Publications

Order by: publication date number of citations

• Prospects of a future multi-TeV muon collider

  M. Casarsa

  SciPost Phys. Proc. 8, 061 (2022) · published 12 July 2022 | Toggle abstract · pdf

  A multi-TeV muon collider is a discovery machine and an invaluable tool for many new standard model precision measurements such as the shape of the Higgs boson potential. The update of the European Strategy for Particle Physics recognized the unique opportunity of a muon collider to reach the energy frontier, despite the challenges to produce intense collimated muon beams. The options of a collider at 3 TeV and a collider at 10 TeV or above are the main focus of the forming International Muon Collider Collaboration as well as of the discussion panels at the ongoing US Snowmass process.

• Energy-saving fast-forward scaling

  Takuya Hatomura

  SciPost Phys. Core 8, 019 (2025) · published 11 February 2025 | Toggle abstract · pdf

  We propose energy-saving fast-forward scaling. Fast-forward scaling is a method which enables us to speed up (or slow down) given dynamics in a certain measurement basis. We introduce energy costs of fast-forward scaling, and find possibility of energy-saving speedup for time-independent measurement bases. As concrete examples, we show such energy-saving fast-forward scaling in a two-level system and quantum annealing of a general Ising spin glass. We also discuss the influence of a time-dependent measurement basis, and give a remedy for unwanted energy costs. The present results pave the way for realization of energy-efficient quantum technologies.

• On the role of non-linear latent features in bipartite generative neural networks

  Tony Bonnaire, Giovanni Catania, Aurélien Decelle, Beatriz Seoane

  SciPost Phys. 19, 141 (2025) · published 1 December 2025 | Toggle abstract · pdf

  We investigate the phase diagram and memory retrieval capabilities of Restricted Boltzmann Machines (RBMs), an archetypal model of bipartite energy-based neural networks, as a function of the prior distribution imposed on their hidden units—including binary, multi-state, and ReLU-like activations. Drawing connections to the Hopfield model and employing analytical tools from statistical physics of disordered systems, we explore how the architectural choices and activation functions shape the thermodynamic properties of these models. Our analysis reveals that standard RBMs with binary hidden nodes and extensive connectivity suffer from reduced critical capacity, limiting their effectiveness as associative memories. To address this, we examine several modifications, such as introducing local biases and adopting richer hidden unit priors. These adjustments restore ordered retrieval phases and markedly improve recall performance, even at finite temperatures. Our theoretical findings, supported by finite-size Monte Carlo simulations, highlight the importance of hidden unit design in enhancing the expressive power of RBMs.

• Workshop on Tau Lepton Physics: $\mathbf{30^{th}}$ Anniversary

  Antonio Pich

  SciPost Phys. Proc. 16, 001 (2025) · published 14 July 2025 | Toggle abstract · pdf

  The first Workshop on Tau Lepton Physics took place at Orsay in 1990. The evolution of the field and some physics highlights are briefly described, following the presentations discussed at the fifteen $\tau$ workshops that have been held since then.

• Wigner function analysis of finite matter-radiation systems

  Eduardo Nahmad-Achar, Ramón López-Peña, Sergio Cordero, Octavio Castaños Garza

  SciPost Phys. Proc. 14, 039 (2023) · published 24 November 2023 | Toggle abstract · pdf

  We show that the behaviour in phase space of the Wigner function associated to the electromagnetic modes carries the information of both, the entanglement properties between matter and field, and the regions in parameter space where quantum phase transitions take place. A finer classification for the continuous phase transitions is obtained through the computation of the surface of minimum fidelity.

• Group theoretical derivation of consistent particle theories

  Giuseppe Nisticò

  SciPost Phys. Proc. 14, 040 (2023) · published 24 November 2023 | Toggle abstract · pdf

  Current quantum theories of an elementary free particle assume unitary space inversion and anti-unitary time reversal operators. In so doing robust classes of possible theories are discarded. The present work shows that consistent theories can be derived through a strictly deductive development from the principle of relativistic invariance and position covariance, also with anti-unitary space inversion and unitary time reversal operators. In doing so the class of possible consistent theories is extended for positive but also zero mass particles. In particular, consistent theories for a Klein-Gordon particle are derived and the non-localizability theorem for a non zero helicity massless particle is extended.

• Updated determinations of |V$_{us}$| with tau decays using new recent estimates of radiative corrections for light-meson leptonic decay rates

  Alberto Lusiani

  SciPost Phys. Proc. 16, 002 (2025) · published 14 July 2025 | Toggle abstract · pdf

  We update the |V$_{us}$| determinations using the HFLAV 2018 report tau branching fraction results with recent new estimates of the $\pi\ell2$ and $K\ell2$ radiative corrections. There are minor changes of the central values and uncertainties.

• Coupled dynamics of resource competition and constrained entrances in a multi-lane bidirectional exclusion process

  Ashish Kumar Pandey, Arvind Kumar Gupta

  SciPost Phys. Core 8, 089 (2025) · published 3 December 2025 | Toggle abstract · pdf

  Motivated by the role of limited particle resources in multi-species bidirectional transport processes observed in various biological and physical systems, we investigate a one-dimensional closed system consisting of two parallel lanes with narrow entrances, where each lane accommodates two oppositely directed particle species. Each particle species is linked to a separate finite reservoir, which is coupled to both lanes and regulates the entry rates of particle into the lanes. To analyze the effect of finite particle reservoirs on the stationary properties of the system, we employ a mean-field theoretical framework to characterize the density profiles, particle currents, and phase behavior, complemented by a boundary layer analysis based on fixed point methods to capture spatial variations near the boundaries. The impact of individual species population, quantified by species-specific filling factors, is systematically examined under both equal and unequal conditions. For equal filling factors, system undergoes spontaneous symmetry breaking and supports both symmetric and asymmetric phases. In contrast, for unequal filling factors, only asymmetric phases are realized, with the phase diagram exhibiting up to five distinct phases. A striking feature observed in both scenarios is the emergence of a back-and-forth transition, along with a non-monotonic dependence of the number of phases on the filling factors. All theoretical findings are extensively validated through stochastic simulations based on the Gillespie algorithm, confirming the robustness of the analytical results.

• Monte Carlo Event Generator updates, for tau pair events at Belle II energies

  Sw. Banerjee, D. Biswas, T. Przedzinski, Z. Was

  SciPost Phys. Proc. 16, 003 (2025) · published 14 July 2025 | Toggle abstract · pdf

  The Monte Carlo for lepton pair production and $\tau$ decays consist of KKMC for lepton pair production, tauola for $\tau$ lepton decays and photos for radiative corrections in decays. An effort for adaptation of the system for precision data to be collected at Belle II experiment lead to extension of phase space generation modules both in photos and tauola to enable decays and/or radiative corrections of additional light lepton pairs. The phase-space and matrix element parts of the programs are separated, that is why extension to processes where lepton pair is produced through narrow resonances, like dark photon, was straight forward. In the present version of tauola, the list of $\tau$ decay channels is enriched with multitude of exotic ones, useful for searches of new physics. The hadronic currents parametrization of main decay channels is prepared for basic simulation in the experiment. The basis for future work on precise fits of hadronic currents including Machine Learning is retained, but development of necessary software solutions is left for the forthcoming years. Presented programs versions are available in stand-alone format from GitLab or through the basf2 system of Belle II software. Official distribution web pages, documenting programs tests, are retained but not necessarily up to date.

• On the use of the operator product expansion in finite-energy sum rules for light-quark correlators

  Diogo Boito, Maarten Golterman, Kim Maltman, Santiago Peris

  SciPost Phys. Proc. 16, 006 (2025) · published 14 July 2025 | Toggle abstract · pdf

  Tau-based finite-energy sum-rule (FESR) analyses often assume that scales $s_0\sim m_\tau^2$ are large enough that (i) integrated duality violations (DVs) can be neglected, and (ii) contributions from non-perturbative OPE condensates of dimension $D$ scale as $(\Lambda_{QCD}/m_\tau )^D$, allowing the OPE series to be truncated at low dimension. The latter assumption is not necessarily valid since the OPE series is not convergent, while the former is open to question given experimental results for the electromagnetic, $I=1$ vector ($V$), $I=1$ axial vector ($A$) and $I=1$ $V+A$ current spectral functions, which show DV oscillations with amplitudes comparable in size to the corresponding $\alpha_s$-dependent perturbative contributions at $s\sim2-3$ GeV$^2$. Here, we discuss recently introduced new tools for assessing the numerical relevance of omitted higher-$D$ OPE contributions. Applying these to the "truncated OPE" strategy used in Refs. [M. Davier et al., Eur. Phys. J. C 74, 2803 (2014); A. Pich and A. Rodríguez-Sánchez, Phys. Rev. D 94, 034027 (2016)] and earlier work by the same authors, we find that this strategy fails to yield reliable results for the strong coupling from hadronic $\tau$ decays.