[mswen]

No, do not get a second PhD. Your opportunity cost is too high. In particular since you are doing computational physics your computational modeling, statistical analysis and understanding of high performance computing should exceed the average AI founder. Second, you will already be capable of self-study of AI type academic publications and you want to be focused on translating those into real life applications not writing grant proposals and other graduate level academic stuff.

By the time you finish a second PhD you might be well along the pathway to business success, or you might fail. But I am convinced that adding a second PhD won't noticeably reduce your risk of failure.

I am almost certain that given the technical capabilities you have already developed that the risk factors in starting a business are product-to-market fit, timing, poor PR, marketing and sales or bad co-founders. By the way I have experience with all of those risk factors - they are real and technical skills or even a second PhD will not make them go away.