**Tsuruichi Hayashi** (林 鶴一, *Hayashi Tsuruichi*, June 13, 1873 – October 4, 1935) was a Japanese mathematician and historian of Japanese mathematics. He was born in Tokushima, Japan.^{ [1] }

He was the founder of the * Tohoku Mathematical Journal *.^{ [2] }

The **Tōhoku region**, **Northeast region**, **Ōu region**, or **Northeast Japan** consists of the northeastern portion of Honshu, the largest island of Japan. This traditional region consists of six prefectures (*ken*): Akita, Aomori, Fukushima, Iwate, Miyagi, and Yamagata.

**Sendai** is the capital city of Miyagi Prefecture, the largest city in the Tōhoku region. As of 1 August 2023, the city had a population of 1,098,335 in 539,698 households, and is one of Japan's 20 designated cities. The city was founded in 1600 by the *daimyō* Date Masamune. It is nicknamed the *City of Trees*; there are Japanese zelkova trees lining many of the main thoroughfares such as Jōzenji Street and Aoba Street. In the summer, the Sendai Tanabata Festival, the largest Tanabata festival in Japan, is held. In winter, the trees are decorated with thousands of lights for the Pageant of Starlight, lasting through most of December. The city is also home to Tohoku University, consistently ranked amongst the top institutions of higher education in Japan. On 11 March 2011, coastal areas of the city suffered catastrophic damage from a magnitude 9.0 offshore earthquake, which triggered a destructive tsunami.

**Tohoku University** is a public research university in Sendai, Miyagi, Japan. It is colloquially referred to as ** Tohokudai** or

**Vegalta Sendai** is a Japanese professional football club based in Sendai, Miyagi Prefecture. They currently play in J2 League, the Japanese second tier of professional football.

**Tohoku Broadcasting Company** is a Japanese TV and radio network affiliated with the Japan News Network (JNN). Its headquarters are located in Miyagi Prefecture, Tōhoku region.

**Sendai Station** is a major junction railway station in Aoba-ku, Sendai, Miyagi, Japan. It is a stop for all Akita, Hokkaido, and Tohoku Shinkansen trains, the eastern terminus for the Senzan Line, and major stop on both the Tohoku Main Line and Senseki Line. It is located on the border between Miyagino and Aoba Wards in Sendai, Miyagi Prefecture.

** Sendai Television Inc.**, callsign **JOOX-DTV** is a Japanese television station based in Sendai that serves as the affiliate of the Fuji News Network (FNN) and Fuji Network System (FNS) for the Miyagi Prefecture. It was established on October 1, 1962.

In the theory of von Neumann algebras, a part of the mathematical field of functional analysis, **Tomita–Takesaki theory** is a method for constructing **modular automorphisms** of von Neumann algebras from the polar decomposition of a certain involution. It is essential for the theory of type III factors, and has led to a good structure theory for these previously intractable objects.

**Jun-ichi Nishizawa** was a Japanese engineer and inventor. He is known for his electronic inventions since the 1950s, including the PIN diode, static induction transistor, static induction thyristor, SIT/SITh. His inventions contributed to the development of internet technology and the Information Age.

The * Tohoku Mathematical Journal* is a mathematical research journal published by Tohoku University in Japan. It was founded in August 1911 by Tsuruichi Hayashi.

**Sendai City Transportation Bureau** is a public transport organization in Sendai, Japan. The organization operates subways and buses within the city. It was founded in 1926.

* Aoba* is the name of a number of train services that formerly operated in Japan by Japanese National Railways (JNR), and most recently an all-stations service operated by East Japan Railway Company until September 1997 on the high-speed Tōhoku Shinkansen in Japan.

**Sakabe Kōhan** was a Japanese mathematician in the Edo period.

The **869 Jōgan earthquake** and its associated tsunami struck the area around Sendai in the northern part of Honshu on 9 July 869. The earthquake had an estimated magnitude of at least 8.6 on the moment magnitude scale, but may have been as high as 9.0, similar to the 2011 Tōhoku earthquake and tsunami. The tsunami caused widespread flooding of the Sendai plain. In 2001, researchers identified sand deposits in a trench more than 4.5 kilometres (2.8 mi) from the coast as coming from this tsunami.

**Shigeo Sasaki** (佐々木 重夫) was a Japanese mathematician working on differential geometry who introduced Sasaki manifolds. He retired from Tohoku University's Mathematical Institute in April 1976.

**Tadao Oda** is a Japanese mathematician working in the field of algebraic geometry, especially toric varieties. The field of toric varieties was developed by Demazure, Mumford, Miyake, Oda and others in the 1970s. He is also known for a book on toric varieties: *Convex Bodies and Algebraic Geometry: An Introduction to the Theory of Toric Varieties.*

**Miyagi Prefecture** is a prefecture of Japan located in the Tōhoku region of Honshu. Miyagi Prefecture has a population of 2,265,724 and has a geographic area of 7,282 km^{2} (2,812 sq mi). Miyagi Prefecture borders Iwate Prefecture to the north, Akita Prefecture to the northwest, Yamagata Prefecture to the west, and Fukushima Prefecture to the south.

**Kunizō Yoneyama** was a Japanese mathematician at Kyoto University working in topology. In 1917, he published the construction of the Lakes of Wada, which he named after his teacher Takeo Wada, to whom he credited the discovery.

**Matsusaburo Fujiwara** was a Japanese mathematician and historian of mathematics.

**Takao Hayashi** is a Japanese mathematics educator, historian of mathematics specializing in Indian mathematics. Hayashi was born in Niigata, Japan. He obtained Bachelor of Science degree form Tohoku University, Sendai, Japan in 1974, Master of Arts degree from Tohuku University, Sendai, Japan in 1976 and a postgraduate degree from Kyoto University, Japan in 1979. He secured the Doctor of Philosophy degree from Brown University, USA in 1985 under the guidance of David Pingree. He was a researcher at Mehta Research Institute for Mathematics and Mathematical Physics, Allahabad, India during 1982–1983, a lecturer at Kyoto Women's College during 1985–1987. He joined Doshisha University, Kyoto as a lecturer in history of science in 1986 and was promoted as professor in 1995. He has also worked in various universities in Japan in different capacities.

- ↑ Fujiwara, Matsusaburô (1935–1936), "Obituary note, Tsuruichi Hayashi (1873–1935)",
*Tohoku Mathematical Journal*,**41**: 265–289. - ↑ Oda, Tadao (2011), "The first hundred years of the Tohoku mathematical journal",
*Tohoku Mathematical Journal*, Second Series,**63**(4): 461–470, doi: 10.2748/tmj/1325886276 , MR 2872951 .

- Kümmerle, Harald (2018). "Hayashi Tsuruichi and the success of the Tôhoku Mathematical Journal as a publication". In Ogawa, T.; Morimoto, M. (eds.).
*Mathematics of Takebe Katahiro and History of Mathematics in East Asia*. Advanced Studies in Pure Mathematics. Vol. 79. Tokyo: Mathematical Society of Japan. pp. 347–358.

- The Extremal Chords of an Oval, by TSURUICHI HAYASHI, Sendai.
- A Remark on the integral Equation solved by Mr. Hirakawa, by TSURUICHI HAYASHI in Sendai.

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