Chiral fermion mass and dispersion relations at finite temperature in the presence of hypermagnetic fields

We study the modifications to the real part of the thermal self-energy for chiral fermions in the presence of a constant external hypermagnetic field. We compute the dispersion relation for fermions occupying a given Landau level to first order in g'^2, g^2 and g_phi^2 and to all orders in g'B, where g' and g are the U(1)_Y and SU(2)_L couplings of the standard model, respectively, g_phi is the fermion Yukawa coupling, and B is the hypermagnetic field strength. We show that in the limit where the temperature is large compared to sqrt{g'B}, left- and right-handed modes acquire finite and different B-dependent masses due to the chiral nature of their coupling with the external field. Given the current bounds on the strength of primordial magnetic fields, we argue that the above is the relevant scenario to study the effects of magnetic fields on the propagation of fermions prior and during the electroweak phase transition.Comment: 11 pages 4 figures, published versio

Cantero tradicional VS Cantero de mutirões: la poética del diseño dentro del cantero auto gestionado

3º congresso – As múltiplas Faces da Arquitetura Contemporânea de 2016 – As múltiplas Faces da Arquitetura Contemporânea – foram apresentados pelos/as estudantes da disciplina de Crítica e História da Arquitetura e da Cidade IV sob orientação da professora Andreia Moassab, do curso de Arquitetura e Urbanismo da Universidade Federal da Integração Latino-americana – UNILA. O congresso é parte da avaliação final da disciplina, no qual os/as estudantes apresentam a sua versão e dialogam com autores/as e textos de referência sobre a arquitetura nas últimas décadasComo centro de debate sobre el cantero de obras, es fundamental destacar las contribuciones de tres arquitectos brasileros: Sergio Ferro, Rodrigo Lefévre y Flávio Imperio. Fundadores del grupo Arquitetura Nova, buscaron redefinir el oficio del arquitecto, de modo revolucionario, juntando osadía poética a una práctica política. Gran parte de los trabajadores, al no tener la posibilidad de acceder al beneficio, continuaban solucionando los problemas relacionados a la falta de moradias, con la autoconstrucción en lotes clandestinos situados en las periferiasUNIL

Copper(I) Thiocyanate Networks with Aliphatic Sulfide Ligands

A total of five new CuSCN-L compounds with alkyl sulfide ligands, L = methyl sulfide (Me2S), ethyl sulfide (Et2S), isopropyl sulfide (Pri2S) or tetrahydrothiophene (THT) have been prepared and characterized. X-ray crystal structures for four of the compounds were obtained. Two compounds were collected from solutions of CuSCN in Me2S: {[Cu(SCN)(Me2S)2]}n (1a) in the form of colorless blocks and (CuSCN)(Me2S) (1b) as a white powder. Neat mixtures of CuSCN in the other alkyl sulfide ligands yielded only one product each: {[Cu(SCN)(Et2S)]}n (2); {[Cu(SCN)(Pri2S)]}n (3); and {[Cu(SCN)(THT)2]}n (4). Crystals of 2 and 4 underwent destructive phase changes at lower temperatures. Two networks types were observed: 1:2 decorated 1-D chains (1a and 4) and 1:2 decorated 1-D ladders (2 and 3). Further network formation through bridging of the organic sulfide ligands was not observed

Density and expansion effects on pion spectra in relativistic heavy-ion collisions

We compute the pion inclusive momentum distribution in heavy-ion collisions at AGS energies, assuming thermal equilibrium and accounting for density and expansion effects at the time of decoupling. We compare to data on mid rapidity charged pions produced in central Au + Au collisions and find a very good agreement. The shape of the distribution at low $m_t-m$ is explained in part as an effect arising from the high mean pion density achieved in these reactions. The difference between the positive and negative pion distributions in the same region is attributed in part to the different average yields of each kind of charged pions.Comment: Minor changes, typo in Fig. 2b corrected, version to appear in Phys. Rev.

The xx-Region of Shadowing Corrections in Nucleon Structure Functions

We discuss the experimental indications on the behaviour of F_2(x,Q^2) at small x both in proton and nuclear targets. By comparing the parametrizations of the data we conclude that shadowing correction effects in a proton target can appear at a noticeable level for x=(2 - 4)\times10^{-4} and Q^2\sim 10^1 GeV^2, namely inside the HERA regime.Comment: 5 pages, Latex, no figure

Fermion scattering off electroweak phase transition kink walls with hypermagnetic fields

We study the scattering of fermions off a finite width kink wall during the electroweak phase transition in the presence of a background hypermagnetic field. We derive and solve the Dirac equation for such fermions and compute the reflection and transmission coefficients for the case when the fermions move from the symmetric to the broken symmetry phase. We show that the chiral nature of the fermion coupling with the background field in the symmetric phase generates an axial asymmetry in the scattering processes. We discuss possible implications of such axial charge segregation for baryon number generation.Comment: 9 pages, 3 Postscript figures, uses RevTeX4. Expanded discussion, published versio

Effective potential at finite temperature in a constant hypermagnetic field: Ring diagrams in the Standard Model

We study the symmetry breaking phenomenon in the standard model during the electroweak phase transition in the presence of a constant hypermagnetic field. We compute the finite temperature effective potential up to the contribution of ring diagrams in the weak field, high temperature limit and show that under these conditions, the phase transition becomes stronger first order.Comment: 15 pages, 8 Postscript figure

NIR spectroscopy of the Sun and HD20010 - Compiling a new linelist in the NIR

Context: Effective temperature, surface gravity, and metallicity are basic spectroscopic stellar parameters necessary to characterize a star or a planetary system. Reliable atmospheric parameters for FGK stars have been obtained mostly from methods that relay on high resolution and high signal-to-noise optical spectroscopy. The advent of a new generation of high resolution near-IR spectrographs opens the possibility of using classic spectroscopic methods with high resolution and high signal-to-noise in the NIR spectral window. Aims: We aim to compile a new iron line list in the NIR from a solar spectrum to derive precise stellar atmospheric parameters, comparable to the ones already obtained from high resolution optical spectra. The spectral range covers 10 000 {\AA} to 25 000 {\AA}, which is equivalent to the Y, J, H, and K bands. Methods: Our spectroscopic analysis is based on the iron excitation and ionization balance done in LTE. We use a high resolution and high signal-to-noise ratio spectrum of the Sun from the Kitt Peak telescope as a starting point to compile the iron line list. The oscillator strengths (log gf) of the iron lines were calibrated for the Sun. The abundance analysis was done using the MOOG code after measuring equivalent widths of 357 solar iron lines. Results: We successfully derived stellar atmospheric parameters for the Sun. Furthermore, we analysed HD20010, a F8IV star, from which we derived stellar atmospheric parameters using the same line list as for the Sun. The spectrum was obtained from the CRIRES- POP database. The results are compatible with the ones found in the literature, confirming the reliability of our line list. However, due to the quality of the data we obtain large errors.Comment: 9 pages and 9 figure