cssi/SciSciGPT-SciSciNet huggingface dataset:
Inferring Parameters of GW170502: The Loudest Intermediate-mass Black Hole Trigger in LIGO’s O1/O2 data

Gravitational wave (GW) measurements provide the most robust constraints of the mass of astrophysical black holes. Using state-of-the-art GW signal models and a unique parameter estimation technique, we infer the source parameters of the loudest marginal trigger, GW170502, found by LIGO from 2015 to 2017. If this trigger is assumed to be a binary black hole merger, we find it corresponds to a total mass in the source frame of $157^{+55}_{-41}~\rm{M}_\odot$ at redshift $z=1.37^{+0.93}_{-0.64}$. The primary and secondary black hole masses are constrained to $94^{+44}_{-28}~\rm{M}_{\odot}$ and $62^{+30}_{-25}~\rm{M}_{\odot}$ respectively, with 90\% confidence. Across all signal models, we find $\gtrsim 70\%$ probability for the effective spin parameter $\chi_\mathrm{eff}>0.1$. Furthermore, we find that the inclusion of higher-order modes in the analysis narrows the confidence region for the primary black hole mass by 10\%, however, the evidence for these modes in the data remains negligible. The techniques outlined in this study could lead to robust inference of the physical parameters for all intermediate-mass black hole binary candidates $(\gtrsim100~\mathrm{M}_\odot)$ in the current GW network.
Diagonal form of the Varchenko matrices

Varchenko (Adv Math 97(1):110–144, 1993) defined the Varchenko matrix associated with any real hyperplane arrangement and computed its determinant. In this paper, we show that the Varchenko matrix of a hyperplane arrangement has a diagonal form if and only if it is semigeneral, i.e., without degeneracy. In the case of semigeneral arrangement, we present an explicit computation of the diagonal form via combinatorial arguments and matrix operations, thus giving a combinatorial interpretation of the diagonal entries.
Metrics for Optimization of Large Synoptic Survey Telescope Observations of Stellar Variables and Transients

The Large Synoptic Survey Telescope (LSST) will be the largest time-domain photometric survey ever. In order to maximize the LSST science yield for a broad array of transient stellar phenomena, it is necessary to optimize the survey cadence, coverage, and depth via quantitative metrics that are specifically designed to characterize the time-domain behavior of various types of stellar transients. In this paper, we present three such metrics built on the LSST Metric Analysis Framework model. Two of the metrics quantify the ability of LSST to detect non-periodic and/or non-recurring transient events and the ability of LSST to reliably measure periodic signals of various timescales. The third metric provides a way to quantify the range of stellar parameters in the stellar populations that LSST will probe. We provide example uses of these metrics and discuss some implications based on these metrics for optimization of the LSST survey for observations of stellar variables and transients.
Interacting Galactic Neutral Hydrogen Filaments and Associated High-frequency Continuum Emission

Galactic H I emission profiles in an area where several large-scale filaments at velocities ranging from –46 km s–1 to 0 km s–1 overlap were decomposed into Gaussian components. Eighteen families of components defined by similarities of center velocity and line width were identified and related to small-scale structure in the high-frequency continuum emission observed by the Wilkinson Microwave Anisotropy Probe spacecraft, as evidenced in the Internal Linear Combination (ILC) map of Hinshaw et al. When the center velocities of the Gaussian families, which summarize the properties of all the H I along the lines of sight in a given area, are used to focus on H I channel maps the phenomenon of close associations between H I and ILC peaks reported in previous papers is dramatically highlighted. Of particular interest, each of two pairs of H I peaks straddles a continuum peak. The previously hypothesized model for producing the continuum radiation involving free-free emission from electrons is re-examined in light of the new data. By choosing reasonable values for the parameters required to evaluate the model, the distance for associated H I-ILC features is of order 30-100 pc. No associated Hα radiation is expected because the electrons involved exist throughout the Milky Way. The mechanism for clumping and separation of neutrals and electrons needs to be explored. It is concluded that the small-scale ILC structure originates in the local interstellar medium and not at cosmological distances.
Imitation Attacks and Defenses for Black-box Machine Translation Systems

Adversaries may look to steal or attack black-box NLP systems, either for financial gain or to exploit model errors. One setting of particular interest is machine translation (MT), where models have high commercial value and errors can be costly. We investigate possible exploitations of black-box MT systems and explore a preliminary defense against such threats. We first show that MT systems can be stolen by querying them with monolingual sentences and training models to imitate their outputs. Using simulated experiments, we demonstrate that MT model stealing is possible even when imitation models have different input data or architectures than their target models. Applying these ideas, we train imitation models that reach within 0.6 BLEU of three production MT systems on both high-resource and low-resource language pairs. We then leverage the similarity of our imitation models to transfer adversarial examples to the production systems. We use gradient-based attacks that expose inputs which lead to semantically-incorrect translations, dropped content, and vulgar model outputs. To mitigate these vulnerabilities, we propose a defense that modifies translation outputs in order to misdirect the optimization of imitation models. This defense degrades the adversary’s BLEU score and attack success rate at some cost in the defender’s BLEU and inference speed.
K3 Surfaces, Modular Forms, and Non-Geometric Heterotic Compactifications

We construct non-geometric compactifications using the F-theory dual of the heterotic string compactified on a two-torus, together with a close connection between Siegel modular forms of genus two and the equations of certain K3 surfaces. The modular group mixes together the Kahler, complex structure, and Wilson line moduli of the torus yielding weakly coupled heterotic string compactifications which have no large radius interpretation.
Is Proxima Centauri b Habitable? A Study of Atmospheric Loss

We address the important question of whether the newly discovered exoplanet, Proxima Centauri b (PCb), is capable of retaining an atmosphere over long periods of time. This is done by adapting a sophisticated multi-species MHD model originally developed for Venus and Mars and computing the ion escape losses from PCb. The results suggest that the ion escape rates are about two orders of magnitude higher than the terrestrial planets of our Solar system if PCb is unmagnetized. In contrast, if the planet does have an intrinsic dipole magnetic field, the rates are lowered for certain values of the stellar wind dynamic pressure, but they are still higher than the observed values for our solar system's terrestrial planets. These results must be interpreted with due caution since most of the relevant parameters for PCb remain partly or wholly unknown.
An Interactive LiDAR to Camera Calibration

Recent progress in the automated driving system and advanced driver assistant system has shown that the combined use of 3D light detection and ranging (LiDAR) and the camera is essential for an intelligent vehicle to perceive the driving scenarios. LiDAR-camera fusion systems require precise intrinsic and extrinsic transformation between sensors. However, due to the limitation of the calibration equipment and susceptibility to noise, algorithms in existing methods tend to fail in finding LiDAR-camera correspondences in long-range terms. In this paper, we introduced an interactive LiDAR to camera calibration toolbox that estimates the intrinsic and extrinsic transform parameters. This toolbox automatically detects the corner of a planer board from a sequence of LiDAR frames and provides a convenient user interface to annotate the corresponding pixels on camera frames. Since the toolbox only detects the top corner of the board, there is no need to prepare a precise polygon planar board or a checkerboard with different reflectivity areas as in the existing methods. Furthermore, the toolbox uses genetic algorithms to estimate the transforms and supports multiple camera models such as the pinhole camera model and the fisheye camera model. Experiments using Velodyne VLP-16 LiDAR and Point Grey Chameleon 3 camera show robust results.
Pairing of Zeros and Critical Points for Random Meromorphic Functions on Riemann Surfaces

We prove that zeros and critical points of a random polynomial $p_N$ of degree $N$ in one complex variable appear in pairs. More precisely, if $p_N$ is conditioned to have $p_N(\xi)=0$ for a fixed $\xi \in \C\backslash\set{0},$ we prove that there is a unique critical point z in the annulus $N^{-1-\ep}<\abs{z-\xi}< N^{-1+\ep}}$ and no critical points closer to $\xi$ with probability at least $1-O(N^{-3/2+3\ep}).$ We also prove an analogous statement in the more general setting of random meromorphic functions on a closed Riemann surface.
Comparison of echo state network output layer classification methods on noisy data

Echo state networks are a recently developed type of recurrent neural network where the internal layer is fixed with random weights, and only the output layer is trained on specific data. Echo state networks are increasingly being used to process spatio-temporal data in real-world settings, including speech recognition, event detection, and robot control. A strength of echo state networks is the simple method used to train the output layer — typically a collection of linear readout weights found using a least squares approach. Although straightforward to train and having a low computational cost to use, this method may not yield acceptable accuracy performance on noisy data. This study compares the performance of three echo state network output layer methods to perform classification on noisy data: using trained linear weights, using sparse trained linear weights, and using trained low-rank approximations of reservoir states. The methods are investigated experimentally on both synthetic and natural datasets. The experiments suggest that using regularized least squares to train linear output weights is superior on data with low noise, but using the low-rank approximations may significantly improve accuracy on datasets contaminated with higher noise levels.
Floating electrode electrowetting on hydrophobic dielectric with an SiO2 layer

Floating electrode electrowetting is caused by dc voltage applied to a liquid droplet on the Cytop surface, without electrical connection to the substrate. The effect is caused by the charge separation in the floating electrode. A highly resistive thermally grown SiO2 layer underneath the Cytop enables the droplet to hold charges without leakage, which is the key contribution. Electrowetting with a SiO2 layer shows a memory effect, where the wetting angle stays the same after the auxiliary electrode is removed from the droplet in both conventional and floating electrode electrowetting. Floating electrode electrowetting provides an alternative configuration for developing advanced electrowetting-based devices.
The Origin of the Exoplanets

We explore two ways in which objects of planetary masses can form. One is in disk systems like the solar system. The other is in dense clusters where stars and brown dwarfs form. We do not yet have the instrumental accuracy to detect multiplanet systems with masses like those in solar system; with our present technology from a distant site, only the effects of Jupiter could be detected. We show that the orbital characteristics (eccentricities and semimajor axes) of stellar, brown dwarf, and exoplanet companions of solar-type stars are all the same within our measuring accuracies and are very different than the planets in the solar system. The period ratios in multiplanet systems do not distinguish between the two models. We conclude that most of the exoplanets found to date are formed like stellar companions and not in disk systems like the solar system. This conclusion explains why metal-poor stars lack planets: because metal-poor stars lack stellar companions with short periods. The distribution of exoplanetary periods for primaries having [Fe/H] < -0.3 fits the distribution for stellar companions of metal-poor stars and not of metal-rich stars.
The Second Nucleus of NGC 7727: Direct Evidence for the Formation and Evolution of an Ultracompact Dwarf Galaxy*

We present new observations of the late-stage merger galaxy NGC 7727, including HST/WFPC2 images and long-slit spectra obtained with the Clay telescope. NGC 7727 is relatively luminous ($M_V = -21.7$) and features two unequal tidal tails, various bluish arcs and star clusters, and two bright nuclei 480 pc apart in projection. These two nuclei have nearly identical redshifts, yet are strikingly different. The primary nucleus, hereafter Nucleus_1, fits smoothly into the central luminosity profile of the galaxy and appears--at various wavelengths--"red and dead." In contrast, Nucleus_2 is very compact, has a tidal radius of 103 pc, and exhibits three signs of recent activity: a post-starburst spectrum, an [O III]_5007 emission line, and a central X-ray point source. Its emission-line ratios place it among Seyfert nuclei. A comparison of Nucleus_2 ($M_V = -15.5$) with ultracompact dwarf galaxies (UCDs) suggests that it may be the best case yet for a massive UCD having formed through tidal stripping of a gas-rich disk galaxy. Evidence for this comes from its extended star-formation history, long blue tidal stream, and elevated dynamical-to-stellar-mass ratio. While the majority of its stars formed $\gtrsim 10$ Gyr ago, about 1/3 by mass formed during starbursts in the past 2 Gyr. Its weak AGN activity is likely driven by a black hole of mass $3\times 10^6 - 3\times 10^8 M_\odot$. We estimate that the former companion's initial mass was less than half that of then-NGC 7727, implying a minor, but significant, merger. By now this former companion has been largely shredded, leaving behind Nucleus_2 as a freshly minted UCD that probably moves on a highly eccentric orbit.
Quantum FFLO state in clean layered superconductors

An updated theoretical framework of a superconducting phase known as the Fulde-Ferrell-Larkin-Ovchinnikov state adds quantum-mechanical considerations that flesh out ideas about how superconductors behave in strong magnetic fields.
Predicting regional and pan-Arctic sea ice anomalies with kernel analog forecasting

Predicting Arctic sea ice extent is a notoriously difficult forecasting problem, even for lead times as short as one month. Motivated by Arctic intraannual variability phenomena such as reemergence of sea surface temperature and sea ice anomalies, we use a prediction approach for sea ice anomalies based on analog forecasting. Traditional analog forecasting relies on identifying a single analog in a historical record, usually by minimizing Euclidean distance, and forming a forecast from the analog’s historical trajectory. Here an ensemble of analogs is used to make forecasts, where the ensemble weights are determined by a dynamics-adapted similarity kernel, which takes into account the nonlinear geometry on the underlying data manifold. We apply this method for forecasting pan-Arctic and regional sea ice area and volume anomalies from multi-century climate model data, and in many cases find improvement over the benchmark damped persistence forecast. Examples of success include the 3–6 month lead time prediction of Arctic sea ice area, the winter sea ice area prediction of some marginal ice zone seas, and the 3–12 month lead time prediction of sea ice volume anomalies in many central Arctic basins. We discuss possible connections between KAF success and sea ice reemergence, and find KAF to be successful in regions and seasons exhibiting high interannual variability.
Empirical field mapping for gradient nonlinearity correction of multi-site diffusion weighted MRI.

Abstract Background Achieving inter-site / inter-scanner reproducibility of diffusion weighted magnetic resonance imaging (DW-MRI) metrics has been challenging given differences in acquisition protocols, analysis models, and hardware factors. Purpose Magnetic field gradients impart scanner-dependent spatial variations in the applied diffusion weighting that can be corrected if the gradient nonlinearities are known. However, retrieving manufacturer nonlinearity specifications is not well supported and may introduce errors in interpretation of units or coordinate systems. We propose an empirical approach to mapping the gradient nonlinearities with sequences that are supported across the major scanner vendors. Study type Prospective observational study. Subjects A spherical isotropic diffusion phantom, and a single human control volunteer. Field strength/sequence 3 T (two scanners). Stejskal-Tanner spin echo sequence with b-values of 1000, 2000 s/mm2 with 12, 32, and 384 diffusion gradient directions per shell. Assessment We compare the proposed correction with the prior approach using manufacturer specifications against typical diffusion pre-processing pipelines (i.e., ignoring spatial gradient nonlinearities). In phantom data, we evaluate metrics against the ground truth. In human and phantom data, we evaluate reproducibility across scans, sessions, and hardware. Statistical tests Wilcoxon rank-sum test between uncorrected and corrected data. Results In phantom data, our correction method reduces variation in mean diffusivity across sessions over uncorrected data (p Conclusion Our method is relatively simple, fast, and can be applied retroactively. We advocate incorporating voxel-specific b-value and b-vector maps should be incorporated in DW-MRI harmonization preprocessing pipelines to improve quantitative accuracy of measured diffusion parameters.
Primordial non-Gaussianities in single field inflationary models with non-trivial initial states

We compute the non-Gaussianities that arise in single field, slow roll inflationary models arising from arbitrary homogeneous initial states, as well as subleading contributions to the power spectrum. Non Bunch-Davies vacuum initial states can arise if the transition to the single field, slow roll inflation phase occurs only shortly before observable modes left the horizon. They can also arise from new physics at high energies that has been integrated out. Our general result for the bispectrum exhibits several features that were previously seen in special cases.
The Type I Superluminous Supernova PS16aqv: Lightcurve Complexity and Deep Limits on Radioactive Ejecta in a Fast Event

[Abridged] We present UV/optical observations of PS16aqv (SN 2016ard), a Type I superluminous supernova (SLSN-I) classified as part of our search for low-$z$ SLSNe. PS16aqv is a fast evolving SLSNe-I that reached a peak absolute magnitude of $M_{r} \approx -22.1$. The lightcurves exhibit a significant undulation at 30 rest-frame days after peak, with a behavior similar to undulations seen in the slowly fading SLSN-I SN 2015bn. This similarity strengthens the case that fast and slow SLSNe-I form a continuum with a common origin. At $\approx\!80$ days after peak, the lightcurves exhibit a transition to a slow decline, followed by significant subsequent steepening, indicative of a plateau phase or a second significant undulation. Deep limits at $\approx280$ days after peak imply a tight constraint on the nickel mass, $M_{\rm Ni} \lesssim 0.35$ M$_{\odot}$ (lower than for previous SLSNe-I), and indicate that some SLSNe-I do not produce significantly more nickel than normal Type Ic SNe. Using MOSFiT, we model the lightcurve with a magnetar central engine model and find $P_{\rm spin} \approx 0.9$ ms, $B \approx 1.5 \times 10^{14}$ G, and $M_{\rm ej} \approx 16$ M$_{\odot}$. The implied rapid spin-down time and large reservoir of available energy coupled with the high ejecta mass may account for the fast evolving lightcurve and slow spectroscopic evolution. We also study the location of PS16aqv in its host galaxy and find that it occurred at an offset of $2.46 \pm 0.21$ kpc from the central star-forming region. We find the host galaxy exhibits low metallicity and spatially varying extinction and star formation rate, with the explosion site exhibiting lower values than the central region. The complexity seen in the lightcurves of PS16aqv and other events highlights the importance of obtaining well-sampled lightcurves for exploring deviations from a uniform decline.
Introduction to gestural similarity in music. An application of category theory to the orchestra

Mathematics, and more generally computational sciences, intervene in several aspects of music. Mathematics describes the acoustics of the sounds giving formal tools to physics, and the matter of mu...
Boundary measurement matrices for directed networks on surfaces

Abstract Franco, Galloni, Penante, and Wen have proposed a boundary measurement map for a graph on any closed orientable surface with boundary. We consider this boundary measurement map which takes as input an edge weighted directed graph embedded on a surface and produces on element of a Grassmannian. Computing the boundary measurement requires a choice of fundamental domain. Here the boundary measurement map is shown to be independent of the choice of fundamental domain Also, a formula for the Plucker coordinates of the element of the Grassmannian in the image of the boundary measurement map is given. The formula expresses the Plucker coordinates as a rational function which can be combinatorially described in terms of paths and cycles in the directed graph.
Reparameterization invariant operator basis for NRQED and HQET

We provide a self-contained discussion of how reparameterization invariance connects a rotationally-invariant heavy particle effective theory with a single heavy fermion to a Lorentz-invariant theory. Furthermore, using Hilbert-series methods, a Lorentz- invariant operator basis is tabulated, up to and including operators of order 1/M4, when the fermion couples to an external U(1) or SU(3) gauge interaction.
Formation of solitary zonal structures via the modulational instability of drift waves

The dynamics of the radial envelope of a weak coherent drift wave is approximately governed by a nonlinear Schr\"odinger equation, which emerges as a limit of the modified Hasegawa--Mima equation. The nonlinear Schr\"odinger equation has well-known soliton solutions, and its modulational instability can naturally generate solitary structures. In this paper, we demonstrate that this simple model can adequately describe the formation of solitary zonal structures in the modified Hasegawa--Mima equation, but only when the amplitude of the coherent drift wave is relatively small. At larger amplitudes, the modulational instability produces stationary zonal structures instead. Furthermore, we find that incoherent drift waves with beam-like spectra can also be modulationally unstable to the formation of solitary or stationary zonal structures, depending on the beam intensity. Notably, we show that these drift waves can be modeled as quantumlike particles (``driftons'') within a recently developed phase-space (Wigner--Moyal) formulation, which intuitively depicts the solitary zonal structures as quasi-monochromatic drifton condensates. Quantumlike effects, such as diffraction, are essential to these condensates; hence, the latter cannot be described by wave-kinetic models that are based on the ray approximation.
Demonstrating 100 Gbps in and out of the public Clouds

There is increased awareness and recognition that public Cloud providers do provide capabilities not found elsewhere, with elasticity being a major driver. The value of elastic scaling is however tightly coupled to the capabilities of the networks that connect all involved resources, both in the public Clouds and at the various research institutions. This paper presents results of measurements involving file transfers inside public Cloud providers, fetching data from on-prem resources into public Cloud instances and fetching data from public Cloud storage into on-prem nodes. The networking of the three major Cloud providers, namely Amazon Web Services, Microsoft Azure and the Google Cloud Platform, has been benchmarked. The on-prem nodes were managed by either the Pacific Research Platform or located at the University of Wisconsin – Madison. The observed sustained throughput was of the order of 100 Gbps in all the tests moving data in and out of the public Clouds and throughput reaching into the Tbps range for data movements inside the public Cloud providers themselves. All the tests used HTTP as the transfer protocol.
WORLDSHEET COVARIANT PATH INTEGRAL QUANTIZATION OF STRINGS

We discuss a covariant functional integral approach to the quantization of the bosonic string. In contrast to approaches relying on noncovariant operator regularizations, interesting operators here are true tensor objects with classical transformation laws, even on target spaces where the theory has a Weyl anomaly. Since no implicit noncovariant gauge choices are involved in the definition of the operators, the anomaly is clearly separated from the issue of operator renormalization and can be understood in isolation, instead of infecting the latter as in other approaches. Our method is of wider applicability to covariant theories that are not Weyl invariant, but where covariant tensor operators are desired. After constructing covariantly regularized vertex operators, we define a class of background-independent path integral measures suitable for string quantization. We show how gauge invariance of the path integral implies the usual physical state conditions in a very conceptually clean way. We then discuss the construction of the BRST action from first principles, obtaining some interesting caveats relating to its general covariance. In our approach, the expected BRST related anomalies are encoded somewhat differently from other approaches. We conclude with an unusual but amusing derivation of the value D = 26 of the critical dimension.
Towards real-time respiratory motion prediction based on long short-term memory neural networks

Radiation therapy of thoracic and abdominal tumors requires incorporating the respiratory motion into treatments. To precisely account for the patient’s respiratory motions and predict the respiratory signals, a generalized model for predictions of different types of patients’ respiratory motions is desired. The aim of this study is to explore the feasibility of developing a long short-term memory (LSTM)-based generalized model for the respiratory signal prediction. To achieve that, 1703 sets of real-time position management (RPM) data were collected from retrospective studies across three clinical institutions. These datasets were separated as the training, internal validity and external validity groups. Among all the datasets, 1187 datasets were used for model development and the remaining 516 datasets were used to test the model’s generality power. Furthermore, an exhaustive grid search was implemented to find the optimal hyper-parameters of the LSTM model. The hyper-parameters are the number of LSTM layers, the number of hidden units, the optimizer, the learning rate, the number of epochs, and the length of time lags. The obtained model achieved superior accuracy over conventional artificial neural network (ANN) models: with the prediction window equaling to 500 ms, the LSTM model achieved an average relative mean absolute error (MAE) of 0.037, an average root mean square error (RMSE) of 0.048, and a maximum error (ME) of 1.687 in the internal validity data, and an average relative MAE of 0.112, an average RMSE of 0.139 and an ME of 1.811 in the external validity data. Compared to the LSTM model trained with default hyper-parameters, the MAE of the optimized model results decreased by 20%, indicating the importance of tuning the hyper-parameters of LSTM models to obtain superior accuracies. This study demonstrates the potential of deep LSTM models for the respiratory signal prediction and illustrates the impacts of major hyper-parameters in LSTM models.
Jet fragmentation functions in proton-proton collisions using soft-collinear effective theory

The jet fragmentation function describes the longitudinal momentum distribution of hadrons inside a reconstructed jet. We study the jet fragmentation function in proton-proton collisions in the framework of soft-collinear effective theory (SCET). We find that, up to power corrections, the jet fragmentation function can be expressed as the ratio of the fragmenting jet function and the unmeasured jet function. Using renormalization group techniques, we are able to resum large logarithms of jet radii R in the perturbative expansion of the cross section. We use our theoretical formalism to describe the jet fragmentation functions for light hadron and heavy meson production measured at the Large Hadron Collider (LHC). Our calculations agree very well with the experimental data for the light hadron production. On the other hand, although our calculations for the heavy meson production inside jets are consistent with the PYTHIA simulation, they fail to describe the LHC data. We find that the jet fragmentation function for heavy meson production is very sensitive to the gluon-to-heavy-meson fragmentation function.
Visualization of nano-plasmons in graphene

We study localized plasmons at the nanoscale (nano-plasmons) in graphene. The collective excitations of induced charge density modulations in graphene are drastically changed in the vicinity of a single impurity compared to graphene's bulk behavior. The dispersion of nano-plasmons depends on the number of electrons and the sign, strength and size of the impurity potential. Due to this rich parameter space the calculated dispersions are intrinsically multidimensional requiring an advanced visualization tool for their efficient analysis, which can be achieved with parallel rendering. To overcome the problem of analyzing thousands of very complex spatial patterns of nano-plasmonic modes, we take a combined visual and quantitative approach to investigate the excitations on the two-dimensional graphene lattice. Our visual and quantitative analysis shows that impurities trigger the formation of localized plasmonic excitations of various symmetries. We visually identify dipolar, quadrupolar and radial modes, and...
Star formation in the LMC: Gravitational instability and dynamical triggering

Evidence for triggered star formation is difficult to establish because energy feedback from massive stars tend to erase the interstellar conditions that led to the star formation. Young stellar objects (YSOs) mark sites of current star formation whose ambient conditions have not been significantly altered. Spitzer observations of the Large Magellanic Cloud (LMC) effectively reveal massive YSOs. The inventory of massive YSOs, in conjunction with surveys of interstellar medium, allows us to examine the conditions for star formation: spontaneous or triggered. We examine the relationship between star formation and gravitational instability on a global scale, and we present evidence of triggered star formation on local scales in the LMC.
Global anomalies, discrete symmetries and hydrodynamic effective actions

We derive effective actions for parity-violating fluids in both (3 + 1) and (2 + 1) dimensions, including those with anomalies. As a corollary we confirm the most general constitutive relations for such systems derived previously using other methods. We discuss in detail connections between parity-odd transport and underlying discrete symmetries. In (3+1) dimensions we elucidate connections between anomalous transport coefficients and global anomalies, and clarify a previous puzzle concerning transports and local gravitational anomalies.
Proposal for resonant detection of relic massive neutrinos

We present a novel method for detecting the relic neutrino background that takes advantage of structured quantum degeneracy to amplify the drag force from neutrinos scattering off a detector. Developing this idea, we present a characterization of the present day relic neutrino distribution in an arbitrary frame, including the influence of neutrino mass and neutrino reheating by $$e^+e^-$$ annihilation. We present explicitly the neutrino velocity and de Broglie wavelength distributions for the case of an Earthbound observer. Considering that relic neutrinos could exhibit quantum liquid features at the present day temperature and density, we discuss the impact of neutrino fluid correlations on the possibility of resonant detection.
Structure and dynamics of the accretion process and wind in TW Hya

Time-domain spectroscopy of the classical accreting T Tauri star, TW Hya, covering a decade and spanning the far UV to the near-infrared spectral regions can identify the radiation sources, the atmospheric structure produced by accretion, and properties of the stellar wind. On timescales from days to years, substantial changes occur in emission line profiles and line strengths. Our extensive time-domain spectroscopy suggests that the broad near-IR, optical, and far-uv emission lines, centered on the star, originate in a turbulent post-shock region and can undergo scattering by the overlying stellar wind as well as some absorption from infalling material. Stable absorption features appear in Hα, apparently caused by an accreting column silhouetted in the stellar wind. Inflow of material onto the star is revealed by the near-IR He I 10830 A line, and its free-fall velocity correlates inversely with the strength of the post-shock emission, consistent with a dipole accretion model. However, the predictions of hydrogen line profiles based on accretion stream models are not well-matched by these observations. Evidence of an accelerating warm to hot stellar wind is shown by the near-IR He I line, and emission profiles of C II, C III, C IV, N V, and O VI. more » The outflow of material changes substantially in both speed and opacity in the yearly sampling of the near-IR He I line over a decade. Terminal outflow velocities that range from 200 km s{sup –1} to almost 400 km s{sup –1} in He I appear to be directly related to the amount of post-shock emission, giving evidence for an accretion-driven stellar wind. Calculations of the emission from realistic post-shock regions are needed. « less
Singularly continuous spectrum of a self-similar Laplacian on the half-line

We investigate the spectrum of the self-similar Laplacian, which generates the so-called “pq random walk” on the integer half-line ℤ+. Using the method of spectral decimation, we prove that the spectral type of the Laplacian is singularly continuous whenever p≠12. This serves as a toy model for generating singularly continuous spectrum, which can be generalized to more complicated settings. We hope it will provide more insight into Fibonacci-type and other weakly self-similar models.
Resolving the Bondi Accretion Flow toward the Supermassive Black Hole of NGC 3115 with Chandra

Gas undergoing Bondi accretion onto a supermassive black hole (SMBH) becomes hotter toward smaller radii. We searched for this signature with a Chandra observation of the hot gas in NGC 3115, which optical observations show has a very massive SMBH. Our analysis suggests that we are resolving, for the first time, the accretion flow within the Bondi radius of an SMBH. We show that the temperature is rising toward the galaxy center as expected in all accretion models in which the black hole is gravitationally capturing the ambient gas. There is no hard central point source that could cause such an apparent rise in temperature. The data support that the Bondi radius is at about 4''-5'' (188-235 pc), suggesting an SMBH of 2 x 10{sup 9} M{sub sun} that is consistent with the upper end of the optical results. The density profile within the Bondi radius has a power-law index of 1.03{sup +0.23}{sub -0.21}, which is consistent with gas in transition from the ambient medium and the accretion flow. The accretion rate at the Bondi radius is determined to be M-dot{sub B} = 2.2x10{sup -2} M{sub sun} yr{sup -1}. Thus, the accretion luminosity with 10% radiative efficiency at the Bondimore » radius (10{sup 44} erg s{sup -1}) is about six orders of magnitude higher than the upper limit of the X-ray luminosity of the nucleus.« less
THERMOPHYSICAL PHENOMENA IN METAL ADDITIVE MANUFACTURING BY SELECTIVE LASER MELTING: FUNDAMENTALS, MODELING, SIMULATION, AND EXPERIMENTATION

Financial support for preparation of this article was provided by the German Academic Exchange Service (DAAD) to C. Meier; Honeywell Federal Manufacturing & Technologies to R. Penny and A.J. Hart; the Swiss National Science Foundation Early Postdoctoral Mobility Fellowship to Y. Zou (Grant: P2EZP2 165278), and United States Navy and the Engineering Duty O cer program to J.S. Gibbs. This work has been partially funded by Honeywell Federal Manufacturing & Technologies, LLC which manages and operates the Department of Energy’s Kansas City National Security Campus under Contract No. DE-NA-0002839.
Shear viscosity and wall slip behavior of dense suspensions of polydisperse particles

The significant problem of wall slip and shear viscosity of dense suspensions is addressed using steady torsional and capillary flows of a silicone polymer, incorporated with polydisperse particles with low aspect ratios, to achieve a relatively high maximum packing fraction, ϕ m = 0.86. Such a high ϕ m allowed the preparation of well-mixed suspensions with a wide range of solid volume fractions, ϕ, i.e., 0.62 ≤ ϕ ≤ 0.82. It is demonstrated that the characterization of the relative viscosity and yield stresses of the particulate suspensions requires a proper treatment of wall slip effects. The wall slip velocity versus the shear stress relationship is governed by the apparent slip mechanism and is predictable using the shear viscosity of the binder and the thickness of the apparent slip layer. At shear stresses which are significantly above the yield stress, the relative shear viscosity of the suspensions depends solely on ϕ / ϕ m. However, at lower shear stresses that are in the vicinity of the yield stresses, the relative shear viscosity becomes functions of both ϕ / ϕ m and the shear stress.The significant problem of wall slip and shear viscosity of dense suspensions is addressed using steady torsional and capillary flows of a silicone polymer, incorporated with polydisperse particles with low aspect ratios, to achieve a relatively high maximum packing fraction, ϕ m = 0.86. Such a high ϕ m allowed the preparation of well-mixed suspensions with a wide range of solid volume fractions, ϕ, i.e., 0.62 ≤ ϕ ≤ 0.82. It is demonstrated that the characterization of the relative viscosity and yield stresses of the particulate suspensions requires a proper treatment of wall slip effects. The wall slip velocity versus the shear stress relationship is governed by the apparent slip mechanism and is predictable using the shear viscosity of the binder and the thickness of the apparent slip layer. At shear stresses which are significantly above the yield stress, the relative shear viscosity of the suspensions depends solely on ϕ / ϕ m. However, at lower shear stresses that are in the vicinity of ...
Sustaining Educational Reforms in Introductory Physics.

While it is well known which curricular practices can improve student performance on measures of conceptual understanding, the sustaining of these practices and the role of faculty members in implementing these practices are less well understood. We present a study of the hand-off of Tutorials in Introductory Physics [McDermott and Schaffer (Prentice-Hall, Upper Saddle River, NJ, 2002)] from initial adopters to other instructors at the University of Colorado, including traditional faculty not involved in physics educational research. The study examines the impact of implementation of tutorials on student conceptual learning across ten first-semester, and seven second-semester courses, for 15 faculty members over 13 semesters, and includes roughly 5000 students. It is possible to demonstrate consistently high, and statistically indistinguishable, student learning gains for different faculty members; however, such results are not the norm and appear to rely on a variety of factors. Student performance varies by faculty background---faculty involved in, or informed by physics education research, consistently post higher student learning gains than less-informed faculty. Student performance in these courses also varies by curricula used---all semesters in which the research-based Tutorials and learning assistants are used have higher student learning gains than those semesters that rely on nonresearch-based materials and do not employ learning assistants.
The Lifetime and Powers of FR IIs in Galaxy Clusters

We have identified and studied a sample of 151 FR?IIs found in brightest cluster galaxies (BCGs) in the MaxBCG cluster catalog with data from FIRST and NVSS. We have compared the radio luminosities and projected lengths of these FR?IIs to the projected length distribution of a range of mock catalogs generated by an FR?II model and estimate the FR?II lifetime to be 1.9 ? 108?yr. The uncertainty in the lifetime calculation is a factor of two, primarily due to uncertainties in the intracluster medium (ICM) density and the FR?II axial ratio. We furthermore measure the jet power distribution of FR?IIs in BCGs and find that it is well described by a log-normal distribution with a median power of 1.1 ? 1037?W and a coefficient of variation of 2.2. These jet powers are nearly linearly related to the observed luminosities, and this relation is steeper than many other estimates, although it is dependent on the jet model. We investigate correlations between FR?II and cluster properties and find that galaxy luminosity is correlated with jet power. This implies that jet power is also correlated with black hole mass, as the stellar luminosity of a BCG should be a good proxy for its spheroid mass and therefore the black hole mass. Jet power, however, is not correlated with cluster richness, nor is FR?II lifetime strongly correlated with any cluster properties. We calculate the enthalpy of the lobes to examine the impact of the FR?IIs on the ICM and find that heating due to adiabatic expansion is too small to offset radiative cooling by a factor of at least six. In contrast, the jet power is approximately an order of magnitude larger than required to counteract cooling. We conclude that if feedback from FR?IIs offsets cooling of the ICM, then heating must be primarily due to another mechanism associated with FR?II expansion.
Electron Heating in Low-Mach-number Perpendicular Shocks. I. Heating Mechanism

Recent X-ray observations of merger shocks in galaxy clusters have shown that the post-shock plasma is two-temperature, with the protons hotter than the electrons. By means of two-dimensional particle-in-cell simulations, we study the physics of electron irreversible heating in perpendicular low Mach number shocks, for a representative case with sonic Mach number of 3 and plasma beta of 16. We find that two basic ingredients are needed for electron entropy production: (i) an electron temperature anisotropy, induced by field amplification coupled to adiabatic invariance; and (ii) a mechanism to break the electron adiabatic invariance itself. In shocks, field amplification occurs at two major sites: at the shock ramp, where density compression leads to an increase of the frozen-in field; and farther downstream, where the shock-driven proton temperature anisotropy generates strong proton cyclotron and mirror modes. The electron temperature anisotropy induced by field amplification exceeds the threshold of the electron whistler instability. The growth of whistler waves breaks the electron adiabatic invariance, and allows for efficient entropy production. We find that the electron heating efficiency displays only a weak dependence on mass ratio (less than 30 percent drop, as we increase the mass ratio from 49 up to 1600). We develop an analytical model of electron irreversible heating and show that it is in excellent agreement with our simulation results.
Holography and the sound of criticality

Using gauge/gravity duality techniques, we discuss the sound-channel retarded correlators of vector and tensor conserved currents in a class of (2+1)-dimensional strongly-coupled field theories at zero temperature and finite charge density, assumed to be holographically dual to the extremal Reissner-Nordstrom AdS4 black hole. Using a combination of analytical and numerical methods, we determine the quasinormal mode spectrum at finite momentum for the coupled gravitational and electromagnetic perturbations, and discuss the appropriate choice of gauge-invariant variables (master fields) in order for the black hole quasinormal frequencies to reproduce the field theory spectrum. We discuss the role of the near horizon AdS2 geometry in determining the low-frequency behavior of retarded correlators in the boundary theory, and comment on the emergence of criticality in the IR. In addition, we establish the existence of a sound mode at zero temperature and compute the speed of sound and sound attenuation constant numerically, obtaining a result consistent with the expectations from the zero temperature limit of hydrodynamics. The dispersion relation of higher resonances is also investigated.
Comparing the density of $D_4$ and $S_4$ quartic extensions of number fields

When ordered by discriminant, it is known that about 83% of quartic fields over Q have associated Galois group S_4, while the remaining 17% have Galois group D_4. We study these proportions over a general number field F. We find that asymptotically 100% of quadratic number fields have more D_4 extensions than S_4 and that the ratio between the number of D_4 and S_4 quartic extensions is biased arbitrarily in favor of D_4 extensions. Under GRH, we give a lower bound that holds for general number fields.
SYMPLECTIC REDUCTION AND SYMMETRY ALGEBRA IN BOUNDARY CHERN–SIMONS THEORY

We derive the Kac–Moody algebra and Virasoro algebra in Chern–Simons theory with boundary by using the symplectic reduction method and the Noether procedures.
NOVEL STRING BANANA TEMPLATE METHOD OF TRACK RECONSTRUCTION FOR HIGH MULTIPLICITY EVENTS WITH SIGNIFICANT MULTIPLE SCATTERING

Novel String Banana Template Method (SBTM) for track reconstruction in high multiplicity events in non-uniform magnetic field spectrometer with emphasis on the lowest momenta tracks with significant Multiple Scattering (MS) is described. Two steps model of track with additional parameter/s which takes into account MS for this particular track is introduced. SBTM is time efficient and demonstrates better resolutions than another method equivalent to the Least Squares method (LSM).
Dust of dark energy

We introduce a novel class of field theories where energy always flows along timelike geodesics, mimicking in that respect dust, yet which possess non-zero pressure. This theory comprises two scalar fields, one of which is a Lagrange multiplier enforcing a constraint between the other's field value and derivative. We show that this system possesses no wave-like modes but retains a single dynamical degree of freedom. Thus, the sound speed is always identically zero on all backgrounds. In particular, cosmological perturbations reproduce the standard behaviour for hydrodynamics in the limit of vanishing sound speed. Using all these properties we propose a model unifying Dark Matter and Dark Energy in a single degree of freedom. In a certain limit this model exactly reproduces the evolution history of ΛCDM, while deviations away from the standard expansion history produce a potentially measurable difference in the evolution of structure.