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A geometric construction of Z2–graded odd and even
orthogonal modular categories is given. Their 0–graded parts
coincide with categories previously obtained by Blanchet and the
author from the category of tangles modulo the Kauffman skein
relations. Quantum dimensions and twist coefficients of 1–graded
simple objects (spinors) are calculated. We show that invariants
coming from our odd and even orthogonal modular categories admit spin
and Z2–cohomological refinements, respectively. The
relation with the quantum group approach is discussed.
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