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arxiv: 2510.26562 · v3 · submitted 2025-10-30 · 🪐 quant-ph

Limits of Absoluteness of Observed Events in Timelike Scenarios: A No-Go Theorem

Sumit Mukherjee , Jonte R. Hance This is my paper

Pith reviewed 2026-05-18 03:04 UTC · model grok-4.3

classification 🪐 quant-ph
keywords quantum foundationsWigner's friend paradoxabsoluteness of observed eventscausal inequalitiesno-go theoremtimelike scenariosretrocausality
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The pith

Quantum mechanics violates a causal inequality from absoluteness of observed events combined with time symmetry.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper constructs a time-ordered version of the Local Friendliness Theorem called the Causal Friendliness Paradox. It shows that assuming events are absolute, there is no retrocausality, pseudo-events screen off influences, and time-ordering plus value assignments are symmetric leads to a bound on correlations. Quantum mechanics exceeds this bound in timelike scenarios. Even when absoluteness is weakened to an operational version that only requires consistent statistics for observed events, the same violations appear. This extends the tension between quantum theory and observer-independent events from spacelike to purely sequential cases.

Core claim

Conjoining Absoluteness of Observed Events, No Retrocausality, Screening via Pseudo Events, and Axiological Time Symmetry produces a causal inequality violated by quantum mechanics. Replacing the full strength of Absoluteness of Observed Events with a weaker operational form that demands only that each observer sees a single definite outcome still generates inequalities that quantum theory breaks.

What carries the argument

The Causal Friendliness Paradox, formed by substituting Axiological Time Symmetry for locality in the structure of the Local Friendliness Theorem while keeping the other three assumptions.

If this is right

  • Any model respecting all four assumptions cannot reproduce the quantum predictions for certain chains of timelike observations.
  • At least one of the four assumptions must fail in quantum theory.
  • The incompatibility survives even when absoluteness is relaxed to require only that each observer registers one outcome.
  • Wigner's-friend-style contradictions appear in purely sequential, non-spacelike settings.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The result suggests the problem with absolute events is not tied to spatial separation but arises from the causal ordering itself.
  • Models that drop time symmetry while keeping absolute events might evade the paradox in sequential quantum experiments.
  • Tests using chained measurements on single particles or sequential observers could check the bounds without requiring superposed laboratories.

Load-bearing premise

Axiological Time Symmetry can stand in for spatial locality while still forcing the same no-go structure on observed events.

What would settle it

A concrete timelike sequence of measurements on entangled systems whose observed correlations stay inside the derived bound instead of exceeding it would falsify the claimed incompatibility.

Figures

Figures reproduced from arXiv: 2510.26562 by Jonte R. Hance, Sumit Mukherjee.

Figure 1
Figure 1. Figure 1: FIG. 1. The extended Wigner’s Friend Scenario for the Local [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Time-ordered measurement scenario for Causal [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Causal influence diagram for the Causal Friendliness [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
read the original abstract

Wigner's Friend-type paradoxes challenge the assumption that events are absolute -- that when we measure a system, we obtain a single result, which is not relative to anything or anyone else. These paradoxes highlight the tension between quantum theory and our intuitions about reality being observer-independent. Building on a recent result that developed these paradoxes into a no-go theorem, namely the Local Friendliness Theorem, we introduce the Causal Friendliness Paradox, a time-ordered analogue of it. In this framework, we replace the usual locality assumption with Axiological Time Symmetry (ATS), and show that, when combined with the assumptions of Absoluteness of Observed Events (AOE), No Retrocausality (NRC), and Screening via Pseudo Events (SPE), we obtain a causal inequality. We then show that quantum mechanics violates this inequality and is therefore incompatible with at least one of these assumptions. To probe which assumption might be incompatible, we then examine whether AOE in its entirety is essential for this no-go result. We propose a weaker, operational form of AOE that still leads to inequalities that quantum mechanics violates. This result shows that even under relaxed assumptions, quantum theory resists reconciliation with classical notions of absolute events, reinforcing the foundational significance of Wigner's Friend-type paradoxes in timelike scenarios.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript introduces the Causal Friendliness Paradox as a timelike analogue of the Local Friendliness Theorem. Combining Absoluteness of Observed Events (AOE), No Retrocausality (NRC), Screening via Pseudo Events (SPE), and Axiological Time Symmetry (ATS) yields a causal inequality; quantum mechanics is shown to violate it. The authors further relax AOE to an operational form and derive additional inequalities that quantum theory still violates, arguing that this limits the absoluteness of observed events even in timelike scenarios.

Significance. If the central derivation holds, the result is significant for quantum foundations: it extends Wigner-friend no-go theorems to purely timelike causal structures by substituting ATS for spatial locality, and it shows that even a weakened operational AOE remains incompatible with quantum predictions. This strengthens the case that quantum mechanics resists classical notions of absolute events without requiring spatial separation.

major comments (2)
  1. [§3] §3 (ATS definition and independence): The claim that ATS supplies a locality substitute whose time-ordering and value-symmetry conditions hold independently of quantum measurement outcomes is load-bearing for the incompatibility result. The text does not explicitly show that the symmetry is formulated at a level that prevents unitary evolution or measurement from correlating effective time-ordering with outcome values; if such correlation is possible, the derived causal inequality does not apply to the quantum case and the no-go theorem does not follow.
  2. [Derivation section] Derivation of the causal inequality (section following the assumption list, prior to the QM violation claim): The explicit form of the inequality obtained from AOE + NRC + SPE + ATS is not stated, nor are the algebraic steps showing how standard quantum predictions (e.g., via unitary evolution on the friend-observer system) violate it. Without this, verification of the violation and of the absence of post-hoc parameter choices is impossible.
minor comments (2)
  1. Notation for pseudo-events and their screening role should be introduced with a small diagram or explicit mapping to the causal structure before the inequality is derived.
  2. The operational relaxation of AOE is defined only informally; a precise operational statement (e.g., in terms of observable statistics) would clarify what is retained versus dropped relative to the original AOE.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading and constructive comments. We address the major comments point by point below, indicating planned revisions where appropriate.

read point-by-point responses

  1. Referee: [§3] §3 (ATS definition and independence): The claim that ATS supplies a locality substitute whose time-ordering and value-symmetry conditions hold independently of quantum measurement outcomes is load-bearing for the incompatibility result. The text does not explicitly show that the symmetry is formulated at a level that prevents unitary evolution or measurement from correlating effective time-ordering with outcome values; if such correlation is possible, the derived causal inequality does not apply to the quantum case and the no-go theorem does not follow.

    Authors: We thank the referee for this observation on the formulation of Axiological Time Symmetry (ATS). ATS is introduced in §3 as an axiological symmetry principle operating at the level of the causal structure itself, prior to and independent of any specific quantum measurement outcomes or unitary evolution. Its time-ordering and value-symmetry conditions are therefore not permitted to become outcome-dependent. To make this independence fully explicit and foreclose the possibility of the correlation the referee describes, we will add a clarifying paragraph in the revised manuscript. revision: yes

  2. Referee: [Derivation section] Derivation of the causal inequality (section following the assumption list, prior to the QM violation claim): The explicit form of the inequality obtained from AOE + NRC + SPE + ATS is not stated, nor are the algebraic steps showing how standard quantum predictions (e.g., via unitary evolution on the friend-observer system) violate it. Without this, verification of the violation and of the absence of post-hoc parameter choices is impossible.

    Authors: We agree that the explicit causal inequality and the algebraic steps establishing its violation by quantum theory were not displayed with sufficient detail. In the revised manuscript we will state the inequality in full and insert the complete derivation, beginning from the joint assumptions and proceeding through the standard unitary evolution on the friend-observer system to the explicit violation. This addition will permit direct verification and confirm the absence of post-hoc adjustments. revision: yes

Circularity Check

0 steps flagged

No significant circularity; derivation self-contained against stated assumptions

full rationale

The paper explicitly lists four assumptions (AOE, NRC, SPE, ATS) and derives a causal inequality from their conjunction before showing violation by standard quantum predictions. This is a conventional no-go structure with no quoted reduction of the target inequality to a fitted parameter, self-definition, or unverified self-citation chain. ATS is introduced as an explicit modeling replacement for locality rather than smuggled in via prior ansatz; the weaker operational AOE is likewise defined separately. No load-bearing step reduces by construction to its own inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 4 axioms · 0 invented entities

The no-go result is built directly on four explicit assumptions plus a weakened fifth; these function as the paper's axioms rather than derived results.

axioms (4)
  • domain assumption Absoluteness of Observed Events (AOE): every observed event has a single, observer-independent outcome.
    Central premise whose relaxation is later tested; invoked to derive the causal inequality.
  • domain assumption No Retrocausality (NRC): future measurements do not influence past outcomes.
    Standard assumption retained from prior no-go theorems.
  • domain assumption Screening via Pseudo Events (SPE): certain intermediate events screen off correlations.
    Used to close the causal structure in the timelike setting.
  • ad hoc to paper Axiological Time Symmetry (ATS): symmetry in how value or utility is assigned across time orderings.
    Introduced to replace spatial locality; specific to this timelike formulation.

pith-pipeline@v0.9.0 · 5763 in / 1555 out tokens · 32895 ms · 2026-05-18T03:04:20.496845+00:00 · methodology

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