Publications

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Hilbert space structure and classical limit of the low energy sector of U(N) quantum Hall ferromagnets

Manuel Calixto, Alberto Mayorgas, Julio Guerrero

SciPost Phys. Proc. 14, 021 (2023) · published 23 November 2023 | · pdf

Using the Lieb–Mattis ordering theorem of electronic energy levels, we identify and construct the Hilbert space of the low energy sector of U(N) quantum Hall/Heisenberg ferromagnets at filling factor M for L Landau/lattice sites. The carrier Hilbert space of irreducible representations of U(N) is described by rectangular Young tableaux of M rows and L columns, and associated with Grassmannian phase spaces U(N)/U(M)×U(N-M). Replacing U(N)-spin operators by their expectation values in a Grassmannian coherent state allows for a semi-classical treatment of the low energy U(N)-spin-wave coherent excitations (skyrmions) of U(N) quantum Hall ferromagnets in terms of Grasmannian nonlinear sigma models.
Search for lepton-flavour-violating decays of the $Z$ boson into a $\tau$-lepton and a light lepton with the ATLAS detector

Wing Sheung Chan on behalf of the ATLAS collaboration

SciPost Phys. Proc. 1, 048 (2019) · published 22 February 2019 | · pdf

Lepton flavour violation in the charged lepton sector is an unambiguous signal of physics beyond the Standard Model. Searches for lepton flavour violation in decays of the $Z$ boson with the ATLAS detector is reported, focusing on decays into an electron or muon and a hadronically decaying $\tau$-lepton, using $pp$ collisions data with a centre-of-mass energy of 13 TeV. Upper limits on the branching ratios of lepton-flavor-violating decays are set at the 95\% confidence level: $\mathcal{B}(Z\to e\tau) < 5.8\times10^{-5}$ and $\mathcal{B}(Z\to \mu\tau) < 2.4\times10^{-5}$. When combined with a previous ATLAS result based on $pp$ collisions data with a centre-of-mass energy of 8 TeV, an upper limit of $\mathcal{B}(Z\to \mu\tau) < 1.3\times10^{-5}$ is obtained.
The tower of Kontsevich deformations for Nambu-Poisson structures on $\mathbb{R}^d$: Dimension-specific micro-graph calculus

Ricardo Buring, Arthemy V. Kiselev

SciPost Phys. Proc. 14, 020 (2023) · published 23 November 2023 | · pdf

In Kontsevich's graph calculus, internal vertices of directed graphs are inhabited by multi - vectors, e.g., Poisson bi - vectors; the Nambu - determinant Poisson brackets are differential - polynomial in the Casimir(s) and density $\varrho$ times Levi - Civita symbol. We resolve the old vertices into subgraphs such that every new internal vertex contains one Casimir or one Levi - Civita symbol×$\varrho$. Using this micro - graph calculus, we show that Kontsevich's tetrahedral $\gamma_3$-flow on the space of Nambu - determinant Poisson brackets over $\mathbb{R}^3$ is a Poisson coboundary: we realize the trivializing vector field $\vec{X}$ over $\mathbb{R}^3$ using micro - graphs. This $\vec{X}$ projects to the known trivializing vector field for the $\gamma_3$-flow over $\mathbb{R}^2$.
Irreducible representations of $\mathbb{Z}_2^2$-graded supersymmetry algebra and their applications

Naruhiko Aizawa

SciPost Phys. Proc. 14, 016 (2023) · published 23 November 2023 | · pdf

We give a brief review on recent developments of $\mathbb{Z}_2^n$-graded symmetry in physics in which hidden $\mathbb{Z}_2^n$-graded symmetries and $\mathbb{Z}_2^n$-graded extensions of known systems are discussed. This elucidates physical relevance of the $\mathbb{Z}_2^n$-graded algebras. As an example of physically interesting algebra, we take $\mathbb{Z}_2^2$-graded supersymmetry (SUSY) algebras and consider their irreducible representations (irreps). A list of irreps for ${\cal N} = 1, 2$ algebras is presented and as an application of the irreps, $\mathbb{Z}_2^2$-graded SUSY classical actions are constructed.
Kurt Bernardo Wolf memorial lecture

George Pogosyan, Mariano A. del Olmo

SciPost Phys. Proc. 14, 010 (2023) · published 23 November 2023 | · pdf

A personal view of the Mexican mathematical physicist Kurt Bernardo Wolf (1942-2022) is presented here.
The prediction of anyons: Its history and wider implications

Gerald A. Goldin

SciPost Phys. Proc. 14, 005 (2023) · published 23 November 2023 | · pdf

Prediction of "anyons," often attributed exclusively to Wilczek, came first from Leinaas and Myrheim in 1977, and independently from Goldin, Menikoff, and Sharp in 1980-81. In 2020, experimentalists successfully created anyonic excitations. This paper discusses why the possibility of quantum particles in two-dimensional space with intermediate exchange statistics eluded physicists for so long after bosons and fermions were understood. The history suggests ideas for the preparation of future researchers. I conclude by addressing failures to attribute scientific achievements accurately, both inadvertent and intentional. Such practices disproportionately hurt women and minorities in physics.
Implications of tau data for CP violation in K decays

Antonio Rodríguez-Sánchez

SciPost Phys. Proc. 1, 005 (2019) · published 18 February 2019 | · pdf

The $D=6$ contribution of the Operator Product Expansion (OPE) of the VV-AA correlator of quark currents can be related to hadronic matrix elements associated to CP violation in non-leptonic kaon decays. We use those relations to find an updated value for $\langle(\pi\pi)_{I=2}|\mathcal{Q}_{8}|K\rangle$ in the chiral limit using the updated ALEPH spectral function. Taking instead values of the matrix elements from the lattice to obtain the $D=6$ vacuum elements provides a new short-distance constraint that allows for an inclusive determination of $f_{\pi}$ and an updated value for the $D=8$ condensate.
Physics motivation and detector upgrades for the new era of the ATLAS experiment

Jason Nielsen

SciPost Phys. Proc. 8, 126 (2022) · published 13 July 2022 | · pdf

The ATLAS experiment at CERN’s Large Hadron Collider (LHC) will be upgraded in two stages to prepare first for the Run 3 data-taking campaign, during which the integrated luminosity will roughly double, and then for the High-Luminosity LHC program with an ultimate integrated luminosity of up to 4 ab-1. These upgrades and high-statistics datasets will allow ATLAS to perform searches and precision measurements to constrain the Standard Model in yet-unexplored phase spaces and in the Higgs sector. This contribution summarizes the ATLAS detector upgrades and selected physics prospects for Run 3 and the HL-LHC.
Photon-ALP oscillations at CTA energies

M. Kachelriess, J. Tjemsland

SciPost Phys. Proc. 12, 043 (2023) · published 4 July 2023 | · pdf

Axions and axion-like-particles (ALPs) are well motivated beyond the standard model particles that can explain a variety of unsolved problems in physics, such as the strong CP problem and the nature of dark matter. These particles are characterised by their two-photon coupling, which leads to so-called photon-ALP oscillation as photons propagate through an external magnetic field. Such oscillations lead to characteristic signatures in the energy spectrum of high-energy photons from astrophysical sources, allowing us to probe the existence of ALPs and possibly dark matter. We review the signatures from ALPs in photon spectra and discuss a new method that can be used to directly search for the energy dependence of the oscillations. The focus is on photons at TeV-energies relevant for the upcoming Cherenkov Telescope Array (CTA).
Measurements of heavy-flavor production as a function of multiplicity with ALICE at the LHC

Yoshini Bailung

SciPost Phys. Proc. 10, 033 (2022) · published 11 August 2022 | · pdf

In this contribution, the production of heavy-flavor hadrons as a function of multiplicity, via the study of the D-meson and heavy-flavor hadron decay leptons self-normalized yields in pp collisions at the center of mass energy $\sqrt{s} = 13$ TeV is discussed. Comparisons are made with similar measurements of J/$\psi$ at $\sqrt{s} = 13$ TeV and various model calculations. The $\mathrm{\Lambda_{c}^{+}/D^{0}}$ and $\mathrm{D^{+}_{s}/D^{0}}$ yield ratios in different multiplicity intervals in pp collisions at $\sqrt{s} = 13$ TeV are also reported. In addition, the ALICE measurement of $\mathrm{\Lambda_{c}^{+}}$ production in p-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV down to transverse momentum ($p_{\rm T}$) = 0 GeV/$c$ is presented. Finally, the nuclear modification factor is shown for open charm hadrons at $\sqrt{s} = 5.02$ TeV in p-Pb collisions. Finally, measurements of the elliptic flow of heavy-flavor hadron decay leptons in p-Pb systems are presented, which hint towards a possible collective behaviour in high multiplicity p-Pb collisions.

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