Results 1 - 10 of 14604
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[en] Here, we consider the coupled nonlinear Dirac equations (NLDEs) in 1+11+1 dimensions with scalar–scalar self-interactions g_1"2/2(ψ̄ψ)"2+g_2"2/2(Φ̄Φ)"2+g_3"2(ψ̄ψ)(Φ̄Φ) as well as vector–vector interactions g_1"2/2(ψ̄γμψ)(ψ̄γμψ)+g_2"2/2(Φ̄γμΦ)(Φ̄γμΦ)+g_3"2(ψ̄γμψ)(Φ̄γμΦ). Writing the two components of the assumed rest frame solution of the coupled NLDE equations in the form ψ=e"–"i"ω"1"tR_1cosθ,R_1sinθφ=e"–"i"ω"2"tR_2cosη,R_2sinη, and assuming that θ(x),η(x) have the same functional form they had when g3 = 0, which is an approximation consistent with the conservation laws, we then find approximate analytic solutions for Ri(x) which are valid for small values of g_3"2/g"2_2 and g_3"2/g_1"2. In the nonrelativistic limit we show that both of these coupled models go over to the same coupled nonlinear Schrödinger equation for which we obtain two exact pulse solutions vanishing at x → ±∞.
[en] In this work, we obtain the exact one-spin intrinsic localized excitation in an anisotropic Heisenberg ferromagnetic spin chain in a constant/variable external magnetic field with Gilbert damping included. We also point out how an appropriate magnitude spin current term in a spin transfer nano-oscillator (STNO) can stabilize the tendency towards damping. Further, we show how this excitation can be sustained in a recently suggested PT -symmetric magnetic nanostructure. We also briefly consider more general spin excitations.
[en] Many-body perturbation theory is used for relativistic calculations of energy levels and of fine-structure intervals for 20 lower states of francium. The zeroth-order approximation is obtained by the relativistic Hartree-Fock method. The second-order correlation corrections are calculated. The accuracy for the s, p and f energy levels is not worse than 0.5%. (orig.)
[en] Ziino (see ibid. vol. 70, p. 87, 1979) suggested that, strictly speaking, light speed invariance is not fully consistent with ordinary space geometry unless one's concept of time is drastically modified. The present author argues against that paper. (Auth.)
[en] The production of highly excited hydrogen atoms by passing a proton beam though a thin carbon foil has been investigated within the energy range 5-30 keV. The population of atoms in states with principal quantum number, n, between 14 and 25 have been determined using the field ionization technique and found to scale as nsup(-4.35+-0.02). (orig.)
[en] The final-state energy spectrum in the photoionization of an initially populated adiabatic dressed state is studied. For weak dressing interactions, Raman coupling between dressed states significantly alters the form of the spectrum. (orig.)
[en] A toroidal current driven by a lower hybrid wave (LHW) is obtained by applying RF power to a toroidal plasma produced by electron cyclotron resonance. The direction as well as the magnitude of the current depend on the supplementary vertical and horizontal magnetic fields, which is explained by confinement of current-carrying electrons in a toroidal device. (orig.)