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Tanmay Vachaspati: on 10/5/12 at 3:44am UTC, wrote Dear Daryl, Thanks a lot for your post. At first read it looks like we...

Daryl Janzen: on 10/4/12 at 22:55pm UTC, wrote Sorry. Here are the figures I meant to attach.

Daryl Janzen: on 10/4/12 at 22:14pm UTC, wrote Dear Tanmay: Thank you for your essay. I'm sorry that I missed it before,...

Sergey Fedosin: on 10/4/12 at 5:38am UTC, wrote If you do not understand why your rating dropped down. As I found ratings...

Tanmay Vachaspati: on 10/4/12 at 0:41am UTC, wrote Dear Georgina, I am glad you enjoyed my essay. The heaven-hell analogy is...

Georgina Parry: on 10/3/12 at 23:32pm UTC, wrote Dear Tanmay Vachaspati, your essay is written very clearly in accessible...

Tanmay Vachaspati: on 10/2/12 at 14:35pm UTC, wrote It is a lot of hard work. I am still going through the list. Thanks for...

Sergey Fedosin: on 10/2/12 at 8:27am UTC, wrote After studying about 250 essays in this contest, I realize now, how can I...

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July 18, 2019

CATEGORY: Questioning the Foundations Essay Contest (2012) [back]
TOPIC: Preferred Observers in Quantum Gravity by Tanmay Vachaspati [refresh]

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Author Tanmay Vachaspati wrote on Aug. 31, 2012 @ 12:06 GMT
Essay Abstract

Parallels are drawn between questions of after-life and questions in quantum gravity. On the basis of black hole physics and cosmology, it is argued that the classical General Relativity notion that “all observers are equal” must be qualified in a quantum theory. Various lines of reasoning suggest that only classical observers who are not trapped will play a role in the quantum theory of gravity. A possible experimental test of this hypothesis is also discussed.

Author Bio

Tanmay Vachaspati is a theoretical physicist working at the intersections of particle physics, astrophysics, general relativity, and cosmology. He has written extensively on cosmic strings, magnetic monopoles, black holes, and cosmological magnetic fields, and has authored the monograph “Kinks and Domain Walls: an introduction to classical and quantum solitons”. He was a Rosenbaum Fellow at the Isaac Newton Institute in Cambridge, Member of the Institute for Advanced Study, Princeton, and is a Fellow of the American Physical Society. Currently he is Professor of Physics and Director of the Cosmology Initiative at Arizona State University.

Download Essay PDF File

James Lee Hoover wrote on Sep. 1, 2012 @ 17:35 GMT
Tanmay,

If a black star is not a transitional phase between a collapsing star and a singularity, what is it, and how do you know the difference when anticipating the study?

Jim

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Author Tanmay Vachaspati replied on Sep. 1, 2012 @ 18:20 GMT
Jim,

Thanks. To probe a black star, we'll need something that can get up close. That is why I propose looking at mergers of candidate black holes. The gravitational wave and other particle emisson during the merger can inform us of the horizon structure.

Best,

Tanmay

Robert H McEachern wrote on Sep. 2, 2012 @ 04:36 GMT
Tanmay,

In your abstract, you state: 'it is argued that the classical General Relativity notion that "all observers are equal" must be qualified in a quantum theory'

The assumption that "all observers are equal" has been demonstrated to be untrue, even in the classical realm.

The amount of a priori knowledge that an observer has, regarding what is being observed, has a direct,...

view entire post

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Anonymous replied on Sep. 2, 2012 @ 17:02 GMT
Robert,

Thanks for your comment. The observation capacity could indeed be different for different experiments and recording setups (which includes histories and amount of remaining disk space etc.). In General Relativity it is assumed that one can have the same setups located everywhere. Perhaps what you are saying is that one cannot put the same observing or recording capacity at...

view entire post

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Robert H McEachern replied on Sep. 2, 2012 @ 20:04 GMT
Tanmay,

Actually, I am saying something much more subtle. For example, do you believe that the words "Relativity", "relativity", "RELATIVITY", "rElEtIvItY" are the same word? In other words, am I using the standard 26 letter English alphabet, or am I using a much larger alphabet, in which "R" is not a capital "r", but a completely different letter? If you do not know the answer, a priori,...

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Member Benjamin F. Dribus wrote on Sep. 2, 2012 @ 08:22 GMT
Tanmay,

Interesting essay. Just to be sure I understand, I have a few questions.

1. You are saying that it is trapped horizons, not singularities, that imply preferred observers, correct?

2. I am trying to fit this into general ideas about covariance. In SR, covariance is a symmetry, and in GR, it is a local symmetry. Is the local symmetry still valid in your picture, since...

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Tanmay Vachaspati replied on Sep. 2, 2012 @ 17:17 GMT
Ben,

I saw your submission and will read it more carefully. In classical GR trapped surfaces lead to singularities according to the singularity theorems. So if one has an event horizon, there will also be an accompanying singularity. The real issue comes up when we include quantum evaporation because the outside observer only sees evaporation, while the inside observer sees a...

view entire post

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Saibal Mitra wrote on Sep. 2, 2012 @ 19:04 GMT
Tanmay,

You point out that the asymptotic observer can see the infalling observer frozen just before entering the event horizon for a very long time while everything gradually evaporates. Does this allow the asymptotic observer to collect enough data to (in principle) reconstruct the time evolution from the point of view of the infalling observer?

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Tanmay Vachaspati replied on Sep. 2, 2012 @ 19:25 GMT
Hello Saibal,

It isn't that there is missing data that prevents the asymptotic observer from finding out what happens to the infalling observer. The parallels between after-life and the black hole situation are extremely tight and help to understand that there are some questions that are not meaningful because they cannot be tested.

Best,

Tanmay

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Steve Dufourny replied on Sep. 2, 2012 @ 19:55 GMT
Hello to both of you,

It is relevant.

ps the singularities are all from the singularity.....

Regards

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Steve Dufourny Jedi of the Sphere replied on Sep. 22, 2012 @ 11:36 GMT
Mr Vachaspati,

Are you a buddhist ?

If the spheres of light are on the road of spherization, so it becomes relevant considering the pure optimization in its pure generality.

The death does not really exist in fact, it is logic in fact.We are inside a beautiful physical 3d sphere and its quantic and cosmological spheres. This aether , this infinite light without motion above...

view entire post

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Sergey G Fedosin wrote on Sep. 10, 2012 @ 16:16 GMT
Dear Tanmay,

What is your opinion about Covariant theory of gravitation, in which black holes are not allowed? If to use the idea of strong gravitation at the level of particles there must be the black holes too. But nucleons are not black holes since their mass do not changed.

Sergey Fedosin

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Author Tanmay Vachaspati replied on Sep. 11, 2012 @ 05:07 GMT
Dear Sergey,

Thank you for your comments and especially for suggesting your theory of gravitation. It is interesting that CTG passes all the current experimental constraints such as gravitational lensing, perihelion of Mercury, millisecond pulsar etc..

Yes, I agree with you, nucleons cannot be black holes because they don't evaporate. They could be extreme charged black holes for...

view entire post

this post was moved here from a different topic

Steve Dufourny Jedi replied on Sep. 22, 2012 @ 12:14 GMT
hello thinkers,

the BH are spheres with a very important volume and mass ....it is logic that they are Black in fact. But it is not rational to say that the quantum BH exist.It is not deterministic.

Regards

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Yuri Danoyan wrote on Sep. 12, 2012 @ 01:29 GMT
Dear Tammay

In my essay http://fqxi.org/community/forum/topic/1413

i used mass of Hawking black holes as a contra to nuclons.

This is just a hypothesis.

What is your opinion?

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Author Tanmay Vachaspati replied on Sep. 12, 2012 @ 02:41 GMT
Dear Yuri,

It is really interesting that you predict black holes of mass 10^{16} gms. These are the ones that are evaporating just about now and producing a gamma ray background. Do you know the recent constraints on black hole masses? I believe the constraint might be right around 10^{16} gms but it would depend on their number density as well.

Best,

Tanmay

Yuri Danoyan wrote on Sep. 12, 2012 @ 03:07 GMT
Tammay

As you see mass of nuclon 10^40 lesser than black hole mass

it is close to

Dirac large numbers hypothesis

http://en.wikipedia.org/wiki/Dirac_large_numbers_h
ypothesis

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Member George F. R. Ellis wrote on Sep. 16, 2012 @ 15:56 GMT
Dear Tanmay

I agree with you that there are preferred observers in realistic solutions of the Einstein Field Equations. It is a significant effect.

I make the same point in a different context in a paper on the nature of time here .

George Ellis

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Member George F. R. Ellis wrote on Sep. 16, 2012 @ 16:00 GMT
Oops: here

Hope that works

George

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Author Tanmay Vachaspati replied on Sep. 16, 2012 @ 22:46 GMT
Dear George,

Very nice to hear from you and thanks for pointing me to your article. I have taken a quick look at the paper but have to understand the EBU better. I find it very fascinating that the preferred observer hypothesis also comes up in your work in the context of the nature of time.

Best,

Tanmay

Peter Jackson wrote on Sep. 17, 2012 @ 12:00 GMT
Tanmay,

A fast moving and free thinking essay. I also found it moving, now and then, in my own direction. Have you yet considered cyclic black holes? And the re-ionization problem?possibly resolved via the 'hot bath of destructive quantum fluctuations' at the core of an em toroid AGN (SMBH) before re-ejection (astrophysical jetting).

As an astronomer I'm an observational cosmologist,...

view entire post

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Author Tanmay Vachaspati replied on Sep. 17, 2012 @ 18:27 GMT
Dear Peter,

It's very interesting that you mention reincarnation in relation to cyclic black holes. This parallel also occurs in the literature in other contexts. For example, observers fall into black holes, go through a wormhole, and emerge in a different universe. I didn't mention this parallel in my essay because the other parallels illustrate the point I wanted to make quite well. The...

view entire post

Peter Jackson replied on Sep. 17, 2012 @ 18:46 GMT
Tanmay,

A strength of astronomy is that we can study the past first hand. It's then quite easy to test hypothesis and observe experiments. i.e. If we measure the accretion rates into an AGN and estimate the outflow of re-ionized matter in the (quasar) jets, we have a pretty solid experimental result when we find they match.

Then we scale up the morphology and match it to the CMBR...

view entire post

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Thomas Howard Ray wrote on Sep. 17, 2012 @ 17:09 GMT
Tanmay,

Am I correct that preferred observers are not equivalent to privileged inertial frames? After all, if " ... A precise formulation of the first law should define spacetimes that are fully 'networked', i.e. they allow for a network of observers who can mutually communicate ..." a simply connected space demands only that the wave function does not collapse, and thus that it avoids the...

view entire post

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Author Tanmay Vachaspati replied on Sep. 17, 2012 @ 18:49 GMT
Hi Tom,

Yes, something more seems to be required from a theory of quantum gravity.

I've downloaded your essay and will give it a read. Thanks for writing.

Best,

Tanmay

this post was moved here from a different topic

Thomas Howard Ray replied on Sep. 22, 2012 @ 10:55 GMT
I like this compact synopsis you gave in a reply to Roger Granet, "The simplest speculation is that infalling observers never fall in and stay at the horizon where they evaporate. This speculation is entirely consistent with the view of the external observer."

I think it can be made rigorous that the horizon condition at every scale plays a key role in what information we can extract from...

view entire post

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John Merryman wrote on Sep. 18, 2012 @ 03:20 GMT
Tanmay,

That is an interesting conceptual connection between final stage gravitational effects and biological death. If I may riff off that somewhat, I draw similar relationships, but use a different conceptual frame.

In my entry, I make the observation that we perceive time as a sequence of events from past to future and physics re-enforces this view by treating it as a...

view entire post

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John Merryman replied on Sep. 18, 2012 @ 03:27 GMT
Corrections:

Time then emerges from this creation and dissolution of information.

as the gravitational density of mass is what coalesces out of future possibility and becomes residually harder.(Being the arrow of time that points from future to past.)

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Author Tanmay Vachaspati replied on Sep. 18, 2012 @ 06:18 GMT
Hi John,

Thanks for the note. I enjoyed your poetic phrases (arc of time) and the example of the blurring photograph with greater information.

Best,

Tanmay

John Merryman replied on Sep. 18, 2012 @ 10:28 GMT
Tanmay,

Thank you.

Obviously it's just a seed of an idea, but I think and as this contest is evidence, physics has peaked out with where the current model can logically go. It's doubtful future generations of physicists will simply worship at the alter of a model that leaves little more to test, now that the search for the Higgs has proven to be a climb up a lonely mountain and not...

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Hoang cao Hai wrote on Sep. 19, 2012 @ 13:45 GMT
Dear

Very interesting to see your essay.

Perhaps all of us are convinced that: the choice of yourself is right!That of course is reasonable.

So may be we should work together to let's the consider clearly defined for the basis foundations theoretical as the most challenging with intellectual of all of us.

Why we do not try to start with a real challenge is very close...

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Author Tanmay Vachaspati replied on Sep. 20, 2012 @ 01:35 GMT
Thanks for your comments, Hoang.

The Higgs, as you well know, is "seen" indirectly due to its decays into photons and other particles. The basic interactions involve left- and right-handed particles which only makes sense if the particles are fundamentally massless. That is why the Higgs is necessary to give them a mass.

Best,

Tanmay

Sridattadev wrote on Sep. 19, 2012 @ 18:32 GMT
Dear Tanmay,

I hope you will find the essay on true nature of our self (singularity) resonate with your ideas. Infact we will all have to go through a black hole (death of the ego) to attain the singularity of our true self (immortality or nirvana or enlightenment).

Conscience is the cosmological constant.

Love,

Sridattadev.

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Author Tanmay Vachaspati replied on Sep. 20, 2012 @ 01:36 GMT
Dear Sridattadev,

Thank you for your kind words.

Tanmay

Avtar Singh wrote on Sep. 19, 2012 @ 22:57 GMT
Dear Tanmay:

I enjoyed reading your well-written and intuitive essay describing the observer paradox in GR and QM as it relates to black holes.

Then, you state that – “…For the purposes of a physical theory, it is sufficient to describe gravitational collapse from the external point of view, just as we are able to describe our physical world regardless of Heaven or Hell. The...

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Author Tanmay Vachaspati replied on Sep. 20, 2012 @ 01:40 GMT
Dear Avtar,

I look forward to reading your essay.

Best,

Tanmay

Roger Granet wrote on Sep. 21, 2012 @ 04:44 GMT
Dr. Vachaspati,

Hi. I think your essay was good because it considered how different observers would view the same thing, a point that I don't see discussed much. Since I'm not a physicist, I can't say I totally understood your essay, but my two comments are:

1. If I understood it correctly, it sounded like you're saying that in developing our theories, we should view things...

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Author Tanmay Vachaspati replied on Sep. 21, 2012 @ 14:56 GMT
Dear Roger,

Thank you for raising a very important point. A physical theory needs to be self-consistent (no self-contradictions) and to have closure (not influenced by agencies that lie outside the system). This is true of the theory as described from the outside point of view. We are free to speculate on what the infalling observer will see -- any description is as good as any other --...

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Pentcho Valev wrote on Sep. 21, 2012 @ 06:50 GMT
Dear Dr. Vachaspati,

Let me call your attention, very politely (so that you could be so kind as not to delete my comment), to an observer who measures VARIABLE speed of the light waves:

Professor Carl Mungan: "Consider the case where the observer moves toward the source. In this case, the observer is rushing head-long into the wavefronts, so that we expect v'>v. In fact, the wave...

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Author Tanmay Vachaspati replied on Sep. 21, 2012 @ 14:58 GMT
Hi Pentcho,

I don't see why special relativity should be in danger. It seems to work very well in accelerators where particles move very close to the speed of light.

Bye,

Tanmay

Pentcho Valev replied on Sep. 22, 2012 @ 09:28 GMT
The fact that the moving observer measures VARIABLE speed of light obviously deserves no mention at all. Thank you, dear Dr. Vachaspati.

Pentcho Valev

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Sergey G Fedosin wrote on Oct. 2, 2012 @ 08:27 GMT
After studying about 250 essays in this contest, I realize now, how can I assess the level of each submitted work. Accordingly, I rated some essays, including yours.

Cood luck.

Sergey Fedosin

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Author Tanmay Vachaspati replied on Oct. 2, 2012 @ 14:35 GMT
It is a lot of hard work. I am still going through the list. Thanks for reading and rating my essay.

Best,

Tanmay

Georgina Parry wrote on Oct. 3, 2012 @ 23:32 GMT
Dear Tanmay Vachaspati,

your essay is written very clearly in accessible language. I really appreciate that. I am a little surprised that you have chosen this particular subject. Especially having looked at the broad scope of your biography. The heaven and hell analogy was a little strange for me. Though I do understand that you are talking about personal experience that can not be corroborated by any other. Observer experience of speculated after life and/or black hole experience seem too "other worldly/abstract" to be -basic- physical assumptions. Having said that , of the "technical" essays in the contest, yours is more readable than many others. It is therefore enjoyable,interesting, and thought provoking rather than a difficult unpleasant chore. Well done, Good luck Georgina : )

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Author Tanmay Vachaspati replied on Oct. 4, 2012 @ 00:41 GMT
Dear Georgina,

I am glad you enjoyed my essay. The heaven-hell analogy is exactly as you said -- personal experiences that cannot be corroborated by any other.

Best of luck to you too!

Tanmay

Sergey G Fedosin wrote on Oct. 4, 2012 @ 05:38 GMT
If you do not understand why your rating dropped down. As I found ratings in the contest are calculated in the next way. Suppose your rating is
$R_1$
and
$N_1$
was the quantity of people which gave you ratings. Then you have
$S_1=R_1 N_1$
of points. After it anyone give you
$dS$
of points so you have
$S_2=S_1+ dS$
of points and
$N_2=N_1+1$
is the common quantity of the people which gave you ratings. At the same time you will have
$S_2=R_2 N_2$
of points. From here, if you want to be R2 > R1 there must be:
$S_2/ N_2>S_1/ N_1$
or
$(S_1+ dS) / (N_1+1) >S_1/ N_1$
or
$dS >S_1/ N_1 =R_1$
In other words if you want to increase rating of anyone you must give him more points
$dS$
then the participant`s rating
$R_1$
was at the moment you rated him. From here it is seen that in the contest are special rules for ratings. And from here there are misunderstanding of some participants what is happened with their ratings. Moreover since community ratings are hided some participants do not sure how increase ratings of others and gives them maximum 10 points. But in the case the scale from 1 to 10 of points do not work, and some essays are overestimated and some essays are drop down. In my opinion it is a bad problem with this Contest rating process. I hope the FQXI community will change the rating process.

Sergey Fedosin

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Daryl Janzen wrote on Oct. 4, 2012 @ 22:14 GMT
Dear Tanmay:

Thank you for your essay. I'm sorry that I missed it before, but I'm really glad now that I've read it. I agree with you about black stars, and I think that taking accurate and consistent account of descriptions according to preferred observers will provide the correct path to a quantum theory of gravity. As such, I particularly liked and agreed with your paragraph that begins...

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Daryl Janzen replied on Oct. 4, 2012 @ 22:55 GMT
Sorry. Here are the figures I meant to attach.

attachments: dS_statical1.pdf, dS_statical2.pdf

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Author Tanmay Vachaspati replied on Oct. 5, 2012 @ 03:44 GMT
Dear Daryl,

Thanks a lot for your post. At first read it looks like we agree but I'll go over your arguments and especially your essay more carefully.

Best,

Tanmay

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