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DOI: 10.4230/LIPIcs.CCC.2026.11

Beyond Bilinear Complexity: What Works and What Breaks with Many Modes?

Authors: Cornelius Brand, Radu Curticapean, Petteri Kaski, Baitian Li, Ian Orzel, Tim Seppelt, and Jiaheng Wang

Published in: LIPIcs, Volume 383, 41st Computational Complexity Conference (CCC 2026)

Abstract

The complexity of bilinear maps (equivalently, of 3-mode tensors) has been studied extensively, most notably in the context of matrix multiplication. While circuit complexity and tensor rank coincide asymptotically for 3-mode tensors, this correspondence breaks down for d ≥ 4 modes. As a result, the complexity of d-mode tensors for larger fixed d remains poorly understood, despite its relevance, e.g., in fine-grained complexity. Our paper explores this intermediate regime. First, we give a "graph-theoretic" proof of Strassen’s 2ω/3 bound on the asymptotic rank exponent of 3-mode tensors. Our proof directly generalizes to an upper bound of (d-1)ω/3 for d-mode tensors. Using refined techniques available only for d ≥ 4 modes, we improve this bound beyond the current state of the art for ω. We also obtain a bound of d/2+1 on the asymptotic exponent of circuit complexity of generic d-mode tensors and optimized bounds for d ∈ {4,5}. To the best of our knowledge, asymptotic circuit complexity (rather than rank) of tensors has not been studied before. To obtain a robust theory, we first ask whether low complexity of T and U imply low complexity of their Kronecker product T ⊗ U. While this crucially holds for rank (and thus for circuit complexity in 3 modes), we show that assumptions from fine-grained complexity rule out such a submultiplicativity for the circuit complexity of tensors with many modes. In particular, assuming the Hyperclique Conjecture, this failure occurs already for d = 8 modes. Nevertheless, we can salvage a restricted notion of submultiplicativity. From a technical perspective, our proofs heavily make use of the graph tensors T_H, as employed by Christandl and Zuiddam (Comput. Complexity 28 (2019) 27-56) and Christandl, Vrana and Zuiddam (Comput. Complexity 28 (2019) 57-111), whose modes correspond to the vertices of undirected graphs H. We make the simple but conceptually crucial observation that Kronecker products T_G ⊗ T_H are isomorphic to T_{G+H}, and that G and H may also be fractional graphs. By asymptotically converting generic tensors to specific graph tensors, we can use nontrivial results from algorithmic graph theory to study the rank and complexity of d-mode tensors for fixed d.

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Cornelius Brand, Radu Curticapean, Petteri Kaski, Baitian Li, Ian Orzel, Tim Seppelt, and Jiaheng Wang. Beyond Bilinear Complexity: What Works and What Breaks with Many Modes?. In 41st Computational Complexity Conference (CCC 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 383, pp. 11:1-11:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{brand_et_al:LIPIcs.CCC.2026.11,
  author =	{Brand, Cornelius and Curticapean, Radu and Kaski, Petteri and Li, Baitian and Orzel, Ian and Seppelt, Tim and Wang, Jiaheng},
  title =	{{Beyond Bilinear Complexity: What Works and What Breaks with Many Modes?}},
  booktitle =	{41st Computational Complexity Conference (CCC 2026)},
  pages =	{11:1--11:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-437-6},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{383},
  editor =	{Moshkovitz, Dana},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CCC.2026.11},
  URN =		{urn:nbn:de:0030-drops-270530},
  doi =		{10.4230/LIPIcs.CCC.2026.11},
  annote =	{Keywords: arithmetic circuits, tensor rank, bilinear complexity, graph tensors}
}

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DOI: 10.4230/LIPIcs.FSTTCS.2025.47

The Algebraic Cost of a Boolean Sum

Authors: Ian Orzel, Srikanth Srinivasan, Sébastien Tavenas, and Amir Yehudayoff

Published in: LIPIcs, Volume 360, 45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025)

Abstract

It is a well-known fact that the permanent polynomial is complete for the complexity class VNP, and it is largely suspected that the determinant does not share this property, despite its similar expression. We study the question of why the VNP-completeness proof of the permanent fails for the determinant. We isolate three fundamental properties that are sufficient to prove a polynomial sequence is VNP-hard, of which two are shared by both the permanent and the determinant. We proceed to show that the permanent satisfies the third property, which we refer to as the "cost of a boolean sum", while the determinant does not, showcasing the fundamental difference between the polynomial families. We further note that this differentiation also applies in the border complexity setting and that our results apply for counting complexity.

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Ian Orzel, Srikanth Srinivasan, Sébastien Tavenas, and Amir Yehudayoff. The Algebraic Cost of a Boolean Sum. In 45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 360, pp. 47:1-47:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{orzel_et_al:LIPIcs.FSTTCS.2025.47,
  author =	{Orzel, Ian and Srinivasan, Srikanth and Tavenas, S\'{e}bastien and Yehudayoff, Amir},
  title =	{{The Algebraic Cost of a Boolean Sum}},
  booktitle =	{45th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2025)},
  pages =	{47:1--47:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-406-2},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{360},
  editor =	{Aiswarya, C. and Mehta, Ruta and Roy, Subhajit},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2025.47},
  URN =		{urn:nbn:de:0030-drops-251271},
  doi =		{10.4230/LIPIcs.FSTTCS.2025.47},
  annote =	{Keywords: Algebraic Complexity, Computational Complexity, Permanent, Determinant}
}

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Beyond Bilinear Complexity: What Works and What Breaks with Many Modes?

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The Algebraic Cost of a Boolean Sum

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