Judson Ryckman <judson.d.ryck...@vanderbilt.edu> wrote> When I use this definition, the simulation runs great.? However, > suppose my epsilon was now eps = -4.4 + 3.9605i.? I could arbitrarily, > change the epsilon term (eps_inf) from 0.3 to -0.2.?
Strictly speaking, eps_inf should always be exactly 1 (the vacuum value); although you can usually get away with positive values in numerical situations, and can ignore the detail if not actually including such high frequencies in your analysis. If eps_inf isn't 1, you have, in essence, done odd things to your spacetime metric ... especially if you've picked a negative value! Numerically, your eps_inf should be positive (or the integration becomes unstable), physically eps_inf should be exactly 1. It's not just dispersion that you need to get exotic eps (or mu), its _causal_ dispersion; and part of that causality (at least from a KK perspective) demands that the limiting value of the high frequency (non vacuum) response is zero. -- ---------------------------------+--------------------------------- Dr. Paul Kinsler Blackett Laboratory (Photonics) (ph) +44-20-759-47734 (fax) 47714 Imperial College London, dr.paul.kins...@physics.org SW7 2AZ, United Kingdom. http://www.qols.ph.ic.ac.uk/~kinsle/ _______________________________________________ meep-discuss mailing list meep-discuss@ab-initio.mit.edu http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
