Mechanism for matter creation in an expanding Universe?

[johne1618]

Hi,

I wonder what people think of the following mechanism for matter creation in an expanding Universe.

Imagine a particle-antiparticle pair coming into existence from the vacuum.

As I understand it, they will annihilate each other in the time that a light signal takes to travel from one particle to the other.

But what happens if space is expanding fast enough so that no light signal can ever travel the (proper) distance between them?

Would the particle pair then fail to annihilate and therefore continue to exist as "real" matter?

John

 

[IsometricPion]

As far as I understand the processes involved (which is mostly at the conceptual level); yes, (certain types of) the virtual particles would become real. However, they become real at the expense of the energy of whatever is causing the expansion. For every process of which I am aware, this means that particle production slows the rate of expansion. Of course, only particle anti-particle pairs that respect all the relevant conservation laws, etc. can actually be formed (e.g., the total final momentum of the field causing the expansion and that of the pair produced must equal the total momentum initially in the field). For more information (and math) see arXiv: Quantum Field Theory in Curved Spacetime.

 

[johne1618]

For every process of which I am aware, this means that particle production slows the rate of expansion.

Perhaps the gravitational attraction of the continuously created particles balances the gravitational repulsion of the dark energy.

 

[IsometricPion]

I am not certain of what types of particles could interact with dark energy and thus be created by it. However, conservation of mass-energy and the fact that it is mass-energy that causes gravitation implies that the gravitational influence of the field at the point/small region where the particle is produced prior to its creation is the same as the gravitational influcence of the particle plus any remaining field mass-energy immediately after the particle is created. If dark energy is due to a cosmological constant-like phenomenon, I would think that the expansion due to it would always be too slow to produce enough particles (assuming a reasonable equation of state) to significantly alter the expansion.