# Jaffe's take on Casimir force

1. Mar 21, 2005

### marcus

http://arxiv.org/hep-th/0503158 [Broken]
The Casimir Effect and the Quantum Vacuum
R. L. Jaffe
9 pages, 3 figures

"In discussions of the cosmological constant, the Casimir effect is often invoked as decisive evidence that the zero point energies of quantum fields are 'real'. On the contrary, Casimir effects can be formulated and Casimir forces can be computed without reference to zero point energies. They are relativistic, quantum forces between charges and currents. The Casimir force (per unit area) between parallel plates vanishes as \alpha, the fine structure constant, goes to zero, and the standard result, which appears to be independent of \alpha, corresponds to the \alpha\to\infty limit."

Jaffe is a senior respected guy at MIT. Not a nut.
He debunks the usual presumption that the Casimir effect has something to do with
the "dark energy" or "vacuum energy" of cosmology.
I like it that he goes against my preconceptions a little. I think it is a really well-written paper and could have Quantum Gravity repercussions.

It isnt yet sure that dark energy is real. after all. Here is another quote from jaffe:

---quote---
As evidence of the “reality” of the quantum fluctuations of fields in the vacuum, theorists often point to the Casimir effect [6]. For example, Weinberg in his introduction to the cosmological constant problem, writes[5],

“Perhaps surprisingly, it was along time before particle physicists began seriously to worry about [quantum zero point fluctuation contributions to ?] despite the demonstration in the Casimir effect of the reality of zero-point energies.”

More recent examples can be found in the widely read reviews by Carroll[7],

“ ... And the vacuum fluctuations themselves are very real, as evidenced by the Casimir effect.”

and by Sahni and Starobinsky [8],[9]

“The existence of zero-point vacuum fluctuations has been spectacularly demonstrated by the Casimir effect.”
---end quote---

it looks like jaffe is nailing prominent figures like Steven Weinberg and
Sean Carroll

---quote---
I have presented an argument that the experimental confirmation of the Casimir effect does not establish the reality of zero point fluctuations. Casimir forces can be calculated without reference to the vacuum and, like any other dynamical effect in QED, vanish as ? ?0. ...

The deeper question remains: Do the zero point energies of quantum fields contribute to the energy density of the vacuum and, mutatis mutandis, to the cosmological constant?

Certainly there is no experimental evidence for the “reality” of zero point energies in quantum field theory (without gravity). Perhaps there is a consistent formulation of relativistic quantum mechanics in which zero point energies never appear. I doubt it. ... Still, no known phenomenon, including the Casimir effect, demonstrates that zero point energies are “real”.
---endquote---

Last edited by a moderator: May 1, 2017
2. Mar 31, 2005

Has this generated any sort of a buzz? I'm having trouble finding any discussions on the matter... (admittedly though, my searching skills in this area are lacking).

The 'Casimir effect' always seemed to strike a cord with me, but I nevertheless find it oddly refreshing to see it being 'attacked'.

3. Mar 31, 2005

### wolram

it looks like jaffe is nailing prominent figures like Steven Weinberg and
Sean Carroll
-------------------------------------------------------
Bravo for Jaffe, it is about time that this ineligant theory is bined

4. Mar 31, 2005

### ohwilleke

The Casmir effect may be the most common experimental justification for ZPE, but keep in mind that this relatively easy acceptance is theoretically well motivated. IIRC, QED calculations require the inclusion of terms which are heuristically associated with ZPE probabilities. Thus, associating Casmir with ZPE is a situation where theory expects something to be there and it is observed, rather than a case where Casmir was discovered and therefore theory had to be reworked in a manner that caused ZPE to arise.

The indirect evidence for ZPE from QED calculations therefore, remains meaningful.

5. Mar 31, 2005

### Chronos

Jaffe is another among my just read list, and some of the same thoughts marcus had crossed my mind. I'm not sold on the approach, but the objections are very sensible and worth considering. The accoustical casimir effect appears to be a very promising investigatory tool.

6. Nov 15, 2006

### Demystifier

7. Nov 15, 2006

### Careful

Ohw, but this is really old, Schwinger tried it in his time and for example Barut and Dowling recuperated the standard Casimir force as an interaction between charges and currents without any reference to zero point fluctuations at all. Nothing new, neither revolutionary about it.

Last edited by a moderator: May 2, 2017
8. Nov 15, 2006

9. Nov 15, 2006

Staff Emeritus
If you read in Smolin's "The Trouble with Physics" his history of string physics, you will find that he discusses several cases where a discovery or theoretical point was made, and repeatedly, but simply ignored by the community until that community decided to investigate the question for some internal reason. The "landscape" is a prime example, the general problem of multiple vacua was asserted a decade or more ago, and it was actually Smolin himself who introduced the term "landscape". But like the legendary duck quack, it found no echo. Until.. it became a fad.

So we can expect all assertions of the nonreality of the vacuum fluctuations to be treated as never written until they become the central issue for some future generation of safe, accepted, theorists.

10. Nov 15, 2006

### Careful

Well, two remarks, what Jaffe proposes does not fully solve the cosmological constant problem of course (it merely says we can believe it to be zero - which is insufficient). Concerning your social comment, hehe I believe having heard about a reaction by Penrose when he was asked the question how he feels that string theorists are now finally taking his spin networks seriously 30 years after their invention (the reporter suggested he must be very proud now to see his work finally recognized). His reaction roughly went like well, I feel like someone being in the desert for a long time while suddenly observing a flock of bizons on a distance ... the problem being that the flock is heading towards me at increased speed ´´

Careful

Last edited: Nov 15, 2006
11. Nov 16, 2006

### Demystifier

I fully agree with that claim!

12. Nov 17, 2006

### Chronos

Scientists are like peacocks - very proud of their plumage. And justly so, providing they do not cling to their claim to fame for more that the standard alotment of ~15 minutes.

13. Nov 17, 2006

### Careful

Peacocks usually end up as supper or lunch, so I wouldn't compare scientists to that.

Last edited: Nov 17, 2006
14. Nov 17, 2006