News / Highlights / Colloquium
EPJ C Highlight - A cautionary tale of machine learning uncertainty
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- 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.
EPJ C – New structure for the theory sections as of 2022
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- Published on 12 January 2022
The publishers of The European Physical Journal C - Particles and Fields (EPJ C) are pleased to announce a new structure for the theory sections of the journal. As of January 2022 the current section ‘Theoretical Physics II: Gravitation, Astroparticle Physics, Cosmology, Quantum Field Theories’ (Editor-in-Chief: Prof. Kostas Skenderis, Deputy Editor-in-Chief Prof. Dominik Schwarz) will be split – into ‘Theoretical Physics II: Astroparticle Physics and Cosmology - Models and Phenomenology’, to be headed by Dominik Schwarz; and ‘Theoretical Physics III: Quantum Field Theory and Gravity - Fundamental and Formal Aspects’, to be headed by Kostas Skenderis. This change reflects the rapid development of the current Theoretical Physics II section under Kostas Skenderis over the past few years. We would like to thank Professor Skenderis for his excellent management of the section and to welcome Professor Schwarz as a new Editor-in-Chief of EPJ C. As head of the Astroparticle Physics and Cosmology Working Group at Bielefeld University, Schwarz is an expert on the interfaces between particle physics and cosmology and between modelling and observational cosmology. His research interests include cosmological inflation and the thermal history of the Universe, the cosmic microwave background and large-scale structures, dark matter and dark energy.
EPJ C Highlight - Hubble tension: Showing the cracks in Gaussian Processes
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- Published on 12 November 2021
Today, Gaussian Processes data reconstruction is viewed as a vital tool in cosmology. Yet through new analysis of tensions in the value of Hubble’s constant, two researchers suggest that the approach may not be as valid as currently thought.
The technique of Gaussian Processes (GP) is widely used to reconstruct cosmological parameters, most notably the expansion rate of the universe, using observational data. For many cosmologists, the crowning achievement of this approach is its ‘model independence’ – meaning it can be applied universally across all models. Through new analysis published in EPJ C, Eoin Ó Colgáin at Sogang University, Seoul, and Mohammad Mehdi Sheikh-Jabbari at IPM, Tehran, use the Hubble constant (H0) to show that this may not be the case – and that it may be time to question the validity of model independence itself.
EPJ C Highlight - The first black hole image: A gravitomagnetic monopole as an alternative explanation
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- Published on 04 November 2021
The Event Horizon Telescope made science history when it captured the first image of the supermassive black hole in the galaxy M87. New research suggests alternative explanations for the massive compact object at the centre of this galaxy questioning if this could contain gravitomagnetic monopole.
The Event Horizon Telescope (EHT) has recently mapped the central compact object of the galaxy M87 with an unprecedented angular resolution. Though the remarkable breakthrough has been interpreted based on theory that M87 contains a rotating or “Kerr” black hole. New research published in EPJ C by Chandrachur Chakraborty and Qingjuan Yu at the Kavli Institute for Astronomy and Astrophysics, Peking University (KIAA-PKU), Masoumeh Ghasemi-Nodehi and Youjun Lu, at the National Astronomical Observatories of China, looks at possible alternative explanations for the image.
EPJ C Highlight - Factoring in gravitomagnetism could do away with dark matter
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- Published on 04 March 2021
Models of galactic rotation curves built of a general relativistic framework could use gravitomagnetism to explain the effects of dark matter.
Observations of galactic rotation curves give one of the strongest lines of evidence pointing towards the existence of dark matter, a non-baryonic form of matter that makes up an estimated 85% of the matter in the observable Universe. Current assessments of galactic rotation curves are based upon a framework of Newtonian accounts of gravity, a new paper published in EPJ C, by Gerson Otto Ludwig, National Institute for Space Research, Brazil, suggests that if this is substituted with a general relativity-based model, the need to recourse to dark matter is relieved, replaced by the effects of gravitomagnetism.
EPJ C Highlight - Placing cosmological constraints on quantum gravity phenomenology
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- Published on 09 February 2021
Researchers have used cosmological data to place stringent new limits on a model which emerges in attempts to reconcile gravity with the principles of quantum mechanics.
A description of gravity compatible with the principles of quantum mechanics has long been a widely pursued goal in physics. Existing theories of this ‘quantum gravity’ often involve mathematical corrections to Heisenberg’s Uncertainty Principle (HUP), which quantifies the inherent limits in the accuracy of any quantum measurement. These corrections arise when gravitational interactions are considered, leading to a ‘Generalized Uncertainty Principle’ (GUP). Two specific GUP models are often used: the first modifies the HUP with a linear correction, while the second introduces a quadratic one. Through new research published in EPJ C, Serena Giardino and Vincenzo Salzano at the University of Szczecin in Poland have used well-established cosmological observations to place tighter constraints on the quadratic model, while discrediting the linear model.
EPJ C Highlight - Tracking the evolution Maxwell knots
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- Published on 15 January 2021
New research investigates the properties of particular solutions of Maxwell equations, tracking their evolution over time and determining a route to combine them with other systems.
Maxwell equations govern the evolution of electromagnetic fields with light being a particular solution of these equations in spaces devoid of electric charge. A new study published in EPJ C by Alexei Morozov and Nikita Tselousov, from the Moscow Institute of Physics and Technology and the Institute of Transmission Problems, Russia, respectively, details peculiar solutions to the Maxwell equations—so-called Maxwell knots. The research could have applications in the fields of mathematical physics and string theory.
EPJ C: Jocelyn Monroe new Editor-in-Chief for Experimental Physics II: Astroparticle Physics
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- Published on 08 January 2021
The publishers of The European Physical Journal C – Particles and Fields are pleased to announce the appointment of Professor Jocelyn Monroe as new Editor-in-Chief for Experimental Physics II: Astroparticle Physics replacing Professor Laura Baudis.
Jocelyn Monroe, head of the Astroparticle Physics Group at Royal Holloway, University of London, is an expert on dark matter direct detection and the interface with neutrino physics. Her research interests include experimental dark matter searches, low-energy neutrino physics and detector development for rare event searches.
EPJ C Highlight - Detecting solar neutrinos with the Borexino experiment
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- Published on 03 December 2020
Neutrinos produced by the CNO cycle within the core of the Sun are being hunted by the Borexino experiment so that we may learn more about this important nuclear process.
Neutrinos are chargeless particles with about a mass about a millionth that of an electron that are created by the nuclear processes that occur in the Sun and other stars. These particles are often colourfully described as the ‘ghosts’ of the particle zoo because they interact so weakly with matter. A paper published in EPJ C by the Borexino collaboration – including XueFeng Ding, Postdoc Associate of Physics at Princeton University, United States – documents the attempts of the Borexino experiment to measure low-energy neutrinos from the Sun’s carbon-nitrogen-oxygen (CNO) cycle for the first time.
EPJ C Highlight - Weak equivalence principle violated in gravitational waves
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- Published on 28 October 2020
Calculations reveal that a key principle of classical physics is broken by quantum particles as they pass through ripples in spacetime.
The Weak Equivalence Principle (WEP) is a key aspect of classical physics. It states that when particles are in freefall, the trajectories they follow are entirely independent of their masses. However, it is not yet clear whether this property also applies within the more complex field of quantum mechanics. In new research published in EPJ C, James Quach at the University of Adelaide, Australia, proves theoretically that the WEP can be violated by quantum particles in gravitational waves – the ripples in spacetime caused by colossal events such as merging black holes.
