English

A computational reduction for many base cases in profinite telescopic algebraic $K$-theory

Algebraic Topology 2021-04-13 v2 K-Theory and Homology

Abstract

For primes p5p\geq 5 , K(KUp)K(KU_p) -- the algebraic KK-theory spectrum of (KU)p(KU)^{\wedge}_p, Morava KK-theory K(1)K(1), and Smith-Toda complex V(1)V(1), Ausoni and Rognes conjectured (alongside related conjectures) that LK(1)S0\mspace1.5mu\mspace2muuniti \mspace7mu(KU)pL_{K(1)}S^0 \mspace{-1.5mu}\xrightarrow{\mspace{-2mu}\text{unit} \, i}~\mspace{-7mu}(KU)^{\wedge}_p induces a map K(LK(1)S0)v21V(1)K(KUp)hZp×v21V(1)K(L_{K(1)}S^0) \wedge v_2^{-1}V(1) \to K(KU_p)^{h\mathbb{Z}^\times_p} \wedge v_2^{-1}V(1) that is an equivalence. Since the definition of this map is not well understood, we consider K(LK(1)S0)v21V(1)(K(KUp)v21V(1))hZp×K(L_{K(1)}S^0) \wedge v_2^{-1}V(1) \to (K(KU_p) \wedge v_2^{-1}V(1))^{h\mathbb{Z}^\times_p}, which is induced by ii and also should be an equivalence. We show that for any closed G<Zp×G < \mathbb{Z}^\times_p, π((K(KUp)v21V(1))hG)\pi_\ast((K(KU_p) \wedge v_2^{-1}V(1))^{hG}) is a direct sum of two pieces given by (co)invariants and a coinduced module, for K(KUp)(V(1))[v21]K(KU_p)_\ast(V(1))[v_2^{-1}]. When G=Zp×G = \mathbb{Z}^\times_p, the direct sum is, conjecturally, K(LK(1)S0)(V(1))[v21]K(L_{K(1)}S^0)_\ast(V(1))[v_2^{-1}] and, by using K(Lp)(V(1))[v21]K(L_p)_\ast(V(1))[v_2^{-1}], where Lp=((KU)p)hZ/((p1)Z)L_p = ((KU)^{\wedge}_p)^{h\mathbb{Z}/((p-1)\mathbb{Z})}, the summands simplify. The Ausoni-Rognes conjecture suggests that in ()hZp×v21V(1)(K(KUp)v21V(1))hZp×,(-)^{h\mathbb{Z}^\times_p} \wedge v_2^{-1}V(1) \simeq (K(KU_p) \wedge v_2^{-1}V(1))^{h\mathbb{Z}^\times_p}, K(KUp)K(KU_p) fills in the blank; we show that for any GG, the blank can be filled by (K(KUp))Odis(K(KU_p))^\mathrm{dis}_\mathcal{O}, a discrete Zp×\mathbb{Z}^\times_p-spectrum built out of K(KUp)K(KU_p).

Keywords

Cite

@article{arxiv.2101.11205,
  title  = {A computational reduction for many base cases in profinite telescopic algebraic $K$-theory},
  author = {Daniel G. Davis},
  journal= {arXiv preprint arXiv:2101.11205},
  year   = {2021}
}

Comments

20 pages; resubmitted for publication; Section 1.1 is new; updated several references

R2 v1 2026-06-23T22:34:20.109Z