Homotopies for Lagrangian field theory

Abstract: Consider the variational bicomplex for $\mathcal{E}$ the space of sections of a graded, affine bundle. Local functionals $\mathcal{F}$ are defined as an equivalence class of density-valued functionals, which represent Lagrangian densities. A choice of a $k$-symplectic local form $\omega$ on $\mathcal{E}$ induces a Lie$[k]$ algebra structure on (Hamiltonian) local functionals $(\mathcal{F}{\mathrm{ham}},{\cdot,\cdot}{\mathrm{ham}})$. For any $\omega$ and any choice of a cohomological vector field $Q$ compatible with $\omega$, we build an explicit $L_\infty$ algebra on a resolution of $\mathcal{F}{\mathrm{ham}}$, which is $L\infty$ quasi-isomorphic to a dgL$[k]$a $(\mathcal{F}{\mathrm{ham}},d{\mathrm{ham}},{\cdot,\cdot}{\mathrm{ham}})$. In the case $k=-1$, this provides an explicit lift of the standard Batalin--Vilkovisky framework to local forms enriched by the $L\infty$ structure, in terms of local homotopies. We further provide a multisymplectic interpretation of the resulting data.