cssi/SciSciGPT-SciSciNet huggingface dataset:
HOW USEFUL ARE FORMAL HIERARCHIES? A CASE STUDY ON AVERAGING DISLOCATION DYNAMICS TO DEFINE MESO-MACRO PLASTICITY

A formal hierarchy of exact evolution equations are derived for physically relevant space-time averages of state functions of microscopic dislocation dynamics. While such hierarchies are undoubtedly of some value, a primary goal here is to expose the intractable complexity of such systems of nonlinear partial differential equations that, furthermore, remain `non-closed' and therefore subject to phenomenological assumptions to be useful. It is instead suggested that such hierarchies be terminated at the earliest stage possible and effort be expended to derive closure relations for the `non-closed' terms that arise from the formal averaging by taking into account the full-stress-coupled microscopic dislocation dynamics, a matter on which these formal hierarchies, whether of kinetic theory type or as pursued here, are silent.
Enhanced thermal emittance of space radiators by ion-discharge chamber texturing

Abstract A discharge chamber of a 30 cm argon ion source was successfully used to texture potential space radiator materials for the purpose of obtaining values of thermal emittance greater than 0.85 at 700 and 900 K. Some samples were also treated in acid before texturing. To evaluate the durability of the textured materials to atomic oxygen, samples were exposed to a plasma asher, a device that produced atomic oxygen. The spectral emittance between 2.0 and 15 μm was measured before and after the textured materials were exposed to the plasma asher. The results indicate that copper with extremely high values of emittance after texturing (0.978 and 0.983) at 700 K and 900 K respectively did not change its values of emittance after ashing, whereas the emittance of stainless steel fell below 0.85 after ashing. These data, scanning electron photomicrographs and the results of texturing and ashing titanium and Nb-1 wt.%Zr are presented in this paper.
How we perform haploidentical stem cell transplantation with posttransplant cyclophosphamide

HLA-haploidentical hematopoietic stem cell transplantation is now one of the most commonly employed alternative donor techniques, with most centers applying T-cell-replete strategies such as that developed by the Baltimore group using high-dose posttransplant cyclophosphamide. HLA-haploidentical hematopoietic stem cell transplantation using posttransplant cyclophosphamide is associated with low rates of severe graft-versus-host disease and nonrelapse mortality and does not require graft manipulation or storage, which results in a low graft acquisition cost. Its remarkable safety when used with reduced-intensity conditioning has been demonstrated in patients up to 75 years old with outcomes similar to those of patients in their 50s. Several large, registry-based retrospective studies have confirmed the efficacy of HLA-haploidentical hematopoietic stem cell transplantation with posttransplant cyclophosphamide, achieving results comparable to those of HLA-matched hematopoietic stem cell transplantation. In this article, we describe our approach to this rapidly available and clinically simple platform and address some of the key clinical questions associated with its use.
Multilevel-Coded Pulse-Position Modulation for Covert Communications Over Binary-Input Discrete Memoryless Channels

We consider the problem of coding to ensure covert communication, which involves ensuring reliable communication between two legitimate parties while simultaneously guaranteeing a low probability of detection by an eavesdropper. Specifically, we develop an optimal low-complexity coding scheme that achieves the information-theoretic limits of covert communications over binary-input discrete memoryless channels (BI-DMCs). To justify our design, we first consider a regime in which information theory proves the possibility of covert communication without shared secret key and show the impossibility of achieving information-theoretic limits using linear codes without secret key. We then circumvent this impossibility by introducing non-linearity into the coding scheme through the use of pulse position modulation (PPM) and multilevel coding (MLC). This MLC-PPM scheme exhibits several appealing properties; in particular, for an appropriate decoder, the channel at a given level is independent of the total number of levels and the codeword length. We exploit these properties to show how one can use families of channel capacity- and channel resolvability-achieving codes to concretely instantiate a covert communication scheme.
A general higher-order shell theory for compressible isotropic hyperelastic materials using orthonormal moving frame

The aim of this study is three-fold: (i) to present a general higher-order shell theory to analyze large deformations of thin or thick shell structures made of general compressible hyperelastic materials; (ii) to utilize the orthonormal or Cartans moving frame in the formulation of shell theory in contrast to the classical tensorial covariant coordinate system; and (iii) to present the nonlinear weak-form Galerkin finite element model for the given shell theory. The displacement field of a point on the line normal to the shell reference surface is approximated by the Taylor series or Legendre polynomials. The kinematics of motion in the assumed coordinate system is derived using the tools of exterior calculus. The use of an orthonormal moving frame makes it possible to represent kinematic quantities, e.g., determinant of the deformation gradient, in a far more efficient manner than the classical tensorial representation of the same with covariant bases. The manipulation of the various tensor used in the kinematics and dynamics of the structures can be carried out with ease and a more computationally efficient manner. The governing equation of the shell has been derived in the general surface coordinates. The methodology developed herein is very much algorithmic, and hence it can also be applied for any arbitrary interpolated surfaces with equal ease. The higher-order nature of the approximation of the displacement field makes the theory suitable for analyzing thick and thin shell structures. The compressible hyperelastic material model used as the constitutive relation of the material. The formulation presented herein can be specialized for various nonlinear hyperelastic constitutive models suitable for use, for example, in bio-mechanics and other soft-material problems (e.g., neo-Hookean material, Mooney-Rivlin material, Generalized power-law neo-Hookean material, and so on).
On the EKL-degree of a Weyl cover

Abstract More than four decades ago, Eisenbud, Khimsiasvili, and Levine introduced an analogue in the algebro-geometric setting of the notion of local degree from differential topology. Their notion of degree, which we call the EKL-degree, can be thought of as a refinement of the usual notion of local degree in algebraic geometry that works over non-algebraically closed base fields, taking values in the Grothendieck-Witt ring. In this note, we compute the EKL-degree at the origin of certain finite covers f : A n → A n induced by quotients under actions of Weyl groups. We use knowledge of the cohomology ring of partial flag varieties as a key input in our proofs, and our computations give interesting explicit examples in the field of A 1 -enumerative geometry.
Two new embedded triply periodic minimal surfaces of genus 4

We add two new 1-parameter families to the short list of known embedded triply periodic minimal surfaces of genus 4 in $$\mathbb {R}^3$$ . Both surfaces can be tiled by minimal pentagons with two straight segments and three planar symmetry curves as boundary. In one case (which has the appearance of the CLP surface of Schwarz with an added handle) the two straight segments are parallel, while they are orthogonal in the second case. The second family has as one limit the Costa surface, showing that this limit can occur for triply periodic minimal surfaces. For the existence proof we solve the 1-dimensional period problem through a combination of an asymptotic analysis of the period integrals and geometric methods.
Construction of Response Surface with Higher Order Continuity and Its Application to Reliability Engineering

The usefulness of piecewise polynomials with C1 and C2 derivative continuity for response surface construction method is examined. A Moving Least Squares (MLS) method is developed and compared with four other interpolation methods, including kriging. First the selected methods are applied and compared with one another in a two-design variables problem with a known theoretical response function. Next the methods are tested in a four-design variables problem from a reliability-based design application. In general the piecewise polynomial with higher order derivative continuity methods produce less error in the response prediction. The MLS method was found to be superior for response surface construction among the methods evaluated.
Identification of Compliant Contact Parameters and Admittance Force Modulation on a Non-stationary Compliant Surface

Although autonomous control of robotic manipulators has been studied for several decades, they are not commonly used in safety-critical applications due to lack of safety and performance guarantees - many of them concerning the modulation of interaction forces. This paper presents a mechanical probing strategy for estimating the environmental impedance parameters of compliant environments, independent a manipulator’s controller design, and configuration. The parameter estimates are used in a position-based adaptive force controller to enable control of interaction forces in compliant, stationary, and non-stationary environments. This approach is targeted for applications where the workspace is constrained and non-stationary, and where force control is critical to task success. These applications include surgical tasks involving manipulation of compliant, delicate, moving tissues. Results show fast parameter estimation and successful force modulation that compensates for motion.
Parallel cross-validation: A scalable fitting method for Gaussian process models

Abstract Gaussian process (GP) models are widely used to analyze spatially referenced data and to predict values at locations without observations. They are based on a statistical framework, which enables uncertainty quantification of the model structure and predictions. Both the evaluation of the likelihood and the prediction involve solving linear systems. Hence, the computational costs are large and limit the amount of data that can be handled. While there are many approximation strategies that lower the computational cost of GP models, they often provide sub-optimal support for the parallel computing capabilities of (high-performance) computing environments. To bridge this gap a parallelizable parameter estimation and prediction method is presented. The key idea is to divide the spatial domain into overlapping subsets and to use cross-validation (CV) to estimate the covariance parameters in parallel. Although simulations show that CV is less effective for parameter estimation than the maximum likelihood method, it is amenable to parallel computing and enables the handling of large datasets. Exploiting the screen effect for spatial prediction helps to arrive at a spatial analysis that is close to a global computation despite performing parallel computations on local regions. Simulation studies assess the accuracy of the parameter estimates and predictions. The implementation shows good weak and strong parallel scaling properties. For illustration, an exponential covariance model is fitted to a scientifically relevant canopy height dataset with 5 million observations. Using 512 processor cores in parallel brings the evaluation time of one covariance parameter configuration to 1.5 minutes.
Moduli of double covers and degree one del Pezzo surfaces

Given a degree one del Pezzo surface with canonical singularities, the linear series generated by twice the anti-canonical divisor exhibits the surface as the double cover of the quadric cone branched along a sextic curve. It is natural to ask if this description extends to the boundary of a compactification of the moduli space of degree one del Pezzo surfaces. The goal of this paper is to show that this is indeed the case. In particular, we give an explicit classification of the boundary of the moduli space of anti-canonically polarized broken del Pezzo surfaces of degree one as double covers of degenerations of the quadric cone.
Simultaneous Dimensionality and Complexity Model Selection for Spectral Graph Clustering

Our problem of interest is to cluster vertices of a graph by identifying underlying community structure. Among various vertex clustering approaches, spectral clustering is one of the most popular m...
Headwaters Fed by Subterranean Ice: Potential Climate Refugia for Mountain Stream Communities?

Near-term extirpations of macroinvertebrates are predicted for mountain streams worldwide as a warming climate drives the recession of high-elevation ice and snow. However, hydrological sources likely vary in their resistance to climate change, and thus streams fed by more resistant sources could persist as climate refugia for imperiled biota. In 2015–2016, we measured habitat characteristics and quantified macroinvertebrate community structure along 6 alpine streams in the Teton Range, Wyoming, USA. Strong differences in habitat characteristics (e.g., temperature, bed stability, conductivity) confirmed 3 major stream sources: surface glaciers, perennial snowfields, and subterranean ice. Subterranean ice-fed streams—termed “icy seeps”—appear common in the Teton Range and elsewhere, yet are globally understudied. Midges in the family Chironomidae dominated our study sites, representing 78.6% of all specimens sampled, with nematodes, caddisflies (Neothremma), and mayflies (Epeorus) also common. At the community scale, glacier- and snowmelt-fed streams differed significantly in multivariate space, with icy-seep communities intermediate between them, incorporating components of both assemblages. Because the thermal environment of subterranean ice, including rock glaciers, is decoupled from large-scale climatic conditions, we predict that icy seeps will remain intact longer than streams fed by surface ice and snow. Furthermore, our results suggest that icy seeps are suitable habitat for many macroinvertebrates occupying streams fed by vulnerable hydrological sources. Thus, icy seeps may act as key climate refugia for mountain stream biodiversity, an idea in need of further investigation.
Stochastic Turing Pattern Formation in a Model with Active and Passive Transport

We investigate Turing pattern formation in a stochastic and spatially discretized version of a reaction-diffusion-advection (RDA) equation, which was previously introduced to model synaptogenesis in C. elegans. The model describes the interactions between a passively diffusing molecular species and an advecting species that switches between anterograde and retrograde motor-driven transport (bidirectional transport). Within the context of synaptogenesis, the diffusing molecules can be identified with the protein kinase CaMKII and the advecting molecules as glutamate receptors. The stochastic dynamics evolves according to an RDA master equation, in which advection and diffusion are both modeled as hopping reactions along a one-dimensional array of chemical compartments. Carrying out a linear noise approximation of the RDA master equation leads to an effective Langevin equation, whose power spectrum provides a means of extending the definition of a Turing instability to stochastic systems, namely in terms of the existence of a peak in the power spectrum at a nonzero spatial frequency. We thus show how noise can significantly extend the range over which spontaneous patterns occur, which is consistent with previous studies of RD systems.
GLSMs for exotic Grassmannians

In this paper we explore nonabelian gauged linear sigma models (GLSMs) for symplectic and orthogonal Grassmannians and flag manifolds, checking e.g. global symmetries, Witten indices, and Calabi-Yau conditions, following up a proposal in the math community. For symplectic Grassmannians, we check that Coulomb branch vacua of the GLSM are consistent with ordinary and equivariant quantum cohomology of the space.
Fourier Sparse Leverage Scores and Approximate Kernel Learning

We prove new explicit upper bounds on the leverage scores of Fourier sparse functions under both the Gaussian and Laplace measures. In particular, we study $s$-sparse functions of the form $f(x) = \sum_{j=1}^s a_j e^{i \lambda_j x}$ for coefficients $a_j \in \mathbb{C}$ and frequencies $\lambda_j \in \mathbb{R}$. Bounding Fourier sparse leverage scores under various measures is of pure mathematical interest in approximation theory, and our work extends existing results for the uniform measure [Erd17,CP19a]. Practically, our bounds are motivated by two important applications in machine learning: 1. Kernel Approximation. They yield a new random Fourier features algorithm for approximating Gaussian and Cauchy (rational quadratic) kernel matrices. For low-dimensional data, our method uses a near optimal number of features, and its runtime is polynomial in the $statistical\ dimension$ of the approximated kernel matrix. It is the first "oblivious sketching method" with this property for any kernel besides the polynomial kernel, resolving an open question of [AKM+17,AKK+20b]. 2. Active Learning. They can be used as non-uniform sampling distributions for robust active learning when data follows a Gaussian or Laplace distribution. Using the framework of [AKM+19], we provide essentially optimal results for bandlimited and multiband interpolation, and Gaussian process regression. These results generalize existing work that only applies to uniformly distributed data.
Typicality and thermality in 2d CFT

We identify typical high energy eigenstates in two-dimensional conformal field theories at finite c and establish that correlation functions of the stress tensor in such states are accurately thermal as defined by the standard canonical ensemble. Typical states of dimension h are shown to be typical level h/c descendants. In the AdS3/CFT2 correspondence, it is such states that should be compared to black holes in the bulk. We also discuss the discrepancy between thermal correlators and those computed in high energy primary states: the latter are reproduced instead by a generalized Gibbs ensemble with extreme values chosen for the chemical potentials conjugate to the KdV charges.
New Distant Companions to Known Nearby Stars. I. GJ 4047B, GJ 718B, GJ 747.2C, GJ 4100B, and GJ 4153B

In an ongoing survey for high proper motion stars at low Galactic latitudes (-25° < b < 25°) in the Digitized Sky Survey, we have identified five previously uncataloged common proper motion companions to stars listed in the Preliminary Version of the Third Catalogue of Nearby Stars (GJ stars). For each system, the relative proper motion between the components is less than 5% of the common proper motion of the pair. Spectra of the pairs have been obtained at the Lick 3 m Shane Telescope, confirming that the systems are indeed wide-separation binaries. The systems are classified as follows: GJ 4047AB = K5 V + M5 V, GJ 718AB = K5 V + M4.5 V, GJ 747.2ABC = (K7 V + K7 V) + M4 Ve, GJ 4100AB = M1 V + M4.5 Ve, and GJ 4153AB = M0.5 V + M3.5 V. The total area surveyed contains 346 Gliese stars, which suggests that ≈1.5% of the stars listed in the Preliminary Version of the Third Catalogue of Nearby Stars have unrecognized proper motion companions. We predict that ≈15–50 more new distant companions to GJ stars will be discovered in the Digitized Sky Survey.
Evolving event-driven programs with SignalGP

We present SignalGP, a new genetic programming (GP) technique designed to incorporate the event-driven programming paradigm into computational evolution's toolbox. Event-driven programming is a software design philosophy that simplifies the development of reactive programs by automatically triggering program modules (event-handlers) in response to external events, such as signals from the environment or messages from other programs. SignalGP incorporates these concepts by extending existing tag-based referencing techniques into an event-driven context. Both events and functions are labeled with evolvable tags; when an event occurs, the function with the closest matching tag is triggered. In this work, we apply SignalGP in the context of linear GP. We demonstrate the value of the event-driven paradigm using two distinct test problems (an environment coordination problem and a distributed leader election problem) by comparing SignalGP to variants that are otherwise identical, but must actively use sensors to process events or messages. In each of these problems, rapid interaction with the environment or other agents is critical for maximizing fitness. We also discuss ways in which SignalGP can be generalized beyond our linear GP implementation.
Cosmic Microwave Background Anisotropy numerical solution (CMBAns) I: An introduction to $C_l$ calculation

Cosmological Boltzmann codes are often used by researchers for calculating the CMB angular power spectra from different theoretical models, for cosmological parameter estimation, etc. Therefore, the accuracy of a Boltzmann code is of utmost importance. Different Markov Chain Monte Carlo based parameter estimation algorithms typically require 10^3 - 10^4 iterations of Boltzmann code. This makes the time complexity of such codes another critical factor. In the last two decades, several Boltzmann packages, such as CMBFAST, CAMB, CMBEasy, CLASS etc., have been developed. In this paper, we present a new cosmological Boltzmann code, CMBAns, that can be used for accurate calculation of the CMB power spectrum. At present, CMBAns is developed for a flat background matrix. It is mostly written in the C language. However, we borrowed the concept of class from C++. This gives researchers the flexibility to develop their own independent package based on CMBAns, without an in-depth understanding of the source code. We also develop multiple stand-alone facilities which can be directly compiled and run on a given parameter set. In this paper, we discuss all the mathematical formulation, approximation schemes, integration methods etc., that are used in CMBAns. The package will be made available through github for public use in the near future.
GRAVITATIONAL INFALL ONTO MOLECULAR FILAMENTS

Two aspects of filamentary molecular cloud evolution are addressed: (1) exploring analytically the role of the environment for the evolution of filaments demonstrates that considering them in isolation (i.e., just addressing the fragmentation stability) will result in unphysical conclusions about the filament's properties. Accretion can also explain the observed decorrelation between FWHM and peak column density. (2) Free-fall accretion onto finite filaments can lead to the characteristic "fans" of infrared-dark clouds around star-forming regions. The fans may form due to tidal forces mostly arising at the ends of the filaments, consistent with numerical models and earlier analytical studies.
Bandit-Based Model Selection for Deformable Object Manipulation

We present a novel approach to deformable object manipulation that does not rely on highly-accurate modeling. The key contribution of this paper is to formulate the task as a Multi-Armed Bandit problem, with each arm representing a model of the deformable object. To “pull” an arm and evaluate its utility, we use the arm’s model to generate a velocity command for the gripper(s) holding the object and execute it. As the task proceeds and the object deforms, the utility of each model can change. Our framework estimates these changes and balances exploration of the model set with exploitation of high-utility models. We also propose an approach based on Kalman Filtering for Non-stationary Multi-armed Normal Bandits (KF-MANB) to leverage the coupling between models to learn more from each arm pull.We demonstrate that our method outperforms previous methods on synthetic trials, and performs competitively on several manipulation tasks in simulation.
Topology and Dynamics of the Contracting Boundary of Cocompact CAT(0) Spaces

Let $X$ be a proper CAT(0) space and let $G$ be a cocompact group of isometries of $X$ which acts properly discontinuously. Charney and Sultan constructed a quasi-isometry invariant boundary for proper CAT(0) spaces which they called the contracting boundary. The contracting boundary imitates the Gromov boundary for $\delta$-hyperbolic spaces. We will make this comparison more precise by establishing some well known results for the Gromov boundary in the case of the contracting boundary. We show that the dynamics on the contracting boundary is very similar to that of a $\delta$-hyperbolic group. In particular the action of $G$ on $\partial_cX$ is minimal if $G$ is not virtually cyclic. We also establish a uniform convergence result that is similar to the $\pi$-convergence of Papasoglu and Swenson and as a consequence we obtain a new north-south dynamics result on the contracting boundary. We additionally investigate the topological properties of the contracting boundary and we find necessary and sufficient conditions for $G$ to be $\delta$-hyperbolic. We prove that if the contracting boundary is compact, locally compact or metrizable, then $G$ is $\delta$-hyperbolic.
Cyclic sieving and plethysm coefficients

A combinatorial expression for the coefficient of the Schur function $s_{\lambda}$ in the expansion of the plethysm $p_{n/d}^d \circ s_{\mu}$ is given for all $d$ dividing $n$ for the cases in which $n=2$ or $\lambda$ is rectangular. In these cases, the coefficient $\langle p_{n/d}^d \circ s_{\mu}, s_{\lambda} \rangle$ is shown to count, up to sign, the number of fixed points of an $\langle s_{\mu}^n, s_{\lambda} \rangle$-element set under the $d^{\text{th}}$ power of an order-$n$ cyclic action. If $n=2$, the action is the Schutzenberger involution on semistandard Young tableaux (also known as evacuation), and, if $\lambda$ is rectangular, the action is a certain power of Schutzenberger and Shimozono's jeu-de-taquin promotion. This work extends results of Stembridge and Rhoades linking fixed points of the Schutzenberger actions to ribbon tableaux enumeration. The conclusion for the case $n=2$ is equivalent to the domino tableaux rule of Carre and Leclerc for discriminating between the symmetric and antisymmetric parts of the square of a Schur function.
The galaxy populations of x-ray detected, poor groups

We determine the quantitative morphology and star formation properties of galaxies in six nearby X-ray-detected, poor groups using multiobject spectroscopy and wide-field R imaging. The mean recessional velocities of the galaxy groups range from 2843 to 7558 km s-1. Each group has 15-38 confirmed members ranging in luminosity from dwarfs to giants (-13.7 ≥ MR - 5 log h ≥ -21.9). We measure structural parameters for each galaxy by fitting a PSF-convolved, two-component model to their surface brightness profiles. To compare the samples directly, we fade, smooth, and rebin each galaxy image so that we effectively observe each galaxy at the same redshift (9000 km s-1) and physical resolution (0.87 h-1 kpc). The structural parameters are combined with [O II] measurements to test for correlations between morphological characteristics and current star formation in these galaxies. We compare results for the groups to a sample of field galaxies. We find that: (1) Galaxies spanning a wide range in morphological type and luminosity are fit well by a de Vaucouleurs bulge with exponential disk profile. (2) Morphologically classifying these nearby group galaxies by their bulge fraction (B/T) is fairly robust on average, even when their redshift has increased by up to a factor of 4 and the effective resolution of the images is degraded by up to a factor of 5. (3) The fraction of bulge-dominated systems in these groups is higher than in the field (~50% versus ~20%). (4) The fraction of bulge-dominated systems in groups decreases with increasing radius, similar to the morphology-radius (~density) relation observed in galaxy clusters. (5) Current star formation in group galaxies is correlated with significant morphological asymmetry for disk-dominated systems (B/T < 0.4). (6) The group galaxies that are most disk dominated (B/T < 0.2) are less star forming and asymmetric on average than their counterparts in the field.
On the scaling relations of disk galaxies

The physical background of scaling laws of disk galaxies is reviewed. The match between analytically derived and observed scaling laws is briefly discussed. Accurate modeling of the fraction of baryons that end up populating a disk, and the conversion efficiency of those into stars, remains a challenging task for numerical simulations. The measurement of rotational velocity tends to be made with criteria of convenience rather than through rigorous definition. And yet, the Tully–Fisher and the disk size versus rotational velocity relations exhibit surprisingly small scatter. Practical recipes (and costs) to optimize the quality of template relations are considered.
Multi-Level Analysis of Compiler-Induced Variability and Performance Tradeoffs

Successful HPC software applications are long-lived. When ported across machines and their compilers, these applications often produce different numerical results, many of which are unacceptable. Such variability is also a concern while optimizing the code more aggressively to gain performance. Efficient tools that help locate the program units (files and functions) within which most of the variability occurs are badly needed, both to plan for code ports and to root-cause errors due to variability when they happen in the field. In this work, we offer an enhanced version of the open-source testing framework FLiT to serve these roles. Key new features of FLiT include a suite of bisection algorithms that help locate the root causes of variability. Another added feature allows an analysis of the tradeoffs between performance and the degree of variability. Our new contributions also include a collection of case studies. Results on the MFEM finite-element library include variability/performance tradeoffs, and the identification of a (hitherto unknown) abnormal level of result-variability even under mild compiler optimizations. Results from studying the Laghos proxy application include identifying a significantly divergent floating-point result-variability and successful root-causing down to the problematic function over as little as 14 program executions. Finally, in an evaluation of 4,376 controlled injections of floating-point perturbations on the LULESH proxy application, we showed that the FLiT framework has 100% precision and recall in discovering the file and function locations of the injections all within an average of only 15 program executions.
On geometric and analytic mixing scales: comparability and convergence rates for transport problems

We are interested in the geometric and analytic mixing scales of solutions to passive scalar problems. Here, we show that both notions are comparable after possibly removing large-scale projections. In order to discuss our techniques in a transparent way, we further introduce a dyadic model problem. In a second part of our article we consider the question of sharp decay rates for both scales for Sobolev regular initial data when evolving under the transport equation and related active and passive scalar equations. Here, we show that slightly faster rates than the expected algebraic decay rates are optimal.
Heat conduction in multifunctional nanotrusses studied using Boltzmann transport equation

Materials that possess low density, low thermal conductivity, and high stiffness are desirable for engineering applications, but most materials cannot realize these properties simultaneously due to the coupling between them. Nanotrusses, which consist of hollow nanoscale beams architected into a periodic truss structure, can potentially break these couplings due to their lattice architecture and nanoscale features. In this work, we study heat conduction in the exact nanotruss geometry by solving the frequency-dependent Boltzmann transport equation using a variance-reduced Monte Carlo algorithm. We show that their thermal conductivity can be described with only two parameters, solid fraction and wall thickness. Our simulations predict that nanotrusses can realize unique combinations of mechanical and thermal properties that are challenging to achieve in typical materials.
Grid Diagrams for Lens Spaces and Combinatorial Knot Floer Homology

Similar to knots in S 3 , any knot in a lens space has a grid diagram from which one can combinatorially compute all of its knot Floer homology invariants. We give an explicit description of the generators, differentials, and rational Maslov and Alexander gradings in terms of combinatorial data on the grid diagram. Motivated by existing results for the Floer homology of knots in S 3 and the similarity of the resulting combinatorics presented here, we conjecture that a certain family of knots is characterized by their Floer homology. Coupled with the work of the third author, an affirmative answer to this would prove the Berge conjecture, which catalogs the knots in S 3 admitting lens space surgeries.
The Vortex-Wave Equation with a Single Vortex as the Limit of the Euler Equation

In this article we consider the physical justification of the Vortex-Wave equation introduced by Marchioro and Pulvirenti (Mechanics, analysis and geometry: 200 years after Lagrange, North-Holland Delta Ser., Amsterdam, North-Holland, pp. 79–95, 1991), in the case of a single point vortex moving in an ambient vorticity. We consider a sequence of solutions for the Euler equation in the plane corresponding to initial data consisting of an ambient vorticity in L 1 ∩ L ∞ and a sequence of concentrated blobs which approach the Dirac distribution. We introduce a notion of a weak solution of the Vortex-Wave equation in terms of velocity (or primitive variables) and then show, for a subsequence of the blobs, the solutions of the Euler equation converge in velocity to a weak solution of the Vortex-Wave equation.
HIERARCHICAL SPARSE BAYESIAN LEARNING FOR STRUCTURAL HEALTH MONITORING WITH INCOMPLETE MODAL DATA

For civil structures, structural damage due to severe loading events such as earthquakes, or due to long-term environmental degradation, usually occurs in localized areas of a structure. A new sparse Bayesian probabilistic framework for computing the probability of localized stiffness reductions induced by damage is presented that uses noisy incomplete modal data from before and after possible damage. This new approach employs system modal parameters of the structure as extra variables for Bayesian model updating with incomplete modal data. A specific hierarchical Bayesian model is constructed that promotes spatial sparseness in the inferred stiffness reductions in a way that is consistent with the Bayesian Ockham razor. To obtain the most plausible model of sparse stiffness reductions together with its uncertainty within a specified class of models, the method employs an optimization scheme that iterates among all uncertain parameters, including the hierarchical hyper-parameters. The approach has four important benefits: (1) it infers spatially sparse stiffness changes based on the identified modal parameters; (2) the uncertainty in the inferred stiffness reductions is quantified; (3) no matching of model and experimental modes is needed, and (4) solving the nonlinear eigenvalue problem of a structural model is not required. The proposed method is applied to two previously studied examples using simulated data: a ten-story shear-building and the three-dimensional braced-frame model from the Phase II Simulated Benchmark problem sponsored by the IASC-ASCE Task Group on Structural Health Monitoring. The results show that the occurrence of false-positive and false-negative damage detection is clearly reduced in the presence of modeling error (differences between the real structural behavior and the model of it). Furthermore, the identified most probable stiffness loss ratios are close to their actual values.
Affine Manifolds and Zero Lyapunov Exponents in Genus 3

In previous work, the author fully classified orbit closures in genus three with maximally many (four) zero Lyapunov exponents of the Kontsevich–Zorich cocycle. In this paper, we prove that there are no higher dimensional orbit closures in genus three with any zero Lyapunov exponents. Furthermore, if a Teichmuller curve in genus three has two zero Lyapunov exponents in the Kontsevich–Zorich cocycle, then it lies in the principal stratum and has at most quadratic trace field. Moreover, there can be at most finitely many such Teichmuller curves.
STAR FORMATION SIGNATURES IN OPTICALLY QUIESCENT EARLY-TYPE GALAXIES

In recent years, an argument has been made that a high fraction of early-type galaxies (ETGs) in the local universe experience low levels ({approx_lt}1 M {sub sun} yr{sup -1}) of star formation (SF) that causes strong excess in UV flux, yet leaves the optical colors red. Many of these studies were based on Galaxy Evolution Explorer imaging of Sloan Digital Sky Survey (SDSS) galaxies (z {approx} 0.1), and were thus limited by its 5'' FWHM. Poor UV resolution left other possibilities for UV excess open, such as the old populations or an active galactic nucleus (AGN). Here, we study high-resolution far-ultraviolet HST/ACS images of optically quiescent early-type galaxies with strong UV excess. The new images show that three-quarters of these moderately massive ({approx}5 x 10{sup 10} M {sub sun}) ETGs shows clear evidence of extended SF, usually in form of wide or concentric UV rings, and in some cases, striking spiral arms. SDSS spectra probably miss these features due to small fiber size. UV-excess ETGs have on average less dust and larger UV sizes (D > 40 kpc) than other green-valley galaxies, which argues for an external origin for the gas that is driving the SF. Thus, most of thesemore » galaxies appear 'rejuvenated' (e.g., through minor gas-rich mergers or intergalactic medium accretion). For a smaller subset of the sample, the declining SF (from the original internal gas) cannot be ruled out. SF is rare in very massive early-types (M {sub *} > 10{sup 11} M {sub sun}), a possible consequence of AGN feedback. In addition to extended UV emission, many galaxies show a compact central source, which may be a weak, optically inconspicuous AGN.« less
On the Origin of Radial Magnetic Fields in Young Supernova Remnants

We study the radio emission from young supernova remnants by means of three-dimensional numerical MHD simulations of the Rayleigh-Taylor instability in the shell of the remnant. The computation is carried out in spherical polar coordinates (r, θ, ) by using a moving grid technique that allows us to resolve the shell finely. The three-dimensional result shows more turbulent (complex) structures in the mixing region than the two-dimensional result, and the instability is found to deform the reverse shock front. Stokes parameters (I, Q, and U) are computed to study the radio properties of the remnant. The total intensity map shows two distinctive regions (inner and outer shells). The inner shell appears to be complex and turbulent, exhibiting loop structures and plumes as a result of the Rayleigh-Taylor instability, while the outer shell is faint and laminar because of the shocked uniform ambient magnetic fields. The inner shell resembles the observed radio structure in the main shell of young SNRs, which is evidence that the Rayleigh-Taylor instability is an ongoing process in young SNRs. When only the peculiar components of the magnetic fields generated by the instability are considered, the polarization B-vector in the inner radio shell is preferentially radial with about 20%-50% of fractional polarization, which is higher than the observed value. The fractional polarization is lowest in the turbulent inner shell and increases outward, which is attributed to the geometric effect. The polarized intensity is found to be correlated with the total intensity. We demonstrate that the polarized intensity from the turbulent region can dominate over the polarized intensity from the shocked uniform fields if the amplified field is sufficiently strong. Therefore, we conclude that the Rayleigh-Taylor instability can explain the dominant radial magnetic field in the main shell of young supernova remnants. However, the outer faint shell shows a dominant tangential field orientation due to the shock-compression because this region is not mixed by the Rayleigh-Taylor instability, which is contrary to observations. Therefore, another mechanism is necessary to produce the radial components of the magnetic field at the outer shock, which we suggest to be a clumpy medium model.
UV Spectral Synthesis of Vega

We show that the UV spectrum (1280-3200 A) of the "superficially normal" A-star Vega, as observed by the International Ultraviolet Explorer (IUE) satellite at a resolution comparable to the star's rotational broadening width, can be fit remarkably well by a single-temperature synthetic spectrum based on LTE atmosphere models and a newly constructed UV line list. If Vega were a normal, equator-on, slow-rotating star, then its spectrum and our analysis would indicate a temperature of T eff 9550 K, surface gravity of log g 3.7, general surface metallicity of [m/H] –0.5, and a microturbulence velocity of v turb 2.0 km s–1. Given its rapid rotation and nearly pole-on orientation, however, these parameters must be regarded as representing averages across the observed hemisphere. Modeling the complex UV line spectrum has allowed us to determine the specific surface abundances for 17 different chemical elements, including CNO, the light metals, and the iron group elements. The resultant abundance pattern agrees in general with previous results, although there is considerable scatter in the literature. Despite its peculiarities, Vega has turned out to provide a powerful test of the extent of our abilities to model the atmospheric properties of the early A-stars, particularly the detailed UV line spectrum. The value of the measurements from this pilot study will increase as this analysis is extended to more objects in the rich high-dispersion IUE data archive, including both normal and peculiar objects.
Does the first chaotic inflation model in supergravity provide the best fit to the Planck data

I describe the first model of chaotic inflation in supergravity, which was proposed by Goncharov and the present author in 1983. The inflaton potential of this model has a plateau-type behavior V0 (1− 8/3 e−√ 6 ||) at large values of the inflaton field. This model predicts ns = 1−2/N ≈ 0.967 and r = 4/3N2 ≈ 4 × 10−4, in good agreement with the Planck data. I propose a slight generalization of this model, which allows to describe not only inflation but also dark energy and supersymmetry breaking.
AN ULTRAVIOLET STUDY OF THE SHORT-PERIOD BINARY OO AQUILAE

OO Aql is a rare W UMa–type eclipsing binary in which the two solar-type stars may have only recently evolved into contact. The binary has an unusually high mass ratio (0.84) and a relatively long orbital period (0.506 days) for its spectral type (mid-G). Twelve ultraviolet spectra of OO Aql were obtained in 1988 with the International Ultraviolet Explorer satellite, including a series of consecutive observations that cover nearly a complete orbital cycle. Chromospheric activity is studied by means of the Mg II h and k emission at 2800 A. The Mg II emission is found to vary, even when the emission is normalized to the adjacent continuum flux. This variation may be correlated with orbital phase in the 1988 observations. It also appears that the normalized Mg II emission varies with time, as seen in spectra obtained at two different epochs in 1988 and when compared with two spectra obtained several years earlier. The level of chromospheric activity in OO Aql is less than that of other W UMa–type binaries of similar colors, but this is attributed to its early stage of contact binary evolution. Ultraviolet light curves were composed from measurements of the ultraviolet continuum in the spectra. These were analyzed, along with visible light curves of OO Aql, to determine the system parameters. The large wavelength range in the light curves enabled a well-constrained fit to a cool spot in the system.
Wilson loops as matrix strings

In the framework of Matrix theory we show that Wilson loops can serve as interpolating fields to define string scattering amplitudes as gauge theory observables.
Numerically modeling Brownian thermal noise in amorphous and crystalline thin coatings

Thermal noise is expected to be one of the noise sources limiting the astrophysical reach of Advanced LIGO (once commissioning is complete) and third-generation detectors. Adopting crystalline materials for thin, reflecting mirror coatings, rather than the amorphous coatings used in current-generation detectors, could potentially reduce thermal noise. Understanding and reducing thermal noise requires accurate theoretical models, but modeling thermal noise analytically is especially challenging with crystalline materials. Thermal noise models typically rely on the fluctuation-dissipation theorem, which relates the power spectral density of the thermal noise to an auxiliary elastic problem. In this paper, we present results from a new, open-source tool that numerically solves the auxiliary elastic problem to compute the Brownian thermal noise for both amorphous and crystalline coatings. We employ open-source frameworks to solve the auxiliary elastic problem using a finite-element method, adaptive mesh refinement, and parallel processing that enables us to use high resolutions capable of resolving the thin reflective coating. We compare with approximate analytic solutions for amorphous materials, and we verify that our solutions scale as expected. Finally, we model the crystalline coating thermal noise in an experiment reported by Cole and collaborators (2013), comparing our results to a simpler numerical calculation that treats the coating as an "effectively amorphous" material. We find that treating the coating as a cubic crystal instead of as an effectively amorphous material increases the thermal noise by about 3%. Our results are a step toward better understanding and reducing thermal noise to increase the reach of future gravitational-wave detectors. (Abstract abbreviated.)
Multichannel interactions of two atoms in an optical tweezer

The authors present a new technique for characterizing the scattering and Feshbach resonances of two different species atoms. A single ultracold Na and Cs atom are trapped in the same optical tweezer and cooled to the ground state. The interactions of the two atoms modify their motional trapping frequencies, which are measured spectroscopically and used to characterize the scattering properties.
Almost-sure scattering for the radial energy-critical nonlinear wave equation in three dimensions

We study the Cauchy problem for the radial energy-critical nonlinear wave equation in three dimensions. Our main result proves almost-sure scattering for radial initial data below the energy space. In order to preserve the spherical symmetry of the initial data, we construct a radial randomization that is based on annular Fourier multipliers. We then use a refined radial Strichartz estimate to prove probabilistic Strichartz estimates for the random linear evolution. The main new ingredient in the analysis of the nonlinear evolution is an interaction flux estimate between the linear and nonlinear components of the solution. We then control the energy of the nonlinear component by a triple bootstrap argument involving the energy, the Morawetz term, and the interaction flux estimate.