Private equity firm GTCR on Tuesday said it's made a strategic investment in Vivid Seats LLC, which sells tickets for live sports, concerts and theater events a la Ticketmaster, owned by Live Nation Entertainment and eBay Inc.-owned StubHub. The amount of the investment was not disclosed, but as part of the transaction, GTCR will work closely with Vivid Seats co-founders Jerry Bednyak and Eric Vassilatos as the company grows, focusing on developing the company's technology and service.