Ovidiu Cristinel Stoica
Apr 23, 2026·quant-ph·PDF Page and Wootters (1983) showed how time and dynamics can emerge in a stationary system containing a clock. Albrecht (1995) later showed, for discrete time, that within this framework any dynamical evolution can be obtained simply by choosing a different clock. Marletto and Vedral (2017) claimed that this ambiguity disappears assuming that the clock and the rest of the world do not interact. I show that their proof relies on an incorrect mathematical assumption. Also, eliminating the ambiguity completely would obstruct spacetime symmetries. Whereas the original clock ambiguity concerns all possible histories of a discrete-time system evolving under arbitrary Hamiltonians, but not the Hamiltonians themselves, I prove a stronger version for continuous and discrete unbounded time: the ambiguity extends to both histories and Hamiltonians, including noninteracting ones. Only the dimension of the Hilbert space remains. One might hope to dismiss the ambiguity as merely perspectival, but I show that this would predict incorrect correlations between outcomes and their records, making even knowledge impossible. Purely relational approaches therefore face both the stronger and the original clock ambiguity problems. The ambiguity is removed by taking into account the physical meaning of the operators.
Frank Wang
We examine the English translation of Albert Einstein's groundbreaking 1925 paper on Bose-Einstein condensation. We guide readers to execute the calculations Einstein outlined for the specific heat above the condensation temperature, correct some numerical errors, and compare his formula with a different one published in the American Journal of Physics in 2004. The history of the acceptance of Einstein's theory will be summarized.
Andrew Fowlie
Prompted by misconceptions in the recent literature, we review the justifications for naturalness arguments and Occam's razor found in Bayesian statistics. We discuss the automatic Occam's razor that emerges in Bayesian formalism, bringing together points of view from diverse fields, including statistics, social sciences, physics and machine learning. In pedagogical calculations, we demonstrate that this automatic razor disfavors unnatural models in which predictions must be fine-tuned to agree with observation.
Emily Adlam
Apr 20, 2026·quant-ph·PDF Recently, Hausmann and Renner have pointed out that several famous paradoxes relating to black holes have a similar character to various Extended Wigner's Friend paradoxes. In this paper I consider what the connection between these things could teach us about the Wigner's Friend scenarios. I argue that if we take the analogy between these cases seriously, the black hole paradoxes appear to favour a certain class of response to the Wigner's Friend scenario - specifically, those which posit intrinsic relationality, rather than effective and emergent relationality, and also those which posit some kind of retrocausality.
James M. Cline
Recently arxiv:2604.12897 urged that the terminology "neutrinoless double beta decay" should be changed to "Majorana double beta decay" to properly give credit to Majorana, and to focus on the positive aspects of the phenomenon -- supposed creation of matter in the laboratory -- rather than the negative: absence of something, embarrassment over false claims of detection, and a "sociology of suspicion." I argue that the current terminology is more accurate and descriptive, and that the claimed reasons for its adoption are lacking in credibility.
Jonathon Sendall
This paper develops a conditional framework for understanding the emergence of measurable physical structure from a pre-metric domain. Contemporary physics provides powerful and precise descriptions of relations among already-defined observables, yet offers comparatively little on the prior question of how observability, separability, and metric structure themselves arise. I propose that if three-dimensional spacetime is the result of an asymmetric projection from a non-orientable pre-geometric regime grounded in a minimal invariant, then a determinate and internally constrained set of consequences follows. These include: time reinterpreted as projection asymmetry rather than as a dimension or entropy gradient; matter as stabilised residue of projection rather than ontological primitive; quantum correlation as pre-separable unity dissolved by non-orientable topology; black holes as regimes of projection saturation rather than information sinks; dark matter as structured lag in the projection process rather than undetected particle species; and gravity as metric tension at sites of high projection density. The framework does not claim empirical confirmation. Its claim is that the proposal is internally coherent, structurally constrained, capable of generating non-trivial research directions, and that several phenomena currently treated as anomalous or paradoxical become expected consequences of the architecture rather than problems requiring additional postulates. An annex presents candidate formal objects and identifies research obligations for each consequence.
Enrico Bozzetto, Jonte R. Hance
Apr 15, 2026·quant-ph·PDF In the literature, there are two differing definitions of contextuality: Kochen and Specker's, and Spekkens' (or ``generalised''). However, researchers using one of these definitions rarely consider the other, meaning comparative analysis of these two notions is rare. In this paper, we advance the idea that Kochen-Specker contextuality provides a generalisation of the idea of system being fundamentally nonclassical, while Spekkens' noncontextuality provides a generalisation of the idea of a system being classical. This allows us to reconcile the two approaches, as different stages in a hierarchy of classicality/nonclassicality.
John B. DeBrota, Christian List
Apr 14, 2026·quant-ph·PDF Consciousness and quantum mechanics are among the most puzzling phenomena studied in the sciences. Some scholars suggest they are related, though others think this claim commits a "minimization of mystery" fallacy. The aim of this programmatic paper is to draw attention to a less widely discussed parallel between consciousness and quantum mechanics: both challenge the classical objectivist worldview of science. Under certain assumptions, they are each in tension with a package of metaphysical theses -- "non-relationalism", "non-fragmentation", and "one world" -- that jointly make up that worldview. This points to three distinct non-objectivist responses: the "relationalist", "fragmentalist", and "many-subjective-worlds" ones. We will map out their pros and cons.
Francesco Vissani
The term 'neutrinoless' is a cornerstone of modern particle physics, yet it defines a fundamental process by what is missing rather than what is created. We trace the origins of this privative neologism to a 1953 experimental claim and show how a 'sociology of suspicion' transformed Ettore Majorana's affirmative ontology into an agnostic shorthand. By examining this linguistic shift, we argue that our current terminology may obscure the profound physical meaning of the search. Reclaiming the language of 'matter creation' is not merely a semantic choice, but a timely conceptual shift to bridge the gap between experimental caution and the radical character of the laws of nature we aim to uncover.
Mikołaj Sienicki, Krzysztof Sienicki
Apr 14, 2026·quant-ph·PDF Roman Schnabel's article argues that the Einstein-Podolsky-Rosen (EPR) paradox can be resolved by identifying a flaw in what the author calls the "EPR implication" and by using radioactive alpha decay as an example showing that predictability does not exclude genuine randomness. The paper is clearly written and addresses an important foundational question. In our view, however, its main conclusion does not follow. The article narrows the original EPR argument, attributes too much to Bell-inequality violations, and replaces the central EPR structure - which involves incompatible observables and locality-based reasoning - with a simpler case of correlated random events. The result is an interesting interpretive remark, but not, we think, a satisfactory scientific resolution of the EPR problem.
Emily Adlam
Apr 13, 2026·quant-ph·PDF I argue that there is a straightforward way to understand the occurrence of wavefunction collapses or 'quantum events' in relational approaches to quantum mechanics: we necessarily encounter a discontinuity in our description when a system interacts with the reference relative to which we are describing it, since the reference system cannot be described relative to itself. This makes it clear how recent concerns around quantum events in relational quantum mechanics should be resolved. However, the solution requires accepting that quantum mechanics is not a complete description of all physical facts, and moreover I argue that this is most likely inevitable if we want to be able to give a precise description of quantum events.
Davide Neri
During the voyages that led him to discover the new continent bearing his name, Amerigo Vespucci made interesting astronomical observations of the southern sky. In the past, his data have been interpreted with criteria that do not follow Vespucci's indications, resulting in identifications that are not credible or even leading to the assertion that the data themselves are incomprehensible. However, it is possible to construct a coherent picture of all the information, arriving at an identification that is in some cases very probable, in other cases almost certain, of the stars described by Vespucci. Analysis of documents shows that he made good-quality measurements, but his incomplete knowledge of ancient texts prevented him from distinguishing the new stars from the already known ones, giving rise to a period of confusion in 16th century celestial cartography.
Vassilios Karakostas
Apr 11, 2026·quant-ph·PDF According to various no-go results in the foundations of quantum mechanics, for any system associated to a Hilbert space of dimension higher than two, it is not possible to assign definite truth values to all propositions pertaining to the system without generating a Kochen-Specker contradiction. In this respect, the Bub-Clifton uniqueness theorem is utilized for arguing that truth-value definiteness is consistently restored with respect to a determinate sublattice of propositions defined by the state of the quantum system concerned and a particular observable to be measured. On this basis, a perspectivist/contextual account of truth valuation in the quantum domain is produced that satisfies Tarski's criterion of material adequacy for a theory of truth. In light of the latter, perspectivist truth conforms to perspective or context-bound correspondence of a de re nature, designating locally an objectively existing state of affairs. Such an account derives by virtue of the microphysical nature of physical reality in displaying a context-dependence of facts; thus, it essentially opposes a non-perspectival, metaphysically fixed point of reference, or a panoptical standpoint from which to state all facts of nature.
Roman Schnabel
Apr 10, 2026·quant-ph·PDF In 1935, Albert Einstein, Boris Podolsky and Nathan Rosen (EPR) published a thought experiment that is entirely correct, has been demonstrated in real experiments, and is now the most famous in quantum physics. Their pioneering work described, for the first time, quantum correlations and can be regarded as a very early glimpse into today's 'deep' quantum technologies, by which I mean those that enhance functionality by making use of quantum correlations. However, their work also contains a paradox that Erwin Schroedinger had already recognised as such in 1935 and which has since been cemented by the so-called Bell experiments. Here, I am now able to pinpoint the origin of the paradox within the chain of reasoning, which ultimately resolves the paradox.
Yoshiyuki Ohmura, Yasuo Kuniyoshi
What is the meaning of physical causal closure? Jaegwon Kim explicitly adopts a conception of causation according to which physical causation is effectively identified with deterministic physical lawfulness, and equates it with physical determinism. While this conception is internally coherent, it differs from currently dominant theories of causation. Physics and the theory of causation serve different descriptive purposes. In this study, we refer to them, respectively, as the Physical Stance and the Causal Stance. Within this framework, physical determinism belongs to the Physical Stance, and physical causal closure is defined only within the Causal Stance. Consequently, the two should not be equated. On this basis, this study reconstructs Davidson's anomalous monism as a materialist position that acknowledges mental causation without contradicting physical determinism. Furthermore, we propose a linguistic framework in which physical causal closure does not hold in the Causal Stance while physical determinism remains intact in the Physical Stance.
Alexey Burov, Alexei Tsvelik
We demonstrate that the system of fine-tuning constraints for life is, in a sense, overdetermined: the a priori probability of its feasibility is extremely low, especially in the chemical sector. This entails that the structure of the physical laws is even more "unreasonable" than Eugene Wigner envisaged.
Carlos Baiget Orts
We present SESCC (Speed-Error Signals Cross-Correlation), a method for dating ancient star catalogues from the cross-correlation between stellar proper-motion speeds and positional residuals. At the true epoch, residuals are independent of proper-motion speed; the epoch estimate is the trial date that minimises this cross-correlation. For ecliptic latitudes, SESCC applies the dot product between speeds and residuals across all catalogue stars without subset selection or linear modelling. For ecliptic longitudes, SESCC-pairs uses pairwise longitude differences between neighbouring stars, making the method immune to any global longitude offset by algebraic construction. Validated against Tycho Brahe (1547 CE, true ~1580 CE) and Ulugh Beg (1452 CE, true 1437 CE), and confirmed invariant under offsets of +-6 deg, the method is applied to the Almagest. Both coordinates yield bootstrap distributions with 74% pre-Christian minima, consistent with a Hipparchan origin and inconsistent with a Ptolemaic one. The near-absence of quarter-degree fractions in the Almagest longitudes, explained as the deterministic consequence of Ptolemy's precession correction, provides independent corroboration.
Richard Healey
Applications of quantum mechanics have led to many successful predictions and explanations of puzzling phenomena, and we now apply quantum mechanics to gain, process, and communicate information in novel ways. We can understand quantum mechanics by understanding how we have applied it. We should not seek agreement on the nature of the world it represents, because this theory does not itself represent the physical world (though its applications do help us to represent it better). When applied to a quantum state, quantum mechanics yields probabiities for physical events: both state and probability are objective--not because they represent elements of phyiscal reality, but because each exerts norrmative authority over the beliefs of anyone who accepts quantum mechanics and applies it relative to a physical situation they may (but need not) occupy. These events may be described by statements that are meaningful in an appropriate environmental context, and quantum mechanics can help one to say when that is. Measurement creates an appropriate context, so here the Born rule indirectly yields probabilities of measurement outcomes. The quantum state of a system does not "collapse" on measurement: a new state must be assigned relative to a physical situation in which information about the outcome is accessible. Understood this way, there is no measurement problem, and violations of Bell inequalities does not demonstrate "spooky" non-local action. Quantum field theories have no physical ontology of their own: a quantum field is a mathematical object in a model whose application helps us to improve and extend our descriptions of the world in other terms. We cannot realise the scenario of Wigner's friend and its recent extensions: but the data that provide overwhelming evidence for quantum mechanics are objective in the same sense as the relative measurement outcomes described in those scenarios.
Richard Healey
I take a pragmatist perspective on quantum theory. This is not a view of the world described by quantum theory. In this view quantum theory itself does not describe the physical world, nor our observatons, experiences or opinions of it. Instead, the theory offers reliable advice on when to expect an event of one kind or another, and on how strongly to expect each possible outcome of that event. The actual outcome is a perspectival fact: a fact relative to a physical context of assessment. Measurement outcomes and quantum states are both perspectival. By noticing that each must be relativized to an appropriate physical context one can resolve the measurement problem and the problem of nonlocal action. But if the outcome of a quantum measurement is not an absolute fact, then why shoud the statistics of such outcomes give us any objective reason to accept quantum theory? One can describe extensions of the scenario of Wigner's friend in which a statement expressing the outcome of a quantum measurement would be true relative to one such context but not relative to another. However, physical conditions in our world prevent us from realizing such scenarios. Since the outcome of every actual quantum measurement is certified at what is essentially a single context of assessment, the outcome relative to that context is an objective fact in the only sense that matters for science. We should accept quantum theory because the statistics these outcomes display are just those it leads us to expect.
Philip Goyal
One hundred years after the creation of quantum theory, there is no consensus on the kind of reality that is described by the theory. Here, I attribute the lack of progress to the prevailing interpretative methodology, which invariably takes the quantum formalism as the starting point for philosophical reflection and analysis. I argue that this methodology is particularly inappropriate, for it invariably marginalizes much of the theory's content, both that implicit in modelling heuristics and experimental practices, and that encapsulated in the mathematical structures of its formalism. In addition, the prevailing methodology offers little protection against undue influence by metaphysically-laden language which invariably accompanies the formalism. Here, I summarize an alternative methodology whose goal is to ensure that an interpretational project take into account all forms of theoretic content. The methodology harnesses the recent results of the quantum reconstruction program. These results distil the mathematical content of the quantum formalism into physical principles and assumptions, which are more readily philosophically digestible than the formalism itself, and bracket much of its metaphysically-laden language. As a case study of reconstruction-based interpretation, I describe the reconstruction of the identical particle formalism, and its step-by-step interpretation, highlighting the key questions that drive the interpretation forwards and the techniques and stances that are employed in each step. The interpretation yields a novel metaphysical profile for systems of identical particles as potential parts of a whole, which can be traced step-by-step to elementary experimental data and the reconstruction's physical postulates and assumptions. I also describe some of the pitfalls that one faces in any attempt to directly interpret the identical particle formalism.