This is a list of this week’s papers on quantum foundations published in various journals or uploaded to preprint servers such as arxiv.org and PhilSci Archive.

CP and other Symmetries of Symmetries. (arXiv:1608.05240v1 [hep-ph])

on 2016-8-19 3:08am GMT

Authors: Andreas Trautner

Outer automorphisms of symmetries (“symmetries of symmetries”) in relativistic quantum field theories are studied, including charge conjugation (C), space-reflection (P) , and time-reversal (T) transformations. The group theory of outer automorphisms is pedagogically introduced and it is shown that CP transformations are special outer automorphisms of the global, local, and space-time symmetries of a theory. It is shown that certain discrete groups allow for a group theoretical prediction of parameter independent CP violating complex phases with fixed geometrical values. The remainder of this thesis pioneers the study of outer automorphisms which are not related to C, P, or T. It is shown how outer automorphisms, in general, relate symmetry invariants and, in theories with spontaneous symmetry breaking, imply relations between different vacuum expectation values. Thereby, outer automorphisms can give rise to emergent symmetries. An example model with a discrete symmetry and three copies of the Standard Model Higgs field is discussed, in which the rich outer automorphism structure completely fixes the Higgs VEVs in their field space direction, including CP violating relative phases. This underlies the phenomenon of spontaneous geometrical CP violation. The possible relevance of outer automorphisms for a wide field of future studies is highlighted.

physics.hist-ph updates on arXiv.org

on 2016-8-19 3:08am GMT

Authors: Angelo Baracca, Silvio Bergia, Flavio Del Santo

We present a reconstruction of the studies on the Foundations of Quantum Mechanics (FQM) carried out in Italy at the turn of the 1960s. Actually, they preceded the revival of the interest of the American physicists towards the FQM around mid-1970s, recently reconstructed by David Kaiser in a book of 2011. An element common to both cases is the role played by the young generation, even though the respective motivations were quite different. In the US they reacted to research cuts after the war in Vietnam, and were inspired by the New Age mood. In Italy the dissatisfaction of the young generations was rooted in the student protests of 1968 and the subsequent labour and social fights, which challenged the role of scientists. The young generations of physicists searched for new scientific approaches and challenged their own scientific knowledge and role. The criticism to the FQM and the perspectives of submitting them to experimental tests were perceived as an innovative research field and this attitude was directly linked to the search for an innovative and radical approach in the history of science. All these initiatives gave rise to booming activity throughout the 1970s, contributing to influence the scientific attitude and the teaching approach.

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-8-19 12:23am GMT

Suárez, Mauricio (2016) The Chances of Propensities. [Preprint]

A persistent particle ontology for QFT in terms of the Dirac sea

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-8-19 12:21am GMT

Deckert, Dirk-André and Esfeld, Michael and Oldofredi, Andrea (2016) A persistent particle ontology for QFT in terms of the Dirac sea. [Preprint]

Constructor Theory of Probability

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences current issue

on 2016-8-17 10:28am GMT

Unitary quantum theory, having no Born Rule, is *non-probabilistic*. Hence the notorious problem of reconciling it with the*unpredictability* and *appearance of stochasticity* in quantum measurements. Generalizing and improving upon the so-called ‘decision-theoretic approach’, I shall recast that problem in the recently proposed *constructor theory of information—*where quantum theory is represented as one of a class of *superinformation theories*, which are *local*, *non-probabilistic* theories conforming to certain constructor-theoretic conditions. I prove that the unpredictability of measurement outcomes (to which constructor theory gives an exact meaning) necessarily arises in superinformation theories. Then I explain how the appearance of stochasticity in (finitely many) repeated measurements can arise under superinformation theories. And I establish sufficient *conditions* for a superinformation theory to inform decisions (made under it) *as if* it were probabilistic, via a Deutsch–Wallace-type argument—thus defining a class of*decision-supporting* superinformation theories. This broadens the domain of applicability of that argument to cover constructor-theory compliant theories. In addition, in this version some of the argument’s assumptions, previously construed as merely decision-theoretic, follow from *physical properties* expressed by constructor-theoretic principles.

Thermodynamics and the structure of quantum theory. (arXiv:1608.04461v1 [quant-ph])

on 2016-8-17 7:17am GMT

Authors: Marius Krumm, Howard Barnum, Jonathan Barrett, Markus P. Mueller

Despite its enormous empirical success, the formalism of quantum theory still raises fundamental questions: why is nature described in terms of complex Hilbert spaces, and what modifications of it could we reasonably expect to find in some regimes of physics? Results in quantum gravity and general ideas of what a fundamental theory should look like suggest that thermodynamics plays a major role in the foundations of physics. In this paper, we address the question of which parts of quantum theory are already determined by compatibility with thermodynamics, and which aspects may still admit modification. We employ two postulates that any probabilistic theory with reasonable thermodynamic behavior should arguably satisfy. In the framework of generalized probabilistic theories, we show that these postulates already imply important aspects of quantum theory, like self-duality and analogues of projective measurements, subspaces and eigenvalues. However, they may still admit a class of theories beyond quantum mechanics. Using a thought experiment by von Neumann, we show that these theories admit a consistent thermodynamic notion of entropy, and prove that the second law holds for projective measurements and mixing procedures. Furthermore, we generalize the concept of state majorization, crucial to recent work in fine-grained quantum thermodynamics, to this class of theories, study additional entropy-like quantities based on measurement probabilities and convex decomposition probabilities, and uncover a relation between one of these quantities and Sorkin’s notion of higher-order interference.

on 2016-8-17 7:17am GMT

Authors: Abhay Ashtekar, Brajesh Gupt

Observational missions have provided us with a reliable model of the evolution of the universe starting from the last scattering surface all the way to future infinity. Furthermore given a specific model of inflation, using quantum field theory on curved space-times this history can be pushed \emph{back in time} to the epoch when space-time curvature was some $10^{62}$ times that at the horizon of a solar mass black hole! However, to extend the history further back to the Planck regime requires input from quantum gravity. An important aspect of this input is the choice of the background quantum geometry and of the Heisenberg state of cosmological perturbations thereon, motivated by Planck scale physics. This paper introduces first steps in that direction. Specifically we propose two principles that link quantum geometry and Heisenberg uncertainties in the Planck epoch with late time physics and explore in detail the observational consequences of the initial conditions they select. We find that the predicted temperature-temperature (T-T) correlations for scalar modes are indistinguishable from standard inflation at small angular scales even though the initial conditions are now set in the deep Planck regime. However, \emph{there is a specific power suppression at large angular scales}. As a result, the predicted spectrum provides a better fit to the PLANCK mission data than standard inflation, where the initial conditions are set in the general relativity regime. Thus, our proposal brings out a deep interplay between the ultraviolet and the infrared. Finally, the proposal also leads to specific predictions for power suppression at large angular scales also for the (T-E and E-E) correlations involving electric polarization. The PLANCK team is expected to release this data in the coming year.

Entanglement as an axiomatic foundation for statistical mechanics. (arXiv:1608.04459v1 [quant-ph])

on 2016-8-17 4:11am GMT

Authors: Giulio Chiribella, Carlo Maria Scandolo

We propose four information-theoretic axioms for the foundations of statistical mechanics in general physical theories. The axioms—Causality, Purity Preservation, Pure Sharpness, and Purification—identify a class of theories where every mixed state can be modelled as the marginal of a pure entangled state and where every unsharp measurement can be modelled as a sharp measurement on a composite system. This class includes quantum theory and a number of alternative theories, such as quantum theory with real amplitudes, as well as a suitable extension of classical probability theory where classical systems can be combined with other non-classical systems. Theories satisfying our axioms support well-behaved notions of majorization, entropy, and Gibbs states, allowing for an information-theoretic derivation of Landauer’s principle.

Would Superluminal Influences Violate the Principle of Relativity?

Philsci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-8-16 6:31pm GMT

Peacock, Kent A. (2014) Would Superluminal Influences Violate the Principle of Relativity? [Published Article or Volume]

on 2016-8-16 1:14pm GMT

Authors: James B. Hartle

We present a formulation of the decoherent (or consistent) histories quantum theory of closed systems starting with records of what histories happen. Alternative routes to a formulation of quantum theory like this one can be useful both for understanding quantum mechanics and for generalizing and extending it to new realms of application and experimental test.

physics.hist-ph updates on arXiv.org

on 2016-8-16 1:13pm GMT

Authors: Howard M. Wiseman, Eleanor G. Rieffel, Eric G. Cavalcanti

We address Gillis’ recent criticism [arXiv:1506.05795] of a series of papers (by different combinations of the present authors) on formulations of Bell’s theorem. Those papers intended to address an unfortunate gap of communication between two broad camps in the quantum foundations community that we identify as “operationalists” and “realists”. Here, we once again urge the readers to approach the question from an unbiased standpoint, and explain that Gillis’ criticism draws too heavily on the philosophical inclinations of one side of that debate — the realist camp. As part of that explanation we discuss intuition versus proof, look again at Bell’s formalizations of locality, and correct misstatements by Gillis of our views, and those of Bell and Einstein.

Popescu-Rohrlich correlations imply efficient instantaneous nonlocal quantum computation

on 2016-8-15 2:00pm GMT

Author(s): Anne Broadbent

In instantaneous nonlocal quantum computation, two parties cooperate in order to perform a quantum computation on their joint inputs, while being restricted to a *single* round of simultaneous communication. Previous results showed that instantaneous nonlocal quantum computation is possible, at the co…

[Phys. Rev. A 94, 022318] Published Mon Aug 15, 2016

Haags Theorem, Apparent Inconsistency, and the Empirical Adequacy of Quantum Field Theory

The British Journal for the Philosophy of Science – Advance Access

on 2016-8-14 4:01pm GMT

Haag’s theorem has been interpreted as establishing that quantum field theory cannot consistently represent interacting fields. Earman and Fraser have clarified how it is possible to give mathematically consistent calculations in scattering theory despite the theorem. However, their analysis does not fully address the worry raised by the result. In particular, I argue that their approach fails to be a complete explanation of why Haag’s theorem does not undermine claims about the empirical adequacy of particular quantum field theories. I then show that such empirical adequacy claims are protected from Haag’s result by the techniques that are required to obtain theoretical predictions for realistic experimental observables. I conclude by showing how Haag’s theorem is illustrative of a general tension between the foundational significance of results that can be obtained in perturbation theory and non-perturbative characterizations of the content of quantum field theory.

**1***Introduction***2***Haag’s Theorem and the Interaction Picture***3***Earman and Fraser on the Success of Scattering Theory***4***Haag’s Theorem and Empirical Adequacy***5***Conclusion*