cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Tilt-induced polar order and topological defects in growing bacterial populations
Creators: name: Shimaya, Takuro
name: Takeuchi, Kazumasa A.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Biological Physics (physics.bio-ph)
subject: Cell Behavior (q-bio.CB)
subject: FOS: Physical sciences
subject: FOS: Biological sciences

description: Rod-shaped bacteria, such as Escherichia coli, commonly live forming mounded colonies. They initially grow two-dimensionally on a surface and finally achieve three-dimensional growth. While it was recently reported that three-dimensional growth is promoted by topological defects of winding number $+1/2$ in populations of motile bacteria, how cellular alignment plays a role in non-motile cases is largely unknown. Here, we investigate the relevance of topological defects in colony formation processes of non-motile E. coli populations, and found that both $\pm 1/2$ topological defects contribute to the three-dimensional growth. Analyzing the cell flow in the bottom layer of the colony, we observe that $+1/2$ defects attract cells and $-1/2$ defects repel cells, in agreement with previous studies on motile cells, in the initial stage of the colony growth. However, later, cells gradually flow toward $-1/2$ defects as well, exhibiting a sharp contrast to the existing knowledge. By investigating three-dimensional cell orientations by confocal microscopy, we find strong vertical tilting of cells near the defects. Crucially, this leads to the emergence of a polar order in the otherwise nematic two-dimensional cell orientation. We extend the theory of active nematics by incorporating this polar order and the vertical tilting, which successfully explains the influx toward $-1/2$ defects in terms of a polarity-induced force. Our work reveals that three-dimensional cell orientations may result in drastic changes in properties of active nematics, especially those of topological defects, which may be generically relevant in active matter systems driven by cellular growth instead of self-propulsion.
description: 13+13 pages, 4+10 figures
Principal modes in multimode fibers: exploring the crossover from weak to strong mode coupling
Creators: name: Xiong, Wen
name: Ambichl, Philipp
name: Bromberg, Yaron
name: Redding, Brandon
name: Rotter, Stefan
name: Cao, Hui
Publisher: name: arXiv
Year: 2016
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: We present experimental and numerical studies on principal modes in a multimode fiber with mode coupling. By applying external stress to the fiber and gradually adjusting the stress, we have realized a transition from weak to strong mode coupling, which corresponds to the transition from single scattering to multiple scattering in mode space. Our experiments show that principal modes have distinct spatial and spectral characteristic in the weak and strong mode coupling regimes. We also investigate the bandwidth of the principal modes, in particular, the dependence of the bandwidth on the delay time, and the effects of the mode-dependent loss. By analyzing the path-length distributions, we discover two distinct mechanisms that are responsible for the bandwidth of principal modes in weak and strong mode coupling regimes. Taking into account the mode-dependent loss in the fiber, our numerical results are in good agreement with our experimental observations. Our study paves the way for exploring potential applications of principal modes in communication, imaging and spectroscopy.
The temporally evolving energy and waiting time statistics of two repeating fast radio bursts
Creators: name: Sang, Yu
name: Lin, Hai-Nan
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Based on two very large samples of repeating fast radio bursts (FRBs), i.e. FRB 20121102A and FRB 20201124A observed by the FAST telescope, we study the statistical properties of energy and waiting time. The bent power-law (BPL) model, thresholded power-law (TPL) model and Band function are used to fit the distribution of energy, and the BPL model and exponential (EXP) model are used to fit the distribution of waiting time. It is found that no single model can fit the distribution of energy or waiting time well in the full range. To investigate the possible temporal evolution, we divide the full samples into several subsamples according to the observing sessions. We find that the distribution of energy for all subsamples can be well fitted by both BPL model and TPL model, while the distribution of waiting time for all subsamples can be well fitted by both BPL model and EXP model. Importantly, for the distribution of energy, the BPL index $β$ of all the subsamples is almost invariant, but the median value parameter $x_b$ varies significantly. Similar situation happens in the distribution of waiting time. Furthermore, for the distribution of waiting time, the occurrence rate parameter $λ$ in EXP model varies significantly. These features show that there may be a common emission mechanism for repeating FRBs, but the burst energy and occurrence rate are temporally evolving.
description: 12 pages, 8 figures, 4 tables; accepted for publication in Monthly Notices of the Royal Astronomical Society
The effect of the ambient solar wind medium on a CME-driven shock and the associated gradual solar energetic particle event
Creators: name: Wijsen, Nicolas
name: Lario, David
name: Sánchez-Cano, Beatriz
name: Jebaraj, Immanuel C.
name: Dresing, Nina
name: Richardson, Ian G.
name: Aran, Angels
name: Kouloumvakos, Athanasios
name: Ding, Zheyi
name: Niemela, Antonio
name: Palmerio, Erika
name: Carcaboso, Fernando
name: Vainio, Rami
name: Afanasiev, Alexandr
name: Pinto, Marco
name: Pacheco, Daniel
name: Poedts, Stefaan
name: Heyner, Daniel
Publisher: name: arXiv
Year: 2023
Subjects: subject: Space Physics (physics.space-ph)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We present simulation results of a gradual solar energetic particle (SEP) event detected on 2021 October 9 by multiple spacecraft, including BepiColombo (Bepi) and near-Earth spacecraft such as the Advanced Composition Explorer (ACE). A peculiarity of this event is that the presence of a high speed stream (HSS) affected the low-energy ion component ($\lesssim 5$ MeV) of the gradual SEP event at both Bepi and ACE, despite the HSS having only a modest solar wind speed increase. Using the EUHFORIA (European Heliospheric FORecasting Information Asset) magnetohydrodynamic model, we replicate the solar wind during the event and the coronal mass ejection (CME) that generated it. We then combine these results with the energetic particle transport model PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration). We find that the structure of the CME-driven shock was affected by the non-uniform solar wind, especially near the HSS, resulting in a shock wavefront with strong variations in its properties such as its compression ratio and obliquity. By scaling the emission of energetic particles from the shock to the solar wind compression at the shock, an excellent match between the PARADISE simulation and in-situ measurements of $\lesssim 5$ MeV ions is obtained. Our modelling shows that the intricate intensity variations observed at both ACE and Bepi were influenced by the non-uniform emission of energetic particles from the deformed shock wave and demonstrates the influence of even modest background solar wind structures on the development of SEP events.
description: 13 pages, 7 figures, accepted for publication in The Astrophysical Journal
Morphology effects on spin-dependent transport and recombination in polyfluorene thin films
Creators: name: Miller, Richards
name: van Schooten, K. J.
name: Malissa, H.
name: Joshi, G.
name: Jamali, S.
name: Lupton, J. M.
name: Boehme, C.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We have studied the role of spin-dependent processes on conductivity in polyfluorene (PFO) thin films by conducting continuous wave (c.w.) electrically detected magnetic resonance (EDMR) spectroscopy at temperatures between 10 K and 293 K using microwave frequencies between about 100 MHz and 20 GHz as well as pulsed EDMR at X-band. Variable frequency EDMR allows us to establish the role of spin-orbit coupling in spin-dependent processes, pulsed EDMR probes coherent spin motion effects. We used PFO for this study in order to allow for the investigation of the effects of microscopic morphological ordering since this material can adopt two distinct intrachain morphologies: an amorphous (glassy) phase, and an ordered (beta) phase. In thin films of organic light-emitting diodes (OLEDs) the appearance of a particular phase can be controlled by deposition parameters, and is verified by electroluminescence spectroscopy. We conducted multi-frequency c.w. EDMR, electrically detected Rabi spinbeat experiments, Hahn-echo and inversion-recovery measurements. Coherent echo spectroscopy reveals electrically detected electron spin-echo envelope modulation (ESEEM) due to the precession of the carrier spins around the protons. Our results demonstrate that while conformational disorder can influence the observed EDMR signals, including the sign of the current changes on resonance as well as the magnitudes of local hyperfine fields and charge carrier spin-orbit interactions, it does not qualitatively affect the nature of spin-dependent transitions in this material. At 293 K and 10 K, polaron-pair recombination through weakly spin-spin coupled intermediate charge carrier pair states is dominant, while at low temperatures, additional signatures of spin-dependent charge transport through the interaction of polarons with triplet excitons are seen in the half-field resonance of a triplet spin-1 species.
description: 27 pages, 2 tables, 11 figures, full abstract in article
One-Port Direct/Reverse Method for Characterizing VNA Calibration Standards
Creators: name: Monsalve, Raul A.
name: Rogers, Alan E. E.
name: Mozdzen, Thomas J.
name: Bowman, Judd D.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: This paper introduces a one-port method for estimating model parameters of VNA calibration standards. The method involves measuring the standards through an asymmetrical passive network connected in direct mode and then in reverse mode, and using these measurements to compute the S-parameters of the network. The free parameters of the calibration standards are estimated by minimizing a figure of merit based on the expected equality of the S-parameters of the network when used in direct and reverse modes. The capabilities of the method are demonstrated through simulations, and real measurements are used to estimate the actual offset delay of a 50-$\mathbfΩ$ calibration load that is assigned zero delay by the manufacturer. The estimated delay is $38.8$ ps with a $1σ$ uncertainty of $2.1$ ps for this particular load. This result is verified through measurements of a terminated airline. The measurements agree better with theoretical models of the airline when the reference plane is calibrated using the new estimate for the load delay.
description: 9 pages, 8 figures, 2 tables. Accepted to IEEE Transactions on Microwave Theory and Techniques
Heide Göttner-Abendroth: Matriarchat in Südchina. Eine Forschungsreise zu den Mosuo
Creators: name: Knödel, Susanne
Publisher: name: ASIEN: The German Journal on Contemporary Asia
Year: 2022

description: ASIEN: The German Journal on Contemporary Asia, Nr. 77 (2000): ASIEN (Oktober)
Yukawa coupling unification in non-supersymmetric SO(10) models with an intermediate scale
Creators: name: Djouadi, Abdelhak
name: Ouyang, Ruiwen
name: Raidal, Martti
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We discuss the possibility of unifying in a simple and economical manner the Yukawa couplings of third generation fermions in a non-supersymmetric SO(10) model with an intermediate symmetry breaking, focusing on two possible patterns with intermediate Pati-Salam and minimal left-right groups. assume a minimal Yukawa sector at high energy, starting with two Higgs bi-doublets at the intermediate scale which then simply reduce to a two Higgs doublet model at the electroweak scale. We first enforce gauge coupling unification at the two-loop level by including the threshold corrections in the renormalisation group running which are generated by the heavy fields that appear at the intermediate symmetry breaking scale. We then study the running of the Yukawa couplings of the top quark, bottom quark and tau lepton at two-loops in these two breaking schemes, when the appropriate matching conditions are imposed. We find that the unification of the third family Yukawa couplings can be achieved while retaining a viable spectrum, provided that the ratio of the vacuum expectation values of the two Higgs doublet fields is large, $\tanβ\approx 60$.
description: 14 pages, 3 figures, published version, comments are welcome
Hyper-parallel Toffoli gate on three-photon system with two degrees of freedom assisted by single-sided optical microcavities
Creators: name: Wei, Hai-Rui
name: Deng, Fu-Guo
name: Long, Gui Lu
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Encoding qubits in multiple degrees of freedom (DOFs) of a quantum system allows less-decoherence quantum information processing with much less quantum resources. We present a compact and scalable quantum circuit to determinately implement a hyper-parallel controlled-controlled-phase-flip (hyper-$\rm{C^2PF}$) gate on a three-photon system in both the polarization and spatial DOFs. In contrast with the one with many qubits encoding in one DOF only, our hyper-$\rm{C^2PF}$ gate operating two independent $\rm{C^2PF}$ gates on a three-photon system with less decoherence, and reduces the quantum resources required in quantum information processing by a half. Additional photons, necessary for many approaches, are not required in the present scheme. Our calculation shows that this hyper-$\rm{C^2PF}$ gate is feasible in experiment.
description: 13 page, 3 figures
Observational Signatures of Circumbinary Discs I: Kinematics
Creators: name: Calcino, Josh
name: Price, Daniel J.
name: Pinte, Christophe
name: Garg, Himanshi
name: Norfolk, Brodie J.
name: Christiaens, Valentin
name: Li, Hui
name: Teague, Richard
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: We present five morphological and kinematic criteria to aid in asserting the binary nature of a protoplanetary disc, based on 3D hydrodynamical simulations of circumbinary discs post-processed with Monte Carlo radiative transfer. We find that circumbinary discs may be identified by i) a central cavity, ii) spiral arms both in and outside of their central cavities, iii) non-localised perturbations in their iso-velocity curves, iv) asymmetry between the lines of maximum speed of the blue and red-shifted wings and v) asymmetry between the area of the blue and red-shifted wings. We provide quantitative metrics for the last two criteria that can be used, in conjunction with the morphological criteria, to signal whether a protoplanetary disc is likely to be a circumbinary disc.
description: 26 pages, 26 figures, accepted to MNRAS
VERTICO VI: Cold-gas asymmetries in Virgo cluster galaxies
Creators: name: Roberts, Ian D.
name: Brown, Toby
name: Zabel, Nikki
name: Wilson, Christine D.
name: Chung, Aeree
name: Parker, Laura C.
name: Bisaria, Dhruv
name: Boselli, Alessandro
name: Catinella, Barbara
name: Chown, Ryan
name: Cortese, Luca
name: Davis, Timothy A.
name: Ellison, Sara
name: Jimenez-Donaire, Maria Jesus
name: Lee, Bumhyun
name: Smith, Rory
name: Spekkens, Kristine
name: Stevens, Adam R. H.
name: Thorp, Mallory
name: Villanueva, Vincente
name: Watts, Adam B.
name: Welker, Charlotte
name: Yoon, Hyein
Publisher: name: arXiv
Year: 2023
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We analyze cold-gas distributions in Virgo cluster galaxies using resolved CO(2-1) (tracing molecular hydrogen, H2) and HI observations from the Virgo Environment Traced In CO (VERTICO) and the VLA Imaging of Virgo in Atomic Gas (VIVA) surveys. From a theoretical perspective, it is expected that environmental processes in clusters will have a stronger influence on diffuse atomic gas compared to the relatively dense molecular gas component, and that these environmental perturbations can compress the cold interstellar medium in cluster galaxies leading to elevated star formation. In this work we observationally test these predictions for star-forming satellite galaxies within the Virgo cluster. We divide our Virgo galaxy sample into HI-normal, HI-tailed, and HI-truncated classes and show, unsurprisingly, that the HI-tailed galaxies have the largest quantitative HI asymmetries. We also compare to a control sample of non-cluster galaxies and find that Virgo galaxies, on average, have HI asymmetries that are 40 +/- 10 per cent larger than the control. There is less separation between control, HI-normal, HI-tailed, and HI-truncated galaxies in terms of H2 asymmetries, and on average, Virgo galaxies have H2 asymmetries that are only marginally (20 +/- 10 per cent) larger than the control sample. We find a weak correlation between HI and H2 asymmetries over our entire sample, but a stronger correlation for those specific galaxies being strongly impacted by environmental perturbations. Finally, we divide the discs of the HI-tailed Virgo galaxies into a leading half and trailing half according to the observed tail direction. We find evidence for excess molecular gas mass on the leading halves of the disc. This excess molecular gas on the leading half is accompanied by an excess in star formation rate such that the depletion time is, on average, unchanged.
description: 15 pages, 8 figures, 1 table, accepted for publication in A&A
Gravity models of networks: integrating maximum-entropy and econometric approaches
Creators: name: Di Vece, Marzio
name: Garlaschelli, Diego
name: Squartini, Tiziano
Publisher: name: arXiv
Year: 2021
Subjects: subject: Physics and Society (physics.soc-ph)
subject: Econometrics (econ.EM)
subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: FOS: Physical sciences
subject: FOS: Economics and business

description: The World Trade Web (WTW) is the network of international trade relationships among world countries. Characterizing both the local link weights (observed trade volumes) and the global network structure (large-scale topology) of the WTW via a single model is still an open issue. While the traditional Gravity Model (GM) successfully replicates the observed trade volumes by employing macroeconomic properties such as GDP and geographic distance, it, unfortunately, predicts a fully connected network, thus returning a completely unrealistic topology of the WTW. To overcome this problem, two different classes of models have been introduced in econometrics and statistical physics. Econometric approaches interpret the traditional GM as the expected value of a probability distribution that can be chosen arbitrarily and tested against alternative distributions. Statistical physics approaches construct maximum-entropy probability distributions of (weighted) graphs from a chosen set of measurable structural constraints and test distributions resulting from different constraints. Here we compare and integrate the two approaches by considering a class of maximum-entropy models that can incorporate macroeconomic properties used in standard econometric models. We find that the integrated approach achieves a better performance than the purely econometric one. These results suggest that the maximum-entropy construction can serve as a viable econometric framework wherein extensive and intensive margins can be separately controlled for, by combining topological constraints and dyadic macroeconomic variables.
description: 22 pages, 5 figures, 4 tables
Lionel Salmen, Kambodscha und die UNO: Der Krieg und seine Eingrenzung von 1978 bis 1993
Creators: name: Grabowsky, Volker
Publisher: name: ASIEN: The German Journal on Contemporary Asia
Year: 2022

description: ASIEN: The German Journal on Contemporary Asia, Nr. 77 (2000): ASIEN (Oktober)
Keck/KPIC Emission Spectroscopy of WASP-33b
Creators: name: Finnerty, Luke
name: Schofield, Tobias
name: Sappey, Ben
name: Xuan, Jerry W.
name: Ruffio, Jean-Baptiste
name: Wang, Jason J.
name: Delorme, Jacques-Robert
name: Blake, Geoffrey A.
name: Buzard, Cam
name: Fitzgerald, Michael P.
name: Baker, Ashley
name: Bartos, Randall
name: Bond, Charlotte Z.
name: Calvin, Benjamin
name: Cetre, Sylvain
name: Doppmann, Greg
name: Echeverri, Daniel
name: Jovanovic, Nemanja
name: Liberman, Joshua
name: Lopez, Ronald A.
name: Martin, Emily C.
name: Mawet, Dimitri
name: Morris, Evan
name: Pezzato, Jacklyn
name: Phillips, Caprice L.
name: Ragland, Sam
name: Skemer, Andrew
name: Venenciano, Taylor
name: Wallace, J. Kent
name: Wallack, Nicole L.
name: Wang, Ji
name: Wizinowich, Peter
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: We present Keck/KPIC high-resolution ($R\sim35,000$) $K$-band thermal emission spectroscopy of the ultra-hot Jupiter WASP-33b. The use of KPIC's single-mode fibers greatly improves both blaze and line-spread stabilities relative to slit spectrographs, enhancing the cross-correlation detection strength. We retrieve the dayside emission spectrum with a nested sampling pipeline which fits for orbital parameters, the atmospheric pressure-temperature profile, and molecular abundances.We strongly detect the thermally-inverted dayside and measure mass-mixing ratios for CO ($\log\rm CO_{MMR} = -1.1^{+0.4}_{-0.6}$), H$_2$O ($\log\rm H_2O_{MMR} = -4.1^{+0.7}_{-0.9}$) and OH ($\log\rm OH_{MMR} = -2.1^{+0.5}_{-1.1}$), suggesting near-complete dayside photodissociation of H$_2$O. The retrieved abundances suggest a carbon- and possibly metal-enriched atmosphere, with a gas-phase C/O ratio of $0.8^{+0.1}_{-0.2}$, consistent with the accretion of high-metallicity gas near the CO$_2$ snow line and post-disk migration or with accretion between the soot and H$_2$O snow lines. We also find tentative evidence for $\rm ^{12}CO/^{13}CO \sim 50$, consistent with values expected in protoplanetary disks, as well as tentative evidence for a metal-enriched atmosphere (2--15$\times$ solar). These observations demonstrate KPIC's ability to characterize close-in planets and the utility of KPIC's improved instrumental stability for cross-correlation techniques.
description: Accepted in AJ, 26 pages, 12 figures
TA2N: Two-Stage Action Alignment Network for Few-shot Action Recognition
Creators: name: Li, Shuyuan
name: Liu, Huabin
name: Qian, Rui
name: Li, Yuxi
name: See, John
name: Fei, Mengjuan
name: Yu, Xiaoyuan
name: Lin, Weiyao
Publisher: name: arXiv
Year: 2021
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: Few-shot action recognition aims to recognize novel action classes (query) using just a few samples (support). The majority of current approaches follow the metric learning paradigm, which learns to compare the similarity between videos. Recently, it has been observed that directly measuring this similarity is not ideal since different action instances may show distinctive temporal distribution, resulting in severe misalignment issues across query and support videos. In this paper, we arrest this problem from two distinct aspects -- action duration misalignment and action evolution misalignment. We address them sequentially through a Two-stage Action Alignment Network (TA2N). The first stage locates the action by learning a temporal affine transform, which warps each video feature to its action duration while dismissing the action-irrelevant feature (e.g. background). Next, the second stage coordinates query feature to match the spatial-temporal action evolution of support by performing temporally rearrange and spatially offset prediction. Extensive experiments on benchmark datasets show the potential of the proposed method in achieving state-of-the-art performance for few-shot action recognition.The code of this project can be found at https://github.com/R00Kie-Liu/TA2N
description: Published in AAAI 2022
Two-Dimensional Melting of two- and three-component mixtures
Creators: name: Li, Yan-Wei
name: Yao, Yugui
name: Ciamarra, Massimo Pica
Publisher: name: arXiv
Year: 2023
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: We elucidate the interplay between diverse two-dimensional melting pathways and establish solid/hexatic and hexatic/liquid transition criteria via the numerical simulations of the melting transition of two- and three-component mixtures of hard polygons and disks. We show that a mixture's melting pathway may differ from its components and demonstrate eutectic mixtures that crystallize at a higher density than their pure components. Comparing the melting scenario of many two- and three-component mixtures, we establish universal melting criteria: the solid and hexatic phases become unstable as the density of topological defects respectively overcomes $ρ_{d,{\rm s}} \simeq 0.046$ and $ρ_{d,{\rm h}}\simeq 0.123$.
description: Phys. Rev. Lett, in press
Ernst Giese, Gundula Bahro und Dirk Betke: Umweltzerstörungen in Trockengebieten Zentralasiens (West- und Ost-Turkestan). Ursachen, Auswirkungen, Maßnahmen
Creators: name: Hoffmann, Thomas
Publisher: name: ASIEN: The German Journal on Contemporary Asia
Year: 2022

description: ASIEN: The German Journal on Contemporary Asia, Nr. 77 (2000): ASIEN (Oktober)
An Energy-Efficient Generic Accuracy Configurable Multiplier Based on Block-Level Voltage Overscaling
Creators: name: Bahoo, Ali Akbar
name: Akbari, Omid
name: Shafique, Muhammad
Publisher: name: arXiv
Year: 2023
Subjects: subject: Hardware Architecture (cs.AR)
subject: FOS: Computer and information sciences

description: Voltage Overscaling (VOS) is one of the well-known techniques to increase the energy efficiency of arithmetic units. Also, it can provide significant lifetime improvements, while still meeting the accuracy requirements of inherently error-resilient applications. This paper proposes a generic accuracy-configurable multiplier that employs the VOS at a coarse-grained level (block-level) to reduce the control logic required for applying VOS and its associated overheads, thus enabling a high degree of trade-off between energy consumption and output quality. The proposed configurable Block-Level VOS-based (BL-VOS) multiplier relies on employing VOS in a multiplier composed of smaller blocks, where applying VOS in different blocks results in structures with various output accuracy levels. To evaluate the proposed concept, we implement 8-bit and 16-bit BL-VOS multipliers with various blocks width in a 15-nm FinFET technology. The results show that the proposed multiplier achieves up to 15% lower energy consumption and up to 21% higher output accuracy compared to the state-of-the-art VOS-based multipliers. Also, the effects of Process Variation (PV) and Bias Temperature Instability (BTI) induced delay on the proposed multiplier are investigated. Finally, the effectiveness of the proposed multiplier is studied for two different image processing applications, in terms of quality and energy efficiency.
description: This paper has been published in IEEE Transactions on Emerging Topics in Computing
X-Rel: Energy-Efficient and Low-Overhead Approximate Reliability Framework for Error-Tolerant Applications Deployed in Critical Systems
Creators: name: Vafaei, Jafar
name: Akbari, Omid
name: Shafique, Muhammad
name: Hochberger, Christian
Publisher: name: arXiv
Year: 2023
Subjects: subject: Hardware Architecture (cs.AR)
subject: FOS: Computer and information sciences

description: Triple Modular Redundancy (TMR) is one of the most common techniques in fault-tolerant systems, in which the output is determined by a majority voter. However, the design diversity of replicated modules and/or soft errors that are more likely to happen in the nanoscale era may affect the majority voting scheme. Besides, the significant overheads of the TMR scheme may limit its usage in energy consumption and area-constrained critical systems. However, for most inherently error-resilient applications such as image processing and vision deployed in critical systems (like autonomous vehicles and robotics), achieving a given level of reliability has more priority than precise results. Therefore, these applications can benefit from the approximate computing paradigm to achieve higher energy efficiency and a lower area. This paper proposes an energy-efficient approximate reliability (X-Rel) framework to overcome the aforementioned challenges of the TMR systems and get the full potential of approximate computing without sacrificing the desired reliability constraint and output quality. The X-Rel framework relies on relaxing the precision of the voter based on a systematical error bounding method that leverages user-defined quality and reliability constraints. Afterward, the size of the achieved voter is used to approximate the TMR modules such that the overall area and energy consumption are minimized. The effectiveness of employing the proposed X-Rel technique in a TMR structure, for different quality constraints as well as with various reliability bounds are evaluated in a 15-nm FinFET technology. The results of the X-Rel voter show delay, area, and energy consumption reductions of up to 86%, 87%, and 98%, respectively, when compared to those of the state-of-the-art approximate TMR voters.
description: This paper has been published in IEEE Transactions on Very Large Scale Integration (VLSI) Systems
The star in RNO 54 -- a post-FUor with short faint jet?
Creators: name: Magakian, T. Yu.
name: Movsessian, T. A.
name: Andreasyan, H. R.
name: Moiseev, A. V.
name: Uklein, R. I.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: The aim of the present study was the spectral analysis of an unusual pre-main-sequence star in the cometary nebula RNO 54, which was suspected by several researchers as a FUori-like object. We performed long-slit spectroscopy of the star on the 6-m telescope with the SCORPIO-2 multi-mode focal reducer. We discover a short ($\sim4$ arcsec or $\sim6000$ AU) and faint emission shock-excited jet from this star, probably oriented toward the long axis of the nebular ellipse. The spectral type of the star is estimated as G0-2 II; the split of absorption Li I line which is a typical sign indicating the FUori-like spectrum, is confirmed. The analysis of the available data shows virtual absence of the photometric variability, for at least the last 20 years. The lower limit of the bolometric luminosity of the star is estimated as 300 Lsun. Our study supports the classification of RNO 54 star as a FUor-like object in the long-after-outburst stage.
description: 4 pages, 4 figures
Magnetic fields of opposite polarity in sunspot penumbrae
Creators: name: Franz, M.
name: Collados, M.
name: Bethge, C.
name: Schlichenmaier, R.
name: Borrero, J. M.
name: Schmidt, W.
name: Lagg, A.
name: Solanki, S. K.
name: Berkefeld, T.
name: Kiess, C.
name: Rezaei, R.
name: Schmidt, D.
name: Sigwarth, M.
name: Soltau, D.
name: Volkmer, R.
name: von der Luhe, O.
name: Waldmann, T.
name: Orozco, D.
name: Yabar, A. Pastor
name: Denker, C.
name: Balthasar, H.
name: Staude, J.
name: Hofmann, A.
name: Strassmeier, K.
name: Feller, A.
name: Nicklas, H.
name: Kneer, F.
name: Sobotka, M.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Context. A significant part of the penumbral magnetic field returns below the surface in the very deep photosphere. For lines in the visible, a large portion of this return field can only be detected indirectly by studying its imprints on strongly asymmetric and three-lobed Stokes V profiles. Infrared lines probe a narrow layer in the very deep photosphere, providing the possibility of directly measuring the orientation of magnetic fields close to the solar surface. Aims. We study the topology of the penumbral magnetic field in the lower photosphere, focusing on regions where it returns below the surface. Methods. We analyzed 71 spectropolarimetric datasets from Hinode and from the GREGOR infrared spectrograph. We inferred the quality and polarimetric accuracy of the infrared data after applying several reduction steps. Techniques of spectral inversion and forward synthesis were used to test the detection algorithm. We compared the morphology and the fractional penumbral area covered by reversed-polarity and three-lobed Stokes V profiles for sunspots at disk center. We determined the amount of reversed-polarity and three-lobed Stokes V profiles in visible and infrared data of sunspots at various heliocentric angles. From the results, we computed center-to-limb variation curves, which were interpreted in the context of existing penumbral models. Results. Observations in visible and near-infrared spectral lines yield a significant difference in the penumbral area covered by magnetic fields of opposite polarity. In the infrared, the number of reversed-polarity Stokes V profiles is smaller by a factor of two than in the visible. For three-lobed Stokes V profiles the numbers differ by up to an order of magnitude.
description: 11 pages 10 figures plus appendix (2 pages 3 figures). Accepted as part of the A&A special issue on the GREGOR solar telescope
Nature of Striation in 21 cm Channel Maps: Velocity Caustics
Creators: name: Hu, Yue
name: Lazarian, A.
name: Alina, D.
name: Pogosyan, D.
name: Ho, Ka Wai
Publisher: name: arXiv
Year: 2023
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: The alignment of striated intensity structures in thin neutral hydrogen (HI) spectroscopic channels with Galactic magnetic fields has been observed. However, the origin and nature of these striations are still debatable. Some studies suggest that the striations result solely from real cold-density filaments without considering the role of turbulent velocity fields, i.e., the velocity caustics effect in shaping the channel's intensity distribution. To determine the relative contribution of density and velocity in forming the striations in channel maps, we analyze synthetic observations of channel maps obtained with simulations that represent realistic magnetized multi-phase HI. We vary the thickness of the channel maps and apply the Velocity Decomposition Algorithm to separate the velocity and density contributions. In parallel, we analyze GALFA HI observations and compare the results. Our analysis shows that the thin channels are dominated by velocity contribution, and velocity caustics mainly generate the HI striations. We show that velocity caustics can cause a correlation between unsharp-masked HI structures and far-infrared emission. We demonstrate that the linear HI fibers revealed by the Rolling Hough Transform (RHT) in thin velocity channels originate from velocity caustics. As the thickness of channel maps increases, the relative contribution of density to fluctuations in channel maps also increases. As a result, more RHT-detected fibers tend to be perpendicular to the magnetic field. Conversely, the alignment with the magnetic field is the most prominent in thin channels. We conclude that similar to the Velocity Channel Gradients (VChGs) approach, RHT traces magnetic fields through the analysis of velocity caustics in thin channel maps.
description: 26 pages, 18 figures, accepted for publication in MNRAS
Multiple quantum phase transitions and superconductivity in Ce-based heavy fermions
Creators: name: Weng, Z. F.
name: Smidman, M.
name: Jiao, L.
name: Lu, X.
name: Yuan, H. Q.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Heavy fermions have served as prototype examples of strongly-correlated electron systems. The occurrence of unconventional superconductivity in close proximity to the electronic instabilities associated with various degrees of freedom points to an intricate relationship between superconductivity and other electronic states, which is unique but also shares some common features with high temperature superconductivity. The magnetic order in heavy fermion compounds can be continuously suppressed by tuning external parameters to a quantum critical point, and the role of quantum criticality in determining the properties of heavy fermion systems is an important unresolved issue. Here we review the recent progress of studies on Ce based heavy fermion superconductors, with an emphasis on the superconductivity emerging on the edge of magnetic and charge instabilities as well as the quantum phase transitions which occur by tuning different parameters, such as pressure, magnetic field and doping. We discuss systems where multiple quantum critical points occur and whether they can be classified in a unified manner, in particular in terms of the evolution of the Fermi surface topology.
description: To appear in Reports on Progress in Physics: Special issue on strongly correlated electron systems, 24 pages, 22 figures
Effective cosmic density field reconstruction with convolutional neural network
Creators: name: Chen, Xinyi
name: Zhu, Fangzhou
name: Gaines, Sasha
name: Padmanabhan, Nikhil
Publisher: name: arXiv
Year: 2023
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: We present a cosmic density field reconstruction method that augments the traditional reconstruction algorithms with a convolutional neural network (CNN). Following Shallue $\&$ Eisenstein (2022), the key component of our method is to use the $\textit{reconstructed}$ density field as the input to the neural network. We extend this previous work by exploring how the performance of these reconstruction ideas depends on the input reconstruction algorithm, the reconstruction parameters, and the shot noise of the density field, as well as the robustness of the method. We build an eight-layer CNN and train the network with reconstructed density fields computed from the Quijote suite of simulations. The reconstructed density fields are generated by both the standard algorithm and a new iterative algorithm. In real space at $z=0$, we find that the reconstructed field is $90\%$ correlated with the true initial density out to $k\sim 0.5 h{\rm Mpc}^{-1}$, a significant improvement over $k\sim 0.2 h{\rm Mpc}^{-1}$ achieved by the input reconstruction algorithms. We find similar improvements in redshift space, including an improved removal of redshift space distortions at small scales. We also find that the method is robust across changes in cosmology. Additionally, the CNN removes much of the variance from the choice of different reconstruction algorithms and reconstruction parameters. However, the effectiveness decreases with increasing shot noise, suggesting that such an approach is best suited to high density samples. This work highlights the additional information in the density field beyond linear scales as well as the power of complementing traditional analysis approaches with machine learning techniques.
description: 10 pages, 8 figures. Matches version accepted for publication in MNRAS
Sunspot Sizes and The Solar Cycle: Analysis Using Kodaikanal White-light Digitized Data
Creators: name: Mandal, Sudip
name: Banerjee, Dipankar
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Sizes of the sunspots vary in a wide range during the progression of a solar cycle. Long-term variation study of different sunspot sizes are key to better understand the underlying process of sunspot formation and their connection to the solar dynamo. Kodaikanal white-light digitized archive provides daily sunspot observations for a period of 90 years (1921-2011). Using different size criteria on the detected individual sunspots, we have generated yearly averaged sunspot area time series for the full Sun as well as for the individual hemispheres. In this paper, we have used the sunspot area values instead of sunspot numbers used in earlier studies. Analysis of these different time series show that different properties of the sunspot cycles depend on the sunspot sizes. The `odd-even rule', double peaks during the cycle maxima and the long-term periodicities in the area data are found to be present for specific sunspot sizes and are absent or not so prominent in other size ranges. Apart from that, we also find a range of periodicities in the asymmetry index which have a dependency on the sunspot sizes. These statistical differences in the different size ranges may indicate that a complex dynamo action is responsible for the generation and dynamics of sunspots with different sizes.
description: Accepted for publication in Astrophysical journal letters (ApJl)
Cohen-Macaulay Property of Feynman Integrals
Creators: name: Tellander, Felix
name: Helmer, Martin
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Mathematical Physics (math-ph)
subject: Algebraic Geometry (math.AG)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: The connection between Feynman integrals and GKZ $A$-hypergeometric systems has been a topic of recent interest with advances in mathematical techniques and computational tools opening new possibilities; in this paper we continue to explore this connection. To each such hypergeometric system there is an associated toric ideal, we prove that the latter has the Cohen-Macaulay property for two large families of Feynman integrals. This implies, for example, that both the number of independent solutions and dynamical singularities are independent of space-time dimension and generalized propagator powers. Furthermore, in particular, it means that the process of finding a series representation of these integrals is fully algorithmic.
description: Clarified some of the technical aspects of the paper and added an appendix by Uli Walther. Also fixed typos
In-situ enrichment in heavy elements of hot Jupiters
Creators: name: Morbidelli, A.
name: Batygin, K.
name: Lega, E.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: Context: Radius and mass measurements of short-period giant planets reveal that many of these planets contain a large amount of heavy elements, in sharp contrast with the expectations of the conventional core-accretion model for the origin of giant planets. Aims: The proposed explanations for the heavy-element enrichment of giant planets fall short of explaining the most enriched planets. We look for additional processes that can explain the full envelope of inferred enrichments. Methods: We revisit the dynamics of pebbles and dust in the vicinity of giant planets using analytic estimates. Although our results are derived in the framework of a viscous alpha-disk we also discuss the case of disks driven by angular momentum removal in magnetized winds. Results: When giant planets are far from the star, dust and pebbles are confined in a pressure bump at the outer edge of the planet-induced gap. Instead, when the planets reach the inner part of the disk (r << 2 au), dust penetrates the gap together with the gas. The dust/gas ratio can be enhanced by more than an order of magnitude if radial drift of dust is not impeded farther out by other barriers. Thus, hot planets undergoing runaway gas accretion can swallow a large amount of dust. Conclusions: Whereas the gas accreted by giant planets in the outer disk is very dust-poor, that accreted by hot planets can be extremely dust-rich. Thus, provided that a large fraction of the atmosphere of hot-Jupiters is accreted in situ, a large amount of dust can be accreted as well. We draw a distinction between this process and pebble accretion, which is ineffective at small stellocentric radii, even for super-Earths. Giant planets farther out in the disk are extremely effective barriers against the flow of pebbles and dust across their gap.
description: In press in Astronomy & Astrophysics
Autonomous estimation of high-dimensional Coulomb diamonds from sparse measurements
Creators: name: Chatterjee, Anasua
name: Ansaloni, Fabio
name: Rasmussen, Torbjørn
name: Brovang, Bertram
name: Fedele, Federico
name: Bohuslavskyi, Heorhii
name: Krause, Oswin
name: Kuemmeth, Ferdinand
Publisher: name: arXiv
Year: 2021
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Quantum dot arrays possess ground states governed by Coulomb energies, utilized prominently by singly occupied quantum dots, each implementing a spin qubit. For such quantum processors, the controlled transitions between ground states are of operational significance, as these allow the control of quantum information within the array such as qubit initialization and entangling gates. For few-dot arrays, ground states are traditionally mapped out by performing dense raster-scan measurements in control-voltage space. These become impractical for larger arrays due to the large number of measurements needed to sample the high-dimensional gate-voltage hypercube and the comparatively little information extracted. We develop a hardware-triggered detection method based on reflectometry, to acquire measurements directly corresponding to transitions between ground states. These measurements are distributed sparsely within the high-dimensional voltage space by executing line searches proposed by a learning algorithm. Our autonomous software-hardware algorithm accurately estimates the polytope of Coulomb blockade boundaries, experimentally demonstrated in a 2$\times$2 array of silicon quantum dots.
description: 10 pages, 4 figures