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 $bulk$ field and a $shell$ field. The $bulk$ part corresponds to a field sourced by the test charge placed in a space-time without the shell. The $shell$ field accounts for the discontinuity of the extrinsic curvature ${\kappa^p}_q$. 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 $Q$, to interpret the shell field in both the interior and exterior regions of the space-time. The self-force on a point charge $q$ in a locally flat geometry with a cylindrical thin-shell of matter is calculated. The charge is repelled from the shell if ${\kappa^{p}}_{p}=\kappa<0$ (ordinary matter) and attracted toward the shell if $\kappa>0$ (exotic matter). The total image charge is zero for exterior problems, while for interior problems $Q/q=-\kappa \, r_e$, with $r_e$ 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 $Q_{\mp}^{wh}/q=-1/ (\kappa_{wh} r_{\pm})$.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

Self-force on an arbitrarily coupled scalar charge in cylindrical thin-shell spacetimes

We consider the arbitrarily coupled field and self-force of a static massless scalar charge in cylindrical spacetimes with one or two asymptotic regions, with the only matter content concentrated in a thin-shell characterized by the trace of the extrinsic curvature jump κ. The self-force is studied numerically and analytically in terms of the curvature coupling ξ. We found the critical values ξc(n)=n/(ρ(rs)κ), with n∈ N and ρ(rs) the metric’s profile function at the position of the shell, for which the scalar field is divergent in the background configuration. The pathological behavior is removed by restricting the coupling to a domain of stability. The coupling has a significant influence over the self-force at the vicinities of the shell, and we identified ξ= 1 / 4 as the value for which the scalar force changes sign at a neighborhood of rs; if κ(1 - 4 ξ) > 0 the shell acts repulsively as an effective potential barrier, while if κ(1 - 4 ξ) < 0 it attracts the charge as a potential well. The sign of the asymptotic self-force only depends on whether there is an angle deficit or not on the external region where the charge is placed; conical asymptotics produce a leading attractive force, while Minkowski regions produce a repulsive asymptotic self-force.Fil: Tomasini, Clara Agustina. 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; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: 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; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; 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; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentin

Electrostatics and self-force in asymptotically flat cylindrical wormholes

The problem of the electrostatics in conical wormholes is revisited, now improving the background geometries with asymptotical flatness. The electric self-force on a point charge placed at different regions in the spacetime of a conical thin-shell wormhole connecting flat outer submanifolds is obtained and compared with the results of previous works. The study is also carried out in terms of a previously introduced analogy in which the effect of the matter shells on the electric field is reproduced by non-gravitating layers of charge located on the boundary surfaces. Besides, a better insight on the physical effects of a non trivial geometry is obtained by means of a further analysis of the electric fluxes across the wormhole throat and at both spatial infinities. It is found that the throat is traversed by a non-arbitrary and finite electric flux determined by the global topology, which is proportional to the charge of the source, and is characteristic of the asymptotically flat cylindrical wormholes regardless of the details of the throat geometry.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: 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

Extremal surfaces and thin-shell wormholes

We study extremal surfaces in a traversable wormhole geometry that connects two locally AdS5 asymptotic regions. In the context of the AdS/CFT correspondence, we use these to compute the holographic entanglement entropy for different configurations: First, we consider an extremal surface anchored at the boundary on a spatial 2-sphere of radius R. The other scenario is a slab configuration which extends in two of the boundary spacelike directions while having a finite size L in the third one. We show that in both cases the divergent and the finite pieces of the holographic entanglement entropy give results consistent with the holographic picture and this is used to explore the phase transitions that the dual theory undergoes. The geometries we consider here are stable thin-shell wormholes with flat codimension-one hypersurfaces at fixed radial coordinate. They appear as electrovacuum solutions of higher-curvature gravity theories coupled to Abelian gauge fields. The presence of the thin shells produces a refraction of the extremal surfaces in the bulk, leading to the presence of cusps in the phase space diagram. Further, the traversable wormhole captures a phase transition for the subsystems made up of a union of disconnected regions in different boundaries. We discuss these and other features of the phase diagram.Fil: Chernicoff, Mariano. Universidad Nacional Autónoma de México; MéxicoFil: Giribet, Gaston Enrique. 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; Argentina. University of New York; Estados UnidosFil: 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; Argentin

Traversable wormholes in five-dimensional Lovelock theory

In general relativity, traversable wormholes are possible provided they do not represent shortcuts in the spacetime. Einstein equations, together with the achronal averaged null energy condition, demand to take longer for an observer to go through the wormhole than through the ambient space. This forbids wormholes from connecting two distant regions in the space. The situation is different when higher-curvature corrections are considered. Here, we construct a traversable wormhole solution connecting two asymptotically flat regions, otherwise disconnected. This geometry is an electrovacuum solution to the Lovelock theory of gravity coupled to an Abelian gauge field. The electric flux suffices to support the wormhole throat and to stabilize the solution. In fact, we show that, in contrast to other wormhole solutions previously found in this theory, the one constructed here turns out to be stable under scalar perturbations. We also consider wormholes in anti-de Sitter (AdS). We present a protection argument showing that, while stable traversable wormholes connecting two asymptotically locally AdS5 spaces do exist in the higher-curvature theory, the region of the parameter space where such solutions are admitted lies outside the causality bounds coming from AdS/CFT.Fil: Giribet, Gaston Enrique. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. 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: Rubín de Celis, Emilio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. 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: Simeone, Claudio Mauricio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. 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

Thin-shell wormholes in AdS5 and string dioptrics

We consider string probes in a traversable wormhole geometry that connects two locally AdS5 asymptotic regions. Holographically, this describes two interacting copies of a 4-dimensional gauge theory. We consider string configurations whose endpoints are located either in the same boundary or in the two different boundaries of the wormhole. A string with both endpoints in the same boundary is dual to a quark-antiquark pair charged under the same gauge field, while a string extending through the wormhole describes a pair of colored particles charged under two different gauge fields. When one considers a quark-antiquark pair in each boundary, the system undergoes a phase transition: while for small separation each pair of charges exhibits Coulomb interaction, for large separation the charges in different field theories pair up. This behavior had previously been observed in other geometric realizations such as locally AdS5 wormhole solutions with hyperbolic throats. The geometries we consider here, in contrast, are stable thin-shell wormholes with flat codimension-one hypersurfaces at fixed radial coordinate. They appear as electrovacuum solutions of higher-curvature gravity theories coupled to Abelian gauge fields. The presence of the thin-shells produces a refraction of the string configurations in the bulk, leading to the presence of cusps in the phase space diagram. We discuss these and other features of the phase diagram, including the analogies and difference with other wormhole solutions considered in related contexts.Fil: Chernicoff, Mariano. Universidad Nacional Autónoma de México; MéxicoFil: García, Edel. Universidad Nacional Autónoma de México; MéxicoFil: Giribet, Gaston Enrique. 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: 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; Argentin

Effects of photooxidation on membrane integrity in Salix nigra seeds

Background and Aims: Salix nigra seeds are desiccation-tolerant, as are orthodox seeds, although in contrast to other orthodox seeds they lose viability in a few weeks at room temperature. They also differ in that the chloroplasts of the embryo tissues conserve their chlorophyll and endomembranes. The aim of this paper was to investigate the role of chlorophyll in seed deterioration. Methods: Seeds were aged at different light intensities and atmospheric conditions. Mean germination time and normal and total germination were evaluated. The formation of free radicals was assessed using electronic spin resonance spectroscopy, and changes in the fatty acid composition from phospholipids, galactolipids and triglycerides using gas-liquid chromatography. Membrane integrity was studied with electronic spin resonance spin probe techniques, electrolyte leakage and transmission electron microscopy. Key Results: Light and oxygen played an important role in free-radical generation, causing a decrease in normal germination and an increase in mean germination time. Both indices were associated with a decrease in polyunsaturated fatty acids derived from membrane lipids as phospholipids and galactolipids. The detection of damage in thylakoid membranes and an increase in plasmalemma permeability were consistent with the decrease in both types of lipids. Triglycerides remained unchanged. Light-induced damage began in outermost tissues and spread inwards, decreasing normal germination. Conclusions: Salix nigra seeds were very susceptible to photooxidation. The thylakoid membranes appeared to be the first target of the photooxidative process since there were large decreases in galactolipids and both these lipids and the activated chlorophyll are contiguous in the structure of that membrane. Changes in normal germination and mean germination time could be explained by the deteriorative effects of oxidation.Instituto de Investigaciones Bioquímicas de La Plat