In this article, we introduce a new approach to obtain the property of the dissipative structure for a system of differential equations. If the system has a viscosity or relaxation term which possesses symmetric property, Shizuta and Kawashima in 1985 introduced the suitable stability condition called in this article Classical Stability Condition for the corresponding eigenvalue problem of the system, and derived the detailed relation between the coefficient matrices of the system and the eigenvalues. However, there are some complicated physical models which possess a non-symmetric viscosity or relaxation term and we cannot apply Classical Stability Condition to these models. Under this situation, our purpose in this article is to extend Classical Stability Condition for complicated models and to make the relation between the coefficient matrices and the corresponding eigenvalues clear. Furthermore, we shall explain the new dissipative structure through the several concrete examples.
Condition (A):A 0 is real symmetric and positive definite, A j (1 ≤ j ≤ n) are real symmetric, while B(ω) and L are not necessarily real symmetric but B(ω) and L are non-negative definite with the non-trivial kernel for each ω ∈ S n−1 . Namely, Condition (A) means that the constant matrices satisfy the followings.for each ω ∈ S n−1 . Here and in the sequel, the superscript T stands for the transposition, and X and X denote the symmetric and skew-symmetric part of the matrix X, respectively. That is X := (X + X T )/2 and X := (X − X T )/2. Furthermore, m × m real matrix X is called positive definite (resp. non-negative definite) on R m if (X ϕ, ϕ) > 0 (resp. (X ϕ, ϕ) ≥ 0) for any ϕ ∈ R m \{0}, where (·, ·) denotes the standard real inner product in R m . Here, we remark that " X is positive definite (resp. non-negative definite) on R m " is equivalent to X ϕ, ϕ > 0 (resp. X ϕ, ϕ ≥ 0) for any ϕ ∈ C m \{0}, and Re Xϕ, ϕ > 0 (resp. Re Xϕ, ϕ ≥ 0) for any ϕ ∈ C m \{0}, where ·, · denotes the standard complex inner product in C m . Furthermore, I and O denote an identity matrix and a zero