Spintronics, from giant magnetoresistance to magnetic skyrmions and topological insulators
This article aims at giving a general presentation of spintronics, an important field of research developing today along many new directions in physics of condensed matter. We tried to present simply the physical phenomena involved in spintronics – no equations but many schematics. We also described the applications of spintronics, those of today and those expected to have an important impact on the next developments of the information and communication technologies.RésuméCet article se veut une présentation générale de la spintronique. C'est aujourd'hui un important domaine de recherche, qui se développe sur de no...
Source: Comptes Rendus Physique - July 19, 2019 Category: Physics Source Type: research
Synchrosqueezing transforms: From low- to high-frequency modulations and perspectives
Publication date: Available online 11 July 2019Source: Comptes Rendus PhysiqueAuthor(s): Sylvain Meignen, Thomas Oberlin, Duong-Hung PhamAbstractThe general aim of this paper is to introduce the concept of synchrosqueezing transforms (SSTs) that was developed to sharpen linear time–frequency representations (TFRs), like the short-time Fourier or the continuous wavelet transforms, in such a way that the sharpened transforms remain invertible. This property is of paramount importance when one seeks to recover the modes of a multicomponent signal (MCS), corresponding to the superimposition of AM/FM modes, a model often used...
Source: Comptes Rendus Physique - July 12, 2019 Category: Physics Source Type: research
In social complex systems, the whole can be more or less than (the sum of) the parts
Publication date: Available online 7 July 2019Source: Comptes Rendus PhysiqueAuthor(s): Éric Bertin, Pablo JensenAbstractWe discuss in a statistical physics framework the idea that “the whole is less than the parts”, as sometimes advocated by sociologists in view of the intrinsic complexity of humans, and try to reconcile this idea with the statistical physicists wisdom according to which “the whole is more than the sum of its parts” due to collective phenomena. We consider a simple mean-field model of interacting agents having an intrinsic complexity modeled by a large number of internal configurations. We show, ...
Source: Comptes Rendus Physique - July 9, 2019 Category: Physics Source Type: research
André Lagarrigue: From cosmic rays to the discovery of the weak neutral currents
Publication date: Available online 3 July 2019Source: Comptes Rendus PhysiqueAuthor(s): Michel DavierAbstractAndré Lagarrigue's scientific career is intimately related to the development of elementary particle physics, from pioneering studies with cosmic rays to the discovery of weak neutral currents. His experience in building detectors, culminating with the construction of large heavy liquid bubble chambers, his vision of the best experimental paths, and his enthusiastic leadership have strongly contributed to the progress of the field. The discovery of weak neutral currents with the giant Gargamelle bubble chamber was ...
Source: Comptes Rendus Physique - July 4, 2019 Category: Physics Source Type: research
Dossier Sommaire
Publication date: March–April 2019Source: Comptes Rendus Physique, Volume 20, Issue 3Author(s): (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - July 3, 2019 Category: Physics Source Type: research
Foreword
Publication date: March–April 2019Source: Comptes Rendus Physique, Volume 20, Issue 3Author(s): Jean-Benoît Agnani, Benoît Denis (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - July 3, 2019 Category: Physics Source Type: research
GNSS: A revolution for precise geopositioning
Publication date: March–April 2019Source: Comptes Rendus Physique, Volume 20, Issue 3Author(s): Félix PerosanzAbstractGlobal Navigation Satellite Systems (GNSS) were not initially designed to be used for precise scientific applications. However, a smart signal processing can provide a satellite–receiver range measurement with millimeter accuracy. If the differential technique has become an essential method, the PPP mode is today an increasingly popular alternative. But, whatever the approach, GNSS have revolutionized the realization of space and time frames and the many applications requiring post-processed or real-ti...
Source: Comptes Rendus Physique - July 3, 2019 Category: Physics Source Type: research
Editorial Board
Publication date: March–April 2019Source: Comptes Rendus Physique, Volume 20, Issue 3Author(s): (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - July 3, 2019 Category: Physics Source Type: research
The politics of physicists' social models
Publication date: Available online 27 June 2019Source: Comptes Rendus PhysiqueAuthor(s): Pablo JensenAbstractI give an overview of the topic of this dossier, the “applications of (statistical) physics to social sciences at large.” I discuss several examples of simple social models put forward by physicists and examine their interest. I argue that while they may be conceptually useful to correct our intuitive models of social mechanisms, their relevance for real social systems is moot. What is more, since physicists have always needed to ‘tame’ the world inside laboratories to make their models relevant, I suggest t...
Source: Comptes Rendus Physique - June 28, 2019 Category: Physics Source Type: research
A structural model of market dynamics, and why it matters
Publication date: Available online 27 June 2019Source: Comptes Rendus PhysiqueAuthor(s): Jonathan Khedair, Reimer KühnAbstractIn this paper, we explore an approach to understanding price fluctuations within a market via considerations of functional dependencies between asset prices. Interestingly, this approach suggests a class of models of a type used earlier to describe the dynamics of real and artificial neural networks. Statistical physics approaches turn out to be suitable for an analysis of their collective properties. In this paper, we first motivate the basic phenomenology and modelling arguments before moving on ...
Source: Comptes Rendus Physique - June 27, 2019 Category: Physics Source Type: research
Lost in diversification
Publication date: Available online 27 June 2019Source: Comptes Rendus PhysiqueAuthor(s): Marco Bardoscia, Daniele d'Arienzo, Matteo Marsili, Valerio VolpatiAbstractAs financial instruments grow in complexity, more and more information is neglected by risk optimization practices. This brings down a curtain of opacity on the origination of risk, which has been one of the main culprits in the 2007–2008 global financial crisis. We discuss how the loss of transparency may be quantified in bits, using information theoretic concepts. We find i) that financial transformations imply large information losses, ii) that portfolios a...
Source: Comptes Rendus Physique - June 27, 2019 Category: Physics Source Type: research
Towards novelty-driven recommender systems
Publication date: Available online 26 June 2019Source: Comptes Rendus PhysiqueAuthor(s): Pietro Gravino, Bernardo Monechi, Vittorio LoretoAbstractWe get recommendations about everything and in a pervasive way. Recommender systems act like compasses for our journey in complex conceptual spaces and we more and more rely on recommendations to ground most of our decisions. Despite their extraordinary efficiency and reliability, recommender systems are far from being flawless. They display instead serious drawbacks that might seriously reduce our open-mindedness and our capacity of experiencing diversity and possibly conflictin...
Source: Comptes Rendus Physique - June 27, 2019 Category: Physics Source Type: research
Reality-inspired voter models: A mini-review
Publication date: Available online 19 June 2019Source: Comptes Rendus PhysiqueAuthor(s): Sidney RednerAbstractThis mini-review presents extensions of the voter model that incorporate various plausible features of real decision-making processes by individuals. Although these generalizations are not calibrated by empirical data, the resulting dynamics are suggestive of realistic collective social behaviors.RésuméCette mini-revue présente des extensions du modèle de l'électeur qui intègrent divers éléments plausibles des processus réels de prise de décision par des individus. Bien que ces généralisations ne soient...
Source: Comptes Rendus Physique - June 20, 2019 Category: Physics Source Type: research
Dynamic nuclear polarization
Publication date: Available online 20 June 2019Source: Comptes Rendus PhysiqueAuthor(s): Maurice GoldmanAbstractDynamic nuclear polarization, or DNP, refers to the increase of the polarization of nuclear spins in condensed matter, liquid or solid, coupled with electronic spins at low relative concentration, by inducing radio or microwave transitions at frequencies close to the electronic resonance frequency in the external magnetic field. Another described method relies on indirect optical pumping methods at temperatures close to room temperature for the nuclear polarization of rare gases. The various mechanisms of DNP are...
Source: Comptes Rendus Physique - June 20, 2019 Category: Physics Source Type: research
