David Thouless obituary by J Michael Kosterlitz (An obituary of a Nobel laureate by a Nobel laureate)

David Thouless, working with Michael Kosterlitz, overturned a theory that had held sway for at least 30 years. 

David Thouless, who has died aged 84, won half of the 2016 Nobel prize in physics, the other half being shared by Duncan Haldane and me. David and I solved an interesting theoretical problem by introducing some new ideas with important implications, and so unknowingly created a new field in the discipline.

Our main innovation came from topology: the mathematical study of the properties preserved when objects are twisted, stretched or crumpled, properties that change only step by step. From 1972 to 1974 we sought a theoretical explanation of a phase transition, a change of state such as water turning into steam and back to water again. The one we examined was from a high-temperature disordered phase, a gas, to a low-temperature partially ordered one, a liquid, in an arrangement operating in two dimensions – a thin film or layer of something not supported by anything else. Previously it had been thought for very good reasons that such a phase transition could not happen in two dimensions, but only in three or more.

David and I managed to overturn that at least 30-year-old theory. We demonstrated that superconductivity, an electrical current flowing with no resistance, could occur at low temperatures in a very thin film. This opened up a hitherto unknown way of doing physics, revolutionised knowledge about phase transitions and later led to understanding topological insulators, which in turn may be used for developments including quantum computers, operating at a much higher level of complexity than conventional ones.

We took up the challenge of a conflict between theory and observation, and were the ideal pair to do so. David was a physical and mathematical genius who knew and understood all the conventional wisdom that said a transition could not exist, but had a very flexible mind that was always prepared to discard conventional wisdom if necessary. On the other hand, I was an energetic postdoctoral researcher looking for any interesting problem in any branch of physics. David talked about concepts that were all completely new to me, and left my head spinning.

After refining the calculations that I took back to him, he decided that we should write them up for publication. The resulting couple of articles in the Journal of Physics C: Solid State Physics did not engender much interest for some years, but in 1978 theory and experiment came together, and in the early 1980s David undertook further research with Haldane.

By the time the Nobel for the three of us came, four decades after the start of the work, David’s mind was affected by dementia. However, he was well enough to enjoy every moment of the Nobel week in Stockholm that we experienced together. I hear that he subsequently enjoyed leafing through the album of photos and mementos assembled by his family.

Born in Bearsden, a northern suburb of Glasgow, David was the son of Robert Thouless, a psychologist and academic, and his wife, Priscilla (nee Gorton), a teacher. At the age of four David taught himself to read, write and count to large numbers. His education started at St Faith’s school for girls in Cambridge, where he was taught with pupils who were two years older. He then attended a boys’ prep school and Winchester college.

From there he went to Trinity Hall, Cambridge, and, following his bachelor’s degree in mathematics, gained a PhD in theoretical physics under Hans Bethe at Cornell University, in Ithaca, New York (1958). After a year at the Lawrence Radiation Laboratory in Berkeley, California, he returned to Britain as a research fellow at Birmingham University (1959-61), working under Rudolf Peierls.

At Churchill College, Cambridge (1961-65), David was director of studies in physics and a university lecturer. He then went to Birmingham University as professor (1965-78), Yale (1979-80), and the University of Washington (1980-2003) in Seattle.

As well as being a giant of theoretical physics, David was a deeply religious and very moral person. He never let others down and always kept all promises, regardless of how inconvenient they might be.

An initial accidental encounter with him in Cambridge in 1962 had left me very impressed with his grasp of advanced mathematics. I got to know him properly at Birmingham in 1970, and began to appreciate the loneliness of a man who did not understand that he was much cleverer than most people he found himself talking to.

David wrote two books on quantum subjects, and with me a chapter in the collection 40 Years of Berezinskii-Kosterlitz-Thouless Theory (2013). He was elected a fellow of the Royal Society (1979) and a member of the US National Academy of Sciences (1995), and awarded the Wolf Prize in Physics (1990) and the Dirac Medal (1993).

In 1958 he married Margaret Scrase, who went on to become a professor of pathobiology. She survives him, along with two sons, Michael and Christopher, and a daughter, Helen.

Source - The Guardian

Scientists Working on a Periodic Table for Ecology

An adult male Green Basilisk lizard hangs out in a tree in the rainforest of Costa Rica. A team of ecologists has been working to summarise and simplify the idea of niche to eventually predict how different ecosystems will evolve as a result of climate change.

In 1867, Russian chemist Dmitri Mendeleev was writing a chemistry textbook, but it wasn't going well. At the time, only 56 elements were known to exist, but Mendeleev was having a tough time figuring out how to organize them in a way that would demonstrate their relationships to each other. But then, as legend has it, he had a dream which showed him not only how to organize the known elements by atomic weight and chemical reactivity, but also allowed him to predict other elements that had yet to be discovered.

Mendeleev accomplished in this single night's sleep what scientists from pretty much every discipline would kill for: a straightforward, predictive way to organize and depict complicated information. For ecologists, for instance, this might be a model that could distill the enormous complexity of how an organism functions within the ecological community in which it lives.

Scientists have been intrigued by the idea since the early 1970s, when Robert MacArthur, an evolutionary ecologist, had the idea of ordering organisms similarly to chemistry’s periodic table, in which elements are organized by the combination of certain chemical properties, the configuration of their electrons and their atomic number (number of protons).

So in 2015, a group of ecologists published a paper in the journal Ecology Letters in order to take a stab at what had long been discussed but had never been attempted: creating a periodic table for ecological niches, similar to the periodic table for elements in chemistry, which would essentially represent the complex roles different species play within a community. This could include how they reproduce, what they do for food and shelter, how they protect themselves, how they interact with their living and nonliving neighbors, and so on.

The approach of producing periodic tables of niches is a way to organize species according to sets of functional traits that have known influences for ecological performance. It is an approach that allows us to make an abstract concept approachable for empirical study.

Instead of looking at all the possible demands a species might make on its living situation — acceptable ranges of nutrients like nitrogen and phosphorous, temperature, moisture, soil type (and one species might have hundreds of requirements) — the authors chose just a few essential properties to capture the idea of a niche: diet, habitat, life history, metabolism and defense mechanisms.

The Lizard Model

The research team published a study in November 2017 in The American Naturalist as a way to begin the task of putting this idea to work on ... the world's lizards. They compiled as much data as they could on 134 lizard species, from 24 of the 38 lizard families living on four of Earth's continents today. Then they took their five essential properties of niche, listing between seven and 15 variables for each, and then began crunching the numbers.

Through creating models of their data, they found what they might have expected to find: that lizards are like many other organisms — they evolve to interact with their habitats, forage for food, and observe active and inactive times each day, no matter where they live. For instance, lizards that fill a certain niche in South America have similar traits to lizards that fill similar niches in Australia, Africa or America, even though they're not very closely related, evolutionarily speaking.

Because we can see similarities between lizards that occupy similar niches in completely different places, summarizing and simplifying the idea of niche in this way might eventually help researchers to predict how different ecosystems will evolve as a result of climate change.

Simplifying the Structure

The researchers have used this lizard study to confirm that it may just be possible to simplify the idea of niche from hundreds of dimensions to just five. So, while we don't have an ecological periodic table just yet, perhaps it's not too far off.

Source - HowStuffWorks.com

2018 global CO2 growth 4th highest on record

According to National Oceanic and Atmospheric Administration (NOAA) data, global growth in atmospheric carbon dioxide (CO2) in 2018 was the 4th-highest in 60 years of record-keeping.

By the end of 2018, NOAA’s atmospheric observatory at Mauna Loa, Hawaii, recorded the fourth-highest annual growth in the concentration of atmospheric carbon dioxide (CO2) in 60 years of record-keeping. Carbon dioxide grew by 2.87 parts per million (ppm) at the mountaintop observatory during 2018, jumping from an average of 407.05 ppm on January 1, 2018, to 409.92 on January 1, 2019, according to a new analysis of air samples collected by NOAA’s Global Monitoring Division (GMD).

That means three of the four highest annual increases have occurred in the past four years.

A chart showing the steadily increasing concentrations of carbon dioxide in the atmosphere (in parts per million) observed at NOAA’s Mauna Loa Observatory over the course of 60 years. Measurements of the greenhouse gas began in 1959.

NOAA captures and analyses air samples from a network of observatories and collecting stations around the world. Situated close to the top of Hawaii’s Mauna Loa volcano, NOAA’s Mauna Loa Observatory samples “background” samples of Northern Hemisphere air. Mauna Loa is the oldest in the network and has the longest record of CO2 measurements.

The increase observed in 2018 ranks behind only 2016’s record jump of 3.01 ppm, 2015’s near-record increase of 2.98 ppm and 1998’s growth of 2.93 ppm/yr in the modern record. The record dates to March 1958 when David Keeling of the Scripps Institution of Oceanography started measuring atmospheric CO2 in what’s known as the Keeling Curve.

Globally averaged CO2 levels increased by a similar amount to what was observed on Mauna Loa during 2018.

Carbon dioxide is by far the most important of the five primary greenhouse gases – carbon dioxide, methane, nitrous oxide, carbon monoxide and ozone – both in total amount and the rate of increase. When the first Mauna Loa samples were analyzed in 1958, CO2 had already risen 35 ppm from the pre-industrial level of 280 ppm. In the past 60 years, CO2 has increased by an additional 95 ppm to 410 ppm today.

In the last two decades, the rate of increase has been roughly 100 times faster than previous natural increases, such as those that occurred at the end of the last ice age 11,000-17,000 years ago. Today’s rise of CO2 is dominated by human activities. It’s not from natural causes.

About NOAA greenhouse gas monitoring

NOAA tracks five primary greenhouse gases (CO2, CH4, CO, N2O, and SF6) that warm the planet by trapping heat from Earth’s surface that would otherwise escape into space, including two chlorofluorocarbons controlled by the Montreal Protocol that damage Earth’s ozone layer. All five gases account for about 96 percent of the atmosphere’s increased heat-trapping capacity since 1750, another climate indicator tracked by NOAA.

Source - EarthSky.org