Miracle-dz/UniFAR-FTUs huggingface dataset:
Hamiltonian diagonalization in hybrid quantum cosmology

We explore the possibility of selecting a natural vacuum state for scalar and tensor gauge-invariant cosmological perturbations in the context of hybrid quantum cosmology, by identifying those variables for the description of the perturbations that display a dynamical behavior adapted in a specific way to the evolution of the entire cosmology. We make use of a canonical formulation of the whole of the cosmological system (background geometry and perturbations) in which the perturbative gauge-invariant degrees of freedom are identified as canonical variables. Introducing background-dependent linear canonical transformations that respect the spatial symmetries of the background on these perturbations and completing those canonical transformations for the entire system, we are able to characterize a generic collection of annihilation and creationlike variables that obey the dynamics dictated by a respective collection of Hamiltonians. We then impose that such Hamiltonians possess no self-interaction terms so that, in a Fock representation with normal ordering, they act diagonally on the basis of n-particle states. This leads to a semilinear first-order partial differential equation with respect to the background for the coefficients that define the annihilation and creationlike variables for all Fourier modes, as well as to a very precise ultraviolet characterization of them. Such first-order equation contains, in the imaginary part of its complex solutions, the complicated second-order field equation that typically arises for the time-dependent frequency of the perturbations in the context of quantum field theory in curved spacetimes. We check that the asymptotic knowledge acquired allows one to select the standard vacua in Minkowski and de Sitter spacetimes. Finally, we discuss the relation of our vacuum and the standard adiabatic vacua, and check that our asymptotic characterization of variables with a diagonal Hamiltonian displays the properties that would be desirable for an adiabatic state of infinite order.
Place image, quality of life, and behavioral intention of residents during the Dajia Mazu Pilgrimage in Taiwan

ABSTRACT Rationale/purpose: This study examines the perceptions of festival host residents of the Dajia Mazu Pilgrimage using the proposed model to evaluate the antecedent and outcome variables of place image. Design/methodology/approach: Using quantitative methods, this study proposes a model to determine host residents’ perceptions based on fit, place image, quality of life, and behavioral intention. Findings: The findings showed that place image is vital in establishing a supportive perception toward the festival host city. Quality of life not only mediates the perceptions of residents’ image and their residency but also independently contributes to the development of residents’ behavioral intentions. The perceptions of place image or the quality of life of residents, especially place image, are significant predictors of residents’ behavioral intentions. Practical implications: This study extends the concepts of fit and place image by taking a psychological perspective to provide strategies for festival management. To evaluate residents’ quality of life and gain their intention to support for the festival, the present study suggests that event organizers and the local government take action on the characteristics of the festival and the host city represents. Providing entertainment activities combine with Mazu culture at nighttime is one of the suggestions. Research contributions: The exploratory model we proposed herein to explain host residents’ viewpoints showed sufficient predictive power. The results underline the importance of fit, which can predict and explain place image. Furthermore, the present study contributes to existing research by applying the concept of fit in the festival context.
Using Spin to Understand the Formation of LIGO and Virgo’s Black Holes

With the growing number of binary black hole (BBH) mergers detected by the Advanced LIGO and Virgo detectors, it is becoming possible to constrain the properties of the underlying population and better understand the formation of these systems. Black hole (BH) spin orientations are one of the cleanest discriminators of formation history, with BHs in dynamically formed binaries in dense stellar environments expected to have spins distributed isotropically, in contrast to isolated populations where stellar evolution is expected to induce spins preferentially aligned with the orbital angular momentum. In this work, we propose a simple, model-agnostic approach to characterizing the spin properties of LIGO/Virgo’s BBH population. Using measurements of the effective spin of the binaries, we introduce a simple parameter to quantify the fraction of the population that is isotropically distributed, regardless of the spin magnitude distribution of the population. Once the orientation characteristics of the population have been determined, we show how measurements of effective spin can be used to directly constrain the BH spin magnitude distribution. We find that most effective spin measurements are too small to be informative, with the first four events showing a slight preference for a population with alignment, with an odds ratio of 1.2. We argue that it will be possible to distinguish symmetric and anti-symmetric populations at high confidence with tens of additional detections, although mixed populations may take significantly longer to disentangle. We also derive BH spin magnitude distributions from LIGO’s first four BBHs under the assumption of aligned or isotropic populations.
Large $N$ Tensor and SYK Models

The SYK model proposed by Sachdev, Ye, and Kitaev consists of Majorana fermions that interact randomly four at a time. The model develops a dense spectrum above the ground state, due to which the model becomes nearly conformal. This suggests that a holographic dual may exist, which makes the SYK model interesting in the study of quantum gravity. It has been found that the SYK model is similar to large $N$ tensor models: in both models, only the melonic diagrams survive in the large $N$ limit. In this thesis, we explore the large $N$ tensor model with $O(N)^3$ symmetry containing two flavors of Majorana fermions in the fundamental representation. Its quartic Hamiltonian depends on a real parameter $\beta$. We derive the kernels of the four point functions. With the spectra that we find from the kernels, we calculate the scaling dimensions of several types of conformal primaries. We also find a duality relation between two Hamiltonians of different values of $\beta$. This is not a perfect duality, because the normalization of energy scales with the transformation. Nevertheless, the ratios of the energies are the same, and the operator dimensions are preserved. In addition, we discover that for $\beta > 1$ or $\beta < 0$ the scaling dimensions of one of the conformal primaries become complex, rendering the model unstable.
Convergence of stochastic algorithms: from the Kushner & Clark theorem to the Lyapounov functional

In the first part of this paper a global Kushner-Clark theorem about the convergence of stochastic algorithms is proved: we show that, under some natural assumptions, one can 'read' from the trajectories of its ODE whether or not an algorithm converges. The classical stochastic optimization results are included in this theorem. In the second part, the above smoothness assumption on the mean vector field of the algorithm is relaxed using a new approach based on a path-dependent Lyapounov functional. Several applications, for non-smooth mean vector fields and/or bounded Lyapounov function settings, are derived. Examples and simulations are provided that illustrate and enlighten the field of application of the theoretical results.
Thermodynamics of the two-dimensional Falicov-Kimball model: a classical Monte Carlo study

The two-dimensional Falicov-Kimball (FK) model is analyzed using the Monte Carlo method. In the case of concentrations of both itinerant and localized particles equal to 0.5 we determine temperature dependence of specific heat, charge density wave susceptibility, and density-density correlation function. In the weak interaction regime we find a first order transition to the ordered state and anomalous temperature dependence of the correlation function. We construct the phase diagram of half-filled FK model. Also, the role of next-nearest-neighbor hopping on the phase diagram is analyzed. Lastly, we discuss the density of states and the spectral functions for the mobile particles in weak and strong interaction regime.
Factors Influencing Continued Wearable Device Use in Older Adult Populations: Quantitative Study

Background The increased use of wearable sensor technology has highlighted the potential for remote telehealth services such as rehabilitation. Telehealth services incorporating wearable sensors are most likely to appeal to the older adult population in remote and rural areas, who may struggle with long commutes to clinics. However, the usability of such systems often discourages patients from adopting these services. Objective This study aimed to understand the usability factors that most influence whether an older adult will decide to continue using a wearable device. Methods Older adults across 4 different regions (Northern Ireland, Ireland, Sweden, and Finland) wore an activity tracker for 7 days under a free-living environment protocol. In total, 4 surveys were administered, and biometrics were measured by the researchers before the trial began. At the end of the trial period, the researchers administered 2 further surveys to gain insights into the perceived usability of the wearable device. These were the standardized System Usability Scale (SUS) and a custom usability questionnaire designed by the research team. Statistical analyses were performed to identify the key factors that affect participants’ intention to continue using the wearable device in the future. Machine learning classifiers were used to provide an early prediction of the intention to continue using the wearable device. Results The study was conducted with older adult volunteers (N=65; mean age 70.52, SD 5.65 years) wearing a Xiaomi Mi Band 3 activity tracker for 7 days in a free-living environment. The results from the SUS survey showed no notable difference in perceived system usability regardless of region, sex, or age, eliminating the notion that usability perception differs based on geographical location, sex, or deviation in participants’ age. There was also no statistically significant difference in SUS score between participants who had previously owned a wearable device and those who wore 1 or 2 devices during the trial. The bespoke usability questionnaire determined that the 2 most important factors that influenced an intention to continue device use in an older adult cohort were device comfort (τ=0.34) and whether the device was fit for purpose (τ=0.34). A computational model providing an early identifier of intention to continue device use was developed using these 2 features. Random forest classifiers were shown to provide the highest predictive performance (80% accuracy). After including the top 8 ranked questions from the bespoke questionnaire as features of our model, the accuracy increased to 88%. Conclusions This study concludes that comfort and accuracy are the 2 main influencing factors in sustaining wearable device use. This study suggests that the reported factors influencing usability are transferable to other wearable sensor systems. Future work will aim to test this hypothesis using the same methodology on a cohort using other wearable technologies.
Stellar coronal mass ejections – I. Estimating occurrence frequencies and mass-loss rates

Stellar coronal mass ejections (CMEs) may play an important role in mass- and angular momentum loss of young Sun-like stars. If occurring frequently, they may also have a strong effect on planetary evolution by increasing atmospheric erosion. So far it has not been possible to infer the occurrence frequency of stellar CMEs from observations. Based on their close relation with flares on the Sun, we develop an empirical model combining solar flare-CME relationships with stellar flare rates to estimate the CME activity of young Sun-like and late-type main-sequence stars. By comparison of the obtained CME mass-loss rates with observations of total mass-loss rates, we find that our modeled rates may exceed those from observations by orders of magnitude for the most active stars. This reveals a possible limit to the extrapolation of such models to the youngest stars. We find that the most uncertain component in the model is the flare-CME association rate adopted from the Sun, which does not properly account for the likely stronger coronal confinement in active stars. Simple estimates of this effect reveal a possible suppression of CME rates by several orders of magnitude for young stars, indicating that this issue should be addressed in more detail in the future.
Lithium abundance and rotation of seismic solar analogues - Solar and stellar connection from Kepler and Hermes observations

Lithium abundance A(Li) and surface rotation are good diagnostic tools to probe the internal mixing and angular momentum transfer in stars. We explore the relation between surface rotation, A(Li) and age in a sample of seismic solar-analogue (SA) stars and study their possible binary nature. We select a sample of 18 SA observed by the NASA Kepler satellite for an in-depth analysis. Their seismic properties and surface rotation are well constrained from previous studies. About 53 hours of high-resolution spectroscopy were obtained to derive fundamental parameters and A(Li). These values were combined and confronted with seismic masses, radii and ages, as well as surface rotation periods. We identify a total of 6 binary systems. A well-defined relation between A(Li) and rotation was obtained. With models constrained by the characterisation of the individual mode frequencies for single stars, we identify a sequence of three SA with similar mass (~1.1Mo) and stellar ages ranging between 1 to 9 Gyr. Within the realistic estimate of ~7% for the mass uncertainty, we find a good agreement between the measured A(Li) and the predicted A(Li) evolution from a grid of models calculated with the Toulouse-Geneva stellar evolution code, which includes rotational internal mixing, calibrated to reproduce solar chemical properties. We present A(Li) for a consistent spectroscopic survey of SA with a mass of 1.00+/-0.15Mo, and characterised through asteroseismology and surface rotation rates based on Kepler observations. The correlation between A(Li) and P_rot supports the gyrochronological concept for stars younger than the Sun. The consensus between measured A(Li) for solar analogues with model grids, calibrated onto the Sun's chemical properties suggests that these targets share the same internal physics. In this light, the solar Li and rotation rate appear to be normal for a star like the Sun.
Spectral Analysis of Stars on Planet-Search Surveys

We present spectroscopic analysis of ",,1000 stars on the Lick, Keck and AAT planet search projects. This analysis provides a quantitative, and unbiased correlation between metallicity and the rate of occurrence of detected gas giant planets with orbital periods shorter than three years. As stellar metallicity increases, the occurrence of planets increases. Stars with [Fe/H] that is one third of solar only have gas giants detected >3% of the time. Stars with solar metallicity have a planet occurrence rate of 5 10%. The occurrence of gas giant planets rises to 20% in stars with a metallicity that is three times solar. At issue is whether the quantitative dependence of planet occurrence on metallicity is primarily an initial condition, or a by-product of accretion of gas-depleted material onto the convective zone of the star. Accretion could be distinguished as the underlying mechanism for enhanced metallicity if: 1) planet-bearing F-type stars with thinner convective envelopes show a higher mean metallicity than planet-bearing Gor K-type stars, or 2) planet-bearing sub-giants with diluted convective zones showed statistically lower metallicity than their main sequence counterparts
Mixed structural face-centered cubic and body-centered cubic orders in near stoichiometric Fe2MnGa alloys

Magnetic and transport properties of near stoichiometric metastable FexMnyGaz alloys (46 ≤ x ≤ 52, 17 ≤ y ≤ 25, 26 ≤ z ≤ 30) with face-centered cubic (FCC), body-centered cubic (BCC), and two-phase (FCC + BCC) structures are investigated. The experimental results are analyzed in terms of first-principles calculations of stoichiometric Fe2MnGa alloy with the L21, L12, and the tetragonally distorted L21 structural orderings. It is shown that the pure BCC and FCC phases have distinct magnetic and transport properties. Two-phase Fe2MnGa alloys have magnetic and transport properties typical of the mixed BCC and FCC phases. Among the investigated alloys, Fe46Mn24Ga30 has a martensitic transformation accompanied with significant changes of its magnetic and transport properties.
A primordial theory

We review the twistor approach to the Zhang-Hu theory of the four-dimensional Quantum Hall effect. We point out the key role played by the group Spin(4,4), as the symmetry group of the boundary. It is argued that this group, which ignores the square root of minus one used in relativity and quantum mechanics, is the focal point of a primordial theory, one where the Cartan concept of triality is paramount, from which the standard theories emerge via a series of phase transitions of the Zhang-Hu fluid. An important role will be played by the Jordan cross-product algebras, particularly the exceptional Jordan algebra associated to the split octaves and by the associated Freudenthal phase space. The geometry and Hamiltonian theory of these spaces is examined in detail. A possible link to the theory of massive particles is outlined.
Angular clustering of point sources at 150 MHz in the TGSS survey

We study the angular clustering of point sources in The GMRT (Giant Metrewave Radio Telescope) Sky Survey (TGSS). The survey at 150 MHz with δ > −53.5° has a sky coverage of 3. 6π steradians, i.e. $90{{\ \rm per\ cent}}$ of the whole sky. We created subsamples by applying different total flux thresholds limit (Sflux ≫ 5σ) for good completeness and measured the angular correlation function ω(θ) of point sources at large scales (≥1°). We find that the amplitude of angular clustering is higher for brighter subsamples; this indicates that higher threshold flux samples are hosted by massive haloes and cluster strongly: this conclusion is based on the assumption that the redshift distribution of sources does not change with flux and this is supported by models of radio sources. We compare our results with other low-frequency studies of clustering of point sources and verify that the amplitude of clustering varies with the flux limit. We quantify this variation as a power-law dependence of the amplitude of correlation function with the flux limit. This dependence can be used to estimate foreground contamination due to clustering of point sources for low-frequency H i intensity mapping surveys for studying the epoch of reionization.
Labyrinthine acoustic metamaterials with space-coiling channels for low-frequency sound control

We numerically analyze the performance of labyrinthine acoustic metamaterials with internal channels folded along a Wunderlich space-filling curve to control low-frequency sound in air. In contrast to previous studies, we perform direct modeling of wave propagation through folded channels, not introducing effective theory assumptions. As a result, we reveal that metastructures with channels, which allow wave propagation in the opposite direction to incident waves, have different dynamics as compared to those for straight slits of equivalent length. The differences are attributed to activated tortuosity effects and result in 100% wave reflection at band gap frequencies. This total reflection phenomenon is found to be insensitive to thermo-viscous dissipation in air. For labyrinthine channels generated by iteration levels, one can achieve broadband total sound reflection by using a metamaterial monolayer and efficiently control the amount of absorbed wave energy by tuning the channel width. Thus, the work contributes to a better understanding of labyrinthine metamaterials with potential applications for reflection and filtering of low-frequency airborne sound.
Antioxidants and antigenotoxic properties of Rhizopus oligosporus fermented cassava (Manihot esculenta Crantz)

The antioxidant and antigenotoxic effects of solid state fermented cassava ( Manihot esculenta Crantz) using Rhizopus oligosporus were investigated. Solid state fermentation was carried out for 72 h at room temperature under acidic and basic conditions. Total phenolic content was significantly (p<0.05) higher in fermented peeled and unpeeled cassava at pH 7 and 5 when compared with unfermented. Similarly, the total flavonoid contents of fermented peeled and unpeeled cassava at pH 4 and 7 were significantly (p<0.05) higher than in unfermented. Allium cepa assay was used to assess the antigenotoxic effects of unfermented and fermented peeled and unpeeled cassava. The fermented extracts did not induce chromosomal type aberrations in the treated cells. The present study thus showed that R. oligosporus has the ability to breakdown cassava and considerably increase the antioxidant properties in peeled and unpeeled fermented cassava, which may serve as natural antioxidants in industrial broiler chickens.
Angular Momentum Accretion onto Disc Galaxies

Abstract Throughout the Hubble time, gas makes its way from the intergalactic medium into galaxies fuelling their star formation and promoting their growth. One of the key properties of the accreting gas is its angular momentum, which has profound implications for the evolution of, in particular, disc galaxies. Here, we discuss how to infer the angular momentum of the accreting gas using observations of present-day galaxy discs. We first summarize evidence for ongoing inside-out growth of star forming discs. We then focus on the chemistry of the discs and show how the observed metallicity gradients can be explained if gas accretes onto a disc rotating with a velocity 20 – 30% lower than the local circular speed. We also show that these gradients are incompatible with accretion occurring at the edge of the discs and flowing radially inward. Finally, we investigate gas accretion from a hot corona with a cosmological angular momentum distribution and describe how simple models of rotating coronae guarantee the inside-out growth of disc galaxies.
Restricted Variance Interactions in Entrepreneurship Research: A Unique Basis for Context-as-Moderator Hypotheses

In this methodological brief, we demonstrate the usefulness of the restricted variance (RV) interaction to entrepreneurship research. RV reasoning can help scholars to specify precise roles for contextual moderators. This specificity allows for strengthening of arguments and for testing of one of the reasons for an interaction. In some cases, it points to otherwise unexpected interaction patterns. We illustrate the power of RV reasoning with a data set of 503 biotech firms to show how RV explains geographic differences in the relationship between number of alliances and initial public offering value. Finally, we show how these interactions can be tested given typical distributions.