59 research outputs found
Quantization of the Hall conductivity well beyond the adiabatic limit in pulsed magnetic fields
We measure the Hall conductivity, , on a Corbino geometry sample
of a high-mobility AlGaAs/GaAs heterostructure in a pulsed magnetic field. At a
bath temperature about 80 mK, we observe well expressed plateaux in
at integer filling factors. In the pulsed magnetic field, the
Laughlin condition of the phase coherence of the electron wave functions is
strongly violated and, hence, is not crucial for quantization.Comment: 4 pages, 4 figures, submitted to PR
Where is the pseudoscalar glueball ?
The pseudoscalar mesons with the masses higher than 1 GeV are assumed to
belong to the meson decuplet including the glueball as the basis state
supplementing the standard nonet of light states
. The decuplet is investigated by means of an algebraic approach based
on hypothesis of vanishing the exotic commutators of "charges" and
their time derivatives. These commutators result in a system of equations
determining contents of the isoscalar octet state in the physical isoscalar
mesons as well as the mass formula including all masses of the decuplet:
, K(1460), , and . The physical
isoscalar mesons , are expressed as superpositions of the "ideal"
states ( and ) and the glueball with the mixing
coefficient matrix following from the exotic commutator restrictions. Among
four one-parameter families of the calculated mixing matrix (numerous solutions
result from bad quality of data on the and K(1460) masses) there is
one family attributing the glueball-dominant composition to the
meson. Similarity between the pseudoscalar and scalar decuplets, analogy
between the whole spectra of the and mesons and affinity of
the glueball with excited states are also noticed.Comment: 18 pp., 2. figs., 2 tabs.; Published version. One of the authors
withdraws his nam
The parafermion Fock space and explicit so(2n+1) representations
The defining relations (triple relations) of n pairs of parafermion operators
f_j^\pm (j=1,...,n) are known to coincide with a set of defining relations for
the Lie algebra so(2n+1) in terms of 2n generators. With the common Hermiticity
conditions, this means that the ``parafermions of order p'' correspond to a
finite-dimensional unitary irreducible representation W(p) of so(2n+1), with
highest weight (p/2, p/2,..., p/2). Although the dimension and character of
W(p) is known by classical formulas, there is no explicit basis of W(p)
available in which the parafermion operators have a natural action. In this
paper we construct an orthogonal basis for W(p), and we present the explicit
actions of the parafermion generators on these basis vectors. We use group
theoretical techniques, in which the u(n) subalgebra of so(2n+1) plays a
crucial role: a set of Gelfand-Zetlin patterns of u(n) will be used to label
the basis vectors of W(p), and also in the explicit action (matrix elements)
certain u(n) Clebsch-Gordan coefficients are essential
Influence of te concentration on the infrared cathodoluminescence of GaAs:Te wafers
Cathodoluminescence (CL) scanning electron microscopy has been used to investigate the nature and distribution of defects involved in the infrared emission of GaAs:Te wafers. Spectral and CL-contrast changes as a function of doping level have been found. Profiles of infrared CL intensity across the wafers show an inverted U shape
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