On the learnability of vector spaces

  • Authors:
  • Valentina S. Harizanov;Frank Stephan

  • Affiliations:
  • Department of Mathematics, George Washington University, Washington, DC 20052, USA;Department of Mathematics and School of Computing, National University of Singapore, 2 Science Drive 2, Singapore 117543, Singapore

  • Venue:
  • Journal of Computer and System Sciences
  • Year:
  • 2007

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Abstract

The central topic of the paper is the learnability of the recursively enumerable subspaces of V"~/V, where V"~ is the standard recursive vector space over the rationals with (countably) infinite dimension and V is a given recursively enumerable subspace of V"~. It is shown that certain types of vector spaces can be characterized in terms of learnability properties: V"~/V is behaviourally correct learnable from text iff V is finite-dimensional, V"~/V is behaviourally correct learnable from switching the type of information iff V is finite-dimensional, 0-thin or 1-thin. On the other hand, learnability from an informant does not correspond to similar algebraic properties of a given space. There are 0-thin spaces W"1 and W"2 such that W"1 is not explanatorily learnable from an informant, and the infinite product (W"1)^~ is not behaviourally correct learnable from an informant, while both W"2 and the infinite product (W"2)^~ are explanatorily learnable from an informant.