Vol. 249, No. 1, 2011

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Homology sequence and excision theorem for Euler class group

Yong Yang

Vol. 249 (2011), No. 1, 237–254
Abstract

Let R be a Noetherian commutative ring with dimR = d and let l be an ideal of R. For an integer n such that 2n d + 3, we define a relative Euler class group En(R,l;R). Using this group, in analogy to homology sequence of the K0-group, we construct an exact sequence

 n        E(p2)   n      E(ρ)   n
E (R,l;R)−−−−→ E  (R; R)−−−→ E  (R∕l;R ∕l),

called the homology sequence of the Euler class group. The excision theorem in K-theory has a corresponding theorem for the Euler class group. An application is that for polynomial and Laurent polynomial rings, we get short split exact sequences

      n            E (p2)  n          E(ρ)   n
0 → E  (R [t],(t);R [t])−−−−→  E (R[t];R[t])−−−→ E  (R;R) → 0

and

     n     −1            −1  E (p2)  n     −1      −1
0 → E (R[t,t ],(t− 1);R[t,t  ])−−−−→  E (R[t,t  ];R[t,t  ])
E(ρ)   n
−−−→ E  (R;R) → 0.

Keywords
Euler class group, K-theory, excision theorem
Mathematical Subject Classification 2000
Primary: 13C10
Secondary: 13B25
Milestones
Received: 17 April 2010
Revised: 27 May 2010
Accepted: 14 June 2010
Published: 3 January 2011
Authors
Yong Yang
Department of Mathematics and Systems Science
National University of Defense Technology
Changsha, Hunan 410073
China