Artificial intelligence startup CoreWeave's shares were up 17 per cent at $43.50 on their third day of trading on Tuesday, above their initial public offering price of $40. On Friday, the Nvidia-backed stock debuted for trading at $39, giving the AI infrastructure firm a valuation of $23 billion on a fully diluted basis. CoreWeave had already taken a hit on Thursday when it had to downsize its IPO. Nvidia contributed a $250-million order as part of CoreWeave's IPO, which raised $1.5 billion,