Stat.Phys. informal seminar

[Cond.Matt. & Stat.Mech.Section]

INFORMAL SEMINAR on
Statistical Physics




Seminar Room -  Leonardo Building  (first floor)





Thursday, 21 January -     11:00 a.m.





Sahand Jamal RAHI   ( Massachusetts Institute of Technology, Cambridge )





"Scattering theory approach to electrodynamic Casimir interactions"



Abstract



We have derived methods for calculating the Casimir force to arbitrary  
accuracy, for any number of objects, arbitrary shapes, susceptibility  
functions, and separations.  The technique is applicable to objects  
immersed in media other than vacuum, nonzero temperatures, and spatial  
arrangements in which one object is enclosed in another.  The method  
combines each object's classical electromagnetic scattering amplitude  
with universal translation matrices, which convert between the bases  
used to calculate scattering for each object, but are otherwise  
independent of the details of the individual objects.  We have  
explored various novel geometries using these techniques, including  
objects interacting with cavities and objects with sharp edges.

The method is further used to examine whether fluctuation-induced  
forces can lead to stable levitation. Neglecting permeabilities, we  
find that any equilibrium position of items subject to such forces is  
also unstable if the permittivities of all objects are higher or lower  
than that of the enveloping medium; the former being the generic case  
for ordinary materials in vacuum. Thus, the Casimir force cannot  
produce stable equilibria in vacuum for ordinary materials.