Michael E. Cates
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View article: Entropy production rate in thermodynamically consistent flocks
Entropy production rate in thermodynamically consistent flocks Open
We study the entropy production rate (EPR) of aligning self-propelled particles which undergo a flocking transition into a state of polarized collective motion. In our thermodynamically consistent lattice model, individual self-propulsion …
View article: Active particles in moving traps: Minimum work protocols and information efficiency of work extraction
Active particles in moving traps: Minimum work protocols and information efficiency of work extraction Open
We revisit the elementary problem of moving a particle in a harmonic trap in finite time with minimal work cost and extend it to the case of an active particle. By comparing the Gaussian case of an Active Ornstein-Uhlenbeck particle and th…
View article: Active particles in moving traps: Minimum work protocols and information efficiency of work extraction
Active particles in moving traps: Minimum work protocols and information efficiency of work extraction Open
We revisit the elementary problem of moving a particle in a harmonic trap in finite time with minimal work cost and extend it to the case of an active particle. By comparing the Gaussian case of an Active Ornstein-Uhlenbeck particle and th…
View article: Optimal Closed-Loop Control of Active Particles and a Minimal Information Engine
Optimal Closed-Loop Control of Active Particles and a Minimal Information Engine Open
We study the elementary problem of moving an active particle by a trap with minimum work input. We show analytically that (open-loop) optimal protocols are not affected by activity, but work fluctuations are always increased. For closed-lo…
View article: Hydrodynamic theory of wetting by active particles
Hydrodynamic theory of wetting by active particles Open
The accumulation of self-propelled particles on repulsive barriers is a widely observed feature in active matter. Despite being implicated in a broad range of biological processes, from biofilm formation to cytoskeletal movement, wetting o…
View article: Geometric theory of (extended) time-reversal symmetries in stochastic processes: II. Field theory
Geometric theory of (extended) time-reversal symmetries in stochastic processes: II. Field theory Open
In this article, we study the time-reversal properties of a generic Markovian stochastic field dynamics with Gaussian noise. We introduce a convenient functional geometric formalism that allows us to straightforwardly generalize known resu…
View article: Physical science of the didodecyldimethylammonium bromide–water system: 1. Equilibrium phase behaviour
Physical science of the didodecyldimethylammonium bromide–water system: 1. Equilibrium phase behaviour Open
Here, we characterize the low temperature equilibrium phase of the DDAB/water system (>3 wt%) as a crystalline dispersion, determine the position and shape of the Krafft eutectic and present an amended broad equilibrium phase diagram.
View article: Geometric theory of (extended) time-reversal symmetries in stochastic processes -- Part II: field theory
Geometric theory of (extended) time-reversal symmetries in stochastic processes -- Part II: field theory Open
In this article, we study the time-reversal properties of a generic Markovian stochastic field dynamics with Gaussian noise. We introduce a convenient functional geometric formalism that allows us to straightforwardly generalize known resu…
View article: Geometric theory of (extended) time-reversal symmetries in stochastic processes: I. Finite dimension
Geometric theory of (extended) time-reversal symmetries in stochastic processes: I. Finite dimension Open
In this article, we analyze three classes of time-reversal of a Markov process with Gaussian noise on a manifold. We first unveil a commutativity constraint for the most general of these time-reversals to be well defined. Then we give a tr…
View article: Effects of phase separation on extinction times in population models
Effects of phase separation on extinction times in population models Open
We study the effect of phase-separating diffusive dynamics on the mean time to extinction (MTE) in several reaction-diffusion models with slow reactions. We consider a continuum theory similar to model AB, and a simple model where individu…
View article: Optimal closed-loop control of active particles and a minimal information engine
Optimal closed-loop control of active particles and a minimal information engine Open
We study the elementary problem of moving an active particle by a trap with minimum work input. We show analytically that (open-loop) optimal protocols are not affected by activity, but work fluctuations are always increased. For closed-lo…
View article: Hyperuniformity in phase ordering: the roles of activity, noise, and non-constant mobility
Hyperuniformity in phase ordering: the roles of activity, noise, and non-constant mobility Open
Hyperuniformity emerges generically in the coarsening regime of phase-separating fluids. Numerical studies of active and passive systems have shown that the structure factor S ( q ) behaves as q ς for q → 0, with hyperuniformity exponent ς…
View article: Thermodynamically consistent flocking: from discontinuous to continuous transitions
Thermodynamically consistent flocking: from discontinuous to continuous transitions Open
We introduce a family of lattice-gas models of flocking, whose thermodynamically consistent dynamics admits a proper equilibrium limit at vanishing self-propulsion. These models are amenable to an exact coarse-graining which allows us to s…
View article: Effects of phase separation on extinction times in population models
Effects of phase separation on extinction times in population models Open
We study the effect of phase separating diffusive dynamics on the mean time to extinction in several reaction-diffusion models with slow reactions. We consider a continuum theory similar to model AB, and a simple model where individual par…
View article: Geometric theory of (extended) time-reversal symmetries in stochastic processes -- Part I: finite dimension
Geometric theory of (extended) time-reversal symmetries in stochastic processes -- Part I: finite dimension Open
In this article, we analyze three classes of time-reversal of a Markov process with Gaussian noise on a manifold. We first unveil a commutativity constraint for the most general of these time-reversals to be well defined. Then we give a tr…
View article: Resolution dependence of most probable pathways with state-dependent diffusivity
Resolution dependence of most probable pathways with state-dependent diffusivity Open
Recent experiments have probed the relative likelihoods of trajectories in stochastic systems by observing survival probabilities within a tube of radius $R$ in spacetime. We measure such probabilities here for a colloidal particle in a co…
View article: Thermodynamically consistent flocking: From discontinuous to continuous transitions
Thermodynamically consistent flocking: From discontinuous to continuous transitions Open
We introduce a family of lattice-gas models of flocking, whose thermodynamically consistent dynamics admits a proper equilibrium limit at vanishing self-propulsion. These models are amenable to an exact coarse-graining which allows us to s…
View article: Theory of Hyperuniformity at the Absorbing State Transition
Theory of Hyperuniformity at the Absorbing State Transition Open
Hyperuniformity, whereby the static structure factor (or density correlator) obeys $S(q)\sim q^ς$ with $ς> 0$, emerges at criticality in systems having multiple absorbing states, such as periodically sheared suspensions. These lie in the c…
View article: Active–passive mixtures with bulk loading: a minimal active engine in one dimension
Active–passive mixtures with bulk loading: a minimal active engine in one dimension Open
We study a one-dimensional mixture of active (run-and-tumble) particles and passive (Brownian) particles, with single-file constraint, in a sawtooth potential. The active particles experience a ratchet effect and this generates a current, …
View article: Active Ising Models of Flocking: A Field-Theoretic Approach
Active Ising Models of Flocking: A Field-Theoretic Approach Open
Using an approach based on Doi-Peliti field theory, we study several different Active Ising Models (AIMs), in each of which collective motion (flocking) of self-propelled particles arises from the spontaneous breaking of a discrete symmetr…
View article: Active-passive mixtures with bulk loading: a minimal active engine in one dimension
Active-passive mixtures with bulk loading: a minimal active engine in one dimension Open
We study a one-dimensional mixture of active (run-and-tumble) particles and passive (Brownian) particles, with single-file constraint, in a sawtooth potential. The active particles experience a ratchet effect: this generates a current, whi…
View article: Two-dimensional crystals far from equilibrium
Two-dimensional crystals far from equilibrium Open
When driven by nonequilibrium fluctuations, particle systems may display phase transitions and physical behaviour with no equilibrium counterpart. We study a two-dimensional particle model initially proposed to describe driven non-Brownian…
View article: Towards a liquid-state theory for active matter
Towards a liquid-state theory for active matter Open
In equilibrium, the collective behaviour of particles interacting via steep, short-ranged potentials is well captured by the virial expansion of the free energy at low density. Here, we extend this approach beyond equilibrium to the case o…
View article: Optical heat flux gauge
Optical heat flux gauge Open
A heat flux gauge comprising first and second thermographic phosphor layers separated by a layer of a thermal insulator wherein each thermographic layer comprises a plurality of respective thermographic phosphors. The gauge may be mounted …
View article: Tricritical behavior in dynamical phase transitions
Tricritical behavior in dynamical phase transitions Open
We identify a new scenario for dynamical phase transitions associated with time-integrated observables occurring in diffusive systems described by the macroscopic fluctuation theory. It is characterized by the pairwise meeting of first- an…
View article: Rheology of dense suspensions under shear rotation
Rheology of dense suspensions under shear rotation Open
Dense non-Brownian suspensions exhibit a spectacular and abrupt drop in viscosity under change of shear direction, as revealed by shear inversions (reversals) or orthogonal superposition. Here, we introduce an experimental setup to systema…
View article: Entropy production and its large deviations in an active lattice gas
Entropy production and its large deviations in an active lattice gas Open
Active systems are characterized by a continuous production of entropy at steady state. We study the statistics of entropy production within a lattice-based model of interacting active particles that is capable of motility-induced phase se…
View article: Fragile dense suspensions under shear rotation
Fragile dense suspensions under shear rotation Open
View article: Active Field Theories
Active Field Theories Open
These notes give an introduction to statistical field theories of active matter. After showing an example of how such theories can be created bottom-up by explicit coarse graining of active particle models, the main approach taken here is …
View article: Getting the most out of maths: How to coordinate mathematical modelling research to support a pandemic, lessons learnt from three initiatives that were part of the COVID-19 response in the UK
Getting the most out of maths: How to coordinate mathematical modelling research to support a pandemic, lessons learnt from three initiatives that were part of the COVID-19 response in the UK Open