In the Casimir effect a negative vacuum energy exists between two plates. Does this cause repulsive gravity?
Can this have consequences for the situation near the big bang, in relation to inflation?
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$\begingroup$ The energy densities in QED aren't really the same thing as GR. In GR the vacuum can be said to have 0 energy density yet in QED the vacuum has infinite energy and the space between casimir plates has infinite - (a constant depending on L^4) energy and this difference of energies is what we experimentally see. $\endgroup$– Sidharth GhoshalCommented Jun 15 at 1:57
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You are talking of this:
In the Casimir effect, two flat plates placed very close together restrict the wavelengths of quanta which can exist between them. This in turn restricts the types and hence number and density of virtual particle pairs which can form in the intervening vacuum and can result in a negative energy density.
you ask:
Can this have consequences for the situation near the big bang, in relation to inflation?
I suppose you mean that "as negative energy can exist", will this have consequences in the inflation era.
If you search there are a number of models that use the concept of negative energy, example from the abstract
We find a unique way of realizing inflation through cyclic phases in an universe with negative vacuum energy.
Also in the cosmological models, negative energy, if it exists, plays a role.
in a universe in which positive energy dominates will eventually collapse in a "Big Crunch", while an "open" universe in which negative energy dominates will either expand indefinitely or eventually disintegrate in a "big rip"
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$\begingroup$ Thanks for elaborating my question. In our universe, there was once slowed down expansion, which nowadays is taken over by acceleration. It looks like matter contributes to positive curvature and the vacuum to negative curvature. Could it be the universe was once so small that the vacuum energy was that small (like between the plates) so the vacuum energy was very negative? For a good bang? $\endgroup$ Commented Feb 10, 2022 at 8:38
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$\begingroup$ The energy between the plates is electromagnetic and very very small. At the beginning of Big Bang the energy densities are huge, and most models have a unification of all four forces at the beginning, so no , not like the energy between the plates. btw, the "big rip" in the quote, has repulsive properties. $\endgroup$– anna vCommented Feb 10, 2022 at 8:51