1, the amplitude function is a function in which the partial derivative of any multiple exponent satisfies some inequality, and it often takes the form of asymptotic expansion.

2. The class of amplitude function was first proposed by L.V.. Historically, the most classic kind of amplitude function is this, in which the function a(x, θ)∈C∞(X×RN) is m-th homogeneous with respect to θ (it obviously belongs to. ) and Helmand's introduction to the above, its main feature is to replace homogeneity with differential inequality.