Cheat sheets/Statistical mechanics

Statistical mechanics is a branch of mathematical physics that studies, using probability theory, the average behaviour of a mechanical system where the state of the system is uncertain. A common use of statistical mechanics is in explaining the thermodynamic behaviour of large systems.

Thermal wavelength

$\lambda ={\frac {h}{\sqrt {2\pi mk_{B}T}}}=h{\sqrt {\frac {\beta }{2\pi m}}}=\hbar {\sqrt {\frac {2\pi \beta }{m}}}$

${1 \over \lambda }={\frac {\sqrt {2\pi mk_{B}T}}{h}}$

Partition function

Canonical: (in 3d)

$Z=\int \prod _{i=1}^{N}{\frac {d^{3}q_{i}d^{3}p_{i}}{h^{3}}}e^{-\beta {\frac {p_{i}^{2}}{2m}}}e^{-\beta U(q_{i})}=\int \prod _{i=1}^{N}{\frac {d^{3}q_{i}d^{3}p_{i}}{h^{3}}}e^{-\beta H}$

See Also

• School of Physics
• Thermodynamics

1. Classical thermodynamics
2. Statistical thermodynamics
3. Heat transfer