Tower (mathematics)

In category theory, a branch of abstract mathematics, a tower is defined as follows. Let ${\displaystyle {\mathcal {I}}}$ be the poset

of whole numbers in reverse order, regarded as a category. A (countable) tower of objects in a category ${\displaystyle {\mathcal {A}}}$ is a functor from ${\displaystyle {\mathcal {I}}}$ to ${\displaystyle {\mathcal {A}}}$.

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