Geometric Invariant Theory and Decorated Principal Bundles - download pdf or read online

Algebraic Geometry

By Alexander H. W. Schmitt

The e-book begins with an creation to Geometric Invariant conception (GIT). the elemental result of Hilbert and Mumford are uncovered in addition to newer issues comparable to the instability flag, the finiteness of the variety of quotients, and the difference of quotients. within the moment half, GIT is utilized to resolve the category challenge of embellished crucial bundles on a compact Riemann floor. the answer is a quasi-projective moduli scheme which parameterizes these items that fulfill a semistability situation originating from gauge concept. The moduli house is supplied with a generalized Hitchin map. through the common KobayashiHitchin correspondence, those moduli areas are relating to moduli areas of options of definite vortex kind equations. capability purposes contain the examine of illustration areas of the elemental workforce of compact Riemann surfaces. The publication concludes with a short dialogue of generalizations of those findings to raised dimensional base kinds, optimistic attribute, and parabolic bundles. The textual content is reasonably self-contained (e.g., the required history from the speculation of imperative bundles is integrated) and lines a variety of examples and routines. It addresses scholars and researchers with a operating wisdom of user-friendly algebraic geometry.

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Extra resources for Geometric Invariant Theory and Decorated Principal Bundles (Zurich Lectures in Advanced Mathematics)

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Let xi j , i, j = 1, . . , n, be the coordinate functions on Mn ( ) and Ü := (xi j )i, j . Then, [Mn ( )]GLn ( ) = [xi j , i, j = 1, . . , n]GLn ( ) = [Trace(Ü), . . , Trace(Ün )]. 4. The above theorem appears already—with a different proof—in the book [93] (the Russian original dates from 1948). The isomorphism Dn //S n Mn ( )//GLn ( ) is a special case of a result of Chevalley on reductive groups. 39. Tuples of Matrices In the next step, we study the action of GLn ( ) on Mn ( ) s : g · (m1 , .

Let I1 , . . , I s ∈ [V] be invariant homogeneous functions whose common vanishing locus is exactly the set of nullforms. Then, [V] is the integral closure of [I1 , . . , I s ] in the field (V). Proof. 2. Together with the following result, this theorem gives a handy criterion for a variety to be a quotient. We will apply it several times in the examples. 12. Let f : X −→ Y be a dominant and finite morphism between irreducible algebraic varieties. If Y is normal and there is a non-empty open subset U ⊂ Y, such that f| f −1 (U) : f −1 (U) −→ U is bijective, then f is an isomorphism.

T 5 are algebraically independent. ) ii) Show that a tuple (m1 , . . , m s ) ∈ Mn ( ) s fails to be semistable, if and only if m1 , . . , m s may simultaneously be brought into upper trigonal form with zeroes on the diagonal. ) Note: In general, one may study the action of a reductive linear algebraic group G on Lie(G) s that is induced by the adjoint representation. Richardson [178] determines, among other things, the unstable tuples (x1 , . . , x s ) ∈ Lie(G) s . Plugging in G = GLn ( ), this implies the above result.

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