The Subspace Flatness Conjecture and Faster Integer Programming


Thomas Rothvoss


Michael Goemans
Abstract (in latex):
In a seminal paper, Kannan and Lov\'asz (1988) considered a quantity $\mu_{KL}(\Lambda,K)$
which denotes the best volume-based lower bound on the \emph{covering radius} $\mu(\Lambda,K)$ of a convex
body $K$ with respect to a lattice $\Lambda$. Kannan and Lov\'asz proved that $\mu(\Lambda,K) \leq n \cdot \mu_{KL}(\Lambda,K)$ and the Subspace Flatness Conjecture by Dadush (2012) claims a $O(\log n)$ factor suffices, which would match
the lower bound from the work of Kannan and Lov\'asz.
We settle this conjecture up to a constant in the exponent by proving that $\mu(\Lambda,K) \leq O(\log^{3}(n)) \cdot \mu_{KL} (\Lambda,K)$. Our proof is
based on the Reverse Minkowski Theorem due to Regev and Stephens-Davidowitz (2017).
Following the work of Dadush (2012, 2019), we obtain a $(\log n)^{O(n)}$-time randomized algorithm to
solve integer programs in $n$ variables.
Another implication of our main result is a near-optimal \emph{flatness constant} of $O(n \log^{3}(n))$.

This is joint work with Victor Reis.