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Forum: Processes Involving Optical Photons
Re: Question Faster Than Light Photons? (Joel Long)
Re: More Re: Faster Than Light Photons? (Joel Long)
Date: 13 Jul, 2012
From: Joel Long <Joel Long>

After extensive debugging, I have determined that my discrepant velocity is a result of an erroneous velocity being set by the Fresnel Refraction implementation in G4OpBoundaryProcess.

This is a result of non-physical group velocity values being calculated in G4MaterialPropertiesTable, which seems to be a result of my use of inputting indices of refraction for aluminum that are less than 1 (though still greater than zero).

My understanding was that the group velocity *could* be greater than the speed of light, and I am reasonably confident in my source for the refractive indices of Aluminum. However, I am also aware that individual photons should *not* be traveling faster than the speed of light - but the group velocity is used to set the velocity of the individual photons.

Does "group velocity" mean something different in Geant4 than I think it does? Should I simply force my refractive indices to 1 if they are actually less than 1?

Thanks everyone for your help, Joel

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1 Feedback: Re: Faster Than Light Photons?   (Gumplinger Peter - 13 Jul, 2012)
(_ Feedback: Re: Faster Than Light Photons?   (Joel Long - 16 Jul, 2012)
(_ Feedback: Re: Faster Than Light Photons?   (Gumplinger Peter - 16 Jul, 2012)
(_ Idea: Re: Faster Than Light Photons?   (Erik Dietz-Laursonn - 14 Sep, 2012)
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