  The topological structure of vacuum is the cornerstone of non-Abelian gauge
theories describing strong and electroweak interactions within the standard
model of particle physics. However, transitions between different topological
sectors of the vacuum (believed to be at the origin of the baryon asymmetry of
the Universe) have never been observed directly. An experimental observation of
such transitions in Quantum Chromodynamics (QCD) has become possible in
heavy-ion collisions, where the chiral magnetic effect converts the chiral
asymmetry (generated by topological transitions in hot QCD matter) into an
electric current, under the presence of the magnetic field produced by the
colliding ions. The Relativistic Heavy Ion Collider program on heavy-ion
collisions such as the Zr-Zr and Ru-Ru isobars, thus has the potential to
uncover the topological structure of vacuum in a laboratory experiment. This
discovery would have far-reaching implications for the understanding of QCD,
the origin of the baryon asymmetry in the present-day Universe, and for other
areas, including condensed matter physics.
