2,452 research outputs found
Dirac Particles in a Gravitational Field
The semiclassical approximation for the Hamiltonian of Dirac particles
interacting with an arbitrary gravitational field is investigated. The time
dependence of the metrics leads to new contributions to the in-band energy
operator in comparison to previous works on the static case. In particular we
find a new coupling term between the linear momentum and the spin, as well as
couplings which contribute to the breaking of the particle - antiparticle
symmetry
Special treatment reduces helium permeation of glass in vacuum systems
Internal surfaces of the glass component of a vacuum system are exposed to cesium in gaseous form to reduce helium permeation. The cesium gas is derived from decomposition of cesium nitrate through heating. Several minutes of exposure of the internal surfaces of the glass vessel are sufficient to complete the treatment
Semiclassical Dynamics of Electrons in Magnetic Bloch Bands: a Hamiltonian Approach
y formally diagonalizing with accuracy the Hamiltonian of electrons
in a crystal subject to electromagnetic perturbations, we resolve the debate on
the Hamiltonian nature of semiclassical equations of motion with Berry-phase
corrections, and therefore confirm the validity of the Liouville theorem. We
show that both the position and momentum operators acquire a Berry-phase
dependence, leading to a non-canonical Hamiltonian dynamics. The equations of
motion turn out to be identical to the ones previously derived in the context
of electron wave-packets dynamics.Comment: 4 page
Extreme vacuum technology including cryosorption, diffusion pump and pressure calibration studies Summary technical report, 1 Feb. 1965 - 1 Mar. 1966
Cryosorption, diffusion pump, and pressure calibration studies in extreme vacuum science and technology application progra
Extreme vacuum technology including cryosorption, diffusion pump and pressure calibration studies Quarterly status report no. 8, 1 May - 1 Aug. 1965
Cryosorption, diffusion pump, and low pressure calibration studies on Penning gauge and cold cathode magnetro
Study of low pressure application of the orbitron
Evaluation of low pressure performance of orbitron ionization gaug
From Feynman Proof of Maxwell Equations to Noncommutative Quantum Mechanics
In 1990, Dyson published a proof due to Feynman of the Maxwell equations
assuming only the commutation relations between position and velocity. With
this minimal assumption, Feynman never supposed the existence of Hamiltonian or
Lagrangian formalism. In the present communication, we review the study of a
relativistic particle using ``Feynman brackets.'' We show that Poincar\'e's
magnetic angular momentum and Dirac magnetic monopole are the consequences of
the structure of the Lorentz Lie algebra defined by the Feynman's brackets.
Then, we extend these ideas to the dual momentum space by considering
noncommutative quantum mechanics. In this context, we show that the
noncommutativity of the coordinates is responsible for a new effect called the
spin Hall effect. We also show its relation with the Berry phase notion. As a
practical application, we found an unusual spin-orbit contribution of a
nonrelativistic particle that could be experimentally tested. Another practical
application is the Berry phase effect on the propagation of light in
inhomogeneous media.Comment: Presented at the 3rd Feynman Festival (Collage Park, Maryland,
U.S.A., August 2006
Recommended from our members
Orientation and distribution of recent gullies in the southern hemisphere of Mars: observations from HRSC/MEX and MOC/MGS data
Abstract not available
Extreme vacuum technology including cryopump, getter-ion pump, diffusion pump and pressure standardization studies Summary technical report, 16 Jun. 1966 - 16 Jun. 1967
Ultrahigh vacuum technology including cryopump, getter ion pump, diffusion pump, and pressure standardization studie
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