Boltzmann factor

The Boltzmann factor of any energy Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle U} is defined by the negative exponential of the ratio of the energy to the thermal energy Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle kT} :

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