On the nature of continuous physical quantities in classical and quantum mechanics

Within the traditional Hilbert space formalism of quantum mechanics, it is not possible to describe a particle as possessing, simultaneously, a sharp position value and a sharp momentum value. Is it possible, though, to describe a particle as possessing just a sharp position value (or just a sharp momentum value)? Some, such as Teller (Journal of Philosophy, 1979), have thought that the answer to this question is No -- that the status of individual continuous quantities is very different in quantum mechanics than in classical mechanics. On the contrary, I shall show that the same subtle issues arise with respect to continuous quantities in classical and quantum mechanics; and that it is, after all, possible to describe a particle as possessing a sharp position value without altering the standard formalism of quantum mechanics.Comment: 26 pages, LaTe

Nonstationary random acoustic and electromagnetic fields as wave diffusion processes

We investigate the effects of relatively rapid variations of the boundaries of an overmoded cavity on the stochastic properties of its interior acoustic or electromagnetic field. For quasi-static variations, this field can be represented as an ideal incoherent and statistically homogeneous isotropic random scalar or vector field, respectively. A physical model is constructed showing that the field dynamics can be characterized as a generalized diffusion process. The Langevin--It\^{o} and Fokker--Planck equations are derived and their associated statistics and distributions for the complex analytic field, its magnitude and energy density are computed. The energy diffusion parameter is found to be proportional to the square of the ratio of the standard deviation of the source field to the characteristic time constant of the dynamic process, but is independent of the initial energy density, to first order. The energy drift vanishes in the asymptotic limit. The time-energy probability distribution is in general not separable, as a result of nonstationarity. A general solution of the Fokker--Planck equation is obtained in integral form, together with explicit closed-form solutions for several asymptotic cases. The findings extend known results on statistics and distributions of quasi-stationary ideal random fields (pure diffusions), which are retrieved as special cases.Comment: 54 pages, 8 figures, to appear in J. Phys. A: Math. Theo

Hyperfine structure of neutral vanadium lines and livels

We have recorded hollow-cathode spectra of neutral vanadium by Fourier transform spectroscopy in the near infrared - visible region (9000-17 000 cm-1). 36 transitions showing hyperfine structure have been analyzed, allowing us to deduce magnetic dipole constants for 27 levels belonging to the 3d44p and 3d34s4p configurations. For 22 of these levels no data were previously available

Radiative lifetime and oscillator strength determination in Mg-like potassium (K VIII)

Theoretical transition probabilities have been obtained for 54 n=3 transitions depopulating the 3s3p 1Po, 3p2 3P, 1D, 1S, 3s3d 1D, 3D and 3p3d 3Po, 3Do, 3Fo, 1Fo, 1 Do, 1Po levels, including 14 transitions not yet observed. Some of these predictions have been compared with experimental lifetimes obtained by beam-foil spectroscopy for four n=3 levels of K7+. An excellent agreement is observed between theory and experiment for all the levels

Radiative lifetimes of 3p ²PoJ in Boron-like Nitrogen

info:eu-repo/semantics/nonPublishe

Measurement of the 2s 2p2^{2}(4^{4}P) 3s 3^{3}P2_{2} lifetime in N II by beam-foil-laser spectroscopy

An accurate value for the radiative lifetime of the 2s 2p$^{2}$($^4$P) 3s $^3$P$_{2}$ level in N II has been obtained using the beam-foil-laser spectroscopy method. The results $(\tau = 0.456\pm 0.020$ ns) is shorter than the beam-foil lifetime values reported previously for the 3s$'$ $^3$P term. No theoretical value for the lifetime of this term is available at the present time.Nous avons mesuré avec précision la durée de vie radiative du niveau 2s 2p$^{2}$($^4$P) 3s $^3$P$_{2}$ de N II par la méthode de spectroscopie faisceau-lame-laser. La durée de vie obtenue $(\tau = 0.456\pm 0.020$ ns) est plus courte que celles mesurées précédemment, par spectroscopie faisceau-lame, pour le terme 3s$'$ $^3$P de N II. Aucune valeur théorique de la durée de vie de ce terme n'est actuellement disponible