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The advent of powerful neural classifiers has increased interest in problems that require both learning and reasoning. These problems are critical for understanding important properties of models, such as trustworthiness, generalization, interpretability, and compliance to safety and structural constraints. However, recent research observed that tasks requiring both learning and reasoning on background knowledge often suffer from reasoning shortcuts (RSs): predictors can solve the downstream reasoning task without associating the correct concepts to the high-dimensional data. To address this issue, we introduce rsbench, a comprehensive benchmark suite designed to systematically evaluate the impact of RSs on models by providing easy access to highly customizable tasks affected by RSs. Furthermore, rsbench implements common metrics for evaluating concept quality and introduces novel formal verification procedures for assessing the presence of RSs in learning tasks. Using rsbench, we highlight that obtaining high quality concepts in both purely neural and neuro-symbolic models is a far-from-solved problem. rsbench is available at: https://unitn-sml.github.io/rsbench.

The Li abundance observed in pre-main sequence and main sequence late-type stars is strongly age-dependent, but also shows a complex pattern depending on several parameters, such as rotation, chromospheric activity and metallicity. The best way to calibrate these effects, with the aim of studying Li as an age indicator for FGK stars, is to calibrate coeval groups of stars, such as open clusters (OCs) and associations. We present a considerable target sample of 42 OCs and associations, ranging from 1 Myr to 5 Gyr, observed within the Gaia-ESO survey (GES), and using the latest data provided by GES iDR6 and the most recent release of Gaia that was then available, EDR3. As part of this study, we update and improve the membership analysis for all 20 OCs presented in our previous article. We perform detailed membership analyses for all target clusters to identify likely candidates, using all available parameters provided by GES and based on numerous criteria: from radial velocity distributions, to the astrometry and photometry provided by Gaia, to gravity indicators, [Fe/H] metallicity, and Li content. We obtain updated lists of cluster members for the whole target sample, as well as a selection of Li-rich giant contaminants obtained as an additional result of the membership process. Each selection of cluster candidates was thoroughly contrasted with numerous existing membership studies using data from Gaia to ensure the most robust results. These final cluster selections will be used in the third and last paper of this series, which reports the results of a comparative study characterising the observable Li dispersion in each cluster and analysing its dependence on several parameters, allowing us to calibrate a Li-age relation and obtain a series of empirical Li envelopes for key ages in our sample., Comment: 83 pages, 246 figures. To be published in A&A, accepted January 27, 2024

We use a Kernel Density Estimator method to evaluate the stellar velocity dispersion in the open cluster NGC 2571. We derive the 3-D velocity dispersion using both proper motions as extracted from Gaia DR3 and single epoch radial velocities as obtained with the instrument FLAMES at ESO VLT. The mean-square velocity along the line-of-sight is found to be larger than the one in the tangential direction by a factor in the interval [6,8]. We argue that the most likely explanation for such an occurrence is the presence of a significant quantity of unresolved binary and multiple stars in the radial velocity sample. Special attention should be paid to single line spectroscopic binaries (SB1) since in this case we observe the spectral lines of the primary component only, and therefore the derived radial velocity is not the velocity of the binary system center of mass. To investigate this scenario, we performed numerical experiments at varying the fractional abundance of SB1 in the observed sample. These experiments show that the increase of the mean-square radial velocity depends actually on the fractional abundance of SB1 to a power in the range of [0.39,0.45]. We used the 3-D velocity dispersion obtained by the dispersions in the tangential directions and the assumption that the radial velocity dispersion is the same as a tangential one to estimate the virial cluster mass and the cluster mass taking into account the gravitational field of the Galaxy and the non-stationarity of the cluster. These estimates are $650\pm30 \; M_\odot$ and $310\pm80 \; M_\odot$, respectively, and they are in substantial agreement with the photometric cluster mass., Comment: 16 pages, 7 figures, accepted for publication in the Astronomical Journal

Building on the recent release of a new \emph{Gaia}-based blue straggler star catalog in Galactic open star clusters (OCs), we explored the properties of these stars in a cluster sample spanning a wide range in fundamental parameters. We employed \emph{Gaia} EDR3 to assess the membership of any individual blue or yellow straggler to their parent cluster. We then made use of the \texttt{ASteCA} code to estimate the fundamental parameters of the selected clusters, in particular, the binary fraction. With all this at hand, we critically revisited the relation of the blue straggler population and the latter. For the first time, we found a correlation between the number of blue stragglers and the host cluster binary fraction and binaries. This supports the hypothesis that binary evolution is the most viable scenario of straggler formation in Galactic star clusters. The distribution of blue stragglers in the Gaia color-magnitude diagram was then compared with a suite of composite evolutionary sequences derived from binary evolutionary models that were run by exploring a range of binary parameters: age, mass ratio, period, and so forth. The excellent comparison between the bulk distribution of blue stragglers and the composite evolutionary sequences loci further supports the binary origin of most stragglers in OCs and paves the way for a detailed study of individual blue stragglers, Comment: 15 pages, in press in Astronomy and Astrophysics

AIMS. We derive the morphology of the stellar component in the outer halo volume, and search for possible overdensities due to substructures therein. METHODS. We made use of some of the data releases of the spectroscopic survey LAMOST DR8-DR9 in tandem with distance determinations for two subsamples, that is, of K-giants and M-giants, respectively, making up 60,000 stars. These distance are obtained through Bayesian techniques that derive absolute magnitudes as a function of measured spectroscopic parameters. Our calculation of the density from these catalogues requires: (1) derivation of the selection function; and (2) a correction for the convolution of the distance errors, which we carried out with Lucy's inversion of the corresponding integral equation. RESULTS. The stellar density distribution of the outer halo (distance to the Galactic centre, $r_G$, of between 25 and 90 kpc) is a smooth monotonously decreasing function with a dependence of approximately $\rho \propto r_G^{-n}$, with $n=4.6\pm 0.4$ for K-giants and $n=4.5\pm 0.2$ for M-giants, and with a insignificant oblateness. The value of $n$ is independent of the angular distance to the Sagittarius tidal stream plane, which is what would be expected if such a stream did not exist in the anticenter positions or had a negligible imprint in the density distribution in the outer halo. Apart from random fluctuations or minor anomalies in some lines of sight, we do not see substructures superimposed in the outer halo volume within the resolution that we are using and limited by the error bars. This constrains the mass of over- and under-densities in the outer halo to be of $\lesssim 10^3$ M$_\odot $/deg$^2$, whereas the total mass of the stellar halo, including inner and outer parts, is $\sim 7\times 10^8$ M$_\odot $., Comment: 11 pages, 14 figures, accepted to be published in A&A

It has long been recognized that it is not enough for a Recommender System (RS) to provide recommendations based only on their relevance to users. Among many other criteria, the set of recommendations may need to be diverse. Diversity is one way of handling recommendation uncertainty and ensuring that recommendations offer users a meaningful choice. The literature reports many ways of measuring diversity and improving the diversity of a set of recommendations, most notably by re-ranking and selecting from a larger set of candidate recommendations. Driven by promising insights from the literature on how to incorporate versatile Large Language Models (LLMs) into the RS pipeline, in this paper we show how LLMs can be used for diversity re-ranking. We begin with an informal study that verifies that LLMs can be used for re-ranking tasks and do have some understanding of the concept of item diversity. Then, we design a more rigorous methodology where LLMs are prompted to generate a diverse ranking from a candidate ranking using various prompt templates with different re-ranking instructions in a zero-shot fashion. We conduct comprehensive experiments testing state-of-the-art LLMs from the GPT and Llama families. We compare their re-ranking capabilities with random re-ranking and various traditional re-ranking methods from the literature. We open-source the code of our experiments for reproducibility. Our findings suggest that the trade-offs (in terms of performance and costs, among others) of LLM-based re-rankers are superior to those of random re-rankers but, as yet, inferior to the ones of traditional re-rankers. However, the LLM approach is promising. LLMs exhibit improved performance on many natural language processing and recommendation tasks and lower inference costs. Given these trends, we can expect LLM-based re-ranking to become more competitive soon., Comment: 32 pages, 2 figures

Time crystals (TCs) are many-body systems displaying spontaneous breaking of time translation symmetry. Here, we demonstrate a TC using driven-dissipative condensates of microcavity exciton-polaritons, spontaneously formed from an incoherent particle bath. In contrast to other realizations, the TC phases can be controlled by the power of continuous-wave non-resonant optical drive exciting the condensate and optomechanical interactions with phonons. Those phases are for increasing power: (i) Larmor precession of pseudo-spins - a signature of continuous TC, (ii) locking of the frequency of precession to self-sustained coherent phonons - stabilized TC, (iii) doubling of TC frequency by phonons - a discrete TC with continuous excitation. These results establish microcavity polaritons as a platform for the investigation of time-broken symmetry in non-hermitian systems., Comment: 25 pages; 15 figures

The ubiquitous phenomenon of synchronization is inherently characteristic of dynamical dissipative non-linear systems. In particular, synchronization has been theoretically and experimentally demonstrated for exciton-polariton condensates with time-independent coupling. Unlike that case, we theoretically investigate the effects of a fixed mechanical harmonic driving, i.e., a coherent phonon population, that induces time modulation in the coupling of two coupled condensates. Our model applies both to electrically generated modulation, through coherent bulk acoustic waves, and to self-induced optomechanical vibrations. We consider linear as well as quadratic phonon-displacement-induced modulations of the polariton coupling. Peculiar asynchronously locked phases are found and analyzed in the context of synchronization and Josephson-type oscillations phenomena that appear in the non-driven case. Notably, Arnold tongues corresponding to the asynchronously locked phases emerge at condensate detunings that correspond to integer numbers of the mechanical frequency and also to rational fractions of it. Unlocked quasiperiodic and chaotic regimes can also be reached. In particular, the phonon-induced fractional locking frequencies arrange in a Farey sequence that produces a devil's staircase of the steady-state dressed detuning between the condensates. Importantly, both polariton-polariton and reservoir-polariton interactions facilitate the realization of coherent phonon-induced asynchronously locked phases. The relation to recent experiments on optomechanically driven condensates in arrays of polariton traps is discussed., Comment: 18 pages, 9 figures

With the unprecedented increase of known star clusters, quick and modern tools are needed for their analysis. In this work, we develop an artificial neural network trained on synthetic clusters to estimate the age, metallicity, extinction, and distance of $Gaia$ open clusters. We implement a novel technique to extract features from the colour-magnitude diagram of clusters by means of the QuadTree tool and we adopt a multi-band approach. We obtain reliable parameters for $\sim 5400$ clusters. We demonstrate the effectiveness of our methodology in accurately determining crucial parameters of $Gaia$ open clusters by performing a comprehensive scientific validation. In particular, with our analysis we have been able to reproduce the Galactic metallicity gradient as it is observed by high-resolution spectroscopic surveys. This demonstrates that our method reliably extracts information on metallicity from colour-magnitude diagrams (CMDs) of stellar clusters. For the sample of clusters studied, we find an intriguing systematic older age compared to previous analyses present in the literature. This work introduces a novel approach to feature extraction using a QuadTree algorithm, effectively tracing sequences in CMDs despite photometric errors and outliers. The adoption of ANNs, rather than Convolutional Neural Networks, maintains the full positional information and improves performance, while also demonstrating the potential for deriving clusters' parameters from simultaneous analysis of multiple photometric bands, beneficial for upcoming telescopes like the Vera Rubin Observatory. The implementation of ANN tools with robust isochrone fit techniques could provide further improvements in the quest for open clusters' parameters., Comment: 24 pages, 15 figures, Accepted in The Astronomical Journal. Temporally, data produced in this work are available at https://phisicslollo0.github.io/cavallo23.html

In this study we estimate the stellar ages of LAMOST DR8 Red Giant Branch (RGB) stars based on the Gradient Boosting Decision Tree algorithm (GBDT). We used 2,643 RGB stars extracted from the APOKASC-2 astero-seismological catalog as training data-set. After selecting the parameterses ([$\alpha$/Fe], [C/Fe], T$_{eff}$, [N/Fe], [C/H], log g) highly correlated with age using GBDT, we apply the same GBDT method to the new catalog of more than 590,000 stars classified as RGB stars. The test data-set shows that the median relative error is around 11.6$\%$ for the method. We also compare the predicted ages of RGB stars with other studies (e.g., based on APOGEE), and find systematic differences. The final uncertainty is about 15 to 30$\%$ compared to open clusters' ages. Then we present the spatial distribution of the RGB sample having an age determination, which could recreate the expected result, and discuss systematic biases. All these diagnostics show that one can apply the GBDT method to other stellar samples to estimate atmospheric parameters and age., Comment: 17 pages, 17 figures, Accepted for publication in The Astrophysical Journal

Detailed analysis of kinematics of the Milky Way disk in the solar neighborhood based on the GAIA DR3 catalog reveals the existence of peculiarities in the stellar velocity distribution perpendicular to the galactic plane. We study the influence of resonances -- the outer Lindblad resonance and the outer vertical Lindblad resonance -- of a rotating bar with stellar oscillations perpendicular to the plane of the disk, and their role in shaping the spatial and the velocity distributions of stars. We find that the $Z$ and $V_Z$ distributions of stars with respect to $L_Z$ are affected by the outer Lindblad resonance. The existence of bar resonance with stellar oscillations perpendicular to the plane of the disk is demonstrated for a long (large semi-axis 5 kpc) and fast rotating bar with $\Omega_{b}= 60.0$ $km~s^{-1}~kpc^{-1}$. We show also that, in the model with the long and fast rotating bar, some stars in the 2:1 OLR region deviate far from their original places, entering the bar region. A combination of resonance excitation of stellar motions at the 2:1 OLR region together with strong interaction of the stars with the bar potential leads to the formation of the group of 'escapees', i.e., stars that deviate in $R$ and $Z$ -- directions at large distances from the resonance region. Simulations, however, do not demonstrate any noticeable effect on $V_Z$-distribution of stars in the solar neighborhood, Comment: 21 pages, 12 figures

The electrostatic double layer force is key to determining the stability and self-assembly of charged colloids and many other soft matter systems. Fully understanding the attractive force between two like-charged surfaces remains a great challenge. Here we apply the modified Gaussian renormalized fluctuation theory to study ion correlation-driven like-charge attraction in multivalent salt solutions. The effects of spatially varying ion correlations on the structure of overlapping double layers and their free energy are self-consistently accounted for. In the presence of multivalent salts, increasing surface charge or counterion valency leads to a short-range attraction. We demonstrate that although both overcharging and like-charge attraction are outcomes of ion correlation, there is no causal relationship between them. Our theory also captures the non-monotonic dependence of like-charge attraction on multivalent salt concentration. The reduction of attraction at high salt concentrations could be a contributing factor towards the reentrant stability of charged colloidal suspensions. Our theoretical predictions are consistent with the observations reported in experiments and simulations.

Graphene aerogel (GA) is a promising material for thermal management applications across many fields due to its lightweight and thermally insulative properties. However, standard values for important thermal properties, such as thermal conductivity, remain elusive due to the lack of reliable characterization techniques for highly porous materials. Comparative infrared thermal microscopy (CITM) is an attractive technique to obtain thermal conductance values of porous materials like GA, due to its non-invasive character, which requires no probing of, or contact with, the often-delicate structures and frameworks. In this study, we improve upon CITM by utilizing a higher resolution imaging setup and reducing the need for pore-filling coating of the sample (previously used to adjust for emissivity). This upgraded setup, verified by characterizing porous silica aerogel, allows for a more accurate confirmation of the fundamental thermal conductivity value of GA while still accounting for the thermal resistance at material boundaries. Using this improved method, we measure a thermal conductivity below 0.036 W/m$\cdot$K for commercial GA using multiple reference materials. These measurements demonstrate the impact of higher resolution thermal imaging to improve accuracy in low density, highly porous materials characterization. This study also reports thermal conductivity for much lower density (less than 15 mg/cm$^3$) GA than previously published studies while maintaining the robustness of the CITM technique., Comment: v3: Submitted to Journal of Porous Materials v2: Resubmitted to correct MathJax typos in abstract

The Gaia-ESO Survey is a public spectroscopic survey that has targeted $\gtrsim10^5$ stars covering all major components of the Milky Way from the end of 2011 to 2018, delivering its public final release in May 2022. Unlike other spectroscopic surveys, Gaia-ESO is the only survey that observed stars across all spectral types with dedicated, specialised analyses: from O ($T_\mathrm{eff} \sim 30,000-52,000$~K) all the way to K-M ($\gtrsim$3,500~K). The physics throughout these stellar regimes varies significantly, which has previously prohibited any detailed comparisons between stars of significantly different type. In the final data release (internal data release 6) of the Gaia-ESO Survey, we provide the final database containing a large number of products such as radial velocities, stellar parameters and elemental abundances, rotational velocity, and also, e.g., activity and accretion indicators in young stars and membership probability in star clusters for more than 114,000 stars. The spectral analysis is coordinated by a number of Working Groups (WGs) within the Survey, which specialise in the various stellar samples. Common targets are analysed across WGs to allow for comparisons (and calibrations) amongst instrumental setups and spectral types. Here we describe the procedures employed to ensure all Survey results are placed on a common scale to arrive at a single set of recommended results for all Survey collaborators to use. We also present some general quality and consistency checks performed over all Survey results., Comment: A&A accepted, minor revision, 36 pages, 38 figures

MITICA (Megavolt ITER Injector & Concept Advancement), the full scale prototype of ITER Heating Neutral Beam, is under realization at the Neutral Beam Test Facility (Padova, Italy). It is designed to deliver 16.5 MW to ITER plasma, obtained by accelerating negative Deuterium ions up to 1 MeV for a total ion current of 40 A and then neutralized. MITICA Acceleration Power Supply is composed of several non-standard equipment, beyond industrial standard for insulation voltage level (-1 MVdc) and dimensions. Voltage withstand tests (up to 1.265 MVdc) have been performed in five subsequent steps (from 2018 to 2019), according to the installation progress, after connecting equipment belonging to different procurements. During integrated commissioning, started in 2021, two breakdowns occurred in a position of the HV plant not still identified, so they could be occurred either in air or in SF6. To identify the locations of possible weak insulation points, the existing diagnostics for partial discharge detection (the precursor of breakdowns) as a first step have been improved on air-insulated parts by consisting in a set of instrumentation, like capacitive probes and off-the-shelf instruments for AC application (acoustic and electromagnetic sensors). The paper deals with the instruments qualification to assess their suitability for DC usage and then with the investigation performed in MITICA, in particular: 1) sensitivity assessment campaign, with artificially produced corona effect to identify the minimum threshold of each diagnostics 2) voltage application to MITICA plant, moving the instrumentation around equipment and increasing progressively the voltage looking for corona phenomena to identify possible weak insulation points., Comment: Nine pages, twelve figures, accepted manuscript of a paper published in Fusion Engineering and Design

UNICEF Innocenti's Report Card 17 explores how the 43 Organisation for Economic Co-operation and Development (OECD) and/or the European Union (EU) countries are faring in providing healthy environments for children. Do children have clean water to drink? Do they have good-quality air to breathe? Are their homes free of lead and mould? How many children live in overcrowded homes? How many have access to green play spaces, safe from road traffic? Data show that a nation's wealth does not guarantee a healthy environment. Far too many children are deprived of a healthy home, irreversibly damaging their current and future well-being. Beyond children's immediate environments, over-consumption in some of the world's richest countries is destroying children's environments globally. This threatens both children worldwide and future generations. To provide all children with safe and healthy environments, governments, policymakers, businesses and all stakeholders are called to act on a set of policy recommendations. The report focuses on the following questions: (1) How do environmental factors affect children's well-being? (2) How are many of the world's richest countries faring in terms of providing a healthy environment in which children can live, develop and thrive? and (3) What actions can these countries take to improve the environments in which children live? [This report was written with contributions from Dominic Richardson, Gunilla Olsson, Celine Little, Dagna Rams, Gro Dehli Villanger, Nicole Quattrini, Tim Huijts, Mirza Balaj and Terje Eikemo.]

PBC J2333.9-2343 is a giant radio galaxy at z = 0.047 with a bright central core associated to a blazar nucleus. If the nuclear blazar jet is a new phase of the jet activity, then the small orientation angle suggest a dramatic change of the jet direction. We present observations obtained between September 2018 and January 2019 (cadence larger than three days) with Effeslberg, SMARTS-1.3m, ZTF, ATLAS, Swift, and Fermi-LAT, and between April-July 2019 (daily cadence) with SMARTS-1.3m and ATLAS. Large (>2x) flux increases are observed on timescales shorter than a month, which are interpreted as flaring events. The cross correlation between the SMARTS-1.3m monitoring in the NIR and optical shows that these data do not show significant time lag within the measured errors. A comparison of the optical variability properties between non-blazars and blazars AGN shows that PBC J2333.9-2343 has properties more comparable to the latter. The SED of the nucleus shows two peaks, that were fitted with a one zone leptonic model. Our data and modelling shows that the high energy peak is dominated by External Compton from the dusty torus with mild contribution from Inverse Compton from the jet. The derived jet angle of 3 degrees is also typical of a blazar. Therefore, we confirm the presence of a blazar-like core in the center of this giant radio galaxy, likely a Flat Spectrum Radio Quasar with peculiar properties., Comment: Accepted for publication in MNRAS. 15 pages, 6 figures, 2 appendix including tables and figures

Very metal-poor stars contain crucial information on the Milky Way's infancy. In our previous study \citep{Plotnikova_2022} we derived a mean age of $\sim$ 13.7 Gyr for a sample of these stars in the Sun's vicinity. In this work, we investigate the chemical and kinematics properties of these stars with the goal of obtaining some insights on their origin and their parent population. We did not find any Al-Mg anti-correlation, which lead us to the conclusion that these stars did not form in globular clusters, while the detailed analysis of their orbital parameters reveals that these stars are most probably associated with the pristine Bulge of the Milky Way. We then sketch a scenario for the formation of the Milky Way in which the first structure to form was the Bulge through rapid collapse. The other components have grown later on, with a significant contribution of accreted structures., Comment: 13 pages, 10 figures, accepted for publication in the Astrophysical Journal