[General] Casimir and van der Waals

[David Mathes]

Andrew,
No matter how difficult or challenging to implement, to justify and perhaps limit the possibilitieswe need 21st century level experiments instead of just 20th century experiments. Any theory should propose an experiment. 
Wikipedia is not a great source, just a good quick view. As knowledge experts I believe we need to quickly check and move on from Wiki. However, it is the public encyclopedia so if it is lacking, then we should be able to make note of it in our lectures and perhaps have it corrected. And occasionally, wiki hits a research home run with a nice diagram, a list of references or something else of value. I think of Wiki as an index card I didn't write and need to verify at the source. 
On the professional level, I pull from a variety of sources defined more by Physics Review Letters than any other source. SPIE clearly is authoritative as well. ArXiv provides a fair amount of sources as well. I am cautiously optimistic when I read translations of Russian and Chinese journals provide a fair amount of value as well as those from specific universities around the world. 
So, given that we have entered a period where the papers are being written and reviewed, I'll leave wiki to the reader and focus on providing PRL or Arxiv sources. 
David
 
      From: Andrew Meulenberg <mules333 at gmail.com>
 To: Nature of Light and Particles - General Discussion <general at lists.natureoflightandparticles.org> 
Cc: David Mathes <davidmathes8 at yahoo.com>; Kyran Williamson <kyran_williamson at hotmail.com>; Philipp Steinmann <philipp.steinmann at gmail.com>; Nick Bailey <nick at bailey-family.org.uk>; Anthony Booth <abooth at ieee.org>; Ariane Mandray <ariane.mandray at wanadoo.fr>; Manohar . <manohar_berlin at hotmail.com> 
 Sent: Monday, April 20, 2015 8:04 PM
 Subject: Re: [General] Casimir and van der Waals
   
Dear John W,

Re: Van der Waals and Casimir.  
I know that you didn't have space for the whole story and I do not think it rare that two different models describing the same mechanism turn out to be identical (e.g. Heisenberg &  Schrodinger representations); nevertheless, it is a very interesting story. I do not know enough about either Casimir or vdW mechanisms to see thru the details, but Martin's comment about the zeroth-order approximation of the material addressed one of my questions. How did dielectrics compare with conducting plates (e.g. just sequentially reversing orientation of 1st surface mirrors after comparing blanks and double-sided mirrors)? I might think that test could provide a 1st order effect. The next step in this direction would be to change the environments to one better known. What happens in the two models and experiment (with the 1st surface mirror sequence) when the external environment is dominated by introduction of mono-energetic light from a laser? I believe this is a case where the two models would also differ.

David's suggestion of testing spin (and other dynamic) effects is good, but more difficult to implement.

I don't have time to look into these details, but I would also love to have a quick look at conclusions from a recent survey source more definitive than Wikipedia. However, that source does compare the more-narrowly-defined vdW & Casimir effects as "The London-van der Waals forces are related to the Casimir effect for dielectric media, the former being the microscopic description of the latter bulk property."
Andrew
_________________________________________

Right ....

Van der Waals and Casimir.  

There are hundreds of published, peer reviewed, papers out there purporting to have measured the Casimir force. I have not read all of them and some of them may well be right. Many of these are "me too" papers confirming someone else's results. Others are papers showing an agreement between the forces measured and the calculations for the Casimir force.

So why, then, do I think that most of these guys have been wasting their time?

That is down to a couple of friends of mine Philipp Steinmann and John Weaver (cheers)- as well as many other excellent people in nanoelectronics in Glasgow who made the experiment possible in the first place.  I'll copy this to Philipp for comment - though he now works in another field. It also comes from, for me, to some understanding of the basic physics due (partly) to an excellent collaboration with Casimir himself many years ago.

The Glasgow guys are seriously excellent set of experimental physicists - with the proper integrity to see things for what they truly are. Casimir was a pleasure to meet and work with. One of the smartest people it has been my pleasure to interact with.

Yes, indeed, the van der Waals force dependence depends on the configuration, as you say David. So does the Casimir force.

John Weaver, Philipp and others, considered measuring the Casimir force using their atomic force microscope (AFM), one of the best in the world at the time. I'm telling you - these guys are good. Easy experiment - plenty of sensitivity - direct measurement -no messing around. Just do it. Indeed, the experiment showed, as have countless others,  a force as predicted by Casimir. Job done? no!

What about other possible forces such as the Van der Waals force?

I think it was Philipp who did most of the work here (corrections guys?). He calculated it and found it was virtually the same as the Casimir force, with the same dependence and the same constants.

Consider, for a moment, the two scenarios ...

One, Casimir. Two parallel mirrors in a vacuum. Excluded QM modes.

Two. vd Waals. Two parallel conductors in a vacuum. Electron wave-function overlaps.

Oh dear: mirrors are conductors ...

Think about it: it is the same physical problem. Different boundary conditions. Same answer.

Surprise?

These guys had the integrity to drop this at that point. Qudos.  Question is, can one trust others to do as good a job?

Now, any paper on "measuring the Casimir force" had, for me, better do a damn good job on the van der Waals force as well. There may be such a paper now. This was not the case for the first few dozen I looked at though. Phillipp? John? anyone else?  Please let me know.

Regards, John W (the other one).


   
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