cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Deviation from Slow-Roll Regime in the EGB Inflationary Models with $r\sim N_e^{-1}$
Creators: name: Pozdeeva, Ekaterina O.
Publisher: name: arXiv
Year: 2021
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We consider Einstein-Gauss-Bonnet (EGB) inflationary models using the effective potential approach. We present evolution equations in the slow-roll regime using the effective potential and the tensor-to-scalar ratio. The choice of the effective potential is related to an expression of the spectral index in terms of e-folding number $N_e$. The satisfaction of the slow-roll regime is mostly related to the form of the tensor-to-scalar ratio $r$. The case of $r\sim1/N^2_e$ leads to a generalization of $α$-attractors inflationary parameters to Einstein-Gauss-Bonnet gravity with exponential effective potential. Moreover, the cosmological attractors include models with $r\sim1/N_e$. And we check the satisfaction of the slow-roll regime during inflation for models with $r\sim1/N_e$.
Functionals of fractional Brownian motion and the three arcsine laws
Creators: name: Sadhu, Tridib
name: Wiese, Kay Jörg
Publisher: name: arXiv
Year: 2021
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Mathematical Physics (math-ph)
subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: FOS: Physical sciences

description: Fractional Brownian motion is a non-Markovian Gaussian process indexed by the Hurst exponent $H\in [0,1]$, generalising standard Brownian motion to account for anomalous diffusion. Functionals of this process are important for practical applications as a standard reference point for non-equilibrium dynamics. We describe a perturbation expansion allowing us to evaluate many non-trivial observables analytically: We generalize the celebrated three arcsine-laws of standard Brownian motion. The functionals are: (i) the fraction of time the process remains positive, (ii) the time when the process last visits the origin, and (iii) the time when it achieves its maximum (or minimum). We derive expressions for the probability of these three functionals as an expansion in $ε= H-\tfrac{1}{2}$, up to second order. We find that the three probabilities are different, except for $H=\tfrac{1}{2}$ where they coincide. Our results are confirmed to high precision by numerical simulations.
description: 50 pages with 28 figures. For a supplemental Mathematica notebook (Ref[76]) see https://www.dropbox.com/s/jcgcjs5u2kfh4fm/SupplementalNotebook.nb?dl=0
PM$_{2.5}$ as a major predictor of COVID-19 basic reproduction number in the USA
Creators: name: Milicevic, Ognjen
name: Salom, Igor
name: Rodic, Andjela
name: Markovic, Sofija
name: Tumbas, Marko
name: Zigic, Dusan
name: Djordjevic, Magdalena
name: Djordjevic, Marko
Publisher: name: arXiv
Year: 2021
Subjects: subject: Populations and Evolution (q-bio.PE)
subject: FOS: Biological sciences

description: Many studies have proposed a relationship between COVID-19 transmissibility and ambient pollution levels. However, a major limitation in establishing such associations is to adequately account for complex disease dynamics, influenced by e.g. significant differences in control measures and testing policies. Another difficulty is appropriately controlling the effects of other potentially important factors, due to both their mutual correlations and a limited dataset. To overcome these difficulties, we will here use the basic reproduction number ($R_0$) that we estimate for USA states using non-linear dynamics methods. To account for a large number of predictors (many of which are mutually strongly correlated), combined with a limited dataset, we employ machine-learning methods. Specifically, to reduce dimensionality without complicating the variable interpretation, we employ Principal Component Analysis on subsets of mutually related (and correlated) predictors. Methods that allow feature (predictor) selection, and ranking their importance, are then used, including both linear regressions with regularization and feature selection (Lasso and Elastic Net) and non-parametric methods based on ensembles of weak-learners (Random Forest and Gradient Boost). Through these substantially different approaches, we robustly obtain that PM$_{2.5}$ is a major predictor of $R_0$ in USA states, with corrections from factors such as other pollutants, prosperity measures, population density, chronic disease levels, and possibly racial composition. As a rough magnitude estimate, we obtain that a relative change in $R_0$, with variations in pollution levels observed in the USA, is typically ~30%, which further underscores the importance of pollution in COVID-19 transmissibility.
description: 25 pages, 4 figures. Environmental Research, in press (2021)
Non-Gaussian estimates of tensions in cosmological parameters
Creators: name: Raveri, Marco
name: Doux, Cyrille
Publisher: name: arXiv
Year: 2021
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: We discuss how to efficiently and reliably estimate the level of agreement and disagreement on parameter determinations from different experiments, fully taking into account non-Gaussianities in the parameter posteriors. We develop two families of scalable algorithms that allow us to perform this type of calculations in increasing number of dimensions and for different levels of tensions. One family of algorithms rely on kernel density estimates of posterior distributions while the other relies on machine learning modeling of the posterior distribution with normalizing flows. We showcase their effectiveness and accuracy with a set of benchmark examples and find both methods agree with each other and the true tension within $0.5σ$ in difficult cases and generally to $0.2σ$ or better. This allows us to study the level of internal agreement between different measurements of the clustering of cosmological structures from the Dark Energy Survey and their agreement with measurements of the Cosmic Microwave Background from the Planck satellite.
description: Code available at https://github.com/mraveri/tensiometer with a documented notebook at https://tensiometer.readthedocs.io/en/latest/non_gaussian_tension.html . Minor modifications wrt v1, including a new pedagogical example. Matches version accepted in PRD
Distributed object management in Raven
Creators: name: Sutanto, Marcel
Publisher: name: University of British Columbia
Year: 2010

description: Raven is an object-oriented distributed system designed to support research in building fault-tolerance distributed systems using an object model. Invocations on Raven objects are executed within a transaction mechanism with provisions for application controlled relaxations. Central to Raven underlying system support is the Object Manager which is responsible for secondary storage management of objects, concurrency control, transaction management, objects distribution and migration, recovery from failures and virtual memory management. Raven objects are encapsulated into object spaces and primary memory is simply used as a cache to object spaces in secondary storage or in remote machines. The physical layout of an object space in primary memory is identical to its layout in secondary storage. An object space represents a unit of concurrency control and recovery in Raven. Raven design integrates virtual memory management, secondary storage management and transaction management into one computation model implemented inside an Object Manager. This allows a highly efficient implementation of the Object Manager. The major work of this thesis is devoted to the design and implementations of the Object Manager in Raven.
Do galaxies die? Different views from simulations and observations in the Local Universe
Creators: name: Corcho-Caballero, Pablo
name: Ascasibar, Yago
name: Scannapieco, Cecilia
Publisher: name: arXiv
Year: 2021
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: For years, the extragalactic community has divided galaxies in two distinct populations. One of them, featuring blue colours, is actively forming stars, while the other is made up of "red-and-dead" objects with negligible star formation. Yet, are these galaxies really dead? Here we would like to highlight that, as previously reported by several independent groups, state-of-the-art cosmological numerical simulations predict the existence of a large number of quenched galaxies that have not formed any star over the last few Gyr. In contrast, observational measurements of large galaxy samples in the nearby Universe suggest that even the most passive systems still form stars at some residual level close to $sSFR\sim10^{-12}~\text{yr}^{-1}$. Unfortunately, extremely low star formation poses a challenge for both approaches. We conclude that, at present, the fraction of truly dead galaxies is still an important open question that must be addressed in order to understand galaxy formation and evolution.
description: Accepted for publication in MNRAS. 9 pages, 8 figures
Millimeter-Thick Single-Walled Carbon Nanotube Forests: Hidden Role of Catalyst Support
Creators: name: Noda, S.
name: Hasegawa, K.
name: Sugime, H.
name: Kakehi, K.
name: Zhang, Z.
name: Maruyama, S.
name: Yamaguchi, Y.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: A parametric study of so-called "super growth" of single-walled carbon nanotubes(SWNTs) was done by using combinatorial libraries of iron/aluminum oxide catalysts. Millimeter-thick forests of nanotubes grew within 10 min, and those grown by using catalysts with a thin Fe layer (about 0.5 nm) were SWNTs. Although nanotube forests grew under a wide range of reaction conditions such as gas composition and temperature, the window for SWNT was narrow. Fe catalysts rapidly grew nanotubes only when supported on aluminum oxide. Aluminum oxide, which is a well-known catalyst in hydrocarbon reforming, plays an essential role in enhancing the nanotube growth rates.
description: 11 pages, 3 figures. Jpn. J. Appl. Phys. (Express Letters) in press
Managing layers of risk: Uncertainty in large development programs combining agile software development and traditional project management
Creators: name: Dingsøyr, Torgeir
name: Petit, Yvan
Publisher: name: arXiv
Year: 2021
Subjects: subject: Software Engineering (cs.SE)
subject: FOS: Computer and information sciences
subject: D.2.9; K.6.1

description: How risks are managed implicitly and explicitly at multiple levels of agile projects has not been extensively studied and there is a need to investigate how risk management can be used in large agile projects. This is the objective of this exploratory study which investigates the following research question: How does a large software/hardware development project using agile practices manage uncertainty at project/subproject and work package levels?
description: 22 pages
Accurate measurement of scattering and absorption loss in microphotonic devices
Creators: name: Borselli, Matthew
name: Johnson, Thomas J.
name: Painter, Oskar
Publisher: name: arXiv
Year: 2007
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: We present a simple measurement and analysis technique to determine the fraction of optical loss due to both radiation (scattering) and linear absorption in microphotonic components. The method is generally applicable to optical materials in which both nonlinear and linear absorption are present, and requires only limited knowledge of absolute optical power levels, material parameters, and the structure geometry. The technique is applied to high quality factor (Q=1-5 X 10^6) silicon-on-insulator microdisk resonators. It is determined that linear absorption can account for more than half the total optical loss in the high-Q regime of these devices.
description: 3 pages, 3 figures
Spatially modulated, orbital selective ferromagnetism in La$_5$Co$_2$Ge$_3$
Creators: name: Cuono, Giuseppe
name: Autieri, Carmine
name: Wysokiński, Marcin M.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We present density functional theory calculations for low-$T_c$ metallic ferromagnet La$_5$Co$_2$Ge$_3$ at ambient and applied pressures. Our investigations reveal that the system is a quasi-one-dimensional ferromagnet with a peculiar coexistence of two different orbital-selective magnetic moments at two crystallographically inequivalent cobalt atoms, Co1 and Co2. Namely, due to different crystal-field splitting, the magnetic moment of Co1 atoms predominantly derives from $d_{xz}$ orbital whereas of Co2 atoms from $d_{xy}$ orbital. Consequently, Co1 and Co2 atoms develop unequal net magnetic moments, a feature that gives rise to a periodic, spatial modulation of magnetization along crystallographic $c$-direction. The amplitude of the spatial modulation, small at ambient pressure, drastically increases with applied pressure, until Co2 atoms become nonmagnetic. With the help of a toy model mimicking found orbital-selective ferromagnetic order, we demonstrate that the increasing amplitude of spatial modulation provides a consistent interpretation to the recently observed resistivity anomaly emerging at applied pressure identified as the appearance of the {\it new state}. Although, proposed here structural origin of the spatial modulation of magnetic moments in La$_5$Co$_2$Ge$_3$ is an alternative one to the advocated for this material ferromagnetic quantum criticality avoidance, the effects of quantum fluctuations can still play an important role at pressure larger than up-to-date measured 5GPa.
description: 8 pages, 10 figures
Interactions, superconducting $T_c$, and fluctuation magnetization for two coupled dots in the crossover between the Gaussian Orthogonal and Unitary ensembles
Creators: name: Zelyak, Oleksandr
name: Murthy, Ganpathy
name: Rozhkov, Igor
Publisher: name: arXiv
Year: 2007
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: We study a system of two quantum dots connected by a hopping bridge. Both the dots and connecting region are assumed to be in universal crossover regimes between Gaussian Orthogonal and Unitary ensembles. Using a diagrammatic approach appropriate for energy separations much larger than the level spacing we obtain the ensemble-averaged one- and two-particle Green's functions. It turns out that the diffuson and cooperon parts of the two-particle Green's function can be described by separate scaling functions. We then use this information to investigate a model interacting system in which one dot has an attractive s-wave reduced Bardeen-Cooper-Schrieffer interaction, while the other is noninteracting but subject to an orbital magnetic field. We find that the critical temperature is {\it nonmonotonic} in the flux through the second dot in a certain regime of interdot coupling. Likewise, the fluctuation magnetization above the critical temperature is also nonmonotonic in this regime, can be either diamagnetic or paramagnetic, and can be deduced from the cooperon scaling function.
description: 53 pages, 9 figures with many subfigures
Groundwater Level Forecasting with Artificial Neural Networks: A Comparison of LSTM, CNN and NARX
Creators: name: Wunsch, Andreas
name: Liesch, Tanja
name: Broda, Stefan
Publisher: name: Karlsruher Institut für Technologie (KIT)
Year: 2020
Subjects: Groundwater
Artificial Neural Networks
Artificial Intelligence
LSTM
CNN
NARX
Forecasting

description: It is now well established to use shallow artificial neural networks (ANN) to obtain accurate and reliable groundwater level forecasts, which are an important tool for sustainable groundwater management. However, we observe an increasing shift from conventional shallow ANNs to state-of-the-art deep learning (DL) techniques, but a direct comparison of the performance is often lacking. Although they have already clearly proven their suitability, especially shallow recurrent networks frequently seem to be excluded from the study design despite the euphoria about new DL techniques and its successes in various disciplines. Therefore, we aim to provide an overview on the predictive ability in terms of groundwater levels of shallow conventional recurrent ANN namely nonlinear autoregressive networks with exogenous inputs (NARX), and popular state-of-the-art DL-techniques such as long short-term memory (LSTM) and convolutional neural networks (CNN). We compare both the performance on sequence-to-value (seq2val) and sequence-to-sequence (seq2seq) forecasting on a 4-year period, while using only few, widely available and easy to measure meteorological input parameters, which makes our approach widely applicable. We observe that for seq2val forecasts NARX models on average perform best, however, CNNs are much faster and only slightly worse in terms of accuracy. For seq2seq forecasts, mostly NARX outperform both DL-models and even almost reach the speed of CNNs. However, NARX are the least robust against initialization effects, which nevertheless can be handled easily using ensemble forecasting. We showed that shallow neural networks, such as NARX, should not be neglected in comparison to DL-techniques; however, LSTMs and CNNs might perform substantially better with a larger data set, where DL really can demonstrate its strengths, which is rarely available in the groundwater domain though.
Additional file 3 of Male engagement guidelines in antenatal care: unintended consequences for pregnant women in Tanzania
Creators: name: Osaki, Haika
name: Sao, Saumya S.
name: Kisigo, Godfrey A.
name: Coleman, Jessica N.
name: Mwamba, Rimel N.
name: Renju, Jenny
name: Mmbaga, Blandina T.
name: Watt, Melissa H.
Publisher: name: figshare
Year: 2021
Subjects: subject: Medicine
subject: Cell Biology
subject: Neuroscience
subject: Pharmacology
subject: Biotechnology
subject: Sociology
subject: FOS: Sociology
subject: Cancer
subject: Mental Health
subject: Infectious Diseases
subject: FOS: Health sciences
subject: Cardiology

description: Additional file 3. In-depth interview guide for women presenting without partners.
Ambitwistor Integrands from Tensionless Chiral Superstring Integrands
Creators: name: Kalyanapuram, Nikhil
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Mathematical Physics (math-ph)
subject: Algebraic Geometry (math.AG)
subject: Differential Geometry (math.DG)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: It is established that in the tensionless limit the chiral superstring integrand is reduced to the chiral integrand of the ambitwistor string.
description: v2: 5 pages, references updated
Tunable Quantum Fluctuation-Controlled Coherent Spin Dynamics
Creators: name: Song, Jun Liang
name: Zhou, Fei
Publisher: name: arXiv
Year: 2007
Subjects: subject: Other Condensed Matter (cond-mat.other)
subject: FOS: Physical sciences

description: Temporal evolution of a macroscopic condensate of ultra cold atoms is usually driven by mean field potentials, either due to scattering between atoms or due to coupling to external fields; and coherent quantum dynamics have been observed in various cold-atom experiments. In this article, we report results of studies of a class of quantum spin dynamics which are purely driven by zero point quantum fluctuations of spin collective coordinates. Unlike the usual mean-field coherent dynamics, quantum fluctuation-controlled spin dynamics or QFCSD studied here are very sensitive to variation of quantum fluctuations and can be tuned by four to five order of magnitude using optical lattices. They have unique dependence on optical lattice potential depths and quadratic Zeeman fields. QFCSD can be potentially used to calibrate quantum fluctuations and investigate correlated fluctuations and various universal scaling properties near quantum critical points.
description: 14 pages, 12 figures included; including detailed discussions on thermal effects, trapping potentials and spin exchange losses. (To appear in PRA)
Swarm Differential Privacy for Purpose Driven Data-Information-Knowledge-Wisdom Architecture
Creators: name: Li, Yingbo
name: Duan, Yucong
name: Maama, Zakaria
name: Che, Haoyang
name: Spulber, Anamaria-Beatrice
name: Fuentes, Stelios
Publisher: name: arXiv
Year: 2021
Subjects: subject: Artificial Intelligence (cs.AI)
subject: Neural and Evolutionary Computing (cs.NE)
subject: FOS: Computer and information sciences

description: Privacy protection has recently been in the spotlight of attention to both academia and industry. Society protects individual data privacy through complex legal frameworks. The increasing number of applications of data science and artificial intelligence has resulted in a higher demand for the ubiquitous application of the data. The privacy protection of the broad Data-Information-Knowledge-Wisdom (DIKW) landscape, the next generation of information organization, has taken a secondary role. In this paper, we will explore DIKW architecture through the applications of the popular swarm intelligence and differential privacy. As differential privacy proved to be an effective data privacy approach, we will look at it from a DIKW domain perspective. Swarm Intelligence can effectively optimize and reduce the number of items in DIKW used in differential privacy, thus accelerating both the effectiveness and the efficiency of differential privacy for crossing multiple modals of conceptual DIKW. The proposed approach is demonstrated through the application of personalized data that is based on the open-sourse IRIS dataset. This experiment demonstrates the efficiency of Swarm Intelligence in reducing computing complexity.
Two-proton radioactivity and three-body decay. III. Integral formulae for decay widths in a simplified semianalytical approach
Creators: name: Grigorenko, L. V.
name: Zhukov, M. V.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: Three-body decays of resonant states are studied using integral formulae for decay widths. Theoretical approach with a simplified Hamiltonian allows semianalytical treatment of the problem. The model is applied to decays of the first excited $3/2^{-}$ state of $^{17}$Ne and the $3/2^{-}$ ground state of $^{45}$Fe. The convergence of three-body hyperspherical model calculations to the exact result for widths and energy distributions are studied. The theoretical results for $^{17}$Ne and $^{45}$Fe decays are updated and uncertainties of the derived values are discussed in detail. Correlations for the decay of $^{17}$Ne $3/2^-$ state are also studied.
description: 19 pages, 20 figures
A qualitative representation for manipulator kinematics and other vector and scalar fields
Creators: name: Dangelmaier, Heidi Therese
Publisher: name: University of British Columbia
Year: 2010

description: Over the last several years a branch of Artificial Intelligence called Qualitative Reasoning has received much attention. A qualitative reasoner use qualitative values such as increasing, boiling and turbulent to analyze the behavior of physical systems. Existing qualitative frameworks have focused on physical systems whose qualitative values can be identified given the value of a single parameter. This precludes the application of qualitative models to physical systems whose properties require the values of several parameters. An example of such a system is the kinematics of a robotic manipulator. With this motivation, this thesis answers the following: What is a Qualitative model? Although current approaches appear diverse, they share a common mathematical foundation. This foundation is used to reformulate the qualitative model as a set of equivalence relations. The other question answered is: What extensions are needed to handle multivariate properties such as those encountered in the manipulator paradigm? The equivalence classes associated with qualitative models are geometrically shown to be connected hyperspaces. We show that existing frameworks are limited in the types of hyperspaces they can represent. The major ideas in this thesis are illustrated using manipulator kinematics.
Concatenated dynamical decoupling in a solid-state spin bath
Creators: name: Witzel, W. M.
name: Sarma, S. Das
Publisher: name: arXiv
Year: 2007
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Concatenated dynamical decoupling (CDD) pulse sequences hold much promise as a strategy to mitigate decoherence in quantum information processing. It is important to investigate the actual performance of these dynamical decoupling strategies in real systems that are promising qubit candidates. In this Rapid Communication, we compute the echo decay of concatenations of the Hahn echo sequence for a solid-state electronic spin qubit in a nuclear spin bath using a cluster expansion technique. We find that each level of concatenation reverses the effect of successive levels of intrabath fluctuations. On the one hand, this advances CDD as a versatile and realistic decoupling strategy. On the other hand, this invalidates, as overly optimistic, results of the simple pair approximation used previously to study restoration, through CDD, of coherence lost to a mesoscopic spin bath.
Additional file 1 of Multiomics landscape of the autosomal dominant osteopetrosis type II disease-specific induced pluripotent stem cells
Creators: name: Li, Chunhong
name: Shangguan, Yu
name: Zhu, Peng
name: Dai, Weier
name: Tang, Donge
name: Ou, Minglin
name: Dai, Yong
Publisher: name: figshare
Year: 2021
Subjects: subject: Genetics
subject: FOS: Biological sciences

description: Additional file 1.
Strong magnon-photon coupling with chip-integrated YIG in the zero-temperature limit
Creators: name: Baity, Paul G.
name: Bozhko, Dmytro A.
name: Macêdo, Rair
name: Smith, William
name: Holland, Rory C.
name: Danilin, Sergey
name: Seferai, Valentino
name: Barbosa, João
name: Peroor, Renju R.
name: Goldman, Sara
name: Nasti, Umberto
name: Paul, Jharna
name: Hadfield, Robert H.
name: McVitie, Stephen
name: Weides, Martin
Publisher: name: arXiv
Year: 2021
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Applied Physics (physics.app-ph)
subject: FOS: Physical sciences

description: The cross-integration of spin-wave and superconducting technologies is a promising method for creating novel hybrid devices for future information processing technologies to store, manipulate, or convert data in both classical and quantum regimes. Hybrid magnon-polariton systems have been widely studied using bulk Yttrium Iron Garnet (Y$_{3}$Fe$_{5}$O$_{12}$, YIG) and three-dimensional microwave photon cavities. However, limitations in YIG growth have thus far prevented its incorporation into CMOS compatible technology such as high quality factor superconducting quantum technology. To overcome this impediment, we have used Plasma Focused Ion Beam (PFIB) technology -- taking advantage of precision placement down to the micron-scale -- to integrate YIG with superconducting microwave devices. Ferromagnetic resonance has been measured at millikelvin temperatures on PFIB-processed YIG samples using planar microwave circuits. Furthermore, we demonstrate strong coupling between superconducting resonator and YIG ferromagnetic resonance modes by maintaining reasonably low loss while reducing the system down to the micron scale. This achievement of strong coupling on-chip is a crucial step toward fabrication of functional hybrid quantum devices that advantage from spin-wave and superconducting components.
description: 10 pages, 6 figures
Predicting the phase behaviors of superionic water at planetary conditions
Creators: name: Cheng, Bingqing
name: Bethkenhagen, Mandy
name: Pickard, Chris J.
name: Hamel, Sebastien
Publisher: name: arXiv
Year: 2021
Subjects: subject: Computational Physics (physics.comp-ph)
subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Materials Science (cond-mat.mtrl-sci)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: Most water in the universe may be superionic, and its thermodynamic and transport properties are crucial for planetary science but difficult to probe experimentally or theoretically. We use machine learning and free energy methods to overcome the limitations of quantum mechanical simulations, and characterize hydrogen diffusion, superionic transitions, and phase behaviors of water at extreme conditions. We predict that a close-packed superionic phase with mixed stacking is stable over a wide temperature and pressure range, while a body-centered cubic phase is only thermodynamically stable in a small window but is kinetically favored. Our phase boundaries, which are consistent with the existing-albeit scarce-experimental observations, help resolve the fractions of insulating ice, different superionic phases, and liquid water inside of ice giants.
Millisecond Exoplanet Imaging, I: Method and Simulation Results
Creators: name: Rodack, Alexander T
name: Frazin, Richard A
name: Males, Jared R
name: Guyon, Olivier
Publisher: name: arXiv
Year: 2021
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: One of the top remaining science challenges in astronomical optics is the direct imaging and characterization of extrasolar planets and planetary systems. Directly imaging exoplanets from ground-based observatories requires combining high-order adaptive optics with a stellar coronagraph observing at wavelengths ranging from the visible to the mid-IR. A limiting factor in achieving the required contrast (planet-to-star intensity ratio) is quasi-static speckles, caused largely by non-common path aberrations (NCPA) in the coronagraph. Starting with a realistic simulator of a telescope with an AO system and a coronagraph, this article provides simulations of several closely related millisecond regression models requiring inputs of the measured wavefronts and science camera images. The simplest regression model, called the naive estimator, does not treat the noise and other sources of information loss in the WFS. The naive estimator provided a useful estimate of the NCPA of $\sim$ 0.5 radian RMS, with an accuracy of $\sim$ 0.06 radian RMS in one minute of simulated sky time on a magnitude 8 star. The bias-corrected estimator generalizes the regression model to account for the noise and information loss in the WFS. A simulation of the bias-corrected estimator with four minutes of sky time included an NCPA of $\sim 0.05 \,$ radian RMS and an extended exoplanet scene. The joint regression of the bias-corrected estimator simultaneously achieved an NCPA estimate with an accuracy of $\sim 5\times10^{-3} \,$radian and contrast of $\sim 10^{-5}$ on the exoplanet scene. In addition, the estimate of the exoplanet image was completely free of the subtraction artifacts that always plague differential imaging. The estimate of the exoplanet image obtained by the joint regression was nearly identical to the image obtained by subtraction of a perfectly known point-spread function.
description: 16 pages, 18 Figures, 4 Tables, submitted to JOSAA
On Chiral Splitting and the Ambitwistor String
Creators: name: Kalyanapuram, Nikhil
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Mathematical Physics (math-ph)
subject: Algebraic Geometry (math.AG)
subject: Differential Geometry (math.DG)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: Scattering amplitudes computed by superstring perturbation theory are known to holomorphically split into chiral half integrands at fixed internal loop momentum. It is established by direct computation that upon reduction to the ordinary moduli space, the chiral half integrands of the superstring match those computed by the ambitwistor string in the limit of zero tension ($α'\rightarrow\infty$). Subtleties that arise at higher genus due to the nonprojectedness of the supermoduli space are considered and arguments as to their resolution are furnished.
description: v2: 14 pages, references updated
Pair-correlation ansatz for the ground state of interacting bosons in an arbitrary one-dimensional potential
Creators: name: Kościk, Przemysław
name: Kuroś, Arkadiusz
name: Pieprzycki, Adam
name: Sowiński, Tomasz
Publisher: name: arXiv
Year: 2021
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We derive and describe a very accurate variational scheme for the ground state of the system of a few ultra-cold bosons confined in one-dimensional traps of arbitrary shapes. It is based on assumption that all inter-particle correlations have two-body nature. By construction, the proposed ansatz is exact in the noninteracting limit, exactly encodes boundary conditions forced by contact interactions, and gives full control on accuracy in the limit of infinite repulsions. We show its efficiency in a whole range of intermediate interactions for different external potentials. Our results manifest that for generic non-parabolic potentials mutual correlations forced by interactions cannot be captured by distance-dependent functions.
description: The authors' version accepted for publication
Z^0 \to 2γand the Twisted Coproduct of the Poincaré Group
Creators: name: Balachandran, A. P.
name: Jo, S. G.
Publisher: name: arXiv
Year: 2007
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: Mathematical Physics (math-ph)
subject: Quantum Algebra (math.QA)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: Yang's theorem forbids the process $Z^0 \to 2γ$ in any Poincaré invariant theory if photons are bosons and their two-particle states transform under the Poincaré group in the standard way (under the standard coproduct of the Poincaré group). This is an important result as it does not depend on the assumptions of quantum field theory. Recent work on noncommutative geometry requires deforming the above coproduct by the Drinfel'd twist. We prove that $Z^0 \to 2γ$ is forbidden for the twisted coproduct as well. This result is also independent of the assumptions of quantum field theory. As an illustration of the use of our general formulae, we further show that $Z^0 \to ν+ ν$ is forbidden for the standard or twisted coproduct of the Poincaré group if the neutrino is massless, even if lepton number is not conserved. This is a special case of our general result that a massive particle of spin $j$ cannot decay into two identical massless particles of the same helicity if $j$ is odd, regardless of the coproduct used.
From ten to four and back again: how to generalize the geometry
Creators: name: Koerber, Paul
name: Martucci, Luca
Publisher: name: arXiv
Year: 2007
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We discuss the four-dimensional N=1 effective approach in the study of warped type II flux compactifications with SU(3)x SU(3)-structure to AdS_4 or flat Minkowski space-time. The non-trivial warping makes it natural to use a supergravity formulation invariant under local complexified Weyl transformations. We obtain the classical superpotential from a standard argument involving domain walls and generalized calibrations and show how the resulting F-flatness and D-flatness equations exactly reproduce the full ten-dimensional supersymmetry equations. Furthermore, we consider the effect of non-perturbative corrections to this superpotential arising from gaugino condensation or Euclidean D-brane instantons. For the latter we derive the supersymmetry conditions in N=1 flux vacua in full generality. We find that the non-perturbative corrections induce a quantum deformation of the internal generalized geometry. Smeared instantons allow to understand KKLT-like AdS vacua from a ten-dimensional point of view. On the other hand, non-smeared instantons in IIB warped Calabi-Yau compactifications 'destabilize' the Calabi-Yau complex structure into a genuine generalized complex one. This deformation gives a geometrical explanation of the non-trivial superpotential for mobile D3-branes induced by the non-perturbative corrections.
description: LaTeX, 47 pages, v2, references, hyperref added, v3, correcting small inaccuracies in eqs. (2.6a) and (5.16)
Half and quarter metals in rhombohedral trilayer graphene
Creators: name: Zhou, Haoxin
name: Xie, Tian
name: Ghazaryan, Areg
name: Holder, Tobias
name: Ehrets, James R.
name: Spanton, Eric M.
name: Taniguchi, Takashi
name: Watanabe, Kenji
name: Berg, Erez
name: Serbyn, Maksym
name: Young, Andrea F.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Ferromagnetism is most common in transition metal compounds but may also arise in low-density two-dimensional electron systems, with signatures observed in silicon, III-V semiconductor systems, and graphene moiré heterostructures. Here we show that gate-tuned van Hove singularities in rhombohedral trilayer graphene drive the spontaneous ferromagnetic polarization of the electron system into one or more spin- and valley flavors. Using capacitance measurements on graphite-gated van der Waals heterostructures, we find a cascade of density- and electronic displacement field tuned phase transitions marked by negative electronic compressibility. The transitions define the boundaries between phases where quantum oscillations have either four-fold, two-fold, or one-fold degeneracy, associated with a spin and valley degenerate normal metal, spin-polarized `half-metal', and spin and valley polarized `quarter metal', respectively. For electron doping, the salient features are well captured by a phenomenological Stoner model with a valley-anisotropic Hund's coupling, likely arising from interactions at the lattice scale. For hole filling, we observe a richer phase diagram featuring a delicate interplay of broken symmetries and transitions in the Fermi surface topology. Finally, by rotational alignment of a hexagonal boron nitride substrate to induce a moiré superlattice, we find that the superlattice perturbs the preexisting isospin order only weakly, leaving the basic phase diagram intact while catalyzing the formation of topologically nontrivial gapped states whenever itinerant half- or quarter metal states occur at half- or quarter superlattice band filling. Our results show that rhombohedral trilayer graphene is an ideal platform for well-controlled tests of many-body theory and reveal magnetism in moiré materials to be fundamentally itinerant in nature.
Diffuse wave density and directionality in anisotropic solids
Creators: name: Norris, Andrew N.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Several general results are derived for diffuse waves in anisotropic solids, including concise expressions for the modal density per unit volume and for the participation factor matrix G. The latter is a second order tensor which describes the orientational distribution of diffuse wave or reverberant energy, and reduces to the identity I under isotropy. Calculations of G for a variety of example materials show significant deviation from I even under moderate levels of anisotropy.
description: 11 pages, 2 figures
Qualitative and quantitative analysis of polyphenols in camelina seed and theirs antioxidant activities
Creators: name: Li, Feifei
name: Li, Zhining
name: Wei, Yue
name: Zhang, Lixian
name: Ning, Erjuan
name: Yu, Liqin
name: Zhu, Jie
name: Wang, Xuefang
name: Ma, Yanni
name: Fan, Yi
Publisher: name: Taylor & Francis
Year: 2022
Subjects: subject: Biochemistry
subject: Medicine
subject: Cell Biology
subject: Pharmacology
subject: Environmental Sciences not elsewhere classified
subject: Chemical Sciences not elsewhere classified
subject: Ecology
subject: FOS: Biological sciences
subject: Sociology
subject: FOS: Sociology
subject: Biological Sciences not elsewhere classified
subject: Cancer

description: Camelina [Camelina sativa (L.) Crantz] seed has long been consumed as a source of food in Canada. But limited information is available concerning the systematical evaluation of the composition, content, and antioxidant activity of Camelina seed polyphenol extract (CSPE). Therefore, the aim of this study was to identify, quantify and evaluate the antioxidant activity of CSPE. The result showed that eight compositions were identified and determined by the UPLC-DAD-ESI-MS2 analysis. CSPE has potent free radical scavenging capacity. CSPE treatment significantly increased the activities of the antioxidant enzymes (superoxide dismutase and catalase) and glutathione content in a dose-dependent manner in RAW264.7 cells with oxidative injury and also reduced malondialdehyde content (P < 0.01). It may be concluded that CSPE has a strong antioxidant activity as depicted by the in vitro experiments and thus possesses the potential to be developed as food antioxidants or as an ingredient in functional foods.
Parameter Priors for Directed Acyclic Graphical Models and the Characterization of Several Probability Distributions
Creators: name: Geiger, Dan
name: Heckerman, David
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (stat.ML)
subject: Machine Learning (cs.LG)
subject: Statistics Theory (math.ST)
subject: FOS: Computer and information sciences
subject: FOS: Mathematics
subject: I.2; G.3

description: We develop simple methods for constructing parameter priors for model choice among Directed Acyclic Graphical (DAG) models. In particular, we introduce several assumptions that permit the construction of parameter priors for a large number of DAG models from a small set of assessments. We then present a method for directly computing the marginal likelihood of every DAG model given a random sample with no missing observations. We apply this methodology to Gaussian DAG models which consist of a recursive set of linear regression models. We show that the only parameter prior for complete Gaussian DAG models that satisfies our assumptions is the normal-Wishart distribution. Our analysis is based on the following new characterization of the Wishart distribution: let $W$ be an $n \times n$, $n \ge 3$, positive-definite symmetric matrix of random variables and $f(W)$ be a pdf of $W$. Then, f$(W)$ is a Wishart distribution if and only if $W_{11} - W_{12} W_{22}^{-1} W'_{12}$ is independent of $\{W_{12},W_{22}\}$ for every block partitioning $W_{11},W_{12}, W'_{12}, W_{22}$ of $W$. Similar characterizations of the normal and normal-Wishart distributions are provided as well.
description: This version has improved pointers to the literature. arXiv admin note: substantial text overlap with arXiv:1301.6697
When the Cramer-Rao Inequality provides no information
Creators: name: Miller, Steven J.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Statistics Theory (math.ST)
subject: FOS: Mathematics

description: We investigate a one-parameter family of probability densities (related to the Pareto distribution, which describes many natural phenomena) where the Cramer-Rao inequality provides no information.
description: 10 pages, 1 figure, to appear in Communications in Information and Systems
Analysis of a 3-RUU Parallel Manipulator
Creators: name: Stigger, Thomas
name: Siegele, Johannes
name: Scharler, Daniel F.
name: Pfurner, Martin
name: Husty, Manfred L.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Robotics (cs.RO)
subject: Algebraic Geometry (math.AG)
subject: FOS: Computer and information sciences
subject: FOS: Mathematics

description: The aim of this paper is to give a detailed examination of the input and output singularities of a 3-RUU parallel manipulator in the translational operation mode. This task is achieved by using algebraic constraint equations. For this type of manipulator a complete workspace representation in Study coordinates is presented after elimination of the input parameters. Both, input and output singularities are mapped into a Study subspace as well as into the joint space. Therewith a detailed singularity investigation of the translational operation mode of a 3-RUU parallel manipulator is provided. This paper is an extended version of a previous publication. The addendum comprises the discovery of a possible transition between two operation modes as well as a self motion and an examination of another component of the output singularity surface, most of them for arbitrary design parameters.
Lower order terms in the 1-level density for families of holomorphic cuspidal newforms
Creators: name: Miller, Steven J.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: 11M26 (primary), 11G40, 11M41, 15A52 (secondary)

description: The Katz-Sarnak density conjecture states that, in the limit as the conductors tend to infinity, the behavior of normalized zeros near the central point of families of L-functions agree with the N -> oo scaling limits of eigenvalues near 1 of subgroups of U(N). Evidence for this has been found for many families by studying the n-level densities; for suitably restricted test functions the main terms agree with random matrix theory. In particular, all one-parameter families of elliptic curves with rank r over Q(T) and the same distribution of signs of functional equations have the same limiting behavior. We break this universality and find family dependent lower order correction terms in many cases; these lower order terms have applications ranging from excess rank to modeling the behavior of zeros near the central point, and depend on the arithmetic of the family. We derive an alternate form of the explicit formula for GL(2) L-functions which simplifies comparisons, replacing sums over powers of Satake parameters by sums of the moments of the Fourier coefficients lambda_f(p). Our formula highlights the differences that we expect to exist from families whose Fourier coefficients obey different laws (for example, we expect Sato-Tate to hold only for non-CM families of elliptic curves). Further, by the work of Rosen and Silverman we expect lower order biases to the Fourier coefficients in families of elliptic curves with rank over Q(T); these biases can be seen in our expansions. We analyze several families of elliptic curves and see different lower order corrections, depending on whether or not the family has complex multiplication, a forced torsion point, or non-zero rank over Q(T).
description: 38 pages, version 2.2: fixed some typos, included some comments from Steven Finch which give more rapidly converging expressions for the constants gamma_{PNT}, gamma_{PNT,1,3} and gamma_{PNT,1,4}, updated references