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A bstract We consider the double scaling limit of a model of Pauli spin operators recently studied in Hanada et al. [1] and evaluate the moments of the Hamiltonian by the chord diagrams. We find that they coincide with those of the double scaled SYK model, which makes it more likely that this model may play an important role in the study of holography. We compare the model with another previously studied model. We also speculate on the form of the Hamiltonian in the double scaling limit.

A bstract Recently, Krylov complexity was proposed as a measure of complexity and chaoticity of quantum systems. We consider the stadium billiard as a typical example of the quantum mechanical system obtained by quantizing a classically chaotic system, and numerically evaluate Krylov complexity for operators and states. Despite no exponential growth of the Krylov complexity, we find a clear correlation between variances of Lanczos coefficients and classical Lyapunov exponents, and also a correlation with the statistical distribution of adjacent spacings of the quantum energy levels. This shows that the variances of Lanczos coefficients can be a measure of quantum chaos. The universality of the result is supported by our similar analysis of Sinai billiards. Our work provides a firm bridge between Krylov complexity and classical/quantum chaos.

A bstract We provide a detailed examination of a thermal out-of-time-order correlator (OTOC) growing exponentially in time in systems without chaos. The system is a one-dimensional quantum mechanics with a potential whose part is an inverted harmonic oscillator. We numerically observe the exponential growth of the OTOC when the temperature is higher than a certain threshold. The Lyapunov exponent is found to be of the order of the classical Lyapunov exponent generated at the hilltop, and it remains non-vanishing even at high temperature. We adopt various shape of the potential and find these features universal. The study confirms that the exponential growth of the thermal OTOC does not necessarily mean chaos when the potential includes a local maximum. We also provide a bound for the Lyapunov exponent of the thermal OTOC in generic quantum mechanics in one dimension, which is of the same form as the chaos bound obtained by Maldacena, Shenker and Stanford.

A bstract Exponential growth of thermal out-of-time-order correlator (OTOC) is an indicator of a possible gravity dual, and a simple toy quantum model showing the growth is being looked for. We consider a system of two harmonic oscillators coupled nonlinearly with each other, and numerically observe that the thermal OTOC grows exponentially in time. The system is well-known to be classically chaotic, and is a reduction of Yang-Mills-Higgs theory. The exponential growth is certified because the growth exponent (quantum Lyapunov exponent) of the thermal OTOC is well matched with the classical Lyapunov exponent, including their energy/temperature dependence. Even in the presence of the exponential growth in the OTOC, the energy level spacings are not sufficient to judge a Wigner distribution, hence the OTOC is a better indicator of quantum chaos.

A bstract We provide a formula to reconstruct bulk spacetime metrics inside black holes by the time dependence of complexity in the dual quantum field theory, based on the complexity=volume (CV) conjecture in the holographic duality.

A bstract We investigate Krylov complexity of the fermion chain operator which consists of multiple Majorana fermions in the double-scaled SYK (DSSYK) model with finite temperature. Using the fact that Krylov complexity is computable from two-point functions, the analysis is performed in the limit where the two-point function becomes simple and we compare the results with those of other previous studies. We confirm the exponential growth of Krylov complexity in the very low temperature regime. In general, Krylov complexity grows at most linearly at very late times in any system with a bounded energy spectrum. Therefore, we have to focus on the initial growth to see differences in the behaviors of systems or operators. Since the DSSYK model is such a bounded system, its chaotic nature can be expected to appear as the initial exponential growth of the Krylov complexity. In particular, the time at which the initial exponential growth of Krylov complexity terminates is independent of the number of degrees of freedom. More generally, and not limited to the DSSYK model, we systematically and specifically study the Lanczos coefficients and Krylov complexity using a toy power spectrum and deepen our understanding of those initial behaviors. In particular, we confirm that the overall sech-like behavior of the power spectrum shows the initial linear growth of the Lanczos coefficient, even when the energy spectrum is bounded.

Grimace scales have been used for pain assessment in different species. This study aimed to develop and validate the Feline Grimace Scale (FGS) to detect naturally-occurring acute pain. Thirty-five client-owned and twenty control cats were video-recorded undisturbed in their cages in a prospective, case-control study. Painful cats received analgesic treatment and videos were repeated one hour later. Five action units (AU) were identified: ear position, orbital tightening, muzzle tension, whiskers change and head position. Four observers independently scored (0–2 for each AU) 110 images of control and painful cats. The FGS scores were higher in painful than in control cats; a very strong correlation with another validated instrument for pain assessment in cats was observed (rho = 0.86, p < 0.001) as well as good overall inter-rater reliability [ICC = 0.89 (95% CI: 0.85–0.92)], excellent intra-rater reliability (ICC > 0.91), and excellent internal consistency (Cronbach’s alpha = 0.89). The FGS detected response to analgesic treatment (scores after analgesia were lower than before) and a cut-off score was determined (total pain score > 0.39 out of 1.0). The FGS is a valid and reliable tool for acute pain assessment in cats.

BackgroundLittle is known about the prospective association between community-level social capital and individual-level frailty onset. Therefore, this study aimed to examine the impact of community-level social capital on frailty onset among older adults using 3-year longitudinal data.MethodsThis prospective cohort study recruited non-institutionalised older adults from the Japan Gerontological Evaluation Study, established in 2013 and robust older adults were followed up for 3 years. We assessed three aspects of community-level social capital (civic participation, social cohesion and reciprocity), and employed a multilevel logistic regression analysis; frailty was evaluated using the Kihon Checklist questionnaire, which has been widely used as a screening tool for frailty in Japan.ResultsIn total, 21 940 older adults (from 384 communities) who were robust at baseline (2013) completed the follow-up survey (2016). Participants’ mean age (SD) was 71.8 (4.9) years, and 51.2% were female. In the follow-up period, frailty onset occurred in 622 participants (2.8%). Regarding community-level social capital variables, civic participation was inversely associated with frailty onset (OR=0.94, 95% CI 0.90 to 0.97, p=0.001), after adjusting for individual-level and community-level covariates. The potential intermediate factors of individual social relationships and health behaviours did not largely change the results. This association was found regardless of individual socioeconomic status.ConclusionsLiving in a community with rich civic participation, such as engagement in social activities, was associated with lower frailty onset among older adults. Community development that fosters social participation is essential for frailty prevention.

In diverse materials science spanning from fine ceramics to lithium-ion batteries and fuel cells, the particle–binder interactions in slurries play a crucial role in governing the ultimate performance. Despite numerous efforts to date, quantitatively elucidating these hidden interactions has remained a longstanding challenge. Here, we demonstrate a dynamic approach to evaluate adsorptive interactions between ceramic particles and polymeric binders entangled in a slurry utilizing differential centrifugal sedimentation (DCS). Particles settling under a centrifugal force field impart significant viscous resistance on the adsorbed binder, leading to its detachment, influenced by particle size and density. This behaviour directly reflects the particle–binder interactions, and detailed DCS spectrum analysis enables the quantitative assessment of nano-Newton-order adsorption forces. An important finding is the strong correlation of these forces with the mechanical properties of the moulded products. Our results provide insight that forming a flexible network structure with appropriate interactions is essential for desirable formability.

The current study investigated the relationship between the frequency of watching sports and depressive symptoms among older adults. This study used cross-sectional data from the Japan Gerontological Evaluation Study, a nationwide mail survey of 21,317 older adults. Depressive symptoms were defined as a Geriatric Depression Scale score of ≥ 5. Participants were queried regarding the average frequency at which they watched sports on-site and via TV/Internet over the past year. Among the 21,317 participants, 4559 (21.4%) had depressive symptoms, while 4808 (22.6%) and 16,576 (77.8%) watched sports on-site and via TV/Internet at least once a year, respectively. Older adults who watched sports on-site a few times/year (prevalence ratio, 0.70; 95% confidence interval, 0.65–0.74) or 1–3 times/month (0.66, 0.53–0.82) were less likely to have depressive symptoms compared to non-spectators after adjusting for frequency of playing sports, exercise activities, and other potential confounders. Meanwhile, a dose–response relationship was confirmed for watching via TV/Internet (prevalence ratio of 0.86, 0.79, and 0.71 for a few times/year, 1–3 times/month, and ≥ 1 time/week, respectively). This study suggested that watching sports on-site or via TV/Internet, regardless of whether they regularly engage in sports, may reduce the risk of depressive symptoms among older adults.