Publications

Order by: publication date number of citations

• Gauging non-invertible symmetries on the lattice

  Sahand Seifnashri, Shu-Heng Shao, Xinping Yang

  SciPost Phys. 19, 063 (2025) · published 29 August 2025 | Toggle abstract · pdf

  We provide a general prescription for gauging finite non-invertible symmetries in 1+1d lattice Hamiltonian systems. Our primary example is the Rep(D$_8$) fusion category generated by the Kennedy-Tasaki transformation, which is the simplest anomaly-free non-invertible symmetry on a spin chain of qubits. We explicitly compute its lattice F-symbols and illustrate our prescription for a particular (non-maximal) gauging of this symmetry. In our gauging procedure, we introduce two qubits around each link, playing the role of "gauge fields" for the non-invertible symmetry, and impose novel Gauss's laws. Similar to the Kramers-Wannier transformation for gauging an ordinary $\mathbb{Z}_2$, our gauging can be summarized by a gauging map, which is part of a larger, continuous non-invertible cosine symmetry.

  3 citations

• Disordered $\mathcal{N} = (2, 2)$ supersymmetric field theories

  Chi-Ming Chang, Xiaoyang Shen

  SciPost Phys. 16, 140 (2024) · published 30 May 2024 | Toggle abstract · pdf

  We investigate a large class of $\mathcal{N}=(2,2)$ supersymmetric field theories in two dimensions, which contains the Murugan-Stanford-Witten model, and can be naturally regarded as a disordered generalization of the two-dimensional Landau-Ginzburg models. We analyze the two and four-point functions of chiral superfields, and extract from them the central charge, the operator spectrum, and the chaos exponent in these models. Some of the models exhibit a conformal manifold parameterized by the variances of the random couplings. We compute the Zamolodchikov metrics on the conformal manifold, and demonstrate that the chaos exponent varies nontrivally along the conformal manifolds. Finally, we introduce and perform some preliminary analysis of a disordered generalization of the gauged linear sigma models, and discuss the low energy theories as ensemble averages of Calabi-Yau sigma models over complex structure moduli space.

  3 citations

• The friction of tilted skates on ice

  J. M. J. van Leeuwen

  SciPost Phys. 8, 059 (2020) · published 16 April 2020 | Toggle abstract · pdf

  The friction felt by a speed skater is calculated as function of the velocity and tilt angle of the skate. This calculation is an extension of the more common theory of friction of upright skates. Not only in rounding a curve the skate has to be tilted, but also in straightforward skating small tilt angles occur, which turn out to be of noticeable influence on the friction. As for the upright skate the friction remains fairly insensitive of the velocities occurring in speed skating.

  3 citations

• Viability of rotation sensing using phonon interferometry in Bose-Einstein condensates

  Charles W. Woffinden, Andrew J. Groszek, Guillaume Gauthier, Bradley J. Mommers, Michael. W. J. Bromley, Simon A. Haine, Halina Rubinsztein-Dunlop, Matthew J. Davis, Tyler W. Neely, Mark Baker

  SciPost Phys. 15, 128 (2023) · published 2 October 2023 | Toggle abstract · pdf

  We demonstrate the use of a ring-shaped Bose-Einstein condensate as a rotation sensor by measuring the interference between two counter-propagating phonon modes imprinted azimuthally around the ring. We observe rapid decay of the excitations, quantified by quality factors of at most Q ≈ 27. We numerically model our experiment using the c-field methodology, allowing us to estimate the parameters that maximise the performance of our sensor. We explore the damping mechanisms underlying the observed phonon decay, and identify two distinct Landau scattering processes that each dominate at different driving amplitudes and temperatures. Our simulations reveal that Q is limited by strong damping of phonons even in the zero temperature limit. We perform an experimental proof-of-principle rotation measurement using persistent currents imprinted around the ring. We demonstrate a rotation sensitivity of up to $\Delta \Omega ≈ 0.3 rad s^{-1}$ from a single image, with a theoretically achievable value of $\Delta \Omega ≈ 0.04 rad s^{-1}$ in the atomic shot-noise limit. This is a significant improvement over the shot-noise-limited $\Delta \Omega ≈ 1 rad s^{-1}$ sensitivity obtained by Marti et al. [Phys. Rev. A 91, 013602 (2015)] for a similar setup.

  3 citations

• Global symmetry and conformal bootstrap in the two-dimensional $Q$-state Potts model

  Rongvoram Nivesvivat

  SciPost Phys. 14, 155 (2023) · published 14 June 2023 | Toggle abstract · pdf

  The Potts conformal field theory is an analytic continuation in the central charge of conformal field theory describing the critical two-dimensional $Q$-state Potts model. Four-point functions of the Potts conformal field theory are dictated by two constraints: the crossing-symmetry equation and $S_Q$ symmetry. We numerically solve the crossing-symmetry equation for several four-point functions of the Potts conformal field theory for $Q\in\mathbb{C}$. In all examples, we find crossing-symmetry solutions that are consistent with $S_Q$ symmetry of the Potts conformal field theory. In particular, we have determined their numbers of crossing-symmetry solutions, their exact spectra, and a few corresponding fusion rules. In contrast to our results for the $O(n)$ model, in most of examples, there are extra crossing-symmetry solutions whose interpretations are still unknown.

  3 citations

• Faraday rotation and transmittance as markers of topological phase transitions in 2D materials

  Manuel Calixto, Alberto Mayorgas, Nicolás A. Cordero, Elvira Romera, Octavio Héctor Castaños Garza

  SciPost Phys. 16, 077 (2024) · published 18 March 2024 | Toggle abstract · pdf

  We analyze the magneto-optical conductivity (and related magnitudes like transmittance and Faraday rotation of the irradiated polarized light) of some elemental two-dimensional Dirac materials of group IV (graphene analogues, buckled honeycomb lattices, like silicene, germanene, stannane, etc.), group V (phosphorene), and zincblende heterostructures (like HgTe/CdTe quantum wells) near the Dirac and gamma points, under out-of-plane magnetic and electric fields, to characterize topological-band insulator phase transitions and their critical points. We provide plots of the Faraday angle and transmittance as a function of the polarized light frequency, for different external electric and magnetic fields, chemical potential, HgTe layer thickness and temperature, to tune the material magneto-optical properties. We have shown that absortance/transmittance acquires extremal values at the critical point, where the Faraday angle changes sign, thus providing fine markers of the topological phase transition. In the case of non-topological materials as phosphorene, a minimum of the transmittance is also observed due to the energy gap closing by an external electric field.

  3 citations

• Elliptic deformation of $\mathcal{W}_N$-algebras

  Jean Avan, Luc Frappat, Eric Ragoucy

  SciPost Phys. 6, 054 (2019) · published 7 May 2019 | Toggle abstract · pdf

  We construct $q$-deformations of quantum $\mathcal{W}_N$ algebras with elliptic structure functions. Their spin $k+1$ generators are built from $2k$ products of the Lax matrix generators of ${\mathcal{A}_{q,p}(\widehat{gl}(N)_c)}$). The closure of the algebras is insured by a critical surface condition relating the parameters $p,q$ and the central charge $c$. Further abelianity conditions are determined, either as $c=-N$ or as a second condition on $p,q,c$. When abelianity is achieved, a Poisson bracket can be defined, that we determine explicitly. One connects these structures with previously built classical $q$-deformed $\mathcal{W}_N$ algebras and quantum $\mathcal{W}_{q,p}(\mathfrak{sl}_N)$.

  3 citations

• Thermodynamic limit and boundary energy of the spin-1 Heisenberg chain with non-diagonal boundary fields

  Zhihan Zheng, Pei Sun, Xiaotian Xu, Tao Yang, Junpeng Cao, Wen-Li Yang

  SciPost Phys. 12, 071 (2022) · published 22 February 2022 | Toggle abstract · pdf

  The thermodynamic limit and boundary energy of the isotropic spin-1 Heisenberg chain with non-diagonal boundary fields are studied. The finite size scaling properties of the inhomogeneous term in the $T-Q$ relation at the ground state are calculated by the density matrix renormalization group. Based on our findings, the boundary energy of the system in the thermodynamic limit can be obtained from Bethe ansatz equations of a related model with parallel boundary fields. These results can be generalized to the $SU(2)$ symmetric high spin Heisenberg model directly.

  3 citations

• A systematic interpolatory method for an impurity in a one-dimensional fermionic background

  Erik J. Lindgren, Rafael E. Barfknecht, Nikolaj T. Zinner

  SciPost Phys. 9, 005 (2020) · published 13 July 2020 | Toggle abstract · pdf

  We explore a new numerical method for studying one-dimensional quantum systems in a trapping potential. We focus on the setup of an impurity in a fermionic background, where a single distinguishable particle interacts through a contact potential with a number of identical fermions. We can accurately describe this system, for various particle numbers, different trapping potentials and arbitrary finite repulsion, by constructing a truncated basis containing states at both zero and infinite repulsion. The results are compared with matrix product states methods and with the analytical result for two particles in a harmonic well.

  3 citations

• Quantum walks on graphs of the ordered Hamming scheme and spin networks

  Hiroshi Miki, Satoshi Tsujimoto, Luc Vinet

  SciPost Phys. 7, 001 (2019) · published 2 July 2019 | Toggle abstract · pdf

  It is shown that the hopping of a single excitation on certain triangular spin lattices with non-uniform couplings and local magnetic fields can be described as the projections of quantum walks on graphs of the ordered Hamming scheme of depth 2. For some values of the parameters the models exhibit perfect state transfer between two summits of the lattice. Fractional revival is also observed in some instances. The bivariate Krawtchouk polynomials of the Tratnik type that form the eigenvalue matrices of the ordered Hamming scheme of depth 2 give the overlaps between the energy eigenstates and the occupational basis vectors.

  3 citations