Ehrenfest had recommended Struik and, after worrying about leaving a teaching post he enjoyed, he decided to accept Schouten 's offer and joined him in Delft. Struik decided to change to the topic he was studying with Schouten, tensor analysis, for his doctoral thesis and he presented his dissertation on applications of tensor methods to Riemannian manifolds in 1922.
Ehrenfest had inirerekomenda Struik at, matapos ang nababahala tungkol sa pagtuturo-alis ng isang post siya masaya, siya ay nagpasya na tanggapin Schouten 's nag-aalok at sumali sa kanya sa Delft. Struik nagpasya na palitan sa ang paksa niya ay pag-aaral na may Schouten, tensor analysis, para sa kanyang tesis ng doktor at ipinapahayag niya ang kanyang disertasyon sa mga aplikasyon ng tensor pamamaraan upang Riemannian manifolds sa 1922.