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.

The Consistent Histories formalism and the measurement problem

on 2015-8-21 8:27pm GMT

Publication date: Available online 20 August 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

Author(s): Elias Okon, Daniel Sudarsky

In response to a recent rebuttal of Okon and Sudarsky (2014b) presented in Griffiths (2015), we defend the claim that the Consistent Histories formulation of quantum mechanics does not solve the measurement problem. In order to do so, we argue that satisfactory solutions to the problem must not only not contain anthropomorphic terms (such as measurement or observer) at the fundamental level, but also that applications of the formalism to concrete situations (e.g., measurements) should not require any input not contained in the description of the situation at hand at the fundamental level. Our assertion is that the Consistent Histories formalism does not meet the second criterion. We also argue that the so-called second measurement problem, i.e., the inability to explain how an experimental result is related to a property possessed by the measured system before the measurement took place, is only a pseudo-problem. As a result, we reject the claim, defended in Griffiths (2015), that the capacity of the Consistent Histories formalism to solve it should count as an advantage over other interpretations.

Emergence in holographic scenarios for gravity

on 2015-8-21 8:27pm GMT

Publication date: Available online 21 August 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

Author(s): Dennis Dieks, Jeroen van Dongen, Sebastian de Haro

‘Holographic’ relations between theories have become an important theme in quantum gravity research. These relations entail that a theory without gravity is equivalent to a gravitational theory with an extra spatial dimension. The idea of holography was first proposed in 1993 by Gerard ׳t Hooft on the basis of his studies of evaporating black holes. Soon afterwards the holographic ‘AdS/CFT’ duality was introduced, which since has been intensively studied in the string theory community and beyond. Recently, Erik Verlinde has proposed that even Newton׳s law of gravitation can be related holographically to the ‘thermodynamics of information’ on screens. We discuss these scenarios, with special attention to the status of the holographic relation in them and to the question of whether they make gravity and spacetime emergent. We conclude that only Verlinde׳s scheme straightforwardly instantiates emergence. However, assuming a non-standard interpretation of AdS/CFT may create room for the emergence of spacetime and gravity there as well.

An argument for ψ-ontology in terms of protective measurements

on 2015-8-21 8:27pm GMT

Publication date: Available online 17 August 2015

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics

Author(s): Shan Gao

The ontological model framework provides a rigorous approach to address the question of whether the quantum state is ontic or epistemic. When considering only conventional projective measurements, auxiliary assumptions are always needed to prove the reality of the quantum state in the framework. For example, the Pusey–Barrett–Rudolph theorem is based on an additional preparation independence assumption. In this paper, we give a new proof of ψ-ontology in terms of protective measurements in the ontological model framework. The proof does not rely on auxiliary assumptions, and it also applies to deterministic theories such as the de Broglie–Bohm theory. In addition, we give a simpler argument for ψ-ontology beyond the framework, which is based on protective measurements and a weaker criterion of reality. The argument may be also appealing for those people who favor an anti-realist view of quantum mechanics.

Can time have a more dynamical role in a quantum field?

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

on 2015-8-19 6:06pm GMT

Yau, Hou (2015) Can time have a more dynamical role in a quantum field? [Preprint]

The British Journal for the Philosophy of Science - Advance Access

on 2015-8-19 2:35pm GMT

If the most familiar overlapping (branching universe) interpretation of Everettian quantum mechanics (EQM) is correct, then each of us is constantly splitting into multiple people. This consequence gives rise to the quantum doomsday argument, which threatens to draw crippling epistemic consequences from EQM. However, a diverging (parallel universe) interpretation of EQM undermines the quantum doomsday argument completely. This appears to tell in favour of the diverging interpretation. But it is surprising that a metaphysical question that is apparently underdetermined by the physics should be settled by purely epistemological considerations; and I argue that the positive case for divergence based on the quantum doomsday effect is ultimately unsuccessful. I discuss how some influential treatments of Everettian confirmation handle the quantum doomsday puzzle, and suggest that it can most satisfyingly be resolved via a naturalistic approach to the metaphysics of modality.

**1.***Introduction***2.***The Doomsday Argument***3.***The Quantum Doomsday Argument***4.***Doomsday and Divergence***5.***Solutions to the Quantitative Problem***6.***Many Worlds and Modal Realism***7.***Conclusion*

Understanding the Pointer States. (arXiv:1508.04101v1 [quant-ph])

on 2015-8-18 3:19am GMT

Authors: Carlos Alexandre Brasil, Leonardo Andreta de Castro

In quantum mechanics, pointer states are eigenstates of the observable of the measurement apparatus that represent the possible positions of the display pointer of the equipment. The origin of this concept lies in attempts to fill the blanks in the Everett's relative-state interpretation, and to make it a fully valid description of physical reality. To achieve this, it was necessary to consider not only the main system interacting with the measurement apparatus (like von Neumann and Everett did) but also the role of the environment in eliminating correlations between different possible measurements when interacting with the measurement apparatus. The interaction of the environment with the main system (and the measurement apparatus) is the core of the decoherence theory, which followed Everett's thesis. In this article, we review the measurement process according to von Neumann, Everett's relative state interpretation, the purpose of decoherence and some of its follow-up until Wojciech Zurek's primordial paper that consolidated the concept of pointer state, previously presented by Heinz Dieter Zeh. Employing a simple physical model consisting of a pair of two-level systems -- one representing the main system, the other the measurement apparatus -- and a thermal bath -- representing the environment -- we show how pointer states emerge, explaining its contributions to the question of measurement in quantum mechanics, as well as its limitations. Finally, we briefly show some of its consequences. This paper is accessible to readers with elementary knowledge about quantum mechanics, on the level of graduate courses.

An axiomatic basis for quantum mechanics. (arXiv:1508.03709v1 [quant-ph])

on 2015-8-18 3:19am GMT

Authors: Gianni Cassinelli, Pekka Lahti

In this paper we use the framework of generalized probabilistic theories to present two sets of basic assumptions, called axioms, for which we show that they lead to the Hilbert space formulation of quantum mechanics. The key results in this derivation are the co-ordinatization of generalized geometries and a theorem of Sol\'er which characterizes Hilbert spaces among the orthomodular spaces. A generalized Wigner theorem is applied to reduce some of the assumptions of the theorem of Sol\'er to the theory of symmetry in quantum mechanics. Since this reduction is only partial we also point out the remaining open questions.

physics.hist-ph updates on arXiv.org

on 2015-8-18 3:19am GMT

Authors: A. S. Sanz

To date, quantum mechanics has proven to be our most successful theoretical model. However, it is still surrounded by a "mysterious halo" that can be summarized in a simple but challenging question: Why quantum phenomena are not understood under the same logic as classical ones? Although this is an open question (probably without an answer), from a pragmatist's point of view there is still room enough to further explore the quantum world, marveling ourselves with new physical insights. We just need to look back in the historical evolution of the quantum theory and thoroughly reconsider three key issues: (1) how this has developed since its early stages at a conceptual level, (2) what kind of experiments can be performed at present in a laboratory, and (3) what nonstandard conceptual models are available to extract some extra information. This contribution is aimed at providing some answers (and, perhaps, also raising some issues) to these questions through one of such models, namely Bohmian mechanics, a hydrodynamic formulation of the quantum theory, which is currently trying to open new pathways of understanding. Specifically, the Chapter constitutes a brief and personal overview on the historic and contextual evolution of this quantum formulation, its physical meaning and interest (leaving aside metaphysical issues), and how it may help to overcome some preconceived paradoxical aspects of the quantum theory.

Please comment with your real name using good manners.