Effects of magnetism on spacetime curvature, and implications

  • #1
jaketodd
Gold Member
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Quotes from Cosmic magnetism, curvature and the expansion dynamics:

"Most interestingly, the coupling between magnetism and geometry implies that even weak fields have a significant impact if the curvature contribution is strong."

"The energy scales involved vary from ∼ 100 MeV at the QCD phase transition, to ∼ 100 GeV in the case of electro-weak (EW) physics and closer to the Planck energy scale for inflation or string cosmology."

The LHC does 13 TeV.

"The tension of the field lines means that the magneto-curvature coupling tends to accelerate positively curved regions..."

A quote from A positively curved visualization of gravity?:

"If one imagines a basketball pressed against the rubber sheet, the portion of the sheet in contact with the ball would be positively curved, but the rest would (as before) be negatively curved, one assumes."

So, accelerating positive curvature, as I understand it, would be like amplifying gravity.

Could this phenomenon ever be used for traveling through space? Or, am I completely misunderstanding this whole topic?

An object accelerating in positive curvature continues to accelerate, as long as the curvature is there. Therefore, there would be no limit to the speed achievable. Reminds me of The warp drive: hyper-fast travel within general relativity. However, in that example, the spacetime, which the spaceship is in, is flat.

Thanks!
 
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  • #2
jaketodd said:
accelerating positive curvature, as I understand it, would be like amplifying gravity.
Not really, no.

jaketodd said:
Could this phenomenon ever be used for traveling through space?
No. The paper you linked to, as you will note, says no such thing. It talks about the effects of cosmic magnetic fields on the expansion of the universe. I am skeptical of the claimed magnitude of the effects, but that will be a matter for the cosmology community to work out as it evaluates the paper.

jaketodd said:
am I completely misunderstanding this whole topic?
Yes.

The "positive curvature" in the PF thread you linked to is spatial curvature, not spacetime curvature. The paper you linked to, OTOH, is talking about the effect of magnetic fields on spacetime curvature. Those are very different things.
 
  • #3
PeterDonis said:
No. The paper you linked to, as you will note, says no such thing. It talks about the effects of cosmic magnetic fields on the expansion of the universe.
If magnetic fields, currently attainable by humans, are much stronger than the ones required for impacting spacetime geometry affecting the expansion of the universe, then why can't we influence much more localized spacetime geometry with magnetism? Thanks
 
  • #4
jaketodd said:
If magnetic fields, currently attainable by humans, are much stronger than the ones required for impacting spacetime geometry affecting the expansion of the universe
They aren't. Humans can't create magnetic fields throughout the entire universe, which is what the paper you referenced is discussing. We can only create magnetic fields in an extremely tiny localized region.

jaketodd said:
why can't we influence much more localized spacetime geometry with magnetism?
Because magnetic fields confined to an extremely tiny localized region are not at all the same thing as magnetic fields throughout the entire universe.
 
  • #5
jaketodd said:
The LHC does 13 TeV.
That doesn't mean the LHC creates magnetic fields of that strength. Nor does it mean the LHC creates any significant spacetime curvature. 13 TeV over a large region, say a few billion light-years in size, and lasting for a long time, say a few billion years, would do so; but 13 TeV confined to the LHC's central chamber and lasting for a miniscule fraction of a second, not so much. And even that ignores the fact that the energy the LHC uses does not appear from nowhere; it is already there, because stress-energy is locally conserved. So whatever spacetime curvature you think the LHC is "creating", it isn't--it's already there.
 
  • #6
PeterDonis said:
Because magnetic fields confined to an extremely tiny localized region are not at all the same thing as magnetic fields throughout the entire universe.
But the fabric of the universe is expanding even in tiny localized regions, right, i.e. dark energy? And even without dark energy, isn't the expanding universe also expanding in more localized regions, just not as uniformly as the universe as a whole? (Because all regions are expanding, perhaps from the locus of the universe.) Are you saying dark energy can do it but not magnetism? So why can't we use magnetism to influence spacetime curvature, and maybe expansion in tiny localized regions? What differentiates magnetic fields encompassing the whole universe, from stronger ones that are more localized? And why do the weaker ones fill the whole universe, while stronger ones only affect a tiny localized region?

PeterDonis said:
That doesn't mean the LHC creates magnetic fields of that strength.
Well what is the strength please? Is eV the wrong unit? I tried converting from eV to Tesla, but couldn't figure it out. Is Tesla the correct unit then? Thanks!
 
  • #7
jaketodd said:
the fabric of the universe is expanding even in tiny localized regions, right, i.e. dark energy?
Dark energy is present everywhere, at least according to our best current models.

jaketodd said:
even without dark energy, isn't the expanding universe also expanding in more localized regions, just not as uniformly as the universe as a whole?
No. In the absence of dark energy, the FRW spacetime model is only an approximation valid on large scales, using the average density of matter on those scales. It does not scale down to localized regions, and in particular you can't say that localized regions are expanding. The model is simply not applicable on those scales.

jaketodd said:
Are you saying dark energy can do it but not magnetism?
I am saying that magnetism created by humans in an extremely tiny localized region is not going to affect the dynamics of the entire universe. Neither would dark energy if it only existed in an extremely tiny localized region. And since the paper you referenced is about the effect of magnetism throughout the entire universe on the dynamics of the entire universe, the kinds of speculations you are making about magnetism in tiny localized regions are simply not supported by the paper you referenced. So unless you have another reference, you are engaging in personal speculation and that is off limits here.

jaketodd said:
Well what is the strength please?
I don't know what magnetic field strength would correspond to the energies that the LHC creates; there might not even be one since magnetic field strength is not the same thing as energy. What I do know is that the question is irrelevant because (a) the LHC is not creating magnetic fields, and (b) the paper you referenced isn't talking about localized effects anyway, as I said above.
 
  • #8
Ok, sorry.
 
  • #9
This thread is now closed.
 

FAQ: Effects of magnetism on spacetime curvature, and implications

What is the relationship between magnetism and spacetime curvature?

Magnetism, like any form of energy and momentum, contributes to the stress-energy tensor in Einstein's field equations of General Relativity. This means that magnetic fields can influence the curvature of spacetime, although their effects are generally much weaker compared to massive objects like stars and planets. The presence of a magnetic field can slightly alter the geometry of spacetime, but these effects are typically only significant in extreme environments, such as near neutron stars or black holes.

How do magnetic fields affect the orbits of objects in curved spacetime?

Magnetic fields can exert forces on charged particles, affecting their trajectories. In curved spacetime, this interaction is more complex due to the interplay between electromagnetic forces and gravitational forces. For instance, in the vicinity of a magnetized neutron star, the combined effects of spacetime curvature and intense magnetic fields can lead to unique orbital dynamics and radiation patterns that would not occur in the absence of such fields.

Can magnetism create or alter black holes?

Magnetism alone cannot create black holes, as black holes are formed from the gravitational collapse of massive objects. However, magnetic fields can influence the dynamics of matter around black holes. For example, in the accretion disks around black holes, magnetic fields can drive the formation of jets and affect the rate at which matter falls into the black hole. These effects can alter the observable properties of black holes but do not change their fundamental nature.

What are the implications of magnetism on the structure of neutron stars?

Neutron stars often possess extremely strong magnetic fields, which can significantly affect their structure and evolution. These magnetic fields can influence the star's shape, cause anisotropic pressure distributions, and affect the emission of electromagnetic radiation. In some cases, the magnetic field can be strong enough to support the star against gravitational collapse, leading to observable phenomena such as pulsars and magnetars.

Are there any practical applications of understanding magnetism's effect on spacetime curvature?

While the direct effects of magnetism on spacetime curvature are primarily of theoretical interest, understanding these interactions can improve our knowledge of astrophysical processes and the behavior of extreme environments in the universe. This knowledge can inform the development of advanced technologies for space exploration, improve our understanding of fundamental physics, and potentially lead to new insights into the unification of gravity with other fundamental forces.

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