, using this energy we also prove pointwise boundedness of the perturbation in a remarkable simple way.Comment: 35 pages. 2 figures. Relevant improvement in the presentation in section 2.

Surrogate endpoints and non-inferiority trials in chronic viral hepatitis.

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Stand-alone wearable system for ubiquitous real-time monitoring of muscle activation potentials

Wearable technology is attracting most attention in healthcare for the acquisition of physiological signals. We propose a stand-alone wearable surface ElectroMyoGraphy (sEMG) system for monitoring the muscle activity in real time. With respect to other wearable sEMG devices, the proposed system includes circuits for detecting the muscle activation potentials and it embeds the complete real-time data processing, without using any external device. The system is optimized with respect to power consumption, with a measured battery life that allows for monitoring the activity during the day. Thanks to its compactness and energy autonomy, it can be used outdoor and it provides a pathway to valuable diagnostic data sets for patients during their own day-life. Our system has performances that are comparable to state-of-art wired equipment in the detection of muscle contractions with the advantage of being wearable, compact, and ubiquitous

On the linear stability of the extreme Kerr black hole under axially symmetric perturbations

We prove that for axially symmetric linear gravitational perturbations of the extreme Kerr black hole, there exists a positive definite and conserved energy. This provides a basic criteria for linear stability in axial symmetry. In the particular case of Minkowski, using this energy we also prove the pointwise boundedness of the perturbation in a remarkably simple way.submittedVersionFil: Dain, Sergio Alejandro. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Dain, Sergio Alejandro. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina.Fil: Dain, Sergio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Enrique Gaviola; Argentina.Fil: Gentile de Austria, Ivan. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Gentile de Austria, Ivan. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina.Fil: Gentile de Austria, Ivan. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Enrique Gaviola; Argentina.Otras Ciencias Física

No-go theorem for static spherically symmetric configurations composed of two charged pressureless fluid species

We present a no-go theorem for spherically symmetric configurations of two charged fluid species in equilibrium. The fluid species are assumed to be dusts, that is, perfect fluids without pressure, and the equilibrium can be attained for a single dust from the balance of electrostatic repulsion and gravitational attraction. We show that this is impossible for two dust species unless both of them are indistinguishable in terms of their electric charge density to matter density ratio. The result is obtained in the main three theories of mechanics, that is, in Newtonian Mechanics, in Special Relativity and in General Relativity. In particular, as charged dust solutions have been used to study the possibility of black hole mimickers, this result shows that such mimickers can not be constructed unless the underlying charged particle has the correct charge to mass ratio.Comment: 14 pages, no figure

Sobre la estabilidad de Kerr extremo ante perturbaciones gravitacionales lineales

Tesis (Doctor en Física)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, 2016.En esta tesis se aborda uno de los problemas abiertos más clásicos de la relatividad general, la estabilidad de la métrica de Kerr. Nos enfocamos puntualmente a la estabilidad a orden lineal ante perturbaciones gravitacionales con simetría axial. Nuestro esfuerzo muestra la existencia de una energía positiva y conservada para el caso de Kerr extremo. Con esta energía se obtienen cotas integrales para dichas perturbaciones. De estas cotas se deducen estimaciones puntuales para la perturbación fuera del horizonte.Fil: Gentile de Austria, Ivan. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina

Superficies maximales con momento lineal en Schwarzschild

Tesis (Lic. en Física)--Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física, 2010.Las superficies maximales son muy importantes a la hora de resolver las ecuaciones de vínculo de Einstein. Estas superficies facilitan la evolución de los datos iniciales mediante los métodos numéricos más utilizados. Con este tipo de superficies se puede generar un espacio-tiempo para describir una colisión entre agujeros negros. En este trabajo se demuestra la existencia de una superficie maximal con momento lineal no nulo para el espacio-tiempo de Schwarzschild.Todas las coordenadas son hatiadas -- Todas las coordenadas son primadas -- Teoremas y lemas