cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Fat tailed distributions for deaths in conflicts and disasters
Creators: name: Chatterjee, Arnab
name: Chakrabarti, Bikas K
Publisher: name: arXiv
Year: 2016
Subjects: subject: Physics and Society (physics.soc-ph)
subject: FOS: Physical sciences

description: We study the statistics of human deaths from wars, conflicts, similar man-made conflicts as well as natural disasters. The probability distribution of number of people killed in natural disasters as well as man made situations show power law decay for the largest sizes, with similar exponent values. Comparisons with natural disasters, when event sizes are measured in terms of physical quantities (e.g., energy released in earthquake, volume of rainfall, land area affected in forest fires, etc.) also show striking resemblances. The universal patterns in their statistics suggest that some subtle similarities in their mechanisms and dynamics might be responsible.
description: 6 pages, 3 figs + 2 tables
Photo-Induced CO Desorption Dominates over Oxidation on Different O+CO Covered Ru(0001) Surfaces
Creators: name: Tetenoire, Auguste
name: Juaristi, J. Iñaki
name: Alducin, Maite
Publisher: name: arXiv
Year: 2023
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The photo-induced desorption and oxidation of CO on Ru(0001) is simulated using ab initio molecular dynamics with electronic friction that accounts for the non-equilibrated excited electrons and phonons. Different (O,CO) coverages are considered, the experimental room temperature coverage consisting in 0.5ML-O+0.25ML- CO (low coverage), the saturation coverage achieved experimentally at low temperatures (0.5ML-O+0.375ML-CO, intermediate coverage), and the equally mixed monolayer that is stable according to our calculations but not experimentally observed yet (0.5ML-O+0.5ML-CO, high coverage). The results of our simulations for the three coverages are consistent with femtosecond laser experiments showing that the CO photo-desorption largely dominates over CO photo-oxidation. These results cannot be explained in terms of the distinct activation energies calculated for the relaxed surfaces. Different (dynamical) factors such as the coupling to the laser-excited electrons and, more importantly, the interadsorbate energy exchange and the strong surface distortions induced in the more crowded surfaces are fundamental to understand the competition between these two processes under the extremely non-equilibrated conditions created by the laser.
On the onset delays of solar energetic electrons and protons: Evidence for a common accelerator
Creators: name: Strauss, R. D.
name: Dresing, N.
name: Richardson, I. G.
name: Berg, J. P. van den
name: Steyn, P. J.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Plasma Physics (physics.plasm-ph)
subject: Space Physics (physics.space-ph)
subject: FOS: Physical sciences

description: The processes responsible for the acceleration of solar energetic particles (SEPs) are still not well understood, including whether SEP electrons and protons are accelerated by common or separate processes. Using a numerical particle transport model that includes both pitch-angle and perpendicular spatial diffusion, we simulate, amongst other quantities, the onset delay for MeV electrons and protons and compare the results to observations of SEPs from widely-separated spacecraft. Such observations have previously been interpreted, in a simple scenario assuming no perpendicular diffusion, as evidence for different electron and proton sources. We show that, by assuming a common particle source together with perpendicular diffusion, we are able to simultaneously reproduce the onset delays for both electrons and protons. We argue that this points towards a common accelerator for these particles. Moreover, a relatively broad particle source is required in the model to correctly describe the observations. This is suggestive of diffusive shock acceleration occurring at large shock structures playing a significant role in the acceleration of these SEPs.
description: Accepted to ApJ
Tau-Herculid meteor shower on night 30/31 May, 2022, and properties of the meteoroids
Creators: name: Koten, Pavel
name: Shrbený, Lukáš
name: Spurný, Pavel
name: Borovička, Jiří
name: Štork, Rostislav
name: Henych, Tomáš
name: Vojáček, Vlastimil
name: Mánek, Jan
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: A tau-Herculid meteor outburst or even a storm was predicted by several models to occur around 5~UT on 31~May, 2022 as a consequence of the break-up of comet 73P/Schwassmann-Wachmann 3 in 1995. The multi-instrument and multi-station experiment was carried-out within the Czech Republic to cover possible earlier activity of the shower between 21 and 1 UT on 30/31 May. Multi-station observations using video and photographic cameras were used for calculation of the atmospheric trajectories and heliocentric orbits of the meteors. Their arrival times are used for determination of the shower activity profile. Physical properties of the meteoroids are evaluated using various criteria based on meteor heights. Evolution of spectra of three meteors are studied as well. This annual but poor meteor shower was active for the whole night many hours before the predicted peak. A comparison with dynamical models shows that a mix of older material ejected after 1900 and fresh particles originating from the 1995 comet fragmentation event was observed. Radiant positions of both groups of meteors were identified and found to be in good agreement with simulated radiants. Meteoroids with masses between 10 mg and 10 kg were recorded. The mass distribution index was slightly higher than 2. A study of the physical properties shows that the tau-Herculid meteoroids belong to the most fragile particles observed ever, especially among higher masses of meteoroids. Exceptionally bright bolide observed during the dawn represents a challenge for the dynamical simulations as it is necessary to explain how to transfer a half metre body to the vicinity of the Earth at the same time as millimetre sized particles.
description: 17 pages, 16 figures, 5 tables
Oscillation Maps in the Broadband Radio Spectrum of the 1 August 2010 Event
Creators: name: Karlicky, M.
name: Rybak, J.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We search for indications of waves in the 25-2000 MHz radio spectrum of the 1 August 2010 event (SOL2010-08-01T08:57:00L075C013), where fast propagating waves in the solar corona with the periods of 181, 69, and 40 seconds were detected in UV observations. Using the wavelet technique we construct a new type of map of oscillations for selected periods in the whole domain of the radio spectrum. While the oscillation with the period of 181 seconds was recognized in the whole 25-2000 MHz radio spectrum, oscillations with periods of 69 and 40 seconds were confirmed only in the 250-870 MHz frequency range. In the 800-2000 MHz range we found periods of 50 and 80 seconds. Moreover, in the 250-870 MHz frequency range, the oscillation with the period of about 420 seconds was detected. We also made maps of phases of the 181-second oscillations in order to analyze their frequency drift. At the beginning of the radio event, in the 2000-500 MHz frequency range the phase of the 181-second oscillation drifts towards lower frequencies. On the other hand, at frequencies 25-500 MHz we found that the phase is nearly synchronous. While the phase drift at higher frequencies can be interpreted as being caused by the UV wave, the synchronization of the phase on lower frequencies is explained by the fast-electron beams, whose acceleration is modulated by the UV wave. Owing to this modulation, the electron beams are accelerated with the period of the UV wave (181 seconds). These beams propagate upwards through the solar corona and generate the 25-500 MHz radio emission with the 181-second period. Due to high beam velocity (~c/3, where c is the light speed) the 25-500 MHz radio emission, corresponding to a large interval of heights in the solar corona, is nearly synchronous.
description: Accepted to Solar Physics journal, 19 pages, 7 figures
Sodium enhancement in evolved cataclysmic variables
Creators: name: Yamaguchi, Natsuko
name: El-Badry, Kareem
name: Rodriguez, Antonio C.
name: Gull, Maude
name: Roulston, Benjamin R.
name: Vanderbosch, Zachary P.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We present follow-up spectroscopy of 21 cataclysmic variables (CVs) with evolved secondaries and ongoing or recently-terminated mass transfer. Evolutionary models predict that the secondaries should have anomalous surface abundances owing to nuclear burning in their cores during their main-sequence evolution and subsequent envelope stripping by their companion white dwarfs. To test these models, we measure sodium (Na) abundances of the donors from the Fraunhofer "D" doublet. Accounting for interstellar absorption, we find that {\it all} objects in our sample have enhanced Na abundances. We measure 0.3 $\lesssim$ [Na/H] $\lesssim$ 1.5 dex across the sample, with a median [Na/H] = 0.956 dex, i.e., about an order of magnitude enhancement over solar values. To interpret these values, we run MESA binary evolution models of CVs in which mass transfer begins just as the donor leaves the main sequence. These generically predict Na enhancement in donors with initial donor masses $\gtrsim 1\,M_{\odot}$, consistent with our observations. In the models, Na enrichment occurs in the donors' cores via the NeNa cycle near the end of their main-sequence evolution. Na-enhanced material is exposed when the binaries reach orbital periods of a few hours. Donors with higher initial masses are predicted to have higher Na abundances at fixed orbital period owing to their higher core temperatures during main-sequence evolution. The observed [Na/H] values are on average $\approx$0.3 dex higher than predicted by the models. Surface abundances of evolved CV donors provide a unique opportunity to study nuclear burning products in the cores of intermediate-mass stars.
description: accepted to MNRAS
SU(1,2) invariance in two-dimensional oscillator
Creators: name: Krivonos, Sergey
name: Nersessian, Armen
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: Performing the Hamiltonian analysis we explicitly established the canonical equivalence of the deformed oscillator, constructed in arXiv:1607.03756[hep-th], with the ordinary one. As an immediate consequence, we proved that the SU(1,2) symmetry is the dynamical symmetry of the ordinary two-dimensional oscillator. The characteristic feature of this SU(1,2) symmetry is a non-polynomial structure of its generators written it terms of the oscillator variables.
description: 7 pages
Extragalactic FXT Candidates Discovered by Chandra (2014-2022)
Creators: name: Quirola-Vásquez, J.
name: Bauer, F. E.
name: Jonker, P. G.
name: Brandt, W. N.
name: Yang, G.
name: Levan, A. J.
name: Xue, Y. Q.
name: Eappachen, D.
name: Camacho, E.
name: Ravasio, M. E.
name: Zheng, X. C.
name: Luo, B.
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Extragalactic fast X-ray transients (FXTs) are short flashes of X-ray photons of unknown origin that last a few minutes to hours. We extend the search for extragalactic FXTs from Quirola et al. 2022 (Paper I; based on sources in the Chandra Source Catalog 2.0, CSC2) to further Chandra archival data between 2014-2022. We extract X-ray data using a method similar to that employed by CSC2 and apply identical search criteria as in Paper I. We report the detection of eight FXT candidates, with peak 0.3-10 keV fluxes between 1$\times$10$^{-13}$ to 1$\times$10$^{-11}$ erg cm$^{-2}$ s$^{-1}$ and $T_{90}$ values from 0.3 to 12.1 ks. This sample of FXTs has likely redshifts between 0.7 to 1.8. Three FXT candidates exhibit light curves with a plateau (${\approx}$1-3 ks duration) followed by a power-law decay and X-ray spectral softening, similar to what was observed for a few previously reported FXTs in Paper I. In light of the new, expanded source lists (eight FXTs with known redshifts from Paper I and this work), we update the event sky rates derived in Paper I, finding 36.9$_{-8.3}^{+9.7}$ deg$^{-2}$ yr$^{-1}$ for the extragalactic samples for a limiting flux of ${\gtrsim}$1${\times}$10$^{-13}$ erg cm$^{-2}$ s$^{-1}$, calculate the first FXT X-ray luminosity function, and compare the volumetric density rate between FXTs and other transient classes. Our latest Chandra-detected extragalactic FXT candidates boost the total Chandra sample by $\sim$50 %, and appear to have a similar diversity of possible progenitors.
description: 37 pages, 19 figures, 11 tables, accepted for publication in A&A. arXiv admin note: text overlap with arXiv:2201.07773
GPU Accelerated Discrete Element Method (DEM) Molecular Dynamics for Conservative, Faceted Particle Simulations
Creators: name: Spellings, Matthew
name: Marson, Ryan L.
name: Anderson, Joshua A.
name: Glotzer, Sharon C.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Computational Physics (physics.comp-ph)
subject: FOS: Physical sciences

description: Faceted shapes, such as polyhedra, are commonly found in systems of nanoscale, colloidal, and granular particles. Many interesting physical phenomena, like crystal nucleation and growth, vacancy motion, and glassy dynamics are challenging to model in these systems because they require detailed dynamical information at the individual particle level. Within the granular materials community the Discrete Element Method has been used extensively to model systems of anisotropic particles under gravity, with friction. We provide an implementation of this method intended for simulation of hard, faceted nanoparticles, with a conservative Weeks-Chandler-Andersen (WCA) interparticle potential, coupled to a thermodynamic ensemble. This method is a natural extension of classical molecular dynamics and enables rigorous thermodynamic calculations for faceted particles.
A Local Universe model for constrained simulations
Creators: name: Pfeifer, Simon
name: Valade, Aurélien
name: Gottlöber, Stefan
name: Hoffman, Yehuda
name: Libeskind, Noam I.
name: Hellwing, Wojciech A.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: The aim of cosmological simulations is to reproduce the properties of the observed Universe, serving as tools to test structure and galaxy formation models. Constrained simulations of our local cosmological region up to a few hundred Mpc/h , the local Universe, are designed to reproduce the actual cosmic web of structures as observed. A question that often arises is how to judge the quality of constrained simulations against the observations of the Local Universe. Here we introduce the Local Universe model (LUM), a new methodology, whereby many constrained simulations can be judged and the ''best'' initial conditions can be identified. By characterising the Local Universe as a set of rich clusters, the model identifies haloes that serve as simulated counterparts to the observed clusters. Their merit is determined against a null hypothesis, the probability that such a counterpart could be identified in a random, unconstrained simulation. This model is applied to 100 constrained simulations using the Cosmicflows-3 data. Cluster counterparts are found for all constrained simulations, their distribution of separation from the true observed cluster position and their mass distribution are investigated. Lastly, the ''best'' constrained simulation is selected using the LUM and discussed in more detail.
description: 10 pages, 8 figures, submitted to MNRAS
Reproducibility and Transparency versus Privacy and Confidentiality: Reflections from a Data Editor
Creators: name: Vilhuber, Lars
Publisher: name: arXiv
Year: 2023
Subjects: subject: General Economics (econ.GN)
subject: Other Statistics (stat.OT)
subject: FOS: Economics and business
subject: FOS: Computer and information sciences

description: Transparency and reproducibility are often seen in opposition to privacy and confidentiality. Data that need to be kept confidential are seen as an impediment to reproducibility, and privacy would seem to inhibit transparency. I bring a more nuanced view to the discussion, and show, using examples from over 1,000 reproducibility assessments, that confidential data can very well be used in reproducible and transparent research. The key insight is that access to most confidential data, while tedious, is open to hundreds if not thousands of researchers. In cases where few researchers can consider accessing such data in the future, reproducibility services, such as those provided by some journals, can provide some evidence for effective reproducibility even when the same data may not be available for future research.
The contribution and relevance of non-neuronal structures and non-synaptic interactions
Creators: name: Bentley, Barry
Publisher: name: figshare
Year: 2023
Subjects: classificationCode: 320904
subject: Computational neuroscience (incl. mathematical neuroscience and theoretical neuroscience)
classificationCode: 320999
subject: Neurosciences not elsewhere classified

description: In past discussions on Whole Brain Emulation (WBE), emphasis has been placed on the need to accurately map connectomes (i.e. the neurons and synapses in the brain), their neurotransmitters and receptors, and to a lesser extent, their functional, genetic, and epigenetic states. These conversations, however, have historically failed to address the contribution of (i) non-neuronal structures and (ii) non-synaptic interactions, and the potential complexities these overlooked aspects may pose.

Studies investigating long-range chemical communication in C. elegans have found the number of non-synaptic interactions via monoamines and neuropeptides to outnumber synaptic interactions by almost an order of magnitude, with the potential to alter the functional properties of entire networks. To add additional complexity, it is becoming clear that extrasynaptic transmission can also exist through the release of extracellular vesicles (EV) that can carry a number of payloads over long distances, with glial diffusion barriers, local uptake and recycling, and active circulation, all influencing the dynamic properties of these non-synaptic interactions.

Furthermore, non-neuronal cells are known to alter the ionic and metabolic states of networks and the neuronal environment, with the ability to physically block (or sometimes actively transport) neurotransmitters in ways that are currently poorly understood. With new molecules constantly being discovered with the ability to both act over long distances and alter the function of neural circuits, it is clear that the synaptic network alone will not be sufficient to reverse engineer behaviours. To emulate a brain, the molecular and physical properties of the entire system – and not just the neurons – must be considered.
The inductive entanglement classification yields ten rather than eight classes of four-qubit entangled states
Creators: name: Backens, Miriam
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Lamata et al. use an inductive approach to classify the entangled pure states of four qubits under stochastic local operations and classical communication (SLOCC) [PRA 75(2), 022318 (2007)]. The inductive method yields a priori ten different entanglement superclasses, of which they discard three as empty. One of the remaining superclasses is split in two, resulting in eight superclasses of genuine four-qubit entanglement. Here, we show that two of the three discarded superclasses are in fact non-empty and should have been retained. We give explicit expressions for the canonical states for those superclasses, up to SLOCC and qubit permutations. Furthermore, we confirm that the third discarded superclass is indeed empty, yielding a total of ten superclasses of genuine four-qubit entanglement under the inductive classification scheme.
description: 9 pages
Free products in the unit group of the integral group ring of a finite group
Creators: name: Janssens, Geoffrey
name: Jespers, Eric
name: Temmerman, Doryan
Publisher: name: arXiv
Year: 2016
Subjects: subject: Rings and Algebras (math.RA)
subject: Group Theory (math.GR)
subject: FOS: Mathematics

description: Let $G$ be a finite group and let $p$ be a prime. We continue the search for generic constructions of free products and free monoids in the unit group $\mathcal{U}(\mathbb{Z}G)$ of the integral group ring $\mathbb{Z}G$. For a nilpotent group $G$ with a non-central element $g$ of order $p$, explicit generic constructions are given of two periodic units $b_1$ and $b_2$ in $\mathcal{U}(\mathbb{Z}G)$ such that $\langle b_1 , b_2\rangle =\langle b_1\rangle \star \langle b_2 \rangle \cong \mathbb{Z}_p \star \mathbb{Z}_{p}$, a free product of two cyclic groups of prime order. Moreover, if $G$ is nilpotent of class $2$ and $g$ has order $p^n$, then also concrete generators for free products $\mathbb{Z}_{p^k} \star \mathbb{Z}_{p^m}$ are constructed (with $1\leq k,m\leq n $). As an application, for finite nilpotent groups, we obtain earlier results of Marciniak-Sehgal and Gon{ç}alves-Passman. Further, for an arbitrary finite group $G$ we give generic constructions of free monoids in $\mathcal{U}(\mathbb{Z}G)$ that generate an infinite solvable subgroup.
description: 10 pages
Toward Development of a New Health Economic Evaluation Definition
Creators: name: Botchkarev, Alexei
Publisher: name: arXiv
Year: 2016
Subjects: subject: General Economics (econ.GN)
subject: FOS: Economics and business

description: Economic evaluation is a dynamically advancing knowledge area of health economics. It has been conceived to provide evidence for allocating scarce resources to gain the best value for money. The problem of efficiency of investments becomes even more crucial with advances in modern medicine and public health which bring about both improved patient outcomes and higher costs. Despite the abundance of literature on the economic evaluation concepts, some key notions including the definition of the health economic evaluation remain open for discussion. Academic literature offers a large number and growing variety of economic evaluation definitions. It testifies to the fact that existing definitions do not meet requirements of economists. The aim of this study was to examine existing definitions and reveal their common features.
Equality of the Hilbert Hamiltonian and the canonical Hamiltonian for gauge theories in a static spacetime
Creators: name: Weldon, H. Arthur
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: The Hilbert energy-momentum tensor for gauge-fixed non-Abelian gauge theories, defined by the variational derivative of the action with respect to the space-time metric, is a tensor under general coordinate transformations, symmetric in its indices, and BRST invariant. The canonical energy-momentum tensor has none of these properties but the canonical Hamiltonian does correctly generate the time dependence of the fields. It is shown that the Hilbert Hamiltonian $\int d^{3}x\,\sqrt{g}\;T^{0}_{\;\; 0}$ is equal to the canonical Hamiltonian for a general gauge theory coupled to spin 1/2 and spin 0 matter fields (including an $Rϕ^{2}$ term) in a static background metric ($\partial_{0}g_{μν}=0$ and $g_{0j}=0$). The equality depends on on the Gauss's law constraint but not on the dynamical Euler-Lagrange equations.
Revisiting Multiple Instance Neural Networks
Creators: name: Wang, Xinggang
name: Yan, Yongluan
name: Tang, Peng
name: Bai, Xiang
name: Liu, Wenyu
Publisher: name: arXiv
Year: 2016
Subjects: subject: Machine Learning (stat.ML)
subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: Recently neural networks and multiple instance learning are both attractive topics in Artificial Intelligence related research fields. Deep neural networks have achieved great success in supervised learning problems, and multiple instance learning as a typical weakly-supervised learning method is effective for many applications in computer vision, biometrics, nature language processing, etc. In this paper, we revisit the problem of solving multiple instance learning problems using neural networks. Neural networks are appealing for solving multiple instance learning problem. The multiple instance neural networks perform multiple instance learning in an end-to-end way, which take a bag with various number of instances as input and directly output bag label. All of the parameters in a multiple instance network are able to be optimized via back-propagation. We propose a new multiple instance neural network to learn bag representations, which is different from the existing multiple instance neural networks that focus on estimating instance label. In addition, recent tricks developed in deep learning have been studied in multiple instance networks, we find deep supervision is effective for boosting bag classification accuracy. In the experiments, the proposed multiple instance networks achieve state-of-the-art or competitive performance on several MIL benchmarks. Moreover, it is extremely fast for both testing and training, e.g., it takes only 0.0003 second to predict a bag and a few seconds to train on a MIL datasets on a moderate CPU.
The cosmic radio dipole: Bayesian estimators on new and old radio surveys
Creators: name: Wagenveld, J. D.
name: Klöckner, H-R.
name: Schwarz, D. J.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: The cosmic radio dipole is an anisotropy in the number counts of radio sources, analogous to the dipole seen in the cosmic microwave background (CMB). Measurements of source counts of large radio surveys have shown that though the radio dipole is generally consistent in direction with the CMB dipole, the amplitudes are in tension. These observations present an intriguing puzzle as to the cause of this discrepancy, with a true anisotropy breaking with the assumptions of the cosmological principle, invalidating the most common cosmological models that are built on these assumptions. We present a novel set of Bayesian estimators to determine the cosmic radio dipole and compare the results with commonly used methods on the Rapid ASKAP Continuum Survey (RACS) and the NRAO VLA Sky Survey (NVSS) radio surveys. In addition, we adapt the Bayesian estimators to take into account systematic effects known to affect such large radio surveys, folding information such as the local noise floor or array configuration directly into the parameter estimation. The enhancement of these estimators allows us to greatly increase the amount of sources used in the parameter estimation, yielding tighter constraints on the cosmic radio dipole estimation than previously achieved with NVSS and RACS. We extend the estimators further to work on multiple catalogues simultaneously, leading to a combined parameter estimation using both NVSS and RACS. The result is a dipole estimate that perfectly aligns with the CMB dipole in terms of direction but with an amplitude that is three times as large, and a significance of 4.8$σ$. This new dipole measurement is made to an unprecedented level of precision for radio sources, which is only matched by recent results using infrared quasars.
description: 14 pages, 11 figures. Accepted for publication in Astronomy & Astrophysics
Star Clusters and the nursery of Binary Black Holes
Creators: name: Torniamenti, Stefano
Publisher: name: Zenodo
Year: 2023

description: Star clusters are the most common birthplace of massive stars, which form as members of binary or multiple systems. In these dense stellar environments, dynamical interactions can shape the properties of binary stars, and govern the formation of binary black holes (BBHs), the best known sources of gravitational waves. In this contribution, I will investigate how the interplay between star clusters and their binary stars and BBHs affects the properties of gravitational-wave sources. Through direct N-body models, I find that the formation channels of BBHs in dynamically-active (massive and dense) and dynamically-quiet (low-mass and loose) star clusters are extremely different. Dynamically-quiet clusters host mainly low-mass BBHs born from binary evolution, while BBHs in dynamically-active clusters are relatively massive and driven by dynamical exchanges. I will show that star-star collisions and repeated black hole mergers are viable mechanisms for the formation of black holes in the pair-instability mass gap (60-120 MSun), which cannot form from isolated stellar and binary evolution. In particular, repeated black hole mergers can extend the black hole mass distribution to values larger than 60 MSun, consistently with the trend inferred from gravitational-wave detections.
The ortho-to-para ratio of interstellar NH$_2$: Quasi-classical trajectory calculations and new simulations
Creators: name: Gal, Romane Le
name: Herbst, Eric
name: Xie, Changjian
name: Li, Anyang
name: Guo, Hua
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Based on recent $Herschel$ results, the ortho-to-para ratio (OPR) of NH$_2$ has been measured towards the following high-mass star-forming regions: W31C (G10.6-0.4), W49N (G43.2-0.1), W51 (G49.5-0.4), and G34.3+0.1. The OPR at thermal equilibrium ranges from the statistical limit of three at high temperatures to infinity as the temperature tends toward zero, unlike the case of H$_{2}$. Depending on the position observed along the lines-of-sight, the OPR was found to lie either slightly below the high temperature limit of three (in the range $2.2-2.9$) or above this limit ($\sim3.5$, $\gtrsim 4.2$, and $\gtrsim 5.0$). In low temperature interstellar gas, where the H$_{2}$ is para-enriched, our nearly pure gas-phase astrochemical models with nuclear-spin chemistry can account for anomalously low observed NH$_2$-OPR values. We have tentatively explained OPR values larger than three by assuming that spin thermalization of NH$_2$ can proceed at least partially by H-atom exchange collisions with atomic hydrogen, thus increasing the OPR with decreasing temperature. In this paper, we present quasi-classical trajectory calculations of the H-exchange reaction NH$_2$ + H, which show the reaction to proceed without a barrier, confirming that the H-exchange will be efficient in the temperature range of interest. With the inclusion of this process, our models suggest both that OPR values below three arise in regions with temperatures $\gtrsim20-25$~K, depending on time, and values above three but lower than the thermal limit arise at still lower temperatures.
description: 12 pages, 12 figures. Accepted for publication in A&A
Multiplicity Boost Of Transit Signal Classifiers: Validation of 69 New Exoplanets Using The Multiplicity Boost of ExoMiner
Creators: name: Valizadegan, Hamed
name: Martinho, Miguel J. S.
name: Jenkins, Jon M.
name: Caldwell, Douglas A.
name: Twicken, Joseph D.
name: Bryson, Stephen T.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Artificial Intelligence (cs.AI)
subject: Machine Learning (cs.LG)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: Most existing exoplanets are discovered using validation techniques rather than being confirmed by complementary observations. These techniques generate a score that is typically the probability of the transit signal being an exoplanet (y(x)=exoplanet) given some information related to that signal (represented by x). Except for the validation technique in Rowe et al. (2014) that uses multiplicity information to generate these probability scores, the existing validation techniques ignore the multiplicity boost information. In this work, we introduce a framework with the following premise: given an existing transit signal vetter (classifier), improve its performance using multiplicity information. We apply this framework to several existing classifiers, which include vespa (Morton et al. 2016), Robovetter (Coughlin et al. 2017), AstroNet (Shallue & Vanderburg 2018), ExoNet (Ansdel et al. 2018), GPC and RFC (Armstrong et al. 2020), and ExoMiner (Valizadegan et al. 2022), to support our claim that this framework is able to improve the performance of a given classifier. We then use the proposed multiplicity boost framework for ExoMiner V1.2, which addresses some of the shortcomings of the original ExoMiner classifier (Valizadegan et al. 2022), and validate 69 new exoplanets for systems with multiple KOIs from the Kepler catalog.
description: The paper is accepted for publication in the Astronomical Journal in April 27th, 2023
Studying the link between radio galaxies and AGN fuelling with relativistic hydrodynamic simulations of flickering jets
Creators: name: Whitehead, Henry W.
name: Matthews, James H.
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We present two- and three-dimensional hydrodynamic simulations of $\sim$kpc-scale AGN jets with mean jet powers in the range $1-7\times10^{45}\,$erg~s$^{-1}$, in which the jet power varies (through variation of the Lorentz factor) according to a flicker or pink noise power spectrum. We find the morphology and dynamics of the jet-cocoon system depends on the amplitude of the variability with a clear correspondence between the shape of the cocoon and the historical activity. The jet advances quickly during high-power states, whereas quiescent periods instead produce passive periods of inflation resembling Sedov-Taylor blast waves. Periods of high activity preferentially produce hotspots and create stronger backflow as they maximise the pressure gradient between the jet head and cocoon. The variability can also lead to propagating internal shock structures along the jet. Our work suggests that variability and flickering in the jet power has important implications, which we discuss, for observations of radio galaxies, ultrahigh energy cosmic ray acceleration and jet power to luminosity correlations. We explore the link between morphology and fuelling, and suggest that chaotic cold accretion should introduce a relatively small scatter in radio luminosity ($\sim0.2$ dex) and modest imprints on morphology; sources such as Hercules A and Fornax A, which show evidence for more dramatic variability, may therefore require redder power spectra, or be triggered by mergers or other discrete events. We suggest ways to search for jet flickering observationally and propose that radio galaxies may be an important diagnostic of Myr timescale AGN fuelling, due to their `long-term memory'.
description: 20 pages, 15 figures, 1 table. Accepted for publication in MNRAS. Animated version of figure 3 available at https://youtu.be/YhDHokWXuKk with other movies on the same youtube channel. Full supplementary material available at https://github.com/jhmatthews/flicker-supplement
Secular dipole-dipole stability of magnetic binaries
Creators: name: Aykroyd, Christopher
name: Bourgoin, Adrien
name: Poncin-Lafitte, Christophe Le
name: Mathis, Stéphane
name: Angonin, Marie-Christine
Publisher: name: arXiv
Year: 2023
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: The presence of strong large-scale stable magnetic fields in a significant portion of early-type stars, white dwarfs, and neutron stars is well established. Despite this, the origins of these fields remain unresolved, with leading propositions advocating fossil fields, mergers, and shear-driven dynamos as the main mechanism. A potential key for further insight could lie in the connection with binarity: notably, magnetism can play a role in the long-term orbital and rotational dynamics of binaries. In gravitational wave astronomy, the advanced sensitivity of upcoming detectors such as LISA and the Einstein Telescope will enable the characterisation of the orbital inspirals of compact systems, including their magnetic properties. A comprehensive understanding of the dynamics of magnetism in these systems is required for the interpretation of the gravitational wave signals and to avoid calibration biases. Furthermore, this knowledge can be used to create new magnetic population models and to provide insight into the nature of their internal fields. The aim of this study is to investigate the secular spin precession dynamics of binary systems under pure magnetic dipole interactions, focusing on stars with strong, stable, dipolar fields. We employ an orbit-averaging procedure for the spin equations and obtain an effective secular description. By minimising the magnetic energy, we derive the configurations of equilibrium. We show that among the four states, only one is stable, consisting of the spin and magnetic axes of one star reversed with respect to the companions', and orthogonal to the orbital plane. Our long-term stability results disagree with usual methods, which tend to neglect orbital motion. Finally, we provide analytical solutions for the system out of equilibrium, which can be used to derive secular orbital evolution in the context of gravitational wave astronomy.
description: 16 pages, 5 figures
Curb EU enthusiasm: how politicisation shapes bureaucratic responsiveness
Creators: name: Yordanova, Nikoleta
name: Khokhlova, Aleksandra
name: Ershova, Anastasia
name: Schmidt, Fabian David
name: Glavaš, Goran
Publisher: name: Taylor & Francis
Year: 2024
Subjects: subject: Sociology
subject: FOS: Sociology
subject: Biological Sciences not elsewhere classified
subject: Mathematical Sciences not elsewhere classified
subject: Science Policy

description: International institutions are often challenged for being detached from the citizens. Focusing on the European Union, this article studies whether this is the case and, if so, when the European Commission responds to public opinion when pursuing policy integration. It argues that the Commission has legitimacy incentives encouraging it to be responsive but politicisation can suppress responsiveness by transmitting competing demands on the Commission from the member states’ citizens. To test these arguments, the contribution applied automated text analysis to estimate the European Union (EU) authority expansion entailed in the Commission’s legislative proposals between 2009 and 2019 and analysed its correspondence with public preferences over EU policy action across the EU states, measured using the Eurobarometer. The results lend support to the hypotheses and suggest that politicisation can undermine the responsiveness of international institutions.
Merger Conditions of Population III Protostar Binaries
Creators: name: Kirihara, Takanobu
name: Susa, Hajime
name: Hosokawa, Takashi
name: Kinugawa, Tomoya
Publisher: name: arXiv
Year: 2023
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Massive close binary stars with extremely small separations have been observed, and they are possible progenitors of gravitational-wave sources. The evolution of massive binaries in the protostellar accretion stage is key to understanding their formation process. We, therefore, investigate how close the protostars, consisting of a high-density core and a vast low-density envelope, can approach each other but not coalesce. To investigate the coalescence conditions, we conduct smoothed particle hydrodynamics simulations following the evolution of equal-mass binaries with different initial separations. Since Population (Pop) I and III protostars have similar interior structures, we adopt a specific Pop~III model with the mass and radius of $7.75\;M_{\odot}$ and $61.1\;R_{\odot}$ obtained by the stellar evolution calculations. Our results show that the binary separation decreases due to the transport of the orbital angular momentum to spin angular momentum. If the initial separation is less than about 80 per~cent of the sum of the protostellar radius, the binary coalesces in a time shorter than the tidal lock timescale. The mass loss up to the merging is $\lesssim 3$ per~cent. After coalescence, the star rotates rapidly, and its interior structure is independent of the initial separation. We conclude that there must be some orbital shrinking mechanism after the protostars contract to enter the zero-age main-sequence stage.
description: 17 pages, 13 figures, Accepted for Publication in ApJ
Some phases of state control of state supported institutions of higher education in Texas with particular reference to the State Board of Education
Creators: name: Sowers, Joseph Cullen
Publisher: name: The University of Texas at Austin
Year: 1949
Subjects: subject: Texas universities
subject: Texas colleges
subject: Texas State Board of Education
subject: Evaluation of Texas State Board of Education
subject: Education and state
subject: Texas--State Board of Education--Evaluation
subject: Education and state--Texas

description: Since its inception in 1929, the State Board of Education has made elaborate statistical studies based on extensive reports, required by law, from each of the state institutions of higher education. In its Biennial Reports this Board has made numerous recommendations pertaining to those institutions. It has also made budget recommendations for each institution to the State Board of Control. It is proposed, therefore, in this study to show, first, how the need for some sort of over-all state planning for higher education in Texas resulted in the assignment of certain duties to the State Board of Education, and second, to show how this Board has approached the various problems and the extent of the effectiveness of its efforts. Since the state's official budgeting agency is the State Board of Control, this study will attempt to show the effectiveness of the budget recommendations of the State Board of Education in determining the final appropriations by the Legislatures for institutions of higher education. Each duty of the State Board of Education specified by law and pertaining to higher education, will be studied to determine what activities have been undertaken, what recommendations have come from the Board, and what changes have actually taken place in the various institutions because of these studies and recommendations. Finally, conclusions will be drawn regarding the state's needs for further unification of its program of higher education, based on the outcomes of this study regarding the effectiveness of the efforts of the State Board of Education
From one-dimensional fields to Vlasov equilibria: Theory and application of Hermite polynomials
Creators: name: Allanson, O.
name: Neukirch, T.
name: Troscheit, S.
name: Wilson, F.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Plasma Physics (physics.plasm-ph)
subject: FOS: Physical sciences

description: We consider the theory and application of a solution method for the inverse problem in collisionless equilibria, namely that of calculating a Vlasov-Maxwell equilibrium for a given macroscopic (fluid) equilibrium. Using Jeans' Theorem, the equilibrium distribution functions are expressed as functions of the constants of motion, in the form of a Maxwellian multiplied by an unknown function of the canonical momenta. In this case it is possible to reduce the inverse problem to inverting Weierstrass transforms, which we achieve by using expansions over Hermite polynomials. A sufficient condition on the pressure tensor is found which guarantees the convergence and the boundedness of the candidate solution, when satisfied. This condition is obtained by elementary means, and it is clear how to put it into practice. We also argue that for a given pressure tensor for which our method applies, there always exists a positive distribution function solution for a sufficiently magnetised plasma. Illustrative examples of the use of this method with both force-free and non-force-free macroscopic equilibria are presented, including the full verification of a recently derived distribution function for the force-free Harris Sheet (Allanson $\textit{et al., Phys. Plasmas}$, vol. 22 (10), 2015, 102116). In the effort to model equilibria with lower values of the plasma beta, solutions for the same macroscopic equilibrium in a new gauge are calculated, with numerical results presented for $β_{pl}=0.05$.
description: Published version is Open Access in Journal of Plasma Physics, 82, 03 (2016). arXiv admin note: substantial text overlap with arXiv:1508.07925
Determination of small-scale magnetic fields on Sun-like stars in the near-infrared using CRIRES$^+$
Creators: name: Hahlin, A.
name: Kochukhov, O.
name: Rains, A. D.
name: Lavail, A.
name: Hatzes, A.
name: Piskunov, N.
name: Reiners, A.
name: Seemann, U.
name: Boldt-Christmas, L.
name: Guenther, E. W.
name: Heiter, U.
name: Nortmann, L.
name: Yan, F.
name: Shulyak, D.
name: Smoker, J. V.
name: Rodler, F.
name: Bristow, P.
name: Dorn, R. J.
name: Jung, Y.
name: Marquart, T.
name: Stempels, E.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We aim to characterise the small-scale magnetic fields for a sample of 16 Sun-like stars and investigate the capabilities of the newly upgraded near-infrared (NIR) instrument CRIRES$^+$ at the VLT in the context of small-scale magnetic field studies. Our targets also had their magnetic fields studied in the optical, which allows us to compare magnetic field properties at different spatial scales on the stellar surface and to contrast small-scale magnetic field measurements at different wavelengths. We analyse the Zeeman broadening signature for six magnetically sensitive and insensitive \ion{Fe}{I} lines in the H-band to measure small-scale magnetic fields on the stellar surface. We use polarised radiative transfer modelling and NLTE departure coefficients in combination with MCMC to determine magnetic field characteristics together with non-magnetic stellar parameters. We use two different approaches to describe small-scale magnetic fields. The first is a two-component model with a single magnetic region and a free magnetic field strength. The second model contains multiple magnetic components with fixed magnetic field strengths. We find average magnetic field strengths ranging from $\sim 0.4$ kG down to $<0.1$ kG. The results align closely with other results from high resolution NIR spectrographs such as SPIRou. We find that the small-scale fields correlate with the large-scale fields and that the small-scale fields are at least 10 times stronger than the large-scale fields inferred with Zeeman Doppler imaging. The two- and multi-component models produce systematically different results as the strong fields from the multi-component model increase the obtained mean magnetic field strength. When comparing our results with the optical measurements of small-scale fields we find a systematic offset of 2--3 times stronger fields in the optical.
description: 28 pages, 23 figures, accepted by A&A