We present a family of conjectural relations in the tautological ring of
the moduli spaces of stable curves which implies the strong double
ramification/Dubrovin–Zhang equivalence conjecture introduced by the authors with
Dubrovin (Comm. Math. Phys. 363 (2018) 191–260). Our tautological relations have
the form of an equality between two different families of tautological classes, only one
of which involves the double ramification cycle. We prove that both families behave
the same way upon pullback and pushforward with respect to forgetting a
marked point. We also prove that our conjectural relations are true in genus
and
and also when first
pushed forward from
to and then
restricted to
for any
.
Finally we show that, for semisimple CohFTs, the DR/DZ equivalence only
depends on a subset of our relations, finite in each genus, which we prove for
.
As an application we find a new formula for the class
as a
linear combination of dual trees intersected with kappa- and psi-classes, and we check
it for
.
Keywords
moduli space of curves, cohomology, double ramification
cycle, partial differential equations