Imperial College London

Arthur Turrell

Faculty of Natural SciencesDepartment of Physics

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Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
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11 results found

Haldane AG, Turrell AE, 2019, Drawing on different disciplines: macroeconomic agent-based models, JOURNAL OF EVOLUTIONARY ECONOMICS, Vol: 29, Pages: 39-66, ISSN: 0936-9937

Journal article

G Haldane A, E Turrell A, 2018, Un modelo interdisciplinario para la macroeconomía, Revista de Economía Institucional, Vol: 21, Pages: 69-110, ISSN: 0124-5996

<jats:p>La modelación macroeconómica está bajo intenso escrutinio desde la gran crisis financiera, que dejó al descubierto los graves defectos de la metodología utilizada para entender la economía en su conjunto. Se critican los supuestos empleados en los modelos dominantes, en particular que los agentes económicos son homogéneos y optimizadores y que la economía se equilibra. Este escrito explora un enfoque interdisciplinario de modelación macroeconómica con técnicas tomadas de otras ciencias, y examina la modelación basada en agentes como ejemplo de esas técnicas. Los modelos basados en agentes complementan los enfoques existentes y son adecuados para responder preguntas macroeconómicas donde la complejidad, la heterogeneidad, las redes y las heurísticas cumplen un papel importante.</jats:p>

Journal article

Braun-Munzinger K, Liu Z, Turrell AE, 2018, An agent-based model of corporate bond trading, QUANTITATIVE FINANCE, Vol: 18, Pages: 591-608, ISSN: 1469-7688

Journal article

Turrell AE, Sherlock M, Rose SJ, 2016, Efficient evaluation of collisional energy transfer terms for plasma particle simulations, JOURNAL OF PLASMA PHYSICS, Vol: 82, ISSN: 0022-3778

Journal article

Turrell A, Sherlock M, Rose SJ, 2015, Ultra-fast collisional ion heating by electrostatic shocks, Nature Communications, Vol: 6, ISSN: 2041-1723

High intensity lasers can be used to generate shockwaves which have found applications in nuclear fusion, proton imaging, cancer therapies, and materials science. Collisionless electrostatic shocks are one type of shockwave widely studied for applications involving ion acceleration. Here we show a novel mechanism for collisionlesselectrostatic shocks to heat small amounts of solid density matter to temperatures of ∼ keV in tens of femtoseconds. Unusually, electrons play no direct role in the heating, and it is the ions which determine the heating rate. Ions are heated due to an interplay between the electric field of the shock, the local density increaseduring the passage of the shock, and collisions between different species of ion. In simulations, these factors combine to produce rapid, localised heating of the lighter ion species. Although the heated volume is modest, this would be one of the fastest heating mechanisms discovered if demonstrated in the laboratory.

Journal article

Turrell AE, Sherlock M, Rose SJ, 2015, Self-consistent inclusion of classical large-angle Coulomb collisions in plasma Monte Carlo simulations, Journal of Computational Physics, Vol: 299, Pages: 144-155, ISSN: 1090-2716

Large-angle Coulomb collisions allow for the exchange of a significant proportion of the energy of a particle in a single collision, but are not included in models of plasmas based on fluids, the Vlasov-Fokker-Planck equation, or currently available plasma Monte Carlo techniques. Their unique effects include the creation of fast ‘knock-on’ ions, which may be more likely to undergo certain reactions, and distortions to ion distribution functions relative to what is predicted by small-angle collision only theories. We present a computational method which uses Monte Carlo techniques to include the effects of large-angle Coulomb collisions in plasmas and which self-consistently evolves distribution functions according to the creation of knock-on ions of any generation. The method is used to demonstrate ion distribution function distortions in an inertial confinement fusion (ICF) relevant scenario of the slowing of fusion products.

Journal article

Turrell AE, Rose SJ, Sherlock M, 2014, Effects of Large-Angle Coulomb Collisions on Inertial Confinement Fusion Plasmas, Physical Review Letters, Vol: 112

Large-angle Coulomb collisions affect the rates of energy and momentum exchange in a plasma, and it is expected that their effects will be important in many plasmas of current research interest, including in inertial confinement fusion. Their inclusion is a long-standing problem, and the first fully self-consistent method for calculating their effects is presented. This method is applied to “burn” in the hot fuel in inertial confinement fusion capsules and finds that the yield increases due to an increase in the rate of temperature equilibration between electrons and ions which is not predicted by small-angle collision theories. The equilibration rate increases are 50%–100% for number densities of 10^{30} m^{−3} and temperatures around1 keV.

Journal article

Turrell AE, Sherlock M, Rose SJ, 2013, A Monte Carlo algorithm for degenerate plasmas, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 249, Pages: 13-21, ISSN: 0021-9991

Journal article

Hill E, Bardoscia M, Turrell A, Solving Heterogeneous General Equilibrium Economic Models with Deep Reinforcement Learning

General equilibrium macroeconomic models are a core tool used by policymakersto understand a nation's economy. They represent the economy as a collection offorward-looking actors whose behaviours combine, possibly with stochasticeffects, to determine global variables (such as prices) in a dynamicequilibrium. However, standard semi-analytical techniques for solving thesemodels make it difficult to include the important effects of heterogeneouseconomic actors. The COVID-19 pandemic has further highlighted the importanceof heterogeneity, for example in age and sector of employment, in macroeconomicoutcomes and the need for models that can more easily incorporate it. We usetechniques from reinforcement learning to solve such models incorporatingheterogeneous agents in a way that is simple, extensible, and computationallyefficient. We demonstrate the method's accuracy and stability on a toy problemfor which there is a known analytical solution, its versatility by solving ageneral equilibrium problem that includes global stochasticity, and itsflexibility by solving a combined macroeconomic and epidemiological model toexplore the economic and health implications of a pandemic. The lattersuccessfully captures plausible economic behaviours induced by differentialhealth risks by age.

Journal article

Haldane A, Turrell A, An Interdisciplinary Model for Macroeconomics, SSRN Electronic Journal

Journal article

Duchini E, Simion S, Turrell A, Pay Transparency and Cracks in the Glass Ceiling

This paper studies firms' and employees' responses to pay transparencyrequirements. Each year since 2018, more than 10,000 UK firms have beenrequired to disclose publicly their gender pay gap and gender composition alongthe wage distribution. Theoretically, pay transparency is meant to act as aninformation shock that alters the bargaining power of male and female employeesvis-\`a-vis the firm in opposite ways. Coupled with the potential negativeeffects of unequal pay on firms' reputation, this shock could improve women'srelative occupational and pay outcomes. We test these theoretical predictionsusing a difference-in-differences strategy that exploits variations in the UKmandate across firm size and time. This analysis delivers four main findings.First, pay transparency increases women's probability of working inabove-median-wage occupations by 5 percent compared to the pre-policy mean.Second, while this effect has not yet translated into a significant rise inwomen's pay, the policy leads to a 2.8 percent decrease in men's real hourlypay, reducing the pre-policy gender pay gap by 15 percent. Third, combining thedifference-in-differences strategy with a text analysis of job listings, wefind suggestive evidence that treated firms adopt female-friendly hiringpractices in ads for high-gender-pay-gap occupations. Fourth, a reputationmotive seems to drive employers' reactions, as firms publishing worse genderequality indicators score lower in YouGov Women's Rankings. Moreover, publiclylisted firms experience a 35-basis-point average fall in cumulative abnormalreturns in the days following their publication of gender equality data.

Journal article

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