On η-periodic Formal Ternary Laws
Abstract
We study the algebraic structure underlying Sp-orientations in the η-periodic motivic stable homotopy category SH(k)[η−1]. Borel classes determine a geometric formal ternary law, but the HW-Hurewicz map shows that its universal coefficients generate a proper W(k)-subalgebra Λsubsetneq (MSp[η−1])*, although Λ[1/2]=(MSp[η−1])*[1/2]. Thus the failure of generation is purely 2-primary. To capture part of the missing information, we introduce framed involutions. The spectrum MSp[η−1] carries a canonical framed involution, yielding a Quillen-type idempotent with telescope MSL[η−1] and a canonical splitting (MSp[η−1])* ≅ ℛfr ⊗ℤ (MSL[η−1])*, where ℛfr is the universal ring of framed involutions. We then axiomatize formal ternary laws, construct the universal Walter ring 𝒲η, and prove that 𝒲η is isomorphic to the Lazard ring L after inverting 2. If W(k)≅ ℤ, the universal geometric formal ternary law together with the canonical framed involution induces a classifying map ϕ:𝒲η→ (MSp[η−1])* that is injective and becomes an isomorphism after inverting 2. Integrally, however, additional secondary power series are needed to recover the full cobordism coefficient ring.
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BibTeX
@misc{huang2026ηperiodic,
title = {{On $η$-periodic Formal Ternary Laws}},
author = {Tao Huang},
howpublished = {HAL},
year = {2026},
month = jul,
doi = {10.48550/arxiv.2607.06795},
eprint = {2607.06795},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05687153v2},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - On η-periodic Formal Ternary Laws
AU - Tao Huang
PY - 2026
DA - 2026/07/07
PB - HAL
DO - 10.48550/arxiv.2607.06795
UR - https://hal.science/hal-05687153v2
AB - We study the algebraic structure underlying Sp-orientations in the η-periodic motivic stable homotopy category SH(k)[η^−1]. Borel classes determine a geometric formal ternary law, but the HW-Hurewicz map shows that its universal coefficients generate a proper W(k)-subalgebra Λsubsetneq (MSp[η^−1])_*, although Λ[1/2]=(MSp[η^−1])_*[1/2]. Thus the failure of generation is purely 2-primary. To capture part of the missing information, we introduce framed involutions. The spectrum MSp[η^−1] carries a canonical framed involution, yielding a Quillen-type idempotent with telescope MSL[η^−1] and a canonical splitting (MSp[η^−1])_* ≅ ℛ_fr ⊗_ℤ (MSL[η^−1])_*, where ℛ_fr is the universal ring of framed involutions. We then axiomatize formal ternary laws, construct the universal Walter ring 𝒲^η, and prove that 𝒲^η is isomorphic to the Lazard ring L after inverting 2. If W(k)≅ ℤ, the universal geometric formal ternary law together with the canonical framed involution induces a classifying map ϕ:𝒲^η→ (MSp[η^−1])_* that is injective and becomes an isomorphism after inverting 2. Integrally, however, additional secondary power series are needed to recover the full cobordism coefficient ring.
ER -