1,470 research outputs found
Do the Robertson-SCHR\"{O}DINGER and the Heisenberg Uncertainty Relations Imply a General Physical Principle ?
It is explicitly shown that there exist physical states (normalized to 1) in
which the Robertson- Schr\"{o}dinger and Heisenberg uncertainty relations are
invalid, namely, the mean values of the physical operators are infinite.
Consequently, these relations cannot imply a general physical principle. The
explanation by the theory of functional analysis is given : for these states
even the definition of the uncertainty notion through the dispersion notion in
the probability theory is irrelevant.Comment: 4 pages, LaTeX, no figur
Canonical and microcanonical ensemble descriptions of thermal pairing within BCS and quasiparticle RPA
We propose a description of pairing properties in finite systems within the
canonical and microcanonical ensembles. The approach is derived by solving the
BCS and self-consistent quasiparticle random-phase approximation with the
Lipkin-Nogami particle-number projection at zero temperature. The obtained
eigenvalues are embedded into the canonical and microcanonical ensembles. The
results obtained are found in quite good agreement with the exact solutions of
the doubly-folded equidistant multilevel pairing model as well as the
experimental data for Fe nucleus. The merit of the present approach
resides in its simplicity and its application to a wider range of particle
number, where the exact solution is impracticable.Comment: 10 pages, 2 figures, accepted for publication in Phys. Rev.
Nuclear pairing at finite temperature and angular momentum
An approach is proposed to nuclear pairing at finite temperature and angular
momentum, which includes the effects of the quasiparticle-number fluctuation
and dynamic coupling to pair vibrations within the self-consistent
quasiparticle random-phase approximation. The numerical calculations of pairing
gaps, total energies, and heat capacities are carried out within a doubly
folded multilevel model as well as several realistic nuclei. The results
obtained show that, in the region of moderate and strong couplings, the sharp
transition between the superconducting and normal phases is smoothed out,
causing a thermal pairing gap, which does not collapse at a critical
temperature predicted by the conventional Bardeen-Cooper-Schrieffer's (BCS)
theory, but has a tail extended to high temperatures. The theory also predicts
the appearance of a thermally assisted pairing in hot rotating nuclei.Comment: 4 pages, 1 figure, To appear in the Proceedings of the First Workshop
on State of the Art in Nuclear Cluster Physics, Strasbourg 13 - 16 May, 200
On the braiding of an Ann-category
A braided Ann-category \A is an Ann-category \A together with the
braiding such that (\A, \otimes, a, c, (I,l,r)) is a braided tensor
category, and is compatible with the distributivity constraints. The paper
shows the dependence of the left (or right) distributivity constraint on other
axioms. Hence, the paper shows the relation to the concepts of {\it
distributivity category} due to M. L. Laplaza and {\it ring-like category} due
to A. Frohlich and C.T.C Wall.
The center construction of an almost strict Ann-category is an example of an
unsymmetric braided Ann-category.Comment: 20 page
A three-phase to single-phase matrix converter for high-frequency induction heating
The paper describes a new three-phase to single-phase matrix converter featuring unity input power factor, very low input total harmonic distortion, and soft-switching over the full power range, for high frequency induction heating applications. A variable output pulse density modulation scheme has been proposed for stable operation of the converter, with the notable feature of requiring no on-line calculations for the synthesis of three-phase input current system. Practical issues in realising the converter, viz. line frequency synchronisation and output current circulation, are described. Good agreement between simulation and experimental results confirm the benefits of the proposed converter
Comparison of single-phase matrix converter and H-bridge converter for radio frequency induction heating
This paper compares the newly developed single-phase matrix converter and the more conventional H- bridge converter for radio frequency induction heating. Both the converters exhibit unity power factor, very low total harmonic distortion at the utility supply interface, good controllability under soft switching condition for a wide range of power, and high efficiencies, whilst still having simple structures. A novel switching control pattern has been proposed for the matrix converter in order to maintain the comparable performance to the H-bridge converter. Simulation and experimental results for both converters are presented. Comparisons between two converters have confirmed the excellent performance of the proposed matrix converter
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