As of: 2026-10-30 13:42 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/person/hal-tasaki/

# Hal Tasaki

Mathematical physicist, Gakushuin University (as of 2026-10-28; source: https://haltasaki.github.io/).

Expert on quantum spin chains (AKLT co-author); studied and explained OpenAI's spin-one Haldane gap proof and extended it with ChatGPT Astra; see 2026-10-06-openai-spin-one-haldane-gap-proof.

## Accounts

- X: https://x.com/Hal_Tasaki

## In the news (2 events, newest first)

- 2026-10-28: [AI-assisted results in the 28 Oct 2026 sweep](https://postcutoff.com/e/2026-10-28-ai-assisted-results-october-28-listing/), Science & math. The 28 Oct sweep covered the arXiv announcement of 26–27 Oct submissions and late papers from 23–26 Oct. Five results have their own entries: Axiom's Lean proof of the Classification of Finite Simple Groups, OpenAI's spin-one Haldane gap proof (found through Hal Tasaki's follow-up), OpenAI's De Giorgi dimension-eight claim, Morgan–Mullen with Claude and Lean, and formula minimization with GPT-Sol-6.1. This page lists the rest. Claude, GPT-6 Astra and GPT-6 Pro supplied ideas, counterexamples or whole arguments in papers on zero-sum sequences, geometric Langlands, quantum dynamics, fire-blocking and spectral bounds.
- 2026-10-06: [OpenAI proves the spin-one Haldane gap (periodic chains)](https://postcutoff.com/e/2026-10-06-openai-spin-one-haldane-gap-proof/), Science & math. Two manuscripts in OpenAI's 6 Oct 2026 math release (dated 24 Sept) prove that the spin-one antiferromagnetic Heisenberg chain has a spectral gap that stays positive as even periodic rings grow. That is the standard finite-volume form of Haldane's 1983 prediction, a central open problem of mathematical physics. Hal Tasaki, a leading expert on the problem, studied the analytic part. He calls it 'remarkably simple and elegant' and wrote two expository notes. He has not checked the computer-assisted estimates. On 25–27 Oct he posted a follow-up paper, written with ChatGPT Astra, that proves uniqueness of the infinite-chain ground state.

## Posts (2)

- 2026-10-11: [“とろけるほどに甘美でしかし凄絶たる悪夢のなかにいるようだ。バックにベルリオーズの幻想交響曲をかけながら、OpenAI の Haldane gap…”](https://postcutoff.com/p/x-hal_tasaki-2109159859845472457/), Hal Tasaki (@Hal_Tasaki), X. Cited in [OpenAI proves the spin-one Haldane gap (periodic chains)](https://postcutoff.com/e/2026-10-06-openai-spin-one-haldane-gap-proof/).
- 2026-10-06: [“OpenAIの新モデルによる数学の成果が公開。自分の研究にも近い話が出てきてびっくり。 これでHaldane gapの存在(＋S=1 Haldane…”](https://postcutoff.com/p/x-masakioshikawa-2107609927351177678/), Masaki Oshikawa (押川 正毅) (@MasakiOshikawa), X. Cited in [OpenAI proves the spin-one Haldane gap (periodic chains)](https://postcutoff.com/e/2026-10-06-openai-spin-one-haldane-gap-proof/).

Profile checked 2026-10-28.