Foreign member of the Chinese Acadamy of Sciences, Professor Shing-Tung Yau (2nd R) from Harvard University introduce the Poincare Conjecture to journalists in Beijing, capital of China, June 3, 2006. [Xinhua]

The pair have published a paper in the US-based Asian Journal of Mathematics, providing complete proof of the Poincar Conjecture promulgated by Frenchman Henri Poincar in 1904.

Professor Cao Huaidong, of Lehigh University in Pennsylvania, and Professor Zhu Xiping, of Zhongshan University in Guangdong Province, co-authored the paper, "A Complete Proof of the Poincar and Geometrization Conjectures - application of the Hamilton-Perelman theory of the Ricci flow," published in the June issue of the journal.

Cao and Zhu put the finishing touches to the complete proof of the Poincar Conjecture, said Professor Shing-Tung Yau, a mathematician at Harvard University and one of the journal's editors.

The conjecture was rated one of the major mathematical puzzles of the 20th Century, said Yau.

"The conjecture is that if in a closed three-dimensional space, any closed curves can shrink to a point continuously, this space can be deformed to a sphere," he explained.

By the end of the 1970s, US mathematician William P. Thurston had produced partial proof of Poincar's Conjecture on geometric structure, and was awarded the Fields Prize for the achievement.

The paper by Cao and Zhu, which ran to more than 300 pages, provided complete proof, said Yau.