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New Theorem Shows Uneven Riffle-Shuffle Mixing Cutoff

6/17/2026

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Story summary
  • A new theorem proves that riffle-shuffle mixing reaches a sharp cutoff even when decks are cut unevenly.
  • Mark Sellke, Jialu Shi and Jiamin Wang established the cutoff phenomenon for non-even deck cuts.
  • Persi Diaconis called the result a brilliant piece of mathematics.
  • The proof extends earlier work that required a perfectly split deck by using barcode tracking of card positions, broadening cutoff theory to more realistic shuffling processes.