Rosa M. Miró-Roig's Determinantal Ideals PDF

By Rosa M. Miró-Roig

ISBN-10: 3764385340

ISBN-13: 9783764385347

Determinantal beliefs are beliefs generated via minors of a homogeneous polynomial matrix. a few classical beliefs that may be generated during this manner are the suitable of the Veronese forms, of the Segre types, and of the rational basic scrolls.

Determinantal beliefs are a significant subject in either commutative algebra and algebraic geometry, and so they have a variety of connections with invariant idea, illustration idea, and combinatorics. as a result of their very important function, their learn has attracted many researchers and has bought substantial awareness within the literature. during this publication 3 the most important difficulties are addressed: CI-liaison category and G-liaison type of normal determinantal beliefs; the multiplicity conjecture for normal determinantal beliefs; and unobstructedness and measurement of households of ordinary determinantal ideals.

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Is a codimension 3 ACM scheme X ⊂ Pn+3 licci if Hm 0 ≤ i ≤ n? 2. 8. 11. Let C ⊂ P4 be a local complete intersection curve of degree d and arithmetic genus g with an almost linear resolution, 0 → R(−s − 3)a → R(−s − 2)b → R(−s − 1)c1 ⊕ R(−s)c0 → I(C) → 0. If d + g − 1 − ac0 = 0, then C is not licci. Idea of the proof. We compute the dimension, 0 l(C)µ := dimµ+5 Hm (KR/I(C) ⊗R I(C)), 0 (KR/I(C) ⊗R I). 8 give us (small letters mean dimension) 2 l(C)µ − l(C)−µ−5 = h1 NC (µ) −µ homR (I(C), Hm (R/I(C))).

We denote by A the matrix obtained by deleting a “suitable” row of B and we call V the subscheme defined by the maximal minors of A . (“Suitable” means that codim(V ) = c. ) ⎛ ⎜ ⎜ A=⎜ ⎜ ⎝ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ • • • • • ⎞ ⎟ ⎟ ⎟ ⎟ ⎠ I(A) = I(V ), codim(V ) = c, 42 Chapter 2. CI-liaison and G-liaison of Standard Determinantal Ideals ⎛ ⎜ ⎜ B=⎜ ⎜ ⎝ ⎛ ∗ ∗ ∗ ∗ ∗ ⎜ ∗ A1 = ⎜ ⎝ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ ⎞ ∗ ∗ ⎟ ⎟ ∗ ⎠ ∗ ⎞ ⎟ ⎟ ⎟ ⎟ ⎠ I(B) = I(X), I(A1 ) = I(V ), codim(X) = c − 1, codim(V ) = c.

Ulrich [52] (see also [56]) proved that some interesting results in codimension 2 do not hold when we link higher-codimensional ideals by complete intersections. In [79], P. S. Golod [30]) and the work [56] strongly suggests that the idea of linking using AG schemes is indeed a natural generalization to higher codimension of the idea of linking using complete intersections. 10]). , an AG) subscheme X ⊂ Pn if I(X) ⊂ I(V1 ) ∩ I(V2 ) and we have I(X) : I(V1 ) = I(V2 ) and I(X) : I(V2 ) = I(V1 ). We will say that V1 and V2 are directly linked when it does not matter if the linking scheme is an AG or a complete intersection scheme.

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Determinantal Ideals by Rosa M. Miró-Roig


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