Publications

Order by: publication date number of citations

• Few-body reactions investigated with the Trojan Horse Method

  Roberta Spartà, Giuseppe G. Rapisarda, Claudio Spitaleri, M. La Cognata, Rosario G. Pizzone, S. Romano, Aurora Tumino

  SciPost Phys. Proc. 3, 033 (2020) · published 26 February 2020 | Toggle abstract · pdf

  The Trojan Horse Method is an indirect method to measure reaction cross sections at energies of interest for nuclear astrophysics, exploiting the nuclei clustering properties. Here it is presented with its general features and detailed for the case of the 2H(d,p)3H and 2H(d,n)3He measurements, where interesting results for astrophysics and energy fusion power plants have been obtained.

• Phase transitions from heating to non-heating in $SU(1,1)$ quantum dynamics: Applications to Bose-Einstein condensates and periodically driven coupled oscillators

  Heng-Hsi Li, Po-Yao Chang

  SciPost Phys. Core 8, 018 (2025) · published 10 February 2025 | Toggle abstract · pdf

  We study the entanglement properties in non-equilibrium quantum systems with the $SU(1,1)$ structure. Through Möbius transformation, we map the dynamics of these systems following a sudden quench or a periodic drive onto three distinct trajectories on the Poincaré disc, corresponding the heating, non-heating, and a phase boundary describing these non-equilibrium quantum states. We consider two experimentally feasible systems where their quantum dynamics exhibit the $SU(1,1)$ structure: the quench dynamics of the Bose-Einstein condensates and the periodically driven coupled oscillators. In both cases, the heating, non-heating phases, and their boundary manifest through distinct signatures in the phonon population where exponential, oscillatory, and linear growths classify these phases. Similarly, the entanglement entropy and negativity also exhibit distinct behaviors (linearly, oscillatory, and logarithmic growths) characterizing these phases, respectively. Notibly, for the periodically driven coupled oscillators, the non-equilibrium properties are characterized by two sets of $SU(1,1)$ generators. The corresponding two sets of the trajectories on two Poincaré discs lead to a more complex phase diagram. We identify two distinct phases within the heating region discernible solely by the growth rate of the entanglement entropy, where a discontinuity is observed when varying the parameters across the phase boundary within in heating region. This discontinuity is not observed in the phonon population.

• Multi-differential studies to explore strangeness enhancement in pp with ALICE at the LHC

  Francesca Ercolessi

  SciPost Phys. Proc. 10, 028 (2022) · published 11 August 2022 | Toggle abstract · pdf

  The study of energy and multiplicity dependence of strange hadron production in proton-proton collisions provides a powerful tool to understand similarities and differences between small and large collision systems. In order to better understand the origin of strangeness enhancement in pp new multi-differential analyses have been performed. The first separates the contribution of soft and hard processes, such as jets, to strange hadron production through two-particle correlation techniques. The second exploits the concept of the effective energy available for particle production in the event, which is estimated by an anti-correlation with the energy deposited in ALICE's Zero Degree Calorimeters. The results indicate that strangeness production emerges from the growth of the underlying event and confirm it is related to the final state multiplicity.

• Critical behavior of a phase transition in the dynamics of interacting populations

  Thibaut Arnoulx de Pirey, Guy Bunin

  SciPost Phys. 18, 051 (2025) · published 13 February 2025 | Toggle abstract · pdf

  Many-variable differential equations with random coefficients provide powerful models for the dynamics of many interacting species in ecology. These models are known to exhibit a dynamical phase transition from a phase where population sizes reach a fixed point, to a phase where they fluctuate indefinitely. Here we provide a theory for the critical behavior close to the phase transition. We show that timescales diverge at the transition and that temporal fluctuations grow continuously upon crossing it. We further show the existence of three different universality classes, with different sets of critical exponents, highlighting the importance of the migration rate coupling the system to its surroundings.

• Universality of closed nested paths in two-dimensional percolation

  Yu-Feng Song, Jesper Lykke Jacobsen, Bernard Nienhuis, Andrea Sportiello, Youjin Deng

  SciPost Phys. 18, 057 (2025) · published 18 February 2025 | Toggle abstract · pdf

  Recent work on percolation in $d=2$ [J. Phys. A: Math. Theor. 55, 204002 (2015)] introduced an operator that gives a weight $k^{\ell}$ to configurations with $\ell$ 'nested paths' (NP), i.e.\ disjoint cycles surrounding the origin, if there exists a cluster that percolates to the boundary of a disc of radius $L$, and weight zero otherwise. It was found that $\mathbb{E}(k^{\ell}) \sim L^{-X_{NP}(k)}$, and a formula for $X_{NP}(k)$ was conjectured. Here we derive an exact result for $X_{NP}(k)$, valid for $k ≥ -1$, replacing the previous conjecture. We find that the probability distribution $\mathbb{P}_\ell (L)$ scales as $ L^{-1/4} (\ln L)^\ell [(1/\ell!) \Lambda^\ell]$ when $\ell ≥ 0$ and $L \gg 1$, with $\Lambda = 1/\sqrt{3} \pi$. Extensive simulations for various critical percolation models confirm our theoretical predictions and support the universality of the NP observables.

• Mesoscopic electron transport and atomic gases, a review of Frank W. J. Hekking's scientific work

  Luigi Amico, Denis M. Basko, F Sebastián Bergeret, Olivier Buisson, Hervé Courtois, Rosario Fazio, Wiebke Guichard, Anna Minguzzi, Jukka Pekola, Gerd Schön

  SciPost Phys. 5, 009 (2018) · published 27 July 2018 | Toggle abstract · pdf

  Frank W. J. Hekking performed his PhD work on "Aspects of Electron Transport in Semiconductor Nanostructures" at the TU Delft in 1992. He then worked as a postdoc at the University of Karlsruhe, the University of Minnesota, the Cavendish Laboratory at the University of Cambridge, and the Ruhr University at Bochum. In 1999 he joined the LPMMC (Laboratoire de Physique et Mod\' elisation des Milieux Condens\' es) in Grenoble and was appointed Professor at the Universit\' e Joseph Fourier and afterwards Universit\' e Grenoble Alpes. Frank Hekking was nominated as a member of the Institut Universitaire de France, for the periods 2002-2007 and 2012-2017. This review provides an overview of his scientific contributions to several fields of mesoscopic electron transport and superconductivity as well as atomic gases, and is organized along sections describing the different themes.

• Renormalization approach to the superconducting Kondo model

  Steffen Sykora, Tobias Meng

  SciPost Phys. 13, 016 (2022) · published 12 August 2022 | Toggle abstract · pdf

  An approach to bound states based on unitary transformations of Hamiltonians is presented. The method is applied to study the interaction between electrons in a BCS $s$-wave superconductor and a quantum spin. It is shown that known results from the t-matrix method and numerical studies are reproduced by this new method. As a main advantage, the method can straightforwardly be extended to study the topological properties of combined bound states in chains of many magnetic impurities. It also provides a uniform picture of the interplay between the Yu-Shiba-Rusinov (YSR) bound states and the Kondo singlet state.

• Dark matter searches and energy accumulation and release in materials

  Sergey Pereverzev

  SciPost Phys. Proc. 12, 009 (2023) · published 3 July 2023 | Toggle abstract · pdf

  Efforts to identify dark matter by detecting nuclear recoils produced by dark matter particles reveal low-energy backgrounds of unknown origin in different types of detectors. In many cases, energy accumulation and delayed burst-like releases of stored energy could provide an explanation. These dynamics follow Prigogine's ideas on systems with energy flow and the general Self-Organized Criticality scenario. We compare these models with properties of excess backgrounds in cryogenic solid-state detectors, relaxation processes in glasses and crystals, our observations of delayed luminescence in NaI(Tl), and make predictions for more phenomena present in these systems and in superconducting photon detectors and qubits. Experiments to create accurate phenomenological models are needed.

• Recent jet and jet substructure measurements at the LHC, and ML based tagging

  Meena Meena

  SciPost Phys. Proc. 10, 022 (2022) · published 10 August 2022 | Toggle abstract · pdf

  Recent jet and jet substructure measurements at the LHC, and of machine-learning-based tagging techniques are presented using proton-proton collision data collected by the ATLAS and CMS experiments at CERN's Large Hadron Collider. These measurements are crucial for precise tests of electroweak and pQCD calculations and searches for physics beyond the Standard Model. The measurements are compared with several Monte Carlo event generator predictions which provide valuable input to the tuning of perturbative and non-perturbative models and to constraining model parameters of advanced parton-shower Monte Carlo programs.

• Search for anomalous quartic gauge couplings in the process $\mu^+\mu^-\to \bar{\nu}\nu\gamma\gamma$ with a nested local outlier factor

  Ke-Xin Chen, Yu-Chen Guo, Ji-Chong Yang

  SciPost Phys. Core 8, 091 (2025) · published 11 December 2025 | Toggle abstract · pdf

  In recent years, with the increasing luminosities of colliders, handling the growing amount of data has become a major challenge for future new physics (NP) phenomenological research. To improve efficiency, machine learning algorithms have been introduced into the field of high-energy physics. As a machine learning algorithm, the local outlier factor (LOF), and the nested LOF (NLOF) are potential tools for NP phenomenological studies. In this work, the possibility of searching for the signals of anomalous quartic gauge couplings (aQGCs) at muon colliders using the NLOF is investigated. Taking the process $\mu^+\mu^-\to \nu\bar{\nu}\gamma\gamma$ as an example, the signals of dimension-8 aQGCs are studied, expected coefficient constraints are presented. The event selection strategy uses unsupervised anomaly scores, with supervised optimization for EFT sensitivity. The NLOF algorithm is shown to outperform the k-means based anomaly detection methods, and a traditional counterpart.