Discussion:
How does indeterminacy arise from Stringiness?
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FearlessFerret
2005-05-25 16:21:36 UTC
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As a dedicated amateur, I can more or less follow along with stuff like Brian
Greene's popular books, although the details of things like Group Theory elude
me. I'm sure that's the reason I feel like I've been missing something, so
hopefully someone here can straighten me out.

Most of the popular press covering string theory seems to be about how the
properties of particles are derivable in principle by reasoning about 'tiny
vibrating strings', but my (sketchy in the extreme) understanding of QFT is that
there are no particles, just the interaction of fields. If string theory is
about explaining particles as strings, where does indeterminacy come from?

/ff
Igor Khavkine
2005-05-26 19:07:51 UTC
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On 2005-05-25, FearlessFerret <***@repliestonewsgrouponly.com> wrote:
> As a dedicated amateur, I can more or less follow along with stuff
> like Brian Greene's popular books, although the details of things like
> Group Theory elude me. I'm sure that's the reason I feel like I've
> been missing something, so hopefully someone here can straighten me
> out.
>
> Most of the popular press covering string theory seems to be about how
> the properties of particles are derivable in principle by reasoning
> about 'tiny vibrating strings', but my (sketchy in the extreme)
> understanding of QFT is that there are no particles, just the
> interaction of fields. If string theory is about explaining particles
> as strings, where does indeterminacy come from?

I'm not sure what you mean by indeterminacy in this concept. I'll give
answers two two questions. Hopefully, at least one of them will give you
an answer.

Quantum field theory can be seen as a theory of both fields and
particles. These descriptions are equivalent to each other. However,
under some exotic circumstances, the particle interpretation breaks down
while the field one doesn't. The theory is the same, but the
interpretation changes. That's why some people say that fields are more
fundamental than particles. So string theory approximates fields in as
much as it approximates particles.

If by indeterminacy you mean the indeterminism of measurement outcomes
in qauntum mechanics, then string theory has little to say about that.
String theory assumes quantum mechanics as.

Igor
FearlessFerret
2005-06-09 23:55:16 UTC
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Igor Khavkine wrote:
>
> I'm not sure what you mean by indeterminacy in this concept. I'll give
> answers two two questions. Hopefully, at least one of them will give you
> an answer.

The fuzziness of my question is a function of the fuzziness of my understanding.
Both these replies were helpful.

> Quantum field theory can be seen as a theory of both fields and
> particles. These descriptions are equivalent to each other. However,
> under some exotic circumstances, the particle interpretation breaks down

What circumstances would you consider 'exotic'?

> while the field one doesn't. The theory is the same, but the
> interpretation changes. That's why some people say that fields are more
> fundamental than particles. So string theory approximates fields in as
> much as it approximates particles.

This is intriguing, but I'm not optimistic that a non-mathematical exposition on
the subject is forthcoming.

> If by indeterminacy you mean the indeterminism of measurement outcomes
> in qauntum mechanics, then string theory has little to say about that.
> String theory assumes quantum mechanics as.

Anyone care to comment on the 'little' that string theory has to say?

/ff
Igor Khavkine
2005-06-11 07:45:11 UTC
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On 2005-06-09, FearlessFerret <***@repliestonewsgrouponly.com> wrote:
> Igor Khavkine wrote:

>> Quantum field theory can be seen as a theory of both fields and
>> particles. These descriptions are equivalent to each other. However,
>> under some exotic circumstances, the particle interpretation breaks
>> down
>
> What circumstances would you consider 'exotic'?

In non-exotic circumstances (which is what you see around you everyday).
The matter fields are pretty much zero everywhere, and you can think of
particles as localized wave packet excitations on top of this ground
state. Whenever excitations of matter fields cannot be described in such
a simple way, the particle description no longer applies. One not so
exotic example is radio waves. They are excitations of the E&M
(radiation) field, just like high energy gamma rays. The
wavelength for radio waves is too large to describe them as localized
wavepackets, while it isn't for gamma rays. So only the field
description applies in the former case, while the particle description
can also apply in the latter case. The situation in QFT is more
sophisticated, but similar in spirit.

>> If by indeterminacy you mean the indeterminism of measurement
>> outcomes in qauntum mechanics, then string theory has little to say
>> about that. String theory assumes quantum mechanics as.
>
> Anyone care to comment on the 'little' that string theory has to say?

I've pretty much already said it. It assumes quantum mechanics as is.
That is it.

Igor
Ken S. Tucker
2005-05-26 19:08:01 UTC
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FearlessFerret wrote:
> As a dedicated amateur, I can more or less follow along with stuff like Brian
> Greene's popular books, although the details of things like Group Theory elude
> me. I'm sure that's the reason I feel like I've been missing something, so
> hopefully someone here can straighten me out.
>
> Most of the popular press covering string theory seems to be about how the
> properties of particles are derivable in principle by reasoning about 'tiny
> vibrating strings', but my (sketchy in the extreme) understanding of QFT is that
> there are no particles, just the interaction of fields. If string theory is
> about explaining particles as strings, where does indeterminacy come from?
>
> /ff

The OP's question is so intriguing, I can't stop from
making a fool of myself by replying...

I'll get to indeterminancy, but let's have fun.

First everyone should glance at,

http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Democritus.html

Democritus, ((he looks stoned at the site, but he's ok in person)).

I think that's a fair place to start with limit of divisiblity
of matter, that formed the basis of the atomic theory,
philosophically.

Remarkably, 20th century technology has been able to investigate
that philosophy from 2000 years ago and find it is basically
truthful, ((hence Democritus has been honored posthumourously by
the Tucker Prize commitee for $1 trillion, accounting for inflation)).

That truth was about matter, but relativity and Quantum Theory
modified Democritus theory to a quantization of *action*.

So measurement is restricted to quantities of action "h",
being PLancks constant...there's much more.

Regards
Ken S. Tucker
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