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    Algebraic geometry

    Contents

    The topics

    • Varieties, the classical dictionary between ideals and subsets of affine and projective space.

    • Sheaves, the sheaf condition, stalks, sheafification, and exactness.

    • Schemes, \(\Spec\) and \(\Proj\), gluing, and how to recognise a scheme’s properties from a ring.

    • Morphisms, separated, proper, finite, flat, smooth, and the valuative criteria.

    • Sheaves of modules, quasicoherence, twisting, and line bundles.

    • Divisors, Weil against Cartier, class groups, and Picard groups.

    • Cohomology, Čech computations, Serre duality, Riemann–Roch.

    • Curves and surfaces, genus in its several senses, Riemann–Hurwitz, embeddings.

    • Toric varieties, the construction from a fan, the orbit-cone correspondence, and the fan and polytope criteria for smoothness, completeness, projectivity, divisor classes, and sections of line bundles.

    • Stacks and moduli, functors of points, the étale and fppf topologies, descent, Hilbert schemes, algebraic spaces and stacks.

    • Resources, references, problem sources, and worked-solution collections.

    • Sample syllabi, topic lists from qualifying and oral examination syllabi.

    Dependencies

    A scheme is a locally ringed space, so the scheme pages use sheaves of rings and their stalks. Sheaf cohomology is defined for sheaves of abelian groups on a topological space and computed on schemes for quasicoherent sheaves. The curves and surfaces pages use Riemann–Roch, Serre duality, and the intersection pairing defined through line bundles.

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