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Sergey Fedosin: on 10/4/12 at 5:36am UTC, wrote If you do not understand why your rating dropped down. As I found ratings...

Sergey Fedosin: on 10/2/12 at 8:23am UTC, wrote After studying about 250 essays in this contest, I realize now, how can I...

Peter Jackson: on 9/21/12 at 16:59pm UTC, wrote Samir Contrary to your proposition I've never seen Planck length physics...

Hoang Hai: on 9/19/12 at 15:18pm UTC, wrote Dear Very interesting to see your essay. Perhaps all of us are convinced...

Yuri Danoyan: on 9/17/12 at 23:31pm UTC, wrote For better clarification my approach I sending to you Frank Wilczek’s 3...

Yuri Danoyan: on 9/17/12 at 19:46pm UTC, wrote For better clarification my approach I sending to you Frank Wilczek’s 3...

Avtar Singh: on 9/13/12 at 17:37pm UTC, wrote Dear Samir: I enjoyed reading your well-written and intuitive essay. ...

Sergey Fedosin: on 9/10/12 at 14:44pm UTC, wrote Dear Samir, In Covariant theory of gravitation it is found the meaning of...


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FQXi FORUM
October 24, 2019

CATEGORY: Questioning the Foundations Essay Contest (2012) [back]
TOPIC: How Quantum Gravity Can Alter Dynamics at Astrophysical Scales by Samir D. Mathur [refresh]
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Author Samir D. Mathur wrote on Aug. 31, 2012 @ 12:07 GMT
Essay Abstract

It is generally assumed that the effects of quantum gravity will be manifest only at lengths scales comparable to or smaller than the planck length $l_p$. We argue that this belief is false; quantum gravity effects make a dramatic change to our understanding of physics on arbitrarily large length scales. The reason this can happen is that when a large number $N$ of particles are involved, the length scale of quantum gravitational effects need not be $l_p$ but $N^\alpha l_p$ for some $\alpha>0$. We explain the mechanism of `fractionation' which leads to the emergence of such a new length scale in string theory. For black holes, this new length scale turns out to be order the horizon radius, and resolves puzzles like the black hole information paradox. In the early Universe we have another situation where a large number $N$ of quanta are crushed together, and we argue that the effect of the emergent length scale is to provide an inflationary `push' to larger volumes resulting from the quantum mechanical measure term in the path integral.

Author Bio

I obtained my Ph.D from the University of Bombay. I held postdoc positions at TIFR and Harvard, was a junior faculty at MIT and am currently a professor at Ohio State. My research interests are gravity and string theory, with a particular focus on resolving the black hole information paradox.

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James Lee Hoover wrote on Aug. 31, 2012 @ 19:27 GMT
Samir,

This is a needed and vital effort -- and intriguing in concept:

"In this essay I will argue that this belief is wrong; quantum gravitational physics does not stay con fined to planck scales, but in fact leaks out to aff ect all scales, including the largest scales of astrophysics and Cosmology."

How do you do it in words?

Empty space is defined by Lawrence Krauss as “a boiling brew of virtual particles that pop in and out of existence in a time so short we cannot see them directly. Quantum gravity theories speak of quantum foam. On a large scale we have the smoothness described by the cosmological principle.

Jim

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Samir replied on Aug. 31, 2012 @ 22:23 GMT
Hi Jim,

Indeed, empty space boils at the planck scale. The question of interest here was: if we put a large number N of particles in this space, does their energy create long distance effects in this `boiling brew' which is N times planck length? This is what happens in string theory, (due to the effect I termed fractionation). And in that situation, we get quantum gravity effects across distances as big as a black hole horizon, or perhaps even on Cosmological scales ...

So what happens is that taking a large number N of densely clustered particles causes the smoothness of spactime to break down .. and in string theory we were able to write down the wavefunction for what it becomes instead -- (this is the fuzzball wavefunction)

Hope this helps,

Samir

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Harlan Swyers wrote on Sep. 1, 2012 @ 00:26 GMT
Samir,

I like your paper, particularly for this line:

"it prevents the formation of a traditional black hole with horizon."

Does that necessitate that in order for the theory to be consistent that the graviton itself can not collapse to a point? Or is the point ground state of the graviton a zero energy state for the string?

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Samir replied on Sep. 1, 2012 @ 01:44 GMT
hi Harian,

the graviton stays collapsed to a point, but what happens is that the other states of the string become very easy to excite, once they are part of a large bound state. So the energy of the hole is not distributed among gravitons, but among the `fractionated' string theory modes...

samir

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Harlan Swyers replied on Sep. 1, 2012 @ 16:47 GMT
Thank Samir,

I read through fractionation and like the concept. Here are my thoughts. I see 1/L and understand L as fundamental length. Whenever I see that I automatically think fundamental frequency (which of course could be understood as energy). I see the string wrapped around an additional dimension, and see it connect to itself. Since these dimensions are curled up, the implication is that the dimension is connected at a point in some ordinary space (a la some variation of Hopf fibration). Ok, we extend the idea to string wrapped around 5 dimension branes. So, is it really then the 5-brane wrapped around the fifth dimension that connects to the same 4 dimension spactime, and are we not talk about some analgous set of 5 fundamental lengths (or 5 fundamental frequencies)?

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Member Benjamin F. Dribus wrote on Sep. 1, 2012 @ 00:51 GMT
Samir,

Very interesting essay. There are not many essays about string theory here. A couple of questions come to mind.

1. I am not quite clear on what role the compactified dimensions are playing in this besides providing the fractionation mechanism. In particular, when you are integrating over 3-geometries, are you taking the compactification to be constant? Is it not dynamically coupled to the matter-energy?

2. It seems as though this idea predicts a nonconstant dark energy effect, since the "push" in a given region depends on the energy density. Would the resulting fluctuations be large enough to observe?

3. Presumably dark matter cannot be described along similar lines, since the effect seems to be the opposite one?

What's motivating these questions is my interest in scale-dependence of phenomena and the theory of path integrals over geometries or analogous structures. You can see my general point of view here:

On the Foundational Assumptions of Modern Physics[link]

I'm a mathematician, not committed to any particular theory, and I know less about string theory than I would like. Your essay supplemented that deficiency a bit!

Take care,

Ben Dribus

Take care,

Ben Dribus

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Member Benjamin F. Dribus replied on Sep. 1, 2012 @ 01:14 GMT
(sorry for the link format; I left out the slash!)

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Samir replied on Sep. 1, 2012 @ 01:49 GMT
hi Benjamin,

(1) As you say, the compactified directions help in getting the fractionation, and that is of course the crucial point. But more abstractly, the compact directions provide extra degrees of freedom, and one can imagine other ways of taking degrees of freedom that will also give similar effects. What is needed are enough degrees of freedom to account for the Bekenstein entropy, and these can come in many ways.

(2) The time dependence (and position dependence) is a good question, which we have not studied yet. I would say that the story is quite well understood for black holes, but very few aspects have been worked out for Cosmology,

regards

Samir

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Peter Warwick Morgan wrote on Sep. 1, 2012 @ 13:21 GMT
An interesting essay, once I had decided not to apply my usual no-string/M-theory-filter for this case. I found it interesting because it seems that your argument may not be confined to a string mathematics. Or do you think it only applies to strings? Thanks.

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Samir replied on Sep. 1, 2012 @ 18:45 GMT
Hi Peter,

I think the lessons here are general, not just for a given theory like strings. Whenever we have enough degrees of freedom to account for the bekenstein entropy, then we have to worry about what so many states will do in the path integral. Of course we knew about the large entropy since the 1972 work of bekenstein, but since the states for this entropy were not manifest, I think we never took its consequence seriously,

Samir

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Anonymous wrote on Sep. 1, 2012 @ 23:38 GMT
Seems like a very good idea!

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Steve Dufourny wrote on Sep. 2, 2012 @ 13:49 GMT
Hello Mr.Mathur,

I am also very intrigued by these BH. The works of Hawking and Bekenstein are relevant considering the steps of entropy and informations. They have a lot of properties. The heat and themo. are essential. The principle of pure themrodynamics are universal after all. My equations can help for a better understanding of these BH. Of course they are spheres with a mass, a...

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Jayakar Johnson Joseph wrote on Sep. 4, 2012 @ 03:29 GMT
Dear Samir D. Mathur,

As quantization is indispensable to describe infinite universe in that quantization of universe in entirety is not empirical, we may think of quantizing the entire universe in its current segmental-fluctuation cycle.

Quantization of the entire 3-D universe is incomplete in the current scenario of dimensionality without string dynamics, as the plank volume by plank length that evolves from speed of light, is assigned in a framework of dynamics of 0-D discrete photons that predicts the universe with black hole singularity.

Thus we need to rethink the dynamics of universe that endorses another scenario of dimensionality, in that the quantization of gravity that emerges as a tensor product of 3-D tetrahedral-branes of 1-D eigen-rotational strings, without any black hole predictions. This implies the definition of unit volume of tetrahedral-brane instead of unit length of plank length that is variable in this scenario, whereas the unit volume of brane is invariant for the segment of holarchial universe it belongs.

With best wishes,

Jayakar

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Jayakar Johnson Joseph replied on Sep. 7, 2012 @ 05:07 GMT
Regret for the repeated spelling mistake by me on this post. Please read, ‘Planck’ instead of ‘Plank’

Jayakar

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Yuri Danoyan wrote on Sep. 9, 2012 @ 17:28 GMT
Samir

Look my table

Big Bang; Present; Big Crunch

c=10^30; c=10^10; c=10^-10

G=10^22; G=10^-8; G=10^-28

h=10^-28; h=10^-28; h=10^-28

alfa =10^-3; 1/ 137; 1

e=0,1 ; e=e ; e=12

String in moment Big Bang c x h = 10^2 erg x sm

String in Present moment c x h = 10^-18 erg x sm

String in moment Big Crunch c x h = 10^-38 erg x sm

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Yuri Danoyan replied on Sep. 10, 2012 @ 08:17 GMT
10^2 erg x sm /10^-38 erg x sm =10^40 Dirac number

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Sergey G Fedosin wrote on Sep. 10, 2012 @ 14:44 GMT
Dear Samir,

In Covariant theory of gravitation it is found the meaning of cosmological constant and supposed the absence of black holes. Also for quantum gravity may be used strong gravitation. Can you comment about it?

Sergey Fedosin

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Avtar Singh wrote on Sep. 13, 2012 @ 17:37 GMT
Dear Samir:

I enjoyed reading your well-written and intuitive essay.

Your statement – “….quantum gravitational physics does not stay confined to Planck scales, but in fact leaks out to affect all scales, including the largest scales of astrophysics and Cosmology” is strongly vindicated in my paper - -“ From Absurd to Elegant Universe”.

My paper shows that once the proper missing physics of spontaneous decay is considered it successfully predicts the observed data at all scales from below Planck scale to beyond cosmological scales. The proposed model not only resolves black hole singularities but also the unresolved paradoxes of physics and cosmology. It also explains the inner workings of QM and eliminates its inconsistencies with relativity.

I would greatly appreciate your comments on my paper. You can contact me at avsingh@alum.mit.edu.

Best of Luck and Regards

Avtar Singh

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Yuri Danoyan wrote on Sep. 17, 2012 @ 19:46 GMT
For better clarification my approach

I sending to you Frank Wilczek’s 3 keen articles

http://ctpweb.lns.mit.edu/physics_today/phystoday/Ab
s_limits393.pdf

http://ctpweb.lns.mit.edu/physics_today/physt
oday/Abs_limits393.pdf

http://ctpweb.lns.mit.edu/physics_toda
y/phystoday/Abs_limits400.pdf

All the best

Yuri danoyan

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Yuri Danoyan replied on Sep. 17, 2012 @ 23:31 GMT
For better clarification my approach

I sending to you Frank Wilczek’s 3 keen articles

http://ctpweb.lns.mit.edu/physics_today/phystoday/Ab
s_limits388.pdf

http://ctpweb.lns.mit.edu/physics_today/physt
oday/Abs_limits393.pdf

http://ctpweb.lns.mit.edu/physics_toda
y/phystoday/Abs_limits400.pdf

All the best

i missed part 1

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Hoang cao Hai wrote on Sep. 19, 2012 @ 15:18 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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Peter Jackson wrote on Sep. 21, 2012 @ 16:59 GMT
Samir

Contrary to your proposition I've never seen Planck length physics as anything other than a means to explain classical effects, giving unification. I've also never been inspired by string theory's ability to derive classical observation, but in building an ontological model the torus figured at all scales, and your reference to it sprang out. But perhaps from a new view point.

Can you see the cylinder of your 2.1(d) as a slice of the body of a torus? A line has no thickness, so if strings 'exist', then must a loop not be a torus!?

And have you considered not just the torus but it's effects as a 'twin vortex' em entity. As an astronomer I'm very familiar with toroids as real em entities from magnetic fields of all bodies to the AGN's (SMBH's) at all galactic centres . They are accretion phenomena, drawing in the disc matter crushing, re-ionizing and ejecting it as astrophysical jets, in a cycle of dormancy and high activity.

From this a cyclic universe seems to emerge, exactly matching the CMB anisotropies that we struggle to rationalise; the helical resolution, quadrupolar symmetry, flow, axis of evil, lower limit, frames last scattered etc. etc. A scale invariant model also provides an interesting derivation of the string force via some work by Tamari on dipoles rotating around the toroid body. But that is an aside to what else emerges.

I enjoyed your essay, well written and clearly presented but found it steeped in outdated concepts with less consistency with observation than arising from the abandonment of more deeply held assumptions. Food for thought? Or too much to consider?

I do hope you'll read my essay and comment anyway.

Best wishes.

Peter

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Sergey G Fedosin wrote on Oct. 2, 2012 @ 08:23 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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Sergey G Fedosin wrote on Oct. 4, 2012 @ 05:36 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. I hope the FQXI community will change the rating process.

Sergey Fedosin

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