tag:blogger.com,1999:blog-22973357.post9147956304329815910..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Is Verlinde’s Emergent Gravity compatible with General Relativity?Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger75125tag:blogger.com,1999:blog-22973357.post-14274229582122948322018-04-11T17:37:02.877-04:002018-04-11T17:37:02.877-04:00Sabine, can you make available the Maple worksheet...Sabine, can you make available the Maple worksheet imposter.mw again in order for me to better understand the equations? I'm mainly interested in the Cosmological solutions. In Eqs. (28)-(29) T stands only for normal matter? You have assumed T=0 before, neglecting baryons.José Fernandohttps://www.blogger.com/profile/15806808121258927904noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-52487529979137644402017-05-23T07:39:07.534-04:002017-05-23T07:39:07.534-04:00My_wan,
I certainly appreciate your elaborate exp...My_wan,<br /><br />I certainly appreciate your elaborate explanations.<br />But the thing is that to make the correct predictions in the context discussed, you need only the Lorentzfactor and a locally preferred frame, in this case the ECI, and as you called it: the principle of the merry-go-round. No SR is needed and no GR needed, no discussions on inertial or non inertial frames needed etc.<br Koenraad Van Spaendonckhttps://www.blogger.com/profile/15090279727324831109noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-40258236981498797742017-05-19T22:48:42.044-04:002017-05-19T22:48:42.044-04:00@Koenraad Van Spaendonck
I don't follow your ...@Koenraad Van Spaendonck<br /><br />I don't follow your argument for locally preferred frames. You mention rotating frames then dismiss it's relevance on the grounds that it disqualifies SR. It no more disqualifies SR than GR disqualifies SR. We also know that a rotating frame is an accelerated frame. Which is absolute except in degree. So those effects must be accounted for in order to my_wanhttps://www.blogger.com/profile/02666718986545629735noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-60349888656417783652017-03-31T05:04:21.857-04:002017-03-31T05:04:21.857-04:00More news incoming: kinda Aether Redux?
http://iop...More news incoming: kinda Aether Redux?<br />http://iopscience.iop.org/article/10.3847/1538-4357/836/2/152Theophanes Raptishttps://www.blogger.com/profile/01269614280130174555noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-24241580248066228882017-03-26T02:20:20.543-04:002017-03-26T02:20:20.543-04:00David,
It's a good question, but I don't ...David,<br /><br />It's a good question, but I don't know the answer. Roughly speaking, the whole ansatz assumes some kind of equilibrium condition already, but clearly that assumption already would require a justification. For this you'd need not only an interaction term but also at least an estimate of the time-dependence and - as the phrase goes - it's beyond the scope of this Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-2598986139700842132017-03-25T17:36:03.945-04:002017-03-25T17:36:03.945-04:00It's mentioned on page 8 of your paper that th...It's mentioned on page 8 of your paper that the "imposter field" can "condense" in the vicinity of matter, (galaxy scale, I think is implied), with a resultant local decrease in the volume of this field, so that the field outside the galaxy "pushes in" and "drags" on the matter, mimicking dark matter, if I'm interpreting it correctly. When the David Schroederhttps://www.blogger.com/profile/18048116250413347228noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-91329140976204640982017-03-22T07:15:20.036-04:002017-03-22T07:15:20.036-04:00m-artins,
It's a vector field, not a scalar f...m-artins,<br /><br />It's a vector field, not a scalar field, so JNW won't help. Also, it's got a very unusual power of the kinetic term, so I doubt any solution that is in the literature will 'coincidentally' fit.<br /><br />There are two solutions that are missing:<br /><br />a) Spherically symmetric with the massive vector field (asymptoting to dS), preferably for a densitySabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-64426435233529889222017-03-22T06:09:52.129-04:002017-03-22T06:09:52.129-04:00@KVS: Non-inertiality is commonly called, alike in...@KVS: Non-inertiality is commonly called, alike in the twin case. Anyway, see this <a href="https://phys.org/news/2017-03-universe-rest.html" rel="nofollow">proposal</a>.<br /><br />@Bee: Regarding VG vs. FLRW metric, do you mean something similar to Schwarzschild solution vs. FLRW? A quick search for that gives <a href="https://arxiv.org/abs/gr-qc/0307006" rel="nofollow">gr-qc/0307006</a>, <a Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-8925851441072109612017-03-21T03:43:53.521-04:002017-03-21T03:43:53.521-04:00Phillip, Tam,
I think I should add that Tam has n...Phillip, Tam,<br /><br />I think I should add that Tam has now submitted two long comments which I didn't approve because they merely repeat (with many words) the questions that have now been answered by various people. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-77629694637869335052017-03-20T08:01:52.917-04:002017-03-20T08:01:52.917-04:00@Phillip Helbig
"Suffice it to say that if a...@Phillip Helbig<br /><br />"Suffice it to say that if anything were wrong with GR at this level then GPS would not work"<br /><br />>The gps-sattelite orbitting one way cannot say anything about a locally preferred frame, it only confirms the time dilatation factor quantitatively (*), as i explained above.<br />It would take - hypothetically of course.. - a sattelite orbitting the Koenraad Van Spaendonckhttps://www.blogger.com/profile/15090279727324831109noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-91122845120337253092017-03-20T05:58:32.807-04:002017-03-20T05:58:32.807-04:00@Tam Hunt: You have a serious misunderstanding abo...@Tam Hunt: You have a <i>serious</i> misunderstanding about what a scientific theory is. Your history is off as well. GR is probably the best example of a theory which was <i>not</i> constructed to explain observations. Of course, it does explain observations, makes testable predictions which have been confirmed, etc---otherwise it wouldn't be a scientific theory. When a reporter asked Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-25779773618967860112017-03-20T05:36:50.473-04:002017-03-20T05:36:50.473-04:00"I could not find the Hafele-Keating experime...<i>"I could not find the Hafele-Keating experiment on Special Relativity."</i><br /><br />Suffice it to say that if anything were wrong with GR at this level then GPS would not work.<br /> Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-24788717223410947692017-03-19T07:09:02.505-04:002017-03-19T07:09:02.505-04:00A small correction on the particle accelerator vel...A small correction on the particle accelerator velocities there : <br />e.g. earth orbit speed + 0.9c. and earth orbit speed - 0.9c would be the more accurate comparison, yielding practically speaking no significant difference for the relativistic mass increases.Koenraad Van Spaendonckhttps://www.blogger.com/profile/15090279727324831109noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-1936242513440352402017-03-18T14:42:52.609-04:002017-03-18T14:42:52.609-04:00Hello Sabine,
I've been looking into the pape...Hello Sabine,<br /><br />I've been looking into the paper above with GR tests. I could not find the Hafele-Keating experiment on Special Relativity.<br /><br />http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/airtim.html<br /><br />Concerning the verification of the existence of a locally preferred frame, this is however a pretty important test, aside from testing the sheer quantitative Koenraad Van Spaendonckhttps://www.blogger.com/profile/15090279727324831109noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-67851308664692904512017-03-18T12:20:15.793-04:002017-03-18T12:20:15.793-04:00Tam,
Sorry for not adding a reference, I just saw...Tam,<br /><br />Sorry for not adding a reference, I just saw that jonduffield (comment above) beat me to it - this was the exact review I had on mind. Even if you don't have the time for such a long review, Googling "precision tests of general relativity" should help. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-51036727505672117452017-03-18T10:39:48.706-04:002017-03-18T10:39:48.706-04:00Tam: GR is one of the best-tested theories we'...Tam: GR is one of the <a href="https://arxiv.org/abs/1403.7377" rel="nofollow">best-tested theories</a> we've got, and it handles "dark matter" just fine. The problem isn't with GR, it's with other theories about WIMPs and inflation etc that haven't been tested at all.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-39243460729945846422017-03-17T17:18:50.088-04:002017-03-17T17:18:50.088-04:00Thanks Philip, but I was asking Bee about the spec...Thanks Philip, but I was asking Bee about the specific precision tests of GR that she thinks would be able to falsify GR if they returned negative results. Again, my point that it seems clear to me that GR has acquired the status of an unfalsifiable theory, in principle, b/c any cosmological or empirical results that seem to cast doubt on GR simply lead to new patches/epicycles, rather than Tam Hunthttps://www.blogger.com/profile/05919461715412820636noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-8496623670898015212017-03-17T07:39:04.708-04:002017-03-17T07:39:04.708-04:00Cliff Will's Was Einstein Right is a good star...Cliff Will's <i>Was Einstein Right</i> is a good starting point. Will has authored several reviews over the years comparing predictions of GR to observation.<br />Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-21959288485383563242017-03-16T15:54:52.544-04:002017-03-16T15:54:52.544-04:00What precision tests of GR are you referring to? What precision tests of GR are you referring to? Tam Hunthttps://www.blogger.com/profile/05919461715412820636noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-69311508494768011752017-03-16T06:57:16.990-04:002017-03-16T06:57:16.990-04:00Tam,
I'm getting quite tired of this. Both I ...Tam,<br /><br />I'm getting quite tired of this. Both I and Phillip have repeatedly explained that you are *wrong* to claim that dark matter and dark energy are 'add ons' to General Relativity. General Relativity does not tell you anything about the sources (other than that stress-energy is conserved). The types of sources that are necessary to get something that behaves like dark Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-83182007775403792432017-03-16T03:37:06.403-04:002017-03-16T03:37:06.403-04:00Let me return to the more basic questions, since I...Let me return to the more basic questions, since I note that you didn't respond substantively to any of my questions. I do value your responses and your taking the time to respond further here, so let me ask you more specifically: if GR can incorporate major add-ons like DM, DE and inflation in order to "make it work" with observations, how can we falsify GR? Again, the iconic Tam Hunthttps://www.blogger.com/profile/05919461715412820636noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-4772718988852474872017-03-16T02:20:26.158-04:002017-03-16T02:20:26.158-04:00Tam,
Uhm, let me see. You comment here on a paper...Tam,<br /><br />Uhm, let me see. You comment here on a paper I just wrote that, erm, proposes a modification of general relativity that does away with particle dark matter but you complain that I'm too narrowminded to ever consider maybe general relativity should be modified. Ok, then. It happens all the time that commenters here build a strawman of my alleged opinions which they then attemptSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-24745474020522335352017-03-15T15:15:33.544-04:002017-03-15T15:15:33.544-04:00Philip, GR is a theory of gravity, of how observab...Philip, GR is a theory of gravity, of how observable mass behaves. As such, arguing that it is unaffected by problems like the Dragonfly galaxy, and it's supposed 99.9% of DM to explain observations, is more than a little absurd. Oh, it's a theory of gravity that can't explain 99.9% of observations unless we add other massive (in all senses of this term) to our universe, "by handTam Hunthttps://www.blogger.com/profile/05919461715412820636noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-69843076634706522662017-03-15T14:47:32.157-04:002017-03-15T14:47:32.157-04:00Hi Sabine, you have with your statement that you &...Hi Sabine, you have with your statement that you "don't care" if patches to GR are ugly entirely eliminated the possibility of falsifying GR. That, of course, is patently unscientific. <br /><br />When literally 99.9% of a galaxy must be conjured up as DM in order to explain its dynamics we have gone well into the realm of unfalsifiable epicycles, no? How can you argue with a Tam Hunthttps://www.blogger.com/profile/05919461715412820636noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-59467507846249430172017-03-15T08:54:46.824-04:002017-03-15T08:54:46.824-04:00Hi Sabine,
I want to react to your response to Ph...Hi Sabine,<br /><br />I want to react to your response to Phillip Helbig. GR says nothing about the sources, all right. But it states that there is a source. So I agree with Phillip when he states that 99% of the source terms is ugly patch - though I would rather name this oversold fairy tales. When I read "A galaxy (namely Dragonfly 44) is composed of 98% dark matter" (not on this blogakidbellehttps://www.blogger.com/profile/12292741599925116131noreply@blogger.com