Majorana fermions

[Tommygun]

I have a quick question about Majorana fermions.

When a Majorana fermion annihilates a fermion, does it release comparable amounts of energy like matter /antimatter?

Will Majorana fermions damage other forms of matter?

[N_las]

I don't think that majorana fermions annihilate with any fermions, but only with other majorana fermions. But I have no knowledge about the subject.

[SSR Kermit]

A majorana fermion is a fermion that is its own anti-particle so it would only annihilate if it collided with the same kind of particle. By their nature, majorana fermions interact very weakly with ordinary matter -- even making such particles candidates for cold dark matter. They lack many moments of Dirac fermions, for example electric moment. To my knowledge, which is roughly undergraduate level, the only candidate presently for a Majorana fermion is the neutrino.

[Skyler4856]

A particle may only annihilate when faced with its respective antiparticle.

[Tommygun]

I wondering if with Majorana fermions you could get similar "benefits" of antimatter, but with a material that is safer to handle.

[Skyler4856]

I wondering if with Majorana fermions you could get similar "benefits" of antimatter, but with a material that is safer to handle.

The fact that it's its own antiparticle would make a pain in the butt to store

[K^2]

Yeah, it's just the opposite of easy to handle. It annihilates with itself.

I wouldn't think on it too much, though. There is no reason for real Majorana fermions to exist, and quasi Majorana fermions aren't going to be any good for energy storage anyhow.

[LLlAMnYP]

Wouldn't storing them (assuming we have them) be quite trivial thanks to Pauli's principle if you get them spin-polarized?

[andrewas]

They are also uncharged and only interact through gravity, so we don't have any way of containing them even if we can keep them from annihilating

[LLlAMnYP]

I didn't say anything about charge, though. But being fermions they must have a half-integer spin. Magnetic moment too, perhaps?

[Tommygun]

Can they have any properties like magnetic monopoles?

[LLlAMnYP]

I don't think so. That would require magnetic charge and then they can't be their own antiparticle. Or which properties did you have in mind?

[SSR Kermit]

Majorana fermions only have toroidal moments-- the behaviour of neutrinos is a good example, although it remains unproven whether the neutrino is a Majorana fermion (the issue has to do with mass and flavour changing).

Neutrinos carry a lot of energy, and there's a lot of them-- everywhere all the time-- but it's only in the incredibly rare occurrence that one actually collides with something that it interacts at all! (Typically it would collide with a water molecule in huge tanks deep underground, causing a tiny flash of blue light-- cherenkov radiation-- that the detector is set up to observe. There's also a project that uses the Antarctic ice sheet as one massive detector.)

Majorana fermions would be the same-- a "gravity bottle" (a one-ended wormhole, or one-sided black hole) is just about the only way to contain them. At that point, in the context of spaceships, a gravity drive is probably better anyway, since it can move between two points in space faster than light can cover the distance.

I wondering if with Majorana fermions you could get similar "benefits" of antimatter, but with a material that is safer to handle.

As pointed out previously, even if you manage to collect and contain them, you would have to make sure none of them touched, or they would annihilate! You would have to either generate them from something else (exotic particles of some kind), or keep each particle separate....

Edited October 6, 2014 by SSR Kermit

[Tommygun]

I don't think so. That would require magnetic charge and then they can't be their own antiparticle. Or which properties did you have in mind?

Nothing specific, I just saw that they are both quasiparticles and that Majorana fermions have unusual magnetic properties.

[LLlAMnYP]

That's not an entirely accurate analogy, though. You can have quasi-Majorana-Fermions and quasi-Magnetic-Monopoles, but we have yet to discover their fundamental (i.e. real) counterparts, although we have a good hunch on the neutrinos.

Magnetic monopoles (the real ones) are spooky though. I've read a long time ago, that they can annihilate everything they touch, that is to say they convert every particle they meet to energy and you're left with gamma radiation and a magnetic monopole ready to continue its rampage. I'm pretty sure, that can't be true, but if it was, a handful of monopoles plus any matter would be a perfect energy source. Who'd wan't silly cold fusion then? :-)