[en] The time-dependent oscillator describing parametric oscillation, the concept of invariant and Noether's theorem are important issues in physics education. Here, it is shown how they can be interconnected in a simple and unified manner.

[en] A system of two magnets hung from two vertical springs and oscillating in the hollows of a pair of coils connected in series is a new, interesting and useful example of coupled oscillators. The electromagnetically coupled oscillations of these oscillators are experimentally and theoretically studied. Its coupling is electromagnetic instead of mechanical, and easily adjustable by the experimenter. The coupling of this new coupled oscillator system is determined by the currents that the magnets induce in two coils connected in series, one to each magnet. It is an interesting case of mechanical oscillators with field-driven coupling, instead of mechanical coupling. Moreover, it is both a coupled and a damped oscillating system that lends itself to a detailed study and presentation of many properties and phenomena of such a system of oscillators. A set of experiments that validates the theoretical model of the oscillators is presented and discussed.

[en] The vibrational transition probability expressions for the forced Morse oscillator have been derived using the commutation relations of the anharmonic Boson operators. The formulation is based on the collinear collision model with the exponential repulsive potential in the framework of semiclassical collision dynamics. The sample calculation results for H₂ + He collision system, where the anharmonicity is large, are in excellent agreement with those from an exact, numerical quantum mechanical study by Clark and Dickinson, using the reactance matrix. Our results,however, are markedly different from those of Ree, Kim, and Shin's in which they approximate the commutation operator I_o as unity, the harmonic oscillator limit. We have concluded that the quantum number dependence in I_o must be retained to get accurate vibrational transition probabilities for the Morse oscillator

[en] High-l nonradial nonadiabatic fundamental oscillations of a star are considered. It is found that the f-mode 5-minute oscillations may be exited only by turbulent convection

[en] The issue of asymmetric modes output of a Ka-band super overmoded coaxial Cerenkov oscillator is analyzed in this paper. Due to serious passband overlapping in a super overmoded coaxial slow wave structure (SWS), the asymmetric competition mode EH₁₁ can hardly be suppressed thoroughly by the methods adopted in moderately overmoded devices, especially in the startup of oscillation. If the output structures reflect the asymmetric modes, the asymmetric mode competition in SWS will be aggravated and the normal operation state will be destroyed. In order to solve this problem, a taper waveguide is inserted at a specific position to achieve the destructive interference of the reflected TM₁₁, and a special support structure is designed to avoid reflection of TE₁₁. With these methods, asymmetric mode competition can be successfully eliminated, and the oscillator is capable of achieving a steady fundamental mode operation performance. (paper)

[en] Amongst all stars observed to pulsate, the Sun has by far the largest number and variety of modes of oscillation. This presents a unique opportunity to apply and test stellar oscillation theory. To match the observational accuracy, very precise calculations of oscillation frequencies are needed. Asymptotic methods have proved useful in the analysis and interpretation of the frequencies. The results provide tight constraints on solar models; they may also enable a direct determination of properties of the solar interior. There are difficulties in reconciling the amplitudes obtained in Doppler velocity with those observed in the apparent position of the solar limb. The excitation of the oscillations is so far not well understood, although it is probable that the interaction between pulsation and convection plays an important role. (orig.)

[en] Observation of global oscillations of the Sun constitutes a primitive seismology of the solar interior. The frequencies, if correctly identified with definite normal modes of vibration. Provide a measure of the average velocity of sound in the interior and thereby of its composition and temperature. Fine structure in the frequencies of nonradial modes may provide information on their character (multiplicity) and on the rotation of the solar interior. Study of the amplitudes and phase fluctuations of the vibrations may clarify the excitation and damping of the vibrations. After a brief historical review emphasizing global velocity spectroscopy an account is given of the present status of the observations of global oscillations in the range of periods of 3 to 160 min. Finally the future capabilities of the observational techniques and their resultant potential is discussed. (orig.)

[en] We report on a novel experiment to generate non-classical atomic states via quantum non-demolition (QND) measurements on cold atomic samples prepared in a high-finesse ring cavity. The heterodyne technique developed for QND detection exhibits an optical shot-noise limited behavior for local oscillator optical power of a few hundred μW, and a detection bandwidth of several GHz. This detection tool is used in a single pass to follow non-destructively the internal state evolution of an atomic sample when subjected to Rabi oscillations or a spin-echo interferometric sequence.

[en] The delayed response of a damped harmonic oscillator (RLC circuit) to a slow periodic disturbance is presented. This communication is supplementary to the paper published recently (Krupska et al 2001 Eur. J. Phys. 22 133-8)

[en] The authors present some initial results of a long-term investigation of resonant three-wave interactions in the solar interior, which indicate that these nonlinear interactions take place in the Sun and are, in fact, responsible for the observed g mode spectrum. The observed g mode spectrum consists of only a few modes. The authors assume that the 160-minute oscillation is a g mode and that the recently identified modes by Delache and Scherrer (1983) are also g modes. They believe that the amplitudes of these selected few modes have been enhanced by resonant interaction so that they may be observed at the Sun's surface. (Auth.)