Autobiography of John Goodenough (1922-2023)

 John Goodenough was an amazing scientist. He made important contributions to our understanding of strongly correlated electron materials, magnetism, solid state chemistry, and materials science and engineering. He developed materials that are widely used in computer RAMs and rechargeable lithium batteries. He kept working in the laboratory and writing papers into his early 90s. Goodenough was awarded the Nobel Prize in Chemistry in 2019. Here is his Nobel Lecture, including text, slides, and video.

In 2008 he published Witness to Grace, a brief autobiography that chronicles his personal, scientific, and spiritual journeys. It is a fascinating story. The book is now out of print and the publisher is out of business. I have scanned a copy. You can download it here. I thank David Purdy for bringing to my attention the need to preserve the book.

What symmetries distinguish liquids, crystals, glasses, and isotropic solids?

 One of the most important ideas in condensed matter physics is that different states of matter are associated with different symmetries. These different symmetries result in different types of elementary excitations such as the Goldstone bosons associated with continuous symmetry breaking. The symmetries of the low-lying excited states reflect the symmetries of the ground state.

For example, consider the transition from a liquid to a cubic crystal. The continuous rotational and translational symmetry of the liquid is broken to the discrete rotational and translational symmetry of the crystal. Long-wavelength sound waves reflect these changes in symmetry. In the crystal, there are three distinct sound waves: one longitudinal and two shear modes. In contrast, in the liquid, there are only longitudinal modes. 

An isotropic solid, such as studied in elasticity theory, supports two types of distortions: compression and shear. Consequently, there are three types of sound waves (longitudinal and transverse phonons. The latter can have two different polarisations). The isotropic solid has continuous, not discrete, rotational and translational symmetries. A glass is an example.

This leads to a fundamental question:

What is the difference between liquids and solids at the level of fundamental symmetries?

In different words, what is the order parameter for the liquid-solid transition? A possible answer is the shear modulus G, which vanishes in the liquid state.

A related question is: What is the fate of the transverse phonons upon transitioning from the solid state to the liquid state?

I would have thought that these questions would have been settled decades ago. However, they have not. Just two years ago, Physical Review E published a 22 page article that aims to address the questions above.

Deformations, relaxation, and broken symmetries in liquids, solids, and glasses: A unified topological field theory

Matteo Baggioli, Michael Landry, and Alessio Zaccone

The paper immediately drew a Comment claiming the paper

"contradicts the known hydrodynamic theory of classical liquids." The authors have a Reply.

I do not have the expertise to give insight on the subtle technical issues in this debate. My only comment is that it is amazing how we are struggling to answer such basic questions.

I thank Jean-Noel Fuchs for getting me interested in these subtle questions. This happened when he kindly pointed out an error in Condensed Matter Physics: A Very Short Introduction. On page 40, I erroneously stated that shear sound waves exist in a liquid. This was part of a confused discussion about how sound waves can be used to distinguish different states of matter.  I have drafted a corrected paragraph and inserted it in my post listing the errors in my book.

I welcome any comments about the issues discussed above.

My mental health update

I have struggled with my mental health on and off since the time of my Ph.D. studies. Several readers have commented that has been helpful for them to hear my story. Here I give a small update on both my health and some recent reading.

I have been thinking about the issue more because I have been invited to give a talk in October for a research centre at UQ, as part of Mental Health Week. I may adapt a talk that I gave for a school colloquium at UQ six years ago. I welcome suggestions for things people think I should talk about.

My mental health is the best it has been for almost a decade. There are probably many reasons for this: retirement, managing stress, no international travel, being connected to a church community, and practising the basics (diet, exercise, less screen time, less caffeine, ...), ...

Until a year ago, I believed I would be on antidepressants for the rest of my life. But my doctor told me we should explore my getting off antidepressants. It is now the view of the medical establishment that there are too many people on them who do not need to be, there can be long-term complications, and that the longer a patient is on them the harder it is to get off them. Over the past 2 years, The Economist had helpful articles along these lines (see below).

In April we agreed that we would start the experiment of reducing my dose, following the now standard practice of slowing reducing the dose every three weeks. He warned me to look for side effects, such as random brain zaps. There were no side effects. I got to zero dosage a month ago.

Unfortunately, I am now experiencing one side effect which I have now learned is not uncommon: uncontrollable sobbing. The first instance was July 21 when I learned that Biden was not going to run again for President. The fact that this triggered ten minutes of sobbing shows there is something not quite right with my brain chemistry!

I had several other incidents with my family. The tears are out of proportion to the significance of the event that triggers them. Sometimes I choke up when talking to people I care about or on an issue that concerns me.

I had an appointment with my doctor this week and we agreed that for now, we would stay the course, not resume the medication, and monitor the situation.

How to make better use of antidepressants: Identify those who really need them, and wean other people off them

(The Economist, October 19, 2022)

Antidepressants are over-prescribed, but genuinely help some patients: In around 15% of cases, they offer large benefits

(The Economist, January 20, 2023)

The graphs above are amazing. They show several striking things.

1. There is a massive placebo effect for antidepressants. This is shown by the two coloured curves being almost identical.

2. There is a massive variation between patients with regard to how effective the drugs are. This is shown by the very broad distribution. It reminds me of journal impact factors: the distribution is so broad that discussions about the mean are meaningless.

Antidepressants can cause withdrawal symptoms – here’s what you need to know

(The Conversation, June 23, 2023)

Psychiatry’s Incurable Hubris: The biology of mental illness is still a mystery, but practitioners don’t want to admit it.

(The Atlantic, April 2019).

Do arrows of explanation point down or up?

The figure above shows the stratification of objects that interest physicists. As one goes down the chain length and time scales get smaller and energy scales get larger.

A reductionist seeks to explain the objects at each strata in terms of the objects that occur at the next lower strata.

In 1987 Steven Weinberg gave a talk at the University of Cambridge at the Tercentenary Celebration of Newton's Principia.

The talk was published in Nature. Newtonianism, Reductionism, and the Art of Congressional Testimony

Part of the talk is about Weinberg's testimony to a US Congressional Committee making the case for the construction of the SSC (Superconducting Super Collider). Phil Anderson spoke against the SSC.

Weinberg argued that the SSC should be built because particle physics is "in some sense more fundamental than other areas of physics." He claims that this is because "the arrows of explanation point down", as in the diagram shown above.

A contrasting perspective is that of Andrew Steane. His book, Science and Humanity, contains the figure below.

In his picture of the explanatory relationship between physics, chemistry, and biology, Steane draws arrows pointing in both directions. The up arrow is denoted “supports [allows and physically embodies the expression of]” and the down arrow is denoted “enarches [exhibits the structures and behaviours that make sense in their own terms and are possible within the framework of].”

Weinberg's article is worth reading in full. It has many insights about science and physics worth considering, including the relationship between emergence and reductionism.

Aside: It is also reproduced in his book of essays, Facing Up: Science and Its Cultural Adversaries, published in 2001.

Emergence, structuralism, realism, and quarks

"Structuralism as an influential intellectual movement of the twentieth century has been advocated by Bertrand Russell, Rudolf Carnap, Nicholas Bourbaki, Noam Chomsky, Talcott Parsons, Claude Levi-Strauss, Jean Piaget, Louis Althusser, and Bas van Fraassen, among many others, and developed in various disciplines such as linguistics, mathematics, psychology, anthropology, sociology, and philosophy." 

In different words, structuralism and post-structualism have been and are still a really big deal in the humanities and social sciences. Structuralism is central to the rise and fall of a multitude of academic fashions, careers and reputations.  

"As a method of enquiry, it takes a structure as a whole rather than its elements as the major or even the only legitimate subject for investigations. Here, a structure is defined either as a system of stable relations among a set of elements, or as a self-regulated whole under transformations, depending on the specific subject under consideration. The structuralist maintains that the character or even the reality of a whole is mainly determined by its structuring laws, and cannot be reduced to its parts; rather, the existence and essence of a part in the whole can only be defined through its place in the whole and its relations with other parts."

In a sense, structuralism favours emergence over reductionism. But, note some of the strong exclusivist language highlighted in bold in the quote above. Structuralism seems to be an overreaction to extreme reductionism. 

Condensed matter physics has something concrete to contribute to these debates. Consider the case of Ising models defined on a range of lattices, as I discussed in a previous post. We do not have an exclusive interest in the whole system or in the parts of the system. Rather, we want to know the relationship between macroscopic properties [different ordered states], mesoscopic properties [domains, long-range correlations, networks], and microscopic properties [the individual spins and their local interactions].

That is the main point of this post. But for more context, keep reading.

The quotations above are taken from a book by Tian Yu Cao. 

From Current Algebra to Quantum Chromodynamics: A Case for Structural Realism

Cao is interested in a broad range of philosophical questions related to QCD, such as "If quarks cannot be observed in isolation should they be considered to be real?"

He continues:

In the epistemically interesting cases involving unobservable entities, the structuralist usually argues that it is only the structure and the structural relations of its elements, rather than the elements themselves (properties or entities with properties) that are empirically accessible to us. It is obvious that such an anti-reductionist holistic stance has lent some support to phenomenalism. 

However, as an effort to combat compartmentalization, which urge is particularly strong in mathematics, linguistics, and anthropology, the structuralist also tries to uncover the unity among various appearances, in addition to invariance or stable correlation under transformations, which can help discover the deep reality embodied in deep structures. Furthermore, if we accept the attribution of reality to structures, then the antirealist implications of the underdetermination thesis [which claims that since evidence cannot uniquely determine (or, worse, can even support conflicting) theoretical claims about certain unobservable entities, no theoretical entities should be taken as representation of reality], is somewhat neutralized, because then we can talk about the realism of structures, or the reality of the structural features of unobservable entities exhibited in evidence, although we cannot directly talk about the reality of the entities themselves that are engaged in the structural relations. In fact, this realist implication of structuralism was one of the starting points of current interests in structural realism.

Clarity about the relationship of emergence, complexity, predictability, and universality

Emergence means different things to different people. Except, that practically everyone likes it! Or at least, likes using the word. Terms associated with emergence include novelty, unpredictability, universality, stratification, and self-organisation. We need to be clearer about what we mean by each of these terms and how they are related or unrelated. Significant progress is reported in a recent preprint.

Software in the natural world: A computational approach to hierarchical emergence

Fernando E. Rosas, Bernhard C. Geiger, Andrea I Luppi, Anil K. Seth, Daniel Polani, Michael Gastpar, Pedro A.M. Mediano

This preprint is the subject of a nice article in Quanta Magazine.

The New Math of How Large-Scale Order Emerges by Philip Ball

Ball defines emergence in terms of unpredictability. He states: 

"Loosely, the behavior of a complex system might be considered emergent if it can’t be predicted from the properties of the parts alone."

He describes the work of Rosas et al. as follows, 

"A complex system exhibits emergence, according to the new framework, by organizing itself into a hierarchy of levels that each operate independently of the details of the lower levels."

This is defining emergence in terms of universality. Rosas et al. use an analogy with software, which runs independently of the details of the hardware of the computer and does not depend on microscopic details such as electron dynamics.

There are three types of closure associated with emergence: informational, causal, and computational.

Informational closure means that to predict the dynamics of the system at the macroscale one does not need any additional  information from the microscale.

Equilibrium thermodynamics is a nice example. 

Causal closure means that the system can be controlled at the macroscale without any knowledge of lower-level information.

"Interventions we make at the macro level, such as changing the software code by typing on the keyboard, are not made more reliable by trying to alter individual electron trajectories."

"...we can use macroscopic variables like pressure and viscosity to talk about (and control) fluid flow, and knowing the positions and trajectories of individual molecules doesn’t add useful information for those purposes. And we can describe the market economy by considering companies as single entities, ignoring any details about the individuals that constitute them."

Computational closure is a more technical concept. 

"a conceptual device called the ε-(epsilon) machine. This device can exist in some finite set of states and can predict its own future state on the basis of its current one. It’s a bit like an elevator, said Rosas; an input to the machine, like pressing a button, will cause the machine to transition to a different state (floor) in a deterministic way that depends on its past history — namely, its current floor, whether it’s going up or down and which other buttons were pressed already. Of course an elevator has myriad component parts, but you don’t need to think about them. Likewise, an ε-machine is an optimal way to represent how unspecified interactions between component parts “compute” — or, one might say, cause — the machine’s future state."

Aside: epsilon-machines featured significantly in my previous post about What is a complex system? 

"Computational mechanics allows the web of interactions between a complex system’s components to be reduced to the simplest description, called its causal state."

"...for an emergent system that is computationally closed, the machines at each level can be constructed by coarse-graining the components on just the level below: They are, in the researchers’ terminology, “strongly lumpable.”"

In some sense, this may be related to the notion of quasiparticles and effective interactions in many-body physics. 

Aside: In 1962, Herbert Simon identified hierarchies as an essential feature of complex systems, both natural and artificial. A key property of a level in the hierarchy is that it is nearly decomposable into smaller units, i.e., it can be viewed as a collection of weakly interacting units. The time required for the evolution of the whole system is significantly decreased due to the hierarchical character. The construction of an artificial complex system, such as a clock, is faster and more reliable if different units are first assembled separately and then the units are brought together into the whole. Simon argues that the reduction in time scales due to modularity is why biological evolution can occur on realistic time scales.  The 1962 article is reprinted in The Sciences of the Artificial.

The paper by Rosas et al. is one of the most important ones I have encountered in the past few years. I am slowly digesting it.

The beauty of the paper that it is mathematically rigorous. All the concepts are precisely defined and the central results are actually theorems. This replaces the vagueness of most discussions of emergence, including by myself.

The paper has helpful figures and considers concrete examples including Ehrenfest's Urn, an Ising model with Glauber dynamics, and a Hopfield neural network model.

I thank Gerard Milburn for bringing the Quanta article to my attention.

Basic realities to accept about applying for funding

The advice that follows is directed to young people who are starting out in requesting funding for a project or an annual budget. My advice is based on about thirty years of experience of writing grant applications, reviewing requests, and being involved in making final decisions about applications. My experience has involved national research funding bodies, internal university schemes, charities, and NGOs. Over the years, I have been involved with requests in the range from a few thousand dollars to a few million dollars.

Accept reality

The world is messed up. Systems are broken. They are not the way they should be. Bad decisions are made. Processes are imperfect. I am all for trying to change things. However, when you make a funding application your chances of success are best if you accept the system and engage with it as it is today. Try to change it tomorrow. 

Put yourself in the shoes of the decision-makers.

You may not respect them or think they are particularly competent or well-qualified to make decisions about your funding request. However, put that aside and consider that they may be in an unenviable position. They are working within an imperfect system. They have limited time to read and evaluate a trove of applications, many on topics they do not really understand. They have limited resources to allocate. Most want to evaluate those scarce resources in a fair and equitable manner. In most contexts the ratio of available funds to the total amount of funds requested by all the applicants is somewhere in the ratio of 0.03 to 0.2. This means they need to reject a lot of applications and slim down the budgets of those that are accepted. 

You have to start with small amounts of money and build up.

Trust and success are incremental. You first get a grant for a few thousand dollars. You show that you have used that well to accomplish something. You may have to do that a few times before you get tens of thousands of dollars. You then use that to accomplish something bigger. And so on it goes.

You may think you deserve to receive several $100Ks and jump this process. However, it is highly unlikely to happen. You need to prove yourself.

In different words, any year do not ask for significantly more than you were budgeted last year. 

Every budget line item must be carefully justified.

Is each item really essential for successful completion of the project? We would all like to have a better computer, more technical support, a personal assistant, lots of international travel to exotic locales, release from other responsibilities, ...

But is each item necessary? Is each item consistent with your level of seniority and experience? Or is there a cheaper option? Could someone else fund it?

These issues are not just about good use of resources but also your credibility as someone who is a team player willing to accept institutional realities and limited resources.

The greater the requested budget the greater the scrutiny of the application.

Hence, asking for less money actually increases your chance of success. If your budget is 2 or 3 times the budget of competing applications the funding agency will almost always think that it is better to fund 2 or 3 groups rather than just one. 

Check your attitude.

You should have confidence that what you are doing is important and worth funding. However, that is not the same as making snide comments about competitors, stroking your ego, overselling the significance of what you are doing, or expressing grievances about perceived past slights and criticisms of your work. Exhibiting such attitudes only hurt your chances of success.