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Carlo Beenakker
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  1. Statement 1 is theorem 2.3 in Grassmannian Frames with Applications to Coding and Communication (2003): $${\rm max}_{k\neq l}|\langle f_k,f_l\rangle|\geq \sqrt{\frac{N-d}{d(N-1)}}$$ for any set of $N$ unit vectors $f_k$ in $d\leq N$ dimensions.

  2. For a precise formulation of statement 2, with a proof, see page 2 of these lecture notes:
    $${\rm Prob}\,\left(|\cos\theta|<\sqrt{\frac{\log d}{d}}\right)>1-\frac{1}{d},$$ where $\theta$ is the angle between two randomly chosen unit vectors in $d$ dimensions.
    notice a typo at the top of the page in those lecture notes, corrected at the bottom, the square root should extend over the entire fraction

Carlo Beenakker
  • 188.1k
  • 18
  • 448
  • 651