Abstract
In the previous chapter, we discuss general soft matter using the theory and method developed for solving soft-matter quasicrystals, where we emphasized one must consider the structure of concrete soft matter. In this chapter, we study a concrete soft matter, i.e., the smectic A liquid crystal and its dislocation and crack problem. These are interesting topics in soft matter. Apart from this, we hope to explore a longstanding puzzle, perhaps a paradox. The solution to the paradox may yield some beneficial results and lessons.