Topos Mediated Gravity: Toward the Categorical Resolution of the   Cosmological Constant Problem
  According to D\"oring and Isham the spectral topos corresponds to any quantum system. The description of a system in the topos becomes similar to this given by classical theory, up to multiplication of observables. Logic of the emergent theory is rather intuitionistic than classical. Adding to the language the type of self-adjoint operators and their products, which are interpreted by the on-stages daseinisations and their products, one gets commuting presheaves in the topos. The interpretation agrees with on-stages daseinisations of squares up to some automorphisms of the topos. The uncertainty principle does not hold for such an interpretation. According to the recent proposition by the author, topoi can modify local smooth spacetime structure. A way how to add gravity into the spectral topos of a system is presented. Assuming that a quantum system modifies the local spacetime structure and interacts with a gravitational field via the spectral topos, the lowest energy modes of a quantum harmonic oscillator are gravitationally nullified. Moreover, a theory of gravity and systems should be symmetric with respect to the 2-group of automorphisms of the category of topoi. Under the $\delta_0$-interpretation for the hamiltonian of a quantum harmonic oscillator, its lowest modes have vanishing contributions to the cosmological constant. This is related with a fundamental higher symmetry group of gravity. Without the $\delta_0$-interpretation, small non-zero value of the effective cosmological constant can be approached. 
Jerzy Kr\'ol