Re: QFT Questions
From: Gregory L. Hansen (glhansen_at_steel.ucs.indiana.edu)
Date: 08/12/04
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Date: Thu, 12 Aug 2004 20:02:48 +0000 (UTC)
In article <Pine.LNX.4.44.0408121359520.7455-100000@erodium.hep.wisc.edu>,
Creighton Hogg <wchogg@hep.wisc.edu> wrote:
>
>
>On Thu, 12 Aug 2004, Gregory L. Hansen wrote:
>
>> In article <Pine.LNX.4.44.0408121155450.7455-100000@erodium.hep.wisc.edu>,
>> Creighton Hogg <wchogg@hep.wisc.edu> wrote:
>> >
>> >Of course it's a little more complicated than that. The naive QFT that
>> >you'd base off of GR crashes and burns. There's basically three options
>> >after that
>> >a) We keep quantum mechanics as is and try to find a theory that can
>> >reduce to GR in some limit.
>> >b) We keep GR as is and expand our concepts of quantization.
>> >c) None of the above.
>> >
>> >a is the path string theory has taken and b the path Loop Quantum Gravity
>> >has taken.
>> >I switch votes between a,b, and c several times a week.
>> >It's a good thing nature doesn't care what I think.
><>
>> I admit that my ignorance of the subject is such that I might have
>> imagined QED with an interaction strength going as -G instead of +e (or
>> whatever alpha would work out to), and calling the job half done.
>
>Well the problem is that the interaction strength *isn't* just G. The
>coupling constant for a graviton vertex isn't a dimensionless constant,
>it's proportional to energy! That's very bad, from the standpoint of QFT.
>Unless you impose an energy cutoff everything goes all to hell. (I have
>this nagging feeling there are still problems even if you do impose an
>energy cutoff, but don't take my word for that.)
Well, maybe you could come up with a prediction in the Newtonian limit.
>
>> Maybe I'll take the time to educate myself on that subject when the real
>> world stops beating me in the face with a 2x4 with a nail in it.
>
>Geez, it sounds like you've been having a rough time lately. Is it your
>research?
Crunching to meet a hard deadline to defend my thesis; I haven't had a
weekend in more than a month. The equipment still doesn't work right.
Nobody's hiring physicists, I'm going to be hearing things like "Doctor
Hansen, there's a wet spill in front of Waldenbooks" when I graduate. I'm
starting to incoherently mutter things through my beard, like "You can't
commercialize the weak force", and "Why does everything have to be so
hard?" I'll wind up buying a cane just to wave at young people a few
years my junior, and hang around coffee shops near college campuses
telling students the value of an education.
>Did you know that the word "research" comes from a Swahili
>phrase meaning "won't work"? No really, it does.
If you're serious about that, I would post the etymology on my office
door. But it looks French.
>
>> >I don't know of any, to be honest. Like you said, it wouldn't be
>> >surprising if there were, but I just haven't ever heard of it. In string
>> >theory the graviton is a massless spin-2 particle. I don't think there is
>> >a well-defined graviton in loop quantum gravity yet.
>>
>> I don't have any references on hand, but here and there in journals like
>> the Phys Revs, Foundations of Physics, and the arXives, every once in a
>> while I find what seems like the most bizarre ideas being explored, which
>> render any crank's accusations of straight-jacketed scientific thinking to
>> be an admission of ignorance and laziness.
>>
>> There've been experimental tests of causality in nuclear matter. There's
>> always been an interest in measuring c+v^a for a moving source.
>> Discussions of aether theories as a general class of theories with special
>> relativity being a special case. And so on. It wouldn't surprise me if
>> some FTL gravity were included.
>
>Oh I agree completely. The Twentieth Century was *the* century for
>bizzare and crazy science. Relativity, quantum mechanics, nuclear
>physics, qft, quantum computers, etc. There were alot of big advances
>that were downright crazy ideas, but they worked. Cranks are full of it
>when they say we don't accept new ideas!
I'm not even talking about the big crazy ideas that worked. Also things
like Woodward's thoughts on the origin of inertia, the special
relativistic Newtonian gravity that Biswas discussed, "Covariant Ether
Theories and Special Relativity" by Kholmetskii (Physica Scripta 67, 381),
an attempt to measure gravity shielding during an eclipse (actually taking
LeSage's hypothesis seriously, Phys Rev D 62, 041101(R)), "Quantum
coherence and closed timelike curves" by Hawking, Phys Rev D 52, 5681, to
list some things off the top of my head or within reach.
Cranks see the pop-sci and the newsgroups, they don't seem to have a good
idea of the breadth of things that are attempted without the measure of
success required to be conveyed to the general public. They only see what
works, and assume nothing else is ever attempted. Or some of them
complain because scientists like Hawking *do* explore ideas like time
travel, rather than because they don't, and still managed to accuse
scientists of a fear of novelty while wanting the world to go back to
19th century science.
-- "I'm giving you the chance to look fate in those pretty eyes of hers and say, 'Step off, bitch. This is my party and you're not invited.'" -- Chris Shugart, _Testosterone Magazine_
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