Do Cosmological Neutrinos Redshift, too ?

[Widdekind]

Would a beam of neutrinos, arcing across the Cosmos, over Cosmological distance & time scales, "redshift", their Wave Functions spreading out with the expansion of the underlying spacetime fabric ?

 

Would neutrinos' slight masses affect their physics any ??

[Martin]

Would a beam of neutrinos, arcing across the Cosmos, over Cosmological distance & time scales, "redshift", their Wave Functions spreading out with the expansion of the underlying spacetime fabric ?

 

Would neutrinos' slight masses affect their physics any ??

 

Short answer is YES neutrinos lose momentum--from the standpoint of observers at rest relative to primordial light (CMB).

 

Since neutrinos have mass, losing momentum means losing speed.

 

An article I read a couple of years ago said that STEVEN WEINBERG in his textbook COSMOLOGY goes through the math for a general particle with mass, traveling over long period of time in expanding space and shows how it loses momentum (so speed) due to expansion.

The author provided what he said was a more concise proof. It is not too surprising.

 

 

People use this fact when they run simulations of structure formation in the universe. Most of the matter is dark matter. so how does DM condense into clouds and cobwebby filaments?

 

Good question. If DM is falling into an overdense region, how can it dump kinetic energy? How can it disipate energy so that it can STAY in the cloud?

 

The answer involves some gravitational interaction so that some DM is trapped and some other DM gets extra and escapes. then the escaped DM gradually due to expansion loses kinetic energy and is able to participate in condensation somewhere else.

 

That is more than you asked about, so ignore it if you want. the main answer is yes expansion does have the effect of draining momentum from stuff (seen from CMB rest) and when it is light we call it REDSHIFT but when it is a particle like neutrino or DM particle then you can think of it as simple SLOWING DOWN.

 

Or I guess you can think of it as redshifting the quantum wavefunction of the particle but that seems a bit fancy when all it is is slowing down.

Edited December 6, 2010 by Martin

[swansont]

The wave function and the wavelength aren't the same thing. The latter would be redshifted.

[Martin]

The wave function and the wavelength aren't the same thing. The latter would be redshifted.

 

Thanks for the correction. Should have said wavelength. Since neutrinos are massive particles I'll just think of them as slowing down as they lose momentum, in contrast to light.