The Only Three Questions Left

We still cannot fully map the landscape where matter moves between:

• solids ? liquids ? plasmas ? exotic quantum phases
• the total number of phases that actually exist
• where every phase boundary intersects
• whether exotic substances have new kinds of triple or critical intersections

This applies directly to:

This is the largest open map in the thermodynamics of the universe.

At extremes, the familiar rules- "solid, liquid, gas", Gibbs equalities, even triple points- may simply fail.

Key unknown regimes include:

• Quantum critical points
• Electron-degenerate matter
• Neutron-rich crusts in neutron stars
• Quark-gluon phases and beyond

We do not yet know whether these regimes host the equivalents of triple or critical points, or whether they obey entirely new organising principles.

For most superheavy elements (Z > 100), we cannot even define ordinary thermodynamic constants. We can only make them a few atoms at a time.

Unknown for these elements:

• Triple points
• Melting curves
• Critical points
• Vaporisation behaviour

Their phase diagrams remain completely uncharted, even though they sit at the far end of the periodic table.