72,944 research outputs found
Propagator poles and an emergent stable state below threshold: general discussion and the E(38) state
In the framework of a simple quantum field theory describing the decay of a
scalar state into two (pseudo)scalar ones we study the pole(s) motion(s) of its
propagator: besides the expected pole on the second Riemann sheet, we find --
for a large enough coupling constant -- a second, additional pole on the first
Riemann sheet below threshold, which corresponds to a stable state. We then
perform a numerical study for a hadronic system in which a scalar particle
couples to pions. We investigate under which conditions a stable state below
the two-pion threshold can emerge. In particular, we study the case in which
this stable state has a mass of 38 MeV, which corresponds to the recently
claimed novel scalar state E(38). Moreover, we also show that the resonance
and the stable state E(38) could be two different manifestation of
the same `object'. Finally, we also estimate the order of magnitude of its
coupling to photons.Comment: 9 pages, 4 figure
Book Review
Review of: WESLEY A. MAGAT & W. KIP VISCUSI, INFORMATIONAL APPROACHES TO REGULATION. (MIT Press 1992) [274 pp.] Appendices, endnotes, illustrations, index, list of titles in the Regulation of Economic Activity series, list of tables and figures, preface, series foreword. LC 91-29483; ISBN 0-262-13277-X. [$32.50 cloth. 55 Hayward Street; Cambridge MA 02142.
Anomalous Hall effect in the Co-based Heusler compounds CoFeSi and CoFeAl
The anomalous Hall effect (AHE) in the Heusler compounds CoFeSi and
CoFeAl is studied in dependence of the annealing temperature to achieve a
general comprehension of its origin. We have demonstrated that the crystal
quality affected by annealing processes is a significant control parameter to
tune the electrical resistivity as well as the anomalous Hall
resistivity . Analyzing the scaling behavior of in
terms of points to a temperature-dependent skew scattering as the
dominant mechanism in both Heusler compounds
Quasi-hermitian Quantum Mechanics in Phase Space
We investigate quasi-hermitian quantum mechanics in phase space using
standard deformation quantization methods: Groenewold star products and Wigner
transforms. We focus on imaginary Liouville theory as a representative example
where exact results are easily obtained. We emphasize spatially periodic
solutions, compute various distribution functions and phase-space metrics, and
explore the relationships between them.Comment: Accepted by Journal of Mathematical Physic
Two-photon decay of heavy hadron molecules
We discuss the two-photon decay width of heavy hadron molecules and study the
dependence on the constituent meson masses and on the binding energy. In
addition finite size effects due to the extended structure of the bound state
are shown to have a strong influence on the predictions for this decay width.Comment: 5 pages, 4 figure
The aspherical Cavicchioli-Hegenbarth-Repovš generalized Fibonacci groups
The Cavicchioli–Hegenbarth–Repovš generalized Fibonacci groups are defined by the presentations Gn (m, k) = 〈x 1, … , xn | xixi+m = xi+k (1 ⩽ i ⩽ n)〉. These cyclically presented groups generalize Conway's Fibonacci groups and the Sieradski groups. Building on a theorem of Bardakov and Vesnin we classify the aspherical presentations Gn (m, k). We determine when Gn (m, k) has infinite abelianization and provide sufficient conditions for Gn (m, k) to be perfect. We conjecture that these are also necessary conditions. Combined with our asphericity theorem, a proof of this conjecture would imply a classification of the finite Cavicchioli–Hegenbarth–Repovš groups
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