Boltzmann factor

The Boltzmann factor of any energy $U$ is defined by the negative exponential of the ratio of the energy to the thermal energy Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle kT} :

$f(U)=\exp \left(-{\frac {U}{k_{B}T}}\right)$