K. Soundararajan

  1. Smooth solutions to the equation A+B=C.

    Authors: K. Soundararajan, Jeffrey C. Lagarias
    Subjects: Number Theory
    Abstract

    This paper studies integer solutions to the ABC equation A+B+C=0 in which
    none of A, B, C has a large prime factor. Set H(A,B, C)= max(|A|,|B|,|C|) and
    set the smoothness S(A, B, C) to be the largest prime factor of ABC. We
    consider primitive solutions (gcd(A, B, C)=1) having smoothness no larger than
    a fixed power p of log H. Assuming the abc Conjecture we show that there are
    finitely many solutions if p<1. We discuss a conditional result, showing that
    the Generalized Riemann Hypothesis (GRH) implies there are infinitely many
    primitive solutions when p>8.

  2. A rule of thumb for riffle shuffling.

    Authors: Persi Diaconis, Sami Assaf, K. Soundararajan
    Subjects: Probability
    Abstract

    We study how many riffle shuffles are required to mix n cards if only certain
    features of the deck are of interest, e.g. suits disregarded or only the colors
    of interest. For these features, the number of shuffles drops from 3/2 log_2(n)
    to log_2(n). We derive closed formulae and an asymptotic `rule of thumb'
    formula which is remarkably accurate.

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