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Cancellation is a Pain

August 27, 2015

How to avoid the pain of estimating tough sums

Cricketing source

Andrew Granville is a number theorist, who has written—besides his own terrific research—some beautiful expository papers, especially on analytic number theory.

Today Ken and I wish to talk about his survey paper earlier this year on the size of gaps between consecutive primes.
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Cryptography And Quicksand

August 14, 2015

A basic question about cryptography that we pretend is not there.


Victor Shoup is one of the top experts in cryptography. He is well known for many things including a soon to be released book that is joint with Dan Boneh on, what else, cryptography; and the implementation of many of the basic functions of cryptography.

Today I want to talk about my recent visit to the Simons Institute in Berkeley where I heard Victor give a special lecture.
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Changing Definitions

August 10, 2015

How important is “backward compatibility” in math and CS?

David Darling source

Henri Lebesgue came the closest of anyone we know to changing the value of a mathematical quantity. Of course he did not do this—it was not like defining π to be 3. What he did was change the accepted definition of integral so that the integral from {a} to {b} of the characteristic function of the rational numbers became a definite {0}. It remains {0} even when integrating over all of {\mathbb{R}}.

Today we talk about changing definitions in mathematics and computer programming and ask when it is important to give up continuity with past practice. Read more…

Four Weddings And A Puzzle

August 2, 2015

An unusual voting problem?

“Four Weddings” is a reality based TV show that appears in America on the cable channel TLC. Yes a TV show: not a researcher, not someone who has recently solved a long-standing open problem. Just a TV show.

Today I want to discuss a curious math puzzle that underlines this show.

The show raises an interesting puzzle about voting schemes:
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Playing Chess With the Devil

July 28, 2015

A new kind of ‘liar’ puzzle using Freestyle chess

By permission of Vierrae (Katerina Suvorova), source

Raymond Smullyan is probably the world’s greatest expert on the logic of lying and the logic of chess. He is still writing books well into his 10th decade. Last year he published a new textbook, A Beginner’s Guide to Mathematical Logic, and in 2013 a new puzzle book named for Kurt Gödel. His 1979 book The Chess Mysteries of Sherlock Holmes introduced retrograde analysis—taking back moves from positions to tell how they could possibly have arisen—to a wide public.

Today Ken and I wish to talk about whether we can ever play perfect chess—or at least better chess than any one chess program—by combining output from multiple programs that sometimes might “lie.” Read more…

Alberto Apostolico, 1948–2015

July 22, 2015

Our condolences on the loss of a colleague

Cropped from TCS journal source

Alberto Apostolico was a Professor in the Georgia Tech College of Computing. He passed away on Monday after a long battle with cancer.

Today Ken and I offer our condolences to his family and friends, and our appreciation for his beautiful work.
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The Long Reach of Reachability

July 12, 2015

Workshop on Infinite State Systems at the Bellairs Institute on Barbados

Cropped from source

Joel Ouaknine is a Professor of Computer Science at Oxford University and a Fellow of St. John’s College there. He was previously a doctoral student at Oxford and made a critical contribution in 1998 of a kind I enjoyed as a student in the 1980s. This was contributing a win in the annual Oxford-Cambridge Varsity Chess Match, which in 1998 was won by Oxford, 5-3.

Today I’d like to report on some of the wonderful things that happened at a workshop on “Infinite-State Systems” hosted by Joel at the Bellairs Institute of McGill University last March 13–20 in Barbados, before we finally opened a chess set and played two games on the last evening.
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