Dear Daniel,

It is a real pleasure to read your recent "Inconsistency of quantum-classical dynamics, and what it implies", quant-ph/0402092 [Ref. 1].

Regarding the inconsistency of quantum-classical dynamics, and the apparent violation of the correspondence principle and energy nonconservation, see

http://members.aon.at/chakalov/Seevinck.html

http://members.aon.at/chakalov/Carlip.html#GR

As to "what it implies", see

http://members.aon.at/chakalov/Kuchar.html#Martin

I believe the quest for quantum gravity should start with the human brain dynamics,

http://members.aon.at/chakalov/white_paper.html#brain

BTW you quoted in ref [20] a paper by Thomas Thiemann [Ref. 2], which is one of the best I've read. It is dated 5 October 2001, and is still waiting to be posted on "Living Reviews". Since it is supposed to be updated "on at least a bi-annual basis", I wrote a nice little note at

http://members.aon.at/chakalov/Thiemann.html

The issue at the link above is known since 1917.

I wonder if you and your colleagues can help Thomas with the update.

Best regards,

Dimi
http://members.aon.at/chakalov
http://members.aon.at/chakalov/white_paper.html
 

References

[Ref. 1] Daniel R. Terno, Inconsistency of quantum-classical dynamics, and what it implies, quant-ph/0402092 v1, Fri, 13 Feb 2004 18:00:40 GMT

"To have a non-trivial quantum-classical dynamics it is necessary to have classical non-observable operators in the interaction term, but their presence leads to the violation of correspondence principle and may result in energy nonconservation.

"As a result, it is impossible to maintain that apparatus is described by classical mechanics through the interaction. The "dual" approaches, where the apparatus is treated either quantum-mechanically or classically [7, 8] are necessary.

"Since the classical gravity (pure or with matter) can be formulated in the Hamiltonian form [20], the above result applies to it as well. Impossibility of the universal mixed dynamics means that to get a fully consistent description of the gravitation phenomena, there must be a quantized theory of gravity."
 

[Ref. 2] T. Thiemann, Introduction to Modern Canonical Quantum General Relativity, gr-qc/0110034 v1, 5 October 2001

"This report is submitted to the on-line journal "Living Reviews" and is thus subject to being updated on at least a bi-annual basis."

[Subject editor: Renate Loll]

============

Subject: Re: Inconsistency of quantum-classical dynamics, and what it implies
Date: Fri, 20 Feb 2004 06:14:04 +0200
From: Dimi Chakalov <dimi@chakalov.net>
To: "E.C.G. Sudarshan" <sudarshan@physics.utexas.edu>
CC: Daniel Terno <dterno@perimeterinstitute.ca>
 

Dear Professor Sudarshan,

I think you were a bit too quick to refute Daniel Terno's work [Ref. 3]. Perhaps you may wish to read it again,

http://members.aon.at/chakalov/Terno.html#1

You introduce "a special kind of quantum system [9, 10, 11, 12] with additional variables that are not observable", and then suggest that "the dynamical description must involve these additional variables." [Ref. 3]

Only these special additional hidden variables lead to an equally special operator Hamiltonian  H  that is *not* an observable either, since it contains *a, *b. [Ibid.]

What physical clock can read the "evolution" of your total Hamiltonian?

I believe that measuring commuting observables can be achieved only by some mystical "instantaneous measurements",

http://members.aon.at/chakalov/intro.html#Balachandran

Of course, if you can suggest a mechanism for relativistic "collapse" of an entangled system, as in the EPR argument, perhaps your "special kind of quantum system" will become acceptable, and will reveal those hidden, never-ever-observable "additional variables". More at

http://members.aon.at/chakalov/Willem.html#STR

http://members.aon.at/chakalov/Seevinck.html

Sincerely yours,

Dimi Chakalov
--
How do we know that Father Christmas has a beard? We know it, because snow falls when he shakes his beard.

Old Tanzanian saying
 

Reference

[Ref. 3] E.C.G. Sudarshan, Consistent measurement of a quantum dynamical variable using classical apparatus, quant-ph/0402134 v1

"Since we need to couple the two systems we must first view a classical system as a special kind of quantum system [9, 10, 11, 12] with additional variables that are not observable. The dynamical description must involve these additional variables.
...

"We now proceed to see how this quantum mechanical description of the classical system can be used to look at the case where it is interacting with a quantum system. As a quantum system we may choose a system with a complete set of dynamical variables, either a spin system or a harmonic oscillator.
...

"The total Hamiltonian is then [...] .
...

"The operator Hamiltonian  H  is not an observable [2] since it contains *a, *b.
...

"I am thankful to Anil Shaji for bringing the inconsistent consistency claims to my attention and for useful discussions."