Publications

Order by: publication date number of citations

• Phase diagram of the $\mathbb{Z}_3$-Fock parafermion chain with pair hopping

  Iman Mahyaeh, Jurriaan Wouters, Dirk Schuricht

  SciPost Phys. Core 3, 011 (2020) · published 12 November 2020 | Toggle abstract · pdf

  We study a tight binding model of $\mathbb{Z}_3$-Fock parafermions with single-particle and pair-hopping terms. The phase diagram has four different phases: a gapped phase, a gapless phase with central charge $c=2$, and two gapless phases with central charge $c=1$. We characterise each phase by analysing the energy gap, entanglement entropy and different correlation functions. The numerical simulations are complemented by analytical arguments.

  6 citations

• Functional renormalization group for non-Hermitian and $\mathcal{PT}$-symmetric systems

  Lukas Grunwald, Volker Meden, Dante M. Kennes

  SciPost Phys. 12, 179 (2022) · published 30 May 2022 | Toggle abstract · pdf

  We generalize the vertex expansion approach of the functional renormalization group to non-Hermitian systems. As certain anomalous expectation values might not vanish, additional terms as compared to the Hermitian case can appear in the flow equations. We investigate the merits and shortcomings of the vertex expansion for non-Hermitian systems by considering an exactly solvable $\mathcal{PT}$-symmetric non-linear toy-model and reveal, that in this model, the fidelity of the vertex expansion in a perturbatively motivated truncation schema is comparable with that of the Hermitian case. The vertex expansion appears to be a viable method for studying correlation effects in non-Hermitian systems.

  6 citations

• Delocalized states in three-terminal superconductor-semiconductor nanowire devices

  P. Yu, B. D. Woods, J. Chen, G. Badawy, E. P. A. M. Bakkers, T. D. Stanescu, S. M. Frolov

  SciPost Phys. 15, 005 (2023) · published 11 July 2023 | Toggle abstract · pdf

  We fabricate three-terminal hybrid devices consisting of a semiconductor nanowire segment proximitized by a grounded superconductor and having tunnel probe contacts on both sides. By performing simultaneous tunneling measurements, we identify delocalized states, which can be observed from both ends, and states localized near one of the tunnel barriers. The delocalized states can be traced from zero magnetic field to fields beyond 0.5 T. Within the regime that supports delocalized states, we search for correlated low-energy features consistent with the presence of Majorana zero modes. While both sides of the device exhibit ubiquitous low-energy features at high fields, no correlation is inferred. Simulations using a one-dimensional effective model suggest that the delocalized states, which extend throughout the whole system, have large characteristic wave vectors, while the lower momentum states expected to give rise to Majorana physics are localized by disorder. To avoid such localization and realize Majorana zero modes, disorder needs to be reduced significantly. We propose a method for estimating the disorder strength based on analyzing the level spacing between delocalized states.

  6 citations

• Quantum chaos in interacting Bose-Bose mixtures

  Tran Duong Anh-Tai, Mathias Mikkelsen, Thomas Busch, Thomás Fogarty

  SciPost Phys. 15, 048 (2023) · published 4 August 2023 | Toggle abstract · pdf

  The appearance of chaotic quantum dynamics significantly depends on the symmetry properties of a system, and in cold atomic systems many of these can be experimentally controlled. In this work, we systematically study the emergence of quantum chaos in a minimal system describing one-dimensional harmonically trapped Bose-Bose mixtures by tuning the particle-particle interactions. Using an improved exact diagonalization scheme, we examine the transition from integrability to chaos when the inter-component interaction changes from weak to strong. Our study is based on the analysis of the level spacing distribution and the distribution of the matrix elements of observables in terms of the eigenstate thermalization hypothesis and their dynamics. We show that one can obtain strong signatures of chaos by increasing the inter-component interaction strength and breaking the symmetry of intra-component interactions.

  6 citations

• Topological defects in Floquet circuits

  Mao Tian Tan, Yifan Wang, Aditi Mitra

  SciPost Phys. 16, 075 (2024) · published 13 March 2024 | Toggle abstract · pdf

  We introduce a Floquet circuit describing the driven Ising chain with topological defects. The corresponding gates include a defect that flips spins as well as the duality defect that explicitly implements the Kramers-Wannier duality transformation. The Floquet unitary evolution operator commutes with such defects, but the duality defect is not unitary, as it projects out half the states. We give two applications of these defects. One is to analyze the return amplitudes in the presence of "space-like" defects stretching around the system. We verify explicitly that the return amplitudes are in agreement with the fusion rules of the defects. The second application is to study unitary evolution in the presence of "time-like" defects that implement anti-periodic and duality-twisted boundary conditions. We show that a single unpaired localized Majorana zero mode appears in the latter case. We explicitly construct this operator, which acts as a symmetry of this Floquet circuit. We also present analytic expressions for the entanglement entropy after a single time step for a system of a few sites, for all of the above defect configurations.

  6 citations

• Hamiltonian truncation crafted for UV-divergent QFTs

  Olivier Delouche, Joan Elias Miro, James Ingoldby

  SciPost Phys. 16, 105 (2024) · published 19 April 2024 | Toggle abstract · pdf

  We develop the theory of Hamiltonian Truncation (HT) to systematically study RG flows that require the renormalization of coupling constants. This is a necessary step towards making HT a fully general method for QFT calculations. We apply this theory to a number of QFTs defined as relevant deformations of d=1+1 CFTs. We investigated three examples of increasing complexity: The deformed Ising, Tricritical-Ising, and non-unitary minimal model M(3,7). The first two examples provide a crosscheck of our methodologies against well established characteristics of these theories. The M(3,7) CFT deformed by its $\mathbb{Z}_2$-even operators shows an intricate phase diagram that we clarify. At a boundary of this phase diagram we show that this theory flows, in the IR, to the M(3,5) CFT.

  6 citations

• Exploring coherent elastic neutrino-nucleus scattering of reactor neutrinos with the NUCLEUS experiment

  C. Goupy, H. Abele, G. Angloher, A. Bento, L. Canonica, F. Cappella, L. Cardani, N. Casali, R. Cerulli, I. Colantoni, A. Cruciani, G. del Castello, M. del Gallo Roccagiovine, A. Doblhammer, S. Dorer, A. Erhart, M. Friendl, A. Garai, V. M. Ghete, D. Hauff, F. Jeanneau, E. Jericha, M. Kaznacheeva, A. Kinast, H. Kluck, A. Langenkämper, T. Lasserre, D. Lhuillier, M. Mancuso, B. Mauri, A. Mazzolari, E. Mazzucato, H. Neyrial, C. Nones, L. Oberauer, T. Ortmann, L. Pattavina, L. Peters, F. Petricca, W. Potzel, F. Pröbst, F. Pucci, F. Riendl, R. Rogly, M. Romagnoni, J. Rothe, N. Schermer, J. Schieck, S. Schönert, C. Schwertner, L. Scola, G. Soum Sidikov, L. Stodolsky, R. Strauss, M. Tamisari, C. Tomei, M. Vignati, M. Vivier, V. Wagner, A. Wex (The NUCLEUS collaboration)

  SciPost Phys. Proc. 12, 053 (2023) · published 5 July 2023 | Toggle abstract · pdf

  The NUCLEUS experiment aims to perform a high-precision measurement of Coherent Elastic Neutrino-Nucleus Scattering (CEvNS) at the EdF Chooz B nuclear power plant in France. CEvNS is a unique process to study neutrino properties and to search for physics beyond the Standard Model. The study of CEvNS is also important for light Dark-Matter searches. It could be a possible irreducible background for high-sensitivity Dark-Matter experiments. NUCLEUS is an experiment under construction based on ultra-low threshold ($\sim$20 eV$_{nr}$) cryogenic calorimeters, operated at tens-of-mK temperatures.

  6 citations

• GrassmannTN: A Python package for Grassmann tensor network computations

  Atis Yosprakob

  SciPost Phys. Codebases 20 (2023) · published 16 November 2023 | Toggle abstract · pdf

  We present GrassmannTN, a Python package for the computation of the Grassmann tensor network. The package is built to assist in the numerical computation without the need to input the fermionic sign factor manually. It prioritizes coding readability by designing every tensor manipulating function around the tensor subscripts. The computation of the Grassmann tensor renormalization group and Grassmann isometries using GrassmannTN are given as the use case examples.

  6 citations

• Normalizing flows for high-dimensional detector simulations

  Florian Ernst, Luigi Favaro, Claudius Krause, Tilman Plehn, David Shih

  SciPost Phys. 18, 081 (2025) · published 5 March 2025 | Toggle abstract · pdf

  Whenever invertible generative networks are needed for LHC physics, normalizing flows show excellent performance. In this work, we investigate their performance for fast calorimeter shower simulations with increasing phase space dimension. We use fast and expressive coupling spline transformations applied to the CaloChallenge datasets. In addition to the base flow architecture we also employ a VAE to compress the dimensionality and train a generative network in the latent space. We evaluate our networks on several metrics, including high-level features, classifiers, and generation timing. Our findings demonstrate that invertible neural networks have competitive performance when compared to autoregressive flows, while being substantially faster during generation.

  6 citations

• Conformal boundary conditions for a 4d scalar field

  Lorenzo Di Pietro, Edoardo Lauria, Pierluigi Niro

  SciPost Phys. 16, 090 (2024) · published 3 April 2024 | Toggle abstract · pdf

  We construct unitary, stable, and interacting conformal boundary conditions for a free massless scalar in four dimensions by coupling it to edge modes living on a boundary. The boundary theories we consider are bosonic and fermionic QED$_3$ with $N_f$ flavors and a Chern-Simons term at level $k$, in the large-$N_f$ limit with fixed $k/N_f$. We find that interacting boundary conditions only exist when $k≠ 0$. To obtain this result we compute the $\beta$ functions of the classically marginal couplings at the first non-vanishing order in the large-$N_f$ expansion, and to all orders in $k/N_f$ and in the couplings. To check vacuum stability we also compute the large-$N_f$ effective potential. We compare our results with the the known conformal bootstrap bounds.

  6 citations