What is "empty space" composed of?

[DiracPool]

I'm trying to sketch out what empty space is composed of and I'm drawing a blank (pun intended). http://instantrimshot.com/

No, really though, I'm trying to wrap my head around just what exists in this newly-modeled seething foam we used to call "nothing." From what I understand, within the vacuum there is a continuous "boil" of quantum fluctuations whereby virtual particles pop in and out of existence in a process called "pair production." That's about all I'm fairly confident of at this point. I have scoured several Wiki pages trying to get a better picture of what is going on. Here are a few of those:

http://en.wikipedia.org/wiki/Quantum_foam
http://en.wikipedia.org/wiki/Quantum_fluctuation
http://en.wikipedia.org/wiki/Dirac_sea
http://en.wikipedia.org/wiki/Virtual_particle
http://en.wikipedia.org/wiki/Zero-point_energy
http://en.wikipedia.org/wiki/Pair_production

One main question I have that I didn't get from reviewing these is whether or not anything besides electrons-positrons are involved in the pair production/quantum fluctuation process. Most specifically, do quark and anti-quark pairs pop in and out of the vacuum. None of these articles say. The closest I could get was this statement from the pair production article:

Pair production is the creation of an elementary particle and its antiparticle, for example an electron and its antiparticle, the positron, a muon and anti-muon, or a tau and anti-tau.

From this statement it looks as though it's just leptons? Am I wrong? What about neutrinos? They are electrically neutral leptons, do they pair produce in the vacuum?

One more thing. The Unruh effect. From the article: http://en.wikipedia.org/wiki/Unruh_effect

Unruh demonstrated theoretically that the notion of vacuum depends on the path of the observer through spacetime. From the viewpoint of the accelerating observer, the vacuum of the inertial observer will look like a state containing many particles in thermal equilibrium—a warm gas.

If, say, pair production in the vacuum were limited to just electrons-positrons, is this what the empty space surrounding an arbitrary inertial observer would look like to an accelerating observer? A warm gas of isolated positrons and electrons in thermal equilibrium? What else might be in there?

 

[Chronos]

An accelerating observer would experience unruh radiation, but, not for the reasons you suggest.

 

[bapowell]

The physical significance of Unruh radiation is unclear, since, although an accelerating particle detector will register the presence of quanta, the stress tensor is zero. See Birrell and Davies' excellent text for further discussion of this point.

 

[DiracPool]

Thanks for the info on the Unruh effect. Does anyone have any insight on the formation of quark-antiquark pairs (sea quarks, maybe?) or other, more exotic, particles in the vacuum?

I ran across an article in New Scientist discussing the lattice QCD model which discussed quark-antiquark pairs popping in and out of the vacuum:http://www.newscientist.com/article...-merely-vacuum-fluctuations.html#.U8BvDPldVqU

Until recently, lattice QCD calculations concentrated on the virtual gluons, and ignored another important component of the vacuum: pairs of virtual quarks and antiquarks.

Quark-antiquark pairs can pop up and momentarily transform a proton into a different, more exotic particle. In fact, the true proton is the sum of all these possibilities going on at once.

However, I believe this model and those simulations are modeled in high energy situations such as in particle colliders. My question is what is happening in the quietest, coldest parts of deep intergalactic space, say in a cubic meter of that space where there are relatively few existing stable protons and leptons? What forms of matter are pair producing there and in what form?

 

[Tanelorn]

"My question is what is happening in the quietest, coldest parts of deep intergalactic space, say in a cubic meter of that space where there are relatively few existing stable protons and leptons? What forms of matter are pair producing there and in what form? "

I would also like to ask same question, what is empty space composed of, but in a volume smaller than say the volume of a proton?

 

[Chronos]

Sten Odenwald suggests space and time is a byproduct of gravity. If you could turn off gravity, space and time would cease to exist. This explanation makes sense in the context of general relativity. See http://www.astronomycafe.net/gravity/gravity.html and http://ws5.com/spacetime/Fundamental Physics.pdf for discussion.

 

[DiracPool]

Thanks for the references, Chronos, especially the Daedalus article, it looks really interesting..