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arXiv · 0802.1928

Bass' $NK$ groups and $cdh$-fibrant Hochschild homology

G. Cortiñas·C. Haesemeyer·Mark E. Walker·C. Weibel
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Abstract

The $K$-theory of a polynomial ring $R[t]$ contains the $K$-theory of $R$ as a summand. For $R$ commutative and containing $\Q$, we describe $K_*(R[t])/K_*(R)$ in terms of Hochschild homology and the cohomology of Kähler differentials for the $cdh$ topology. We use this to address Bass' question, on whether $K_n(R)=K_n(R[t])$ implies $K_n(R)=K_n(R[t_1,t_2])$. The answer is positive over fields of infinite transcendence degree; the companion paper arXiv:1004.3829 provides a counterexample over a number field.

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G. Cortiñas, C. Haesemeyer, Mark E. Walker, C. Weibel. 2010-04-25. Bass' $NK$ groups and $cdh$-fibrant Hochschild homology. https://arxiv.org/abs/0802.1928

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