tag:blogger.com,1999:blog-22973357.post6789751066575862953..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: The Casimir EffectSabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger41125tag:blogger.com,1999:blog-22973357.post-91943684435336751312011-02-11T15:56:31.106-05:002011-02-11T15:56:31.106-05:00Late to the party.
Take two small styrofoam balls...Late to the party.<br /><br />Take two small styrofoam balls and cover them with aluminum foil. Suspend them with strings an inch apart. <br /><br />Put a negative charge on one of them. The neutral ball will be attracted. The electrons on the front side of the neutral ball will be repelled by the electrons on the charged ball and will tend to retreat to the far side. The remaining positive J Thomashttps://www.blogger.com/profile/03201350482758221085noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-12615778996692781312007-11-09T11:28:00.000-05:002007-11-09T11:28:00.000-05:00Bee --After having seen the EM Casimir effect meas...Bee --<BR/><BR/>After having seen the EM Casimir effect measured to be real, what interests/worries me most is the implications for vacuum energy, and by extension cosmology. We are now reasonably sure that _changes_ in vacuum energy are real and match with what would be described in QFT as zero-point modes. But at the same time we know that the absolute value of vacuum energy, if GR is to be Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-30139864936747350972007-11-09T10:25:00.000-05:002007-11-09T10:25:00.000-05:00Hi Anonymous:Thanks for pointing out the paper. I ...Hi Anonymous:<BR/><BR/>Thanks for pointing out the paper. I didn't read it, and given that I already have an issue with the first sentence of their abstract (it seems to refer to the paper I have mentioned above, the argument in which I can't quite follow) it doesn't rank especially high on my to do list reading it.<BR/>Best,<BR/><BR/>B.<BR/><BR/>PS: I have deleted the duplicate comment.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-21513157532647956752007-11-09T07:17:00.000-05:002007-11-09T07:17:00.000-05:00Hi Bee, what do you think of arXiv:0711.1206?Hi Bee, what do you think of arXiv:0711.1206?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-36335815929085957522007-11-07T04:54:00.000-05:002007-11-07T04:54:00.000-05:00Sorry Bee, I didn't mean to be snipy. And the pape...Sorry Bee, I didn't mean to be snipy. And the papers you'd have to read are not my own.<BR/><BR/><I>Sure you can cling to Lorentz invariance not being exactly true, and since every experiment is done with finite precision only</I><BR/><BR/>Actually, I think that the known particles satisfy Lorentz symmetry exactly. I think that there are some people at PI that occasionally write papers messing CarlBrannenhttps://www.blogger.com/profile/17180079098492232258noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-89082764179355678962007-11-06T21:07:00.000-05:002007-11-06T21:07:00.000-05:00Scharnhorst effect: Measuring increased c within ...Scharnhorst effect: Measuring increased c within a Casimir etalon is not hurt by the short distance. Pulse gamma photons in vacuum through a grating of thicknesses of Casimatter and void. The photons will visit the detector in two bunches - and one will be too soon. A continuum of scattered background provides more calibration.<BR/><BR/>Aluminum, magnesium, lithium, and fluorine are all lightAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-87864405808306421602007-11-06T19:55:00.000-05:002007-11-06T19:55:00.000-05:00Hi Carl:And you already know what is true about ph...Hi Carl:<BR/><BR/><I>And you already know what is true about physics, so why should you waste your time with a long reading list put together by an insane amateur? Tell you what. I won't give you the list and you won't ignore it.</I><BR/><BR/>I find this comment pretty much insulting. True, I don't have time to read a whole bunch of your papers, and given that I am not particularly interested in Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-9732930461218875372007-11-06T19:21:00.000-05:002007-11-06T19:21:00.000-05:00Rillian, QFT + Curved space works just fine in the...Rillian, QFT + Curved space works just fine in the path integral approach, contrary to what you might have heard. People used this to figure out things like the Hawking effect. <BR/><BR/>The problem is its still just an effective field theory, and a nasty one at that. Gravity is nonrenormalizable, so you cannot trust its predictions beyond some cutoff (where the energy scale approaches the Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-60431359740587418492007-11-06T17:32:00.000-05:002007-11-06T17:32:00.000-05:00[holy shit, this wasn't posted when I came back. I...[holy shit, this wasn't posted when I came back. I can't believe the reply wasn't erased by my errant usage of copy and paste!]<BR/><BR/>javier:<BR/><BR/>Podkeltnov is a scam artist and a crank. He has given his experimental setup out - repeatedly - and nobody can replicate what he claims he did. He cannot even replicate what he claims he did. NASA has spent millions of dollars trying to eric gissehttps://www.blogger.com/profile/10598878490537720448noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-69253584443791668662007-11-06T14:34:00.000-05:002007-11-06T14:34:00.000-05:00"Hi Carl, I see - you're a composite fan. How do y..."<I>Hi Carl, I see - you're a composite fan. How do you get the photon to be massless? Best, B.</I>"<BR/><BR/>If you were going to build photons from fermions like electrons you'd be in a world of hurt cause electrons have mass. But the standard model fermions are built from chiral handed states that are massless, which makes it a little less impossible.<BR/><BR/>As to it being possible, you CarlBrannenhttps://www.blogger.com/profile/17180079098492232258noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-16248875393784091372007-11-06T13:37:00.000-05:002007-11-06T13:37:00.000-05:00superconducting nanotubes, reduce errorbarssuperconducting nanotubes, reduce errorbarsSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-70927543710110745262007-11-06T13:32:00.000-05:002007-11-06T13:32:00.000-05:00Casimatter is Casimir etalons *only* - alternating...Casimatter is Casimir etalons *only* - alternating stacked minimal thickness of best reflector with shortest possible wavelength transparent dielectric spacer. It does not go below ~115 nm optical spacing (physical gap times refractive index). Casimir force should degrade to van der Waals interaction with decreasing separation, hence the need for falsifying experiment. This is top down and notAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-26654835777456496672007-11-06T13:15:00.000-05:002007-11-06T13:15:00.000-05:00False Vacuum to the TrueSee the "bubble nucleation...<A HREF="http://bp0.blogger.com/_cldxKGOzgeM/RhOT3ozBeGI/AAAAAAAAAdI/bMmSSekmvLM/s200/network3.gif" REL="nofollow">False Vacuum to the True</A><BR/><BR/>See the "bubble nucleation process" it is not hard to follow what goes on in the early universe in a geometrical sense.PlatoHagelhttps://www.blogger.com/profile/00849253658526056393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-86180451149889472732007-11-06T12:51:00.000-05:002007-11-06T12:51:00.000-05:00Hi Anonymous: of courseHi Cynthia: Well, people ha...Hi Anonymous: of course<BR/><BR/>Hi Cynthia: Well, people have examined all kinds of 'matter' as dark matter and/or energy, depending on the equation of state it comes as one or the other 'essence' or 'field'. I am certainly in favor of trying negative energy densities, but it takes more effort to make it work than just calling it Casimatter. Best.<BR/><BR/>B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-87497801365211721042007-11-06T12:33:00.000-05:002007-11-06T12:33:00.000-05:00Even if the Casimir effect has nothing to do with ...Even if the Casimir effect has nothing to do with quantum gravity, I rather like Uncle Al's idea of Casimatter--whether it's a candidate for dark matter or for dark energy.;-)Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-15525400339182990722007-11-06T11:56:00.000-05:002007-11-06T11:56:00.000-05:00What I find somewhat 'suspicious' is that one can ...<I>What I find somewhat 'suspicious' is that one can calculate the qft effect for a lot of fields, and they should all exist, but afaik the only one that has ever been measured is the one for the electromagnetic field.</I><BR/><BR/>That might have something to do with the fact that it is quite easy to experimentally impose Dirichlet boundary conditions on the e.m. field (conducting plates will doAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-6845256248636223612007-11-06T11:01:00.000-05:002007-11-06T11:01:00.000-05:00Ok. I just wanted to let you know. Not being an ex...Ok. I just wanted to let you know. Not being an experimentalist the point I usually see in this caes is that the persons who do the experiments are condensed matter physicians and not experts in quantum gravity theory so their temptative explanations usually are a bit naive. <BR/><BR/> In brief, my opinion is that they are curiosities wotrting to be aware of them, but not to expend too mucch timeJavierhttps://www.blogger.com/profile/17845977289427117418noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-46189017455731393172007-11-06T10:28:00.000-05:002007-11-06T10:28:00.000-05:00No, I have only one head and I prefer using it to ...No, I have only one head and I prefer using it to talk about well documented, reproducible experiments and reliable calculations. <A HREF="http://backreaction.blogspot.com/2007/05/millikan-oil-drops.html" REL="nofollow">You might be interested in this</A>, that's about far as I will go into this direction. Best,<BR/><BR/>B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-43470931081697948892007-11-06T10:21:00.000-05:002007-11-06T10:21:00.000-05:00Have you head to talk about Podkeltnov? A few year...Have you head to talk about Podkeltnov?<BR/><BR/> A few years ago, around the 98 or so, he claimed that he had found some gravitatory shielding in experiments with a very complicate superconducting device he was studiying for diferent purposes.<BR/><BR/> The effect hasnĀ“t been reproduced, among other reasons because he refuses to give the exact nature of the orignial (and subsequent) experiment.Javierhttps://www.blogger.com/profile/17845977289427117418noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-73812055084388179472007-11-06T07:51:00.000-05:002007-11-06T07:51:00.000-05:00Hi Anonymous,When can we expect your book for the ...Hi Anonymous,<BR/><BR/><I>When can we expect your book for the really interested layperson ? You might even get your own TV-show !</I><BR/><BR/>Book: not until I'm tenured. TV: categorically not. But thanks for the nice words,<BR/><BR/>B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-80772561595720907812007-11-06T07:43:00.000-05:002007-11-06T07:43:00.000-05:00Hi Carl, I see - you're a composite fan. How do yo...Hi Carl, I see - you're a composite fan. How do you get the <A HREF="http://en.wikipedia.org/wiki/Weinberg-Witten_theorem" REL="nofollow">photon to be massless?</A> Best, B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-25483752938796104672007-11-05T23:28:00.000-05:002007-11-05T23:28:00.000-05:00Bee, Well, what about scalar fiels? Vector fields?...Bee, <I>Well, what about scalar fiels? Vector fields?</I><BR/><BR/>Sorry, I do live in my own little version of physics. I only care about the foundations, and I want them as simple as possible.<BR/><BR/>There are no known, observed, fundamental scalar particles. As for the vector particles, my guess is that they are composites made also from spin-1/2 sorts of things. This, you know how to do, soCarlBrannenhttps://www.blogger.com/profile/17180079098492232258noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-20591163837818007022007-11-05T20:04:00.000-05:002007-11-05T20:04:00.000-05:00Hi There,First an apology for being brief, but I a...Hi There,<BR/><BR/>First an apology for being brief, but I am pretty much tied up this week with <A HREF="http://backreaction.blogspot.com/2007/10/experimental-search-for-quantum-gravity.html" REL="nofollow">the previously mentioned workshop on Experimental Search for Quantum Gravity</A>. The IT guys are impressively fast, the fist talks are <A HREF="http://www.perimeterinstitute.ca/Events/Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-6370986686585097002007-11-05T17:43:00.000-05:002007-11-05T17:43:00.000-05:00Ah,thank you for reminding me of that idea of your...Ah,<BR/><BR/>thank you for reminding me of that idea of yours :-)<BR/><BR/>BTW, although a bit off-topic, it seems that with the methods used by Jaffe, one can now calculate <A HREF="http://arxiv.org/abs/0707.1862" REL="nofollow">Casimir forces between arbitrary compact objects</A> (arXiv:0707.1862v2, PRL <B> 99</B> (2007) 170403)...<BR/><BR/>Best, Stefanstefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-67212486789322260122007-11-05T16:49:00.000-05:002007-11-05T16:49:00.000-05:00Bee,Thomas above gave this Jaffe preprinthttp://ar...Bee,<BR/>Thomas above gave this Jaffe preprint<BR/><BR/>http://arxiv.org/abs/hep-th/0503158<BR/><BR/>which argues I believe that the Casimir effect goes to zero as the fine structure constant goes to zero; the Itzykson-Zuber type calculation is the limit when the fine structure constant is infinite.<BR/><BR/>I'm basing all this on a vague memory of having seen it before, so it is possible I'm Arunhttps://www.blogger.com/profile/03451666670728177970noreply@blogger.com