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1.
Electric field gradient q and quadrupole interaction frequency
calculated at 256.7 K in the high pressure phase (orthorhombic) of
Ga metal are reported. The results are: q=+0.251 atomic units (au),
=5.479 MHz. These are compared with results from experiment and previous calculation available for the monoclinic phase of
Ga metal at normal pressure. The results from the previous calculation at 248 K are: q=-0.250 au and
=5.318 MHz. The result from experiment extrapolated to 256.7 K is:
=4.871 MHz. The sign reversal of the calculated q is attributed mainly to the change of point symmetry of the lattice from the orthorhombic to monoclinic. That the interaction frequency in high pressure phase is higher than experiment may be partly due to the increase of pressure and partly to the structural phase change. 相似文献
2.
The crystal structure and magnetic properties of the Al and Cr cosubstituted disordered spinel series NiAlxCrxFe2-2xO4
are investigated by means of Xray diffraction, magnetization, a.c. susceptibility and Mössbauer effect measurements. The lattice constants are determined and the applicability of Vegard's law has been tested. The variation of the saturation magnetic moment per formula unit measured at 77 K and 300 K with Al–Cr content is satisfactorily explained on the basis of Neel's collinear spin ordering model for
=0.1–0.5. The Mössbauer spectra at 300 K have been fitted with two sextets in the ferrimagnetic state corresponding to Fe3+ at tetrahedral (A) and octahedral (B) sites for
0.5. Mössbauer results confirm a collinear ferrimagnetic structure for
=0.1–0.5. The Curie temperature obtained from a.c. susceptibility decreases nearly linear with increase of Al–Cr concentration from
=0.1 to 0.5. 相似文献
3.
A. Werthmüller A. Adamczak R. Jacot‐Guillarmod F. Mulhauser L.A. Schaller L. Schellenberg H. Schneuwly Y.‐A. Thalmann S. Tresch 《Hyperfine Interactions》1998,116(1-4):1-16
The charge exchange reaction of negative muons from the
atom to oxygen has been measured in gaseous mixtures of H2 + O2. The measurements were performed at three different relative oxygen concentrations ranging from 0.2% to 0.8% and total pressures 3.5–15 bar. A mean transfer rate of
, describing the transfer from the ground state of thermalized
atoms to oxygen, was determined. In order to investigate the energy dependence of the transfer rate, Monte Carlo simulations of the
thermalization and the muon transfer were carried out. The comparison of measured and simulated time spectra yielded an epithermal transfer rate
=3.9
1011 s-1 in the energy interval 0.12–0.22 eV. The analysis with the model of Two components shows that all measured time spectra can be reproduced with the same set of parameters. 相似文献
4.
Stan Gudder 《Foundations of Physics》1999,29(6):877-897
This article begins with a review of the framework of fuzzy probability theory. The basic structure is given by the -effect algebra of effects (fuzzy events)
and the set of probability measures
on a measurable space
. An observable
is defined, where
is the value space of X. It is noted that there exists a one-to-one correspondence between states on
and elements of
and between observables
and -morphisms from
to
. Various combinations of observables are discussed. These include compositions, products, direct products, and mixtures. Fuzzy stochastic processes are introduced and an application to quantum dynamics is considered. Quantum effects are characterized from among a more general class of effects. An alternative definition of a statistical map
is given and it is shown that any statistical map has a unique extension to a statistical operator. Finally, various combinations of statistical maps are discussed and their relationships to the corresponding combinations of observables are derived. 相似文献
5.
Let
be von Neumann algebras acting on a Hilbert space
and let
be a common cyclic and separating vector. We say that
have the modular intersection property with respect to
if(1)
-half-sided modular inclusions,(2)
(If (1) holds the strong limit exists.) We show that under these conditions the modular groups of
and
generate a 2-dim. Lie group.This observation is the basis for obtaining group representations of Sl(2,
)/Z
2 generated by modular groups. 相似文献
6.
Michael Keyl 《International Journal of Theoretical Physics》1998,37(1):375-385
The major subject of algebraic quantum fieldtheory is the study of nets of local C*-algebras, i.e.,maps
(
) assigning to each open,relatively compact region of space-time (M, g) aC*-algebra
(
), whose self-adjoint elements describe localobservables measurable in the region
. A question discussed recently in a number ofpapers is how much information about the geometricstructure of the underlying space-time (M, g) is encoded in the algebraicstructure of the net
(
). Followingthese ideas, it is demonstrated in this paper howspace-time-related concepts like causality and observerscan be described in a purely algebraic way, i.e., using only thelocal algebras
(
).These results are then used to show how the space-time(M, g) can be reconstructed from the set
loc := {
(
)|
M open,
compact} of local algebras. 相似文献
7.
D. Arnaudon 《Czechoslovak Journal of Physics》1997,47(11):1075-1082
Irreducible representations of
at roots of unity in the restricted specialisation are described with the Gelfand-Zetlin basis. This basis is redefined to allow the Casimir operator of the quantum subalgebra
not to be completely diagonalised. Some irreducible representations of
indeed contain indecomposable
-modules. The set of redefined (mixed) states is described as a teepee inside the pyramid made with the whole representation. 相似文献
8.
The CPT Group of the Dirac Field 总被引:2,自引:2,他引:0
Miguel Socolovsky 《International Journal of Theoretical Physics》2004,43(9):1941-1967
Using the standard representation of the Dirac equation, we show that, up to signs, there exist only two sets of consistent solutions for the matrices of charge conjugation (C), parity (P), and time reversal (T), which give the transformation of fields
,
and
, where
and
. These sets are given by
,
,
and
,
,
. Then
, and two successive applications of the parity transformation to fermion fields necessarily amount to a 2 rotation. Each of these sets generates a non abelian group of 16 elements, respectively,
and
, which are non isomorphic subgroups of the Dirac algebra, which, being a Clifford algebra, gives a geometric nature to the generators, in particular to charge conjugation. It turns out that
and
, where
is the dihedral group of eight elements, the group of symmetries of the square, and 16E is a non trivial extension of
by
, isomorphic to a semidirect product of these groups; S6 and S8 are the symmetric groups of six and eight elements. The matrices are also given in the Weyl representation, suitable for taking the massless limit, and in the Majorana representation, describing self-conjugate fields. Instead, the quantum operators C, P and T, acting on the Hilbert space, generate a unique group
, which we call the CPT group of the Dirac field. This group, however, is compatible only with the second of the above two matrix solutions, namely with
, which is then called the matrix CPT group. It turns out that
, where
is the dicyclic group of 8 elements and S10 is the symmetric group of 10 elements. Since
, the quaternion group, and
, the 0-sphere, then
. 相似文献
9.
S. Ole Warnaar 《Journal of statistical physics》2001,102(3-4):1065-1081
A refinement of the q-trinomial coefficients is introduced, which has a very powerful iterative property. This
-invariance is applied to derive new Virasoro character identities related to the exceptional simply-laced Lie algebras E
, E
and E
. 相似文献
10.
The authors deal with the tunneling of electrons across an inhomogeneous delta-barrier defined by the potential energy
(where
0$$
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and
0$$
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are two constants). In particular, the perpendicular incidence of an electron with a given value
of the wave vector
is considered. The electron is forward-scattered into the region behind the barrier (region 2:
0$$
" align="middle" border="0">
), i. e. the wave function
is composed of plane waves with all wave vectors
such that
and
\left. 0 \right)} $$
" align="middle" border="0">
) (where
). Therefore, if
0$$
" align="middle" border="0">
, the wave function of the electron is represented as
, where
. An approximate formula is derived for the amplitude
. The authors pay a special attention to the flow density
and calculate this function in two cases: 1. for the plane
and 2. for high values of
is the diffraction angle). The authors discuss the relevance of their diffraction problem in a prospective quantum-mechanical theory of the tunneling of electrons across a randomly inhomogeneous Schottky barrier. 相似文献