Thermodynamics Relevance to String Theory, Advice Please help me make a very important decision! I only need to hear a bit from a String Theorist or Quantum Field Theorist (or anyone close to such people and areas of research) to tell me about how relevant thermodynamics as a second year module will be for a String Theory career path. Is it one of those you-only-need-a-basic-understanding-and-so-you-can-pick-it-up-later-or-maybe-even-forget-it-and-never-need-it subject to String Theory? I have a strong feeling I will not need it OR IF I DO it would probably only be 5% like what heat and temperature is, the laws of thermodynamics, entropy and that's it. I can't imagine needing to know about the ideal gas equation (and if I do it will be something I could pick up whilst doing a PhD in String Theory). I know for a fact that I will need things like EMF, relativity, quantum mechanics, QFT and so on but thermodynamics, as I already, is probably something I will forget about from the time I do it (second year BSc) all the way to the time I begin String Theory (PhD). Also, yes, my university does teach String Theory at PhD level and even offers it at an introductory level at MSc.
 A: This seems like a strange question, unless I've misunderstood, as you're asking more about university module advice as opposed to a more general question about thermodynamics & string theory (as the title implies)? It'd be helpful to know if you're asking whether you should pick it over a different module, or just whether you can not study very hard in it, or something different?
Regardless, working in/on string theory is a much wider field than just a few specific research topics, and there are undoubtedly many areas where thermodynamics is not just necessary but integral to the work. Just look at the whole field of black hole thermodynamics in string theory for example. Similarly, there are many areas where it won't be directly useful and will have little impact on the majority of the work done. Overall I'd definitely say that thermodynamics in general, encompassing such a large amount of physics, plays a big enough role in string theory/quantum gravity that it shouldn't be discounted as being irrelevant or not useful for those topics.
However, in 2nd year of undergrad your modules should be based around your general (theoretical) physics knowledge, not just what you presume will be useful for a potential PhD.
