In mathematics, physics, mechanics and the like, one encounters eigen as a prefix in eigenvalues and eigenvectors, as well as in eigenstrain and eigenstress. The word comes from German and means “own” or “intrinsic”. In the English scientific literature eigen is widely accepted and commonly employed.
Have the terms eigenvecteur and eigenvaleurs ever been used in French (even as neologisms)? Is their use in French acceptable (university level and higher) nowadays (in place of the adjective propre; that is, "valeurs propres, vecteurs propres")?
In that case the diphthong ei should be pronounced as in German (aï) ?
If its use isn't acceptable, what reasons could explain why eigen was not introduced in French?