What is the Fuzzball Hypothesis?

[relativityfan]

hi, how can we be sure that quantum gravity effects appear only at the Planck scale?

when i look at the quantum mechanics effects, there seem to be a relationship with general relativity so both could be the same phenomena . i thought that the aim of quantum gravity is to find out the relationship between both theories, and then of course quantum gravity would be testable at any scale, not only the Planck scale.
what do you think of this?

 

[Naty1]

Sounds like you are on the right track:

Quantum gravity (QG) is the field of theoretical physics attempting to unify quantum mechanics with general relativity in a self-consistent manner, or more precisely, to formulate a self-consistent theory which reduces to ordinary quantum mechanics in the limit of weak gravity (potentials much less than c2) and which reduces to Einsteinian general relativity in the limit of large actions (action much larger than reduced Planck's constant).

http://en.wikipedia.org/wiki/Quantum_gravity

THREE ROADS TO QUANTUM GRAVITY by Lee Smolin, 2001, is an easy read and points out this fly in the ointment:

While quantum theory changed radically the assumptions about the relationship between the observer and the observed...it accepted Newton's old answer ..of what space and time are...Just the oppostie happened with Einstein'sgeneral theory of relativity in which the concept of space and time was radically altered...we must find a single theory which brings together the insights gained from relativity and quantum theory...it is called the quantum theory of gravity...

It's a good read w/o mathematics and gives many viewpoints from loop quantum gravity, quantum cosmology, string theory and other pieces of the puzzle...

My own novice veiwpoint still wonders if we are missing some fundamental relatonships bewteen things like self organizing systems, chaos theory, Heisenberg uncertainty, and the lack of objective "reality" within both quantum theory and relativity...

And Smolin has one comment I really like:

After all, atoms do fall so the relationship between gravity and the quantum is not a problem for nature.

Smolin's guess is we have some misconception about space and time...

 

[atyy]

We do have a quantum theory of gravity for low energies.

We don't have one for high energies.

It is true that quantum gravity effects at medium scales are not ruled out. Some such effects would be consistent with string theory. But the non-observation of those effects would not be inconsistent with string theory.

 

[relativityfan]

We do have a quantum theory of gravity for low energies.

I believe that this theory gives the same results as quantum mechanics because the intensity of gravity is very low so that there is no gravity at all, am i right?
but what about describing quantum mechanics in a similar way as general relativity? i mean the typical quantum mechanics effects could be the manifestation of a spacetime curvature? , so that gravity would be testable at the quantum scale too, what do you think?

 

[Chronos]

Does your conjecture [whatever it might be] fit WMAP results? Put your cards on the table. I am all in.

 

[arivero]

Randall Sundrum

 

[atyy]

I believe that this theory gives the same results as quantum mechanics because the intensity of gravity is very low so that there is no gravity at all, am i right?
but what about describing quantum mechanics in a similar way as general relativity? i mean the typical quantum mechanics effects could be the manifestation of a spacetime curvature? , so that gravity would be testable at the quantum scale too, what do you think?

No, there is gravity (quantum general relativity) in the quantum theory I'm referring to.

http://arxiv.org/abs/gr-qc/9712070

 

[tom.stoer]

hi, how can we be sure that quantum gravity effects appear only at the Planck scale?

As some colleagues just explained we cannot be sure, but there are some rather convincing reasons:
1) we do not see effects in experiments which should be explained via quantum gravity. The only effects we know are perfectly explained by just using quantum mechanics and general relativity w/o any deep integration of these two theories (e.g. red-shift of light in gravitational fields measured via the Mössbauer effect)
2) the reason why we believe that these two theories must be harmonized on Planck scale is just because of dimensional reasons. There is no other energy scale (length scale) than Planck energy (Planck length) at which we expect new effects to show up.
3) if quantum gravity effects show up at other scales there must be some "magnifying glass" for such effects; one may speculate that the universe itself may be such a magnifying glass, but up to know no effects have been found (e.g. energy dependent speed of light seems to have been ruled out by astrophysical data)

i thought that the aim of quantum gravity is to find out the relationship between both theories, and then of course quantum gravity would be testable at any scale, not only the Planck scale.

Yes and no: electroweak theory unifies the weak and the electromagnetic force but it does not provide a means to find new effects caused by the weak force in a new energy range.

 

[czes]

I would like to know what the equation means:
lp / l x ) * (lp / l y ) = -a Fg / Fe
where:
lp * lp – Planck length squared = hG/c3
l x , l y –Compton wave length of two interacting particles x,y l= h/mc
a – alfa=ke2 /hc = fine structure constant
Fg – Gravitational Newton's interaction Fg = Gm(x) m(y) /r2
Fe - Electrostatic Coulomb interaction Fe = ke2 /r2

On the left side we have relation between Planck and Compton scale and on the right side there is relation between gravity and EM force.
Does it mean the oscillation of the massive particle due to Compton wavelength causes a curvature of the spacetime of the Planck unit ?
Does it mean the gravity isn't a force at all but a correction of the spacetime because of the oscillation of the particle ?

 

[qsa]

As some colleagues just explained we cannot be sure, but there are some rather convincing reasons:
1) we do not see effects in experiments which should be explained via quantum gravity. The only effects we know are perfectly explained by just using quantum mechanics and general relativity w/o any deep integration of these two theories (e.g. red-shift of light in gravitational fields measured via the Mössbauer effect)
2) the reason why we believe that these two theories must be harmonized on Planck scale is just because of dimensional reasons. There is no other energy scale (length scale) than Planck energy (Planck length) at which we expect new effects to show up.
3) if quantum gravity effects show up at other scales there must be some "magnifying glass" for such effects; one may speculate that the universe itself may be such a magnifying glass, but up to know no effects have been found (e.g. energy dependent speed of light seems to have been ruled out by astrophysical data).

What about theories based on minimum length (other than Planck) and their effect on many low energy systems.

as in this thread

https://www.physicsforums.com/showthread.php?t=432711

 

[qsa]

Yes and no: electroweak theory unifies the weak and the electromagnetic force but it does not provide a means to find new effects caused by the weak force in a new energy range.

are you saying we only see the effects when the running coupling becomes constant, if that is so, then there is no point in making a large collider to probe Planck energy since G will be running really fast and no effect should be seen.

 

[qsa]

I would like to know what the equation means:
lp / l x ) * (lp / l y ) = -a Fg / Fe
where:
lp * lp – Planck length squared = hG/c3
l x , l y –Compton wave length of two interacting particles x,y l= h/mc
a – alfa=ke2 /hc = fine structure constant
Fg – Gravitational Newton's interaction Fg = Gm(x) m(y) /r2
Fe - Electrostatic Coulomb interaction Fe = ke2 /r2

On the left side we have relation between Planck and Compton scale and on the right side there is relation between gravity and EM force.
Does it mean the oscillation of the massive particle due to Compton wavelength causes a curvature of the spacetime of the Planck unit ?
Does it mean the gravity isn't a force at all but a correction of the spacetime because of the oscillation of the particle ?

I know you are so fond of this formula it looks nice and it is. if you make lx=lp and set a=1 you get Fg=Fe i.e. unification. my theory I hope will soon show why that is true.

 

[tom.stoer]

are you saying we only see the effects when the running coupling becomes constant, if that is so, then there is no point in making a large collider to probe Planck energy since G will be running really fast and no effect should be seen.

I didn't consider a running coupling constant. I responded to the idea that

" due to a relationship between both theories ... quantum gravity would be testable at any scale, not only the Planck scale".

It is not the case that due to a unification the domain of testability is enlarged. You see this in el.-weak theory: it's range of testability is defined by the Fermi constant. The introduction of the el.-weak theory relates the Fermi constant to the W- and Z-boson masses but that does not mean that the range of testability is enlarged towards lower energies = towards a typical QED scale.

 

[czes]

I know you are so fond of this formula it looks nice and it is. if you make lx=lp and set a=1 you get Fg=Fe i.e. unification. my theory I hope will soon show why that is true.

(lp / l x)*(lp / l y) = a Fg / Fe
(tp / tx)*(tp / ty) = a Fg / Fe
May be it is a trivial formula but if each quantum interaction causes a Planck length contraction and Planck time dilation it creates our space-time then.
What if the relation (Planck length/Compton length) is the most fundamental ?
If we integrate it over the sum of the quantum events we get the curvature of the space-time and gravitational time dilation.
Doesn't it solve the problem of the origin of the distance and time due to holographic principle ?
Is it too simple ?

 

[suprised]

According to the fuzzball hypothesis, quantum gravity effects can be hugely non-local and spread out over much larger distances than the Planck Length (ie, fill out the interior of a macroscopic black hole). Not all people support this picture, but at any rate it seems that gravity has a lot of surprises in store.

check out:
http://www-spires.dur.ac.uk/cgi-bin/spiface/hep/www?eprint=arXiv:0810.4525
http://www.physics.ohio-state.edu/~mathur/faq2.pdf