Electron-phonon interaction in atomic-scale conductors: Einstein oscillators versus full phonon modes

Two extreme pictures of electron-phonon interactions in nanoscale conductors are compared: one in which the vibrations are treated as independent Einstein atomic oscillators, and one in which electrons are allowed to couple to the full, extended phonon modes of the conductor. It is shown that, under a broad range of conditions, the full-mode picture and the Einstein picture produce essentially the same net power at any given atom in the nanojunction. The two pictures begin to differ significantly in the limit of low lattice temperature and low applied voltages, where electron-phonon scattering is controlled by the detailed phonon energy spectrum. As an illustration of the behaviour in this limit, we study the competition between trapped vibrational modes and extended modes in shaping the inelastic current-voltage characteristics of one-dimensional atomic wires.

The Reduction of Oxygen in Various Room Temperature Ionic Liquids in the Temperature Range 293-318 K: Exploring the Applicability of the Stokes-Einstein Relationship in Room Temperature Ionic Liquids

The voltammetry for the reduction of oxygen at a microdisk electrode is reported in six commonly used RTILs: [C(4)mim][NTf2], [C(4)mpyrr][NTf2], [C(4)dmim][NTf2], [C(4)mim][BF4], [C(4)mim][PF6], and [N-6.2.2.2][NTf2], where [C(4)mim](+) is 1-butyl-3-methylimidazolium, [NTf2](-) is bis(trifluoromethanesulfonyl)imide, [C(4)mpyrr](+) is N-butyl-N-methylpyrrolidinium, [C(4)dmim](+) is 1-butyl-2,3-methylimidazolium, [BF4](-) is tetrafluoroborate, [PF6](-) is hexafluorophosphate, and [N-6.2.2.2](+) is n-hexyltriethylammonium at varying scan rates (50-4000 mV s(-1)) and temperatures (293-318 K). Diffusion coefficients, D, of oxygen are deduced at each temperature from potential-step chronoamperometry, and diffusional activation energies are calculated. Oxygen solubilities are also reported as a function of temperature. In the six ionic liquids, the Stokes-Einstein relationship (D proportional to eta(-1)) was found to apply only very approximately for oxygen. This is considered in relationship to the behavior of other diverse solutes in RTILs.

Characterization of Bose-Hubbard models with quantum nondemolition measurements

We propose a scheme for the detection of quantum phase transitions in the one-dimensional (1D) Bose-Hubbard (BH) and 1D Extended Bose-Hubbard (EBH) models, using the nondemolition measurement technique of quantum polarization spectroscopy. We use collective measurements of the effective total angular momentum of a particular spatial mode to characterize the Mott insulator to superfluid phase transition in the BH model and the transition to a density wave state in the EBH model. We extend the application of collective measurements to the ground states at various deformations of a superlattice potential.

Studies on scattering and thermodynamics of black holes in f(R) theory and Einstein's theory

One of the interesting consequences of Einstein's General Theory of Relativity is the black hole solutions. Until the observation made by Hawking in 1970s, it was believed that black holes are perfectly black. The General Theory of Relativity says that black holes are objects which absorb both matter and radiation crossing the event horizon. The event horizon is a surface through which even light is not able to escape. It acts as a one sided membrane that allows the passage of particles only in one direction i.e. towards the center of black holes. All the particles that are absorbed by black hole increases the mass of the black hole and thus the size of event horizon also increases. Hawking showed in 1970s that when applying quantum mechanical laws to black holes they are not perfectly black but they can emit radiation. Thus the black hole can have temperature known as Hawking temperature. In the thesis we have studied some aspects of black holes in f(R) theory of gravity and Einstein's General Theory of Relativity. The scattering of scalar field in this background space time studied in the first chapter shows that the extended black hole will scatter scalar waves and have a scattering cross section and applying tunneling mechanism we have obtained the Hawking temperature of this black hole. In the following chapter we have investigated the quasinormal properties of the extended black hole. We have studied the electromagnetic and scalar perturbations in this space-time and find that the black hole frequencies are complex and show exponential damping indicating the black hole is stable against the perturbations. In the present study we show that not only the black holes exist in modified gravities but also they have similar properties of black hole space times in General Theory of Relativity. 2 + 1 black holes or three dimensional black holes are simplified examples of more complicated four dimensional black holes. Thus these models of black holes are known as toy models of black holes in four dimensional black holes in General theory of Relativity. We have studied some properties of these types of black holes in Einstein model (General Theory of Relativity). A three dimensional black hole known as MSW is taken for our study. The thermodynamics and spectroscopy of MSW black hole are studied and obtained the area spectrum which is equispaced and different thermo dynamical properties are studied. The Dirac perturbation of this three dimensional black hole is studied and the resulting quasinormal spectrum of this three dimensional black hole is obtained. The different quasinormal frequencies are tabulated in tables and these values show an exponential damping of oscillations indicating the black hole is stable against the mass less Dirac perturbation. In General Theory of Relativity almost all solutions contain singularities. The cosmological solution and different black hole solutions of Einstein's field equation contain singularities. The regular black hole solutions are those which are solutions of Einstein's equation and have no singularity at the origin. These solutions possess event horizon but have no central singularity. Such a solution was first put forward by Bardeen. Hayward proposed a similar regular black hole solution. We have studied the thermodynamics and spectroscopy of Hay-ward regular black holes. We have also obtained the different thermodynamic properties and the area spectrum. The area spectrum is a function of the horizon radius. The entropy-heat capacity curve has a discontinuity at some value of entropy showing a phase transition.

2005 internacional de la física : año Einstein : historia de la ecuación : E=mc2.

Resumen tomado del autor. Resumen también en inglés

La historia de la ciencia como estrategia para la enseñanza en el Bachillerato : análisis interdisciplinar de la figura de Albert Einstein.

Resumen tomado de la publicación

De Einstein a Teilhard de Chardin : (1ª parte).

Se recoge la biografía de Albert Einstein, debido a que el año 2005 ha sido declarado Año Internacional de la Física en el que se celebra el centenario de la presentación de la Teoría de la Relatividad. También se recoge la biografía de de Pierre Teilhard de Chardin debido a la importancia para el Humanismo de este año. Se exponen las teorías más importantes de Einstein y sus reconocimientos más destacados. Se relaciona a Einstein con Teilhard de Chardin sobre todo porque Chardin se baso en la teoría de la relatividad de Einstein para desarrollar su evolución cósmica.

De Einstein a Teilhard de Chardin : (segunda parte).

Se recoge la biografía de Teilhard de Chardin, debido a su aportación a la educación y a las ciencias emergentes. Su obra al igual que la de Einstein nos enseña que el universo y la vida tienen un propósito, no son accidentales, que lo universal es siempre mejor que lo parcial, que la educación es uno de los motores principales de la evolución de la humanidad y que todo lo que se eleva converge.

La Literatura como profeta de la Ciencia : Einstein y El Quijote : VII Escuela de Verano : Centro Regional de Educaci??n de Personas Adultas de la Comunidad de Madrid (CREPA) : 29 y 30 de junio de 2005

En este volumen se recogen las actas de la S??ptima Escuela de Verano de Educaci??n de Personas Adultas organizada por el Centro Regional de Personas Adultas (CREPA) y el Centro Regional de Innovaci??n y Formaci??n (CRIF) 'Las Acacias', de la Comunidad de Madrid. La celebraci??n del centenario de la teor??a de la relatividad, del cincuentenario de la muerte de Albert Einstein, y del IV centenario de la publicaci??n de El Quijote es el punto de partida de las ponencias, grupos de debate, talleres y comunicaciones llevados a cabo en este encuentro. Los trabajos est??n relacionados con la ciencia, la lengua, la literatura, las nuevas tecnolog??as, la formaci??n profesional, la interculturalidad, la psicolog??a, la educaci??n y el consumo.

A Albert Einstein : in memoriam

Reflexi??n sobre la concepci??n desarrollada por Albert Einstein sobre el espacio en su teor??a especial de la relatividad y sobre la gravedad en su teor??a general de la relatividad, que revoluciona las creencias tradicionales sobre el universo y funda la cosmolog??a moderna.