General Variational Formulas for Abelian Differentials

We use the jump problem technique developed in a recent paper [9] to compute the variational formula of any stable differential and its periods to arbitrary precision in plumbing coordinates. In particular, we give the explicit variational formula for the degeneration of the period matrix, easily reproving the results of Yamada [21] for nodal curves with one node and extending them to an arbitrary stable curve. Concrete examples are included. We also apply the same technique to give an alternative proof of the sufficiency part of the theorem in [1] on the closures of strata of differentials with prescribed multiplicities of zeroes and poles.

Blobbed topological recursion: properties and applications

We study the set of solutions (ωg,n)g⩾0,n⩾1 of abstract loop equations. We prove that ωg,n is determined by its purely holomorphic part: this results in a decomposition that we call “blobbed topological recursion”. This is a generalisation of the theory of the topological recursion, in which the initial data (ω0,1, ω0,2) is enriched by non-zero symmetric holomorphic forms in n variables (φg,n)2g−2+n>0. In particular, we establish for any solution of abstract loop equations: (1) a graphical representation of ωg,n in terms of φg,n; (2) a graphical representation of ωg,n in terms of intersection numbers on the moduli space of curves; (3) variational formulas under infinitesimal transformation of φg,n; (4) a definition for the free energies ωg,0 = Fg respecting the variational formulas. We discuss in detail the application to the multi-trace matrix model and enumeration of stuffed maps.

Discrete Hardy-type Inequalities

This paper studies the Hardy-type inequalities on the discrete intervals. Firstly, two variational formulas for the optimal constants are introduced. Based on these formulas, an approximating procedure and the known basic estimates of the optimal constants are deduced. Thirdly, as the main innovation of this paper, an improved factor for the upper estimates is presented, which is smaller than the known one and is the best possible. Finally, some comparison results are included for comparing the optimal constants on different intervals.