tag:blogger.com,1999:blog-22973357.comments2017-02-19T13:26:26.641-05:00BackreactionSabine Hossenfelderhttps://plus.google.com/111136225362929878171noreply@blogger.comBlogger43313125tag: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-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.comtag:blogger.com,1999:blog-22973357.post-9003967514874062302017-02-18T11:46:08.077-05:002017-02-18T11:46:08.077-05:00Is the horizon of BH the cause of the problem or j...Is the horizon of BH the cause of the problem or just the start? What I mean is that once inside the horizon, every move closer to the horizon makes something inaccessible to something further out but still inside the horizon. Given this, it seems that to solve the paradox requires understanding the true nature of the singularity at the center. Michael Mussonhttp://www.blogger.com/profile/17360143418083381579noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-73898642331648298102017-02-18T10:48:15.207-05:002017-02-18T10:48:15.207-05:00How does the Born law relate to Information loss?
...How does the Born law relate to Information loss?<br /><br />Even without black holes, it seems to me that information is lost due to Born's law.<br /><br />A book burning is reversible (in principle). Does this mean there are no occurrences/applications of the Born law in a book burning, or that Born's law is reversible?<br /><br />Or is this whole issue contingent on ignoring the Born Jim Graberhttp://www.blogger.com/profile/15258259890780748550noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-67728110669295578862017-02-18T09:55:32.119-05:002017-02-18T09:55:32.119-05:00JimV,
I don't know what you mean by "in ...JimV,<br /><br />I don't know what you mean by "in principle it could be." In usual quantum mechanics, it isn't. It's a reversible process. You can try to modify quantum mechanics to try to change that, yes. But modifying quantum mechanics is, if anything, even harder than modifying general relativity. Either way, you have to change something about the existing theories to Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-16831329302059113222017-02-18T09:53:03.106-05:002017-02-18T09:53:03.106-05:00Hopefully,
The 2nd law of thermodynamics is an ag...Hopefully,<br /><br />The 2nd law of thermodynamics is an aggregate description. It merely tells you what's likely or not. Fundamentally, everything is reversible, it's just that many time-reversed processes require so finely tuned initial conditions we never observe them. The exception is black hole evaporation. According to Hawking's result, it's not reversible. Words and Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-9802611763345062742017-02-18T09:35:40.484-05:002017-02-18T09:35:40.484-05:00It seems to me that in principle the book-burning ...It seems to me that in principle the book-burning could also be irreversible once QM is included - but I see Miki Weiss has already stated that objection, and been answered that the evolution of the QM state via a Hamiltonian is deterministic. Which I guess means that once events have occurred the past is fixed, and running the equations backwards will reproduce it. (Why this is not also true forJimVhttp://www.blogger.com/profile/10198704789965278981noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-66888701190100929362017-02-18T08:53:02.694-05:002017-02-18T08:53:02.694-05:00Once again a delightfully informative blog post. T...Once again a delightfully informative blog post. Thanks a lot.John Fredstedhttp://www.blogger.com/profile/14392519442398073571noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-6871907591297545262017-02-18T07:16:47.570-05:002017-02-18T07:16:47.570-05:00Thanks Bee, but I can still interpret this in two ...Thanks Bee, but I can still interpret this in two very different ways:<br />"Looks very different....irreversible" just sounds to me like standard second law thermodynamics. Put a book into BH, get Hawking radiation out, never observed Hawking radiation happening in a micro state corresponding to a book. True, but isn't that just a very low probability event? If this were not a BH HopefullyAskingMeaningfulQuestionshttp://www.blogger.com/profile/17614731150556974798noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-82823791862663528752017-02-18T00:14:37.849-05:002017-02-18T00:14:37.849-05:00Bill,
The difference between these objects is in ...Bill,<br /><br />The difference between these objects is in the way that the elementary particles are arranged relative to each other. That the black hole can't tell the difference is exactly the problem! Best,<br /><br />B.Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-55578368545172053512017-02-18T00:12:53.946-05:002017-02-18T00:12:53.946-05:00Henry,
It's both together. A good way to thin...Henry,<br /><br />It's both together. A good way to think about it is to imagine some initial state in which the particles are very far away from each other and basically don't interact (the usual initial state in qft). They approach each other, collapse and form a black hole, the black hole evarporates. Particles disperse out to infinity again where they barely interact with each other. Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-89833800319262956422017-02-18T00:09:50.039-05:002017-02-18T00:09:50.039-05:00Miki,
You might also recall that the time-evoluti...Miki,<br /><br />You might also recall that the time-evolution is deterministic. There's a Hamiltonian operator. It can be run forwards and backwards. Not so with black holes. Best,<br /><br />B.Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-70715663019873865462017-02-18T00:08:27.784-05:002017-02-18T00:08:27.784-05:00Hopefully,
That a process is reversible doesn'...Hopefully,<br /><br />That a process is reversible doesn't mean it's invariant under that reversal. Clearly the formation and subsequent evaporation of the black hole looks very different forwards than backwards. You shouldn't get hung up on the word 'information'. Forget about information. The black hole information loss paradox is that in a quantum field theory there's Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-26079739614360016472017-02-18T00:04:09.984-05:002017-02-18T00:04:09.984-05:00akidbelle,
Yes, one can estimate the accretion ra...akidbelle,<br /><br />Yes, one can estimate the accretion rate of dark matter (and other stuff) onto black holes (and neutron stars) etc, and one finds numbers somewhere in the literature. I don't know what this has to do with information loss however. Best,<br /><br />B.Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-23454515317945140812017-02-18T00:02:34.086-05:002017-02-18T00:02:34.086-05:00Evan,
At first thought, no. At second thought, ma...Evan,<br /><br />At first thought, no. At second thought, maybe. The reason is that a modification of gravity generally has the prospect of changing something about the way that black holes evaporate. I do not, however, presently see how Verlinde's approach could solve the problem. If you believe that it's a consequence of string theory, then of course it kinda has solved the problem Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-84920363793887664922017-02-17T23:59:55.034-05:002017-02-17T23:59:55.034-05:00Ivan,
What you say is wrong. A system does not ne...Ivan,<br /><br />What you say is wrong. A system does not need to have entanglement between different parts to be in a pure state. Besides this, the black hole isn't a quantum state in this treatment to begin with.<br /><br />Indeed, the black hole is a bubble of nothing. It's defined by the causal properties of the space-time. Best,<br /><br />B. Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-20514895752679897892017-02-17T19:26:16.402-05:002017-02-17T19:26:16.402-05:00Sabine,
"That’s the paradox: Black hole evap...Sabine,<br /><br />"That’s the paradox: Black hole evaporation is a process that cannot be run backward. It is, as we say, not reversible."<br /><br />My question is not about the physics, but about the wording. Isn't it "the falling of information into the black hole", rather than the evaporation of the black hole, which is the irreversible process?TheBigHenryhttp://www.blogger.com/profile/04917973198063733316noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-43492700142112896622017-02-17T18:13:06.199-05:002017-02-17T18:13:06.199-05:00Bill, there isn't any difference between a roc...Bill, there isn't any difference between a rock and a book as far as fundamental information is concerned, meaning the information required to describe the positions and velocities of the particles comprising the rock or book. The information in a written Shakespeare's sonnet is far less than the information required to describe the paper on which it is written.Andrew Thomashttp://www.blogger.com/profile/11075608749064975687noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-74356328556881026342017-02-17T15:35:08.353-05:002017-02-17T15:35:08.353-05:00"This is because the laws of nature, to our b..."This is because the laws of nature, to our best current understanding, can be run both forwards and backwards – every unique initial-state corresponds to a unique end-state"<br />From my "ancient" 2 quantum mechanics college courses, I still remember that QM interactions are random in nature, so we cant say anything about a specific outcome of an interaction, only Miki Weisshttp://www.blogger.com/profile/12448204299298989587noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-52027591012388090942017-02-17T15:09:48.466-05:002017-02-17T15:09:48.466-05:00Bee,
I have the same Guess that information should...Bee,<br />I have the same Guess that information should be conserved, but what worries me is that I can't base that on anything.<br />I understand how conservation principles arise from Noether. Can you explain what symmetry is dual to "information"? You seem to be identifying it as time-reversal, but the dual of that is not information (or not as I understand it), it is simply timeHopefullyAskingMeaningfulQuestionshttp://www.blogger.com/profile/17614731150556974798noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-2110167224830481732017-02-17T14:51:30.762-05:002017-02-17T14:51:30.762-05:00Hi Sabine,
considering the time needed for evapor...Hi Sabine,<br /><br />considering the time needed for evaporation, I wonder how much dark matter (particles) would fall there in the meantime. Any idea?<br /><br />And how much of the standard (repulsive) scalar field should be trapped?<br /><br />After all those two guys are supposedly energy like everything else.<br /><br />Best,<br />J.<br />akidbellehttp://www.blogger.com/profile/12292741599925116131noreply@blogger.com