PreprintCC BY 4.0arXiv
PL Recognition After Two S2× S2 Stabilisations is PSPACE-Hard
Abstract
Let Z be any fixed closed connected PL $4$-manifold. We give a polynomial-time many-to-one reduction from the compressed word problem in Thompson's group F to fixed-target recognition of Z#2(S2× S2). Once a finite triangulation of Z has been fixed, the construction sends a straight-line program A to a closed triangulated PL $4$-manifold XA,Z such that val(A)=1 in F if and only if XA,Z is PL-homeomorphic to Z#2(S2× S2). Since the compressed word problem in F is PSPACE-complete, every such recognition problem is PSPACE-hard. In particular, fixed-target recognition of #n(S2× S2) is PSPACE-hard for every fixed n≥2.
Related
BibTeX
@misc{burke2026recognition,
title = {{PL Recognition After Two $S^2\times S^2$ Stabilisations is PSPACE-Hard}},
author = {Rhuaidi Antonio Burke},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.15890},
eprint = {2609.15890},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.15890},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - PL Recognition After Two S^2× S^2 Stabilisations is PSPACE-Hard
AU - Rhuaidi Antonio Burke
PY - 2026
DA - 2026/09/14
PB - arXiv
DO - 10.48550/arxiv.2609.15890
UR - https://arxiv.org/abs/2609.15890
AB - Let Z be any fixed closed connected PL $4$-manifold. We give a polynomial-time many-to-one reduction from the compressed word problem in Thompson's group F to fixed-target recognition of Z#_2(S^2× S^2). Once a finite triangulation of Z has been fixed, the construction sends a straight-line program A to a closed triangulated PL $4$-manifold X_A,Z such that val(A)=1 in F if and only if X_A,Z is PL-homeomorphic to Z#_2(S^2× S^2). Since the compressed word problem in F is PSPACE-complete, every such recognition problem is PSPACE-hard. In particular, fixed-target recognition of #_n(S^2× S^2) is PSPACE-hard for every fixed n≥2.
ER -