cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Restriction on the form of quark anomalous magnetic moment from lattice QCD results
Creators: name: Kawaguchi, Mamiya
name: Huang, Mei
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Lattice (hep-lat)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: The quark anomalous magnetic moment (AMM) is dynamically generated through the spontaneous chiral symmetry breaking. It has been revealed that even though its exact form is still unknown, the quark AMM is essential to explore quark matter properties and QCD phase structure under external magnetic fields. In this study, we take three different forms of the quark AMM and investigate its influence on the chiral phase transition under magnetic field. In general, a negative quark AMM plays the role as magnetic catalyzer and a positive quark AMM plays the role of magnetic inhibition. It is found that a constant quark AMM drives an unexpected 1st order chiral phase transition; a quark AMM proportional to the chiral condensate gives a flip of the sign on the chiral condensate; and a quark AMM proportional to the square of chiral condensate can produce results of chiral condensate as functions of the temperature and the magnetic field in good agreement with the lattice result.
description: 14 pages, 13 figures
Experimentally realized in situ backpropagation for deep learning in nanophotonic neural networks
Creators: name: Pai, Sunil
name: Sun, Zhanghao
name: Hughes, Tyler W.
name: Park, Taewon
name: Bartlett, Ben
name: Williamson, Ian A. D.
name: Minkov, Momchil
name: Milanizadeh, Maziyar
name: Abebe, Nathnael
name: Morichetti, Francesco
name: Melloni, Andrea
name: Fan, Shanhui
name: Solgaard, Olav
name: Miller, David A. B.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Emerging Technologies (cs.ET)
subject: Machine Learning (cs.LG)
subject: Optics (physics.optics)
subject: FOS: Computer and information sciences
subject: FOS: Physical sciences

description: Neural networks are widely deployed models across many scientific disciplines and commercial endeavors ranging from edge computing and sensing to large-scale signal processing in data centers. The most efficient and well-entrenched method to train such networks is backpropagation, or reverse-mode automatic differentiation. To counter an exponentially increasing energy budget in the artificial intelligence sector, there has been recent interest in analog implementations of neural networks, specifically nanophotonic neural networks for which no analog backpropagation demonstration exists. We design mass-manufacturable silicon photonic neural networks that alternately cascade our custom designed "photonic mesh" accelerator with digitally implemented nonlinearities. These reconfigurable photonic meshes program computationally intensive arbitrary matrix multiplication by setting physical voltages that tune the interference of optically encoded input data propagating through integrated Mach-Zehnder interferometer networks. Here, using our packaged photonic chip, we demonstrate in situ backpropagation for the first time to solve classification tasks and evaluate a new protocol to keep the entire gradient measurement and update of physical device voltages in the analog domain, improving on past theoretical proposals. Our method is made possible by introducing three changes to typical photonic meshes: (1) measurements at optical "grating tap" monitors, (2) bidirectional optical signal propagation automated by fiber switch, and (3) universal generation and readout of optical amplitude and phase. After training, our classification achieves accuracies similar to digital equivalents even in presence of systematic error. Our findings suggest a new training paradigm for photonics-accelerated artificial intelligence based entirely on a physical analog of the popular backpropagation technique.
description: 23 pages, 10 figures
Codes for: A High-Eigenfrequency Differential Stiffness Probe for High-Speed Scanning Probe Microscopy
Creators: name: Dey, Somnath
Publisher: name: Zenodo
Year: 2023

description: The codes and data are used to produce the figures in Dey et al. (2023). These codes were written by Dr. S. Dey.
Emergent mechanical control of vascular morphogenesis.
Creators: name: Whisler, Jordan
name: Shahreza, Somayeh
name: Schlegelmilch, Karin
name: Ege, Nil
name: Javanmardi, Yousef
name: Malandrino, Andrea
name: Agrawal, Ayushi
name: Fantin, Alessandro
name: Serwinski, Bianca
name: Azizgolshani, Hesham
name: Park, Clara
name: Shone, Victoria
name: Demuren, Olukunle O
name: Del Rosario, Amanda
name: Butty, Vincent L
name: Holroyd, Natalie
name: Domart, Marie-Charlotte
name: Hooper, Steven
name: Szita, Nicolas
name: Boyer, Laurie A
name: Walker-Samuel, Simon
name: Djordjevic, Boris
name: Sheridan, Graham K
name: Collinson, Lucy
name: Calvo, Fernando
name: Ruhrberg, Christiana
name: Sahai, Erik
name: Kamm, Roger
name: Moeendarbary, Emad
Publisher: name: The Francis Crick Institute
Year: 2023
Subjects: Model organisms
Imaging
Tumour Biology
Human Biology & Physiology
Cell Biology

description: Vascularization is driven by morphogen signals and mechanical cues that coordinately regulate cellular force generation, migration, and shape change to sculpt the developing vascular network. However, it remains unclear whether developing vasculature actively regulates its own mechanical properties to achieve effective vascularization. We engineered tissue constructs containing endothelial cells and fibroblasts to investigate the mechanics of vascularization. Tissue stiffness increases during vascular morphogenesis resulting from emergent interactions between endothelial cells, fibroblasts, and ECM and correlates with enhanced vascular function. Contractile cellular forces are key to emergent tissue stiffening and synergize with ECM mechanical properties to modulate the mechanics of vascularization. Emergent tissue stiffening and vascular function rely on mechanotransduction signaling within fibroblasts, mediated by YAP1. Mouse embryos lacking YAP1 in fibroblasts exhibit both reduced tissue stiffness and develop lethal vascular defects. Translating our findings through biology-inspired vascular tissue engineering approaches will have substantial implications in regenerative medicine.
An implicit, conservative and asymptotic-preserving electrostatic particle-in-cell algorithm for arbitrarily magnetized plasmas in uniform magnetic fields
Creators: name: Chen, Guangye
name: Chacón, Luis
Publisher: name: arXiv
Year: 2022
Subjects: subject: Computational Physics (physics.comp-ph)
subject: Plasma Physics (physics.plasm-ph)
subject: FOS: Physical sciences

description: We introduce a new electrostatic particle-in-cell algorithm capable of using large timesteps compared to particle gyro-period under a uniform external magnetic field. The algorithm extends earlier electrostatic fully implicit PIC implementations with a new asymptotic-preserving particle-push scheme that allows timesteps much larger than particle gyroperiods. In the large-timestep limit, the integrator preserves all particle drifts, while recovering the full orbit for small timesteps. The scheme allows for a seamless, efficient treatment of particles with coexisting magnetized and unmagnetized species, and conserves energy and charge exactly without spoiling implicit solver performance. We demonstrate by numerical experiment with several problems of variable species magnetization (diocotron instability, modified two-stream instability, and drift instability) that orders of magnitude wall-clock-time speedups vs. the standard fully implicit electrostatic PIC algorithm are possible without sacrificing solution accuracy.
The Halos and Environments of Nearby Galaxies (HERON) Survey
Creators: name: Rich, R. Michael
name: Brosch, Noah
name: Bullock, James
name: Burkert, Andreas
name: Collins, Michelle
name: de Groot, Laura
name: Kennefick, Julia
name: Koch, Andreas
name: Longstaff, Francis
name: Sales, Laura
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We have used dedicated 0.7m telescopes in California and Israel to image the halos of ~200 galaxies in the Local Volume to 29 mag/sq arcsec, the sample mainly drawn from the 2MASS Large Galaxy Atlas (LGA). We supplement the LGA sample with dwarf galaxies and more distant giant ellipticals. Low surface brightness halos exceeding 50 kpc in diameter are found only in galaxies more luminous than L* and classic interaction signatures are relatively infrequent. Halo diameter is correlated with total galaxy luminosity. Extended low surface brightness halos are present even in galaxies as faint as M_V=-18. Edge-on galaxies with boxy bulges tend to lack extended spheroidal halos, while those with large classical bulges exhibit extended round halos, supporting the notions that boxy or barlike bulges originate from disks. Most face-on spiral galaxies present features that appear to be irregular extensions of spiral arms, although rare cases show smooth boundaries with no sign of star formation. Although we serendipitously discovered a dwarf galaxy undergoing tidal disruption in the halo of NGC 4449, we found no comparable examples in our general survey. A search for similar examples in the Local Volume identified hcc087, a tidally disrupting dwarf galaxy in the Hercules Cluster, but we do not confirm an anomalously large half-light radius reported for the dwarf VCC 1661.
description: 4 pages, 4 figures
Zeros in the Character Tables of Symmetric Groups with an $\ell$-Core Index
Creators: name: McSpirit, Eleanor
name: Ono, Ken
Publisher: name: arXiv
Year: 2022
Subjects: subject: Number Theory (math.NT)
subject: Combinatorics (math.CO)
subject: Representation Theory (math.RT)
subject: FOS: Mathematics

description: Let $\mathcal{C}_n =\left [χ_λ(μ)\right]_{λ, μ}$ be the character table for $S_n,$ where the indices $λ$ and $μ$ run over the $p(n)$ many integer partitions of $n.$ In this note we study $Z_{\ell}(n),$ the number of zero entries $χ_λ(μ)$ in $\mathcal{C}_n,$ where $λ$ is an $\ell$-core partition of $n.$ For every prime $\ell\geq 5,$ we prove an asymptotic formula of the form $$ Z_{\ell}(n)\sim α_{\ell}\cdot σ_{\ell}(n+δ_{\ell})p(n)\gg_{\ell} n^{\frac{\ell-5}{2}}e^{π\sqrt{2n/3}},$$ where $σ_{\ell}(n)$ is a twisted Legendre symbol divisor function, $δ_{\ell}:=(\ell^2-1)/24,$ and $1/α_{\ell}>0$ is a normalization of the Dirichlet $L$-value $L\left(\left(\frac{\cdot}{\ell}\right),\frac{\ell-1}{2}\right).$ For primes $\ell$ and $n>\ell^6/24,$ we show that $χ_λ(μ)=0$ whenever $λ$ and $μ$ are both $\ell$-cores. Furthermore, if $Z^*_{\ell}(n)$ is the number of zero entries indexed by two $\ell$-cores, then for $\ell\geq 5$ we obtain the asymptotic $$ Z^*_{\ell}(n)\sim α_{\ell}^2 \cdot σ_{\ell}( n+δ_{\ell})^2 \gg_{\ell} n^{\ell-3}. $$
description: 8 pages, 1 figure
Influence of departures from LTE on calcium, titanium, and iron abundance determinations in cool giants of different metallicities
Creators: name: Mashonkina, Lyudmila
name: Sitnova, Tatyana
name: Pakhomov, Yuri
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Non-local thermodynamic equilibrium (non-LTE) line formation for Ca I-Ca II, Ti I-Ti II, and Fe I-Fe II is considered in model atmospheres of giant stars with an effective temperature of 4000 K $\le$ Teff $\le$ 5000 K and a metal abundance of -4 $\le$ [Fe/H] $\le$ 0. The departures from LTE are analyzed depending on atmospheric parameters. We present the non-LTE abundance corrections for 28 lines of Ca I, 42 lines of Ti I, 54 lines of Ti II, and 262 lines of Fe I and a three-dimensional interpolation code to obtain the non-LTE correction online (http://spectrum.inasan.ru/nLTE/) for an individual spectral line and given atmospheric parameters.
description: 14 pages, 7 figures, published in Astronomy Letters, 42, 606-615 (2016)
Identifying Gravitational Wave Counterparts with Near-infrared Image Subtraction: Automating the Detection of GW Counterparts for VISTA
Creators: name: Rosetti, Skye Sonja
Publisher: name: University of Leicester
Year: 2022
Subjects: Uncategorized

description: The field of gravitational wave observational astronomy has only just begun, with the first binary black hole merger detected in 2015 and the first electromagnetic counterpart associated to a GW event being found in 2017. With the recent introduction of new entries into the detector network (e.g. Virgo, KAGRA), the planned expansion of the network (e.g. LISA) and with frequent improvements being made to existing detectors, the number of GW detections is set to increase in the coming years. This will encourage additional electromagnetic follow-up, particularly in the infra-red in the search for kilonovae. This thesis is framed around the primary motivation for this work – to automate the process of investigating near-infrared follow up images obtained from the VISTA telescope. This involves both the identification of potential transient objects which might be associated with an event, and the photometric analysis of known kilonova detections. To demonstrate the effectiveness of this work, the automated pipeline is tested against data obtained within the localisation regions of GW170814, GW190814 and GW200114. A revised estimate is also produced for GW170817 photometry which is in accordance with previous studies. Overall, the IGNIS (Identifying Gravitational wave counterparts with near Infrared Image Subtraction) pipeline is proven to be almost as effective as manually searching for transient objects to depths of mAB = 20.5 - 22, with automated detection improved on longer exposures (240s+). This work estimates VISTA-associated false positive rates at 0.048-0.06 objects per tile (one object found per 16.7-20.8 deg2).
Neural network for multi-exponential sound energy decay analysis
Creators: name: Götz, Georg
name: Pérez, Ricardo Falcón
name: Schlecht, Sebastian J.
name: Pulkki, Ville
Publisher: name: arXiv
Year: 2022
Subjects: subject: Audio and Speech Processing (eess.AS)
subject: Sound (cs.SD)
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Computer and information sciences

description: An established model for sound energy decay functions (EDFs) is the superposition of multiple exponentials and a noise term. This work proposes a neural-network-based approach for estimating the model parameters from EDFs. The network is trained on synthetic EDFs and evaluated on two large datasets of over 20000 EDF measurements conducted in various acoustic environments. The evaluation shows that the proposed neural network architecture robustly estimates the model parameters from large datasets of measured EDFs, while being lightweight and computationally efficient. An implementation of the proposed neural network is publicly available.
description: The following article has been submitted to the Journal of the Acoustical Society of America (JASA). After it is published, it will be found at http://asa.scitation.org/journal/jas
Mega electrorheological phenomena in graphene nanogels
Creators: name: Dhar, Purbarun
name: Katiyar, Ajay
name: Pattamatta, Arvind
name: Das, Sarit K
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Soft Condensed Matter (cond-mat.soft)
subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: Unprecedentedly massive electrorheology has been reported for dilute graphene nanoflakes based ER fluids that have been engineered as novel, readily synthesizable polymeric gels. Polyethylene glycol based graphene gels have been synthesized and very high ER response, 25,000 percent enhancement in viscosity under influence of electric field, has been observed for low concentration systems 2 wt. percent. The gels overcome several drawbacks innate to ER fluids. The gels exhibit long term stability, high graphene packing ratio which ensures very high ER response and the microstructure of the gels ensure that fibrillation of the graphene nanoflakes under field is undisturbed by thermal fluctuations, further leading to mega ER. The gels exhibit large yield stress handling caliber with yield stress observed as high as 13 kPa at 2 wt. perc. graphene. Detailed investigations on the effects of graphene concentration, electric field strength, imposed shear resistance and transients of electric field actuation on the ER response of the gels have been performed. The gels show nearly negligible hysteresis with respect to electro viscous effects which speak of the stability and responsiveness required in transient situations. Indepth analyses with explanations have been provided for the observations and effects, such as sheet over-crowding induced loss of structural integrity at high concentrations and inter flake lubrication or slip induced augmented ER response. The present gels show great promise as potential ER gels for variant smart applications, such as damping and vibration control in active aircraft and vehicle structures, micronanoscale electroactuation, in suspensions or braking clutching in high performance specialized vehicular systems, etc.
description: 29 pages 10 figures
Quenched decay of correlations for nonuniformly hyperbolic random maps with an ergodic driving system
Creators: name: Alves, José F.
name: Bahsoun, Wael
name: Ruziboev, Marks
name: Varandas, Paulo
Publisher: name: arXiv
Year: 2022
Subjects: subject: Dynamical Systems (math.DS)
subject: Chaotic Dynamics (nlin.CD)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: In this article we study random tower maps driven by an ergodic automorphism. We prove quenched exponential correlations decay for tower maps admitting exponential tails. Our technique is based on constructing suitable cones of functions, defined on the random towers, which contract with respect to the Hilbert metric under the action of appropriate transfer operators. We apply our results to obtain quenched exponential correlations decay for several non-iid random dynamical systems including small random perturbations of Lorenz maps and Axiom A attractors.
description: Revised version. To appear in Nonlinearity
Neonatal Outcomes and Exposure to Diabetes in Utero: A scoping review
Creators: name: Morgan-Daniel, Jane
name: Howell, Breanna
name: Bodison, Stefanie C.
name: Major, Jordan
Publisher: name: OSF Registries
Year: 2023
Subjects: subject: Medicine and Health Sciences

description: The rate at which preexisting (Type 1 and Type 2) diabetes is increasing puts pregnant people with preexisting diabetes and the neonate at higher risk of adverse outcomes. We want to see what elements of preexisting diabetes during pregnancy most impact the health of the neonate. This scoping review aims to summarize and synthesize studies that have compared neonatal outcomes to exposure to type 1 and type 2 diabetes in utero.
Experimental Device-Independent Tests of Classical and Quantum Entropy
Creators: name: Zhu, Feng
name: Zhang, Wei
name: Chen, Sijing
name: You, Lixing
name: Wang, Zhen
name: Huang, Yidong
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: In this paper, we report an experiment about the device-independent tests of classical and quantum entropy based on a recent proposal [Phys. Rev. Lett. 115, 110501 (2015)], in which the states are encoded on the polarization of a biphoton system and measured by the state tomography technology. We also theoretically obtained the minimal quantum entropy for three widely used linear dimension witnesses. The experimental results agree well with the theoretical analysis, demonstrating that lower entropy is needed in quantum systems than that in classical systems under given values of the dimension witness.
The Oscillatory Universe, phantom crossing and the Hubble tension
Creators: name: Sharma, Mohit K.
name: Pacif, Shibesh Kumar Jas
name: Yergaliyeva, Gulmira
name: Yesmakhanova, Kuralay
Publisher: name: arXiv
Year: 2022
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We investigate the validity of cosmological models with an oscillating scale factor in relation to late-time cosmological observations. We show that these models not only meet the required late time observational constraints but can also alleviate the Hubble tension. As a generic feature of the model, the Hubble parameter increases near the current epoch due to its cyclical nature exhibiting the phantom nature allowing to address the said issue related to late time acceleration.
description: 10 pages, 7 figures
A protocol to create a multi-particle entangled state for quantum-enhanced sensing
Creators: name: Sawant, Rahul
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Physics (quant-ph)
subject: Applied Physics (physics.app-ph)
subject: Atomic Physics (physics.atom-ph)
subject: FOS: Physical sciences

description: We propose a protocol for generating multi-particle entangled states using coherent manipulation of atoms trapped in an optical cavity. We show how entanglement can be adiabatically produced with two control beams and by exploiting cavity-mediated interactions between the atoms. Our methods will allow for optimal generation of entanglement for the measurement protocol we propose. We discuss an experimental implementation and compare the performance of the states produced with those of classical states and ideal maximally-entangled Dicke states. We find that our states always feature metrological gain and even outperform ideal Dicke states in the measurement of magnetic field gradients. Due to the easy scalability, our entanglement protocol is a promising tool for quantum state engineering.
Energy-Efficient Quantum Computing
Creators: name: Ikonen, Joni
name: Salmilehto, Juha
name: Möttönen, Mikko
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: In the near future, a major challenge in quantum computing is to scale up robust qubit prototypes to practical problem sizes and to implement comprehensive error correction for computational precision. Due to inevitable quantum uncertainties in resonant control pulses, increasing the precision of quantum gates comes with the expense of increased energy consumption. Consequently, the power dissipated in the vicinity of the processor in a well-working large-scale quantum computer seems unacceptably large in typical systems requiring low operation temperatures. Here, we introduce a method for qubit driving and show that it serves to decrease the single-qubit gate error without increasing the average power dissipated per gate. Previously, single-qubit gate error induced by a bosonic drive mode has been considered to be inversely proportional to the energy of the control pulse, but we circumvent this bound by reusing and correcting itinerant control pulses. Thus our work suggests that heat dissipation does not pose a fundamental limitation, but a necessary practical challenge in future implementations of large-scale quantum computers.
description: 12 pages, 9 figures
Properties of particles in the ergosphere of black holes
Creators: name: Grib, A. A.
name: Pavlov, Yu. V.
Publisher: name: arXiv
Year: 2016
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: A new feature of the rotating black holes is the existence in their ergosphere of trajectories of particles with negative and zero energies. Here we analyze general properties of such trajectories comparing them with usual trajectories of particles with positive energy. A comparison with the situation in rotating coordinate frame in Minkowski space-time is made. The possibility of the unbounded growth of the energy of two colliding particles in the centre of mass frame in the ergosphere is analysed.
description: 13 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1601.02592
A Modified Vortex Search Algorithm for Numerical Function Optimization
Creators: name: Doğan, Berat
Publisher: name: arXiv
Year: 2016
Subjects: subject: Artificial Intelligence (cs.AI)
subject: FOS: Computer and information sciences

description: The Vortex Search (VS) algorithm is one of the recently proposed metaheuristic algorithms which was inspired from the vortical flow of the stirred fluids. Although the VS algorithm is shown to be a good candidate for the solution of certain optimization problems, it also has some drawbacks. In the VS algorithm, candidate solutions are generated around the current best solution by using a Gaussian distribution at each iteration pass. This provides simplicity to the algorithm but it also leads to some problems along. Especially, for the functions those have a number of local minimum points, to select a single point to generate candidate solutions leads the algorithm to being trapped into a local minimum point. Due to the adaptive step-size adjustment scheme used in the VS algorithm, the locality of the created candidate solutions is increased at each iteration pass. Therefore, if the algorithm cannot escape a local point as quickly as possible, it becomes much more difficult for the algorithm to escape from that point in the latter iterations. In this study, a modified Vortex Search algorithm (MVS) is proposed to overcome above mentioned drawback of the existing VS algorithm. In the MVS algorithm, the candidate solutions are generated around a number of points at each iteration pass. Computational results showed that with the help of this modification the global search ability of the existing VS algorithm is improved and the MVS algorithm outperformed the existing VS algorithm, PSO2011 and ABC algorithms for the benchmark numerical function set.
description: 18 pages, 7 figures
Is the line-like optical afterglow SED of GRB 050709 due to a flare?
Creators: name: Liu, Cong
name: Jin, Zhi-Ping
name: Wei, Da-Ming
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Recently Jin et al. (2016) reanalyzed the optical observation data of GRB 050709 and reported a line-like spectral energy distribution (SED) component observed by the Very Large Telescope at $t\sim 2.5$ days after the trigger of the burst, which had been interpreted as a broadened line signal arising from a macronova dominated by iron group. In this work we show that an optical flare origin of such a peculiar optical SED is still possible. Interestingly, even in such a model, an "unusual" origin of the late-time long-lasting Hubble Space Telescope F814W-band emission is still needed and a macronova/kilonova is the natural interpretation.
description: 5 pages, 4 figures, accepted for publication in the Astrophysical Journal
Theory of terahertz emission from femtosecond-laser-induced micro-plasmas
Creators: name: Thiele, I.
name: Nuter, R.
name: Bousquet, B.
name: Tikhonchuk, V.
name: Davoine, X.
name: Gremillet, L.
name: Bergé, L.
name: Skupin, S.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Plasma Physics (physics.plasm-ph)
subject: FOS: Physical sciences

description: We present a theoretical investigation of terahertz (THz) generation in laser-induced gas plasmas. The work is strongly motivated by recent experimental results on micro-plasmas, but our general findings are not limited to such a configuration. The electrons and ions are created by tunnel-ionization of neutral atoms, and the resulting plasma is heated by collisions. Electrons are driven by electromagnetic, convective and diffusive sources and produce a macroscopic current which is responsible for THz emission. The model naturally includes both, ionization current and transition-Cherenkov mechanisms for THz emission, which are usually investigated separately in the literature. The latter mechanism is shown to dominate for single-color multi-cycle lasers pulses, where the observed THz radiation originates from longitudinal electron currents. However, we find that the often discussed oscillations at the plasma frequency do not contribute to the THz emission spectrum. In order to predict the scaling of the conversion efficiency with pulse energy and focusing conditions, we propose a simplified description that is in excellent agreement with rigorous particle-in-cell simulations.
MESA meets MURaM: Surface effects in main-sequence solar-like oscillators computed using three-dimensional radiation hydrodynamics simulations
Creators: name: Ball, W. H.
name: Beeck, B.
name: Cameron, R. H.
name: Gizon, L.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: ... [C]urrent stellar models predict oscillation frequencies that are systematically affected by simplified modelling of the near-surface layers. We use three-dimensional radiation hydrodynamics simulations to better model the near-surface equilibrium structure of dwarfs with spectral types F3, G2, K0 and K5, and examine the differences between oscillation mode frequencies. ... We precisely match stellar models to the simulations' gravities and effective temperatures at the surface, and to the temporally- and horizontally-averaged densities and pressures at their deepest points. We then replace the near-surface structure with that of the averaged simulation and compute the change in the oscillation mode frequencies. We also fit the differences using several parametric models currently available in the literature. The surface effect in the stars of solar-type and later is qualitatively similar and changes steadily with decreasing effective temperature. In particular, the point of greatest frequency difference decreases slightly as a fraction of the acoustic cut-off frequency and the overall scale of the surface effect decreases. The surface effect in the hot, F3-type star follows the same trend in scale (i.e. it is larger in magnitude) but shows a different overall variation with mode frequency. We find that the two-term fit by Ball & Gizon (2014) is best able to reproduce the surface terms across all four spectral types, although the scaled solar term and a modified Lorentzian function also match the three cooler simulations reasonably well. ... Our simplified results suggest that the surface effect is generally larger in hotter stars (and correspondingly smaller in cooler stars) and of similar shape in stars of solar type and cooler. However, we cannot presently predict whether this will remain so when other components of the surface effect are included.
description: 8 pages, 7 figures. Accepted for publication in Astronomy & Astrophysics
Impurity effects on BCS-BEC crossover in ultracold atomic Fermi gases
Creators: name: Che, Yanming
name: Chen, Qijin
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: We present a systematic investigation of the effects of "nonmagnetic" impurities on the $s$-wave BCS-BEC crossover in atomic Fermi gases within a pairing fluctuation theory. Both pairing and impurity scattering $T$-matrices are treated self-consistently at the same time. While the system is less sensitive to impurity scattering in the Born limit, for strong impurity scatterers, both the frequency and the gap function are highly renormalized, leading to significant suppression of the superfluid $T_c$, the order parameter and the superfluid density. We also find the formation of impurity bands and smearing of coherence peak in the fermion density of states, leading to a spectrum weight transfer and finite lifetime of Bogoliubov quasiparticles. In the BCS regime, the superfluidity may be readily destroyed by the impurity of high density. In comparison, the superfluidity in unitary and BEC regimes is relatively more robust.
description: 9 pages, 9 figures
Auroral imaging with combined Suomi 100 nanosatellite and ground-based observations: A case study
Creators: name: Kallio, Esa
name: Harri, Ari-Matti
name: Knuuttila, Olli
name: Jarvinen, Riku
name: Kauristie, Kirsti
name: Kestilä, Antti
name: Kivekäs, Jarmo
name: Koskimaa, Petri
name: Lukkari, Juha-Matti
name: Partamies, Noora
name: Rynö, Jouni
name: Syrjäsuo, Mikko
Publisher: name: arXiv
Year: 2022
Subjects: subject: Space Physics (physics.space-ph)
subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: Auroras can be regarded as the most fascinating manifestation of space weather and they are continuously observed by ground-based and, nowadays more and more, also by space-based measurements. Investigations of auroras and geospace comprise the main research goals of the Suomi 100 nanosatellite, the first Finnish space research satellite, which has been measuring the Earth's ionosphere since its launch on Dec. 3, 2018. In this work, we present a case study where the satellite's camera observations of an aurora over Northern Europe are combined with ground-based observations of the same event. The analyzed image is, to the authors' best knowledge, the first auroral image ever taken by a cubesat. Our data analysis shows that a satellite vantage point provides complementary, novel information of such phenomena. The 3D auroral location reconstruction of the analyzed auroral event demonstrates how information from a 2D image can be used to provide location information of auroras under study. The location modelling also suggests that the Earth's limb direction, which was the case in the analyzed image, is an ideal direction to observe faint auroras. Although imaging on a small satellite has some large disadvantages compared with ground-based imaging (the camera cannot be repaired, a fast moving spinning satellite), the data analysis and modelling demonstrate how even a small 1-Unit (size: 10 cm x 10 cm x 10 cm) CubeSat and its camera, build using cheap commercial off-the-shelf components, can open new possibilities for auroral research, especially, when its measurements are combined with ground-based observations.
description: Accepted manuscript 34 pages, 17 figures
Apsidal motion in the massive binary HD152218
Creators: name: Rauw, G.
name: Rosu, S.
name: Noels, A.
name: Mahy, L.
name: Schmitt, J. H. M. M.
name: Godart, M.
name: Dupret, M. -A.
name: Gosset, E.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Massive binary systems are important laboratories in which to probe the properties of massive stars and stellar physics in general. In this context, we analysed optical spectroscopy and photometry of the eccentric short-period early-type binary HD 152218 in the young open cluster NGC 6231. We reconstructed the spectra of the individual stars using a separating code. The individual spectra were then compared with synthetic spectra obtained with the CMFGEN model atmosphere code. We furthermore analysed the light curve of the binary and used it to constrain the orbital inclination and to derive absolute masses of 19.8 +/- 1.5 and 15.0 +/- 1.1 solar masses. Combining radial velocity measurements from over 60 years, we show that the system displays apsidal motion at a rate of (2.04^{+.23}_{-.24}) degree/year. Solving the Clairaut-Radau equation, we used stellar evolution models, obtained with the CLES code, to compute the internal structure constants and to evaluate the theoretically predicted rate of apsidal motion as a function of stellar age and primary mass. In this way, we determine an age of 5.8 +/- 0.6 Myr for HD 152218, which is towards the higher end of, but compatible with, the range of ages of the massive star population of NGC 6231 as determined from isochrone fitting.
description: Accepted for publication in Astronomy & Astrophysics
Transport spectroscopy of ultraclean tunable band gaps in bilayer graphene
Creators: name: Icking, E.
name: Banszerus, L.
name: Wörtche, F.
name: Volmer, F.
name: Schmidt, P.
name: Steiner, C.
name: Engels, S.
name: Hesselmann, J.
name: Goldsche, M.
name: Watanabe, K.
name: Taniguchi, T.
name: Volk, C.
name: Beschoten, B.
name: Stampfer, C.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The importance of controlling both the charge carrier density and the band gap of a semiconductor cannot be overstated, as it opens the doors to a wide range of applications, including, e.g., highly-tunable transistors, photodetectors, and lasers. Bernal-stacked bilayer graphene is a unique van-der-Waals material that allows tuning the band gap by an out-of-plane electric field. Although the first evidence of the tunable gap was already found ten years ago, it took until recent to fabricate sufficiently clean heterostructures where the electrically induced gap could be used to fully suppress transport or confine charge carriers. Here, we present a detailed study of the tunable band gap in gated bilayer graphene characterized by temperature-activated transport and finite-bias spectroscopy measurements. The latter method allows comparing different gate materials and device technologies, which directly affects the disorder potential in bilayer graphene. We show that graphite-gated bilayer graphene exhibits extremely low disorder and as good as no subgap states resulting in ultraclean tunable band gaps up to 120 meV. The size of the band gaps are in good agreement with theory and allow complete current suppression making a wide range of semiconductor applications possible.
description: 21 pages, 10 figures
Developing skills vs reinforcing concepts in physics labs: Insight from E-CLASS
Creators: name: Wilcox, Bethany R.
name: Lewandowski, H. J.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Physics Education (physics.ed-ph)
subject: FOS: Physical sciences

description: Physics laboratory courses have been generally acknowledged as an important component of the undergraduate curriculum, particularly with respect to developing students' interest in, and understanding of, experimental physics. There are a number of possible learning goals for these courses including reinforcing physics concepts, developing laboratory skills, and promoting expert-like beliefs about the nature of experimental physics. However, there is little consensus among instructors and researchers interested in the laboratory learning environment as to relative importance of these various learning goals. Here, we contribute data to this debate through the analysis of students' responses to the laboratory-focused assessment known as the Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS). Using a large, national data set of students' responses, we compare students' E-CLASS performance in classes in which the instructor self-reported focusing on developing skills, reinforcing concepts, or both. As the classification of courses was based on instructor self-report, we also provide additional description of these course with respect to how often students engage in particular activities in the lab. We find that courses that focus specifically on developing lab skills have more expert-like postinstruction E-CLASS responses than courses that focus either on reinforcing physics concepts or on both goals. Within first-year courses, this effect is larger for women. Moreover, these findings hold when controlling for the variance in postinstruction scores that is associated with preinstruction E-CLASS score, student major, and student gender.
description: 8 pages, 2 figures, submitted to Phys. Rev. - PER. arXiv admin note: text overlap with arXiv:1608.01621
Probing spin dynamics of ultra-thin van der Waals magnets via photon-magnon coupling
Creators: name: Zollitsch, Christoph W.
name: Khan, Safe
name: Nam, Vu Thanh Trung
name: Verzhbitskiy, Ivan A.
name: Sagkovits, Dimitrios
name: O'Sullivan, James
name: Kennedy, Oscar W.
name: Strungaru, Mara
name: Santos, Elton J. G.
name: Morton, John J. L.
name: Eda, Goki
name: Kurebayashi, Hidekazu
Publisher: name: arXiv
Year: 2022
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Layered van der Waals (vdW) magnets can maintain a magnetic order even down to the single-layer regime and hold promise for integrated spintronic devices. While the magnetic ground state of vdW magnets was extensively studied, key parameters of spin dynamics, like the Gilbert damping, crucial for designing ultra-fast spintronic devices, remains largely unexplored. Despite recent studies by optical excitation and detection, achieving spin wave control with microwaves is highly desirable, as modern integrated information technologies predominantly are operated with these. The intrinsically small numbers of spins, however, poses a major challenge to this. Here, we present a hybrid approach to detect spin dynamics mediated by photon-magnon coupling between high-Q superconducting resonators and ultra-thin flakes of Cr$_2$Ge$_2$Te$_6$ (CGT) as thin as 11\,nm. We test and benchmark our technique with 23 individual CGT flakes and extract an upper limit for the Gilbert damping parameter. These results are crucial in designing on-chip integrated circuits using vdW magnets and offer prospects for probing spin dynamics of monolayer vdW magnets.
Data, simulations/projections, and supporting materials for simulated hydrologic responses to climate-change projections for the Lake Tahoe basin: subbasin-scale results
Creators: name: Dettinger, Michael
name: Rajagopal, Seshadri
Publisher: name: Zenodo
Year: 2023
Subjects: subject: Earth and related environmental sciences
subject: FOS: Earth and related environmental sciences
subject: Lake Tahoe Basin
subject: California and Nevada
subject: Climate change
subject: Hydrologic responses
subject: simulations

description: This dataset contains data, simulations, projections, and supporting materials associated with simulated hydrologic responses, at the scale of 60 subbasins comprising the Lake Tahoe Basin, California and Nevada, to a 16-member ensemble of statistically-downscaled projections of climate change, 1950-2099. The process and results are described in detail in Dettinger, M., & Rajagopal, S., 2023, Simulated hydrologic responses to climate-change projections for the Lake Tahoe Basin: Desert Research Institute Publication 41292, 99 p., which is included here. The dataset as presented here contains 6 files, including one large zipped file that itself contains some 1,975 files, mostly simple text files of data, simulation outputs, and analytical results organized into dozens and dozens of subdirectories to allow specific elements to be identified and isolated. Beyond this large collection, the zipped file also contains copies of the report(s), selected supporting documents, graphical files, codes, and copious #readme.txt files to orient the user.
description: Funding provided by: California Tahoe Conservancy*
Crossref Funder Registry ID:
Award Number: 20 016L
description: Simulations with PRMS hydrologic model of the Lake Tahoe Basin, daily resolutions on 300 m grid, compiled for each of 60 subbasins comprising the whole basin. Models, simulations, model validations, projections, and results described in detail in the subject report (available online and as a pdf file in the top level of this data set).
Learning Thermodynamics with Boltzmann Machines
Creators: name: Torlai, Giacomo
name: Melko, Roger G.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: Machine Learning (cs.LG)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: A Boltzmann machine is a stochastic neural network that has been extensively used in the layers of deep architectures for modern machine learning applications. In this paper, we develop a Boltzmann machine that is capable of modelling thermodynamic observables for physical systems in thermal equilibrium. Through unsupervised learning, we train the Boltzmann machine on data sets constructed with spin configurations importance-sampled from the partition function of an Ising Hamiltonian at different temperatures using Monte Carlo (MC) methods. The trained Boltzmann machine is then used to generate spin states, for which we compare thermodynamic observables to those computed by direct MC sampling. We demonstrate that the Boltzmann machine can faithfully reproduce the observables of the physical system. Further, we observe that the number of neurons required to obtain accurate results increases as the system is brought close to criticality.
description: 8 pages, 5 figures
Towards Limited Scale-free Topology with Dynamic Peer Participation
Creators: name: Lu, Xiaoyan
name: Bulut, Eyuphan
name: Szymanski, Boleslaw
Publisher: name: arXiv
Year: 2016
Subjects: subject: Physics and Society (physics.soc-ph)
subject: Social and Information Networks (cs.SI)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: Growth models have been proposed for constructing the scale-free overlay topology to improve the performance of unstructured peer-to-peer (P2P) networks. However, previous growth models are able to maintain the limited scale-free topology when nodes only join but do not leave the network; the case of nodes leaving the network while preserving a precise scaling parameter is not included in the solution. Thus, the full dynamic of node participation, inherent in P2P networks, is not considered in these models. In order to handle both nodes joining and leaving the network, we propose a robust growth model E-SRA, which is capable of producing the perfect limited scale-free overlay topology with user-defined scaling parameter and hard cut-offs. Scalability of our approach is ensured since no global information is required to add or remove a node. E-SRA is also tolerant to individual node failure caused by errors or attacks. Simulations have shown that E-SRA outperforms other growth models by producing topologies with high adherence to the desired scale-free property. Search algorithms, including flooding and normalized flooding, achieve higher efficiency over the topologies produced by E-SRA.
A Direct Probe of the Evolutionary History of the Primordial Universe
Creators: name: Chen, Xingang
name: Namjoo, Mohammad Hossein
name: Wang, Yi
Publisher: name: arXiv
Year: 2016
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Since Hubble and Lamaitre's discovery of the expanding universe using galaxies till the recent discovery of the accelerating universe using standard candles, direct measurements of the evolution of the scale factor of the universe a(t) have played central roles in establishing the standard model of cosmology. In this letter, we show that such a measurement may be extended to the primordial universe using massive fields as standard clocks, providing a direct evidence for the scenario responsible for the Big Bang. This is a short and non-technical introduction to the idea of classical and quantum primordial standard clocks.
description: 10 pages; a short and non-technical introduction to primordial standard clocks, to appear in Science China