Scar States Research Articles

η -pairing states as true scars in an extended Hubbard model

The eta-pairing states are a set of exactly known eigenstates of the Hubbard model on hypercubic lattices, first discovered by Yang [Phys. Rev. Lett. 63, 2144 (1989)]. These states are not many-body scar states in the Hubbard model because they occupy unique symmetry sectors defined by the so-called "eta-pairing SU(2)" symmetry. We study an extended Hubbard model with bond-charge interactions, popularized by Hirsch [Physica C 158, 326 (1989)], where the eta-pairing states survive without the eta-pairing symmetry and become true scar states. We also discuss similarities between the eta-pairing states and exact scar towers in the spin-1 XY model found by Schecter and Iadecola [Phys. Rev. Lett. 123, 147201 (2019)], and systematically arrive at all nearest-neighbor terms that preserve such scar towers in 1D. We also generalize these terms to arbitrary bipartite lattices. Our study of the spin-1 XY model also leads us to several new scarred models, including a spin-1/2 $J_1-J_2$ model with Dzyaloshinkskii-Moriya interaction, in realistic quantum magnet settings in 1D and 2D.

Exact Floquet quantum many-body scars under Rydberg blockade

Quantum many-body scars have attracted much interest as a violation of the eigenstate thermalization hypothesis (ETH) due to recent experimental observation in Rydberg atoms and related theoretical studies. In this paper, we construct a model hosting exact Floquet quantum many-body scars, which violate the Floquet version of ETH. We consider two uniformly-driven static Hamiltonians prohibiting neighboring up spins (Rydberg blockade) like the PXP model, and construct a binary drive composed of them. We show that there exists a four-dimensional subspace which completely avoids thermalization to infinite temperature and that any other states, including some special scar states reported in the static PXP model, are vulnerable to heating and relax to infinite temperature. We also construct a more generalized periodic drive composed of time-dependent PXP-type Hamiltonians showing exact Floquet quantum many-body scars and discuss possible experimental realization of the model in Rydberg atoms.

Slow thermalization of exact quantum many-body scar states under perturbations

Quantum many-body scar states are exceptional finite energy density eigenstates in an otherwise thermalizing system that do not satisfy the eigenstate thermalization hypothesis. We investigate the fate of exact many-body scar states under perturbations. At small system sizes, deformed scar states described by perturbation theory survive. However, we argue for their eventual thermalization in the thermodynamic limit from the finite-size scaling of the off-diagonal matrix elements. Nevertheless, we show numerically and analytically that the nonthermal properties of the scars survive for a parametrically long time in quench experiments. We present a rigorous argument that lower-bounds the thermalization time for any scar state as $t^{*} \sim O(\lambda^{-1/(1+d)})$, where $d$ is the spatial dimension of the system and $\lambda$ is the perturbation strength.

Quantum many-body scar states in two-dimensional Rydberg atom arrays

We find exponentially many exact quantum many-body scar states in a two-dimensional PXP model---an effective model for a two-dimensional Rydberg atom array in the nearest-neighbor blockade regime. Such scar states are remarkably simple valence bond solids despite being at an effectively infinite temperature, and thus strongly violate the eigenstate thermalization hypothesis. For a particular boundary condition, such eigenstates have integer-valued energies. Moreover, certain charge-density-wave initial states give rise to strong oscillations in the Rydberg excitation density after a quantum quench and towerlike structures in their overlaps with eigenstates.

Unified structure for exact towers of scar states in the Affleck-Kennedy-Lieb-Tasaki and other models

Quantum many-body scar states are many-body states with finite energy density in non-integrable models that do not obey the eigenstate thermalization hypothesis. Recent works have revealed "towers" of scar states that are exactly known and are equally spaced in energy, specifically in the AKLT model, the spin-1 XY model, and a spin-1/2 model that conserves number of domain walls. We provide a common framework to understand and prove known exact towers of scars in these systems, by evaluating the commutator of the Hamiltonian and a ladder operator. In particular we provide a simple proof of the scar towers in the integer-spin 1d AKLT models by studying two-site spin projectors. Through this picture we deduce a family of Hamiltonians that share the scar tower with the AKLT model, and also find common parent Hamiltonians for the AKLT and XY model scars. We also introduce new towers of exact states, organized in a "pyramid" structure, in the spin-1/2 model through successive application of a non-local ladder operator.

Onsager's Scars in Disordered Spin Chains.

We propose a class of nonintegrable quantum spin chains that exhibit quantum many-body scars even in the presence of disorder. With the use of the so-called Onsager symmetry, we construct scarred models for arbitrary spin quantum number S. There are two types of scar states, namely, coherent states associated with an Onsager-algebra element and one-magnon scar states. While both of them are highly excited states, they have area-law entanglement and can be written as a matrix product state. Therefore, they explicitly violate the eigenstate thermalization hypothesis. We also investigate the dynamics of the fidelity and entanglement entropy for several initial states. The results clearly show that the scar states are trapped in a perfectly periodic orbit in the Hilbert subspace and never thermalize, whereas other generic states do rapidly. To our knowledge, our model is the first explicit example of disordered quantum many-body scarred models.

Quantum scars as embeddings of weakly broken Lie algebra representations

We present an interpretation of scar states and quantum revivals as weakly "broken" representations of Lie algebras spanned by a subset of eigenstates of a many-body quantum system. We show that the PXP model, describing strongly-interacting Rydberg atoms, supports a "loose" embedding of multiple $\mathrm{su(2)}$ Lie algebras corresponding to distinct families of scarred eigenstates. Moreover, we demonstrate that these embeddings can be made progressively more accurate via an iterative process which results in optimal perturbations that stabilize revivals from arbitrary charge density wave product states, $|\mathbb{Z}_n\rangle$, including ones that show no revivals in the unperturbed PXP model. We discuss the relation between the loose embeddings of Lie algebras present in the PXP model and recent exact constructions of scarred states in related models.

Exact eigenstates in the Lesanovsky model, proximity to integrability and the PXP model, and approximate scar states

We study a model of Rydberg atoms in a nearest-neighbor Rydberg blockaded regime, introduced by Lesanovsky [Phys. Rev. Lett. 108, 105301 (2012)]. This many-body model (which has one parameter $z$) has an exactly known gapped liquid ground state, and two exactly known low-lying excitations. We discover two exact low-lying eigenstates. We also discuss behavior of the model at small parameter $z$ and its proximity to an integrable model. Lastly, we discuss connections between the Lesanovsky model at intermediate $z$ and the so-called PXP model. The PXP model describes a recent experiment that observed unusual revivals from a charge-density-wave initial state, which are attributed to a set of many-body ``scar states'' which do not obey the eigenstate thermalization hypothesis. We discuss the possibility of approximate scar states in the Lesanovsky model and present two approximations for them.

Disentangling quantum matter with measurements

Measurements destroy entanglement. Building on ideas used to study `quantum disentangled liquids', we explore the use of this effect to characterize states of matter. We focus on systems with multiple components, such as charge and spin in a Hubbard model, or local moments and conduction electrons in a Kondo lattice model. In such systems, measurements of (a subset of) one of the components can leave behind a quantum state of the other that is easy to understand, for example in terms of scaling of entanglement entropy of subregions. We bound the outcome of this protocol, for any choice of measurement, in terms of more standard information-theoretic quantities. We apply this quantum disentangling protocol to several problems of physical interest, including gapless topological phases, heavy fermions, and scar states in Hubbard model.

Quantum many-body scar states with emergent kinetic constraints and finite-entanglement revivals

We construct a set of exact, highly excited eigenstates for a nonintegrable spin-1/2 model in one dimension that is relevant to experiments on Rydberg atoms in the antiblockade regime. These states provide a new solvable example of quantum many-body scars: their sub-volume-law entanglement and equal energy spacing allow for infinitely long-lived coherent oscillations of local observables following a suitable quantum quench. While previous works on scars have interpreted such oscillations in terms of the precession of an emergent macroscopic SU(2) spin, the present model evades this description due to a set of emergent kinetic constraints in the scarred eigenstates that are absent in the underlying Hamiltonian. We also analyze the set of initial states that give rise to periodic revivals, which persist as approximate revivals on a finite timescale when the underlying model is perturbed. Remarkably, a subset of these initial states coincides with the family of area-law entangled Rokhsar-Kivelson states shown by Lesanovsky to be exact ground states for a class of models relevant to experiments on Rydberg-blockaded atomic lattices.

Изучение влияния соединений церия на послеожоговый рубец в эксперименте in vivo методом трансмиссионной электронной микроскопии

The effect of nanosized cerium dioxide and a solution of cerium (III) chloride on the state of a post-burn scar was studied in an in vivo experiment via transmission electron microscopy. The intracellular accumulation of cerium compounds with their agglomeration with cytoplasmic and/ or lysosomal localization was observed after 4 injections of nanodispersed cerium dioxide or cerium (III) chloride solution at concentrations of 0.5% and 0.05% in the formed scar area. The application of the cerium preparations both in nanodisperse form (sol) and in solution did not cause inflammatory reactions or cell destruction and had a positive effect on a regenerative process; it contributed to the full-fledged tissue regeneration in a shorter time and changed the scar characteristics for the better. sol, nanodispersed cerium dioxide, cerium (III) chloride solution, electron microscopy, post-burn scar, functional activity of cells

Topological many-body scar states in dimensions one, two, and three

We propose an exact construction for atypical excited states of a class of non-integrable quantum many-body Hamiltonians in one dimension (1D), two dimensions (2D), and three dimensins (3D) that display area law entanglement entropy. These examples of many-body `scar' states have, by design, other properties, such as topological degeneracies, usually associated with the gapped ground states of symmetry protected topological phases or topologically ordered phases of matter.

Dynamical Scar States in Driven Fracton Systems.

One-dimensional fracton systems can exhibit perfect localization, failing to reach thermal equilibrium under arbitrary local unitary time evolution. We investigate how this nonergodic behavior manifests in the dynamics of a driven fracton system, specifically a one-dimensional Floquet quantum circuit model featuring conservation of a U(1) charge and its dipole moment. For a typical basis of initial conditions, a majority of states heat up to a thermal state at near-infinite temperature. In contrast, a small number of states flow to a localized steady state under the Floquet time evolution. We refer to these athermal steady states as "dynamical scars," in analogy with the scar states observed in the spectra of certain many-body Hamiltonians. Despite their small number, these dynamical scars are experimentally relevant due to their high overlap with easily prepared product states. Each scar state displays a single agglomerated fracton peak, in agreement with the steady-state configurations of fractonic random circuits. The details of these scars are insensitive to the precise form of the Floquet operator, which is constructed from random unitary matrices. Rather, dynamical scar states arise directly from fracton conservation laws, providing a concrete mechanism for the appearance of scars in systems with constrained quantum dynamics.

Exact Quantum Many-Body Scar States in the Rydberg-Blockaded Atom Chain.

A recent experiment in the Rydberg atom chain observed unusual oscillatory quench dynamics with a charge density wave initial state, and theoretical works identified a set of many-body "scar states" showing nonthermal behavior in the Hamiltonian as potentially responsible for the atypical dynamics. In the same nonintegrable Hamiltonian, we discover several eigenstates at an infinite temperature that can be represented exactly as matrix product states with a finite bond dimension, for both periodic boundary conditions (two exact E=0 states) and open boundary conditions (two E=0 states and one each E=±sqrt[2]). This discovery explicitly demonstrates the violation of the strong eigenstate thermalization hypothesis in this model and uncovers exact quantum many-body scar states. These states show signatures of translational symmetry breaking with a period-2 bond-centered pattern, despite being in one dimension at an infinite temperature. We show that the nearby many-body scar states can be well approximated as "quasiparticle excitations" on top of our exact E=0 scar states and propose a quasiparticle explanation of the strong oscillations observed in experiments.

Prediction of Hepatic Clearance of Stereoselective Metabolism of Carvedilol in Liver Microsomes and Hepatocytes of Sprague-Dawley and Cytochrome P450 2D-Deficient Dark Agouti Rats

Hepatic clearance (CLh) of carvedilol (CAR), which is eliminated via stereoselective metabolism by the CYP2D subfamily of cytochromes P450 (CYPs), was predicted using liver microsomes and hepatocytes from Sprague-Dawley (SD) rats and CYP2D-deficient Dark Agouti (DA) rats to determine the usefulness of prediction method. Plasma concentrations of CAR following intravenous injection to DA rats were higher than those in SD rats. The volume of distribution at steady state and total clearance (CLtot) of S-CAR were approximately two times greater than those of R-CAR in both strains. CLh predicted from in vitro studies using DA rat liver microsomes was different from that obtained from in vivo studies. In contrast, in vitro CLh prediction using DA rat hepatocytes was nearly identical to the CLh observed in DA rats in vivo, and was lower than that in SD rats. The predicted CLh in vitro using hepatocytes correlated well with the observed CLtot in vivo, which is expected to be nearly the same as CLh. These results suggest that in vitro metabolic studies using hepatocytes are more relevant with regard to stereoselectively predicting CLh of CAR than those using liver microsomes.

Semiclassical quantization of highly excited scar states

The semiclassical quantization of Hamiltonian systems with classically chaotic dynamics is restricted to low excited states, close to the ground state, because the number of required periodic orbits grows exponentially with energy. Nevertheless, here we demonstrate that it is possible to find eigenenergies of highly excited states scarred by a short periodic orbit. Specifically, by using 18146 homoclinic orbits (HO)s of the shortest periodic orbit of the hyperbola billiard, we find eigenenergies of the strongest scars over a range which includes 630 even eigenfunctions. The analysis of data reveals that the used semiclassical formula presents two regimes. First, when all HOs with excursion time smaller than the Heisenberg time tH are included, the error is around 3.3% of the mean level spacing. Second, in the energy region defined by , where is the maximum excursion time included in the calculation, the error is around 15% of the mean level spacing.

The Relationship between Self-Esteem, Depression and Anxiety: Comparing Vulnerability and Scar Model in the Italian Context

Abstract Background : The relationship between low self-esteem and depression and anxiety disorders has solicited a growing body of empirical research. The most important explanation models are two: the vulnerability model states that low self-esteem is a risk factor for depression and anxiety, and the scar model states that low self-esteem is an outcome, not a cause, of depression and anxiety. Method: In the present research we tested the two different models using a sample of Italian preadolescent, aged 11 to 14 years, recruited from an Italian secondary school. To test the models, the path analysis technique was used: one in which self-esteem predicted anxiety and depression (Model 1), and one in which anxiety and depression predicted self-esteem (Model 2). Gender and age were included in the models as covariate. Conclusions: our findings suggest that the both models had the same good fit, although the effects of self-esteem on depressive and anxiety symptoms were significantly higher than the effects of anxiety and depression on self-esteem. In both models gender was positively associated with anxiety and self-esteem: girls tend to report higher levels of anxiety than boys. In the scar model age was positively related with depression; older preadolescents tend to report higher levels of depression than younger preadolescents. Keywords : self-esteem, anxiety, depression, early adolescence

Thyroid Cancer-Specific Quality of Life and Health-Related Quality of Life in Young Adult Thyroid Cancer Survivors.

There is a lack of health-related quality of life (HRQOL) research in thyroid cancer (TC) survivors, especially young adults (YAs). This study aims to assess the socio-demographic and clinical factors that most influence TC-specific QOL domains and estimate the impact of different health conditions on HRQOL in a large cohort of YA TC survivors. TC survivors ≥17 years of age were recruited through the thyroid cancer survivor (ThyCa) Web site. Mean scores for the seven domains and six items of THYCA-QoL, MCS and PCS of SF-12v1, and derived SF-6D were compared between factors as well as age groups (YA: 17-39 years, adult ≥40 years), and to the normal population. Regression analyses estimated the relationship between the socio-demographic, clinical, and THYCA-QoL measures and HRQOL in YAs only. Of 1028 survivors, 277 (27%) were YAs. Most YAs were female (93.5%), white (86.6%), insured (96.8%), married or in a stable relationship (69%), and listed a comorbidity (43.7%); all reported their entire thyroid had been removed. Average survivorship time was 46.2 months (SD = 51.0). Almost every socio-demographic and clinical factor significantly influenced one or more domain of THYCA-QoL in both YAs and older adults. In both groups, a higher level of education, female sex, unemployment, and having a comorbidity resulted in significantly higher THYCA-QoL scores (more complaints) and lower SF-6D scores (lower HRQOL; p < 0.05). Current YAs had less neuromuscular, voice, sympathetic, and throat/mouth complaints but more grievances involving their scar, headaches, anxiety, and overall psychological state (p < 0.05). The average SF-6D for YAs was 0.70 (SD = 0.13), which was similar to the older adults but significantly different from the normal age-matched population in females (p < 0.01). All THYCA-QoL domains were strongly associated with a lower HRQOL (adj R(2) > 0.5) in YAs. The simplest, best regression model (adj R(2) = 0.53) in YAs included neuromuscular, concentration, and anxiety complaints, as well as having a comorbidity predicting lower HRQOL. TC-specific QOL is significantly influenced by many socio-demographic and clinical factors. HRQOL is lower in female YA TC survivors compared with the normal age-matched population. Neuromuscular, concentration, and anxiety complaints had the greatest impact on HRQOL in YA TC survivors.

Effect of pH value on the fretting wear behavior of Inconel 690 alloy

The fretting test was carried out using a SRV IV fretting test rig in order to investigate the effect of pH value on the fretting wear behavior of Inconel 690. The experiment was performed in pH values of 1, 4, 7, 10 and 13. The worn scars were studied by laser scanning confocal microscope (LSCM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The electrochemical data was also obtained to study its corrosion behavior. The results revealed that the pH value had a big influence on the fretting behavior of Inconel 690 due to the change of the galvanic corrosion degree of the fretting pairs with pH value. The surface state of the worn scar also changed at different pH values, which had a big influence on the friction coefficient, wear volume and the electrochemical behavior. Faradays law was used to qualitatively analyzes the relationship between the wear volume and the corrosion current of the fretting pair.

The optimization of reparative processes after cesarean section (clinical-experimental research)

Development and introduction of materials influenced on reparation process in a myometrium is actual direction of modern obstetrics in connection with the increase of cesarean section rate. One of such preparation is «Collost», it stimulates the processes of neoangio- and myogenesis and excludes the disorderly growth of scars tissue. Aim: To study the influence of bioplastic material «Collost» on the reparation process in myometrium after cesarean section. Objectives: to estimate the morpho-functional state of scar on uterus after cesarean sections depending on implantation of collagen membrane. Material and methods: There were included 13 female rabbits in experimental part of the study. In clinical part of the study there were included 20 pregnant woman with intraoperative application of «Collost» (main group), 30 pregnant woman without «Collost» implantation (comparison group) and 10 pregnant with vaginal delivery (control group). Results: histological, immunohistological and immunological findings of postoperative uterine scars of female rabbits showed significant differences of expressions of miosin, vascular endothelial growth factor and collagen I type. The myometrium was significantly thicker in the area of uterine scar in main group (with collagen membrane implantation) than in comparison group. Conclusions: bioplastic material «Collost» leads to full formation of muscular wall and vascular ture in the area of postoperative uterine scar.