We discuss four general features of the force-free evolution of wave packets: 1 The spatial spread of a packet changes with time in a simple way. 2 For sufficiently short durations related to the spread in the momentum of the packet the probability distribution will move with uniform speed and little change in shape. 3 After a sufficiently long time related to the initial spatial spread the wav...

Time-resolved transient grating techniques ~TG! arising from four-wave mixing ~FWM! processes are explored for the study of molecular dynamics in gas-phase systems ranging from single atoms to large polyatomic molecules. For atomic species such as Ar and Xe, each TG signal shows only a peak at zero time delay when all three incident pulses are overlapped temporally. For diatomic O2 and N2 and l...

We construct a semiclassical theory for propagation of an optical wave packet in a nonconducting medium with a periodic structure of dielectric permittivity and magnetic permeability, i.e., a nonconducting photonic crystal. We employ a quantum-mechanical formalism in order to clarify its link to those of electronic systems. It involves the geometrical phase, i.e., Berry's phase, in a natural wa...

General arguments in favor of the necessity of a wave packet description of neutrino oscillations are presented, drawing from analogies with other wave phenomena. We present a wave packet description of neutrino oscillations in stationary beams using the density matrix formalism. Recent claims of the necessity of an equal energy of different massive neutrinos are refuted.

Topological physics is based on topological invariants such as the Chern number, which integral of Berry curvature. The quantum metric complementary to curvature in geometric tensor, but its role much less understood. authors show here that it becomes dominant for wave-packet dynamics at exceptional points strongly non-Hermitian systems. demonstrate that, thanks divergent metric, wave packets (...

In the Majorana equation for particles with arbitrary spin, the wave packet is due not only to the uncertainty affecting position and momentum but also to the infinite components with decreasing mass forming the Majorana spinor. In this paper we prove that such components contribute to increase the spreading of the wave packet. Moreover, as occurs in the time propagation of the Dirac wave packe...

We demonstrate an information hiding and retrieval scheme with the relative phases between states in a Rydberg wave packet acting as the bits of a data register. We use a terahertz half-cycle pulse (HCP) to transfer phase-encoded information from an optically accessible angular momentum manifold to another manifold which is not directly accessed by our laser pulses, effectively hiding the infor...

This paper deals with peristaltic flow of a Johnson–Segalman fluid in an asymmetric channel under long-wavelength and lowReynolds number considerations. The channel asymmetry is caused due to the peristaltic wave train on the walls having different amplitudes and phase. A series solution for small Weissenberg number is obtained for the stream function, axial velocity, axial pressure gradient an...

Here we propose an experimental set-up in which it is possible to obtain the entanglement of a two-mode Gaussian state, be it pure or mixed, using only simple linear optical measurement devices. After a proper unitary manipulation of the two-mode Gaussian state only number and purity measurements of just one of the modes suffice to give us a complete and exact knowledge of the state’s entanglem...