The weight of matter

Einstein's traceless 1919 gravitational theory is analyzed from a variational viewpoint. It is shown to be equivalent to a transverse (invariant only under diffeomorphisms that preserve the Lebesgue measure) theory, with an additional Weyl symmetry, in which the gauge is partially fixed so that the metric becomes unimodular. In spite of the fact that this symmetry forbids direct coupling of the potential energy with the gravitational sector, the equivalence principle is recovered in the unimodular gauge owing to Bianchi's identities.Comment: LaTeX, 11 page

A Change of Variables to the Dual and Factorization of Composite Anomalous Jacobians

Changes of variables giving the dual model are constructed explicitly for sigma-models without isotropy. In particular, the jacobian is calculated to give the known results. The global aspects of the abelian case as well as some of those of the cases where the isometry group is simply connected are considered. Considering the anomalous case, we infer by a consistency argument that the `multiplicative anomaly' should be replaceable by adequate rules for factorization of composite jacobians. These rules are then generalized in a simple way for composite jacobians defined in spaces of different types. Implimentation of these rules then gives specific formulas for the anomally for semisimple algebras and also for solvable ones.Comment: 15 pages, no figures, Latex file, A treatment of the global aspects of the abelian and of semisimple duality groups are added. General formulas for the mixed anomaly are derive

Recursos gemorfológicos: evolución morfológica de las marmitas de erosión en el río Miño

5 páginas, 4 figuras.-- VII Simpósio Ibérico sobre a Bacia Hidrográfica do Rio Minho, Vilanova de Cerveira, 7-8 novembro 2014En el río Miño, que discurre en su mayor parte sobre granitos, se distinguen zonas en las que la corriente circula directamente sobre la roca madre con formas características de erosión fluvial. Una de las más comunes son las marmitas (potholes) que se van a generar en condiciones dependientes del régimen hídrico y la estacionalidad del flujo del río. Junto a otras formas, las marmitas son parte del patrimonio geomorfológico fluvial asociado al río Miño. En este estudio se presenta una secuenciación evolutiva diferenciada en cuatro fases, para las cuales se han establecido valores umbral que marcan cambios en la morfologíaPeer reviewe

Growth of sculpted forms in bedrock channels (Miño River, northwest Spain)

7 páginas, 4 tablas, 6 figurasA total of 216 sculpted forms were registered on the granitic bedrock of the Miño River, northwest Iberian Peninsula. Analysis of in situ measurements (length, width and depth) revealed three general type-sets: incipient forms, longitudinal furrows and circular pot-holes. Maximum depth and upper radius (at the incision surface) were identified as key variables to mathematically determine the growth rate in each set. Three regression models are presented revealing that the development of the forms depends on a power law explaining their size and shape. Morphological and dimensional thresholds were established to better identify stages from incipient active growth) and inherited (stationary growth) formsM.A.A.V. is supported by the Xunta de Galicia through the Plan Galego de investigación, innovación e crecemento 2011-2015 (Plan I2C) in collaboration with the International Campus do Mar (Predoc ED481A-2015/410)Peer reviewe

Dual Instantons

We show how to map the Belavin-Polyakov instantons of the O(3)-nonlinear $\sigma-$model to a dual theory where they then appear as nontopological solitons. They are stationary points of the Euclidean action in the dual theory, and moreover, the dual action and the O(3)-nonlinear $\sigma-$model action agree on shell.Comment: 13 page

Momentum distributions of α\alpha-particles from decaying low-lying 12^{12}C-resonances

The complex scaled hyperspherical adiabatic expansion method is used to compute momentum and energy distributions of the three $\alpha$-particles emerging from the decay of low-lying $^{12}$C-resonances. The large distance continuum properties of the wave functions are crucial and must be accurately calculated. We discuss separately decays of natural parity states: two $0^+$, one $1^{-}$, three $2^+$, one $3^-$, two $4^+$, one $6^+$, and one of each of unnatural parity, $1^{+}$, $2^-$, $3^+$, $4^-$. The lowest natural parity state of each $J^{\pi}$ decays predominantly sequentially via the $^{8}$Be ground state whereas other states including unnatural parity states predominantly decay directly to the continuum. We present Dalitz plots and systematic detailed momentum correlations of the emerging $\alpha$-particles.Comment: 11 pages, 7 figures, accepted for publication in Physical Review

The use of arc-erosion as a patterning technique for transparent conductive materials

Within the framework of cost-effective patterning processes a novel technique that saves photolithographic processing steps, easily scalable to wide area production, is proposed. It consists of a tip-probe, which is biased with respect to a conductive substrate and slides on it, keeping contact with the material. The sliding tip leaves an insulating path (which currently is as narrow as 30 μm) across the material, which enables the drawing of tracks and pads electrically insulated from the surroundings. This ablation method, called arc-erosion, requires an experimental set up that had to be customized for this purpose and is described. Upon instrumental monitoring, a brief proposal of the physics below this process is also presented. As a result an optimal control of the patterning process has been acquired. The system has been used on different substrates, including indium tin oxide either on glass or on polyethylene terephtalate, as well as alloys like Au/Cr, and Al. The influence of conditions such as tip speed and applied voltage is discusse

Rudiments of Holography

An elementary introduction to Maldacena's AdS/CFT correspondence is given, with some emphasis in the Fefferman-Graham construction. This is based on lectures given by one of us (E.A.) at the Universidad Autonoma de Madrid.Comment: 60 pages, additional misprints corrected, references adde

Few-body decay and recombination in nuclear astrophysics

Three-body continuum problems are investigated for light nuclei of astrophysical relevance. We focus on three-body decays of resonances or recombination via resonances or the continuum background. The concepts of widths, decay mechanisms and dynamic evolution are discussed. We also discuss results for the triple $\alpha$ decay in connection with $2^+$ resonances and density and temperature dependence rates of recombination into light nuclei from $\alpha$-particles and neutrons.Comment: 9 pages, 8 figures. Proceedings of the 21st European Few Body Conference held in Salamanca (Spain) in August-September 201