Electron degeneracy and intrinsic magnetic properties of epitaxial Nb:SrTiO3_3 thin-films controlled by defects

We report thermoelectric power experiments in e-doped thin films of SrTiO$_3$ (STO) which demonstrate that the electronic band degeneracy can be lifted through defect management during growth. We show that even small amounts of cationic vacancies, combined with epitaxial stress, produce a homogeneous tetragonal distortion of the films, resulting in a Kondo-like resistance upturn at low temperature, large anisotropic magnetoresistance, and non-linear Hall effect. Ab-initio calculations confirm a different occupation of each band depending on the degree of tetragonal distortion. The phenomenology reported in this paper for tetragonally distorted e-doped STO thin films, is similarto that observed in LaAlO$_3$/STO interfaces and magnetic STO quantum wells.Comment: 5 pages, 5 figure

Aspects of the Unitarized Soft Multipomeron Approach in DIS and Diffraction

We study in detail the main features of the unitarized Regge model (CFKS), recently proposed to describe the small-$Q^2$ domain. It takes into account a two-component description with two types of unitarized contributions: one is the multiple pomeron exchange contribution, interacting with the large dipole configurations, and the other one consists of a unitarized dipole cross section, describing the interaction with the small size dipoles. We analyze the ratio between soft and hard pieces as a function of the virtuality, and also compare the resulting dipole cross section to that from the saturation model. Diffraction dissociation is also considered, showing the scaling violations in diffractive DIS and estimating the corresponding logarithmic slope.Comment: 14 pages, 5 postscript figures. Version to be published in Eur. Phys. J.

Resolving the J/\psi RHIC puzzles at LHC

Experiments with gold-gold collisions at RHIC have revealed (i) stronger suppression of charmonium production at forward rapidity than at midrapidity and (ii) the similarity between the suppression degrees at RHIC and SPS energies. To describe these findings we employ the model that includes nuclear shadowing effects, calculated within the Glauber-Gribov theory, rapidity-dependent absorptive mechanism, caused by energy-momentum conservation, and dissociation and recombination of the charmonium due to interaction with co-moving matter. The free parameters of the model are tuned and fixed by comparison with experimental data at lower energies. A good agreement with the RHIC results concerning the rapidity and centrality distributions is obtained for both heavy Au+Au and light Cu+Cu colliding system. For pA and A+A collisions at LHC the model predicts stronger suppression of the charmonium and bottomonium yields in stark contrast to thermal model predictions.Comment: SQM2008 proceedings, 6 page

Local Anomalies, Local Equivariant Cohomology and the Variational Bicomplex

The locality conditions for the vanishing of local anomalies in field theory are shown to admit a geometrical interpretation in terms of local equivariant cohomology, thus providing a method to deal with the problem of locality in the geometrical approaches to the study of local anomalies based on the Atiyah-Singer index theorem. The local cohomology is shown to be related to the cohomology of jet bundles by means of the variational bicomplex theory. Using these results and the techniques for the computation of the cohomology of invariant variational bicomplexes in terms of relative Gel'fand-Fuks cohomology introduced in [6], we obtain necessary and sufficient conditions for the cancellation of local gravitational and mixed anomalies.Comment: 36 pages. The paper is divided in two part

A multifractal approach to characterize cumulative rainfall and tillage effects on soil surface micro-topography and to predict depression storage

Most of the indices currently employed for assessing soil surface micro-topography, such as random roughness (RR), are merely descriptors of its vertical component. Recently, multifractal analysis provided a new insight for describing the spatial configuration of soil surface roughness. The main objective of this study was to test the ability of multifractal parameters to assess in field conditions the decay of initial surface roughness induced by natural rainfall under different soil tillage systems. In addition, we evaluated the potential of the joint use of multifractal indices plus RR to improve predictions of water storage in depressions of the soil surface (MDS). Field experiments were performed on an Oxisol at Campinas, São Paulo State (Brazil). Six tillage treatments, namely, disc harrow, disc plough, chisel plough, disc harrow + disc level, disc plough + disc level and chisel plough + disc level were tested. In each treatment soil surface micro-topography was measured four times, with increasing amounts of natural rainfall, using a pin meter. The sampling scheme was a square grid with 25 × 25 mm point spacing and the plot size was 1350 × 1350 mm (≈1.8 m<sup>2</sup>), so that each data set consisted of 3025 individual elevation points. Duplicated measurements were taken per treatment and date, yielding a total of 48 experimental data sets. MDS was estimated from grid elevation data with a depression-filling algorithm. Multifractal analysis was performed for experimental data sets as well as for oriented and random surface conditions obtained from the former by removing slope and slope plus tillage marks, respectively. All the investigated microplots exhibited multifractal behaviour, irrespective of surface condition, but the degree of multifractality showed wide differences between them. Multifractal parameters provided valuable information for characterizing the spatial features of soil micro-topography as they were able to discriminate data sets with similar values for the vertical component of roughness. Conversely, both, rough and smooth soil surfaces, with high and low roughness values, respectively, can display similar levels of spectral complexity. Although in most of the studied cases trend removal produces increasing homogeneity in the spatial configuration of height readings, spectral complexity of individual data sets may increase or decrease, when slope or slope plus tillage tool marks are filtered. Increased cumulative rainfall had significant effects on various parameters from the generalized dimension, <i>D</i><sub>q</sub>, and singularity spectrum, <i>f</i>(α). Overall, micro-topography decay by rainfall was reflected on a shift of the singularity spectra, <i>f</i>(α) from the left side (<i>q</i>>>0) to the right side (<i>q</i><<0) and also on a shift of the generalized dimension spectra from the right side (<i>q</i>>>0) to the left side (<i>q</i><<0). The use of an exponential model of vertical roughness indices, RR, and multifractal parameters accounting for the spatial configuration such as <i>D</i><sub>1</sub> or <i>D</i><sub>5</sub> improved estimation of water stored in surface depressions

From Euclidean to Minkowski space with the Cauchy-Riemann equations

We present an elementary method to obtain Green's functions in non-perturbative quantum field theory in Minkowski space from calculated Green's functions in Euclidean space. Since in non-perturbative field theory the analytical structure of amplitudes is many times unknown, especially in the presence of confined fields, dispersive representations suffer from systematic uncertainties. Therefore we suggest to use the Cauchy-Riemann equations, that perform the analytical continuation without assuming global information on the function in the entire complex plane, only in the region through which the equations are solved. We use as example the quark propagator in Landau gauge Quantum Chromodynamics, that is known from lattice and Dyson-Schwinger studies in Euclidean space. The drawback of the method is the instability of the Cauchy-Riemann equations to high-frequency noise, that makes difficult to achieve good accuracy. We also point out a few curiosities related to the Wick rotation.Comment: 12 pages in EPJ double-column format, 16 figures. This version: added paragraph, two reference

Geometric Scaling in Inclusive Charm Production

We show that the cross section for inclusive charm production exhibits geometric scaling in a large range of photon virtualities. In the HERA kinematic domain the saturation momentum $Q_{sat}^2(x)$ stays below the hard scale $\mu_c^2=4m_c^2$, implying charm production probing mostly the color transparency regime and unitarization effects being almost negligible. We derive our results considering two saturation models which are able to describe the DESY ep collider HERA data for the proton structure function at small values of the Bjorken variable $x$. A striking feature is the scaling on $\tau=Q_2^2/Q_{sat}^2(x)$ above saturation limit, corroborating recent theoretical studies.Comment: 4 pages, 2 figures. Version to be published in Physical Review Letter

A Fixed-Target ExpeRiment at the LHC (AFTER@LHC) : luminosities, target polarisation and a selection of physics studies

We report on a future multi-purpose fixed-target experiment with the proton or lead ion LHC beams extracted by a bent crystal. The multi-TeV LHC beams allow for the most energetic fixed-target experiments ever performed. Such an experiment, tentatively named AFTER for "A Fixed-Target ExperRiment", gives access to new domains of particle and nuclear physics complementing that of collider experiments, in particular at RHIC and at the EIC projects. The instantaneous luminosity at AFTER using typical targets surpasses that of RHIC by more than 3 orders of magnitude. Beam extraction by a bent crystal offers an ideal way to obtain a clean and very collimated high-energy beam, without decreasing the performance of the LHC. The fixed-target mode also has the advantage of allowing for spin measurements with a polarised target and for an access over the full backward rapidity domain up to xF ~ - 1. Here, we elaborate on the reachable luminosities, the target polarisation and a selection of measurements with hydrogen and deuterium targets.Comment: 6 pages. Proceedings of the Sixth International Conference on Quarks and Nuclear Physics QNP2012 (16-20 April 2012, Ecole Polytechnique, Palaiseau,France

Universal behavior of baryons and mesons' transverse momentum distributions in the framework of percolation of strings

In the framework of percolation of strings, we present predictions for the $R_{AA}$ and $R_{CP}$ for mesons and baryons and for $\bar{p}/\pi^{0}$ ratios at LHC energies.Comment: Presented at "Heavy Ion Collisions at the LHC: last call for predictions", Geneva Switzerland, May 14th-June 8t

Monitorization of Polyamide Microplastics Weathering Using Attenuated Total Reflectance and Microreflectance Infrared Spectrometry

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] The EU goal to reduce marine plastic litter by ca. 30% by 2020 stressed the need to deploy analytical methods to ascertain the polymeric nature of a residue. Furthermore, as plastics age under natural conditions and usual databases do not include their weathered spectra, (micro)plastics in environmental samples may be unidentified. In this paper, polyamide (nylon) microplastics weathering was monitored because of its ubiquity in household commodities, clothes, fishery items and industry, whose residues end up frequently in the environment. Infrared spectra (ATR and microreflectance) and Scanning Electron Microscopy (SEM) images were collected periodically while exposing nylon to controlled weathering. It was seen that ATR was more sensitive than microreflectance to monitor the structural evolution of polyamide and that the spectra and the surface of weathered microplastics showed remarkable differences with the pristine material, which stresses the need for considering its evolution when identifying microplastics in environmental studies. The evolution of six band ratios related to the chemical evolution of this polymer are presented. SEM images revealed the formation of secondary microplastics at the most advanced weathering stages of polyamide.This work was supported through the JPI-Oceans BASEMAN and MicroplastiX projects, sponsored by the Spanish Ministry of Science and Innovation (Agencia Estatal de Investigación) -partially financed by the European Regional Development Fund program- (Grants: PCIN-2015-170-C02-01; PCIN- PCI2020-112145 and CTM2016-77945-C3-3-R, ARPA-ACUA). The Program ‘Consolidación e Estructuración de Unidades de Investigación Competitiva’ of the Galician Government (Xunta de Galicia) is also acknowledged (Grant: ED431C-2017/28)Xunta de Galicia; ED431C-2017/2