Chicago Journal of Theoretical Computer Science

Volume 2025

Article 1

Published by the Department of Computer Science, The University of Chicago.


On Lifting Lower Bounds for Noncommutative Circuits using Automata

V. Arvind
The Institute of Mathematical Sciences, Chennai
Chennai, India
arvind AT imsc DOT res DOT in

and

Abhranil Chatterjee
Department of Computer Science and Engineering
Indian Institute of Technology Kanpur
Kanpur, India
abhranil AT cse DOT iitk DOT ac DOT in

April 14, 2025

Abstract

We revisit the main result of Carmosino et al [CILM18] which shows that an $\Omega(n^{\omega/2+\gamma})$ size noncommutative arithmetic circuit size lower bound (where $\omega$ is the matrix multiplication exponent) for a constant-degree $n$-variate polynomial family $(g_n)_n$, where each $g_n$ is a noncommutative polynomial, can be ``lifted'' to an exponential size circuit size lower bound for another polynomial family $(f_n)$ obtained from $(g_n)$ by a lifting process. In this paper, we present a simpler and more conceptual automata-theoretic proof of their result.


Submitted December 3, 2023, revised February 15, 2025, published April 14, 2025.

DOI: 10.4086/cjtcs.2025.001


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