Weekly Papers on Quantum Foundations (11)

Projective measurement of black holes. (arXiv:2203.04968v1 [hep-th])

We study the effect of projective measurements on the entanglement structure of quantum black holes. It is shown that the entanglement verification in monitored quantum circuits, recently discussed in condensed matter physics, is equivalent to the information recovery from a black hole with projective measurements. This correspondence provides useful predictions about non-perturbative effects on quantum gravity and some insights on the black hole interior as well as the final state proposal.

PQM and the GUP: Implications of Lattice Dynamics and Minimal Uncertainties in Quantum Mechanics and Cosmology. (arXiv:2203.05398v1 [gr-qc])

We compare two alternative representations of quantum mechanics: Polymer Quantum Mechanics (PQM), which presents features similar to Loop Quantum Gravity and Loop Quantum Cosmology, and the Generalized Uncertainty Principle (GUP) representation, that through a modified Algebra yields an alternative uncertainty principle similar to those derived in String Theories and Brane Cosmology. These formalisms can be recast to apparently look similar, but while the GUP yields an absolute minimal uncertainty on position, PQM implements some kind of ultraviolet cut-off through a lattice and does not have a minimal uncertainty. Then we implement them on the anisotropic Bianchi I model in Misner-like variables on a semiclassical level: PQM always implies a removal of the singularities, while the GUP fails to do so, highlighting once again how the two representations are fundamentally incompatible.

A mathematical framework for operational fine tunings. (arXiv:2003.10050v3 [quant-ph] UPDATED)

In the framework of ontological models, the inherently nonclassical features of quantum theory always seem to involve properties that are fine tuned, i.e. properties that hold at the operational level but break at the ontological level. Their appearance at the operational level is due to unexplained special choices of the ontological parameters, which is what we mean by a fine tuning. Famous examples of such features are contextuality and nonlocality. In this article, we develop a theory-independent mathematical framework for characterizing operational fine tunings. These are distinct from causal fine tunings — already introduced by Wood and Spekkens in [NJP,17 033002(2015)] — as the definition of an operational fine tuning does not involve any assumptions about the underlying causal structure. We show how known examples of operational fine tunings, such as Spekkens’ generalized contextuality, violation of parameter independence in Bell experiment, and ontological time asymmetry, fit into our framework. We discuss the possibility of finding new fine tunings and we use the framework to shed new light on the relation between nonlocality and generalized contextuality. Although nonlocality has often been argued to be a form of contextuality, this is only true when nonlocality consists of a violation of parameter independence. We formulate our framework also in the language of category theory using the concept of functors.

A note on Penrose’s Spin-Geometry Theorem and the geometry of empirical quantum angles’. (arXiv:2112.14538v2 [gr-qc] UPDATED)

In the traditional formalism of quantum mechanics, a simple direct proof of (a version of) the Spin Geometry Theorem of Penrose is given; and the structure of a model of the space of the quantum directions’, defined in terms of elementary $SU(2)$-invariant observables of the quantum mechanical systems, is sketched.

Why gauge? Conceptual Aspects of Gauge theories. (arXiv:2203.05339v1 [physics.hist-ph])

Authors: Henrique Gomes

This thesis is about conceptual aspects of gauge theories.

Gauge theories lie at the heart of modern physics: in particular, they constitute the standard model of particle physics. At its simplest, the idea of gauge is that nature is best described using a descriptively redundant language; the different descriptions are said to be related by a gauge symmetry. The over-arching question the thesis aims to answer is: how can descriptive redundancy be fruitful for physics?

The Forces outside the static limit in the rotating frame. (arXiv:2203.05263v1 [gr-qc])

In this paper we consider the rotating frame of the Minkowski spacetime in order to describe the inertial forces outside the static limit. We consider the inertial forces inside the static limit to find the classical analogue afterwards we find out the expressions for these forces outside the static limit where we can’t consider the limit $\frac{v}{c}\to 0$. We show that in general case if the angular velocity of the object $\Omega$ is equal to the angular momentum $\omega$ then the acceleration is equal to zero.

A New Guest in the Third Quantized Multiverse. (arXiv:2203.05387v1 [gr-qc])

Authors: Samuel Barroso BellidoFabian Wagner

In the present article we point out a conceptual issue of the Third Quantization formalism for Canonical Quantum Gravity. Based on earlier results on interuniversal entanglement, the theory and with it the picture of noninteracting universe-antiuniverse pairs is incomplete. In particular, the variation of the entanglement entropy with the scale factor, understood as a measure of time, implies either an interaction between pairs of universes or universes with a heat bath. We propose a simple solution to the problem by adding a new quantum field to the formalism. Correspondingly, particles of this field mediate interactions between universes — depending on the model at tree level or one loop — and may further provide a heat bath in the background.

The Physics and Metaphysics of Pure Shape Dynamics

Vassallo, Antonio and Naranjo, Pedro and Koslowski, Tim (2022) The Physics and Metaphysics of Pure Shape Dynamics. [Preprint]

Quantum Mechanics in a Time-Asymmetric Universe: On the Nature of the Initial Quantum State

Chen, Eddy Keming (2018) Quantum Mechanics in a Time-Asymmetric Universe: On the Nature of the Initial Quantum State. The British Journal for the Philosophy of Science, 72 (4). ISSN 1464-3537

Strong Determinism

Chen, Eddy Keming (2022) Strong Determinism. [Preprint]

What Represents Space-time? And What Follows for Substantivalism vs. Relationalism and Gravitational Energy?

Pitts, J. Brian (2022) What Represents Space-time? And What Follows for Substantivalism vs. Relationalism and Gravitational Energy? [Preprint]

On Two Slights to Noether’s First Theorem: Mental Causation and General Relativity

Pitts, J. Brian (2022) On Two Slights to Noether’s First Theorem: Mental Causation and General Relativity. Rethinking the Concept of Laws of Nature: Natural Order in the Light of Contemporary Science.

Arithmetic logical Irreversibility and the Turing’s Halt Problem

Lapin, Yair (2021) Arithmetic logical Irreversibility and the Turing’s Halt Problem. [Preprint]

Smooth Infinitesimals in the Metaphysical Foundation of Spacetime Theories

Chen, Lu and Chen, Lu (2022) Smooth Infinitesimals in the Metaphysical Foundation of Spacetime Theories. [Preprint]

Nonlocal nonlinear phononics

Nature Physics, Published online: 07 March 2022; doi:10.1038/s41567-022-01512-3

Nonlinear phononics is a method for creating transient structural changes in solids, but its effect is limited to the region of optical excitation. Now, coupling to a propagating polariton allows nonlinear phononics to drive a nonlocal response.