Weekly Papers on Quantum Foundations (43)

Authors: Mariam Bouhmadi-LópezChe-Yu ChenPisin Chen

We re-examine the quantum geometrodynamical approach within the Eddington-inspired-Born-Infeld theory of gravity, which was first proposed in our previous work [1]. A thorough analysis of the classical Hamiltonian with constraints is carried and the correctness and self-consistency of the modified Wheeler-DeWitt equation (WDW) is studied. We find that based on the newly obtained WDW equation derived with the use of the Dirac brackets, the conclusion reached in Ref.[1] can be corroborated. The big rip singularity present in the classical theory, and induced by a phantom perfect fluid, is expected to be avoided when quantum effects encoded on the modified WDW equation are taken into account.

Publication date: Available online 19 October 2018

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

Author(s): Trevor Teitel

Abstract

Background independence begins life as an informal property that a physical theory might have, often glossed as ‘doesn’t posit a fixed spacetime background’. Interest in trying to offer a precise account of background independence has been sparked by the pronouncements of several theorists working on quantum gravity that background independence embodies in some sense an essential discovery of the General Theory of Relativity, and a feature we should strive to carry forward to future physical theories. This paper has two goals. The first is to investigate what a world must be like in order to be truly described by a background independent theory given extant accounts of background independence. The second is to argue that there are no non-empirical reasons to be more confident in theories that satisfy extant accounts of background independence than in theories that don’t. The paper concludes by drawing a general moral about a way in which focussing primarily on mathematical formulations of our physical theories can adversely affect debates in the metaphysics of physics.

Authors: Aurélien Drezet

This is a short Memo about the recently published paper ‘Quantum theory cannot consistently describe the use of itself’ by D. Frauchiger and R. Renner. Here I decipher the paradox and argue as a Bohmian should do.

Abstract

According to recent arguments for panpsychism, all (or most) physical properties are dispositional, dispositions require categorical grounds, and the only categorical properties we know are phenomenal properties. Therefore, phenomenal properties can be posited as the categorical grounds of all (or most) physical properties—in order to solve the mind–body problem and/or in order avoid noumenalism about the grounds of the physical world. One challenge to this case comes from dispositionalism, which agrees that all physical properties are dispositional, but denies that dispositions require categorical grounds. In this paper, I propose that this challenge can be met by the claim that the only (fundamentally) dispositional properties we know are phenomenal properties, in particular, phenomenal properties associated with agency, intention and/or motivation. Versions of this claim have been common in the history of philosophy, and have also been supported by a number of contemporary dispositionalists (and other realists about causal powers). I will defend a new and updated version of it. Combined with other premises from the original case for panpsychism—which are not affected by the challenge from dispositionalism—it forms an argument that dispositionalism entails panpsychism.

de Ronde, Christian and Fernández Mouján, Raimundo and Cesar, Massri (2018) Taking Mermin’s Relational Interpretation of QM Beyond Cabello’s and Seevinck’s No-Go Theorems. [Preprint]
François, Jordan (2018) Artificial vs Substantial Gauge Symmetries: a Criterion and an Application to the Electroweak Model. [Preprint]
Weatherall, James Owen (2018) Geometry and Motion in General Relativity. [Preprint]

Abstract

Parallel lives (PL) is an ontological model of nature in which quantum mechanics and special relativity are unified in a single universe with a single space-time. Point-like objects called lives are the only fundamental objects in this space-time, and they propagate at or below c, and interact with one another only locally at point-like events in space-time, very much like classical point particles. Lives are not alive in any sense, nor do they possess consciousness or any agency to make decisions—they are simply point objects which encode memory at events in space-time. The only causes and effects in the universe occur when lives meet locally, and thus the causal structure of interaction events in space-time is Lorentz invariant. Each life traces a continuous world-line through space-time, and experiences its own relative world, fully defined by the outcomes of past events along its world-line (never superpositions), which are encoded in its external memory. A quantum field comprises a continuum of lives throughout space-time, and familiar physical systems like particles each comprise a sub-continuum of the lives of the field. Each life carries a hidden internal memory containing a local relative wavefunction, which is a local piece of a pure universal wavefunction, but it is the relative wavefunctions in the local memories throughout space-time which are physically real in PL, and not the universal wavefunction in configuration space. Furthermore, while the universal wavefunction tracks the average behavior of the lives of a system, it fails to track their individual dynamics and trajectories. There is always a preferred separable basis, and for an irreducible physical system, each orthogonal term in this basis is a different relative world—each containing some fraction of the lives of the system. The relative wavefunctions in the lives’ internal memories govern which lives of different systems can meet during future local interactions, and thereby enforce entanglement correlations—including Bell inequality violations. These, and many other details, are explored here, but several aspects of this framework are not yet fleshed out, and work is ongoing.

Swanson, Noel (2018) Deciphering the Algebraic CPT Theorem. [Preprint]
Bradley, Clara (2018) The Non-Equivalence of Einstein and Lorentz. [Preprint]
Gambini, Rodolfo and Garcia-Pintos, Luis Pedro and Pullin, Jorge (2018) A single-world consistent interpretation of quantum mechanics from fundamental time and length uncertainties. [Preprint]

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