Cosmic magnetic fields and dark energy in extended electromagnetism

We discuss an extended version of electromagnetism in which the usual gauge fixing term is promoted into a physical contribution that introduces a new scalar state in the theory. This new state can be generated from vacuum quantum fluctuations during an inflationary era and, on super-Hubble scales, gives rise to an effective cosmological constant. The value of such a cosmological constant coincides with the one inferred from observations as long as inflation took place at the electroweak scale. On the other hand, the new state also generates an effective electric charge density on sub-Hubble scales that produces both vorticity and magnetic fields with coherent lengths as large as the present Hubble horizon.Comment: 4 pages, 2 figures. Contribution to the proceedings of Spanish Relativity Meeting 2010, Granada, Spain, 6-10 September 201

Cosmology with a Continuous Tower of Scalar Fields

We study the cosmological evolution for a universe in the presence of a continuous tower of massive scalar fields which can drive the current phase of accelerated expansion of the universe and, in addition, can contribute as a dark matter component. The tower consists of a continuous set of massive scalar fields with a gaussian mass distribution. We show that, in a certain region of the parameter space, the {\it heavy} modes of the tower (those with masses much larger than the Hubble expansion rate) dominate at early times and make the tower behave like the usual single scalar field whose coherent oscillations around the minimum of the potential give a matter-like contribution. On the other hand, at late times, the {\it light} modes (those with masses much smaller than the Hubble expansion rate) overcome the energy density of the tower and they behave like a perfect fluid with equation of state ranging from 0 to -1, depending on the spectral index of the initial spectrum. This is a distinctive feature of the tower with respect to the case of quintessence fields, since a massive scalar field can only give acceleration with equation of state close to -1. Such unique property is the result of a synergy effect between the different mass modes. Interestingly, we find that, for some choices of the spectral index, the tower tracks the matter component at high redshifts (or it can even play the role of the dark matter) and eventually becomes the dominant component of the universe and give rise to an accelerated expansion.Comment: 13 pages, 8 figures. V2: minor changes to match published versio

Screening Vector Field Modifications of General Relativity

A screening mechanism for conformal vector-tensor modifications of general relativity is proposed. The conformal factor depends on the norm of the vector field and makes the field to vanish in high dense regions, whereas drives it to a non-null value in low density environments. Such process occurs due to a spontaneous symmetry breaking mechanism and gives rise to both the screening of fifth forces as well as Lorentz violations. The cosmology and local constraints are also computed.Comment: 10 pages, 4 figures, revised version, to be published in PL

Palaeo-European studies: Languages, writings, epigraphic cultures

The objective of Palaeo-European studies is to undertake interdisciplinary, comparative and comprehensive research into the sets of local languages, writing systems and epigraphic practices that form the furthermost stratum of written European culture. These are understood as organic systems of knowledge and communicative practice that combine language, script, and support in order to record or transmit messages in well-defined social and ideological contexts. This is not, then, a strictly new field of investigation. The oldest languages, scripts, and inscriptions of Europe, such as the Etruscan or Iberian for example, have been the object of academic scrutiny for centuries. They have traditionally been addressed separately, however, so that their study has never been structured around a single scientific discipline, nor have scientific journals or conferences focussing on their joint study been created. On the contrary, approaches have predominantly been partial and biased more towards linguistics or history; or they have been regional studies, generally centred sectorally on Hispania, Italy, or Gaul; or they have had specialised foci according to language families (Indo-European, Celtic, Italian) or historical periods (Orientalizing, Romanization…). ..

Estimación del error de discretización en elementos de deformaciones supuestas

El artículo presenta el fundamento teórico de un nuevo estimador del error de discretización utilizable con elementos de deformaciones supuestas. fiente a estimadores de otras clases, su principal ventaja desde el punto de vista práctico es que se evalúa elemento a elemento de forma independiente, sin ser necesario el cálculo de promedios nodales ni de saltos interelementales. Desde el punto de vista teórico, no impone para su aplicación ningún requisito de suavidad para la solución teórica, esto es, la solución exacta puede exhibir discontinuidades sin que se perturbe la aplicabilidad del estimador. Las pruebas preliminares realizadas con el estimador muestran algunas dificultades para su aplicación general como medida del error global; sin embargo, su utilización como indicador de error en procesos de remallaje adaptativo parece sencilla y económica.Peer Reviewe

Estimación del error de discretización en elementos de deformaciones supuestas

El artículo presenta el fundamento teórico de un nuevo estimador del error de discretización utilizable con elementos de deformaciones supuestas. fiente a estimadores de otras clases, su principal ventaja desde el punto de vista práctico es que se evalúa elemento a elemento de forma independiente, sin ser necesario el cálculo de promedios nodales ni de saltos interelementales. Desde el punto de vista teórico, no impone para su aplicación ningún requisito de suavidad para la solución teórica, esto es, la solución exacta puede exhibir discontinuidades sin que se perturbe la aplicabilidad del estimador. Las pruebas preliminares realizadas con el estimador muestran algunas dificultades para su aplicación general como medida del error global; sin embargo, su utilización como indicador de error en procesos de remallaje adaptativo parece sencilla y económica.Peer Reviewe

Chemical Segregation in Hot Cores With Disk Candidates: An investigation with ALMA

In the study of high-mass star formation, hot cores are empirically defined stages where chemically rich emission is detected toward a massive YSO. It is unknown whether the physical origin of this emission is a disk, inner envelope, or outflow cavity wall and whether the hot core stage is common to all massive stars. We investigate the chemical make up of several hot molecular cores to determine physical and chemical structure. We use high spectral and spatial resolution Cycle 0 ALMA observations to determine how this stage fits into the formation sequence of a high mass star. We observed the G35.20-0.74N and G35.03+0.35 hot cores at 350 GHz. We analyzed spectra and maps from four continuum peaks (A, B1, B2 and B3) in G35.20, separated by 1000-2000 AU, and one continuum peak in G35.03. We made all possible line identifications across 8 GHz of spectral windows of molecular emission lines and determined column densities and temperatures for as many as 35 species assuming local thermodynamic equilibrium. In comparing the spectra of the four peaks, we find each has a distinct chemical composition expressed in over 400 different transitions. In G35.20, B1 and B2 contain oxygen- and sulfur-bearing organic and inorganic species but few nitrogen-bearing species whereas A and B3 are strong sources of O, S, and N-bearing species (especially those with the CN-bond). CH$_2$DCN is clearly detected in A and B3 with D/H ratios of 8 and 13$\%$, respectively, but is much weaker at B1 and undetected at B2. No deuterated species are detected in G35.03, but similar molecular abundances to G35.20 were found in other species. We also find co-spatial emission of HNCO and NH$_2$CHO in both sources indicating a strong chemical link between the two species. The chemical segregation between N-bearing organic species and others in G35.20 suggests the presence of multiple protostars, surrounded by a disk or torus.Comment: 14 pages with 13 figures main text, 54 pages appendi