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1.
Vlastislav Červený 《Czechoslovak Journal of Physics》1959,9(1):101-111
Zusammenfassung In der vorliegenden Arbeit werden die Kopfwellen untersucht, die beim Auffallen einer harmonischen Schall-Kugelwelle auf die Ebene Grenzfläche zwischen zwei flüssigen Medien entstehen. Vorausgesetzt wird, daß die Grenzfläche schwach ist, d. h. daß die Geschwindigkeit der Schallwellen im Medium mit der Erregungsquelle nur um weniges kleiner ist als die Geschwindigkeit der Schallwellen im Medium ohne die Quelle.
,
, . , , . . .相似文献
2.
E. Žižka 《Czechoslovak Journal of Physics》1960,10(4):327-333
. , 760 mm . .
Formation of cathode spots and current density distribution in cathode spots of short-time high-intensity electric discharge
The connection between the current density distribution in a spot and the vapour jets was found for a short-time high-intensity electric discharge by studying the structure of partial cathode traces and measuring the current density on the cathode. The variation of the current density on the spot with the current gradient was also found and the etching of the cathode surface with ionic bombardment at a pressure of 760 mm Hg was observed.相似文献
3.
Nuclear emulsions were used to study the energy spectrum and forward-backward asymmetry of neutrons from the Co59(p,n) reaction forE
p
6·5 MeV. It was found that the decay of the compound nucleus makes a maximum contribution of 50% to the reaction yield. Energies of some excited states of the Ni59 nucleus were also determined.
The authors would like to thank all those who helped in this work, particularly all members of the cyclotron group of the Nuclear Research Institute of the Czechoslovak Academy of Sciences, who so willingly helped with the irradiation, and H. Koutová from the Faculty of Technical and Nuclear Physics, who carefully measured the emulsions. Our thanks are also due to R. Krejová from the Faculty of Technical and Nuclear Physics for developing the emulsions and J. Kopecký from the Nuclear Research Institute for providing the cobalt target. 相似文献
Co59(p,n) E p 6,5 MeV
- Co59(p,n) E p 6,5 MeV. , 50%. , Ni59.
The authors would like to thank all those who helped in this work, particularly all members of the cyclotron group of the Nuclear Research Institute of the Czechoslovak Academy of Sciences, who so willingly helped with the irradiation, and H. Koutová from the Faculty of Technical and Nuclear Physics, who carefully measured the emulsions. Our thanks are also due to R. Krejová from the Faculty of Technical and Nuclear Physics for developing the emulsions and J. Kopecký from the Nuclear Research Institute for providing the cobalt target. 相似文献
4.
Ola Bratteli Richard H. Herman Derek W. Robinson 《Communications in Mathematical Physics》1978,59(2):167-196
For automorphism groups of operator algebras we show how properties of the difference
t
– '
t
are reflected in relations between the generators , . Indeed for a von Neumann algebraM with separable predual we show that if t – 't 0.28 for smallt, then = 0(+)°-1 where is an inner automorphism ofM and is a bounded derivation ofM. If the difference
t
– '
t
=O(t) ast ; 0, then = + and if
t
– '
t
0.28 for allt then =. We prove analogous results for unitary groups on a Hilbert space andC
0,C
0
*
groups on a Banach space.This paper subsumes an earlier work of the same title which appeared as a report from Z.I.F. der Universität BielefeldWith partial support of the U.S. National Science Foundation 相似文献
5.
Within the general framework ofC*-algebra approach to mathematical foundation of statistical mechanics, we prove a theorem which gives a natural explanation for the appearance of the chemical potential (as a thermodynamical parameter labelling equilibrium states) in the presence of a symmetry (under gauge transformations of the first kind). As a symmetry, we consider a compact abelian groupG acting as *-automorphisms of aC*-algebra
(quasi-local field algebra) and commuting (elementwise) with the time translation automorphisms
t
of
. Under a technical assumption which is satisfied by examples of physical interest, we prove that the set of all extremal
t
-KMS states (pure phases) ofG-fixed-point subalgebra
(quasi-local observable algebra) of
satisfying a certain faithfulness condition is in one-to-one correspondence with the set of all extremalG-invariant
t
·
t
-KMS states – of
with varying over one-parameter subgroups ofG (the specification of being the specification of the chemical potential), where the correspondence is that the restriction of – to
is . 相似文献
6.
Vladimír Dvořák 《Czechoslovak Journal of Physics》1959,9(6):710-716
The possibility of explaining the existence of a surface layer on BaTiO3 crystals by the presence of Schottky defects in the crystal is investigated. The magnitude of the potential difference between the surface and the interior of the crystal and the thickness of the surface layer, which at temperatures of over 400°C agrees with the measured values, are calculated for the cubic phase from a simplified ionic model.
In conclusion the author would like to thank Dr. M. Trlifaj and V. Janovec, candidates of physics and mathematics, for valuable remarks. 相似文献
BaTiO3
iO3 . , 400° .
In conclusion the author would like to thank Dr. M. Trlifaj and V. Janovec, candidates of physics and mathematics, for valuable remarks. 相似文献
7.
G. Benfatto C. Marchioro E. Presutti M. Pulvirenti 《Journal of statistical physics》1980,22(3):349-362
We consider an anharmonic crystal described by variablesS
x
,x
d
,S
x
, with one-body interaction ¦S
x
¦
and nearest neighbor (n.n.) two body interaction ¦S
x
–S
y
¦. We prove that, for
d
bounded, , where
is the correlation function for the free boundary condition Gibbs state in ,>0 and are suitable constants independent of and . This generalizes previous results obtained in the case.Research partially supported by Consiglio Nazionale delle Ricerche. 相似文献
8.
0,6 25 . , , . , 13,4 20,4 , , , . . , . .
A contribution to the absorption spectrum of amorphous selenium in the infra-red region
The absorption spectrum of amorphous selenium was measured in the region of 0·6 to 25 on samples of high purity and homogeneity. The absorption bands of amorphous and liquid sulphur were also measured in the same wave-length region. The measurements showed that the absorption bands 13·4 and 20·4 , appearing in the spectrum of amorphous selenium, are its intrinsic absorption bands and are not caused by impurities, as some authors think. The similarity between the infra-red spectra of selenium and sulphur is shown.相似文献
9.
In the present article, undoped and Codoped Mtype Srhexaferrites have been prepared at low temperatures down to 980
C for the first time by the usual ceramic procedure and sintering technique. On these materials, a CoK
Xray diffraction analysis and the room temperature 57Fe Mössbauer spectroscopy (MES) were carefully performed. The results obtained are described and interpreted. The mechanism of Co substitution partially in place of iron and the site of its occupancy were proposed and established. 相似文献
10.
G. Dorda 《Czechoslovak Journal of Physics》1960,10(11):820-829
A study was made of the influence of the relative humidity (from 0.5–90%) on the surface conductivity of bothp- andn-type germanium having differing resistivity. It was. found that the range of changes in the surface potential did not depend on the volume properties of germanium. An analysis of the experimental results shows that the surface potential has values approximately in the range from
s
=–3kT/q to
s
=+5kT/q for a change in humidity from 0.5 to 90%. Assuming that the Fermi level changes on the outer side of the oxide layer by approximately the same value as on the germaniumgermanium oxide boundary as a result of the increase and decrease of slow states, it follows that the levels of the slow centres are considerably distant from the Fermi level during the whole humidity range. It is also shown that on the first monomolecular layer of adsorbed water there is an increment of (7.5±0.8) x 1010 donor levels per cm2. This increase in levels either decreases with the number of adsorbed monomolecular layers of water and for 90% humidity has approximately the value 2×1010 cm–2 or remains almost unchanged with the number of layers, if it is assumed that for
s
=6.0kT/q the Fermi level passes through the centres of adsorbed water.
In conclusion the author thanks Dr. J. Taue for instigating this work and S. Koc, C. Sc., for remarks and the interest with which he followed the work. He also thanks A.Müller for measuring the Hall constant in the samples. 相似文献
0,5 90% p n. . , s =– 3kT/q s =+ 5kT/q 0,5 90%. , - , , . , (7,5 ±0,8). 1010 cm2. 90% . 2. 1010 cm–2 , , , s =6,0kT/q .
In conclusion the author thanks Dr. J. Taue for instigating this work and S. Koc, C. Sc., for remarks and the interest with which he followed the work. He also thanks A.Müller for measuring the Hall constant in the samples. 相似文献
11.
In ordinary quantum mechanics for finite systems, the time evolution induced by Hamiltonians of the form
is studied from the point of view of *-automorphisms of the CCRC*-algebra
(see Ref. [1, 2]). It is proved that those Hamiltonians do not induce *-automorphisms of this algebra in the cases: a)
and b)V L
(,dx) L
1 (,dx), except when the potential is trivial. 相似文献
12.
P. Kratochvíl 《Czechoslovak Journal of Physics》1960,10(12):927-930
The applicability of Tiller's considerations on the production of dislocations is proved. The density of dislocations appearing during impurity microsegregation increases with increasing rate of growth as a consequence of the corresponding change in the effective distribution coefficient. The real value of C at the microsegregation boundaries is at least twice as great as the average value of the concentration of impurities in the crystal in question.
. , , . C , .相似文献
13.
Radko Seidl 《Czechoslovak Journal of Physics》1959,9(5):597-605
Zusammenfassung Es werden die zwei einfachsten Fälle der Exoelektronenemission untersucht und auf Grund dessen geeignete Verfahren zur Verarbeitung der Versuchsergebnisse vorgeschlagen.
.相似文献
14.
15.
L. Dunajský 《Czechoslovak Journal of Physics》1961,11(12):871-873
, .
Energy flux through thin dielectric film when total reflection is disturbed
It is shown that the energy flux through a thin dielectric film when total reflection is disturbed is brought about by the interference Poynting vector.相似文献
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17.
18.
Anastasios Mallios Ioannis Raptis 《International Journal of Theoretical Physics》2003,42(7):1479-1619
We continue recent work (Mallios and Raptis, International Journal of Theoretical Physics
40, 1885, 2001; in press) and formulate the gravitational vacuum Einstein equations over a locally finite space-time by using the basic axiomatics, techniques, ideas, and working philosophy of Abstract Differential Geometry. The main kinematical structure involved, originally introduced and explored in (Mallios and Raptis, International Journal of Theoretical Physics
40, 1885, 2001), is a curved principal finitary space-time sheaf of incidence algebras, which have been interpreted as quantum causal sets, together with a nontrivial locally finite spin-Loretzian connection on it which lays the structural foundation for the formulation of a covariant dynamics of quantum causality in terms of sheaf morphisms. Our scheme is innately algebraic and it supports a categorical version of the principle of general covariance that is manifestly independent of a background
-smooth space-time manifold M. Thus, we entertain the possibility of developing a fully covariant path integral-type of quantum dynamical scenario for these connections that avoids ab initio various problems that such a dynamics encounters in other current quantization schemes for gravity—either canonical (Hamiltonian) or covariant (Lagrangian)—involving an external, base differential space-time manifold, namely, the choice of a diffeomorphism-invariant measure on the moduli space of gauge-equivalent (self-dual) gravitational spin-Lorentzian connections and the (Hilbert space) inner product that could in principle be constructed relative to that measure in the quantum theory—the so-called inner product problem, as well as the problem of time that also involves the Diff(M) structure group of the classical
-smooth space-time continuum of general relativity. Hence, by using the inherently algebraico—sheaf—theoretic and calculus-free ideas of Abstract Differential Geometry, we are able to draw preliminary, albeit suggestive, connections between certain nonperturbative (canonical or covariant) approaches to quantum general relativity (e.g., Ashtekar's new variables and the loop formalism that has been developed along with them) and Sorkin et al.'s causal set program. As it were, we noncommutatively algebraize, differential geometrize and, as a result, dynamically vary causal sets. At the end, we anticipate various consequences that such a scenario for a locally finite, causal and quantal vacuum Einstein gravity might have for the obstinate (from the viewpoint of the smooth continuum) problem of
-smooth space-time singularities. 相似文献
19.
André Lichnerowicz 《Letters in Mathematical Physics》1987,13(4):331-344
In terms of the Dirac operator P, we introduce on any field a first-order operator D and show that the operator (–) on the spinors (=(n/4(n–1))R; dim W=n) is positive. By means of a universal formula, we show that, on a compact spin manifold of dimension 3, the Hijazi inequality [8] holds for every spinor field such that (P, P) =
2(, ) (=const.). In the limiting case, the manifold admits a Killing spinor which can be evaluated in terms of . Different properties of spin manifolds admitting Killing spinors are proved. D is nothing but the twistor operator. 相似文献
20.
Horng-Tzer Yau 《Communications in Mathematical Physics》1996,181(2):367-408
Let
denote the grand canonical Gibbs measure of a lattice gas in a cube of sizeL with the chemical potential and a fixed boundary condition. Let
be the corresponding canonical measure defined by conditioning
on
. Consider the lattice gas dynamics for which each particle performs random walk with rates depending on near-by particles. The rates are chosen such that, for everyn andL fixed,
is a reversible measure. Suppose that the Dobrushin-Shlosman mixing conditions holds for
forall chemical potentials . We prove that
for any probability densityf with respect to
; here the constant is independent ofn orL andD denotes the Dirichlet form of the dynamics. The dependence onL is optimal.Research partially supported by U.S. National Science Foundations grant 9403462, Sloan Foundation Fellowship and David and Lucile Packard Foundation Fellowship. 相似文献