Condensed concepts

I want to begin by stating some hypotheses. Some may be obvious. Others may be contentious. I will number them so that people can easily make comments about specific ones. The underlying issues are illustrated in recent debates about the possible origins of covid-19. 1. Systematic critical thinking is essential to scientific progress and public policy. Healthy doses of skepticism can be valuable. 2. Science progresses well by making multiple hypotheses  and examining carefully what evidence is consistent with each of the hypotheses. This is something that Murray Gell-Mann wished someone had told him when he was twenty years old. 3. Transparency is essential to science. People need to share data, including primary data. The more that such data is publicly available the better. This is what open science advocates.  4. Science is built on ethical conduct, both implicit and explicit. It is important that declarations of conflicts of interest are not just a box-ticking exercise. 5. Scienti

 A metal and a band insulator are distinct states of matter.  A suitable order parameter is the Drude weigh t, defined as the integral over frequency of the frequency-dependent conductivity at zero temperature. How might a single material undergo a transition between a band insulator and a metal?  The schematic below (from Kittel) illustrates three distinct possibilities for the band structure and band fillings. (a) Band insulator. The bands do not overlap and the lower band is full. This occurs if there is an integer number of electrons per primitive cell in the crystal.  (b) Metal I. The bands overlap and the system is a metal regardless of the number density of electrons. (c) Metal II. The bands do not overlap. There is a non-integer number of electrons per primitive cell. Suppose the number of electrons is fixed, (i.e. there is no chemical doping). How can a metal-insulator transition occur when some physical parameter (such as pressure) changes? Scenario A. There is no structural

 It is no surprise to most readers that I do not believe that "the university is a (billion-dollar) business and so should be run accordingly." I reject the " entrepreneurial model " and think this has been a disaster, particularly for Australian and UK universities. Universities are not a business. Universities are also not a family, a finishing school for wealthy children , a community service organisation, a job training school, or a government department, ... Universities are universities. They are about thinking. Previously, I have posted that  management is not leadership , and how the "full economic cost model" in the UK has been a disaster. But, having said that it might surprise some readers that it is not unusual for me to look at "business" literature on leadership, project management, and managing employees. The Harvard Business Review (HBR) is a particularly good source of helpful and stimulating ideas. Previously, I have mentioned a

What is condensed matter physics about?  In his beautiful book, The Problems of Physics (originally published in 1987), Leggett has a nice chapter about condensed matter physics,  Physics on a human scale . The abstract begins: This chapter argues that the widespread notion that the discipline of condensed matter physics is devoted to deriving the properties of complex many-body systems from that of their atomic-level components is a myth , and that the analogy of map-making is much more appropriate. Here are some quotes that clarify Leggett's argument. a number of cases, particularly in the traditional areas of the physics of gases and crystalline solids, in which a model which treats the behaviour of the whole as essentially just the sum of that of its parts (atoms or electrons) has been quite successful; and a few more in which, even if a ‘one- particle’ picture fails, a description in terms of pairs of particles interacting in a way which is not particularly sensitive to the