{ "id": "1103.4508", "version": "v1", "published": "2011-03-23T13:22:29.000Z", "updated": "2011-03-23T13:22:29.000Z", "title": "Discrete spectra and Pisot numbers", "authors": [ "Shigeki Akiyama", "Vilmos Komornik" ], "categories": [ "math.NT" ], "abstract": "By the m-spectrum of a real number q>1 we mean the set Y^m(q) of values p(q) where p runs over the height m polynomials with integer coefficients. These sets have been extensively investigated during the last fifty years because of their intimate connections with infinite Bernoulli convolutions, spectral properties of substitutive point sets and expansions in noninteger bases. We prove that Y^m(q) has an accumulation point if and only if q