tag:blogger.com,1999:blog-22973357.post704180130480561711..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: The problem with Poincaré-invariant networksSabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger16125tag:blogger.com,1999:blog-22973357.post-28481075105788207762015-08-13T01:44:12.941-04:002015-08-13T01:44:12.941-04:00DSR doesn't work in position space to begin wi...DSR doesn't work in position space to begin with, you can do it in momentum space, yes.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-80619216346590433122015-08-12T22:53:32.245-04:002015-08-12T22:53:32.245-04:00Would this argument still apply in doubly-special ...Would this argument still apply in doubly-special relativity, if the nearest-neighbor links are of the order of the invariant plank scale?Rhttps://www.blogger.com/profile/18277926218867241820noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-19065877052051733382015-04-29T00:19:06.020-04:002015-04-29T00:19:06.020-04:00I believe the claim in [3] is stronger than that: ...I believe the claim in [3] is stronger than that: in Minkowski space a realization of the Poisson process cannot even determine a preferred direction locally (no reference to averaging over volumes). As opposed to, say, the Euclidean analog, where a realization of the Poisson process <i>can</i> determine a direction at any point that breaks the rotational symmetry, while it still respects the Anonymoushttps://www.blogger.com/profile/18283928497795975993noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-69387280623785463622015-04-28T12:00:53.773-04:002015-04-28T12:00:53.773-04:00Arun: This has never been proved. These deformatio...Arun: This has never been proved. These deformations are problematic for other reasons, but they don't suffer from the density problem that I alluded to here, if that is what you mean, yes. LQG itself isn't actually based on a space-time network so the argument doesn't apply to it either. The recovery of Lorentz-invariance in LQG though is to my knowledge an unsolved problem. Best,<brSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-27546936363609150892015-04-28T11:30:19.128-04:002015-04-28T11:30:19.128-04:00Dear Bee,
But LQG results in a deformed Poincare ...Dear Bee,<br /><br />But LQG results in a deformed Poincare invariance, no? If so, does that work?<br /><br />Thanks!<br />-Arun<br />Arunhttps://www.blogger.com/profile/03451666670728177970noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-90926809287219080112015-04-28T05:42:45.473-04:002015-04-28T05:42:45.473-04:00Dear Arun,
Well, I suppose one could say that thi...Dear Arun,<br /><br />Well, I suppose one could say that this is exactly what LQG tries to do? Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-81420659701163557832015-04-28T05:42:03.640-04:002015-04-28T05:42:03.640-04:00Michael,
Sorry, I don't see what you think is...Michael,<br /><br />Sorry, I don't see what you think is in contradiction, I agree with the quote. I believe what they mean with 'physical' is what I referred to as averaged over large volumes, which makes sense. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-20217325586063195182015-04-27T23:21:08.363-04:002015-04-27T23:21:08.363-04:00Dear Bee,
So it seems classically discretizing spa...Dear Bee,<br />So it seems classically discretizing space-time - in terms of lines, points, surfaces, etc., is a somewhat quixotic venture. <br /><br />Is there some purely "quantum" way of discretizing space-time? One would avoid a analogous classical discretization by requiring that the limit of zero length scale and the classical limit don't commute.<br /><br />Arunhttps://www.blogger.com/profile/03451666670728177970noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-40808598749986596862015-04-27T19:27:34.713-04:002015-04-27T19:27:34.713-04:00Hi Sabine,
In your paper you state "It has b...Hi Sabine,<br /><br />In your paper you state "It has been known for some while however that there are Poincaré-invariant random distributions of points in Minkowski-space that are locally finite [3]. They are invariant in the stochastical sense, so that averaged over a large number of repetitions (or a large sample of volumes respectively) they are invariant, even though any single point Anonymoushttps://www.blogger.com/profile/18283928497795975993noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-36486050912201681482015-04-26T15:04:04.233-04:002015-04-26T15:04:04.233-04:00Space-time seems to do a wonderful job to conceal ...Space-time seems to do a wonderful job to conceal its quantum properties.I have always thought that to achieve such a feat a Fourier superposition was at work.Stuart https://www.blogger.com/profile/12767480095489975264noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-51812213301449624322015-04-25T23:29:13.584-04:002015-04-25T23:29:13.584-04:00This comment has been removed by the author.regretacleshttps://www.blogger.com/profile/00849406662712673245noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-63372809114154203412015-04-25T12:27:15.067-04:002015-04-25T12:27:15.067-04:00"you have to explain how you want to recover ..."<i>you have to explain how you want to recover local Lorentz-invariance</i>" "<i>The universe isn't Poincaré-invariant</i>" "<i>doesn't conflict with existing constraints on Lorentz-invariance violation</i>" Lorentz-invariance may not be empirically exact. Derivation cannot detect incomplete postulates, Newton versus relativity and QM. Look.<br /><br />Uncle Alhttps://www.blogger.com/profile/05056804084187606211noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56077394595604787462015-04-25T05:47:43.781-04:002015-04-25T05:47:43.781-04:00Sudip:
They're not necessarily connected with...Sudip:<br /><br />They're not necessarily connected with the center tile, I'm counting all links that 'pinch the surface of'. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-62199409054467282172015-04-25T04:15:45.891-04:002015-04-25T04:15:45.891-04:00In the paper you write, "Because all the link...In the paper you write, "Because all the links are arbitrarily close to the lightcones, we must count all the<br />points in the volume-tiles that can send light-signals to or receive light signals from the volume we considered."<br /><br />Why do we need to count all the points that are lightlike separated? I understand that the neighbors are a subset of the lightlike separated points.sudiphttps://www.blogger.com/profile/11478911457960803441noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56034255557437628382015-04-24T14:44:14.973-04:002015-04-24T14:44:14.973-04:00Wolfgang,
Thanks! In fact it's pretty much th...Wolfgang,<br /><br />Thanks! In fact it's pretty much the same argument. Except that Lorentz-invariance isn't enough, you also need homogeneity, otherwise it's easy to circumvent the conclusion. I will add this reference in an update. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-84068085162265881152015-04-24T14:13:13.114-04:002015-04-24T14:13:13.114-04:00I believe Cris Moore showed something similar in
P...I believe Cris Moore showed something similar in<br />Physical Review Letters 60 (1988) 655.<br /><br />Here is a pdf:<br />http://tuvalu.santafe.edu/~moore/comment.pdfWolfganghttps://www.blogger.com/profile/07086991199438418163noreply@blogger.com