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Electronic Colloquium on Computational Complexity

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REPORTS > AUTHORS > NIKOLAI CHUKHIN:
All reports by Author Nikolai Chukhin:

TR26-157 | 27th August 2026
Nikolai Chukhin, Alexander Kulikov, Ivan Mihajlin, Alexander Smal

A Tight Cycle-Cover Inequality for Shortest Common Superstring

In the Shortest Common Superstring problem (SCS), one is given a finite set of strings and is asked to find a shortest string containing every input string as a substring. Its best known approximation ratio is $2.466$, whereas the currently strongest upper bound on the approximation guarantee of the maximum-overlap ... more >>>


TR26-135 | 7th August 2026
Nikolai Chukhin, Alexander Kulikov, Maksim Levitskii, Ivan Mihajlin

Quantum Algorithms for Subset SUM and $k$-SUM: Faster and Simpler

The Subset Sum problem asks whether, given $n$ integers and a target, some subset of the integers sums to the target. Its best known worst-case running time is $O^*(2^{n/2})$ (Horowitz and Sahni, 1974), whereas the best quantum upper bound is $O^*(2^{n/3})$ (Bernstein, Jeffery, Lange, and Meurer, 2013). The $k$-SUM problem ... more >>>


TR26-122 | 10th July 2026
Grigorii Braulov, Nikolai Chukhin, Alexander Kulikov, Ivan Mihajlin

Complexity of the Graph Homomorphism Problem w.r.t. Degeneracy

The graph homomorphism problem HOM is: given an $n$-vertex source graph $G$ and an $h$-vertex target graph $H$, is there a mapping from $V(G)$ to $V(H)$ that preserves edges? A straightforward brute-force algorithm for HOM has running time $O(2^{n \log h})$ and it is known that, under ETH, there are ... more >>>


TR26-041 | 18th March 2026
Nikolai Chukhin

A Note on Conditional Complexity Hardness of Matrix Rigidity and Tensor Rank

Recently, together with Kulikov, Mihajlin, and Smirnova (STACS 2026), we gave conditional constructions of functions with large monotone circuit complexity, matrices with high rigidity, and $3$-dimensional tensors of strongly superlinear rank.
In this note, I strengthen the rigidity construction under the same assumption and, as a direct consequence, immediately obtain ... more >>>


TR25-038 | 4th April 2025
Nikolai Chukhin, Alexander Kulikov, Ivan Mihajlin, Arina Smirnova

Conditional Complexity Hardness: Monotone Circuit Size, Matrix Rigidity, and Tensor Rank Under NSETH and Beyond

Revisions: 3

Proving complexity lower bounds remains a challenging task: currently, we only know how to prove conditional uniform (algorithm) lower bounds and nonuniform (circuit) lower bounds in restricted circuit models. About a decade ago, Williams (STOC 2010) showed how to derive nonuniform lower bounds from uniform upper bounds: roughly, by designing ... more >>>




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