Re: Article: A Century of Einstein

From: Gregory L. Hansen (glhansen_at_steel.ucs.indiana.edu)
Date: 08/30/04 

Date: Mon, 30 Aug 2004 14:17:15 +0000 (UTC)

In article <qhxYc.12891$D7.10789@news-server.bigpond.net.au>,
Bill Hobba <bhobba@rubbish.net.au> wrote:
>
>"Gregory L. Hansen" <glhansen@steel.ucs.indiana.edu> wrote in message
>news:cgu2uh$974$1@hood.uits.indiana.edu...
>> In article <%psYc.12658$D7.10501@news-server.bigpond.net.au>,
>> Bill Hobba <bhobba@rubbish.net.au> wrote:
>> >
>> >"Ole D. Rughede" <ole.rughede@privat.dk> wrote in message
>> >news:413204ed$0$211$edfadb0f@dread11.news.tele.dk...
>>
>> >
>> >Blah, blah, blah - your references to explaining the photoelectric effect
>> >without particles please?
>>
>> Wald, in his book "Quantum Field Theory in Curved Spacetime and Black Hole
>> Thermodynamics", stresses that quantum field theory is a theory of fields.
>> That in asymptotically flat spacetimes there's a natural particle
>> interpretation, but there is no particle interpretation in arbitrary
>> spacetimes, and particles are never needed.
>>
>> That, of course, doesn't mean that photons are any less of a particle than
>> electrons are.
>
>My point being electrons, photons, and everything else we know of, are all
>just quantum stuff which are called quantum particles. The desire to
>introduce nomenclature like 'energy-elements' is an attempt to introduce
>layers of obstupefaction to cloud the issue; and is a standard crank
>technique.

"Energy-elements" sounds a lot like "I don't want to admit they're
particles" to me.

>
>>It's just that particles aren't what people usually think
>> they are. Fundamentally we have fields, and DeBroglie's relation and the
>> probabilistic interpretation of a wavefunction applies to them.
>
>Correct Gregory - according to QFT everything is a field - but the
>observables of those fields are always composed of creation and anihliation
>operators of particles - see the chapter 4 page 169 of Weinberg the Quantum
>Theory of Fields. QFT gives normal QM as a limit so that the quantum fields
>(which come about for particles from the process of second quantisisation on
>the quantum state and for classical fields the process of quantiisisation on
>the field - see chapter 4 - page 167 Classical Mechanics, Quantum
>Mechanics, Field Theory by Amon Katz) can be approximated by the usual
>quantum state as found in any book on normal QM - eg Diracs Principles of
>QM. But that in no way changes the evidence we have, which is that
>everything, including light, consist of quantum particles regardless of if
>we consider them to obey the rules of QFT of we consider the approximation
>of normal QM.

Well, that's what I was just saying Wald was saying. There's a particle
interpretation of the fields for asymptotically flat spacetimes, but not
in arbitrary spacetimes, and not of necessity. We don't have fields made
of particles, we have fields that we can sometimes call particles. 

-- 
"In any case, don't stress too much--cortisol inhibits muscular
hypertrophy. " -- Eric Dodd

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