Extending canonical Monte Carlo methods II

Previously, we have presented a methodology to extend canonical Monte Carlo methods inspired on a suitable extension of the canonical fluctuation relation $C=\beta^{2}$ compatible with negative heat capacities $C<0$. Now, we improve this methodology by introducing a better treatment of finite size effects affecting the precision of a direct determination of the microcanonical caloric curve $\beta (E) =\partial S(E) /\partial E$, as well as a better implementation of MC schemes. We shall show that despite the modifications considered, the extended canonical MC methods possibility an impressive overcome of the so-called \textit{super-critical slowing down} observed close to the region of a temperature driven first-order phase transition. In this case, the dependence of the decorrelation time $\tau$ with the system size $N$ is reduced from an exponential growth to a weak power-law behavior $\tau(N)\propto N^{\alpha}$, which is shown in the particular case of the 2D seven-state Potts model where the exponent $\alpha=0.14-0.18$.Comment: Version submitted to JSTA

Photo-ionization of planetary winds: case study HD209458b

Close-in hot Jupiters are exposed to a tremendous photon flux that ionizes the neutral escaping material from the planet leaving an observable imprint that makes them an interesting laboratory for testing theoretical models. In this work we present 3D hydrodynamic simulations with radiation transfer calculations of a close-in exoplanet in a blow-off state. We calculate the Ly-$\alpha$ absorption and compare it with observations of HD 209458b an previous simplified model results.Our results show that the hydrodynamic interaction together with a proper calculation of the photoionization proccess are able to reproduce the main features of the observed Ly-$\alpha$ absorption, in particular at the blue-shifted wings of the line. We found that the ionizing stellar flux produce an almost linear effect on the amount of absorption in the wake. Varying the planetary mass loss rate and the radiation flux, we were able to reproduce the $10\%$ absorption observed at $-100~\mathrm{km~s^{-1}}$.Comment: 9 pages, 6 figure

A Supernova Remnant Collision with a Stellar Wind

Numerical simulations of the interaction between supernova ejecta and a stellar wind are presented. We follow the temporal evolution of the shock fronts that are formed through such an interaction and determine the velocities, temperatures and densities. We model the X-ray emission from the SNR-stellar wind collision region and we compare it with recent results from X-ray observations carried out with the Chandra satellite of the SMC supernova remnant SNR 0057-7226 which could be interacting with the wind of the Wolf-Rayet system HD 5980. The simulations predict the presence of shell-like regions of enhanced X-ray emission which are consistent with the presence of X-ray emitting arcs in the Chandra image. Also the observed X-ray luminosity is comparable to the X-ray luminosities we obtain from the simulations for a supernova with an initial energy in the (1-5)E50 erg range.Comment: 9 files into a tar.gz file (the Latex file of manuscript, 7 jpg figures, 1 style file: aastex.cls). Accepted by ApJ, Vol. 584, 2003 February 1

Transitioning out of Open Access: A Closer Look at Institutions for Management of Groundwater Rights in France, California, and Spain

[EN] Many regions around the world are transitioning out of open access to groundwater resources in order to tackle over extraction by irrigated agriculture. However, the state has limited capacities to regulate effectively agricultural groundwater use. This paper evaluates how users and public authorities can co-manage groundwater extraction by agriculture. Based on Schlager and Ostrom¿s ¿bundle of rights¿ framework, the paper examines how decisions over access and use of groundwater resources are made in France, Spain and California. The three cases share a common strive to involve groundwater users in decisions over how to reduce over extraction of groundwater resources. However, different choices were made regarding the institutional set-up for user involvement in allocation decisions. The paper presents the diversity of institutional arrangements influencing groundwater allocations in the three cases, and the relative involvement and power of users and public authorities over these institutions. The papers show the different ways in which ¿comanagement¿ may be made operational for managing agricultural groundwater use.This research benefited from funding of the EU H2020 RURECO project (grant agreement 750553) and from Montpellier University I-Site MUSE. This study has also received funding from the eGROUNDWATER project (GA n. 1921), part of the PRIMA programme supported by the European Union's Horizon 2020 research and innovation programmeRouillard, J.; Babbitt, C.; Pulido-Velazquez, M.; Rinaudo, J. (2021). Transitioning out of Open Access: A Closer Look at Institutions for Management of Groundwater Rights in France, California, and Spain. Water Resources Research. 57(4):1-20. https://doi.org/10.1029/2020WR028951S12057

Disaster Resilience Education and Research Roadmap for Europe 2030 : ANDROID Report

A disaster resilience education and research roadmap for Europe 2030 has been launched. This roadmap represents an important output of the ANDROID disaster resilience network, bringing together existing literature in the field, as well as the results of various analysis and study projects undertaken by project partners.The roadmap sets out five key challenges and opportunities in moving from 2015 to 2030 and aimed at addressing the challenges of the recently announced Sendai Framework for Disaster Risk Reduction 2015-2030. This roadmap was developed as part of the ANDROID Disaster Resilience Network, led by Professor Richard Haigh of the Global Disaster Resilience Centre (www.hud.ac.uk/gdrc ) at the School of Art, Design and Architecture at the University of Huddersfield, UK. The ANDROID consortium of applied, human, social and natural scientists, supported by international organisations and a stakeholder board, worked together to map the field in disaster resilience education, pool their results and findings, develop interdisciplinary explanations, develop capacity, move forward innovative education agendas, discuss methods, and inform policy development. Further information on ANDROID Disaster Resilience network is available at: http://www.disaster-resilience.netAn ANDROID Disaster Resilience Network ReportANDROI

Fluctuation geometry: A counterpart approach of inference geometry

Starting from an axiomatic perspective, \emph{fluctuation geometry} is developed as a counterpart approach of inference geometry. This approach is inspired on the existence of a notable analogy between the general theorems of \emph{inference theory} and the the \emph{general fluctuation theorems} associated with a parametric family of distribution functions $dp(I|\theta)=\rho(I|\theta)dI$, which describes the behavior of a set of \emph{continuous stochastic variables} driven by a set of control parameters $\theta$. In this approach, statistical properties are rephrased as purely geometric notions derived from the \emph{Riemannian structure} on the manifold $\mathcal{M}_{\theta}$ of stochastic variables $I$. Consequently, this theory arises as an alternative framework for applying the powerful methods of differential geometry for the statistical analysis. Fluctuation geometry has direct implications on statistics and physics. This geometric approach inspires a Riemannian reformulation of Einstein fluctuation theory as well as a geometric redefinition of the information entropy for a continuous distribution.Comment: Version submitted to J. Phys. A. 26 pages + 2 eps figure

A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: IV. Modeling the Sagittarius Tidal Tails

M giants recovered from the Two Micron All-Sky Survey (2MASS) have recently been used to map the position and velocity distributions of tidal debris from the Sagittarius (Sgr) dwarf spheroidal galaxy entirely around the Galaxy. We compare this data set to both test particle orbits and N-body simulations of satellite destruction run within a variety of rigid Milky Way potentials and find that the mass of the Milky Way within 50 kpc of its center should be 3.8-5.6 x 10^11 Msun in order for any Sgr orbit to simultaneously fit the velocity gradient in the Sgr trailing debris and the apocenter of the Sgr leading debris. Orbital pole precession of young debris and leading debris velocities in regions corresponding to older debris provide contradictory evidence in favor of oblate/prolate Galactic halo potentials respectively, leading us to conclude that the orbit of Sgr has evolved over the past few Gyr. Based upon the velocity dispersion and width along the trailing tidal stream we estimate the current bound mass of Sgr to be M_Sgr = 2 - 5 x 10^8 Msun independant of the form of the Galactic potential; this corresponds to a range of mass to light ratios (M/L)_Sgr = 14 - 36 (M/L)_Sun for the Sgr core. Models with masses in this range best fit the apocenter of leading Sgr tidal debris when they orbit with a radial period of roughly 0.85 Gyr and have periGalactica and apoGalactica of about 15 kpc and 60 kpc respectively. These distances will scale with the assumed distance to the Sgr dwarf and the assumed depth of the Galactic potential. The density distribution of debris along the orbit in these models is consistent with the M giant observations, and debris at all orbital phases where M giants are obviously present is younger (i.e. was lost more recently from the satellite) than the typical age of a Sgr M giant star.Comment: 42 pages, 13 figures; Accepted for publication by ApJ (October 08, 2004; originally submitted May 10, 2004). Fixed typos and added references. PDF file with high resolution figures may be downloaded from http://www.astro.caltech.edu/~drlaw/Papers/Sgr_paper4.pd