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991.
Frederick?M.?KronzEmail author Tracy?A.?Lupher 《International Journal of Theoretical Physics》2005,44(8):1239-1258
It has been maintained that the physical content of a model of a system is completely contained in the C∗-algebra of quasi-local observables
that is associated with the system. The reason given for this is that the unitarily inequivalent representations of
are physically equivalent. But, this view is dubious for at least two reasons. First, it is not clear why the physical content
does not extend to the elements of the von Neumann algebras that are generated by representations of
. It is shown here that although the unitarily inequivalent representations of
are physically equivalent, the extended representations are not. Second, this view detracts from special global features
of physical systems such as temperature and chemical potential by effectively relegating them to the status of fixed parameters.
It is desirable to characterize such observables theoretically as elements of the algebra that is associated with a system
rather than as parameters, and thereby give a uniform treatment to all observables. This can be accomplished by going to larger
algebras. One such algebra is the universal enveloping von Neumann algebra, which is generated by the universal representation
of
; another is the direct integral of factor representations that are associated with the set of values of the global features.
Placing interpretive significance on the von Neumann algebras mentioned earlier sheds light on the significance of unitarily
inequivalent representations of
, and it serves to show the limitations of the notion of physical equivalence. 相似文献
992.
The quantum discrete kinetic equations are solved to study the propagation of plane waves in a system of composite particles
with hard-sphere interactions and the filling factor (ν) being 1/2. We compare the dispersion relations thus obtained by the
relevant Pauli-blocking parameter B which describes the different-statistics particles for the quantum analog of the discrete Boltzmann system when B is positive (Bose gases), zero (Boltzmann gases), and negative (Fermi Gases). We found, as the effective magnetic field being
zero (ν = 1/2 using the composite fermion formulation), the electric field effect will induce anomalous dispersion relations. 相似文献
993.
In this paper it is shown by using the Clifford algebra formalism that the usual Lorentz transformations of the three-dimensional (3D) vectors of the electric and magnetic fields E and B (which will be named as standard transformations (ST)) are different than the Lorentz transformations (LT) of well-defined quantities from the 4D spacetime. This difference between the ST and the LT is obtained regardless of the used algebraic objects (1-vectors or bivectors) for the representation of the electric and magnetic fields in the usual observer dependent decompositions of F. The LT correctly transform the whole 4D quantity, e.g., Ef : F · γ0, whereas the ST are the result of the application of the LT only to the part of Ef, i.e., to F, but leaving γ0 unchanged. The new decompositions of F in terms of 4D quantities that are defined without reference frames, i.e., the absolute quantities, are introduced and discussed. It is shown that the LT of the 4D quantities representing electric and magnetic fields correctly describe the motional electromotive force (emf) for all relatively moving inertial observers, whereas it is not the case with the ST of the 3D E and B. 相似文献
994.
I argue that quantum mechanics is fundamentally a theory about the representation and manipulation of information, not a theory about the mechanics of nonclassical waves or particles. The notion of quantum information is to be understood as a new physical primitive---just as, following Einsteins special theory of relativity, a field is no longer regarded as the physical manifestation of vibrations in a mechanical medium, but recognized as a new physical entity in its own right. 相似文献
995.
996.
J.?DubowikEmail author F.?Stobiecki I.?Go?ciańska Y. P.?Lee A.?Paetzold K.?R?ll 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,45(2):283-288
The temperature dependencies of the ferromagnetic
resonance (FMR) linewidth and the resonance field-shift have been
investigated for NiO/NiFe exchange-biased bilayers from 78 K to 450 K. A broad maximum in the linewidth of 500 Oe, solely due to the
exchange-bias, is observed at ≈150 K when the magnetic
field is applied along the film plane. When the magnetic field is
applied perpendicular to the film plane, the maximum in the
linewidth is less pronounced and amounts to 100 Oe at the same
temperature. Such a behavior of the FMR linewidth is accompanied
with a monotonic increase in the negative resonance field-shift
with decreasing temperature. Our results are compared with the
previous experimental FMR and Brillouin light scattering data for
various ferromagnetic/antiferromagnetic (FM/AF) structures, and
suggest that spin dynamics (spin-wave damping and anomalous
resonance field-shift) in the FM/AF structures can be described in
a consistent way by a single mechanism of the so-called
slow-relaxation. 相似文献
997.
998.
G.?Kl?mkeEmail author K.?M?nig 《The European Physical Journal C - Particles and Fields》2005,42(3):261-270
A Monte-Carlo analysis on production and decay of supersymmetric charginos at a future photon-collider is presented. A photon collider offers the possibility of a direct branching-ratio measurement. In this study, the process
has been considered for a specific mSUGRA scenario. Various backgrounds and a parameterised detector simulation have been included. Depending on the centre-of-mass energy, a statistical error for the directly measurable branching ratio BR(
) of up to 3.5% can be reached.Received: 14 March 2005, Revised: 31 May 2005, Published online: 28 June 2005G. Klämke: Now at: Institut für Theoretische Physik, Universität Karlsruhe, Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, Germany 相似文献
999.
A.?N.?WilsonEmail author G.?D.?Dracoulis A.?P.?Byrne P.?M.?Davidson G.?J.?Lane R.?M.?Clark P.?Fallon A.?G?rgen A.?O.?Macchiavelli D.?Ward 《The European Physical Journal A - Hadrons and Nuclei》2005,24(2):179-183
A superdeformed band has been observed in the N = 108 isotope 190Pb. This is the most neutron-deficient Pb isotope in which superdeformed states have been observed. Several theoretical approaches have predicted that N = 108 will mark the limit of observable superdeformation in the Pb isotopes. The band, which consists of five (possibly six) transitions, is observed to feed at least one isomeric level in its decay to the ground state. This decay pattern supports a spin assignment of 10 for the lowest observed level. 相似文献
1000.
Meral Birbir Hüsniye Hac?o?lu Ya?ar Birbir Gül?en Altu? 《Journal of Electrostatics》2009,67(4):640-645
Inactivation effect of alternative electric current on Escherichia coli ATCC 25922 and fecal E. coli MAAG 1405 found resistant to antibiotics was examined in water samples collected from Ayamama River, Sar?su River, and their discharge points into sea and from Black Sea and Marmara Sea. In addition to water samples, lauryl sulfate broth was used as an organic rich medium. Both test strains were inactivated within 1–3 min in media containing marine waters (1 A), 5–10 min in Ayamama River water (1 A), 5 min in Sar?su River water (0.5 A), 20–35 min in lauryl sulfate broth (1 A) by applying alternative electric current. 相似文献