Derivation of chemical abundances in star-forming galaxies at intermediate redshift

We have studied a sample of 11 blue, luminous, metal-poor galaxies at redshift 0.744 < z < 0.835 from the DEEP2 redshift survey. They were selected by the presence of the [OIII]4363 auroral line and the [OII]3726,3729 doublet together with the strong emission nebular [OIII] lines in their spectra from a sample of around 6000 galaxies within a narrow redshift range. All the spectra have been taken with DEIMOS, which is a multi-slit, double-beam spectrograph which uses slitmasks to allow the spectra from many objects to be imaged at the same time. The selected objects present high luminosities (20.3 < MB < 18.5), remarkable blue color index, and total oxygen abundances between 7.69 and 8.15 which represent 1/3 to 1/10 of the solar value. The wide spectral coverage (from 6500 to 9100 angstroms) of the DEIMOS spectrograph and its high spectral resolution, R around 5000, bring us an opportunity to study the behaviour of these star-forming galaxies at intermediate redshift with high quality spectra. We put in context our results together with others presented in the literature up to date to try to understand the luminosity-metallicity relation this kind of objects define. The star-forming metal-poor galaxies would be of special relevance in showing the diversity among galaxies of similar luminosities and could serve to understand the processes of galaxy evolution.Comment: 22 pages, 7 figures, Master Thesis, Universidad Autonoma de Madri

Partition function based analysis of CMB maps

We present an alternative method to analyse cosmic microwave background (CMB) maps. We base our analysis on the study of the partition function. This function is used to examine the CMB maps making use of the different information embedded at different scales and moments. Using the partition function in a likelihood analysis in two dimensions (Q_rms,n), we find the best-fitting model to the best data available at present the COBE--DMR 4 years data set. By means of this analysis we find a maximum in the likelihood function for n=1.8 (-0.65 +0.35) and Q_rms-PS = 10 (-2.5 +3) muK (95 % confidence level) in agreement with the results of other similar analyses (Smoot et al. 1994 (1 yr), Bennet et al. 1996 (4 yr)). Also making use of the partition function we perform a multifractal analysis and study the possible fractal nature of the CMB sky. We find that the measure used in the analysis is not a fractal. Finally, we use the partition function for testing the statistical distribution of the COBE--DMR data set. We conclude that no evidence of non-Gaussianity can be found by means of this method.Comment: 9 pages, 7 figures. To be published in MNRA

Quadratic differentials and asymptotics of Laguerre polynomials with varying complex parameters

In this paper we study the asymptotics (as $n\to \infty$) of the sequences of Laguerre polynomials with varying complex parameters $\alpha$ depending on the degree $n$. More precisely, we assume that $\alpha_n = n A_n,$ and $\lim_n A_n=A \in \mathbb{C}$. This study has been carried out previously only for $\alpha_n\in \mathbb{R}$, but complex values of $A$ introduce an asymmetry that makes the problem more difficult. The main ingredient of the asymptotic analysis is the right choice of the contour of orthogonality, which requires the analysis of the global structure of trajectories of an associated quadratic differential on the complex plane, which may have an independent interest. While the weak asymptotics is obtained by reduction to the theorem of Gonchar--Rakhmanov--Stahl, the strong asymptotic results are derived via the non-commutative steepest descent analysis based on the Riemann-Hilbert characterization of the Laguerre polynomials.Comment: 40 pages, 11 figures. To appear in J. Math. Anal. Appl. arXiv admin note: text overlap with arXiv:math/0204248 by other authors. text overlap with arXiv:math/0204248 by other author

The Magnetic Fields of the Quiet Sun

This work reviews our understanding of the magnetic fields observed in the quiet Sun. The subject has undergone a major change during the last decade (quiet revolution), and it will remain changing since the techniques of diagnostic employed so far are known to be severely biased. Keeping these caveats in mind, our work covers the main observational properties of the quiet Sun magnetic fields: magnetic field strengths, unsigned magnetic flux densities, magnetic field inclinations, as well as the temporal evolution on short time-scales (loop emergence), and long time-scales (solar cycle). We also summarize the main theoretical ideas put forward to explain the origin of the quiet Sun magnetism. A final prospective section points out various areas of solar physics where the quiet Sun magnetism may have an important physical role to play (chromospheric and coronal structure, solar wind acceleration, and solar elemental abundances).Comment: Review talk presented to the 6th Solar Polarization Workshop held in Maui HI, USA, May-June 201

Efficient phase-tunable Josephson thermal rectifier

Josephson tunnel junctions are proposed as efficient phase-tunable thermal rectifiers. The latter exploit the strong temperature dependence of the superconducting density of states and phase-dependence of heat currents flowing through Josephson junctions to operate. Remarkably, large heat rectification coefficients up to 800% can potentially be achieved using conventional materials and standard fabrication methods. In addition, these devices allow for the in-situ fine tuning of the thermal rectification magnitude and direction.Comment: 4 pages, 5 color figure

Comment on "Thermal fluctuations of magnetic nanoparticles" [arXiv:1209.0298]

We comment on some misleading and biased statements appearing in the manuscript arXiv:1209.0298 ("Thermal fluctuations of magnetic nanoparticles") about the use of the damped Landau-Lifshitz equation and the kinetic Langer theory for the calculation of the relaxation rate of magnetic nanoclusters. We reiterate simple scientific arguments, part of which is well known to the whole community, demonstrating that the authors' criticisms are unfounded and that they overstate the issue of damping in the Landau-Lifshitz equation with no unanimous experimental evidence.Comment: 3 page

Indirect searches for SUSY Dark Matter with the MAGIC Cherenkov Telescope

Neutralinos are the natural well-motivated candidates to provide the non-baryonic dark matter of the universe which may produce detectable signals through their annihilation into neutrinos, photons or positrons. Due to its high flux sensitivity and low energy threshold, the MAGIC Cherenkov telescope could potentially detect the neutralino annihilation high energy photon products. In the framework of minimal supergravity, the neutralino SUSY parameter space can be scanned in different benchmark scenarios defined after accelerator and cosmology constraints. Moreover, the neutralino density profiles in galaxy halos and sub-halos have to be understood to infer which is the optimal observation region to be explored by the MAGIC telescope for the detection of neutralino photon signatures within our Galaxy and our Local Group.Comment: 4 pages, proceedings of the conference "Satellites and tidal streams

The Anomalous Chromomagnetic Dipole Moment of the Top Quark

We calculate the one loop corrections to the chromomagnetic dipole moment of the top quark in the framework of the Standard Model, the two Higgs doublet model and the Minimal Supersymmetric Standard Model. In the Standard Model we consider the QCD and the electroweak corrections generated by gluon and Higgs boson exchanges, respectively. In the Minimal Supersymmetric Standard Model, we calculate the SUSY- QCD corrections, including the mixing effects between the stop coming from the left- and right-handed sectors. We obtain that the Standard Model contribution is of the order of -0.004< delta kappa_g^t < -0.001, and the values for diferents scenarios are of the order of -0.001 < \delta \kappa_g^t < -0.01.Comment: Latex file, 15 pages, 5 ps figure

B meson decay anomaly with a non-universal U(1)' extension

We propose an extension of the standard model with an extra U(1)' abelian symmetry, three Higgs doublets and one Higgs singlet, where the new U(1)' charges are flavour non-universal. As a result, the model introduces an enlarger particle spectrum in the TeV scale with large new physics possibilities. The model reproduces the mixing angles and mass structures of the quarks, charged and neutral leptons. We found that the observed anomaly of the $B^{+}\rightarrow K^+ \ell \ell$ decay can be explained due to the existence of couplings with new extra fermions at the TeV scale.Comment: 10 captioned figure

Topological dynamics and current-induced motion in a skyrmion lattice

We study the Thiele equation for current-induced motion in a skyrmion lattice through two soluble models of the pinning potential. Comprised by a Magnus term, a dissipative term and a pinning force, Thiele's equation resembles Newton's law but in virtue of the topological character of the first two, it differs significantly from Newtonian mechanics and because the Magnus force is dominant, unlike its mechanical counterpart, the Coriolis force, skyrmion trajectories do not necessarily have mechanical counterparts. This is important if we are to understand skykrmion dynamics and tap into its potential for data-storage technology. We identify a pinning threshold velocity for the one-dimensional potential and for a two-dimensional potential we find a pinning point and the skyrmion trajectories toward the point are spirals whose frequency (compare Kepler's second law) and amplitude decay depends only on the Gilbert constant and potential at the pinning point.Comment: 14 pages, 5 figure