Inflationary gravitational waves from unified spinor fields Luis Santiago Ridao, Marcos R. A. Arcodía, Jesús Martín Romero and Mauricio Bellini Eur. Phys. J. Plus, 133 12 (2018) 507 Published online: 11 December 2018 DOI: 10.1140/epjp/i2018-12337-x