Partition regularity of IP sets

ID: partition-regularity-of-ip-sets

Every finite coloring of an IP set has a color class that is an IP set. Here is a reduction to the ordinary Hindman theorem. Given in the original set, color an integer by the color of , where the support consists of positions of its nonzero digits in the binary expansion. The Hindman theorem produces with monochromatic . Replace the by consecutive, disjoint finite block sums with separated binary supports: after a block has been chosen, take above all previously used positions; two of partial sums of a fresh tail agree modulo , so their positive difference supplies the next block sum divisible by . Now binary addition of distinct has no carries. Therefore generates a monochromatic finite-sums set in the original IP set.

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