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1.
G. Dietz K. Richter F. Stein H. C. Schäfer 《Zeitschrift für Physik B Condensed Matter》1990,81(2):223-228
Dependent on
is produced through electrodeposition in three modifications: microcrystalline if
, amorphous if
and in a mixed state containing both components if
. The interpretation of results of large and small angle X-ray scattering, of measurements of the coercivity and of the mechanical density shows that the three modifications consist of two phases. The structure of the grain boundary phase in the microcrystalline alloys differs considerably from that of the amorphous phase. This arises from the dependence of the atomic volume on the average phosphorus content
. The volume fraction of the crystalline component decreases with increasing
up to
. But even in alloys revealing X-ray patterns without any peaks coming from crystalline particles small angle X-ray scattering indicates the existence of metal-rich inclusions occupying some percent of the total volume. 相似文献
2.
Models of random systems whose Hamiltonian reads
, where
and
i
,=1,...,n are independent, identically distributed random variables are discussed.J
ij
are assumed to be symmetric, with respect toJ
0, random variables and also symmetric functions of components of
. A question of dependence of a phase diagram on a probability distribution of
is addressed. A class of distributions and interactionsJ
ij
, which give rise to phase diagrams called typical is selected. Then a problem of obtaining typical phase diagrams, containing a certain region with an infinite number of pure phases, is studied. 相似文献
3.
T. Nattermann M. Feigelman I. Lyuksyutov 《Zeitschrift für Physik B Condensed Matter》1991,84(3):353-359
We analyze the influence of thermal and frozen-in disorder on the flux line (FL) density
close to the lower critical fieldH
c1. Arguments which consider the steric repulsion of fluctuating FLs give
with the roughness exponent of a single FL andd the space dimensionality. We show by a phenomenological scaling approach and a renormalization group treatment, that this is correct only fordd
c
=2/–1, i.e. for
. Ford>d
c
the steric FL repulsion at scales more than some critical one is irrelevant and
. For disordered superconductorsd
c
=2 and
ford=2, 3. We also found the melting line for a FL lattice in the presence of frozen-in impurities close toH
c1. 相似文献
4.
A. Möbius 《Zeitschrift für Physik B Condensed Matter》1990,80(2):213-223
A detailed phenomenological re-analysis of previously published conductivity data, (T, x), is presented. It was shown in [1] that the cusp-like low-temperature contribution can be described by
wherep=0.19±0.03. Starting from this result, two furtherT dependent contributions are separated: The high-temperature region is dominated by a positive contribution ht (T, x), which is approximately independent ofx, nearly linear inT above 100 K and nearly quadratic inT below 30 K. ForT 4 K, there is a small deviation, increasing withT, from the superposition of the above mechanisms. The relation between
, being negative, and theT independent part,
, exhibits a singularity,
where
and=0.68±0.05 –(p–0.19). This singularity should be related to the metal-semiconductor transition, taking place atT
c
0.14. The quantity
should be interpreted as minimum metallic conductivity. The limitingT dependences asxx
c
+0 agrees quantitatively with that one obtained previously for the activated region,xx
c
–0. Extrapolation of the phenomenological model obtained leads to the hypothesis that the interplay of
and ht could be the main origin of the temperature coefficient changing its sign in the Mooijregion, at
tc=0. The model enables several trend predictions concerning the value of
tc=0. 相似文献
5.
We use the real-space renormalization group method to study the critical behavior of self-avoiding walks (SAWs) on both site percolation clusters at percolation threshold and site lattice animals in a square lattice. The correlation length exponents of SAWs are found to be
on the percolation clusters atp
c
and
SAW
LA
=0.804 on lattice animals. These results are compared with Kremer's suggestion of modified Flory formula
where
is the fractal dimension of the fractal object. 相似文献
6.
We use the recursion method to calculate the vibrational density of states
of site percolation clusters slightly above the percolation threshold. It is found that
is proportional to at long wavelengths. At shorter length scales,
is proportional to
, with the fraction dimension
. The cross-over from phonon to fraction regime is characterized by a rapid rise in
in agreement with effective medium calculations. 相似文献
7.
A. E. Dorokhov N. I. Kochelev Yu. A. Zubov 《Zeitschrift fur Physik C Particles and Fields》1995,65(4):667-679
The spectrum of
, Jp=0+, 2+ mesons is discussed. We have shown that due to instanton-induced forces the physical states are strong mixtures of theSU
f
(3) group basis states. The cross-sections for annihilation of the
system into
mesons are obtained. Thea
0(980) meson is considered as
meson consisting of 9
f
and 36
f
plets. The branchings are also predicted for the cross-sections for production of thea
0(980) and tensor
mesons in
annihilation. 相似文献
8.
P. Häussler 《Zeitschrift für Physik B Condensed Matter》1983,53(1):15-26
It will be shown that binary amorphous alloys with a noble metal and a polyvalent non-transition element, as constituents, can be described essentially as a Hume-Rothery phase. Some structural as well as transport properties depend on
, the average number of the conduction electrons per atom. A strong similarity between the amorphous and the corresponding liquid alloys was found. Alloys of the type mentioned can exist in a homogeneous amorphous phase within a concentration range which is limited on the noble-metal rich side by
=1.8 and on the other side by about 20 at% noble-metal content. The influence of the conduction electrons, manifested in the Friedel oscillations of the effective pair potentials, is responsible for structural and electronic transport properties. For amorphous and liquid alloys with
=1.8 it is interesting to note thatk
pe
, the wave number at which the maximum in the structure factor occurs, is equal to 2k
F
, the diameter of the Fermi sphere. As far as we have determined, all amorphous alloys with
=1.8 containing the same noble metal have the same crystallization temperature and the same Hall coefficient independent of the polyvalent element. The individual influence of the polyvalent constituents can only be seen with increasing
. 相似文献
9.
The influence of spin dynamics on the Kondo effect manifestations in the Kondo lattices is investigated within perturbation theory with respect to thes-f interaction. It may give rise to Kondo-like divergencies in the electron self-energy already in the second order, resulting in an appreciable effective mass enhancement. As for usual Kondo contributions to thermodynamic and transport properties, the effect of spin dynamics reduces roughly to the replacement ln
, with
the characteristic spin-fluctuation energy. The thermoelectric power of dense Kondo systems is discussed. Singular contributions to the electron self-energies in the ferro-and antiferromagnetic state are considered. Kondo-like corrections to the intersite exchange interactions, saturation magnetic moment and total energy in a magnetically ordered state are calculated. The strong-coupling regionT<T
K
is investigated within the Anderson lattice model. A decrease ofT
K
due to spin fluctuations is demonstrated. 相似文献
10.
An explicit construction in a manifestly Lorentz-invariant and cyclically symmetric form is given for a three-hadron (H) coupling through their respective (q
) constituents interacting via a quark triangle loop under the most general conditions of unequal mass kinematics atboth the elementary quark and composite-hadron levels. The only ansatz employed is that theHq
vertex function H at each vertexi is a function of
i
, the relative momentumtransverse to the corresponding hadron momentumP
i, an assumption which can be justified from several independent angles. The resulting structure
, withD(
) being a model-independent function, has proved crucial for an explicit integration over the time-like component of the loop momentum, and thus provided an analytical, cyclically symmetric structure free of overlapping pole singularities. The applicational potential of this quantity is outlined. 相似文献
11.
Pin-Zhen Bi 《Zeitschrift fur Physik C Particles and Fields》1991,52(1):105-109
The ellipsoidal bag model is used to describe heavy quark systems such asQ
,Q
g andQ
2
. Instead of two step model, these states are described by an uniform picture. The potential derived from the ellipsoidal bag forQ
is almost equivalent to the Cornell potential. For aQ
2
system with large quark pair separation, an improvement of 70 MeV is obtained comparing with the spherical bag. 相似文献
12.
In magnetic systems the radio frequency fieldH
1 seen by the nuclei is often enhanced by a factor . If the atomic spins are distributed in multi directions, as in Bloch walls or spin glasses, one has to consider a spatial distribution (r) of enhancement factors. The usual way to define a mean enhancement factor
is shown to lead to inconsistent results giving rise to errors up to more than 100%. One has to distinguish between two mean factors,
and
, depending on measuring conditions. Their deviations from the true value
are discussed. 相似文献
13.
A. Bartl W. Majerotto B. Mösslacher N. Oshimo 《Zeitschrift fur Physik C Particles and Fields》1991,52(4):677-684
We present a detailed study of
and
and the subsequent decays of
,
, and
at the LHC
. We explore the relevant supersymmetry parameter range. We calculate the cross sections as well as the rates for interesting signatures such as the production of one or two leptons on the lepton side. 相似文献
14.
R. F. Streater 《Communications in Mathematical Physics》1966,2(1):354-374
The dynamical variables of a classical system form a Lie algebra
, where the Lie multiplication is given by the Poisson bracket. Following the ideas ofSouriau andSegal, but with some modifications, we show that it is possible to realize
as a concrete algebra of smooth transformations of the functionals on the manifold
of smooth solutions to the classical equations of motion. It is even possible to do this in such a way that the action of a chosen dynamical variable, say the Hamiltonian, is given by the classical motion on the manifold, so that the quantum and classical motions coincide. In this realization, constant functionals are realized by multiples of the identity operator. For a finite number of degrees of freedom,n, the space of functionals can be made into a Hilbert space using the invariant Liouville volume element; the dynamical variablesF become operators
in this space. We prove that for any hamiltonianH quadratic in the canonical variablesq
1...q
n
,p
1...p
n
there exists a subspace
1 which is invariant under the action of
and
, and such that the restriction of
to
1 form an irreducible set of operators. Therefore,Souriau's quantization rule agrees with the usual one for quadratic hamiltonians. In fact, it gives the Bargmann-Segal holomorphic function realization. For non-linear problems in general, however, the operators
form a reducible set on any subspace of invariant under the action of the Hamiltonian. In particular this happens for
. Therefore,Souriau's rule cannot agree with the usual quantization procedure for general non-linear systems.The method can be applied to the quantization of a non-linear wave equation and differs from the usual attempts in that (1) at any fixed time the field and its conjugate momentum may form a reducible set (2) the theory is less singular than usual.For a particular wave equation
, we show heuristically that the interacting field may be defined as a first order differential operator acting onc
-functions on the manifold of solutions. In order to make this space into a Hilbert space, one must define a suitable method of functional integration on the manifold; this problem is discussed, without, however, arriving at a satisfactory conclusion.On leave from Physics Department, Imperial College, London SW7.Work partly supported by the Office of Scientific Research, U.S. Air Force. 相似文献
15.
We have studied the growth of atomically rough bcc and hcp4He crystals from the superfluid phase for temperaturesT>0.9 K. The growth coefficient displays a temperature dependence which can be represented bym
4
K
. The parameter E is found to be in close agreement with the energy gap of rotons, suggesting that these thermal excitations dominate the growth kinetics. Besides, the absolute value of the growth coefficient depends on crystal orientation, with an anisotropy for the hcp phase of about a factor of 2.5 between the
and {0001} planes.Dedicated to K. Dransfeld on the occasion of his 60th birthday 相似文献
16.
A quantum analogue of the dual pair
is introduced in terms of the oscillator representation of U
q
. Its commutant and the associated identity of Capelli type are discussed. 相似文献
17.
J. Chýla 《Czechoslovak Journal of Physics》1986,36(11):1259-1266
Recent results of lattice Monte-Carlo calculations in QCD are used to estimate the value of
. Special attention is paid to the role played by the light quarks in the construction of the continuum limit in QCD. The resulting value of
turns out to be strongly dependent onn
f
, the number of light quarks taken into account.Dedicated to the 30th anniversary of the Joint Institute for Nuclear Research.On leave of absence from theInstitute of Physics, Czechosl. Accd. Sci., Na Slovance 2, 180 40 Praha 8, Czechoslovakia. 相似文献
18.
Kiselev V. V. Likhoded A. K. Shevlyagin M. V. 《Zeitschrift fur Physik C Particles and Fields》1994,63(1):77-86
The cross-section for the production of
quarks ine
+
e
– annihilation, that proves to be at a level of
for
is calculated within the frames of the QCD perturbation theory. The cross sections for the associated production of 1S-and 2S-wave states ofB
c-meson in the reaction
were calculated in the nonrelativistic model of a heavy quarkonium. The number of
bc
-hyperons to be expected at LEP is estimated on the basis of the assumption on quark-hadron duality. 相似文献
19.
heide Narnhofer 《Letters in Mathematical Physics》1984,8(6):501-506
For M a factor of type III1 we can find for every automorphism group s that commutes with a modular automorphism group t and another modular automorphism group
, an automorphism group
that commutes with
is connected with s by an inner cocycle. 相似文献
20.
Let
be a finite-dimensional complex simple Lie algebra and Uq(
) the associated quantum group (q is a nonzero complex number which we assume is transcendental). IfV is a finitedimensional irreducible representation of Uq(
), an affinization ofV is an irreducible representationVV of the quantum affine algebra Uq(
) which containsV with multiplicity one and is such that all other irreducible Uq(
)-components ofV have highest weight strictly smaller than the highest weight ofV. There is a natural partial order on the set of Uq(
) classes of affinizations, and we look for the minimal one(s). In earlier papers, we showed that (i) if
is of typeA, B, C, F orG, the minimal affinization is unique up to Uq(
)-isomorphism; (ii) if
is of typeD orE and is not orthogonal to the triple node of the Dynkin diagram of
, there are either one or three minimal affinizations (depending on ). In this paper, we show, in contrast to the regular case, that if Uq(
) is of typeD
4 and is orthogonal to the triple node, the number of minimal affinizations has no upper bound independent of .As a by-product of our methods, we disprove a conjecture according to which, if
is of typeA
n,every affinization is isomorphic to a tensor product of representations of Uq(
) which are irreducible under Uq(
) (in an earlier paper, we proved this conjecture whenn=1).Both authors were partially supported by the NSF, DMS-9207701. 相似文献