Can (ordo) Fermions convert to Bosons?

[RobbyQ]

TL;DR

Fermions to Bosons

Can Fermions turn into Bosons and thus share the same quantum state and become compressible?

And/Or is the opposite also possible?

 

[anuttarasammyak]

An electron and a positron meet and become two photons. The system quantum state is conserved and photons are compressible. The reverse process is possible.

 

[renormalize]

An electron and a positron meet and become two photons. The system quantum state is conserved and photons are compressible. The reverse process is possible.

Can you explain what you mean by "(t)he system quantum state is conserved" and in what sense "photons are compressible"?

 

[anuttarasammyak]

At least energy, momentum, angular momentum of the system is conserved. I hesitate to refer spin or helicity or other pure quantum states due to my poor understanding.
We can change volume of photon gas. On the other hand, I hesitate to say that electron gas is incompressible.

 

[pines-demon]

TL;DR: Fermions to Bosons

Can Fermions turn into Bosons and thus share the same quantum state and become compressible?

And/Or is the opposite also possible?

A single fermion in vacuum cannot turn into a single boson in vacuum due to conservation laws (can you tell which?). If you want to consider more than one particle please develop.

 

[PeterDonis]

share the same quantum state and become compressible?

"Compressible" is a poor term. The key thing that a system of bosons can do that a system of fermions can't is to form a Bose-Einstein condensate.