| Topic: |
Science > Physics |
| User: |
"Edward Green" |
| Date: |
15 Feb 2007 05:46:42 PM |
| Object: |
The classical quantum Casimir effect |
[Restricting our attention to zero-point modes, we take another pass
at the Casimir effect.]
Energy is the currency, and entropy the greed: conservation of energy
is the accounting balance, whereas creation of entropy tells us the
direction of the deal. It is often possible however to take reduction
of energy as a surrogate for creation of entropy, perhaps because many
systems harbor energy in excess of thermal requirements, whose release
is therefore favored by creation of entropy.
That said, suppose at absolute zero two conducting plates are
separated by a gap, and that the desnity of zero-point energy between
the plates is less than that outside the plates, though still
annoyingly infinite (I guess we have to renormalize to find the
difference). Accept this makes sense.
By a purely geometric/energetic argument, moving the plates closer
together transfers volume from the inside to the outside, hence raises
the overall energy of the field. Hence, we conclude, the force
between the plates is repulsive. An analogical picture would be a
space everywhere in tension - filled with a network of rubber bands -
but a lower tension (energy) inside the gap. Hence the plates are
pulled apart.
This does not seem to be the normal prediction?
The standard analogy is not rubber bands but ocean waves: when ships
are close together the waves, which transfer momentum, die out between
the hulls, and so the ships are pushed further together. The
analogous phenomenon would be radiation pressure. Forgeting zero-
point field, thermal radiation at a finite temperature would push the
plates together in the expected manner, increasing entropy in the
process, even though locally we are doing work _and_ increasing the
energy of the field: license to do miracle this lies in heat flows.
I am uncertain what license we have to reserve the predicted direction
of the zero-point effect. Are we still going to claim heat flows from
the surroundings to balance the energy books, while allowing an
entropy-driven attractive force? Since this heat flow does not
increase the temperature, shall we say the system has an infinite heat
capacity so long as the plates are moving together?
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| User: "Uncle Al" |
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| Title: Re: The classical quantum Casimir effect |
15 Feb 2007 06:13:23 PM |
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Edward Green wrote:
[snip]
Heys stooopid, since "classical" means "not quantized"...
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
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| User: "Edward Green" |
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| Title: Re: The classical quantum Casimir effect |
16 Feb 2007 01:06:51 AM |
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On Feb 15, 7:13 pm, Uncle Al <Uncle...@hate.spam.net> wrote:
Edward Green wrote:
[snip]
Heys stooopid, since "classical" means "not quantized"...
How clever of you. It also means "old school" or "original", which in
this case means "the effect based on (quantum) zero point energy, as
opposed to an effect qualitatively understandable in terms of
(classical) thermal radiation, commented on elsewhere. I therefore
refer to the classical quantum effect as opposed to the non-classical
classical effect.
Got it?
Now that I've clarified the literary irony for you (a device sometimes
used among the educated), perhaps you have some substantive comments
on the question:
-- Energetic considerations alone suggest a repulsive force between
the plates associated with zero-point energy, rather than attractive,
as usually suggested. Why? --
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| User: "Sue..." |
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| Title: Re: The classical quantum Casimir effect |
16 Feb 2007 02:06:57 AM |
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On Feb 16, 2:06 am, "Edward Green" <spamspamsp...@netzero.com> wrote:
On Feb 15, 7:13 pm, Uncle Al <Uncle...@hate.spam.net> wrote:
Edward Green wrote:
[snip]
Heys stooopid, since "classical" means "not quantized"...
How clever of you. It also means "old school" or "original", which in
this case means "the effect based on (quantum) zero point energy, as
opposed to an effect qualitatively understandable in terms of
(classical) thermal radiation, commented on elsewhere. I therefore
refer to the classical quantum effect as opposed to the non-classical
classical effect.
Got it?
Now that I've clarified the literary irony for you (a device sometimes
used among the educated), perhaps you have some substantive comments
on the question:
-- Energetic considerations alone suggest a repulsive force between
the plates associated with zero-point energy, rather than attractive,
as usually suggested. Why? --
http://arxiv.org/abs/hep-ph/0610339v1
<< Repulsive forces dominate on short distance scales
resulting from the Pauli exclusion principal while an
attractive force dominates on longer scales resulting
from the dipole moment of the van der Waals dispersion
forces. >>
http://rac.uits.iu.edu/rats/research/grapes/grapes.shtml
Sue...
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| User: "Edward Green" |
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| Title: Re: The classical quantum Casimir effect |
16 Feb 2007 03:25:04 PM |
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On Feb 16, 4:06 am, "Sue..." <suzysewns...@yahoo.com.au> wrote:
<< Repulsive forces dominate on short distance scales
resulting from the Pauli exclusion principal while an
attractive force dominates on longer scales resulting
from the dipole moment of the van der Waals dispersion
forces.>>
Curiouser and curiouser. Neither repulsive forces attributable to the
Pauli exclusion principle nor Van der Waals forces have any obvious
connection to the exclusion of longer wavelength modes by the
dimensions of a cavity.
By the way, you asked me recently, in the apparent tone of "I bet you
haven't thought out this poorly thought out statement at all, have
you?", "What is a 'quantum effect'". I meant to answer.
First of all, that was _my_ straw dog talking, and I can make my straw
puppy utter whatever inane phrase I like, without _my_ being held
responsible for it: it's the law. It's like citing a web page. ;-)
Second of all, I think the conventional sense of a "quantum effect" is
clear enough: an effect difficult or impossible to explain using
classical physics which has a quantum explanation; therefore, a
species of evidence that, yes, Virginia, there _is_ a Quantum Klaus.
Verstehen sie?
I claim, via the mouth of my straw dog, that the Casimir effect is
widely taken as a "quantum effect" in the sense that it shows us that
quantum mechanics is operational, and possibly that the zero-point
field is everywhere, and so forth.
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| User: "Sue..." |
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| Title: Re: The classical quantum Casimir effect |
16 Feb 2007 03:48:11 PM |
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On Feb 16, 4:25 pm, "Edward Green" <spamspamsp...@netzero.com> wrote:
On Feb 16, 4:06 am, "Sue..." <suzysewns...@yahoo.com.au> wrote:
<< Repulsive forces dominate on short distance scales
resulting from the Pauli exclusion principal while an
attractive force dominates on longer scales resulting
from the dipole moment of the van der Waals dispersion
forces.>>
Curiouser and curiouser. Neither repulsive forces attributable to the
Pauli exclusion principle nor Van der Waals forces have any obvious
connection to the exclusion of longer wavelength modes by the
dimensions of a cavity.
By the way, you asked me recently, in the apparent tone of "I bet you
haven't thought out this poorly thought out statement at all, have
you?", "What is a 'quantum effect'". I meant to answer.
First of all, that was _my_ straw dog talking, and I can make my straw
puppy utter whatever inane phrase I like, without _my_ being held
responsible for it: it's the law. It's like citing a web page. ;-)
LOL... Why not take a career detour and compare magnetic
and Van der Waals forces, which really ARE classical.
Then the ozone of abstration won't overwhelm you if Casimir
and cavities really have anything to offer in your quest.
Second of all, I think the conventional sense of a "quantum effect" is
clear enough: an effect difficult or impossible to explain using
classical physics which has a quantum explanation; therefore, a
species of evidence that, yes, Virginia, there _is_ a Quantum Klaus.
Hmmm where is my URL for the magic shop? :o)
Verstehen sie?
I claim, via the mouth of my straw dog, that the Casimir effect is
widely taken as a "quantum effect" in the sense that it shows us that
quantum mechanics is operational, and possibly that the zero-point
field is everywhere, and so forth.
Einstein and Mach seemed to think that "gravity there, makes
inertia here" If is is there, it ain't here.
If it ain't here, it ain't everywhere. ;-)
Sue...
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| User: "Edward Green" |
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| Title: Re: The classical quantum Casimir effect |
16 Feb 2007 03:27:47 PM |
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On Feb 16, 4:06 am, "Sue..." <suzysewns...@yahoo.com.au> wrote:
http://arxiv.org/abs/hep-ph/0610339v1
<< Repulsive forces dominate on short distance scales
resulting from the Pauli exclusion principal while an
attractive force dominates on longer scales resulting
from the dipole moment of the van der Waals dispersion
forces. >>
http://rac.uits.iu.edu/rats/research/grapes/grapes.shtml
P.S.: I don't find that quote either of those places.
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| User: "Sue..." |
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| Title: Re: The classical quantum Casimir effect |
16 Feb 2007 03:53:06 PM |
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On Feb 16, 4:27 pm, "Edward Green" <spamspamsp...@netzero.com> wrote:
On Feb 16, 4:06 am, "Sue..." <suzysewns...@yahoo.com.au> wrote:
http://arxiv.org/abs/hep-ph/0610339v1
<< Repulsive forces dominate on short distance scales
resulting from the Pauli exclusion principal while an
attractive force dominates on longer scales resulting
from the dipole moment of the van der Waals dispersion
forces. >>
http://rac.uits.iu.edu/rats/research/grapes/grapes.shtml
P.S.: I don't find that quote either of those places.
My straw hound dog fetches it up on about the third occurance
of "repu".
http://www.google.com/search?hl=en&q=free+web+browser&btnG=Google+Search
:o)
Sue...
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| User: "Edward Green" |
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| Title: Re: The classical quantum Casimir effect |
16 Feb 2007 07:11:01 PM |
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On Feb 16, 5:53 pm, "Sue..." <suzysewns...@yahoo.com.au> wrote:
On Feb 16, 4:27 pm, "Edward Green" <spamspamsp...@netzero.com> wrote:
On Feb 16, 4:06 am, "Sue..." <suzysewns...@yahoo.com.au> wrote:
http://arxiv.org/abs/hep-ph/0610339v1
<< Repulsive forces dominate on short distance scales
resulting from the Pauli exclusion principal while an
attractive force dominates on longer scales resulting
from the dipole moment of the van der Waals dispersion
forces. >>
http://rac.uits.iu.edu/rats/research/grapes/grapes.shtml
P.S.: I don't find that quote either of those places.
My straw hound dog fetches it up on about the third occurance
of "repu".
Ok... I frankly didn't search the second page, because it looked
irrelevant, and guessed nothing about Casimir effect was there.
Full quote:
"Lennard-Jones force and potential:
* g(x)=2.0*pow(x,-7.0)-pow(x,-4.0) (lj.table)
* g(x)=pow(x,-6.0)-pow(x,-3.0) (ljpot.table)
The Lennard-Jones potential models the interaction between pairs of
electrically neutral atoms with filled electron shells (noble gases).
Repulsive forces dominate on short distance scales resulting from the
Pauli exclusion principal while an attractive force dominates on
longer scales resulting from the dipole moment of the van der Waals
dispersion forces."
Now, there may be some connection between the interaction of two many
electron atoms, and the alleged Casimir effect, between two many
electron conducting plates. In fact, when you put it that way, it
seems inevitable that there should be.
Damn... you're good: without actually commiting yourself to saying
anything, you give references somehow bizarrely related to the
question for the creative mind. I have to give you credit: it's a kind
of magic talent. :-)
One _might_ have thought the statement you quoted was intended as a
direct commentary on the Casimir effect, in context...
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| User: "galathaea" |
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| Title: Re: The classical quantum Casimir effect |
18 Feb 2007 04:37:34 PM |
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On Feb 15, 3:46 pm, "Edward Green" <spamspamsp...@netzero.com> wrote:
[Restricting our attention to zero-point modes, we take another pass
at the Casimir effect.]
Energy is the currency, and entropy the greed: conservation of energy
is the accounting balance, whereas creation of entropy tells us the
direction of the deal. It is often possible however to take reduction
of energy as a surrogate for creation of entropy, perhaps because many
systems harbor energy in excess of thermal requirements, whose release
is therefore favored by creation of entropy.
That said, suppose at absolute zero two conducting plates are
separated by a gap, and that the desnity of zero-point energy between
the plates is less than that outside the plates, though still
annoyingly infinite (I guess we have to renormalize to find the
difference). Accept this makes sense.
its already the difference that matters
modes are being excluded between the conductors
because of the vanishing of tangential components
different modes for the different geometries
inside / outside
By a purely geometric/energetic argument, moving the plates closer
together transfers volume from the inside to the outside, hence raises
the overall energy of the field. Hence, we conclude, the force
between the plates is repulsive. An analogical picture would be a
space everywhere in tension - filled with a network of rubber bands -
but a lower tension (energy) inside the gap. Hence the plates are
pulled apart.
you don't "push energy outside"!
there are many more modes available outside
as the plates approach there are even more modes available
and fewer on the inside
but energetically this says nothing
there are potentially infinite ways to interpret this
depending on the ordering of field operators
and maybe it would help to use so-called "normal" ordering
which eliminates vacuum contributions
and reinterprets them in source contributions?
in this picture
it is the induced dipole field
+|- +|-
+|- +|-
+|- +|-
that is the source of casimir
as the plates approach
there is increased dipole induction
and therefore a predicted attractive force
what field participates in the transaction
varies across the various operator orderings
but the same result is always predicted
This does not seem to be the normal prediction?
The standard analogy is not rubber bands but ocean waves: when ships
are close together the waves, which transfer momentum, die out between
the hulls, and so the ships are pushed further together. The
analogous phenomenon would be radiation pressure. Forgeting zero-
point field, thermal radiation at a finite temperature would push the
plates together in the expected manner, increasing entropy in the
process, even though locally we are doing work _and_ increasing the
energy of the field: license to do miracle this lies in heat flows.
except for turnarounds
i don't think the process must produce entropy
ie. constant velocity plate movement
looks like a potentially reversible process
the geometry is linear and separable
so there is no more added uncertainty in state space
...
the reason i am cautious
of associating an entropic component to casimir
is that some systems that look suspiciously like casimir
are used in models to violate the second law
in one class
macroscopic potential gradients
energetically select thermodynamics states
andreas trupp has even shown a model system
using liquid dielectrics
I am uncertain what license we have to reserve the predicted direction
of the zero-point effect. Are we still going to claim heat flows from
the surroundings to balance the energy books, while allowing an
entropy-driven attractive force? Since this heat flow does not
increase the temperature, shall we say the system has an infinite heat
capacity so long as the plates are moving together?
i think the analogy with heat
may be what is confusing here
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
galathaea: prankster, fablist, magician, liar
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