# Dark energy and virtual particles

If space time is accelerating away from itself everywhere due to dark energy, could this acceleration be the cause of virtual particles, essentially Unruh radiation?

• It seems that you believe that virtual particles are physical particles rather than mathematical constructs of QFT. Right? I like the question though. – Benjamin Apr 1 '16 at 22:21
• Not really sure about their ontology, just spend too much time thinking and curious if there is any discussion of any connection between Unruh and them! – Ilya Grushevskiy Apr 1 '16 at 22:42
• While I agree that virtual particles don't exist except on paper, I would also go with the general direction of the question... do the fields we know about couple to a quantized background that exchanges energy and momentum? I think intuitively the idea may have some merit, at least locally. – CuriousOne Apr 2 '16 at 2:49

If space time is accelerating away from itself everywhere due to dark energy,

In general , given asymmetric mass distributions, gravitational waves are generated from the space time distortions.

could this acceleration be the cause of virtual particles,

Assuming quantization of gravity and the reality of gravitons, the gravitons are not virtual they are real. Graviton particle interactions have very small probability and any virtual diagrams thought up will have a very small probability of acting on other fields. Since in terms of energy the expansion is very small it is only soft real photons that could come from such graviton interactions.

The Unruh effect is a surprising prediction of quantum field theory: From the point of view of an accelerating observer or detector, empty space contains a gas of particles at a temperature proportional to the acceleration. Direct experimental confirmation is difficult because the linear acceleration needed to reach a temperature $1~\rm K$ is of order $10^{20}~\mathrm{m/s^2} .$