tag:blogger.com,1999:blog-5880610.post3580363368137887001..comments2020-11-29T02:07:43.911-05:00Comments on Information Processing: Black hole firewalls and all thatSteve Hsuhttp://www.blogger.com/profile/02428333897272913660noreply@blogger.comBlogger10125tag:blogger.com,1999:blog-5880610.post-40831351657785127302013-08-24T12:45:46.432-04:002013-08-24T12:45:46.432-04:00What's the precise mathematical definition of ...What's the precise mathematical definition of a semi-classical observer? I'm pretty sure what you say is true as far as I understand it but is it at theorem status? Here is my trivial understanding of QM so please correct me because it will help me to understand this better. Consider a a state vector for the entire universe that evolves through a unitary transformation. Now consider Carson Chownoreply@blogger.comtag:blogger.com,1999:blog-5880610.post-48171044842301635402013-08-23T08:27:38.834-04:002013-08-23T08:27:38.834-04:00Well, I agree that giving up EP so quickly is craz...Well, I agree that giving up EP so quickly is crazy. <br /><br /><br />But I do think if ~30 really top theorists (check out the workshop participants at KITP) have thought hard about it for ~1 year and can't sort it out then it's nontrivial ...steve hsuhttp://duende.uoregon.edu/noreply@blogger.comtag:blogger.com,1999:blog-5880610.post-29221665972216625912013-08-23T08:25:03.720-04:002013-08-23T08:25:03.720-04:00Not sure I understand, but I think you mean that t...Not sure I understand, but I think you mean that to a particular semiclassical observer it appears the BH destroys information whereas a global observer (who can see the all branches of the wavefunction of the universe) sees unitary evolution. If so, I agee :-)<br /><br /><br />Note there is an exact parallel to ordinary QM measurement (e.g., Stern-Gerlach), which *appears* to collapse the wavefnsteve hsuhttp://duende.uoregon.edu/noreply@blogger.comtag:blogger.com,1999:blog-5880610.post-90515276946341503172013-08-23T08:09:55.360-04:002013-08-23T08:09:55.360-04:00Looking carefully at AMPS, and not being able to f...Looking carefully at AMPS, and not being able to find the problem, are *not* the same thing as *really* believing in the existence of firewalls! My attitude, and I *hope* the attitude of most people, is that firewalls can't exist: it's just a matter of finding the problem[s] in AMPS. My comment about GR was based on the way people talk about "no drama" at the event horizon, as Rastus Odinga-Odinganoreply@blogger.comtag:blogger.com,1999:blog-5880610.post-35562229150669610852013-08-23T07:06:46.125-04:002013-08-23T07:06:46.125-04:00Is it a theorem that if you start with a pure stat...Is it a theorem that if you start with a pure state of particle(s) and a black hole and evolve that unitarily you will end up with a system on which any continuous branch that an observer lives on is mixed in the sense that the BH forces you to marginalize over the rest of the universe states. I probably don't have the language right but the black hole automatically radiates to all the Carson Chownoreply@blogger.comtag:blogger.com,1999:blog-5880610.post-21102756952201126662013-08-23T06:36:53.717-04:002013-08-23T06:36:53.717-04:00Surprisingly many! In fact a significant number of...Surprisingly many! In fact a significant number of theorists whose brainpower I admire have (a) looked carefully at AMPS and (b) can't find the problem. Among the people who share my perspective I can only count Nomura and co. and Lubos!<br /><br /><br />I don't think it's a problem with understanding of GR. The subtle aspect is really in the QM part.steve hsuhttp://duende.uoregon.edu/noreply@blogger.comtag:blogger.com,1999:blog-5880610.post-37690812531069407552013-08-23T06:33:37.284-04:002013-08-23T06:33:37.284-04:00Actually, in some sense the BH information problem...Actually, in some sense the BH information problem is *posed* within a many worlds framework -- does the quantum state of the BH + radiation + environment evolve unitarily (pure state to pure state), or do BHs cause pure states to evolve to mixed (Hawking's original claim)? <br /><br />Unfortunately I can't make it to the meeting -- my day job interferes with doing physics :-( But I'steve hsuhttp://duende.uoregon.edu/noreply@blogger.comtag:blogger.com,1999:blog-5880610.post-33524385338394666552013-08-23T00:08:33.465-04:002013-08-23T00:08:33.465-04:00So your argument is basically that accepting Many ...So your argument is basically that accepting Many Worlds resolves the firewall paradox as well as the black hole information problem. Sounds plausible to me. Are you headed to Santa Barbara?Carson Chownoreply@blogger.comtag:blogger.com,1999:blog-5880610.post-20998932051665206132013-08-22T23:03:16.768-04:002013-08-22T23:03:16.768-04:00A really interesting question: how many people *re...A really interesting question: how many people *really* believe that firewalls exist? My feeling is that those people are a tiny minority. Thank God. The fact that any such people exist is a jarring reminder that the standard of the General Relativity courses nearly everywhere is utterly abysmal.Rastus Odinga-Odinganoreply@blogger.comtag:blogger.com,1999:blog-5880610.post-6977614042918484152013-08-22T21:48:27.898-04:002013-08-22T21:48:27.898-04:00Preskill is tweeting with the hashtag #fuzzorfirePreskill is tweeting with the hashtag #fuzzorfireDavid Coughlinnoreply@blogger.com