Strong Approximation for Linear Groups

Abstract

The original Strong Approximation Theorem, commonly attributed to the ancient Chinese, says that ℤ is dense in the profinite group П _p ℤ _p An analogous formulation is valid for the additive group of an algebraic number field. Such a group may be viewed as the ℚ -rational points of a linear algebraic group over ℚ, and one is led to consider the question of strong approximation in linear groups.