The Orlik-Terao algebra and 2-formality
Abstract
The Orlik-Solomon algebra is the cohomology ring of the complement of a hyperplane arrangement A in Cn; it is the quotient of an exterior algebra E(V) on |A| generators. Orlik and Terao introduced a commutative analog S(V)/I of the Orlik-Solomon algebra to answer a question of Aomoto and showed the Hilbert series depends only on the intersection lattice L(A). Motivated by topological considerations, Falk and Randell introduced the property of 2-formality; we study the relation between 2-formality and the Orlik-Terao algebra. Our main result is a necessary and sufficient condition for 2-formality in terms of the quadratic component I2 of the Orlik-Terao ideal I: 2-formality is determined by the tangent space Tp(V(I2)) at a generic point p.
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