Trust is a core value in science, trust in data, analysis, concepts, models. This is achieved in physics by open publishing, scientific discourse, testing, repeating experiments, asking critical questions and designing new tests. Fortunately, science is self-correcting in the long term. Hype includes predictions which sensationalise scientific discoveries and exaggerate the future impact. Increasing competition for funding, visibility or job security can make this more attractive. But it also erodes trust in science by the public and investors and has negative social effects on us the researchers. How can we balance them?
Saturday, June 29, 2024
Quantum BS: piling it higher
Wednesday, June 26, 2024
Emergence talk at University of the Philippines
Today I am giving a seminar on emergence at the University of Philippines Los Banos, in the Institute of Mathematical Sciences and Physics.
Here are my slides.
Friday, June 21, 2024
10 key ideas about emergence
Consider a system comprised of many interacting components.
1. Many different definitions of emergence have been given. I take the defining characteristic of an emergent property of the system is novelty, i.e, the individual components of the system do not have this property.
2. Many other characteristics have been associated with emergence, such as universality, unpredictability, irreducibility, diversity, self-organisation, discontinuities, and singularities. However, it has not been established whether these characteristics are necessary or sufficient for novelty.
3. Emergent properties are ubiquitous across scientific disciplines from physics to biology to sociology to computer science. Emergence is central to many of the biggest scientific challenges today and some of the greatest societal problems.
4. Reality is stratified. A key concept is that of strata or hierarchies. At each level or stratum, there is a distinct ontology (properties, phenomena, processes, entities, and effective interactions) and epistemology (theories, concepts, models, and methods). This stratification of reality leads to semi-autonomous scientific disciplines and sub-disciplines.
5. A common challenge is understanding the relationship between emergent properties observed at the macroscopic scale (whether in societies or in solids) and what is known about the microscopic scale: the components (whether individual humans or atoms) and their interactions. Often a key (but profound) insight is identifying an emergent mesoscopic scale (i.e., a scale intermediate between the macro- and micro- scales) at which new entities emerge and interact with one another weakly.
6. A key theoretical method is the development and study of effective theories and toy models. Effective theories can describe phenomena at the mesoscopic scale and be used to bridge the microscopic and macroscopic scales. Toy models involve just a few degrees of freedom, interactions, and parameters. Toy models are amenable to analytical and computational analysis and may reveal the minimal requirements for an emergent property to occur. The Ising model is a toy model that elucidates critical phenomena and key characteristics of emergence.
7. Condensed matter physics elucidates many of the key features and challenges of emergence. Unlike brains and economies, condensed states of matter are simple enough to be amenable to detailed and definitive analysis but complex enough to exhibit rich and diverse emergent phenomena.
8. The ideas above about emergence matter for scientific strategy in terms of choosing methodologies, setting priorities, and allocating resources.
9. An emergent perspective that does not privilege the parts or the whole can address contentious issues and fashions in the humanities and social sciences, particularly around structuralism.
10. Emergence is also at the heart of issues in philosophy including the nature of consciousness, truth, reality, and the sciences.
Tuesday, June 11, 2024
The interplay of ecological and evolutionary dynamics: immigration, extinction, and chaos (and DMFT?)
"Ecological and evolutionary dynamics are intrinsically entwined. On short timescales, ecological interactions determine the fate and impact of new mutants, while on longer timescales evolution shapes the entire community."
Spatiotemporal ecological chaos enables gradual evolutionary diversification without niches or tradeoffs Aditya Mahadevan, Michael T Pearce, and Daniel S Fisher
Understanding this interplay is "one of the biggest open problems in evolution and ecology."
New experimental techniques for measuring the properties of large microbial ecosystems have stimulated significant theoretical work, including from some with a background in theoretical condensed matter physics. For an excellent accessible introduction see:
Understanding chaos and diversity in complex ecosystems – insights from statistical physics
This is a nice 2.5-page article by Pankaj Mehta at the Journal Club for Condensed Matter. He clearly introduces an important problem in theoretical ecology and evolution and describes how some recent work has provided new insights using techniques adapted from Dynamical Mean-Field Theory, which was originally developed to describe strongly correlated electron systems.
Here are just a few highlights of the article. It may be better to just read the actual article.
Fifty years ago, Robert May "argued that the more diverse an ecosystem is (roughly defined as the number of species present), the less stable it becomes." He derived this counter-intuitive result using a simple model and results from Random Matrix Theory. This is an example of an emergent property: qualitative difference occurs as a system of interacting parts becomes sufficiently large.
"One major deficiency of May’s argument is that it does not allow for the possibility that complex ecosystems can self organize through immigration and extinction. The simplest model that contains all these processes is the Generalized [to many species] Lotka-Volterra model (GLV)".
"Despite its simplicity, this equation holds many surprises, especially when the number of species is large".
Another case of how simple models can exhibit complex behaviour.
One special case is when the interactions are reciprocal – how species i affects species j is identical to how species j affects species I. "In the presence of non-reciprocity the system can exhibit complex dynamical behavior including chaos." Understanding this case was an open problem until the two papers reviewed by Mehta. For a detailed but pedagogical introduction see:
Les Houches Lectures on Community Ecology: From Niche Theory to Statistical Mechanics, Wenping Cui, Robert Marsland III, Pankaj Mehta
This is relevant to understanding the origin of the fine grained diversity observed in sequencing experiments of microbial ecosystems.
Aside: de Pirey and Bunin "derive analytic expressions for the steady-state abundance distribution and an analogue of the fluctuation-dissipation theorem for chaotic dynamics relating static and dynamics correlation functions."
"Using a DMFT solution, they derive a number of remarkable predictions... in the chaotic system the species fall into two groups: species at high abundances and species at low abundances near the immigration floor. de Pirey and Bunin show that even in the chaotic regime, the number of high abundance species in the ecosystem will always be less than the May stability bound. This result is quite surprising since it suggests that ecosystems self-organize in such a way that the high abundance species still follow May’s diversity bound even when they are chaotic."
Saturday, June 1, 2024
Should Ph.D. students choose to teach?
In Australia, most Ph.D. students are fully funded by scholarships to allow them to focus on their research. This is unlike in the USA where many students must be TAs (teaching assistants) to be paid.
In most Australian universities, such Ph.D. students can earn extra income by being tutors (same as TAs) for undergraduate courses. Many do, as earning extra money is attractive. Ph.D. students doing teaching saves universities tons of money as it means they don't need to hire and pay permanent academic staff to do this tutoring.
What is my advice to students who have this option? Here are some of the advantages and disadvantages for a Ph.D. student doing such tutoring.
Advantages
You earn additional income.
Having teaching experience listed on your CV may help you get a faculty position at some institutions. For example, in Australia, this seems to be almost a pre-requisite these days. Furthermore, if you can be innovative, and get high student evaluations, that may be viewed favourably. But that really concerns lecturing and not tutoring.
You usually learn a lot from teaching, even lower-level courses.
It can be enjoyable and satisfying. It can provide a break from thinking just about your Ph.D. research.
If you are fortunate enough to eventually get a faculty position this experience will make it easier to handle the formidable challenges of starting out teaching.
It may create some goodwill towards you in your department. You may be seen as a team player and a good departmental citizen.
You may need the money. For example, if you are supporting a family or if you are from a Majority World country and want to send money home to extended family.
Disadvantages
Foremost, it can consume a large amount of time and energy that reduces your research productivity. It reduces your mental space. You may lose research momentum and not complete your Ph.D. on time.
There can be a significant financial opportunity cost. Suppose that doing the teaching delays you completing your Ph.D. by six months. The lost six-month salary will probably be much greater than the amount you earned from doing the teaching.
It can be frustrating to deal with students who are not that interested in learning and are only concerned with grades. Furthermore, there may be the added stress of having to deal with students who make formal complaints about your teaching or their grades.
It may not add a lot to your CV, particularly if your student evaluations are average. They will probably be average or even below average since you are starting out.
If you don't do a stellar job and/or there are a few disgruntled students your reputation in the department may suffer, perhaps unjustly.
On balance, I think it depends on the individual: their personal financial situation, personality, career goals and stage in the Ph.D. In some cases, I encourage people to do this, although only for one or two semesters. In other cases, I discourage it. The main thing is to make a well-informed decision which takes into account the pros and cons.
Students also need to be wary of the vested interests of faculty and university management that will push them towards teaching, possibly against the student's best long-term interests.
Aside. I often forget what posts I have written in the past. I really thought I had written this post before. All I could find is one on Should postdocs teach?
I welcome comments, particularly from current and former Ph.D. students who have negotiated this issue. What would you advise?
Friday, May 31, 2024
Straining gnats and swallowing camels on campus
The world is being run by accountants, lawyers, and marketing consultants. They work for corporations, universities, trade unions, and government. Some are "rent seekers" and parasites who project themselves as standing for justice and fairness.
We also live in a world where people are not allowed to make even small mistakes.
These painful realities were highlighted to me this week in an email some colleagues received from the President of their university.
"I am writing to advise staff about the outcome of a pay review initiated in October 2021 and the actions taken as part of this to further strengthen our pay systems and processes.
The University commenced this external review to ensure our staff are paid accurately and in accordance with our Enterprise Agreement (EA) applicable at the time.
The review took 18 months. How much staff time and money was spent to engage these external consultants on this review?
While staff were paid for the time they worked, the review identified 2 areas of our EA were not always correctly applied. These relate to the minimum hours of engagement for casual academic and casual professional staff and the use of a different pay rate for casual academic staff with a relevant PhD.
As a result, the University has determined that over a 7-year period (January 2017 to December 2023), an amount of $7.88 million (excluding superannuation and interest) should have been paid to 9743 staff. The median amount to be paid is $243.03.
Note. This corresponds to staff being underpaid by less than one dollar per week!
I unreservedly apologise to those staff who have been affected by these errors – they should not have happened. I want to assure our community that affected staff will receive all the pay due, including superannuation and interest for the relevant period.
This week, we are writing individually to affected current staff outlining the payment due, with these payments to commence from 14 June.
We will also be writing individually to affected former staff outlining the payment due and the process for remediation.
A comprehensive program is underway to upgrade our systems and processes to further ensure ongoing pay accuracy. Actions being taken include the introduction of a whole-of-Univ timesheet system, compulsory training for managers and staff and additional fortnightly payroll reporting.
Does this mean faculty will now fill out time sheets?
We are also investing further in our HR systems, with new time and attendance and payroll systems planned.
Sounds like a whole new layer of bureaucracy.
Throughout this process we have worked closely with the Office of the Fair Work Ombudsman and have advised them of these outcomes.
Again, I apologise that this has occurred and reaffirm our commitment to ensuring staff are appropriately and accurately paid for the work they do on behalf of the University."
Meanwhile I don't hear of any external reviews or apologies for the treatment by university management of people such as Gerd Shroder-Turk, Drew Pavlou, Paul Frijters, or James Allan, ...
Two thousand years ago the following was written.
“Woe to you, teachers of the law and Pharisees, you hypocrites! You give a tenth of your spices—mint, dill and cumin. But you have neglected the more important matters of the law—justice, mercy and faithfulness. You should have practiced the latter, without neglecting the former.
You blind guides! You strain out a gnat but swallow a camel.
Woe to you, teachers of the law and Pharisees, you hypocrites! You clean the outside of the cup and dish, but inside they are full of greed and self-indulgence."
Friday, May 24, 2024
More superconductivity in Hollywood
I wrote a post about superconductivity being central to the plot of the cult-classic movie, Joe Versus the Volcano. A commenter on the post kindly pointed out that the movie Avatar also features superconductivity. It is nicely captured in this scene.
The Wikipedia entry for Unobtanium is interesting as it describes the long history of the term, predating the movie by decades. I had not heard the term before. It does capture much of the hype and fantasy about research in "advanced materials".
About Avatar the entry states
In the 2009 film Avatar,[23] "Unobtanium" is the common name of a rare-earth mineral found exclusively in the exomoon Pandora (where the movie takes place, being the fifth moon of the gas giant Polyphemus, which orbits Alpha Centauri A), highly prized (and priced) because of its application as a powerful superconductor material; because of its unusual magnetic properties, entire mountains with high concentrations of unobtanium "levitate" in the atmosphere of Pandora.
What does this movie tell us about the modern university?
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