Improved limit on electron neutrino charge radius through a new evaluation of the weak mixing angle

We have obtained a new limit on the electron neutrino effective charge radius from a new evaluation of the weak mixing angle by a combined fit of all electron-(anti)neutrino electron elastic scattering measurements. Weak mixing angle is found to be sin^2 theta_W=0.259 \pm 0.025 in the low energy regime below 100 MeV. The electron neutrino charge radius squared is bounded to be in the range -0.13 10^-32 cm^2 < r^2 < 3.32 10^-32 cm^2 at 90 % C.L. Both results improve previously published analyses. We also discuss perspectives of future experiments to improve these constraints.Comment: 10 pages, 2 figures. Final published versio

Aportacions de Pierre Bourdieu a la "teoria de la ideologia"

El present escrit pretén fer un petit balanç de les aportacions que la perspectiva de l'estructuralisme genètic de Pierre Bourdieu ens ofereix per a l'estudi de les ideologies o per a la teoria de la ideologia. En concret, l'objectiu és valorar el potencial analític d'aquesta perspectiva, dels conceptes i models proposats, per comprendre aquella temàtica, més que no pas valorar les proposicions concretes de l'autor. L'escrit consta de tres apartats. El primer (el més breu) pretén una breu introducció a l'obra de Bourdieu que ajudi a entendre millor l'aproximació de l'autor a la nostra temàtica. En el segon (el més extens) s'ofereix una panoràmica de l'aproximació de Bourdieu a l'anàlisi de les ideologies, allò que ell en diu dominació simbòlica. Ens entretindrem a explicitar què entenia amb els seus principals conceptes i acabarem posant l'exemple pràctic de com es podria analitzar la dominació simbòlica del neoliberalisme des de l'òptica bourdeniana. I, finalment, al tercer apartat, conclourem valorant conquestes i virtuts, alhora que alguns punts crítics, que la perspectiva ens ofereix per a l'anàlisi de la temàtica

Sensitivity of low energy neutrino experiments to physics beyond the standard model

We study the sensitivity of future low energy neutrino experiments to extra neutral gauge bosons, leptoquarks and R-parity breaking interactions. We focus on future proposals to measure coherent neutrino-nuclei scattering and neutrino-electron elastic scattering. We introduce a new comparative analysis between these experiments and show that in different types of new physics it is possible to obtain competitive bounds to those of present and future collider experiments. For the cases of leptoquarks and R-parity breaking interactions we found that the expected sensitivity for most of the future low energy experimental setups is better than the current constraints.Comment: 21 pages, 5 figures. A more detailed analysis of systematic errors is done. Final version to be published in PR

Electronic structure of few-electron concentric double quantum rings

The ground state structure of few-electron concentric double quantum rings is investigated within the local spin density approximation. Signatures of inter-ring coupling in the addition energy spectrum are identified and discussed. We show that the electronic configurations in these structures can be greatly modulated by the inter-ring distance: At short and long distances the low-lying electron states localize in the inner and outer rings, respectively, and the energy structure is essentially that of an isolated single quantum ring. However, at intermediate distances the electron states localized in the inner and the outer ring become quasi-degenerate and a rather entangled, strongly-correlated system is formed.Comment: 16 pages (preprint format), 6 figure

Low energy neutrino experiments sensitivity to physics beyond the Standard Model

We study the sensitivity of future low energy neutrino experiments to extra neutral gauge bosons, leptoquarks and R-parity breaking interactions. We focus in future proposals to measure coherent neutrino-nuclei scattering and neutrino electron elastic scattering. We show that in all these three different types of new physics it is possible to obtain competitive bounds to those of future collider experiments. For the particular case of leptoquarks we found that the expected sensitivity to the coupling and mass for most of the future experimental setups is quite better than the current constraint. We also show specific parameters for extra neutral gauge bosons and R-parity breaking interactions that could be better restricted than current constraints

Spin-orbit effects in GaAs quantum wells: Interplay between Rashba, Dresselhaus, and Zeeman interactions

The interplay between Rashba, Dresselhaus and Zeeman interactions in a quantum well submitted to an external magnetic field is studied by means of an accurate analytical solution of the Hamiltonian, including electron-electron interactions in a sum rule approach. This solution allows to discuss the influence of the spin-orbit coupling on some relevant quantities that have been measured in inelastic light scattering and electron-spin resonance experiments on quantum wells. In particular, we have evaluated the spin-orbit contribution to the spin splitting of the Landau levels and to the splitting of charge- and spin-density excitations. We also discuss how the spin-orbit effects change if the applied magnetic field is tilted with respect to the direction perpendicular to the quantum well.Comment: 26 pages (with 3 figures included

Thermally assisted quantum cavitation in solutions of 3He in 4He

We have investigated the quantum-to-thermal crossover temperature T* for cavitation in liquid helium mixtures up to 0.05 3He concentrations. With respect to the pure 4He case, T* is sizeably reduced, to a value below 50 mK for 3He concentrations above 0.02. As in pure 4He, the homogeneous cavitation pressure is systematically found close to the spinodal pressure.Comment: Typeset using Revtex, 9 pages and 4 figure

Dressed-State Approach to Population Trapping in the Jaynes-Cummings Model

The phenomenon of atomic population trapping in the Jaynes-Cummings Model is analysed from a dressed-state point of view. A general condition for the occurrence of partial or total trapping from an arbitrary, pure initial atom-field state is obtained in the form of a bound to the variation of the atomic inversion. More generally, it is found that in the presence of initial atomic or atom-field coherence the population dynamics is governed not by the field's initial photon distribution, but by a `weighted dressedness' distribution characterising the joint atom-field state. In particular, individual revivals in the inversion can be analytically described to good approximation in terms of that distribution, even in the limit of large population trapping. This result is obtained through a generalisation of the Poisson Summation Formula method for analytical description of revivals developed by Fleischhauer and Schleich [Phys. Rev. A {\bf 47}, 4258 (1993)].Comment: 24 pages, 5 figures, to appear in J. Mod. Op