Slow light.. is not C constant some sort of rule that can not be broken one is at first prompted to ask...
However the researchers point out.......
Slowing light this way doesn't violate any principle of physics. Einstein's theory of relativity places an upper, but not lower, limit on the speed of light.
http://www.cosmosmagazine.com/news/8...speed-internet
I thought this may be interesting
alex