cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Mechanism for giant enhancement of transport induced by active fluctuations
Creators: name: Białas, Karol
name: Spiechowicz, Jakub
Publisher: name: arXiv
Year: 2023
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: Understanding the role of active fluctuations in physics is a problem in statu nascendi appearing both as a hot topic and a major challenge. The reason for this is the fact that they are inherently non-equilibrium. This feature opens a landscape of phenomena yet to be explored that are absent in the presence of thermal fluctuations alone. Recently a paradoxical effect has been briefly communicated in which a free particle transport induced by active fluctuations in the form white Poisson shot noise can be enormously boosted when the particle is additionally subjected to a periodic potential. In this work we considerably extend the original predictions and investigate the impact of statistics of active noise on the occurrence of this effect. We construct a toy-model of the jump-relaxation process that allow us to identify different regimes of the free particle transport boost and explain their corresponding mechanisms. Moreover, we formulate and interpret the conditions for statistics of active fluctuations that are necessary for the emergence of giant enhancement of the free particle transport induced by the periodic potential. Our results are relevant not only for microscopic physical systems but also for biological ones such as e.g. living cells where fluctuations generated by metabolic activities are active by default.
description: in press in Phys. Rev. E
S-type stars from LAMOST DR10: classification of intrinsic and extrinsic stars
Creators: name: Chen, Jing
name: Li, Yin-Bi
name: Luo, A-Li
name: Ma, Xiao-Xiao
name: Li, Shuo
Publisher: name: arXiv
Year: 2023
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: In this paper, we found 2939 S-type stars from LAMOST Data Release 10 using two machine-learning methods, and 2306 of them were reported for the first time. The main purpose of this work is to study how to divide S-type stars into intrinsic and extrinsic stars with photometric data and LAMOST spectra. Using infrared photometric data, we adopted two methods to distinguish S-type stars, i.e., XGBoost algorithm and color-color diagrams. We trained XGBoost model with 15 input features consisting of colors and absolute magnitudes of Two Micron All Sky Survey (2MASS), AllWISE, AKARI, and IRAS, and found that the model trained by input features with 2MASS, AKARI, and IRAS data has the highest accuracy of 95.52%. Furthermore, using this XGBoost model, we found four color-color diagrams with six infrared color criteria to divide S-type stars, which has an accuracy of about 90%. Applying the two methods to the 2939 S-type stars, 381 (XGBoost)/336 (color-color diagrams) intrinsic and 495 (XGBoost)/82 (color-color diagrams) extrinsic stars were classified, respectively. Using these photometrically classified intrinsic and extrinsic stars, we retrained XGBoost model with their blue and red medium-resolution spectra, and the 2939 stars were divided into 855 intrinsic and 2056 extrinsic stars from spectra with an accuracy of 94.82%. In addition, we also found four spectral regions of Zr I (6451.6A), Ne II (6539.6A), Hα (6564.5A), and Fe I (6609.1A) and C I (6611.4A) are the most important features, which can reach an accuracy of 92.1% when using them to classify S-type stars.
description: 21 pages,13 figures, Accepted by ApJS
Addendum: Weyl cocycles, (Class.Quantum Grav. 3 (1986) 635)
Creators: name: Bonora, Loriano
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Weyl 0- and 1-cocycles of canonical dimension 6 in six dimensions, which were computed earlier in ref.\cite{bonorabregolapasti1986}, are recalculated from scratch. The analysis yields five Weyl invariants (0-cocycles), instead of four, and the same four non-trivial 1-cocycles (possible trace anomalies), like in that reference (up to the correction of one typo)
description: 8 pages
Thermopower of molecular junctions: Tunneling to hopping crossover in DNA
Creators: name: Korol, Roman
name: Kilgour, Michael
name: Segal, Dvira
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We study the electrical conductance $G$ and the thermopower $S$ of single-molecule junctions, and reveal signatures of different transport mechanisms: off-resonant tunneling, on-resonant coherent (ballistic) motion, and multi-step hopping. These mechanisms are identified by studying the behavior of $G$ and $S$ while varying molecular length and temperature. Based on a simple one-dimensional model for molecular junctions, we derive approximate expressions for the thermopower in these different regimes. Analytical results are compared to numerical simulations, performed using a variant of Büttiker's probe technique, the so-called voltage-temperature probe, which allows us to phenomenologically introduce environmentally-induced elastic and inelastic electron scattering effects, while applying both voltage and temperature biases across the junction. We further simulate the thermopower of GC-rich DNA molecules with mediating A:T blocks, and manifest the tunneling-to-hopping crossover in both the electrical conductance and the thermopower, in accord with measurements by Y. Li et al., Nature Comm. 7, 11294 (2016).
InstaLoc: One-shot Global Lidar Localisation in Indoor Environments through Instance Learning
Creators: name: Zhang, Lintong
name: Digumarti, Tejaswi
name: Tinchev, Georgi
name: Fallon, Maurice
Publisher: name: arXiv
Year: 2023
Subjects: subject: Robotics (cs.RO)
subject: FOS: Computer and information sciences

description: Localization for autonomous robots in prior maps is crucial for their functionality. This paper offers a solution to this problem for indoor environments called InstaLoc, which operates on an individual lidar scan to localize it within a prior map. We draw on inspiration from how humans navigate and position themselves by recognizing the layout of distinctive objects and structures. Mimicking the human approach, InstaLoc identifies and matches object instances in the scene with those from a prior map. As far as we know, this is the first method to use panoptic segmentation directly inferring on 3D lidar scans for indoor localization. InstaLoc operates through two networks based on spatially sparse tensors to directly infer dense 3D lidar point clouds. The first network is a panoptic segmentation network that produces object instances and their semantic classes. The second smaller network produces a descriptor for each object instance. A consensus based matching algorithm then matches the instances to the prior map and estimates a six degrees of freedom (DoF) pose for the input cloud in the prior map. The significance of InstaLoc is that it has two efficient networks. It requires only one to two hours of training on a mobile GPU and runs in real-time at 1 Hz. Our method achieves between two and four times more detections when localizing, as compared to baseline methods, and achieves higher precision on these detections.
Close Encounters of the Third Kind: Eccentric Black Hole Mergers in Star Clusters
Creators: name: , Marco
Publisher: name: Zenodo
Year: 2023
Subjects: Black Holes

description: Binary black holes (BBHs) residing in dense stellar environments lead dynamically complex lives as they undergo strong interactions with other black holes (BHs). These interactions can excite the eccentricity of the BBHs and even lead to their merger. In contrast, isolated binaries struggle to produce BBHs with significant eccentricity during the merger process. Factors such as tides, mass transfer episodes, and common envelope events, typically circularize the orbit of a binary star before it evolves into a BBH. Consequently, eccentric mergers are commonly associated with BBHs formed in dynamically active environments. If detected in the waveform of a merger, eccentricity can serve as a tool to infer the dynamical origin of a BBH. In my presentation, I will explore how dynamical interactions within star clusters might serve as a valid pathway for producing eccentric BBH mergers. I will present how these interactions impact the population of BH mergers in young, globular, and nuclear star clusters. I will investigate the role of these interactions in the formation of eccentric BBH mergers. The hosting environment significantly influences the properties of the BBH merger population and also plays a crucial role in dynamical ejections. Lastly, I will discuss how the dynamics of the cluster can leave distinctive signatures on the merger properties. Not only eccentricity, but also total masses and spins of the BH mergers, can be employed as indicators of their dynamical formation.
Decoherence in quantum systems in a static gravitational field
Creators: name: Shariati, Ahmad
name: Khorrami, Mohammad
name: Loran, Farhang
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: A small quantum system is studied which is a superposition of states localized in different positions in a static gravitational field. The time evolution of the correlation between different positions is investigated, and it is seen that there are two time scales for such an evolution (decoherence). Both time scales are inversely proportional to the red shift difference between the two points. These time scales correspond to decoherences which are linear and quadratic, respectively, in time.
description: 9 pages
Giant Bulk Electro-photovoltaic Effect in Hetero-nodal-line Systems
Creators: name: Jiang, Xiao
name: Kang, Lei
name: Wang, Jianfeng
name: Huang, Bing
Publisher: name: arXiv
Year: 2023
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Realization of giant and continuously tunable second-order photocurrent is desired for many nonlinear optical (NLO) and optoelectronic applications, which remains to be a great challenge. Here, based on a simple two-band model, we propose a concept of bulk electro-photovoltaic effect, that is, an out-of-plane external electric-field ($E_{ext}$) can continuously tune in-plane shift current along with its sign flip in a hetero-nodal-line (HNL) system. While strong linear optical transition around the nodal-loop may potentially generate giant shift current, an $E_{ext}$ can effectively control the radius of nodal-loop, which can continuously modulate the shift-vector components inside and outside nodal-loop holding opposite signs. This concept has been demonstrated in the HNL HSnN/MoS$_2$ system using first-principles calculations. The HSnN/MoS$_2$ hetero-bilayer not only can produce giant shift current with 1~2 magnitude order larger than other reported systems, but also can realize a giant bulk electro-photovoltaic effect. Our finding opens new routes to create and manipulate giant NLO responses in 2D materials.
Hidden Markov model tracking of continuous gravitational waves from a neutron star with wandering spin
Creators: name: Suvorova, S.
name: Sun, L.
name: Melatos, A.
name: Moran, W.
name: Evans, R. J.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Gravitational wave searches for continuous-wave signals from neutron stars are especially challenging when the star's spin frequency is unknown a priori from electromagnetic observations and wanders stochastically under the action of internal (e.g. superfluid or magnetospheric) or external (e.g. accretion) torques. It is shown that frequency tracking by hidden Markov model (HMM) methods can be combined with existing maximum likelihood coherent matched filters like the F-statistic to surmount some of the challenges raised by spin wandering. Specifically it is found that, for an isolated, biaxial rotor whose spin frequency walks randomly, HMM tracking of the F-statistic output from coherent segments with duration T_drift = 10d over a total observation time of T_obs = 1yr can detect signals with wave strains h0 > 2e-26 at a noise level characteristic of the Advanced Laser Interferometer Gravitational Wave Observatory (Advanced LIGO). For a biaxial rotor with randomly walking spin in a binary orbit, whose orbital period and semi-major axis are known approximately from electromagnetic observations, HMM tracking of the Bessel-weighted F-statistic output can detect signals with h0 > 8e-26. An efficient, recursive, HMM solver based on the Viterbi algorithm is demonstrated, which requires ~10^3 CPU-hours for a typical, broadband (0.5-kHz) search for the low-mass X-ray binary Scorpius X-1, including generation of the relevant F-statistic input. In a "realistic" observational scenario, Viterbi tracking successfully detects 41 out of 50 synthetic signals without spin wandering in Stage I of the Scorpius X-1 Mock Data Challenge convened by the LIGO Scientific Collaboration down to a wave strain of h0 = 1.1e-25, recovering the frequency with a root-mean-square accuracy of <= 4.3e-3 Hz.
Monte-Carlo modelling of multi-object adaptive optics performance on the European Extremely Large Telescope
Creators: name: Basden, Alastair
name: Morris, Tim
Publisher: name: arXiv
Year: 2016
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: The performance of a wide-field adaptive optics system depends on input design parameters. Here we investigate the performance of a multi-object adaptive optics system design for the European Extremely Large Telescope, using an end-to-end Monte-Carlo adaptive optics simulation tool, DASP, with relevance for proposed instruments such as MOSAIC. We consider parameters such as the number of laser guide stars, sodium layer depth, wavefront sensor pixel scale, actuator pitch and natural guide star availability. We provide potential areas where costs savings can be made, and investigate trade-offs between performance and cost, and provide solutions that would enable such an instrument to be built with currently available technology. Our key recommendations include a trade-off for laser guide star wavefront sensor pixel scale of about 0.7 arcseconds per pixel, and a field of view of at least 7 arcseconds, that EMCCD technology should be used for natural guide star wavefront sensors even if reduced frame rate is necessary, and that sky coverage can be improved by a slight reduction in natural guide star sub-aperture count without significantly affecting tomographic performance. We find that adaptive optics correction can be maintained across a wide field of view, up to 7 arcminutes in diameter. We also recommend the use of at least 4 laser guide stars, and include ground-layer and multi-object adaptive optics performance estimates.
description: Accepted for publication in MNRAS
$ Δ$ baryon spectroscopy in lattice QCD
Creators: name: Hockley, Liam
name: Kamleh, Waseem
name: Leinweber, Derek
name: Thomas, Anthony
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Physics - Lattice (hep-lat)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: A variational analysis is performed within the framework of lattice QCD to extract the masses of the spin-3/2 positive parity $ Δ^+ $ baryons, including radial excitations. $2+1$ flavour dynamical gauge-field configurations provided by the PACS-CS collaboration via the ILDG are considered. To improve our interpolator basis, we perform an iterative process of source and sink smearing and solve a generalised eigenvalue problem using the resulting fermion operators. We obtain a clear signal for the ground and first excited states at a light quark mass corresponding to $ m_π= 413 $ MeV. Furthermore, we show that one can use the eigenvectors obtained in this method to investigate the nature of these states, allowing us to classify our results as $ 1s $ and $ 2s $ states for the ground and first excited states respectively. Finally, we briefly highlight the method of Hamiltonian Effective Field Theory which can be used to make comparison with quark model expectations.
description: 12 pages, 3 figures. Contribution to a special issue of Few Body Systems: "Emergence and Structure of Baryons -- Selected Contributions from the International Conference Baryons 2022"
The non-relativistic limit of first-order relativistic viscous fluids
Creators: name: R, Abhishek Hegade K
name: Ripley, Justin L.
name: Yunes, Nicolás
Publisher: name: arXiv
Year: 2023
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: Mathematical Physics (math-ph)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: Out-of-equilibrium effects may play an important role in the dynamics of neutron star mergers and in heavy-ion collisions. Bemfica, Disconzi, Noronha and Kovtun (BDNK) recently derived a causal, locally well-posed, and modally stable relativistic fluid model that incorporates the effects of viscosity and heat diffusion. We study the non-relativistic limit of this fluid model and show that causality for relativistic motion restricts the transport coefficients in the non-relativistic limit. This restriction provides an upper bound on the ratio of the shear viscosity to the entropy density for fluids that can be described as relativistic within the BDNK model and can be exactly modeled using the Navier-Stokes equation in the non-relativistic limit. Furthermore, we show that the Fourier law of heat conduction must be modified by higher gradient corrections for such fluids. We also show that the non-relativistic limit of the BDNK equations of motion are never hyperbolic, in contrast to the non-relativistic limit of extended variable models, whose non-relativistic equations of motion can be hyperbolic or not depending on the scaling of the transport coefficients present in the auxiliary equations for viscous degrees of freedom.
description: v2-matches published version in PRD
Study of young stellar clusters: The dynamical evolution of the Orion Complex
Creators: name: Sánchez-Sanjuán, Sergio
Publisher: name: Zenodo
Year: 2023
Subjects: Star formation
Young star cluster
Kinematics
Astrometry

description: In recent years, the study of young stellar clusters has become a topic of raising interest thanks to the role played by large scale surveys with unprecedented precision; particularly in the solar neighbourhood where several close star-forming regions are placed such as the Orion Complex.This work is a kinematic study of the Orion Complex in the 6D phase space, which is performed after the detection of groups composed by stars that share both spatial and kinematic coherence between 250 and 500 pc from the Sun using a Hierarchical Clustering Algorithm. As preliminary results, we detected that several sectors of the complex undergo current expansion and rotation processes. Also, there are likely scenarios of cluster merging in the next 20 Myr. This will allow us to carry out future works on the development of N-body simulations for a better statistical analysis in the early stages of the detected young stellar clusters.
description: None
Delensing of Cosmic Microwave Background Polarization with machine learning
Creators: name: Yan, Ye-Peng
name: Wang, Guo-Jian
name: Li, Si-Yu
name: Xia, Jun-Qing
Publisher: name: arXiv
Year: 2023
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Primordial B-mode detection is one of the main goals of next-generation cosmic microwave background (CMB) experiments. Primordial B-modes are a unique signature of primordial gravitational waves (PGWs). However, the gravitational interaction of CMB photons with large-scale structures will distort the primordial E modes, adding a lensing B-mode component to the primordial B-mode signal. Removing the lensing effect (`delensing') from observed CMB polarization maps will be necessary to improve the constraint of PGWs and obtain a primordial E-mode signal. Here, we introduce a deep convolutional neural network model named multi-input multi-output U-net (MIMO-UNet) to perform CMB delensing. The networks are trained on simulated CMB maps with size $20^{\circ} \times 20^{\circ}$. We first use MIMO-UNet to reconstruct the unlensing CMB polarization ($Q$ and $U$) maps from observed CMB maps. The recovered E-mode power spectrum exhibits excellent agreement with the primordial EE power spectrum. The recovery of the primordial B-mode power spectrum for noise levels of 0, 1, and 2 $μ$K-arcmin is greater than 98\% at the angular scale of $\ell<150$. We additionally reconstruct the lensing B map from observed CMB maps. The recovery of the lensing B-mode power spectrum is greater than roughly 99\% at the scales of $\ell>200$. We delens observed B-mode power spectrum by subtracting reconstructed lensing B-mode spectrum. The recovery of tensor B-mode power spectrum for noise levels of 0, 1, 2 $μ$K-arcmin is greater than 98 \% at the angular scales of $\ell<120$. Even at $\ell=160$, the recovery of tensor B-mode power spectrum is still around 71 \%.
description: 18 pages, 14 figures, 1 table, accepted by ApJS
Lepto-hadronic interpretation of 2021 RS Ophiuchi nova outburst
Creators: name: De Sarkar, Agnibha
name: J., Nayana A.
name: Roy, Nirupam
name: Razzaque, Soebur
name: Anupama, G. C.
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Very high energy (VHE; 100 GeV $<$ E $\leq$ 100 TeV) and high energy (HE; 100 MeV $<$ E $\leq$ 100 GeV) gamma-rays were observed from the symbiotic recurrent nova RS Ophiuchi (RS Oph) during its outburst in August 2021, by various observatories such as High Energy Stereoscopic System (H.E.S.S.), Major Atmospheric Gamma Imaging Cherenkov (MAGIC), and {\it Fermi}-Large Area Telescope (LAT). The models explored so far tend to favor a hadronic scenario of particle acceleration over an alternative leptonic scenario. This paper explores a time-dependent lepto-hadronic scenario to explain the emission from the RS Oph source region. We have used simultaneous low frequency radio data observed by various observatories, along with the data provided by H.E.S.S., MAGIC, and \textit{Fermi}-LAT, to explain the multi-wavelength (MWL) spectral energy distributions (SEDs) corresponding to 4 days after the outburst. Our results show that a lepto-hadronic interpretation of the source not only explains the observed HE-VHE gamma-ray data but the corresponding model synchrotron component is also consistent with the first 4 days of low radio frequency data, indicating the presence of non-thermal radio emission at the initial stage of nova outburst. We have also calculated the expected neutrino flux from the source region and discussed the possibility of detecting neutrinos.
description: 18 pages, 5 figures, 2 tables; accepted for publication in The Astrophysical Journal (ApJ)
Phonon anharmonicity and negative thermal expansion in SnSe
Creators: name: Bansal, Dipanshu
name: Hong, Jiawang
name: Li, Chen W.
name: May, Andrew F.
name: Porter, Wallace
name: Hu, Michael Y.
name: Abernathy, Douglas L.
name: Delaire, Olivier
Publisher: name: arXiv
Year: 2016
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The anharmonic phonon properties of SnSe in the Pnma phase were investigated with a combination of experiments and first-principles simulations. Using inelastic neutron scattering (INS) and nuclear resonant inelastic X-ray scattering (NRIXS), we have measured the phonon dispersions and density of states (DOS) and their temperature dependence, which revealed a strong, inhomogeneous shift and broadening of the spectrum on warming. First-principles simulations were performed to rationalize these measurements, and to explain the previously reported anisotropic thermal expansion, in particular the negative thermal expansion within the Sn-Se bilayers. Including the anisotropic strain dependence of the phonon free energy, in addition to the electronic ground state energy, is essential to reproduce the negative thermal expansion. From the phonon DOS obtained with INS and additional calorimetry measurements, we quantify the harmonic, dilational, and anharmonic components of the phonon entropy, heat capacity, and free energy. The origin of the anharmonic phonon thermodynamics is linked to the electronic structure.
description: 14 pages, 12 figures
A type II solar radio burst without a coronal mass ejection
Creators: name: Morosan, D. E.
name: Pomoell, J.
name: Kumari, A.
name: Kilpua, E. K. J.
name: Vainio, R.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Space Physics (physics.space-ph)
subject: FOS: Physical sciences

description: The Sun produces the most powerful explosions in the solar system, solar flares, that can also be accompanied by large eruptions of magnetised plasma, coronal mass ejections (CMEs). These processes can accelerate electron beams up to relativistic energies through magnetic reconnection processes during solar flares and CME-driven shocks. Energetic electron beams can in turn generate radio bursts through the plasma emission mechanism. CME shocks, in particular, are usually associated with type II solar radio bursts. However, on a few occasions, type II bursts have been reported to occur either in the absence of CMEs or shown to be more likely related with the flaring process. It is currently an open question how a shock generating type II bursts forms without the occurrence of a CME eruption. Here, we aim to determine the physical mechanism responsible for a type II burst which occurs in the absence a CME. By using radio imaging from the Nan{\c c}ay Radioheliograph, combined with observations from the Solar Dynamics Observatory and the Solar Terrestrial Relations Observatory spacecraft, we investigate the origin of a type II radio burst that appears to have no temporal association with a white-light CME. We identify a typical type II radio burst with band-split structure that is associated with a C-class solar flare. The type II burst source is located above the flaring active region and ahead of disturbed coronal loops observed in extreme ultraviolet images. The type II is also preceded by type III radio bursts, some of which are in fact J-bursts indicating that accelerated electron beams do not all escape along open field lines. The type II sources show single-frequency movement towards the flaring active region. The type II is located ahead of a faint extreme-ultraviolet (EUV) front propagating through the corona.
description: 10 pages, 8 figures
Thermal spikes induced sublimation of carbon nanotubes
Creators: name: Javeed, Sumera
name: Ahmad, Shoaib
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We report and provide justification for the consistently observed four experimental facts of the mass spectrometric data of carbon cluster emission from the low-energy Cs irradiated single-walled carbon nanotubes . Firstly, the diatomic carbon C(2) is the most abundant sputtered species for Cs+ in the energy range 0.2 keV to 2.0 keV. Secondly, monatomic carbon C(1) is emitted with the least sputtering yield. Thirdly, at low cesium energies i the emitted species are C(2), C(3) and C(4). Lastly, as the irradiating Cs+ energy increases, the normalized yield of atomic carbon monotonically increases while clusters show gradual decrease and saturation. Sputtering of clusters is proved here to be due to thermal spikes. Binary collision cascade theory does not explain cluster sputtering. A statistical thermal model is developed to explain the experimentally observed data. The probability of a cluster C(x) to be emitted is shown to be proportional to that for the creation of an x-member vacancy with formation energy E at temperature T as {exp(E/kT)+1}^(-1). The energies of formation of single and double vacancies from DFT calculations and the ratio of normalized experimental yields have been used to estimate spike temperature. We show that by invoking thermal spikes, cluster emission from, and the multiple vacancy generation in, the Cs+-irradiated SWCNTs can be explained. We also suggest modifications to Monte Carlo type calculations of sputtering.
description: 15 pages, 3 figures
Sapaki: Galactic O3If* star possibly born in isolation
Creators: name: Plaza, M. S. Zarricueta
name: Roman-Lopes, A.
name: Sanmartim, D.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Context: The study of high-mass stars found to be isolated in the field of the Milky Way may help to probe the feasibility of the core-accretion mechanism in the case of massive star formation. The existence of truly isolated stars may efficiently probe the possibility that individual massive stars can be born in isolation. Aims: We observed WR67a (hereafter Sapaki), an O3If* star that appears to be isolated close to the center of a well-developed giant cavity that is aptly traced by 8.0 $μ$m hot dust emission. Methods: We acquired medium-resolution ($R=4100$) and moderate signal-to-noise ($S/N = 95$ at 4500 Å) spectra for Sapaki in the range of 3800-10500 Å with the Magellan Echellette (MagE) at Las Campanas Observatory. We computed the line-of-sight total extinctions. Additionally, we restricted its heliocentric distance by using a range of different estimators. Moreover, we measured its radial velocity from several lines in its spectrum. Finally, we analyzed its proper motions from Gaia to examine its possible runaway status. Results: The star has been classified as having the spectral type O3If* given its resemblance to standard examples of the class. In addition, we found that Sapaki is highly obscured, reaching a line-of-sight extinction value of $A_{V} = 7.87$. We estimated the heliocentric distance to be in the range of $d = 4-7$ kpc. We also estimated its radial velocity to be $V_{r} = -34.2 \pm 15.6$ km/s. We may also discard its runaway status solely based on its 2D kinematics. Furthermore, by analyzing proper motions and parallaxes provided by Gaia, we found only one other star with compatible measurements. Conclusions: Given its apparent non-runaway status and the absence of clustering, Sapaki appears to be a solid candidate for isolated high-mass star formation in the Milky Way.
description: 7 pages, 3 figures, 2 tables
Binary systems as probes of cluster internal dynamics
Creators: name: Cadelano, Mario
Publisher: name: Zenodo
Year: 2023

description: Globular clusters are old and dense aggregates of several hundred thousands of stars orbiting
 galaxy bulges and halos. They are the only stellar systems where interactions among stars and binaries frequently occur and progressively modify the structural properties of the cluster, erasing memory of the initial conditions: the so-called “dynamical evolution”. In this respect, binary systems are powerful tools to investigate the cluster dynamical evolution since their average mass is larger than that of single stars. Here I will present the first results of a large project aimed at studying, with a homogeneous technique, the radial variation of the binary fraction in a representative sample of globular clusters characterized by different levels of internal dynamical evolution. Preliminary results show that the level of internal dynamical evolution is the main driver in shaping the radial distribution of binaries. In fact, in most of the clusters the binary fraction shows a peak in the center, a decrease at intermediate distances, and finally a steep increase in the cluster outer regions. I will discuss these results in terms of dynamical evolution, mass-loss, and also their possible use to constrain the primordial binary fraction of globular clusters. Finally, I will compare these distributions with those measured for the population of blue straggler stars, which are an exotic by-product of binary evolution and interactions and recognized probes of internal dynamical evolution.
A detector interferometric calibration experiment for high precision astrometry
Creators: name: Crouzier, A.
name: Malbet, F.
name: Henault, F.
name: Leger, A.
name: Cara, C.
name: LeDuigou, J. M.
name: Preis, O.
name: Kern, P.
name: Delboulbe, A.
name: Martin, G.
name: Feautrier, P.
name: Stadler, E.
name: Lafrasse, S.
name: Rochat, S.
name: Ketchazo, C.
name: Donati, M.
name: Doumayrou, E.
name: Lagage, P. O.
name: Shao, M.
name: Goullioud, R.
name: Nemati, B.
name: Zhai, C.
name: Behar, E.
name: Potin, S.
name: Saint-Pe, M.
name: Dupont, J.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: Context: Exoplanet science has made staggering progress in the last two decades, due to the relentless exploration of new detection methods and refinement of existing ones. Yet astrometry offers a unique and untapped potential of discovery of habitable-zone low-mass planets around all the solar-like stars of the solar neighborhood. To fulfill this goal, astrometry must be paired with high precision calibration of the detector. Aims: We present a way to calibrate a detector for high accuracy astrometry. An experimental testbed combining an astrometric simulator and an interferometric calibration system is used to validate both the hardware needed for the calibration and the signal processing methods. The objective is an accuracy of 5e-6 pixel on the location of a Nyquist sampled polychromatic point spread function. Methods: The interferometric calibration system produced modulated Young fringes on the detector. The Young fringes were parametrized as products of time and space dependent functions, based on various pixel parameters. The minimization of func- tion parameters was done iteratively, until convergence was obtained, revealing the pixel information needed for the calibration of astrometric measurements. Results: The calibration system yielded the pixel positions to an accuracy estimated at 4e-4 pixel. After including the pixel position information, an astrometric accuracy of 6e-5 pixel was obtained, for a PSF motion over more than five pixels. In the static mode (small jitter motion of less than 1e-3 pixel), a photon noise limited precision of 3e-5 pixel was reached.
The 14 Her Planetary System: Companion Masses and Architecture from Radial Velocities and Astrometry
Creators: name: Benedict, G. F.
name: McArthur, B. E.
name: Nelan, E. P.
name: Bean, J. L.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We combine Hubble Space Telescope (HST) Fine Guidance Sensor, Hipparcos, and Gaia DR3 astrometric observations of the K0 V star 14 Her with the results of an analysis of extensive ground-based radial velocity data to determine perturbation orbits and masses for two previously known companions, 14 Her b and c. Radial velocities obtained with the Hobby-Eberly Telescope and from the literature now span over twenty five years. With these data we obtain improved RV orbital elements for both the inner companion, 14 Her b and the long-period outer companion, 14 Her c. We also find evidence of an additional RV signal with P $/sim$ 3789d. We then model astrometry from Hipparcos, HST, and Gaia with RV results to obtain system parallax and proper motion, perturbation periods, inclinations, and sizes due to 14 Her b and c. We find P_b = 1767.6 +/- 0.2 d, perturbation semi-major axis α_b = 1.3 +/- 0.1 mas, and inclination i_b = 36 +/- 3 degrees, P_c = 52160 +/- 1028 d, perturbation semi-major axis α_c = 10.3 +/- 0.7 mas, and inclination i_c = 82 +/- 14 degrees. In agreement with a past investigation, the 14 Her b, c orbits exhibit significant mutual inclination. Assuming a primary mass M = 0.98 +/- 0.04Msun, we obtain companion masses M_b = 8.5 +/- 1.0Mjup and M_c = 7.1 +/- 1.0Mjup.
description: To appear in the Astronomical Journal. arXiv admin note: substantial text overlap with arXiv:2204.13706
On Truncated Generalized Gibbs Ensembles in the Ising Field Theory
Creators: name: Essler, F. H. L.
name: Mussardo, G.
name: Panfil, M.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We discuss the implementation of two different truncated Generalized Gibbs Ensembles (GGE) describing the stationary state after a mass quench process in the Ising Field Theory. One truncated GGE is based on the semi-local charges of the model, the other on regularized versions of its ultra-local charges. We test the efficiency of the two different ensembles by comparing their predictions for the stationary state values of the single-particle Green's function $G(x) = \langle ψ^{\dagger}(x) ψ(0) \rangle$ of the complex fermion field $ψ(x)$. We find that both truncated GGEs are able to recover $G(x)$, but for a given number of charges the semi-local version performs better.
description: 12 pages, 7 figures
Evaluation of medium-large Language Models at zero-shot closed book generative question answering
Creators: name: Peinl, René
name: Wirth, Johannes
Publisher: name: arXiv
Year: 2023
Subjects: subject: Computation and Language (cs.CL)
subject: FOS: Computer and information sciences
subject: I.2.7

description: Large language models (LLMs) have garnered significant attention, but the definition of "large" lacks clarity. This paper focuses on medium-sized language models (MLMs), defined as having at least six billion parameters but less than 100 billion. The study evaluates MLMs regarding zero-shot generative question answering, which requires models to provide elaborate answers without external document retrieval. The paper introduces an own test dataset and presents results from human evaluation. Results show that combining the best answers from different MLMs yielded an overall correct answer rate of 82.7% which is better than the 60.9% of ChatGPT. The best MLM achieved 71.8% and has 33B parameters, which highlights the importance of using appropriate training data for fine-tuning rather than solely relying on the number of parameters. More fine-grained feedback should be used to further improve the quality of answers. The open source community is quickly closing the gap to the best commercial models.
A Novel Method for Solving the Linearized 1D Vlasov--Poisson Equation
Creators: name: Lee, Frank M.
name: Shadwick, B. A.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Plasma Physics (physics.plasm-ph)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: We present a novel method for solving the linearized Vlasov--Poisson equation, based on analyticity properties of the equilibrium and initial condition through Cauchy-type integrals, that produces algebraic expressions for the distribution and field, i.e., the solution is expressed without integrals. Standard extant approaches involve deformations of the Bromwich contour that give erroneous results for certain physically reasonable configurations or eigenfunction expansions that are misleading as to the temporal structure of the solution. Our method is more transparent, lacks these defects, and predicts previously unrecognized behavior.
description: Accepted for publication as a letter at PRE
Density functional theory calculations of the stress of oxidised (110) silicon surfaces
Creators: name: Melis, C
name: Giordano, S
name: Colombo, L
name: Mana, G
Publisher: name: arXiv
Year: 2016
Subjects: subject: Computational Physics (physics.comp-ph)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The measurement of the lattice-parameter of silicon by x-ray interferometry assumes the use of strain-free crystals. This might not be the case because surface relaxation, reconstruction, and oxidation cause strains without the application of any external force. In a previous work, this intrinsic strain was estimated by a finite element analysis, where the surface stress was modeled by an elastic membrane having a 1 N/m tensile strength. The present paper quantities the surface stress by a density functional theory calculation. We found a value exceeding the nominal value used, which potentially affects the measurement accuracy.
Data-driven Structured Realization
Creators: name: Schulze, Philipp
name: Unger, Benjamin
name: Beattie, Christopher
name: Gugercin, Serkan
Publisher: name: arXiv
Year: 2016
Subjects: subject: Systems and Control (eess.SY)
subject: Numerical Analysis (math.NA)
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Mathematics
subject: 93B15, 30E05, 93C05

description: We present a framework for constructing structured realizations of linear dynamical systems having transfer functions of the form $C(\sum_{k=1}^K h_k(s)A_k)^{-1}B$ where $h_1,h_2,\ldots,h_K$ are prescribed functions that specify the surmised structure of the model. Our construction is data-driven in the sense that an interpolant is derived entirely from measurements of a transfer function. Our approach extends the Loewner realization framework to more general system structure that includes second-order (and higher) systems as well as systems with internal delays. Numerical examples demonstrate the advantages of this approach.
Constraints on the gamma-ray emission from Small Solar System Bodies with the Fermi Large Area Telescope data
Creators: name: De Gaetano, S.
name: Di Venere, L.
name: Gargano, F.
name: Loparco, F.
name: Lorusso, L.
name: Mazziotta, M. N.
name: Panzarini, G.
name: Pillera, R.
name: Serini, D.
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: All known Small Solar System Bodies have diameters between a few meters and a few thousands of kilometers. Based on the collisional evolution of Solar System Bodies, a larger number of asteroids with diameters down to $\sim 2$ m is thought to exist. As all Solar System Bodies, Small Bodies can be passive sources of high-energy gamma rays, produced by the interaction of energetic cosmic rays impinging on their surfaces. Since the majority of known asteroids are in orbits between Mars and Jupiter (in a region known as the Main Belt), we expect them to produce a diffuse emission close to the ecliptic plane. In this work we have studied the gamma-ray emission coming from the ecliptic using the data collected by the Large Area Telescope onboard the Fermi satellite. We have fit the results with simulations of the gamma-ray intensity at source level (calculated with the software FLUKA) to constrain the Small Solar System Bodies population. Finally, we have proposed a model describing the distribution of asteroid sizes and we have used the LAT data to constrain the gamma-ray emission expected from this model and, in turn, on the model itself.
description: 21 pages, 18 figures; accepted for publication in ApJ;
Thin Pyramidal Cones in Nematic Liquid Crystal
Creators: name: Seyednejad, Seyed Reza
name: Shoarinejad, Saeedeh
name: Mozaffari, Mohammad Reza
name: Joneghani, Faezeh Amini
Publisher: name: arXiv
Year: 2023
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: The present study investigates the arrangement of hollow pyramidal cone shells and their interactions with degenerate planar anchoring on the inner and outer surfaces of particles within the nematic host. The shell thickness is in order of the nematic coherence length. The numerical behavior of colloids is determined by minimizing the Landau-de Gennes free energy in the presence of the Fournier surface energy and using the finite element method. Colloidal pyramidal cones can orient parallel and perpendicular with the far director orientation. In the parallel alignment, we found the splay director distortion into the pyramid with two boojum defects at the inner and outer tips. The director shows bending distortion without defect patterns when the pyramid is aligned perpendicularly. They induce long-range dipolar interaction and can form nested structures in close contact.
Limitations and biases in the retrieval of the polar magnetic field I: the role of the magnetic filling factor in Milne-Eddington inversions of simulated Hinode/SP data
Creators: name: Centeno, Rebecca
name: Milić, Ivan
name: Rempel, Matthias
name: Nitta, Nariaki V.
name: Sun, Xudong
Publisher: name: arXiv
Year: 2023
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We study the extent to which Milne-Eddington inversions are able to retrieve and characterize the magnetic landscape of the solar poles from observations by the spectropolarimeter onboard Hinode. In particular, we evaluate whether a variable magnetic filling factor is an adequate modeling technique for retrieving the intrinsic magnetic properties from every pixel in the polar field of view. We first generate synthetic spectra emerging from a numerical simulation of a "plage" region at an inclined line of sight of 65$^{\circ}$, and degrade the data to emulate real observations. Then, we invert the synthetic spectra with two Milne-Eddington inversion codes that feature different treatments of the magnetic filling factor, and relate the retrieved magnetic quantities back to their original values in the simulation cube. We find that while the apparent retrieved magnetic properties map well the spatially-degraded simulation, the intrinsic magnetic quantities bear little relation to the magnetic field at the native resolution of the simulation. We discuss the systematic biases caused by line-of-sight foreshortening, spatial degradation, photon noise and modeling assumptions embedded in the inversion algorithm.
description: Accepted for publication in ApJ
Janus-Facedness of the Pion: Analytic Instantaneous Bethe-Salpeter Models
Creators: name: Lucha, Wolfgang
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: Inversion enables the construction of interaction potentials underlying - under fortunate circumstances even analytic - instantaneous Bethe-Salpeter descriptions of all lightest pseudoscalar mesons as quark-antiquark bound states of Goldstone-boson nature.
description: 5 pages, 3 figures, contributed to "QCD@Work 2016 - International Workshop on Quantum Chromodynamics: Theory and Experiment" (27 - 30 June 2016, Martina Franca, Italy)