Orthogonal webs and semisimplification

We define a diagrammatic category that is equivalent to tilting representations for the orthogonal group. Our construction works in characteristic not equal to two. We also describe the semisimplification of this category.Mathematics Subject Classifications: Primary:18M05, 20G05; Secondary:18M30,~20J15Keywords: Representations of linear algebraic groups, webs, Howe duality, diagrammatic presentation, positive characteristic, semisimplification