# Ecuación de Christoffel

${\displaystyle \kappa \left(\gamma {\textbf {C}}\gamma ^{T}\right){\textbf {u}}=\rho \omega ^{2}{\textbf {u}}}$,
where ${\displaystyle \kappa }$ is wavenumber, ${\displaystyle \gamma }$ is the direction cosine matrix, C is the stiffness tensor, u the particle displacement vector, ${\displaystyle \rho }$ the density, and ${\displaystyle \omega }$ the angular frequency. The quantity in parentheses is called the Christoffel matrix.