共查询到20条相似文献,搜索用时 31 毫秒
1.
A. G. Lipnitskii A. V. Nikiforov V. M. Silkin E. V. Chulkov 《Russian Physics Journal》1991,34(10):888-893
The surface electronic band structure of the Pb (001) was calculated using the self-consistent, first-principles linear-augmented-plane-wave method and the norm-conserving pseudopotentiai method. In the nonrelativistic case, forbidden gaps appear above and below the Fermi levelin the bulk projected band structure of lead. An occupied surface state at the
point and two surface states in a wide forbidden gap above EF are found. A characteristic feature of the electronic structure of the Pb (001) surface is the absence of a surface state within the forbidden S-P gap in the vicinity of the
point. The inclusion of scalar-relativistic effects leads to the merger of several S-P gaps into one wide gap extending throughout the entire Brillouin zone. At the same time, the occupied state at point
extends to point
and its energy decreases by 2 eV. New, relatively weak surface states in the
direction and unoccupied states in the vicinity of the
point appear. An unoccupied surface state is found at the bottom of the forbidden gap at point
. Including the contribution of the spinorbit pseudopotentiai leads to the appearance of two-spin orbit gas; however, the surface level structure is practically unchanged (except for the disappearance of the unoccupied surface state of Pz-symmetry at point
).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 47–53, October, 1991. 相似文献
2.
O. V. Kibis 《Russian Physics Journal》1997,40(8):780-783
Taking the inelastic nature of the interaction of electrons with acoustic phonons into account is crucial in crystals having
a conduction band width Δɛ comparable to the maximum acoustic phonon energy
. In view of this, the laws of conservation of energy and wave vector impose stringent constraints on possible electron scattering
processes, and single-phonon scattering becomes impossible for
. The phonon contribution to the resistance may be negligible, therefore, in narrow-band conductors.
Novosibirsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, p. 78–82, August, 1997. 相似文献
3.
A. M. Ermolaev 《Hyperfine Interactions》1989,44(1-4):375-386
Partial and total close-coupled semiclassical (impact parameter) cross sections and total classical Monte-Carlo cross sections
for interactions in
and
, p+H collisions are computed in the intermediate keV range for antiprotons,
, up to 100 keV lab. Total cross sections for antihydrogen,
, formation are found to be large, 10−20×10−16 cm2 in a wider energy range than was anticipated earlier, up to some 20 keV lab. New estimates of cross sections for ionisation
of atomic hydrogen by antiproton impact are reported for the low-energy range 1–30 keV lab where they are 10−20×10−17 cm2, being much larger than the corresponding cross sections for ionisation of hydrogen by proton impact. Data for excitation
of H by
impact is also presented. 相似文献
4.
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
5.
The existence of a topological double-covering for the GL(n, R) and diffeomorphism groups is reviewed. These groups do not
have finite-dimensional faithful representations. An explicit construction and the classification of all
(n, R), n=3,4 unitary irreducible representations is presented. Infinite-component spinorial and tensorial
fields, “manifields”, are introduced. Particle content of the ladder manifields, as given by the
(3, R) “little” group, is determined. The manifields are lifted to the corresponding world spinorial and tensorial manifields
by making use of generalized infinite-component frame fields. World manifields transform w.r.t. corresponding
representations, which are constructed explicitly.
Supported in part by the Science Foundation (Belgrade). 相似文献
6.
Yu. M. Kasumov 《Russian Physics Journal》1968,11(9):68-73
The annihilation of a lepton-antilepton pair into a pair of
or
-hyperons is examined. Expressions are found for the differential cross section in the CM system with an account of the strange-particle form factors, and with separate accounts of the random polarization of the initial and final particles.In conclusion, the author thanks Doctor of Physicomathematical Sciences B. K. Kerimov for suggesting the topic and for valuable advice. 相似文献
7.
D. H. D. West V. J. McBrierty C. F. G. Delaney 《Applied Physics A: Materials Science & Processing》1975,7(3):171-174
The decay time τl ofo-Ps by the electron pickoff process has been measured in polystyrene as a function of molecular weight. For samples below
their glass transition temperature τl is essentially independent of
. In the low molecular weight region,
, τl increased with decreasing
in line with earlier theoretical predictions. The overall behaviour reflects closely the dependence of free volume on
. The effects of molecular motion on τl are examined and it is concluded that the decay time is insensitive to such motions in polystyrene below the melting point,
in contrast to what is observed in polytetrafluoroethylene. 相似文献
8.
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
9.
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
10.
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
11.
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
12.
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
13.
14.
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
15.
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
16.
Peter Herczeg 《Zeitschrift fur Physik C Particles and Fields》1992,56(Z1):S129-S134
We review the available information on the identity of the neutrino states emitted in muon decay, and discuss the exotic decay
. 相似文献
17.
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
18.
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
19.
We study analogues of the Yangian of the Lie algebra
for the other classical Lie algebras
and
. We call them twisted Yangians. They are coideal subalgebras in the Yangian of
and admit homomorphisms onto the universal enveloping algebras U(
) and U(
) respectively. In every twisted Yangian we construct a family of maximal commutative subalgebras parametrized by the regular semisimple elements of the corresponding classical Lie algebra. The images in U(
) and U(
) of these subalgebras are also maximal commutative. 相似文献
20.
Two functionals
and
are introduced forC
*-dynamical systems with invariant states and stationary channels. It is shown that the Kolmogorov-Sinai-type theorems hold for these functionals
and
. Our functionals
and
are set within the framework of quantum information theory and generalize a quantum KS entropy by CNT and the mutual entropy by Ohya. 相似文献