cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
A local order metric for condensed phase environments
Creators: name: Martelli, Fausto
name: Ko, Hsin-Yu
name: Oguz, Erdal C.
name: Car, Roberto
Publisher: name: arXiv
Year: 2016
Subjects: subject: Computational Physics (physics.comp-ph)
subject: Materials Science (cond-mat.mtrl-sci)
subject: Atomic and Molecular Clusters (physics.atm-clus)
subject: Chemical Physics (physics.chem-ph)
subject: FOS: Physical sciences

description: We introduce a local order metric (LOM) that measures the degree of order in the neighborhood of an atomic or molecular site in a condensed medium. The LOM maximizes the overlap between the spatial distribution of sites belonging to that neighborhood and the corresponding distribution in a suitable reference system. The LOM takes a value tending to zero for completely disordered environments and tending to one for environments that match perfectly the reference. The site averaged LOM and its standard deviation define two scalar order parameters, $S$ and $δS$, that characterize with excellent resolution crystals, liquids, and amorphous materials. We show with molecular dynamics simulations that $S$, $δS$ and the LOM provide very insightful information in the study of structural transformations, such as those occurring when ice spontaneously nucleates from supercooled water or when a supercooled water sample becomes amorphous upon progressive cooling.
Entanglement of self interacting scalar fields in an expanding spacetime
Creators: name: Alexander, Helder
name: de Souza, Gustavo
name: Mansfield, Paul
name: da Paz, I. G.
name: Sampaio, Marcos
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We evaluate self-interaction effects on the quantum correlations of field modes of opposite momenta for scalar $λϕ^4$ theory in a two-dimensional asymptotically flat Robertson-Walker spacetime. Such correlations are encoded both in the von-Neumann entropy defined through the reduced density matrix in one of the modes and in the covariance expressed in terms of the expectation value of the number operators for each mode in the evolved state. The entanglement between field modes carries information about the underlying spacetime evolution.
description: 6 pages, 3 figuras
The mass determination of TOI-519 b: a close-in giant planet transiting a metal-rich mid-M dwarf
Creators: name: Kagetani, Taiki
name: Narita, Norio
name: Kimura, Tadahiro
name: Hirano, Teruyuki
name: Ikoma, Masahiro
name: Ishikawa, Hiroyuki Tako
name: Giacalone, Steven
name: Fukui, Akihiko
name: Kodama, Takanori
name: Gore, Rebecca
name: Schroeder, Ashley
name: Hori, Yasunori
name: Kawauchi, Kiyoe
name: Watanabe, Noriharu
name: Mori, Mayuko
name: Zou, Yujie
name: Ikuta, Kai
name: Krishnamurthy, Vigneshwaran
name: Zink, Jon
name: Hardegree-Ullman, Kevin
name: Harakawa, Hiroki
name: Kudo, Tomoyuki
name: Kotani, Takayuki
name: Kurokawa, Takashi
name: Kusakabe, Nobuhiko
name: Kuzuhara, Masayuki
name: de Leon, Jerome P.
name: Livingston, John H.
name: Nishikawa, Jun
name: Omiya, Masashi
name: Palle, Enric
name: Parviainen, Hannu
name: Serizawa, Takuma
name: Teng, Huan-Yu
name: Ueda, Akitoshi
name: Tamura, Motohide
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: We report the mass determination of TOI-519 b, a transiting substellar object around a mid-M dwarf. We carried out radial velocity measurements using Subaru / InfraRed Doppler (IRD), revealing that TOI-519 b is a planet with a mass of $0.463^{+0.082}_{-0.088}~M_{\rm Jup}$. We also find that the host star is metal rich ($\rm [Fe/H] = 0.27 \pm 0.09$ dex) and has the lowest effective temperature ($T_{\rm eff}=3322 \pm 49$ K) among all stars hosting known close-in giant planets based on the IRD spectra and mid-resolution infrared spectra obtained with NASA Infrared Telescope Facility / SpeX. The core mass of TOI-519 b inferred from a thermal evolution model ranges from $0$ to $\sim30~M_\oplus$, which can be explained by both the core accretion and disk instability models as the formation origins of this planet. However, TOI-519 is in line with the emerging trend that M dwarfs with close-in giant planets tend to have high metallicity, which may indicate that they formed in the core accretion model. The system is also consistent with the potential trend that close-in giant planets around M dwarfs tend to be less massive than those around FGK dwarfs.
description: 10 pages, 5 figures. Accepted for publication in PASJ
Estimating motion with principal component regression strategies
Creators: name: Carmo, Felipe P. do
name: Estrela, Vania Vieira
name: de Assis, Joaquim Teixeira
Publisher: name: arXiv
Year: 2016
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: In this paper, two simple principal component regression methods for estimating the optical flow between frames of video sequences according to a pel-recursive manner are introduced. These are easy alternatives to dealing with mixtures of motion vectors in addition to the lack of prior information on spatial-temporal statistics (although they are supposed to be normal in a local sense). The 2D motion vector estimation approaches take into consideration simple image properties and are used to harmonize regularized least square estimates. Their main advantage is that no knowledge of the noise distribution is necessary, although there is an underlying assumption of localized smoothness. Preliminary experiments indicate that this approach provides robust estimates of the optical flow.
description: 6 pages, 3 figures. arXiv admin note: substantial text overlap with arXiv:1610.02923
Computational study of III-V direct-gap semiconductors for thermoradiative cell applications
Creators: name: Hanna, Muhammad Y.
name: Majidi, Muhammad Aziz
name: Nugraha, Ahmad R. T.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We investigate the performance of thermoradiative (TR) cells using the III-V group of semiconductors, which include GaAs, GaSb, InAs, and InP, with the aim of determining their efficiency and finding the best TR cell materials among the III-V group. The TR cells generate electricity from thermal radiation, and their efficiency is influenced by several factors such as the bandgap, temperature difference, and absorption spectrum. To create a realistic model, we incorporate sub-bandgap and heat losses in our calculations and utilize density-functional theory to determine the energy gap and optical properties of each material. Our findings suggest that the effect of absorptivity on the material, especially when the sub-bandgap and heat losses are considered, can decrease the efficiency of TR cells. However, careful treatment of the absorptivity indicates that not all materials have the same trend of decrease in the TR cell efficiency when taking the loss mechanisms into account. We observe that GaSb exhibits the highest power density, while InP demonstrates the lowest one. Moreover, GaAs and InP exhibit relatively high efficiency without the sub-bandgap and heat losses, whereas InAs display lower efficiency without considering the losses, yet exhibit higher resistance to sub-bandgap and heat losses compared to the other materials, thus effectively becoming the best TR cell material in the III-V group of semiconductors.
Compact Coding Using Multi-Photon Tolerant Quantum Protocols for Quantum Communication
Creators: name: Hajj, Rasha El
name: Verma, Pramode
name: Chan, Kam Wai Clifford
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: This paper presents a new encryption scheme called Compact Coding that encodes information in time, phase, and intensity domains, simultaneously. While these approaches have previously been used one at a time, the proposed scheme brings to bear for the first time their strengths simultaneously leading to an increase in the secure information transfer rate. The proposed scheme is applicable to both optical fibers and free space optics, and can be considered as an alternative to polarization coding. This paper applies the proposed compact coding scheme to multi-photon tolerant quantum protocols in order to produce quantum-level security during information transfer. We present the structure of the proposed coding scheme in a multi-photon environment and address its operation.
description: 18 pages, 14 figures, 1 table
Introduction to Machine Protection
Creators: name: Schmidt, R.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Accelerator Physics (physics.acc-ph)
subject: FOS: Physical sciences

description: Protection of accelerator equipment is as old as accelerator technology and was for many years related to high-power equipment. Examples are the protection of powering equipment from overheating (magnets, power converters, high-current cables), of superconducting magnets from damage after a quench and of klystrons. The protection of equipment from beam accidents is more recent, although there was one paper that discussed beam-induced damage for the SLAC linac (Stanford Linear Accelerator Center) as early as in 1967. It is related to the increasing beam power of high-power proton accelerators, to the emission of synchrotron light by electron-positron accelerators and to the increase of energy stored in the beam. Designing a machine protection system requires an excellent understanding of accelerator physics and operation to anticipate possible failures that could lead to damage. Machine protection includes beam and equipment monitoring, a system to safely stop beam operation (e.g. dumping the beam or stopping the beam at low energy) and an interlock system providing the glue between these systems. The most recent accelerator, LHC, will operate with about 3 x 10$^{14}$ protons per beam, corresponding to an energy stored in each beam of 360 MJ. This energy can cause massive damage to accelerator equipment in case of uncontrolled beam loss, and a single accident damaging vital parts of the accelerator could interrupt operation for years. This lecture will provide an overview of the requirements for protection of accelerator equipment and introduces various protection systems. Examples are mainly from LHC and ESS.
description: 20 pages, contribution to the 2014 Joint International Accelerator School: Beam Loss and Accelerator Protection, Newport Beach, CA, USA , 5-14 Nov 2014. arXiv admin note: text overlap with arXiv:1601.05207
Quark-Meson Coupling model based upon the Nambu-Jona Lasinio model
Creators: name: Whittenbury, D. L.
name: Carrillo-Serrano, M. E.
name: Thomas, A. W.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: The NJL model for the octet baryons, using proper time regularization to simulate some of the features of confinement, is solved self-consistently in nuclear matter. This provides an alternative framework to the MIT bag model which has been used in the quark-meson coupling model. After fitting the parameters of the model to the saturation properties of symmetric nuclear matter the model is used to explore the equation of state of pure neutron matter as well as nuclear matter at densities relevant to heavy ion collisions. With a view to future studies of high mass neutron stars, the binding of hyperons is also explored.
description: 7 pages and 4 figures
Orbital dynamics of a solar sail accelerated by thermal desorption of coatings
Creators: name: Ancona, Elena
name: Kezerashvili, Roman Ya.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Space Physics (physics.space-ph)
subject: FOS: Physical sciences

description: In this study we considered a solar sail coated with materials that undergo thermal desorption at a specific temperature, as a result of heating by solar radiation at a particular heliocentric distance. Three different scenarios, that only differ in the way the sail approaches the Sun, were analyzed and compared. In every case once the perihelion is reached, the sail coat undergoes thermal desorption. When the desorption process ends, the sail then escapes the Solar System having the conventional acceleration due to solar radiation pressure. Thermal desorption here comes as an additional source of solar sail acceleration beside traditional propulsion systems for extrasolar space exploration. The compared scenarios are the following: i. Hohmann transfer plus thermal desorption. In this scenario the sail would be carried as a payload to the perihelion with a conventional propulsion system by an Hohmann transfer from Earth's orbit to an orbit very close to the Sun (almost at 0.1 AU) and then be deployed there. ii. Elliptical transfer plus Slingshot plus thermal desorption. In this scenario the transfer occurs from Earth's orbit to Jupiter's orbit. A Jupiter's fly-by leads to the orbit close to the Sun, where the sail is deployed. iii. Two stage acceleration of the solar sail through thermal desorption. The proposed sail has two coats of the materials that undergo thermal desorption at different temperatures depending on the heliocentric distance. The first desorption occurs at the Earth orbit and provides the thrust needed to propel the solar sail toward the Sun. The second desorption is equivalent to that of the other scenarios.
description: 12 pages, 7 figures
The Io, Europa and Ganymede auroral footprints at Jupiter in the ultraviolet: positions and equatorial lead angles
Creators: name: Hue, Vincent
name: Gladstone, Randy
name: Louis, Corentin K.
name: Greathouse, Thomas K.
name: Bonfond, Bertrand
name: Szalay, Jamey R.
name: Moirano, Alessandro
name: Giles, Rohini S.
name: Kammer, Joshua A.
name: Imai, Masafumi
name: Mura, Alessandro
name: Versteeg, Maarten H.
name: Clark, George
name: Gérard, Jean-Claude
name: Grodent, Denis C.
name: Rabia, Jonas
name: Sulaiman, Ali H.
name: Bolton, Scott J.
name: Connerney, John E. P.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: Jupiter's satellite auroral footprints are a consequence of the interaction between the Jovian magnetic field with co-rotating iogenic plasma and the Galilean moons. The disturbances created near the moons propagate as Alfvén waves along the magnetic field lines. The position of the moons is therefore "Alfvénically" connected to their respective auroral footprint. The angular separation from the instantaneous magnetic footprint can be estimated by the so-called lead angle. That lead angle varies periodically as a function of orbital longitude, since the time for the Alfvén waves to reach the Jovian ionosphere varies accordingly. Using spectral images of the Main Alfvén Wing auroral spots collected by Juno-UVS during the first forty-three orbits, this work provides the first empirical model of the Io, Europa and Ganymede equatorial lead angles for the northern and southern hemispheres. Alfvén travel times between the three innermost Galilean moons to Jupiter's northern and southern hemispheres are estimated from the lead angle measurements. We also demonstrate the accuracy of the mapping from the Juno magnetic field reference model (JRM33) at the completion of the prime mission for M-shells extending to at least 15RJ . Finally, we shows how the added knowledge of the lead angle can improve the interpretation of the moon-induced decametric emissions.
description: 20 pages, 8 figures, Accepted for publication in Journal of Geophysical Research: Space Physics on 20 April 2023
The asteroseismic surface effect from a grid of 3D convection simulations. I. Frequency shifts from convective expansion of stellar atmospheres
Creators: name: Trampedach, Regner
name: Aarslev, Magnus J.
name: Houdek, Günter
name: Collet, Remo
name: Christensen-Dalsgaard, Jørgen
name: Stein, Robert F.
name: Asplund, Martin
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We analyse the effect on adiabatic stellar oscillation frequencies of replacing the near-surface layers in 1D stellar structure models with averaged 3D stellar surface convection simulations. The main difference is an expansion of the atmosphere by 3D convection, expected to explain a major part of the asteroseismic surface effect; a systematic overestimation of p-mode frequencies due to inadequate surface physics. We employ pairs of 1D stellar envelope models and 3D simulations from a previous calibration of the mixing-length parameter, alpha. That calibration constitutes the hitherto most consistent matching of 1D models to 3D simulations, ensuring that their differences are not spurious, but entirely due to the 3D nature of convection. The resulting frequency shift is identified as the structural part of the surface effect. The important, typically non-adiabatic, modal components of the surface effect are not included in the present analysis, but relegated to future papers. Evaluating the structural surface effect at the frequency of maximum mode amplitude, $ν_{\rm max}$, we find shifts from $δν$=-0.8 microHz for giants at $\log g$=2.2 to -35 microHz for a ($T_{\rm eff}=6901$ K, $\log g$=4.29) dwarf. The fractional effect $δν(ν_{\rm max})/ν_{\rm max}$, ranges from -0.1% for a cool dwarf (4185 K, 4.74) to -6% for a warm giant (4962 K, 2.20).
description: 5 pages, 7 figures, accepted for publication in MNRAS
Self-inversive polynomials, curves, and codes
Creators: name: Joyner, David
name: Shaska, Tony
Publisher: name: arXiv
Year: 2016
Subjects: subject: Complex Variables (math.CV)
subject: FOS: Mathematics

description: We study connections between self-inversive and self-reciprocal polynomials, reduction theory of binary forms, minimal models of curves, and formally self-dual codes. We prove that if $\mathcal X$ is a superelliptic curve defined over $\mathbb C$ and its reduced automorphism group is nontrivial or not isomorphic to a cyclic group, then we can write its equation as $y^n = f(x)$ or $y^n = x f(x)$, where $f(x)$ is a self-inversive or self-reciprocal polynomial. Moreover, we state a conjecture on the coefficients of the zeta polynomial of extremal formally self-dual codes.
The Infrared Imaging Spectrograph (IRIS) for TMT: optical design of IRIS imager with "Co-axis double TMA"
Creators: name: Tsuzuki, Toshihiro
name: Suzuki, Ryuji
name: Harakawa, Hiroki
name: Ikenoue, Bungo
name: Larkin, James
name: Moore, Anna
name: Obuchi, Yoshiyuki
name: Phillips, Andrew C
name: Saito, Sakae
name: Uraguchi, Fumihiro
name: Wincentsen, James
name: Wright, Shelley
name: Hayano, Yutaka
Publisher: name: arXiv
Year: 2016
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: IRIS (InfraRed Imaging Spectrograph) is one of the first-generation instruments for the Thirty Meter Telescope (TMT). IRIS is composed of a combination of near-infrared (0.84--2.4 $μ$m) diffraction limited imager and integral field spectrograph. To achieve near-diffraction limited resolutions in the near-infrared wavelength region, IRIS uses the advanced adaptive optics system NFIRAOS (Narrow Field Infrared Adaptive Optics System) and integrated on-instrument wavefront sensors (OIWFS). However, IRIS itself has challenging specifications. First, the overall system wavefront error should be less than 40 nm in Y, z, J, and H-band and 42 nm in K-band over a 34.0 $\times$ 34.0 arcsecond field of view. Second, the throughput of the imager components should be more than 42 percent. To achieve the extremely low wavefront error and high throughput, all reflective design has been newly proposed. We have adopted a new design policy called "Co-Axis double-TMA", which cancels the asymmetric aberrations generated by "collimator/TMA" and "camera/TMA" efficiently. The latest imager design meets all specifications, and, in particular, the wavefront error is less than 17.3 nm and throughput is more than 50.8 percent. However, to meet the specification of wavefront error and throughput as built performance, the IRIS imager requires both mirrors with low surface irregularity after high-reflection coating in cryogenic and high-level Assembly Integration and Verification (AIV). To deal with these technical challenges, we have done the tolerance analysis and found that total pass rate is almost 99 percent in the case of gauss distribution and more than 90 percent in the case of parabolic distribution using four compensators. We also have made an AIV plan and feasibility check of the optical elements. In this paper, we will present the details of this optical system.
description: 18 pages, 14 figures, Proceeding 9908-386 of the SPIE Astronomical Telescopes + Instrumentation 2016
Spectral disentangling with Spectangular
Creators: name: Sablowski, Daniel P.
name: Weber, Michael
Publisher: name: arXiv
Year: 2016
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: The paper introduces the software Spectangular for spectral disentangling via singular value decomposition with global optimisation of the orbital parameters of the stellar system or radial velocities of the individual observations. We will describe the procedure and the different options implemented in our program. Furthermore, we will demonstrate the performance and the applicability using tests on artificial data. Additionally, we use high-resolution spectra of Capella to demonstrate the performance of our code on real-world data. The novelty of this package is the implemented global optimisation algorithm and the graphical user interface (GUI) for ease of use. We have implemented the code to tackle SB1 and SB2 systems with the option of also dealing with telluric (static) lines.
$β$-decay spectroscopy of neutron-deficient nuclei
Creators: name: Orrigo, S. E. A.
name: Rubio, B.
name: Gelletly, W.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences

description: A systematic study of the $β$-decay of neutron-deficient nuclei has been carried out and has provided spectroscopic information of importance for both nuclear structure and nuclear astrophysics. Following an overview of the most relevant achievements, we focus on the latest results on the $β$ decay of $^{60}$Ge and $^{62}$Ge. We also summarise our results on the mass excesses in comparison with systematics and a recent measurement. Finally, we present updated half-life trends for $T_z=$ -1/2, -1 and -2 neutron-deficient nuclides.
description: 5 pages, 3 figures. Conference Nuclear Physics in Astrophysics-X (NPA-X 2022)
D5.1 - WP5 Final Report
Creators: name: Jensterle, Miha
name: Montella, Luisa
Publisher: name: Zenodo
Year: 2023
Subjects: Scalability
Industry
Deployment
Replicability
Waste Heat/Cold Recovery

description: Work Package 5 of EMB3Rs project – Platform Scalability and Deployment used a combination of the
 insights from WP4 Sector-Specific Platform Demonstration, desktop research,
 lessons learned from previous work in the RHC (residual heat and cold) domain and
 interviews with experts and practitioners to address the following tasks:
  T 5.1 Scalability and Replicability of Proposed Solutions
  T 5.2 Industry Wide Solutions and Multi-Sectorial Applications
  T 5.3 Path to Finance and Wide-Scale Deployment of Waste Heat/Cold Recovery
 Task 5.1 first analyses the replicability of the solutions by comparing the context and
 scope of the problems solved in the seven Case Studies to those of the overall, reallife
 industrial environment that the EMB3Rs platform can be expected to tackle. Next,
 the potential to scale the platform is assessed based on two main factors – limits to
 its functionality and data requirements.
 The assessment of the replicability of solutions was carried out in a systematic way
 for each parameter defining the scope of solutions, sources, sinks and grid that was
 identified as relevant for the replicability. An overview of the findings is provided in
 Table 1 below. It shows that to a large extent, the platform has covered in the Case
 Studies the relevant range of the problems that it can be expected to encounter when
 applied to real-life problems outside of the project, and be expected to replicate valid
 solutions. The one exception to this is the number of sinks, where the range covered
 by the platform were two orders of magnitude lower than the biggest district heating
 networks in existence currently. However, the platform is not intended to model
 problems of this scale, as this is the domain of dedicated teams of RHC experts with
 professional, commercial tools. For all other central parameters of the RHC use, the
 solutions provided by the platform demonstrate that it can cover the entire range of
 potential problems which it will be applied to.
Amann-Zehnder type results for p-Laplace problems
Creators: name: Cingolani, Silvia
name: Degiovanni, Marco
name: Vannella, Giuseppina
Publisher: name: arXiv
Year: 2016
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: 35J62, 35J92, 58E05

description: The existence of a nontrivial solution is proved for a class of quasilinear elliptic equations involving, as principal part, either the p-Laplace operator or the operator related to the p-area functional, and a nonlinearity with p-linear growth at infinity. To this aim, Morse theory techniques are combined with critical groups estimates.
Nonlinear Stabilization of High-Energy and Ultrashort Pulses in Passively Modelocked Lasers with Fast Saturable Absorption
Creators: name: Wang, Shaokang
name: Marks, Brian S.
name: Menyuk, Curtis R.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: The two most commonly used models for passively modelocked lasers with fast saturable absorbers are the Haus modelocking equation (HME) and the cubic-quintic modelocking equation (CQME). The HME corresponds to a special limit of the CQME in which only a cubic nonlinearity in the fast saturable absorber is kept in the model. Here, we use singular perturbation theory to demonstrate that the CQME has a stable high-energy solution for an arbitrarily small but non-zero quintic contribution to the fast saturable absorber. As a consequence, we find that the CQME predicts the existence of stable modelocked pulses when the cubic nonlinearity is orders of magnitude larger than the value at which the HME predicts that modelocked pulses become unstable. This intrinsically larger stability range is consistent with experiments. Our results suggest a possible path to obtain high-energy and ultrashort pulses by fine tuning the higher-order nonlinear terms in the fast saturable absorber.
description: 8 pages, 6 figures, submitted to PRA
Vacuum polarization alters the spectra of accreting X-ray pulsars
Creators: name: Sokolova-Lapa, E.
name: Stierhof, J.
name: Dauser, T.
name: Wilms, J.
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: It is a common belief that for magnetic fields typical for accreting neutron stars in High-Mass X-ray Binaries vacuum polarization only affects the propagation of polarized emission in the neutron star magnetosphere. We show that vacuum resonances can significantly alter the emission from the poles of accreting neutron stars. The effect is similar to vacuum polarization in the atmospheres of isolated neutron stars and can result in suppression of the continuum and the cyclotron lines. It is enhanced by magnetic Comptonization in the hot plasma and proximity to the electron cyclotron resonance. We present several models to illustrate the vacuum polarization effect for various optically thick media and discuss how the choice of polarization modes affects the properties of the emergent radiation by simulating polarized energy- and angle-dependent radiative transfer. Polarization effects, including vacuum polarization, crucially alter the emission properties. Together with strongly angle- and energy- dependent magnetic Comptonization, they result in a complex spectral shape, which can be described by dips and humps on top of a power-law-like continuum with high-energy cutoff. These effects provide a possible explanation for the common necessity of additional broad Gaussian components and two-component Comptonization models that are used to describe spectra of accreting X-ray pulsars. We also demonstrate the character of depolarization introduced by the radiation field's propagation inside the inhomogeneous emission region.
description: 4 pages, 6 figures, accepted for publication in A&A Letters
Accretion at the periastron passage of Eta Carinae
Creators: name: Kashi, Amit
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We present high resolution numerical simulations of the colliding wind system $η$ Carinae, showing accretion onto the secondary star close to periastron passage. Our hydrodynamical simulations include self gravity and radiative cooling. The smooth stellar winds collide and develop instabilities, mainly the non-linear thin shell instability, and form filaments and clumps. We find that a few days before periastron passage the dense filaments and clumps flow towards the secondary as a result of its gravitational attraction, and reach the zone where we inject the secondary wind. We run our simulations for the conventional stellar masses, $M_1=120 ~\rm{M_\odot}$ and $M_2=30 ~\rm{M_\odot}$, and for a high mass model, $M_1=170 ~\rm{M_\odot}$ and $M_2=80 ~\rm{M_\odot}$, that was proposed to better fit the history of giant eruptions. As expected, the simulations results show that the accretion processes is more pronounced for a more massive secondary star.
description: Accepted for publication in MNRAS. See MNRAS version for color figures
Recent galaxy mergers and residual star formation of red sequence galaxies in galaxy clusters
Creators: name: Sheen, Yun-Kyeong
name: Yi, Sukyoung K.
name: Ree, Chang H.
name: Jaffé, Yara
name: Demarco, Ricardo
name: Treister, Ezequiel
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: This study explored the GALEX ultraviolet (UV) properties of optical red sequence galaxies in 4 rich Abell clusters at z \leq 0.1. In particular, we tried to find a hint of merger-induced recent star formation (RSF) in red sequence galaxies. Using the NUV - r' colors of the galaxies, RSF fractions were derived based on various criteria for post-merger galaxies and normal galaxies. Following k-correction, about 36% of the post-merger galaxies were classified as RSF galaxies with a conservative criterion (NUV - r' \leq 5), and that number was doubled (~ 72%) when using a generous criterion (NUV - r' \leq 5.4). The trend was the same when we restricted the sample to galaxies within 0.5xR_{200}. Post-merger galaxies with strong UV emission showed more violent, asymmetric features in the deep optical images. The RSF fractions did not show any trend along the clustocentric distance within R_{200}. We performed a Dressler-Shectman test to check whether the RSF galaxies had any correlation with the sub-structures in the galaxy clusters. Within R_{200} of each cluster, the RSF galaxies did not appear to be preferentially related to the clusters' sub-structures. Our results suggested that only 30% of RSF red sequence galaxies show morphological hints of recent galaxy mergers. This implies that internal processes (e.g., stellar mass-loss or hot gas cooling) for the supply of cold gas to early-type galaxies may play a significant role in the residual star formation of early-type galaxies at a recent epoch.
description: Accepted for publication in ApJ
Signatures of phonon and defect-assisted tunneling in planar metal-hexagonal boron nitride-graphene junctions
Creators: name: Chandni, U.
name: Watanabe, K.
name: Taniguchi, T.
name: Eisenstein, J. P.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Electron tunneling spectroscopy measurements on van der Waals heterostructures consisting of metal and graphene (or graphite) electrodes separated by atomically thin hexagonal boron nitride tunnel barriers are reported. The tunneling conductance dI/dV at low voltages is relatively weak, with a strong enhancement reproducibly observed to occur at around |V| ~ 50 mV. While the weak tunneling at low energies is attributed to the absence of substantial overlap, in momentum space, of the metal and graphene Fermi surfaces, the enhancement at higher energies signals the onset of inelastic processes in which phonons in the heterostructure provide the momentum necessary to link the Fermi surfaces. Pronounced peaks in the second derivative of the tunnel current, are observed at voltages where known phonon modes in the tunnel junction have a high density of states. In addition, features in the tunneling conductance attributed to single electron charging of nanometer-scale defects in the boron nitride are also observed in these devices. The small electronic density of states of graphene allows the charging spectra of these defect states to be electrostatically tuned, leading to Coulomb diamonds in the tunneling conductance.
The Infrared Imaging Spectrograph (IRIS) for TMT: Prototyping of cryogenic compatible stage for the Imager
Creators: name: Uraguchi, Fumihiro
name: Obuchi, Yoshiyuki
name: Ikenoue, Bungo
name: Saito, Sakae
name: Suzuki, Ryuji
name: Hayano, Yutaka
Publisher: name: arXiv
Year: 2016
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: The IRIS Imager requires opt-mechanical stages which are operable under vacuum and cryogenic environment. Also the stage for the IRIS Imager is required to survive for 10 years without maintenance. To achieve these requirements, we decided prototyping of a two axis stage with 80 mm clear aperture. The prototype was designed as a double-deck stage, upper rotary stage and lower linear stage. Most of components are selected to take advantage of heritage from existing astronomical instruments. In contrast, mechanical components with lubricants such as bearings, linear motion guides and ball screws were modified to survive cryogenic environment. The performance proving test was carried out to evaluate errors such as wobbling, rotary and linear positioning error. We achieved 0.002 $\rm deg_{rms}$ wobbling, 0.08 $\rm deg_{0-p}$ rotational positioning error and 0.07 $\rm mm_{0-p}$ translational positioning error. Also durability test under anticipated load condition has been conducted. In this article, we report the detail of mechanical design, fabrication, performance and durability of the prototype.
description: 10 pages, 9 figures, Proceeding 9908-380 of the SPIE Astronomical Telescopes + Instrumentation 2016
Fast Cosine Transform to increase speed-up and efficiency of Karhunen-Loeve Transform for lossy image compression
Creators: name: Mastriani, Mario
name: Gambini, Juliana
Publisher: name: arXiv
Year: 2016
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: In this work, we present a comparison between two techniques of image compression. In the first case, the image is divided in blocks which are collected according to zig-zag scan. In the second one, we apply the Fast Cosine Transform to the image, and then the transformed image is divided in blocks which are collected according to zig-zag scan too. Later, in both cases, the Karhunen-Loeve transform is applied to mentioned blocks. On the other hand, we present three new metrics based on eigenvalues for a better comparative evaluation of the techniques. Simulations show that the combined version is the best, with minor Mean Absolute Error (MAE) and Mean Squared Error (MSE), higher Peak Signal to Noise Ratio (PSNR) and better image quality. Finally, new technique was far superior to JPEG and JPEG2000.
description: 10 pages, 20 figures, 2 tables
A Heuristic Method of Generating Diameter 3 Graphs for Order/Degree Problem
Creators: name: Kitasuka, Teruaki
name: Iida, Masahiro
Publisher: name: arXiv
Year: 2016
Subjects: subject: Data Structures and Algorithms (cs.DS)
subject: FOS: Computer and information sciences

description: We propose a heuristic method that generates a graph for order/degree problem. Target graphs of our heuristics have large order (> 4000) and diameter 3. We describe the ob- servation of smaller graphs and basic structure of our heuristics. We also explain an evaluation function of each edge for efficient 2-opt local search. Using them, we found the best solutions for several graphs.
description: Proceedings of 10th IEEE/ACM International Symposium on Networks-on-Chip, Nara, Japan, Aug. 2016
Revised Properties and Dynamical History for the HD 17156 System
Creators: name: Kane, Stephen R.
name: Hill, Michelle L.
name: Dalba, Paul A.
name: Fetherolf, Tara
name: Henry, Gregory W.
name: Fajardo-Acosta, Sergio B.
name: Gnilka, Crystal L.
name: Howard, Andrew W.
name: Howell, Steve B.
name: Isaacson, Howard
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: From the thousands of known exoplanets, those that transit bright host stars provide the greatest accessibility toward detailed system characterization. The first known such planets were generally discovered using the radial velocity technique, then later found to transit. HD 17156b is particularly notable among these initial discoveries because it diverged from the typical hot Jupiter population, occupying a 21.2 day eccentric ($e = 0.68$) orbit, offering preliminary insights into the evolution of planets in extreme orbits. Here we present new data for this system, including ground and space-based photometry, radial velocities, and speckle imaging, that further constrain the system properties and stellar/planetary multiplicity. These data include photometry from the Transiting Exoplanet Survey Satellite (TESS) that cover five transits of the known planet. We show that the system does not harbor any additional giant planets interior to 10 AU. The lack of stellar companions and the age of the system indicate that the eccentricity of the known planet may have resulted from a previous planet-planet scattering event. We provide the results from dynamical simulations that suggest possible properties of an additional planet that culminated in ejection from the system, leaving a legacy of the observed high eccentricity for HD 17156b.
description: 15 pages, 7 figures, accepted for publication in the Astronomical Journal
Unified Band Theoretic Description of Electronic and Magnetic Properties of Vanadium Dioxide Phases
Creators: name: Xu, Sheng
name: Shen, Xiao
name: Hallman, Kent A.
name: Haglund, Richard F.
name: Pantelides, Sokrates T.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The debate about whether the insulating phases of vanadium dioxide (VO2) can be described by band theory or must be described by a theory of strong electron correlations remains unresolved even after decades of research. Energy-band calculations using hybrid exchange functionals or including self-energy corrections account for the insulating or metallic nature of different phases, but have not yet successfully accounted for the observed magnetic orderings. Strongly-correlated theories have had limited quantitative success. Here we report that, by using hard pseudopotentials and an optimized hybrid exchange functional, the energy gaps and magnetic orderings of both monoclinic VO2 phases and the metallic nature of the high-temperature rutile phase are consistent with available experimental data, obviating an explicit role for strong correlations. We also report a potential candidate for the newly-found metallic monoclinic phase and present a detailed magnetic structure of the M2 monoclinic phase.
Gödel-type universes in energy-momentum-squared gravity
Creators: name: Canuto, Á. J. C.
name: Santos, A. F.
Publisher: name: arXiv
Year: 2023
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: In this paper, a modification of general relativity is considered. It consists of generalizing the Lagrangian of matter in a non-linear way, that is, replacing the curvature scalar $R$ by a function $f(R,T_{μν} T^{μν} )$, where $T_{μν}$ is the energy-momentum tensor. The main objective is to investigate the issue of causality in this gravitational model. To study the causality and/or its violation the Gödel-type solutions are used. For such development, different matter contents are chosen. A critical radius, beyond which causality is violated, is calculated. It is shown that both causal and non-causal solutions are allowed.
description: 15 pages, accepted for publication in EPJC
MeerKAT discovery of 13 new pulsars in Omega Centauri
Creators: name: Chen, W.
name: Freire, P.C.C.
name: Ridolfi, A.
name: Barr, E.D.
name: Stappers, B.
name: Kramer, M.
name: Possenti, A.
name: Ransom, S.M.
name: Levin, L.
name: Breton, R.P.
name: Burgay, M.
name: Camilo, F.
name: Buchner, S.
name: Champion, D.J.
name: Abbate, F.
name: Venkatraman Krishnan, V.
name: Padmanabh, P.V.
name: Gautam, T.
name: Vleeschower, L.
name: Geyer, M.
name: Grießmeier, J.-M.
name: Men, Y.P.
name: Balakrishnan, V.
name: Bezuidenhout, M.C.
Publisher: name: Oxford : Oxford Univ. Press
Year: 2023
Subjects: subject: Binary
subject: Globular cluster
subject: Pulsar
subject: Dewey Decimal Classification::500 | Naturwissenschaften::520 | Astronomie, Kartographie

description: The most massive globular cluster in our Galaxy, Omega Centauri, is an interesting target for pulsar searches, because of its multiple stellar populations and the intriguing possibility that it was once the nucleus of a galaxy that was absorbed into the Milky Way. The recent discoveries of pulsars in this globular cluster and their association with known X-ray sources was a hint that, given the large number of known X-ray sources, there is a much larger undiscovered pulsar population. We used the superior sensitivity of the MeerKAT radio telescope to search for pulsars in Omega Centauri. In this paper, we present some of the first results of this survey, including the discovery of 13 new pulsars; the total number of known pulsars in this cluster currently stands at 18. At least half of them are in binary systems and preliminary orbital constraints suggest that most of the binaries have light companions. We also discuss the ratio between isolated and binaries pulsars, and how they were formed in this cluster.
Influence of thermomechanical treatment on the shape memory effect and pseudoelasticity behavior of conventional and additive manufactured Fe–Mn–Si–Cr–Ni-(V,C) shape memory alloys
Creators: name: Mohri, Maryam
name: Ferretto, Irene
name: Khodaverdi, Hesamodin
name: Leinenbach, Christian
name: Ghafoori, Elyas
Publisher: name: Rio de Janeiro : Elsevier
Year: 2023
Subjects: subject: 4D printing
subject: Fe-based shape memory alloy
subject: Metal AM
subject: Pseudoelasticity
subject: Shape memory effect
subject: Training
subject: Dewey Decimal Classification::600 | Technik::670 | Industrielle und handwerkliche Fertigung

description: This study evaluated the influence of heat treatment and thermomechanical training on the microstructural evolution and mechanical characteristics of conventional and additive-manufactured FeMnSi-based shape memory alloys. The conventional samples were produced by casting and rolling. The additive-manufactured samples were manufactured using the laser powder bed fusion (L-PBF) technique. Both specimens were subjected to the same heat treatment and thermomechanical training. The heat treatment involved solution annealing at 1050 °C for 2 h and aging at 750 °C for 6 h, and the thermomechanical training concluded with a 4% elongation at ambient temperature followed by annealing at 250 °C for 15 min. This training cycle was repeated four times for each sample after heat treatment. The heat treatment improved the pseudoelasticity and shape memory effect of the samples. Although training further enhanced the pseudoelasticity, it also reduced the shape memory effect. Thermomechanical training led to the formation of a large number of stacking faults, which facilitated the inverse phase transformation of martensite (ε) to austenite (γ) during unloading, resulting in improved pseudoelasticity. The heat-treated additive-manufactured samples showed the highest total recovery strain owing to the pseudoelasticity and shape memory effect. This characteristic could be due to the smaller grain size and higher volume fraction of precipitates. The precipitates and grain refinement improved the conditions for partial dislocation motion by increasing the back stresses on the martensite tip.
Improvement of thermo-mechanical position stability of the beam position monitor in PLS-II
Creators: name: Ha, Taekyun
name: Hong, Mansu
name: Kwon, Hyuckchae
name: Han, Hongsik
name: Park, Chongdo
Publisher: name: arXiv
Year: 2016
Subjects: subject: Instrumentation and Detectors (physics.ins-det)
subject: Accelerator Physics (physics.acc-ph)
subject: FOS: Physical sciences

description: In the storage ring of PLS-II, we reduced mechanical displacement of electron beam position monitors (e-BPMs) that is caused by heating during e-beam storage. The orbit feedback system intends that the electron beam pass through the center of the BPM, so to provide stable photon beam into beamlines the BPM pickup itself must be stable to sub-micrometer precision. Thermal deformation of the vacuum chambers on which the BPM pickups are mounted is inevitable when the electron beam current is changed by unintended beam abort. We reduced this deformation by improving the vacuum chamber support and by enhancing the water cooling. We report the thermo-mechanical analysis and displacement measurements of BPM pickups after the improvements.
description: 12 pages, 5 figures, conference