Tuesday, December 22, 2015

Will burning lots of coal lift people out of poverty?

A few months ago I attended a symposium at UQ on Energy in India. The talks can be viewed on Youtube. The one by Alexie Seller is particularly inspiring.

In the presentation of Chris Greig he showed a slide similar to that below with the title "Electricity affects Human well being".

He did not say it, but sometimes graphs like this are used to make claims such as "the more electricity people consume the better off they will be..."  or "the only way to lift people out of poverty is to burn more coal..."

Sometimes people show graphs that correlate GDP with energy consumption. But this one is better because it uses the Human Development Index, a multi-dimensional measure of human well being (as it includes life expectancy and education).

Two things are very striking about the graph.
First, the initial slope is very large. Second, the graph levels off quickly.
A little bit of electricity makes a huge difference. If you don't have electric lighting or minimal electricity to run hospitals, schools, basic communications, water pumps and treatment plants, ... then life is going to be difficult.
However, once you get to about 2000 kW hours per person per year, all the extra electricity beyond that makes little difference to basic human well being. This is frivolous use of air conditioners, aluminium smelters, conspicuous consumption, ...

Finally, we always need to distinguish correlation and causality. As people become more prosperous they do tend to consume more electricity. However, it is not necessarily the electricity consumption that is making them more prosperous. This is clearly seen by how flat the top of the curve is. Electricity consumption in Canada is almost four times that of Spain!

A more detailed discussion of the graph is in this book chapter by Vaclav Smil.

Friday, December 18, 2015

How do you find mental space?

I wish I knew. This is something I continue to struggle with.

To think clearly and creatively one needs to find "space" that is free from distractions and stresses.
I find it hard to believe that one can be really productive in the midst of noise, chaos, and multiple demands. I can't.

I know there are some individuals who are good at multi-tasking and even seem relish all the noise and hyper-activity. But, deep down I wonder if some are just "cranking the handle" and publishing the same paper again and again.

I contend that slow science is not just enjoyable but necessary.

Yet finding "mental space" is increasingly a problem because of fast pace of "modern" life. This is increased by greater demands for "productivity" and all the background noise from email, social media, and mobile phones.

So how does one find the necessary "mental space"?

I welcome suggestions.
Here are mine.

Turn off your email and/or phone.

Block out times for specific tasks. e.g. reading, thinking, writing, coding, and calculating.

Try and focus on one thing at a time.

Get organised.

Find "physical spaces" that are free from distractions.

Many mornings I work at home for the first few hours.
On the other hand, if you have young children at home, that is probably a bad idea!
Go to the library if that helps.
Sometimes I have done that when there was construction noise near my building.

Take a sabbatical.

Clear your desk (ugh!...)

What do you think?
I welcome suggestions.

Wednesday, December 16, 2015

A valuable new book on thermoelectricity

Kamran Behnia has published a book Fundamentals of Thermoelectricity

Such a monograph is overdue. I think the topic is particularly important and interesting for several reasons. (This is illustrated by the fact that I have written almost 40 blog posts on the topic).
  • The thermoelectric power is a transport property that presents a number of rich and outstanding puzzles.
  • The sign, magnitude, spatial anisotropy, and temperature dependence of the thermopower can put significant constraints on theories because the thermopower is so sensitive to particle-hole asymmetry. In comparison, often it may not be too hard to cook up a theory can get a resistivity that agrees with experiment. However, the thermopower is another story.
  • Thermoelectric materials are technologically important. Furthermore, if someone can find a material with a "Figure of merit" that is just twice that of the best current materials we could throw out all our refrigerators with moving parts!
The book has a nice preface. Here are a few choice quotes.
To many readers of this book, it should be a surprise to learn that a consistent and unified theory for phonon drag is still missing.... 
Three chapters devoted to a survey of experimental facts aim to revive a number of forgotten puzzles...
But the embarrassment [discussed below] has vanished thanks for our forgetfulness and not to our cleverness....
Even more enigmatic than the positive Seebeck coefficient of noble metals at room temperature is their thermoelectric response at very low temperatures.... 
Before beginning to write this book, I did not know that there is an three-orders -of-magnitude gap between theory and experiment regarding the thermoelectric response of Bogoliubov quasi-particles of a superconductor....
Why such facts have gradually faded from the collective memory of the condensed matter physics community is another question that deserves to be raised but is not addressed by this book.
Section 6.5 "Origin of the Positive Seebeck Coefficient of Noble Metals"
begins with the following quote from Robinson in 1967.
For more than thirty years the absolute thermoelectric power of pure samples of monovalent metals has remained a nagging embarrassment to the theory of the ordinary electronic transport properties of solids. All familiar simple theory has promised us that in these materials the sign of the electron-diffusion contribution to the thermopower should be that of the charge carriers as determined by the Hall effect, i.e. negative; but instead it turns out to be positive for Cu, Ag, Au and—even more perversely—for Li alone of the solid alkalies. At least two generations of experimentalists have remained completely unshaken in testifying to these results as obstinate facts of life.
A great value of the book is that it brings together a diverse set of experimental data from a wide range of materials.

I have a few minor quibbles.

I could find no mention of:

a. the Kelvin formula and the associated nice treatment of it by Michael Peterson and Sriram Shastry.

b. Dynamical Mean-Field Theory (DMFT) and how it nicely describes the thermopower as there is a crossover with increasing temperature from a Fermi liquid to a bad metal.

c. experimental techniques. What are the challenges, problems and obstacles to accurate and reliable measurements?

The caption of Figure 8.5 claims that for an organic charge transfer salt kappa-(BEDT-TTF)2Cu(NCS)2 "The expectations of a tight-binding model is in good agreement with the experimental data". The text says this is a "rare achievement in the case of correlated metals".
However, this "agreement" requires an arbitrary and unjustified rescaling of all the band energies by a factor of about five! This data and the theoretical challenge it presents is discussed in detail here.

The book is written by an experimentalist. I learnt from the back cover that there is also a new book, Modern Theory of Thermoelectricity by Zlatic and Monnier. I am looking forward to reading that.

Kamran Behnia has done a great service to the community by writing the book. Thank you!

Monday, December 14, 2015

Density Functional Theory (DFT) is exact. It is never wrong.

Some readers might be surprised to hear me claim this since I often highlight the problems and errors associated with calculations involving DFT. The problem is density functional approximations not the underlying theory.

There are two key ideas associated with DFT.

1. A theorem.
The ground state energy of an interacting electron gas is the minimum value of a unique functional of the charge density n(r) in the system.
This is an exact result.

The problem is that to determine the exact density and energy one needs to know the "exchange-correlation" functional.

2. An approximation.
One can make a local density approximation (LDA) to the exchange-correlation functional so that the density is written in terms of a set of "orbitals" that are found by solving a set of self-consistent equations that have a mathematical structure similar to the Hartree-Fock equations for the same system.

These distinct ideas are respectively associated with two different papers, published 50 years ago. The first is by Hohenberg and Kohn. The second is by Kohn and Sham. 
Aside: The history and significance of these papers has been nicely summarised recently in a Physics Today article by Andrew Zangwill.

I think the community needs to be more precise when they talk about DFT.

Broadly speaking, some people in the chemistry community give me the impression that they think if they can just tweak the parameters in their favourite exchange correlational functional then they are going to be able to get agreement with experiment for everything.

In contrast, consider this paragraph from the introduction of a recent physics paper:
Density functional theory (DFT), in essence a sophisticated mean field treatment of electron-electron interactions, provides a very good approximation to the interacting electron problem, enabling the theoretical description from first principles of many properties of many compounds. However, DFT does not describe all electronic properties of all materials, and the cases where it fails can be taken to define the “strong correlation problem.”
Surely, it would be better to replace DFT here with DFA=Density Functional Approximations.

Aside: I should say that besides this paragraph I really like the paper and the authors.

The distinction I am making here was particularly stressed in a recent talk I heard by Tim Gould.

Friday, December 11, 2015

Should people get credit for papers that are influential but wrong?

A colleague once told me a story about his research field.
"Ten years ago Professor X got some surprising experimental results. He then made bold claims about what this meant. Some people did not believe it. But, people then did detailed experimental and theoretical work to test his results and claims. They basically found that he was wrong but in the process they made some valuable and interesting discoveries and clarified several issues in the field. To half the people in the field he was a hero and to the other half he was a pariah."
The hero status was assigned because if he did not exist or had not made these claims, the new discoveries would not have been made (or might have been made much later).
The pariah status was assigned because he did not do careful scientific work and misled people.

How much credit should people get who open up new scientific directions with “wrong” papers or with unsubstantiated speculation?

Different people I talk to have quite different views about this.

My view is that such people should get very little credit, particularly if their work is sloppy and/or they engage in hype, self-promotion, and unsubstantiated speculation. 

On balance, I think such individuals have a negative overall influence on science. This problem has been compounded by the speculative and hype culture enhanced by the rise of the luxury journals. Rewarding people for doing bad science is just going to promote more bad science. Maybe one in fifty bad papers will have fruitful consequences. But the other 49 will waste time and resources and create confusion.

What do you think?

Wednesday, December 9, 2015

Emergent quasi-particles and adiabatic (dis)continuity

In quantum many-body physics quasi-particles are emergent entities. But, it is worth making a distinction between two cases.

1. Adiabatic continuity.
As one gradually turns on the interactions the excited states of the system smoothly evolve from those in the non-interacting system. As a result the quasi-particles have the same quantum numbers and statistics as the constituent particles. The most prominent example is in Landau's Fermi liquid theory which describes elemental metals and liquid 3He.

2. Adiabatic discontinuity.
The  quasi-particles do NOT have the same quantum numbers and statistics as the constituent particles. One example, is magnons (spin waves) in a spin-1/2 Heisenberg antiferromagnet. They have spin one and act like bosons. In contrast, the constituent particles are localised electron that are fermions with spin-1/2. An even more dramatic example occurs in the fractional quantum Hall effect. The constituent particles are electrons with charge -e and obey Fermi-Dirac statistics. But, the quasi-particles have fractional charge and obey anyon statistics.

This was recently stressed by Brijesh Kumar after a talk I gave.

The distinction is interesting because if you use Berry's criteria for emergence [a singular asymptotic expansion] (which I do like) then only in the second case would you define the quasi-particles as emergent.
The figure above describing adiabatic continuity is from Piers Coleman.

Tuesday, December 8, 2015

A comparative appreciation of P.W. Anderson and Linus Pauling

Andrew Zangwill contacted me because he is working on scientific biography of Phil Anderson. I think this is overdue. I would argue that Phil is the greatest theoretical physicist of the second half of the twentieth century. I would argue this on similar grounds to why I think Linus Pauling was the greatest theoretical chemist of the first half of the twentieth century. Crucially, their scientific legacies have extended far beyond condensed matter physics and chemistry, respectively.

Specifically, Pauling did not just make essential contributions to our understanding of chemical bonding, x-ray crystallography, and quantum chemistry. His impact went far beyond chemistry. Francis Crick said Pauling was the "father of molecular biology." He proposed and elucidated alpha helices and beta sheets in proteins. Furthermore, he began the whole field of molecular medicine, by showing the molecular basis of a specific disease, sickle cell anemia.

Phil Anderson has made incredibly diverse and valuable contributions to condensed matter physics (anti-ferromagnetism, localisation, weak localisation, magnetic impurities in metals, Kondo problem, poor mans scaling, superfluid 3He, spin liquids, RVB theory of superconductivity... ).
I can think of three significant and profound influences of Phil beyond condensed matter physics.

Codifying and elucidating the concept of emergence (and the limitations of reductionism) in all of science, in More is Different in 1972.

Laying ground work for the Higgs boson in 1963 by connecting spontaneous gauge symmetry breaking and mass. 

Elucidating spin glasses in a way that was key to John Hopfield's development of a particular neural network and to the notion of a "rugged landscape", relevant in protein folding and evolution. Anderson described these connections nicely in two pages in Physics Today in 1990.

Are there other examples?

Who do you think is the greatest theoretical physicist of the second half of the twentieth century?
[n.b. If you are thinking Feynman, he did path integrals and QED before 1950].

Friday, December 4, 2015

All rankings should include error bars

In introductory science courses we try and instill in undergraduates the basic notion that any measurement has an error and you should estimate that error and report it with your measurement. Yet "Professors" who are in senior management don't do that.

Today in Australia the results of the Excellence in Research Australia (ERA) ranking exercise were announced. Every research field at every university is given a score. A colleague wisely pointed out that given the ad hoc procedure involved all the rankings should include error bars. He conjectured that the error bar was about one. Hence, one cannot distinguish the difference between a 4 and 5. Yet, this is a distinction that university managers and marketing departments make a lot off.

I think for almost all ranking exercises it would be quite straight forward for the compilers to calculate/estimate the uncertainty in their ranking. This is because almost all rankings are based on the average of rankings or scores produced by a number of assessors. One simply needs to report the standard deviation in those scores/rankings. I think the conclusion of this will be that rankings largely tell us what we knew already and that any movement up or down since the last ranking is within the error bars. John Quiggin has made such arguments in more detail.

The ERA is largely modelled on the UK equivalent; originally, called the RAE but now the REF. This has been widely criticised; it wastes massive amounts of time and money, involves flawed methodology, and has been devastating for staff morale. These issues are nicely (and depressingly) chronicled in a blog post by Liz Morrish. One academic Derek Sayer fought to be excluded from the RAE as a protest.  He explains in detail why it is such a flawed measure of real scholarship.

 It is also worth looking at The Metric Tide: Report of the Independent Review of the Role of Metrics in Research Assessment and Management, commissioned by The Higher Education Funding Council which is responsible for the REF. Reading the recommendations is strange. It sounds a bit like "most people thing metrics are rubbish but we are going to use them anyway...".

Wednesday, December 2, 2015

What is omega/T scaling?

And why is it so elusive?

Quantum many-body systems are characterised by many different energy scales (e.g. Fermi energy, Debye frequency, superconducting energy gap, Kondo temperature, ....). However, in many systems properties are "universal" in that they are determined by a single energy scale. This means that the frequency (omega) and temperature (T) dependence of a spectral function can be written in a form such as
where here  T_ K is the relevant energy scale and I set hbar =1 and k_B = 1.

However, what happens in the limit where the relevant energy scale T_K goes to zero, for example near a quantum critical point? Then the only energy scale present is that defined by the temperature T and we now expect a functional dependence of the form
This is omega/T scaling.

In one dimension the form of the scaling function is specified by conformal field theory and for quantum impurity problems (e.g. Kondo) by boundary conformal field theory.

In 1989 Varma et al. showed that many of the anomalous properties of the metallic phase of the cuprate superconductors at optimal doping could be described in terms of a “marginal Fermi liquid” self energy. They associate this with a spin (and charge) fluctuation spectrum that exhibited omega/T scaling (for all wave vectors). Specifically, the spectral function was linear in frequency at low frequencies, up to a frequency of order T.

Some claims about quantum criticality in cuprates are debatable, as discussed here.

Finding concrete realistic theoretical microscopic fermion models that exhibit such scaling has proven challenging.

In his Quantum phase transitions book Sachdev reviews several spin models (e.g. transverse field Ising model in one dimension) that exhibit omega/T scaling in the quantum critical region, associated with a quantum critical point.

 In 1999 Parcollet and Georges  considered a particular limit of a random Heisenberg model which had a spin liquid ground state and a local spin susceptibility chi’’(omega) that exhibited a form consistent with that conjectured in the marginal Fermi liquid scenario.

Local quantum criticality has been observed in a few heavy fermion compounds.  Specifically, in 2000 Schroder et al. observed inelastic neutron scattering gives the following \omega/T scaling,

In 2008 Kirchner and Si showed that near the quantum critical point in the Ising-anisotropic Bose-Fermi Kondo model (BFKM) with a sub-ohmic bath (i.e. a very specific model!) they obtained omega/T scaling similar to that associated with boundary conformal field theory, even though the model has no obvious conformal invariance.

This is my potted history and understanding. I welcome corrections and clarifications.

Monday, November 30, 2015

A student's questions about scientists responding to climate change

A first year undergraduate student who is deeply concerned about climate change asked me a number of questions by email and then came to my office to discuss them. Since I think they are excellent questions I thought I would post them here (with his permission) and give a brief version of my answers. I welcome readers to give their own answers.
I am interested in and passionate about climate change. At the moment, I'm considering my uni options - wondering what I can study to best equip me to help in the great, global effort to mitigate (I'm a bit less interested in adaptation) climate change. I have a couple of questions to ask of you.
1. How would you respond to each of the following, somewhat contradictory statements: 
- 'Climate change can be mitigated by developing and deploying renewable energy and energy efficiency technologies, without significantly impacting on our standard of living.' 
- 'Environmental crises, including climate change, require us to move away from a social and economic system based on consumerism and growth' .
First, I am no expert on this complex issue. An economist at UQ who is an expert is John Quiggin. But, my view is that with energy efficiency measures, renewable energy, and some modest lifestyle changes significant progress can be made towards mitigating climate change. On the other hand, I think there are compelling social  and political reasons why the world, particularly the Western world, would be better off if we moved away from this mindless and insatiable pursuit of consumerism and economic growth.

But, I really think the biggest obstacle to concerted and significant global action is a lack of political will and leadership. This is particularly driven by "fear mongering" from vested business and political interests who claim the first option is true. "If we don't burn more coal we will all end up back in the caves or at least riding bicycles..."
I don't think the biggest obstacle is missing technical and economic solutions. Of course, if someone can make a durable and reliable photovoltaic cell with 20 per cent efficiency, that costs 20 cents per square metre to manufacture, and with a lifetime of 20 years, it would "solve" the problem. But, I only foresee incremental advances in the next decade. The case of Gratzel cells is quite discouraging.
2. If the institutional ethos of the UQ science faculty were a person, how would he/she respond to the above statements? 
I think you would really encounter a range of views, probably reflecting a rang of political convictions. I would hope most staff would believe that climate change is real, a result of human activity, and a major issue to address. On the other hand, I am occasionally surprised and disappointed to meet scientists, who are skeptics, even though 97 per cent of climate scientists are not.

I think you would find that some would also claim we need lots more research money (especially for new technologies) to address these issues, but they are clouded by self interest.
3. What facets of science would you recommend that I study:  
- Earth science (better understanding of the climate system)
- Physics/Engineering (renewable energy technology) 
- Psychology (Why do people behave the way they do) 
- Ecology (how ecosystems respond to climate change and other pressures)
Given that I think the major obstacles are political I think that becoming a political activist you may have the biggest impact. Studying sociology and psychology may help design the most effective campaigns. But you do need to understand the technical issues.
On the other hand, you should consider what you are good at and enjoy. There is no point trying to put square pegs in round holes.
Hence, I think you should let your own interests and abilities be a consideration. But studying a mix of the above could be very helpful.
I am wondering if UQ has plans to develop a specific course, or even a program, devoted to climate change?
Not that I am aware of. There are significant postgraduate activities at The Global Change Institute and the Energy Initiative. There was recently a review of the Bachelor of Science. The possibility of some elective courses that are multi-disciplinary has been floated and climate change is one. However, my experience is that such courses become a can of worms once you get multiple departments involved. Everyone wants a piece of the pie, to do it their way, but are not willing to take responsibility, or to "force" their own students to take the course so it is viable. Hence, I doubt you will see the kind of course you are hoping for during your time here. Sorry.

We ended our discussion with me lending the student a copy of The Eye of the Storm: the autobiography of Sir John Houghton. He is nice example of someone who moved from basic research in climate science to public policy and advocacy.

I wish I had more discussions like this with students.

I welcome people to give their own answers.

Friday, November 27, 2015

I believe in irreproducible results

At UQ we just had an interesting colloquium from Signe Riemer-Sorensen about Dark matter emission - seeing the invisible. Central to the talk was the data below. Focus on the red data around 3.6 keV.

This has stimulated more than 100 theory papers!
This reminds me of the faster than speed of light neutrinos and the 17 keV neutrino, 500 GeV particles seen by the Fermi gamma ray telescope, BICEP2 "evidence" for cosmic inflation, ....

The above data is discussed in detail here.

I don't want to just pick on my astrophysics and high energy physics colleagues as this happens in condensed matter and chemistry too... remember cold fusion... think about periodic reports of room temperature superconductors!

The painful reality is that cutting edge science is hard. One can be incredibly careful about noise, subtracting background signals, statistical analysis, sample preparation, .... but in the end there is Murphy's law .... things do go wrong .... and crap happens...

Skepticism and caution should always be the default reaction; all the more so the greater the possible significance or surprise of the "observed" result.

I believe in irreproducible results.

Update (14 December).
Clifford Taubes brought to my attention two relevant papers on the possible 3.5 keV line. The first paper rules out a dark matter origin of the line and even mentions Occam's razor. The second has a mundane alternative explanation of the line in terms of charge exchange between hydrogen gas and sulfur ions.

Thursday, November 26, 2015

How the 80-20 rule may be undermining university quality

I recently learned about the Pareto principle, which according to Wikipedia

"(also known as the 80–20 rule, the law of the vital few, and the principle of factor sparsity) states that, for many events, roughly 80% of the effects come from 20% of the causes."

For example, if you are supervising a team of employees, 80% of your time will be spent in dealing with 20% of them, probably the mostly poorly performing or most vocal.

This past year I have had a minor administrative role, as a "Research Committee" chair. Probably 80% of the time, involves co-ordinating, supporting, and assessing grant funding applications, both internal and external to the university. Most of these grant programs have success rates at the 10-20% level. Virtually none of my time is actually spent on initiatives to help improve the quality or quantity of research done by the bulk of faculty members.

My experience has also made me more aware of what people in senior management appear to spend their time doing and what gets their interest and attention. Increasingly, it seems to be focussed on "high status" activities associated with "esteem measures" such as "prestigious" grants and fellowships, and of course, publication in luxury journals. The issue is well illustrated with a story about some researchers who were making a pitch for a new supercomputer centre.

University VP (Research): Will this help you get a Nature paper?

Researcher: Probably not, but it will help other researchers at the university publish a hundred other papers.

The problem is again that little attention or resources are directed to most of the research that is going on.

Tuesday, November 24, 2015

Postdoc available to work with me on strongly correlated electrons

UQ has just advertised for a new postdoc to work with me on a project, "The bad metallic state in quantum materials", funded by the Australian Research Council.
The position is for 2 years and 9 months.
Applications close on 31 January, 2016.

The official advertisement and job description is here and contains a link to a portal through which a formal application should be made.

Looking at the "bad metals" label on the blog will give a flavour of some of the problems I am interested in.

Looking at the "career advice" label will give some flavour of my philosophy and expectations of working together.

Monday, November 23, 2015

Quantum critical spin dynamics of a magnetic impurity in a semiconductor

There is an interesting paper
Quantum critical dynamics of a magnetic impurity in a semiconducting host
Nagamalleswararao Dasari, Swagata Acharya, A. Taraphder, Juana Moreno, Mark Jarrell, N. S. Vidhyadhiraja

The key physics of the Kondo model is the formation of a spin singlet state between the impurity spin and the spins of the electrons in the conduction band. We say, the impurity spin is “screened” by the spins in the conduction band.
The "screening" electrons involved span from the Fermi energy up to some higher energy.
The relevant energy scale is the Kondo temperature which depends in a non-analytic way on the density of states (DOS) at the Fermi energy, and is roughly the binding energy of the spin singlet.
As the DOS goes to zero the Kondo temperature goes to zero.

But, what if there is an energy gap at the Fermi energy, as in a semiconductor?
One might expect that the Kondo effect disappears and the local moment is no longer screened.
Specifically, is there a critical non-zero value of the energy gap below which the Kondo effect survives and one observes at Fermi liquid?
How about if the temperature is larger than the energy gap but less than the Kondo temperature?
Then perhaps the electrons that are thermally excited into the conduction band can screen the impurity spin.

The above fundamental questions are relevant to understanding magnetic semiconductors. They can be addressed by studying the gapped single impurity Anderson model. A number of numerical and analytical studies over the years have produced different answers to the above questions. The current paper gives definitive answers based on state-of-the art Quantum Monte Carlo calculations.

The phase diagram is shown below, with temperature versus the energy gap, delta.
Both are scaled by the Kondo temperature in the absence of the gap. LM denotes an unscreened local moment and GFL a Generalised Fermi Liquid.
The phase diagram is universal in the sense that it is independent of U in the Kondo regime (for large U) and the only relevant energy scale is the Kondo temperature (not the band width or the hybridisation energy).
It is not at all obvious (at least to me) that the universality of the delta=0 case has to extend to the non-zero delta case. But it does.

One sees that the critical value of the energy gap is zero.
Furthermore, above some non-zero temperature, of the order of a fraction of Kondo temperature and about one half of delta, a Generalised Fermi liquid forms where the local moment is completely screened.
The authors also show that the dynamic spin susceptibility associated the spin of impurity exhibits “quantum critical scaling” in the sense that it depends only on omega/T where T is the temperature and omega is the frequency.

Hopefully the paper will stimulate some experiments, either in quantum dots or in semiconductors, to observe this fascinating physics.

Friday, November 20, 2015

Fulfilling the bureaucratic minimum

There is no doubt that universities and research institutions are becoming more bureaucratic. This is arguably from the increased demand for accountability and from the rise of the managerial class. This means more paperwork, more boring meetings, and more rules and regulations. How do we cope?
Let me first give two extreme responses and suggest an alternative.
John and Joan could be faculty, postdocs, or graduate students.

1. John is focussed on research and teaching. Afterall that is the mission of the university not all this bureacractic nonsense. Any emails from administrators are deleted. In fact he has placed a “block sender” on some. He never responds to requests to complete on line surveys, fire safety training, or annual reports. He does not attend departmental meetings. If forced to attend meetings he brings his laptop and catches up on email.
Deadlines for reports, drafts of grant applications, and exam papers are missed. The only way he will complete an administrative task, even after several email requests, is if someone comes and knocks on his door. Sometimes he tells secretaries, administrators, or colleagues if they want the task done they should do it for him. The only tasks he does actually complete are done at the last minute.
John is not “well liked” either by colleagues or local administrators.

2. Joan is the opposite of John. She is a very conscientiousness member of the community. She reads all the admin emails (including the attachments) carefully, actively participates in all the meetings, updates all the databases, and writes carefully crafted reports. She completes all the tasks in a timely manner. Sometimes she agonises about the content and wording of her reports and gets colleagues to give her feedback on drafts. She gives managers detailed and constructive feedback about a range of their iniatives and issues.

Both extremes present problems.
Basically, John is selfish because he leaves others to cover for him, on some tasks that one just cannot avoid doing.
On the other hand, Joan is wasting a lot of her time, that could arguably be better spent on teaching or research (or on non-work pursuits!). She is also “enabling” the propogators of bureacratic nonsense.

Somehow we need to find a balance between John and Joan. Let me suggest a simple question to decide what to do and what not to do.
If I don’t complete this task (or at least complete it in a timely manner) is it going to inconvenience someone else (because they will have to do it or keep bugging me to do it)?
Fulfilling this bureacratic minimum leaves significant room for tuning out a lot of the noise, deleting a lot of email, skipping some meetings, and quickly completing reports by "box ticking" and cutting and pasting.

Wednesday, November 18, 2015

Emergent quantum matter at JNU

Today I am giving a seminar on Emergent Quantum Matter in the School of Physical Sciences at JNU. My host is Brijesh Kumar. Here are the slides.

Last time I gave this talk, someone asked the tricky and controversial question "Is ferromagnetism an example of spontaneously broken symmetry?" Peierls said yes. Anderson says no. I previously discussed their exchange here.

Aside. One thing I  enjoy about JNU is the very large posters that student political activists have placed on buildings. Many contain challenging quotations that are worth considering, such as this one.

Tuesday, November 17, 2015

Spin liquid state in the spin-1 Kagome antiferromagnet

There is a nice paper
Plaquette-triplon analysis of a trimerized spin-1 Kagomé Heisenberg antiferromagnet 
Pratyay Ghosh, Akhilesh Kumar Verma, Brijesh Kumar

They consider an antiferromagnetic Heisenberg model on the Kagome lattice with three different interactions, J, J', and J'', shown below.
The case J'=J and J''=0 is the regular Kagome lattice model.

For J'=J''=0 one has isolated triangles for which the ground state is a singlet with an energy gap to three low-lying triplet states.
[Aside: for a nice general treatment of such triangles (and tetrahedrons) see this paper].
This state is the starting point for an analysis using bosonic excitations corresponding the triplet excitations on the triangular plaquette.
The calculated phase diagram is below.
One sees that turning on the inter triangle interaction J' has no effect on the quantum numbers or symmetry of the ground state. It remains a singlet, with no spontaneously broken symmetry, with an energy gap to the lowest lying triplet, i.e. a spin liquid. 

I found this surprising and interesting. But, it is also consistent with some numerical work, such as a recent DMRG study by Changlani and Lauchli. 

Only when one turns on the further frustrating next nearest neighbour interaction (J'') does one obtain a different ground state. Furthermore, a relatively small value of J''/J less than 0.2 is sufficient.

For a discussion about a possible spin liquid grounds state in the spin-1/2 Kagome model, see the suggested reading in an earlier post.

I thank the authors for helping me understand the paper.

Monday, November 16, 2015

Hydrogen bonding talks in Delhi

Today I am giving a seminar "Effect of Quantum Nuclear Motion on Hydrogen Bonding" in the Chemistry Department at IIT Delhi. My host is Charusita Chakravarty.

On thursday I am giving a similar talk in a seminar in the School of Physical Sciences at JNU (Jawaharlal Nehru University). There my host is Brijesh Kumar.

Here is the current version of the slides.

What is a "world class" undergraduate science education?

Most undergraduate science curricula are essentially what they were fifty years ago. Furthermore, in Australia they are very specialised. Due to internal university politics and funding pressures departments actually design programs to discourage students from taking courses in other departments. For example, in one university that loves to promote itself as "world class" chemistry majors are not required to take any courses in physics and mathematics. How can you even do basic physical chemistry with only high school maths and physics?

This specialisation is antiquated. Consider what science is like today. It is very multi-disciplinary. Furthermore, the vast majority of research, both pure and applied, involves biology or materials. Biology and medicine are becoming increasingly quantitative. Everything involves substantial use of computers and advanced instrumentation. Previously, I posted about one course every science undergraduate should take. But that is not enough, if you really want to be "world class".

Science students should get a solid basic foundation in physics, chemistry, biology, computing, statistics, and mathematics.

Consider also what type of jobs the majority of science graduates end up doing. These non-research jobs include high school teaching, engineering, industry, and computing. Again multi-disciplinarity is usually central.

There was a time when all Caltech students had to do a quantum mechanics course.
I recently visited the Indian Institute for Science Education and Research (IISER) at Pune. I was very impressed to see that all of their undergraduates do the same courses for the first two years (physics, chemistry, maths, biology) at the beginning of a 5 year BS/MS.  
To me this is "world class".

Friday, November 13, 2015

Comparing theory and experiment for metals: look at the frequency dependence of the reflectivity not the conductivity

The frequency dependence of the real part of the conductivity of a metal gives a lot of information, both qualitative and quantitatively. For example, one can extract a scattering rate and see if a Drude model is relevant. Hence, it is natural that experimentalists present “measurements” of this quantity.

However, it is important to acknowledge that the conductivity is not directly measured; rather, the reflectivity or absorption of a thin film or single crystal.
The real and imaginary parts of the conductivity are then extracted from a Kramers-Kronig analysis. This procedure is only stable and reliable if there is experimental data out to sufficiently high frequencies.
Several experimentalists have privately told me this can be a can of worms. It is not clear how high a frequency cutoff you need and interband transitions can complicate things…
Hence, one should be particularly nervous about people claiming exotica such as quantum criticality and non-Fermi liquid behaviour such as anomalous power laws.

There is a simple way to avoid these complications and ambiguities when comparing theory and experiment. The reflectivity can be written in terms of the conductivity as follows

From theory one can calculate the full complex conductivity and thus the reflectivity and
compare this to experiment.

This is the procedure followed by Jure Kokalj, Nigel Hussey, and I in this paper about overdoped cuprates.

I thank Swagata Acharya for motivating this post.

Thursday, November 12, 2015

When the conflicting values of faculty and students collide

Previously I posted about how faculty members should respond to student evaluations of teaching. 
There is an interesting article at Faculty Focus, that highlights the increasingly conflicting values and expectations between some faculty, students and parents. It’s Not Me, It’s You: Coping with Student Resistance by Nicola Winstanley.
Nearly 20 years ago, Neil Postman warned in The End of Education that education was being replaced by “schooling,” a means whereby learning becomes deeply embedded in a capitalist structure that values knowledge only for its industrial utility. In other words, education is a means to an end—getting a job—rather than an ongoing process at the heart of culture. It’s within this context that some students have come to see education as no more than a deliverable—one that they have paid for dearly. 
The fact that many students accept this paradigm is made evident every day in both their comments and behavior. For instance, some students may think that pedagogical deviation from hard facts and skills is simply a waste of time. Some may even go so far as to abdicate all responsibility for learning anything, because, after all, they’ve paid for it, and as practiced consumers they are used to getting what they want as long as they lay down the cash.
This reminded me of a colleague who taught with a flipped classroom. A student complained that this is not what he paid for. The student said he paid the lecturer to be teach him, not to leave the student to figure things out for himself!

It also reminded me of a colleague at an Ivy League university who encountered students and parents who thought that because they were paying $40K per year the student was entitled to an A! In Australia it is not unheard of for full fee paying international students to claim that they are entitled to a degree because they are paying for it. The fact that they do minimal work and are unable to complete the most rudimentary academic tasks (e.g. write a coherent paragraph in English) is considered irrelevant.

 Reading the beginning of the article I found it disturbing and sad to seeing the negative impact of the student evaluations on the mental health of the author. I now realise that I need to add an additional point to my Survival and sanity guide to new faculty. Don’t take too personally negative feedback from students. It may say more about them than you.

These conflicts of values can be particularly acute in the Majority World where there is a fixation on rote learning and "teaching to the test". This is nicely and sadly described in a recent New York Times article, "Teaching the Common Core in China.".

I thank Chacko Jacob for bringing the article to my attention.

Wednesday, November 11, 2015

The robustness of any materials computation needs to be tested

A blessing and curse is the easy and wide availability of powerful software for computational materials modelling: classical molecular dynamics, quantum chemistry, density functional theory based methods, …
Although easy to use, interpreting the results, and establishing their robustness and reliability can be subtle and challenging.

Any computation requires the user to make many choices from an alphabet zoo.
For example, for classical molecular dynamics simulations of water there is a multitude of force fields (TIP3P, SPC/E, TIP4P-D, …).
For density functional theory (DFT) one has to choose between LDA, GGA, and  different density functionals (B3LYP, PBE, ….).
For plane wave approaches one must choose the energy cutoff.
For quantum chemistry of molecules one has to choose the basis set (STO-3G, cc-pVDZ -Double-zeta,... ) and the level of theory for treating electron correlations (HF, MP2, CCSD, CAS-SCF, …)
If one does combined quantum-classical simulations (e.g. for a chromophore in a solvent or protein) one has to choose the quantum-classical boundary (i.e. how much of the sub-system to treat fully quantum mechanically)…

I encounter two extremes that are disconcerting and unhelpful.

1. Someone has a favourite and specific choice and does all of their calculations with this single choice for a specific system.
They may justify this by giving one or more references that they claim have systematically established this is the best choice.
The problem is that they may be sweeping under the rug that different choices may give significantly different results, possibly not just quantitively but also qualitatively.

A dramatic example is in any system with moderate strength hydrogen bonds. As discussed here, the energy barrier in the proton transfer potential can vary dramatically with the level of theory or density functional that is used. In general the more interesting the system (usually the more complex and the existence of new and interesting physics and/or chemistry) (e.g. because of the presence of strong correlations) the more likely that “standard” choices will be problematic.

Users really should be making some alternative choices from the alphabet zoo to test and justify the reliability of their results.

2. Someone does an exhaustive study using a plethora of methods and choices.
This is probably motivated by the dream of Jacob's ladder.
Their paper has lots of tables and results and comparisons but there is little insight about the relative merits of the different possible choices. Furthermore, sometimes it is claimed that one choice may be better than the rest just because it gets one or maybe a few experimental numbers "correct." To me these may just be a Pauling point.
It is also disturbing that I encounter papers that compare methods but do not contain comparisons with experiment, even when there is data available. (I gave a specific example here).

Another basic point that I (and others) have made before is that the paper needs to give enough specifics of the technical details so that the calculations and results can be reproduced by readers.
Too often I am told by people that they have not been able to reproduce the results in someone else’s paper. This does not inspire confidence. It is also worrisome how some people actually deliberately omit special "tricks of the trade" so they can keep ahead of their "competitors".

Monday, November 9, 2015

Emergent quantum matter talk at IIT Kharagpur

The next two days I am visiting the Physics Department at IIT Kharagpur. My host is Arghya Taraphder. I am giving my regular talk on "Emergent quantum matter". Here is the latest versions of the slides.

I have given this talk about half a dozen times now. Yet last time I gave it I realised there was a significant typo in the formula for the Hall resistance of the Fractional quantum Hall effect. It is amazing that neither I nor anyone in my audiences caught this typo before. I am not sure what that says...

Wednesday, November 4, 2015

There is no metal-insulator transition in extremely large magnetoresistance materials. II

Two months ago I made this claim. I made some specific suggestions as to how one could quantitatively analyse the experimental data to support the claim. The same day of my post I received an email from Zhili Xiao with a copy of a submitted manuscript that had already done exactly what I suggested. The paper has now been published:

Origin of the turn-on temperature behavior in WTe2 
Y. L. Wang, L. R. Thoutam, Z. L. Xiao,  J. Hu, S. Das, Z. Q. Mao, J. Wei, R. Divan, A. Luican-Mayer, G. W. Crabtree, and W. K. Kwok

Below I show the relevant Kohler plot.

This is consistent with the simple idea that the origin of the magnetoresistence is simply the Lorentz force, the same as in elemental metals such as copper and zinc!
No exotic physics is required.

Tuesday, November 3, 2015

The challenge of the infra-red spectra of hydrogen bonded systems

The schematic picture below shows the evolution of the spectral line of an OH stretch mode in a hydrogen bonded system as the donor acceptor distance R changes.
Not only does the mode frequency significantly red shift but the spectral intensity, line width and line shape changes significantly.
The figure is taken from a helpful (short) review from 1991 by S. Bratos, H. Ratajczak, P. Viot

The redshift with increasing bond strength (and decreasing R) is quantitatively described and explained here. I am currently using the same model with collaborators to describe the increase in spectral intensity (by up to two orders of magnitude).

The problem of the line width and the line shape is more difficult and controversial. I discussed some related issues previously here and here.

Saturday, October 31, 2015

Reading the grant guidelines and regulations

Every grant and fellowship program comes with many pages of rules, regulations, guidelines, criteria, ... How carefully should you read them? What can you learn from them?

I have two separate points.

First, as the applicant it is your responsibility to read and to take note of these regulations. This is time consuming and boring. But it is still your responsibility. Don't expect or demand someone else to do it for you. It is not the responsibility of your supervisor, department chair, local research administrator, group secretary, or the funding agency. Don't ask questions when the answers are there in the rules if you actually read them. And don't ignore the rules. For example, if it clearly states you have to be 5 years past your Ph.D, don't apply anyway if you are 3 years past your Ph.D. This may seem inane to some readers, but it does happen. Also, just because it says you can do something does not meet it is a good idea. For example, with regard to budget requests, you may be allowed to ask for $1 million over 5 years, but if you look at the successful applicants you will find almost all get about $300-400K over 3 years.

Second, if possible find out the real inside story about priorities and preferences from the people who actually make the decisions, e.g. someone who has served on the relevant committee. Many grant and fellowship programs will make claims about priorities or preferences, whether it is for specific research fields, women and minorities, renewable energy, early career researchers, national citizens, ..
However, this is sometimes just platitudes and was inserted in the guidelines to sound good or to pacify someone. Don't get your hopes up (or down) if you do (not) fall into this sub-class of applicants. On the other hand, sometimes these are real priorities and if you don't meet this criteria you are wasting your time applying.
Also, not all parts of the application are equally important. Some applicants agonise over preparing sections that actually receive little scrutiny. I know of one program where the actually scientific project and the letters of reference get virtually no attention. It is all based on the CV. The only way you will find out what does and does not matter is to talk to someone.

Thursday, October 29, 2015

Hydrogen bonding in Hyderabad

Tomorrow in the School of Chemistry at Central University of Hyderabad I am giving a talk, "Effect of quantum nuclear motion on hydrogen bonding". Here are the slides.
My host is Susanta Mahapatra.

Monday, October 26, 2015

What is the origin of noise in this bad metal?

Last week I had a helpful discussion with Arindam Ghosh about this recent paper

Conductivity noise study of the insulator-metal transition and phase coexistence in epitaxial samarium nickelate thin films 
Anindita Sahoo, Sieu D Ha, Shriram Ramanathan, and Arindam Ghosh

The abstract states
The normalized magnitude of noise is found to be extremely large, being nearly eight orders of magnitude higher than thin films of common disordered metallic systems, and indicates electrical conduction via classical percolation in a spatially inhomogeneous medium.  
The higher-order statistics of the fluctuations indicate a strong non-Gaussian component of noise close to the transition, attributing the inhomogeneity to the coexistence of the metallic and insulating phases. 
The figure below shows how the non-Gaussian component [measured by the kurtosis] increases dramatically as the temperature decreases below the metal-insulator transition.

Some of the fundamental and related questions that arise are:

How much is the noise due to extrinsic disorder [i.e. due to impurities] and how much due to intrinsic disorder [inhomogeneities arising from phase separation at a first-order metal-insulator transition]?

What happens in a very clean system?

How does one actually do a microscopic calculation of this 1/f noise [e.g. from a disordered Hubbard model]?

What happens in a clean system when the temperature crosses over from a Fermi liquid at low temperatures to a bad metal with increasing temperature?

In a recent PRL there is also noise data for  an organic charge transfer salt, in which the disorder and proximity to the Mott transition can be tuned with the cooling rate.

Friday, October 23, 2015

The limitations of Skype meetings

Skype and similar teleconferencing tools are great. I use them regularly to keep in touch with family while travelling and occasionally to talk to collaborators. It is much better than the phone and way better than exchanging emails.

There are some techno-enthusiasts who claim we don't need to have conferences anymore because we can do it all on line and save lots of money. In companies there are those who push for tele-commuting and only have a central office with hot desks that people occasionally use. I have even heard of Australian universities who have hired faculty members from overseas solely based on a Skype interview!

I think such enthusiasm is a big mistake. I have been at a few conferences where some "big shot" did not attend but gave their talk via tele-conferencing. It really wasn't the same as having them in the room. Even without technical glitches, it was not very engaging. Once I was even at a social event where a couple "attended" via Skype. It was inane and awkward.

Recently I attended a committee meeting via Skype. This was the first time I had done that. On a basic level it was o.k., particularly because the subjects under discussion were not that weighty. However, I did notice how different it was to actually being in the room. In particular, I had no sense of body language, facial cues, or tone of voice. I could not really tell how what I said was being received or get much sense of the mood in the room. It was also harder just to engage with the meeting. I struggle with that sometimes, even when I am in the room!

I think when you know the other parties well and the subject is not controversial this is all fine. However, I think on any sensitive subjects or with people you don't really know for important meetings there is no substitute for a face-to-face meeting. People are intrinsically relational and emotional.

Thursday, October 22, 2015

Engaging Indian school students in real science experiments

Science education in schools in the Majority World faces many challenges including lack of resources, poorly trained teachers, and a fixation on rote learning from text books. Even at “good” schools few students rarely ever do experiments or hands on demonstrations. The focus is on preparing standard answers for exam questions.

One recent big change in school education in the Majority World is the proliferation of low-cost private schools, even in extremely poor communities. Most of these are English medium. A recent cover story in The Economist chronicled this development.

While in India, I enjoy reading The Hindu newspaper each day. I think the quality of journalism and the substance of the issues covered is much higher than most Western newspapers. More than once a week there is an op-ed piece or article about the problems with Indian school education. Topics covered include the stifling of critical and creative thinking, the lack of autonomy given to teachers by all knowing and controlling principals, …

The last two saturday mornings my wife and I have visited a small private school to give a science lesson for about 2 hours. This school is run by a Charitable Trust. It has a couple of hundred students. A significant fraction are orphans (biological or economic) who live in a children's home also run by the Trust. Annual school fees are about 15,000 Rupees (roughly US$300) including uniform and textbooks. This covers less than half the actual cost; the rest is made up by private donations. Particularly poor students receive scholarships or fee relief. Unlike some Indian private schools this one does not expel students who do poorly on exams. (Schools do this so they can boost their average exam performance). Our personal connection with the school is that the Trust is connected to the church we attend in Bangalore. Both of our own adult children have volunteered at the school and children's home.

Here is roughly what I did in the science lesson. One week we had year 9 (called 9th standard in India) and the next week year 10.

The main goal is give a hands on experience that will help the students see that what they read in the textbook or memorise for the exam actually has something to do with the real world.
It is centred around a baking soda and vinegar film canister rocket. Since this involves cheap household chemicals the hope is the children and/or their teachers might do it again.

I begin with a brief discussion of the scientific "method": ask a question, make a hypothesis (a big idea), design an experiment, make measurements, record data, analysis data, conclusion, and communicate results. I then illustrate this by sticking a wooden skewer in a balloon then show how you can actually put the skewer through the balloon.

I do the film canister rocket experiment. I then just mix a little vinegar and baking soda so they can see gas is being produced. Why is there gas? What gas is it?

I then explain what chemistry is and illustrate with the chemical reaction of baking soda and vinegar,  using full chemical names and chemical formula. Since carbon dioxide is a product we briefly discuss   global warming. I highlight that different compounds in the chemical reaction are gas, solid, or liquid.

I then turn to physics. There are two relevant ideas here:
1. Newton's third law [which they all know word perfect!] and that drives the rocket.
2. When you convert a fixed mass of liquid or solid to gas the total volume increases by a thousandfold. A few grams of carbon dioxide has a volume of several hundred millilitres. Compressing that into the film canister produces a huge pressure.

Now the fun and most important part. We go outside and the students work in pairs where they systematically vary the amount of vinegar they add to the film canister and measure (estimate) the height the rocket goes to. Does more vinegar increase or decrease the height? Why or why not? They record their results. The quicker students I get to repeat their measurements.

After a lot of fun we return to the classroom. I review the chemistry and physics again. Then we compare measurements between different groups, discuss measurement error, and try and draw some conclusions.

The second week I was really happy because a friend came who just finished a Ph.D at Indian Institute of Science. He came from a similar socio-economic background to many of the students. I asked him to tell his life story to the class in the hope it would inspire the students. I don't think a wealthy white Western guy telling poor Indian kids they should study hard and have a lofty goal such as to become a scientist is particularly effective or appropriate.

Follow up. The following week I did the same session with three high school students who were being home schooled by their parents. I was very impressed by their creativity and critical thinking. On their own initiative they realised that it was difficult to make accurate measurements of the height that the rocket went to. Their solution was within about ten minutes to construct the launch device below. Instead of measuring the vertical distance they used a tape measure to measure the horizontal distance the rocket travelled.

Monday, October 19, 2015

Seminar at IISc & a FQHE quasi-particle question

Tomorrow I am giving a seminar in the Physics Department at the Indian Institute of Science in Bangalore. The talk "Emergent states of quantum matter" is similar to the one I gave two weeks ago at JNCASR. 

Then an interesting question was raised. "There are two complementary pictures of the quasi-particles in the Fractional Quantum Hall Effect: composite fermions and fractionally charged anyons. Can one explicitly show they are equivalent?"
I am not sure. One can certainly show that the overlap of the relevant variational wave functions, Laughlin's and the composite fermion ones, is significant and that for small systems that the overlap of both of these wave functions with exact numerical wave function.
However, that "black box" proof is not quite the same as establishing "adiabatic continuity" between the two different representations. Has anyone explicitly done that?

I welcome other answers to this question.

Saturday, October 17, 2015

Coffee table books for nerds

This past northern summer I was on vacation on Lopez Island in Washington state [near my wife's hometown]. While browsing in the bookstore I came across this fantastic "coffee table" book The Elements by Theodore Gray (co-founder of Wolfram Research).

There is a page for each element with a fascinating description and beautiful photos. A sample is above. You can view all the pages on the book webpage.
I bought a softcover version for US$25. I think it is important to support local bookstores, particularly given the vagaries of Amazon.

 I was thinking that it would be really nice if there was also a book about molecules, since they are a lot more interesting than atoms. A week later I was in the U of Washington bookstore and I came across Molecules by Theodore Gray! He has also developed some fancy mobile phone apps.

Now the hardcopy cost me US$15. This tells you something else about bookstores...

I am also told that some young kids love these books.

Thursday, October 15, 2015

A video worth showing non-scientists

Sometimes I give talks about science to high school students and to community groups, mostly churches. Recently I showed this one.

Besides the "wow factor" I think it is valuable because it demonstrates some very basic but profound and important points about science.

1. Common sense observation and experience can be misleading.

2. Consequently, nature appears sometimes to be counter intuitive.

3. The way to discover the way things really are is by doing experiments.

One can explain the historical significance of this experiment. Aristotle advocated basing science on common sense observations [heavy objects fall faster, objects that start their motion eventually slow down unless a force is applied to them, objects on earth move in a qualitatively different manner to those in the heavens, ....]. In contrast, Galileo went against this and did real experiments, dropping two balls of different mass [probably not from the leaning tower of Pisa].

This can also lead to a discussion of how scientific observations today confront us today with many counter-intuitive realities such as wave-particle duality, Schrodinger's cat, dark matter, ....

For high school or introductory college students who know Newton's laws of motion and gravitation one can explain how this illustrates the equality of inertial and gravitational mass.

Aside. Thanks to insights from my wife, I stop the video before the very end when Brian Cox starts talking about Einstein and the Principle of Equivalence. Non-scientists find this too confusing, get fixated on it since it is the last thing they hear, and then get distracted from the more basic stuff such as the above.

If your game, you could then discuss the problems with string theory....

Friday, October 9, 2015

Preserving my mental health

In Australia this week is Mental Health Week. 10 October is World Mental Health day.
I have been told that some of my posts and talks about  mental health issues have been helpful and so here are a few random observations.

These are just some things that I have recently noticed and are helpful for myself. They are personal and so may not be helpful  for others. But, hopefully they may stimulate you to think about your own situation.

This is one reason to turn off email occasionally.
Do you really need email on your phone?
It is one of the reasons I don’t even have dumb phone!
I am currently in India and something I like about one of the places we regularly stay is there is no internet in our room. You have to walk outside 100 metres to a different building to access it.

Short breaks.
Several times a day I take a brief walk on campus to clear my head.
UQ has quite a nice campus and so this helps.

The more that it is integrated into your weekly/daily routine the better. I am fortunate that my home is 25 minutes walk from my office. A few years ago I started walking home several times a week.
Now I actually walk both to and from work on most days.

Take a Mental health day.
Minimise particularly stressful situations.
I have slowly learnt that there are certain individuals, activities, and organisations [whether social or professional] that take me a while to recover from. It is not possible to avoid all of them! On the one hand, I don't encourage people to run away from problems and difficult situations. On the other hand, you don't have to be a masochist. Sometimes it is best to opt out.

Get enough.
One or two nights with little sleep, either due to stress or travel, gives me a very bleak view of the world.

Daily victories and small satisfactions.
My view of life is much more positive is on each day I can achieve at least one small thing I think is of value or enjoyable. This is where this blog helps. Writing a post gives a concrete and tangible achievement for the day. I struggle to get such satisfaction from administrative responsibilities or research dead ends!

Physical illness may reflect stress and poor mental health.
I got a cold/flu a few months ago. I realised that I had not been sick for a year and that the last few years I rarely get sick. In contrast, in times when I have had a lot of stress I often got sick and sometimes it took me more than a week to shake off a cold/flu. There is a general folklore that stress increases the susceptibility of individuals to colds, flu, and infections. I did a quick search of the medical literature to see if this is really firmly established but could not find anything particularly convincing. Does anyone know of a relevant study?

Nature and humour.
These are two of the best drugs! The video below combines both!

Monday, October 5, 2015

Emergent quantum matter talk at JNCASR

Tomorrow I am giving a seminar, "Emergent states of quantum matter" at JNCASR in Bangalore. Here are the slides. My host is N.S. Vidhyadhiraja

Thursday, October 1, 2015

Wrapping up an undergraduate research thesis

How do you do it while maintaining sanity and quality?

In Australia a Bachelor of Science is a three year degree. Students have the option of doing an additional year, and being awarded an Honours degree. This is necessary to do a Ph.D. and may help to get into some government jobs.
The honours year is roughly half course work and half a research project leading to a thesis.
The thesis is a bit like a mini Masters degree in other countries.
The thesis is meant to involve original research. For the best students their results may be part of a publication. The thesis is typically 40-80 pages.

I believe that Princeton is unusual among US universities in requiring ALL their students to complete a senior thesis.

Assigning, supervising, and completing these projects is particularly challenging for both advisors and students. Previously I posted advice for students giving seminar talks based on these projects.
Now I turn to the thesis.

First, students don’t actually know much science or have much real research experience. Although there are now a host of summer scholarship schemes and other  opportunities for working in research groups.
Second, the greatest challenge is that there is a fixed deadline for submission of the thesis.
This is quite unlike a Masters or Ph.D where people tend to submit when they “have enough results”. I realise that funding running out or starting a new job sometimes plays a role in when students submit.
Unfortunately, it often seems that just when a student starts to get some useful results, or worst they just appear on the horizon, the thesis deadline is looming. Further stress is created by impending final exams!
Students can also put a lot of pressure on themselves, because getting a good grade for the thesis may influence their future options, particularly if they want to do a Ph.D.

So what should students (and advisors) do to maintain sanity and produce a quality thesis?

Don't wait until the last minute to start writing.
Too many students do this in the hope they are going to finally get their experiment or calculation to work and then slap together a thesis at the last minute, sometimes pulling “all nighters”.

Realistic expectations.
Face your perfectionism.
You are not going to write the best thesis ever.
Look at copies of theses from previous years.
You may have higher expectations than your examiners.

Know what is expected or hoped for.
The presentation of the thesis is as important as any new scientific content.
Examiners enjoy learning something new.

Again, start writing early. 
Don’t wait until you get your results.
Introduction. Literature review. Clear description of the project and its goals.
Methods. Polish what you have. This can all be done sooner than later.

Watch your mental health.