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1.
The influence of the concentration of an activator (C NaI) and of plastic deformation on a change in the contribution of a slow component to the decay of the -scintillations of CsI–Na crystals was investigated, as well as the influence of C NaI on a change in the shape of the luminescence excitation spectrum in the region of absorption of activator centers (AC) and of vacancy-related centers (VRC) and also on a change in the intercenter time of deexcitation of the centers indicated. It is shown that AC and VRC participate in the photoluminescence and -scintillations of CsI–Na crystals. In the -scintillations, AC are responsible for the component 1 = 370 nsec, whereas the components 1 = 460 nsec and 2 2 sec are associated with VRC. The reduction of 1 from 770 to 560 nsec with an increase in C NaI from 2·10–3 to 3·10–2 mole% and from 570 to 470 nsec after plastic deformation of the crystals ( = 5%) along the 111 axis is caused by a decrease in the number of VRC. The mechanisms underlying the -scintillations of the CaI–Na crystals containing AC and VRC and also the decrease in the number of VRC are discussed.  相似文献   

2.
Let : [0, 1][0, 1] be a piecewise monotonie expanding map. Then admits an absolutely continuous invariant measure. A result of Kosyakin and Sandler shows that can be approximated by a sequence of absolutely continuous measures n invariant under piecewise linear Markov maps itn. Each itn is constructed on the inverse images of the turning points of . The easily computable measures n are used to estimate the Liapunov exponent of . The idea of using Markov maps for estimating the Liapunov exponent is applied to both expanding and nonexpanding maps.  相似文献   

3.
We investigate the influence of long range interactions on the relaxation behaviour of a lattice model with an on-site potential of 4-type and infinite range harmonic interactions. For finite number of particlesN, it is shown that the autocorrelation functions <E n(t)E n > of the fluctuations of the one-particle energiesE n(t) decays exponentially. The corresponding relaxation time is proportional toN and is given by (T, N) =N0(T). The temperature dependent time scale 0 can explicitly be related to the dynamics of a one-particle correlator of the noninteracting system. The results are derived using Mori-Zwanzig projection formalism. The corresponding memory kernel is calculated within a mode coupling approximation and by a perturbative approach. Both results agree in leading order in 1/N. It is speculated that any interaction of range generates a timescale .  相似文献   

4.
The variation of the convergence time, as a function of the storage capacity is studied numerically for systems ranging in size fromN=1000 toN=16,000 neurons. is found to increase likeexp[–A(c–)] as one nears the critical storage capacity c =0.142=0.002.  相似文献   

5.
The paramagnetic state (+e) in Si and Te was observed in a longitudinal magnetic field. The mean lifetimes of these states were obtained: Si = 1.45(3) s, Te = 12.5(8) s at 290 K, Te = 12(2) s at 250 K.  相似文献   

6.
Every convex subset of a locally convex Hausdorff space (X, ) is equipped with the (-algebra generated by its-relatively open subsets. Within the set () of probability measures on two particular convex subsets are considered: (a) the set s () of probability measures with a separable support, and (b) the set c () of probability measures with a compact convex support. If is the base of a cone inX, then there exists an affine barycenter map from c () onto whose composition with the natural embedding of in c () yields the identity map on , and every-continuous affine transformation of can be represented by an affine transformation of c () that is induced by a Markov kernel. If (X, ) is a Banach space and is a closed, bounded, generating cone base inX that is contained in a hyperplane, then analogous results are obtained with respect to s (). Since the state spaces considered in noncommutative measure theory are cone bases and every change in time of an empirical system can be thought of as an affine transformation of the associated state space (Schrödinger picture), the existence of these representation theorems implies that the time evolution of general empirical systems can be described by dynamical concepts borrowed from classical probability theory.  相似文献   

7.
We consider the mechanism of macroscopic polarization of semiconducting plates owing to the interaction of free carriers with an impurity level, in which role the level of the residual impurity of compensated semiconductors may appear. This mechanism, in combination with the diffusion-drift mechanism of polarization, results in additional dispersion of the real () and imaginary () parts of the dielectric permittivity, this being particularly significant for semiconductors of thickness smaller than the screening length Ls of free carriers. The character of the behavior of and depends on the relation between the Maxwell relation time M and the times of carrier capture: c and ejection e by an impurity center. For cetm and (/Ls) e/c1 the dispersion of and is the same as for thick plates (/Ls1). For c m e and (/Ls)e/c1 the () curve has a characteristic kink in the region 1/e, indicating additional absorption associated with the ejection of carriers into the surface region.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 11–13, October, 1981.  相似文献   

8.
Let be an action of a compact abelian groupG on aC*-algebraA, and assume that the fixed-point subalgebraA is an AF-algebra. We show that if is a closed *-derivation onA commuting with , and the restriction of toA generates a one-parameter group of *-automorphisms, then itself is a generator. In particular, the result applies if is an infinite product action ofG on a UHF algebra. Furthermore, if in this situation 1 and 2 are two derivations both satisfying the hypotheses on , and 1 and 2 have the same restriction toA , then there exists a one-parameter subgroup of the action with generator 0 such thatD(1)D(2)D(0) is a joint core for the three derivations, and 2=1+0 on this core.  相似文献   

9.
The vacuum line element inside an infinitely long rotating hollow cylinder is the usual flat space line element. It is fitted in a most general way to the general cylindrical vacuum field outside at the singular hypersurfaceR 0=const, representing the infinitely thin hollow cylinder. With the use of the jump conditions atR 0=const the surface densities , of which the energy-momentum-stress tensor of the shell consists, are calculated. The physical properties of the cylinder, as derived from the eigenvalues and -vectors of , and the generated gravitational field are discussed in full detail.  相似文献   

10.
We propose a new class of cluster growth models where growth sites have a finite lifetime , which contains as special cases the Eden model ( = ) and the kinetic growth walk ( = 1). For finite but large values the growth process can be characterized by a crossover timet X; for times belowt X an Eden-type cluster is formed, while for times abovet X the growth process belongs to the universality class of the self-avoiding random walk. The crossover time increases monotonically with . We develop a scaling theory for the time evolution of the mean end-to-end distance between the seed and the last-added site, and for the average number of growth sites by which the kinetics of the growth process can be characterized. We test this scaling theory by extensive Monte Carlo simulations. We also extend our results to inhomogeneous media (percolation systems).  相似文献   

11.
Expressions are derived for the differential probability for the decay e(). The possibly nonzero mass of and the polarizations of both the decaying lepton and the charged lepton which is produced are all taken into account. A quantitative analysis is carried out for various masses of the neutrino and for various energies of the lepton emitted during the decay.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 97–100, June 1981.  相似文献   

12.
We present a method for obtaining bounds on the magnetic moment of the lepton. In order to do this, we study the radiative decayW as a function of the anomalous magnetic moment of the ,a . One can obtain bounds as good asa < 4.05×10–2, 2.25×10–2, 4.5×10–3, and 2.5×10–3 at the present Fermilab, future Fermilab, SSC, and LHC, respectively.  相似文献   

13.
On the basis of an arbitrary (V, A) structure of the neutral weak ¯ee and LL currents (L=, M0) a study is made of the processes of production in colliding electron-positron beams of pairs of heavy leptons with subsequent decays in accordance with the schemes e+evµv) + +( anything) and e+eM0e+ve) + M0( anything). The energy spectrum and asymmetry of the distribution of the produced muons are investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 66–70, February, 1981.  相似文献   

14.
Conductance fluctuations are studied in twodimensional mesoscopic electron system with a two-hold valley degeneracy (n v =2), which corresponds to the inversion layer of Si-MOSFET formed in (1,0,0) plane. It is shown that the intervalley scattering modifies conductance fluctuations depending on the ratio, Min { c , T }/ v , where v = ( – 2)/2 and c , T , and are, respectively, system traversal time, thermal diffusion time, intervalley scattering time and total life time of electrons. Conductance fluctuations are no longer universal and vary from G univ 0.862·e 2/h to {ie223-5} at low temperatures even for isotropic systems. The conductance fluctuations increase with decreasing system size, increasing electron density and increasing intervalley scattering time. The effect of intervalley scattering is essentially the same as that of intersubband scattering as previously reported. At finite temperatures where T c , the intervalley scattering modifies the fluctuations through the change in the energy correlation range to results in the reduction of the conductance fluctuations. In Si-MOSFET formed in (1, 1, 1) plane, wheren v =6, more enhanced fluctuations are expected. Experimental studies are desired on theoretically predicted points.  相似文献   

15.
The magnetoresistance of thin magnesium films in the weakly localized regime has been measured at 4.2 K as a function of film thickness. The results are analysed in a new and simple way based on the theory of Hikami et al. [1]. We use only two adjustable parameters, the inelastic relaxation time i and the spin-orbit scattering time so. Whereas so is found to be almost independent of thickness, i changes significantly. The variation of i with thickness is discussed in the light of the theories for the enhanced electron-electron interaction, but it does not seem to tie up with any of the existing theories.  相似文献   

16.
We study perturbative QCD at the five-loop level. In particular we considerR = tot(e + e hadrons)/(e + e + ) andR = ( v+hadrons)/( ev). We use our method to estimate the five-loop coefficients. As a result, we obtain s (M z ) = 0.1186(11) and s (34 GeV) = 0.1396(16), which are accurate at the 1% level. We also findR = 3.8350(18), which is consistent withR and is accurate to 0.05%.  相似文献   

17.
For a space-time which admits a closed timelike smooth curve it is estimated that 2 · 10–24 · l 2, where is the real time andl the spatial length associated with the timelike curve, and is the density of material.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 16, No. 9, pp. 33–36, September, 1973.  相似文献   

18.
We show the existence of a constant (0, ) such that if n is the extinction time for a supercritical contact process on [1, n] d starting from full occupancy, then {log(E[ n])}/n d tend to as n tends to infinity.  相似文献   

19.
A carrier transport model to explain the high-frequency response in high-speed MQW lasers is described. The ambipolar approximation, which is unsuitable for dealing with the high-speed carrier dynamics in MQW structures, was not adopted for small-signal analysis. The carrier transport effect can be characterized by four time constants: the electron transport time, bmn; the hole transport time, bmp; the electron escape time, wbn; and the hole escape time, wbp. The frequency response was interpreted as the sum of the constant response term due to the fast electron current and the roll-off term due to the slow hole transport time. The ratio of the electron contribution to the total response was proportional to the ratio of electron contribution to the total differential gain, , and reciprocally proportional to n0 = 1 + bmn/wbn. The value of was calculated to be about 0.5 for typical MQW lasers. The roll-off frequency is mainly determined by . The ratio p0 = 1 + bmp/wbp affects the resonant frequency and the damping rate in the high-bias condition.  相似文献   

20.
Kinetics of phase transitions are investigated in systems with nonconserved one-component order parameter (i.e., generalized time-dependent Ginzburg-Landau models ind dimensions). The correct static critical behavior as well as fluctuation effects on the kinetics are incorporated by a suitable adaptation of the theory on spinodal decomposition by Langer, Baron and Miller. Both the case of quenches from temperaturesT above to below the critical pointT c and the case of magnetic field changesH from positive to negative values are treated, and both time-dependent order parameter m() and structure factorS(q, ) are obtained numerically ford=2, 3. In the case of quenches atH=0, we find that m()0 andS(q, ) —S(q, ) exp(– 1/2/7.2) , withS(q, )q –2. In the case of field changes we find that forH not exceeding some critical valueH * the system is trapped in a metastable state with infinite lifetime. In contrast to the meanfield-spinodal, the susceptibility does not seem to diverge atH *. These results are compared with other treatments, in particular the Monte Carlo simulations of kinetic Ising models by Binder and Müller-Krumbhaar. While our theory describes some properties of the metastable states reasonably,H * distinctly exceeds the observed limit of metastability. We argue that the present theory does not take into account nucleation fluctuations, and also fails to describe correctly the domain growth in the late stages of the relaxation. Contrary to Langer et al. we suggest that universality holds for nonlinear relaxation and spinodal decomposition nearT c .Supported in part by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 130  相似文献   

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