## EPJ H Highlight - Legacy of a molecular dynamics trailblazer

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- Published on 04 November 2022

Computer simulations meet biochemistry

Life is motion. And so, to understand how living organisms function, one must understand the movement and reorganisation of the atoms and molecules that compose them. The approach called “molecular dynamics simulation” enables scientists to use computer programmes to simulate the dynamic motion of all the atoms in a molecular system as a function of time.

In a new paper in * EPJ H: Historical Perspectives on Contemporary Physics*, Daniele Macuglia from Peking University in Beijing, China, Benoît Roux from the University of Chicago, USA, and Giovanni Ciccotti from the University of Rome, Italy, explain how the theoretical chemist Martin Karplus and his team carried out the first molecular dynamics simulation of a large biological molecule, a protein, deeply impacting biology and the physical sciences in the 20th and 21st centuries. Currently, machine learning researchers are using biomolecular simulations to better understand their time-dependent motions and the function that governs the forces between them.

## EPJ H Highlight - Fermi’s ground-breaking figure

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- Published on 22 September 2022

How the radial wave function transformed physics

One way to better understand an atom is to shoot a particle at it and infer the atom’s properties based on how the particle bounces off it. In the mid-1930s, the physicist Enrico Fermi showed that one measurable number – the scattering length – illuminated everything that could be known about an electron scattering off an atom, or a neutron scattering off a nucleus. In a new paper in * EPJ H: Historical Perspectives on Contemporary Physics*, Chris Gould from North Carolina State University in Raleigh, USA, explains how Fermi’s simple sketch of a radial wave function laid the groundwork for a better understanding of low energy scattering phenomena, and led in turn to the concept of the pseudopotential, widely used in many areas of physics, including ultracold atom research and studies of qubits in realisations of quantum computers.

## EPJ H Highlight - A step towards quantum gravity

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- Published on 11 August 2022

Resolving the problem of time

In Einstein’s theory of general relativity, gravity arises when a massive object distorts
the fabric of spacetime the way a ball sinks into a piece of stretched cloth. Solving Einstein’s equations by using quantities that apply across all space and time coordinates could enable physicists to eventually find their ‘white whale’: a quantum theory of gravity. In a new article in * EPJ H: Historical Perspectives on Contemporary Physics*, Donald Salisbury from Austin College in Sherman, USA, explains how Peter Bergmann and Arthur Komar first proposed a way to get one step closer to this goal by using Hamilton-Jacobi techniques. These arose in the study of particle motion in order to obtain the complete set of solutions from a single function of particle position and constants of the motion.

## EPJ H Highlight - Revisiting the history of CPT theorem

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- Published on 24 May 2022

A new review looks at an important and often overlooked aspect of physics that suggested symmetry in the particle zoo and how it could be broken.

At the beginning of the 20th century the development of quantum mechanics and relativity changed the face of physics forever. While much has been written about this revolution, less is known about the development of the CPT theorem — vital to quantum field theory and modern physics.

A new paper published in *EPJ H* and authored by Alexander S. Blum and Andres Martınez de Velasco from Max Planck Institute for the History of Science, Berlin, looks at the roots of CPT theorem and its influence over modern physics.

## EPJ H Highlight - Documenting the first attempt at a gravitational-wave observatory in Europe

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- Published on 21 March 2022

EUROGRAV was set to be a network of gravitational wave antennas in Europe. A new paper looks at the reasons it never happened.

First predicted in Einstein’s theory of general relativity, gravitational waves are tiny ripples in spacetime generated by titanic and powerful cosmic events. The great physicist believed that no equipment would ever be sensitive to detect these faint cosmic ripples. Fortunately, Einstein was wrong, but that doesn’t mean that the detection of gravitational waves has been easy.

The history of a planned array interferometer gravitational wave detectors to be built in Europe during the late 1980s, the reasons this failed, and the parallels with current detectors, are documented in a new paper published in *EPJ H*, authored by Adele La Rana, University of Verona, and INFN Section of Sapienza University, Italy.

## EPJ H Highlight - Acknowledging Fermi’s contributions to early quantum statistics

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- Published on 18 March 2022

Enrico Fermi’s ideas played a key role in the origins of quantum statistics, but so far, they have been largely overlooked in historical analysis

Within large systems of identical fermions, Fermi-Dirac statistics describes how identical fermions may never occupy the same quantum state. First introduced by Italian physicist, Enrico Fermi, this concept was a key step in our early understanding of quantum mechanics – yet so far, Fermi’s contributions have been largely overlooked in historical analysis. Through new research published in *EPJ H*, Enric Pérez and Joana Ibáñez, both at the University of Barcelona, Spain, offer a critical analysis of Fermi’s ideas, and assess their immediate impact on our early conceptions of quantum mechanics.

## EPJ H Highlight - Assessing the modern relevance of Schrödinger’s time reversal

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- Published on 18 March 2022

Erwin Schrödinger’s landmark 1931 paper provided a basis for several important conceptions in quantum mechanics, but a new translation and commentary highlights its continuing relevance in modern statistical nanophysics

In 1931, Erwin Schrödinger published a ground-breaking paper, named ‘On the Reversal of the Laws of Nature.’ The study aimed to prove the possibility of a classical structure governed by probability, which displays a property called ‘time reversal symmetry’: where the physical laws underlying the system would remain the same, whether time flowed forwards or backwards. A new English translation of Schrödinger’s paper, published in *EPJ H*, has now been made by Raphael Chetrite at the University of Nice Sophia Antipolis; Paolo Muratore-Ginanneschi at University of Helsinki; and Kai Schwieger at iteratc GmbH Stuttgart. In an additional commentary, the team emphasise the relevance of his intuitions for modern developments in statistical nanophysics.

## EPJ H Highlight - Deciphering Boltzmann’s response to Loschmidt’s paradox

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- Published on 28 February 2022

New analysis offers a clarified translation and detailed commentary of Boltzmann’s original reaction to Loschmidt’s paradox

In 1876, Austrian physicist Josef Loschmidt published his ‘reversibility paradox,’ arguing that the time-symmetric processes demanded by fundamental physics are at odds with the second law of thermodynamics. A few months later, Loschmidt’s friend Ludwig Boltzmann, renowned for his statistical interpretation of thermodynamics, published his reaction to the paradox. However, the convoluted nature of his response has long remained baffling to modern readers. Through new analysis published in *EPJ H*, Olivier Darrigol at the CNRS in France clarifies Boltzmann’s main points, through a new translation and detailed commentary of his 1877 text.

## EPJ H Highlight - A shifting approach to modelling phase transitions

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- Published on 25 January 2022

Between the years 1937 and 1970, physicists went from taking a ‘naturalistic’ approach to modelling phase transitions, to a ‘caricature’ approach – which incorporated far less realistic models. New analysis of this period provides new insights into this profound shift in thinking.

Models of complex physical systems are a central aspect of theoretical physics. Yet despite their importance, there isn’t a single, overarching approach to the practice: meaning researchers in separate branches of physics will rarely use the same methods to construct their models. In one particularly interesting case, approaches for modelling phase transitions underwent a drastic transformation, between the years of 1937 and 1970. In a new paper published in *EPJ H*, Martin Niss at Roskilde University, Denmark, characterises this fundamental change in thinking.

## EPJ H Highlight - Black hole thermodynamics: a history from Penrose to Hawking

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- Published on 05 October 2021

New research explores the historical context of Penrose’s theory of black hole energy extraction, and how it inspired collaborations across political boundaries: ultimately leading to Stephen Hawking’s celebrated theory of black hole radiation.

In 1969, English physicist Roger Penrose discovered a property which would later allow for a long-awaited link between thermodynamics, and the far stranger mechanics of black holes. Through new analysis published in *EPJ H*, Carla Rodrigues Almeida, based at the University of São Paulo, Brazil, sheds new light on Penrose’s motivations and methods, and explores their historical influence on the groundbreaking discovery of Hawking radiation.