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1.
V. V. Vecheslavov 《Journal of Experimental and Theoretical Physics》1999,89(1):182-187
This report is a continuation of an analysis, initiated elsewhere V.V. Vecheslavov and B. V. Chirikov, Zh. éksp. Teor. Fiz.
114, 1516 (1998) [JETP 86, 823 (1998)], of the effect of splitting of the separatrix of a nonlinear resonance for the model of standard mapping, based
on results of direct measurements of the splitting angle α(K), where K is the system parameter. Measurements were made in the previously used wide range 0.1≳α≳10−208 (1⩾K⩾0.0004), but with significantly higher relative (better than 1050) and average (∼10−55) accuracy. This procedure made it possible to substantially refine the effects observed in Ref. 1 and construct qualitatively
new empirical dependences providing reliable extrapolation of the data obtained for the angle and the invariant in the intermediate
asymptotic limit K≲10−2 beyond the limits of the investigated region. The results obtained by us can be useful for further development of the theory
of separatrix splitting and formation of the stochastic layer of a nonlinear resonance.
Zh. éksp. Teor. Fiz. 116, 336–346 (July 1999) 相似文献
2.
Viêt Hà Hoàng 《Communications in Mathematical Physics》2000,214(2):411-428
The paper considers the singularly perturbed Dirichlet problem −ɛΔu
ɛ+u
ɛ=f in a randomly perforated domain Ωɛ, which is obtained from a bounded open set Ω in R
N
after removing many holes of size ɛ
q
. The perforated domain is described in terms of an ergodic dynamical system acting on a probability space. Imposing certain
conditions on the domain, the behaviour of u
ɛ when ɛ→ 0 in Lebesgue spaces L
n
(Ω) is studied. Test functions together with the Birkhoff ergodic theorem are the main tools of analysis. The Poisson distribution
of holes of size ɛ
p
with the intensity λɛ−
r
is then considered. The above results apply in some cases; other cases are treated by the Wiener sausage approach.
Received: 15 December 1999 / Accepted: 14 April 2000 相似文献
3.
The effect of weak magnetic fields (0.1–0.8 T) on the internal friction and Young’s-modulus defect of LiF crystals is investigated
over a range of relative strain amplitudes ɛ
0 from 10−6 to 10−4 at frequencies of 40 and 80 kHz. Experiments with these fields show that the internal friction increases and the effective
elastic modulus decreases, indicating an increase in the plasticity of the samples. Plots are obtained of the internal friction
versus the magnitude of the magnetic field at various values of the strain amplitude ɛ
0.
Fiz. Tverd. Tela (St. Petersburg) 41, 1035–1040 (June 1999) 相似文献
4.
A. A. Rajabi 《Few-Body Systems》2005,37(4):197-213
A mathematical method is presented for solving the Schr?dinger equation for a system of identical body forces. The N-body forces are more easily introduced and treated within the hyperspherical harmonics. The problem of the N-body potential has been used at the level of both classical and quantum mechanics.
The hypercentral interacting potential is assumed to depend on the hyperradius x = (ξ12 + ξ22 + ⋯ + ξN−12)1/2 only, where ξ1,ξ2,…,ξN−1 are Jacobi relative coordinates which are functions of N-particle relative positions r12,r23,…,rN1. The problem of the harmonic oscillator and the Coulomb-type potential has been widely studied in different contexts.
Using the N-body potential V(x) = ax2 + bx − (c/x) as an example, and assuming an ansatz for the eigenfunction, an exact analytical solution of the Schr?dinger equation for
an N-body system in three dimensions is obtained. This method is also applicable to some other types of potentials for N-identical interacting particles. 相似文献
5.
Md. Salimullah R. R. Sharma V. K. Tripathi 《Applied Physics A: Materials Science & Processing》1981,25(3):361-365
Using the fluid model for the nonlinear response of ions, we have studied the nonlinear scattering of an electromagnetic ion
cyclotron wave off the ion acoustic wave in a plasma. The low frequency nonlinearity arises through the parallel ponderomotive
force on ions and the high frequency nonlinearity arises through the nonlinear current density of ions. For a typical nonisothermal
plasma (T
e/T
i∼10) the threshold for this instability in a uniform plasma is ∼1mW/cm2. At power densities ≳102 W/cm2, the growth rate for backscatter turns out to be ∼104s−1. 相似文献
6.
A parametric study of the electron energy distribution function (EEDF) and the electron mobility in the mixture Na + Ar +
N2 is carried out. An analysis is made of the conditions that obtain in a photoplasma when the detachment of the mean electron
energy from the neutral gas temperature is due to superelastic collisions (collisions of the second kind) with excited sodium
atoms. The case of low ionization of the medium at low vibrational temperatures of the ground state of the nitrogen molecules
is considered. To find the EEDF a numerical solution of the Boltzmann transport equation is carried out. It is found that
in the indicated mixture the presence of nitrogen leads to a depletion of the EEDF in the region of efficient vibrational
excitation of the molecules and promotes the formation of inversion in the EEDF ∂f(ɛ)/∂ɛ>0 in the energy range corresponding to the Ramsauer minimum in the cross section of elastic collisions of electrons with
the argon atoms. It is shown that the nonequilibrium character of the EEDF leads to a complicated dependence of the electron
mobility on the partial ratios of the components of the mixture, the degree of ionization of the medium, and the population
of the resonantly excited sodium atoms.
Zh. Tekh. Fiz. 69, 14–19 (April 1999) 相似文献
7.
8.
Sineeba Ramadas Vishnu M. Bannur 《The European Physical Journal C - Particles and Fields》2012,72(4):1975
From an analogy with non-relativistic degenerate QED plasma we make an estimate of the coupling strength of QGP hypothesized
to be present in compact star interiors. At densities ranging from 3ρ
0–10ρ
0 (normal nuclear density ρ
0=0.16 fm−3), quark matter is found to be strongly to intermediately coupled. The equation of state for QED plasma obtained via Pade
approximation, modified to QGP, yields stable stellar sequences with maximum mass ≳2M
⊙ for B
1/4≲215 MeV. 相似文献
9.
E. V. Kuz’min 《Physics of the Solid State》1997,39(2):169-178
The problem of the ground state of the electronic system in the Hubbard model for U=∞ is discussed. The author investigates the normal (singlet or nonmagnetic) N state of the electronic system over the entire
range of electron densities n⩽1. It is shown that the energy of the N state ɛ
0
(1)
(n) in a one-particle approximation, such as (e.g.) the extended Hartree-Fock approximation, is lower than the energy of the
saturated ferromagnetic FM state ɛ
FM(n) for all n. The dynamic magnetic susceptibility is calculated in the random phase approximation, and it is shown that the N state is
stable over the entire range of electron densities: The static susceptibility (ω=0) does not have a band singularity in the zero-wave vector limit q→0. A formally exact representation is obtained for the mass operator of the one-particle Green’s function, and an approximation
of this operator is proposed: M
k(E)⋍λF(E), where λ=n(1−n)/(1−n/2)z is the kinematic interaction parameter, z is the number of nearest neighbors, and F(E) is the total single-site Green’s function. For an elliptical density of states the integral equation for F(E) is solved exactly, ad it is shown that the spectral intensity rigorously satisfies the sum rule. The calculated energy of
the strongly correlated N state ɛ
0(n)<ɛ
FM(n) for all n, and in light of this relationship the author discusses the hypothesis that the ground state of the system is the normal
(singlet) state in the thermodynamic limit. The electron distribution function at T=0 differs significantly from the Fermi step; it is “smeared” along the entire energy spectrum, and discontinuities do not
occur in the region of the chemical potential m.
Fiz. Tverd. Tela (St. Petersburg) 39, 193–203 (February 1997) 相似文献
10.
V. P. Ruban 《Journal of Experimental and Theoretical Physics》2010,111(5):776-785
We consider slow, compared to the speed of sound, motions of an ideal compressible fluid (gas) in a gravitational field in
the presence of two isentropic layers with a small specific-entropy difference between them. Assuming the flow to be potential
in each of the layers (v
1, 2 = ▿ϕ1, 2) and neglecting the acoustic degrees of freedom (div($
\bar \rho
$
\bar \rho
(z)▿ϕ1, 2) ≈ 0, where $
\bar \rho
$
\bar \rho
(z) is the average equilibrium density), we derive the equations of motion for the boundary in terms of the shape of the surface
z = η(x, y, t) itself and the difference between the boundary values of the two velocity field potentials: ψ(x, y, t) = ψ1 − ψ2. We prove the Hamilto nian structure of the derived equations specified by a Lagrangian of the form ℒ = ∫$
\bar \rho
$
\bar \rho
(η)η
t
ψdxdy − ℋ{η, ψ}. The system under consideration is the simplest theoretical model for studying internal waves in a sharply stratified
atmosphere in which the decrease in equilibrium gas density due to gas compressibility with increasing height is essentially
taken into account. For plane flows, we make a generalization to the case where each of the layers has its own constant potential
vorticity. We investigate a system with a model dependence $
\bar \rho
$
\bar \rho
(z) ∝ e
−2αz
with which the Hamiltonian ℋ{η, ψ} can be represented explicitly. We consider a long-wavelength dynamic regime with dispersion
corrections and derive an approximate nonlinear equation of the form u
t
+ auu
x
− b[−$
\hat \partial _x^2
$
\hat \partial _x^2
+ α2]1/2
u
x
= 0 (Smith’s equation) for the slow evolution of a traveling wave. 相似文献
11.
On the basis of the total cross sections for neutron-proton scattering in the region of laboratory energies below 150 keV,
the value of σ0 = 20.4288(146) b was obtained for the total cross sections for neutron-proton scattering at zero energy. This value is in
very good agreement with the experimental cross sections obtained by Houke and Hurst, but it is at odds with Dilg’s experimental
cross section. By using the value that we found for σ0 and the experimental values of the neutron-proton coherent scattering length f, the deuteron binding energy ɛ
t
, the deuteron effective radius ρ
t
(−ɛ
t
, −ɛ
t
), and the total cross section in the region of energies below 5 MeV, the following values were found in the shape-parameter
approximation for the low-energy parameters of neutron-proton scattering in the spin-triplet and spin-singlet states: a
t
= 5.4114(27) fm, r
0t
= 1.7606(35) fm, v
2t
= 0.157 fm3, a
s
= −23.7154(80) fm, r
0s
= 2.706(67) fm, and v
2s
= 0.491 fm3. 相似文献
12.
The dielectric nonlinearity of ferroelectric Li2−x
NaxGe4O9 (x≈0.23) crystals is measured in the neighborhood of the phase transition temperatures. The magnitude of the nonlinear coefficient
β is estimated from the shift in T
c and the reduction in ɛ
max under the influence of E
=, from the dielectric nonlinearity in the paraphase, and from the temperature dependence of P
s in crystalline Li2−x
NaxGe4O9 (x≈0.23). The resulting values of β are 1.87, 1.26, 2.17, and 1.17×10−9 (CGSE cm2)−2, respectively. The mechanism for the phase transition in crystalline Li2−x
NaxGe4O9 (x≈0.23) is discussed.
Fiz. Tverd. Tela (St. Petersburg) 41, 1070–1072 (June 1999) 相似文献
13.
We study hypoelliptic operators with polynomially bounded coefficients that are of the form K=∑
i=1
m
X
i
T
X
i
+X
0+f, where the X
j
denote first order differential operators, f is a function with at most polynomial growth, and X
i
T
denotes the formal adjoint of X
i
in L
2. For any ɛ>0 we show that an inequality of the form ||u||δ,δ≤C(||u||0,ɛ+||(K+iy)u||0,0) holds for suitable δ and C which are independent of yR, in weighted Sobolev spaces (the first index is the derivative, and the second the growth). We apply this result to the Fokker-Planck
operator for an anharmonic chain of oscillators coupled to two heat baths. Using a method of Hérau and Nier [HN02], we conclude
that its spectrum lies in a cusp {x+iy|x≥|y|τ−c,τ(0,1],cR}.
Received: 30 July 2002 / Accepted: 18 October 2002 Published online: 25 February 2003
RID="*"
ID="*" Present address: Mathematics Research Centre of the University of Warwick
Communicated by A. Kupiainen 相似文献
14.
A large stack of lead-emulsion sandwich detector assembly was flown over Hyderabad, India. High energy gamma rays at the float
altitude were unambiguously identified from the cascades they induced, and their energies reliably determined by improved
methods. From an analysis of 163 gamma rays of energy ≳ 30 GeV, it is found that the differential energy spectrum is represented
by the power lawJ
r
(E)= 129·4E
−2·62±0·12 photons m−2 sr−1sec−1 GeV−1 at an effective atmospheric depth of 14·3 g cm−2; this is the first reliable balloon measurement of atmospheric gamma rays in the energy range 40–1000 GeV. After correcting
for the gamma rays radiated by the primary cosmic ray electrons, the production spectrum of gamma rays, resulting from the
collisions of cosmic ray nuclei with air nuclei, at the top of the atmosphere isP
r
(E, 0)=8·2 × 10−4 E2.60±0.09 photons g−1sr−1sec−1 GeV−1. The atmospheric propagation of the electromagnetic component due to the cascade process is also derived from the gamma ray
production spectrum. 相似文献
15.
E. Z. Meilikhov 《Journal of Experimental and Theoretical Physics》1999,88(4):819-825
Models of thermally activated linear and high-field nonlinear conductivity of a dielectric phase in granular metals (nanocomposites),
i.e., aggregates of small metallic grains in a dielectric matrix, have been suggested. Given a sufficiently large spread of
grain sizes, the temperature dependence of the nanocomposite conductivity should be described by a universal “power-1/2” law:
G∝exp[−(T
0/T)1/2]. An analytical expression for T
0 has been obtained. It is found that there are two regimes of nonlinear conductivity in a high electric field, namely, a low-field
regime, when both the number and mobility of carriers change with the field strength, and a high-field regime, when only the
mobility of carriers is variable. Analytical expressions for the nonlinear conductance in both regimes have been obtained.
Zh. éksp. Teor. Fiz. 115, 1484–1496 (April 1999) 相似文献
16.
We showed in Part I that the Hopf algebra ℋ of Feynman graphs in a given QFT is the algebra of coordinates on a complex infinite
dimensional Lie group G and that the renormalized theory is obtained from the unrenormalized one by evaluating at ɛ= 0 the holomorphic part γ+(ɛ) of the Riemann–Hilbert decomposition γ−(ɛ)− 1γ+(ɛ) of the loop γ(ɛ)∈G provided by dimensional regularization. We show in this paper that the group G acts naturally on the complex space X of dimensionless coupling constants of the theory. More precisely, the formula g
0=gZ
1
Z
3
−3/2 for the effective coupling constant, when viewed as a formal power series, does define a Hopf algebra homomorphism between
the Hopf algebra of
coordinates on the group of formal diffeomorphisms to the Hopf algebra ℋ. This allows first of all to read off directly, without
using the group G, the bare coupling constant and the renormalized one from the Riemann–Hilbert decomposition of the unrenormalized effective
coupling constant viewed as a loop of formal diffeomorphisms. This shows that renormalization is intimately related with the
theory of non-linear complex bundles on the Riemann sphere of the dimensional regularization parameter ɛ. It also allows to
lift both the renormalization group and the β-function as the asymptotic scaling in the group G. This exploits the full power of the Riemann–Hilbert decomposition together with the invariance of γ−(ɛ) under a change of unit of mass. This not only gives a conceptual proof of the existence of the renormalization group but
also delivers a scattering formula in the group G for the full higher pole
structure of minimal subtracted counterterms in terms of the residue.
Received: 21 March 2000 / Accepted: 3 October 2000 相似文献
17.
Summary The spin-orbit parameter Δ, spin-lattice relaxation timeT
1, and spin-mixing parameter ɛ ofF
H(OH−) andF
H(CN−) centers in several alkali halides have been studied with magnetic circular dichroism at ∼2 K. A close comparison of the
experimental results before and after optically induced association of theF center with the molecular ion has been made. In crystals of NaCl structure the negative spin-orbit parameter Δ changes little
betweenF andF
H centers in the same host. For CsCl and CsBr two values of Δ have been derived forF
H(CN−) centers with axis parallel or perpendicular to the magnetic field. In all studied systems, the spin-lattice relaxation timeT
1 is already shorter before aggregation compared toF formation. The spin-mixing parameter ɛ decreases slightly forF
H(OH−) compared toF centers, while it increases drastically forF
H(CN−) defects and reaches its maximum possible value ɛ=0.5 in cesium halides. First attempts to interpret these magneto-optical
results will be presented.
In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching. 相似文献
18.
S. B. Bogdanova S. O. Gladkov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(10):1335-1339
The longitudinal component of the magnetic susceptibility tensor χ
zz
of a fractal ferrodielectric with dimension d
F
= 3 − ɛ, where ɛ > 0, is calculated. The magnon dispersion in this case is shown to be a strongly anisotropic function of
the parameter ɛ which, in turn, leads to nontrivial frequency dependences of χ
zz
. 相似文献
19.
A. B. Voitkiv 《Technical Physics》1998,43(3):265-270
Expressions for the cross sections for single and double ionization of atomic helium in collisions with fast multiply charged
ions are obtained in the collision parameter range υ
2≫Z≳υ, υ
0<c, where Z and υ are, respectively, the ion charge and ion velocity, υ
0 is the characteristic velocity of electrons in the atomic helium ground state, and c is the velocity of light.
Zh. Tekh. Fiz. 68, 1–7 (March 1998) 相似文献
20.
I. N. Andryushina K. P. Andryushin O. N. Razumovskaya L. A. Shilkina L. A. Reznichenko Yu. I. Yurasov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1127-1129
The behavior of the relative permittivity ɛ/ɛ0 of PbZr1 − x
Ti
x
O3 (PZT) solid solutions (0.495 ≤ x ≤ 0.51) in the temperature range of 100–300 K at frequencies from 1 × 10−2 to 2 × 107 Hz was investigated. Diffuse, strongly relaxing maxima at T = 230−260 K (x = 0.495−0.505) and 150–160 K (x = 0.510) were observed in the PZT studied. The relaxation processes are well described by the Vogel-Fulcher law, and the
dielectric spectra are approximated by the Cole-Cole formula. 相似文献