Chiral transport equation from the quantum Dirac Hamiltonian and the on-shell effective field theory

We derive the relativistic chiral transport equation for massless fermions and antifermions by performing a semiclassical Foldy-Wouthuysen diagonalization of the quantum Dirac Hamiltonian. The Berry connection naturally emerges in the diagonalization process to modify the classical equations of motion of a fermion in an electromagnetic field. We also see that the fermion and antifermion dispersion relations are corrected at first order in the Planck constant by the Berry curvature, as previously derived by Son and Yamamoto for the particular case of vanishing temperature. Our approach does not require knowledge of the state of the system, and thus it can also be applied at high temperature. We provide support for our result by an alternative computation using an effective field theory for fermions and antifermions: the on-shell effective field theory. In this formalism, the off-shell fermionic modes are integrated out to generate an effective Lagrangian for the quasi-on-shell fermions/antifermions. The dispersion relation at leading order exactly matches the result from the semiclassical diagonalization. From the transport equation, we explicitly show how the axial and gauge anomalies are not modified at finite temperature and density despite the incorporation of the new dispersion relation into the distribution function.Comment: 9 pages, no figures. v2: Some comments and more details added, typos fixed and reference list updated. Final version matching the published articl

Dynamical evolution of the chiral magnetic effect: Applications to the quark-gluon plasma

We study the dynamical evolution of the so-called chiral magnetic effect in an electromagnetic conductor. To this end, we consider the coupled set of corresponding Maxwell and chiral anomaly equations, and we prove that these can be derived from chiral kinetic theory. After integrating the chiral anomaly equation over space in a closed volume, it leads to a quantum conservation law of the total helicity of the system. A change in the magnetic helicity density comes together with a modification of the chiral fermion density. We study in Fourier space the coupled set of anomalous equations and we obtain the dynamical evolution of the magnetic fields, magnetic helicity density, and chiral fermion imbalance. Depending on the initial conditions we observe how the helicity might be transferred from the fermions to the magnetic fields, or vice versa, and find that the rate of this transfer also depends on the scale of wavelengths of the gauge fields in consideration. We then focus our attention on the quark-gluon plasma phase, and analyze the dynamical evolution of the chiral magnetic effect in a very simple toy model. We conclude that an existing chiral fermion imbalance in peripheral heavy ion collisions would affect the magnetic field dynamics, and consequently, the charge dependent correlations measured in these experiments.Comment: 41 pages, 14 figures, 3 appendices. Version 2: new global structure (appendix added), more explanations and additional references. Version accepted for publication in Physical Review D journa

Kinetically Constrained Models

In this chapter we summarize recent developments in the study of kinetically constrained models (KCMs) as models for glass formers. After recalling the definition of the KCMs which we cover we study the possible occurrence of ergodicity breaking transitions and discuss in some detail how, before any such transition occurs, relaxation timescales depend on the relevant control parameter (density or temperature). Then we turn to the main issue: the prediction of KCMs for dynamical heterogeneities. We focus in particular on multipoint correlation functions and susceptibilities, and decoupling in the transport coefficients. Finally we discuss the recent view of KCMs as being at first order coexistence between an active and an inactive space-time phase.Comment: Chapter of "Dynamical heterogeneities in glasses, colloids, and granular media", Eds.: L. Berthier, G. Biroli, J-P Bouchaud, L. Cipelletti and W. van Saarloos (Oxford University Press, to appear), more info at http://w3.lcvn.univ-montp2.fr/~lucacip/DH_book.ht

The CLARIS LPB database: constructing a long-term daily hydro-meteorological dataset for La Plata Basin, Southern South America

CLARIS LPB database was built within the framework of the CLARIS LPB project “A Europe-South America Network for climate Change Assessment and Impact Studies in La Plata Basin” of the European Community's Seventh Framework Programme (FP7). The main variables available in the database are rainfall, temperature, radiation, heliophany and streamflow, constituting a high-quality daily hydro-meteorological dataset for scientific purpose available at http://wp32.at.fcen.uba.ar/. The objective of this article is to describe CLARIS LPB database construction, quality control and spatial and temporal characteristics. Due to the interactions with more than 60 institutions, the network of stations expanded from 107 stations in the FP6 CLARIS to more than 9000 stations in the FP7 CLARIS LPB. More than 800 maximum and minimum temperatures series, more than 8000 rainfall series, 68 radiation series, 29 heliophany series, and 58 streamflow series are available in the database webpage. The number of stations also varied greatly as a function of time, and decadal variations were evident in both rainfall and temperature stations with at least 20% of data missing. According to the characteristics analysed, this dataset provides spatially consistent climatic time series which enable a variety of empirical climate studies. It was already used as input for hydrological models, for the validation and analysis of present-day regional and global climate model outputs, for improvement in the analysis of recent past climate variability in La Plata Basin, for analysing palaeohydrological reconstructions of the past climate variability, among others. Finally, the spatially highly dense daily database of rainfall and maximum and minimum temperatures allowed the generation of gridded products.Fil: Penalba, Olga Clorinda. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rivera, Juan Antonio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pántano, Vanesa Cristina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

A cane-based low cost sensor to implement attention mechanisms in telecare robots

Telepresence robots have been recently used for Comprehensive Geriatric Assessment (CGA). Since the robot can not track a person continuously, there are several strategies to decide when to check them, from cyclic checks to simple requests from users and/or caregivers. In order to adapt to the user needs and condition, it is preferable to perform CGA as soon as regularities appear. However, this requires detection of potential issues in users to offer immediate service. In this work we propose a new low cost force sensor system to detect user’s condition and attract attention of CGA robots, so they can perform a full examination on a need basis. The main advantages of this system are: i) it can be attached to any standard commercial cane; ii) its power consumption is very reduced; and iii) it provides continuous information as long as the user walks. It has been tested with several elderly volunteers in care facilities. Results have proven that the sensor readings are indeed correlated with the users’ condition.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Manipulación y selección del alimento en el cangrejo grapsoideo omnívoro Neohelice granulata (Decapoda: Varunidae)

Neohelice granulata es un cangrejo semiterrestre cavador y omnívoro, endémico de las marismas del Atlántico sudoccidental. Se comporta como herbívoro cuando habita en áreas con vegetación halófila y como sedimentívoro cuando habita en llanuras fangosas. Se estudiaron en el laboratorio dos aspectos del comportamiento alimentario de este cangrejo para comprender cómo logra mantenerse en base a dietas de baja calidad: i) la manera en que usa los apéndices bucales para manipular los diferentes tipos de alimento comúnmente consumidos en cada hábitat (hojas de plantas halófitas y sedimento), y ii) su habilidad para seleccionar partículas cuando se alimenta de fango, comparando la composición de las partículas alimenticias presentes en el estómago y en el sedimento. Los cangrejos utilizaron diferentes piezas bucales y tuvieron distintos comportamientos de acuerdo al tipo de alimento consumido. Además, la manipulación de las hojas de plantas halófitas difirió entre sexos. El contenido estomacal de los cangrejos alimentados con fango mostró una mayor concentración de partículas ricas en N que el sedimento. El análisis del contenido de C y N del sedimento y las heces evidenció además la capacidad de selección de partículas nutritivas. N. granulata puede ser un sedimentívoro eficiente aunque sus piezas bucales no posean las características comúnmente asociadas al consumo de este tipo de alimento.Neohelice granulata is an omnivorous, semi-terrestrial burrowing crab endemic to southwestern Atlantic saltmarshes that behaves as a herbivore when it inhabits vegetated saltmarsh areas or a deposit feeder on bare mudflats. In order to gain insights into how non-specialized crabs manage to rely on low quality diets, we studied in laboratory i) how they use feeding appendages to manipulate the food items commonly eaten (halophytic plant leaves and sediment), and ii) their ability to sort particles when they act as deposit feeders by analysing the food particle content of sediment and stomach. According to the source of food consumed, different behaviours and mouthparts involved in food processing were observed. Sex differences were found in handling halophytic plant leaves in the herbivore feeding mode. In deposit feeding, a concentration of potentially N-rich items of animal origin was detected in stomach contents. Indirect evidence of food item concentration from sediment was revealed by analysis of the C and N content of sediment and feces. N. granulata seems to be an effective deposit feeder even though it lacks the characteristic mouthparts commonly associated with this type of food source.Fil: Lancia, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Bas, Claudia Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Spivak, Eduardo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentin