On the spaces of $(d+d^c)$-harmonic forms and $(d+d^{\mathrm{\Lambda }})$-harmonic forms on almost Hermitian manifolds and complex surfaces

We study the spaces of $(d+d^c)$-harmonic forms and $(d+d^{\mathrm{\Lambda }})$-harmonic forms, the natural generalization of the spaces of Bott-Chern harmonic forms, resp. symplectic harmonic forms from complex, resp. symplectic, manifolds to almost Hermitian manifolds. With the same techniques, we also prove that Bott-Chern and Aeppli numbers of compact complex surfaces depend only on the topology of the underlying manifold, a fact that was well-known for Hodge numbers of compact complex surfaces. We give several applications to compact quotients of Lie groups by a lattice.