這篇論文中我們將要比較下列三個方程式：線性熱方程，雙曲型p方程組，和黏滯性p方程組。我們討論的重點在於這些方程式之解的基本性質，特別是其正則性，長時間行為，以及遞減速度。除此之外，我們也重新整理解釋與這三個方程相關的一些重要結果。

　In this paper we will compare the following three partial differential equations: the linear heat equation, hyperbolic p-system and viscous p-system. The main point of the argument lies in the fundamental properties of solutions for these equations, especially their regularity, large-time behaviors and decay rates. In addition, we also review and interpret some important results related to the three equations.

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