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Michael Cates
Michael Cates
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Michael Elmhirst Cates (born 5 May 1961) is a British physicist. He is the 19th Lucasian Professor of Mathematics at the University of Cambridge and has held this position since 1 July 2015.[1] He was previously professor of natural philosophy at the University of Edinburgh, and held a Royal Society Research Professorship from 2007 to 2022.[2]

Key Information

His work focuses on the theory of soft matter, such as polymers, colloids, gels, liquid crystals, and granular material. A recurring goal of his research is to create a mathematical model that predicts the stress in a flowing material as a functional of the flow history of that material. Such a mathematical model is called a constitutive equation. He has worked on theories of active matter, particularly dense suspensions of self-propelled particles which can include motile bacteria. His interests also include fundamental field theories of active systems in which time-reversal symmetry (T-symmetry, and more generally, CPT symmetry) is absent. Such theories are characterised by non-zero steady-state entropy production. His recent work has focussed on phase separation in active systems, including phenomena such as nucleation, interfacial fluctuations, and wetting.

At Edinburgh, Cates was the principal investigator of an EPSRC Programme Grant, awarded in 2011, entitled Design Principles for New Soft Materials.[3] On his departure for Cambridge, Cait MacPhee took over as principal investigator until conclusion of the grant in 2017. Cates remains an honorary professor at Edinburgh, where he serves on the advisory board of the Higgs Centre for Theoretical Physics.

Early life

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Cates was born on 5 May 1961.[4] He read Natural Sciences and earned a PhD at Trinity College, Cambridge, in 1985, where he studied with Sam Edwards.

Academic career

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Cates was a research fellow and lecturer at the Cavendish Laboratory, University of Cambridge before moving to Edinburgh in 1995.

Honours

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Cates won the Bingham Medal of the US Society of Rheology in 2016.[5] He had previously won the 2013 Weissenberg Award of the European Society of Rheology[6] and the 2009 Gold Medal of the British Society of Rheology. He was awarded the 2009 Dirac Prize by the Institute of Physics. He won the 1991 Maxwell Medal and Prize. He has served as an elected member of the Council of the Royal Society; as chair of the International Scientific Committee of ESPCI ParisTech, and as a Trustee of The Cyprus Institute. He was an honorary fellow of Trinity College, Cambridge from 2013 until 2016, when he became instead a senior research fellow.

Cates was elected a member of the National Academy of Engineering in 2019 for research on the rheology, dynamics, and thermodynamics of complex fluids, and for scientific leadership in the European Community. In 2021 he was elected an International Member of the US National Academy of Sciences.[7]

Works

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Michael Cates has over 400 refereed scientific publications, with over 50,000 citations. His h-index is 118.[8]

Publications include:

  • Milner, S. T.; Witten, T. A.; Cates, M. E. (1988). "Theory of the grafted polymer brush". Macromolecules. 21 (8). American Chemical Society (ACS): 2610–2619. Bibcode:1988MaMol..21.2610M. doi:10.1021/ma00186a051. ISSN 0024-9297.
  • Cates, M E; Candau, S J (20 August 1990). "Statics and dynamics of worm-like surfactant micelles". Journal of Physics: Condensed Matter. 2 (33). IOP Publishing: 6869–6892. doi:10.1088/0953-8984/2/33/001. ISSN 0953-8984. S2CID 250743546.
  • Cates, M. E. (1987). "Reptation of living polymers: dynamics of entangled polymers in the presence of reversible chain-scission reactions". Macromolecules. 20 (9). American Chemical Society (ACS): 2289–2296. Bibcode:1987MaMol..20.2289C. doi:10.1021/ma00175a038. ISSN 0024-9297.
  • Sollich, Peter; Lequeux, François; Hébraud, Pascal; Cates, Michael E. (10 March 1997). "Rheology of Soft Glassy Materials". Physical Review Letters. 78 (10). American Physical Society (APS): 2020–2023. arXiv:cond-mat/9611228. Bibcode:1997PhRvL..78.2020S. doi:10.1103/physrevlett.78.2020. ISSN 0031-9007. S2CID 14392727.
  • Cates, M. E.; Wittmer, J. P.; Bouchaud, J.-P.; Claudin, P. (31 August 1998). "Jamming, Force Chains, and Fragile Matter". Physical Review Letters. 81 (9). American Physical Society (APS): 1841–1844. arXiv:cond-mat/9803197. Bibcode:1998PhRvL..81.1841C. doi:10.1103/physrevlett.81.1841. ISSN 0031-9007. S2CID 119378758.
  • Pham, K. N. (5 April 2002). "Multiple Glassy States in a Simple Model System". Science. 296 (5565). American Association for the Advancement of Science (AAAS): 104–106. Bibcode:2002Sci...296..104P. doi:10.1126/science.1068238. ISSN 0036-8075. PMID 11935020. S2CID 34313265.
  • Stratford, K. (30 September 2005). "Colloidal Jamming at Interfaces: A Route to Fluid-Bicontinuous Gels". Science. 309 (5744). American Association for the Advancement of Science (AAAS): 2198–2201. arXiv:cond-mat/0510040. Bibcode:2005Sci...309.2198S. doi:10.1126/science.1116589. ISSN 0036-8075. PMID 16195456. S2CID 14719880.
  • Tailleur, J.; Cates, M. E. (29 May 2008). "Statistical Mechanics of Interacting Run-and-Tumble Bacteria". Physical Review Letters. 100 (21) 218103. arXiv:0803.1069. Bibcode:2008PhRvL.100u8103T. doi:10.1103/physrevlett.100.218103. ISSN 0031-9007. PMID 18518641. S2CID 9651052.
  • Wyart, M.; Cates, M. E. (6 March 2014). "Discontinuous shear thickening without inertia in dense non-Brownian suspensions". Physical Review Letters. 112 098302. arXiv:1311.4099. doi:10.1103/PhysRevLett.112.098302.
  • Fodor, E.; Nardini, C.; Cates, M. E.; Tailleur, J.; Visco., P.; van Wijland, F. (13 July 2016). "How far from equilibrium is active matter?". Physical Review Letters. 117 038103. arXiv:1604.00953. doi:10.1103/PhysRevLett.117.038103.
  • Tjhung, E.; Nardini, C.; Cates, M. E. (24 September 2018). "Cluster phases and bubbly phase separation in active fluids: Reversal of the Ostwald process". Physical Review X. 112 031080. arXiv:1801.07687. doi:10.1103/PhysRevX.8.031080.

References

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from Grokipedia
Michael Elmhirst Cates FRS FRSE (born 1961) is a British theoretical specializing in the of soft condensed matter and . He is the 19th at the , a position he has held since 2015. Born and raised in Bristol, England, Cates earned his undergraduate degrees in Physics and Theoretical Physics from the University of Cambridge in 1982, followed by a PhD in statistical physics there in 1985 under the supervision of Sam Edwards. After postdoctoral positions at Exxon Corporate Research and the University of California, Santa Barbara, he joined the at as a faculty member in 1989. In 1995, he moved to the , where he served as Chair of Natural Philosophy until 2015 and held a Research Professorship from 2007 to 2022. Upon returning to , he became a Fellow of Trinity College and heads the research group in the Department of and Theoretical Physics. Cates's research centers on the and flow behavior of complex fluids, including viscoelastic surfactant solutions, dense suspensions, emulsions, gels, and foams, using tools from , elasticity, and computational modeling. He has pioneered models for phenomena such as jamming in glasses and foams, the in soft materials, and the dynamics of systems like and bacterial suspensions. His interdisciplinary work bridges with experimental collaborations, addressing nonequilibrium problems in biological and industrial contexts, such as joint-lubricating fluids and cornstarch solidification under impact. Among his numerous honors, Cates was elected a in 2007 and of the Royal Society of Edinburgh in 2005, and became an International Member of the in 2021 and of the in 2019. He received the Maxwell Medal and Prize from the Institute of Physics in 1991, the Medal and Prize in 2009 for pioneering work in soft materials physics, the Gold Medal of the British Society of in 2009, the Weissenberg Award from the European Society of in 2013, the Bingham Medal from the Society of in 2016, and the Pierre Gilles de Gennes Prize from the European Physical Journal in 2011.

Early Life and Education

Early Years

Michael Cates was born in 1961 in , . He was raised in this southwestern English city, where he spent his formative early years. Cates grew up as one of six children in a large extended family. While specific details on his childhood interests or early exposures to science are not widely documented, Cates' path led him to pursue formal studies in physics at the .

Academic Training

Michael Cates began his formal academic training at the , where he earned a degree in Physics and in 1982. He continued his studies at Cambridge, completing a PhD in in 1985 under the supervision of Sir Sam Edwards. His doctoral thesis, titled The of complex polymers, explored foundational aspects of , including the dynamics of complex polymer structures analyzed through statistical mechanical frameworks. This work established early expertise in theory by addressing how statistical mechanics governs the behavior of entangled and branched polymers, laying groundwork for later contributions in the field.

Academic Career

Early Positions

Following his PhD in 1985 under Sam Edwards at the , Michael Cates held postdoctoral positions at Exxon Corporation and the , before returning to in 1988. There, he began his academic career at the as a University from 1988 to 1989. He progressed to University Assistant Lecturer from 1989 to 1992 and then University Lecturer from 1992 to 1995, all at the . Concurrently, he served as Junior Research Fellow at , from 1985 to 1989. In these early roles, Cates took on initial teaching responsibilities as a at from 1990 to 1995, where he contributed to undergraduate instruction in and related natural sciences courses. This period marked his establishment as an educator in the Cavendish's theoretical physics group, balancing lectures and supervision with emerging research duties. Cates' research during this time at the Cavendish focused on theoretical aspects of colloidal systems and polymers, extending the statistical physics approaches from his doctoral work on polymeric materials. He engaged in key projects exploring the dynamics and behavior of these systems, often in collaboration with fellow theorists in the department, such as through joint efforts on entanglement models that built directly on Edwards' foundational ideas. These activities laid the groundwork for his later contributions, emphasizing conceptual frameworks for complex material interactions without experimental components.

Major Appointments

In 1995, Michael Cates was appointed as Professor of in the School of Physics and Astronomy at the , a position he held until 2015. During this tenure, he led significant research initiatives in soft condensed matter, including serving as for the EPSRC-funded Design Principles for New Soft Materials programme grant, awarded in 2011. In 2007, Cates was awarded a Royal Society Research Professorship, one of the UK's most prestigious research appointments, which he held until 2022; this role provided dedicated support for his research while based at . On 20 March 2015, Cates was elected as the 19th at the , succeeding , with the appointment taking effect on 1 July 2015. In this capacity, he joined the Department of Applied Mathematics and (DAMTP), formerly served as a Research Professor (2007–2022), and leads the research group. Following his departure from the full-time at , Cates was granted honorary status in the College of Science and Engineering at the in April 2015, facilitating ongoing collaborations with the School of Physics and Astronomy.

Research Contributions

Soft Matter Physics

Michael Cates has made foundational contributions to the of passive soft condensed systems, encompassing colloids, , emulsions, foams, and granular materials. His work emphasizes the phase and rheological of these complex fluids, often employing theoretical models to predict transitions between fluid-like and solid-like states under equilibrium or near-equilibrium conditions. For instance, in colloidal systems, Cates developed theories for depletion forces arising from -mediated attractions, which drive and gelation in suspensions. These interactions, quantified through effective potentials derived from Asakura-Oosawa models adapted for finite sizes, highlight how imbalances induce aggregation without direct bonding. Early in his career, Cates advanced understanding of dynamics, particularly entanglement and in living polymers subject to reversible scission reactions. In a seminal model, he extended the framework to account for chain breakage and reformation, predicting enhanced rates compared to permanent polymers due to scission-assisted reptation, with effective exponents reduced from the classical τN3\tau \sim N^3. This work illuminated the viscoelastic behavior of transiently entangled systems like solutions. Complementing this, his theory of grafted brushes described their equilibrium structure under good solvent conditions, where the brush height hh follows hNσ1/3h \sim N \sigma^{1/3} with grafting density σ\sigma, influencing phase behavior in polymer-colloid mixtures. These models provided conceptual tools for designing responsive materials. Cates' research on surfactants and liquid crystal dynamics focused on wormlike micelles, which form nematic phases akin to liquid crystals. He derived constitutive equations for their nonlinear rheology, capturing shear-thinning and alignment under flow through a balance of bending elasticity and scission kinetics; the stress σ\sigma relates to shear rate γ˙\dot{\gamma} via ση0γ˙(1+(γ˙τ)2)1/2\sigma \sim \eta_0 \dot{\gamma} (1 + (\dot{\gamma} \tau)^2)^{-1/2}, where τ\tau is a characteristic time. This framework explained oscillatory instabilities in flowing micellar solutions, bridging microscopic dynamics to macroscopic flow properties. In , Cates pioneered the soft glassy (SGR) model for yield-stress fluids like foams, emulsions, and gels, where structural elements rearrange via activated processes over a broad distribution of barriers. The model yields a constitutive relation for the σ\sigma and rate γ˙\dot{\gamma}, incorporating and structural disorder: γ˙exp(x/xg)\dot{\gamma} \sim \exp(-x / x_g), with xx the local yield strain and xgx_g a glassiness parameter, predicting aging and shear . For driven suspensions, he developed equations for shear-thickening transitions in dense colloids, attributing discontinuous jumps to hydrodynamic clustering; in non-Brownian limits, η\eta diverges as η(ϕcϕ)2\eta \sim (\phi_c - \phi)^{-2} near packing fraction ϕc\phi_c, without inertial effects. These theories apply to emulsions and foams, where he analyzed coarsening stabilization via osmotic gradients, reducing drainage rates in polydisperse systems. Cates explored jamming transitions in granular materials and colloidal gels using statistical mechanics, identifying force chains as precursors to rigidity. In granular flows, jamming occurs when coordination number z6z \approx 6 for spheres, leading to exponential force distributions P(f)exp(f/f0)P(f) \sim \exp(-f/f_0); this fragile state exhibits heterogeneous stress propagation. For colloidal gels, simulations incorporating simplified Stokesian dynamics—approximating hydrodynamic interactions via Fi=ζvi+jGijFj\mathbf{F}_i = -\zeta \mathbf{v}_i + \sum_j \mathbf{G}_{ij} \cdot \mathbf{F}_j, with mobility ζ\zeta and Oseen tensor G\mathbf{G}—revealed multiple glassy states and aging via caging. Key concepts include giant density fluctuations in near-jammed gels, where number variance (ΔN)2/N21/N\langle (\Delta N)^2 \rangle / \langle N \rangle^2 \gg 1/\langle N \rangle arises from coupled stress and density modes, enhancing susceptibility to shear. Later extensions of these passive models to active systems, such as self-propelled colloids, build on the phase behavior and frameworks developed here.

Active Matter Systems

Active matter systems consist of self-propelled constituents, such as or synthetic microswimmers, that continuously dissipate energy at the microscopic scale, leading to non-zero and violation of , in contrast to passive systems at . These nonequilibrium dynamics enable novel collective behaviors, including spontaneous and phase transitions driven by activity rather than attractive interactions. Michael Cates has been a key figure in developing theoretical frameworks for these systems, emphasizing their departure from equilibrium through field-theoretic and hydrodynamic models. A seminal contribution from Cates is the theory of motility-induced phase separation (MIPS), where self-propelled particles spontaneously separate into dense and dilute phases due to density-dependent motility slowdowns, without requiring cohesion or alignment. In this mechanism, particles slow down in crowded regions because collisions reduce their effective propulsion speed, causing accumulation that further increases local density and slows motion, creating a positive feedback loop analogous to phase separation in passive fluids but driven purely by activity. The core phenomenology is captured by a continuity equation for the density ρ\rho, with flux J=ρv(ρ)Dρ\mathbf{J} = \rho v(\rho) - D \nabla \rho, where v(ρ)v(\rho) is the density-dependent swim speed that decreases at high ρ\rho (e.g., via excluded volume effects), and DD is a diffusion constant; phase separation emerges when the condition ρv(ρ)/v(ρ)<1\rho v'(\rho)/v(\rho) < -1 holds, leading to an effective spinodal instability. Cates extended MIPS to wet active matter, where particles are immersed in a momentum-conserving fluid, incorporating hydrodynamic interactions that can suppress through long-range flows and torques. In bacterial flocks, such models predict flocking transitions where MIPS-like clustering facilitates collective motion, with quorum-sensing mechanisms modulating v(ρ)v(\rho) to promote formation. Scalar active matter theories, such as Active Model H—an extension of the passive Model H coupling density to a velocity field—further generalize these ideas, allowing for conservation and revealing giant number fluctuations or in states. To describe phase equilibria in these systems, Cates and collaborators developed generalized , adapting concepts like and pressure to nonequilibrium settings while accounting for rates that quantify irreversibility. For MIPS, phase diagrams feature binodals determined by equal s or pressures (depending on the microscopic model) and spinodals marking linear instabilities, valid in both 2D and 3D; these differ from passive cases due to activity-induced asymmetries. , absent in equilibrium, concentrates at interfaces in phase-separated states and can be computed via field theories as S˙=j22Dρdr\dot{S} = \int \frac{ \mathbf{j}^2 }{ 2D \rho } d\mathbf{r} in simple models, highlighting how activity sustains steady-state fluxes. Recent work (as of 2025) includes analyses of new phenomenology in active and hyperuniformity in phase ordering kinetics driven by activity.

Awards and Honors

Major Prizes

Michael Cates has been recognized with several major prizes from leading physics and organizations for his foundational contributions to , particularly in and complex fluids. In 1991, he received the Maxwell Medal and Prize from the Institute of Physics for his early contributions to . In 1994, he received the Prix Franco-Britannique from the Academy of Sciences. In 2009, Cates was awarded the Gold Medal from the British Society of in recognition of his contributions to the theoretical of complex fluids. That same year, he earned the Dirac Medal and Prize from the Institute of Physics for pioneering work in the of soft materials, particularly in relation to their flow behaviour. In 2011, Cates received the Lecture Prize from the European Physical Journal E for his leading research on the of soft condensed matter. The European Society of Rheology honored him with the Weissenberg Award in 2013 for his long-term achievements in rheological modeling of complex fluids. In 2016, he was awarded the Bingham Medal from the Society of for outstanding contributions to the understanding of complex fluid dynamics.

Academy Memberships

Michael Cates was elected a (FRS) in 2007, recognizing his outstanding contributions to the of complex fluids and systems. In 2005, he became a of Edinburgh (FRSE). Cates was elected an International Member of the in 2019, cited for his research on the , dynamics, and of complex fluids, and for scientific in the European Community. In 2021, he was elected an International Member of the National Academy of Sciences in Section 33: Applied Physical Sciences, acknowledging his fundamental advances in the theory of active and passive soft materials.

Publications and Impact

Key Publications

Michael Cates has authored over 400 peer-reviewed publications, spanning physics, , and systems. His contributions include numerous high-impact papers in leading journals such as Physical Review Letters and Science, often co-authored with collaborators like S. T. Milner, J. Tailleur, and P. Sollich. Among his early influential works on , Cates co-authored the 1988 paper "Theory of the grafted polymer brush" with S. T. Milner and T. A. Witten, published in Macromolecules, which explored the structure and properties of polymer brushes. In 1990, he published "Statics and dynamics of worm-like micelles" with S. J. Candau in Journal of Physics: Condensed Matter, addressing the behavior of living polymer solutions. Key 1990s contributions on jamming and glassy dynamics include the 1997 paper " of soft glassy materials" with P. Sollich, F. Lequeux, and P. Hébraud in Physical Review Letters, introducing a model for yield-stress fluids. This was followed by "Jamming, force chains, and fragile matter" in 1998 with J. P. Wittmer, J. P. Bouchaud, and P. Claudin, also in Physical Review Letters, which analyzed mechanical stability in granular and colloidal systems. In , Cates' seminal papers include "Statistical mechanics of interacting run-and-tumble " from 2008, co-authored with J. Tailleur and published in , modeling collective bacterial dynamics. His 2012 review "Diffusive transport without in motile : does need statistical physics?" appeared in Reports on Progress in Physics, surveying non-equilibrium effects in bacterial suspensions. A landmark review is the 2015 article "Motility-induced " with J. Tailleur in , elucidating phase behavior in active systems. Other notable reviews include "Aging and in soft materials" from 2000 with S. M. Fielding and P. Sollich in Journal of Rheology.

Scholarly Influence

Michael Cates' scholarly output has garnered significant recognition, with over 53,000 citations and an of 119 as of 2025, reflecting the enduring impact of his contributions to soft and physics. His work has profoundly influenced fields such as , , and biological applications, where concepts from provide frameworks for understanding in . For instance, the motility-induced (MIPS) paradigm, co-developed by Cates, has inspired models of bacterial colony formation on plates, linking microscopic to macroscopic pattern emergence without invoking attractive interactions. Through mentorship and collaborations, Cates has advanced the field by supervising PhD students in the Soft Matter Research Group at the and fostering joint projects that integrate theoretical predictions with experimental outcomes. Notable collaborations, such as those on active field theories, have yielded seminal frameworks for nonequilibrium systems, enabling broader adoption in statistical physics and . As the at since 2015, Cates' legacy lies in bridging theoretical modeling with experimental verification in , with post-2020 research emphasizing energetic costs and irreversibility in active systems to guide ongoing interdisciplinary applications.

References

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