Publications

Order by: publication date number of citations

• An exact local mapping from clock-spins to fermions

  Simone Traverso, Christoph Fleckenstein, Maura Sassetti, Niccolò Traverso Ziani

  SciPost Phys. Core 6, 055 (2023) · published 15 August 2023 | Toggle abstract · pdf

  Clock-spin models are attracting great interest, due to both their rich phase diagram and their connection to parafermions. In this context, we derive an exact local mapping from clock-spin to fermionic partition functions. Such mapping, akin to techniques introduced by Fedotov and Popov for spin $\frac{1}{2}$ chains, grants access to well established numerical tools for the perturbative treatment of fermionic systems in the clock-spin framework. Moreover, in one dimension, it allows to use bosonization to access the low energy properties of clock-spin models. Finally, aside from the direct application in clock-spin models, this new mapping enables the conception of interesting fermionic models, based on the clock-spin counterparts.

  1 citation

• Abelian combinatorial gauge symmetry

  Hongji Yu, Dmitry Green, Andrei E. Ruckenstein, Claudio Chamon

  SciPost Phys. Core 7, 014 (2024) · published 26 March 2024 | Toggle abstract · pdf

  Combinatorial gauge symmetry is a principle that allows us to construct lattice gauge theories with two key and distinguishing properties: a) only one- and two-body interactions are needed; and b) the symmetry is exact rather than emergent in an effective or perturbative limit. The ground state exhibits topological order for a range of parameters. This paper is a generalization of the construction to any finite Abelian group. In addition to the general mathematical construction, we present a physical implementation in superconducting wire arrays, which offers a route to the experimental realization of lattice gauge theories with static Hamiltonians.

  1 citation

• On correlation functions for the open XXZ chain with non-longitudinal boundary fields: The case with a constraint

  Giuliano Niccoli, Véronique Terras

  SciPost Phys. 16, 099 (2024) · published 9 April 2024 | Toggle abstract · pdf

  This paper is a continuation of [J. Phys. A: Math. Theor. 55, 405203 (2022)], in which a set of matrix elements of local operators was computed for the XXZ spin-1/2 open chain with a particular case of unparallel boundary fields. Here, we extend these results to the more general case in which both fields are non-longitudinal and related by one constraint, allowing for a partial description of the spectrum by usual Bethe equations. More precisely, the complete spectrum and eigenstates can be characterized within the Separation of Variables (SoV) framework. One uses here the fact that, under the constraint, a part of this SoV spectrum can be described via solutions of a usual, homogeneous, TQ-equation, with corresponding transfer matrix eigenstates coinciding with generalized Bethe states. We explain how to generically compute the action of a basis of local operators on such kind of states, and this under the most general boundary condition on the last site of the chain. As a result, we can compute the matrix elements of some of these basis elements in any eigenstate described by the homogenous TQ-equation. Assuming, following a conjecture of Nepomechie and Ravanini, that the ground state itself can be described in this framework, we obtain multiple integral representations for these matrix elements in the half-infinite chain limit, generalizing those previously obtained in the case of longitudinal boundary fields and in the case of the special boundary conditions considered in [J. Phys. A: Math. Theor. 55, 405203 (2022)].

  1 citation

• Strengthening the atom-field coupling through the deep-strong regime via pseudo-Hermitian Hamiltonians

  M. A. de Ponte, F. Oliveira Neto, P. M. Soares, M. H. Y. Moussa

  SciPost Phys. 15, 091 (2023) · published 13 September 2023 | Toggle abstract · pdf

  We present a strategy for strengthening the atom-field interaction through a pseudo-Hermitian Jaynes-Cummings Hamiltonian. Apart from the engineering of an effective non-Hermitian Hamiltonian, our strategy also relies on the accomplishment of short-time measurements on canonically conjugate variables. The resulting fast Rabi oscillations may be used for many quantum optics purposes and specially to shorten the processing time of quantum information.

  1 citation

• Spatial separation of spin currents in transition metal dichalcogenides

  Antonio L. R. Manesco, Artem Pulkin

  SciPost Phys. Core 6, 036 (2023) · published 1 May 2023 | Toggle abstract · pdf

  We theoretically predict spatial separation of spin-polarized ballistic currents in transition metal dichalcogenides (TMDs) due to trigonal warping. We quantify the effect in terms of spin polarization of charge carrier currents in a prototypical 3-terminal ballistic device where spin-up and spin-down charge carriers are collected by different leads. We show that the magnitude of the current spin polarization depends strongly on the charge carrier energy and the direction with respect to crystallographic orientations in the device. We study the (negative) effect of lattice imperfections and disorder on the observed spin polarization. Our investigation provides an avenue towards observing spin discrimination in a defect-free time reversal-invariant material.

  1 citation

• Downfolding the Su-Schrieffer-Heeger model

  Arne Schobert, Jan Berges, Tim Wehling, Erik van Loon

  SciPost Phys. 11, 079 (2021) · published 20 October 2021 | Toggle abstract · pdf

  Charge-density waves are responsible for symmetry-breaking displacements of atoms and concomitant changes in the electronic structure. Linear response theories, in particular density-functional perturbation theory, provide a way to study the effect of displacements on both the total energy and the electronic structure based on a single ab initio calculation. In downfolding approaches, the electronic system is reduced to a smaller number of bands, allowing for the incorporation of additional correlation and environmental effects on these bands. However, the physical contents of this downfolded model and its potential limitations are not always obvious. Here, we study the potential-energy landscape and electronic structure of the Su-Schrieffer-Heeger (SSH) model, where all relevant quantities can be evaluated analytically. We compare the exact results at arbitrary displacement with diagrammatic perturbation theory both in the full model and in a downfolded effective single-band model, which gives an instructive insight into the properties of downfolding. An exact reconstruction of the potential-energy landscape is possible in a downfolded model, which requires a dynamical electron-biphonon interaction. The dispersion of the bands upon atomic displacement is also found correctly, where the downfolded model by construction only captures spectral weight in the target space. In the SSH model, the electron-phonon coupling mechanism involves exclusively hybridization between the low- and high-energy bands and this limits the computational efficiency gain of downfolded models.

  1 citation

• Prospects for $\tau$ lepton physics at Belle II

  Michel Hernandez Villanueva on behalf of the Belle II collaboration

  SciPost Phys. Proc. 1, 003 (2019) · published 18 February 2019 | Toggle abstract · pdf

  The Belle II experiment is an upgrade of the Belle detector and will operate at the SuperKEKB energy-asymmetric $e^+e^-$ collider. The accelerator has already successfully completed the first phase of commissioning and first electron positron-collisions in Belle II were observed in April 2018. The design luminosity of SuperKEKB is 8x10$^{35}$ cm$^{-2}$s$^{-1}$ and the Belle II experiment aims to record 50 ab$^{-1}$ of data, a factor of 50 more than the Belle experiment. Belle II has a broad program of $\tau$ physics, in particular, precision measurements of Standard Model parameters and searches of lepton flavor and lepton number violations (LFV and LNV), benefiting from the large cross-section of the pairwise $\tau$ lepton production in $e^+e^-$ collisions. In this talk, we will review the $\tau$ lepton physics program of Belle II.

  1 citation

• Punitive Subjectivities and Emotions in Immigration Detention

  Alethia Fernández de la Reguera Ahedo

  Mig. Pol. 3, 004 (2024) · published 11 October 2024 | Toggle abstract · pdf

  In immigration detention centres, emotions run high; tensions, conflicts, anxiety, and affection occur amid bureaucratic procedures, paperwork, files, lists of people, systematisation of cases, buses that come and go with detainees, and people who will be deported. Although immigration detention belongs to administrative law, in practice, detention centres operate closer to penal detention. Little is known about the operation of these places in Mexico, including how punishment takes place in daily practice. Even less is known about the people who work there, especially the rationale and emotions behind their daily decisions and the different ways in which they collaborate with a system that promotes punishment as a central element of immigration detention. In this article, I study how fear and disgust are emotions embedded in institutional practices that reinforce punishment in immigration detention, while empathy can challenge it. I analyse working conditions and daily interactions in detention centres, immigration control facilities and their surroundings. I argue that immigration agents can develop punitive subjectivities to channel emotions derived from anxieties and frustrations of daily work, as well as to embrace a sense of institutional belonging and the illusion of order and control. However, border officers also show empathy towards migrants to cope with emotional distress and humanise their daily work. I intend to answer the questions in this paper: Under what institutional conditions do emotions become power in immigration detention settings? What do emotions reveal about the functioning of punishment in immigration detention centres? How do emotions expressed by INM agents (such as fear, disgust and empathy) enhance or challenge punitive subjectivities?

  1 citation

• SU(3) hybrid static potentials at small quark-antiquark separations from fine lattices

  Carolin Schlosser, Marc Wagner

  SciPost Phys. Proc. 6, 009 (2022) · published 31 May 2022 | Toggle abstract · pdf

  We summarize our recent lattice gauge theory computation of the $\Pi_u$ and $\Sigma_u^-$ hybrid static potentials at small quark-antiquark separations. We provide parameterizations of the resulting lattice data points, which can be used for investigating masses and properties of heavy hybrid mesons in the Born-Oppenheimer approximation.

  1 citation

• Smuggling critique into impact: Research design principles for critical and actionable migration research

  Maybritt Jill Alpes

  Mig. Pol. 4, 004 (2025) · published 12 June 2025 | Toggle abstract · pdf

  This article introduces critical and actionable migration research as an approach for scholars seeking to mobilize their epistemic resources to resist migration laws and policies that violate human rights principles in the short and medium term. While academia is increasingly shaped by a neoliberal “impact agenda,” violence at physical and administrative borders, as well human rights violations continue to intensify - raising questions about the potential role of academic knowledge in resisting these dynamics. Using ideal types as simplified analytical constructs, the article suggests that the limited transformative potential of academic knowledge stems from a persistant dichotomy: applied research is often not critical and critical research is often not actionable. Overcoming this dichotomy, critical and actionable migration research advances structural transformations and reframes while simultaneously remaining actionable for state actors in the short and medium term. As such, critical and actionable migration research is not applied research, nor devoid of theoretical considerations. Using the metaphor of smuggling, this article asks how migration researchers can reclaim the meaning of “impact” so that it contains the grains of critique that resist border violence and human rights violations in the short and medium term. The article’s answer is based on autobiographical explorations of what it means for an anthropologist to produce knowledge on migration from within law faculties and as policy officer and research consultant for human and refugee rights organizations. Based on this material, the article argues that “impact” is nothing to be “done” once the research is completed. To engage in critical and actionable migration research, scholars should instead theorize transformative knowledge encounters between academics and practitioners as integral parts of the research design. After a discussion of the autobiographical data and a conceptual discussion of transformative knowledge encounters, the article highlights three specific research design principles for critical and actionable migration research: (1) building innovative knowledge alliances, (2) theorizing knowledge needs, and (3) brokering the validity of truth claims.

  1 citation