# QM and Statistical mechanics

At my school, you have to take Quantum mechanics at the same time as Statistical mechanics (co-requisites) in either junior or Senior year as a physics major; why is this?
What is the relationship between the 2?

stevendaryl
Staff Emeritus
They are independent topics, although they can be combined in quantum statistical mechanics. There is also a strange connection between them that Feynman and Hibbs discuss in their book "Quantum mechanics and path integrals": mathematically, the quantum mechanical propagator, which gives the probability amplitude for a particle to go from one point to another as a function of time, is related to the partition function of quantum statistical mechanics, where the inverse temperature ##\beta = \frac{1}{kT}## acts as a kind of imaginary time. That's kind of an advanced topic, and is not usual covered in the first course of statistical mechanics (if ever).

bhobba and SJay16
ZapperZ
Staff Emeritus