Publications

Order by: publication date number of citations

• Identifying biases of the Majorana scattering invariant

  Isidora Araya Day, Antonio L. R. Manesco, Michael Wimmer, Anton R. Akhmerov

  SciPost Phys. Core 8, 047 (2025) · published 4 July 2025 | Toggle abstract · pdf

  The easily accessible experimental signatures of Majorana modes are ambiguous and only probe topology indirectly: for example, quasi-Majorana states mimic most properties of Majoranas. Establishing a correspondence between an experiment and a theoretical model known to be topological resolves this ambiguity. Here we demonstrate that already theoretically determining whether a finite system is topological is by itself ambiguous. In particular, we show that the scattering topological invariant—a probe of topology most closely related to transport signatures of Majoranas—has multiple biases in finite systems. For example, we identify that quasi-Majorana states also mimic the scattering invariant of Majorana zero modes in intermediate-sized systems. We expect that the bias due to finite size effects is universal, and advocate that the analysis of topology in finite systems should be accompanied by a comparison with the thermodynamic limit. Our results are directly relevant to the applications of the topological gap protocol.

• Functional renormalization group approach for signal detection

  Vincent Lahoche, Dine Ousmane Samary, Mohamed Tamaazousti

  SciPost Phys. Core 7, 077 (2024) · published 2 December 2024 | Toggle abstract · pdf

  This review paper utilizes renormalization group techniques for signal detection in nearly continuous positive spectra. We emphasize the universal aspects of the analogue field-theory approach. The primary objective is to present an extended self-consistent construction of the analogue effective field-theory framework for data, which can be interpreted as a maximum entropy model. In particular, we leverage universality arguments to justify the $\mathbb{Z}_2$ symmetry of the classical action, highlighting the existence of both a large-scale (local) regime and a small-scale (nonlocal) regime. Secondly, in relation to noise models, we observe the universal relationship between phase transitions and symmetry breaking near the detection threshold. Finally, we address the challenge of defining the covariance matrix for tensor-like data. Based on the cutting graph prescription, we note the superiority of definitions that rely on complete graphs of large size for data analysis.

• Exact solution of the Izergin-Korepin Gaudin model with periodic and open boundaries

  Xiaotian Xu, Pei Sun, Xin Zhang, Junpeng Cao, Tao Yang

  SciPost Phys. Core 8, 041 (2025) · published 21 May 2025 | Toggle abstract · pdf

  We study the Izergin-Korepin Gaudin models with both periodic and open integrable boundary conditions, which describe quantum systems exhibiting novel long-range interactions. Using the Bethe Ansatz approach, we derive the eigenvalues of the Gaudin operators and the corresponding Bethe Ansatz equations.

• Unraveling complexity: Singular value decomposition in complex experimental data analysis

  Judith F. Stein, Aviad Frydman, Richard Berkovits

  SciPost Phys. Core 7, 061 (2024) · published 11 September 2024 | Toggle abstract · pdf

  Analyzing complex experimental data with multiple parameters is challenging. We propose using Singular Value Decomposition (SVD) as an effective solution. This method, demonstrated through real experimental data analysis, surpasses conventional approaches in understanding complex physics data. Singular values and vectors distinguish and highlight various physical mechanisms and scales, revealing previously challenging elements. SVD emerges as a powerful tool for navigating complex experimental landscapes, showing promise for diverse experimental measurements.

• Domain-wall melting and entanglement in free-fermion chains with a band structure

  Viktor Eisler

  SciPost Phys. Core 8, 069 (2025) · published 14 October 2025 | Toggle abstract · pdf

  We study the melting of a domain wall in free-fermion chains, where the periodic variation of the hopping amplitudes gives rise to a band structure. It is shown that the entanglement grows logarithmically in time, and the prefactor is proportional to the number of filled bands in the initial state. For a dimerized chain the particle density and current are found to have the same expressions as in the homogeneous case, up to a rescaling of the velocity. The universal contribution to the entropy profile is then doubled, while the non-universal part can be extracted numerically from block-Toeplitz matrices.

• Freelance holography, part II: Moving boundary in gauge/gravity correspondence

  Aliasghar Parvizi, Mohammad M. Sheikh-Jabbari, Vahid Taghiloo

  SciPost Phys. Core 8, 075 (2025) · published 31 October 2025 | Toggle abstract · pdf

  We continue developing the freelance holography program, formulating gauge/gravity correspondence where the gravity side is formulated on a space bounded by a generic timelike codimension-one surface inside AdS and arbitrary boundary conditions are imposed on the gravity fields on the surface. Our analysis is performed within the Covariant Phase Space Formalism (CPSF). We discuss how a given boundary condition on the bulk fields on a generic boundary evolves as we move the boundary to another boundary inside AdS and work out how this evolution is encoded in deformations of the holographic effective boundary theory. Our analyses here extend the extensively studied $\text{T}\bar{\text{T}}$-deformation by relaxing the boundary conditions at asymptotic AdS or at the cutoff surface to be any arbitrary one (besides Dirichlet). We discuss some of the implications of our general freelance holography setting.

• How to unfold top decays

  Luigi Favaro, Roman Kogler, Alexander Paasch, Sofia Palacios Schweitzer, Tilman Plehn, Dennis Schwarz

  SciPost Phys. Core 8, 053 (2025) · published 18 August 2025 | Toggle abstract · pdf

  Using unfolded top-quark decay data we can measure the top quark mass, as well as search for unexpected kinematic effects. We present a new generative unfolding method for the two tasks and show how they both benefit from unbinned, high-dimensional unfolding. Unlike weight-based or iterative generative methods we include a targeted unbiasing with respect to the training data. This shows significant advantages over standard, iterative methods, in terms of applicability, flexibility and accuracy.

• Two-loop gradient-flow renormalization of scalar QCD

  Janosh Borgulat, Nils Felten, Robert V. Harlander, Jonas T. Kohnen

  SciPost Phys. Core 8, 032 (2025) · published 21 March 2025 | Toggle abstract · pdf

  The gradient-flow formalism is applied to a non-Abelian gauge theory with scalar and fermionic particles, dubbed "scalar QCD". It is shown that the flowed scalar quark requires a field renormalization, albeit only beyond the one-loop level. A pseudo-physical, flow-time dependent renormalization scheme is defined, and the corresponding renormalization constant is evaluated at the two-loop level. We also calculate the gluon action density as well as the condensates of the scalar and the fermionic quark at three-loop level in this theory. The results validate the consistency of the gradient-flow formalism in this theory and provide a further step towards applying the gradient-flow formalism to the full Standard Model.

• Site-wise dynamic defects in a non-conserving exclusion process

  Nikhil Bhatia, Arvind Kumar Gupta

  SciPost Phys. Core 8, 009 (2025) · published 27 January 2025 | Toggle abstract · pdf

  Motivated by the significant influence of the defects in the dynamics of the natural or man-made transportation systems, we propose an open, dynamically disordered, totally asymmetric simple exclusion process featuring bulk particle attachment and detachment. The site-wise dynamic defects might randomly emerge or vanish at any lattice location, and their presence slows down the motion of the particles. Using a mean-field approach, we obtain an analytical expression for both particle and defect density and validate them using Monte Carlo simulation. The study investigates the steady-state characteristics of the system, including phase transitions, analysis of boundary layers, and phase diagrams. Our approach streamlines the defect dynamics by integrating two parameters into one called the obstruction factor, which helps in determining an effective binding constant. The impact of the obstruction factor on the phase diagram is explored across various combinations of binding constants and detachment rates. A critical value of the obstruction factor is obtained, about which an infinitesimal change results in a substantial qualitative change in the structure of the phase diagrams. Further, the effect of the detachment rate is studied, and critical values along which the system observes a quantitative transition of the stationary phases are obtained as a function of the obstruction factor. Overall, the system shows stationary phases ranging from three to seven depending upon the value of the obstruction factor, the binding constant, and the detachment rate. Moreover, we scrutinized the impact of the obstruction factor on the shock dynamics and found no finite-size effect.

• Dissipation and noise in strongly driven Josephson junctions

  Vasilii Vadimov, Yoshiki Sunada, Mikko Möttönen

  SciPost Phys. Core 8, 065 (2025) · published 6 October 2025 | Toggle abstract · pdf

  In circuit quantum electrodynamical systems, the quasiparticle-related losses in Josephson junctions are suppressed due to the gap in the superconducting density of states which is much higher than the typical energy of a microwave photon. In this work, we show that a strong drive even at a frequency lower than twice the superconductor gap parameter can activate dissipation in the junctions due to photon-assisted breaking of the Cooper pairs. Both the decay rate and noise strength associated with the losses are sensitive to the dc phase bias of the junction and can be tuned in a broad range by the amplitude and the frequency of the external driving field, making the suggested mechanism potentially attractive for designing tunable dissipative elements. We also predict pronounced memory effects in the driven Josephson junctions, which are appealing for both theoretical and experimental studies of non-Markovian physics in superconducting quantum circuits. We illustrate our theoretical findings by studying the spectral properties and the steady-state population of a low-impedance resonator coupled to the driven Josephson junction: we show the emergence of non-Lorentzian spectral lines and broad tunability of effective temperature of the steady state.