Some modular varieties of low dimension (Q1578072)

From the introduction of the paper: Generally spoken it is hard to find projective models for modular varieties. So it is reasonable to modify the question as follows: Find arithmetic groups \(\Gamma \subset O(2,n)\) such that the Bailey Borel compactification \(X(\Gamma)\) admits a fine covering \(X(\Gamma) \rightarrow \mathbb{P}^n(\mathbb{C})\) of known degree and such that the ramification divisor can explicitly be described as a linear combination of quadratic divisors. In this paper we propose some examples for further study.