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1.
Ola Bratteli 《Letters in Mathematical Physics》1982,6(6):499-504
Let δ be a quasi-free derivation of the CAR algebra, and let
be a closed *-derivation which is an extension of δ. We use Price's techniques from [6] to show that if the polynomials in
the linear field operators a(f)→a
*
(f) in D(
) is a core for
, then
is quasi-free. 相似文献
2.
KN sigma commutator has been calculated in the framework of the (6,
)+(
, 6) model. It is found that though this model could not be discarded in favour of the (3,
)+(
, 3) or (8, 8) model, a very large value forKN sigma term is required to get a positive value ofπN sigma term. 相似文献
3.
Summary Grain growth is studied in polycrystalline ice, consisting of elongated grains, of (200÷300) μm mean width
and (2÷3) mm mean length
. The samples are annealed at different temperatures, between 0°C and −10°C. It is found that
is not affected by annealing, while
increases with the annealing time. Below the melting point,
(t) tends to a limit value
. This behaviour is related to the pinning action of air bubbles, which would be similar to that found for solid inclusions
in metals. By assuming
where
is the mean bubble diameter andf is the volume fraction of air dissolved in water, reasonable values are found for
. The activation energy of the phenomenon is evaluated on the basis of the present and of Jellinek and Gouda's results. It
is foundQ=0.6 eV, which value approximately coincides with that for bulk self-diffusion as it occurs for metals, several degrees below
the melting point. This coincidence suggests that, for ice, grain growth would be controlled by bulk impurity diffusion up
to the very melting point.
Instituto de Matemática, Astronomía y Física, Universidad Nacional de Córdoba and CONICET. 相似文献
4.
B. I. Deutch 《Hyperfine Interactions》1992,73(1-2):175-191
The main suggested routes for atomic antihydrogen (
) formation will be reviewed in a pedestrian fashion. These are the following reactions:
, and (iii)
. The present status of the projects related to these reactions, as well as the projects' experimental scope, will also be
discussed or referred to. Some speculations will be made regarding the physics that can be yielded by an antihydrogen probe. 相似文献
5.
W. Bernreuther G. W. Botz O. Nachtmann P. Overmann 《Zeitschrift fur Physik C Particles and Fields》1991,52(4):567-573
We calculate CP-odd correlations inZ decays to leptons,
. These correlations are sensitive to the weak dipole moment
of the . With 107 producedZ particles and with observation of the decay channels
and v
we estimate that
can be determined with an accuracy of about
(1 s.d.). 相似文献
6.
Summary We present EELS cross-section data of surface phonons on Ag(001) along
. The inelastic intensity is due to the contribution of different modes which are not solved by the EEL spectrometer. However,
the shape of the inelastic intensity shows a strong dependence on impact energy for all wave vectors, which allows tuning
the EELS on the different modes. The dependence of the loss frequency on impact energy is at variance with the one reported
previously for
, leading to the conclusion that other modes contribute to the inelastic intensity besidesS
1 andL
1 which dominate at
.
In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching. 相似文献
7.
The maximum number of non-vanishing and independent second order photoelastic coefficients required by the seven pentagonal
and the two icosahedral point groups 5(C5),
(S10),
(C5h
),
m2(D5h
), 52(D5), 5m(C5v
),
2m(D5d
); 235(I), 2/m
(I
h
)—that describe the quasicrystals symmetry groups in two and three dimensions—is obtained. The schemes of non-vanishing and
independent coefficients have been calculated and listed. Finally the results of this group-theoretical study are briefly
discussed. 相似文献
8.
We discuss the behavior of magnetically trapped antihydrogen (
) at temperatures relevant for gravity and spectroscopy experiments (well below 1 K) and the possibilities of attaining these
temperatures. Two possible options are considered. In the discussion of the first one, i.e.
as admixture in cold H gas, we develop the quantum-mechanical theory of
-H (and also
-H) elastic and rearrangement collisions at ultra-low (sub-Kelvin) energies, when s-wave scattering in the incoming channel
dominates. The rate constant of rearrangement leading to
decay turns out to be large, which makes the possibilities for
collisional cooling in H gas and
-H coexistence rather limited. As we show, the most promising is the other option, i.e.
atoms in the collisionless regime. For this regime the possibility of one-dimensional adiabatic cooling of
is demonstrated by using the example of the Ioffe trap. This phenomenon, interesting from the fundamental point of view,
offers the opportunity to cool
below 1 mK. 相似文献
9.
Bronisław Rozenfeld Stanisław Chabik 《Applied Physics A: Materials Science & Processing》1977,13(1):81-85
The angular correlation of annihilation radiation was measured for single crystals of Mg, Zn, and Cd in seven crystallographic
direction. The results of distribution of thez-component of the conduction electron momenta were compared with the crossectional-area distribution of the double Brillouin
zone for two directions [0001] and
. The results were analyzed also by the Mijnarend's method. The distributions of the electron momenta densities in the [0001]
and [
] directions are preliminarily discussed.
Supported by Instytut Niskich Temperatur i Badan Strukturalnych Polskiej Akademii Nauk we Wrocławiu (Institute for Low Temperature
and Structure Research, Polish Academy of Sciences in Wroclaw, Poland). 相似文献
10.
R. Shimizu 《Applied Physics A: Materials Science & Processing》1979,18(4):425-426
The statistics of the sputtering process, which has been used to explain sputterbroadening effect due to surface roughness,
has been treated with conditional probabilities. This results in the relationship,
, instead of
derived by S. Hofmann [Appl. Phys.9, 59 (1976)], where δz,z, and
are the depth resolution, sputtered depth and sputtering yield, respectively. 相似文献
11.
J. Nowotny M. Rekas W. Weppner 《Applied Physics A: Materials Science & Processing》1988,47(2):205-208
Thermoelectric power (TP) and electrical conductivity (EC) measurements were performed for YEa2Cu3Ox at 1128 K under controlled oxygen partial pressure varying between 50 and 105 Pa. Three regimes are observed for the electrical properties. At low
both TP and EC remain constant with
. In the medium range
sharp changes of both electrical parameters occur; TP changes sign from positive above 4×102 Pa to negative below this
value. In the high
region (>7.6×103 Pa) TP vs log
exhibits two slopes; 5.1 below 1.5×104 Pa and 8.4 above this
value. The slopes can be discussed in terms of the defect structure involving singly and doubly ionized oxygen vacancies below and above 7.6×103 Pa, respectively. 相似文献
12.
Gely F. Zharkov 《Central European Journal of Physics》2005,3(1):77-103
Self-consistent solutions of the nonlinear Ginzburg-Landau (GL) equations are investigated numerically for a superconducting
(SC) cylinder, placed in an axial magnetic field, with a single vortex on the axis (m=1). Two modes, which show the original state of the cylinder, SC or normal (s
0 andn
0), are studied. The field increase (FI) and the field decrease (FD) regimes are studied. The critical fields destroying the
SC state withm=1 are found in both regimes. It is shown that in a cylinder of radiusR and GL-parameter ϰ, there exist a number of solutions depending only on the radial co-ordinater corresponding to different states such as M,e, d, p,i, n,
,n
*, and the state diagram on the plane of the variables (ϰ,R) is described. The critical fields corresponding to intrastate transitions and the onset of hysteresis are obtained. The
critical fieldH
0(R) dividing the paramagnetic and diamagnetic states of the cylinder withm=1 is determined. The limiting fields of supercooling or superheating of the normal state at which the restoration of the
SC state occurs are established. It is shown, that (in both casesm=1,0) there exist two critical parameters,
and
, which divide bulk SC into three groups (with
and
), in accordance with the behavior in a magnetic field. The parameters
and
mark the boundary for the existence of a supercooled normal
-state in FD-regime and a superheated SC M-state in FI-regime respectively. It is shown, that the value
, which was claimed in a number of papers as related to type-I superconductors, is illusory.
We regret to inform that Professor Gely Zharkov passed away on 9th July 2004. 相似文献
13.
Garry Ludwig 《General Relativity and Gravitation》1983,15(11):1085-1097
In a recent paper it was shown how to construct, under certain circumstances, asymptotic (Newman-Unti) series expansions for
the spin-coefficient variables for real space-times from data obtained from a given left-flat space in an appropriate frame.
If these expansions represent asymptotically flat space-times the latter have the given left-flat space as their H space.
The method was described in a frame in which the asymptotic left-shear
was zero whereas
was not. For the discussion of algebraically special left-flat spaces it is more convenient to have
vanish and
remain nonzero. In this paper we determine all algebraically special left-flat spaces with diverging rays, utilizing Penrose's
conformal technique, and then show in detail how to find the “initial data” for the construction of asymptotic series expansions
for the corresponding real space-times. 相似文献
14.
C. Chris Wu 《Journal of statistical physics》1996,88(5-6):1399-1408
We consider an inhomogeneous contact process on a tree
of degreek, where the infection rate at any site isλ, the death rate at any site in
isδ (with 0 <δ ⩽ 1) and that at any site in
is 1. Denote by
the critical value for thehomogeneous model (i.e.,δ=1) on
and byϑ(δ, λ) the survival probability of the inhomogeneous model on
. We prove that whenk > 4, if
, a subtree embedded in
, with 1 ⩽σ ⩽ √k, then three existsδ
c
σ
strictly between (
) and 1 such that (
) whenδ >δ
c
σ
andϑ(δ, λ
c(
) > 0 whenδ <δ
c
σ
; ifS={o}, the origin of
, then
for anyδ ε (0, 1). 相似文献
15.
Yu. D. Fiveiskii 《Russian Physics Journal》1967,10(2):15-17
A method is given for calculating the cross section for neutralization of
for medium and heavy nuclei in terms of the optical potential, by addition of the neutralization operator
. The method is reasonable for energies
. Explicit forms are obtained for the differential and total cross sections for an optical potential in the form of a complex rectangular well, V(r) = V0., in which V0 differs; from zero within the nucleus and
. The value of Vo corresponding to the observed cross section for lead is derived. The dependence of the total cross section on V0 for copper is given.I am indebted to P. E. Nemirovskii for direction and valuable advice. 相似文献
16.
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
17.
Explicit evaluation of the following parameters has been carried out in the extraU (1) superstring inspired model: (i) As Mz2 varies from 555 GeV to 620 GeV and (m
t) CDF = 175.6 ± 5.7 GeV (Table 1): (a) SNew varies from -0.100 ± 0.089 to -0.130 ± 0.090, (b) TNew varies from -0.098 ± 0.097 to -0.129 ± 0.098, (c) UNew varies from -0.229 ± 0.177 to -0.253 ± 0.206, (d) Τz varies from 2.487 ± 0.027 to 2.486 ± 0.027, (e) ALR varies from 0.0125 ± 0.0003 to 0.0126 ± 0.0003, (f) A
FB
b
remains constant at 0.0080 ± 0.0007. Almost identical values are obtained for (m
t)D0 = 169 GeV (see table 2). (ii) Triple gauge boson vertices (TGV) contributions: AsMz
2 varies from 555 GeV to 620 GeV and (m
t) CDF = 175.6 ±5.7 GeV. (a)√s = 500 GeV, asymptotic case:
varies from -0.301 to -0.179;
varies from -0.622 to -0.379;
varies from +0.0061 to 0.0056;
varies from -3.691 to -2.186.
varies from +0.270 to +0.118;
varies from +0.552 to 0.238;
varies from +0.0004 to +0.0002;
remains constant at -0.110. (b)√s = 700 GeV, asymptotic case:
varies from -0.297 to -0.176;
varies from -0.609 to -0.370;
varies from -0.0082 to -0.0078;
varies from -3.680 to -2.171.√s = 700 GeV, nonasymptotic case:
varies from -0.173 to -0.299;
varies from-0.343 to -0.591;
varies from -0.005 to -0.011;
remains constant at -0.110.
The pattern of form factors values for√s = 1000, 1200 GeV is almost identical to that of√s= 700 GeV. Further the values of the form factors for (m
t)D0 (=169 GeV) follow identical pattern as that of (m
t) CDF form factors values (see tables 5, 6, 9, 10).
We conclude that the values of all the form factors with the exception of these of
,
are comparable or larger than theS, T values and therefore the TGV contributions are important while deciding the use of extraU (1) model for doing physics beyond standard model. 相似文献
18.
Mohammad Sami 《Pramana》1982,18(5):451-460
The associated production of Higgs particles andZ (W) bosons inpp and
collisions is studied. The total cross-section of the processpp
→HXl
+
l
− is estimated. 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.
R. Orbach 《Hyperfine Interactions》1989,49(1-4):325-333
The excitation dynamics of site diluted magnets can be described at low energies (long length scales) by magnons, and above
a crossover frequency, ωc, (short length scales) by fractons. The density of fracton states is given by
, where
is the fracton dimensionality. Dilution gives rise to a characteristic length ξ∝(p−p
c)ν, wherep
c is the critical concentration for (magnetic) percolation. The crossover frequency ωc is proportional to ξ-1[1+(θ/2)], where θ is the rate at which the diffusion constant decays with distance for diffusion on an equivalent network. A fractal
dimensionD describes the density of magnetic sites on the infinite network, and
. For percolating networks,
for all dimensions ≥2. Neutron scattering structure factor measurements by Uemura and Birgeneau compare well with calculations
using fracton concepts.
Magnons are extended at low energies, while the fracton states are geometrically localized, with a wave function envelope
proportional to exp
. Here,
is the fracton length scale at frequency ω. The exponentd
ϕ lies between 1 andd
min, the chemical length index (of the order of 1.6 in three dimensions). The localization of the magnetic excitations causes
a spread in the NMR relaxation rates. A given nuclear moment will experience only a limited set of fracton excitations, resulting
in an overall non-exponential decay of the NMR relaxation signal. When strong cross-relaxation is present, the relaxation
will be exponential, but the temperature dependence will be strongly altered from the concentrated result. 相似文献