![[IOP]](http://images.iop.org/cws/icons/themes/phw/colophon-small.png){kind=icon}
Subir Sachdev.
By Hamish Johnston in Waterloo, Canada
Harvard’s Subir Sachdev has just taken the audience here at the Convergence conference on a delightful romp through the phase diagram of the cuprate high-temperature superconductors. What I found most interesting was not the superconducting phase, but rather Sachdev’s description of the “strange metal” phase.
This phase occurs when the cuprate copper-oxide layer is highly doped with holes and has perplexed physicists for some time – hence its strange moniker. It has no quasiparticles and lots of low-energy excitations so there is no easy way to describe the collective behaviour of the electrons.
In his talk, however, Sachdev pointed out an intriguing connection between the entropy of the strange metal and the entropy of a black hole. That’s all I am going to say here because I didn’t grasp all of the details, but if you want to know more take a look at this pre-print: “Bekenstein–Hawking entropy and strange metals”.
“Sachdev pointed out an intriguing connection between the entropy of the strange metal and the entropy of a black hole.”
This is a connection between one theory/model and another theory/model – not yet observed phenomena. No wonder.
Physicists should take care not to treat models and theories as if they are actual observed phenomena. This is the point where you can guarantee that the eventually observed phenomena will confound the theory.
Hawking radiation is a questionable hypotheses that one can find multiple objections to and has never been observed. The liberties it takes should equally allow a ‘black’ hole to radiate directly and simply without the contrivance of virtual pair separation etc etc. And observations seem to agree more with that.