Results 1 - 10 of 79145
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[en] It is shown that the (quantum or classical) observables for a spin-1/2 massive electron are invariant under a local one-parameter group of gauge transformations whose generator is dependent on the fermion 'fields' of the theory, as well as conventional (constant) Lie algebra generators. This one-parameter family of local transformations is 2 → 1 homomorphic to a set of operators common to both the 'little group' of the four-velocity and the 'little group' of the Pauli-Lubanski spin vector. This symmetry is called the 'local little symmetry' to emphasize its connection to Wigner's 'little group'. The physical origin of this local little symmetry' is discussed. This symmetry is employed to explain a degeneracy exhibited by some classical models of an electron with spin
[en] Recent studies have attributed certain properties of the Earth's atmosphere to excess orbital angular momentum of impinging meteoroids. A realistic analysis of meteor observations does not support the existence of this excess. (Auth.)
[en] The Wigner function of a pure continuous-variable quantum state is non-negative if and only if the state is Gaussian. Here we show that for the canonical pair angle and angular momentum, the only pure states with non-negative Wigner functions are the eigenstates of the angular momentum. Some implications of this surprising result are discussed.
[en] Transverse-momentum-dependent parton distributions (TMDs) are crucial ingredients for a complete understanding of the dynamics of confined par-tons. They allow for a 3-dimensional description of the nucleon in momentum space, and could provide insights into the yet unmeasured quark orbital angular momentum. At CLAS several TMDs are explored in Fourier analysis of azimuthal asymmetries measured in semi-inclusive DIS. An overview of the main CLAS results as well as selected CLAS12 projected results is presented.
[en] A remarkably consistent ordering of excited atomic states with the quantity k < n + l, for small values of the orbital angular momentum l, was pointed out by Sternheimer. This fact is readily interpreted in terms of the variation of the quantum defects with l, and simple rules for the k ordering are given. The reasons for the observed variation of the quantum defects can be understood in terms of the accumulation of zero-energy scattering phase shifts with l and with Z, as calculated by Manson from a realistic atomic potential
[en] Using an experimental setup that simulates a turbulent atmosphere, we study the secret key rate for quantum key distribution (QKD) protocols in orbital angular momentum based free space quantum communication. The QKD protocols under consideration include the Ekert 91 protocol for different choices of mutually unbiased bases and the six-state protocol. We find that the secret key rate of these protocols decay to zero, roughly at the same scale where the entanglement of formation decays to zero. (paper)
[en] We study the establishment of vortex entanglement in remote Bose-Einstein condensates (BECs). We consider a two-mode photonic resource entangled in its orbital angular momentum (OAM) degree of freedom and, by exploiting the process of light-to-BEC OAM transfer, demonstrate that such entanglement can be efficiently passed to the matterlike systems. Our proposal thus represents a building block for novel dissipation-free and long-memory communication channels based on OAM. We discuss issues of practical realizability, stressing the feasibility of our scheme, and present an operative technique for the indirect inference of the set vortex entanglement.