tag:blogger.com,1999:blog-22973357.post442541614588730057..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: String theory pros and cons [video - no singing!]Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger61125tag:blogger.com,1999:blog-22973357.post-29882811513888949102018-11-25T10:55:21.884-05:002018-11-25T10:55:21.884-05:00Actually the answer to life and everything was 16....Actually the answer to life and everything was 16. Deep Thought just misprinted 4^2 ;)Lindsay Forbeshttps://www.blogger.com/profile/02027656071652397830noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-74928071173797730352018-11-04T12:11:20.259-05:002018-11-04T12:11:20.259-05:00Sabine,
The story you tell of the pitfalls and the...Sabine,<br />The story you tell of the pitfalls and theorists determined efforts to diagnose its fundamental issues was quite interesting. It kind of reminded me of bug-checking a huge messy program, in which the root cause has not yet been found... lots of work-arounds and fixes...making everything all the messier.<br /><br />IMHO, the string as representation geometry story goes awry very WRLhttps://www.blogger.com/profile/04323354407920835050noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-66217083350846144422018-11-04T11:50:37.807-05:002018-11-04T11:50:37.807-05:00@Georg,
good thinking.. except the hooks. LQG pro...@Georg,<br />good thinking.. except the hooks. LQG proved background independence is required.<br />A string with stiffness is a Band... and the topic of my DPF '15 paper. Bands have three natural quantum-distinct ground states, which the band oscillates between. That yields an ideal representation geometry for neutrinos. They can also model QC/ED state algebras.WRLhttps://www.blogger.com/profile/04323354407920835050noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-32423729466805795322018-11-01T05:25:35.238-04:002018-11-01T05:25:35.238-04:00I wish I see more comments like this I wish I see more comments like this Sheeverhttps://www.blogger.com/profile/12931916936543585461noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-24637932438446253642018-10-27T23:19:20.190-04:002018-10-27T23:19:20.190-04:00Unknown,
First, I say this constantly: If you rea...Unknown,<br /><br />First, I say this constantly: If you really want to post as "Unknown" could you please at least enumerate yourself? How is anyone supposed to know now whether you are the same Unknown as the earlier one?<br /><br />Second, I actually agree with this. I don't a priori have problem with people who write stories - of the math-kind or of the verbal kind - because we Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-8323521420024835822018-10-27T20:55:03.996-04:002018-10-27T20:55:03.996-04:00Sorry, string theory skeptics, but string theory w...Sorry, string theory skeptics, but string theory will not be going away. It's too connected to gauge theory and quantum gravity, it's too flexible to be abandoned even if the susy-GUT synthesis isn't working out, and it's too close to reality and too potentially predictive to just ignore. Mitchellhttps://www.blogger.com/profile/10768655514143252049noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-18215724075741399542018-10-27T12:53:07.507-04:002018-10-27T12:53:07.507-04:00neo,
No one knows what the "correct" en...neo,<br /><br />No one knows what the "correct" entropy of a black hole is because no one has measured it. And any theory that reproduces the semi-classical limit must reproduce Hawking's result for the radiation.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-48846803089758494402018-10-27T12:14:47.914-04:002018-10-27T12:14:47.914-04:00yes, but the second constraint,
do they also corr...yes, but the second constraint,<br /><br />do they also correctly reproduce Hawking entropy and radiation for black holes?<br /><br />in addition to positive CC<br /><br />LQG apparently does both. neohttps://www.blogger.com/profile/17318664916557810347noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-33916371277426959342018-10-27T11:55:42.078-04:002018-10-27T11:55:42.078-04:00neo,
Asymptotically safe gravity is perfectly com...neo,<br /><br />Asymptotically safe gravity is perfectly compatible with a positive cosmological constant, and I am not aware that it is a problem for causal dynamical triangulations. Causal sets famously predict the cosmological constant (as in: actually predict, not post-dict), and some approaches to emergent gravity come with a cosmological constant by exploiting that it appears in the Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-50824014270918643552018-10-27T10:04:11.996-04:002018-10-27T10:04:11.996-04:00Sabine
i'll remember to do that lol.
since y...Sabine<br /><br />i'll remember to do that lol.<br /><br />since your background is QG, of all the QG candidate theories out there, that is professionally researched, <br /><br />is LQG the only candidate QG that is compatible with deSitter spacetime and reproduces Black hole entropy in DeSitter spacetime, unlike string theory?<br /><br />if so, shouldn't more research attention be given neohttps://www.blogger.com/profile/17318664916557810347noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-87156984707223457182018-10-27T09:22:53.367-04:002018-10-27T09:22:53.367-04:00I have to give a hand to Bee's counter argumen...I have to give a hand to Bee's counter argument to the money argument. This is rather typical these days, and is employed to knock not just theoretical physics but everything from art to astronomy. So goes this rather stout type of argument, where it implies we should be hedge fund managers, or some such. Really??? What good in the end do the investor class generate other than grab more moneyLawrence Crowellhttps://www.blogger.com/profile/12090839464038445335noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-77868110783830144782018-10-27T09:01:05.323-04:002018-10-27T09:01:05.323-04:00Bee,
The point is there is a mass gap that preven...Bee,<br /><br />The point is there is a mass gap that prevents the occurrence of Minkowski spacetime. The T-duality of qubits, or to avoid stringy language the hyperbolic discrete transformations of conjugate variables or quantum observables, means the departure from Bekenstein's bound for small N and convergence as N → ∞ to that bound. This is a dual interpretation for momentum p ~ 1/Nℓ_p Lawrence Crowellhttps://www.blogger.com/profile/12090839464038445335noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-26618896418485150762018-10-27T08:49:39.181-04:002018-10-27T08:49:39.181-04:00(That, of course, does not include expenses for ex...(That, of course, does not include expenses for experiments.)Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-37782982104772223392018-10-27T08:46:50.378-04:002018-10-27T08:46:50.378-04:00Oh, yeah, that's another one of those "ar...Oh, yeah, that's another one of those "arguments" I am tired of hearing: Money is wasted elsewhere too, so who cares? Well, I care. Wasting money on 15,000 people to produce math-fiction means 15,000 other people whose research could benefit mankind are not getting paid. <br /><br />Since someone above asked for numbers, a quick estimate is $100,000 per person per year. It's Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-36694905905243328412018-10-27T02:19:55.749-04:002018-10-27T02:19:55.749-04:00Lawrence,
That's an interesting point and muc...Lawrence,<br /><br />That's an interesting point and much sharper than my rather vague elaboration. There seems to be a sentence missing in your comment, however, maybe you can fill in the blank. <br /><br />What you say is much sharper because from what I said you could argue (and I have spoken to people who have argued this) that you just don't care: You can simply define the flat-spaceSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-90549048646395874442018-10-27T02:07:30.643-04:002018-10-27T02:07:30.643-04:00neo, should I ever write a paper about BPS black h...neo, should I ever write a paper about BPS black holes in AdS, please hit me over the head and throw me in the gutter. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-47240203394942744122018-10-26T19:58:20.230-04:002018-10-26T19:58:20.230-04:00Bee: I wish wormholes where possible so I could ex...Bee: I wish wormholes where possible so I could extend a hand over to your side of the world to shake your hand. Your intuition or thinking that Λ → 0 is not continuous may be entirely correct. This is a feature of BTZ black holes that have a duality with AdS_3. I will try to make this gentle and this is in part due to Witten in his paper arXiv:0706.3359v1 <i>Three Dimensional Gravity Revisited</Lawrence Crowellhttps://www.blogger.com/profile/12090839464038445335noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-19365572395176471082018-10-26T17:22:20.965-04:002018-10-26T17:22:20.965-04:00Your video is well done except that some of the bo...Your video is well done except that some of the books you showed never got completely in frame. But that is no matter; Mr. Google makes it easy to find them even with only partial info.<br /><br />Thanks for your work.<br /><br />sean s.sean s.https://www.blogger.com/profile/04190153587965701495noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-31112309273188699102018-10-26T13:37:35.736-04:002018-10-26T13:37:35.736-04:00bee thanks.
btw
" Frankly I haven't ...bee thanks.<br /><br /> <br /><br />btw<br /><br />" Frankly I haven't followed this because I consider it a waste of time anyway and I have better things to do. "<br /><br />i thought your research interests were in QG and included black hole physics, entropy, though i know your most recent papers were in covariant gravity and MONDneohttps://www.blogger.com/profile/17318664916557810347noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-84415447384656859962018-10-26T11:21:52.161-04:002018-10-26T11:21:52.161-04:00neo,
I think there have been some papers about ne...neo,<br /><br />I think there have been some papers about near-extremal black holes & it seems to me that those methods can be extended to the general case. Frankly I haven't followed this because I consider it a waste of time anyway and I have better things to do.<br /><br />As to why I don't think the AdS case will help with the dS case, I have explained this elsewhere, but here we Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-27710441930632616862018-10-26T11:07:14.143-04:002018-10-26T11:07:14.143-04:00bee, lawrence,
thanks. but if it is potentially ...bee, lawrence, <br /><br />thanks. but if it is potentially solvable, why in all these years (decades? - since the extremel result was offered in mid 90s iirc) hasn't it been provided in non-extremel case (in AdS)?<br /><br />Bee, without going into great detail, can you explain in a sentence why you think the issue with black hole entropy in DeSitter can't be solved in string theory?<br neohttps://www.blogger.com/profile/17318664916557810347noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-20351362780132902142018-10-26T10:54:40.563-04:002018-10-26T10:54:40.563-04:00Dr. Hossenfelder,
Do you have any information on ...Dr. Hossenfelder,<br /><br />Do you have any information on the percentage of funding that is directed to string theory?<br /><br />Or how about a chart showing arXiv papers focused on string theory by year?<br /><br />Thanks<br /><br />JAnonymoushttps://www.blogger.com/profile/06444073442376283232noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-30449856786755512022018-10-26T09:09:52.962-04:002018-10-26T09:09:52.962-04:00I meant to send this link with my last transmissio...I meant to send this link with my last transmission. It illustrates the AdS connection with black holes.<br /><br />https://physics.stackexchange.com/questions/262735/ads-black-holes/262744#262744Lawrence Crowellhttps://www.blogger.com/profile/12090839464038445335noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-67448150490583319692018-10-26T09:09:04.075-04:002018-10-26T09:09:04.075-04:00Neo,
The stringy content is often in BPS charges....Neo,<br /><br />The stringy content is often in BPS charges. This pertains to extremal black hole, which in this setting is a sort of ensemble of elementary quantum units of black hole. The black hole is placed in an AdS, which is the only possible "bottle" that can hold a black hole. Remember Gauss' law and that any massive shell around a central mass is not gravitationally coupledLawrence Crowellhttps://www.blogger.com/profile/12090839464038445335noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-82211164754054513742018-10-26T08:44:33.420-04:002018-10-26T08:44:33.420-04:00neo,
Yes, that too, but I believe this to be a so...neo,<br /><br />Yes, that too, but I believe this to be a solvable problem. That these calculations only work in AdS, otoh, I think is an unsolvable problem. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.com