https://phys.org/news/2018-06-periodic-table.html

The possibility that heavy baryonic matter has a udQM ground state rather than a hadronic one is described in a paper published in Physical Review Letters by University of Toronto physicists Bob Holdom, Jing Ren, and Chen Zhang.

The idea that some kind of quark matter might form the ground state of baryonic matter is not new. In a famous paper from 1984, physicist Edward Witten suggested that strange quark matter (SQM) might fulfill this role. However, SQM consists of comparable amounts of up, down, and strange quarks. One of the new results of the latest study is that quark matter without strange quarks, i.e., udQM, has lower bulk energy per baryon than either SQM or hadronic matter, making it energetically favorable.