Severian

I don't believe it is genetic. There may be a propensity that is genetically influenced, but I would say that is true for all things. I think sexual orientation is very much a choice, but for most it is probably not a choice that is easily altered.

So isn't this an act of faith then? After all, you are only believing the universe is 13.7 billion years old because someone in authority, whom you trust, has told you that it is. How is this different from a creationist believing that the Earth is six thousand years old because their priest or religious scholar tells them it is? You are both just taking the word of someone you trust.

If Hitler hadn't existed then maybe Germany would have had a competent war time leader, who didn't make silly mistakes like invading the USSR. Maybe we would all have been speaking German by now.

I think Einstein is meaning that no matter how clever we get in phrasing the laws of physics, or writing them in an economical form, we will always be left with at least one equation or principle at the end. Even if we just have one equation, or maybe say that the laws of the universe are derived from one underlying principle, we can always ask, "Why that equation?" or "Why that principle?" In other words, "it didn't have to be that way" is asking why shouldn't it have been some other principle or equation. In some sense that final equation is God because it creates all things, all things are ruled by it, and all things come from it.

I am curious about this comment. The age of the universe has been determined by the WMAP experiment launching a satellite into space and making difficult astrophysical observations. Do you regard the result as "obvious"? Of course, one does not have to be so accurate as WMAP - the poll simply says "billions" - but I am not really seeing how one even gets to within a few orders of magnitude of 13.7 billion years by using "obvious" means. Can you please clarify your methodology?

The Higgs boson is perfectly compatible with string theory.

I don't like the quantum fluctuation idea because it is anthropic. Quantum fluctuations are allowed to borrow energy for a time [math]\Delta t \sim \hbar / \Delta E[/math]. Since the energy of the universe is very large, the time it exists should be very small. This is of course a statistical relation, so in other words, the probability of our universe arising is extremely small. You would more naturally expect much smaller and shorter lived universes. Since we need a long lived one to exist, you are then forced to say that we observe a long lived one simply because we exist - an anthropic argument. And this is only if you are willing to claim that space and time weren't created at the Big bang but pre-existed, in order to give you a space-time continuum in which the fluctuation can occur.

The current thinking is to use CP violating effects. Basically, the laws of physics are not the same for particles and antiparticles. This effect is know as CP violation, and is an observed phenomenon. So produce equal numbers of particles and antiparticles in the big bang, then evolves the particles and antiparticles separately. You then have slightly fewer antiparticles than particles so when they annihilate you have particles left over. The conditions required for this to happen are known as the Sakharov conditions. Unfortunately the CP violation observed so far is too small to do this...

Why do I need a justification to believe in a god?

These will be quite a while coming. The spin is relatively easy to measure at the LHC; the couplings to other particles can be measured to some degree - probably not terribly accurately but enough to tell if the coupling are approximately proportional to the mass. The hard one will be measuring the Higgs boson self couplings. This is really the most important test because it is a reconstruction of the Mexican Hat potential itself. The triple Higgs coupling may be measurable at the LHC but the quartic coupling will not be.

I would disagree with that statement. The Copenhagen interpretation is not needed for quantum mechanics. That is why it is an "interpretation". It is used by us to "philosophically make sense" of quantum mechanical predictions. But the predictions would stand without it.

In particle physics the word "particle" really just means a quantized field, so particles never exist in a form that is separate from fields. So I would say that the universe is indeed composed entirely of (quantum) fields. I think the notion of wave particle duality is just confusing to students, and in my opinion shouldn't be taught.

I think something you are missing is that electric charge isn't fundamental. It is a mixture of hypercharge and weak isospin according to [math]Q=I_3+\frac{1}{2}Y[/math] left over after the symmetry breaking. So your charge +2/3 up quark has this value because it has [math]I_3=\frac{1}{2}[/math] and hypercharge [math]Y=\frac{1}{3}[/math]. Similarly the down quark has charge -1/3 because it has [math]I_3=-\frac{1}{2}[/math] and hypercharge [math]Y=\frac{1}{3}[/math]. In contrast the left handed electron has [math]I_3=-\frac{1}{2}[/math] but hypercharge [math]Y=-1[/math], giving charge -1. The neutrino has [math]I_3=\frac{1}{2}[/math] but hypercharge [math]Y=-1[/math], giving charge 0. So hypercharge is more fundamental, and there is a particle that carries only hypercharge: the right handed electron. As I said before, if you are willing to accept an SU(5) GUT model, these hypercharge assignments fall out of the group algebra. I suspect what you want to do though is consider a quark as a bound state of an object carrying only colour and an object carrying only hypercharge. Is this correct? I am afraid this cannot be done since they need to have at least some quantum number in common in order to interact. Otherwise there would be no force that could act on both.

Of course. The only criterion for suggesting something new is the better explanation of data. So if a preon theory for example could explain the masses of the quarks, or the flavour interaction structure, it would have value as a theory to replace the SM. But as I said, none of them so far work convincingly. That is fairly easy to explain with GUT theories (though the explanation I can give has no direct evidence in support of it yet). You could have an SU(5) symmetry at very high energies which is broken by a high energy analogue of the Higgs mechanism. Then the SU(5) breaks fairly neatly into SU(3)xSU(2)xU(1), the gauge group of the Standard Model. The nice thing here is that the representations of SU(5) tell you automatically what the U(1) charges should be after breaking, and consequently the value of the electric charge for each particle. Miraculously, it all falls out beautifully. SO(10) and E6 both work nicely too.

A neutrino may, or may not, be its own antiparticle. This is an interesting question that is currently being tested by Neutrinoless Double Beta Decay experiments. To answer alpha2cen's question. The anti means (mathematically) just take the complex conjugate. So if the particle is represented by a real number, it is its own antiparticle. If it is represented by a complex number, it is not.

People do look for this. In fact, there are a few models about that speculate that the current "fundamental" particles are indeed composite particles, composed of more fundamental things. However, all these theories make predictions that can be tested (as all good theories should) and so far all of them have failed the tests.

The mass is defined by the two-point correlation function. Basically, every theory is described by an equation called a Lagranian. This contains all the information about the theory, including input masses and interactions. It is written in terms of the particle fields and their space-time derivatives. For example, a universe consisting of just one free real scalar particle [math]\phi[/math] with mass [math]m[/math] would be: [math] L = \frac{1}{2} (\partial_\mu \phi \partial^\mu \phi - m^2 \phi^2 ) [/math] Notice that the second term contains the mass. A "mass term" is a term which contains exactly two powers of the field. Basically, when you quantise the fields, each [math]\phi[/math] will be linear in both creation and annihilation operators, so each [math]\phi[/math] can create or destroy exactly one particle. Therefore a [math]\phi^2[/math] can create a particle at one point and destroy it at another, so tells you how the particle freely moves through space. The coefficient of this term is either the mass squared, for a boson, or the mass itself, for a fermion. The corresponding term for a fermion would be [math] m \bar \psi \psi[/math] (in this case the fermion field is [math]\psi[/math]). Part of the problem is that terms like this would violate the electroweak symmetry. This is because the mass term mixes the left and right handed fields, while the weak force only wants to play with left handed particles. (You can see this quite physically - a left handed particle is one which has spin in the opposite direction from the direction it is travelling. But a massive particle travels slower than light, so I can switch it from left to right handed by overtaking it. Left and right handedness become frame dependent, but how can a force act on the particle in one frame but not in another?) So instead (and I am simplifying a bit here) you could write a term [math]\lambda \phi \bar \psi \psi[/math] which is an interaction of a boson with a fermion (now since each field creates or annihilates one particle, this term includes things like a fermion emitting a boson, or a boson turning into two fermions. The [math]\phi[/math] is (the analogue of) the Higgs field (in this toy example). [math]\lambda[/math] is just a coefficient (called the Yukawa coupling) which is a property of the fermion. Now, if the lowest energy state of the system is for when the Higgs field has a non-zero value, the universe will oscillate about this value, and we should re-express the Higgs field to remove the constant piece. So write [math] \phi = \langle \phi \rangle + h[/math] where [math]\langle \phi \rangle[/math] is a constant which is the value of the Higgs field in the lowest energy configuration. In other words, we expand around this point rather than around zero. Then the interaction I wrote above becomes: [math]\lambda \phi \bar \psi \psi = \lambda \langle \phi \rangle \bar \psi \psi + \lambda h \bar \psi \psi[/math] The first term is now a mass for the fermion, because it contains only two fields ([math]\langle \phi \rangle[/math] is just a constant) and the mass is [math]m=\lambda \langle \phi \rangle[/math]. The second term is an interaction between the Higgs boson and the fermion, and notice that, since [math]\langle \phi \rangle[/math] is the same for all fermions, the mass and the interaction coupling are proportional to one another. Did this answer the initial question? To answer the last question in the OP, the SM Higgs can't be used as the inflaton, since it has the wrong properties, but you can insert another scalar into the theory, which is also a Higgs boson (sort of) which can be used as the inflaton.

In the UK there is a 4 year deadline imposed on Research Council funded PhDs. If the student goes over the 4 years, his or her supervisor will be penalized in the next funding round.

Why? It is not so ludicrous to suspect that there is substructure to quarks.

If the dyson sphere were the same mass as the star (but negative) it would exactly cancel, so the combined object would have no gravitational attraction.

To start with I didn't get offered any postdocs at all. Then, during the summer, someone pulled out of a (rather good) postdoc job, and they needed a replacement quickly. I was just at the right place at the right time. In other words, just like in every other walk of life, whether you are successful or not is largely random.

I got the first faculty position I applied for.

These is one coming on in the new year hosted by Brian Cox and Dara O'Brian, but I have forgotten the name. Edit: Found it. It is called Stargazing Live http://www.bbc.co.uk/programmes/b00wnvpf

The short answer is, no-one has any idea. Anyone who says they do, is just guessing.

We would see a resonance in a decay channel. This tells us that there is definitely a particle there, of a particular mass, that couples to the same particle we expect the Higgs to couple to. But of course that doesn't mean that it is the Higgs. To really prove that, we will have to measure its spin (we have never seen a fundamental particle with no spin before) and all its couplings. Crucially, the Higgs self coupling will allow us to experimentally map the shape of the Higgs potential (the Mexican hat), but that is really way beyond the LHC's capabilities.