Results 1 - 10 of 96585
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[en] We discuss the problem of subbarrier fusion processes in reactions involving weakly-bound projectiles, in particular with respect to the effect of the strong coupling to break-up channels. Within a simple schematic coupled-channel model we show that the coupling to reaction channels (including continuum break-up channels) seems to predict enhancement of fusion below the barrier (for total fusion and, to a lesser degree, also for complete fusion), when the reaction process is treated within the conventional approach, with proper modifications due to weak-binding nature of halo systems (as for example the long range of formfactors and potentials)
[en] Here we present a determination of the strong coupling constant from lattice QCD using the moments of pseudo-scalar charmonium correlators calculated using highly improved staggerered quark action. We obtain a value α_s(μ = mc) = 0.3397(56), which is the lowest energy determination of the strong coupling constant so far.
[en] We examine the appearance of Zeno and anti-Zeno effects (Misra and Sudarshan 1977 J. Math. Phys. 18 756; Kofman and Kurizki 2000 Nature 405 546; Kofman and Kurizki 1996 Phys. Rev. A 54 3750; Facchi et al 2001 Phys. Rev. Lett. 86 2699) in the entanglement dynamics of two qubits off-resonantly coupled to the same lossy cavity when the unitary evolution of the system is interrupted by repeated projective measurements. We describe in detail these quantum effects by comparing the measurement-induced coarse-grained dynamics to the entanglement evolution in the absence of measurements in several scenarios (Francica et al 2009 Phys. Rev. A 79 032310). In particular, we examine the strong and weak coupling regimes, the role of the relative coupling strengths between the two qubits and the reservoir and the effect of the detuning from the main cavity frequency. We show that the anti-Zeno effect can occur in the entanglement dynamics when the qubit frequencies are detuned from the main reservoir frequency. Furthermore, we find that Zeno and anti-Zeno effects can even appear sequentially many times as a function of the interval between the measurements. Finally, we show that, in the off-resonant regime, we can preserve the entanglement using the quantum Zeno effect more efficiently than in the resonant limit (Maniscalco et al 2008 Phys. Rev. Lett. 100 090503), even if, in this case, no sub-radiant state exists.
[en] Results indicating the important role of the electron-phonon coupling in high-temperature superconductivity compounds are presented, with emphasis on its implications for angle-resolved photoemission and optical conductivity. The dimensionless phonon coupling constant λ is determined by comparing the experimental and theoretical results. Although undoped materials are in the strong-coupling (λ ∼ 1) regime, hole doping decreases λ, bringing compounds to the intermediate-coupling regime at optimum hole concentrations. (reviews of topical problems)
[en] We present recent results from Jefferson Lab on sum rules related to the spin structure of the nucleon. We then discuss how the Bjorken sum rule with its connection to the Gerasimov-Drell-Hearn sum, allows us to conveniently define an effective coupling for the strong force at all distances.
[en] We investigate the vortex core shrinking effect in three-layered superconductors based on the inter-layer coupling Bogoliubov de Gennes (BdG) equations. It is found that the vortex core contraction is due to the quasiparticle interference effect. We point out that a rapid vortex core contraction is controlled by inter-layer couplings and a magnetic field. We also find that the quasiparticle interference effect in the vortex induces vortex charges which show an oscillation behavior. This oscillation behavior explains the local density of states (LDOSs) oscillation found in experiments.
[en] We study numerically the localization-delocalization transition in a class of one-dimensional tight-binding Hamiltonians H with non-random power-law inter-site coupling Hmn=J/|m-n|μ and random on-site energy. This model is critical with respect to the magnitude of disorder at one of the band edges, provided 1<μ<((3)/(2)). We demonstrate that at some value of the magnitude of disorder Δc, interpreted as the critical one, the ratio of the standard deviation to the mean of the participation number distribution is a size-invariant parameter: all curves of this ratio versus the magnitude of disorder, plotted for different system sizes, have a joint intersection point at Δc. This value is finite for 1<μ<((3)/(2)) implying the existence of the transition, while in the marginal case (at μ=((3)/(2))) the intersection point is at Δc=0 implying localization of all the eigenstates