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On the binary expansions of algebraic numbers David H. Bailey Jonathan M. Borwein Richard E. Crandall Carl Pomerance
ABSTRACT: Employing concepts from additive number theory, together with results on binary
evaluations and partial series, we establish bounds on the density of 1's in the binary expansions
of real algebraic numbers. A central result is that if a real y has algebraic degree D > 1,
then the number \#(vbar y vbar, N) of 1-bits in the expansion of vbar y vbar through bit position N satisfies
\#(vbar y vbar, N) > CN^1/D for a positive number C (depending on y) and sufficiently large N. This
in itself establishes the transcendency of a class of reals \sum_n \geq 0 1/2^f(n) where
theinteger-valued function f grows sufficiently fast; say, faster than any fixed power of n. By
these methods we re-establish the transcendency of the Kempner--Mahler number \sum_n \geq
01/2^2^n, yet we can also handle numbers with a substantially denser occurrence of 1's. Though
the number z = \sum_n \geq 01/2^n^2 has too high a 1's density for application of our central
result, we are able to invoke some rather intricate number-theoretical analysis and extended
computations to reveal aspects of the binary structure of z<sup 2>.
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