# Statistical Physics vs QFT vs General relativity

• Courses
• Strohmann
So, the advice I was trying to give is that if you are not interested in QFT or GR, then you can probably get away with not taking them. However, if you are thinking about doing a PHD in physics, and you want to specialize in one of these fields, then you should probably take one of the courses.f

#### Strohmann

Good day,

I'm starting my master in physics, and it's time for me to choose my courses.
I will take one or two of the following three courses, which are: Statistical Physics, QFT and General relativity.

Now, I'm finding it very hard to decide as on the one hand, I'm interested in QFT and General relativity. I can also not imagine a physics phd that has never heard about QFT and General relativity?
On the other hand, statistical phyiscs seems to be quite important for most research areas. Especially if I'm not planning to go into the field of particle physics. Is that correct? Or am I completely fine in most phd programs if I never heard a course in stat physics?

Now I've already done some StatMech in my Bachelors degree, but definitely not as advanced as will be treated here. I know about Fermi Dirac and Bose Einstein, and the different canonical ensembles, but that's about it.

As for the actual contents of the courses:

Statistical Physics
Basics of phenomenological thermodynamics, three laws of thermodynamics.
Basics of kinetic gas theory: conservation laws, H-theorem, Boltzmann-Equations, Maxwell distribution.
Classical statistical physics: microcanonical ensembles, canonical ensembles and grandcanonical ensembles, applications to simple systems.
Quantum statistical physics: single particle, ideal quantum gases, fermions and bosons.
Bose-Einstein condensation: Bogolyubov theory, superfluidity.
Mean field and Landau theory: Ising model, Heisenberg model, Landau theory of phase transitions, fluctuations.
Critical phenomena: mean field, series expansions, scaling behavior, universality.
Renormalization group: fixed points, simple models.
Linear response theory: general formulation, response in mean field, sum rules, collective modes, fluctuation dissipation theorem.

QFT I:
This course discusses the quantisation of fields in order to introduce a coherent formalism for the combination of quantum mechanics and special relativity.
Topics include:
- Relativistic quantum mechanics
- Quantisation of bosonic and fermionic fields
- Interactions in perturbation theory
- Scattering processes and decays

I can realistically take like one or two of the three courses. I might also be able to take the other course a year from now, although I'm not sure if that'll work out. If I left out anything important, please let me know!

I guess programs differs a lot from place to place, but where I did my master statmechanics is mandatory.

If you have to choose, then go for whatever is closer to your planned research area.

Strohmann
I'd say that if you plan to do high energy physics, I would go for QFT/GR. I had a lousy course on stat.mech. and I didn't loose much because of that in my PhD.

Strohmann
I guess programs differs a lot from place to place, but where I did my master statmechanics is mandatory.

If you have to choose, then go for whatever is closer to your planned research area.
That would be quantum optics

That would be quantum optics

I don't know much of quantum optics, but I doubt it is closely related to general relativity (unless you go for quantum optics in curved spacetime or something exotic like that).

So, I guess QFT, specially QED is the way to go for you.

Strohmann
Have you taken your qualifiers or candidacy exams. Usually Stat Mech is a core component of the exam. Also if you are going to be in the program for a few more years, you can take QFT or GR later. Because you are starting your masters, I think stat mech would be higher priority than the others.

Quantum Optics is pretty far removed from GR. I examined some quantum optics treatments and they have their own way of treating QFT (and this is by no means lesser than, but it is alternative to), than the conventional treatment you get in QFT. To get an idea of these differences, you can look at the prefaces in the textbooks.

For example a QFT course that emphasizes meson theory is less applicable to quantum optics than one that emphasizes atoms and photons.

As far as researchers with a doctorate that I know about. I would say 1 in 10 to 1 in 5 have never had a course in general relativity. Sometimes GR is taught alternative years. My research advisor suggested electives that were more useful directly to our research area.
Or am I completely fine in most phd programs if I never heard a course in stat physics?

1 in 5 to 1 in 3 have never had a course in QFT. Every researcher I know of had a graduate course in statistical mechanics, without exception.

PhDeezNutz and Strohmann
Correction to my earlier post. I said never rather than ever. Even if my grammar was wrong, the point I am trying to make is Stat Mech among physics PHD's was universal. physics PHD's with General relativity and QFT courses were (at best) in the minority. (i.e. < 50 %). I think the reason for this is not lack of interest. Almost everybody wants to learn these exciting fields. On the other hand research advisors are less happy to fund courses that distract from their own research areas. They want grad students to hit the ground running and obtain research results.

Strohmann