1,720 research outputs found
Multiboson effects in multiparticle production
The influence of multiboson effects on pion multiplicities, single-pion
spectra and two-pion correlation functions is discussed in terms of an
analytically solvable model. The applicability of its basic factorization
assumption is clarified. An approximate scaling of the basic observables with
the phase space density is demonstrated in the low density (gas) limit. This
scaling and also its violation at high densities due to the condensate
formation is described by approximate analytical formulae which allow, in
principle, for the identification of the multiboson effects among others. For
moderate densities indicated by the experimental data, a fast saturation of
multiboson effects with the number of contributing cumulants is obtained,
allowing for the account of these effects in realistic transport code
simulations. At high densities, the spectra are mainly determined by the
universal condensate term and the initially narrow Poisson multiplicity
distribution approaches a wide Bose-Einstein one. As a result, the intercepts
of the inclusive and fixed- correlation functions (properly normalized to 1
at large relative momenta) approach 2 and 1, respectively and their widths
logarithmically increase with the increasing phase space density. It is shown
that the neglect of energy-momentum constraints in the model is justified
except near a multipion threshold, where these constraints practically exclude
the possibility of a very cold condensate production. It is argued that
spectacular multiboson effects are likely to be observed only in the rare
events containing sufficiently high density (speckle) fluctuations.Comment: 30 pages including 10 figures, LaTex, a revised version of SUBATECH
99-04 (aps1999_mar21_001) resubmitted to Phys. Rev. C; Chapter II made
shorter, figure description made more clear, a comparison with most recent
works added in Chapter V
Bose-Einstein condensation of magnons under incoherent pumping
Bose-Einstein condensation in a gas of magnons pumped by an incoherent
pumping source is experimentally studied at room temperature. We demonstrate
that the condensation can be achieved in a gas of bosons under conditions of
incoherent pumping. Moreover, we show the critical transition point is almost
independent of the frequency spectrum of the pumping source and is solely
determined by the density of magnons. The electromagnetic power radiated by the
magnon condensate was found to scale quadratically with the pumping power,
which is in accordance with the theory of Bose-Einstein condensation in magnon
gases
Theoretical backgrounds of durability analysis by normalized equivalent stress functionals
Generalized durability diagrams and their properties are considered for a material under a multiaxial loading given by an arbitrary function of time. Material strength and durability under such loading are described in terms of durability, safety factor and normalized equivalent stress. Relations between these functionals are analysed. We discuss some material properties including time and load stability, self-degradation (ageing), and monotonic damaging. Phenomenological strength conditions are presented in terms of the normalized equivalent stress. It is shown that the damage based durability analysis is reduced to a particular case of such strength conditions. Examples of the reduction are presented for some known durability models. The approach is applicable to the strength and durability description at creep and impact loading and their combination
On bosonic limits of two recent supersymmetric extensions of the Harry Dym hierarchy
Two generalized Harry Dym equations, recently found by Brunelli, Das and
Popowicz in the bosonic limit of new supersymmetric extensions of the Harry Dym
hierarchy [J. Math. Phys. 44:4756--4767 (2003)], are transformed into
previously known integrable systems: one--into a pair of decoupled KdV
equations, the other one--into a pair of coupled mKdV equations from a
bi-Hamiltonian hierarchy of Kupershmidt.Comment: 7 page
Structure and control of self-sustained target waves in excitable small-world networks
Small-world networks describe many important practical systems among which
neural networks consisting of excitable nodes are the most typical ones. In
this paper we study self-sustained oscillations of target waves in excitable
small-world networks. A novel dominant phase-advanced driving (DPAD) method,
which is generally applicable for analyzing all oscillatory complex networks
consisting of nonoscillatory nodes, is proposed to reveal the self-organized
structures supporting this type of oscillations. The DPAD method explicitly
explores the oscillation sources and wave propagation paths of the systems,
which are otherwise deeply hidden in the complicated patterns of randomly
distributed target groups. Based on the understanding of the self-organized
structure, the oscillatory patterns can be controlled with extremely high
efficiency.Comment: 16 pages 5 figure
Measurement of the - mixing angle in and beams with GAMS- Setup
The results of mixing angle measurement for , mesons generated
in charge exchange reactions with and beams are preseneted.
When the , mesons are described in nonstrange(NS)--strange(S)
quark basis the and beams allow to study and
parts of the meson wave function. The cross section ratio at
(GeV/c) in the beam is , results in mixing angle . For
beam the ratio is . It was found that
gluonium content in is . The
experiment was carried out with GAMS-4 Setup.Comment: 6 pages, 4 figures, 1 table, to be submitted in European physical
journal C. Minor changes, the Bibliography extende
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