Witnessing Reality: How Records Confirm Observation in Quantum Mechanics

A new approach to understanding the role of the observer in relational quantum mechanics proposes that lasting, coherent records are crucial for establishing verifiable observations.
![The study establishes a relationship between pressure and density in symmetric nuclear matter, constrained by heavy-ion collision data-specifically [latex]Au+Au[/latex]-and informed by chiral nuclear force calculations at [latex]N^{2}LO[/latex] and [latex]N^{3}LO[/latex] orders, alongside constraints derived from kaon production.](https://arxiv.org/html/2603.01933v1/2603.01933v1/figure/Prho.png)
![The scaling test of effective field theory frequency shifts for [latex]\mathcal{O}_{9}[/latex] and [latex]\mathcal{O}_{10}[/latex] at [latex]\ell=2[/latex] demonstrates a predominantly linear dependence on the coupling ζ, as evidenced by the near-flat behavior of [latex]\Re\!\left(\delta_{\rm Leaver}/\zeta\right)[/latex] and [latex]\Im\!\left(\delta_{\rm Leaver}/\zeta\right)[/latex], though deviations at larger ζ values suggest the emergence of higher-order contributions that complicate the system’s graceful aging.](https://arxiv.org/html/2603.01456v1/2603.01456v1/x4.png)


![Existing and proposed fixed-target experiments-including HADES, BM@N, AGS, STAR, NA49, NA61/SHINE, NA60, CBM, J-PARC, and SMOG-collectively map the [latex]\sqrt{s_{NN}}[/latex] collision energy landscape, with the projected Electron-Ion Collider measurements extending this reach into previously unexplored regimes.](https://arxiv.org/html/2603.00265v1/2603.00265v1/figures/energy_AA.png)

