tag:blogger.com,1999:blog-22973357.post5341841040403572793..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: No evidence for spacetime foamSabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger36125tag:blogger.com,1999:blog-22973357.post-25353652898175117882012-02-08T03:32:56.961-05:002012-02-08T03:32:56.961-05:00Hi Eric,
My question was, for α=2/3, what is the ...Hi Eric,<br /><br />My question was, for α=2/3, what is the constraint on the parameter "a"? I couldn't find that in your paper, and I'd be interested to know. It makes more sense to me to think of it this way, because there isn't really a continuum of models with different values of α. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-91122567011928928192012-02-07T15:24:17.028-05:002012-02-07T15:24:17.028-05:00Zephir,
I'm very familiar with the Sloan su...Zephir, <br /><br />I'm very familiar with the Sloan survey and I am not aware of their making any claim about spacetime foam - can you please post the link to the paper rather than an article in Discovery (which link, btw, does not work)?<br /><br />Also, the CMBR structure and redshift are completely unrelated to what we call spacetime foam. I'd like to know how you think they might Eric Perlmanhttps://www.blogger.com/profile/10009979214509557818noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-73076740034726680302012-02-06T10:42:08.418-05:002012-02-06T10:42:08.418-05:00Bee said:
> I think "fundamentally flawed...Bee said:<br /><br />> I think "fundamentally flawed" is a quite strong <br />> expression to use here. We can agree that it's not a <br />> very good paper. I see that in the paper from Nov <br />> 2011 it is argued that Tamburini et al have used an <br />> inappropriate distance measure which means they <br />> have overestimated the effect.<br /><br />The use ofEric Perlmanhttps://www.blogger.com/profile/10009979214509557818noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-38053036030788863122012-02-05T15:46:53.135-05:002012-02-05T15:46:53.135-05:00Bee, you're welcome and sorry I dawdled gettin...Bee, you're welcome and sorry I dawdled getting back to you (busy in various ways.) Here is yet another area of physics that remains controversial and unexplicated - we still just don't know the score.Neil Bateshttps://www.blogger.com/profile/04564859009749481136noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-59437779721541763532012-02-04T22:26:07.465-05:002012-02-04T22:26:07.465-05:00There are many evidences of "space-time"...There are many evidences of "space-time" foam: the CMBR noise, the dispersion of light called the red shift, the remote galaxies are blurred, etc. It's simply random hyperbolic noise analogous to density fluctuations inside of gas.Zephirhttps://www.blogger.com/profile/06010623752049244967noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-11166488886542356862012-02-04T11:52:56.709-05:002012-02-04T11:52:56.709-05:00DocG: I don't know whether he did express thou...DocG: I don't know whether he did express thoughts on that - just that on the last page of QED: Strange Theory he was complaining about theories purporting to deal with gravity that postulate stuff nobody sees, and are non-renormalizable, and it is experimentally intractable anyway. It seems he was quite burned out on the whole subject. I think it's a shame because only a few years after joel ricehttps://www.blogger.com/profile/06048310899055838262noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-69477191804220384852012-02-04T10:17:47.078-05:002012-02-04T10:17:47.078-05:00Stefan, "...you need inhomogenities and fluct...Stefan, "<i>...you need inhomogenities and fluctuations to avoid destructive interference ruining the scattering.</i>"<br /><br />Bragg interference has similar footnotes. A perfect crystal lattice quenches its output. An overly good crystal is dipped in liquid nitrogen. The thermal shock adds a trace of disorde (mosaicity).<br /><br />Perhaps things work not because they are Uncle Alhttps://www.blogger.com/profile/05056804084187606211noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-74409745431719436632012-02-04T09:31:20.324-05:002012-02-04T09:31:20.324-05:00Thanks, Uncle, Stefan! I had never pu together the...Thanks, Uncle, Stefan! I had never pu together the idea that the sky is blue is a strong indication that matter is atomic.<br /><br />It goes with why the night sky is dark as pointing to a fundamental truth about the world.Arunhttps://www.blogger.com/profile/03451666670728177970noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-65493946816435189082012-02-04T02:14:24.302-05:002012-02-04T02:14:24.302-05:00"that is" not "that it"
need ..."that is" not "that it"<br /><br />need coffee. now.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56085744144646258352012-02-04T02:12:25.637-05:002012-02-04T02:12:25.637-05:00For completeness, I found that there is a Nature n...For completeness, I found that there is a Nature news article by Amelino-Camelia on the Tamburini paper:<br /><br /><a href="http://www.nature.com/nature/journal/v478/n7370/full/478466a.html" rel="nofollow">Shedding light on the fabric of space-time</a><br /><br />It is actually very well written and readable (except for it not being open access that it).Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-91090047748999513182012-02-04T02:10:47.729-05:002012-02-04T02:10:47.729-05:00I should better have written: constraint on the pa...I should better have written: constraint on the parameter "a" given \alpha =2/3.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-28278693634327609142012-02-04T02:02:55.312-05:002012-02-04T02:02:55.312-05:00Hi Eric, Omni,
I think "fundamentally flawed...Hi Eric, Omni,<br /><br />I think "fundamentally flawed" is a quite strong expression to use here. We can agree that it's not a very good paper. I see that in the paper from Nov 2011 it is argued that Tamburini et al have used an inappropriate distance measure which means they have overestimated the effect. But we're talking here about an overestimation by an order of magnitude,Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-81097869170249147092012-02-04T01:41:16.650-05:002012-02-04T01:41:16.650-05:00It is claimed that:
Tamburini et al is wrong, see...It is claimed that:<br /><br />Tamburini et al is wrong, see:<br />arXiv:1110.4986[astro-ph.CO], Astronomy & Astrophysics 535, L9 (2011)<br /><br />Claim by Abdo et al (based on new Fermi Gamma-ray Space Telescope results) is wrong, see:<br />arXiv:0912.0535, Phys. Rev. D83, 084003 (2011)Omnihttps://www.blogger.com/profile/06470586734220576179noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-27733977266331925902012-02-03T23:15:55.448-05:002012-02-03T23:15:55.448-05:00Bee, since you characterize your work as "phe...Bee, since you characterize your work as "phenomenology" I would like to think you are open to a broader approach to scientific research than what might be called, if you will pardon the expression, "crude empiricism."<br /><br />In this spirit I would urge you to go a bit further to consider certain issues in semiotics, insofar as semiotics can be considered a science, not DocGhttps://www.blogger.com/profile/17359004200002936544noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-90231379600521623172012-02-03T22:27:24.439-05:002012-02-03T22:27:24.439-05:00"He also stresses, in sections 1.4 and 2.1, t..."He also stresses, in sections 1.4 and 2.1, the inappropriateness of the Copenhagen interpretation of quantum mechanics in a cosmological context." <br /><br />Thanks, Joel, but that wasn't my point. I should have made myself more clear. The complementarity I was referring to is the complementarity between General Relativity and Quantum Mechanics, which strike me as fundamentally DocGhttps://www.blogger.com/profile/17359004200002936544noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-49295996047696723502012-02-03T17:33:11.867-05:002012-02-03T17:33:11.867-05:00Hi Arun,
thanks for digging out the book by John ...Hi Arun,<br /><br />thanks for digging out the book by John Hardy - it seems to be quite helpful. One can have a look inside at <a href="http://www.amazon.com/Adaptive-Astronomical-Telescopes-Optical-Sciences/dp/0195090195" rel="nofollow">amazon.com</a>.<br /><br />There is also a derivation of the formula in Born&Wolf (<a href="http://books.google.de/books?id=aoX0gYLuENoC&pg=PA522" rel="stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-61127262177330059852012-02-03T15:20:23.260-05:002012-02-03T15:20:23.260-05:00The Tamburini paper is fundamentally flawed, as we...The Tamburini paper is fundamentally flawed, as we showed in a paper published two months later in A&A. See http://adsabs.harvard.edu/abs/2011A%26A...535L...9P.<br /><br />The problems we point out are as follows: <br /><br />(1) they do not calculate the length element properly,<br />and overestimate the expected effect of spacetime foam on existing observations (and hence overestimate howEric Perlmanhttps://www.blogger.com/profile/10009979214509557818noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-86943678797524149952012-02-03T11:48:53.040-05:002012-02-03T11:48:53.040-05:00@Arun: Rayleigh scattering (atmospheric to unders...@Arun: Rayleigh scattering (atmospheric to undersea cable fiberoptic) validates atomicity, <br /><br />http://en.wikipedia.org/wiki/Rayleigh_scattering <br />http://www.its.bldrdoc.gov/pub/ntia-rpt/81-59/81-59_ocr.pdf<br /> 2.3.3 Fiber Dispersion<br /><br />Billion lighyear pathlengths, gamma to radio photons, empirically reduce spacetime foam to a snark hunt. Compactified dimensions are Uncle Alhttps://www.blogger.com/profile/05056804084187606211noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-67900093490174909042012-02-03T11:12:28.259-05:002012-02-03T11:12:28.259-05:00At the outset it must be re-emphasized that the te...<i>At the outset it must be re-emphasized that the test<br />for spacetime foam effects is a null test. A theoretical model for spacetime foam is disproved if images of a dis-tant point source do not exhibit the blurring predicted<br />by theoretical spacetime foam models.</i> <b>See</b>: <a href="http://arxiv.org/pdf/0912.0535v3.pdf" rel="nofollow">Limits on Spacetime Foam</a><br /><br />Best,PlatoHagelhttps://www.blogger.com/profile/00849253658526056393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-49382713384826298842012-02-03T10:56:26.340-05:002012-02-03T10:56:26.340-05:00I just can't get away from how blurry things c...I just can't get away from how <a href="http://science.nasa.gov/media/medialibrary/2004/03/24/26mar_einstein_resources/bend_med.gif" rel="nofollow">blurry things can look</a> but have a suitable explanation. <br /><br />It's as if one is raising the landscape issue again as to discern the viability of "hills and valleys" as a interpretation of the cosmic landscape? <br /><br />PlatoHagelhttps://www.blogger.com/profile/00849253658526056393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-18049599950921571132012-02-03T10:25:01.480-05:002012-02-03T10:25:01.480-05:00DocG: just looking at the Feynman lectures on Gra...DocG: just looking at the Feynman lectures on Gravitation and see on page xvi the remark "He also stresses, in sections 1.4 and 2.1, the inappropriateness of the Copenhagen interpretation of quantum mechanics in a cosmological context." Perhaps briefly - given Heisenberg uncertainty - what is delta x if the universe is expanding ? How would that affect H's explanation of the joel ricehttps://www.blogger.com/profile/06048310899055838262noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-15576055724777882182012-02-03T10:05:09.155-05:002012-02-03T10:05:09.155-05:00Psychologists call it "motivated cognition&qu...Psychologists call it "motivated cognition" ;o)Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-54867213001906612812012-02-03T10:01:22.834-05:002012-02-03T10:01:22.834-05:00Hi Bee,
If optical wavelengths can't be used ...Hi Bee,<br /><br />If optical wavelengths can't be used to detect the atomicity of matter, then I'm dubious that they can be used to detect structure at the Planck scale.<br /><br />Of course, the phenomenological models of quantum gravity are designed with the hope that some effect will show up. It is hardly surprising that they get shot down so readily.<br /><br />-ArunArunhttps://www.blogger.com/profile/03451666670728177970noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-12509582428583475092012-02-03T07:09:28.437-05:002012-02-03T07:09:28.437-05:00Hi Bee,
A most interesting piece which could leav...Hi Bee,<br /><br />A most interesting piece which could leave those such as Roger Penrose certainly discouraged. However I would point out that businesses such as Star Bucks not only depend on the concept of foam as being a good one, yet more so as actually in being able to create them benefitting by the many who enjoy them. So although reality might not present to be a Latte, there are many Phil Warnellhttps://www.blogger.com/profile/15671311338712852659noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-5935040574932495782012-02-03T07:04:09.372-05:002012-02-03T07:04:09.372-05:00Space-time foam is easily visible at the results o...Space-time foam is easily visible at the results of Sloan survey http://discovermagazine.com/2009/mar/06-world.s-hardest-working-telescope/sloanmap.jpg The quantization of red-shift is visible there too.Zephirhttps://www.blogger.com/profile/06010623752049244967noreply@blogger.com