[en] Classes and examples of potentials which give a classical deflection function equal to zero for any value of the impact parameter at a fixed energy are given. Thus these potentials are completely transparent for a classical collision at this energy

[en] A theorem of Lee Hwa Chung suggests a possible generalization of the symmetry concept in classical mechanics. It is shown that the theory of Konstant-Souriau-Kirillov can be adapted to this more general case. The theory is illustrated with a number of exaples.(author)

[en] The didactic approach to Noether's theorem in classical mechanics presented in Marinho Jr (2007 Eur. J. Phys. 28 37-43) is re-examined. (letters and comments)

[en] Long term simulations of Hamiltonian dynamical systems benefit from enforcing the symplectic symmetry. One of the several available methods to perform this symplectification is provided by the recently developed theory of extended generating functions. The theory offers an infinite supply of generator types that can be used for symplectification. Using Hofer's metric, a condition for optimal symplectification is given. In the weakly nonlinear case, the condition provides a generator type that, based on the limited information available on the system, in general gives optimal results

[en] Students’ misconceptions about Newton's second law in frictionless outer space were investigated. The research was formed according to an epistemic game theoretical framework. The term ‘epistemic’ refers to students’ participation in problem-solving activities as a means of constructing new knowledge. The term ‘game’ refers to a coherent activity that consists of moves and rules. A set of questions in which students are asked to solve two similar Newton's second law problems, one of which is on the Earth and the other in outer space, was administered to 116 undergraduate students. The findings indicate that there is a significant difference between students’ epistemic game preferences and race-type (outer space or frictional surface) question. So students who used Newton's second law on the ground did not apply this law and used primitive reasoning when it came to space. Among these students, voluntary interviews were conducted with 18 students. Analysis of interview transcripts showed that: (1) the term ‘space’ causes spontaneity among students that prevents the use of the law; (2) students hesitate to apply Newton's second law in space due to the lack of a condition—the friction; (3) students feel that Newton's second law is not valid in space for a variety of reasons, but mostly for the fact that the body in space is not in contact with a surface. (paper)

[en] It is shown that for a solid body following a curvilinear trajectory its rotation angle due to the effect of the special theory of relativity (Thomson precession) is numerically equal to the rest-frame-observed solid angle through which the body-fixed axis turns as a consequence of the rotation change the body image undergoes due to Lorentz length contraction and the retardation of the light emitted by various portions of the body. In classical mechanics, the same relation connects the solid-body rotation angle to the actual solid angle that the body-fixed axis describes as the body performs a conical motion - which is a consequence of Ishlinskii's theorem. (methodological notes)

[en] At the request of the Cedar Valley College science department, the Accelerator Systems Division offered to develop an introductory physics course for their undergraduate students. The two-semester course was given by a Supercollider staff scientist for the first time at the College during the 1992-93 academic year. The course includes lectures, laboratory experiments, problem sessions, and tests, of course. The material covered consists of Newtonian mechanics and electromagnetic field theory. The students purchase a popular textbook which contains numerous problems from which homework assignments are made; however, hundreds of transparencies specially prepared for use during course lectures are handed out to the students to provide them with study material

No abstract available

[en] Classical and quantum motions of particles are very different. Indeed one cannot assign a trajectory to a quantum particle. However one has the physical intuition that quantum particles wander around the corresponding classical path in phase space by an amount of h. Deviations come from the uncertainty principle. Underlying this picture, there are two ideas: i) there is some kind of probability associated with possible paths; ii) this probability concentrates around the classical path in a region whose magnitude is related to h. We want to show that there exists in phase space a probabilistic schema which accounts in a much more transparent way for the intuitive ideas alluded above. It is convenient to deal with the description of quantum states not in term of wave function but in term of Wigner functions. It allows a more symmetrical treatment of phase-space variables. Also it is expected to be a less singular object than the wave function in the classical limit. Second section is devoted to describe the elementary results concerning Wigner function. It also describes the time development equation of these functions. In the third section we describe the quantum flow which represents the quantum dynamics in phase space. In the last section, we study the asymptotics of this flow showing that it tends in a suitable sense to the classical flow. The most useful tool for this study is the Ventsel's theory of large deviations. This theory already proved to be very efficient in the study of classical limit. However it has not been used for jump processes up to now

[en] We introduce a new concept allowing the recasting of the reciprocity gap method into a variational method. The reciprocity likelihood functional maximization gives rise to nested approximation properties when performed on minimization spaces with increasing dimensions and leads to direct identification methods grounded on the reciprocity property. Application to the identification of point sources is given for illustration of the solution procedure of identification, and an analysis of the effect of noisy data shows that the proposed methods exhibit very good robustness. (authors)