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ON A PROBABILISTIC ITERATED FACTOR METHOD

2025, ON A PROBABILISTIC ITERATED FACTOR METHOD

Abstract

We introduce a probabilistic version of the iterated factor method introduced in our previous investigations. Let $n$ be drawn uniformly from $\{1,2,\ldots,M\}$. Set $$s:=s(n)=\left \lfloor \frac{\sqrt{\log_2n}}{\log \log_2n} \right\rfloor \quad \textbf{and} \quad t(n)=\sqrt{\log \log n}$$ and $$k_n=\left \lfloor \frac{n}{2}\right \rfloor_s.$$ Then as $N\longrightarrow \infty$ with $Z_n\sim N(0,1)$~(normally distributed) and additionally that $$\mathrm{Pr}[\nu(k_n)\leq s \quad \mathbf{and} \quad |Z_n|\leq t]\longrightarrow 1$$ we show that inequality $$\iota(2^n-1)\leq n-1+\log_2n+C\sqrt{\frac{\log_2n}{\log \log_2n}}$$ for some absolute constant $C>0$. This breaks the $O(\frac{\log n}{\log \log n})$ barrier that is guaranteed to be achieved using the Brauer method \cite{brauer1939addition}. This result can be seen as injecting probabilistic methods into the theory of addition chains.

References (1)

  1. A. Brauer, On addition chains, Bulletin of the American mathematical Society, vol. 45:10, 1939, 736-739.