On Wednesday, April 3, 2019 at 9:51:22 PM UTC-5, Lawrence Crowell wrote:   
   > The Unruh-Hawking radiation physics is semi-classical physics. It   
   > assumes a classical geometry to spacetime.   
      
   That's nothing but an evasion to avoid the inconvenient conclusions that   
   are forced on you -- much like the evasion that took place in the late   
   1800's and early 1900's with the issue of the aether.   
      
   There is no alternative. It assumes what is necessary; the alternative   
   being mathematically impossible and quite likely subject to a no-go   
   theorem.   
      
   There is no getting away from classical geometry; that's nothing more   
   than a folklore meme. Classical geometry is there, no matter what you   
   do, by the Correspondence Limit. It is there in the form of the space of   
   coherent states (each coherent state corresponding to a classical   
   geometry.)   
      
   If the coherent states do *not* correspond to classical geometries, then   
   that also means the *classical limit* does not have those classical   
   geometries either. In that case, the mismatch that obstructs the   
   creation of a unified formalism for quantum theory and general   
   relativity lies in classical physics; not quantum physics at all.   
      
   But that's highly doubtful; since we're already have classical   
   experiments by now that would detect any such misfit.   
      
   But even if so, there too, you're still dealing with a classical   
   "geometry" ("geometry" being whatever it is in the classical limit that   
   replaced the Riemann-Cartan geometry). Quantum theory will be a red   
   herring here too.   
      
   You've have 100+ years now. It's time to stop evading the matter and   
   avoiding issues.   
      
   There is no such thing as a quantum theory:   
   > (a) with classical general relativity as its classical limit in   
   > which (b) the Weyl tensor is a q-number.)   
      
   and there never will be. Nothing that has been developed over the past   
   100+ years -- be it Carmelli's SL(2,C) gauge gravity theory (which is   
   renormalizable) or 2+1-D quantum gravity alters that conclusion one   
   bit. Among other things, any quantum theory of gravity in which the Weyl   
   tensor is a q-number will violate causality.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)