Searcharxiv⌕ Search

arXiv subjects

Paul Kinsler

Publications and source records attributed to Paul Kinsler.

At least 19 recordsLinked to original sources
arXiv2026

LdT: An indicator of ionospheric activity based on statistical distributions in GNSS-derived TEC rates of change

Many aspects of our societies now depend upon satellite telecommunications, such as those requiring Global Navigation Satellite Systems (GNSS). GNSS is based on radio waves that propagate through the ionosphere and experience complicated propagation effects caused by inhomogeneities in its electron density. The Earth's ionosphere forms part of the solar-terrestrial environment, and its state is determined by the spatial distribution and temporal evolution of its electron density. It varies in response to the "space weather" combination of solar activity and geomagnetic conditions. Notably, the radio waves used in satellite telecommunications suffer due to the dispersive nature of the ionospheric plasma. Scales and indices that summarise the state of the solar-terrestrial environment due to solar activity and geomagnetic conditions already exist. However, the response of the ionosphere to active geomagnetic conditions, its geoeffectiveness, and its likely impact on systems and services are not encapsulated by these. This is due to the ionosphere's intrinsic day-to-day variability, persistent seasonal patterns, and because radio wave measurements of the ionosphere depend upon many factors. Here we develop a novel index that describes the state of the ionosphere during specific space weather conditions. It is based on propagation disturbances in GNSS signals, and is able to characterise the spatio-temporal evolution of ionospheric disturbances in near real time. This new scale encapsulates day-to-day variability, seasonal patterns, and the geo-effective response of the ionosphere to disturbed space weather conditions; and can be applied to data from any GNSS network. It is intended that this new scale will be utilised by agencies providing space weather services, as well as by service operators to appreciate the current conditions in the ionosphere, thus informing their operations.

physics.space-ph↗
arXiv2024

A multi-agent model of hierarchical decision dynamics

Decision making can be difficult when there are many actors (or agents) who may be coordinating or competing to achieve their various ideas of the optimum outcome. Here I present a simple decision making model with an explicitly hierarchical binary-tree structure, and evaluate how this might cooperate to take actions that match its various evaluations of the uncertain state of the world. Key features of agent behaviour are (a) the separation of its decision making process into three distinct steps: observation, judgement, and action; and (b) the evolution of coordination by the sharing of judgements.

cs.MA↗
arXiv2023

Stylized innovation: generating timelines by interrogating incrementally available randomised dictionaries

A key challenge when trying to understand innovation is that it is a dynamic, ongoing process, which can be highly contingent on ephemeral factors such as culture, economics, or luck. This means that any analysis of the real-world process must necessarily be historical - and thus probably too late to be most useful - but also cannot be sure what the properties of the web of connections between innovations is or was. Here I try to address this by designing and generating a set of synthetic innovation web "dictionaries" that can be used to host sampled innovation timelines, probe the overall statistics and behaviours of these processes, and determine the degree of their reliance on the structure or generating algorithm. Thus, inspired by the work of Fink, Reeves, Palma and Farr (2017) on innovation in language, gastronomy, and technology, I study how new symbol discovery manifests itself in terms of additional "word" vocabulary being available from dictionaries generated from a finite number of symbols. Several distinct dictionary generation models are investigated using numerical simulation, with emphasis on the scaling of knowledge as dictionary generators and parameters are varied, and the role of which order the symbols are discovered in.

cs.AI↗
arXiv2023

Agent swarms: cooperation and coordination under stringent communications constraint

Here we consider the communications tactics appropriate for a group of agents that need to "swarm" together in a highly adversarial environment. Specfically, whilst they need to cooperate by exchanging information with each other about their location and their plans; at the same time they also need to keep such communications to an absolute minimum. This might be due to a need for stealth, or otherwise be relevant to situations where communications are signficantly restricted. Complicating this process is that we assume each agent has (a) no means of passively locating others, (b) it must rely on being updated by reception of appropriate messages; and if no such update messages arrive, (c) then their own beliefs about other agents will gradually become out of date and increasingly inaccurate. Here we use a geometry-free multi-agent model that is capable of allowing for message-based information transfer between agents with different intrinsic connectivities, as would be present in a spatial arrangement of agents. We present agent-centric performance metrics that require only minimal assumptions, and show how simulated outcome distributions, risks, and connectivities depend on the ratio of information gain to loss. We also show that checking for too-long round-trip times can be an effective minimal-information filter for determining which agents to no longer target with messages.

cs.MA↗
arXiv2022

Electromagnetism, Axions, and Topology: a first-order operator approach to constitutive responses provides greater freedom

We show how the standard constitutive assumptions for the macroscopic Maxwell equations can be relaxed. This is done by arguing that the Maxwellian excitation fields (D,H) should be dispensed with, on the grounds that they (a) cannot be measured, and (b) act solely as gauge potentials for the charge and current. In the resulting theory, it is only the links between the fields (E,B) and the charge and current (ρ,J) that matter; and so we introduce appropriate linear operator equations that combine the Gauss and Maxwell-Ampere equations with the constitutive relations, eliminating (D,H). The result is that we can admit more types of electromagnetic media -- notably, the new relations can allow coupling in the bulk to a homogeneous axionic material; in contrast to standard EM where any homogeneous axion-like field is completely decoupled in the bulk, and only accessible at boundaries. We also consider a wider context, including the role of topology, extended non-axionic constitutive parameters, and treatment of Ohmic currents. A range of examples including an axonic response material is presented, including static electromagnetic scenarios, a possible metamaterial implementation, and how the transformation optics paradigm would be modified. Notably, these examples include one where topological considerations make it impossible to model using (D,H).

physics.optics↗
arXiv2022

Temporary Singularities and Axions: an analytic solution that challenges charge conservation

We construct an analytic solution to Maxwell's equations that violates global charge conservation, by building on the possibilities demonstrated in [Foundations of Physics 49, 330 (2019)]. The construction is valid for a spacetime containing a temporary singularity and a Maxwellian electrodynamics containing a proposed "topological" axion field. As such, it demonstrates that although "physics breaks down" at a singularity, the physical laws on the spacetime still impose constraints on what can happen. Further, the concepts of transformation optics can be applied to show that our specific mathematical solution has a much wider applicability.

gr-qc↗
arXiv2022

Evaporating black-holes, wormholes, and vacuum polarisation: must they always conserve charge?

A careful examination of the fundamentals of electromagnetic theory shows that due to the underlying mathematical assumptions required for Stokes' Theorem, global charge conservation cannot be guaranteed in topologically non-trivial spacetimes. However, in order to break the charge conservation mechanism we must also allow the electromagnetic excitation fields D, H to possess a gauge freedom, just as the electromagnetic scalar and vector potentials phi and A do. This has implications for the treatment of electromagnetism in spacetimes where black holes both form and then evaporate, as well as extending the possibilities for treating vacuum polarisation. Using this gauge freedom of D, H we also propose an alternative to the accepted notion that a charge passing through a wormhole necessarily leads to an additional (effective) charge on the wormhole's mouth.

gr-qc↗
arXiv2022

The surprising persistence of time-dependent quantum entanglement

The mismatch between elegant theoretical models and the detailed experimental reality is particularly pronounced in quantum nonlinear interferometry (QNI). In stark contrast to theory, experiments contain pump beams that start in impure states and that are depleted, quantum noise that affects -- and drives -- any otherwise gradual build up of the signal and idler fields, and nonlinear materials that are far from ideal and have a complicated time-dependent dispersive response. Notably, we would normally expect group velocity mismatches to destroy any possibility of measurable or visible entanglement, even though it remains intact -- the mismatches change the relative timings of induced signal-idler entanglements, thus generating "which path" information. Using a "positive-P" approach ideally suited to such problems, we show how the time-domain entanglement crucial for QNI can be -- and is -- recoverable despite the obscuring effects of real-world complications.

quant-ph↗
arXiv2021

Temporal boundaries in electromagnetic materials

Temporally modulated optical media are important in both abstract and applied applications, such as spacetime transformation optics, relativistic laser-plasma interactions, and dynamic metamaterials. Here we investigate the behaviour of temporal boundaries, and show that traditional approaches that assume constant dielectric properties, with loss incorporated as an imaginary part, necessarily lead to unphysical solutions. Further, although physically reasonable predictions can be recovered with a narrowband approximation, we show that appropriate models should use materials with a temporal response and dispersive behaviour.

physics.optics↗
arXiv2021

An introduction to spatial dispersion: revisiting the basic concepts

I describe three ways that the spatial properties of a wave propagation medium can cause dispersion, and propose that they should form the basics for correctly understanding and naming phenomena described as "spatial dispersion". In particular, I emphasise the specific spatial properties which generate the resulting dispersive -- i.e. spatially dispersive -- behaviour. The mechanisms are geometry, structure, and dynamics.

physics.optics↗
arXiv2020

Faraday's Law and Magnetic Induction: cause and effect, experiment and theory

Faraday's Law of induction is often stated as "a change in magnetic flux causes an EMF"; or, more cautiously, "a change in magnetic flux is associated with an EMF"; It is as well that the more cautious form exists, because the first "causes" form is incompatible with the usual expression $V = - \partial_t Φ$. This is not, however, to deny the causality as reasonably inferred from experimental observation - it is the equation for Faraday's Law of induction which does not represent the claimed cause-and-effect relationship. Here I investigate a selection of different approaches, trying to see how an explicitly causal mathematical equation, which attempts to encapsulate the "a change in magnetic flux causes ..." idea, might arise.

physics.class-ph↗
arXiv2019

Maxwell's (D, H ) excitation fields: lessons from permanent magnets

Macroscopic Maxwellian electrodynamics consists of four field quantities along with electric charges and electric currents. The fields occur in pairs, the primary ones being the electric and magnetic fields (E,B), and the other the excitation fields (D,H). The link between the two pairs of field is provided by constitutive relations, which specify (D,H) in terms of (E,B); this last connection enabling Maxwell's (differential) equations to be combined in a way that supports waves. In this paper we examine the role played by the excitation fields (D,H), showing that they can be regarded as not having a physical existence, and are merely playing a mathematically convenient role. This point of view is made particularly relevant when we consider competing constitutive models of permanent magnets, which although having the same measurable magnetic properties, have startlingly different behaviours for the magnetic excitation field H.

physics.class-ph↗
arXiv2018

Mode profile shaping in wire media: Towards an experimental verification

We show that an experimentally plausible system consisting of a modulated wire medium hosted in a metal cavity can preserve the longitudinal field profile shaping predicted by Boyd et al. (2018) on the basis of a perfectly periodic wire-only structure. These new frequency domain numerical results are a significant step towards justifying the construction of an experimental apparatus to test the field profile shaping in practise.

physics.app-ph↗
arXiv2018

The deconstructed hydrodynamic model for plasmonics

I give an exact but deconstructed version of the second-order wave-like equation that encapsulates the hydrodynamic model for plasmonics. Comprising two first order equations, the deconstruction has potential uses in understanding or interpreting the hydrodynamic model, since its meaning is not obscured by approximation. However, as the physical interpretation of the deconstructed model is difficult, due to the choice of the polarization as the significant quantity, I also consider a alternate model based on the polarization current. This alternate model has a clear and direct physical interpretation.

physics.optics↗
arXiv2018

How to be causal: time, spacetime, and spectra

I explain a simple definition of causality in widespread use, and indicate how it links to the Kramers Kronig relations. The specification of causality in terms of temporal differential eqations then shows us the way to write down dynamical models so that their causal nature /in the sense used here/ should be obvious to all. To extend existing treatments of causality that work only in the frequency domain, I derive a reformulation of the long-standing Kramers Kronig relations applicable not only to just temporal causality, but also to spacetime "light-cone" causality based on signals carried by waves. I also apply this causal reasoning to Maxwell's equations, which is an instructive example since their casual properties are sometimes debated.

physics.class-ph↗
arXiv2018

Customized longitudinal electric field profiles: using spatial dispersion in dielectric wire arrays

We show how spatial dispersion can be used as a mechanism to customize the longitudinal profiles of electric fields inside modulated wire media, using a fast and remarkably accurate 1D inhomogeneous model. This customization gives fine control of the sub-wavelength behaviour of the field, as has been achieved recently for transverse fields in simpler slotted-slab media. Our scheme avoids any necessity to run a long series of computationally intensive 3D simulations of specific structures, in order to iteratively converge (or brute-force search) to an empirical `best-performance' design according to an abstract figure-of-merit. Instead, if supplied with an `ideal waveform' profile, we could now calculate how to construct it directly. Notably, and unlike most work on photonic crystal structures, our focus is specifically on the field profiles because of their potential utility, rather than other issues such as band-gap control, and/or transmission and reflection coefficients.

physics.app-ph↗
arXiv2017

Generalized Transformation Design: metrics, speeds, and diffusion

We show that a unified and maximally generalized approach to spatial transformation design is possible, one that encompasses all second order waves, rays, and diffusion processes in anisotropic media. Until the final step, it is unnecessary to specify the physical process for which a specific transformation design is to be implemented. The principal approximation is the neglect of wave impedance, an attribute that plays no role in ray propagation, and is therefore irrelevant for pure ray devices; another constraint is that for waves the spatial variation in material parameters needs to be sufficiently small compared with the wavelength. The key link between our general formulation and a specific implementation is how the spatial metric relates to the speed of disturbance in a given medium, whether it is electromagnetic, acoustic, or diffusive. Notably, we show that our generalised ray theory, in allowing for anisotropic indexes (speeds), generates the same predictions as does a wave theory, and the results are closely related to those for diffusion processes.

physics.class-ph↗