Anomalous exchange interaction between intrinsic spins in conducting graphene systems

We address the nature and possible observable consequences of singular one-electron states that appear when strong defects are introduced in the metallic family of graphene, namely, metallic carbon nanotubes and nanotori. In its simplest form, after creating two defects on the same sublattice, a state may emerge at the Fermi energy presenting very unusual properties: It is unique, normalizable, and features a wave function equally distributed around both defects. As a result, the exchange coupling between the magnetic moments generated by the two defects is anomalous. The intrinsic spins couple ferromagnetically, as expected, but do not present an antiferromagnetic excited state at any distance. We propose the use of metallic carbon nanotubes as a novel electronic device based on this anomalous coupling between spins which can be useful for the robust transmission of magnetic information at large distances.Comment: 5 pages 5 fugure

Critical comparison of electrode models in density functional theory based quantum transport calculations

We study the performance of two different electrode models in quantum transport calculations based on density functional theory: Parametrized Bethe lattices and quasi-one dimensional wires or nanowires. A detailed account of implementation details in both cases is given. From the systematic study of nanocontacts made of representative metallic elements, we can conclude that parametrized electrode models represent an excellent compromise between computational cost and electronic structure definition as long as the aim is to compare with experiments where the precise atomic structure of the electrodes is not relevant or defined with precision. The results obtained using parametrized Bethe lattices are essentially similar to the ones obtained with quasi one dimensional electrodes for large enough sections of these, adding a natural smearing to the transmission curves that mimics the true nature of polycrystalline electrodes. The latter are more demanding from the computational point of view, but present the advantage of expanding the range of applicability of transport calculations to situations where the electrodes have a well-defined atomic structure, as is case for carbon nanotubes, graphene nanoribbons or semiconducting nanowires. All the analysis is done with the help of codes developed by the authors which can be found in the quantum transport toolbox Alacant and are publicly available.Comment: 17 pages, 12 figure

Correlation functions of one-dimensional Bose-Fermi mixtures

We calculate the asymptotic behaviour of correlation functions as a function of the microscopic parameters for a Bose-Fermi mixture with repulsive interaction in one dimension. For two cases, namely polarized and unpolarized fermions the singularities of the momentum distribution functions are characterized as a function of the coupling constant and the relative density of bosons.Comment: RevTeX 4, 10 pages, 2 figure

Nonlinear response of superparamagnets with finite damping: an analytical approach

The strongly damping-dependent nonlinear dynamical response of classical superparamagnets is investigated by means of an analytical approach. Using rigorous balance equations for the spin occupation numbers a simple approximate expression is derived for the nonlinear susceptibility. The results are in good agreement with those obtained from the exact (continued-fraction) solution of the Fokker-Planck equation. The formula obtained could be of assistance in the modelling of the experimental data and the determination of the damping coefficient in superparamagnets.Comment: 7 PR pages, 2 figure

El Amor al Mundo en tiempos de oscuridad. Un siglo de Hannah Arendt, una pensadora secular

Se cumple un siglo del nacimiento de Hannah Arendt. Según Heidegger, el indicio más seguro de la creatividad de un pensamiento es la discusión que provoca. A más de treinta años de su muerte, siguen apareciendo traducciones castellanas así como tesis y críticas sobre su legado.Sin embargo, la predominancia de lo político en élno oculta su conexión con otras dimensiones(narratividad, memoria, juicio, etc.) ni tampoco, sobre todo, su fundamento en un interés originario y mayor por el humano como un ser espacial, un ser de vínculos. Como alguien que necesita delmundo y es necesitado, individualmente, por el mundo. El amor mundi es la gran inspiración de su obra intelectual. Una respuesta generosa a la experiencia de haber presenciado y sido víctima dela destrucción del mundo

The Originality of The Philosophical Gaze. On The Philosophy in Citizenship and University

Las siguientes reflexiones derivan de una experiencia de 23 años enseñando filosofía en dos ciudades del norte del Perú. Son también una respuesta a los prejuicios comunes, mayores en el precario contexto de esta parte del planeta, que ven en ella la inutilidad, el debate estéril o la especialización a espaldas de lo real. La genuina filosofía es el ejercicio de una pasión por el mundo y de una búsqueda interminable que, consciente de la finitud humana, necesita de las diferencias y alienta, por ello, la conversación, la convivencia y el cuidado de los espacios en que se encuentran todas las miradas.The following reflections derive from a 23-year experience teaching philosophy in two cities of northern Peru. They are too an answer to the various prejudices –most frequent in this part of the world–, that see in philosophy the futility, sterile debate or specialization behind the real. The genuine philosophy is the exercise of a passion for the world and the endless search that, conscious of human infnity, needs the diversity. Therefore, philosophy encourages conversation, coexistence and care of the spaces in which the people’s looks are found

Reflections on power, friendship and sexuality within the person

La experiencia del cambio se divide entre la euforia y la nostalgia. El libro-objeto creó hábitos, afectos, espacios, conductas y un modo de pensar que la digitalización altera irreversiblemente. El libro digitalizado no es solo otro depósito, sino una nueva relación con las ideas y con uno mismo. Sin embargo, el carácter físico y biográfico del libro-objeto proporciona un contrapeso en un mundo vertiginoso en que la identidad personal corre el peligro del desconcierto y la disolución

Loneliness, Writing and Celebration of the Finite Condition into The Essays of Michel de Montaigne

Montaigne traza una conciencia de la individualidad en un punto medio que evita tanto la deploración del yo del luteranismo como la absolutización de la razón del cartesianismo. Somos un punto en el tiempo y el espacio, pequeñez que desestima cualquier divinización del juicio personal y, de paso, explica la pluralidad del mundo. Pequeñez que alienta tanto el trato con la interioridad como el interés por los otros.Montaigne fosters a sort of awareness of the individuality, which is halfway in between the lutheran denial of the self and the cartesian absolutization of reason. We are just a tiny dot in time and space; a fact that prevents us from deifying our person