tag:blogger.com,1999:blog-22973357.post3011966243462397056..comments2017-03-25T17:36:03.945-04:00Comments on Backreaction: Black Hole Information - Still LostSabine Hossenfelderhttps://plus.google.com/111136225362929878171noreply@blogger.comBlogger55125tag:blogger.com,1999:blog-22973357.post-58383031459298292732017-03-03T01:27:56.829-05:002017-03-03T01:27:56.829-05:00(Maybe I phrased that oddly. I meant "informa...(Maybe I phrased that oddly. I meant "information emitted by the particle before t_1 would only need a finite amount of coordinate time" etc. - in other words, would the coordinate time of emission be the important one, and the particle's radial coordinate at t_1 would be where the event horizon is defined to be at t_1?)Ambi Valenthttp://www.blogger.com/profile/03488247852564879628noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-41249522823797691462017-03-02T12:29:07.281-05:002017-03-02T12:29:07.281-05:00Sabine,
two questions:
First, when astrophysicis...Sabine,<br /><br />two questions:<br /><br />First, when astrophysicists say a particle of matter passes the event horizon after a finite (likely short) amount of coordinate time (call that t_1), do they mean they calculated that before coordinate time t_1 information from the particle could get to an observer in the vacuum outside the body in finite coordinate time, while after t_1, it would Ambi Valenthttp://www.blogger.com/profile/03488247852564879628noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-83358014140396174202017-02-23T13:03:38.373-05:002017-02-23T13:03:38.373-05:00For the cases that it can, how does string theory ...For the cases that it can, how does string theory resolve this question?Unknownhttp://www.blogger.com/profile/16018083681054370026noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-54231166131473485492017-02-21T12:44:05.957-05:002017-02-21T12:44:05.957-05:00Regarding information loss in collapse vs BH. Even...Regarding information loss in collapse vs BH. Even if QM collapse agrees perfectly with observation it ought to be a reason to worry if it violates principles of time symmetry and conservation of information. May be observation bears out information loss information loss in BH. Wouldn't we then still worry about these principles? orezenohttp://www.blogger.com/profile/15089974340293214427noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-73642089413139369122017-02-20T17:07:37.097-05:002017-02-20T17:07:37.097-05:00Yes, indeed, it's totally irrelevant, it is al...Yes, indeed, it's totally irrelevant, it is always possible to imagine an thought experiment which would send information in a black hole (using a modulated laser for example) and which would make it grow. Information could never come out.<br /><br />The source of information does not have to be natural and to go through an accretion disk.nicolas pouparthttp://www.blogger.com/profile/17722878242014554884noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-9681498079567951332017-02-20T11:53:04.691-05:002017-02-20T11:53:04.691-05:00Michael,
If you want a quantum-answer, the intera...Michael,<br /><br />If you want a quantum-answer, the interaction is exchanged by virtual gravitons which are not blocked by the horizon. But please keep in mind that gravity here is *not* quantized. It's a classical field, there isn't anything like an exchange particle associated with it. The black hole is simply a solution to the field equations and that's that. Best,<br /><br />B.Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-25893544627976967262017-02-20T11:26:58.315-05:002017-02-20T11:26:58.315-05:00At the risk of asking a dumb question, how does th...At the risk of asking a dumb question, how does the mass of the black hole curve spacetime when that mass is cloaked by the event horizon? Is it ok to say that the event horizon is not impermeable to gravitons? If so can those gravitons carry information out?Michael Mussonhttp://www.blogger.com/profile/17360143418083381579noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-74337233918096925492017-02-20T10:00:05.557-05:002017-02-20T10:00:05.557-05:00orezeno,
Because that's usual quantum mechani...orezeno,<br /><br />Because that's usual quantum mechanics and we know that it describes our observations very well. No, it's not a matter of interpretation, it's a mathematical inconsistency.Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-42585678382594650952017-02-20T09:41:16.206-05:002017-02-20T09:41:16.206-05:00Why are people not as worried about collapse of va...Why are people not as worried about collapse of various possibilities into one final state when it comes to losing information on running their thing backwards. Why doesn't it become a big deal only when a black hole does it :) <br /><br />If its just about interpretation can't we create some QM like interpretation to wiggle out of this one too? orezenohttp://www.blogger.com/profile/15089974340293214427noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-20860414735451552902017-02-20T07:54:37.250-05:002017-02-20T07:54:37.250-05:00nicolas,
That's totally irrelevant. As I said...nicolas,<br /><br />That's totally irrelevant. As I said, it's a mathematical inconsistency. How much information is in chemical bonds is entirely besides the point. Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-18240064666436647202017-02-20T07:26:29.858-05:002017-02-20T07:26:29.858-05:00It should not be forgotten that most of the inform...It should not be forgotten that most of the information contained in matter is in the chemical bonds that break and the information dissipates into light, escaping the black hole. What passes the horizon is only ionized and homogenized gas, containing little information. We should first prove that 10 micrograms of black hole can not contain enough information to reconstruct its accretion history.nicolas pouparthttp://www.blogger.com/profile/17722878242014554884noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-62683837912275702342017-02-20T03:20:42.502-05:002017-02-20T03:20:42.502-05:00AT,
The calculation for Hawking radiation is made...AT,<br /><br />The calculation for Hawking radiation is made in the asymptotic limit which is hair-free. Needless to say, it's been tried many times to find a way to use the earlier 'hair' to imprint the outgoing radiation, alas, unsuccessfully. Think about it for a moment: It is highly implausible (and hard to achieve mathematically) that *all* the information about the ingoing stateSabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-89117764891479680722017-02-20T02:55:40.083-05:002017-02-20T02:55:40.083-05:00Hi Sabine,
I agree that the asymptotic black hole...Hi Sabine,<br /><br />I agree that the asymptotic black hole end state (Schwarzschild, Kerr, etc) is the always same (no hair theorem or so).<br /><br />But a physical black does not just sit there since the beginning of time but is formed during the actual collapse of matter. Thus I wonder whether this asymptotic end state is ever exactly reached or whether there is an ever decreasing differenceAThttp://www.blogger.com/profile/12346214191858746628noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-30947086031872467122017-02-20T01:01:04.303-05:002017-02-20T01:01:04.303-05:00akidbelle,
Depends on what happens with the entro...akidbelle,<br /><br />Depends on what happens with the entropy during evaporation. But speaking of entropy is in my opinion not a good way to phrase the problem because it isn't really clear what the entropy of a black hole is. I mean not in numbers - there's little argument about it - but in terms of interpretation. Best,<br /><br />B.Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-59413711530328382732017-02-20T00:57:41.068-05:002017-02-20T00:57:41.068-05:00AT,
1) It can't run backwards because the end...AT,<br /><br />1) It can't run backwards because the end state of evaporation is the same for all black holes with the same mass. You can't tell from this what formed the black hole, hence you can't run it backwards. <br /><br />2) You get the problem if you combine GR with quantum field theory. <br /><br />Best,<br /><br />B.Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-8807588935073831882017-02-20T00:55:21.160-05:002017-02-20T00:55:21.160-05:00JimV,
Yes, exactly! It's all about the unique...JimV,<br /><br />Yes, exactly! It's all about the unique mapping from initial states to end-states that black holes prevent - the measurement happens only after that. In the case of a neutron star, the information wouldn't escape immediately, would it would escape eventually. Best,<br /><br />B.Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-2205821005890518742017-02-19T13:26:26.641-05:002017-02-19T13:26:26.641-05:00I see the difference now, I think. I was slightly ...I see the difference now, I think. I was slightly hung up on the fact that it could be impossible to reassemble the information (of the burned book), not just for (classically) practical reasons, but because of the Uncertainty Principle and other QM features. However, as the post pointed out, this is a case of the information being made inaccessible but not destroyed.<br /><br />The other point IJimVhttp://www.blogger.com/profile/10198704789965278981noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-62237842654189088822017-02-19T12:19:18.717-05:002017-02-19T12:19:18.717-05:00Dumb question 1: Why can black hole evaporation no...Dumb question 1: Why can black hole evaporation not run backwards?<br /><br />Naively I would expect that I can add mass to a black hole by feeding it with enough photons per unit time arriving (randomly?) from various space directions...<br /><br />Dumb question 2: General relativity seems invariant against time reversal, quantum electrodynamics (lets ignore CP violation for a moment) hopefully AThttp://www.blogger.com/profile/12346214191858746628noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-47230407372547127752017-02-19T12:11:41.406-05:002017-02-19T12:11:41.406-05:00Grimm,
"These kind of theoretical problems c...Grimm,<br /><br /><i>"These kind of theoretical problems cannot be solved by theoretical phenomenological physicists who have no understanding of the foundations of physics and the corresponding foundations of mathematics. So yes, you are right. When it comes to the contributions of theoretical phenomenological physicists the black hole information paradox will outlive them all. Accept it.&Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-81616660123879596462017-02-19T11:39:01.035-05:002017-02-19T11:39:01.035-05:00Hi Sabine,
you discuss information loss, but isn&...Hi Sabine,<br /><br />you discuss information loss, but isn't the problem more general? i.e. would an evaporating black hole generate negative entropy? (information loss or not).<br /><br />Thanks,<br />J.akidbellehttp://www.blogger.com/profile/12292741599925116131noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-34086309169926851182017-02-19T08:44:48.996-05:002017-02-19T08:44:48.996-05:00“Black holes emit radiation and this radiation doe...“Black holes emit radiation and this radiation doesn’t carry information”<br /><br />It depends on the answer of the question: “What is information”. If theoretical phenomenological physicists have the conviction that information is something that can be transformed in an understandable way from configuration A to configuration B, the discrete radiation of a black hole carries information. Just S.E. Grimmhttp://www.blogger.com/profile/00290346316355388367noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-44242770583113823922017-02-19T02:47:29.956-05:002017-02-19T02:47:29.956-05:00Michael,
The horizon isn't the problem. The h...Michael,<br /><br />The horizon isn't the problem. The horizon is merely the place beyond which information becomes inaccessible from the outside. It's the singularity that destroys the information and, eventually, results in the outgoing radiation missing information. (It turns from a pure state into a mixed state, in case you know the technical terms. Note however that even this pure Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-42379778930253307312017-02-19T02:44:29.889-05:002017-02-19T02:44:29.889-05:00Jim,
What is Born's law? Do you mean Born'...Jim,<br /><br />What is Born's law? Do you mean Born's rule? It doesn't change anything about the problem, the inconsistency comes about already before measurement. You can try to argue, well, then why not just accept it because in the end we only measure probabilities anyway, so we can never prove a time-evolution was indeed unitary and so on. Yes, you can do that. Again, that Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-34122951202518871612017-02-19T02:40:50.131-05:002017-02-19T02:40:50.131-05:00Jeff,
It is a point that is generally entirely un...Jeff,<br /><br />It is a point that is generally entirely underappreciated by laymen, that it is really hard to change anything about the existing theories so that the new theory is both internally consistent and consistent with all existing data. <br /><br />There are some tricks that theoretical physicists have developed by help of which you can amend the present theories so that they still Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-86545898602029127982017-02-18T21:41:45.579-05:002017-02-18T21:41:45.579-05:00Hi Bee, not a physicist here. Question about your ...Hi Bee, not a physicist here. Question about your statement "But modifying quantum mechanics is, if anything, even harder than modifying general relativity." Is the difficulty theoretical or experimental? In other words: is it difficult to conceive a mathematical modification that would fit existing data for QM, but cause reversibility to break down in regions of extreme curvature? Or Jeffhttp://www.blogger.com/profile/06140726210295297492noreply@blogger.com