My Notes from Inaugural IGC conference at Penn State, Aug 8-11
These notes need cleaning up. And editing. Maybe someday…
Any mistakes are all my fault.—Jim Graber
Jim Cronin, Nobel laureate, and head of Auger on cosmic rays:
His published title was
“Solving the Mystery of the Highest Energy Cosmic Rays: 1938-2007”
He changed title by adding “Moving toward” as the first two words.
Began with History.
Presented results from earlier experiments, then talked about Auger.
Emphasized Auger was built to find origin of Cosmic rays.
Strongly supported existence of GZK cutoff.
Showed slide of galaxies nearer than GZK cutoff distance indicating significant nonisotropic distribution.
Seemed to me to indicate that a paper on some form of nonisotropy or other source location information was under preparation. (For highest energy cosmic rays).
In question period, was asked how much longer Auger would have to run before he was personally convinced that something important along these lines had been seen.
Answered “Minus three months.” Emphasized that much better info will be available in a few years, and even more so after northern branch is built.
Was pressed further during coffee break (not by me), but refused to say more, other than it takes time for a large coalition to agree on an important paper.
There were several other speakers from Auger. One also mentioned nonisotropy and the said, “but I can’t tell you too much about that”
Another Auger speaker repeated info given at Mexican meeting of international cosmic ray conference, failing to confirm all previously reported nonisotropies, including clusters, point sources, the galactic center, etc. and also just a general non-isotropy.
That’s what the Auger people said; my best guess, and this is just Jim Graber speculating, is that they will announce firm evidence for a general non-isotropy, but at a lower level than previously reported by other experiments. That would good enough, but anything else would be even more interesting and more exciting.
In question period, I asked about the few events seen that are clearly beyond GZK cutoff.
(During talk he had mentioned two 3×10^20 events, an early one from Volcano Ranch, that I had not heard of, and the famous one from Fly’s Eye). He replied that Auger had two more at approx 1.2 and 1.7 or 1.9 x10^20. he said they were definitely real and could be explained by “local” sources inside the GZK range (of about 30 Mpc, I think.)
Polchinski on Black hole information loss
Joe Polchinski’s talk was on Steven Hawking’s black hole evaporation information loss paradox.
Began with history.
Quoted Hawking “God not only plays dice, sometimes he throws the dice where we can not see them.”
(I personally remember hearing Hawking say that long ago at another conference.)
Three main classes of solution:
Info is really lost
Small remnant contains info.
Info comes out in radiation.
Said he favored third alternative, info escapes.
Briefly criticized small remnant on grounds of excessively large amount of info it must contain.
Showed lots of Penrose diagrams, with horizons and singularities.
Indicated that information was widely spread in Penrose diagram, and that a substantial part of space falls into the singularity, well inside the horizon.
Hence argued that a very significant nonlocality was necessary for info to escape.
(gave Lenny Susskind partial or full credit for originating this idea.).
Emphasized that this nonlocality was different and potentially stronger (in the sense of transporting more information) than Bell type nonlocality.
Said he disagreed with the new Hawking-Maldacena solution, their effect was too small to explain how all the info gets out.
Also very briefly mentioned that it was different from LQG –Ashtekhar approach.
Abhay briefly replied during comment period mentioning discreteness of spacetime.
He only had time for a few sentences, and I am not sure I understood what he said.
All three of above approaches are “info gets out”. Later in cocktail party Polchinski said lots of people still support “info gets lost”, after I remarked that a consensus for “info gets out “ seems to be forming, or at least it’s the current fad.
(I believe Mukhanov, also made a comment supporting still another approach, but if so, I could not understand it, or perhaps I am confused and he did not speak at this point.)
I also think that near the end of his talk Polchinski mentioned the Many worlds interpretation, inflation and the multiverse. He then suggested the idea that somehow the
Many worlds of the MWI and the many worlds of the multiverse are the same, or are connected. I believe he also mentioned it again later during the cocktail party that preceded the banquet.
((This also appears to require a very virulent (or virile) form of nonlocality.))
((( Back at the APS meeting at Jacksonville, I also spoke briefly with Polchinski after his string theory talk. At that time, I asked about the assertion of the LQG folks that they had found a mathematically consistent way of Quantising gravity. He referred to some mathematics and was quite confident that this could not be so, or at least that it could not be consistently extended to cover real matter. I asked about Bob Wald’s talk at the same conference, about the state of quantum mechanics on curved spacetime, which is another very serious attempt to unify gravity with QM. Polchinski was very forthright in saying that he had not gone to the talk, had not followed this particular approach, and was not familiar with the details, but that he was confident that if it differed from string theory, in the end it would turn out to be inconsistent or botherwise wrong.)))
By the way Polchinski mentioned string theory very little at Penn State.
I did not hear any ST vs LQG debates at PS, nor did I try to start any.
Of course, I only attended about two and one tenth of the parallel talks about ST and LQG, which were mostly LQG oriented, and understood very little of those.
During cocktail party Joe Polchinski was being interviewed by a Science News reporter, but I got to talk with him a little and ask a few questions. I brought up Hawkings quote about the dice, because it recognizes the problem with loss of unitarity in a collapse, and the necessity to consider the average of many events and not just a single event to discuss the preservation of unitarity. In my recollection, this was the point of Hawking’s dice remark. (I think, but am not sure, that Polchinski basically agreed with this.) I also pointed out that collapse leads to nonunitarity as well as loss of information. Polchinski said that collapse was a confusing subject, in particular the relation of collapse with unitarity, and again reiterated that the nonlocality in his and Susskind’s argument was a different kind than the nonlocality traditionally considered.
About this time we moved on top the banquet. I ended up at the same table with Polchinski, the Science News reporter, Clifford Will, Karsten Danzman, Slava Mukhanov, I think Nicolas Yunes, and another grad student and his wife who didn’t say very much. I’m probably missing one other person.
Karsten Danzman on LISA
During dinner, I asked Karsten Danzman (from ESA, head of the LISA project, which is being lead by Europe, but with equal participation from NASA) what the effect would be on LISA if NASA ranked LISA first, second, or third or lower in the current competition. (During this entire conversation, Cliff Will, who I think is on the committee of judges for NASA sat right beside Karsten and never said a single word. He also kept a pretty good poker face, as far as I could tell.) (I am terrible at poker. I can’t possibly keep a poker face, and I am not terribly good at reading others.) Karsten said he was almost certain LISA would place second or higher and that that was good enough for LISA. He thought the US teams might need to get some more money somewhere to survive in the interim if LISA was ranked second.
The next day in his talk, KD said that LISA pathfinder was nearing completion and would fly in 2009. Technically, LISA could fly as early as 2015, if everything went well. (so called success oriented scheduling), but that ESA had budgeted LISA for late 2018 or early 2019 and that budget was the real schedule driver. He expected another round of budget negotiations with NASA soon after the NASA competition results are announced on September 8.
Jim Graber skips out on Laurent Friedel.
I got through the first three slides, maybe ten minutes, and concluded I was basically understanding very little and could spend my time more productively listening to other talks.
Loop theory/String theory talks drew 40-50 people, grav waves 20-30, general astronomy/everything else also 20 -30.
Last day, end of last session;
Abhay Ashtekhar starts conversation about Grav wave data analysis. Cliff Will, Ben Owen and others there. Appears to want to know if some area is not being covered well. Raises questions about dimensionality of problem, stability, and back reaction of waves.
Somewhat Intense discussion arises about effect of distant waves. Will and Owens assure him that these are weak effects and under control FAPP, Abhay persists, and I chime in, reminding him that the waves are weak and leave the scene at the speed of light. Abhay drops the discussion, but I am not sure he was really convinced, but he was very polite and friendly. I think he is looking for areas for the new institute to expand into.
It was well past the scheduled closing time. I head for my car and the long drive home.
Lunch at Indian restaurant. Questions about LISA and white dwarfs. next day Karsten says 21 million white dwarfs.
When I got home and found time,
I ArXiv searched Polchinski and information.
The best hit is:
. arXiv:hep-th/9903228 [ps, pdf, other] Title: Negative Energy, Superluminosity and Holography Authors: Joseph Polchinski, Leonard Susskind, Nicolaos Toumbas Comments: Expanded version replacing earlier hep-th/9902182
which includes Susskind and definitely also mentions nonlocality.
Roger Penrose on collapse and Black hole evaporation.
His title: Conformal cyclic cosmology, Dark matter, and Black hole evaporation.
I have heard him give a similar talk on several recent occasions.
He also showed lots of Penrose diagrams, which he called “conformal diagrams” rather than “Penrose diagrams”.
His theory suggests a very slow change in the values of physical constants.
It is also a cyclic cosmology with an infinite conformal expansion at the beginning of the universe and an infinite conformal contraction at the end of the universe.
He said that the conformal idea was an old one, as was the Weyl tensor, which indeed, I have heard him speak of many times over the years, but that the cyclic idea was new and just added within the last two years.
I have not found a reference for a paper with this cyclic part. If anyone knows one, please tell me. Thanks.
He suggested that the evaporation of a black hole not only leads to loss of information, (I think) but also a reduction in the dimensionality of the universe spacetime (which I am sure of). ((Not sure if he said “dimension” or “dimensionality” and of what “spacetime?” universe?”, but his diagram showed one side reducing to a point.))
In the Q&A period, I pointed out that von Neumann projection, or QM collapse also leads to a reduction in dimensions (in this case, of the Hilbert space) and asked if he saw any inverse process which would raise or increase the dimensions of the universe. He immediately replied that in fact he thought that collapse was such a process, and that collapse, by its introduction of probability, actually raised the dimension of the universe.
Blew my mind right out, it did. I’m pretty sure I saw a few other shocked faces and raised eyebrows.
Later on when I was talking to him during the coffee break, he made it clear that he still believes collapse to be an actual physical occurrence, and that it is related to gravity. He also believes this is experimentally testable.
He referred me to an experimental proposal by Bouwmeester, neglecting to mention that he was a coauthor.
The ref is:
1. arXiv:quant-ph/0210001 [ps, pdf, other] Title: Towards quantum superpositions of a mirror Authors: William Marshall, Christoph Simon, Roger Penrose, Dik Bouwmeester Comments: 5 pages, 2 figures, submitted to Phys. Rev. Lett Journal-ref: Phys. Rev. Lett. 91, 130401 (2003) Subjects: Quantum Physics (quant-ph) They had a public session with a speaker from National Geographic, and two from industry, one yahoo or google I think. One of the main topics was public outreach. Another was new directions or exploring. There was supposed to be a public discussion, but time ran out, so at the banquet they asked if any one wished to make a comment. I suggested they sponsor a blog, slightly more serious than Cosmic Variance, with an ask the scientist type feature. I mentioned that Mark was one of the sponsors of CV, but he did not speak. I did not know it, but Penn State had already done an “Ask the scientist” thing online some years ago, and next day during a break, one of the main participants came up and told me about it. What killed it off was not lack of support, or flame wars, but too many high school students asking for help on their physics homework.Maybe something like this could still work with a one week built in delay or something similar. The main thing I remember from Slava Mukhanov’s talk is that he said you could make lots of quite strong predictions just from the general idea of inflation, without knowing the details of any particular inflationary model, and one of those was that the tensor waves should be quite strong around 10 or 15% of the strength of the scalar waves. This could be detecterd from the polarization of the CMB. At the banquet when I questioned him, he agreed that it might also be seen by the pulsar timing experiments if they get around 50 really gtood pulsars, but he didn’t think it would be seen by LISA or LIGO.
I am going up to the Many worlds at 50 cofernce at PI next month. I will argue against MWI, and in favor of a real, physically observable collapse.Its good to know that I’m not the only one who believes this.
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