Did Schrodinger's cat explore Tolkien's garden?

In 1935 Schrodinger wrote his famous paper (with the cat) introducing the term entanglement, in response to the Einstein-Podolsky-Rosen paper published earlier that year.

When Schrodinger wrote the paper he was living in a house on Northmoor Road, Oxford. This was the same house where Schrodinger learned he had been awarded the Nobel Prize.

I recently learned some fascinating historical trivia.
Schrodinger was a neighbour of J.R.R. Tolkien, who during that time was finishing up work on The Hobbit.

It would be nice to see this landmark honoured, such as the one on Tolkien's house. However, it seems Schrodinger's house does not meet the criteria of Oxfordshire Blue Plaques Board, because he lived there for three years, less than the required minimum of five years.

Another option would be a plaque of the Institute of Physics, such as this one.

The most important concept in economics is emergence

This is not based on the hubris of a condensed matter physicist, but rather the claim of three economists in an Econtalk podcast,  where Don Boudreaux, Michael Munger, and Russ Roberts discuss Emergent Order. For example, Boudreaux states

the notion of spontaneous order is indeed the most profound, single most profound insight of good economics. It remains the insight that is most elusive to the general public. Sadly, it remains an insight that is elusive to a lot of professional economists these days.

The discussion centres around Robert's poem, "Its a wonderful loaf", the website for which has an animation of the poem and a nice list of related resources. The key idea is that free markets lead to an emergent order of prices, division of labour, and matching of supply and demand. This order is Adam Smith's "invisible hand" that guides the economy. It is actually "bottom up", not top down. Many of the ideas discussed are those originating with F. A. Hayek, in the context of not just economics but also in social and political philosophy. A summary I found helpful of Hayek's ideas is in a recent paper by Paul Lewis.

There is some disagreement between the three participants about whether the relevant terminology is "spontaneous order", "emergent order", or "self-organising system", but I did not find that particularly  insightful.

One weakness of the discussion is that the three economists all have libertarian sympathies [i.e. they believe less regulation of markets the better] and there is an undercurrent in the discussion that this is justified by an emergent perspective. However, there are some really good comments on the podcast blog that eloquently argue against this and discuss the complexity of finding the right balance between free markets and government regulation. The comments are worth reading.

I thank my economist son for bringing the podcast to my attention and listening to it with me.

Managing my mental health

I have received positive feedback about previous posts about mental health and so I share some recent experiences in the hope it may be helpful to some.

I have had three significant times where my mental health deteriorated to the point I could not function “normally”. The first was during my Ph.D and the second about 15 years ago. The most recent experience was roughly six months ago. Here are a few things I learnt [or re-learnt] from this last experience.

The decline is often gradual and not perceived or denied.
It is like the proverbial frog in boiling water. It does not notice how the temperature is increasing and never jumps out.

The longer you wait to address the issue the slower the recovery.
Don't think things will get better on their own.

Mental illness is irrational.
That's the point. When I now think about some of the thoughts and perceptions that seemed “real” and “true” to me 6-12 months ago it is sad and bizarre.

Relapse is not uncommon.
If you have had previous incidents and recovered don't think it will never happen again.

Complexity.
There is high causal density. Diverse circumstances and stresses, whether work, family, social, or relational, may all contribute to varying degrees. Hence, the most effective solutions and treatments are likely to be multi-faceted.

Professional help.
Get it sooner than later.
Don’t self-diagnose.
Getting help also relieves the burden on family and friends.

Aside: In Australia (which is blessed with a reasonable national health scheme) a GP doctor can prescribe a mental health treatment plan which entitles the patient to subsidised sessions with a psychologist or psychiatrist.
[Mind you due to bureaucratic errors it took several phone calls and two visits to the Medicare office before the paperwork was actually processed properly…].

I went to see the same psychologist who I saw 15 years ago. This was helpful because she knew my history and issues. Also, I trusted her and knew she could help. I think one simple but significant value of these visits is the accountability to be making changes and addressing issues.

Medication.
It does not work for everyone. Some people have bad side effects.
There is a debate about whether antidepressants are over-prescribed. Medication should not be a substitute for talking therapies and lifestyle changes. However, medication sure works for me! After several years without, I went back on a small dose of an antidepressant. I still find it amazing the difference it makes. Just a little fine tuning of the brain chemistry....

Mindfulness.
Some of these meditation exercises may seem like New Age mumbo jumbo. However, when I did them 15 years ago, I learnt for the first time in my life to control my thoughts.
Again, going back to them really helped.

You will get better.
When you are physically ill, whether from flu or surgery, life can seem pretty bleak and it is hard to remember what normal was, and you may wonder whether you will ever get better. It is the same with mental illness. With appropriate treatment, healing usually does occur. But hope and patience are key.

Postscript (14 October).
Things are really getting better.
Thanks for the kind messages from people, including those who have shared some of their own stories.
It is encouraging that the President of University of British Columbia, Santa Ono, is speaking about his own struggles.

From instrumentation to climate change advocacy

I learned a lot from reading In the Eye of the Storm: The Autobiography of Sir John Houghton (with Gill Tavner). He is arguably best known for being the lead editor of the first three reports of the IPCC (Intergovernmental Panel on Climate Change). He started his scientific life as an atmospheric physicist at Oxford. Here are a few things that struck me.

The value of development of new instruments.
At Oxford Houghton was largely involved in finding new ways to use rocket based instruments measure the temperature and composition of the atmosphere at different heights. These were crucial for getting accurate data that revealed the extent of climate change and understanding climate dynamics. It was good for me to read this. As a theorist, I am often skeptical or at least unappreciative of the value of developing new instruments. I think it is partly because I have heard too many talks about instrument design where it really wasn't clear they were going to generate useful and reliable information, particularly that could be connected to theory.

A reluctant administrator.
I think the best people for senior management are those who don't want the job. The worst are those who desperately want the job. It is interesting to see that Houghton was quite reluctant to leave Oxford when he was asked to be director of Rutherford-Appleton Lab. Then he wanted to go back to Oxford but was persuaded to become head of the Meteorological Office. It is also refreshing to see how he pushed back against some of the "management" nonsense that people wanted to impose on the organisations that he led.

Rigorous peer review at the IPCC.
Just because something is peer reviewed does not mean it is true. However, when there is an overwhelming consensus about some issue in peer-reviewed literature, we can high confidence it is true. Furthermore, at the IPCC there was really a double layer of peer review. The reports were based on reviews of the peer-reviewed literature. Every sentence in the reports was debated and ultimately voted on by a committee of leading scientists with relevant expertise. It is very hard to get scientists to agree on anything. However, when they can agree it means there must be a high probability it is true.

Dirty tactics of denialists.
There are a few stories about the different antics of "observers" at IPCC meetings who worked tirelessly to get IPCC to dilute their reports and sow doubt. Unfortunately, Federick Seitz features along with the lawyer/lobbyist Don Pearlman, who worked for the Global Climate Coalition.

Gracious public engagement.
The book describes how Houghton has worked hard to engage with climate change denialists, particularly among Conservative Christian leaders in the USA.

Finally, the book makes a strong case for concerted action on climate change. The most striking figure in the book was the map of Bangladesh showing how much will go under water, with just a one-metre rise in sea level. As often the case it is the poor that suffer the most.

Subtle paths to effective Hamiltonians in complex materials

Many of the most interesting materials involve significant chemical and structural complexity. Indeed, it is not unusual for a unit cell for a crystal to contain the order of one hundred atoms.
Yet, for a given class of materials, one would like to find an effective Hamiltonian involving as few degrees of freedom and parameters as possible.

Following Kino and Fukuyama, twenty years ago I argued that the simplest possible effective Hamiltonian for a large class of superconducting organic charge transfer salts was a one-band Hubbard model on an anisotropic triangular lattice at half filling.
It seemed natural to then argue that the relevant model for the spin degrees of freedom in the Mott insulating phase is the corresponding frustrated Heisenberg model with spatial anisotropy determined by the anisotropy in the tight-binding model.

However, it turns out this is not the case.
There are some subtle quantum interference effects that I overlooked in the "derivation"  of these effective models, leading to a different spatial anisotropy.
This is shown by some of my colleagues in a nice recent paper, accepted for PRL.

Dynamical reduction of the dimensionality of exchange interactions and the "spin-liquid" phase of κ-(BEDT-TTF)2X 
B. J. Powell, E. P. Kenny, J. Merino

This raises questions about what the relevant effective Hamiltonian is for the metallic, superconducting, and (possibly) ferroelectric phases.

The paper's significance goes beyond organic charge transfer salts to the general problem of finding effective Hamiltonians in complex materials.

Similar interference effects have been found to arise in quite a different class of materials.

Heisenberg and Dzyaloshinskii-Moriya interactions controlled by molecular packing in trinuclear organometallic clusters 
B. J. Powell, J. Merino, A. L. Khosla, and A. C. Jacko

This also reminds me of subtleties (and debates) that occur in the Zhang-Rice "derivation" of the t-J model from a three-band Hubbard model.

Who was the greatest theoretical chemist of the 19th century?

Dimitri Mendeleev, who proposed the periodic table of the elements, purely from phenomenology and without quantum mechanics!
He even successfully predicted the existence of new elements and their properties.

A friend who is a high school teacher [but not a scientist] asked me about how he should teach the periodic table to chemistry students. It is something that students often memorise, especially in rote-learning cultures, but have little idea about what it means and represents. It makes logical sense, even without quantum mechanics. This video nicely captures both how brilliant Mendeleev was and the logic behind the table.



A key idea is how each column contains elements with similar chemical and physical properties and that as one goes down the column there are systematic trends.
It is good for students to see this with their own eyes.
This video from the Royal Society of Chemistry shows in spectacular fashion how the alkali metals are all highly reactive and that as one goes down the column the reactivity increases.



The next amazing part of the story is how once quantum theory came along it all started to make sense!

The role of the Platonic ideal in solid state physics

In the book Who Got Einstein's Office?, about the Institute for Advanced Study at Princeton, the author Ed Regis, mocks it as the "One True Platonic Heaven" because he claims its members are Platonic idealists, who are interested in pure theory, and disdain such "impurities" as computers and applied mathematics.

Platonic solids

This stimulated me to think about the limited but useful role of pure mathematics, Platonic idealism, and aesthetics in solid state theory. People seem particularly excited when topology and/or geometry plays a role.

The first example I could think of is the notion of a perfect crystal.

Then comes Bloch's theorem, which surely is the central idea of introductory solid state physics.

The icosahedron is central to quasi-crystals.

Beautiful examples where advanced pure maths plays are role are
Chern-Simons theory of edge states in the Quantum Hall Effect
and topological terms in the action for quantum spin chains, as elucidated by Haldane.

As I have said before I think topological insulators is a beautiful, fascinating, and important topic. However, I am concerned by the disproportionately large number of people working on the topic and the associated hype. I wonder if some of the appeal and infatuation is driven by Platonic idealism.

For a classic example of how Platonism leads to imperfect theory is Kepler's Platonic solid model of the Solar System from Mysterium Cosmographicum (1596).

Good theory finds a balance between beauty and the necessity of dirty details.

Can you think of other examples where Platonic idealism plays a positive role in condensed matter theory?