- Organized by
Giulio Biroli, Ph.D.CEA Saclay
David R. Reichman, Ph.D.Columbia University
Sidney Nagel, Ph.D.Stein-Freiler Distinguished Service Professor in Physics, University of Chicago
The goal of the Simons Collaboration on Cracking the Glass Problem is to develop a complete and quantitative description of the glass transition, connecting the explicit and quantitative mean-field and zero-temperature theories that have been developed. The aim is to create a similarly quantitative and predictive theory of glassy dynamics in finite dimension at finite temperatures. The third annual meeting of the collaboration will highlight the progress that has been made in pursuing these goals. This work has provided a new vision for this branch of statistical and mathematical physics; it has implications for a wide range of experimental systems and the tools developed in creating such a framework is having important ramifications for a broad range of fields. The talks during the meeting will outline some of these activities.
Thursday, March 7
8:30 AM CHECK-IN & BREAKFAST 9:30 AM Sidney Nagel | The State of the Collaboration 10:30 AM BREAK 11:00 AM Lisa Manning | How do Glasses Flow and Fail in Dimensions from Two to Infinity? 12:00 PM LUNCH 1:00 PM Vincenzo Vitelli | Odd Elasticity 2:00 PM BREAK 2:30 PM Andrea Liu | Exploiting Complex Landscapes to Design Metamaterials 3:30 PM BREAK 4:00 PM Marc Mézard | Statistical Physics and Statistical Inference 5:00 PM DAY ONE CONCLUDES
Friday, March 8
8:30 AM CHECK-IN & BREAKFAST 9:30 AM Frances Hellman | Ideality and Tunneling Level Systems (TLS) in Amorphous Silicon Films 10:30 AM BREAK 11:00 AM Mark Ediger | Exploring the Limits of Amorphous Packing with Vapor-deposited Glasses 12:00 PM LUNCH 1:00 PM Jorge Kurchan | Glassy Dynamics 2:00 PM MEETING CONCLUDES
Wednesday March 6, 2019
See lecture page for registration and further information.
Scientists are customarily taught to understand solid materials by treating them as ideal crystals. This approach, however, becomes untenable in an intrinsically disordered material such as a glass: A crystal is an abysmal starting point for understanding the rigidity or excitations of a glass with no obvious long-range order.
In this lecture, Sidney Nagel will discuss how physicists are working to understand glassy matter. He will explain jamming, an alternative starting point for describing solids where order, rather than disorder, is treated as a perturbation. He will then show how physicists have learned to exploit disorder to create solids with unique, varied, textured and tunable behavior including long-range interactions inspired by the allosteric behavior of proteins. Applying these techniques, however, requires computing the response of each bond between particles. Can such detailed computations be avoided? Because a material has a memory of the conditions under which it was prepared and subsequently aged, scientists can now direct aging using Nature’s (as distinct from a computer’s) so-called greedy algorithms to achieve novel kinds of mechanical functionality.
University of Wisconsin, Madison
Exploring the Limits of Amorphous Packing with Vapor-Deposited Glasses
Glasses formed by cooling a liquid inherit both their structure and their limited stability from the liquid state. In contrast, glasses prepared by vapor deposition can avoid both of these limitations. By utilizing the high mobility present near the free surface of many organic glasses, vapor deposition can build glasses with low-enthalpy, high-density and high-thermal stability. Based upon their position on the potential energy landscape, these materials approach “ideal glass” packing that otherwise could only be achieved by annealing a liquid-cooled glass for thousands or millions of years. Vapor deposition of organic semiconductors produces glasses with improved properties for organic electronics, including the ability to produce anisotropic glasses with a wide range of structures. Remarkably, this “anti-epitaxy” process uses the free-surface structure as its template, rather than the substrate structure. Recent work has shown that optimizing vapor deposition can produce organic light emitting diodes (OLEDs) that are more efficient and have extended lifetimes.
University of California, Berkeley
Ideality and Tunneling Level Systems (TLS) in Amorphous Silicon Films
Heat capacity, sound velocity and internal friction of covalently bonded amorphous silicon (a-Si) films with and without hydrogen show that low-energy excitations, commonly called tunneling or two level systems (TLS), can be tuned over nearly three decades, from below-detectable limits to the range commonly seen in glassy systems. This tuning is accomplished by growth temperature, thickness, growth rate, light soaking or annealing. We see a strong correlation with atomic density in a-Si and in literature analysis of other glasses, as well as with dangling bond density, sound velocity and bond angle distribution as measured by Raman spectroscopy, but TLS density varies by orders of magnitude while these other measures of disorder vary by less than a factor of two. The lowest TLS films are grown at temperatures near 0.8 of the theoretical glass transition temperature of Si, similar to work on polymer films and suggestive that the high surface mobility at relatively low temperature of vapor deposition can produce materials close to an ideal glass, with higher density, lower energy and low TLS due to fewer nearby configurations with similarly low energy. The TLS measured by heat capacity and internal friction are strongly correlated for pure a-Si, but not for hydrogenated a-Si, suggesting that the standard TLS model works for a-Si, but that a-Si:H possess TLS that are decoupled from the acoustic waves measured by internal friction. Internal friction measures those TLS that introduce mechanical damping; Hellman is in the process of measuring low T dielectric loss, which yield TLS with dipole moments, in order to explore the correlation between different types of TLS. Additionally, a strong correlation is found between an excess T3 term (well above the sound velocity-derived Debye contribution) and the linear term in heat capacity, suggesting a common origin.
Almost every meaningful scientific question we ask about supercooled liquids and glasses involves dynamics. If we want to control their behavior, we need to understand the way these systems flow, age or respond to external fields or violent stresses. However, there is another aspect about why the study of glassy dynamics is so basic: it has emergent and universal behavior — quantities and rules that transcend the immediate example being studied. These rules are independent of the microscopic structure of any particular material or example. Thus, what we learn by studying the dynamics in glasses and liquids teaches us lessons that are applicable far beyond the original manifestation.
University of Pennsylvania
Exploiting Complex Landscapes to Design Metamaterials
Systems with complex landscapes have far more variation in their properties than those with simple ones. This natural variation can be pushed even further by design, allowing us to tune in unusual properties and novel functions into materials. For example, when most materials are stretched in one direction, they tend to shrink in the orthogonal directions. Materials that do the opposite and expand in the orthogonal directions when stretched are ‘auxetic’ and have attracted attention for applications such as high energy absorption. We have found that mechanical spring networks can be tuned easily to the extreme limit of auxetic behavior. Likewise, our collaboration has shown that properties common in living matter, such as the ability of proteins (e.g., hemoglobin) to change their conformations upon binding of an atom (oxygen) or molecule, the ability of the brain’s vascular network to send enhanced blood flow and oxygen to specific areas of the brain associated with a given task, or the ability to retain a memory, can be designed into disordered systems using similar principles. The ability to design properties and functions further gives new insight into the relation between microscopic structure and function that may help us both to understand living systems and to design new biologically inspired materials.
How Do Glasses Flow and Fail in Dimensions from Two to Infinity?
Solids resist shear forces, but under enough applied strain, they will yield and deform. We have recently established exact infinite-dimensional solutions for amorphous solids under strain, which predict where a solid will remain stable as a function of strain and density and provide a strong foundation for understanding rheology in glasses. However, infinite-dimensional theories cannot predict the temporal and spatial dynamics of deformation in amorphous solids, which vary dramatically from ductile and homogeneous flow in poorly annealed glasses to brittle fracture in deeply quenched glasses. We now understand that these processes are controlled by quasi-localized excitations that are common in 2-D and 3-D but disappear in higher dimensions. Analytically solvable elasto-plastic models include a mean-field coupling between localized excitations. We have demonstrated that the dynamics of such models are quite similar to those in 2-D and 3-D numerical simulations and indicate that the brittle-to-ductile transition is a random critical point. To make these theories quantitatively predictive, we are currently working to understand how material preparation and shear affect the population of low energy excitations, how the coupling between excitations differs from mean-field and how finite strain rates and temperatures impact these quantities.
École Normale Supérieure
Statistical Physics and Statistical Inference
A major challenge of contemporary statistical inference is the large-scale limit, where one wants to discover the values of many hidden parameters, using large amounts of data. In recent years, ideas from statistical physics of disordered systems, notably the cavity method, have helped to develop new algorithms for important inference problems, ranging from community detection to compressed sensing, machine learning (notably neural networks) and generalized linear regression. The talk will review these developments and explain how they can be used, together with the replica method, to identify phase transitions in benchmark statistical ensembles of inference problems.
University of Chicago
The State of the Collaboration
This talk will review the state of the collaboration Cracking the Glass Problem. Nagel will first review the fundamental issues about glasses, jamming and the nature of the amorphous state that initially inspired the collaboration’s work. The collaboration has made great strides in finding solutions to some of these problems, and Nagel will describe what the team has accomplished so far. These include finding new algorithms for extending simulations of glassy dynamics into new regimes, understanding the Garner phase of matter, deriving the dynamics in the mean-field limit and the extension to the creation of metamaterials. These accomplishments have opened up new opportunities for further work. Nagel will give a vision of our plans for the future and where we are going.
James Franck Institute
Hooke’s law states that the deformations or strains experienced by an elastic object are proportional to the applied forces or stresses. The number of coefficients of proportionality between stress and strain (i.e., the elastic moduli) is constrained by energy conservation. In this talk, we generalize continuum elasticity to active media with nonconservative (or nonreciprocal) microscopic interactions. This generalization, which we dub ‘odd elasticity,’ reveals that two additional elastic moduli can exist in a 2-D isotropic solid with strain-dependent activity. Such an odd-elastic solid can be regarded as a distributed engine: work is locally extracted, or injected, during quasi-static cycles of deformation. By coarse graining illustrative microscopic models, we show how odd elasticity emerges in active metamaterials composed of springs that actuate internal torques in response to strain. Our predictions, corroborated by simulations, uncover phenomena ranging from activity-induced auxetic behavior and buckling, to wave propagation powered by self-sustained active elastic cycles.
Ada Altieri École Normale Supérieure Glassy features and collective phenomena in large ecosystems Marco Baity Jesi Columbia University Dynamics of glasses: from infinite to three dimensions Horst-Holger Boltz University of Chicago Fluctuation distributions of energy minima in complex landscapes Carolina Brito Universidade Federal do Rio Grande do Sul Theory for Swap Acceleration near the Glass and Jamming Transition Davide Facoetti École Normale Supérieure Toy glasses and toy black holes Varda Faghir Hagh University of Chicago The Marginality Gap, From Low Dimensions to Mean-Field Elijah Flenner Colorado State University TBA Giampaolo Folena Università di Roma/LPTMS, Université Paris Sud Memories from the ergodic phase: the awkward dynamics of mixed p-spin models Benjamin Guiselin Université de Montpellier Probing the hidden equilibrium phase transition in glass-forming liquids Daniel Hexner University of Chicago Can a large packing be assembled from smaller ones? Yi Hu Duke University Dynamical transition of random Lorenz gas Harukuni Ikeda École Normale Supérieure Universality of jamming of nonspherical particles Atsushi Ikeda University of Tokyo Spatial structure of quasilocalized vibrations in nearly jammed amorphous solids Dmytro Khomenko École Normale Supérieure Statistics of Two-Level systems in polydisperse amorphous solids. Robert Leheny Johns Hopkins University Microscopic Dynamics of Stress Relaxation in a Soft Glass Cathy Li University of Pennsylvania Marginal Stability in Mean-field and Low-dimensional Jammed Packings Peter Morse Syracuse Univesity The relationship between shear and random force in jammed systems Anshul Deep Singh Parmar Universite de Montpellier Knocking at the bottom of the energy landscape: Extended Kob-Andersen model Nidhi Pashine University of Chicago Directed aging and memory: Teaching an old foam new tricks Marko Popovic EPFL Does inertia kill criticality in depinning and friction? Mark Robbins Johns Hopkins University Probing large viscosities in glass formers with nonequilibrium simulations Valentina Ros École Normale Supérieure Geometrical properties of high-dimensional landscapes: local minima, barriers and topology trivialization transitions Grant Rotskoff Courant Institute Global convergence of neuron birth-death dynamics Miguel Ruiz Garcia University of Pennsylvania Tunning and jamming reduced to their minima Hajime Yoshino Osaka University A stability-reversibility map unifies elasticity, plasticity and jamming in hardsphere glasses Ge Zhang University of Pennsylvania Interplay of softness and rearrangements during avalanche propagation
Air and Train
Group AThe foundation will arrange and pay for all air and train travel to the conference for those in Group A. Please provide your travel specifications by clicking the registration link above. If you are unsure of your group, please refer to your invitation sent via email.
Group BTThe foundation will arrange and pay for hotel accommodations for individuals in Group B for up to three nights in correlation with the meeting dates. Please provide your arrival and departure dates by clicking the registration link above. If you are unsure of your group, please refer to your invitation sent via email.
Group CIndividuals in Group C will not receive travel or hotel support. Please register at the link above so that we can capture your dietary requirements. If you are unsure of your group, please refer to your invitation sent via email.
Personal CarFor participants driving to Manhattan, The Roger Hotel offers valet parking. Please note there are no in-and-out privileges when using the hotel’s garage, therefore it is encouraged that participants walk or take public transportation to the Simons Foundation.
Participants in Groups A & B who require accommodations are hosted by the foundation for a maximum of three nights at The Roger hotel. Any additional nights are at the attendee’s own expense.
The Roger New York
131 Madison Avenue
New York, NY 10016
(between 30th and 31st Streets)
To arrange accommodations, please register at the link above.
For driving directions to The Roger, please click here.