Kummer’s theorem in MathComp

1.1 Prime and p-adic valuation

Definition 1.1 p-adic valuation
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For a prime \(p\) and a natural number \(m\), \(\operatorname {logn}(p, m)\) is the largest \(k\) such that \(p^k\) divides \(m\). In MathComp this is logn p m.

Definition 1.2 Truncated logarithm
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For \(p \geq 2\) and \(n \in \mathbb {N}\), \(\texttt{trunc\_ log}(p, n)\) is the largest \(k\) such that \(p^k \leq n\).

Lemma 1.3 Multiplicativity of logn
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For prime \(p\) and \(m, n {\gt} 0\),

\[ \operatorname {logn}(p, m \cdot n) = \operatorname {logn}(p, m) + \operatorname {logn}(p, n). \]

Lemma 1.4 logn of prime powers
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For prime \(p\),

\[ \operatorname {logn}(p, p^n) = n. \]

Lemma 1.5 Truncated log bounds

For \(p \geq 2\) and \(n {\gt} 0\),

\[ p^{\texttt{trunc\_ log}(p, n)} \leq n {\lt} p^{\texttt{trunc\_ log}(p, n) + 1}. \]

Lemma 1.6 Truncated log upper bound
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For \(p \geq 2\) and \(n {\gt} 0\),

\[ n {\lt} p^{\texttt{trunc\_ log}(p, n) + 1}. \]