Noether symmetries and conserved quantities for fractional Birkhoffian systems with time delay

•The fractional Birkhoffian systems with time delay are studied.•We propose the fractional Pfaff–Birkhoff principle with time delay.•The fractional Birkhoff's equations with time delay are derived.•Noether symmetries and conserved quantities with time delay are discussed.•Some special cases of the results we obtained are discussed.

The Noether symmetries and the conserved quantities for fractional Birkhoffian systems with time delay in terms of Riemann–Liouville fractional derivatives are proposed and studied. First, the fractional Pfaff–Birkhoff principle with time delay is proposed, and the fractional Birkhoff's equations with time delay are obtained. Second, based on the invariance of the fractional Pfaff action with time delay under a group of infinitesimal transformations, the Noether symmetric transformations and the Noether quasi-symmetric transformations of the system are defined, and the criteria of the Noether symmetries are established. Finally, the relationship between the symmetries and the conserved quantities are studied, and the Noether theorems for fractional Birkhoffian systems with time delay are established. Some examples are given to illustrate the application of the results.