cssi/SciSciGPT-SciSciNet huggingface dataset:
Iterated Decomposition of Biased Permutations via New Bounds on the Spectral Gap of Markov Chains.

The spectral gap of a Markov chain can be bounded by the spectral gaps of constituent "restriction" chains and a "projection" chain, and the strength of such a bound is the content of various decomposition theorems. In this paper, we introduce a new parameter that allows us to improve upon these bounds. We further define a notion of orthogonality between the restriction chains and "complementary" restriction chains. This leads to a new Complementary Decomposition theorem, which does not require analyzing the projection chain. For $\epsilon$-orthogonal chains, this theorem may be iterated $O(1/\epsilon)$ times while only giving away a constant multiplicative factor on the overall spectral gap. As an application, we provide a $1/n$-orthogonal decomposition of the nearest neighbor Markov chain over $k$-class biased monotone permutations on [$n$], as long as the number of particles in each class is at least $C\log n$. This allows us to apply the Complementary Decomposition theorem iteratively $n$ times to prove the first polynomial bound on the spectral gap when $k$ is as large as $\Theta(n/\log n)$. The previous best known bound assumed $k$ was at most a constant.
Molecular mechanism for rotational switching of the bacterial flagellar motor

The bacterial flagellar motor can rotate in counterclockwise (CCW) or clockwise (CW) senses, and transitions are controlled by the phosphorylated form of the response regulator CheY (CheY-P). To dissect the mechanism underlying flagellar rotational switching, we use Borrelia burgdorferi as a model system to determine high-resolution in situ motor structures in cheX and cheY3 mutants, in which motors are locked in either CCW or CW rotation. The structures showed that CheY3-P interacts directly with a switch protein, FliM, inducing a major remodeling of another switch protein, FliG2, and altering its interaction with the torque generator. Our findings lead to a model in which the torque generator rotates in response to an inward flow of H+ driven by the proton motive force, and conformational changes in FliG2 driven by CheY3-P allow the switch complex to interact with opposite sides of the rotating torque generator, facilitating rotational switching. In situ cryo-ET analyses of Borrelia burgdorferi flagellar motors locked in clockwise or counterclockwise rotation provide insights into rotational switching.
Boosting Random Forests to Reduce Bias; One-Step Boosted Forest and Its Variance Estimate

In this article, we propose using the principle of boosting to reduce the bias of a random forest prediction in the regression setting. From the original random forest fit, we extract the residuals...
Packing Disks by Flipping and Flowing

We provide a new type of proof for the Koebe–Andreev–Thurston (KAT) planar circle packing theorem based on combinatorial edge-flips. In particular, we show that starting from a disk packing with a maximal planar contact graph G, one can remove any flippable edge $$e^-$$ of this graph and then continuously flow the disks in the plane, so that at the end of the flow, one obtains a new disk packing whose contact graph is the graph resulting from flipping the edge $$e^-$$ in G. This flow is parameterized by a single inversive distance.
q-nonabelianization for line defects

We consider the q-nonabelianization map, which maps links L in a 3-manifold M to combinations of links $$ \tilde{L} $$ in a branched N -fold cover $$ \tilde{M} $$ . In quantum field theory terms, q-nonabelianization is the UV-IR map relating two different sorts of defect: in the UV we have the six-dimensional (2, 0) superconformal field theory of type $$ \mathfrak{gl} $$ (N ) on M × ℝ2,1, and we consider surface defects placed on L × {x4 = x5 = 0}; in the IR we have the (2, 0) theory of type gl (1) on $$ \tilde{M} $$ × ℝ2,1, and put the defects on $$ \tilde{L} $$ × {x4 = x5 = 0}. In the case M = ℝ3, q-nonabelianization computes the Jones polynomial of a link, or its analogue associated to the group U(N ). In the case M = C × ℝ, when the projection of L to C is a simple non-contractible loop, q-nonabelianization computes the protected spin character for framed BPS states in 4d $$ \mathcal{N} $$ = 2 theories of class S. In the case N = 2 and M = C × ℝ, we give a concrete construction of the q-nonabelianization map. The construction uses the data of the WKB foliations associated to a holomorphic covering $$ \tilde{C}\to C $$ .
Fundraising for Stigmatized Groups: A Text Message Donation Experiment

As government welfare programming contracts and NGOs increasingly assume core aid functions, they must address a long-standing challenge—that people in need often belong to stigmatized groups. To study other-regarding behavior, we fielded an experiment through a text-to-give campaign in Greece. Donations did not increase with an appeal to the in-group (Greek child) relative to a control (child), but they were halved with reference to a stigmatized out-group (Roma child). An appeal to fundamental rights, a common advocacy strategy, did not reduce the generosity gap. Donations to all groups were lower near Roma communities and declined disproportionately for the Roma appeal. Qualitative research in 12 communities complements our experiment. We conclude that NGO fundraising strategies that narrowly emphasize either in-groups or out-groups, or fundamental rights language, may not be as effective as broader appeals, and we discuss implications for public goods provision in an era of growing nationalism.
Geriatric Syndromes and Atrial Fibrillation: Prevalence and Association with Anticoagulant Use in a National Cohort of Older Americans.

Background Although guidelines recommend focusing primarily on stroke risk to recommend anticoagulants in atrial fibrillation (AF), physicians report that geriatric syndromes (e.g., falls and disability) are important when considering anticoagulants. Little is known about the prevalence of geriatric syndromes in older adults with AF or the association with anticoagulant use. Methods We performed a cross-sectional analysis of the 2014 Health and Retirement Study, a nationally representative study of older Americans. Participants were asked questions to assess domains of aging, including function, cognition, and medical conditions. We included participants 65 years and older with 2 years of continuous Medicare enrollment who met AF diagnosis criteria by claims codes. We examined five geriatric syndromes: one or more falls within the last 2 years, receiving help with activities of daily living (ADLs) or instrumental ADLs (IADL), experienced incontinence, and cognitive impairment. We determined the prevalence of geriatric syndromes and their association with anticoagulant use, adjusting for ischemic stroke risk (i.e., CHA2 DS2 -VASc score [congestive heart failure, hypertension, age, diabetes mellitus, stroke, vascular disease, and sex]). Results In this study of 779 participants with AF (median age = 80 years; median CHA2 DS2 -VASc score = 4), 82% had one or more geriatric syndromes. Geriatric syndromes were common: 49% reported falls, 38% had ADL impairments, 42% had IADL impairments, 37% had cognitive impairments, and 43% reported incontinence. Overall, 65% reported anticoagulant use; guidelines recommend anticoagulant use for 97% of participants. Anticoagulant use rate decreased for each additional geriatric syndrome (average marginal effect = -3.7%; 95% confidence interval = -1.4% to -5.9%). Lower rates of anticoagulant use were reported in participants with ADL dependency, IADL dependency, and dementia. Conclusion Most older adults with AF had at least one geriatric syndrome, and geriatric syndromes were associated with reduced anticoagulant use. The high prevalence of geriatric syndromes may explain the lower than expected anticoagulant use in older adults.
PointNet on FPGA for Real-Time LiDAR Point Cloud Processing

LiDAR sensors have been widely used in many autonomous vehicle modalities, such as perception, mapping, and localization. This paper presents an FPGA-based deep learning platform for real-time point cloud processing targeted on autonomous vehicles. The software driver for the Velodyne LiDAR sensor is modified and moved into the on-chip processor system, while the programmable logic is designed as a customized hardware accelerator. As the state-of-art deep learning algorithm for point cloud processing, PointNet is successfully implemented on the proposed FPGA platform. Targeted on a Xilinx Zynq UltraScale+ MPSoC ZCU104 development board, the FPGA implementations of PointNet achieve the computing performance of 182.1 GOPS and 280.0 GOPS for classification and segmentation respectively. The proposed design can support an input up to 4096 points per frame. The processing time is 19.8 ms for classification and 34.6 ms for segmentation, which meets the real-time requirement for most of the existing LiDAR sensors.
QAlign: aligning nanopore reads accurately using current-level modeling.

Motivation Efficient and accurate alignment of DNA/RNA sequence reads to each other or to a reference genome/transcriptome is an important problem in genomic analysis. Nanopore sequencing has emerged as a major sequencing technology and many long-read aligners have been designed for aligning nanopore reads. However, the high error rate makes accurate and efficient alignment difficult. Utilizing the noise and error characteristics inherent in the sequencing process properly can play a vital role in constructing a robust aligner. In this article, we design QAlign, a pre-processor that can be used with any long-read aligner for aligning long reads to a genome/transcriptome or to other long reads. The key idea in QAlign is to convert the nucleotide reads into discretized current levels that capture the error modes of the nanopore sequencer before running it through a sequence aligner. Results We show that QAlign is able to improve alignment rates from around 80% up to 90% with nanopore reads when aligning to the genome. We also show that QAlign improves the average overlap quality by 9.2, 2.5 and 10.8% in three real datasets for read-to-read alignment. Read-to-transcriptome alignment rates are improved from 51.6% to 75.4% and 82.6% to 90% in two real datasets. Availability and implementation https://github.com/joshidhaivat/QAlign.git. Supplementary information Supplementary data are available at Bioinformatics online.
Effects of Coulomb coupling on stopping power and a link to macroscopic transport

Molecular dynamics simulations are used to assess the influence of Coulomb coupling on the energy evolution of charged projectiles in the classical one-component plasma. The average projectile kinetic energy is found to decrease linearly with time when να/ωp ≲ 10−2, where να is the Coulomb collision frequency between the projectile and the medium, and ωp is the plasma frequency. Stopping power is obtained from the slope of this curve. In comparison to the weakly coupled limit, strong Coulomb coupling causes the magnitude of the dimensionless stopping power, (a/kBT)dE/dx, to increase, the Bragg peak to shift to several times the plasma thermal speed, and for the stopping power curve to broaden substantially. The rate of change of the total projectile kinetic energy averaged over many independent simulations is shown to consist of two measurable components: a component associated with a one-dimensional friction force and a thermal energy exchange rate. In the limit of a slow and massive projectile, these can be related to the macroscopic transport rates of self-diffusion and temperature relaxation in the plasma. Simulation results are compared with available theoretical models for stopping power, self-diffusion, and temperature relaxation.
Alignment of the diamond nitrogen vacancy center by strain engineering

The nitrogen vacancy (NV) center in diamond is a sensitive probe of magnetic field and a promising qubit candidate for quantum information processing. The performance of many NV-based devices improves by aligning the NV(s) parallel to a single crystallographic direction. Using ab initio theoretical techniques, we show that NV orientation can be controlled by high-temperature annealing in the presence of strain under currently accessible experimental conditions. We find that (89 ± 7)% of NVs align along the [111] crystallographic direction under 2% compressive biaxial strain (perpendicular to [111]) and an annealing temperature of 970 °C.
A Geometrical Look at MOSPA Estimation Using Transportation Theory

It was shown in [J. R. Hoffman and R. P. Mahler, “Multitarget miss distance via optimal assignment,” IEEE Trans. Syst., Man, Cybern. A, Syst. Humans , vol. 34, no. 3, pp. 327–336, May 2004.] that the Wasserstein distance is equivalent to the mean optimal subpattern assignment (MOSPA) measure for empirical probability density functions. A more recent paper [M. Baum, K. Peter, and D. Uwe Hanebeck, “On Wasserstein barycenters and MMOSPA estimation,” IEEE Signal Process. Lett. , vol. 22, no. 10, pp. 1511–1515, Oct. 2015.] extends on it by drawing new connections between the MOSPA concept, which is getting a foothold in the multitarget tracking community, and the Wasserstein distance, a metric widely used in theoretical statistics. However, the comparison between the two concepts has been overlooked. In this letter, we prove that the equivalence of Wasserstein distance with the MOSPA measure holds for general types of the probability density function. This nontrivial result allows us to leverage one recent finding in the computational geometry literature to show that the Minimum MOSPA (MMOSPA) estimates are the centroids of additive weighted Voronoi regions with a specific choice of the weights.
Atomic Data for Permitted Resonance Lines of Atoms and Ions from H to Si, and S, Ar, Ca, and Fe

The authors list vacuum wavelengths, energy levels, statistical weights, transition probabilities, and oscillator strengths for permitted resonance spectral lines of all ions of 18 astrophysically important elements (H through Si, S, Ar, Ca, Fe). Using a compilation of experimental energy levels, the authors derived accurate wavelengths for 5599 lines of 1828 ground-term multiplets which have gf-values calculated in the Opacity Project. They recalculated the Opacity Project multiplet gf-values to oscillator strengths and transition probabilities of individual lines. For completeness, the authors added 372 resonance lines of Ne I, Ar I, Fe I, and Fe II ions which are not covered by the Opacity Project. Intercombination and forbidden lines are not included in the present compilation. 99 refs., 1 fig., 3 tabs.
Ecological invasion, roughened fronts, and a competitor's extreme advance: integrating stochastic spatial-growth models.

Both community ecology and conservation biology seek further understanding of factors governing the advance of an invasive species. We model biological invasion as an individual-based, stochastic process on a two-dimensional landscape. An ecologically superior invader and a resident species compete for space preemptively. Our general model includes the basic contact process and a variant of the Eden model as special cases. We employ the concept of a “roughened” front to quantify effects of discreteness and stochasticity on invasion; we emphasize the probability distribution of the front-runner’s relative position. That is, we analyze the location of the most advanced invader as the extreme deviation about the front’s mean position. We find that a class of models with different assumptions about neighborhood interactions exhibits universal characteristics. That is, key features of the invasion dynamics span a class of models, independently of locally detailed demographic rules. Our results integrate theories of invasive spatial growth and generate novel hypotheses linking habitat or landscape size (length of the invading front) to invasion velocity, and to the relative position of the most advanced invader.
Intrinsically linked graphs and even linking number

We study intrinsically linked graphs where we require that every embedding of the graph contains not just a non-split link, but a link that satisfies some additional property. Examples of properties we address in this paper are: a two component link with lk(A, L) = k2 r , k 6 0, a non-split n-component link where all linking numbers are even, or an n-component link with components L, Ai where lk(L, Ai) = 3k, k 6 0. Links with other properties are considered as well. For a given property, we prove that every embedding of a certain complete graph contains a link with that property. The size of the complete graph is determined by the property in question. AMS Classification 57M15; 57M25,05C10
Extrasolar planet interactions

The dynamical interactions of planetary systems may be a clue to their formation histories. Therefore, the distribution of these interactions provides important constraints on models of planet formation. We focus on each system's apsidal motion and proximity to dynamical instability. Although only ∼25 multiple planet systems have been discovered to date, our analyses in these terms have revealed several important features of planetary interactions. 1) Many systems interact such that they are near the boundary between stability and instability. 2) Planets tend to form such that at least one planet's eccentricity periodically drops to near zero. 3) Mean-motion resonant pairs would be unstable if not for the resonance. 4) Scattering of approximately equal mass planets is unlikely to produce the observed distribution of apsidal behavior. 5) Resonant interactions may be identified through calculating a system's proximity to instability, regardless of knowledge of angles such as mean longitude and longitude of periastron (e.g. GJ 317 b and c are probably in a 4:1 resonance). These properties of planetary systems have been identified through calculation of two parameters that describe the interaction. The apsidal interaction can be quantified by determining how close a planet is to an apsidal separatrix (a boundary between qualitatively different types of apsidal oscillations, e.g. libration or circulation of the major axes). This value can be calculated through short numerical integrations. The proximity to instability can be measured by comparing the observed orbital elements to an analytic boundary that describes a type of stability known as Hill stability. We have set up a website dedicated to presenting the most up-to-date information on dynamical interactions: http://www.lpl.arizona.edu/~rory/research/xsp/dynamics.
Do prices coordinate markets

Walrasian equilibrium prices have a remarkable property: they allow each buyer to purchase a bundle of goods that she finds the most desirable, while guaranteeing that the induced allocation over all buyers will globally maximize social welfare. However, this clean story has two caveats. * First, the prices may induce indifferences. In fact, the minimal equilibrium prices necessarily induce indifferences. Accordingly, buyers may need to coordinate with one another to arrive at a socially optimal outcome---the prices alone are not sufficient to coordinate the market. * Second, although natural procedures converge to Walrasian equilibrium prices on a fixed population, in practice buyers typically observe prices without participating in a price computation process. These prices cannot be perfect Walrasian equilibrium prices, but instead somehow reflect distributional information about the market. To better understand the performance of Walrasian prices when facing these two problems, we give two results. First, we propose a mild genericity condition on valuations under which the minimal Walrasian equilibrium prices induce allocations which result in low over-demand, no matter how the buyers break ties. In fact, under genericity the over-demand of any good can be bounded by 1, which is the best possible at the minimal prices. We demonstrate our results for unit demand valuations and give an extension to matroid based valuations (MBV), conjectured to be equivalent to gross substitute valuations (GS). Second, we use techniques from learning theory to argue that the over-demand and welfare induced by a price vector converge to their expectations uniformly over the class of all price vectors, with respective sample complexity linear and quadratic in the number of goods in the market. These results make no assumption on the form of the valuation functions. These two results imply that under a mild genericity condition, the exact Walrasian equilibrium prices computed in a market are guaranteed to induce both low over-demand and high welfare when used in a new market where agents are sampled independently from the same distribution, whenever the number of agents is larger than the number of commodities in the market.
Ideal Membership in $$H^\infty $$: Toeplitz Corona Approach

We study the ideal membership problem in $$H^\infty $$ on the unit disc. Thus, given functions $$f,f_1,\ldots ,f_n$$ in $$H^\infty $$ , we seek sufficient conditions on the size of f in order for f to belong to the ideal of $$H^\infty $$ generated by $$f_1,\ldots ,f_n$$ . We provide a different proof of a theorem of Treil, which gives the sharpest known sufficient condition. To this end, we solve a closely related problem in the Hilbert space $$H^2$$ , which is equivalent to the ideal membership problem by the Nevanlinna–Pick property of $$H^2$$ .
SAFARI: Searching Asteroids for Activity Revealing Indicators

Active asteroids behave dynamically like asteroids but display comet-like comae. These objects are poorly understood, with only about 30 identified to date. We have conducted one of the deepest systematic searches for asteroid activity by making use of deep images from the Dark Energy Camera (DECam) ideally suited to the task. We looked for activity indicators amongst 11,703 unique asteroids extracted from 35,640 images. We detected three previously-identified active asteroids ((62412), (1) Ceres and (779) Nina), though only (62412) showed signs of activity. Our activity occurrence rate of 1 in 11,703 is consistent with the prevailing 1 in 10,000 activity occurrence rate estimate. Our proof of concept demonstrates 1) our novel informatics approach can locate active asteroids and 2) DECam data are well-suited to the search for active asteroids.
Forecasting [C ii] Line-intensity Mapping Measurements between the End of Reionization and the Epoch of Galaxy Assembly

We combine recent simulation work on the SFR--[C II] correlation at high redshift with empirical modeling of the galaxy--halo connection (via UniverseMachine) to forecast [C II] auto power spectra from $z\sim4$ to $z\sim8$. We compare these to sensitivities realistically expected from various instruments expected to come on-line in the next decade. If the predictions of our model are correct, [C II] should be detectable up to $z\sim6$ in this generation of surveys, but detecting [C II] past the end of reionization will require a generational leap in line-intensity survey capabilities.
The Generation of the Distant Kuiper Belt by Planet Nine from an Initially Broad Perihelion Distribution

The observation that the orbits of long-period Kuiper Belt objects (KBOs) are anomalously clustered in physical space has recently prompted the Planet Nine hypothesis—the proposed existence of a distant and eccentric planetary member of our solar system. Within the framework of this model, a Neptune-like perturber sculpts the orbital distribution of distant KBOs through a complex interplay of resonant and secular effects, such that in addition to perihelion-circulating objects, the surviving orbits get organized into apsidally aligned and anti-aligned configurations with respect to Planet Nine's orbit. In this work, we investigate the role of Kuiper Belt initial conditions on the evolution of the outer solar system using numerical simulations. Intriguingly, we find that the final perihelion distance distribution depends strongly on the primordial state of the system, and we demonstrate that a bimodal structure corresponding to the existence of both aligned and anti-aligned clusters is only reproduced if the initial perihelion distribution is assumed to extend well beyond ~36 au. The bimodality in the final perihelion distance distribution is due to the existence of permanently stable objects, with the lower perihelion peak corresponding to the anti-aligned orbits and the higher perihelion peak corresponding to the aligned orbits. We identify the mechanisms that enable the persistent stability of these objects and locate the regions of phase space in which they reside. The obtained results contextualize the Planet Nine hypothesis within the broader narrative of solar system formation and offer further insight into the observational search for Planet Nine.
FINITE-SIZE SPIN-WAVE THEORY OF A COLLINEAR ANTIFERROMAGNET

The ground-state and low-energy properties of the two-dimensional J1-J2 Heisenberg model in the collinear phase are investigated using finite-size spin-wave theory [Q. F. Zhong and S. Sorella, Europhys. Lett.21, 629 (1993)], and Lanczos exact diagonalizations. For spin one-half — where the effects of quantization are the strongest — the spin-wave expansion turns out to be quantitatively accurate for J2/J1≳0.8. In this regime, both the magnetic structure factor and the spin susceptibility are very close to the spin-wave predictions. The spin-wave estimate of the order parameter in the collinear phase, m†≃0.3, is in remarkable agreement with recent neutron scattering measurements on Li2VOSiO4.
Impact of non-unitary spin squeezing on atomic clock performance

Spin squeezing is a form of entanglement that can improve the stability of quantum sensors operating with multiple particles, by inducing inter-particle correlations that redistribute the quantum projection noise. Previous analyses of potential metrological gain when using spin squeezing were performed on theoretically ideal states, without incorporating experimental imperfections or inherent limitations which result in non-unitary quantum state evolution. Here, we show that potential gains in clock stability are substantially reduced when the spin squeezing is non-unitary, and derive analytic formulas for the clock performance as a function of squeezing, excess spin noise, and interferometer contrast. Our results highlight the importance of creating and employing nearly pure entangled states for improving atomic clocks.
Transverse localization of transmission eigenchannels

Transmission eigenchannels are building blocks of coherent wave transport in diffusive media, and selective excitation of individual eigenchannels can lead to diverse transport behaviour. An essential yet poorly understood property is the transverse spatial profile of each eigenchannel, which is relevant for the associated energy density and critical for coupling light into and out of it. Here, we discover that the transmission eigenchannels of a disordered slab possess exponentially localized incident and outgoing profiles, even in the diffusive regime far from Anderson localization. Such transverse localization arises from a combination of reciprocity, local coupling of spatial modes and non-local correlations of scattered waves. Experimentally, we observe signatures of such localization even with finite illumination area. The transverse localization of high-transmission channels enhances optical energy densities inside turbid media, which will be important for light–matter interactions and imaging applications. Transverse localization of transmission eigenchannels is discovered in random optical media even in the diffusive regime of propagation far from Anderson localization. These findings will have significant impact on imaging and the control of light–matter interactions in scattering systems.
Powers of edge ideals with linear resolutions

We show that if G is a gap-free and diamond-free graph, then I(G)s has a linear minimal free resolution for every s≥2.
Rejoinder: Gibbs Sampling, Exponential Families and Orthogonal Polynomials

We are thankful to the discussants for their hard, interesting work. The main purpose of our paper was to give reasonably sharp rates of convergence for some simple examples of the Gibbs sampler. We chose examples from expository accounts where direct use of available techniques gave practically useless answers. Careful treatment of these simple examples grew into bivariate modeling and Lancaster families. Since bounding rates of convergence is our primary focus, let us begin there.
Algebraic Lattices in QFT Renormalization

The structure of overlapping subdivergences, which appear in the perturbative expansions of quantum field theory, is analyzed using algebraic lattice theory. It is shown that for specific QFTs the sets of subdivergences of Feynman diagrams form algebraic lattices. This class of QFTs includes the standard model. In kinematic renormalization schemes, in which tadpole diagrams vanish, these lattices are semimodular. This implies that the Hopf algebra of Feynman diagrams is graded by the coradical degree or equivalently that every maximal forest has the same length in the scope of BPHZ renormalization. As an application of this framework, a formula for the counter terms in zero-dimensional QFT is given together with some examples of the enumeration of primitive or skeleton diagrams.
On curves and polygons with the equiangular chord property

Let C be a smooth, convex curve on either the sphere S 2 , the hyperbolic plane H 2 or the Euclidean plane E 2 , with the following property: there exists , and parameterizations x(t);y(t) of C such that for each t, the angle between the chord connecting x(t) to y(t) and C is at both ends. Assuming that C is not a circle, E. Gutkin completely charac- terized the angles for which such a curve exists in the Euclidean case. We study the infinitesimal version of this problem in the context of the other two constant curvature geometries, and in particular we provide a complete characterization of the angles for which there exists a non-trivial infinitesimal deformation of a circle through such curves with corresponding angle . We also consider a discrete version of this property for Euclidean polygons, and in this case we give a complete description of all non-trivial solutions.
Utility Design for Distributed Resource Allocation—Part I: Characterizing and Optimizing the Exact Price of Anarchy

Game theory has emerged as a fruitful paradigm for the design of networked multiagent systems. A fundamental component of this approach is the design of agents’ utility functions so that their self-interested maximization results in a desirable collective behavior. In this article, we focus on a well-studied class of distributed resource allocation problems, where each agent is requested to select a subset of resources with the goal of optimizing a given system-level objective. Our core contribution is the development of a novel framework to tightly characterize the worst-case performance of any resulting Nash equilibrium (price of anarchy) as a function of the chosen agents’ utility functions. Leveraging this result, we identify how to design such utilities so as to optimize the price of anarchy through a tractable linear program. This provides us with a priori performance certificates applicable to any existing learning algorithm capable of driving the system to an equilibrium. Part II of this article specializes these results to submodular and supermodular objectives, discusses the complexity of computing Nash equilibria, and provides multiple illustrations of the theoretical findings.
The Dynamics of Merging Clusters: A Monte Carlo Solution Applied to the Bullet and Musket Ball Clusters

Merging galaxy clusters have become one of the most important probes of dark matter, providing evidence for dark matter over modified gravity and even constraints on the dark matter self-interaction cross-section. To properly constrain the dark matter cross-section it is necessary to understand the dynamics of the merger, as the inferred cross-section is a function of both the velocity of the collision and the observed time since collision. While the best understanding of merging system dynamics comes from N-body simulations, these are computationally intensive and often explore only a limited volume of the merger phase space allowed by observed parameter uncertainty. Simple analytic models exist but the assumptions of these methods invalidate their results near the collision time, plus error propagation of the highly correlated merger parameters is unfeasible. To address these weaknesses I develop a Monte Carlo method to discern the properties of dissociative mergers and propagate the uncertainty of the measured cluster parameters in an accurate and Bayesian manner. I introduce this method, verify it against an existing hydrodynamic N-body simulation, and apply it to two known dissociative mergers: 1ES 0657-558 (Bullet Cluster) and DLSCL J0916.2+2951 (Musket Ball Cluster). I find that this method surpasses existing analytic models—providing accurate (10% level) dynamic parameter and uncertainty estimates throughout the merger history. This, coupled with minimal required a priori information (subcluster mass, redshift, and projected separation) and relatively fast computation (~6 CPU hours), makes this method ideal for large samples of dissociative merging clusters.
The high-dimensional cohomology of the moduli space of curves with level structures

We prove that the moduli space of curves with level structures has an enormous amount of rational cohomology in its cohomological dimension. As an application, we prove that the coherent cohomological dimension of the moduli space of curves is at least g-2. Well known conjectures of Looijenga would imply that this is sharp.
Benchmarking materials property prediction methods: the Matbench test set and Automatminer reference algorithm

Author(s): Dunn, A; Wang, Q; Ganose, A; Dopp, D; Jain, A | Abstract: We present a benchmark test suite and an automated machine learning procedure for evaluating supervised machine learning (ML) models for predicting properties of inorganic bulk materials. The test suite, Matbench, is a set of 13 ML tasks that range in size from 312 to 132k samples and contain data from 10 density functional theory-derived and experimental sources. Tasks include predicting optical, thermal, electronic, thermodynamic, tensile, and elastic properties given a material’s composition and/or crystal structure. The reference algorithm, Automatminer, is a highly-extensible, fully automated ML pipeline for predicting materials properties from materials primitives (such as composition and crystal structure) without user intervention or hyperparameter tuning. We test Automatminer on the Matbench test suite and compare its predictive power with state-of-the-art crystal graph neural networks and a traditional descriptor-based Random Forest model. We find Automatminer achieves the best performance on 8 of 13 tasks in the benchmark. We also show our test suite is capable of exposing predictive advantages of each algorithm—namely, that crystal graph methods appear to outperform traditional machine learning methods given ~104 or greater data points. We encourage evaluating materials ML algorithms on the Matbench benchmark and comparing them against the latest version of Automatminer.
Surface bundles over surfaces with arbitrarily many fiberings

In this paper we give the first example of a surface bundle over a surface with at least three fiberings. In fact, for each n 3 we construct 4‐manifolds E admitting at least n distinct fiberings piW E!Ugi as a surface bundle over a surface with base and fiber both closed surfaces of negative Euler characteristic. We give examples of surface bundles admitting multiple fiberings for which the monodromy representation has image in the Torelli group, showing the necessity of all of the assumptions made in the main theorem of a recent paper of ours. Our examples show that the number of surface bundle structures that can be realized on a 4‐manifold E with Euler characteristic d grows exponentially with d . 57R22
GraphChallenge.org: Raising the Bar on Graph Analytic Performance

The rise of graph analytic systems has created a need for new ways to measure and compare the capabilities of graph processing systems. The MIT/Amazon/IEEE Graph Challenge has been developed to provide a well-defined community venue for stimulating research and highlighting innovations in graph analysis software, hardware, algorithms, and systems. GraphChallenge.org provides a wide range of pre-parsed graph data sets, graph generators, mathematically defined graph algorithms, example serial implementations in a variety of languages, and specific metrics for measuring performance. Graph Challenge 2017 received 22 submissions by 111 authors from 36 organizations. The submissions highlighted graph analytic innovations in hardware, software, algorithms, systems, and visualization. These submissions produced many comparable performance measurements that can be used for assessing the current state of the art of the field. There were numerous submissions that implemented the triangle counting challenge and resulted in over 350 distinct measurements. Analysis of these submissions show that their execution time is a strong function of the number of edges in the graph, $N_{e}$ , and is typically proportional to $N_{e}^{4/3}$ for large values of $N_{e}$ . Combining the model fits of the submissions presents a picture of the current state of the art of graph analysis, which is typically 108 edges processed per second for graphs with 108 edges. These results are 30 times faster than serial implementations commonly used by many graph analysts and underscore the importance of making these performance benefits available to the broader community. Graph Challenge provides a clear picture of current graph analysis systems and underscores the need for new innovations to achieve high performance on very large graphs.
Optimization of nonhomogeneous indium-gallium-nitride Schottky-barrier thin-film solar cells

A two-dimensional model was developed to simulate the optoelectronic characteristics of indium-gallium-nitride (InξGa1 − ξN), thin-film, Schottky-barrier solar cells. The solar cells comprise a window designed to reduce the reflection of incident light, Schottky-barrier and ohmic front electrodes, an n-doped InξGa1 − ξN wafer, and a metallic periodically corrugated backreflector. The ratio of indium to gallium in the wafer varies periodically throughout the thickness of absorbing layer of the solar cell. Thus, the resulting InξGa1 − ξN wafer’s optical and electrical properties are made to vary periodically. This material nonhomogeneity could be physically achieved by varying the fractional composition of indium and gallium during deposition. Empirical models for indium nitride and gallium nitride were combined using Vegard’s law to determine the optical and electrical constitutive properties of the alloy. The nonhomogeneity of the electrical properties of the InξGa1 − ξN aids in the separation of the excited electron–hole pairs, whereas the periodicities of optical properties and the backreflector enable the incident light to couple to multiple guided wave modes. The profile of the resulting charge-carrier-generation rate when the solar cell is illuminated by the AM1.5G spectrum was calculated using the rigorous coupled-wave approach. The steady-state drift-diffusion equations were solved using COMSOL, which employs finite-volume methods, to calculate the current density as a function of the voltage. Midband Shockley–Read–Hall, Auger, and radiative recombination rates were taken to be the dominant methods of recombination. The model was used to study the effects of the solar-cell geometry and the shape of the periodic material nonhomogeneity on efficiency. The solar-cell efficiency was optimized using the differential evolution algorithm.
Formation of exomoons: a solar system perspective

Satellite formation is a natural by-product of planet formation. With the discovery of numerous extrasolar planets, it is likely that moons of extrasolar planets (exomoons) will soon be discovered....
Infinitesimal Deformations of a Formal Symplectic Groupoid

Given a formal symplectic groupoid G over a Poisson manifold (M, π0), we define a new object, an infinitesimal deformation of G, which can be thought of as a formal symplectic groupoid over the manifold M equipped with an infinitesimal deformation \({\pi_0 + \varepsilon \pi_1}\) of the Poisson bivector field π0. To any pair of natural star products \({(\ast,\tilde\ast)}\) having the same formal symplectic groupoid G we relate an infinitesimal deformation of G. We call it the deformation groupoid of the pair \({(\ast,\tilde\ast)}\) . To each star product with separation of variables \({\ast}\) on a Kahler–Poisson manifold M we relate another star product with separation of variables \({\hat\ast}\) on M. We build an algorithm for calculating the principal symbols of the components of the logarithm of the formal Berezin transform of a star product with separation of variables \({\ast}\) . This algorithm is based upon the deformation groupoid of the pair \({(\ast,\hat\ast)}\) .
Exploring the Role of Argument Structure in Online Debate Persuasion

Online debate forums provide users a platform to express their opinions on controversial topics while being exposed to opinions from diverse set of viewpoints. Existing work in Natural Language Processing (NLP) has shown that linguistic features extracted from the debate text and features encoding the characteristics of the audience are both critical in persuasion studies. In this paper, we aim to further investigate the role of discourse structure of the arguments from online debates in their persuasiveness. In particular, we use the factor graph model to obtain features for the argument structure of debates from an online debating platform and incorporate these features to an LSTM-based model to predict the debater that makes the most convincing arguments. We find that incorporating argument structure features play an essential role in achieving the best predictive performance in assessing the persuasiveness of the arguments on online debates.
Prediction and typicality in multiverse cosmology

In the absence of a fundamental theory that precisely predicts values for observable parameters, anthropic reasoning attempts to constrain probability distributions over those parameters in order to facilitate the extraction of testable predictions. The utility of this approach has been vigorously debated of late, particularly in light of theories that claim we live in a multiverse, where parameters may take differing values in regions lying outside our observable horizon. Within this cosmological framework, we investigate the efficacy of top-down anthropic reasoning based on the weak anthropic principle. We argue contrary to recent claims that it is not clear one can either dispense with notions of typicality altogether or presume typicality, in comparing resulting probability distributions with observations. We show in a concrete, top-down setting related to dark matter, that assumptions about typicality can dramatically affect predictions, thereby providing a guide to how errors in reasoning regarding typicality translate to errors in the assessment of predictive power. We conjecture that this dependence on typicality is an integral feature of anthropic reasoning in broader cosmological contexts, and argue in favour of the explicit inclusion of measures of typicality in schemes invoking anthropic reasoning, with a view to extracting predictions from multiverse scenarios.
The Evolution of Planet-Disk Systems That Are Mildly Inclined to the Orbit of a Binary Companion

We determine the evolution of a giant planet–disk system that orbits a member of a binary star system and is mildly inclined with respect to the binary orbital plane. The planet orbit and disk are initially mutually coplanar. We analyze the evolution of the planet and the disk by analytic means and hydrodynamic simulations. We generally find that the planet and the disk do not remain coplanar unless the disk mass is very large or the gap that separates the planet from the disk is very small. The relative planet–disk tilt undergoes secular oscillations whose initial amplitudes are typically of the order of the initial disk tilt relative to the binary orbital plane for disk masses ~1% of the binary mass or less. The effects of a secular resonance and the disk tilt decay enhance the planet–disk misalignment. The secular resonance plays an important role for disk masses greater than the planet mass. At later times, the accretion of disk gas by the planet causes its orbit to evolve toward alignment, if the disk mass is sufficiently large. The results have several implications for the evolution of massive planets in binary systems.
To Cool is to Accrete: Analytic Scalings for Nebular Accretion of Planetary Atmospheres

Planets acquire atmospheres from their parent circumstellar disks. We derive a general analytic expression for how the atmospheric mass grows with time $t$, as a function of the underlying core mass $M_{\rm core}$ and nebular conditions, including the gas metallicity $Z$. Planets accrete as much gas as can cool: an atmosphere's doubling time is given by its Kelvin-Helmholtz time. Dusty atmospheres behave differently from atmospheres made dust-free by grain growth and sedimentation. The gas-to-core mass ratio (GCR) of a dusty atmosphere scales as GCR $\propto t^{0.4} M_{\rm core}^{1.7} Z^{-0.4} \mu_{\rm rcb}^{3.4}$, where $\mu_{\rm rcb} \propto 1/(1-Z)$ (for $Z$ not too close to 1) is the mean molecular weight at the innermost radiative-convective boundary. This scaling applies across all orbital distances and nebular conditions for dusty atmospheres; their radiative-convective boundaries, which regulate cooling, are not set by the external environment, but rather by the internal microphysics of dust sublimation, H$_2$ dissociation, and the formation of H$^-$. By contrast, dust-free atmospheres have their radiative boundaries at temperatures $T_{\rm rcb}$ close to nebular temperatures $T_{\rm out}$, and grow faster at larger orbital distances where cooler temperatures, and by extension lower opacities, prevail. At 0.1 AU in a gas-poor nebula, GCR $\propto t^{0.4} T_{\rm rcb}^{-1.9} M_{\rm core}^{1.6} Z^{-0.4} \mu_{\rm rcb}^{3.3}$, while beyond 1 AU in a gas-rich nebula, GCR $\propto t^{0.4} T_{\rm rcb}^{-1.5} M_{\rm core}^1 Z^{-0.4}\mu_{\rm rcb}^{2.2}$. We confirm our analytic scalings against detailed numerical models for objects ranging in mass from Mars (0.1 $M_\oplus$) to the most extreme super-Earths (10-20 $M_\oplus$), and explain why heating from planetesimal accretion cannot prevent the latter from undergoing runaway gas accretion.