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.

Violation of the Holographic Principle in the Loop Quantum Gravity. (arXiv:1509.00843v1 [gr-qc])

on 2015-9-05 7:26am GMT

Authors: Ozan Sargın, Mir Faizal

In this paper, we analyze the holographic principle using loop quantum gravity (LQG). This will be done by analysing a simple quantum mechanical system using polymeric quantization. As the polymeric quantization is the characteristic feature of loop quantum gravity, we will argue that this calculation will indicate the effect on the holographic principle from the loop quantum gravity. Thus, we will be able to explicitly demonstrate the violation of the holographic principle in the loop quantum gravity.

Thermal Equilibrium of a Macroscopic Quantum System in a Pure State

on 2015-9-04 2:00pm GMT

Author(s): Sheldon Goldstein, David A. Huse, Joel L. Lebowitz, and Roderich Tumulka

Thermal equilibrium can be indicated macroscopically by spatially uniform temperature and chemical potentials, but also by a microscopic property emerging from quantum entanglement.

[Phys. Rev. Lett. 115, 100402] Published Fri Sep 04, 2015

Dualities and emergent gravity: Gauge/gravity duality

on 2015-9-04 12:12pm GMT

Publication date: Available online 2 September 2015

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

Author(s): Sebastian de Haro

In this paper I develop a framework for relating dualities and emergence: two notions that are close to each other but also exclude one another. I adopt the conception of duality as ‘isomorphism’, from the physics literature, cashing it out in terms of three conditions. These three conditions prompt two conceptually different ways in which a duality can be modified to make room for emergence; and I argue that this exhausts the possibilities for combining dualities and emergence (via coarse-graining). I apply this framework to gauge/gravity dualities, considering in detail three examples: AdS/CFT, Verlinde׳s scheme, and black holes. My main point about gauge/gravity dualities is that the theories involved, qua theories of gravity, must be background-independent. I distinguish two senses of background-independence: (i) minimalistic and (ii) extended. I argue that the former is sufficiently strong to allow for a consistent theory of quantum gravity; and that AdS/CFT is background-independent on this account; while Verlinde׳s scheme best fits the extended sense of background-independence. I argue that this extended sense should be applied with some caution: on pain of throwing the baby (general relativity) out with the bath-water (extended background-independence). Nevertheless, it is an interesting and potentially fruitful heuristic principle for quantum gravity theory construction. It suggests some directions for possible generalisations of gauge/gravity dualities. The interpretation of dualities is discussed; and the so-called ‘internal’ vs. ‘external’ viewpoints are articulated in terms of: (i) epistemic and metaphysical commitments; (ii) parts vs. wholes. I then analyse the emergence of gravity in gauge/gravity dualities in terms of the two available conceptualisations of emergence; and I show how emergence in AdS/CFT and in Verlinde׳s scenario differ from each other. Finally, I give a novel derivation of the Bekenstein–Hawking black hole entropy formula based on Verlinde׳s scheme; the derivation sheds light on several aspects of Verlinde׳s scheme and how it compares to Bekenstein׳s original calculation.

A Non-local Reality: Is There a Phase Uncertainty in Quantum Mechanics?

Latest Results for Foundations of Physics

on 2015-9-04 12:00am GMT

**Abstract**

A century after the advent of quantum mechanics and general relativity, both theories enjoy incredible empirical success, constituting the cornerstones of modern physics. Yet, paradoxically, they suffer from deep-rooted, so-far intractable, conflicts. Motivations for violations of the notion of relativistic locality include the Bell’s inequalities for hidden variable theories, the cosmological horizon problem, and Lorentz-violating approaches to quantum geometrodynamics, such as Horava–Lifshitz gravity. Here, we explore a recent proposal for a “real ensemble” non-local description of quantum mechanics, in which “particles” can copy each others’ observable values AND phases, independent of their spatial separation. We first specify the exact theory, ensuring that it is consistent and has (ordinary) quantum mechanics as a fixed point, where all particles with the same values for a given observable have the same phases. We then study the stability of this fixed point numerically, and analytically, for simple models. We provide evidence that most systems (in our study) are locally stable to small deviations from quantum mechanics, and furthermore, the phase variance per value of the observable, as well as systematic deviations from quantum mechanics, decay as \(\sim \) (energy \(\times \) time) \(^{-2n}\), where \(n \ge 1\) . Interestingly, this convergence is controlled by the *absolute* value of energy (and not energy difference), suggesting a possible connection to gravitational physics. Finally, we discuss different issues related to this theory, as well as potential novel applications for the spectrum of primordial cosmological perturbations and the cosmological constant problem.

Introduction: The Metaphysics of Quantum Mechanics

on 2015-9-04 12:00am GMT

Can Bohmian Mechanics Be Made Background Independent?

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

on 2015-9-03 7:50pm GMT

Vassallo, Antonio (2015) Can Bohmian Mechanics Be Made Background Independent? [Preprint]

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

on 2015-9-02 5:12pm GMT

Allori, Valia (2015) How to Make Sense of Quantum Mechanics(and More):Fundamental Physical Theories and Primitive Ontology. [Preprint]

Is the Composite Fermion a Dirac Particle?

Recent Articles in Phys. Rev. X

on 2015-9-02 2:00pm GMT

Author(s): Dam Thanh Son

Quantum phenomena include the fractional quantum Hall effect, whose quasiparticle is the composite fermion. Theorists show that composite fermions possess different quantum numbers than the electrons or holes they were derived from.

[Phys. Rev. X 5, 031027] Published Wed Sep 02, 2015

Latest Results for Foundations of Physics

on 2015-9-02 12:00am GMT

on 2015-9-01 1:47am GMT

Authors: Rainer Kaltenbaek

Quantum superposition is central to quantum theory but challenges our concepts of reality and spacetime when applied to macroscopic objects like Schr\”odinger’s cat. For that reason, it has been a long-standing question whether quantum physics remains valid unmodified even for truly macroscopic objects. By now, the predictions of quantum theory have been confirmed via matter-wave interferometry for massive objects up to $10^4\,$ atomic mass units (amu). The rapid development of new technologies promises to soon allow tests of quantum theory for significantly higher test masses by using novel techniques of quantum optomechanics and high-mass matter-wave interferometry. Such experiments may yield novel insights into the foundations of quantum theory, pose stringent limits on alternative theoretical models or even uncover deviations from quantum physics. However, performing experiments of this type on Earth may soon face principal limitations due to requirements of long times of flight, ultra-low vibrations, and extremely high vacuum. Here, we present a short overview of recent developments towards the implementation of the proposed space-mission MAQRO, which promises to overcome those limitations and to perform matter-wave interferometry in a parameter regime orders of magnitude beyond state-of-the-art.

on 2015-9-01 1:47am GMT

Authors: Lev Vaidman

Bartkiewicz et al. [Phys. Rev. A 91, 012103 (2015)] provided an alternative analysis of experiment performed by Danan et al. [Phys. Rev. Lett. 111, 240402 (2013)] which presented surprising evidence regarding the past of photons passing through an interferometer. They argued that the quantity used by Danan et al. is not a suitable which-path witness, and proposed an alternative. It is argued that the quantum and classical analyses of Bartkiewicz et al. are inconsistent and both are inappropriate for describing the past of photons in a properly working interferometer.

An argument for psi-ontology in terms of protective measurements. (arXiv:1508.07684v1 [quant-ph])

on 2015-9-01 1:47am GMT

Authors: 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 psi-ontology in terms of protective measurements in the ontological model framework. The proof does not rely on auxiliary assumptions, and also applies to deterministic theories such as the de Broglie-Bohm theory. In addition, we give a simpler argument for psi-ontology beyond the framework, which is only 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.

Unitary inequivalence in classical systems

on 2015-9-01 12:00am GMT

**Abstract**

Ruetsche (Interpreting quantum theories, 2011) argues that a *problem of unitarily inequivalent representations* arises in quantum theories with infinitely many degrees of freedom. I provide an algebraic formulation of classical field theories and show that unitarily inequivalent representations arise there as well. I argue that the classical case helps us rule out one possible response to the problem of unitarily inequivalent representations called Hilbert Space Conservatism.

“Formal” Versus “Empirical” Approaches to Quantum–Classical Reduction

on 2015-9-01 12:00am GMT

**Abstract**

I distinguish two types of reduction within the context of quantum-classical relations, which I designate “formal” and “empirical”. Formal reduction holds or fails to hold solely by virtue of the mathematical relationship between two theories; it is therefore a two-place, a priori relation between theories. Empirical reduction requires one theory to encompass the range of physical behaviors that are well-modeled in another theory; in a certain sense, it is a three-place, a posteriori relation connecting the theories and the domain of physical reality that both serve to describe. Focusing on the relationship between classical and quantum mechanics, I argue that while certain formal results concerning singular \(\hbar \rightarrow 0\) limits have been taken to preclude the possibility of reduction between these theories, such results at most provide support for the claim that singular limits block reduction in the formal sense; little if any reason has been given for thinking that they block reduction in the empirical sense. I then briefly outline a strategy for empirical reduction that is suggested by work on decoherence theory, arguing that this sort of account remains a fully viable route to the empirical reduction of classical to quantum mechanics and is unaffected by such singular limits.

Comment on “Role of potentials in the Aharonov-Bohm effect”

on 2015-8-31 2:00pm GMT

Author(s): Yakir Aharonov, Eliahu Cohen, and Daniel Rohrlich

Are the electromagnetic scalar and vector potentials dispensable? Vaidman [Phys. Rev. A **86**, 040101(R) (2012)] has suggested that local interactions of gauge-invariant quantities, e.g., magnetic torques, suffice for the description of all quantum electromagnetic phenomena. We analyze six thought expe…

[Phys. Rev. A 92, 026101] Published Mon Aug 31, 2015

Nonlinear optics: A matter of gravity

Nature Physics – AOP – nature.com science feeds

on 2015-8-31 12:00am GMT

Nature Physics. doi:10.1038/nphys3480

Author: Daniele Faccio

Nonlocal, nonlinear interactions of optical beams can be described by the Newton–Schrödinger equation for quantum gravity, offering an analogue for studying gravitational phenomena.