
The Search for Neutrons That Leak into Our World from Other Universes - lelf
https://medium.com/the-physics-arxiv-blog/the-search-for-neutrons-that-leak-into-our-world-from-other-universes-318bfff97f0f
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snowwrestler
This is pretty close to the premise of the Isaac Asimov novel _The Gods
Themselves_. In that story, humans create an infinite source of energy by
trading material with a parallel universe in which the nuclear strong force is
slightly stronger than ours. (Or is it infinite...)

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trhway
i read it in the way that another universe is the ultimate "landfill" to
export your entropy.

Which actually brings up the dark matter/energy - can't it be just the stuff
leaking (or being "dumped/exported") from a nearby brane?

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ochoseis
In string theory isn't Gravity the only force that can go across branes? I
thought that might explain:

-why gravity's relatively weak (distributed) compared to the other three forces, as well as

-dark matter that we have an otherwise hard time observing apart from gravity

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imglorp
No mention was made specifically of how to rule out spontaneous pair
production, although I'm guessing it would be the same answer as how they rule
out cosmic sources? Would spontaneous pair production be dependent on anything
external at all?

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tjradcliffe
Getting rid of cosmic ray neutrons is a ridiculously hard problem that they
are going to deal with mostly by looking at how the neutron detection rate
varies as they change the distance between the detector and the reactor core.

The most pernicious source for experiments like this are "fireball neutrons"
that are generated from a high-energy muon producing an event that blows up a
nucleus in the surrounding rock (via an intermediate pion shower IIRC). This
gives you a source of neutrons with energies well up into the 100's of MeV,
which will merrily pass through metres of shielding, and a few of them are
bound to thermalize in the detector, although most will pass right through.

They've obviously run the numbers on all this (these are very well-known
problems for detector design) and decided they can discriminate against
backgrounds of this type sufficiently well to make the experiment worthwhile,
which all else being equal it certainly is: the possibility of putting brane-
world theories to the test is simply too delightful to pass up.

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marcosdumay
Are they talking about Superstring Theory branes?

Also, this: "So any change in this gravitational field should influence the
rate at which the neutrons leak in and out of our brane."

How can this happen in a unverse that obeys both the relativisc principle and
the gravity acceleration equivalence? Will different observers see a different
number of particles written at the detector display?

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pavel_lishin
Dumb question: how do they distinguish between neutrons tunneling to another
brane and back, and 'quantum tunneling'?

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tjradcliffe
Quantum tunneling can only happen over a very short range, on the order of the
de Broglie wavelength for the particle, which will be a subatomic distance for
interesting neutron energies. They are measuring neutrons that pass
through/around metres of material, so tunneling is unimportant.

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Xcelerate
I always find it funny how news articles are able to take the most basic (but
interesting) type of work in physics and turn into the craziest headlines.

I don't really fancy their usage of "universe" though, since it's normally
defined to be all that exists.

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lloeki
> _defined to be all that exists_

"universe" may be as shortsighted as our ancestors calling our favorite space-
faring rock "uniearth". Such a sibylline definition falls on its head as soon
as one tries to define "existence" and finds it ultimately bound to lowly
concepts of space or time. What to say of a "uni"-verse that is a constant
collapse of probabilistic functions, where every possible permutation
simultaneously exists until observed? Let's be humble, and cut some slack at
putting words on what we're looking at, because we're really not quite so
sure.

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charlieflowers
Or naming the atom "atom".

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xg15
And right now, Philipp Pullman is feeling happy and doesn't know why.

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bglazer
What would be the ramifications of a positive result?

