English

On relative Ulrich bundles and generalized Clifford algebras

Algebraic Geometry 2026-04-21 v4 Commutative Algebra Representation Theory

Abstract

Let XX be a smooth projective scheme and EE a vector bundle on XX. For a relative hypersurface YfP(E)Y_f \subset \mathbb{P}(E) of degree dd defined by a global section ff, we establish a functorial equivalence between the category of relatively Ulrich bundles on YfY_f and the category of representations of the associated generalized Clifford algebra CfC_f. This equivalence generalizes the classical Ulrich-Clifford correspondence of Coskun-Kulkarni-Mustopa and provides a purely algebraic framework that bypasses geometric obstructions in the relative setting. As a first application, we prove that relative hypersurfaces are Ulrich-wild: there exist families of indecomposable relatively Ulrich bundles {EN}\{E_N\} with dimExtYf1(EN,EN)as N. \dim \mathrm{Ext}^1_{Y_f}(E_N, E_N) \to \infty \quad \text{as } N \to \infty. We further show that relative hyperplanes possess a minimal Ulrich complexity of one. Moving beyond degree one, we illustrate how unavoidable homological obstructions require complex machinery, such as matrix factorizations, equivalently generalized Clifford algebras, to find solutions.

Keywords

Cite

@article{arxiv.2604.01611,
  title  = {On relative Ulrich bundles and generalized Clifford algebras},
  author = {Soham Mondal and Anindya Mukherjee},
  journal= {arXiv preprint arXiv:2604.01611},
  year   = {2026}
}

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