We investigate an interface in the transverse field quantum Ising chain connecting an ordered ferromagnetic phase and a disordered paramagnetic phase that are Kramers-Wannier duals of each other. Unlike prior studies focused on non-invertible defects, this interface exhibits a symmetry that combines Kramers-Wannier transformation with spatial reflection. We demonstrate that, under open boundary conditions, this setup gives rise to a discrete $\mathbb{Z}_4$ symmetry, encompassing the conventional $\mathbb{Z}_2$ Ising parity as a subgroup, while in a closed geometry a non-invertible symmetry emerges. Using the Jordan-Wigner transformation, we map the spin chain onto a solvable quadratic Majorana fermion system. In this formulation, the $\mathbb{Z}_4$ symmetry is realized manifestly as a parity-dependent reflection with respect to a Majorana site, in contrast to the conventional reflection which mirrors with respect to the central link of the Majorana chain. Additionally, we construct Majorana strong zero modes that retain the $\mathbb{Z}_4$ symmetry, ensure degeneracies of all energy eigenstates, and are robust under generic local symmetry-preserving perturbations of the fermion model, including interactions. Finally, we develop quantum circuit realizations of our model paving the way towards the creation of exact Majorana strong zero modes with digital quantum hardware.
We demonstrate deterministic preparation, cooling, and fluorescence detection of individual strontium-88 atoms trapped in optical tweezers. We compare trapping, cooling and imaging in the established wavelength of 813 nm and the technically more convenient wavelength of 532 nm. Moreover, we demonstrate sorting of the atoms into an array without vacancies.
Rindler worldsheets are well known to transition into a tensionless regime in the infinite acceleration limit, acquiring an emergent Carrollian structure. In this work, we uncover an entirely new manifestation of such tensionless dynamics by constructing a time-evolving Milne worldsheet within the future (expanding) and past (contracting) regions of the background target spacetime. We show that as the Milne worldsheet approaches its null horizons, it reveals a deep and previously unexplored interplay between tensionless string dynamics and an emergent Carrollian structure, governed by an ultra-high frequency limit in time evolution. Our results demonstrate that non-inertial string dynamics can emerge in two structurally independent yet complementary settings—governed either by worldsheet acceleration (Rindler) or by the frequency of its intrinsic time evolution (Milne). Remarkably, we uncover a non-trivial duality-like correspondence between Rindler and Milne worldsheets near their respective null horizons, both exhibiting identical tensionless physics despite their distinct causal and dynamical origins. This discovery positions the Milne construction as a genuine time-like counterpart to the ultra-relativistic (Carrollian) or infinite-boost limit, offering new foundational insights into the deep structure of non-inertial string theory.
The scalar potential of any particle-physics model must be bounded from below (BFB). We consider the extension of the Standard electroweak Model with three SU(2) doublets of scalars and a symmetry under which each of those doublets changes sign. In the absence of necessary and sufficient conditions for boundedness from below (BnessFB) for this specific model, we argue that one may use increasingly stringent sets of necessary conditions. We introduce a Mathematica code, StableWein, that implements this idea. The user is allowed to choose the level of accuracy that they want in the determination of BnessFB; more precision means the use of more necessary conditions, and usually entails a longer running time for the code. Our investigation suggests that our procedure and code can be extremely precise in the determination of the potentials that are BFB. In addition, we introduce a machine-learning code that identifies, with more than 99% accuracy, which potentials are BFB.
Using data about the number of local minimal energy structures and the energy of the global minima structures of the Lennard-Jones potential for 9 <= N <= 16 atoms and dimension 1 <= D <= N - 1, we propose new expressions to extrapolate these quantities taking advantage of the new multidimensional results. These expressions are obtained based on both multidimensional data fitting and neural networks to dimensionally move from known values, providing then new and more reliable extrapolations of the number of local minima energy structures, compared with previous methods based only on extrapolation of the number of three-dimensional local minimal energy structures for N <= 15 atoms. Our estimations of the number of local minima in terms of N and D show that the maximum number of stable structures of the potential is found at D = 3. We also propose an expression to estimate the energies of the global minima energy structures, beyond the dimension D = 3 case. Surprisingly, we found that for each value of N, the energy of the global minimum can be divided into two regimes: when D <= [N/2] and when D >= [N/2], where [X] means the whole part of X, each exhibiting a significantly different trend from the other. While the data are limited, the observed trends appear robust, and the resulting fits provide reliable estimates even for values of N beyond current computational feasibility.
The quantum phase transitions of a three-level Tavis-Cummings model in the $\Xi$-configuration driven by a single-mode electromagnetic field in a QED cavity are studied for $n_a=1,\,2$, and $4$ atoms. Although conventional observables like photon number and energy level populations suffice to locate quantum phase transitions, they often lack sensitivity to finite-size effects. Here, we show that the expectation values of the quadratic Casimir invariants associated with the atomic subsystems offer a more robust measure, exhibiting sharp signatures of criticality that are validated by fidelity calculations. Additionally, the von Neumann entropy is employed to map the entanglement landscape between matter and the quantized field. A key finding is that the external driving field acts as a control parameter that shrinks the normal phase region; as the driving intensity increases, the separable ground state vanishes, leading to the dominance of field-matter entanglement across the parameter space.
We construct a previously missing \mathbb{Z}_2 ℤ 2 topological invariant for three-dimensional band structures in symmetry class CI defined by parity-time (PT) and parity-particle-hole (PC) symmetries. PT symmetry allows one to define a real Berry connection and, based on the \eta η -invariant, a spin-Chern–Simons (spin-CS) action. We show that PC symmetry quantizes the spin-CS action to \{0,2\pi\} { 0 , 2 π } with 4\pi 4 π periodicity, thereby yielding a well-defined \mathbb{Z}_2 ℤ 2 invariant. This invariant is additive under direct sums of isolated band structures, reduces to a known \mathbb{Z}_2 ℤ 2 index when a global Takagi factorization exists, and in general depends on the choice of spin structure. Finally, we demonstrate lattice models in which this newly introduced \mathbb{Z}_2 ℤ 2 invariant distinguishes topological phases that cannot be detected by the previously known topological indices.
We investigate the standard quantum teleportation protocol for a single-qubit state, focusing on the scenario where the qubit undergoes a class of non-unitary evolution governed by parity-time (PT)-symmetric non-Hermitian Hamiltonians. Additionally, we examine the case where the entangled pair shared by Alice and Bob is exposed to a noise channel. In the PT-symmetric regime, the teleportation fidelity exhibits time-dependent oscillations. Compared to the conventional case without non-Hermitian operations, periodic enhancements in fidelity are observed, and we analytically derive their dependence on the parameters of both the non-Hermitian Hamiltonian and noise channel. When the PT symmetry is broken, the fidelity ceases to oscillate and instead decays to a steady value. Notably, even in this regime, non-Hermitian operations can yield fidelity improvements over conventional schemes. We further investigate the teleportation of quantum Fisher information (QFI) and find that its evolutionary behavior differs from that of fidelity. Analytical results reveal that QFIs corresponding to different estimated parameters exhibit distinct outcomes at Bob's receiving end during teleportation. Furthermore, we derive a trade-off inequality between fidelity and QFI, offering a theoretical tool to coordinately optimize these two quantities in the teleportation process.
Optical Fabry-Perot cavities are crucial tools for metrology experiments, where they achieve extreme length stability, and for some atomic physics experiments, where tunability to atomic transitions enables atom-light interactions. However, achieving both frequency stability and tunability in a single cavity has remained a challenge, forcing metrology experiments exploiting atom-cavity interactions to rely on external active feedback systems to stabilize the length of the cavity. Here, we describe a piezoelectrically-tunable cavity with a cancellation of the coefficient of thermal expansion at around 5^∘C, achieving fractional frequency instabilities at the 4× 10^-13 level for 1 s integration time. This advance eliminates the need for external stabilization in many atom-cavity experiments, making this design ideal for applications such as ultra-stable superradiant lasers and other cavity quantum electrodynamics experiments.
In this work, we will continue our analysis of some general probe M5 brane solutions from our previous work in AdS7 x S4 spacetime (appeared in arXiv: 2109.08551). These are codimension-2 in AdS7 and preserve at least 2 supercharges when the worldvolume 3-form flux field strength is zero. We will turn on the field strength and find that the embedding conditions are modified, excluding certain branes contained in the previous result. The new main result here is very general, so we pick simpler embedding conditions that describe highly symmetric examples that preserve half of the supersymmetry of the 11 dimensions. When the flux field is zero, worldvolumes have AdS5 x S1 topology. We turn the flux field value non-zero in these examples and analyze how the shape of the worldvolume deforms as supersymmetry is broken by some additional fractions.
The Nekrasov instanton partition function of the 4d $\mathcal{N}=2^*$ $U(N)$ gauge theory (a mass deformation of 4d $\mathcal{N}=4$ super-Yang-Mills theory), which is a generating series of equivariant integrals over instanton moduli spaces, is given by a sum over colored partitions weighted by a counting parameter $\mathfrak{q}$. This note proves convergence of the series in the unit disk $|\mathfrak{q}|<1$ for generic parameters. Specifically, the absolute convergence radius of this sum is determined, assuming that mass and Coulomb branch parameters avoid some lattice. If the ratio $b^2=ε_1/ε_2$ of equivariant parameters is in $\mathbb{C}\setminus[0,+\infty)$, the radius is $1$, as expected. If $b^2$ is non-negative, three cases arise: the radius is finite if $b^2$ has finite exponential type (a generalization of Brjuno numbers), namely there exists $C>0$ such that $|b^2-p/q|>\exp(-Cq)$ for all integers $p,q\neq 0$; the series diverges if $b^2$ is super-exponentially well approximable by rationals; and if $b^2$ is rational some terms are singular. The AGT correspondence translates these results to convergence of torus one-point conformal blocks of the Virasoro and $W_N$ algebras with non-real $b$, within the unit disk. For the Virasoro algebra this corresponds to a central charge in $\mathbb{C}\setminus[25,+\infty)$.
The stochastic dynamics of flagellar beating for micro-swimmers, such as flagellated cells, sperms and microalgae, is dominated by a feedback mechanism between flagellar shape and the rate of activation/de-activation of the N ≫ 1 driving molecular motors. In the context of the so-called rigid filament models, where the axoneme is described by a single degree of freedom X(t), we investigate the effect of direct coupling between the activity dynamics of adjacent motors, parametrized by K ≥ 0. A functional Fokker-Planck equation for X and the state of the N motors is obtained. In the limit of small coupling K ≪ 1, we derive a system of equations governing the dynamics of the Fourier modes of the active motor density, obtaining estimates for several observables and the fluctuations' quality factor Q. For larger K we resort to numerical simulations. The effect of introducing the coupling K>0 is to increase characteristic times and the beating period. Moreover at large Ks the limit cycle becomes bi-stable, with abrupt avalanches of the motor dynamics. Increasing K is similar to what observed in the case K=0 when the confining elastic force is strongly reduced. The quality factor of fluctuations has a non-monotonic behavior: it first increases with K, then decreases. This is accompanied by the reduction and eventual disappearance of regions where the fraction of activated motor is nor 0 neither 1.
In this work, we will continue our analysis of some general probe M5 brane solutions from our previous work in $AdS_7 × S^4$ spacetime (appeared in arXiv: 2109.08551). These are codimension-2 in $AdS_7$ and preserve at least 2 supercharges when the worldvolume 3-form flux field strength is zero. We will turn on the field strength and find that the embedding conditions are modified, excluding certain branes contained in the previous result. The new main result here is very general, so we pick simpler embedding conditions that describe highly symmetric examples that preserve half of the supersymmetry of the 11 dimensions. When the flux field is zero, worldvolumes have $AdS_5 × S^1$ topology. We turn the flux field value non-zero in these examples and analyze how the shape of the worldvolume deforms as supersymmetry is broken by some additional fractions.
Recently, researchers have proposed the Asymmetric Bethe Ansatz method, a theoretical tool that extends the scope of Bethe Ansatz-solvable models by "breaking" partial mirror symmetry via the introduction of a fully reflecting boundary. Within this framework, the integrability conditions which were originally put forward by Gaudin have been further generalized. In this work, building on Gaudin's generalized kaleidoscope model, we present a detailed investigation of the relationship between dihedral symmetry and its Bethe-type solvability. We identify a scattering-consistency relation, which we refer to as the Kaleidoscope Yang-Baxter Equation (KYBE), and use it to organize the Bethe-type construction in the present two-dimensional setting. Furthermore, we show that the solvability of a model via the coordinate Bethe Ansatz depends not only on the consistency relations satisfied by scattering matrices, but also on the model’s boundary conditions and the symmetry of the subspace where solutions are sought. Through finite-element-based numerical studies, we further confirm that Bethe Ansatz integrability arises in a specific symmetry sector. Finally, by analyzing the algebraic structure of the Kaleidoscope Yang-Baxter Equation, we derive a family of algebraic identities within the framework of quantum torus algebra.
We investigate how strongly broken spatial symmetries affect the Kohn-Luttinger (KL) mechanism, in which superconductivity emerges purely from repulsive interactions. While the original KL argument assumes continuous rotational symmetry, real materials possess only discrete point-group symmetries, raising a central question: can sufficiently strong symmetry breaking suppress or eliminate KL superconductivity? Using controlled perturbation theory and explicit two-dimensional models with Ising and Rashba spin-orbit coupling (SOC), we find that KL superconductivity is broadly robust and exhibits qualitatively universal behavior across models: the transition temperature $T_c$ is nonmonotonic in the symmetry-breaking field, shows a pronounced maximum at scales of the order of the Fermi energy, and decays exponentially toward zero at asymptotically large fields. However, the physical mechanisms determining this suppression may differ between models. Overall, these results demonstrate that KL-type superconductivity can persist across a wide class of spin-orbit-coupled systems.
While in pristine bilayer graphene the Berry curvature dipole (BCD) vanishes, uniaxial strain can give rise to finite BCD. We investigate this by using a tight-binding (TB) approach built on the Slater-Koster parametrization to capture lattice deformation effects often missed by continuum models. We demonstrate that the BCD's evolution with strain and doping is highly sensitive to the choice in parametrization, particularly when including the longer range interlayer skew hoppings. Additionally, out-of-plane compression enhances the response by broadening the Dirac cones. By comparing TB and continuum calculations, we identify regimes in which substantial deviations between the two approaches arise at larger strain or higher carrier density. Our results provide a realistic microscopic benchmark for the intrinsic band-geometric contribution to nonlinear Hall transport in strained bilayer graphene.
Neural Quantum States (NQS) are powerful tools used to represent complex quantum many-body states in an increasingly wide range of applications. However, despite their popularity, at present only a rudimentary understanding of their limitations exists. In this work, we investigate the dependence of NQS on the choice of the computational basis, focusing on restricted Boltzmann machines. Considering a family of rotated Hamiltonians corresponding to the paradigmatic transverse-field Ising model, we discuss the properties of ground states responsible for the dependence of NQS performance, namely the presence of ground state degeneracies as well as the uniformity of amplitudes and phases, carefully examining their interplay. We identify that the basis-dependence of the performance is linked to the convergence properties of a cluster or cumulant expansion of multi-spin operators – providing a framework to directly connect physical, basis-dependent properties, to performance itself. Our results provide insights that may be used to gauge the applicability of NQS to new problems and to identify the optimal basis for numerical computations.
We present a solvable one-dimensional spin-1/2 model on the diamond chain featuring three-spin interactions, which displays both, mobile excitations driving a second-order phase transition between an ordered and a Z2-symmetry broken phase, as well as non-trivial fully immobile excitations. The model is motivated by the physics of fracton excitations, which only possess mobility in a reduced dimension compared to the full model. We provide an exact mapping of this model to an arbitrary number of independent transverse-field Ising chain segments with open boundary conditions. The number and lengths of these segments correspond directly to the number of immobile excitations and their respective distances from one another. Furthermore, we demonstrate that multiple immobile excitations exhibit Casimir-like forces between them, resulting in a non-trivial spectrum.
We study the interplay of non-Hermitian topological phases under point- and line-gap conditions. Using natural homomorphisms from line-gap to point-gap phases, we distinguish extrinsic phases, reducible to Hermitian or anti-Hermitian line-gapped phases, from intrinsic phases, which are genuinely non-Hermitian without Hermitian counterparts. Although classification tables for all symmetry classes were already presented in earlier work, the present paper develops a unified formulation and provides explicit computations for all internal symmetries.
