Cartan invariants and defect zero elements

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In this note we prove relations between Cartan invariants in characteristc p and p defect zero elements. Exploiting duality arguments in characteristic two we show that the existence of real 2-defect zero elements is equivalent to the existence of odd diagonal entries in the Cartan matrix corresponding to real-valued Brauer characters. In addition, we present an independent and elementary proof of Theorem 3.3 part (iii) in [2].