Periodic perturbations with delay of coupled differential equations on   manifolds with application to a sunflower-like equation
  We investigate the structure of the set of $T$-periodic solutions to periodically perturbed coupled delay differential equations on differentiable manifolds. By using fixed point index and degree-theoretic methods we prove the existence of branches of $T$-periodic solutions to the considered equations. As main application of our methods, we study a generalized version of the sunflower equation. 
Luca Bisconti, Marco Spadini
math.CA