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1.
We study the relationship between POV-measures in quantum theory and asymptotic morphisms in the operator algebra E-theory of Connes–Higson. This is done by introducing the theory of “asymptotic” PV-measures and their integral correspondence
with positive asymptotic morphisms on locally compact spaces. Examples and applications involving various aspects of quantum
physics, including quantum noise models, semiclassical limits, strong deformation quantizations, and pure half-spin particles,
are also discussed.
Received: 27 December 2000 / Accepted: 8 October 2001 相似文献
2.
This paper investigates the photodetachment of the negative hydrogen ion H near an elastic wall in a magnetic field.The magnetic field confines the perpendicular motion of the electron,which results in a real three-dimensional well for the detached electron.The analytical formulas for the cross section of the photodetachment in the threedimensional quantum well are derived based on both the quantum approach and closed-orbit theory.The magnetic field and the elastic surface lead to two completely different modulations to the cross section of the photodetachment.The oscillation amplitude depends on the strength of the magnetic field,the ion-wall distance and the photon polarization as well.Specially,for the circularly polarized photon-induced photodetachment,the cross sections display a suppressed(E E th) 1/2 threshold law with energy E in the vicinity above Landau energy E th,contrasting with the(E E th) 1/2 threshold law in the presence of only the magnetic field.The semiclassical calculation fits the quantum result quite well,although there are still small deviations.The difference is attributed to the failure of semiclassical mechanics. 相似文献
3.
4.
Although quantum tunneling between phase space tori occurs, it is suppressed in the semiclassical limit for the Schr?dinger equation of a particle in ℝ
d
under the influence of a smooth periodic potential.
In particular this implies that the distribution of quantum group velocities near energy E converges to the distribution of the classical asymptotic velocities near E, up to a term of the order .
Received: 14 December 1998 / Accepted: 19 February 1999 相似文献
5.
A. M. Ermolaev 《Hyperfine Interactions》1993,76(1):335-341
The theoretical ratioR
i of antiproton/proton cross sections for nondissociative ionization of hydrogen molecule has been obtained as a function of
the impact energyE in the range 30⩽E⩽2500 KeV lab. The required cross sections were computed in the close-coupling formulation of the semiclassical impact parameter
theory using a simple one-active electron model for the molecular target. The ratioR
i is important for the analysis of the recent experimental data of Andersen et al. on antiproton scattering and the understanding
of the collisional mechanisms in the KeV range. 相似文献
6.
MJ Singh DO Kataria N Madhavan P Sugathan JJ Das DK Awasthi AK Sinha R Shanker 《Pramana》1999,53(4):743-764
A projectile ion-recoil ion coincidence technique has been employed to study the multiple ionization and the charge transfer
processes in collisions of 60–120 MeV Si
q+ (q = 4−14) ions with neutral argon atoms. The relative contribution of different ionization channels, namely; direct ionization,
electron capture and electron loss leading to the production of slow moving multiply charged argon recoil ions have been investigated.
The data reported on the present collision system result from a direct measurement in the considered impact energy for the
first time. The total ionization cross-sections for the recoil ions are shown to scale as q
1.7/E
p
0.5
, where E
p is the energy in MeV of the projectile and q its charge state. The recoil fractions for the cases of total- and direct ionizations are found to decrease with increasing
recoil charge state j. The total ionization fractions of the recoils are seen to depend on q and to show the presence of a ‘shell-effect’ of the target. Further, the fractions are found to vary as 1/j
2 upto j = 8+. The average recoil charge state 〈j〉 increases slowly with q and with the number of lost or captured electrons from or into the projectile respectively. The projectile charge changing
cross-sections σ
qq′ are found to decrease with increasing q for loss ionization and to increase with q for direct-and capture ionization processes respectively. The physics behind various scaling rules that are found to follow
our data for different ionization processes is reviewed and discussed. 相似文献
7.
Eduard Prugovečki 《Foundations of Physics Letters》1989,2(2):163-190
A second-quantized bundleE, called the quantum gravitational bundle, is constructed from graviton bundles in accordance with outlined general principles for geometro-stochastic second quantization, and quantum gravitational frame fields are introduced in it. The gravitational bundleE is the carrier of a semiclassical connection
that can be used as a stepping stone in the construction of a second-quantized gravitational connection. The geometro-stochastic quantum propagations governed by such connections can be expressed in terms of path integrals over causal stochastic paths which embody stochastic parallel transport under free-fall conditions. Their epistemic implications for the quantum theory of measurement are discussed.1. Supported in part by the NSERC Research Grant No. A5206. 相似文献
8.
The invariant integration method for Chern-Simons theory defined on compact hyperbolic spaces of the form Γℍ3 is verified in the semiclassical approximation. The semiclassical limit for the partition function is calculated. The contribution
to the sum over topologies in three-dimensional quantum gravity is briefly discussed.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 2, 65–69 (25 July 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
9.
Yu-Quan Yuan Xiao-Xiong Zeng Zhi-Jian Zhou Liang-Ping Jin 《General Relativity and Gravitation》2009,41(12):2771-2780
Recently, fermions tunneling beyond semiclassical approximation from an uncharged static black hole was investigated by Majhi,
which was based on the work of Banerjee and Majhi, it was found that the black hole entropy correction can be produced as
the quantum effect of a particle is taken into account. In this paper, we further extend this idea to the stationary Kerr
black hole to discuss its entropy correction. To get the corrections correctly, the proportionality parameters of quantum
corrections of action I
i
to the semiclassical action I
0 in this case are regarded as the inverse of the product of Planck Length and Planck Mass. The result shows that entropy corrections
to the stationary black hole also include the logarithmic term and inverse area term in Bekenstein–Hawking entropy beyond
semiclassical approximation. 相似文献
10.
11.
In this paper we discuss the existence and properties of the Bianchi transformations for pseudospherical surfaces in E
4. The results of the paper show that the theory of Bianchi transformations in the discussed case is essentially different
from the well-known case of pseudospherical surfaces in E
3 (in general n-manifolds of constant and negative curvature in E
2 n − 1).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
An analysis is made of the ionization of deep impurity centers by high-intensity far-infrared and submillimeter-wavelength
radiation, with photon energies tens of times lower than the impurity ionization energy. Within a broad range of intensities
and wavelengths, terahertz electric fields of the exciting radiation act as a dc field. Under these conditions, deep-center
ionization can be described as multiphonon-assisted tunneling, in which carrier emission is accompanied by defect tunneling
in configuration space and electron tunneling in the electric field. The field dependence of the ionization probability permits
one to determine the defect tunneling times and the character of the defect adiabatic potentials. The ionization probability
deviates from the field dependence e(E) ∝ exp(E
2/E
c
2
) (where E is the wave field, and E
c is a characteristic field) corresponding to multiphonon-assisted tunneling ionization in relatively low fields, where the
defects are ionized through the Poole-Frenkel effect, and in very strong fields, where the ionization is produced by direct
tunneling without thermal activation. The effects resulting from the high radiation frequency are considered and it is shown
that, at low temperatures, they become dominant.
Fiz. Tverd. Tela (St. Petersburg) 39, 1905–1932 (November 1997) 相似文献
13.
14.
Electron impact single ionization cross sections of copper have been calculated in the binary encounter approximation using
accurate expression for σ
ΔE as given by Vriens and Hartree-Fock momentum distribution for the target electron. The BEA calculation based on the usual
procedure does not show satisfactory agreement with experiment in this case but a striking modification is found to be successful
in explaining the experimental observations. The discrepancy is linked with the ionization of the 3d
10 electrons and probably effective single ionization does not take place from 3d shell of copper leading to smaller values of experimental cross sections. 相似文献
15.
An investigation of the probability of hydrogen atom ionization by ultra‐short electromagnetic pulses is carried out in the frame of perturbation theory We consider the case when the electric field strength amplitude E0 in a pulse by two orders lower than characteristic atomic field strength Ea (Ea ? 5.1 · 109 V/cm). A detailed investigation of the dependence of the probabilities on the pulse duration was performed for Gaussian pulse shapes. In the case where the carrier frequency of the Gaussian pulse is larger than the atomic ionization potential, the probability goes to the standard limit of perturbation per unit time. At the same pulse durations, the probabilities for carrier frequencies less than the ionization potential go to zero. The frequency dependence of the ionization probability becomes equal to the standard threshold dependence with increasing pulse duration time. A comparison between the ionization effects caused by wavelet pulses without carrier frequency and Gaussian pulses with carrier frequency shows that the same ionization probability values are achieved when the pulse carrier frequency is detuned by about 20% from the ionization threshold. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
16.
A. Alastuey V. Ballenegger F. Cornu Ph. A. Martin 《Journal of statistical physics》2008,130(6):1119-1176
We study hydrogen in the Saha regime, within the physical picture in terms of a quantum proton-electron plasma. Long ago,
Saha showed that, at sufficiently low densities and low temperatures, the system behaves almost as an ideal mixture made with
hydrogen atoms in their groundstate, ionized protons and ionized electrons. More recently, that result has been rigorously
proved in some scaling limit where both temperature and density vanish. In that Saha regime, we derive exact low-temperature
expansions for the pressure and internal energy, where density ρ is rescaled in units of a temperature-dependent density ρ
*
which controls the cross-over between full ionization (ρ
≪
ρ
*
) and full atomic recombination (ρ≫ρ
*
). Each term reduces to a function of ρ/ρ
*
times temperature-dependent functions which decay exponentially fast when temperature T vanishes. Scaled expansions are ordered with respect to the corresponding decay rates. Leading terms do reduce to ideal contributions
obtained within Saha theory. We consistently compute all corrections which are exponentially smaller by a factor exp (β
E
H
) at most, where E
H
is the negative groundstate energy of a hydrogen atom and β=1/(k
B
T). They include all effects arising from both the Coulomb potential and the quantum nature of the particles: excitations of
atoms H, formation of molecules H
2, ions H
2+ and H
−, thermal and pressure ionization, plasma polarization, screening, interactions between atoms and ionized charges, etc. Scaled
low-temperature expansions can be viewed as partial resummations of usual virial expansions up to arbitrary high orders in
the density. 相似文献
17.
Using a nonperturbative quantum electrodynamics theory of high-order harmonic generation (HHG), a scaling law of HHG is established. The scaling law states that when the atomic binding energy Eb, the wavelength λ and the intensity I of the laser field change simultaneously to kEb, λ/k, and k3I, respectively. The characteristics of the HHG spectrum remain unchanged, while the harmonic yield is enhanced k3 times. That HHG obeys the same scaling law with above-threshold ionization is a solid proof of the fact that the two physical processes have similar physical mechanisms. The variation of integrated harmonic yields is also discussed. 相似文献
18.
Wang Zhi-wen Han Qiu-ju Hu Mu-hong Yang Di Li Jin-ying 《Frontiers of Physics in China》2006,1(1):102-107
The ionization potentials and fine structure splittings of 1s2
nl (l = s, p, and d; n ⩽ 9) states for lithium-like V20+ ion are calculated by using the full-core plus correlation (FCPC) method. The quantum defects of these three Rydberg series
are determined according to the single-channel quantum defect theory (QDT). The energies of any highly excited states with
n ⩾ 10 for these series can be reliably predicted using the quantum defects that are function of energy. The dipole oscillator
strengths for the 1s22s–1s2
np and 1s22p–1s2
nd (n ⩽ 9) transitions of V20+ ion are calculated with the energies and FCPC wave functions obtained above. Combining the QDT with the discrete oscillator
strengths, the discrete oscillator strengths for the transitions from the given initial state to highly excited states (n ⩾ 10) and the oscillator strength density corresponding to the bound-free transitions are obtained.
Translated from Chinese Journal of Atomic and Molecular Physics, 2005(2) (in Chinese) 相似文献
19.
K N Joshipura 《Pramana》1998,50(6):555-561
In this review paper, scattering of intermediate to high energy electrons on well-known as well as exotic molecular targets
is considered. The ‘additivity rule’ and its modifications for calculating various total cross sections are discussed against
the background of an extensive experimental data. The theory succeeds at high impact energies (E
i>100 eV). Tentative upper and lower limits of e-molecule ionization cross sections are identified. Fitting formulas to represent
total cross sections as functions of energy are also given. 相似文献
20.
We describe an approach to the noncommutative instantons on the 4-sphere based on quantum group theory. We quantize the Hopf
bundle ?7→?4 making use of the concept of quantum coisotropic subgroups. The analysis of the semiclassical Poisson–Lie structure of U(4) shows that the diagonal SU(2) must be conjugated to be properly quantized. The quantum coisotropic subgroup we obtain is the standard SU
q
(2); it determines a new deformation of the 4-sphere ∑4
q
as the algebra of coinvariants in ?
q
7. We show that the quantum vector bundle associated to the fundamental corepresentation of SU
q
(2) is finitely generated and projective and we compute the explicit projector. We give the unitary representations of ∑4
q
, we define two 0-summable Fredholm modules and we compute the
Chern–Connes pairing between the projector and their characters. It comes out that even the zero class in cyclic homology
is non-trivial.
Received: 3 January 2001 / Accepted: 14 November 2001 相似文献