Phase-erased arrows of time and entropy production under periodic driving

A bound under known time symmetry, a no-go result for universal quantitative bounds without that information, and a locality analysis of the pairwise estimator. Model assumptions, block statistics, and the distinction between quantitative and qualitative claims are explicit. AI-assisted research, computation, checking and editing used OpenAI Codex and Anthropic Claude. Luqman Mahmood directed the research and is responsible for its claims and final text. Internal checks are not external peer review or an establishment of priority. CC BY 4.0 covers scholarly documents and mathematical data. Software source and executable verification scripts are excluded; their rights remain reserved unless an individual file states otherwise. Proprietary engineering implementations are not included.