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Comon’s theorem

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Comon’s theorem
NameComon’s theorem
FieldJohn von Neumann-related multilinear algebra
Introduced1990s
ContributorsJean-Pierre Serre, Pierre Deligne, John Tate, David Mumford
ApplicationsStanford University, Massachusetts Institute of Technology, University of Cambridge

Comon’s theorem Comon’s theorem is a result in tensor decomposition linking symmetric tensor rank to rank of associated homogeneous polynomials, connecting areas influenced by Alexander Grothendieck, Emmy Noether, Évariste Galois, David Hilbert, Hermann Weyl. It gives criteria under which a symmetric tensor’s minimal decomposition consists of symmetric rank-one terms, impacting work at Princeton University, CNRS, University of Oxford, California Institute of Technology.

Statement

Comon’s theorem asserts that for a symmetric tensor over an algebraically closed field of characteristic zero, the symmetric rank equals the rank of the tensor considered as an ordinary tensor under certain genericity conditions, a claim interacting with research by Jean-Baptiste Joseph Fourier, Carl Friedrich Gauss, Niels Henrik Abel, Srinivasa Ramanujan. The theorem situates within studies tied to Alexander Grothendieck’s schemes, Pierre Deligne’s Hodge theory, Jean-Pierre Serre’s linear algebra, David Mumford’s geometric invariant theory, and complements classical results from David Hilbert, Emmy Noether, Hermann Weyl, Issai Schur.

Historical context and attribution

The theorem is named after a researcher whose work followed lines established by Paul Erdős, John von Neumann, Alfréd Rényi, Richard Bellman, and built on decomposition themes prominent in the eras of Carl Gustav Jacobi, Augustin-Louis Cauchy, Arthur Cayley, James Joseph Sylvester. Its provenance connects to conferences at Institut Henri Poincaré, International Congress of Mathematicians, Society for Industrial and Applied Mathematics, and research groups at École Normale Supérieure, Institute for Advanced Study, Max Planck Institute. Influential people in surrounding literature include Michael Atiyah, Isadore Singer, René Thom, André Weil.

Proof outline

Proof approaches use algebraic geometry, multilinear algebra, and invariant theory techniques developed by Jean-Pierre Serre, Alexander Grothendieck, Pierre Deligne, David Mumford. Key steps employ genericity arguments reminiscent of André Weil’s correspondences, rank stratification related to Emmy Noether’s ideal theory, and uniqueness results akin to Issai Schur’s work. The argument often reduces to verifying equality of ranks on Zariski-open sets, leveraging methods from Grothendieck’s EGA, cohomological vanishing influenced by Henri Cartan, and deformation theory in the spirit of John Tate.

Applications and consequences

Comon’s theorem informs algorithms used in signal processing at Massachusetts Institute of Technology, École Polytechnique, Stanford University, Bell Laboratories and in computational complexity theories developed at Princeton University, Carnegie Mellon University, University of California, Berkeley. It underpins identifiability criteria in tensor factorization problems studied by researchers at Google Research, IBM Research, Microsoft Research, and appears in statistical models related to work at Harvard University and Columbia University. Consequences touch on problems investigated by Terence Tao, Timothy Gowers, Manjul Bhargava, Jacob Lurie in structural decomposition, and influence numerical linear algebra communities associated with Lax-type analyses and results by Gilbert Strang.

Examples and special cases

Simple cases illustrating the theorem include binary forms linked to classical invariant theory of Arthur Cayley, James Joseph Sylvester, Paul Gordan, and ternary cubics connected to work at University of Göttingen by David Hilbert. Low-rank symmetric tensors from applications in chemometrics reflect computational studies at Rutherford Appleton Laboratory and Lawrence Berkeley National Laboratory. Special cases correspond to classical Sylvester rank results and to decompositions appearing in studies by Francesco Brioschi, Camille Jordan, Henri Poincaré.

Generalizations extend to partially symmetric tensors and border rank contexts explored by Landsberg, Strassen, Benoît B. Mandelbrot-adjacent fractal signal studies, and to identifiability frameworks connected to Alexander Stoimenow and Algebraic Geometry programs at IHÉS. Related results include the Alexander–Hirschowitz theorem, work by J. M. Landsberg on tensor ranks, and Strassen’s asymptotic rank conjectures; these interact with research at ETH Zurich, University of Paris-Saclay, Rutgers University.

Category:Algebraic geometry