cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Chemical abundances in Seyfert galaxies X. Sulphur abundance estimates
Creators: name: Dors, O. L.
name: Valerdi, M.
name: Riffel, R. A.
name: Riffel, R.
name: Cardaci, M. V.
name: Hägele, G. F.
name: Armah, M.
name: Revalski, M.
name: Flury, S. R.
name: Freitas-Lemes, P.
name: Amôres, E. B.
name: Krabbe, A. C.
name: Binette, L.
name: Feltre, A.
name: Storchi-Bergmann, T.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: For the first time, the sulphur abundance relative to hydrogen (S/H) in the Narrow Line Regions of a sample of Seyfert 2 nuclei (Sy 2s) has been derived via direct estimation of the electron temperature. Narrow emission line intensities from the SDSS DR17 [in the wavelength range 3000 < $λ$ < 9100] and from the literature for a sample of 45 nearby ($z$ < 0.08) Sy 2s were considered. Our direct estimates indicate that Sy 2s have similar temperatures in the gas region where most of the S+ ions are located in comparison with that of star-forming regions (SFs). However, Sy 2s present higher temperature values ($\sim$10000 K) in the region where most of the S++ ions are located relative to that of SFs. We derive the total sulphur abundance in the range of 6.2 < 12 + log(S/H) < 7.5, corresponding to 0.1-1.8 times the solar value. These sulphur abundance values are lower by $\sim$0.4 dex than those derived in SFs with similar metallicity, indicating a distinct chemical enrichment of the ISM for these object classes. The S/O values for our Sy 2 sample present an abrupt ($\sim$0.5 dex) decrease with increasing O/H for the high metallicity regime [12 + log(O/H) > 8.7)], what is not seen for the SFs. However, when our Sy 2 estimates are combined with those from a large sample of star-forming regions, we did not find any dependence between S/O and O/H.
description: Accepted for publication in MNRAS. 19 pages, 11 figures, 7 tables
Zero-range process with finite compartments: Gentile's statistics and glassiness
Creators: name: Ryabov, Artem
Publisher: name: arXiv
Year: 2013
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: We discuss statics and dynamics of condensation in a zero-range process with compartments of limited sizes. For the symmetric dynamics the stationary state has a factorized form. For the asymmetric dynamics the steady state factorizes only for special hopping rules which allow for overjumps of fully occupied compartments. In the limit of large system size the grand canonical analysis is exact also in a condensed phase, and for a broader class of hopping rates as compared to the previously studied systems with infinite compartments. The dynamics of condensation exhibits a dynamical self-blocking which significantly prolongs relaxation times. These general features are illustrated with a concrete example: an inhomogeneous system with hopping rates that result in Bose-Einstein-like condensations.
A possible signature of the influence of tidal perturbations in dwarf galaxy scaling relations
Creators: name: Watkins, A. E.
name: Salo, H.
name: Kaviraj, S.
name: Collins, C. A.
name: Knapen, J. H.
name: Venhola, A.
name: Román, J.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Dwarf galaxies are excellent cosmological probes, because their shallow potential wells make them very sensitive to the key processes that drive galaxy evolution, including baryonic feedback, tidal interactions, and ram pressure stripping. However, some of the key parameters of dwarf galaxies, which help trace the effects of these processes, are still debated, including the relationship between their sizes and masses. We re-examine the Fornax Cluster dwarf population from the point of view of isomass-radius--stellar mass relations (IRSMRs) using the Fornax Deep Survey Dwarf galaxy Catalogue, with the centrally located (among dwarfs) $3.63 \mathcal{M}_{\odot}$~pc$^{-2}$ isodensity radius defining our fiducial relation. This relation is a powerful diagnostic tool for identifying dwarfs with unusual structure, as dwarf galaxies' remarkable monotonicity in light profile shapes, as a function of stellar mass, reduces the relation's scatter tremendously. By examining how different dwarf properties (colour, tenth-nearest-neighbour distance, etc.) correlate with distance from our fiducial relation, we find a significant population of structural outliers with comparatively lower central mass surface density and larger half-light-radii, residing in locally denser regions in the cluster, albeit with similar red colours. We propose that these faint, extended outliers likely formed through tidal disturbances, which make the dwarfs more diffuse, but with little mass loss. Comparing these outliers with ultra-diffuse galaxies (UDGs), we find that the term UDG lacks discriminatory power; UDGs in the Fornax Cluster lie both on and off of IRSMRs defined at small radii, while IRSMR outliers with masses below $\sim 10^{7.5} \mathcal{M}_{\odot}$ are excluded from the UDG classification due to their small effective radii.
description: 16 pages (+2 appendix), 10 figures, accepted for publication in MNRAS
Variations in the initial mass function in early-type galaxies: A critical comparison between dynamical and spectroscopic results
Creators: name: Smith, Russell J.
Publisher: name: arXiv
Year: 2014
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: I present a comparison between published dynamical (ATLAS3D) and spectroscopic (Conroy & van Dokkum) constraints on the stellar initial mass function (IMF) in early-type galaxies, using the 34 galaxies in common between the two works. Both studies infer an average IMF mass factor $α$ (the stellar mass relative to a Kroupa-IMF population of similar age and metallicity) greater than unity, i.e. both methods favour an IMF which is heavier than that of the Milky Way, on average over the sample. However, on a galaxy-by-galaxy basis, there is no correlation between $α$ inferred from the two approaches. I investigate how the two estimates of $α$ are correlated systematically with the galaxy velocity dispersion, $σ$, and with the Mg/Fe abundance ratio. The spectroscopic method, based on the strengths of metal absorption lines, yields a correlation only with metal abundance ratios: at fixed Mg/Fe, there is no residual correlation with $σ$. The dynamical method, applied to exactly the same galaxy sample, yields the opposite result: the IMF variation correlates only with dynamics, with no residual correlation with Mg/Fe after controlling for $σ$. Hence although both methods indicate a heavy IMF on average in ellipticals, they lead to incompatible results for the systematic trends, when applied to the same set of galaxies. The sense of the disagreement could suggest that one (or both) of the methods has not accounted fully for the main confounding factors, i.e. element abundance ratios or dark matter contributions. Alternatively, the poor agreement might indicate additional variation in the detailed shape of the IMF, beyond what can currently be inferred from the spectroscopic features.
description: MNRAS in press
The 2019 outburst of AMXP SAX J1808.4-3658 and radio follow up of MAXI J0911-655 and XTE J1701-462
Creators: name: Gasealahwe, K. V. S.
name: Monageng, I. M.
name: Fender, R. P.
name: Woudt, P. A.
name: Motta, S. E.
name: Eijnden, J. van den
name: Williams, D. R. A.
name: Heywood, I.
name: Bloemen, S.
name: Groot, P. J.
name: Vreeswijk, P.
name: McBride, V.
name: Klein-Wolt, M.
name: Körding, E.
name: Poole, R. Le
name: Pieterse, D.
name: de Wet, S.
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We present radio coverage of the 2019 outburst of the accreting millisecond X-ray pulsar SAX J1808.4-3658, obtained with MeerKAT. We compare these data to contemporaneous X-ray and optical measurements in order to investigate the coupling between accretion and jet formation in this system, while the optical lightcurve provides greater detail of the outburst. The reflaring activity following the main outburst peak was associated with a radio re-brightening, indicating a strengthening of the jet in this phase of the outburst. We place quasi-simultaneous radio and X-ray measurements on the global radio:X-ray plane for X-ray binaries, and show they reside in the same region of luminosity space as previous outburst measurements, but significantly refine the correlation for this source. We also present upper limits on the radio emission from the accreting millisecond X-ray pulsar MAXI J0911-655 and the transitional Z/Atoll-type transient XTE J1701-462. In the latter source we also confirm that nearby large-scale structures reported in previous radio observations of the source are persistent over a period of ~15 years, and so are almost certainly background radio galaxies and not associated with the X-ray transient.
description: Contains 9 pages and 3 figures, accepted for publication in MNRAS
The Epoch of Reionization Window: II. Statistical Methods for Foreground Wedge Reduction
Creators: name: Liu, Adrian
name: Parsons, Aaron R.
name: Trott, Cathryn M.
Publisher: name: arXiv
Year: 2014
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: For there to be a successful measurement of the 21 cm Epoch of Reionization (EoR) power spectrum, it is crucial that strong foreground contaminants be robustly suppressed. These foregrounds come from a variety of sources (such as Galactic synchrotron emission and extragalactic point sources), but almost all share the property of being spectrally smooth, and when viewed through the chromatic response of an interferometer, occupy a signature "wedge" region in cylindrical $k_\perp k_\parallel$ Fourier space. The complement of the foreground wedge is termed the "EoR window", and is expected to be mostly foreground-free, allowing clean measurements of the power spectrum. This paper is a sequel to a previous paper that established a rigorous mathematical framework for describing the foreground wedge and the EoR window. Here, we use our framework to explore statistical methods by which the EoR window can be enlarged, thereby increasing the sensitivity of a power spectrum measurement. We adapt the FKP approximation (commonly used in galaxy surveys) for 21 cm cosmology, and also compare the optimal quadratic estimator to simpler estimators that ignore covariances between different Fourier modes. The optimal quadratic estimator is found to suppress foregrounds by an extra factor of $\sim 10^5$ in power at the peripheries of the EoR window, boosting the detection of the cosmological signal from $12σ$ to $50σ$ at the midpoint of reionization in our fiducial models. If numerical issues can be finessed, decorrelation techniques allow the EoR window to be further enlarged, enabling measurements to be made deep within the foreground wedge. These techniques do not assume that foreground are Gaussian-distributed, and we additionally prove that a final round of foreground subtraction can be performed after decorrelation in a way that is guaranteed to have no cosmological signal loss.
description: 19 pages, 8 figures. v2: Updated to match published PRD version. Fixed typos, added figure showing fiducial theoretical model, appendix about Fisher matrices, and detection significance figures in response to referee comments. Main conclusions unchanged
Scalable and Energy-Efficient SIMT Systems for Deep Learning and Data Center Microservices
Creators: name: Abdallah, Mahmoud Khairy A.
Publisher: name: Purdue University Graduate School
Year: 2022
Subjects: Operating systems
Distributed systems and algorithms
Programming languages

description: Moore’s law is dead. The physical and economic principles that enabled an exponential rise in transistors per chip have reached their breaking point. As a result, High-Performance Computing (HPC) domain and cloud data centers are encountering significant energy, cost, and environmental hurdles that have led them to embrace custom hardware/software solutions. Single Instruction Multiple Thread (SIMT) accelerators, like Graphics Processing Units (GPUs), are compelling solutions to achieve considerable energy efficiency while still preserving programmability in the twilight of Moore’s Law. In the HPC and Deep Learning (DL) domain, the death of single-chip GPU performance scaling will usher in a renaissance in multi-chip Non-Uniform Memory Access (NUMA) scaling. Advances in silicon interposers and other inter-chip signaling technology will enable single-package systems, composed of multiple chiplets that continue to scale even as per-chip transistors do not. Given this evolving, massively parallel NUMA landscape, the placement of data on each chiplet, or discrete GPU card, and the scheduling of the threads that use that data is a critical factor in system performance and power consumption. Aside from the supercomputer space, general-purpose compute units are still the main driver of data center’s total cost of ownership (TCO). CPUs consume 60% of the total data center power budget, half of which comes from the CPU pipeline’s frontend. Coupled with the hardware efficiency crisis is an increased desire for programmer productivity, flexible scalability, and nimble software updates that have led to the rise of software microservices. Consequently, single servers are now packed with many threads executing the same, relatively small task on different data. In this dissertation, I discuss these new paradigm shifts, addressing the following concerns: (1) how do we overcome the non-uniform memory access overhead for next-generation multi-chiplet GPUs in the era of DL-driven workloads?; (2) how can we improve the energy efficiency of data center’s CPUs in the light of microservices evolution and request similarity?; and (3) how to study such rapidly-evolving systems with an accurate and extensible SIMT performance modeling?
A Continuum of H- to He-Rich Tidal Disruption Candidates With a Preference for E+A Galaxies
Creators: name: Arcavi, Iair
name: Gal-Yam, Avishay
name: Sullivan, Mark
name: Pan, Yen-Chen
name: Cenko, S. Bradley
name: Horesh, Assaf
name: Ofek, Eran O.
name: De Cia, Annalisa
name: Yan, Lin
name: Yang, Chen-Wei
name: Howell, D. A.
name: Tal, David
name: Kulkarni, Shrinivas R.
name: Tendulkar, Shriharsh P.
name: Tang, Sumin
name: Xu, Dong
name: Sternberg, Assaf
name: Cohen, Judith G.
name: Bloom, Joshua S.
name: Nugent, Peter E.
name: Kasliwal, Mansi M.
name: Perley, Daniel A.
name: Quimby, Robert M.
name: Miller, Adam A.
name: Theissen, Christopher A.
name: Laher, Russ R.
Publisher: name: arXiv
Year: 2014
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We present the results of a Palomar Transient Factory (PTF) archival search for blue transients which lie in the magnitude range between "normal" core-collapse and superluminous supernovae (i.e. with $-21\,{\leq}M_{R\,(peak)}\,{\leq}-19$). Of the six events found after excluding all interacting Type~IIn and Ia-CSM supernovae, three (PTF09ge, 09axc and 09djl) are coincident with the centers of their hosts, one (10iam) is offset from the center, and for two (10nuj and 11glr) a precise offset can not be determined. All the central events have similar rise times to the He-rich tidal disruption candidate PS1-10jh, and the event with the best-sampled light curve also has similar colors and power-law decay. Spectroscopically, PTF09ge is He-rich, while PTF09axc and 09djl display broad hydrogen features around peak magnitude. All three central events are in low star-formation hosts, two of which are E+A galaxies. Our spectrum of the host of PS1-10jh displays similar properties. PTF10iam, the one offset event, is different photometrically and spectroscopically from the central events and its host displays a higher star formation rate. Finding no obvious evidence for ongoing galactic nuclei activity or recent star formation, we conclude that the three central transients likely arise from the tidal disruption of a star by a super-massive black hole. We compare the spectra of these events to tidal disruption candidates from the literature and find that all of these objects can be unified on a continuous scale of spectral properties. The accumulated evidence of this expanded sample strongly supports a tidal disruption origin for this class of nuclear transients.
description: Minor changes and clarifications, added radio non-detection limits for one of the events, accepted to ApJ
X3: a high-mass Young Stellar Object close to the supermassive black hole Sgr~A*
Creators: name: Peißker, Florian
name: Zajacek, Michal
name: Sabha, Nadeen B.
name: Tsuboi, Masato
name: Moultaka, Jihane
name: Labadie, Lucas
name: Eckart, Andreas
name: Karas, Vladimir
name: Steiniger, Lukas
name: Subroweit, Matthias
name: Suresh, Anjana
name: Melamed, Maria
name: Clenet, Yann
Publisher: name: arXiv
Year: 2023
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: To date, the proposed observation of Young Stellar Objects (YSOs) in the Galactic center (GC) still raises the question where and how these objects could have formed due to the violent vicinity of Sgr~A*. Here, we report the multi-wavelength detection of a highly dynamic YSO close to Sgr~A* that might be a member of the IRS13 cluster. We observe the beforehand known coreless bow-shock source X3 in the near- and mid-infrared (NIR/MIR) with SINFONI (VLT), NACO (VLT), ISAAC (VLT), VISIR (VLT), SHARP (NTT), and NIRCAM2 (KECK). In the radio domain, we use CO continuum and H30$α$ ALMA observations to identify system components at different temperatures and locations concerning the central stellar source. It is suggested that these radio/submm observations in combination with the NIR Br$γ$ line can be associated with a protoplanetary disk of the YSO which is consistent with manifold VISIR observations that reveal complex molecules and elements such as PAH, SIV, NeII and ArIII in a dense and compact region. Based on the photometric multi-wavelength analysis, we infer the mass of $15^{+10}_{-5} M_{\odot}$ for the YSO with a related age of a few $10^4$ yr. Due to this age estimate and the required relaxation time scales for high-mass stars, this finding is an indication for ongoing star formation in the inner parsec. The proper motion and 3d distance imply a relation of X3 and IRS13. We argue that IRS13 may serve as a birthplace for young stars that are ejected due to the evaporation of the cluster.
description: 36 pages, 28 figures, accepted by ApJ
Dynamical localization and eigenstate localization in trap models
Creators: name: Flegel, Franziska
name: Sokolov, Igor M.
Publisher: name: arXiv
Year: 2014
Subjects: subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: The one-dimensional random trap model with a power-law distribution of mean sojourn times exhibits a phenomenon of dynamical localization in the case where diffusion is anomalous: The probability to find two independent walkers at the same site, as given by the participation ratio, stays constant and high in a broad domain of intermediate times. This phenomenon is absent in dimensions two and higher. In finite lattices of all dimensions the participation ratio finally equilibrates to a different final value. We numerically investigate two-particle properties in a random trap model in one and in three dimensions, using a method based on spectral decomposition of the transition rate matrix. The method delivers a very effective computational scheme producing numerically exact results for the averages over thermal histories and initial conditions in a given landscape realization. Only a single averaging procedure over disorder realizations is necessary. The behavior of the participation ratio is compared to other measures of localization, as for example to the states' gyration radius, according to which the dynamically localized states are extended. This means that although the particles are found at the same site with a high probability, the typical distance between them grows. Moreover the final equilibrium state is extended both with respect to its gyration radius and to its Lyapunov exponent. In addition, we show that the phenomenon of dynamical localization is only marginally connected with the spectrum of the transition rate matrix, and is dominated by the properties of its eigenfunctions which differ significantly in dimensions one and three.
description: 10 pages, 10 figures, submitted to EPJB
Geometry and Uncertainty in Deep Learning for Computer Vision
Creators: name: Kendall, Alex Guy
Publisher: name: Apollo - University of Cambridge Repository
Year: 2019
Subjects: Deep Learning
Computer Vision
Machine Learning
Robotics

description: Deep learning and convolutional neural networks have become the dominant tool for computer vision. These techniques excel at learning complicated representations from data using supervised learning. In particular, image recognition models now out-perform human baselines under constrained settings. However, the science of computer vision aims to build machines which can see. This requires models which can extract richer information than recognition, from images and video. In general, applying these deep learning models from recognition to other problems in computer vision is significantly more challenging. This thesis presents end-to-end deep learning architectures for a number of core computer vision problems; scene understanding, camera pose estimation, stereo vision and video semantic segmentation. Our models outperform traditional approaches and advance state-of-the-art on a number of challenging computer vision benchmarks. However, these end-to-end models are often not interpretable and require enormous quantities of training data. To address this, we make two observations: (i) we do not need to learn everything from scratch, we know a lot about the physical world, and (ii) we cannot know everything from data, our models should be aware of what they do not know. This thesis explores these ideas using concepts from geometry and uncertainty. Specifically, we show how to improve end-to-end deep learning models by leveraging the underlying geometry of the problem. We explicitly model concepts such as epipolar geometry to learn with unsupervised learning, which improves performance. Secondly, we introduce ideas from probabilistic modelling and Bayesian deep learning to understand uncertainty in computer vision models. We show how to quantify different types of uncertainty, improving safety for real world applications.
description: My PhD was funded by the Woolf Fisher Trust
Low-temperature dynamics of Long-Ranged Spin-Glasses : full hierarchy of relaxation times via real-space renormalization
Creators: name: Monthus, Cecile
Publisher: name: arXiv
Year: 2014
Subjects: subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: FOS: Physical sciences

description: We consider the long-ranged Ising spin-glass with random couplings decaying as a power-law of the distance, in the region of parameters where the spin-glass phase exists with a positive droplet exponent. For the Metropolis single-spin-flip dynamics near zero temperature, we construct via real-space renormalization the full hierarchy of relaxation times of the master equation for any given realization of the random couplings. We then analyze the probability distribution of dynamical barriers as a function of the spatial scale. This real-space renormalization procedure represents a simple explicit example of the droplet scaling theory, where the convergence towards local equilibrium on larger and larger scales is governed by a strong hierarchy of activated dynamical processes, with valleys within valleys.
description: v2=final version
Accretion within the innermost stable circular orbit: analytical thermodynamic solutions in the adiabatic limit
Creators: name: Mummery, Andrew
name: Balbus, Steven
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We present analytical solutions for the thermodynamic (temperature, pressure, density, etc.) properties of thin accretion flows in the region within the innermost stable circular orbit (ISCO) of a Kerr black hole, the first analytical solutions of their kind. These solutions are constructed in the adiabatic limit and neglect radiative losses, an idealisation valid for a restricted region of parameter space. We highlight a number of remarkable properties of these solutions, including that these solutions cool for radii $r_I/2 < r < r_I$, before increasing in temperature for $0 < r < r_I/2$, independent of black hole spin and assumptions regarding the equation of state of the accretion flow. The radiative temperature of these solutions can, for some values of the free parameters of the theory, peak within the ISCO and not in the main body of the disc. These solutions represent a fundamentally new class of analytical accretion solutions, which are both non-circular and non-radial in character.
description: 17 pages, with 5 appendices. 12 figures. Accepted for publication in MNRAS
DEff-GAN: Diverse Attribute Transfer for Few-Shot Image Synthesis
Creators: name: Kumar, Rajiv
name: Sivakumar, G.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: Requirements of large amounts of data is a difficulty in training many GANs. Data efficient GANs involve fitting a generators continuous target distribution with a limited discrete set of data samples, which is a difficult task. Single image methods have focused on modeling the internal distribution of a single image and generating its samples. While single image methods can synthesize image samples with diversity, they do not model multiple images or capture the inherent relationship possible between two images. Given only a handful of images, we are interested in generating samples and exploiting the commonalities in the input images. In this work, we extend the single-image GAN method to model multiple images for sample synthesis. We modify the discriminator with an auxiliary classifier branch, which helps to generate a wide variety of samples and to classify the input labels. Our Data-Efficient GAN (DEff-GAN) generates excellent results when similarities and correspondences can be drawn between the input images or classes.
FPCD: An Open Aerial VHR Dataset for Farm Pond Change Detection
Creators: name: Tundia, Chintan
name: Kumar, Rajiv
name: Damani, Om
name: Sivakumar, G.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: Change detection for aerial imagery involves locating and identifying changes associated with the areas of interest between co-registered bi-temporal or multi-temporal images of a geographical location. Farm ponds are man-made structures belonging to the category of minor irrigation structures used to collect surface run-off water for future irrigation purposes. Detection of farm ponds from aerial imagery and their evolution over time helps in land surveying to analyze the agricultural shifts, policy implementation, seasonal effects and climate changes. In this paper, we introduce a publicly available object detection and instance segmentation (OD/IS) dataset for localizing farm ponds from aerial imagery. We also collected and annotated the bi-temporal data over a time-span of 14 years across 17 villages, resulting in a binary change detection dataset called \textbf{F}arm \textbf{P}ond \textbf{C}hange \textbf{D}etection Dataset (\textbf{FPCD}). We have benchmarked and analyzed the performance of various object detection and instance segmentation methods on our OD/IS dataset and the change detection methods over the FPCD dataset. The datasets are publicly accessible at this page: \textit{\url{https://huggingface.co/datasets/ctundia/FPCD}}
Relaxation mechanisms in a disordered system with the Poisson level statistics
Creators: name: Bonca, Janez
name: Mierzejewski, Marcin
Publisher: name: arXiv
Year: 2023
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: FOS: Physical sciences

description: We discuss the interplay between many-body localization and spin-symmetry. To this end, we study the time evolution of several observables in the anisotropic t-J model. Like the Hubbard chain, the studied model contains charge and spin degrees of freedom, yet it has smaller Hilbert space and thus allows for numerical studies of larger systems. We compare the field disorder that breaks the Z_2 spin symmetry and a potential disorder that preserves the latter symmetry. In the former case, sufficiently strong disorder leads to localization of all studied observables, at least for the studied system sizes. However, in the case of symmetry-preserving disorder, we observe that odd operators under the Z_2 spin transformation relax towards the equilibrium value at relatively short time scales that grow only polynomially with the disorder strength. On the other hand, the dynamics of even operators and the level statistics within each symmetry sector are consistent with localization. Our results indicate that localization exists within each symmetry sector for symmetry preserving disorder. Odd operators' apparent relaxation is due to their time evolution between distinct symmetry sectors.
Temporal Scalability of Dynamic Volume Data Using Mesh Compensated Wavelet Lifting
Creators: name: Schnurrer, Wolfgang
name: Pallast, Niklas
name: Richter, Thomas
name: Kaup, André
Publisher: name: arXiv
Year: 2023
Subjects: subject: Image and Video Processing (eess.IV)
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: Due to their high resolution, dynamic medical 2D+t and 3D+t volumes from computed tomography (CT) and magnetic resonance tomography (MR) reach a size which makes them very unhandy for teleradiologic applications. A lossless scalable representation offers the advantage of a down-scaled version which can be used for orientation or previewing, while the remaining information for reconstructing the full resolution is transmitted on demand. The wavelet transform offers the desired scalability. A very high quality of the lowpass sub-band is crucial in order to use it as a down-scaled representation. We propose an approach based on compensated wavelet lifting for obtaining a scalable representation of dynamic CT and MR volumes with very high quality. The mesh compensation is feasible to model the displacement in dynamic volumes which is mainly given by expansion and contraction of tissue over time. To achieve this, we propose an optimized estimation of the mesh compensation parameters to optimally fit for dynamic volumes. Within the lifting structure, the inversion of the motion compensation is crucial in the update step. We propose to take this inversion directly into account during the estimation step and can improve the quality of the lowpass sub-band by 0.63 and 0.43 dB on average for our tested dynamic CT and MR volumes at the cost of an increase of the rate by 2.4% and 1.2% on average.
Holographic thermal field theory on curved spacetimes
Creators: name: Marolf, Donald
name: Rangamani, Mukund
name: Wiseman, Toby
Publisher: name: arXiv
Year: 2013
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: The AdS/CFT correspondence relates certain strongly coupled CFTs with large effective central charge $c_\text{eff}$ to semi-classical gravitational theories with AdS asymptotics. We describe recent progress in understanding gravity duals for CFTs on non-trivial spacetimes at finite temperature, both in and out of equilibrium. Such gravity methods provide powerful new tools to access the physics of these strongly coupled theories, which often differs qualitatively from that found at weak coupling. Our discussion begins with basic aspects of AdS/CFT and progresses through thermal CFTs on the Einstein Static Universe and on periodically identified Minkowski spacetime. In the latter context we focus on states describing so-called plasma balls, which become stable at large $c_\text{eff}$. We then proceed to out-of-equilibrium situations associated with dynamical bulk black holes. In particular, the non-compact nature of these bulk black holes allows stationary solutions with non-Killing horizons that describe time-independent flows of CFT plasma. As final a topic we consider CFTs on black hole spacetimes. This discussion provides insight into how the CFT transports heat between general heat sources and sinks of finite size. In certain phases the coupling to small sources can be strongly suppressed, resulting in negligible heat transport despite the presence of a deconfined plasma with sizeable thermal conductivity. We also present a new result, explaining how this so-called droplet behaviour is related to confinement via a change of conformal frame.
description: 77 pages. 9 figures. Invited review for CQG. v2: added refs. v3: typos fixed. published version
Star Formation Rate and Extinction in Faint z~4 Lyman-Break Galaxies
Creators: name: To, Chun-Hao
name: Wang, Wei-Hao
name: Owen, Frazer N.
Publisher: name: arXiv
Year: 2014
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We present a statistical detection of 1.5 GHz radio continuum emission from a sample of faint z~4 Lyman-break galaxies (LBGs). LBGs are key tracers of the high-redshift star formation history and important sources of UV photons that ionized the intergalactic medium in the early universe. In order to better constrain the extinction and intrinsic star formation rate (SFR) of high-redshift LBGs, we combine the latest ultradeep Karl G. Jansky Very Large Array 1.5 GHz radio image and the Hubble Space Telescope Advance Camera for Surveys (ACS) optical images in the Great Observatories Origins Deep Survey-North. We select a large sample of 1771 z~4 LBGs from the ACS catalogue using $\bband$-dropout color criteria. Our LBG samples have $\iband$~25-28 (AB), ~0-3 magnitudes fainter than M*_UV at z~4. In our stacked radio images, we find the LBGs to be point-like under our 2" angular resolution. We measure their mean 1.5 GHz flux by stacking the measurements on the individual objects. We achieve a statistical detection of $S_{1.5GHz}$=0.210+-0.075 uJy at ~3 sigma, first time on such a faint LBG population at z~4. The measurement takes into account the effects of source size and blending of multiple objects. The detection is visually confirmed by stacking the radio images of the LBGs, and the uncertainty is quantified with Monte Carlo simulations on the radio image. The stacked radio flux corresponds to an intrinsic SFR of 16.0+-5.7 M/yr, which is 2.8X the SFR derived from the rest-frame UV continuum luminosity. This factor of 2.8 is in excellent agreement with the extinction correction derived from the observed UV continuum spectral slope, using the local calibration of meurer99. This result supports the use of the local calibration on high-redshift LBGs for deriving the extinction correction and SFR, and also disfavors a steep reddening curve such as that of the Small Magellanic Cloud.
description: 9 pages, 6 figures, 1 table. Accepted to ApJ. Comments are welcome
Noise reduction on single-shot images using an autoencoder
Creators: name: Bartlett, Oliver. J.
name: Benoit, David. M.
name: Pimbblet, Kevin. A.
name: Simmons, Brooke
name: Hunt, Laura
Publisher: name: arXiv
Year: 2023
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We present an application of autoencoders to the problem of noise reduction in single-shot astronomical images and explore its suitability for upcoming large-scale surveys. Autoencoders are a machine learning model that summarises an input to identify its key features, then from this knowledge predicts a representation of a different input. The broad aim of our autoencoder model is to retain morphological information (e.g., non-parametric morphological information) from the survey data whilst simultaneously reducing the noise contained in the image. We implement an autoencoder with convolutional and maxpooling layers. We test our implementation on images from the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) that contain varying levels of noise and report how successful our autoencoder is by considering Mean Squared Error (MSE), Structural Similarity Index (SSIM), the second-order moment of the brightest 20 percent of the galaxy's flux M20, and the Gini coefficient, whilst noting how the results vary between the original images, stacked images, and noise reduced images. We show that we are able to reduce noice, over many different targets of observations, whilst retaining the galaxy's morphology, with metric evaluation on a target by target analysis. We establish that this process manages to achieve a positive result in a matter of minutes, and by only using one single shot image compared to multiple survey images found in other noise reduction techniques.
description: 13 pages, 6 figures, 6 tables, Accepted for publication in MNRAS
Practical Applications of IIIF Webinar Slides
Creators: name: Padfield, J.
name: Terras, M.
name: T. Crane, C. Bolland
Publisher: name: Zenodo
Year: 2021
Subjects: IIIF, Towards a National Collection

description: Session 01 - Using IIIF resources for Research and Education Introduction and Welcome (J. Padfield) Explore the Raphael Cartoons at the V&A - Luca Carini will present this great new resource from the V&A highlighting how IIIF has allowed them to present these wonderful Raphael cartoons to the general public and a research audience. Embedding IIIF resources into teaching and course work at The University of St. Andrews - Andrew Wilson will present their work with Exhibit.so and how this flexible IIIF based tool has allowed them to provide rich interactive teaching resources during the Covid-19 pandemic. Re-using IIIF resources in documentation solutions - Joe Padfield will present details of how IIIF has been used as the basis for the National Gallery’s internal image sharing and presentation system and how these resources have been re-used to create a digital documentation system to record the delicate process of sampling old master paintings. Session 1 Q&A Session 02 - Practical applications of IIIF (The Project) Tudor Portrait Demonstrator - Charlotte Bolland will present a user perspective on the development of a IIIF demonstrator to facilitate image-led research into a significant dataset of Tudor portraits collated in collaboration with the Yale Center for British Art. IIIF Manifest builders - Tom Crane will present on the various ways IIIF Manifests are built, and what tools and libraries are available to help with this process. Most manifests are transformations of other data, but sometimes you want to build them by hand. User evaluation: Making use of IIIF resources - Melissa Terras will introduce plans for a user focused examination of IIIF, engaging with the wider research and IIIF communities to explore IIIF experiences for users from different backgrounds. Using existing IIIF resources to create your own IIIF presentations - Joe Padfield will present details of the Simple Site GitHub project and how it can be used by researchers to create their own IIIF workspace to explore, compare and present their own arrangement of existing IIIF resources. Session 2 Q&A The Practical Applications of IIIF is a Foundation project within the the AHRC funded Towards a National Collection Programme.
Particlelike solutions in modified gravity: the Higgs monopole
Creators: name: Schlogel, Sandrine
name: Rinaldi, Massimiliano
name: Staelens, Francois
name: Fuzfa, Andre
Publisher: name: arXiv
Year: 2014
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Higgs inflation has received a remarkable attention in the last few years due to its simplicity and predictive power. The key point of this model is the nonminimal coupling to gravity in unitary gauge. As such, this theory is in fact a scalar-tensor modification of gravity that needs to be studied also below the energy scales of inflation. Motivated by this goal, we study in great analytical and numerical detail the static and spherically symmetric solutions of the equations of motion in the presence of standard baryonic matter, called "Higgs monopoles" and presented in 1305.2640. These particlelike solutions may arise naturally in tensor-scalar gravity with mexican hat potential and are the only globally regular asymptotically flat solutions with finite classical energy. In the case when the parameters of the potential are taken to be the ones of the standard model, we find that the deviations from general relativity are extremely small, especially for bodies of astrophysical size and density. This allows to derive a simplified description of the monopole, for which the metric inside the spherical matter distribution can be approximated by the standard metric of general relativity. We study how the properties of these monopoles depend on the strength of the nonminimal coupling to gravity and on the baryonic mass and compactness. An important and original result is the existence of a mechanism of resonant amplification of the Higgs field inside the monopole that comes into play for large nonminimal coupling. We show that this mechanism might degenerate into divergences of the Higgs field that reveal the existence of forbidden combinations of radius and baryonic energy density.
description: 19 pages, 17 figures, version accepted by PRD
H2 superglass on an amorphous carbon substrate
Creators: name: Gordillo, M. C.
name: Boronat, J.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Other Condensed Matter (cond-mat.other)
subject: FOS: Physical sciences

description: The phase diagram of a para-H2 monolayer absorbed on a experimentally syntetized amorphous carbon sheet was calculated using a diffusion Monte Carlo technique. We found that the ground state of that system changed drastically from a perfectly flat substrate to a situation in which the carbon atoms were allowed a certain degree of disorder in the $z$ direction. In the first case, at zero pressure we have a glass of density 0.056 $\pm$ 0.003 Å$^{-2}$ in equilibrium with an incommensurate solid of 0.068 $\pm$ 0.002 Å$^{-2}$. At the equilibrium density, the glass was found to have a tiny, but non-negligible superfluid faction of less than 1 \% (0.44 $\pm$ 0.05 \%). In the $z$-disordered substrate, we observe a significant enhancement of the superfluid fraction in the glass phase as well as a smaller but not zero value in the incommensurate crystal.
Practical IIIF Webinar - Practical Applications of IIIF
Creators: name: Padfield, J.
name: Terras, M.
name: T. Crane
name: C. Bolland
name: A. Wilson
name: L. Carini
Publisher: name: Zenodo
Year: 2021
Subjects: IIIF
Towards a National Collection
Examples
Practical IIIF

description: Session 01 - Using IIIF resources for Research and Education Introduction and Welcome (J. Padfield) Explore the Raphael Cartoons at the V&A - Luca Carini will present this great new resource from the V&A highlighting how IIIF has allowed them to present these wonderful Raphael cartoons to the general public and a research audience. Embedding IIIF resources into teaching and course work at The University of St. Andrews - Andrew Wilson will present their work with Exhibit.so and how this flexible IIIF based tool has allowed them to provide rich interactive teaching resources during the Covid-19 pandemic. Re-using IIIF resources in documentation solutions - Joe Padfield will present details of how IIIF has been used as the basis for the National Gallery’s internal image sharing and presentation system and how these resources have been re-used to create a digital documentation system to record the delicate process of sampling old master paintings. Session 1 Q&A Session 02 - Practical applications of IIIF (The Project) Tudor Portrait Demonstrator - Charlotte Bolland will present a user perspective on the development of a IIIF demonstrator to facilitate image-led research into a significant dataset of Tudor portraits collated in collaboration with the Yale Center for British Art. IIIF Manifest builders - Tom Crane will present on the various ways IIIF Manifests are built, and what tools and libraries are available to help with this process. Most manifests are transformations of other data, but sometimes you want to build them by hand. User evaluation: Making use of IIIF resources - Melissa Terras will introduce plans for a user focused examination of IIIF, engaging with the wider research and IIIF communities to explore IIIF experiences for users from different backgrounds. Using existing IIIF resources to create your own IIIF presentations - Joe Padfield will present details of the Simple Site GitHub project and how it can be used by researchers to create their own IIIF workspace to explore, compare and present their own arrangement of existing IIIF resources. Session 2 Q&A This webinar was organised as part of the Practical applications of IIIF Foundation project within the the AHRC funded Towards a National Collection Programme.
Reproduction of Experimental Gap Structure in LiFeAs based on the Orbital-Spin Fluctuation Theory: $s_{++}$-wave, $s_\pm$-wave, and hole-$s_\pm$-wave states
Creators: name: Saito, Tetsuro
name: Onari, Seiichiro
name: Yamakawa, Youichi
name: Kontani, Hiroshi
name: Borisenko, Sergey V.
name: Zabolotnyy, Volodymyr B.
Publisher: name: arXiv
Year: 2014
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: The absence of nesting between electron and hole-pockets in LiFeAs with $T_c = 18$K attracts great attention, as an important hint to understand the pairing mechanism of Fe-based superconductors. Here, we study the five-orbital model of LiFeAs based on the recently-developed orbital-spin fluctuation theories. It is found that the experimentally observed gap structure of LiFeAs, which is a "fingerprint" of the pairing mechanism, is quantitatively reproduced in terms of the orbital-fluctuation-mediated $s_{++}$-wave state. Especially, the largest gap observed on the small two hole-pockets composed of ($d_{xz}, d_{yz}$) orbitals can be explained, and this is a hallmark of the orbital-fluctuation-mediated superconductivity. The $s_{++}$-wave gap structure becomes more anisotropic in the presence of weak spin fluctuations. As the spin fluctuations increase, we obtain the "hole-$s_\pm$-wave state", in which only the gap of the large hole-pocket made of $d_{xy}$-orbital is sign-reversed, due to the cooperation of orbital and spin fluctuations. %out of the five pockets. This gap structure with "sign-reversal between hole-pockets" is similar to that recently reported in (Ba,K)Fe$_2$As$_2$.
description: 11 pages, 10 figures, figures and explanations have been revised, to be published in Phys. Rev. B