I think he is drawing an unwarranted conclusion.  The fact that a physical
clock must have finite extent doesn't mean it can't work.  Diffeomorphism
invariance is a requirement we impose on our theories to reflect the fact that
choice of coordinates is a matter of description, not physics.  To suppose that
somehow restricts what clocks can measure is to turn the principle on it's

Brent Meeker

>-----Original Message-----
>From: Stephen Paul King [mailto:[EMAIL PROTECTED]
>Sent: Sunday, May 08, 2005 3:19 AM
>To: Brent Meeker
>Cc: Stephen P. King
>Subject: Re: quantum field theories are problematic
>Dear Brent,
>    Did you understand the discussion of the implication of Diffeomorphism
>invartiance? That is the key point to Hitoshi's point. This requirement that
>the laws of physics are invariant under any possible coordinate
>transformation requires that one's clocks and rules be definable only on
>infinitesimal points. This destroys the possibility of defining a "physical
>clock" and thus the "multi-fingered time" idea collapses.
>----- Original Message -----
>From: "Brent Meeker" <[EMAIL PROTECTED]>
>To: "Stephen Paul King" <[EMAIL PROTECTED]>
>Sent: Saturday, May 07, 2005 2:22 PM
>Subject: RE: quantum field theories are problematic
>>>-----Original Message-----
>>>From: Stephen Paul King [mailto:[EMAIL PROTECTED]
>>>Sent: Sunday, May 08, 2005 12:41 AM
>>>To: Brent Meeker
>>>Subject: Re: quantum field theories are problematic
>>>Dear Brent,
>>>    Did you read Hitoshi's take on the problem on his website:
>>>Thanks for the reference, I will find the book and read it.
>> Yes I read it. Hitoshi seems confused to me.  First, he supposes that the
>> singularity theorems of Penrose and Hawking arise from imposing a global
>> coordinate system.  This is not so; the singularities are not artifacts of
>> coordinate choice.
>> Second, his discussion of time corresponds to what is called
>> "many-fingered"
>> time in GR - it's just the observation that physical time, as measured by
>> a
>> clock, is different for each different path the clock takes through
>> spacetime.
>> But that time is not necessarily the "t" that multiplies the Hamiltonian
>> in
>> exp(-itH).  That "t" is just a coordinate and there is not uncertainity
>> relation between it and the energy.  Physical time is what is measured by
>> a
>> physical clock.
>> Modeling an ideal clock in QM is non-trivial.  Asher Peres has a good
>> discussion of it in his text book "Quantum Theory, Concepts and Methods".
>> The
>> time that is measured by coupling such a physical clock to other QM events
>> does
>> have an uncertainity relation with energy.
>> Brent Meeker

Reply via email to