| Time: | The first and third Friday of the month, noon-1:00pm |
| Place: | Room 206, Science and Tech I |
Observation of the magnetic vector potential a la’ Aharonov-Bohm along one-dimension in a magnetic field in the correspondence limit
Abstract: We report here the observation of the curl-free vector potential a la’ Aharonov-Bohm in the classical macro-domain for the one-dimensional motion of charged particle in a magnetic field. The nature of this observation is emphasized here as being a hitherto unfamiliar quantum manifestation of the behavior of the transition amplitude in the correspondence limit of large Landau quantum numbers.
Electron beam microwave devices: interactions of particles and waves
Abstract: I will discuss research conducted at the Waves and Fields Lab at George Mason in conjunction with Microwave Technologies, Inc. Most of the focus will be on our work on field emitting arrays and dielectric traveling wave tubes. These technologies have great potential for improving the microwave power amplifiers used in today's radar and communication systems.
Seven reasons that neutrinos may be tachyons
Abstract: Most physicists believe that material objects and information can not travel faster than c, the speed of light in vacuum. Tachyons, hypothetical faster-than-light particles were first proposed in 1962. Although direct experimental searches for tachyons have been negative, there are reasons to believe that neutrinos may be tachyonic.
Energy transport and solitons in a biopolymer
Abstract: The intrinsic dynamics of two types of biopolymers, described respectively by the wormlike chain (WLC) and the wormlike rod chain (WLRC) models, is studied using a geometric formalism. Considering the polymer to be a slender elastic rod whose central axis is a space curve, the appropriate moving triad frame is constructed for each model. The non-extensibility of the polymer during time evolution entails compatibility conditions on the frame fields. The nonlinear excitations supported by the systems are shown to be solitons, demonstrating that energy can propagate along the polymer like a localized wave packet in both types of biopolymers. The solutions may be interpreted as the explicit manifestation of the so-called conformon, an entity that has been hypothesized by various authors to play an important role in biology --- for instance, as localized packets of conformational strain on mitochondria.
Using chaotic signals to detect damage in structures
Abstract: We employ chaotic forcing to vibrate linear structures (e.g. beams) to determine when parameters of the structure change, i.e. damage has ocurred, during the lifetime of the structure. We explain the procedure and show proof of concept first using a circuit simulation of a structure. We show applications of this technique in structural experiments with cantelevered beams, composite beams with lap joints, and 2D steel plates with broken welds. For all these tests the chaotic forcing approach equaled or bettered the standard modal approach to damage detection. A further advantage is that the method is model free. The data itself is the model.
Analogies between lasers and epidemics - Universal characteristics in single and coupled systems with delays
Abstract: Many population models of epidemics, lasers, and mass action chemistry, can be shown to belong to a very general class of perturbed Hamiltonian models. In the first part the talk, I will show how a single population model can be shown to possess chaotic-like behavior in the presence of noise. The theory will be applied to both laser and epidemic models The second part of the talk will discuss new scaling relationships when populations are coupled to each other with delayed transport. Experimental results from a coupled lasers by the UMD group will be shown to corroborate the theory.
Schedule for previous years: Fall01 schedule,Spring02 schedule,Fall03 schedule,Spring04 schedule