- Published on 07 March 2022
By decorrelating the performance of machine learning algorithms with imperfections in the simulations used to train them, researchers could be estimating uncertainties that are lower than their true values.
The Standard Model of particle physics offers a robust theoretical picture of the fundamental particles, and most fundamental forces which compose the universe. All the same, there are several aspects of the universe: from the existence of dark matter, to the oscillating nature of neutrinos, which the model can’t explain – suggesting that the mathematical descriptions it provides are incomplete. While experiments so far have been unable to identify significant deviations from the Standard Model, physicists hope that these gaps could start to appear as experimental techniques become increasingly sensitive.
A key element of these improvements is the use of machine learning algorithms, which can automatically improve upon classical techniques by using higher-dimensional inputs, and extracting patterns from many training examples. Yet in new analysis published in EPJ C, Aishik Ghosh at the University of California, Irvine, and Benjamin Nachman at the Lawrence Berkeley National Laboratory, USA, show that researchers using machine learning methods could risk underestimating uncertainties in their final results.
- Published on 04 March 2022
Guest Editors: G. Corti, B. Heinemann, P. Hernandez, P. Koppenburg, M. McCullough, A.-S. Müller, A. Seryi, J. Tanaka
This Focus Point on the FCC-ee maps the current status and the challenges lying forward to realize a future Higgs and electroweak factory like the one envisioned by the Future Circular Collider design study for the post-LHC era. This strategic guideline from the 2020 update of the European Strategy for Particle Physics (ESPP 2020) defines an electron-positron Higgs and electroweak factory "as the highest-priority next collider" that would allow a wide range of precise measurements of the Standard Model parameters including the recently discovered Higgs boson. The proposed FCC-ee best complies with this guideline, and consequently offers, in a cost-effective fashion, the broadest physics discovery potential and the most ambitious perspective towards a 100 TeV high-energy proton collider housed in the same tunnel and profiting from the new infrastructure.
The invited authors evaluate the progress toward the realisation of FCCs since the publication of the FCC Conceptual Design Report. Topics highlight the challenges lying ahead on the accelerator design of FCC-ee, ongoing work for the experiments and detector development, the open theoretical questions informing this endeavour and finally the computational and software challenges that should be tackled. These challenges also set opportunities for a wider community of scientists and engineers who are invited to join the diverse and dynamic environment offered by the FCC collaboration.
- 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.
- Published on 18 February 2022
A new summary of the study of neutrinos, and the ways in which they interact with regular matter, could inspire both new and senior neutrino researchers to open up new areas of investigation within the field.
The history of our understanding of neutrinos, from their astrophysical origins to their elusive interactions with matter, is full of surprises. Although we know that they are the second most abundant particles in the universe after photons, they are also the least well understood. In this special issue of EPJ ST, M. Sajjad Athar and S.K. Singh at Aligarh Muslim University present a short overview of the study of neutrinos, and the ways in which they interact with other forms of matter at mid-to-high energies.
- Published on 09 February 2022
In a new Colloquium published in EPJB, S. Biswas (Universidad de Guadalajara, Mexico) and F. Leyvraz (Universidad Nacional Autónoma de México, Mexico) review several related systems. In the simplest, all particles move in a straight line at constant velocity in one dimension, and upon meeting, irreversibly react to an inert species. The simplest approach to such systems involves the “law of mass action” which leads, for large times, to a concentration decay of 1/t. The model described above for which all particles move with two possible distinct velocities only, has been solved exactly. In this case, it is shown that the concentration decay goes as t-1/2, so that the law of mass action is strongly violated.
- Published on 08 February 2022
A new collection of papers provides new experimental and theoretical perspectives on the interaction between matter and intense laser beams
Studies of laser-matter interactions are an important and rapidly growing area of physics. This special issue of EPJ ST, edited by Sivarama Krishnan at the Indian Institute of Technology Madras and Marcel Mudrich at Aarhus University, Denmark, contains a set of 21 articles in this field, encompassing a broad range of experimental and theoretical approaches. The collection provides researchers with useful insights into this burgeoning area of science, and the exciting applications it may soon lead to.
EPJ Web of Conferences Highlight - vConf21: A Virtual Tribute to Quark Confinement and the Hadron Spectrum
- Published on 31 January 2022
Drawing on the state-of-the-art in remote conferencing and amended by a rich outreach program, this virtual event was organized as substitute for the postponed 14th Confinement conference by the Institute for Mathematics and Physics at the University of Stavanger, Norway, between August 2-6 2021.
The Confinement conference series was inaugurated in 1994 and has since become an important forum for scientists working on strong interactions, stimulating exchange among theorists and experimentalists, as well as across adjacent fields.
- Published on 27 January 2022
The European Optical Society Annual Meeting, EOSAM, took place onsite in Rome from 13th to 17th September 2021, bringing back the awaited in-person EOS events.
EOSAM is a major international scientific conference covering all aspects of optics and photonics. It is attended by top researchers, key leaders, students, and industry experts.
- Published on 25 January 2022
A novel theory can link abrupt, non-equilibrium changes to the state of the economy to a central principle of dynamics and thermodynamics
Equilibrium is a fundamental concept in economics: describing situations where the many interacting variables governing the state of the economy are static and perfectly balanced. Yet in reality, the inherent uncertainty and randomness associated with these variables, combined with the fragility of economists’ expectations, mean that the economy can never really be in true equilibrium. In new research published in EPJ B, a research team led by Kun Zhang from the Changchun Institute of Applied Chemistry of the Chinese Academy of Sciences, and Jin Wang at State University of New York at Stony Brook, use new mathematical theories to capture the economy’s true non-equilibrium nature and to show how it can be quantified.
- Published on 25 January 2022
A new method for optimising the arrangements of complex sensor networks could lead to improvements in a variety of cutting-edge experiments: including the ongoing search for Dark Matter
Rather than using a single, centralised sensor to gather data, many experiments deploy multiple sensors in complex networks. This offers numerous advantages: including higher sensitivities and resolutions in experimental measurements, and the ability to catch and correct errors more effectively. Yet with all the complexities involved in managing each sensor, and collecting all of their data streams at once, it can be extremely challenging to determine how the sensors should be arranged to obtain optimal results. Through new research published in EPJ D, Joseph Smiga at Johannes Gutenberg University Mainz proposes a new way to quantify the quality of sensor networks, and uses his methods to suggest improvements to existing experiments.