Nonequilibrium charge noise and dephasing from a spin-incoherent Luttinger liquid

We theoretically investigate the charge noise and dephasing in a metallic device in close proximity to a spin incoherent Luttinger liquid with a small but finite current. The frequency dependence of the charge noise exhibits a loss of frequency peaks corresponding to the 2kF part of the density correlations in the electron liquid when the temperature T is increased from values below the magnetic exchange energy J of the electron gas to values above it. The dephasing rate in a nearby metallic nanostructure also shows a crossover for T~J and may exhibit a nonmonotonic temperature dependence. For a range of temperatures the dephasing rate decreases with increasing temperatures. The proposed experiments provide a convenient approach to probe the spin-incoherent Luttinger liquid and should be implementable in a wide variety of systems

Tunneling exponents sensitive to impurity scattering in quantum wires

We show that the scaling exponent for tunneling into a quantum wire in the "Coulomb Tonks gas" regime of impenetrable, but otherwise free, electrons is affected by impurity scattering in the wire. The exponent for tunneling into such a wire thus depends on the conductance through the wire. This striking effect originates from a many-body scattering resonance reminiscent of the Kondo effect. The predicted anomalous scaling is stable against weak perturbations of the ideal Tonks gas limit at sufficiently high energies, similar to the phenomenology of a quantum critical point.Comment: 5 pages, 2 figures; slightly extended version of the published articl

Scaling and interaction-assisted transport in graphene with one-dimensional defects

We analyze the scattering from one-dimensional defects in intrinsic graphene. The Coulomb repulsion between electrons is found to be able to induce singularities of such scattering at zero temperature as in one-dimensional conductors. In striking contrast to electrons in one space dimension, however, repulsive interactions here can enhance transport. We present explicit calculations for the scattering from vector potentials that appear when strips of the material are under strain. There the predicted effects are exponentially large for strong scatterers.Comment: 4 pages, 2 figure

Influences sociostructurelles du groupe de pairs sur la motivation scolaire des jeunes enfants

Cette étude examine les contingences comportementales en tant que processus par lesquels les pairs influencent la motivation scolaire des enfants pendant les interactions sociales en classe. Les regroupements affiliatifs au sein de la classe d'enfants de 10 à 11 ans ont été identifiés à partir d'une procédure de nomination. Les observations longitudinales ont montré qu'au début de l'année scolaire, les élèves fortement motivés ont reçu plus d'approbation de leurs amis par rapport à leur engagement dans les activités scolaires, alors que les élèves faiblement motivés ont reçu plus de désapprobation des camarades surtout par rapport à leurs conduites perturbatrices. L'étude révèle que ces deux schemes de contingence, mis en conjonction avec l'insertion sociale des enfants dans le réseau arhliatif de leur classe, contribuent au changement dans leur motivation tout au long de l'année scolaire.This study examines behavior contingencies as a process by which peers influence the school motivation of children during classroom interactions. Peer groupings in a classroom of children aged 10 to 11 years were identified through a naming procedure. Longitudinal observations showed that at the beginning of the school year those students who are strongly motivated received more approval for their participation in school activities while those poorly motivated received peer disapproval specifically with regards to their disturbing behaviors. The study shows that these two models, in conjunction with children's social integration within the peer network of their class, contributes to modify their motivation during the school year.Este estudio examina las contingencias comportamentales en tanto que proceso por intermedio del cual los companeros influencian la motivacion escolar del nino durante las interacciones sociales en clase. Los reagrupamientos en el seno de la clase de ninos de 10 all anos han sido indentificados a partir de un procedimiento nominative Las observaciones longitudinales mostraron que al principio del ano escolar, los alumnos muy motivados reci- bieron la aprobacion de sus amigos respecto de su implicaciôn en las actividades escolares, mientras que aquellos que estaban poco motivados recibieron la desaprobacion de sus camaradas, principalement^ cuendo se trata de conductas perturbadoras. El estudio révéla que esos dos esquemas de contingencia, puestos en conjuncion con la inserciôn social de los ninos en la red de amigos de su clase, contribuyen al cambio en la motivacion a Io largo de todo el ano escolar.Dieser Studie liegt die Uberzeugung zu Grunde, dass es sich bei der Verhaltenskontingenz um einen Prozess handelt, mit dessen Hilfe bestimmte Schiller die schu- lische Motivation ihrer Klassenkameraden wâhrend der sozialen Interaktion in der Klasse beeinflussen. Mit Hilfe eines Stimmenabgabesystems wurden die Gruppenbildungen inner- halb einer Klasse von Zehn- bis Elfjâhrigen identifiziert. Langzeitbeobachtungen haben ergeben, dass die stark motivierten Schuler am Anfang des Schuljahres von ihren Kameraden Anerkennung erhielten in Beziehung auf ihren Lerneifer, wohingegen die schwach motivierten Schuler bei ihren Kameraden auf Ablehnung stiefien vor allem auf Grund ihres Storverhaltens. Aus der Untersuchung geht weiter hervor, dass die beiden Kontingenzschemata, wenn man sie zur sozialen Eingliederung in ihre Klassengruppe in Beziehung setzt, wahrend des ganzen Schuljahres zum Motivationswechsel beitragen

Agriculture, Population, Land and Water Scarcity in a Changing World – The Role of Irrigation

Fertile land and fresh water constitute two of the most fundamental resources for food production. These resources are affected by environmental, political, economic, and technical developments. Regional impacts may transmit to the world through increased trade. With a global forest and agricultural sector model, we quantify the impacts of increased demand for food due to population growth and economic development on potential land and water use. In particular, we investigate producer adaptation regarding crop and irrigation choice, agricultural market adjustments, and changes in the values of land and water.Irrigation, Food supply, Integrated assessment, Water use intensity, Agricultural adaptation, Land scarcity, Partial equilibrium model, Resource /Energy Economics and Policy,

The spin-incoherent Luttinger liquid

In contrast to the well known Fermi liquid theory of three dimensions, interacting one-dimensional and quasi one-dimensional systems of fermions are described at low energy by an effective theory known as Luttinger liquid theory. This theory is expressed in terms of collective many-body excitations that show exotic behavior such as spin-charge separation. Luttinger liquid theory is commonly applied on the premise that "low energy" describes both the spin and charge sectors. However, when the interactions in the system are very strong, as they typically are at low particle densities, the ratio of spin to charge energy may become exponentially small. It is then possible at very low temperatures for the energy to be low compared to the characteristic charge energy, but still high compared to the characteristic spin energy. This energy window of near ground-state charge degrees of freedom, but highly thermally excited spin degrees of freedom is called a spin-incoherent Luttinger liquid. The spin-incoherent Luttinger liquid exhibits a higher degree universality than the Luttinger liquid and its properties are qualitatively distinct. In this colloquium I detail some of the recent theoretical developments in the field and describe experimental indications of such a regime in gated semiconductor quantum wires.Comment: 21 pages, 18 figures. Updated references, corrected typo in Eq.(20) in journal versio