Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

What was the proportion of dark matter/energy to other matters/energy at the moments after the beginning of the universe (standard Big Bang model)?

share|improve this question
    
What do you mean by "moments"? Are we talking seconds, minutes, ...? The very early universe was a busy time with a lot of different reactions going on. After about the first hour or so things settle down a lot and it gets very easy to describe. –  Michael Brown May 3 '13 at 3:07

3 Answers 3

It is important to remember that very early ($10^{-10}$ seconds) on in the universe history there was no distinction between dark matter and normal matter as it is expected that all the forces were unified and there would be no difference between dark matter particles and normal matter particles since there were "no particles" in the classic sense. Recall that in QFT particles are excitations of fields, but if all the fields were coupled then there would be no difference between dark matter and non-dark matter. Also at very high energies, the excitations wouldn't last long enough to be meaningful.

If one takes inflation into account, I suppose the ratio of energy in the primordial matter fields vs. inflationary fields would depend on the exact model of inflation.

share|improve this answer

This question doesn't have a "correct" answer yet because we simply don't know what dark matter is.

That aside, assuming dark matter consists of particles (WIMPS for example), the LHC hasn't turned up any sign of dark matter production yet. Since the number of locations in the Universe that are able to reach LHC energies are very limited compared to the overall Universe, it's likely that nearly all of the dark matter today was produced very shortly after the big bang. There simply aren't enough energetic processes to be generating the quantity of dark matter we think there is today. That is, assuming a WIMP model of dark matter, the vast majority of the particles we estimate there are today are primordial remnants of the big bang.

Of course the above doesn't apply to other models. For example, here is a paper exploring primordial black holes as the source of dark matter.

share|improve this answer
    
This doesn't really address the OP's question, which is about the proportions of the different things in the early universe. –  Ben Crowell Jun 2 '13 at 15:36

In an FRW cosmology, we have a scale factor $a$. For example, if $a$ grows by a factor of 2, galaxies have gotten twice as far away as before. The contribution to the stress-energy tensor from radiation goes like $a^{-4}$, from massive particles $a^{-3}$, and from a cosmological constant $a^0$, i.e., it's constant. For these reasons, the universe has gone through three epochs: radiation-dominated, then matter-dominated, and now a vacuum-dominated epoch in which dark energy is dominant.

It's true that we don't know much about dark matter and dark energy, but we do know that dark matter consists of massive particles (otherwise you can't make the models fit the observations) and that the equation of state of dark energy is very close to that of a cosmological constant (Carnero 2011, Allen 2008, Biesiada 2011). For these reasons we can expect that dark energy and dark matter played negligible roles in the early universe.

Allen 2008, http://arxiv.org/abs/0706.0033

Biesiada 2011, http://arxiv.org/abs/arXiv:1105.0946

Carnero 2011, http://arxiv.org/abs/1104.5426

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.