Black diholes

We present and analyze exact solutions of the Einstein-Maxwell and Einstein-Maxwell-dilaton equations that describe static pairs of oppositely charged extremal black holes, i.e., black diholes. The holes are suspended in equilibrium in an external magnetic field, or held apart by cosmic strings. We comment as well on the relation of these solutions to brane-antibrane configurations in string and M theory

Phase transition in a super superspin glass

We here confirm the occurrence of spin glass phase transition and extract estimates of associated critical exponents of a highly monodisperse and densely compacted system of bare maghemite nanoparticles. This system has earlier been found to behave like an archetypal spin glass, with e.g. a sharp transition from paramagnetic to non-equilibrium behavior, suggesting that this system undergoes a spin-glass phase transition at a relatively high temperature, $T_g$ $\sim$ 140 K.Comment: 4 pages, 3 figure

A Novel PMSM Hybrid Sensorless Control Strategy for EV Applications Based on PLL and HFI

In this paper, a novel hybrid sensorless control strategy for Permanent Magnet Synchronous Machine (PMSM) drives applied to Electric Vehicles (EV) is presented. This sensorless strategy covers the EV full speed range and also has speed reversal capability. It combines a High Frequency Injection (HFI) technique for low and zero speeds, and a Phase-Locked Loop (PLL) for the medium and high speed regions. A solution to achieve smooth transitions between the PLL and the HFI strategies is also proposed, allowing to correctly detect the rotor position polarity when HFI takes part. Wide speed and torque four-quadrant simulation results are provided, which validate the proposed sensorless strategy for being further implemented in EV.Peer ReviewedPostprint (author's final draft

IPMSM torque control strategies based on LUTs and VCT feedback for robust control under machine parameter variations

In recent years, Interior Permanent Magnet Synchronous Machines (IPMSMs) have attracted a considerable attention in the scientific community and industry for Electric and Hybrid Electric Vehicle (HEV) propulsion systems. Lookup Table (LUT) based Field Oriented Control (FOC) strategies are widely used for IPMSM torque control. However, LUTs strongly depend on machine parameters. Deviations of these parameters due to machine ageing, temperature or manufacturing inaccuracies can lead to control instabilities in the field weakening region. In this paper, two novel hybrid IPMSM control strategies combining the usage of LUTs and Voltage Constraint Tracking (VCT) feedbacks are proposed in order to overcome the aforementioned controllability issues. Simulation results that demonstrate the validity of the proposed approaches are presented.Postprint (author's final draft

Vertical Cracks Excited in Lock-in Vibrothermography Experiments: Identification of Open and Inhomogeneous Heat Fluxes

Lock-in vibrothermography has proven to be very useful to characterizing kissing cracks producing ideal, homogeneous, and compact heat sources. Here, we approach real situations by addressing the characterization of non-compact (strip-shaped) heat sources produced by open cracks and inhomogeneous fluxes. We propose combining lock-in vibrothermography data at several modulation frequencies in order to gather penetration and precision data. The approach consists in inverting surface temperature amplitude and phase data by means of a least-squares minimization algorithm without previous knowledge of the geometry of the heat source, only assuming knowledge of the vertical plane where it is confined. We propose a methodology to solve this illposed inverse problem by including in the objective function penalty terms based on the expected properties of the solution. These terms are described in a comprehensive and intuitive manner. Inversions of synthetic data show that the geometry of non-compact heat sources is identified correctly and that the contours are rounded due to the penalization. Inhomogeneous smoothly varying fluxes are also qualitatively retrieved, but steep variations of the flux are hard to recover. These findings are confirmed by inversions of experimental data taken on calibrated samples. The proposed methodology is capable of identifying heat sources generated in lock-in vibrothermography experiments. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Universal quasinormal modes of black holes in the limit of large number of dimensions

We show that in the limit where the number of spacetime dimensions D grows to infinity a very large class of black holes (including nonextremal, static, asymptotically flat ones, with any number of gauge-field charges, possibly coupled to dilatons) possess a universal set of quasinormal modes whose complex frequencies depend only on the horizon radius and no other black hole parameters. The damping ratio of these modes vanishes like D − 2 / 3 , so they are almost normal modes, or "quasiparticle" excitations of the black hole. The structure responsible for the existence of these modes at large D is also present very generally in other black holes

Strong cosmic censorship in the BTZ black hole

Recently it has been shown that quantum fields can be regular on the inner, Cauchy horizon of a rotating BTZ black hole, which appears to indicate a failure of strong cosmic censorship. We argue that, instead, what these results imply is that the inner horizon remains non-singular when leading-order backreaction of the quantum fields is computed, but, after next-order backreaction is accounted for, it will become singular. Then, strong cosmic censorship will be enforced in the BTZ black hole. We support our claims using a four-dimensional holographic dual of the system, which connects the instability of the inner horizon of the BTZ black hole to that of Kerr-type black holes

New class of accelerating black hole solutions

We construct several new families of vacuum solutions that describe black holes in uniformly accelerated motion. They generalize the C metric to the case where the energy density and tension of the strings that pull (or push) on the black holes are independent parameters. These strings create large curvatures near their axis and when they have infinite length they modify the asymptotic properties of the spacetime, but we discuss how these features can be dealt with physically, in particular, in terms of "wiggly cosmic strings." We comment on possible extensions and extract lessons for the problem of finding higher-dimensional accelerating black hole solutions

Estudios de diversidad genética en poblaciones de maíz (Zea mays L.) evaluadas con microsatélites

En este trabajo de Tesis se evalúo de manera extensiva la diversidad genética presente en los maíces nativos de Latinoamérica, combinando datos fenotípicos y genotípicos, con dos propósitos diferentes. El primero, un estudio donde la diversidad genética, las relaciones interpoblacionales y la estructura poblacional de los materiales nativos permitieron ligar aspectos históricos, antropológicos y arqueológicos del maíz para crear una historia consolidada de la migración del maíz desde su centro de origen en Mesoamérica hacia el Caribe y Sudamérica. El segundo, es explorado el potencial de las razas de maíz para proporcionar nuevos alelos favorables para mejoramiento. La evaluación fenotípica y genotípica conjunta de accesiones del Banco de Germoplasma con material mejorado por CIMMYT permitió identificar fuentes de variación alélica importante para algunos caracteres de interés como tolerancia a la sequía. La caracterización de la diversidad genética de los materiales nativos para la conservación y explotación con fines de mejoramiento es un enfoque muy prometedor en particular con el desarrollo constante de nuevas herramientas genéticas.In this thesis work, the genetic diversity of Latin American maize landraces was evaluated extensively combining phenotypic and genotypic data, for two different purposes. First, to study the genetic diversity, relationships, and population structure of native materials allowing the linkage of historical, anthropological and archaeological data to create a consolidated history of maize migration from its origin center in Mesoamerica towards The Caribbean and South America. Second, to explore the potential of maize landraces to provide new elite alleles for breeding, the phenotypic and genotypic characterization of gene bank accessions compared to improved material from CIMMYT allowed the identification of important sources of allelic variation for traits of interest including drought tolerance. The characterization of native genetic diversity for conservation and exploitation towards breeding is a very promising approach, especially considering on going development of new genetic tools and methodologie