Cool experiments with dry ice

Yesterday my wife and I did our latest kids science demo gig, at a holidays kid club at our church. My son has encouraged us to come up with some new demonstrations since some of the kids have already seen some of the old favourites, such as Elephants toothpaste, coke and mentos rocket, and a few others here.

At first I was pretty excited when I saw this Youtube video of an LED powered by a lemon. Watch it and see what you think. I even got some LEDs to tried and do it. At the end of the post I tell the rest of the story.

We settled on a few demos with dry ice [solid carbon dioxide]. The unique feature is that at atmospheric pressure the solid does not melt [become liquid] but sublimates [becomes vapour]. This is because in the phase diagram the pressure of the triple point [5 atm] is above atmospheric pressure.

Here are some of the demonstrations. Many of them rely on the simple fact that the volume of one gram of vapour is of the order of five hundred times larger than the volume of one gram of solid. A good exercise for high school and college students [and you!] is to come up with a simple "back of the envelope" argument as to why this is so.

A. Put a few pellets of dry ice in a zip lock bag and seal it.
After a few minutes the pressure build up due to sublimation causes the bag to "pop". I quite like this because the pop is not so loud that it scares little children and the bag is usually not damaged and so you can keep doing this again and again. Each kid gets to have bag.

B. Dry ice in a balloon. Just add a few pellets to a balloon and tie it up. Wait a few minutes and it will expand, and perhaps pop.

C. Smash a gummy bear [snake in Australia]. Make as slurry of dry ice and car antifreeze. Add a gummy bear. Take it out and smash it with a hammer. Aside: a technical discussion is here.

D. The cauldron. Simply add dry ice to some water and watch it "boil". This should actually lead to a good discussion of the difference between "bubbling" and "boiling".

Here is one compilation including a massive soap bubble by the "Crazy Russian Hacker". I did not do all of these!

In the USA I believe you can buy dry ice at some grocery stores. In Australia, it is harder; we had to go to a BOC Gas and Gear store in Brisbane and buy 1 kg of pellets for $10. They last about half a day before they completely sublimate. Pellets are easier to work with, but they don't last as long.

Postscript. The Youtube video of the LED lighting up when it is stuck in a lemon is a hoax. Because I saw it with my eyes I thought it was real. I am embarrassed; I really should have realised it could not be true. The key feature of a battery [electrochemical cell] is that the anode and the cathode have to be different materials so they have a different electrochemical potential.
But, I think making a real lemon battery would be cool. But it does require 3 to 4 lemons hooked up in series to produce the necessary minimum voltage to light the LED. I want to think about how this could be done in thermodynamics class to illustrate certain important concepts such as the chemical potential.

What is so great about the von Neumann entropy?

I got a referee report for a paper submitted to PhysChemChemPhys that looks at the quantum entanglement of electronic and nuclear degrees of freedom in molecules. The paper goes beyond the calculations considered here, and explores subtle issues about how entanglement may or may not be related to the breakdown of the Born Oppenheimer approximation.

One referee asked a good but basic question, "Why is the von Neumann entropy the appropriate measure of entanglement to consider here?"

Here is my answer. I think experts could do better and so I welcome suggestions.

The von Neumann entropy is widely accepted as the best measure of quantum entanglement for pure quantum states defined on bipartite systems, such as that considered here. This is because the von Neumann entropy satisfies certain desired criteria, including vanishing for separable states, monotonicity (it does not increase under local operations or classical communication between the subsystems), additivity, convexity, and continuity.

It was a bit of work to come up with this answer, because this is all second nature to people who work in quantum information. It is hard to find a place where this is clearly stated and discussed in detail. The Quantiki wiki entry on entanglement measures  and the axiomatic approach, along with the review article by the Horodecki family helps.

Anyone suggest a place where this basic issue is discussed and worked out in detail?

The big challenge is defining entanglement measures for multi-partite systems and for mixed quantum states.

The tension between accountability and trust

On the one hand I think it is very important that people and institutions should be accountable for their actions. Human nature is such that if people are not accountable they will often choose to act in selfish ways that lead at best to mediocrity and at worst to corruption, exploitation, and waste of precious resources (financial, human, and environmental).

On the other hand, at some level you need to trust people and give them freedom to get on with their job. Too much regulation and oversight can be dehumanising, discouraging, stifle initiative, and also waste resources. For example, the fact that at most universities half of the staff are administrative should be a serious concern.

Consider the following contrasting situations. The levels of accountability and trust are wide ranging.

Sepp Blatter thinks that FIFA should be self-regulating and left to get its own house in order.

CEO's of mining companies will claim that they will "do the right thing" when it comes to environmental protection and the government should reduce regulations.

In one state university in the USA, after one gets a Federal government research grant, one must then undergo an extensive internal review of the project goals, procedures, and budgets. Regular internal progress reports are required in addition to the reports required by the granting agency. Faculty hire administrative staff to manage this process for large grants.

In one department staff and graduate students can use the stationary cupboard, the photocopier, and computer printers as much as they choose. No personal accounts are kept.

I have held grants ranging from $8K to $800K where the reporting requirements were comparable.

In one country a research grant can be spent in any manner and proportion that the PI (Principal Investigator) pleases: postdocs, students, travel, computers, equipment, ...
In another country the funding agency breaks down the budget and specifies exactly what can be spent on each item.

In one university when a PI wants to hire a postdoc, the decision is made solely by them. In another, the PI has to convene a selection committee including the department chair, a faculty member from a different department, and must include gender diversity.

In one university after a faculty member teaches a course they have to file a log showing the content of each lecture and it is checked whether they covered all the material stated in the course profile. At another university no one checks.

At one university if a faculty member wants to take even a single day of vacation it has to be approved by the department chair and logged. At another university no one even keeps track.

Notice how in some of the situations above the institution is clearing trusting people to make the best possible choices. In other situations there is clearly a lack of trust, even in the smallest matters.

How does one find the appropriate balance between trust and accountability?
I am not sure. I would welcome suggestions.

Here are some rough thoughts.

1. The level of accountability should scale with the level of damage that can be done by misconduct.
A mining company clearing thousands of hectares of pristine rainforest is not the same as a graduate student using the department printer to print a gossip magazine article.
I think we actually need significantly more regulation of the rich and powerful and much less of people at the grass roots.

2. Accountability structures need rigorous cost-benefit analysis.
Will the amount of money potentially saved [whether in increased productivity or reduced misuse of resources] be actually be less than the money lost through increased administrative costs, lower staff productivity to reduced morale, inefficient use of resources due to inflexibility?

3. We should be realistic about the limited effectiveness of accountability structures.
The rich, powerful, and gifted are very good at getting around them.
Yet politicians and managers seem to think if they design a new policy, send an email, and require a report everything is going to alright. People game the system.

What do you think? 

The challenge of the pseudogap in organic charge transfer salts

I am often sprucing [Aussie slang for promoting] Dynamical Mean Field Theory (DMFT), and particularly how it captures many quantitative details of charge transport and bad metals in organic charge transfer salts.
However, it is always good and important to be transparent about the limitations of any theory, particularly one that you are enthusiastic about.

There is a nice paper
Repulsive versus attractive Hubbard model: Transport properties and spin-lattice relaxation rate 
Rok Žitko, Žiga Osolin, and Peter Jeglič

The authors use DMFT to calculate various spectral functions using the numerical renormalisation group (NRG) as the impurity solver. This is probably, the most reliable method, at least for low temperatures.

There is a lot I found interesting in the paper. But for now I just want to focus on one result in the paper: the temperature dependence of the NMR relaxation rate, 1/T_1.
1/(T_1 T) is proportional to the slope of the local spin fluctuation spectral function

The authors find that in the metallic phase of the repulsive Hubbard model this slope monotonically decreases with increasing temperature. Similar results were found 20 years ago (with a more approximate treatment) by Jarrell and Pruschke.

Why is this interesting?
In the organic charge transfer salts 1/T1T versus temperature is not monotonic, but has a maximum at a temperature (T_NMR) around the coherence temperature, T_coh, marking the approximate crossover from a bad metal (at high temperatures) to a Fermi liquid (at low temperatures). Actual data for a wide range of materials is shown in the Figure below, (n.b. this is a plot of T_1 T vs. T not 1/T_1T) taken from a paper, with Ben Powell and Eddy Yusuf.

That paper also emphasised the discrepancy with single site DMFT.
But, it was good to be reminded of it again.
What is going on?
Basically, like in the cuprates a pseudogap must be opening up. A cluster DMFT calculation, such as this one by Jaime Merino and Olle Gunnarsson [or one by Emanuel Gull ] captures this.
But, it remains to be shown in detail that the NMR data can be quantitatively described and the relationship between the two temperature scales T_coh and T_NMR needs to be elucidated.

The two biggest obstacles to science Ph.D's getting a job in industry

Over the past few years I have been watching with interest a number of postdocs transitioning from academia to industry. From my very limited experience, reading, and some discussions I think there are two obstacles that need to be faced head on. Both involve wrong perceptions and misunderstandings.

1. Industry is not interested in me because my highly specialised technical skills are not relevant.
This is true. Industry could not care less about spinons, lattice gauge theory, Bell's theorem, synchrotrons, femtosecond spectroscopy, cosmology, ....
However, industry is VERY interested in some of the skills you do have and probably take for grant: problem solving, critical thinking, analyse complex data, ability to learn new technical skills quite, write and debug large computer code, not being scared of big data, technical communication [written and verbal], work in teams.... Furthermore, it is important to appreciate that the vast majority of people, including many with MBAs, finance and law degrees, can really struggle to do some of these things at the most basic level.
So, do not underestimate what you have to offer.
There are actually head hunting firms who have people working full time trying to "poach" people from academia for jobs in industry. An Australian example is here.

2. I should use the same CV and cover letter for academic and industry positions.
No! No! No!
Industry could not care about how many papers you have, journal impact factors, citations, invited talks at "prestigious" conferences, ...
You need to rewrite your CV from scratch. Make it short and emphasise the skills above. Find someone you know who recently got a job in industry and ask them for a copy of their CV and cover letter.

Many of these issues are no doubt covered in depth by two books I recently recommended.

I welcome comments and suggestions from people who have made the transition and know much more about this than me.

What are the ten key concepts in quantum many-body physics?

Here I consider quantum many-body theory, as it spans from quantum field theory to nuclear physics to ultra cold atomic gases to solid state physics to quantum chemistry.

Here is my tentative list of the ten most important key concepts.
n.b. I am not concerned with key techniques (e.g. path integrals, renormalisation group, Green's functions, Feynman diagrams, imaginary time (KMS), numerical methods....). That is a separate topic. Unfortunately, in most many-body theory texts the concepts are lost in the midst of all the technical details. Furthermore, concepts are what experimentalists need to know and understand.

1. Emergence
This is the overarching concept that underscores almost all the others. Reality is stratified and at each length, energy, and time scale distinctly new phenomena, interactions and entities can emerge. More is different.

2. Effective Hamiltonians
At each strata there is some Hamiltonian that describes the "particles" and interactions between them. The parameters in this Hamiltonian can sometimes be determined from experiment.

3. Quasi-particles
There are two cases. In the simplest case, due to adiabatic continuity, the quasi-particles have the same quantum numbers and statistics as the constituent particles (e.g., Fermi liquid theory). But, their mass and spin-g factors can be significantly different from the free particles. The second and more exciting case is where the quasi-particles have different quantum numbers and/or statistics to
the constituent particles (e.g. Fractional Quantum Hall effect, spinons, and Luttinger liquid).

4. Renormalisation
This explains how the effective interactions at one strata are related to those at a lower strata (or equivalently how high energy virtual processes lead to low energy real interactions). Examples range from weak interactions in a Fermi liquid to asymptotic freedom in QCD to the van der Waals attraction between two neutral atoms.

5. Incoherent excitations
Sum rules provide a means to understand the redistribution of spectral weight. Quasi-particles don't exhaust the total spectral weight.
This also connects to Hubbard bands, bad metals, quantum decoherence, and the condensate fraction for superfluids and superconductors.

6. Spontaneously Broken Symmetry
This leads to new states of matter and new collective excitations, including Goldstone bosons (e.g. phonons and magnons) and massive particles such as the Higgs boson. This is also connected to rigidity, but that does have a classical analogue too.

7. Emergent energy scales
These can be orders of magnitude different (always smaller?) from the energy scales in the underlying Hamiltonian. Often they reflect non-perturbative effects, as in the BCS energy gap or the Kondo temperature.

8. Emergent length scales

9. The fluctuation-dissipation theorem
This means we can calculate linear transport (i.e. non-equilibrium) properties from fluctuations in thermal equilibrium. Inelastic scattering experiments can then be related to dynamical correlations.

10. Topology sometimes matters
Examples include topological excitations (e.g. vortices), topological terms in the action (e.g. for quantum spin chains and the Haldane conjecture), topological insulators, and topological order in the Quantum Hall effect. Topology is also somehow involved in anomaly cancellation.

Piers Coleman's article (focussing on condensed matter) provides a nice discussion of some of these concepts.

What do you think? What should I add or subtract from this list?

Some might suggest entanglement and/or quantum criticality or there own current favourite hot topic. However, I still remain to be convinced that these are key organising principles that are essential for understanding broad ranges of systems, rather than currently fashionable exotica.

I might include the Mott insulator, but I am not clear how that is relevant beyond solid state physics.

Is the list helpful? I am considering spending more time on this: perhaps a blog post on each concept, then a colloquium style talk, and a short tutorial review article.
I think the only mathematical entity needed to understand and illustrate all of this is a spectral function.
Any feedback would be appreciated.

What is the chiral anomaly?

Why is it so central in Quantum Field Theory?
Has it been observed in solid state physics?

At the Journal Club of Condensed Matter, Patrick Lee has a very nice and helpful commentary, Observation of the chiral anomaly in solids, that highlights a preprint, based on a recent talk by Phuan Ong at the APS March meeting.
Later I hope to write more about the solid state physics, earlier work of which I have mentioned before.

I just want to highlight a beautiful and succinct paragraph from the preprint that explains why the chiral anomaly is so important in quantum field theory.

A bit of topological physics fell into quantum field theory (QFT) in the late 1960s [8–11]. The charged pions π± are remarkably long-lived mesons (lifetimes τ ∼ 2.3 × 10−8 s) because, being the lightest hadron, they can only decay by the weak interaction into muons and neutrinos via the processes π− → μ− + ν ̄μ and π+ → μ+ + νμ. Mysteriously, the neutral pion π0 decays much more quickly (by a factor of 300 million) even though it is a member of the same isospin triplet. Instead of the slow leptonic channels, π0 decays by coupling to the electromagnetic field Fμν in the process π0 → 2γ. The relevant diagram (shown below), called the Adler-Bell-Jackiw anomaly [8, 9], is a triangular fermion loop that links the π0 (the axial current) to the 2 photons (vector currents) [10, 11]. 

A hint of the topological nature of the anomaly is that the one-loop diagram receives no further corrections to all orders of perturbation theory. Subsequent research revealed that the anomaly expresses the breaking of a classical symmetry by quantum fluctuations. In modern QFT, the anomaly plays the fundamental role of killing unviable gauge theories [10, 11]. A proposed chiral gauge theory must be anomaly free. Otherwise it is not renormalizable. Arguably the most important example of the anomaly-free rule is the Glashow- Salam-Weinberg electroweak theory, in which the 4 triangle anomalies linking the lepton and quark doublets with gauge bosons sum exactly to zero within each generation. This fortuitous cancellation has been called “magical” [10]. 

A measure of the importance of this idea of anomaly cancellation is the fact that much of the initial string theory hype in 1980s arose because it was found that certain string theories with certain symmetry groups did have the sought after anomaly cancellations. See here for more.

Addendum (23 June, 2015): Peter Woit just posted about a recent talk "Anomalies Revisited" by Ed Witten.

The fundamental issue is that these are theories where the path integral does not determine the phase of the partition function. Part of story here is the well-known story of anomalies, perturbative and global. One interesting point Witten makes is that vanishing of these anomalies is not sufficient to be able to consistently choose the phase of the partition function, and he gives a conjecture for a necessary condition that is stronger than anomaly cancellation.

Witten discusses the specific case of three-dimensional massless Majorana fermions that may be realised in a topological superconductor.

Adapting to career transitions with pleasure

There are several important career transitions that the fortunate few need to adapt to.
Getting a potentially "permanent" job. (e.g., Assistant Professor).
Getting Tenure.
Getting promoted to full Professor.

Previously I wrote my survival and sanity guide to young faculty.
My general observation is that people don't adapt well to these transitions. In particularly, they tend to just continue to operate in the same mode.

Unlike in North America, in Australia promotion to full Professor is not the natural trajectory. Thirty years ago, there was virtually no promotion. You had to get a separately advertised "Chair". Sometimes there was only one per department and they were the default department head. Most people ended their careers as Senior Lecturers or Readers. Now there is no limit on the number of Professors, but only a few will attain it. [Also in Australia, tenure no longer strictly exists, but that is another story].
Some will run themselves ragged, particularly taking on burdensome administrative tasks, chasing funding, or pandering to managers and/or students, in order to jump through this hoop (or over the hurdle).

Once you have tenure and/or become full Professor you should make the most of the freedom you have. John Baez has the following sage advice:

The great challenge at the beginning of ones career in academia is to get tenure at a decent university. Personally I got tenure before I started messing with quantum gravity, and this approach has some real advantages. Before you have tenure, you have to please people. After you have tenure, you can do whatever ... you want - so long as it's legal, and so long as your department doesn't put a lot of pressure on you to get grants. (This is one reason I'm happier in a math department than I would be in a physics department. Mathematicians have more trouble getting grants, so there's a bit less pressure to get them.) 

The great thing about tenure is that it means your research can be driven by your actual interests instead of the ever-changing winds of fashion. The problem is, by the time many people get tenure, they've become such slaves of fashion that they no longer know what it means to follow their own interests. They've spent the best years of their life trying to keep up with the Joneses instead of developing their own personal style! So, bear in mind that getting tenure is only half the battle: getting tenure while keeping your soul is the really hard part. To do this, you have to make sure you never lose that raw naive curiosity that got you interested in science in the first place. Don't get too wrapped up seriousness. The universe is a cool place; exploring it is fun! 

 So: keep playing around with all sorts of ideas, techniques and tools. Read voraciously. Don't be scared of experts and their jargon. Become one yourself, but then give the game away by explaining things in simple language whenever possible. Talk to lots of people! Teach them; learn from them; don't worry too much about impressing them. Don't be scared to ask basic questions - and don't be surprised when nobody knows the answers. The simplest questions are the last to be answered.

I found this quite refreshing, encouraging, and liberating.

What do you think? Do people adapt well to these transitions? If you have been fortunate to go through one of them, did you change? Do you have regrets?

Rebutting the historical conflict thesis

Last friday we had Peter Harrison give the Physics colloquium on "The Progress of Science and the Decline of Religion?"
He is a historian, who prior to coming back to UQ, held a chair at Oxford, and in 2011 gave The Gifford Lectures, which were recently published.
He is probably best known for arguing that changing approaches to Biblical interpretation, associated with the Reformation [moving away from an emphasis on allegorical interpretations towards more literal and historical interpretations] changed peoples conception of "nature" and had a significant influence on the development of modern science.
Peter is director of the Centre for the History of European Discourses at UQ and attracts many stimulating and distinguished seminar speakers, some of whom I have blogged about before.

One issue Peter addressed head on is the "conflict thesis" which claims that science and religion have always been in conflict and particularly that religion has impeded the progress of science. This view is popular in the public realm but not among historians of science. [The Wikipedia page is worth reading]. Like most issues the reality is much more complex.

Peter mentioned several widely cited historical "conflict" incidents such as Galileo and Darwin. In both cases there were people who opposed them and who supported them using religious and scientific arguments. For the Galileo affair the main contention was about competing scientific models and different philosophical perspectives. Furthermore, Galileo's scientific case was hardly solid; no stellar parallax had been observed and his argument using the tides was (in hindsight) wrong. In Darwin's case he was opposed by Lord Kelvin (who had miscalculated the age of the earth) and supported by Asa Gray and some conservative theologians.
John Heilbron's book, The Sun in the Church "illuminates the niches protected and financed by the Catholic Church in which science and mathematics thrived."
Stephen Gaukroger's book, The Emergence of a Scientific Culture: Science and the Shaping of Modernity emphasised how science had religious sanctions.

If you have a few hours (and $200!) you can watch some very nice lectures on the above historical issues. I highly recommend a course given by Lawrence Principe (Johns Hopkins) and sold by The Great Courses [The Learning Company in Australia]. [Peter Harrison recommended these to me and I bought them on special for A$52 including shipping].

Peter also discussed more recent history including some sociological studies, which seemed to attract the most questions from the audience.
He gave a similar talk at BrisScience a few years ago and can be viewed here.

Why reviewing grants makes me grumpy

Here are some of the emotions I experience when I have to review a bunch of research grant applications. This has become accentuated because I now have to review some applications outside physics and chemistry.

Guilt. I don't spend as much time on each application as perhaps I should. I don't read every word, cross check details, learn the necessary science, find an expert, ...

Guilt. I do sometimes look at metrics. But, in my defense this is very coarse-grained. Most of the time it tells me little or what I can guess already. However, occasionally I think it does help. For example, someone who is decades past their Ph.D and with only single digit citations on their hundred plus papers. Or, someone with a few recent papers with 50-100 citations, may mean something.

Frustration. That I have to assess non-competitive applications. Why did this person waste all the time preparing an application. Did any senior colleague advise against it? Or does the applicant live in a dream world or have a massive ego?

Irritation. Applicants should know their application will be reviewed by a multi-disciplinary panel but still fill it with jargon.

Irritation. Most applicants list journal impact factors to 4 or 5 significant figures. I know journals do this, but it reflects an uncritical acceptance of what the numbers really mean. This reflects poorly on the applicant. If one looks at the broad distribution of citation rates for papers in a specific journal, not just the average citation rates, one can see that at best only two significant figures is meaningful.

Concern. Many excellent junior people living on soft money. The success or failure of this application may determine whether they leave science. They should not be in this situation.

Sympathetic. Although I am scathing about those with High Impact Factor syndrome, I do see how seductive it is, particularly when reviewing applications from other fields. It provides an easy way out from the hard work and subjectiveness of a real scientific assessment.

Irritation. Hype about the applicant, research field, or project.

Joy. When I learn something new or when I see someone is doing something cool or worthwhile for global society (or at least appears to be).

Anxious. Writing a grant proposal that sells is not the same skill as doing excellent research. I may be deceived and backing the wrong people [those good at marketing] rather than really creative and solid scientists who don't have the skills or motivation to sell themselves or their project.

Concerned. There is too much hyperactivity (lots of papers, conferences, seminars, grad. students, ...). It seems quantity trumps quality. I desperately seek to find just one significant nugget of scientific knowledge that each applicant has produced.

Relief. When I am done.

But I am still grumpy for a few days afterwards.

Violation of quantum bounds on the viscosity of strongly interacting fermion fluids

Nandan Pakhira and I just finished a paper
Shear viscosity of strongly interacting fermionic quantum fluids

Eighty years ago Eyring proposed that the shear viscosity of a liquid, η, has a quantum limit η larger than n hbar where n is the density of the fluid. Using holographic duality and the AdS/CFT correspondence in string theory Kovtun, Son, and Starinets (KSS) conjectured a universal bound η/s ≥ hbar/4πk_B for the ratio between the shear viscosity and the entropy density, s.

Using Dynamical Mean-Field Theory (DMFT) we calculate the shear viscosity and entropy density for an fermion fluid described by a single band Hubbard model at half filling. Our calculated shear viscosity as a function of temperature is compared with experimental data for liquid 3He. At low temperature the shear viscosity is found to be well above the quantum limit and is proportional to the characteristic Fermi liquid 1/T^2 dependence, where T is the temperature. With increasing temperature and interaction strength U there is significant deviation from the Fermi liquid form.

Also, the shear viscosity violates the quantum limit near the crossover from coherent quasi-particle based transport to incoherent transport (the bad metal regime). Finally, the ratio of the shear viscosity to the entropy density is found to be comparable to the KSS bound for parameters appropriate to liquid 3He. However, this bound is found to be strongly violated in the bad metal regime for parameters appropriate to lattice electronic systems such as organic charge transfer salts.

We welcome any comments.

The challenge of innovative teaching

On monday I went to two interesting talks at UQ by Eric Mazur.
The slides are available here.

For reasons I discuss at the end I found the talks both inspiring and discouraging.

The first talk, "Flat Space, Deep Learning" described a new course Mazur developed at Harvard, AP50, a calculus based introductory physics course for engineers. The whole goal is get students to "own their own learning". There are no lectures, just 2 three hour class sessions. The "exams" are non-traditional. Students don't do regular labs, but rather four team projects. Students have to read the relevant part of the text before class and annotate an online version with questions and answers to other students questions. Central to the course is extensive use of the Learning Catalytics software, developed by Mazur, King, and Lukoff, and subsequently sold to Pearson.



The second talk, "Teaching Physics, Conservation Laws First" was an infomercial for Mazur's new text (s), Principles and Practice of Physics. It takes quite an original approach, which is described in this video.



Key changes from traditional courses are to put concepts before mathematics.
The central features include

* start with conservation principles. this means that one can solve many problems with algebra not calculus. Conservation of kinetic energy in elastic collisions is derived from the empirical observation of "conservation of relative velocity". [Aside: I got confused about this. I tried to derive it, and found that the relative velocity is not "conserved" but "reversed" by the collision].

* do everything in one dimension for the first 10 chapters. this delays the introduction of vector notation.

* emphasise the role of symmetry and the concept of a system.

* introduce entropy before heat, using a microscopic approach. [I agree on former but not the latter but that is another matter].

* physically realistic diagrams play a central role.

Overall I found the presentations both inspiring, challenging, and discouraging.
It was inspiring to see that the data shows that Mazur really does get the students to engage with the material, learn something, and have fun!

The challenge is to find ways to implement these ideas in your own situation.
What works and is possible at Harvard does not easily translate to elsewhere.
This relates both to the nature of the student body and the resources available to faculty.

Students at Harvard are pretty uniformly highly gifted and highly motivated and with strong academic backgrounds and social skills. [When I was a TA at Princeton I did encounter a few exceptions!] Given the right environment and prods they will rise to a challenge.
In contrast, at UQ [which is one of the better universities in Australia and as our management and marketing department endlessly reminds us is "ranked" in the top 100 globally] physics students are quite diverse in their gifting, their academic backgrounds, motivations, and work ethic.
Getting them to "own their education" is not easy.
Yet, some of my colleagues in Physics at UQ have implemented some of Mazur's ideas about the "flipped classroom" and "peer based instruction".

Previously I posted about how I gave up on some innovations, particularly in assessment (relatively tame compared to Mazur's) for an advanced fourth year class due to complaints from students.

What about resources?
Mazur was given a year off teaching in order to develop the course. He seems to teach it with a colleague (whose only responsibility is teaching) and to have one full-time TA for every 20 students.
Mazur also runs a successful research group which probably partly runs on "auto pilot" because it is populated with highly gifted and motivated grad students and postdocs.
Yet, he did offer two valuable qualifiers. First, a similar course is being implemented at University of Central Florida which is much less resource rich! Second, his work is "front loaded", i.e. extensive in setting up the course, but less to actually run it.

These differences from Harvard are not reason to keep with old methods that are of limited value. They just should be kept in mind when trying to implement them.

These innovations also illustrate to me how problematic MOOC's are. From traditional instruction, they keep what does not work [lectures] and throw away what does work [personal interaction between students in small groups].

Answer the question!

Politicians are famous for not answering the question.
A colleague recently told me how in a Q and A session with some university managers it was amazing the ability that they had to not answer the question.
Undergraduate students in the humanities often write essays that don't answer the question being asked.

If at a seminar a nervous young graduate student misunderstands a question and struggles to answer it that is understandable. Similar things sometimes happen in job interviews.

However, this post is about something different, that is not excusable. Unfortunately, I am in the thick of reviewing a bunch of research grant proposals, from a range of fields. Here is my rant.
Previously, I posted about how the question "What are your major contributions to a research field?" gets irrelevant answers involving grants, job offers, journal impact factors, and citations, ....

I have now encountered a few more, paraphrased below.

What scientific hypothesis is this project testing?
That the project will make a significant contribution to the field (seriously!). It will generate new knowledge and insights.

What is the specific role of the investigator Professor Jones in the project?
He has published a lot of highly cited papers.

What is your most significant scientific accomplishment?
This excellent project will generate new insights and test key hypotheses in the field...

I should point out that applicants were not asked these questions, but rather they are writing something under a specific section heading. But, it helpful to think as the section heading as a question.

So when you are asked a question, listen carefully, pause, think, and then answer the question. Don't answer a different question, even if you think what you have to say is important.