arXiv subjects

David Theurel

Publications and source records attributed to David Theurel.

4 recordsLinked to original sources

arXiv2025

The limits of knowledge in classical physics resemble the quantum uncertainty relation

Building upon a recent analysis of the measurement process in Hamiltonian mechanics, this article investigates the Bayesian epistemology of classical physics -- the landscape of accessible probability distributions over phase space. I prove a thermodynamic limitation on the information that can be obtained about a classical system by means of observations: A direct analogue of the Robertson-Schr\"odinger quantum uncertainty relation controls the acquisition of information at the classical microscale. Central to this theorem is the notion of the "quality" of a measuring probe; a temperature-dependent strictly positive quantity that serves as a figure of merit of the probe, and that plays the role of $1/\hbar$ in the classical uncertainty relation. This study sets the stage for a new area of research into resource theories of classical measurement, in which high-quality measurements and high-information states of knowledge are the limited resources.

cond-mat.stat-mech↗

arXiv2021

Incompatible observables in classical physics: A closer look at measurement in Hamiltonian mechanics

Quantum theory famously entails the existence of incompatible measurements; pairs of observables which cannot be simultaneously measured to arbitrary precision. Incompatibility is widely regarded to be a uniquely quantum phenomenon, linked to failure to commute of quantum operators. Even in the face of deep parallels between quantum commutators and classical Poisson brackets, no connection has been established between the Poisson algebra and any intrinsic limitations to classical measurement. Here I examine measurement in classical Hamiltonian physics as a process involving the joint evolution of an object-system and a finite-temperature measuring apparatus. Instead of the ideal measurement capable of extracting information without disturbing the system, I find a Heisenberg-like precision-disturbance relation: Measuring an observable leaves all Poisson-commuting observables undisturbed but inevitably disturbs all non-Poisson-commuting observables. In this relation the role of h-bar is played by an apparatus-specific quantity, q-bar. While not a universal constant, q-bar takes a finite positive value for any apparatus that can be built. I show that a classical version of Ozawa's model of quantum measurement, originally proposed as a means to violate the Heisenberg relation, does not violate the classical relation. Hence, incompatibility may prove to be a feature not only of quantum, but of classical physics too. This approach points the way to studying the Bayesian epistemology of classical physics, which was until now assumed to be trivial. It now seems possible that it is non-trivial and bears a resemblance to the quantum formalism. These findings may be of interest to researchers working on foundations of quantum mechanics, particularly for psi-epistemic interpretations. And there may be applications in the fields of precision measurement, nanoengineering and molecular machines.

quant-ph↗

arXiv2021

Vector-based Pedestrian Navigation in Cities

How do pedestrians choose their paths within city street networks? Researchers have tried to shed light on this matter through strictly controlled experiments, but an ultimate answer based on real-world mobility data is still lacking. Here, we analyze salient features of human path planning through a statistical analysis of a massive dataset of GPS traces, which reveals that (1) people increasingly deviate from the shortest path when the distance between origin and destination increases, and (2) chosen paths are statistically different when origin and destination are swapped. We posit that direction to goal is a main driver of path planning and develop a vector-based navigation model that is a statistically better predictor of human paths than a model based on minimizing distance with stochastic effects. Our findings generalize across two major US cities with different street networks, hinting to the fact that vector-based navigation might be a universal property of human path planning.

q-bio.NC↗

arXiv2014

Extragalactic gamma-ray signal from dark matter annihilation: an appraisal

We re-evaluate the extragalactic gamma-ray flux prediction from dark matter annihilation in the approach of integrating over the nonlinear matter power spectrum, extrapolated to the free-streaming scale. We provide an estimate of the uncertainty based entirely on available N-body simulation results and minimal theoretical assumptions. We illustrate how an improvement in the simulation resolution, exemplified by the comparison between the Millennium and Millennium II simulations, affects our estimate of the flux uncertainty and we provide a "best guess" value for the flux multiplier, based on the assumption of stable clustering for the dark matter perturbations described as a collision-less fluid. We achieve results comparable to traditional Halo Model calculations, but with a much simpler procedure and a more general approach, as it relies only on one, directly measurable quantity. In addition we discuss the extension of our calculation to include baryonic effects as modeled in hydrodynamical cosmological simulations and other possible sources of uncertainty that would in turn affect indirect dark matter signals. Upper limit on the integrated power spectrum from supernovae lensing magnification are also derived and compared with theoretical expectations.

astro-ph.CO↗