Independent subspace analysis is unique, given irreducibility

  • Authors:
  • Harold W. Gutch;Fabian J. Theis

  • Affiliations:
  • Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany;Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany

  • Venue:
  • ICA'07 Proceedings of the 7th international conference on Independent component analysis and signal separation
  • Year:
  • 2007

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Abstract

Independent Subspace Analysis (ISA) is a generalization of ICA. It tries to find a basis in which a given random vector can be decomposed into groups of mutually independent random vectors. Since the first introduction of ISA, various algorithms to solve this problem have been introduced, however a general proof of the uniqueness of ISA decompositions remained an open question. In this contribution we address this question and sketch a proof for the separability of ISA. The key condition for separability is to require the subspaces to be not further decomposable (irreducible). Based on a decomposition into irreducible components, we formulate a general model for ISA without restrictions on the group sizes. The validity of the uniqueness result is illustrated on a toy example. Moreover, an extension of ISA to subspace extraction is introduced and its indeterminacies are discussed.