Programme of the day
13:00 Coffee and Welcome
13:30 Explanation of DIEP context and goals (by Mark Golden)
13:45 How is everyone connected to emergence? A short round of 2min presentations
14:30 Discussions of the proposed topics
15:30 Discussion into smaller groups: find common projects
16:30 General discussion on the results and identification of key questions.
The National Science Agenda compiled a list of scientific questions based on public interest. This questions were assigned to different scientific routes. Based on these questions and their associated problems, DIEP formulated a set of topics/projects meant to make progress in different areas and provide satisfactory answers to these difficult problems. A more exhaustive description of the topics and relevant questions is found in the attached slides. Below you find short descriptions and some of the questions brought up during the brainstorming session.
#1 CONNECTING DIFFERENT LEVELS OF REALITY
Many processes in nature are described by theories where different levels of reality meet. Perhaps the simplest example is that of Brownian motion: both molecular forces (microscopic) and viscous forces (macroscopic) play a role. But there is a plethora of other processes that fall into the same category: the under standing of lightning, the emergence of large scale cosmological structures, quantum materials, biochemical networks, complex self-assembly and different hydrodynamic flows.
Discussion: How to coarse-grain and reverse the map from macro to micro scales? What variables should be integrated over? Generically, how to predict the dynamics and the state of certain quantities? How to deal with processes with many different scales and how to integrate variables to obtain descriptions at intermediate scales? What are models/reality? If you had a description at all scales, would you call it reality? Can machine learning and data assisted modelling help in identifying microscopic laws?
A lot of natural phenomena exhibits self-organising behaviour. Self-organisation of polymers and biomolecules, bacteria, flocks of birds, herds of sheep, self-organisation of large cosmological objects, etc. Is a general theory of self-organisation possible? Again, is it important to understand the microscopics of these theories? How would we go about to do it?
Discussion: Need new concepts to understand assembling of building blocks. What do mathematical models of self-assembly have in common? Are bacterias organising themselves in a similar manner as flocks of birds or galaxies? How to properly describe non-equilibrium systems? In what conditions can we separate scales in given system? How to describe rare events such as catastrophes and avalanches? Most theories use statistical mechanics but how to describe driven systems and classify transient states?
#3 EMERGENT MATERIALS
Examples of emergent materials could be high-temperature superconductors, topological states of matter, new synthetic soft matter materials, elementary bio-materials, machine materials... Do we need a theory of emergence to design/build these materials? How would it help?
Discussion: Can we use bio/machine materials, trial and error, to understand a general theory of emergence? Would that be even possible? Numerics are still lagging behind: better exploration of computer simulations? How to mimic processes in the brain to better process information? Would a general theory of emergence help in understanding daily-life materials? The understanding liquid crystals came after the LCD screen. If emergence can be tested this would open up room for "experimental philosophy". Mathematically speaking: what is emergence? Can we use string theory, gravity, hydrodynamics, etc, to better understand it?
#4 SYMMETRIES AND SYMMETRY BREAKING
Symmetries take a crucial role in many physical phenomena. For instance, critical phenomena and phase transitions are usually mostly dependent on the symmetries of the system and not on all the microscopic details of the theory. This has a wide range of applicability such as in all sorts of quantum and classical systems but also in traffic jams and stock markets. In addition, symmetry breaking takes a crucial role in emergent behaviour: it is often the case in both condensed and soft matter systems that the intractability of the emergence behaviour is due to symmetry breaking of microscopic theory.
Discussion: How to understand disorder and Anderson localisation? Can a theory of emergence be described by a general theory of symmetry breaking? The Ising model is a good test case: it has an emergent E8 symmetry.
#5 THE FUNDAMENTAL BUILDING BLOCKS OF THE UNIVERSE, GRAVITY AND BLACK HOLES
There are many hints that space, time and hence gravity is an emergent phenomena at macroscopic scales. How can this be studied? String theory is a pioneer in understanding how gravity emerges from quantum theories and hints towards the existence of many potentially many different particles. How is this type of emergent phenomena related to other examples? In this line of research, there is still a lot more to explore, in particular, its implication for dark energy, dark matter and black holes. Developments in these areas will require help from new observational methods.
Discussion: Emergence of space and time can sometimes occur from an auxiliary systems with no gravity, such as in the context of the AdS/CFT correspondence. It can provide an alternative description of certain materials like high-temperature superconductors.
#6 EMERGENCE OF GEOMETRY AND TOPOLOGY
Geometry and topology emerge in a huge variety of situations: emergence of space and time, emergence of defects in hydrodynamic flows in active matter, pattern formation in shells and bones, topological states/defects in quantum matter, defects in biomembranes and conformational changes of polymer assemblies to name a few. Surely, a lot of mathematical tools must be common to deal with all these examples such as deformations of surfaces, complexity theory, chaos, dynamic systems, hydrodynamics, topological spaces, etc.
Discussion: Emergence of space and time can sometimes occur from an auxiliary systems with no gravity, such as in the context of the AdS/CFT correspondence. It can provide an alternative description of certain materials like high-temperature superconductors. There is a strong connection between quantum information theory, entanglement and the emergence of spacetime geometry and topology.
#7 WHAT IS EMERGENCE ?
Within history and philosophy of science many definitions have been put forth, but there is still no accepted overarching definition, neither a complete classification of emergent phenomena. This is an area of research where input from all sciences can be useful not only to provide input to a potential categorisation of emergent phenomena but because the result of that categorisation can lead to a better understanding of how theories are related to each other and what the crucial issues are.
Discussion: Is it possible to have a complete categorisation of emergence in terms of an epistemic/ontological distinction? Numerical simulations have rarely been the focus of philosophy of emergence.
#8 TOWARDS THE EMERGENCE OF THE CLASSICAL WORLD FROM QUANTUM THEORY
We are still far from understanding in all detail how classical physics emerges from quantum theory and when quantum effects become unimportant in macroscopic processes. To reach a proper answer to this question requires exploring quantum decoherence and deformation quantisation. Is this sufficient? What else is necessary? What is not understood is the way emergent properties of classical physics arises from QM, notably: solution of measurement problem (i.e. collapse of Schrodinger cat states) and (spontaneous) symmetry breaking etc. Decoherence is not enough to achieve even the former (let alone the latter). Mechanism behind SSB might be the same as behind resolution of measurement problem - this is one advantage of using general framework of Emergence in this context.
Hypothetical Research Directions in 30min
All the participant scientist gathered into groups of 4 and did their best to come up with some ideas slightly sensical after 30min of coffee.
#1 Driven systems: what type of emergent phenomena explains this? Nature paper: Emergent topology and pattern formation in non-equilibrium non-collinear magnets.
#2 Energy landscapes at different scales. First (review) paper: Universality in glassy systems from atoms to the universe. Second paper: understanding new phases only present at short timescales (transient/metastable phases and their properties). Discussion: What is the philosophical definition of non-equilibrium? Connections well with biological applications such as genotype/phenotype shape and landscapes.
#3 Connecting the hydrodynamic flows of electrons, fluids and the atmosphere. At the electron scale, one tracks collective motion. At the soft matter scale, one tracks individual motion. At the atmospheric scale one tracks voxel "particles".
#4 Feedback onto the fundamental level. Nature paper: Evolutionary dynamics and feedback on electron dynamics.