Marginally Trapped Surfaces and AdS/CFT

It has been proposed that the areas of marginally trapped or anti-trapped surfaces (also known as leaves of holographic screens) may encode some notion of entropy. To connect this to AdS/CFT, we study the case of marginally trapped surfaces anchored to an AdS boundary. We establish that such boundary-anchored leaves lie between the causal and extremal surfaces defined by the anchor and that they have area bounded below by that of the minimal extremal surface. This suggests that the area of any leaf represents a coarse-grained von Neumann entropy for the associated region of the dual CFT. We further demonstrate that the leading area-divergence of a boundary-anchored marginally trapped surface agrees with that for the associated extremal surface, though subleading divergences generally differ. Finally, we generalize an argument of Bousso and Engelhardt to show that holographic screens with all leaves anchored to the same boundary set have leaf-areas that increase monotonically along the screen, and we describe a construction through which this monotonicity can take the more standard form of requiring entropy to increase with boundary time. This construction is related to what one might call future causal holographic information, which in such cases also provides an upper bound on the area of the associated leaves.Comment: 23 pages, 5 figure

A perturbative perspective on self-supporting wormholes

We describe a class of wormholes that generically become traversable after incorporating gravitational back-reaction from linear quantum fields satisfying appropriate (periodic or anti-periodic) boundary conditions around a non-contractible cycle, but with natural boundary conditions at infinity (i.e., without additional boundary interactions). The class includes both asymptotically flat and asymptotically AdS examples. Simple asymptotically AdS$_3$ or asymptotically AdS$_3 \times S^1$ examples with a single periodic scalar field are then studied in detail. When the examples admit a smooth extremal limit, our perturbative analysis indicates the back-reacted wormhole remains traversable at later and later times as this limit is approached. This suggests that a fully non-perturbative treatment would find a self-supporting eternal traversable wormhole. While the general case remains to be analyzed in detail, the likely relation of the above effect to other known instabilities of extreme black holes may make the construction of eternal traversable wormholes more straightforward than previously expected.Comment: Minor corrections (including fixing a factor of 2 in several formulas/plots

Some Considerations on Tunneling Losses in Field-Effect Devices for Low-Voltage Microcontrollers

The loss power density associated with the tunneling current in a typical MOS cell with a floating gate is evaluated for high electric-field strengths in the oxide layer. Furthermore, problems related to oxide thickness are discussed

Evaluation of Bonding Orbitals in Amorphous Silicon by Means of the Chemical Pseudopotential Method

The chemical pseudopotential method has been used by a number of workers in order to study the valence bands of amorphous tetrahedrally bonded semiconductors. However, various problems related to this method are unsolved. In this paper, a theoretical formulation tending to clarify some of these. problems is presented. This formulation concerns bonding orbitals and is valid, in principle, for amorphous silicon

A Discussion on the Phonon Density of States of Amorphous Germanium for the Infrared Range

A theoretical formulation for the phonon density of states of amorphous germanium in the infrared range is proposed. This formulation is based upon the quasi-harmonic approximation and is compared with previous results

A Brief Note on Coherent Feedback in Semiconductor Lasers

Some aspects on coherent feedback in a laser diode are investigated. In particular, weak optical feedback is considered in the context of the feedback-induced frequency shift. In addition, the Lang-Kobayashi equations are considered

A Brief Study to Clarify Some Aspects Related to Vibrational Density of States for the Far Infrared Range in Amorphous Semiconductors

Phonon density of states of amorphous semiconductors for the far-infrared range is examined analytically. On the basis of this formulation, optical absorption corresponding to structural disorder is evaluated and discussed at the far-infrared range for a-Ge and a-Si

Charles Darwin y la evolución de las especies ornamentales en la Alhambra de Owen Jones

Three years before Darwin published his famous work on the Origin of the Species, Owen Jones published The Grammar of Ornament (1856). In this book –which was a reference handbook for the School of Design–, Jones stablished 37 laws that ruled over form and color in the «true beautiful» ornament, and he did so by applying a methodology similar to the one Natural Sciences were using at that moment. Jones searched for those principles which are present in every style of the History of the Ornament and he explained through them the metamorphoses of the decorative patterns. This paper finds that there are connections between the way Darwin explains the sequences of the evolution of the species and the way Jones describes the evolution of form in the ornament patterns. El arquitecto Owen Jones estableció los 37 principios que rigen la forma «auténticamente bella», según expuso en su Grammar of Ornament (1856) un manual de Diseño que se publica tan sólo tres años antes del Origen de las Especies de Darwin, y donde desarrolla metodologías afines a las que se están empleando en las Ciencias Naturales del momento. Como en el campo de la zoología y botánica, Jones busca unos principios estructurales mediante los cuales explicar las metamorfosis de la forma. El artículo encuentra que entre las propuestas decorativas de Jones y las de Darwin hay patrones de evolución y desarrollo coincidentes a la hora de explicar la evolución del ornamento y del desarrollo de las especies

Herencias del paisaje Pop: Marketing y visión del territorio en el arte actual

Lo que en 1957 Hamilton mostró con ironía en la exposición “This Is Tomorrow” -es decir, la transformación del hogar del ciudadano medio contaminado por el virus del consumismo y la excitación del futuro tecnológico-, bien puede compararse con la manera en la que hemos acabado transformando nuestro entorno natural. Obras como las de Dibbets o Perejaume ponen en evidencia que nuestro patrón de visión repercute en la manera en la que experimentamos el territorio y la naturaleza en general. Esta visión antropocéntrica es revisada por arquitectos paisajistas como MacHarg y Berque así como por artistas como Mendieta, y Goldsworthy -cuyas obras manifiestan un concepto de naturaleza sistémico, haciéndose eco de las teorías científicas de Bertalanffy, o Lovelock. Otros artistas como Maider López, Studer y Van der Berg usan la ironía para llamarnos la atención sobre la manera en la que habitamos eso que llamamos naturaleza. [ABSTRACT] In the exhibition This Is Tomorrow, (1957) Hamilton showed with irony how the interior of the middle class houses were transformed by the consumer demand and the excitement of a technological future. This transformation could be compared with the way we have already altered our natural environment. Works by Dibbets or Perejaume prove that our visual patterns have an effect on the way we experiment the territory and nature in general. This anthropocentric sight is also revised by landscape architects such as MacHarg and Berque, or artists such as Mendieta and Goldsworthy. Their work manifests a concept of nature based on systemic processes of the Universe which are analyzed here under the Bertalanffy´s and Lovelock´s scientific theories. Maider López´s, and Studer and Van der Berg´s works use the irony to bring our attention to the way we still understand that we call `nature´

Efectos de la integración económica europea sobre el comercio exterior de la industria vasca

El objetivo principal de este trabajo consiste en observar la evolución del sector exterior de los productos industriales del País Vasco, analizar los cambios surgidos, relacionarlos con los hitos que han marcado el proceso de integración europeo e interpretar las consecuencias en términos de pérdida o ganancia de competitividad del comercio exterior . Los cambios que se pretenden localizar serían los de tipo estructural, es decir , los que alteran la estructura del comercio exterior ; y así como los que tienen efectos en un prolongad o período de tiempo. Una vez hecho esto, se obtendrán las pertinentes conclusiones acerca de las consecuencias que podrían tener