In 1923, Steinmetz would publish Four Lectures on Relativity and Space. Around 1924, Jan Arnoldus Schouten would develop the modern notation and formalism for the Ricci calculus framework during the absolute differential calculus applications to general relativity and differential geometry in the early twentieth century. In 1925, Enrico Fermi would describe a system comprising many identical particles that obey the Pauli exclusion principle, afterwards developing a diffusion equation (Fermi age equation).
In 1923, Steinmetz published "Four Lectures on Relativity and Space." Around 1924, Schouten developed the modern notation for Ricci calculus within the context of absolute differential calculus applications to general relativity and differential geometry in the early twentieth century. In 1925, Fermi described a system with identical particles obeying the Pauli exclusion principle, which he later used to develop a diffusion equation (Fermi age equation).