Of Mathematics, Magic and Persi Diaconis

Bangalore: Flipping a coin is a great way to make a choice at random – the ultimate gamble, don’t you think? Well, it isn’t. Professor Persi Diaconis, now the Mary V. Sunseri Professor of Statistics and Mathe­matics at Stanford Univer­sity, is known for tackling problems involving randomness and randomisation, like coin flipping and shuffling playing cards. “If you hit a coin with the same force in the same place, it always does the same thing,” he said. Prof. Diaconis, is a mathemagician.

Diaconis began his career with a disappearing act. Having taught himself card tricks at the age 5, he spent his boyhood traipsing in and out of NYC’s magic shops. When he was 14, he ran away from home to travel with legendary card sharp Dai Vernon. “I was 24 when I went off to college,” Prof. Diaconis said. “The link between magic and mathematics is quite obvious, isn’t it,” he added, with a wink.
Today, Professor Diaconis is 68. His lecture at IISc had him up on stage rifle-shuffling a pack of cards. “A deck of 52 cards needs to be rifle-shuffled at least 7 times,” he said.

In 1962, when Diaconis was 17, he exposed a Caribbean casino that had allegedly used shaved dice to boost the house odds. Determined to figure out the shaved-dice trick, the 18-year-old Diaconis bou­ght himself a copy of An Introduction to Probability and its Applications. This didn’t take him very far, because he didn’t know Calculus. This led him deeper into Mathematics and at the age of 24, he enrolled himself into night school at New York Community College, to get a degree in Mathematics.

Diaconis gave the world the random walk, patience sorting and most importantly, the Freedman – Diaconis rule – used to select the size of the bins in a histogram. “You would have done just as much as me when you’re my age,” he said, with a laugh, insisting that he is a far better magician than mathematician!