nucleation

LIT-1666: Stable Facts, Relative Facts

1 min read

Properties5
StatusActive — read in full 2026-10-27 (NOTE-1226), from arXiv v3, which is the journal's typeset text; worth reading as the definition of RQM's stable facts: a fact relative to one system is stable for another when the other may sum over it classically, which decoherence gives to order ε, only for a system that cannot reach the environment. Stability is approximate and relational, not a step toward observer-independence. Short; its one derivation is a partial trace, and inter-observer agreement gets one sentence.
Version2
Tagsquantum-foundations
Cited as “paper” byNOTE-1226 — Di Biagio & Rovelli — Stable facts, relative facts
Cited as “source” byTHEORY-1075 — In relational quantum mechanics as Di Biagio and Rovelli define it, a fact relative to one system is stable for another, so that the other may sum over it classically, only approximately and only relative to that other system: decoherence of the first system by an environment the second cannot reach gives the classical rule to order of the environment states' overlap, a differently coupled system may still see interference, and a fact can be stable for a system for which it is not yet a fact, THEORY-1081 — Di Biagio and Rovelli locate the Frauchiger–Renner contradiction and the violation of the Local Friendliness inequalities in one step, a superobserver using facts relative to a friend he holds in full quantum control as if they were his own, which is the classical sum rule applied where those facts are not stable for him; they base quantum ontology on facts relative to systems rather than on stable facts, arguing that stability is itself relational and only approximate and counting the Local Friendliness violation as evidence, with an absolute macroreality emerging only approximately and only relative to systems for which decoherence is strong, THEORY-1230 — In relational quantum mechanics, with facts fixed by interaction and the classical sum rule used only within one context or where facts are stable, facts relative to different systems never yield contradictory predictions in extended Wigner's-friend scenarios, and a superobserver's later facts agree with his friend's

Graph View

Di Biagio, A., & Rovelli, C. (2021). Stable facts, relative facts. Foundations of Physics, 51(1), 30. doi:10.1007/s10701-021-00429-w.

Read in full on 2026-10-27 (NOTE-1226).

Why this is here

A19 §3 called it “extraordinarily close to our multiscale thesis”: a relation established by interaction becomes stable enough for an effective observer-independent description. A19 and A23 §VII used it for observation without a conscious observer. It is the record’s next step past Rovelli 1996 (LIT-1635, read). It bears on QUESTION-285 and CLAIM-478.

Backlinks