Publications

Order by: publication date number of citations

• Beyond-mean-field analysis of the Townes soliton and its breathing mode

  Dmitry S. Petrov

  SciPost Phys. 19, 037 (2025) · published 13 August 2025 | Toggle abstract · pdf

  By using the Bogoliubov perturbation theory we describe the self-bound ground state and excited breathing states of $N$ two-dimensional bosons with zero-range attractive interactions. Our results for the ground state energy $B_N$ and size $R_N$ improve previously known large-$N$ asymptotes and we better understand the crossover to the few-body regime. The breathing oscillations, absent at the mean-field level, result from the quantum-mechanical breaking of the mean-field scale symmetry. The breathing-mode frequency scales as $\Omega\propto |B_N|/\sqrt{N}$ at large $N$.

• Characterizing the hadronization of parton showers using the HOMER method

  Benoît Assi, Christian Bierlich, Philip Ilten, Tony Menzo, Stephen Mrenna, Manuel Szewc, Michael K. Wilkinson, Ahmed Youssef, Jure Zupan

  SciPost Phys. 19, 125 (2025) · published 11 November 2025 | Toggle abstract · pdf

  We update the HOMER method, a technique to solve a restricted version of the inverse problem of hadronization – extracting the Lund string fragmentation function $f(z)$ from data using only observable information. Here, we demonstrate its utility by extracting $f(z)$ from synthetic Pythia simulations using high-level observables constructed on an event-by-event basis, such as multiplicities and shape variables. Four cases of increasing complexity are considered, corresponding to $e^+e^-$ collisions at a center-of-mass energy of $90≥v$ producing either a string stretched between a $q$ and $\bar{q}$ containing no gluons; the same string containing one gluon $g$ with fixed kinematics; the same but the gluon has varying kinematics; and the most realistic case, strings with an unrestricted number of gluons that is the end-result of a parton shower. We demonstrate the extraction of $f(z)$ in each case, with the result of only a relatively modest degradation in performance of the HOMER method with the increased complexity of the string system.

• Dark matter or millisecond pulsars? A deep learning-based analysis of the Fermi Galactic Centre Excess

  Florian List, Nicholas L. Rodd, Geraint F. Lewis

  SciPost Phys. Proc. 12, 034 (2023) · published 4 July 2023 | Toggle abstract · pdf

  The $\gamma$-ray Galactic Centre Excess (GCE) remains one of the few observed high-energy signals for which a dark matter (DM) origin is a plausible explanation. We present a deep learning-based analysis of the $\gamma$-ray sky in the Galactic Centre region, carefully accounting for the mathematical degeneracy between faint point-sources (PSs) such as millisecond pulsars (MSPs) and DM-like Poisson emission. Using recent models for the Galactic foregrounds, we find that relatively few bright PSs just below Fermi's detection threshold seem unlikely to explain the GCE, although we continue to find evidence for PSs. Looking ahead, further improvements in the modelling of the $\gamma$-ray sky will be crucial for distinguishing between a DM-like and point-like morphology of the signal.

• Exponential networks for linear partitions

  Sibasish Banerjee, Mauricio Romo, Raphael Senghaas, Johannes Walcher

  SciPost Phys. 18, 128 (2025) · published 15 April 2025 | Toggle abstract · pdf

  Previous work has given proof and evidence that BPS states in local Calabi-Yau 3-folds can be described and counted by exponential networks on the punctured plane, with the help of a suitable non-abelianization map to the mirror curve. This provides an appealing elementary depiction of moduli of special Lagrangian submanifolds, but so far only a handful of examples have been successfully worked out in detail. In this note, we exhibit an explicit correspondence between torus fixed points of the Hilbert scheme of points on $\mathbb C^2\subset\mathbb C^3$ and anomaly free exponential networks attached to the quadratically framed pair of pants. This description realizes an interesting, and seemingly novel, "age decomposition" of linear partitions. We also provide further details about the networks' perspective on the full D-brane moduli space.

• Searches for lepton flavor violation in meson decays at Belle

  Sourav Patra

  SciPost Phys. Proc. 17, 009 (2025) · published 23 July 2025 | Toggle abstract · pdf

  We report the results of recent searches on charged lepton flavor violation using the $e^+e^-$ collision data collected by the Belle detector. In the first section, we present a search for the lepton-flavor-violating decays $B{}^0_s → \ell^{\mp}\tau^{±}$, where $\ell = e, \mu$, using $121\ \mathrm{fb}^{-1}$ data collected at the $\Upsilon(5S)$ resonance. We also search for the lepton-flavour-violating decays $B^+ \to K^+ \tau^± \ell^\mp$, with $\ell = (e, \mu)$, using $711\ \mathrm{fb}^{-1}$ $\Upsilon(4S)$ data sample. Finally, we present a search for the charged lepton-flavor-violating decays $\Upsilon(1S)→\ell^±\ell^{\prime\mp}$ and radiative charged lepton-flavour-violating decays $\Upsilon(1S)→\gamma\ell^±\ell^{\prime\mp}$ [$\ell,\ell^\prime = e, \mu, \tau$] using $25\ \mathrm{fb}^{-1}$ data recorded at $\Upsilon(2S)$ resonance. This search uses $\Upsilon(1S)$ mesons produced in $\Upsilon(2S)→\pi^+\pi^-\Upsilon(1S)$ transitions.

• A field theory representation of sum of powers of principal minors and physical applications

  Morteza Nattagh Najafi, Abolfazl Ramezanpour, Mohammad Ali Rajabpour

  SciPost Phys. Core 8, 051 (2025) · published 12 August 2025 | Toggle abstract · pdf

  We introduce a novel field theory representation for the Sum of Powers of Principal Minors (SPPM), a mathematical construct with profound implications in quantum mechanics and statistical physics. We begin by establishing a Berezin integral formulation of the SPPM problem, showcasing its versatility through various symmetries including $SU(n)$, its subgroups, and particle-hole symmetry. This representation not only facilitates new analytical approaches but also offers deeper insights into the symmetries of complex quantum systems. For instance, it enables the representation of the Hubbard model's partition function in terms of the SPPM problem. We further develop three mean field techniques to approximate SPPM, each providing unique perspectives and utilities: the first method focuses on the evolution of symmetries post-mean field approximation, the second, based on the bosonic representation, enhances our understanding of the stability of mean field results, and the third employs a variational approach to establish a lower bound for SPPM. These methods converge to identical consistency relations and values for SPPM, illustrating their robustness. The practical applications of our theoretical advancements are demonstrated through two compelling case studies. First, we exactly solve the SPPM problem for the Laplacian matrix of a chain, a symmetric tridiagonal matrix, allowing for precise benchmarking of mean-field theory results. Second, we present the first analytical calculation of the Shannon-Rényi entropy for the transverse field Ising chain, revealing critical insights into phase transitions and symmetry breaking in the ferromagnetic phase. This work not only bridges theoretical gaps in understanding principal minors within quantum systems but also sets the stage for future explorations in more complex quantum and statistical physics models.

• A Fermi surface descriptor quantifying the correlations between anomalous Hall effect and Fermi surface geometry

  Elena Derunova, Jacob Gayles, Yan Sun, Michael W. Gaultois, Mazhar N. Ali

  SciPost Phys. Core 8, 085 (2025) · published 18 November 2025 | Toggle abstract · pdf

  In the last few decades, basic ideas of topology have completely transformed the prediction of quantum transport phenomena. Following this trend, we go deeper into the incorporation of modern mathematics into quantum material science focusing on geometry. Here we investigate the relation between the geometrical type of the Fermi surface and Anomalous and Spin Hall Effects. An index, $\mathbb{H}_F$, quantifying the hyperbolic geometry of the Fermi surface, shows a universal correlation (R$^2$ = 0.97) with the experimentally measured intrinsic anomalous Hall conductivity, of 16 different compounds spanning a wide variety of crystal, chemical, and electronic structure families, including those where topological methods give R$^2$ = 0.52. This raises a question about the predictive limits of topological physics and its transformation into a wider study of bandstructures' and Fermi surfaces' geometries and relating them to the quantum geometry theory of a more general metric of eigenstates, opening horizon for the prediction of phenomena beyond topological understanding.

• Quantized fragmentation of three-dimensional QCD string

  S. Todorova-Nova

  SciPost Phys. Proc. 10, 013 (2022) · published 10 August 2022 | Toggle abstract · pdf

  Recent developments of the model of quantized helical QCD string are presented, notably the baryon production. An overview of the experimental evidence is discussed as well as possible applications.

• Density-matrix mean-field theory

  Junyi Zhang, Zhengqian Cheng

  SciPost Phys. 17, 062 (2024) · published 23 August 2024 | Toggle abstract · pdf

  Mean-field theories have proven to be efficient tools for exploring diverse phases of matter, complementing alternative methods that are more precise but also more computationally demanding. Conventional mean-field theories often fall short in capturing quantum fluctuations, which restricts their applicability to systems with significant quantum effects. In this article, we propose an improved mean-field theory, density-matrix mean-field theory (DMMFT). DMMFT constructs effective Hamiltonians, incorporating quantum environments shaped by entanglements, quantified by the reduced density matrices. Therefore, it offers a systematic and unbiased approach to account for the effects of fluctuations and entanglements in quantum ordered phases. As demonstrative examples, we show that DMMFT can not only quantitatively evaluate the renormalization of order parameters induced by quantum fluctuations, but can also detect the topological quantum phases. Additionally, we discuss the extensions of DMMFT for systems at finite temperatures and those with disorders. Our work provides an efficient approach to explore phases exhibiting unconventional quantum orders, which can be particularly beneficial for investigating frustrated spin systems in high spatial dimensions.

• New determination of the production cross section for secondary positrons and electrons in the Galaxy

  Luca Orusa, Mattia Di Mauro, Fiorenza Donato, Michael Korsmeier

  SciPost Phys. Proc. 13, 006 (2023) · published 28 September 2023 | Toggle abstract · pdf

  The cosmic-ray fluxes of electrons and positrons ($e^{±}$) are measured with high precision by the space-borne particle spectrometer AMS-02. To infer a precise interpretation of the production processes for $e^{±}$ in our Galaxy, it is necessary to have an accurate description of the secondary component, produced by the interaction of cosmic-ray proton and helium with the interstellar medium atoms. We determine new analytical functions of the Lorentz invariant cross section for the production of $e^±$ by fitting data from collider experiments. The total differential cross section $d\sigma/dT_{e^±}(p+p→ e^±+X)$ is predicted with an uncertainty of about 5-7% in the energies relevant for AMS-02 positron flux. For further information about this work refer to [Phys. Rev. D 105, 123021 (2022)].