409 research outputs found
On Martin-Löf convergence of Solomonoff’s mixture
We study the convergence of Solomonoff’s universal mixture on individual Martin-Löf random sequences. A new result is presented extending the work of Hutter and Muchnik (2004) by showing that there does not exist a universal mixture that converges on all Martin-Löf random sequences
Two-particle interference of electron pairs on a molecular level
We investigate the photo-doubleionization of molecules with 400 eV
photons. We find that the emitted electrons do not show any sign of two-center
interference fringes in their angular emission distributions if considered
separately. In contrast, the quasi-particle consisting of both electrons (i.e.
the "dielectron") does. The work highlights the fact that non-local effects are
embedded everywhere in nature where many-particle processes are involved
Optical pumping NMR in the compensated semiconductor InP:Fe
The optical pumping NMR effect in the compensated semiconductor InP:Fe has
been investigated in terms of the dependences of photon energy (E_p), helicity
(sigma+-), and exposure time (tau_L) of infrared lights. The {31}P and {115}In
signal enhancements show large sigma+- asymmetries and anomalous oscillations
as a function of E_p. We find that (i) the oscillation period as a function of
E_p is similar for {31}P and {115}In and almost field independent in spite of
significant reduction of the enhancement in higher fields. (ii) A
characteristic time for buildup of the {31}P polarization under the light
exposure shows strong E_p-dependence, but is almost independent of sigma+-.
(iii) The buildup times for {31}P and {115}In are of the same order (10^3 s),
although the spin-lattice relaxation times (T_1) are different by more than
three orders of magnitude between them. The results are discussed in terms of
(1) discrete energy spectra due to donor-acceptor pairs (DAPs) in compensated
semiconductors, and (2) interplay between {31}P and dipolar ordered indium
nuclei, which are optically induced.Comment: 8 pages, 6 figures, submitted to Physical Review
Near-threshold Lambda(1520) production by the gamma p -> K+Lambda(1520) reaction at forward K+ angles
Differential cross sections and photon-beam asymmetries for the gamma p -> K+
Lambda(1520) reaction have been measured with linearly polarized photon beams
at energies from the threshold to 2.4 GeV at 0.6<cos(theta)<1. A new bump
structure was found at W=2.11 GeV in the cross sections. The bump is not well
reproduced by theoretical calculations introducing a nucleon resonance with
J<=3/2. This result suggests that the bump might be produced by a nucleon
resonance possibly with J>=5/2 or by a new reaction process, for example an
interference effect with the phi photoproduction having a similar bump
structure in the cross sections.Comment: 5 pages, 4 figures, published in Phys. Rev. Let
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