Severian

Your posts would be much more readable if you latexed your equations.

You see the same effect in rivers. Where rivers are wide they flow very slowly while where they are narrow they flow very fast. Simple conservation of water (as Sisyphus said already).

http://en.wikipedia.org/wiki/Cosmic_inflation

No - not really. They are just different representations of the symmetry groups which you use to define your theory. In fact, in supersymmetric theories, the fermions and bosons are just different projections onto orthogonal directions.

No, its not. Putting aside minor subtleties (caused by renormalization in quantum field theories) mass is the invariant length of the momentum four vector. Proof invalid!

What is more of a shame is that it usually is.

You don't really need to worry about the infra-red divergences. They are divergences in our results when you take the momentum in the problem to zero (so a particle loop where you are summing over all momentum including zero, or the emission of a really really "soft" gluon etc). But they are really just an artifact of the way we do the calculations (ie. perturbation theory). They cancel in all physical quantities, without the need to do any renormalization (but are a pain in the butt when doing the calculation).

Or to phrase it another way (to apply the shock-paddles to this thread), in Ben's example, if it turned out that [math]D=3 \times 10^{-22}[/math] would you think that there should be a good reason why A + B and C almost cancel, or would you be happy saying it was just coincidence?

No. Spinless particles are bosons, so described by the Klein-Gordon Equation, not the Dirac equation. Having said that, we have never observed a fundamental (ie. non-composite) spinless object.

Proof requested.

You shouldn't be so ashamed of the porn sites you visit - you should embrace your sexuality!

I disagree. It is a symptom of voters feeling disenfranchised by mainstream politicians. Palin being "folksie" makes people identify with her - they believe that she will represent their interests because she is like them. There is no point in having a competent president who gets things done, if the things he gets done are not what you want done. Palin's possible incompetence is less of a barrier because (they think) at least she is trying to do good (and how can she be incompetent if she is governor of Alaska?)

Who is your supervisor at Southampton AlphaNumeric?

I thought he was commenting on dirtyamerica's statement that "Earth is already in a slightly elliptical orbit, being closest to the sun in the Winter and farthest in the Summer" and saying that the minimum of the elliptic orbit was during the southern hemisphere's summer. I am not saying this is wrong. I genuinely don't know, but if it were true, then there should be some mechanism to explain why it would be true, and I would like to know what that is (although I suppose it could just be coincidence).

I don't think so. Distance from the sun has no effect on the seasons, so I wouldn't expect them to be correlated.

In my (prejudiced) opinion, I think they will be Majorana. It seems clear by now that there should be a right-handed neutrino state if the SM is going to make any sense. For a Dirac neutrino, that state is just like the left-handed one except it has no electroweak interaction, and its coupling to the left handed electron (that is, its mass) must be very small. But if we are going to have a right-handed neutrino, then it must be neutral to all forces except gravity. It has no charge, no isospin and no color. That means that there is no symmetry to protect its mass from quantum effects and its mass should naturally be at the scale of gravity. So it needs to be very very heavy. If this is the case, then the "see-saw" mechanism comes into play. The pre-see-saw left-handed neutrino could naturally have a mass similar to the other leptons, but then mixing with the heavy right-handed state pushes this down to very small masses we see and make it a Majorana particle. Sort of. You have to define how you are going to recognise an antineutrino, and in the things you have read, they are probably recognising them by their interactions.

I would support Palin running for the Republican nomination in 2012 too. I think the bigger choice of candidates one has in a democracy the better, and I think having strong women standing on both sides of the political divide has to be a good thing. I wouldn't vote for her, but I would support her standing.

That is not necessarily true. Theoretically it is quite easy to construct a particle which is its own antiparticle. For a boson, that is just making the field real, so under complex conjugation it maps onto itself. For a fermion, it is a case of making the lower two entries of the Dirac spinor (in the Dirac representation) the conjugate of the upper two. Indeed, the jury is still out on whether the neutrino i a Dirac or Majorana particle. If it turns out to be Majorana, then it is its own antiparticle. Also, if minimal supersymmetry turns out to be true, then the neutralino would be its own antiparticle despite having weak interactions.

No - much simpler and more practically minded. I do calculations in [math]4-2 \epsilon[/math] dimensions, where [math]\epsilon[/math] is small. Moving away from 4-d regulates the infra-red and ultra-violet divergences one gets in quntum field theories, allowing the infra-red divergences to cancel in physical predictions, or to renormalise the ultra-violet ones away. Then I take the limit [math] \epsilon \to 0[/math] at the end.

When you consider a quantum mechanical wave equation, usually people think of Schroedinger's Equation. However, that is non-relativistic - it doesn't take relativity into account. You can try an construct an equivalent equation which includes relativity in two ways. The first way gives you something called the Klein-Gordon equation, which we now know describes particles like the photon. The second way gives you the Dirac Equation, which we now know describes particles like the electron. The neat thing is that if you just work through the maths, you discover that any particle described by the Dirac Equation must have an intrinsic angular momentum we now call "spin". This is a prediction of the equation. So the spin of an electron is a prediction of making its equation work with relativity. Of course, you can just give a particle an intrinsic angular momentum in a non-relativistic framework, but that is 'ad hoc', and not a prediction.

There was no logical reason to suspect he would invade Iraq either.

If he really wants to give Obama a hard time, he could invade Iran.

I even routinely do calculations in non-integer numbers of dimensions.

Oh - don't get me wrong, I like supersymmetry and dislike fine-tuning. I agree that it is a problem we can't overlook. But this is not the view of many physicists. I was simply stating the contrary viewpoint to stimulate discussion.

I had read his blog profile before posting. My question remains. Not only is he a "physicist", he is a physicist working on (or at least has worked on) an area where cosmological arguments play a role. Maybe it says more about Syracuse that the OP though... So let me answer the first few questions: The Big Bang model does not say this at all. The BB model describes the evolution of the universe from a (very short) time after any possible implicit creation event to the present. It says nothing about the times before this and makes no attempt to explain creation. Indeed, we know nothing (or very little) about physics above the TeV scale. They are still there! Since the Big Bang has no singularity, it is better to describe your "universe in a point" conjecture by saying that in the limit where we take time to 0, the distance between any 2 points tends to zero. Every point is still surrounded by infinitely many points just like at any other time. The only difference is that points which will later be very far apart, are at this time really really close together. A better analogy would be to ask if you are happy with there being no point on Earth further north than the North pole? Naively perhaps, but since we don't have a theory of quantum gravity, is your conjecture based upon anything other than speculation? Well, we don't have a concrete explanation for these yet, though a wimp and a cosmological constant would do just fine. What is your problem with these? I presume you are referring to inflation here. If so, then SR is only restricting the speed of real physical things, like particles, stars or galaxies, whereas in inflation it is really the particle horizon which is expanding. So the faster then light bit of inflation is a bit like how an infinitely bright spotlight shining on clouds would move faster than light if you reduce the angle enough. Well, your size is governed by the strength of the electromagnetic interaction - not gravity. So you would not expand. Galaxies not expanding are a bit harder to understand, since their size is gravity induced. However, it comes down to the clumpiness of matter - the expansion comes about because the universe is very uniform on large distance scales (ie. it is with this ansatz that the expanding metric is a solution to the GR equations). For clumped matter, the equations are quite different, and the non-expansion of galaxies falls out. Isn't reposting material from blogs a violation of SFN rules?