tag:blogger.com,1999:blog-22973357.post5860068175321382692..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Dear Dr. B: Why do physicists worry so much about the black hole information paradox?Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger85125tag:blogger.com,1999:blog-22973357.post-23463129095355409222017-04-24T06:45:50.985-04:002017-04-24T06:45:50.985-04:00Andy,
The paper's wrong and should not have g...Andy,<br /><br />The paper's wrong and should not have gotten published. <a href="http://backreaction.blogspot.de/2016/01/does-arxiv-censor-submissions.html" rel="nofollow">Read this and comments on this post.</a> <br /><br />There are a couple of other papers that have made similar claims. They're also wrong, though each for other reasons. Some have a wrong definition of temperature. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-22912837867779959192017-04-24T05:08:39.481-04:002017-04-24T05:08:39.481-04:00Sabine, I could not find any mention in your artic...Sabine, I could not find any mention in your article or the comments of this 2015 <a href="http://doi.org/10.1016/j.physleta.2015.07.017" rel="nofollow">paper</a> by Thiago Guerreiro and Fernando Monteiro. According to this brief <a href="http://doi.org/10.1016/j.physleta.2015.07.017" rel="nofollow">overview</a> by Viktor Toth, it purports to "solve" the paradox by showing that nothingAnonymoushttps://www.blogger.com/profile/15729194602104030005noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-5997160208779568952017-04-17T12:03:34.073-04:002017-04-17T12:03:34.073-04:00Unknown unit,
This is a good starting point.Unknown unit,<br /><br /><a href="https://arxiv.org/abs/1703.02140" rel="nofollow">This is a good starting point.</a>Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56513878240960622752017-04-17T07:09:04.129-04:002017-04-17T07:09:04.129-04:00Hi Sabine,
Thank you for your great posts. Actual...Hi Sabine,<br /><br />Thank you for your great posts. Actually measurement process is non unitary mapping pure states into mixed ones, at least not considering decoherence. So adding a few axioms to qft like the measurement ones it should be possibile to have a theory which behaves like a qft with at low energies but it's not always unitary, especially when dealing with gravity. What do you Unknownhttps://www.blogger.com/profile/11453264117086069974noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-67099381623692873452017-04-13T11:29:47.332-04:002017-04-13T11:29:47.332-04:00Ambi Valent,
He probably doesn't mean that it...Ambi Valent,<br /><br />He probably doesn't mean that it's the same particles that come out, because they will interact with each other and so on, but that they continue in a 'normal' QFT time evolution (ie with a Hamiltonian operator). If you want to speak about 'existence' I can't help unless you give me a definition for 'existence'. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-17505225935033146622017-04-13T11:25:00.225-04:002017-04-13T11:25:00.225-04:00Richard,
What's the Lindblad operator, where ...Richard,<br /><br />What's the Lindblad operator, where does it come from, what happens to Lorentz-invariance, how come we've never noticed any of that? The problem is: The Standard Model of Particle Physics is an extremely precisely tested theory. You can't just change something about it and hope to still reproduce all predictions.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-53167122164479684052017-04-13T10:54:19.943-04:002017-04-13T10:54:19.943-04:00Sabine,
Thanks for mentioning that abandoning rev...Sabine,<br /><br />Thanks for mentioning that abandoning reversibility is not easy to do in quantum field theory.<br /><br />As a computer scientist whose knowledge of QM is in the context of quantum computing (admittedly ignorant of QFT), I'd like to try to understand what fundamental problem arises. If we try to express QFT in terms of Markovian (Lindblad) evolution to encompass black hole Unknownhttps://www.blogger.com/profile/10711554063288581343noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56087979953351334642017-04-13T08:08:26.596-04:002017-04-13T08:08:26.596-04:00Personally, i don't worry about it,i can not b... Personally, i don't worry about it,i can not be consumed by nonsense,Black Hole Information and it's paradoxes should only be seen in children's books.Anonymoushttps://www.blogger.com/profile/12746502254495546496noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-75746716223400675882017-04-13T07:22:56.802-04:002017-04-13T07:22:56.802-04:00Sabine,
apparently I was too long-winded... so a ...Sabine,<br /><br />apparently I was too long-winded... so a much shorter question: In that Hawking quote: “The absence of event horizons mean that there are no black holes – in the sense of regimes from which light can’t escape to infinity.” does Hawking mean with "escape" that the particles and photons still exist beyond the horizon and are eventually freed (that's what I thought Ambi Valenthttps://www.blogger.com/profile/03488247852564879628noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-81417590364857743352017-04-13T02:43:38.592-04:002017-04-13T02:43:38.592-04:00Richard,
You can't just 'abandon' irr...Richard,<br /><br />You can't just 'abandon' irreversibility. It's deeply built into quantum field theory. You'll have to rewrite the whole theory - and do that without ruining any of its achievements. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-89547125270627296792017-04-12T16:52:26.822-04:002017-04-12T16:52:26.822-04:00Hi Sabine,
You wrote "irreversible processes...Hi Sabine,<br /><br />You wrote "irreversible processes however don’t exist in quantum field theory" and "entropy increase usually does not imply a fundamental irreversibility, but merely a practical one".<br /><br />How do we know irreversibility is wrong? If we abandon the assumption of reversibility, does this make the black-hole information paradox go away?<br /><br />WhatUnknownhttps://www.blogger.com/profile/10711554063288581343noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-15627073130400807532017-04-12T09:09:19.315-04:002017-04-12T09:09:19.315-04:00Sabine, thanks for the explanation --Gil
Sabine, thanks for the explanation --Gil<br /><br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-3845243578619973262017-04-12T02:55:35.403-04:002017-04-12T02:55:35.403-04:00Ambi Valent,
I mean that pretty much nobody belie...Ambi Valent,<br /><br />I mean that pretty much nobody believes it's consistent with GR. I'm referring to gravastars and similar things. I believe this is a misunderstanding, your further comment makes me think you had something else in mind. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-70072358037043698722017-04-12T02:52:26.165-04:002017-04-12T02:52:26.165-04:00Mike,
I agree with what you say. Of course they d...Mike,<br /><br />I agree with what you say. Of course they did toss the paper in the bin. Of course I think we'll end up being right. Let me add that the distinction between the 'strong' and 'weak' interpretation of the BH entropy didn't come from us, though I don't know where it originated. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-54360714472838456532017-04-11T18:04:41.433-04:002017-04-11T18:04:41.433-04:00Trying to clarify: "the info comes out late&q...Trying to clarify: "the info comes out late" refers not to what you & Lee called "strong form" entropy, but more like your "weak form". So, microstates vs. observables. E.g., a distant observer gathers up all the Hawking radiation & tests for correlations. To reconstruct the 1st bit, you have to wait for half the mass to evaporate. The so-called Page timeMikePhttps://www.blogger.com/profile/13000103039799177943noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-46727910167519252802017-04-11T15:55:05.242-04:002017-04-11T15:55:05.242-04:00Sabine,
thanks for the link to "If it quacks...Sabine,<br /><br />thanks for the link to "If it quacks like a black hole". I think I'm mostly in agreement to what's written there, and if I understood things correctly, I support your conservative scenario 3.<br /><br />What I'm not sure about is if there are disagreements to the following paragraph: <i>"It is very unfortunate that this statement by Hawking has been Ambi Valenthttps://www.blogger.com/profile/03488247852564879628noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-24434476444188997452017-04-11T04:06:01.454-04:002017-04-11T04:06:01.454-04:00Tim
I explained the difference between eternal an...Tim<br /><br />I explained the difference between eternal and apparent horizon <a href="http://backreaction.blogspot.de/2014/01/if-it-quacks-like-black-hole.html" rel="nofollow">here</a>. Regarding lifetime, well, that depends on the amount of information you have to get out. Seeing that there's no bound on what might be in, it could be arbitrarily large. About how fast it comes out, there Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-49495493450533027102017-04-11T03:54:27.582-04:002017-04-11T03:54:27.582-04:00Regarding the difference between BH information pa...Regarding the difference between BH information paradox and quantum state collapse by measurement. I would say that in one measurement setting, the collapse is from one pure state to another pure state, but not via a unitary evolution. For BH information paradox, it is evolution of a pure to a mix state in one setting (i.e. one black hole). In technical jargon, it becomes an improper mixture, tytunghttps://www.blogger.com/profile/05777947785613061617noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-50682727108763664612017-04-10T16:14:46.342-04:002017-04-10T16:14:46.342-04:00Interesting stuff Sabine. Particularly after readi...Interesting stuff Sabine. Particularly after reading <a href="http://www.nature.com/articles/nphys4079.epdf?author_access_token=dMVHpyeLS-NjURH8w2YMvdRgN0jAjWel9jnR3ZoTv0P_mUIBWwidhH-m_DEyWfyPEmxrqKJGmG1wRPAvM7TmEnWiQAKO043-f7r3iLjOmZMvLKGZFIOVANQT2nh0ZdPz" rel="nofollow">your Nature commentary</a>. Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-25760024025036364932017-04-10T09:55:51.884-04:002017-04-10T09:55:51.884-04:00Thanks for that...can you also explain, or point a...Thanks for that...can you also explain, or point a place, about the changed notion of a horizon in this case, and what time is meant in "after a very long time". Coordinate time in some coordinate system?Anonymoushttps://www.blogger.com/profile/17918668471205376513noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-34783170776305878842017-04-10T09:50:11.489-04:002017-04-10T09:50:11.489-04:00Tim,
For that very reason I carefully avoided usi...Tim,<br /><br />For that very reason I carefully avoided using the word 'remnant' in my blogpost! It goes in the literature under the name 'remnant solution' but this is a misnomer. The reason for the naming is that it's taken as settled that in the case when the solution comes out late the remaining state must be very long lived. It's hence either eternal (an actual Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-2627488576913895472017-04-10T09:09:46.408-04:002017-04-10T09:09:46.408-04:00Dear Sabine,
I am not following quite your termin...Dear Sabine,<br /><br />I am not following quite your terminology here. As I understand the term, if there is a remnant then it is not that "the information comes out late" but that the information does not "come out" at all. (You can make sense of "come out" by reference to the sort of Penrose diagram that has en evaporation event and a proper event horizon of the Anonymoushttps://www.blogger.com/profile/17918668471205376513noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-24128795186660752512017-04-10T04:34:36.548-04:002017-04-10T04:34:36.548-04:00We'll have to dig up the old cliche then once ...We'll have to dig up the old cliche then once again :<br /><br />" A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it. "<br /><br />Max Planck<br /><br /><br /><br />Best, Koenraad<br />Koenraad Van Spaendonckhttps://www.blogger.com/profile/15090279727324831109noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-81103011577827253932017-04-10T03:04:00.774-04:002017-04-10T03:04:00.774-04:00gilkalai,
I wrote about this here.
The supposed...gilkalai,<br /><br /><a href="http://backreaction.blogspot.de/2015/10/black-holes-and-academic-walls.html" rel="nofollow">I wrote about this here.</a> <br /><br />The supposed problem of the firewall rests on a proof that allegedly shows that four assumptions are mutually inconsistent, ie at least one of them must be dropped for the rest to be consistent. All the literature that has followed Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-5497813715548949592017-04-10T02:49:36.038-04:002017-04-10T02:49:36.038-04:00Sabine: "the so-called firewall problem, whic...Sabine: "the so-called firewall problem, which isn't a problem but just a mathematical mistake." Sabine, please do explain or give links (or both) why do you regard the firework problem as simply a mathematical mistake. (It looks that much effort is devoted to discuss and understand this problem, and to relate it to a lot of interesting things.)<br /><br />Anonymousnoreply@blogger.com