共查询到20条相似文献,搜索用时 640 毫秒
1.
I. I. Gurevich I. G. Ivanter B. A. Nikolsky A. N. Ponomarev V. S. Roganov V. I. Selivanov V. A. Suetin 《Hyperfine Interactions》1979,6(1-4):175-176
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
2.
A. A. Lipnik 《Russian Physics Journal》1977,20(2):209-212
The electronic absorption coefficient (e) of meso-ultrasound (p –1 en, t, ee; ql 1, where p, en, t are the times of pulse relaxation, energy, and current carrier traps;
ee
–1
is the frequency of intraelectron collisions; , q are the frequency and wave vector of sound; l is the carrier mean free path) in the presence of a permanent external field E0 e
0
–1
q0T is calculated for anisotropic single-valley semiconductors with piezoelectrical and potential-deformation acoustoelectronic interaction. Considered arbitrary are: 1) the anisotropy of the tensors
* and
p (and other crystal parameters); 2) the degree of Fermi degeneration of the carriers; 3) the dependence of
p on the carrier energy . The acoustoheat nonlinearity is neglected. The possibility of meso-ultrasound amplification by the transverse field (E0 - q) is predicted. By changing the orientation of the vector q relative to the crystal axes, the transverse threshold field (E
thr
) can be controlled smoothly and within broad limits, This permits the production of a mechanical sound-amplification regulator or a modulator of its intensity. The ratio between E
thr
and E
thr
yields a measure of the relative anisotropy of the mobility.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 87–92, February, 1977. 相似文献
3.
P. E. Lindelof J. Nørregaard J. Bindslev Hansen 《Zeitschrift für Physik B Condensed Matter》1985,59(4):423-428
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
4.
Masaaki Watanabe 《Journal of statistical physics》1980,22(5):553-562
Mori's scaling method is used to derive the kinetic equation for a dilute, nonuniform electron plasma in the kinetic region where the space-time cutoff (b, t
c) satisfies
Dbl
f
,
D
t
c
f
, with
D the Debye length,
D
–1=
p
the plasma frequency, andl
f
and
f
the mean free path and time, respectively. The kinetic equation takes account of the nonuniformity of the order ofl
f and
D for the single-and the two-particle distribution function, respectively. Thus the Vlasov term associated with the two-particle distribution function is retained. This kinetic equation is deduced from the kinetic equation in the coherent region obtained by Morita, Mori, and Tokuyama, where the space-time cutoff of the coherent region satisfies
Dbr
0,
Dt
c
0, withr
0 the Landau length and
0 the corresponding time scale. 相似文献
5.
A physical framework has been proposed which describes manifestly covariant relativistic evolution using a scalar time . Studies in electromagnetism, measurement, and the nature of time have demonstrated that in this framework, electromagnetism must be formulated in terms of -dependent fields. Such an electromagnetic theory has been developed. Gravitation must also use of -dependent fields, but many references do not take the metric's dependence on fully into account. Others differ markedly from general relativity in their formulation. In contrast, this paper outlines steps towards a -dependent classical intrinsic formulation of gravitation, patterned after general relativity, which we call parametrized general relativity (PGR). Given the existence of a preferred foliation, the Hamiltonian constraint is removed. We find that some nonmetricity in the connection is allowed, unlike in general relativity. Conditions on the allowable nonmetricity are found. Consideration of the initial value problem confirms that the metric signature should normally be O(3, 2) rather than O(4, 1). Following the lead of earlier works, we argue that concatenation (integration over ) is unnecessary for relating parametrized physics to experience, and propose an alternative to it. Finally, we compare and contrast PGR with other relevant gravitational theories. 相似文献
6.
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
7.
M. Ghosh A. K. Sen B. K. Chakrabarti G. A. Kohring 《Journal of statistical physics》1990,61(1-2):501-504
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
8.
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
9.
Shuichi Iwabuchi 《Zeitschrift für Physik B Condensed Matter》1995,98(2):223-229
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
10.
This paper discuses the , decay process in a field formed by the super-position of two fields: a crossed constant field and and electromagnetic plane-wave field. An expression is derived for the decay probability under the assumption of a nonzero -neutrino mass. The dependence of the decay probability on the lepton spin and on the external-field parameters is analyzed. The variation of the decay probability with the neutrino mass and lepton spin yields information which may be useful for ascertaining the neutrino mass.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 27–32, December, 1985.The authors are indebted to Professor V. R. Khalilov for a formulation of the problem and many valuable comments. 相似文献
11.
The temperature dependence of total conductivity in KCl and NaCl monocrystals with calcium impurity in the audio frequency range is studied, It is established that in the temperature range 50–350°C only one of the observed relaxation processes is described by the dipole relaxation mechanism with characteristic time = 0exp (E/T); the values 0 = 10–14sec, E = 0.65eV, and 0 = 10–14sec, E = 0.7eV are obtained for KCl and NaCl respectively. Relaxations with values of 0 and E differing from those above which were observed in the given temperature and frequency range are produced by resistance of the near electrode region.Translated from Izvestiya VUZ. Fizika, No. 6, pp. 101–106, June, 1973. 相似文献
12.
T. M. Aliev N. A. Guliev I. G. Dzhafarov F. T. Khalil-Zade 《Russian Physics Journal》1981,24(2):159-163
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+e––(µ–vµv) + +( anything) and e+e–M0(µ–e+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
13.
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
14.
H. E. Wilhelm 《Applied Physics A: Materials Science & Processing》1988,46(1):17-23
In the macroscopic electrodynamics (MED) of good conductors (metals) based on Ohm's law j=E, the momentum relaxation time =m/ne2 of the electrons limits the application to electromagnetic (EM) processes with characteristic timest. An interesting physical difficulty occurs in MED since the EM field damping time R=/ of metals is very small compared with the minimum macroscopic time scale, R. Consequently, the damping and propagation of EM waves and pulses in good conductors cannot be correctly described within the frame of conventional MED. New hyperbolic EM wave equations with relaxation and memory are proposed, which no longer exhibit the R deficiency. The latter is caused by Ohm's law, which breaks down for short-time processes, due to neglect of electron inertia. The advantages of the proposed and the disadvantages of the conventional EM wave equations for good conductors are discussed in applications. 相似文献
15.
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
16.
Jouko Mickelsson 《Letters in Mathematical Physics》1991,22(2):131-139
An extension
of the symmetry group GL of Sato's universal Grassmannian GM is constructed. The extension plays a similar role to that of the central extension
in the approach of Segal and Wilson to functions and KP hierarchy. Our group G contains GLres as a subgroup and the associated function is a deformation of the usual function, leading to a deformed KP hierarchy. A relation to current algebra of Yang-Mills theory in 3+1 dimension is discussed. 相似文献
17.
In this second part of a two-part presentation, we continue with the model introduced in Part I. In this part, the initial configuration has one particle at each site to the left of 0 and no particle elsewhere. The expected number of particles observed at a site moving at speed has an exponential growth rate (speed- growth rate) that is computed explicitly. The result reveals two characteristic wavefront speeds: 1, the speed of the front of zero growth (rightmost particle), and 2, the speed of the front of maximal growth. The latter speed exhibits a phase transition, changing from zero to positive as the drift in the migration crosses a threshold. The qualitative shape of the growth rate as a function of changes as well. In particular, below the threshold there appears a linear piece, which corresponds to the system exhibiting an intermittency effect. 相似文献
18.
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
19.
A study is made of a metal-dielectric-semiconductor-dielectric-metal structure subjected to a linearly increasing external voltage. On the assumption of quasistatic screening conditions, the carrier-density and field distribution in the near-anode and nearcathode regions of the semiconductor are determined. This distribution proves to be nonuniform not only in the region of the surface space charge induced by the external field, but also within the interior of the semiconductor to a depth E0·tM/0, where is the lifetime and the mobility of the carriers, E0/0 is the rise rate of the external field, and tM is the Maxwellian relaxation time. The character of the distribution for opposite faces of the semiconductor is different, since in the near-cathode region for n-type semiconductors allowance must be made for the effect of the uncompensated space charge of the current carriers on the conductivity.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 7–10, February, 1973.We are indebted to G. M. Guro and V. B. Sandomirskii for a discussion of the work. 相似文献
20.
L. H'walisz P. Jung P. Hänggi P. Talkner L. Schimansky-Geier 《Zeitschrift für Physik B Condensed Matter》1989,77(3):471-483
We present a novel approximation scheme, termed unified colored noise approximation (UCNA), for colored Gaussian noise driven nonlinear systems with inertia. This approximation allows one to evaluate static (stationary distributions, moments) as well as dynamical quantities (correlation functions) for small-to-moderate-to-large values of the correlation time. The approximation replaces a three-dimensional Markovian process by a reduced, two-dimensional Markovian dynamics with new drift and diffusion coefficients. For a harmonic potential the stationary moments are reproduced exactly. Most importantly, we present a criterion involving the noise strengthD, the friction strength and the noise color , which describes the region of validity of UCNA in the parameter space given by (D, , ). At small -values we contrast the UCNA with the well-known small approximation. In order to have a comparison onanalytical grounds, we test the static and dynamical predictions of UCNA versus the well-known analytical results obtained from a three-dimensional Ornstein-Uhlenbeck process. 相似文献