Tech stocks surge as wave of interest in AI drives $4tn rally

Shares in some firms involved in AI technology more than double in value as traders bet on massive growth in industryA rush of interest in artificial intelligence (AI) has helped to fuel a $4tn (£3.2tn) rally in technology stocks this year, with the US Nasdaq exchange reaching its highest level since last August in a week that saw the chipmaker Nvidia poised to become the next trillion-dollar company.Some stocks seen as AI winners – such as semiconductor makers and software developer