Skip to main content
added tag
Link
Bill Johnson
  • 31.5k
  • 5
  • 90
  • 138
Source Link
Mark Meckes
  • 11.4k
  • 3
  • 38
  • 69

Self-dual finite-dimensional complex normed spaces

Suppose $X$ is a complex normed space of dimension 2 or 3 and $X$ is isometrically isomorphic to its dual. Is $X$ a Hilbert space?

Remarks: There are easy counterexamples in the real case, and in higher dimensions one can construct counterexamples from sums of 2-dimensional spaces which are not isometric to their duals. Similarly a 3-dimensional counterexample can be constructed from a 2-dimensional counterexample.