Isomonodromic Deformations Along the Caustic of a Dubrovin–Frobenius Manifold

We study the family of ordinary differential equations associated to a Dubrovin–Frobenius manifold along its caustic. Upon just loosing an idempotent at the caustic and under a non-degeneracy condition, we write down a normal form for this family and prove that the corresponding fundamental matrix solutions are strongly isomonodromic. It is shown that the exponent of formal monodromy is related to the multiplication structure of the Dubrovin–Frobenius manifold along its caustic.