40th International Workshop on High Energy Density Physics with Intense Ion and Laser Beams

There are three basic points for discussions on perspectives of HED@FAIR experimental study of unexplored phenomena: (*1*) – how to arrange HIB energy deposition; (*2*) – how to arrange diagnostics; (*3*) – what fundamental physical phenomenon should be explored to justify our using such huge facilities like FAIR, LHC, NICA *etc* for thermophysical investigations. In my talk I plan to continue my previous discussions on point (*3*). I.e. – very plausible but still hypothetical objects – *anomalous thermodynamics regions* (ATR) accompanying *entropic phase transitions* (*S*-PT). Remarkable feature of ATR - negative isochoric pressure/temperature derivative (*∂P/∂T*)*V* leads to non-standard sequence of expansion and compression of isochorically heated sample within HIHEX scenario. Another feature of ATR – anomalous negative isentropic pressure/temperature derivative (*∂T/∂P*)*S* leads to non-standard behavior of temperature on isentropic compression within LAPLAS scheme, i.e. *T*-decreasing instead of naively expected *T*-increasing, and anomalous *T*-increasing instead of expected *T*-decreasing along isentropic expansion in second stage of HIHEX. In my discussions I base on example of hot dense nitrogen as the material with (*S*-PT + ATR) anomalies, which were predicted by dynamic experiments and by the First-Principle numerical simulation. This work is supported by the Presidium RAS Scientific Program “Novel approaches to investigations of matter under high energy density conditions”