Typewriter sequence

ID: typewriter-sequence

On , for and , the displayed indicator functions form a sequence that converges to zero in every finite Lp norm while failing to converge pointwise anywhere. Indeed, for ,
Every point belongs to exactly one interval in each dyadic block, and for it misses at least one other interval in that block. Thus every point sees infinitely many ones and infinitely many zeros. Half-open intervals specify the behaviour at dyadic endpoints. This separates norm convergence in an Lp space from pointwise convergence and convergence almost everywhere.

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