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Non-degenerate Hilbert cubes in random sets

Csaba Sándor (2007)

Journal de Théorie des Nombres de Bordeaux

A slight modification of the proof of Szemerédi’s cube lemma gives that if a set S [ 1 , n ] satisfies | S | n 2 , then S must contain a non-degenerate Hilbert cube of dimension log 2 log 2 n - 3 . In this paper we prove that in a random set S determined by Pr { s S } = 1 2 for 1 s n , the maximal dimension of non-degenerate Hilbert cubes is a.e. nearly log 2 log 2 n + log 2 log 2 log 2 n and determine the threshold function for a non-degenerate k -cube.

Non-existence and splitting theorems for normal integral bases

Cornelius Greither, Henri Johnston (2012)

Annales de l’institut Fourier

We establish new conditions that prevent the existence of (weak) normal integral bases in tame Galois extensions of number fields. This leads to the following result: under appropriate technical hypotheses, the existence of a normal integral basis in the upper layer of an abelian tower K L forces the tower to be split in a very strong sense.

Non-existence of points rational over number fields on Shimura curves

Keisuke Arai (2016)

Acta Arithmetica

Jordan, Rotger and de Vera-Piquero proved that Shimura curves have no points rational over imaginary quadratic fields under a certain assumption. In this article, we extend their results to the case of number fields of higher degree. We also give counterexamples to the Hasse principle on Shimura curves.

Non-Kähler compact complex manifolds associated to number fields

Karl Oeljeklaus, Matei Toma (2005)

Annales de l’institut Fourier

For algebraic number fields K with s > 0 real and 2 t > 0 complex embeddings and “admissible” subgroups U of the multiplicative group of integer units of K we construct and investigate certain ( s + t ) -dimensional compact complex manifolds X ( K , U ) . We show among other things that such manifolds are non-Kähler but admit locally conformally Kähler metrics when t = 1 . In particular we disprove a conjecture of I. Vaisman.

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