cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Explaining Mercury via a single giant impact is highly unlikely
Creators: name: Franco, P.
name: Izidoro, A.
name: Winter, O. C.
name: Torres, K. S.
name: Amarante, A.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: The classical scenario of terrestrial planet formation is characterized by a phase of giant impacts among Moon-to-Mars mass planetary embryos. While the classic model and its adaptations have produced adequate analogs of the outer three terrestrial planets, Mercury's origin remains elusive. Mercury's high-core mass fraction compared to the Earth's is particularly outstanding. Among collisional hypotheses, this feature has been long interpreted as the outcome of an energetic giant impact among two massive protoplanets. Here, we revisit the classical scenario of terrestrial planet formation with focus on the outcome of giant impacts. We have performed a large number of N-body simulations considering different initial distributions of planetary embryos and planetesimals. Our simulations tested the effects of different giant planet configurations, from virtually circular to very eccentric configurations. We compare the giant impacts produced in our simulations with those that are more likely to account for the formation of Mercury and the Moon according to smoothed hydrodynamic simulations. Impact events that could lead to Moon's formation are observed in all our simulations with up to ~20% of all giant impacts, consistent with the range of the expected Moon-forming event conditions. On the other hand, Mercury-forming events via a single giant impact are extremely rare, accounting for less than ~1% of all giant impacts. Our results suggest that producing Mercury as a remnant of a single giant impact that strips out the mantle of a differentiated planetary object with Earth-like iron-silicate ratio is challenging and alternative scenarios may be required (e.g. multiple collisions).
description: Accepted for publications in MNRAS
Limitations on the recovery of the true AGN variability parameters using Damped Random Walk modeling
Creators: name: Kozłowski, Szymon
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Context: The damped random walk (DRW) stochastic process is nowadays frequently used to model aperiodic light curves of AGNs. A number of correlations between the DRW model parameters, the signal decorrelation timescale and amplitude, and the physical AGN parameters such as the black hole mass or luminosity have been reported. Aims: We are interested in whether it is plausible to correctly measure the DRW parameters from a typical ground-based survey, in particular how accurate the recovered DRW parameters are compared to the input ones. Methods: By means of Monte Carlo simulations of AGN light curves, we study the impact of the light curve length, the source magnitude, cadence, and additional light on the DRW model parameters. Results: The most significant finding is that currently existing surveys are going to return unconstrained DRW decorrelation timescales, because typical rest-frame data do not probe long enough timescales or the white noise part of PSD for DRW. The experiment length must be at least ten times longer than the true DRW timescale, being presumably in the vicinity of one year, meaning a minimum 10-years-long AGN light curves (rest-frame). The DRW timescales for sufficiently long light curves are typically weakly biased, and the exact bias depends on the fitting method and used priors. The DRW amplitude is mostly affected by the photometric noise (so the source magnitude or the signal-to-noise ratio), cadence, and the AGN host light. Conclusions: Because the DRW parameters appear to be incorrectly determined from typically existing data, the reported correlations of the DRW variability and physical AGN parameters from other works seem unlikely to be correct. In particular, the anti-correlation of the DRW timescale with redshift is a manifestation of the survey length being too short. Application of DRW to modeling typical AGN optical light curves is questioned.
description: 8 pages, 5 figures; accepted for publication in Astronomy&Astrophysics
Mapping the self-generated magnetic fields due to thermal Weibel instability
Creators: name: Zhang, Chaojie
name: Wu, Yipeng
name: Sinclair, Mitchell
name: Farrell, Audrey
name: Marsh, Kenneth A.
name: Petrushina, Irina
name: Vafaei-Najafabadi, Navid
name: Gawked, Apurva
name: Kupfer, Rotem
name: Kusche, Karl
name: Fedurin, Mikhail
name: Pogorelsky, Igor
name: Polyanskiy, Mikhail
name: Huang, Chen-Kang
name: Hua, Jianfei
name: Lu, Wei
name: Mori, Warren B.
name: Joshi, Chan
Publisher: name: arXiv
Year: 2022
Subjects: subject: Plasma Physics (physics.plasm-ph)
subject: FOS: Physical sciences

description: Weibel-type instability can self-generate and amplify magnetic fields in both space and laboratory plasmas with temperature anisotropy. The electron Weibel instability has generally proven more challenging to measure than its ion counterpart owing to the much smaller inertia of electrons, resulting in a faster growth rate and smaller characteristic wavelength. Here, we have probed the evolution of the two-dimensional distribution of the magnetic field components and the current density due to electron Weibel instability, in $\rm CO_2$-ionized hydrogen gas (plasma) with picosecond resolution using a relativistic electron beam. We find that the wavenumber spectra of the magnetic fields are initially broad but eventually shrink to a narrow spectrum representing the dominant quasi-single mode. The measured $k$-resolved growth rates of the instability validate kinetic theory. Concurrently, self-organization of microscopic plasma currents is observed to amplify the current modulation magnitude that converts up to $\sim 1\%$ of the plasma thermal energy into magnetic energy.
description: 24 pages, 4 figures
Determination of the proton-to-helium ratio in cosmic rays at ultra-high energies from the tail of the $X_{\rm max}$ distribution
Creators: name: Yushkov, Alexey
name: Risse, Markus
name: Werner, Marek
name: Krieg, Julius
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We present a method to determine the proton-to-helium ratio in cosmic rays at ultra-high energies. It makes use of the exponential slope, $Λ$, of the tail of the $X_{\rm max}$ distribution measured by an air shower experiment. The method is quite robust with respect to uncertainties from modeling hadronic interactions and to systematic errors on $X_{\rm max}$ and energy, and to the possible presence of primary nuclei heavier than helium. Obtaining the proton-to-helium ratio with air shower experiments would be a remarkable achievement. To quantify the applicability of a particular mass-sensitive variable for mass composition analysis despite hadronic uncertainties we introduce as a metric the `analysis indicator' and find an improved performance of the $Λ$ method compared to other variables currently used in the literature. The fraction of events in the tail of the $X_{\rm max}$ distribution can provide additional information on the presence of nuclei heavier than helium in the primary beam.
description: Added journal reference
EUROSHIP Working Paper No. 31: The politics of minimum income schemes reforms in seven European countries.
Creators: name: Panaro, Angelo Vito
name: Shahini, Viola
name: Jessoula, Matteo
Publisher: name: figshare
Year: 2023
Subjects: Sociology not elsewhere classified

description: This is a publication in a project`s working paper series.
A universal model for the evolution of tidally stripped systems
Creators: name: Drakos, Nicole E.
name: Taylor, James E.
name: Benson, Andrew J.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Accurate models of the structural evolution of dark matter subhaloes, as they orbit within larger systems, are fundamental to understanding the detailed distribution of dark matter at the present day. Numerical simulations of subhalo evolution support the idea that the mass loss associated with tidal stripping is most naturally understood in energy space, with the particles that are the least bound being removed first. Starting from this premise, we recently proposed a zero-parameter "energy-truncation model" for subhalo evolution. We tested this model with simulations of tidal stripping of satellites with initial NFW profiles, and showed that the energy-truncation model accurately predicts both the mass loss and density profiles. In this work, we apply the model to a variety of Hernquist, Einasto and King profiles. We show that it matches the simulation results quite closely in all cases, indicating that it may serve as a universal model to describe tidally stripped collisionless systems. A key prediction of the energy-truncation model is that the central density of dark matter subhaloes is conserved as they lose mass; this has important implications for dark matter annihilation calculations, and for other observational tests of dark matter.
description: 19 pages, 14 figures. Accepted for publication in MNRAS
The Energetics of cross reinnervated rat skeletal muscle
Creators: name: Ziccone, Sebastian.
Publisher: name: Monash University
Year: 2022

description: This thesis was scanned from the print manuscript for digital preservation and is copyright the author.
 Researchers can access this thesis by asking their local university, institution or public library to
 make a request on their behalf. Monash staff and postgraduate students can use the link in the References field.
Radio fossils, relics, and haloes in Abell 3266: cluster archaeology with ASKAP-EMU and the ATCA
Creators: name: Riseley, C. J.
name: Bonnassieux, E.
name: Vernstrom, T.
name: Galvin, T. J.
name: Chokshi, A.
name: Botteon, A.
name: Rajpurohit, K.
name: Duchesne, S. W.
name: Bonafede, A.
name: Rudnick, L.
name: Hoeft, M.
name: Quici, B.
name: Eckert, D.
name: Brienza, M.
name: Tasse, C.
name: Carretti, E.
name: Collier, J. D.
name: Diego, J. M.
name: Di Mascolo, L.
name: Hopkins, A. M.
name: Johnston-Hollitt, M.
name: Keel, R. R.
name: Koribalski, B. S.
name: Reiprich, T. H.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Abell 3266 is a massive and complex merging galaxy cluster that exhibits significant substructure. We present new, highly sensitive radio continuum observations of Abell 3266 performed with the Australian Square Kilometre Array Pathfinder (0.8$-$1.1 GHz) and the Australia Telescope Compact Array (1.1$-$3.1 GHz). These deep observations provide new insights into recently-reported diffuse non-thermal phenomena associated with the intracluster medium, including a 'wrong-way' relic, a fossil plasma source, and an as-yet unclassified central diffuse ridge, which we reveal comprises the brightest part of a large-scale radio halo detected here for the first time. The 'wrong-way' relic is highly atypical of its kind: it exhibits many classical signatures of a shock-related radio relic, while at the same time exhibiting strong spectral steepening. While radio relics are generally consistent with a quasi-stationary shock scenario, the 'wrong-way' relic is not. We study the spectral properties of the fossil plasma source; it exhibits an ultra-steep and highly curved radio spectrum, indicating an extremely aged electron population. The larger-scale radio halo fills much of the cluster centre, and presents a strong connection between the thermal and non-thermal components of the intracluster medium, along with evidence of substructure. Whether the central diffuse ridge is simply a brighter component of the halo, or a mini-halo, remains an open question. Finally, we study the morphological and spectral properties of the multiple complex radio galaxies in this cluster in unprecedented detail, tracing their evolutionary history.
description: Main article contains 26 pages, 15 figures, 6 tables. Supplementary material contains figures illustrating the improvement gain by applying third-generation calibration and imaging techniques to ATCA and ASKAP data. Manuscript published Open Access in MNRAS on August 1st
Interstellar extinction correction in ionised regions using HeI lines
Creators: name: Zamora, S.
name: Díaz, Ángeles I.
name: Terlevich, Elena
name: Fernández, Vital
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: The logarithmic extinction coefficient, c(H$β$), is usually derived using the H$α$/H$β$ ratio for case B recombination and assuming standard values of electron density and temperature. However, the use of strong Balmer lines can lead to selection biases when studying regions with different surface brightness, such as extended nebulae, with the use of single integral field spectroscopy observations, since, in some cases, the H$α$ line can be saturated in moderate to long exposures. In this work, we present a method to derive extinction corrections based only on the weaker lines of HeI, taking into account the presence of triplet states in these atoms and its influence on recombination lines. We have applied this procedure to calculate the extinction of different regions of the 30 Doradus nebula from MUSE integral-field spectroscopy data. The comparison between helium and hydrogen c(H$β$) determinations has been found to yield results fully compatible within the errors and the use of both sets of lines simultaneously reduces considerably the error in the derivation.
description: 9 pages, 5 figures, accepted for publication in MNRAS
FIRST INDICATION OF SOLAR NEUTRINOS FROM THE CNO CYCLE REACTIONS WITH THE BOREXINO EXPERIMENT
Creators: name: BASILICO, DAVIDE
Publisher: name: Universit� degli Studi di Milano
Year: 2020

description: Solar neutrinos play a unique and irreplaceable role for the comprehension of the mechanisms powering our star. The study of solar neutrino fluxes allows us to definitely prove that the Sun is powered by thermonuclear reactions occurring in its core. Several questions concerning solar neutrinos are still unsolved. In particular, neutrinos emitted in the CNO cycle of reactions are the only undetected piece of the solar fusion puzzle. This cycle is believed to be the main engine of very massive stars, while it is expected to contribute only ~1% to the solar luminosity. Observing neutrinos from the CNO reactions would have a striking importance in astrophysics, providing the first direct confirmation of the existence of this important energy source in the core of the stars. The Borexino detector is an ultrapure liquid scintillator-based detector located at the Laboratori Nazionali del Gran Sasso. Throughout a more than ten-year long data taking, Borexino has achieved outstanding results about solar neutrino physics, measuring all the neutrino fluxes emitted from the pp-chain nuclear reactions. This thesis is devoted to the CNO solar neutrino search with Borexino: analyzing the latest three years of data-taking (Phase-III) I provide the first direct experimental indication of a signal of CNO neutrinos. I describe the details of the analysis, the CNO neutrino results and their implications in terms of solar physics.
Photometric variability in star-forming galaxies as evidence for low-mass AGN and a precursor to quenching
Creators: name: Cleland, Cressida
name: McGee, Sean L.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We measure the optical variability in $\sim$ 16500 low-redshift (z $\sim$ 0.1) galaxies to map the relations between AGN activity and galaxy stellar mass, specific star-formation rate, half-light radius and bulge-to-total ratio. To do this, we use a reduced $χ^2$ variability measure on > 10 epoch lightcurves from the Zwicky Transient Facility and combine with spectroscopic data and derived galaxy parameters from the Sloan Digital Sky Survey. We find that below stellar mass of $10^{11} M_\odot$, galaxies classed as star-forming via the BPT diagram have higher mean variabilities than AGN or composite galaxies. Revealingly, the highest mean variabilities occur in star-forming galaxies in a narrow range of specific star-formation, $-11<\log($sSFR/yr$^{-1})<-10$. In very actively star-forming galaxies $(\log($sSFR/yr$^{-1})>-10)$, the reduced variability implies a lack of instantaneous correlation with star-formation rate. Our results may indicate that a high level of variability, and thus black hole growth, acts as a precursor for reduced star-formation, bulge growth, and revealed AGN-like emission lines. These results add to the mounting evidence that optical variability can act as a viable tracer for low-mass AGNs and that such AGNs can strongly affect their host galaxy.
description: 10 pages, 8 figures, accepted in MNRAS
Solvable model for a dynamical quantum phase transition from fast to slow scrambling
Creators: name: Banerjee, Sumilan
name: Altman, Ehud
Publisher: name: arXiv
Year: 2016
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences
subject: 82B26, 81Q50, 82B44, 82C10

description: We propose an extension of the Sachdev-Ye-Kitaev (SYK) model that exhibits a quantum phase transition from the previously identified non-Fermi liquid fixed point to a Fermi liquid like state, while still allowing an exact solution in a suitable large $N$ limit. The extended model involves coupling the interacting $N$-site SYK model to a new set of $pN$ peripheral sites with only quadratic hopping terms between them. The conformal fixed point of the SYK model remains a stable low energy phase below a critical ratio of peripheral sites $pp_c$ the quadratic sites effectively screen the SYK dynamics, leading to a quadratic fixed point in the low temperature and frequency limit. The interactions have a perturbative effect in this regime leading to scrambling with Lyapunov exponent $λ_L\propto T^2$.
description: 20 pages, 12 figures, added the calculation for Lyapunov exponent away from the particle-hole symmetric situation
Duality Origami: Emergent Ensemble Symmetries in Holography and Swampland
Creators: name: Ashwinkumar, Meer
name: Leedom, Jacob M.
name: Yamazaki, Masahito
Publisher: name: Deutsches Elektronen-Synchrotron, DESY, Hamburg
Year: 2023
Subjects: symmetry, global
duality, holography
string, compactification
spectral
T-duality
quantum gravity
moduli space
orbit
ultraviolet
effective field theory
landscape

description: We discuss interrelations between several ideas in quantum gravity. One is the Swampland program, which states that a low-energy effective field theory should satisfy non-trivial constraints to have an ultraviolet (UV) completion in quantum gravity. Another is the concept of ensemble averaging in holography, where a coarse-grained description is obtained by an integral over a moduli space. To examine the relation between the two, we study ensemble averages of generalized Narain-type theories associated with a general even quadratic form and their holographic duals. We establish the emergence of global symmetries and discuss their consistency with the Swampland conjecture forbidding exact global symmetries. Out of all the zero-form symmetries, the quantum symmetries in the bulk are truly emergent, while classical symmetries are identified as vestiges of T-duality of the Narain-type theories. The latter mechanism can be formulated very generally as a ``folding'' of T-duality orbits via the Siegel-Weil Theorem. We also discuss the interrelations between the Swampland distance conjecture, on one hand, and ensemble averaging and spectral decompositions, on the other. The spectral decomposition also illustrates how ensemble averaging sits within the low-energy limit of certain string compactifications. Our analysis suggests fascinating links between the Swampland, the Landscape, and ensemble averaging.
Gaia-supported re-discovery of a remarkable weak line quasar from a variability and proper motion survey
Creators: name: Meusinger, H.
name: Scholz, R. -D.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We demonstrate that VPMS J170850.95+433223.7 is a weak line quasar (WLQ) which is remarkable in several respects. It was already classified as a probable quasar two decades ago, but with considerable uncertainty. The non-significant proper motion and parallax from the Gaia early data release 3 have solidified this assumption. Based on previously unpublished spectra, we show that VPMS J170850.95+433223.7 is a WLQ at z = 2.345 with immeasurably faint broad emission lines in the rest-frame ultraviolet. A preliminary estimate suggests that it hosts a supermassive black hole of ~10^9 M_sun accreting close to the Eddington limit, perhaps at the super-Eddington level. We identify two absorber systems with blueward velocity offsets of 0.05c and 0.1c, which could represent high-velocity outflows, which are perhaps related to the high accretion state of the quasar.
description: 5 pages, 5 figures, accepted for publication in A&A
Mapping the aliphatic hydrocarbon content of interstellar dust in the Galactic plane
Creators: name: Günay, B.
name: Burton, M. G.
name: Afşar, M.
name: Schmidt, T. W.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: We implement a new observational method for mapping the aliphatic hydrocarbon content in the solid phase in our Galaxy, based on spectrophotometric imaging of the 3.4 $μ$m absorption feature from interstellar dust. We previously demonstrated this method in a field including the Galactic Centre cluster. We applied the method to a new field in the Galactic centre where the 3.4 $μ$m absorption feature has not been previously measured and we extended the measurements to a field in the Galactic plane to sample the diffuse local interstellar medium, where the 3.4 $μ$m absorption feature has been previously measured. We have analysed 3.4 $μ$m optical depth and aliphatic hydrocarbon column density maps for these fields. Optical depths are found to be reasonably uniform in each field, without large source-to-source variations. There is, however, a weak trend towards increasing optical depth in a direction towards $b=0^{\circ}$ in the Galactic centre. The mean value of column densities and abundances for aliphatic hydrocarbon were found to be about several $\rm \times 10^{18} \, cm^{-2}$ and several tens $\times 10^{-6}$, respectively for the new sightlines in the Galactic plane. We conclude that at least 10-20% of the carbon in the Galactic plane lies in aliphatic form.
Y-Z cut lithium niobate longitudinal piezoelectric resonant photoelastic modulator
Creators: name: Atalar, Okan
name: Yee, Steven
name: Safavi-Naeini, Amir H.
name: Arbabian, Amin
Publisher: name: arXiv
Year: 2022
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: The capability to modulate the intensity of an optical beam has scientific and practical significance. In this work, we demonstrate Y-Z cut lithium niobate acousto-optic modulators with record-high modulation efficiency, requiring only $1.5~\text{W}/\text{cm}^2$ for 100% modulation at 7 MHz. These modulators use a simple fabrication process; coating the top and bottom surfaces of a thin lithium niobate wafer with transparent electrodes. The fundamental shear acoustic mode of the wafer is excited through the transparent electrodes by applying voltage with frequency corresponding to the resonant frequency of this mode, confining an acoustic standing wave to the electrode region. Polarization of light propagating through this region is modulated at the applied frequency. Polarization modulation is converted to intensity modulation by placing the modulator between polarizers. To showcase an important application space for this modulator, we integrate it with a standard image sensor and demonstrate 4 megapixel time-of-flight imaging
description: 18 pages, 8 figures
Some performance characteristics of simple polycrystalline back-wall cuprous oxide solar cells :
Creators: name: Harris, John Cecil.
Publisher: name: Monash University
Year: 2022

description: This thesis was scanned from the print manuscript for digital preservation and is copyright the author.
 Researchers can access this thesis by asking their local university, institution or public library to
 make a request on their behalf. Monash staff and postgraduate students can use the link in the References field.
Effect of radiation drag on the line-force-driven winds
Creators: name: Wang, Bei-Chuan
name: Yang, Xiao-Hong
name: Bu, De-Fu
name: Huang, Shu-Su
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Ultra-fast outflows (UFOs) with mildly relativistic velocities are measured using the X-ray spectra of radio-quiet and -loud active galactic nuclei (AGNs). In general, UFOs are believed to be generated from the accretion disk around a black hole (BH). A line-force driving model is suggested to be the mechanism to drive UFOs from the accretion disk. In this paper, we use the non-hydrodynamic approach to examine the influences of radiation-drag effects on the line-force-driven winds generated from the accretion disk. We find that the radiation-drag effects can significantly weaken the line-force-driven winds. Compared with the case without the radiation-drag effects, when the radiation-drag effects are considered, the maximum speed of winds is reduced by $\sim$60\%--70\%, the mass outflow rate is reduced by $\sim$50\%--80\%, and the kinetic power is reduced by about an order of magnitude. The radiation-drag effects narrow the area where the winds are generated.
description: 11 pages, 6 figures, Accepted for publication in MNRAS
Spatial variations of PAH properties in M17SW revealed by Spitzer/IRS spectral mapping
Creators: name: Yamagishi, M.
name: Kaneda, H.
name: Ishihara, D.
name: Oyabu, S.
name: Suzuki, T.
name: Onaka, T.
name: Nagayama, T.
name: Umemoto, T.
name: Minamidani, T.
name: Nishimura, A.
name: Matsuo, M.
name: Fujita, S.
name: Tsuda, Y.
name: Kohno, M.
name: Ohashi, S.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We present $Spitzer$/IRS mid-infrared spectral maps of the Galactic star-forming region M17 as well as IRSF/SIRIUS Br$γ$ and Nobeyama 45-m/FOREST $^{13}$CO ($J$=1--0) maps. The spectra show prominent features due to polycyclic aromatic hydrocarbons (PAHs) at wavelengths of 6.2, 7.7, 8.6, 11.3, 12.0, 12.7, 13.5, and 14.2 $μ$m. We find that the PAH emission features are bright in the region between the HII region traced by Br$γ$ and the molecular cloud traced by $^{13}$CO, supporting that the PAH emission originates mostly from photo-dissociation regions. Based on the spatially-resolved $Spitzer$/IRS maps, we examine spatial variations of the PAH properties in detail. As a result, we find that the interband ratio of PAH 7.7 $μ$m/PAH 11.3 $μ$m varies locally near M17SW, but rather independently of the distance from the OB stars in M17, suggesting that the degree of PAH ionization is mainly controlled by local conditions rather than the global UV environments determined by the OB stars in M17. We also find that the interband ratios of the PAH 12.0 $μ$m, 12.7 $μ$m, 13.5 $μ$m, and 14.2 $μ$m features to the PAH 11.3 $μ$m feature are high near the M17 center, which suggests structural changes of PAHs through processing due to intense UV radiation, producing abundant edgy irregular PAHs near the M17 center.
description: 22 pages, 12 figures, ApJ accepted
Electron transfer reactions of ascorbic acid
Creators: name: Williams, Nicola Hilda.
Publisher: name: Monash University
Year: 2022

description: This thesis was scanned from the print manuscript for digital preservation and is copyright the author.
 Researchers can access this thesis by asking their local university, institution or public library to
 make a request on their behalf. Monash staff and postgraduate students can use the link in the References field.
Spin-Orbital States and Strong Antiferromagnetism of Layered Eu$_2$SrFe$_2$O$_6$ and Sr$_3$Fe$_2$O$_4$Cl$_2$
Creators: name: Lu, Di
name: Yang, Ke
name: Liu, Lu
name: Wang, Guangyu
name: Wu, Hua
Publisher: name: arXiv
Year: 2022
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The insulating iron compounds Eu$_2$SrFe$_2$O$_6$ and Sr$_3$Fe$_2$O$_4$Cl$_2$ have high-temperature antiferromagnetic (AF) order despite their different layered structures. Here we carry out density functional calculations and Monte Carlo simulations to study their electronic structures and magnetic properties aided with analyses of the crystal field, magnetic anisotropy, and superexchange. We find that both compounds are Mott insulators and in the high-spin (HS) Fe$^{2+}$ state ($S$ = 2) accompanied by the weakened crystal field. Although they have different local coordination and crystal fields, the Fe$^{2+}$ ions have the same level sequence and ground-state configuration $(3z^2-r^2)^2(xz,yz)^2(xy)^1(x^2-y^2)^1$. Then, the multiorbital superexchange produces strong AF couplings, and the $(3z^2-r^2)/(xz,yz)$ mixing via the spin-orbit coupling (SOC) yields a small in-plane orbital moment and anisotropy. Indeed, by tracing a set of different spin-orbital states, our density functional calculations confirm the strong AF couplings and the easy planar magnetization for both compounds. Moreover, using the derived magnetic parameters, our Monte Carlo simulations give the Néel temperature $T_{\rm N}$ = 420 K (372 K) for the former (the latter), which well reproduce the experimental results. Therefore, the present study provides a unified picture for Eu$_2$SrFe$_2$O$_6$ and Sr$_3$Fe$_2$O$_4$Cl$_2$ concerning their electronic and magnetic properties.
description: 7 pages, 9 figures, 2 tables
Why Shape Coding? Asymptotic Analysis of the Entropy Rate for Digital Images
Creators: name: Xin, Gangtao
name: Fan, Pingyi
name: Letaief, Khaled B.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Information Theory (cs.IT)
subject: Image and Video Processing (eess.IV)
subject: Statistics Theory (math.ST)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Mathematics

description: This paper focuses on the ultimate limit theory of image compression. It proves that for an image source, there exists a coding method with shapes that can achieve the entropy rate under a certain condition where the shape-pixel ratio in the encoder/decoder is $O({1 \over {\log t}})$. Based on the new finding, an image coding framework with shapes is proposed and proved to be asymptotically optimal for stationary and ergodic processes. Moreover, the condition $O({1 \over {\log t}})$ of shape-pixel ratio in the encoder/decoder has been confirmed in the image database MNIST, which illustrates the soft compression with shape coding is a near-optimal scheme for lossless compression of images.
A Roche Lobe-filling hot Subdwarf and White Dwarf Binary: possible detection of an ejected common envelope
Creators: name: Li, Jiangdan
name: Onken, Christopher A.
name: Wolf, Christian
name: Németh, Péter
name: Bessell, Mike
name: Li, Zhenwei
name: Zhang, Xiaobin
name: Li, Jiao
name: Wang, Luqian
name: Li, Lifang
name: Luo, Yangping
name: Chen, Hailiang
name: Ji, Kaifan
name: Chen, Xuefei
name: Han, Zhanwen
Publisher: name: arXiv
Year: 2022
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Binaries consisting of a hot subdwarf star and an accreting white dwarf (WD) are sources of gravitational wave radiation at low frequencies and possible progenitors of type Ia supernovae if the WD mass is large enough. Here, we report the discovery of the third binary known of this kind: it consists of a hot subdwarf O (sdO) star and a WD with an orbital period of 3.495 hours and an orbital shrinkage of 0.1 s in 6 yr. The sdO star overfills its Roche lobe and likely transfers mass to the WD via an accretion disk. From spectroscopy, we obtain an effective temperature of $T_{\mathrm{eff}}=54\,240\pm1\,840$ K and a surface gravity of $\log{g}=4.841\pm0.108$ for the sdO star. From the light curve analysis, we obtain a sdO mass of $M_{\mathrm{sdO}}=0.55$ ${\mathrm{M_{\odot}}}$ and a mass ratio of $q=M_{\mathrm{WD}}/M_{\mathrm{sdO}}=0.738\pm0.001$. Also, we estimate that the disk has a radius of $\sim 0.41R_\odot$ and a thickness of $\sim 0.18R_\odot$. The origin of this binary is probably a common envelope ejection channel, where the progenitor of the sdO star is either an RGB star or, more likely, an early AGB star; the sdO star will subsequently evolve into a WD and merge with its WD companion, likely resulting in an R CrB star. The outstanding feature in the spectrum of this object is strong Ca H&K lines, which are blueshifted by $\sim$200 km/s and likely originate from the recently ejected common envelope, and we estimated that the remnant CE material in the binary system has a density $\sim 6\times 10^{-10} {\rm g/cm^3}$.
description: 13 pages, 15 figures, to be published in MNRAS
Recurrence CFD - a novel approach to simulate multiphase flows with strongly separated time scales
Creators: name: Lichtenegger, Thomas
name: Pirker, Stefan
Publisher: name: arXiv
Year: 2016
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: Classical Computational Fluid Dynamics (CFD) of long-time processes with strongly separated time scales is computationally extremely demanding if not impossible. Consequently, the state-of-the-art description of such systems is not capable of real-time simulations or online process monitoring. In order to bridge this gap, we propose a new method suitable to decouple slow from fast degrees of freedom in many cases. Based on the recurrence statistics of unsteady flow fields, we deduce a recurrence process which enables the generic representation of pseudo-periodic motion at high spatial and temporal resolution. Based on these fields, passive scalars can be traced by recurrence CFD. While a first, Eulerian Model A solves a passive transport equation in a classical implicit finite-volume environment, a second, Lagrangian Model B propagates fluid particles obeying a stochastic differential equation explicitly. Finally, this new concept is tested by two multiphase processes - a lab scale oscillating bubble column and an industrial scale steelmaking converter. Results of tracer distribution obtained by recurrence CFD are in very good agreement with full CFD simulations, while computational times are dramatically reduced. Actually, recurrence CFD is a promising candidate for online simulations of passive transport processes at full CFD resolution, which opens the door towards improved process monitoring.
description: final version, accepted for publication in Chemical Engineering Science
Modeling multi-phase gases in cosmological simulations using compressible multi-fluid hydrodynamics
Creators: name: Weinberger, Rainer
name: Hernquist, Lars
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: The diffuse medium in and around galaxies can exist in a multi-phase state: small, cold gas clouds contributing significantly to the total mass embedded in pressure equilibrium with a hotter, more diffuse volume-filling component. Modeling this multi-phase state in cosmological simulations poses a significant challenge due to the requirements to spatially resolve the clouds and consequently the interactions between the phases. In this paper, we present a novel method to model this gas state in cosmological hydrodynamical simulations. We solve the compressible two-fluid hydrodynamic equations using a moving-mesh finite-volume method and define mass, momentum and energy exchange terms between the phases as operator-split source terms. Using a stratified flow model, our implementation is able to maintain volume fraction discontinuities in pressure equilibrium to machine precision, allowing for the treatment of both resolved and unresolved multi-phase fluids. The solver remains second order accurate on smooth hydrodynamics problems. We use the source and sink terms of an existing two-phase model for the interstellar medium to demonstrate the value of this type of approach in simulations of galaxy formation, compare it to its effective equation of state implementation, and discuss its advantages in future large-scale simulations of galaxy formation.
description: 16 pages, 19 figures, accepted in MNRAS, comments welcome
A New Window into Gravitationally Produced Scalar Dark Matter
Creators: name: Garcia, Marcos A. G.
name: Pierre, Mathias
name: Verner, Sarunas
Publisher: name: Deutsches Elektronen-Synchrotron, DESY, Hamburg
Year: 2023
Subjects: dark matter, scalar
nucleosynthesis, big bang
dark matter, mass
coupling, nonminimal
coupling, minimal
gravitation
isocurvature
cosmic background radiation
tension
power spectrum
Hubble constant
relic density
inflation

description: Conventional scenarios of purely gravitationally produced dark matter with masses below the Hubble parameter at the end of inflation are in tension with Cosmic Microwave Background (CMB) constraints on the isocurvature power spectrum. We explore a more general scenario with a non-minimal coupling between the scalar dark matter field and gravity, which allows for significantly lighter scalar dark matter masses compared to minimal coupling predictions. By imposing relic abundance, isocurvature, Lyman-$\alpha$, and Big Bang Nucleosynthesis (BBN) constraints, we show the viable parameter space for these models. Our findings demonstrate that the presence of a non-minimal coupling expands the parameter space, yielding a dark matter mass lower bound of $2 \times 10^{-4} \, \rm{eV}$.
Cumulants and nonlinear response of high $p_T$ harmonic flow at $\sqrt{s_{NN}}=5.02$ TeV
Creators: name: Noronha-Hostler, Jacquelyn
name: Betz, Barbara
name: Gyulassy, Miklos
name: Luzum, Matthew
name: Noronha, Jorge
name: Portillo, Israel
name: Ratti, Claudia
Publisher: name: arXiv
Year: 2016
Subjects: subject: Nuclear Theory (nucl-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences

description: Event-by-event fluctuations caused by quantum mechanical fluctuations in the wave function of colliding nuclei in ultrarelativistic heavy ion collisions were recently shown to be necessary for the simultaneous description of $R_{AA}$ as well as the elliptic and triangular flow harmonics at high $p_T$ in PbPb collisions at the Large Hadron Collider. In fact, the presence of a finite triangular flow as well as cumulants of the flow harmonic distribution that differ from the mean are only possible when these event-by-event fluctuations are considered. In this paper we combine event-by-event viscous hydrodynamics and jet quenching to make predictions for high $p_T$ $R_{AA}$, $v_2\{2\}$, $v_3\{2\}$, and $v_2\{4\}$ in PbPb collisions at $\sqrt{s_{NN}}=5.02$ TeV. With an order of magnitude larger statistics we find that high $p_T$ elliptic flow does not scale linearly with the soft elliptical flow, as originally thought, but has deviations from perfectly linear scaling. A new experimental observable, which involves the difference between the ratio of harmonic flow cumulants at high and low $p_T$, is proposed to investigate the fluctuations of high $p_T$ flow harmonics and measure this nonlinear response. By varying the path length dependence of the energy loss and the viscosity of the evolving medium we find that $R_{AA}(p_T)$ and $v_2\{2\}(p_T)$ strongly depend on the choice for the path length dependence of the energy loss, which can be constrained using the new LHC run 2 data.
description: 23 pages, 17 figures; v2 updated text
HI-selected Galaxies in Hierarchical Models of Galaxy Formation and Evolution
Creators: name: Zoldan, Anna
name: De Lucia, Gabriella
name: Xie, Lizhi
name: Fontanot, Fabio
name: Hirschmann, Michaela
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: In this work, we study the basic statistical properties of HI-selected galaxies extracted from six different semi-analytic models, all run on the same cosmological N-body simulation. One model includes an explicit treatment for the partition of cold gas into atomic and molecular hydrogen. All models considered agree nicely with the measured HI mass function in the local Universe, with the measured scaling relations between HI and galaxy stellar mass, and with the predicted 2-point correlation function for HI rich galaxies. One exception is given by one model that predicts very little HI associated with galaxies in haloes above 10^12 Msun: we argue this is due to a too efficient radio-mode feedback for central galaxies, and to a combination of efficient stellar feedback and instantaneous stripping of hot gas for satellites. We demonstrate that treatment of satellite galaxies introduces large uncertainties at low HI masses. While models assuming non instantaneous stripping of hot gas tend to form satellite galaxies with HI masses slightly smaller than those of centrals with the same stellar mass, instantaneous gas stripping does not translate necessarily in lower HI masses. In fact, the adopted stellar feedback and star formation affect the satellites too. We analyze the relation between HI content and spin of simulated haloes: low spin haloes tend to host HI poor galaxies while high spin haloes are populated by galaxies in a wide range of HI mass. In our simulations, this is due to a correlation between the initial gas disk size and the halo spin.
description: 20 pages, 15 figures, accepted for publication in MNRAS
Laser Guide Star uplink beam: scattering and Raman emission measurements with the 10.4m Gran Telescopio CANARIAS
Creators: name: Lombardi, G.
name: Calia, D. Bonaccini
name: Centrone, M.
name: Postigo, A. de Ugarte
name: Geier, S.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: Laser Guide Star Adaptive Optics (LGS-AO) is becoming routine in several astronomical observatories. The use of powerful lasers generates sensible Raman emissions on the uplink laser beam path, plus secondary Rayleigh scattering from atmospheric molecules and Mie scattering from aerosols. This paper reports the results of a campaign done with the 10.4m Gran Telescopio CANARIAS (GTC); this campaign was undertaken to assess the spectral and photometric contamination coming from a 589 nm laser uplink beam scattering and Raman emission induced on the GTC spectro-imager OSIRIS by laser launched about 1 km off-axis. The photometric contamination is due to primary and secondary scattering of the uplink photons, as well by the Raman inelastic scattering. We have propagated the laser beam creating a mesospheric LGS, then pointed and focused the GTC telescope toward the uplink laser beam, at different heights and up to the LGS, taking into account the observing geometry. In our observations, the Raman emissions for O2 and N2 vibrational lines are visible at 20 km, weakening with altitude and becoming undetectable above 30 km. The scattering of the focused uplink beam is detectable at less than +/-0.2 arcmin from the center of the beam, while for the focused LGS the scattering is narrower, being detectable at less than +/-0.1 arcmin around the plume. Recommendations for Laser Traffic Control Systems (LTCS) are given accordingly.
description: Accepted for publication in MNRAS. 12 pages, 13 Figures, 5 Tables
Deletion Operations on Deterministic Families of Automata
Creators: name: Eremondi, Joey
name: Ibarra, Oscar H.
name: McQuillan, Ian
Publisher: name: arXiv
Year: 2016
Subjects: subject: Formal Languages and Automata Theory (cs.FL)
subject: FOS: Computer and information sciences

description: Many different deletion operations are investigated applied to languages accepted by one-way and two-way deterministic reversal-bounded multicounter machines, deterministic pushdown automata, and finite automata. Operations studied include the prefix, suffix, infix and outfix operations, as well as left and right quotient with languages from different families. It is often expected that language families defined from deterministic machines will not be closed under deletion operations. However, here, it is shown that one-way deterministic reversal-bounded multicounter languages are closed under right quotient with languages from many different language families; even those defined by nondeterministic machines such as the context-free languages. Also, it is shown that when starting with one-way deterministic machines with one counter that makes only one reversal, taking the left quotient with languages from many different language families -- again including those defined by nondeterministic machines such as the context-free languages -- yields only one-way deterministic reversal-bounded multicounter languages (by increasing the number of counters). However, if there are two more reversals on the counter, or a second 1-reversal-bounded counter, taking the left quotient (or even just the suffix operation) yields languages that can neither be accepted by deterministic reversal-bounded multicounter machines, nor by 2-way nondeterministic machines with one reversal-bounded counter.
description: 20 pages, accepted version to Information and Computation