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1.
E. Hbivnák 《Czechoslovak Journal of Physics》1960,10(9):633-644
The Bardeen-Shockley formula for the mobility of an electron or hole in a homopolar semi-conductor is derived in a different way to that in which its authors obtained it. The interaction energy of the electron with the acoustic lattice oscillations is derived in an original way. A new possibility for determining the energy gap is given.
-
- , , , . . .相似文献
2.
V. Čápek 《Czechoslovak Journal of Physics》1990,40(8):857-863
The symmetric spin-boson model without external field is treated for any type of coupling to the boson bath and any initial bath density matrix. With initially fully aligned spin (z (0)= =1), the proof is given that a partial relaxation (z (+) t1<) implies that there is no asymptotic-time (up-and-down) symmetry breaking (i.e. that z (+)=0). For the problem of a particle (interacting with free bosons) in a symmetric double well without spatial symmetry breaking before the infinite time limit, this means that att + the particle distribution becomes symmetric (irrespective of the full initial asymmetry) unless the particle fully remains (att + ) in Ihe starting well. 相似文献
3.
The paper contains an interpretation of the domain patterns found on iron whiskers. An explanation of the closure structure at the end of a whisker grown in the [111] direction is given on the basis of a quantitative analysis. Structures, which form on whiskers strained by axial pressure and bending, are also dealt with. The results are in good agreement with experiment.
, . [111]. , . .相似文献
4.
F. Janouch 《Czechoslovak Journal of Physics》1960,10(1):1-6
Double beta decay is discussed in relation to parity non-conservation. Two possible ways of neutrino-less double beta decay (allowed and forbidden) are investigated and the half-life of decay is calculated. For allowed transitions we obtain for Ca48 an estimatedT1/2=2×1019 years. The negative results of the experiments by Lukjanov et al., who give the valueT1/2=0.7×1019 years for the lower limit of the half-life of double beta decay of Ca48, cannot therefore be regarded as a definitive solution of the question, whether the neutrino is a Dirac or Majorana particle. Further study of double beta decay, aimed at finding higher values of the lower limit of half-life, are of considerable importance for theory.
In conclusion the author thanks Prof. I. S. apiro for suggesting this work and help in elaborating it. 相似文献
-
- . - ( ) . 48 T1/221019 . - . [1] ( - 48 T1/2 0,71019 ), , . - .
In conclusion the author thanks Prof. I. S. apiro for suggesting this work and help in elaborating it. 相似文献
5.
Anders Martin-Löf 《Communications in Mathematical Physics》1973,32(1):75-92
For the Ising model with nearest neighbour interaction it is shown that the spin correlations
A
B
-
A
B
decrease exponentially asd(A, B) in a pure phase when the temperature is well belowT
c. This is used to prove that the free energyF(,h) is infinitely differentiable in and has one sided derivatives inh of all orders forh=0. The bounds are also used to prove that the central limit theorem holds for several variables such as e.g. the total energy and the total magnetization of the system, the limit distribution being gaussian with variances determined by the second derivatives ofF(,h). 相似文献
6.
Experimental results on the dynamical polarization of protons in various polymers irradiated by neutrons are recapitulated. The measurements were performed at liquid nitrogen temperatures. The dependence was investigated of the degree of polarization on the microwave power, on the irradiation dose and on the change in frequency of the nuclear magnetic resonance. The maximum enhancement of polarization was obtained for polyethylene of a density 0·95 g/cm3 and was equal to 30.
In conclusion we thank R. Tichý for assistance in the measurements and S. Roda for help in the construction of the apparatus. 相似文献
SOLID EFFECT
. . , . , 30, 0,95 g/cm3.
In conclusion we thank R. Tichý for assistance in the measurements and S. Roda for help in the construction of the apparatus. 相似文献
7.
On the concept of attractor 总被引:14,自引:0,他引:14
John Milnor 《Communications in Mathematical Physics》1985,99(2):177-195
This note proposes a definition for the concept of attractor, based on the probable asymptotic behavior of orbits. The definition is sufficiently broad so that every smooth compact dynamical system has at least one attractor. 相似文献
8.
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
9.
We consider the problem of directed polymers in a random medium of a finitedimensional lattice. In the high-temperature phase of this system it is known that the annealed and quenched free energies coincide. Upper bounds on the transition temperature to a low-temperature phase had previously been obtained by calculating the first two moments Z and Z2 of the partition function. We improve these bounds by estimating noninteger moments Z
for 1<<2. 相似文献
10.
A. M. Mariz F. van Wijland H. J. Hilhorst S. R. Gomes Júnior C. Tsallis 《Journal of statistical physics》2001,102(1-2):259-283
The Riemann walk is the lattice version of the Lévy flight. For the one-dimensional Riemann walk of Lévy exponent 0<<2 we study the statistics of the support, i.e., set of visited sites, after t steps. We consider a wide class of support related observables M(t), including the number S(t) of visited sites and the number I(t) of sequences of adjacent visited sites. For t we obtain the asymptotic power laws for the averages, variances, and correlations of these observables. Logarithmic correction factors appear for =2/3 and =1. Bulk and surface observables have different power laws for 1<2. Fluctuations are shown to be universal for 2/3 <2. This means that in the limit t the deviations from average M(t)M(t)–M-0304;(t-0304;) are fully described either by a single M independent stochastic process (when 2/3 <1) or by two such processes, one for the bulk and one for the surface observables (when 1<<2). 相似文献
11.
12.
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
13.
I. S. Nurgaliev 《Russian Physics Journal》1982,25(7):672-675
The solution r2 for a scalar field (gravitational constant), which is asymptotically exact for supercompact configurations and which Saakyan and Mnatsakanyan obtained from the numerical solution of the hydrostatics equations in the Newtonian approximation of the Jordan-Brans-Dicke theory, is used to study the gravitational stability of such configurations. We have found the stability condition 2/3 for polytropic configurations ( is the polytropic exponent) instead of 4/3, which is known for configurations of low compactness. Analytic solutions of the equations of internal structure are found for configurations which are intermediate with respect to stability (=2/3) and for some other important series of configurations.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 98–102, July, 1982.In conclusion, the present author expresses his indebtedness and gratitude to V. N. Ponomarev, for assistance in executing the work. 相似文献
14.
Jan Fischer 《Czechoslovak Journal of Physics》1956,6(1):65-72
. . , . , . , . coo , 13. 5. 1954 . - . 相似文献
15.
On the planar hexagonal lattice
, we analyze the Markov process whose state (t), in
, updates each site v asynchronously in continuous time t0, so that
v
(t) agrees with a majority of its (three) neighbors. The initial
v
(0)'s are i.i.d. with P[
v
(0)=+1]=p[0,1]. We study, both rigorously and by Monte Carlo simulation, the existence and nature of the percolation transition as t and p1/2. Denoting by +(t,p) the expected size of the plus cluster containing the origin, we (1) prove that +(,1/2)= and (2) study numerically critical exponents associated with the divergence of +(,p) as p1/2. A detailed finite-size scaling analysis suggests that the exponents and of this t= (dependent) percolation model have the same values, 4/3 and 43/18, as standard two-dimensional independent percolation. We also present numerical evidence that the rate at which (t)() as t is exponential. 相似文献
16.
O. Costa de Beauregard 《Foundations of Physics》1985,15(8):871-887
Quite often the compatibility of the EPR correlations with the relativity theory has been questioned; it has been stated that the first in time of two correlated measurements instantaneously collapses the other subsystem; it has been suggested that a causal asymmetry is built into the Feynman propagator. However, the EPR transition amplitude, as derived from the S matrix, is Lorentz andCPT invariant; the correlation formula is symmetric in the two measurements irrespective of their time ordering, so that the link of the correlations is the Feynman zigzag, and that causality isCPT invariant at the microlevel; finally, although the Feynman propagator has theP andCT symmetries, no causal asymmetry follows from that. As for Stapp's views concerning process and becoming, and his Whiteheadean concept of an advancing front, I object that they belong to factlike macrophysics, and are refuted at the microlevel by the EPR phenomenology, which displays direct Fokker-like space-time connections. The reason for this is a radical one. The very blending of a space-time picture and of a probability calculus is a paradox. The only adequate paradigm is one denying objectivity to space-time—but this, of course, is also required by the complementary of the x and the k pictures, which only look compatible at the macrolevel. Therefore, the classical objectivity must yield in favor of intersubjectivity. Only the macroscopic preparing and measuring devices have factlike objectivity; the transition of the quantal system takes place beyond both thex and thek 4-spaces. Then, the intrinsic symmetries between retarded and advanced waves, and statistical prediction and retrodiction, entails that the future has no less (but no more) existence than the past. It is the future that is significant in creative process, the elementary forms of which should be termed precognition or psychokinesis—respectively symmetric to the factlike taboos that we can neither know into the future nor act into the past. It is gratifying that Robert Jahn, at the Engineering School of Princeton University, is conducting (after others) conclusive experiments demonstrating low level psychokinesis—a phenomenon implied by the very symmetry of the negentropy-information transition. So, what pierces the veil of maya is the (rare) occurrence of paranormal phenomena. The essential severance between act and potentia is not a spacelike advancing front, but the out of and the into factlike space-time. Finally, I do not feel that an adequate understanding of the EPR phenomenology requires going beyond the present status of relativistic quantum mechanics. Rather, I believe that the potentialities of this formalism have not yet been fully exploited. 相似文献
17.
In order to model any macroscopic system, it is necessary to aggregate both spatially and taxonomically. If average processes are assumed, then kinetic equations of population dynamics can be derived. Much effort has gone into showing the important effects introduced by non-average effects (fluctuations) in generating symmetry-breaking transitions and creating structure and form. However, the effects of microscopic diversity have been largely neglected. We show that evolution will select for populations which retain variability, even though this is, at any given time, loss-making, predicting that we shall not observe populations with optimal behavior, but populations which can learn. This lesser short-term efficiency may be why natural diversity is so great. Evolution is seen to be driven by the noise to which it leads. 相似文献
18.
František Lukeš 《Czechoslovak Journal of Physics》1956,6(4):359-363
(GaSb), - 120–340 °K. : E2=(0,773–0,75.10–6
T
2) ., - . 相似文献
19.
Ralf P. Averbeck 《Czechoslovak Journal of Physics》1995,45(7-8):637-643
A systematic study of neutral meson production in heavy-ion reactions at 2 GeV/u was started with a12C+12C experiment using the photon spectrometer TAPS. Special emphasis is put on the possible observation of the-meson in a heavy-ion reaction exploiting the decay channel 0.Presented at the International School-Workshop Relativistic Heavy-Ion Physics, Prague (Czech Republic), 19–23 September 1994. 相似文献
20.
Antonín Rrokeš 《Czechoslovak Journal of Physics》1957,7(3):320-325
50–100 , 1–2 1–10 . - . - . , , - . -. 相似文献