James Harris Simons, shortly Jim Simons, is a 84 year old American mathematician, and the billionaire hedge fund manager at Renaissance Technologies.

At Renaissance Tech, they are using mathematical models and algorithms to make investment gains from market inefficiencies. Due to the long-term aggregate investment returns of Renaissance and its Medallion Fund, Simons is described as the "greatest investor on Wall Street," and more specifically "the most successful hedge fund manager of all time."

but how does Jim Simons invest and in what he invests?

Simons is known for his studies on pattern recognition. For more than two decades, Simons' Renaissance Technologies' hedge funds, which trade in markets around the world, have employed mathematical models to analyze and execute trades, many automated.

Renaissance uses computer-based models to predict price changes in financial instruments. These models are based on analyzing as much data as can be gathered, then looking for non-random movements to make predictions.

For example this is their portfolio in Sep 2021 (and maybe some of them still there):

With a top ten holdings concentration of 12.38%, Simons’ fund is concentrated in the information technology, industrials, healthcare, consumer staples, communications, and consumer discretionary sectors.

Novo Nordisk A/S (NYSE:NVO) - 33% of the portfolio
Microsoft Corporation (NASDAQ:MSFT),
Zoom Video Communications, Inc. (NASDAQ:ZM),
Amazon.com, Inc. (NASDAQ:AMZN),
Apple Inc. (NASDAQ:AAPL),
and Alphabet Inc. (NASDAQ:GOOG)

Jim Simons’ Renaissance Technologies holds 504,393 shares of China Yuchai International Limited (NYSE:CYD) as of September 2021,

China Yuchai International Limited (NYSE:CYD)’s subsidiary,

Jim's attitude towards crypto market

in April 2020 Renaissance Technologies has received permission to trade Bitcoin futures on the Chicago Mercantile Exchange (CME). since then they haven't played big in Crypto market, but it seems they don't want to miss their share of the pie too!

sources:

• https://en.wikipedia.org/wiki/Jim_Simons_(mathematician)
• https://www.bloomberg.com/opinion/articles/2022-02-15/you-get-the-crypto-rules-you-pay-for
• https://www.cryptonary.com/renaissance-technologies-to-enter-the-crypto-market/
• https://finance.yahoo.com/news/jim-simons-renaissance-technologies-portfolio-132850998.html