Three years after OpenAI and Nvidia Corp. helped kick off the global artificial intelligence frenzy, the two firms are joining forces to pave the way for a more costly phase of development with a deal that’s quickly revived fears of an AI bubble. Nvidia on Monday said it will invest as much as $100 billion in OpenAI to help the ChatGPT maker support a massive build-out of data centers equipped with Nvidia’s chips — a deal that some analysts say raises questions about whether Nvidia is investing heavily to p ...