Diagnosing order by disorder in quantum spin systems

In this paper we study the frustrated J1-J2 quantum Heisenberg model on the square lattice for J2 > 2J1, in a magnetic field. In this regime the classical system is known to have a degenerate manifold of lowest energy configurations, where standard thermal order by disorder occurs. In order to study its quantum version we use a path integral formulation in terms of coherent states. We show that the classical degeneracy in the plane transverse to the magnetic field is lifted by quantum fluctuations. Collinear states are then selected, in a similar pattern to that set by thermal order by disorder, leaving a Z2 degeneracy. A careful analysis reveals a purely quantum mechanical effect given by the tunneling between the two minima selected by fluctuations. The effective description contains two planar (XY -like) fields conjugate to the total magnetization and the difference of the two sublattice magnetizations. Disorder in either or both of these fields produces the locking of their conjugate observables. Furthermore, within this scenario we argue that the quantum state is close to a product state.Comment: 8 pages, 3 figure

Still no free lunches: the price to pay for tighter PAC-Bayes bounds

“No free lunch” results state the impossibility of obtaining meaningful bounds on the error of a learning algorithm without prior assumptions and modelling, which is more or less realistic for a given problem. Some models are “expensive” (strong assumptions, such as sub-Gaussian tails), others are “cheap” (simply finite variance). As it is well known, the more you pay, the more you get: in other words, the most expensive models yield the more interesting bounds. Recent advances in robust statistics have investigated procedures to obtain tight bounds while keeping the cost of assumptions minimal. The present paper explores and exhibits what the limits are for obtaining tight probably approximately correct (PAC)-Bayes bounds in a robust setting for cheap models

Sobre la necesidad de un libro rojo «moderno» para China

7 p.Peer reviewe

Les associations d'aide à la personne face à la règle de concurrence.Enjeux de légitimité territoriale et renouvellement des proximités

1National audienc

A multivariate regional test for detection of trends in extreme rainfall: the case of extreme daily rainfall in the French Mediterranean area

In this paper we present a multivariate regional test we developed for the detection of trends in extreme rainfall, which takes into account the spatial dependence between rainfall measurements with copula functions. The test is based on four steps. It was applied to a set of 92 series of Annual Daily Maxima (ADM) rainfall in the French Mediterranean area, sampled during the 1949–2004 observation period. The results show a low significant trend, concerning mainly the mountains area in the west part of the French Mediterranean region. The position's parameters of the ADM rainfall probability distribution functions present a low but significant increasing trend of about 5% to 10%, the same increase as that observed in ADM rainfall quantiles in the last 56 years. Further work is needed to understand if this significative trend is related to the global climate change or to the natural variability of Mediterranean climate

La gouvernance locale du microcrédit professionnel entre jeux de proximités et lock in effect

National audienc

La stratégie des associations d'aide à la personne face à la nouvelle réglementation : coalitions stratégiques et re-territorialisation des activités

Date du colloque : 2009/06International audienc

Nouvelle régulation concurrentielle et nouveaux jeux de proximités. Les associations d’aide à la personne à la reconquête de leur légitimité territoriale

The French home care services, organized around non-for-profit organizations, have been changed by the introduction of a new competitive regulation in 2005. Previously, these organizations were agreeing to share territories. They were benefiting from a strong territorial legitimacy, thus constituting territorial monopolies. These monopolies were based on both geographical and organized proximities, linked to the geographical constraints of such an activity and to the historical ties developed with local actors. Face to competition, their territorial legitimacy is today at stake. This article shows that non-for-profit organizations seek to establish their legitimacy by developing new proximity arrangements according to the departmental different policies and to the competitive intensity resulting from these policies. So the organized proximity is crucial in this process. It can be based on one hand on non-rivalry and non-intrusion agreements. On the other hand it can rely on rules aiming at the absorption of the weakest non-for-profit organizations

Dispatcher3 D4.2 - Prototype package (first release) - User manual

This deliverable along with deliverable D4.1. Technical documentation first release consists of the release of the first prototype of Dispatcher3. The release consists of the binaries and Docker version of the prototype (sent to the Topic Manager). The first release prototype package consists of a set on individual machine learning models which can be executed using Jupyter notebooks. It also includes the integration of the outcome of some of these individual models into a visualisation which would be part of the advice generator to provide high-level information to the end users. All models described in the Deliverable D4.1 will be available and executable in this release. Data required to run the models (with some examples) are also provided. If data are public raw sample values are provided, otherwise pre-computed features are delivered so that the models can be run on individual flight examples. The prototypes can be run using local data (provided in the release) or with data stored in cloud storage (Amazon Web Services (AWS)). This deliverable serves as a manual for the execution of the first release prototype software

Increasing Access to Augmentative and Alternative Communication Services for People with Complex Communication Needs During COVID-19 and Beyond

The COVID-19 global pandemic has affected the disability network across the world. In the United States, there are millions of people who cannot use their natural speech to communicate. Augmentative and alternative communication (AAC), a form of assistive technology (AT), helps people with complex communication needs (CCNs) to communicate with others. Examples of AAC include printed pictures and speech-generating devices. A team of professionals work together with the person with CCNs and their caregivers to choose the right type of AAC. Often, people with CCNs need face-to-face and ongoing AAC support. Prior to the COVID-19 pandemic, this population already faced multiple challenges to receive on-going support and services due to multiple factors, including limited access to AAC specialists and travel constraints. As a result of the COVID-19 pandemic, many services for people with CCNs stopped to abide by stay-at-home orders and ensure the safety of the person with CCNs and their caregivers. This paper describes how one AT Program at a University Center for Excellence in Developmental Disabilities (UCEDD) adapted AAC services and increased access to support using (a) tele-AAC assessment practices, (b) services through a partnership with our state AT Act program, and (c) tele-coaching strategies to help providers and caregivers in their facilitation and implementation of AAC services. We also discuss key considerations in tele-AAC practices to help people with CCNs and their caregivers during COVID-19 and beyond