Measuring von Neumann entanglement entropies without wave functions

We present a method to measure the von Neumann entanglement entropy of ground states of quantum many-body systems which does not require access to the system wave function. The technique is based on a direct thermodynamic study of entanglement Hamiltonians, whose functional form is available from field theoretical insights. The method is applicable to classical simulations such as quantum Monte Carlo methods, and to experiments that allow for thermodynamic measurements such as the density of states, accessible via quantum quenches. We benchmark our technique on critical quantum spin chains, and apply it to several two-dimensional quantum magnets, where we are able to unambiguously determine the onset of area law in the entanglement entropy, the number of Goldstone bosons, and to check a recent conjecture on geometric entanglement contribution at critical points described by strongly coupled field theories

Cavity Soliton Laser based on mutually coupled semiconductor microresonators

We report on experimental observation of localized structures in two mutually coupled broad-areahttp://hal.archives-ouvertes.fr/images/calendar.gif semiconductor resonators. These structures coexist with a dark homogeneous background and they have the same properties as cavity solitons without requiring the presence of a driving beam into the system. They can be switched individually on and off by means of a local addressing beam

Looking for differences in wood properties as a function of the felling date: lunar phase-correlated variations in the drying behavior of Norway Spruce (Picea abies Karst.) and Sweet Chestnut (Castanea sativa Mill.)

A large-scale field experiment on the drying behavior of Norway Spruce (Picea abies Karst.) and Sweet Chestnut (Castanea sativa Mill.) in relation to the felling date was conducted over a period of 24weeks in order to investigate the existence of variations linked to lunar rhythms, which are mentioned as having a role in many traditional forestry practices. The measured criteria were the water loss from fresh to dry state, the shrinkage linked to this water loss, and the relative density (ratio between the dry density and the initial fresh density) for both sapwood and heartwood in Picea and heartwood in Castanea. In addition to seasonal trends, slight but significant variations with lunar periodicities (both synodic and sidereal; to a much lesser extent tropic) characterize the three investigated criteria. These lunar rhythmicities occur in both Picea and Castanea, in heartwood and sapwood. These results raise new questions and perspectives about a rhythmic character of the wood–water relation

An electrostratigraphic cross-section across the central Po plain : bearings on subsurface geology and hydrostratigraphy

A 72-km-long N\u2013S cross-section was surveyed with direct current resistivity soundings through the Quaternary clastic infill of the Apennine foredeep in the Po plain of Lombardy (Northern Italy). The aims are (1) to test the potential of DC resistivity methods at the regional scale; (2) to draw the electrostratigraphic picture of the basin fill, down to the pre-Quaternary substratum; (3) to refine and test the methodology and concepts of hierarchic electrostratigraphy at the basin scale; (4) to contribute to characterize the regional hydrostratigraphy of a relevant hydrogeological basin. 163 resistivity-versus-depth profiles with a maximum investigation depth of 450 m were obtained from vertical electrical soundings. To draw the electrostratigraphic cross-section, the polarity of the resistivity contrast across resistivity interfaces (i.e. resistive over conductive layers or vice versa) was considered and the discontinuities were correlated according to the persisting pattern from north to south. Doing so, the hierarchic assemblage of four major electrostratigraphic boundaries and the five intervening groups of electrostratigraphic units (EsUs) was established. The resulting picture was compared to the available subsurface reconstructions from the literature, using the 1-D borehole data only to check the geophysical image at some random sample sites. The results show that the electrostratigraphic picture captures the geological and hydrostratigraphic complexity of the subsurface of the basin comparing well with the available direct subsurface geological and hydrostratigraphic reconstructions. At the regional scale of the cross-section, two hierarchic orders of EsUs and correlative boundaries could be drawn (first-order groups and second-order individual EsUs), while the lowermost third-order rank, the electrolayer, is recognized at the single-VES sites only

Evidence of breakdown of the spin symmetry in diluted 2D electron gases

Recent claims of an experimental demonstration of spontaneous spin polarisation in dilute electron gases \cite{young99} revived long standing theoretical discussions \cite{ceper99,bloch}. In two dimensions, the stabilisation of a ferromagnetic fluid might be hindered by the occurrence of the metal-insulator transition at low densities \cite{abra79}. To circumvent localisation in the two-dimensional electron gas (2DEG) we investigated the low populated second electron subband, where the disorder potential is mainly screened by the high density of the first subband. This letter reports on the breakdown of the spin symmetry in a 2DEG, revealed by the abrupt enhancement of the exchange and correlation terms of the Coulomb interaction, as determined from the energies of the collective charge and spin excitations. Inelastic light scattering experiments and calculations within the time-dependent local spin-density approximation give strong evidence for the existence of a ferromagnetic ground state in the diluted regime.Comment: 4 pages, 4 figures, Revte

Looking for differences in wood properties as a function of the felling date: lunar phase-correlated variations in the drying behavior of Norway Spruce ( Picea abies Karst.) and Sweet Chestnut ( Castanea sativa Mill.)

A large-scale field experiment on the drying behavior of Norway Spruce (Picea abies Karst.) and Sweet Chestnut (Castanea sativa Mill.) in relation to the felling date was conducted over a period of 24weeks in order to investigate the existence of variations linked to lunar rhythms, which are mentioned as having a role in many traditional forestry practices. The measured criteria were the water loss from fresh to dry state, the shrinkage linked to this water loss, and the relative density (ratio between the dry density and the initial fresh density) for both sapwood and heartwood in Picea and heartwood in Castanea. In addition to seasonal trends, slight but significant variations with lunar periodicities (both synodic and sidereal; to a much lesser extent tropic) characterize the three investigated criteria. These lunar rhythmicities occur in both Picea and Castanea, in heartwood and sapwood. These results raise new questions and perspectives about a rhythmic character of the wood-water relatio

All-optical delay line using semiconductor cavity solitons

An all-optical delay line based on the lateral drift of cavity solitons in semiconductor microresonators is proposed and experimentally demonstrated. The functionalities of the device proposed as well as its performance is analyzed and compared with recent alternative methods based on the decrease of group velocity in the vicinity of resonances. We show that the current limitations can be overcome using broader devices with tailored material responses

Successful scaling in social franchising: The case of Impact Hub

Social entrepreneurs increasingly use franchising to scale social value. Tracey and Jarvis (2007) described how social franchising is similar to commercial franchising, but also noted critical challenges arising from dual social and commercial goals. We investigate a social franchisor that overcame these challenges and describe how the social mission became the source of innovation for its business model. We show that the social mission fostered a shared identity that motivated and guided the search for adaptations to the franchise model. In particular, the shared mission-driven identity created pressure toward (1) decentralized decision-making, (2) shared governance, and (3) a new role for the franchisor as orchestrator of collaborative knowledge sharing among franchisees. Findings should help social franchisors avoid common pitfalls and suggest future research questions for social entrepreneurship and franchising scholars