Monday, April 26, 2021

Is this a good book preface?

 I have never written a book before. Hence, I have never written a preface. For what it is worth, according an article on, Writing 101: How to Write a Preface for a Book

In one or two pages, an author’s preface is meant to:

  • Explain why the author chose to write about this topic
  • Reveal their motivation and inspiration for writing the book
  • Describe the process of researching the topic of the book
  • Outline the process of writing the book, including any challenges and how long it took.

Based on this I wrote the following draft of a Preface to Condensed Matter Physics: A Very Short Introduction. 


I love learning new things. I find joy in understanding, particularly if it is profound and important.  I love trying to communicate that understanding, particularly in ways that may appeal and inspire. I find beauty in ideas, images, and stories. I am a “big picture” person. I love seeing connections, whether deep or anecdotal, between different pieces of knowledge. Hence, it is not surprising that I was excited when I discovered the Very Short Introductions series. My eclectic interests are reflected in some of the VSI titles on my bookshelf including Marx, Depression, Complexity, Adam Smith, Water, Corruption, Social and Cultural Anthropology, and Epidemology.

Condensed matter physics is one of the largest and most vibrant sub-fields of physics. It is a rich source of ideas, concepts, and techniques that have cross-fertilised with not just other sub-fields of physics, such as elementary particles, but also other scientific disciplines (chemistry, biology, computer science, sociology, economics) and engineering (electrical, materials, chemical). In the past thirty years, the Nobel Prize in Physics has been awarded thirteen times for work on condensed matter. In the past twenty years, eight condensed matter physicists have received the Nobel Prize in Chemistry. 

The last thirty-five years I have worked in condensed matter physics: learning, teaching, and researching. I have come to love the discipline and to appreciate its’ importance, intellectual richness, beauty, and coherence. Given there are now more than 500 titles in the VSI series I was surprised and disappointed that there was no title on condensed matter. There were titles on subjects such as Magnetism, Superconductivity, Crystallography, and now Soft Matter, that are related to condensed matter, but they miss the unity of the whole discipline. Hence, I am glad to have the opportunity to contribute to the series.

Condensed matter physics is all about emergence; the whole is greater than the sum of the parts. A system composed of many interacting parts (atoms) has properties (a state of matter) that are qualitatively different from the properties of the individual parts. This commonality is why condensed matter physics has had such a fruitful cross-fertilisation with other sciences. It is arguably the field with the greatest success at understanding emergent phenomena in complex systems, particularly at the quantitative level. This is not because condensed matter physicists are smarter than sociologists, economists, or neuroscientists. It is because the materials we study are much “simpler” than societies, economies, and brains. 

Even after I finished a undergraduate degree in physics in Australia in 1982, I would not have been able to answer the question, “what is condensed matter physics?” There was no such course at my university. The only related one was in “solid state physics” and I did not take that course because the lecturer was boring and incompetent. I then went to Princeton University in the USA to pursue a Ph.D. in physics and ended up working in theoretical condensed matter physics. But, even then I don’t think I was clear what the field is really about. In hindsight, I think this failing arose due to my own lack of attention to broader intellectual issues.

In the past two decades several circumstances have shaped the emergence of the shape and content of this book. One of the best ways to learn and understand a subject is to try and teach it, particularly to novices. In 2000, I started working at the University of Queensland and I was assigned to teach a course for second year science undergraduates entitled, “Thermodynamics and Condensed Matter Physics.” As is too often the case in universities the curriculum for this course did not arise from of a grand and coherent educational vision but rather from historical circumstances involving politics and personnel. Nevertheless, serendipity is a powerful means of discovery. Order can emerge from chaos, and beauty can rise from ashes. In most undergraduate programs, condensed matter physics is only taught in the third or fourth year, if at all, and usually as an elective for physics majors. This is because courses build on advanced subjects such as quantum theory and statistical mechanics, and the associated mathematical machinery. However, many of the most important ideas in condensed matter can be understood without reference to these advanced subjects. This is the approach I take here, with some of the material drawing from the experience of teaching that course. 

In 2009, I started writing a blog, Condensed Concepts: Ruminations on Emergent Phenomena in Condensed Phases of Matter. A great beauty of blogging is that you can write about whatever you like and in whatever format you choose. I have now written more than two thousand posts on diverse topics, including technical commentary on specific scientific papers, presentations to school students, history, university politics, job advice, philosophy of science, and the relation of condensed matter to other sciences, from biology to economics. Blogging improved my ability to write for a broad audience and clarified my thinking about condensed matter physics in a broad intellectual context. Some of the material presented in this book is loosely based on my blog posts.

Over the past decade I have had significant and fruitful intellectual interactions with colleagues in a range of disciplines including law, economics, sociology, history, engineering, anthropology and biology. This has been facilitated and stimulated by being part of several informal networks (local, national, and international) of academics, with a particular interest in the relationship between our academic disciplines, Christian theology, and human flourishing. This has clarified my understanding of my own discipline and how to discuss it with those outside.

Condensed matter physics as a research field is not just defined by the objects that it studies (states of matter in materials), but rather by a particular approach to the study of these objects. The aim is to address fundamental questions and to find unifying concepts that can be used to describe and understand a wide range of phenomena in materials that are chemically and structurally diverse. My aim has not been to write a popular summary of the main topics covered in a textbook. Rather it is an essay that I hope brings joy and appreciation and a desire to learn more. I have chosen to emphasise concepts rather than trying to explain technical details. 

To make the book more interesting and engaging in most of the chapters I have consciously included several elements. A key concept, some connection to everyday experience, an interesting anecdote, a technological application, and a connection to another discipline. There are no mathematical equations and many figures.

This VSI is shaped by an important intellectual legacy that should be acknowledged and only became apparent to me when much of it was written. In his wonderful recent biography, Mind over Matter: Philip Anderson and the Physics of the Very Many, Andrew Zangwill states “more than any other twentieth-century physicist, he [Anderson] transformed the patchwork of ideas and techniques formerly called solid-state physics into the deep, subtle, and intellectually coherent discipline known today as condensed matter physics.” I hope that what I have written does honour this rich legacy of Phil Anderson (1923-2020).

I have really enjoyed writing this book. I hope I can convince you that condensed matter physics is fascinating, significant, exciting, beautiful, and profound.  

What do you think? Is this a good Preface? Would this motivate your aunt or your colleague in law to start reading the book?

Wednesday, April 21, 2021

Implicit versus explicit beliefs

 How can we design a room-temperature superconductor? How can a government stimulate economic growth? How can an NGO help reduce domestic violence? Why do communities become segregated on racial lines? How can I improve my mental health?

These important questions may seem unrelated. However, I propose that often there is a common issue about the strategies that people (whether individuals, professions, NGOs, funding agencies, governments, ...) propose to find answers or when definite answers are proposed.

Many strategies and answers involve a heavy dose of implicit beliefs. These are assumptions that are never stated. They may be elements of a worldview, which according to one definition, is

a commitment, a fundamental orientation of the heart, that can be expressed as a story or in a set of presuppositions (assumptions which may be true, partially true, or entirely false) which we hold (consciously or subconsciously, consistently or inconsistently) about the basic construction of reality, and that provides the foundation on which we live and move and have our being.

 James W. Sire, The Universe Next Door: A basic worldview catalog

These implicit beliefs may relate to values and morality. But I want to focus more on implicit beliefs that are related to academic disciplines such as philosophy of science, psychology, political science, theology, economics, anthropology,  sociology, ...  Most of us have never studied these disciplines and some of us may be skeptical about some of them. But, my point is that everyone has implicit ideas about what is true with regard to the objects these disciplines study. Everyone has a philosophy of science. Everyone has ideas about how minds work and how to change societies. It is just that these beliefs are rarely stated. 

Why does this matter? If implicit beliefs are never stated, they can never be tested, evaluated, critiqued, refined, or rejected. I believe that implicit beliefs are too often based on intuition, prejudice, common sense, or culture (social pressure to conform to accepted wisdom). This is not necessarily bad. Sometimes intuition, common sense, and culture are helpful and correct. We could not survive in life if we did not have them. We simply don't have the time, energy, and resources to constantly question and validate everything. On the other hand, if there is a vacuum, it will get filled with something. A major lesson from scientific history is that intuition, prejudice, common sense are sometimes wrong.

I now give three concrete examples of implicit beliefs. They cover computational materials science, public policy, and social activism.

Understanding materials using computers

Amongst others, there are two things, we would like more computational power to be able to do. One is to do reliable ab initio calculations of the properties of complex molecules and solids, from proteins to crystals with unit cells containing large numbers of atoms.  Another is to do exact diagonalisation (or some alternative reliable method) of many-body Hamiltonians, such as the Hubbard model, on large enough lattices that finite-size effects are minimal or can be reliably accounted for.

Over the past decade, there has been a lot of hype about how quantum computers and/or machine learning techniques will solve these problems and thus initiate a new era of materials understanding, discovery, and design with significant technological and economic benefits. My problem is that these claims usually seem to have the implicit belief that the only obstacle to progress is one of computational power. This fallacy has recently been deconstructed and critiqued in detail in three beautiful essays by Roald Hoffmann and Jean-Paul Malrieu, Simulation vs. Understanding: A Tension, in Quantum Chemistry and Beyond.

Public policy

National economies around the world have been battered by the covid-19 pandemic. In response, governments of prosperous countries are spending big on stimulus packages. This involves taking on massive amounts of debt and significant government intervention in "free" market economies. Will these initiatives achieved their goals, particularly in the long term? Could they actually make things worse? Responses from pundits, both for and against, are laden with implicit beliefs. Unfortunately, economists cannot agree on the answer to the basic question, "Does government stimulus spending actually produce economic growth?" This issue is nicely discussed in a pre-pandemic podcast at Econtalk. 

NGOs and social activism

Many NGOs are about change. They aim to build a better world, addressing problems such as domestic violence, poverty, climate change, corruption, racism,... They aim to promote education, human rights, good governance, democracy, health, transparency, .. I love NGOs. I support many: philosophically, financially, and practically. To survive most NGOs have to raise funds, whether from many small donors or large philanthropies. This requires a well-honed pitch that aims to inspire potential donors to give. Furthermore, the whole operation of most NGOs is laden with implicit beliefs, whether those of the founders, staff or donors.

Consider a hypothetical NGO whose goal is to reduce the number of murders in a country. I chose this example because it may at first appear less controversial and contentious than some. Almost everyone thinks murder is wrong (always) and societies should stop reduce it. But why do murders occur? Revenge, passion, drugs, alcohol, money, politics, racism, ... Will making the purchase of guns difficult reduce the murder rate? Gun lobbyists will claim "Guns don't kill people. Criminals do! Law-abiding citizens need guns for self-defense." (cringe). There are many other alternative strategies: increasing penalties (longer jail terms or even the death penalty), the number of police, weapons for police, community policing, drug rehabilitation, breaking up gangs, ... Wow! It's complicated. My main point is that the hypothetical NGO will probably have an implicit belief that one particular strategy is the best one. Furthermore, if you identify and question this belief reasonable debate may not follow, but it may even be claimed that you don't care about stopping murder.

Some NGOs and philanthropies have become mindful of these issues. In response to a grant application that I helped an NGO write we were asked what our "theory of change" was? I discovered that there is a whole associated "industry. According to (!)

One organisation which began to focus on these issues was the US-based Aspen Institute and its Roundtable on Community Change. ... [leading] to the publication in 1995 of New Approaches to Evaluating Comprehensive Community Initiatives. In that book, Carol Weiss, ... hypothesized that a key reason complex programs are so difficult to evaluate is that the assumptions that inspire them are poorly articulated. She argued that stakeholders of complex community initiatives typically are unclear about how the change process will unfold and therefore give little attention to the early and mid-term changes that need to happen in order for a longer term goal to be reached.  
This led to software designed to help organisations plan initiatives, with a particular emphasis on teasing out assumptions embedded in plans. A related method is construction of a logframe matrix [logical framework].

All models are wrong but some are useful. I first learnt this aphorism from Scott Page, in his wonderful course Model Thinking at Coursera.  Models help us think more clearly. Simple quantitative models, such as agent-based models, in the social sciences, have the value that their assumptions can be clearly stated, and then the consequences of these assumptions can be investigated in a rigorous manner.

What do you think? Are there examples that you think involve implicit beliefs that need to be stated explicitly?

Thursday, April 15, 2021

Fifty years ago: three big discoveries in condensed matter

For the marketing plan for my Very Short Introduction, I was recently asked whether there were any significant anniversaries happening in condensed matter physics (and associated conferences). This is not something I normally think about.

I realised that fifty years ago there were three big discoveries. All eventually led to Nobel Prizes. Each discovery had a profound effect on the formation of condensed matter as a distinct discipline built around a few unifying concepts. At the time the discoveries and ideas appeared quite independent, but there are deep connections between them.

Renormalisation group and critical phenomena

In 1971 Ken Wilson published two papers  [PRB 4, 3174, and PRB 4, 3184] laying the foundations, followed by two PRLs in 1972, including one with the provocative title, Critical Exponents in 3.99 Dimensions

Wilson received the Nobel Prize in 1982. This work had many implications and applications. 

Explained universality in critical phenomena.

Highlighted how spatial dimensionality changes physics.

Illustrates why effective Hamiltonians work (so well).

Showed the power of quantum field theory techniques.

Defined concepts of scaling and fixed points.

Superfluidity in liquid 3He

In 1972,  Osheroff, Richardson, and Lee reported new phase transitions in liquid/solid 3He. Tony Leggett identified these transitions as due a superfluid phases and also identified the order parameters. The experimentalists shared the Nobel Prize in 1996 and Leggett in 2003. The discovery was significant for many reasons, beyond just being a new state of matter.

It provided a rich example of a state of matter with multiple broken symmetries. The order parameter has eighteen components, which can be viewed as a combined superfluid, ferromagnet, and liquid crystal.

The rich order parameter led to an exploration of diverse topological defects, from superfluid vortices with magnetic cores to boojums. This highlighted the concepts of broken symmetry, rigidity, and topological defects.

This was the first example of an unconventional fermionic superfluid. Specifically, it could be described by BCS theory, but not with s-wave pairing nor with the pairing mechanism of the electron-phonon interaction in elemental superconductors. This showed the adaptability of BCS theory. It laid the groundwork for understanding unconventional superconductivity in heavy fermions, organics, and cuprates.

Berezinskii-Kosterlitz-Thouless phase transitions

In Berezinskii published papers in 1970 and 1971, and Kosterlitz and Thouless published papers in 1972 and 1973. This work was significant for reasons including the following.

It showed states of matter and phase transitions were qualitatively different in two and three dimensions.

New concepts such as topological order, quasi-long-range order, essential singularities, and defect-mediated phase transitions were introduced.

Like that of Wilson, this work highlighted universality. There were connections between superfluids, superconductors, and XY magnets.

Scaling equations provided insight.

Kosterlitz and Thouless were awarded the Nobel Prize in 2016

We should celebrate!

Wow! Quite the Golden Jubilee!

Does anyone know of any conferences, events, or books that are planned to mark these anniversaries?

Monday, April 12, 2021

Time management and stress reduction

I am not the greatest manager of my time. I am easily distracted and too often ruled by the tyranny of the urgent. I let the good become the enemy of the excellent. I look at my email too often...

Here are just a few points that I do find helpful to keep in mind and act on. They not only lead to better use of time but also reduce stress. I struggle with all of them.

1. It can wait.

We live in an urgent world with many people and tasks demanding immediate attention. There are some very rigid deadlines, such as for most grant applications. However, there are many other tasks such as submitting a paper, checking an experiment, replying to an email, ... that can wait for another today. It is time to log off, literally and mentally and relax. The world will not fall apart if you wait another day, week, or even month.

2. Delegate

Do I personally need to do this task or take on this responsibility? Is there someone else who is able and available to do it instead? Might they actually do it better than me? Even if they might not do it as well, would it be better that they do it anyway and free me up to do more important things?

Having said this, I am slow learn and have become aware that there are some cautions needed in delegating. 

First, suppose I delegate to a person of lower "authority" than me, but who I have full confidence in. Others may not think they have the appropriate authority and so may be reluctant to act on or support what my delegate is.

Second, delegating tasks is no good if the person does not have the time, energy, and resources to complete the tasks. I may also need to provide the necessary resources and help them to see how they might delegate some tasks too.

3. Before embarking on a task, large or small, be clear on what your goal is.

This reduces the chance of getting distracted. Here is a concrete example. I often want to look for a paper on a specific question I have. Yet, I find that an hour later I am looking at my fourth paper because I got distracted by something I found interesting... and I have forgotten my initial question.

Some earlier thoughts on time management are here.

I welcome other suggestions.

Thursday, April 1, 2021

Where might condensed matter physics be heading?

Will there be big new discoveries? Will old problems be solved?  

I have finished my draft of, "An endless frontier" the last chapter of Condensed Matter Physics: A Very Short Introduction.

I aim to give a balanced perspective that is optimistic but realistic. Have I? Obviously, this is highly subjective.

I am interested in general feedback, particularly on whether your aunt or uncle or an eager undergraduate would find this interesting and engaging.

Besides your own research area :), are there particular topics that you think are ripe for exploration?

Perhaps, a cartoon about predicting the future. Maybe one of these two?