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1.
We show that ifb andb are two boundary conditions (b.c.) for general spin systems on d such that the difference in the energies of a spin configuration in d is uniformly bounded, |H ,b ()–H ,b()|C < , then any infinite-volume Gibbs states and obtained with these b.c. have the same measure-zero sets. This implies that the decompositions of and into extremal Gibbs states are equivalent (mutually absolutely continuous). In particular, if is extremal,=. Application of this observation yields in an easy way (among other things) (a) the uniqueness of the Gibbs states for one-dimensional systems with forces that are not too long-range; (b) the fact that various b.c. that are natural candidates for producing non-translation-invariant Gibbs states cannot lead to such an extremal Gibbs state in two dimensions.Supported in part by NSF Grant PHY 78–15920 and by the Swiss National Foundation For Scientific Research.  相似文献   

2.
The shell model without the nuclear centre-of-mass spuriosity is applied to 16,17,18O isotopes, predicting the bunched and dense hypernuclear energy levels. The (K, ) reaction cross sections are calculated at several angles with the =0° ones being in good agreement with the experimental data on 16O and 18O. The realistic N effective interaction derived on the basis of the Nijmegen Model-D is employed and the N J=0+ pairing correlation is found to be repulsive, which is reflected in the18O(K,) 18O excitation function.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985.The author is thankful to Professor H. Bando. Professor Y. Yamamoto and Professor H. Ikeda for collaboration and useful discussion.  相似文献   

3.
The binding energy of the double hypernucleus Be10 analyzed using an -particle model. A relationship is found between B, the binding energy of two -particlcs, and ¯V, the - potential integral. For the experimental value B = 17.5 Me V ¯V varies from 250 to 850 MeV-F3 according to the form of the - potential used.In conclusion, I wish to thank S. N. Kryuchkova for carrying out these calculations on a Minsk-2 electronic computer. I also wish to thank my senior colleague, V. A. Filimonov, for his support in the completion of the present work.  相似文献   

4.
The decay probabilities of the hypernuclei H4 and He4 are calculated within the framework of the mesonless decay model of hypernuclei with direct conversion of to a neutron. All possible channels are considered: H4 tn, d2n, p3n and He4 He3n, tp, dd, dpn, 2p2n. Interaction in the final state between the decay products was neglected, but Pauli's principle for the final identical particles was taken into account completely. The predominant decay channels are three- and four-particle paths. The results are compared with experimental data.Translated from Izvestiya VUZ. Fizika, No. 1, pp. 86–94, January, 1972.  相似文献   

5.
We propose a simple method for determining the redshift z m at which the angular size of an extragalactic source with fixed proper diameter takes its minimal value. A closed analytical expression, which is often convenient for numerical evaluation is derived. The method is exemplified with the following FRW type expanding universes: the open matter dominated models ( = 0), a critical density model with cosmological constant ( 0), and the class of scalar field cosmologies proposed by Ratra and Peebles. The influence of systematic evolutionary effects is briefly discussed.  相似文献   

6.
Zusammenfassung Es wird der Proze des Anhaftens von Exzitonen an Vakanzen und F-Zentren in den Ionenkristallen studiert. Die Bewegung der Exzitonen im Felde der Vakanz und des F-Zentrums wird in adiabatischer Annäherung untersucht. Mit Hilfe der klassischen Methoden werden die Wirkungsquerschnitte des Anhaftens des Exzitons an den Vakanzen und F-Zentren bestimmt und diskutiert.
F- . F- . F- .
  相似文献   

7.
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.
E. Hiyama 《Few-Body Systems》2004,34(1-3):79-84
From the viewpoint of critical stability, we discuss the three- and four-body structure of 6He, 7He, 4He, and 4H. With the + + N three-body model, 6He is found to have a three-layer structure of the matter distribution: core, a skin and neutron halo. Also the level structure of 7He with the three-body model of 5He + n + n is predicted. This stimulates a new study of neutron-rich and proton-rich hypernuclei. By performing a four-body calculation with both NNN and NNN channels and with both NN and NNN channels, we show that the N-N and -N couplings are very important in critical stability of few-body hypernuclear systems.  相似文献   

9.
A system of coordinates on a set of selfdual lattices in a two-dimensionalp-adic symplectic space (V,) is suggested. A unitary irreducible representation of the Heisenberg group of the space (V,) depending on a lattice (an analogue of the Cartier representation) is constructed and its properties are investigated. By the use of such representations for three different lattices one defines the Maslov index =(1,2,3) of a triple of lattices. Properties of the index are investigated and values of in coordinates for different triples of lattices are calculated.  相似文献   

10.
The constant-amplitude solutions with wavelength of a semiclassical laser model exhibit three different instabilities in the (, )-plane for pumpparameters above threshold.  相似文献   

11.
This paper relates two mathematical concepts of long-range order of a set of atoms , each of which is based on restrictions on the set of interatomic distances –. A set in n is aMeyer set if is a Delone set and there is a finite setF such that . Meyer proposed that such sets include the possible structures of quasicrystals. He obtained a structure theory for such sets, which reformulates results that he obtained in harmonic analysis around 1970, and which relates these sets to cut-and-project sets. In geometric crystallography V.I. Galiulin introduced the concept ofquasiregular set, which is a set such that both and – are Delone sets. This paper shows that these two concepts are identical.  相似文献   

12.
13.
The above problem is met, for example, in the case of the collision of molecules of the atmosphere with an artificial earth satellite and leads to the problem of determining the probability distribution of the absolute value of the vector sum of a constant vector and a Maxwell vector (the latter being a vector, whose rectangular components are distributed normally, with the same standard deviation and mean value zero). The resultant probability density is given by equation (18), the complement to the distribution function by (24), the mean value by (27) and the variance by (31). These results are obtained by transforming the corresponding three-dimensional normal distribution to spherical co-ordinates and integrating over the co-ordinate angles and , which yields the required probability density; the other results are then obtained from it by the usual methods.
, , (. . , ). (18), -(24), -(27) (31). , ; .
  相似文献   

14.
( ) , . , . [1] , , .
Partially inserted block in square lattice
The paper gives a theory of the partially inserted block (control rod) in a reactor of finite height, consisting of a square lattice of fuel blocks and a moderator. The partially inserted block replaces the block of the original lattice which was located in the axis of cylindrical symmetry of the reactor. The results obtained agree with the relations for a homogeneous medium in paper [1] and are thereby justified for homogeneized reactors.
  相似文献   

15.
16.
The paper gives the experimental results of studying the spectral composition of thermoluminescence in the different maxima in photo-chemically coloured pure NaCl crystals or NaCl-crystals containing Cu in different concentrations.
NaCl
NaCl .
  相似文献   

17.
An experimental investigation is made into the domain structure of cobalt whiskers by the colloid technique. A new type of domain structure was found; the width of the domains is studied as a function of the thickness of the whisker. This dependence follows a two-thirds power law and does not agree with existing theories which predict a half power law.
. . , .


In conclusion the authors wish to thank V. Janovec and F. Kroupa for valuable remarks and A. Tahalová for help in growing the whiskers.  相似文献   

18.
During a systematic investigation of the parameters of a moving stratification in a glow discharge in helium and neon it was found that the spatial period of the striations is a simple, unique function of the d-c (constant) component of the longitudinal electric field strengthE. It was found that this dependence is hyperbolic and that the simple relation (1) or (2) thus holds. In the relation has the significance of a potential fall between the corresponding points of two neighbouring striations and in the measured range of pressures, currents and diameters of discharge tubes it depends only on the sort of gas and type of striations.
, , E. , , , (1) (2). (1) (2). , .


The principal results of this work were reported at the 1st conference on electronics in Prague on April 26, 1960.  相似文献   

19.
The charge fluctuations in classical Coulomb systems   总被引:1,自引:0,他引:1  
We study the asymptotic behavior of the charge fluctuations (Q – (Q )2 in infinite classical systems of charged particles, and show, under certain clustering assumptions, that if the charge fluctuations are not extensive, then they are necessarily of the order of the surface ¦¦. Moreover, when the canonical sum rules that are typical for equilibrium states of particles interacting with long-range forces hold true, we prove a central limit theorem for the normalized charge variable ¦¦–1/2((Q – (Q )) in two and three dimensions. In one dimension, the probability distribution of the charge itself converges. The latter case is illustrated by the example of the one-dimensional Coulomb gas.  相似文献   

20.
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.
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   

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