A quantum field model that incorporates Bose-condensed systems near their phase transition into a superfluid phase and velocity fluctuations is proposed. The stochastic Navier-Stokes equation is used for a generation of the velocity fluctuations. As such this model generalizes model F of critical dynamics. The field-theoretic action is derived using the Martin-Siggia-Rose formalism and path int...

Geometric dispersion is commonly observed in shallow water marine data due to post-critical multiples in the water layer over a hard seafloor. Characteristics of the guided waves include formation of distinct propagation modes and associated divergence of phase and group velocity. Methods have been available since 1981 to image phase velocity dispersion curves. Here we report a method to direct...

We present a theoretical and experimental study of the interplay between spin-orbit coupling (SOC), Coulomb interaction, and motion of conduction electrons in a magnetized two-dimensional electron gas. Via a transformation of the many-body Hamiltonian we introduce the concept of spin-orbit twisted spin waves, whose energy dispersions and damping rates are obtained by a simple wave-vector shift ...

Coherent control of reflected and transmitted pulses is investigated theoretically through a slab doped with atoms in a duplicated two-level configuration. When a strong control field and a relatively weak probe field are employed, coherent control of the group velocity is achieved via changing the phase shift φ between control and probe fields. Furthermore, the peak values in the delay time of...

It is shown that the combination of pulse-front slant, kappa -vector tilt, and crystal birefringence often permits exact matching of both phase and group velocities for three-wave mixing in birefringent crystals. This exact match makes possible more-efficient mixing of short light pulses, and it permits efficient mixing of chirped or broadband light. I analyze this process and present examples.

We present 20fs(2) accuracy laser-induced group velocity dispersion (LI-GVD) measurements, resulting from propagation of a femtosecond laser pulse in 1mm of fused silica, as a function of peak intensity. For a 5.5 × 10(11) W/cm(2) peak intensity, LI-GVD values are found to vary from -3 to + 15 times the material GVD. Normal induced dispersion can be explained by the Kerr effect, but anomalous L...

The transient response of an elastic cylinder to a laser impact is studied. When the laser source is a line perpendicular to the cylinder axis, modes guided along the cylinder are generated. For a millimetric steel cylinder up to ten narrow resonances can be locally detected by a laser interferometer below 8 MHz. These resonances correspond to Zero-Group Velocity guided modes or to circumferent...

An easily configurable experimental system is described in which negative group velocity tunneling of electrical pulses can be studied. Negative group velocity corresponds to the case in which the peak of a tunneled pulse exits before the peak of the incident pulse has entered the sample. In the experiments outlined herein, the tunneling occurs through the forbidden transmission region of a qua...

We present several different statistical methods to determine the transverse velocity vector of M31. The underlying assumptions are that the M31 satellites on average follow the motion of M31 through space, and that the galaxies in the outer parts of the Local Group on average follow the motion of the Local Group barycenter through space. We apply the methods to the line-of-sight velocities of ...

* The work is supported by DOE SBIR No. DE-FG03-96ER82213. Abstract Synchronous wakefields in a dispersive waveguide are formulated in a general form. The fundamental role of group velocity in wakefield propagation, calculation of attenuation, amplitudes, form-factors and loss-factors is demonstrated for single-bunch and multi-bunch train. Waveguide adiabatic tapering and bunch density variatio...