Noncommutative Einstein-Maxwell pp-waves

The field equations coupling a Seiberg-Witten electromagnetic field to noncommutative gravity, as described by a formal power series in the noncommutativity parameters $\theta^{\alpha\beta}$, is investigated. A large family of solutions, up to order one in $\theta^{\alpha\beta}$, describing Einstein-Maxwell null pp-waves is obtained. The order-one contributions can be viewed as providing noncommutative corrections to pp-waves. In our solutions, noncommutativity enters the spacetime metric through a conformal factor and is responsible for dilating/contracting the separation between points in the same null surface. The noncommutative corrections to the electromagnetic waves, while preserving the wave null character, include constant polarization, higher harmonic generation and inhomogeneous susceptibility. As compared to pure noncommutative gravity, the novelty is that nonzero corrections to the metric already occur at order one in $\theta^{\alpha\beta}$.Comment: 19 revtex pages. One refrence suppressed, two references added. Minor wording changes in the abstract, introduction and conclusio

Inversion mechanism for the transport current in type-II superconductors

The longitudinal transport problem (the current is applied parallel to some bias magnetic field) in type-II superconductors is analyzed theoretically. Based on analytical results for simplified configurations, and relying on numerical studies for general scenarios, it is shown that a remarkable inversion of the current flow in a surface layer may be predicted under a wide set of experimental conditions. Strongly inhomogeneous current density profiles, characterized by enhanced transport toward the center and reduced, or even negative, values at the periphery of the conductor, are expected when the physical mechanisms of flux depinning and consumption (via line cutting) are recalled. A number of striking collateral effects, such as local and global paramagnetic behavior, are predicted. Our geometrical description of the macroscopic material laws allows a pictorial interpretation of the physical phenomena underlying the transport backflow.Comment: 8 pages, 6 figures (Best quality pictures are available by author's contact

Drived diffusion of vector fields

A model for the diffusion of vector fields driven by external forces is proposed. Using the renormalization group and the $\epsilon$-expansion, the dynamical critical properties of the model with gaussian noise for dimensions below the critical dimension are investigated and new transport universality classes are obtained.Comment: 11 pages, title changed, anisotropic diffusion further discussed and emphasize

Sterile neutrino decay and the LSND experiment

We propose a new explanation of the intriguing LSND evidence for electron antineutrino appearance in terms of heavy (mostly sterile) neutrino decay via a coupling with a light scalar and light (mostly active) neutrinos. We perform a fit to the LSND data, as well as all relevant null-result experiments, taking into account the distortion of the spectrum due to decay. By requiring a coupling g ~ 10^{-5}, a heavy neutrino mass m_4 ~ 100 keV and a mixing with muon neutrinos |U_{mu 4}|^2 ~ 10^{-2}, we show that this model explains all existing data evading constraints that disfavor standard (3+1) neutrino models.Comment: 3pp. Talk given at 9th International Conference on Astroparticle and Underground Physics (TAUP 2005), Zaragoza, Spain, 10-14 Sep 200

Material Laws and Numerical Methods in Applied Superconductivity

Contents Preface I Electromagnetism of type II superconductors 1 General Statements Of The Critical State 1.1 The CS In The Maxwell Equations Formalism 1.2 The CS Regime And The MQS Limit 2 Variational Theory for CS Problems 2.1 General Principles Of The Variational Method 2.2 The Material Law: SCs with magnetic anisotropy 2.2.1 Onto the 1D Critical States 2.2.2 Towards The 3D Critical States 3 Computational Method Conclusions I References I II Critical State Problems:Effects & Applications 4 Type-II SCs With Intrinsic Magnetic Anisotropy 4.1 3D variational statement in slab geometry 4.2 Isotropic predictions in -3D- configurations 4.3 T-states in -3D- configurations 4.4 CT-states in -3D- configurations 4.5 Smooth critical states in -3D- configurations Appendix I Critical angle gradient in -3D- configurations 5 The Longitudinal Transport Problem 5.1 Simplified analytical models and beyond 5.1.1 The simplest analytical model 5.1.2 The SDCST statement and the BM's approach 5.2 Magnetic anisotropy and the uncommon effects 5.2.1 Extremal case: The T-states model 5.2.2 Material laws with magnetic anisotropy: CT\chi - models 6 Electromagnetism For Superconducting Wires 6.1 Theoretical framework and general considerations 6.2 SC wires subjected to isolated external sources 6.2.1 Wires with an injected AC transport current 6.2.2 Wires under an external AC magnetic flux 6.2.3 Ultimate considerations on the AC losses 6.3 SC wires under simultaneous AC excitations (B_{0},I_{tr}) 6.3.1 Synchronous excitations 6.3.2 Asynchronous excitations Conclusions II References II Supplementary Material II III Microscopical aspects also analyzed 7 E-Ph Theory And The Nodal Kink Effect In HTSC 8 Is it necessary to go beyond the E-Ph mode? Conclusions III References III Supplementary Material III IV AddendaComment: Dissertation Condensed Matter Physics Department of University of Zaragoza, Materials Science Institute of Arag\'on (ICMA), The Spanish National Research Council (CSIC). Cite together arXiv code as: http://hdl.handle.net/10261/46732 Digital CSIC open science: Dissertations ICM

Characterization of the Turbulent Magnetic Integral Length in the Solar Wind: From 0.3 to 5 Astronomical Units

The solar wind is a structured and complex system, in which the fields vary strongly over a wide range of spatial and temporal scales. As an example, the turbulent activity in the wind affects the evolution in the heliosphere of the integral turbulent scale or correlation length [{\lambda}], usually associated with the breakpoint in the turbulent-energy spectrum that separates the inertial range from the injection range. This large variability of the fields demands a statistical description of the solar wind. In this work, we study the probability distribution function (PDF) of the magnetic autocorrelation lengths observed in the solar wind at different distances from the Sun. We use observations from Helios, ACE, and Ulysses spacecraft. We distinguish between the usual solar wind and one of its transient components (Interplanetary Coronal Mass Ejections, ICMEs), and study also solar wind samples with low and high proton beta [\beta_p ]. We find that in the last 3 regimes the PDF of {\lambda} is a log-normal function, consistent with the multiplicative and non-linear processes that take place in the solar wind, the initial {\lambda} (before the Alfv\'enic point) being larger in ICMEs