A sign of Antchain, the blockchain technology branch under Ant Group, is seen at Ant Group's booth during the World Artificial Intelligence Conference (WAIC) in Shanghai, China, July 8, 2021. REUTERS/Yilei Sun/File Photo Aug 7 (Reuters) - A number of global investors are opting out of Ant Group's (688688.SS) proposed share buyback after the Chinese fintech's valuation was slashed by more than 70%, Bloomberg News reported on Monday. Among the investors not participating in the buyback are Warburg Pincus, Canada Pension Plan Investment Board (CPPIB), Carlyle Group (CG.O) and GIC Pte, Bloomberg said, citing people familiar with the matter. However,...