474 research outputs found
Reaction-diffusion processes and non-perturbative renormalisation group
This paper is devoted to investigating non-equilibrium phase transitions to
an absorbing state, which are generically encountered in reaction-diffusion
processes. It is a review, based on [Phys. Rev. Lett. 92, 195703; Phys. Rev.
Lett. 92, 255703; Phys. Rev. Lett. 95, 100601], of recent progress in this
field that has been allowed by a non-perturbative renormalisation group
approach. We mainly focus on branching and annihilating random walks and show
that their critical properties strongly rely on non-perturbative features and
that hence the use of a non-perturbative method turns out to be crucial to get
a correct picture of the physics of these models.Comment: 14 pages, submitted to J. Phys. A for the proceedings of the
conference 'Renormalization Group 2005', Helsink
General framework of the non-perturbative renormalization group for non-equilibrium steady states
This paper is devoted to presenting in detail the non-perturbative
renormalization group (NPRG) formalism to investigate out-of-equilibrium
systems and critical dynamics in statistical physics. The general NPRG
framework for studying non-equilibrium steady states in stochastic models is
expounded and fundamental technicalities are stressed, mainly regarding the
role of causality and of Ito's discretization. We analyze the consequences of
Ito's prescription in the NPRG framework and eventually provide an adequate
regularization to encode them automatically. Besides, we show how to build a
supersymmetric NPRG formalism with emphasis on time-reversal symmetric
problems, whose supersymmetric structure allows for a particularly simple
implementation of NPRG in which causality issues are transparent. We illustrate
the two approaches on the example of Model A within the derivative expansion
approximation at order two, and check that they yield identical results.Comment: 28 pages, 1 figure, minor corrections prior to publicatio
Repensant, reescrivint, refent o aprenent a ensenyar ciències mitjançant l'anglès
Es presenten les reflexions sobre didàctica de les ciències generades a partir de les revisions del material didàctic AICLE (ciències naturals en anglès) per a 1r d'ESO, realizades a la UAB durant les tutories amb la Dra. Cristina Escobar, de Didàctica de la Llengua, i la Dra. Neus Sanmartí, de Didàctica de les Ciències. Els materials han estat experimentats a l'Institut Montserrat amb un grup de 30 alumnes gràcies al Pla Experimental de Llengües Estrangeres concedit pel Departament d'Educaci
El valencià en l'església: 1707-2007
Felip V va respectar els concordats vigents i no va abolir els furs eclesiàstics, per això el decret de Nova Planta no va tindre una incidència directa sobre l’ús del valencià a l’església valentina. No obstant, de forma indirecta sí hi va influir, potenciant el procés castellanitzador que ja venia donant-se amb anterioritat. Pauta, aquesta, que arriba fins el concili Vaticà II i que, increïblement, no millora en els anys posteriors al mateix.Felipe V respetó los concordatos vigentes y no abolió los fueros eclesiásticos, por eso el decreto de Nueva Planta no tuvo una incidencia directa sobre el uso del valenciano en la iglesia valentina. No obstante, de forma indirecta sí influyó, potenciando el proceso castellanizador que ya venia dándose con anterioridad. Pauta, ésta, que llega hasta el concilio Vaticano II y que, increíblemente, no mejora en los años posteriores al mismo.Philip V respected the concordats in force and did not abolish the ecclesiastical privileges. Thus the Nueva Planta decree had no direct impact on the use of the Valencian language in the Valencian Church. Nevertheless it did have an indirect influence, favouring the process of castilianization which had started beforehand. This situation continues until the Second Vatican Council and, surprisingly, it is not altered in the years to follow
Single-site approximation for reaction-diffusion processes
We consider the branching and annihilating random walk and with reaction rates and , respectively, and hopping rate
, and study the phase diagram in the plane. According
to standard mean-field theory, this system is in an active state for all
, and perturbative renormalization suggests that this mean-field
result is valid for ; however, nonperturbative renormalization predicts
that for all there is a phase transition line to an absorbing state in the
plane. We show here that a simple single-site
approximation reproduces with minimal effort the nonperturbative phase diagram
both qualitatively and quantitatively for all dimensions . We expect the
approach to be useful for other reaction-diffusion processes involving
absorbing state transitions.Comment: 15 pages, 2 figures, published versio
Large-scale structures in the stellar wind of fast-rotating stars spawned by the presence of Earth-like planets
Forming planets around young, fast-rotating solar-like stars are exposed to
an intense X-ray/extreme ultraviolet radiation field and strongly magnetized
stellar winds, as a consequence of the high magnetic activity of these stars.
Under these conditions, Earth-like exoplanets may experience a rapid loss of
their primordial hydrogen atmospheres, resulting in atmosphere-less rocky
obstacles for the stellar winds. The interaction of stellar winds with those
planets leads to the formation of potentially observable structures due to the
formation of large-scale magnetic field and density disturbances in the
vicinity of these planets, such as bow shocks, induced magnetospheres and
comet-like tails. In this work, we study the interaction between the stellar
winds of active, fast-rotating solar-like stars in the superfast-magnetosonic
regime with Earth-like, unmagnetized, tenuous atmosphere, planetary obstacles
through numerical 3D simulations using the PLUTO magnetohydrodynamical code.
The properties of AB Doradus, a nearby young star with a small rotation period
(0.51 days) and a strong flaring activity, have been used to parameterize this
early wind state. Bow shock and induced magnetosphere formation are
characterized through the alfv\'enic Mach number MA of the wind, for different
stellar wind configurations. Large bow shocks, up to an extension of ~7.0
planetary radii are found for low-MA winds. The general increase of density,
temperature and magnetic field in these large-scale structures formed around
planets may result in potentially detectable spectral signatures
Mid-term report for the CORE Organic II funded project. “Innovative cropping Practices to increase soil health of organic fruit tree orchards” BIO-INCROP
Activities performed in the first part of BIO-INCROP project concern five of the eight main objectives fixed in the project proposal. They are:
Evaluation of soil borne pest and pathogens involved in replant disease
Role of rhizospheric bacterial and fungal communities in plant health
Selection of naturally available resources to increase microbial diversity and biomass
Compost and organic amendments
Evaluation of biologically active formulates
The document reports main research results and shows main items of dissemination activity performed in the first part of the project
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