Recent content by Jezza

As an update, I've found a different crystallography book (Space groups for solid state scientists by Glazer and Burns - highly recommended) which explains things a lot more clearly than the one I was reading which, as you can probably tell, I found extremely confusing.

Are you sure about this? What happens to f at T=0?

I'm revising for my condensed matter exam, and I've never understood the point group notation, in particular of the 32 crystallographic point groups, so let me try and explain what I understand of it and point out where my confusion lies. Please point out any other misunderstandings I have. We...

I have to sit an exam on non linear dynamical systems in a couple of weeks. Something that's been asked in the past is to name physical examples of different types of bifurcation. I've consulted Strogatz's book and the internet to try and find some, but I can't seem to find many (or even any)...

Hmm... I've been viewing this 'coupling' as the probability amplitude of a quantum superposition. That is the W decays (for example) into an u and an anti-d', where d' is a superposition of the d, s and b with mostly d, some s and a small amount of b. For us to not get any events with a b...

We've recently been looking at the hadronic decays of the W boson. In this one example, we looked at possible decays for the W boson being produced near its resonance peak, meaning the centre of mass energy is sufficient to produce u,d,c,s & b quarks. However, because we're below the mass of...

As a physics undergrad, a set of natural units is nothing strange to me, we use them all the time. Having said this, I've never used Planck units. Does any area of research use them on a typical day in the office? There also seems to be this idea that I hear from time to time, perpetuated by...

So is it divided up differently for less massive particles?

My textbook "The physics of quantum mechanics" by James Binney and David Skinner, describes the pseudo-vector operators \vec{J}, \vec{L} & \vec{S} as generators of various transformations of the system. \vec{J} is the generator of rotations of the system as a whole, \vec{L} is the generator of...

The book does indeed have a very clear explanation. Thank you very much :)

Thanks for the recommendation, our library has it so I'll go and have a look.

I've never understood Clebsch-Gordan coefficients, but I've never thought of them as simply the coefficients in a basis transformation, so thanks for this. I'll go away and read about them again and hopefully they'll make much more sense to me!

I suppose what I meant by this is one cannot deduce it's value merely from its being in an eigenstate of J^2, L^2, S^2. Is that fair to say? But thank you everyone I think this makes a lot more sense now. I think, then, the short answer is |l-s| \leq j \leq l+s.

There are two types of angular momentum: orbital and spin. If we define their operators as pseudo-vectors \vec{L} and \vec{S}, then we can also define the total angular momentum operator \vec{J} = \vec{L}+\vec{S}. Standard commutation relations will show that we can have simultaneous well...

Thank you for all the responses! I think I'm beginning to see what's going on. The first place I read about it considers paths where |\vec{r}| is kept constant, so that paths lie on a sphere (or circle in 2D) (A similar explanation is here - pg6 onwards: https://arxiv.org/abs/hep-th/9209066)...