Quantum kinematics are considered for two classes of systems: (i) the coordinate space is a homogeneous Riemannian manifold and the kinetic energy is the Laplace–Beltrami operator, (ii) the phase-space is a homogeneous Kählerian manifold where the algebra of observables is the universal enveloping algebra of the symmetry group. In both the cases, the path integrals are derived from more fundamental principles. The derivation enables a definite description of the classes of trajectories which constitute the domain of integration in the path integrals. The specification of the classes of functions is important for consistency of the approach. The standard action functional and the variational principle appear in the steepest descent method corresponding to the semiclassical approximation.
Abstract A definition of Feynmann’s ‘integral over all paths’ is given in precise mathematical terms, namely, it is shown, subject to some restrictions on the nature of the Lagrangian, that the ratio of the ‘integral’ to a certain normalization factor is uniquely determined by postulating: (i) the composition law, (ii) the possibility of taking any factor independent of the paths outside the integration over paths, and (iii) that the quantity in question should not involve any arbitrary ‘universal’ constants of the dimensions of inverse time. The nature of the normalization factor, referred to above, is also examined. Finally, a method of parametrization of paths is introduced, and it is shown that Feynmann’s ‘integral over all paths’ can, alternatively, be defined in terms of this parametrization.
In this paper we present the results of a research-based teaching-learning sequence on introductory quantum physics based on Feynman's sum over paths approach in the Italian high school.Our study focuses on students' understanding of two founding ideas of quantum physics, wave particle duality and the uncertainty principle.In view of recent research reporting the fragmentation of students' mental models of quantum concepts after initial instruction, we collected and analyzed data using the assessment tools provided by knowledge integration theory.Our results on the group of n ¼ 14 students who performed the final test indicate that the functional explanation of wave particle duality provided by the sum over paths approach may be effective in leading students to build consistent mental models of quantum objects, and in providing them with a unified perspective on both the photon and the electron.Results on the uncertainty principle are less clear cut, as the improvements over traditional instruction appear less significant.Given the low number of students in the sample, this work should be interpreted as a case study, and we do not attempt to draw definitive conclusions.However, our study suggests that (i) the sum over paths approach may deserve more attention from researchers and educators as a possible route to introduce basic concepts of quantum physics in high school, and (ii) more research should be focused not only on the correctness of students' mental models on individual concepts, but also on the ability of students to connect different ideas and experiments related to quantum theory in an organized whole.