  In this paper, we discuss a general framework for multicontinuum
homogenization. Multicontinuum models are widely used in many applications and
some derivations for these models are established. In these models, several
macroscopic variables at each macroscale point are defined and the resulting
multicontinuum equations are formulated. In this paper, we propose a general
formulation and associated ingredients that allow performing multicontinuum
homogenization. Our derivation consists of several main parts. In the first
part, we propose a general expansion, where the solution is expressed via the
product of multiple macro variables and associated cell problems. The second
part consists of formulating the cell problems. The cell problems are
formulated as saddle point problems with constraints for each continua.
Defining the continua via test functions, we set the constraints as an integral
representation. Finally, substituting the expansion to the original system, we
obtain multicontinuum systems. We present an application to the mixed
formulation of elliptic equations. This is a challenging system as the system
does not have symmetry. We discuss the local problems and various macroscale
representations for the solution and its gradient. Using various order
approximations, one can obtain different systems of equations. We discuss the
applicability of multicontinuum homogenization and relate this to high contrast
in the cell problem. Numerical results are presented.
