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RECENT POSTS IN THIS TOPIC

Sergey Fedosin: on 10/4/12 at 4:30am UTC, wrote If you do not understand why your rating dropped down. As I found ratings...

Benjamin Dribus: on 10/3/12 at 23:54pm UTC, wrote Dear Maulik, You are one of the few authors whose writing and science...

Lawrence Crowell: on 10/3/12 at 23:25pm UTC, wrote Conformal invariance is important. This is a consequence of the Yangian...

Edwin Klingman: on 10/3/12 at 20:13pm UTC, wrote Dear Maulik Parikh, I just wanted to thank you for writing your essay on...

Peter Jackson: on 10/3/12 at 19:43pm UTC, wrote Maulik A real eye opening essay, giving a clarity of viewpoint I've never...

Peter Jackson: on 10/3/12 at 19:38pm UTC, wrote Maulik A real eye opening essay, giving a clarity of viewpoint I've never...

Georgina Woodward: on 10/3/12 at 9:21am UTC, wrote Dear Maulik Parikh, I really like the way in which your essay is written....

Maulik Parikh: on 10/3/12 at 4:04am UTC, wrote Yes, a new principle, like perhaps conformal invariance, may be necessary...


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FQXi FORUM
July 19, 2019

CATEGORY: Questioning the Foundations Essay Contest (2012) [back]
TOPIC: Forbidden Spacetimes by Maulik Parikh [refresh]
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Author wrote on Sep. 5, 2012 @ 11:32 GMT
Essay Abstract

Without any additional physical inputs, Einstein's equations become almost tautological, permitting virtually all spacetimes as solutions. Typically, various energy conditions, reflecting the positivity of local matter-energy, are used to constrain these solutions. I will argue that this is a mistake: the energy conditions do not come from matter at all. Instead, I will proposal two possible alternatives that could determine which spacetimes are physically allowed and which are forbidden.

Author Bio

Maulik Parikh is an associate professor in physics at Arizona State University. He obtained his bachelor's degree from the University of California at Berkeley and his PhD in physics from Princeton University. An essay he wrote on black holes won the first prize from the Gravity Research Foundation. He has also won prizes in two previous FQXi essay contests.

Download Essay PDF File

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Christian Corda wrote on Sep. 5, 2012 @ 16:45 GMT
Hi Maulik,

Excellent Essay.

Maybe you could be interested to my recent paper which received an Honorable Mention at 2012 Gravity Research Foundation Awards where I used your important result on the non-strictly thermal character of Hawking Radiation, by introducing an effective temperature, to show that black hole's entropy, i.e. your eq. (4) in your present FQXi Essay, is a function of a quantum number n which represents the quantum state of excitation of the black hole in terms of quasi-normal modes, see http://arxiv.org/abs/1205.5251

Cheers,

Ch.

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Yuri Danoyan wrote on Sep. 5, 2012 @ 17:32 GMT
Hi Maulik

1.I think Newton first law is tautology also.

2.We must sacrifice second law of thermodinamics.

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

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Anton Lorenz Vrba wrote on Sep. 5, 2012 @ 21:43 GMT
Hi Maulik,

I enjoyed your essay and presentation style, it certainly will be favourably received. You raise many questions and then propose to find the solutions in a higher order of complexity, namely string theory.

Possibly, a retrograde step may bring us further. Let me elaborate:

You wrote "It is important to recognize that these conjectures are not conjectures in the sense that, say, mathematicians use that word. Their truth or falsity cannot be established. They are simply axiomatic prejudices regarding which spacetimes are allowed and which forbidden."

As I understood it "these conjectures" refer to the consequences of special and general relativity (SR and GR), but equally well the truth or falsity of SR and GR cannot be established, or so we thought.

The Michelson-Morley experiment is explained by the special relativity theory, that is what we are being taught. What we are not shown, is a counter example, derived from the MM experiment geometry, that actually falsifies special relativity; the energy of the light beam, at a instance in time, contained between the mirrors of the apparatus varies under the SR transformations to different reference systems. This mathematically contradicts SR's first axiom.

This is one of many points I discuss in my essay.

Regards

Anton @ (  ../topic/1458  )

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Sergey G Fedosin wrote on Sep. 8, 2012 @ 14:41 GMT
Dear Maulik ,

I suppose that the link between quantum field theory and gravitation is the Lorentz-invariant theory of gravitation (LITG). Both theories are Lorentz covariant, and LITG can easily receive quantum form. This is a consequence of similarity equation of LITG and Maxwell equation. In curved space LITG transform into Covariant theory of gravitation (KTG). KTG is an alternative to general relativity. The LITG and KTG have stress-energy tensor of gravitational field which is absent in general relativity. Also we find a meaning of cosmological constant - it is proportional to density of substance of system at infinity. See the paper: The Principle of Least Action in Covariant Theory of Gravitation. Hadronic Journal, February 2012, Vol. 35, No. 1, P. 35 - 70. I hope you can evaluate my essay with such ideas on gravitation including strong gravitation.

Sergey Fedosin Essay

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Constantinos Ragazas wrote on Sep. 9, 2012 @ 03:27 GMT
Dear Maulik,

Thank you for your essay. Questioning Spacetime is indeed fundamental and important. The concept of Spacetime may prove to be the underlying reason for the many paradoxes in modern physics, especially in Cosmology. And certainly there are many approaches to examine this. I like to suggest another way of looking at this problem.

The Spacetime continuum assumes physical time as 'instantaneous', t=s. Thus, physical events depicted as points in the Spacetime continuum are assumed to be 'instantaneous' at each instant of time t=s. The Second Law of Thermodynamics, however, requires that “every physical event takes some positive duration of time to occur”. (see my Chapter, “The Thermodynamics in Planck's Law”) Thus, physical time is 'duration', t-s. And not 'instantiation', t=s. And so physical events require some positive 'duration of time' to occur. Rather than occurring at an instant t.

Each moment of a particle moving along a smooth worldline is a 'physical event' requiring a positive duration of time to occur. Spacetime violates this requirement of the Second Law. This, in my opinion, explains why Cosmology is in conflict with Thermodynamics.

Best regards,

Constantinos

“The Metaphysics of Physics”

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Hoang cao Hai wrote on Sep. 19, 2012 @ 14:49 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 and are the focus of interest of the human science: it is a matter of mass and grain Higg boson of the standard model.

Knowledge and belief reasoning of you will to express an opinion on this matter:

You have think that: the Mass is the expression of the impact force to material - so no impact force, we do not feel the Higg boson - similar to the case of no weight outside the Earth's atmosphere.

Does there need to be a particle with mass for everything have volume? If so, then why the mass of everything change when moving from the Earth to the Moon? Higg boson is lighter by the Moon's gravity is weaker than of Earth?

The LHC particle accelerator used to "Smashed" until "Ejected" Higg boson, but why only when the "Smashed" can see it,and when off then not see it ?

Can be "locked" Higg particles? so when "released" if we do not force to it by any the Force, how to know that it is "out" or not?

You are should be boldly to give a definition of weight that you think is right for us to enjoy, or oppose my opinion.

Because in the process of research, the value of "failure" or "success" is the similar with science. The purpose of a correct theory be must is without any a wrong point ?

Glad to see from you comments soon,because still have too many of the same problems.

Regards !

Hải.Caohoàng of THE INCORRECT ASSUMPTIONS AND A CORRECT THEORY

August 23, 2012 - 11:51 GMT on this essay contest.

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James Lee Hoover wrote on Sep. 29, 2012 @ 01:50 GMT
Maulik,

True that all space-times are not equal, but you speak of singularities and black holes as the exception. How about empty space between the eruption of virtual particles. Are you saying that mass and energy are not two faces of matter? Can space-time be altered to permit a massless state? I speak of some of those conditions.

Jim

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Sergey G Fedosin wrote on Oct. 2, 2012 @ 07:33 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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Lawrence B. Crowell wrote on Oct. 2, 2012 @ 18:40 GMT
I found your essay here, which is a gem buried too far down the community list. The Virasoro algebra extending sl(2) is conformal. Conformal theory gives gravity with the proper energy conditions.

The averaged weak energy condition E = T^{00} >= 0 is violated softly in the case of this φ^4 theory. One can always add a positive constant to the minimum of the field potential to set the potential minimum at zero. The problem comes primarily if there is no minimum, or the energy eigen-spectrum is not bounded below. You raise an interesting point, and I think there is some subtle issue here. A quantum field theory with a minimum potential that is below zero is not I think the same as the “exotic field” which is required for a worm hole or other strange or forbidden spacetimes. I am not sure if there has been some analysis on this as yet. If not it might be interesting to look at.

Cheers LC

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Member Maulik Parikh replied on Oct. 3, 2012 @ 04:04 GMT
Yes, a new principle, like perhaps conformal invariance, may be necessary to cull the solutions of Einstein's equations. In string theory, worldsheet conformal symmetry leads directly to Einstein's equations on spacetime but another requirement is needed to restrict the space of solutions.

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Lawrence B Crowell replied on Oct. 3, 2012 @ 23:25 GMT
Conformal invariance is important. This is a consequence of the Yangian system that is implied by the BCFW recursion relationship. My essay focuses on some “braney” physics and this formula in a twistor context. I did not go into the Yangian structure in my essay due to space limits and that the ink used in my calculations is still wet on the pages. I went into some detail on this on Torsten Asselmeyer-Maluga’s essay page , and in particular recently at the end posted October 3. Torsten’s essay if fascinating.

Cheers LC

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Jayakar Johnson Joseph wrote on Oct. 3, 2012 @ 03:11 GMT
Dear Maulik Parikh,

In Coherently-cyclic cluster-matter paradigm of universe; energy conditions on eigen-rotations of string-matters is the laws of thermodynamics in that thermodynamics emerges from eigen-rotations. Thus in this paradigm, the two dimensional quantum gravity expressional by worldsheet string theory for particles is not applicable, as the fundamental matters are ascribed as string like structures, in that gravity emerges from the eigen-rotations of string-matters on formation of three-dimensional tetrahedral-branes of fractals.

With best wishes

Jayakar

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Georgina Woodward wrote on Oct. 3, 2012 @ 09:21 GMT
Dear Maulik Parikh,

I really like the way in which your essay is written. The wild west theme for the "lawlessness" of space-time works well. By returning to the wild west theme in several places you put the abstract subject matter into a familiar setting, which ironically then feels safer. I did enjoy it even though the subject matter becomes a little two advanced for me to fully appreciate. You chose an interesting topic to address. I hope you get more appreciative readers. Good luck,

Georgina : )

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Peter Jackson wrote on Oct. 3, 2012 @ 19:38 GMT
Maulik

A real eye opening essay, giving a clarity of viewpoint I've never come across before, though a little disappointing reverting to string theory as yet again the only possible escape from our Mad Hatters tea party (In Toombstone). Nevertheless an excellent enlightening read and a valuable fresh viewpoint. Very well written, and thank you.

I'd be honoured and grateful if you'd check out my own bit of theatre, a contemporary take on Shakespeare, and even with a sonnet. But all is to give a kinetic thought process to a different escape hatch from the tea party to a very hard underlying reality. It's withstood all falsification so far but I think and hope you're the man for the job.

Best wishes

Peter

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Peter Jackson wrote on Oct. 3, 2012 @ 19:43 GMT
Maulik

A real eye opening essay, giving a clarity of viewpoint I've never come across before, though a little disappointing reverting to string theory as yet again the only possible escape from our Mad Hatters tea party (In Toombstone). Nevertheless an excellent enlightening read and a valuable fresh viewpoint. Very well written, and thank you.

I'd be honoured and grateful if you'd check out my own bit of theatre, a contemporary take on Shakespeare, and even with a sonnet. But all is to give a kinetic thought process to a different escape hatch from the tea party to a very hard underlying reality. It's withstood all falsification so far but I think and hope you're the man for the job.

Best wishes

Peter

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Edwin Eugene Klingman wrote on Oct. 3, 2012 @ 20:13 GMT
Dear Maulik Parikh,

I just wanted to thank you for writing your essay on 'Forbidden Spacetimes'. It gave me more insight into the character of general relativity in a few pages than anything else I have read, including a number of general relativity texts. I had not heretofore appreciated that "Einstein's equations become almost tautological, permitting virtually all spacetimes as solutions" unless suitably (?) constrained. Thank you for spelling this out so clearly.

I have no strong opinion as to which of your proposals is correct.

Although you are clearly well versed in QFT, you may wish to read my essay, The Nature of the Wave Function, on non-relativistic quantum mechanics, relating the physical wave [derived from weak-field relativity] to the probabilistic wave function. I hope it may enlarge your view of QM just a tiny fraction as much as you have enlarged my view of GR.

Best wishes,

Edwin Eugene Klingman

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Member Benjamin F. Dribus wrote on Oct. 3, 2012 @ 23:54 GMT
Dear Maulik,

You are one of the few authors whose writing and science strike me as equally excellent. I thoroughly enjoyed reading your essay. A few remarks:

1. Generally, I tend to prefer “local” constraints to “global” ones (page 3). (The reason for the quotation marks is because ultimately I mean these terms in the interaction sense rather than the metric sense;...

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Sergey G Fedosin wrote on Oct. 4, 2012 @ 04:30 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
and
was the quantity of people which gave you ratings. Then you have
of points. After it anyone give you
of points so you have
of points and
is the common quantity of the people which gave you ratings. At the same time you will have
of points. From here, if you want to be R2 > R1 there must be:
or
or
In other words if you want to increase rating of anyone you must give him more points
then the participant`s rating
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.

Sergey Fedosin

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