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arXiv 1707.01799math.ATmath.KT
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关于拓扑循环同调

On topological cyclic homology

Thomas Nikolaus, Peter Scholze

摘要:

拓扑循环同调是Connes-Tsygan的循环同调的一种改进,Connes-Tsygan的循环同调是由Bökstedt-Hsiang-Madsen在1993年作为代数$K$ -理论的一种近似而提出的。有一个从代数$K$ -理论到拓扑循环同调的迹映射,Dundas-Goodwillie-McCarthy的一个定理断言,这导致了幂零浸入的相关理论的等价性,这给出了在各种情况下计算$K$ -理论的方法。拓扑循环同调的构造是基于真正的等变同伦理论,使用明确的点集模型,和一个分圆谱的详细概念。本文的目标是重新审视这一理论只使用同伦不变的概念。特别地,我们给出了拓扑循环同调的一个新的构造。这是基于一个新的定义的$\infty$ -类别的分圆谱:我们定义一个分圆谱是一个谱$X$与$S^1$ -行动(在最天真的意义上)连同$S^1$ -等变地图$φ_p: X\to X^{tC_p}$的所有素数$p$。这里的$X^{tC_p}=\mathrm{cofib}(\mathrm{Nm}: X_{hC_p}\to X^{hC_p})$是Tate结构。在下有界谱上,我们证明了这与以前的定义是一致的。由此得到了一个新的简单的拓扑循环同调公式。为了构造拓扑霍赫希尔德同调例子中的映射$φ_p: X\to X^{tC_p}$,我们引入并研究了谱的Tate对角线和交换环谱的Frobenius同态.特别是,我们证明了一个版本的西格尔猜想的泰特对角线,并与这些Frobenius同态的电源操作。

英文摘要:

Topological cyclic homology is a refinement of Connes--Tsygan's cyclic homology which was introduced by Bökstedt--Hsiang--Madsen in 1993 as an approximation to algebraic $K$-theory. There is a trace map from algebraic $K$-theory to topological cyclic homology, and a theorem of Dundas--Goodwillie--McCarthy asserts that this induces an equivalence of relative theories for nilpotent immersions, which gives a way for computing $K$-theory in various situations. The construction of topological cyclic homology is based on genuine equivariant homotopy theory, the use of explicit point-set models, and the elaborate notion of a cyclotomic spectrum. The goal of this paper is to revisit this theory using only homotopy-invariant notions. In particular, we give a new construction of topological cyclic homology. This is based on a new definition of the $\infty$-category of cyclotomic spectra: We define a cyclotomic spectrum to be a spectrum $X$ with $S^1$-action (in the most naive sense) together with $S^1$-equivariant maps $φ_p: X\to X^{tC_p}$ for all primes $p$. Here $X^{tC_p}=\mathrm{cofib}(\mathrm{Nm}: X_{hC_p}\to X^{hC_p})$ is the Tate construction. On bounded below spectra, we prove that this agrees with previous definitions. As a consequence, we obtain a new and simple formula for topological cyclic homology. In order to construct the maps $φ_p: X\to X^{tC_p}$ in the example of topological Hochschild homology we introduce and study Tate diagonals for spectra and Frobenius homomorphisms of commutative ring spectra. In particular we prove a version of the Segal conjecture for the Tate diagonals and relate these Frobenius homomorphisms to power operations.

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