"What came after the Big Bang is still a big question. We don't know exactly what happened there. But we know that the universe was probably filled with a quark-gluon plasma millions of seconds after the Big Bang. The big difference to today's universe was that it was extremely hot and extremely dense," FIAS Fellow Hannah Petersen explains in the podcast of Welt der Physik.
Hannah Petersen also describes how she investigates this state of matter with theoretical means and together with her experimental colleagues at modern particle accelerator facilities.
You can find the complete podcast (in german) on the pages of Welt der Physik: