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

Causality and chance in relativistic quantum field theories

on 2014-11-29 11:57am GMT

Publication date: November 2014

**Source:**Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, Volume 48, Part B

Author(s): Richard A. Healey

Bell appealed to the theory of relativity in formulating his principle of local causality. But he maintained that quantum field theories do not conform to that principle, even when their field equations are relativistically covariant and their observable algebras satisfy a relativistically motivated microcausality condition. A pragmatist view of quantum theory and an interventionist approach to causation prompt the reevaluation of local causality and microcausality. Local causality cannot be understood as a reasonable requirement on relativistic quantum field theories: it is unmotivated even if applicable to them. But microcausality emerges as a sufficient condition for the consistent application of a relativistic quantum field theory.

Black holes as particle accelerators: a brief review

Classical and Quantum Gravity – latest papers

on 2014-11-28 12:00am GMT

Rapidly rotating Kerr black holes can accelerate particles to arbitrarily high energy if the angular momentum of the particle is fine-tuned to some critical value. This phenomenon is robust as it is founded on the basic properties of geodesic orbits around a near-extremal Kerr black hole. On the other hand, the maximum energy of the acceleration is subjected to several physical effects. There is convincing evidence that the particle acceleration to arbitrarily high energy is one of the universal properties of general near-extremal black holes. We also discuss gravitational particle acceleration in a more general context. This article is intended to provide a pedagogical introduction to and a brief overview of this topic for non-specialists.

Killer Collapse: Empirically Probing the Philosophically Unsatisfactory Region of GRW

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

on 2014-11-27 8:39pm GMT

Sebens, Charles (2014) Killer Collapse: Empirically Probing the Philosophically Unsatisfactory Region of GRW. In: [2014] Philosophy of Science Assoc. 24th Biennial Mtg (Chicago, IL) .

on 2014-11-27 2:41am GMT

Authors: Daniel Bedingham

We describe a previously unexplored effect of the continuous spontaneous localization model whereby a correlation develops in the distributions of two nearby non-interacting particles following a period of diffusion. We propose the use of this effect as an experimental test differentiating between the continuous spontaneous localization model and standard quantum theory. The test involves building a joint probability distribution for the locations of the two particles by repeatedly releasing them from two nearby traps and subsequently measuring their positions after a brief period of time. We examine the scales of time, trap size, and particle mass necessary for observation.

Bulk Locality and Quantum Error Correction in AdS/CFT. (arXiv:1411.7041v1 [hep-th])

on 2014-11-27 2:41am GMT

Authors: Ahmed Almheiri, Xi Dong, Daniel Harlow

We point out a connection between the emergence of bulk locality in AdS/CFT and the theory of quantum error correction. Bulk notions such as Bogoliubov transformations, location in the radial direction, and the holographic entropy bound all have natural CFT interpretations in the language of quantum error correction. We also show that the question of whether bulk operator reconstruction works only in the causal wedge or all the way to the extremal surface is related to the question of whether or not the quantum error correcting code realized by AdS/CFT is also a “quantum secret sharing scheme”, and suggest a tensor network calculation that may settle the issue. Interestingly, the version of quantum error correction which is best suited to our analysis is the somewhat nonstandard “operator algebra quantum error correction” of Beny, Kempf, and Kribs. Our proposal gives a precise formulation of the idea of “subregion-subregion” duality in AdS/CFT, and clarifies the limits of its validity.

Bell Inequalities, Experimental Protocols and Contextuality. (arXiv:1411.7085v1 [quant-ph])

on 2014-11-27 2:41am GMT

Authors: Marian Kupczynski

The violation of Bell, CHSH and CH inequalities indicates only that the assumption of “conterfactual definiteness” and/or the probabilistic models used in proofs were incorrect. In this paper we discuss in detail an intimate relation between experimental protocols and probabilistic models. In particular we show that local realistic and stochastic hidden variable models are inconsistent with the experimental protocols used in spin polarization correlation experiments. In particular these models neglect a contextual character of quantum theory (QT) and do not describe properly quantum measurements. We argue that the violation of various inequalities gives arguments against the irreducible randomness of act of the measurement. Therefore quantum probabilities are reducible what means that QT is emergent. In this case one could expect to discover in time series of data some unpredicted fine structures proving that QT is not predictably complete what would be a major discovery.

Retrocausality at no extra cost

on 2014-11-27 12:00am GMT

Abstract

One obstacle faced by proposals of retrocausal influences in quantum mechanics is the perceived high conceptual cost of making such a proposal. I assemble here a metaphysical picture consistent with the possibility of retrocausality and not precluded by the known physical structure of our reality. This picture employs two relatively well-established positions—the block universe model of time and the interventionist account of causation—and requires the dismantling of our ordinary asymmetric causal intuition and our ordinary intuition about epistemic access to the past. The picture is then built upon an existing model of agent deliberation that permits us to strike a harmony between our causal intuitions and the fixity of the block universe view. I conclude that given the right mix of these reasonable metaphysical and epistemological ingredients there is no conceptual cost to such a retrocausal picture of quantum mechanics.

on 2014-11-25 8:23am GMT

Authors: Floyd W. Stecker (NASA/UCLA), Sean T. Scully (JMU), Stefano Liberati (SISSA), David Mattingly (UNH)

High energy cosmic neutrino observations provide a sensitive test of Lorentz invariance violation, which may be a consequence of quantum gravity theories. We consider a class of non-renormalizable, Lorentz invariance violating operators that arise in an effective field theory description of Lorentz invariance violation in the neutrino sector inspired by Planck-scale physics and quantum gravity models. We assume a conservative generic scenario for the redshift distribution of extragalactic neutrino sources and employ Monte Carlo techniques to describe superluminal neutrino propagation, treating kinematically allowed energy losses of superluminal neutrinos caused by both vacuum pair emission and neutrino splitting. We consider EFTs with both non-renormalizable CPT-odd and non-renormalizable CPT-even operator dominance. We then compare the spectra derived using our Monte Carlo calculations in both cases with the spectrum observed by IceCube in order to determine the implications of our results regarding Planck-scale physics. We find that if the drop off in the neutrino flux above ~2 PeV is caused by Planck scale physics, rather than by a limiting energy in the source emission, a potentially significant pileup effect would be produced just below the drop off energy in the case of CPT-even operator dominance. However, such a clear drop off effect would not be observed if the CPT-odd, CPT-violating term dominates.

Probing deformed commutators with macroscopic harmonic oscillators. (arXiv:1411.6410v1 [gr-qc])

on 2014-11-25 8:23am GMT

Authors: Mateusz Bawaj, Ciro Biancofiore, Michele Bonaldi, Federica Bonfigli, Antonio Borrielli, Giovanni Di Giuseppe, Lorenzo Marconi, Francesco Marino, Riccardo Natali, Antonio Pontin, Giovanni A. Prodi, Enrico Serra, David Vitali, Francesco Marin

A minimal observable length is a common feature of theories that aim to merge quantum physics and gravity. Quantum mechanically, this concept is associated to a nonzero minimal uncertainty in position measurements, which is encoded in deformed commutation relations. In spite of increasing theoretical interest, the subject suffers from the complete lack of dedicated experiments and bounds to the deformation parameters are roughly extrapolated from indirect measurements. As recently proposed, low-energy mechanical oscillators could allow to reveal the effect of a modified commutator. Here we analyze the free evolution of high quality factor micro- and nano-oscillators, spanning a wide range of masses around the Planck mass $m_{\mathrm{P}}$ (${\approx 22\,\mu\mathrm{g}}$), and compare it with a model of deformed dynamics. Previous limits to the parameters quantifying the commutator deformation are substantially lowered.

Quantum Evolution Leading to Classicality: A Concrete Example. (arXiv:1404.2605v3 [gr-qc] UPDATED)

on 2014-11-25 8:23am GMT

Authors: Kinjalk Lochan, Krishnamohan Parattu, T. Padmanabhan

Can certain degrees of freedom of a closed physical system, described by a time-independent Hamiltonian, become more and more classical as they evolve from some state? This question is important because our universe seems to have done just that! We construct an explicit, simple, example of such a system with just two degrees of freedom, of which one achieves `spontaneous classicalization’. It starts from a quantum state and under the usual Hamiltonian evolution, becomes more and more classical (in a well-defined manner in terms of the Wigner function) as time progresses. This is achieved without the usual procedures of integrating out a large number of environmental degrees of freedom or conventional decoherence. We consider different ranges of parameter space and identify the conditions under which spontaneous classicalization occurs in our model. The mutual interaction between the sub-systems of a larger system can indeed drive some of the subsystems to a classical configuration, with a phase space trajectory of evolution. We also argue that the results of our toy model may well be general characteristics of certain class of interacting systems. Several implications are discussed.

Heating of trapped ultracold atoms by collapse dynamics

on 2014-11-24 3:00pm GMT

Author(s): Franck Laloë, William J. Mullin, and Philip Pearle

The continuous spontaneous localization (CSL) theory alters the Schrödinger equation. It describes wave-function collapse as a dynamical process instead of an ill-defined postulate, thereby providing macroscopic uniqueness and solving the so-called measurement problem of standard quantum theory. CSL…

[Phys. Rev. A 90, 052119] Published Mon Nov 24, 2014

Horizons and non-local time evolution of quantum mechanical systems. (arXiv:1411.5848v1 [gr-qc])

on 2014-11-24 4:11am GMT

Authors: R. Casadio

According to general relativity, trapping surfaces and horizons are classical causal structures that arise in systems with sharply defined energy and corresponding gravitational radius. The latter concept can be extended to a quantum mechanical state simply by means of the spectral decomposition, which allows one to define an associated “horizon wave-function”. Since this auxiliary wave-function contains crucial information about the causal structure of space-time, a new proposal is formulated for the time-evolution of quantum states in order to account for the fundamental classical property that outer observers cannot receive signals from inside a horizon. The simple case of a single massive free particle at rest is used throughout the paper as a toy model to illustrate the main ideas.

A PBR-like argument for psi-ontology in terms of protective measurements

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

on 2014-11-23 11:03pm GMT

Gao, Shan (2014) A PBR-like argument for psi-ontology in terms of protective measurements. [Preprint]