Speed of sound in QCD matter at finite temperature and density Guo-yun Shao, Xin-ran Yang, Chong-long Xie and Wei-bo He Eur. Phys. J. Plus, 138 1 (2023) 44 Published online: 18 January 2023 DOI: 10.1140/epjp/s13360-023-03696-w