Ferromagnetism in the large-U Hubbard model

We study the Hubbard model on a hypercubic lattice with regard to the possibility of itinerant ferromagnetism. The Dynamical Mean Field theory is used to map the lattice model on an effective local problem, which is treated with help of the Non Crossing Approximation. By investigating spin dependent one-particle Green's functions and the magnetic susceptibility, a region with nonvanishing ferromagnetic polarization is found in the limit $U\to\infty$. The $\delta$-T-phase diagram as well as thermodynamic quantities are discussed. The dependence of the Curie temperature on the Coulomb interaction and the competition between ferromagnetism and antiferromagnetism are studied in the large $U$ limit of the Hubbard model.Comment: 4 pages, 5 figures, accepted for publication in Physical Review B, Rapid Communication

A low-cost high-repetition-rate picosecond laser diode pulse generator

International audienc

Enseignement et évaluation de l’électronique analogique à distance en IUT première année

La crise sanitaire causée par la pandémie mondiale de la Covid 19 a profondément modifié notre société. L’enseignement à distance s'est imposé comme une alternative à l’enseignement en présentiel. L’électronique analogique est une matière très appliquée et il est indispensable de manipuler et de pratiquer. Cet article décrit la solution qui a été mise en place pour l’enseignement de l’électronique analogique à l’IUT de Haguenau et notamment les travaux pratiques et l’évaluation du module d’enseignement à distance

Real-time, wide-field, and quantitative oxygenation imaging using spatiotemporal modulation of light.

Quantitative diffuse optical imaging has the potential to provide valuable functional information about tissue status, such as oxygen saturation or blood content to healthcare practitioners in real time. However, significant technical challenges have so far prevented such tools from being deployed in the clinic. Toward achieving this goal, prior research introduced methods based on spatial frequency domain imaging (SFDI) that allow real-time (within milliseconds) wide-field imaging of optical properties but at a single wavelength. However, for this technology to be useful to clinicians, images must be displayed in terms of metrics related to the physiological state of the tissue, hence interpretable to guide decision-making. For this purpose, recent developments introduced multispectral SFDI methods for rapid imaging of oxygenation parameters up to 16 frames per seconds (fps). We introduce real-time, wide-field, and quantitative blood parameters imaging using spatiotemporal modulation of light. Using this method, we are able to quantitatively obtain optical properties at 100 fps at two wavelengths (665 and 860 nm), and therefore oxygenation, oxyhemoglobin, and deoxyhemoglobin, using a single camera with, at most, 4.2% error in comparison with standard SFDI acquisitions