About

John Wettlaufer is the A.M. Bateman Professor in the Department of Earth & Planetary Sciences at Yale University. He is trained in statistical physics and studies stochastic processes, asymptotic analysis, and other approaches and methods from modern applied mathematics and physics. His research includes numerical simulations to probe a broad range of problems such as the microscopic theory of melting, the mechanisms underlying cosmogony, climate dynamics, information theory, and turbulence.

Research topics

• Physics
• Computer Science
• Artificial Intelligence
• Psychology
• Climatology
• Atmospheric sciences
• Geography
• Mathematics
• Geology
• Mechanics
• Engineering
• Communication
• Environmental science
• Archaeology
• Geodesy

Selected publications

• Electric field effects on the collision efficiency of uncharged water droplets in a linear flow

  Physical Review Fluids · 2025-10-01

  articleOpen accessSenior author

  We study the dynamics of collisions between a pair of uncharged conducting droplets under the influence of a uniaxial compressional flow and an external electric field. The near-field asymptotic expression for the electric-field-induced attractive force demonstrates that surface-to-surface contact in finite time is facilitated by overcoming lubrication resistance. We demonstrate the significant role of the external electric field on the relative trajectories of two droplets in a compressional flow and provide estimates of the correlation between collision efficiency and the forces induced by the electric field. For droplet collisions in clouds, continuum lubrication approximations become inadequate to capture collision dynamics, and thus we incorporate noncontinuum lubrication interactions into our analysis to address this complexity. Our findings reveal the dependence of collision efficiency on the strength of the electric field, geometry of the two interacting droplets, noncontinuum effects, and van der Waals forces. We show that the electric fields typical of strongly electrified clouds substantially enhance the efficiency of droplet collisions. In contrast, the electric fields typical of fair-weather conditions have a negligible influence on the dynamics of droplet collisions.

  PublisherDOI

• Latch, Spring and Release: The Efficiency of Power-Amplified Jumping

  ArXiv.org · 2025-10-17

  preprintOpen access

  Many small animals, particularly insects, use power-amplification to generate rapid motions, such as jumping, that would otherwise be impossible given the standard power density of muscle. A common framework for understanding this power amplification is Latch-Mediated, Spring Actuated (or LaMSA) jumping, in which a spring is slowly compressed, latched in its compressed state and the latch released to allow jumping. Motivated by the jumps of certain insect larvae, we consider an external latching mechanism via adhesion to a substrate that is quickly released for jumping. We show that the rate at which this adhesion is lost is crucial in determining the efficiency of jumping and, indeed, whether jumping occurs at all. As well as showing how release rate should be chosen to facilitate optimal jumping, our analysis underscores the importance of the interaction between latch-release dynamics and the elastic deformation of the jumper for power amplification, thereby providing new insight into post-latch jumping control.

  PublisherOA PDFDOI

• Accelerated First-Passage Dynamics in a Non-Markovian Feedback Ornstein–Uhlenbeck Process

  Journal of Statistical Physics · 2025-09-13 · 1 citations

  articleOpen accessSenior author

  We study the first-passage dynamics of a non-Markovian stochastic process with time-averaged feedback, which we model as a one-dimensional Ornstein-Uhlenbeck process wherein the particle drift is modified by the empirical mean of its trajectory. This process maps onto a class of self-interacting diffusions. Using weak-noise large deviation theory, we calculate the leading order asymptotics of the time-dependent distribution of the particle position, derive the most probable paths that reach the specified position at a given time and quantify their likelihood via the action functional. We compute the feedback-modified Kramers rate and its inverse, which approximates the mean first-passage time, and show that the feedback accelerates dynamics by storing finite-time fluctuations, thereby lowering the effective energy barrier and shifting the optimal first-passage time from infinite to finite. Although we identify alternative mechanisms, such as slingshot and ballistic trajectories, we find that they remain sub-optimal and hence do not accelerate the dynamics. These results show how memory feedback reshapes rare event statistics, thereby offering a mechanism to potentially control first-passage dynamics.

  PublisherOA PDFDOI

• Electric field effects on the collision efficiency of uncharged water droplets in a linear flow

  ArXiv.org · 2025-05-21

  preprintOpen accessSenior author

  We study the dynamics of collisions between a pair of uncharged conducting droplets under the influence of a uniaxial compressional flow and an external electric field. The near-field asymptotic expression for the electric-field-induced attractive force demonstrate that surface-to-surface contact in finite time is facilitated by overcoming lubrication resistance. We demonstrate the significant role of the external electric field on the relative trajectories of two droplets in a compressional flow and provide estimates of the correlation between collision efficiency and the forces induced by the electric field. For droplet collisions in clouds, continuum lubrication approximations become inadequate to capture collision dynamics, and thus we incorporate non-continuum lubrication interactions into our analysis to address this complexity. Our findings reveal the dependence of collision efficiency on the strength of the electric field, geometry of the two interacting droplets, non-continuum effects, and van der Waals forces.

  PublisherOA PDFDOI

• Midlatitude Interactions Expand the Hadley Circulation

  Journal of the Atmospheric Sciences · 2025-04-16 · 1 citations

  articleOpen accessSenior author

  Abstract The Hadley circulation describes a planetary-scale tropical atmospheric flow, which has a major influence on climate. Contemporary theoretical understanding is based upon angular momentum conservation, the basic dynamical constraint governing the state of the flow pattern, and scaling relationships characterizing the macroturbulence created by synoptic eddies. However, despite the degree of success in representing the Hadley circulation, the canonical theoretical model of Held and Hou does not treat interactions with other regions, particularly the midlatitudes. Here, we extend their model to include the influence of midlatitude large-scale atmospheric dynamics, which we treat using the planetary-scale heat equation with a parameterized poleward heat flux driven by synoptic eddies. The energy flux balance within the Hadley cell includes the poleward heat flux at the poleward edge of the cell, which is controlled by the baroclinic instability of the subtropical jet. We find that an increase (decrease) in the poleward heat flux leads to a strengthening (weakening) tropical convection, driving an equatorward (poleward) shift of the edge of the Hadley cell. Thus, our theoretical solutions suggest that global warming, which can reduce the baroclinicity of the subtropical jet, can lead to the poleward expansion of the Hadley cell due to the change in energy flux balance within it. Significance Statement The Hadley circulation is a principal dynamical feature in the tropics, acting as an engine that transfers heat and momentum to high latitudes. At the same time, the extratropical regions can influence the Hadley circulation. Under global warming, high latitudes warm faster than low latitudes, reducing the equator to pole temperature difference and the poleward heat flux in the midlatitudes. The theory described here shows that the decrease in the poleward heat flux can lead to the expansion of the Hadley cell and a poleward shift of subtropical dry zones.

  PublisherOA PDFDOI

• Analytical Survival Analysis of the Non-autonomous Ornstein–Uhlenbeck Process

  Journal of Statistical Physics · 2024-10-22 · 3 citations

  articleOpen accessSenior author

  Abstract The survival probability for a periodic non-autonomous Ornstein–Uhlenbeck process is calculated analytically using two different methods. The first uses an asymptotic approach. We treat the associated Kolmogorov Backward Equation with an absorbing boundary by dividing the domain into an interior region, centered around the origin, and a “boundary layer” near the absorbing boundary. In each region we determine the leading-order analytical solutions, and construct a uniformly valid solution over the entire domain using asymptotic matching. In the second method we examine the integral relationship between the probability density function and the mean first passage time probability density function. These allow us to determine approximate analytical forms for the exit rate. The validity of the solutions derived from both methods is assessed numerically, and we find the asymptotic method to be superior.

  PublisherOA PDFDOI

• Soft matter physics of the ground beneath our feet

  Soft Matter · 2024-01-01 · 8 citations

  reviewOpen access

  The soft part of the Earth's surface - the ground beneath our feet - constitutes the basis for life and natural resources, yet a general physical understanding of the ground is still lacking. In this critical time of climate change, cross-pollination of scientific approaches is urgently needed to better understand the behavior of our planet's surface. The major topics in current research in this area cross different disciplines, spanning geosciences, and various aspects of engineering, material sciences, physics, chemistry, and biology. Among these, soft matter physics has emerged as a fundamental nexus connecting and underpinning many research questions. This perspective article is a multi-voice effort to bring together different views and approaches, questions and insights, from researchers that work in this emerging area, the soft matter physics of the ground beneath our feet. In particular, we identify four major challenges concerned with the dynamics in and of the ground: (I) modeling from the grain scale, (II) near-criticality, (III) bridging scales, and (IV) life. For each challenge, we present a selection of topics by individual authors, providing specific context, recent advances, and open questions. Through this, we seek to provide an overview of the opportunities for the broad Soft Matter community to contribute to the fundamental understanding of the physics of the ground, strive towards a common language, and encourage new collaborations across the broad spectrum of scientists interested in the matter of the Earth's surface.

  PublisherOA PDFDOI

• Prograde and meandering wall modes in rotating Rayleigh–Bénard convection with conducting walls

  Journal of Fluid Mechanics · 2024-10-31 · 3 citations

  articleOpen accessSenior author

  We use direct numerical simulations to study convection in rotating Rayleigh–Bénard convection in horizontally confined geometries of a given aspect ratio, with the walls held at fixed temperatures. We show that this arrangement is unconditionally unstable to flow that takes the form of wall-adjacent convection rolls. For wall temperatures close to the temperatures of the upper or lower boundaries, we show that the base state undergoes a Hopf bifurcation to a state comprised of spatiotemporal oscillations – ‘wall modes’ – precessing in a retrograde direction. We study the saturated nonlinear state of these modes, and show that the velocity boundary conditions at the upper and lower boundaries are crucial to the formation and propagation of the wall modes: asymmetric velocity boundary conditions at the upper and lower boundaries can lead to prograde wall modes, while stress-free boundary conditions at both walls can lead to wall modes that have no preferred direction of propagation.

  PublisherOA PDFDOI

• Stochastic reorientations and the hydrodynamics of microswimmers near deformable interfaces

  Physical Review Fluids · 2024-02-14 · 3 citations

  articleOpen accessSenior author

  We study the hydrodynamic interaction between a microswimmer and a deformable interface when the swimmer can stochastically reorient itself. We consider a force- and torque-free swimmer, modeled as a slender body, that can execute random orientation tumbles or active Brownian rotations in the plane of the deformable interface. When the swimmer is in the more viscous fluid, our analysis shows that both tumbles and Brownian rotations acting on timescales comparable to that of interface deformations can lead to a pusher-type swimmer rotating away from the interface, while enhancing its attraction towards the interface. In turn, the intrinsic orientational stochasticity of the microswimmer favors a stronger migration of pushers towards the interface at short times, but migration away from the interface in the long-time limit. However, irrespective of the viscosity ratio of the two fluid medium, the tendency of a pusher to align parallel to the interface is suppressed; the results for puller-type swimmers are the opposite. Our study has potential consequences for the residence time of swimming microorganisms near deformable boundaries. Published by the American Physical Society 2024

  PublisherOA PDFDOI

• Analytical Survival Analysis of the Non-autonomous Ornstein-Uhlenbeck Process

  arXiv (Cornell University) · 2024-06-05

  preprintOpen accessSenior author

  The survival probability for a periodic non-autonomous Ornstein-Uhlenbeck process is calculated analytically using two different methods. The first uses an asymptotic approach. We treat the associated Kolmogorov Backward Equation with an absorbing boundary by dividing the domain into an interior region, centered around the origin, and a "boundary layer" near the absorbing boundary. In each region we determine the leading-order analytical solutions, and construct a uniformly valid solution over the entire domain using asymptotic matching. In the second method we examine the integral relationship between the probability density function and the mean first passage time probability density function. These allow us to determine approximate analytical forms for the exit rate. The validity of the solutions derived from both methods is assessed numerically, and we find the asymptotic method to be superior.

  PublisherOA PDFDOI

Recent grants

• EAGER: Scalable PetaScale Computing for Dielectric Response in Biophysical, Optomechanical, and Geophysical Systems

  NSF · $258k · 2010–2012

• Interfacial Premelting and Geophysical Implications

  NSF · $710k · 2005–2010

Frequent coauthors

• Woosok Moon

  189 shared

• L. T. Giorgini

  97 shared

• Sahil Agarwal

  Christ University

  87 shared

• Srikanth Toppaladoddi

  75 shared

• Robert W. Style

  69 shared

• Eric R. Dufresne

  49 shared

• Andrew Wells

  University of Oxford

  48 shared

• Andong He

  Yale University

  41 shared