Events as Spacetime Anchors: Local Irreversibility at the Interface of Quantum Field Theory and Relativity

The Problem of Descriptive Primitives

General Relativity (GR) and Quantum Field Theory (QFT) rely on fundamentally different building blocks. GR is built upon spacetime events—localized occurrences with invariant causal relations—that form the skeleton of physical history. QFT, conversely, is built upon unitary evolution of states and operators, which are inherently reversible and lack an internal mechanism to designate when a process culminates in a definite, objective fact. This paper addresses the gap between these two theories by defining the criteria for when a quantum process becomes an 'anchored' spacetime event.

Local Generative Freezing

The author introduces the concept of 'local generative freezing' to describe the transition from quantum potentiality to relativistic facticity. This transition is not a modification of quantum mechanics but an operational characterization of how information becomes embedded in the environment. An event is considered 'anchored' when it satisfies three jointly sufficient conditions:

1. Local Classicalization: The system's reduced state becomes approximately diagonal in a preferred pointer basis, effectively suppressing quantum interference.
2. Redundant Record Formation: The outcome is imprinted across multiple environmental fragments, ensuring the information is robust and publicly accessible.
3. Irreversibility Against Recovery: The effective channel between the system and the environment becomes entanglement-breaking, meaning the original quantum coherence cannot be recovered even with global access to the environment.

Spacetime as a Causal Skeleton

By satisfying these criteria, a quantum interaction ceases to be a mere coherent amplitude and becomes a stable node in a causal network. The author demonstrates through a repeated-collision model that these conditions are reached at a specific 'freezing time.' This framework suggests that physical history is not a continuous trajectory in state space, but rather a partially ordered skeleton of frozen events. This approach remains fully compatible with standard QFT and relativistic causality, providing a way to reconcile the unitary nature of quantum mechanics with the event-based structure of spacetime.