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Concept

Règle de la main droite

Cette règle permet d'interpréter géométriquement le phénomène d'induction de Lorentz (conducteur électrique en mouvement dans un champ magnétique constant) régi par la formule : : q\vec {v} \wedge \vec {B} = \vec {F} La force de Lorentz \vec {F} s'exerce sur les porteurs de charge et explique la naissance d'une f.e.m. induite dans le circuit en mouvement générant un courant circulant dans la même direction que la force de Lorentz. e=\int_\Gamma\frac{\vec{F}}{q}. \mathrm d\vec l. Ce phénomène peut aussi s'expliquer par la loi de Faraday. En appliquant la règle de la main droite afin de représenter ce produit vectoriel dans l'espace, on obtient : Un autre moyen mnémotechnique est F-I-B :

Pouce = sens de la force (« pousse ») \vec {F}
Index = sens du courant (I comme Index) \vec {I}
Majeur = direction du champ magnétique (M comme Magnétique) \vec {B}

Imitation d'un tire boucho

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PHYS-101(en): General physics : mechanics (English)

Students will learn the principles of mechanics to enable a better understanding of physical phenomena, such as the kinematics and dyamics of point masses and solid bodies. Students will acquire the capacity to quantitatively analyze these effects with the appropriate theoretical tools.

ME-104: Introduction to structural mechanics

The student will acquire the basis for the analysis of static structures and deformation of simple structural elements. The focus is given to problem-solving skills in the context of engineering design.

PHYS-114: General physics: electromagnetism

The course first develops the basic laws of electricity and magnetism and illustrates the use in understanding various electromagnetic phenomena.

Moment cinétique

En mécanique classique, le moment cinétique (ou moment angulaire par anglicisme) d'un point matériel M par rapport à un point O est le moment de la quantité de mouvement \vec{p} par rap

Champ magnétique

En physique, dans le domaine de l'électromagnétisme, le champ magnétique est une grandeur ayant le caractère d'un champ vectoriel, c'est-à-dire caractérisée par la donnée d'une norme, d’une directio

Vecteur euclidien

En mathématiques, et plus précisément en géométrie euclidienne, un vecteur euclidien est un objet géométrique possédant une direction, un sens et une norme. On l'utilise par exemple en physique et e

Leptogenesis with an almost conserved lepton number

Steve Blanchet

Seesaw models with a slightly broken lepton number symmetry can explain small neutrino masses, and allow for low-scale leptogenesis. We make a thorough analysis of leptogenesis within the simplest model with two right-handed (RH) neutrinos (or with N_3 decoupled). We obtain a semi-analytical formula for the final asymmetry in both supersymmetric and non-supersymmetric cases with a simple dependence on each parameter. The low-energy parameters factorize from the high-energy ones, and the high-energy phase must be non-zero. The role of the PMNS phases is carefully studied. Moreover, we find that the breaking parameter in the Yukawa coupling matrix must be relatively large, \epsilon_h > 10^{-3} for normal and 10^{-2} for inverted hierarchy. Therefore, leptogenesis in our simple model is incompatible with RH neutrino signals at future colliders or sizable lepton-flavor violation. The other breaking parameter, \epsilon_M, which appears in the RH neutrino mass matrix, can be much smaller, and actually needs to be so in order to have low-scale leptogenesis.

2008

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Leptogenesis with heavy neutrino flavours: from density matrix to Boltzmann equations

Steve Blanchet

Leptogenesis with heavy neutrino flavours is discussed within a density matrix formalism. We write the density matrix equation, describing the generation of the matter-antimatter asymmetry, for an arbitrary choice of the right-handed (RH) neutrino masses. For hierarchical RH neutrino masses lying in the fully flavoured regimes, this reduces to multiple-stage Boltzmann equations. In this case we recover and extend results previously derived within a quantum state collapse description. We confirm the generic existence of phantom terms. However, taking into account the effect of gauge interactions, we show that they are washed out at the production with a wash-out rate that is halved compared to that one acting on the total asymmetry. In the N-1-dominated scenario they cancel without contributing to the final baryon asymmetry. In other scenarios they do not in general and they have to be taken into account. We also confirm that there is a (orthogonal) component in the asymmetry produced by the heavier RH neutrinos which completely escapes the washout from the lighter RH neutrinos and show that phantom terms additionally contribute to it. The other (parallel) component is washed out with the usual exponential factor, even for weak washout. Finally, as an illustration, we study the two RH neutrino model in the light of the above findings, showing that phantom terms can contribute to the final asymmetry also in this case.

Iop Publishing Ltd2013

Chargement

Tunable polarization converter based on one-dimensional graphene metasurfaces

Babak Rahmani

We introduce a new metasurface structure for controlling the polarization of light by leveraging a well-harmonized combination of graphene and dielectric. The proposed metasurface is composed of an array of rectangular pillars laterally sandwiched by ribbons of graphene. Being able to dynamically change the polarization state of the reflected wave, the proposed structure is employed to realize a switchable polarization converter, which is able to act as a reflector (co-polarizer)/right-hand circular (RHC) quarter-wave plate or RHC/cross/left-hand circular (LHC) polarizer based on its design configuration. The reflected amplitude in all states of functionality is remarkably high. It is also shown that, for some states, the proposed polarization converter demonstrates broad working bandwidth both spatially and spectrally. Therefore, it could find applications in tera-hertz imaging, sensing, and communication and also could be easily used to realize other beam-shaping functionalities such as lensing. (C) 2018 Optical Society of America

OPTICAL SOC AMER2018

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