# EPJ E interview – Daan Frenkel. Simulating soft matter through the lens of statistical mechanics

- Details
- Published on 23 June 2016

Daan Frenkel has been awarded the most important prize in the field of statistical mechanics, the 2016 Boltzmann Medal. The award recognises Frenkel’s seminal contributions to the statistical-mechanical understanding of the kinetics, self-assembly and phase behaviour of soft matter. The honour recognises Frenkel’s highly creative large-scale simulations of soft matter capable of explaining the self-assembly of complex macromolecular systems, colloidal and biomolecular systems.

Frenkel is Professor of Theoretical Chemistry at the University of Cambridge, UK and has been Editor in Chief of EPJ E between 2010 and 2014. In this interview with Sabine Louet, Frenkel gives his views on statistical physics, which has become more relevant than ever for interdisciplinary research. He also offers some pearls of wisdom for the next generation Statistical Mechanics experts. The full interview is published in the June issue of EPJE.

**The following is an excerpt.**

**Sabine Louet: What future do you see for statistical physics as a research field?**

Daan Frenkel: There is no branch of physics that has so much impact on other fields as statistical physics. And that impact will grow. The definition of statistical physics is much broader now than it used to be. Any problem that can be treated with the methods of statistical physics, is statistical physics. The boundaries are disappearing with genomics, evolution, biology, data-analytics, economics, social sciences, to name but a few. There are also new problem areas being explored, such as the study of active matter, epitomised by the behaviour of flocks of birds.

**SL: What defines a statistical physicist nowadays?**

DF: What has changed today is that we have new experiments gathering large volume of information on a system and the computational power to analyse them relying on statistical mechanical tools. For example, there are many real-life problems involving large populations, such as economics and biophysics. Statistical mechanics can also help to model evolutionary processes, e.g. to trace back the origin of genetic defects in a population. Whereas continuum approaches often use differential equations, Statistical Mechanics is intrinsically “atomistic”: it uses a particle- (or agent-) based approach.

In essence, statistical physics plays a key role in describing the properties of such systems with many degrees of freedom. Many-body system exhibit “emergent” behaviour that is absent in systems with few particles. Statistical physicists recognise that noise or fluctuations may contain crucial information. And, they all have a deep respect for the second law of thermodynamics, which allows them to appreciate the crucial role of entropy in many physical phenomena.

What are the most controversial issues in your field of study today? There is quite a bit of debate on the nature of the glass transition, particularly the relative importance of structural and dynamical aspects. Of course, there are always debates in statistical mechanics, but the divergence of views is often a matter of interpretation. Different theories focus on different aspects of the same problem. There is also always discussion about the microscopic interpretation of the second law of thermodynamics and about the relation between entropy and information. In addition, there are occasionally papers that claim that the Second Law can be violated. However, these papers tend to focus on semantics, they never show that it is possible to have a sustained, spontaneous heat flow from cold to hot.

**SL: If you had not become a scientist, what would you have most likely ended up doing?**

DF: If I were not a scientist, I would probably be a historian or a cook, or both. I would enjoy it, but I would not be very good at it. Being a scientist is not a profession, it is an attitude. It is my attitude. Hence, I find it hard to imagine working outside a scientific discipline. But it does not have to be physics. If I had to start now, I would probably apply statistical physics thinking to understand the relation between the microbiome and its host.

**Read the full interview: Interview with Daan Frenkel, Boltzmann Medallist 2016. Simulating soft matter through the lens of statistical mechanics. Eur. Phys. J. E (2016) 39: 68**