In June 2010 a conference Probability Approximations and Beyond was held at the National
University of Singapore (NUS) in honor of pioneering mathematician Louis Chen. Chen made the
first of several seminal contributions to the theory and application of Stein's method. One of
his most important contributions has been to turn Stein's concentration inequality idea into an
effective tool for providing error bounds for the normal approximation in many settings and in
particular for sums of random variables exhibiting only local dependence. This conference
attracted a large audience that came to pay homage to Chen and to hear presentations by
colleagues who have worked with him in special ways over the past 40+ years. The papers in this
volume attest to how Louis Chen's cutting-edge ideas influenced and continue to influence such
areas as molecular biology and computer science. He has developed applications of his work on
Poisson approximation to problems of signal detection in computational biology. The original
papers contained in this book provide historical context for Chen's work alongside commentary
on some of his major contributions by noteworthy statisticians and mathematicians working
today.
