EPJ Plus Focus Point Issue: Machine Learning for Materials Physics: From Pitfalls to Best Practices
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- Published on 02 September 2025
Guest Editors: Domenico Di Sante and Anirvan M. Sengupta
The fusion of machine learning (ML) and materials science is opening unprecedented opportunities in research and innovation. As traditional methods struggle to face the complexity of modern materials and their vast datasets, ML is intervening to accelerate discovery, optimize properties, and shed light on intricate phenomena.
In the Focus Point "Machine Learning for Materials Physics: From Pitfalls to Best Practices" six studies showcase how ML is permeating this field. From modeling quantum many-body systems to predicting new superconducting materials, these papers highlight how ML algorithms are driving efficiency, enhancing precision, and offering new possibilities. This Focus Point also addresses key challenges, such as interpretability and scalability, highlighting the need for interdisciplinary collaboration between ML experts and materials scientists.
Dive into this special issue to explore the cutting-edge innovations reshaping materials science—and see how ML is revolutionizing our understanding of the physical world.
All articles are available here and are freely accessible until 31 October 2025. For further information, read the Editorial.
EPJ Plus Focus Point Issue: Higher Derivatives in Quantum Gravity: Theory, Tests, Phenomenology
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- Published on 29 August 2025
Guest Editors: Luca Buoninfante, Andrea Giusti, Aaron Held, Benjamin Knorr & Alessia Platania
Quantizing General Relativity using standard perturbative quantum field theory results in a perturbatively non-renormalizable theory. This has led to a variety of alternative approaches to quantum gravity, each based on different assumptions, ideas, and quantization techniques. A common feature in many of these approaches is the appearance of higher-derivative operators, alongside the Einstein-Hilbert action, which play a crucial role in classifying quantum-gravitational effects in an effective field theory fashion. This focus point issue brings together different perspectives on the role of higher derivatives in quantum gravity. It explores their theoretical role and implications in different approaches as well as their impact on phenomenology. The issue collects perspectives on how higher-derivative terms appear in quantum gravity theories and what insights they may offer into the fundamental nature of spacetime.
All articles are available here and are freely accessible until 31 October 2025. For further information, read the Editorial.
EPJ Plus Highlight - Readying photoacoustic spectroscopy for studies of advanced nanostructures
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- Published on 22 August 2025
Innovations to the existing photoacoustic spectroscopy setup could make the technique far better suited to studying advanced, specially engineered nanostructures
When a material sample absorbs light, its resulting thermal expansion can generate an acoustic wave in the surrounding air. Named the photoacoustic effect, this phenomenon is now widely exploited in experimental physics to measure the wavelengths absorbed by materials via the sound waves they emit. This technique is called photoacoustic spectroscopy (PAS), and has now been applied across fields from gas sensing and biomedical imaging to observations of ultrafast reactions. So far, however, PAS has proven less reliable when studying photoacoustic responses in specially engineered nanostructures.
Through new research published in EPJ Plus, Emilija Petronijevic and colleagues at Sapienza University of Rome introduce several improvements to the PAS setup, making it better suited to measuring intricate nanoscale structures. Their innovations could lead to powerful new methods for measuring features like single and aggregated nanoparticles, ultra-thin films and metasurfaces, and nanowire assemblies – currently at the leading edge of experimental physics.
EPJ Plus Focus Point Issue: Accelerator-based Photon Science Strategy, Prospects and Roadmap in Europe
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- Published on 23 July 2025
Guest Editors: Rafael Abela, Thomas Tschentscher, Jean Susini, Gastón García
The League of European Accelerator-based Photon Sources (LEAPS) is an alliance of all synchrotron and free electron laser user facilities in Europe. These facilities are an essential element of the scientific landscape in Europe and elsewhere, undergoing fast and profound changes of great relevance for the scientific community and with a substantial societal impact. This focus point issue features the current status and future scientific strategy of LEAPS. The collection includes papers about most of the LEAPS members, along with two specific papers on the LEAPS general strategy and the critical aspect of data.
All articles are available here and are freely accessible until 22 September 2025. For further information, read this highlight.
EPJ Plus Highlight - Hybrid algorithm uncovers robust scar states for quantum computing
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- Published on 14 July 2025
An algorithm that merges classical and quantum computing resources could help reveal robust quantum states hidden within chaotic, noisy systems
Since today’s quantum computing architectures are inherently noisy, they still struggle to generate large amounts of entanglement between qubits. One promising solution could be to target quantum scar states, which can emerge in complex, many-body systems. These states are unusually simple compared with their chaotic surroundings, and they may offer a more robust way to store quantum information – making them especially attractive for building stable quantum logic gates.
Through new research published in EPJ Plus, an international team led by Gabriele Cenedese at the University of Insubria, Italy, demonstrates how the limited entanglement in noisy quantum computers could be transformed into an advantage, making it easier to identify scar states within chaotic quantum systems. Involving a specialised hybrid algorithm, the team’s approach could help pave the way toward more scalable quantum architectures – reducing the need for complex and costly error-correction techniques.
EPJ Plus Focus Point Issue: Laser-driven neutron sources and their applications
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- Published on 23 June 2025
Guest Editors: S. Charisopoulos, M. Roth
Recent advances in high-power laser technology have led to the development of lasers producing extremely short light pulses in the femtosecond range with very high intensities exceeding 1021 Watt/cm2. By guiding these pulses onto a solid foil, intense sources of photons, ions and neutrons can be generated, which can subsequently be used for a wide spectrum of applications, such as non-destructive testing methods in aerospace; radiographic imaging of large objects; in-operando diagnostics of lithium-ion batteries; radiation processing to fabricate smart, functional materials; and active interrogation of sensitive nuclear materials, including nuclear waste characterization. Due to these features, Laser-Driven Neutron and X-ray sources may have a large potential for contributing to socio-economic development.
The present Focus Point on Laser-Driven Neutron Sources and Their Applications is a collection of papers addressing some of the potential applications of laser driven neutron sources as well as some R&D work aiming at optimizing setups and procedures for the production of high-flux neutrons using state-of-the art laser systems.
All articles are available here and are freely accessible until 16 August 2025. For further information, read the Editorial.
EPJ Plus Highlight - Exploring the experimental potential of electron-hole pair production in graphene
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- Published on 16 June 2025
Electron-hole pair production in graphene can mimic many of the key quantum signatures of electron-positron pair production in a vacuum – but with key differences depending on the polarisations of the electric fields applied
Graphene provides a promising platform for exploring exotic quantum phenomena. For example, when an electron in graphene is excited to a higher energy level by an electric field, it leaves behind a positively charged ‘hole – a quasiparticle that essentially behaves like a particle of antimatter. This process is analogous to the production of electron-positron pairs in a vacuum when exposed to strong electromagnetic fields.
Through new research published in EPJ Plus, Zi-Liang Li and colleagues at China University of Mining and Technology provided new insights into how electron-hole pairs form in graphene, when subjected to two polarised electric fields separated by a time delay. Their results show that under the right conditions, graphene can provide a useful platform for precise, controllable, and easily implementable experiments for simulating pair production – offering opportunities to explore quantum effects which would otherwise be extremely difficult to access.
EPJ Plus Highlight - A gentle introduction to black hole thermodynamics
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- Published on 23 May 2025
Notes provide a useful introduction to the extensive and deeply complex topic of black hole thermodynamics, offering a valuable starting point for more in-depth research.
Beyond a black hole’s event horizon, the gravitational pull becomes so strong that not even light can escape. As a result, the process of any object being captured by a black hole is `irreversible’. The basic idea of black hole thermodynamics, as developed originally by Bekenstein and Hawking half a century ago, is that this irreversibility is of the same nature as the thermodynamic irreversibility that is familiar in everyday life.
EPJ Plus Highlight - Quantum refrigerators explored with a new theoretical framework
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- Published on 23 May 2025
New research takes the Carnot cycle to the realm of quantum physics to explore an ideal refrigeration system
A Carnot refrigerator is a theoretical ideal model of a cooling system that operates in the most efficient way possible. Based on the principles of thermodynamics and the Carnot cycle first theorised by French physicist Sadi Carnot in 1824, Carnot refrigeration has enthralled scientists for over 200 years, even when not directly implemented, providing inspiration for “real-life” cooling systems like fridges and air-conditioners.
A new paper published in the journal the EPJ Plus by Bolu Abant Izzet Baysal University physicist Ferdi Altintas offers a framework for designing quantum refrigerators, relevant for cooling in quantum technologies like quantum computing.
EPJ Plus Highlight - Understanding explosive transitions in propagating flames
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- Published on 19 May 2025
Mathematical analysis sheds new light on the mechanisms which unfold as propagating flames transition from one type of combustion to another
As a flame propagates through a mixture of air and flammable fuel, it can suddenly transition from one type of combustion to another. While it initially spreads at subsonic speeds through a process named ‘deflagration’, the flame will suddenly switch to a supersonic motion, driving a shockwave which compresses and ignites the fuel directly in front of it: a process named ‘detonation’. To date, however, some details of the mechanisms which unfold as this transition takes place are still being investigated.
