Recent content by phsopher

Indeed, my thought was to draw a parallel with neutrinos. If a relativistic species decoupled sufficiently early then subsequent annihilation processes, such as electron-positron annihilation, would heat up the photon fluid but not this decoupled component. Thus resulting in lower temperature...

"Not as far as we know" as in it's not possible or as in there does't exist a dark radiation component? I was not aware that the forum rules don't allow discussion of unproven things. I was under the impression that they merely prohibit things that challenge the mainstream. To my knowledge an...

While the above replies are correct, I guess it's also possible that there is a "dark" radiation component which interacts very weakly with ordinary matter. If it decoupled early, at least before electron-positron annihilation, then it would have a lower temperature than the CMB. Sort of like...

If I choose the energy to be ##E=m## (outside the instability band) instead of ##E=m/2## (inside the instability band) then the WKB gives an excellent fit over many cycles: With respect to the various time scales of the system the two cases are pretty much the same. So my question is how...

That's an interesting paper; however, I don't think it quite answers my question as far as I've been able to tell. What they appear to be considering is a solution which passes through the resonance region, which in the above case would correspond to x-dipendent energy ##E(x)##. What I want to...

The Mathieu equation has been studied for over a hundred years. It is known that for certain parameter values there is a parametric resonance where the solutions get exponentially amplified.

I'm trying to understand why the WKB approximation doesn't seem to work in the following case. Suppose you have a particle of mass ##m## in a potential ##V(x)=q m\cos(2mx/\hbar)##, where ##q\ll 1##. Consider then the stationary solution with energy ##E=m/2##. The Schroedinger equation is then...

You can also use regular partial derivatives but you have to keep in mind that the term ##\sqrt{-g}## depends on time in FRW so you must take that into account in the partial integration: \frac{1}{\sqrt{-g}}\partial_{\mu}\left(\sqrt{-g}\partial^{\mu}\phi\right) + V' = 0 For FRW, the...

This doesn't really answer my question, which was that if new physics modifies the electroweak dynamics, such as to push the EW phase transition to higher energies, wouldn't we already have seen that at accelerators. There is no evidence of new physics up to energies of about 10 TeV. Like...

What I'm getting at is that when you say that in some models the Higgs turns on earlier do you mean that other higgses turn on earlier or that the SM one does? I don't see why it would be that latter. We've probed the energies up to 10 TeV in accelerators, if new physics pushed the symmetry...

Like I said I don't know anything about the GUTs so I may be well off the mark here but it was my understanding that the higgs responsible for the symmetry breaking at the GUT scale would have to be a different Higgs, that is, not the Standard Model Higgs responsible for electroweak symmetry...

The OP is asking when the Higgs is turned on. I interpret this to mean the time when the Higgs obtains a non-zero VEV thus breaking the electroweak symmetry and giving masses to weak gauge bosons, quarks and leptons. This happens at ##T\sim \mathcal O(\text{100 GeV})##. I don't have my copy of...

The electroweak symmetry is restored in the Standard Model above the temerature of the order of 100 GeV. As the universe cooled down below this point the Higgs would have obtained a non-zero vacuum expectation value (VEV) giving weak gauge bosons and fermions (other than neutrinos) their...

Now I'm confused; when I asked you in the beginning of the thread if you were considering an expanding clock you answered no and said that the time would the same as that measured by rigid clocks. Putting that aside, yes, the rate of an expanding clock will change; however, since the actual...

It has been my understanding that the void models are increasingly difficult to reconcile with data. The most recent paper you've cited is over two years old. It would be nice to see what the latest data have to say. I haven't been following this area myself. Perhaps it's worth noting that...