772 research outputs found
Effect of a cylindrical thin-shell of matter on the electrostatic self-force on a charge
The electrostatic self-force on a point charge in cylindrical thin-shell
space-times is interpreted as the sum of a field and a field.
The part corresponds to a field sourced by the test charge placed in a
space-time without the shell. The field accounts for the discontinuity
of the extrinsic curvature . An equivalent electric problem is
stated, in which the effect of the shell of matter on the field is
reconstructed with the electric potential produced by a non-gravitating charge
distribution of total image charge , to interpret the shell field in both
the interior and exterior regions of the space-time. The self-force on a point
charge in a locally flat geometry with a cylindrical thin-shell of matter
is calculated. The charge is repelled from the shell if
(ordinary matter) and attracted toward the shell if
(exotic matter). The total image charge is zero for exterior
problems, while for interior problems , with the
external radius of the shell. The procedure is general and can be applied to
interpret self-forces in other space-times with shells, e.g., for locally flat
wormholes we found .Comment: (15 pages, 6 figures; the work had been extended, corrected and
reformulated from version v1 to v2, and minor misprints corrected from v2 to
v3
Perturbative dynamics of thin-shell wormholes beyond general relativity: An alternative approach
Recent studies relating the approximations for the equations-of-state for thin shells and their consequent perturbative evolution are extended to thin-shell wormholes in theories beyond general relativity and more than four spacetime dimensions. The assumption of equations-of-state of the same form for static and slowly evolving shells appears as a strong restriction excluding the possibility of oscillatory evolutions. Then the new results considerably differ from previous ones obtained within the usual linearized approach.Fil: Rubín de Celis, Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Tomasini, Cecilia. Universidad de Buenos Aires; ArgentinaFil: Simeone, Claudio Mauricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin
Probing global aspects of a geometry by the self-force on a charge: Spherical thin-shell wormholes
The self-interaction for a static point charge in the space-time of a
thin-shell wormhole constructed connecting two identical Schwarzschild
geometries is calculated in a series expansion. The electrostatic self-force is
evaluated numerically. It is found to be attractive towards the throat except
for some values of the throat radius proximate to the value of the
Schwarzschild horizon for which the force is repulsive or attractive depending
on the position of the charge. The result differs from the self-force in the
space-time of the Schwarzschild black hole, where it is always repulsive from
the center. Although these wormhole and black hole geometries are locally
indistinguishable, the different topologies of both backgrounds are manifested
in the electrostatic field of a point charge.Comment: 17 pages, 4 figue
Felix Hänseler (1780-1841), a german-born spanish botanist and pharmacist who lived in Málaga at one time
La biografía botánica más completa y fiable de este destacado investigador hispano-alemán –más conocido por el apellido paterno de Haenseler o Henseler–, continúa siendo la publicada a mediados del siglo XIX en la revista científica berlinesa Botanische Zeitung (1846); que fue confeccionada conjuntamente por sus amigos y colegas Pablo Prolongo García (1806-1885) y Moritz Willkomm (1821-1895)1, cuya versión española presentaron Juan A. Devesa y Mª del Carmen Viera (2001).
La gran importancia del personaje y de sus investigaciones naturalísticas multidisciplinares en la provincia de Málaga merecen ser revalorizadas. En este artículo partiremos de la referida publicación bio-bibliográfica de 1846 en la que integraremos la muy atomizada información disponible actualmente sobre nuestro biografiado, de quien en el contexto académico nacional únicamente hay una escueta referencia recogida en la Flora Ibéric
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