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Modular lattices from finite projective planes

Tathagata Basak (2014)

Journal de Théorie des Nombres de Bordeaux

Using the geometry of the projective plane over the finite field 𝔽 q , we construct a Hermitian Lorentzian lattice L q of dimension ( q 2 + q + 2 ) defined over a certain number ring 𝒪 that depends on q . We show that infinitely many of these lattices are p -modular, that is, p L q ' = L q , where p is some prime in 𝒪 such that | p | 2 = q .The Lorentzian lattices L q sometimes lead to construction of interesting positive definite lattices. In particular, if q 3 mod 4 is a rational prime such that ( q 2 + q + 1 ) is norm of some element in [ - q ] , then we find a 2 q ( q + 1 ) dimensional...

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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