Distribution of single-particle strength due to short-range and tensor correlations

The distribution of single-particle strength in nuclear matter is calculated for a realistic nucleon-nucleon interaction. The influence of the short-range repulsion and the tensor component of the nuclear force on the spectral functions is to move approximately 13% of the total strength for all single-particle states beyond 100 MeV into the particle domain. This result is related to the abundantly observed quenching phenomena in nuclei which include the reduction of spectroscopic factors observed in (e,ep) reactions and the missing strength in low energy response functions.

Dynamically generated open-charm baryons beyond the zero-range approximation

The interaction of the low-lying pseudoscalar mesons with the ground-state baryons in the charm sector is studied within a coupled-channel approach using a t-channel vector-exchange driving force. The amplitudes describing the scattering of the pseudoscalar mesons off the ground-state baryons are obtained by solving the Lippmann-Schwinger equation. We analyze in detail the effects of going beyond the t=0 approximation. Our model predicts the dynamical generation of several open-charm baryon resonances in different isospin and strangeness channels, some of which can be clearly identified with recently observed states.

Brownian motion in short range random potentials

A numerical study of Brownian motion of noninteracting particles in random potentials is presented. The dynamics are modeled by Langevin equations in the high friction limit. The random potentials are Gaussian distributed and short ranged. The simulations are performed in one and two dimensions. Different dynamical regimes are found and explained. Effective subdiffusive exponents are obtained and commented on.

Fragile-glass behavior of a short-range p-spin model

We propose a short-range generalization of the p-spin interaction spin-glass model. The model is well suited to test the idea that an entropy collapse is at the bottom line of the dynamical singularity encountered in structural glasses. The model is studied in three dimensions through Monte Carlo simulations, which put in evidence fragile glass behavior with stretched exponential relaxation and super-Arrhenius behavior of the relaxation time. Our data are in favor of a Vogel-Fulcher behavior of the relaxation time, related to an entropy collapse at the Kauzmann temperature. We, however, encounter difficulties analogous to those found in experimental systems when extrapolating thermodynamical data at low temperatures. We study the spin-glass susceptibility, investigating the behavior of the correlation length in the system. We find that the increase of the relaxation time is accompanied by a very slow growth of the correlation length. We discuss the scaling properties of off-equilibrium dynamics in the glassy regime, finding qualitative agreement with the mean-field theory.

Interactions among systems of finite size en predictive relativistic mechanics III. Short-range interaction and second-order terms

We compute up to and including all the c-2 terms in the dynamical equations for extended bodies interacting through electromagnetic, gravitational, or short-range fields. We show that these equations can be reduced to those of point particles with intrinsic angular momentum assuming spherical symmetry.

Long-range-interactions induced ordered structures in deposition processes

We present a new model of sequential adsorption in which the adsorbing particles experience dipolar interactions. We show that in the presence of these long-range interactions, highly ordered structures in the adsorbed layer may be induced at low temperatures. The new phenomenology is manifest through significant variations of the pair correlation function and the jamming limit, with respect to the case of noninteracting particles. Our study could be relevant in understanding the adsorption of magnetic colloidal particles in the presence of a magnetic field.

Long-range correlations in diffusive systems away from equilibrium

We study the dynamics of density fluctuations in purely diffusive systems away from equilibrium. Under some conditions the static density correlation function becomes long ranged. We then analyze this behavior in the framework of nonequilibrium fluctuating hydrodynamics.

Long-range ferromagnetic dipolar ordering of high-spin molecular clusters

We report the first example of a transition to long-range magnetic order in a purely dipolarly interacting molecular magnet. For the magnetic cluster compound Mn6O4Br4(Et2dbm)6, the anisotropy experienced by the total spin S=12 of each cluster is so small that spin-lattice relaxation remains fast down to the lowest temperatures, thus enabling dipolar order to occur within experimental times at Tc=0.16 K. In high magnetic fields, the relaxation rate becomes drastically reduced and the interplay between nuclear- and electron-spin lattice relaxation is revealed.

Space Competition and Time Delays in Human Range Expansions. Application to the Neolithic Transition

Space competition effects are well-known in many microbiological and ecological systems. Here we analyze such an effectin human populations. The Neolithic transition (change from foraging to farming) was mainly the outcome of a demographic process that spread gradually throughout Europe from the Near East. In Northern Europe, archaeological data show a slowdown on the Neolithic rate of spread that can be related to a high indigenous (Mesolithic) population density hindering the advance as a result of the space competition between the two populations. We measure this slowdown from a database of 902 Early Neolithic sites and develop a time-delayed reaction-diffusion model with space competition between Neolithic and Mesolithic populations, to predict the observed speeds. The comparison of the predicted speed with the observations and with a previous non-delayed model show that both effects, the time delay effect due to the generation lag and the space competition between populations, are crucial in order to understand the observations

Dynamic range extension of SiPM detectors with the time-gated operation

The silicon photomultiplier (SiPM) is a novel detector technology that has undergone a fast development in the last few years, owing to its single-photon resolution and ultra-fast response time. However, the typical high dark count rates of the sensor may prevent the detection of low intensity radiation fluxes. In this article, the time-gated operation with short active periods in the nanosecond range is proposed as a solution to reduce the number of cells fired due to noise and thus increase the dynamic range. The technique is aimed at application fields that function under a trigger command, such as gated fluorescence lifetime imaging microscopy.

Arqueología de paisajes altimontanos pirenaicos: formas de explotación y usos del medio en época romana en valle del Madriu-Perafita-Claror (Andorra) y en la Sierra del Cadí (Alt Urgell)

long-term cultural history of the Madriu-Perafita-Claror valleys (Andorra) and the Cadí Range (Catalonia) has been investigated thanks to the combination of archaeological surveys and excavation, analysis of written sources, multiproxy alaeoenvironment analysis (pollen, NPP, micro and macro charcoal, sedimentology and geochemistry), and digital technologies such as stereophotogrammetry, multispectral imaging, DGPS and GIS. The project has been designed from a landscape archaeology approach and the study area has been selected due to the suitable setting it provides for a meaningful application of the aforementioned techniques. Consequently, archaeological, historical and palaeoenvironmental data have been all treated as cultural proxies. Their comparison has allowed obtaining not only coherent but also complementary results. The project outcomes show an uninterrupted occupation of these high mountain valleys (2000-2600 m a.s.l.) from the Mesolithic until the present. This human occupation shows strong spatial and chronological variability in human practices ranging from a stable long term group occupation in the Late Neolithic to the diversification of representative practices during the Roman period (metallurgy, pine resin exploitation, charcoal production, pastoralism, etc.). This high diversity of activities leads to complex cultural landscapes in the high Pyrenean areas. The reconstruction of the cultural history at the study areas will allow the development of more sustainable politics for these landscapes management.