cssi/SciSciGPT-SciSciNet huggingface dataset:
Scarring for quantum maps with simple spectrum

In (4) we introduced a family of symplectic maps of the torus whose quantiza- tion exhibits scarring on invariant co-isotropic submanifolds. The purpose of this note is to show that in contrast to other examples, where failure of Quantum Unique Ergodicity is attributed to high multiplicities in the spectrum, for these examples the spectrum is (generically) simple.
Linear Recurrences for Cylindrical Networks

We prove a general theorem that gives a linear recurrence for tuples of paths in every cylindrical network. This can be seen as a cylindrical analog of the Lindstrom-Gessel-Viennot theorem. We illustrate the result by applying it to Schur functions, plane partitions, and domino tilings.
Shapes of pored membranes

We study the shapes of pored membranes within the framework of the Helfrich theory under the constraints of fixed area and pore size. We show that the mean curvature term leads to a budding-like structure, while the Gaussian curvature term tends to flatten the membrane near the pore; this is corroborated by simulation. We propose a scheme to deduce the ratio of the Gaussian rigidity to the bending rigidity simply by observing the shape of the pored membrane. This ratio is usually difficult to measure experimentally. In addition, we briefly discuss the stability of a pore by relaxing the constraint of a fixed pore size and adding the line tension. Finally, the flattening effect due to the Gaussian curvature as found in studying pored membranes is extended to two-component membranes. We find that sufficiently high contrast between the components' Gaussian rigidities leads to budding which is distinct from that due to the line tension.
Puzzles and pitfalls involving Haar-typicality in holography

Holographic states that have a well-defined geometric dual in AdS/CFT are not faithfully represented by Haar-typical states in finite-dimensional models. As such, trying to apply principles and lessons from Haar-random ensembles of states to holographic states can lead to apparent puzzles and contradictions. We point out a handful of these pitfalls.
Two-Photon Excitation Enhanced High-Efficiency and Phase-Conjugate Stimulated Mie Scattering of Perovskite Nanocrystals Suspended in n-Hexane

Two-photon excitation enhanced backward stimulated Mie scattering (SMS) is generated in a system of perovskite (CsPbBrxI3-x) nanocrystals (NCs) of ∼11 nm size suspended in n-hexane, when pumped wit...
Equations for stochastic macromolecular mechanics of single proteins: Equilibrium fluctuations, transient kinetics, and nonequilibrium steady-state

A modeling framework for the internal conformational dynamics and external mechanical movement of single biological macromolecules in aqueous solution at constant temperature is developed. Both the internal dynamics and the external movement are stochastic; the former is represented by a master equation for a set of discrete states, and the latter is described by a continuous Smoluchowski equation. Combining these two equations into one yields a comprehensive theory for the Brownian dynamics and statistical thermodynamics of single macromolecules. This approach is shown to have wide applications. It is applied to protein−ligand dissociation under external force, unfolding of polyglobular proteins under extension, movement along linear tracks of motor proteins against load, and enzyme catalysis by single fluctuating proteins. As a generalization of the classic polymer theory, the dynamic equation is capable of characterizing a single macromolecule in aqueous solution, in probabilistic terms, (1) its thermo...
Modeling interacting dynamic networks: II. Systematic study of the statistical properties of cross-links between two networks with preferred degrees

In a recent work (Liu et al, 2013 J. Stat. Mech. P08001), we introduced dynamic networks with preferred degrees and presented simulation and analytic studies of a single, homogeneous system as well as two interacting networks. Here, we extend these studies to a wider range of parameter space, in a more systematic fashion. Though the interaction we introduced seems simple and intuitive, it produced dramatically different behavior in the single- and two-network systems. Specifically, partitioning the single network into two identical sectors, we find the cross-link distribution to be a sharply peaked Gaussian. In stark contrast, we find a very broad and flat plateau in the case of two interacting identical networks. A sound understanding of this phenomenon remains elusive. Exploring more asymmetric interacting networks, we discover a kind of 'universal behavior' for systems in which the 'introverts' (nodes with smaller preferred degree) are far outnumbered. Remarkably, an approximation scheme for their degree distribution can be formulated, leading to very successful predictions.
Search cost for a nearly optimal path in a binary tree

Consider a binary tree, to the vertices of which are assigned independent Bernoulli random variables with mean p≤1/2. How many of these Bernoullis one must look at in order to find a path of length n from the root which maximizes, up to a factor of 1−ɛ, the sum of the Bernoullis along the path? In the case p=1/2 (the critical value for nontriviality), it is shown to take Θ(ɛ−1n) steps. In the case p<1/2, the number of steps is shown to be at least n⋅exp(const ɛ−1/2). This last result matches the known upper bound from [Algorithmica 22 (1998) 388–412] in a certain family of subcases.
On the Wind Generation of Water Waves

In this work, we consider the mathematical theory of wind generated water waves. This entails determining the stability properties of the family of laminar flow solutions to the two-phase interface Euler equation. We present a rigorous derivation of the linearized evolution equations about an arbitrary steady solution, and, using this, we give a complete proof of the instability criterion of Miles [16]. Our analysis is valid even in the presence of surface tension and a vortex sheet (discontinuity in the tangential velocity across the air–sea interface). We are thus able to give a unified equation connecting the Kelvin–Helmholtz and quasi-laminar models of wave generation.
Relativistic Dynamics and Mass Exchange in Binary Black Hole Mini-Disks

We present the first exploration of relativistic gas dynamics in the immediate vicinity of binary black holes as the system inspirals close to merger in the gravitational radiation-driven regime. We focus on 2D hydrodynamical studies of comparable-mass, non-spinning systems. Relativistic effects alter the dynamics of gas in this environment in several ways. Because the gravitational potential between the two black holes becomes shallower than in the Newtonian regime, the mini-disks stretch toward the L1 point and the amount of gas passing back and forth between the mini-disks increases sharply with decreasing binary separation. This "sloshing" is quasi-periodically modulated at $2$ and $2.75$ times the binary orbital frequency, corresponding to timescales of hours to days for supermassive binary black holes. In addition, relativistic effects add an $m=1$ component to the tidally-driven spiral waves in the disks that are purely $m=2$ in Newtonian gravity; this component becomes dominant when the separation is $\lesssim 100$ gravitational radii. Both the sloshing and the spiral waves have the potential to create distinctive radiation features that may uniquely mark supermassive binary black holes in the relativistic regime.
AN EFFICIENT METHOD FOR MODELING HIGH-MAGNIFICATION PLANETARY MICROLENSING EVENTS

I present a previously unpublished method for calculating and modeling multiple lens microlensing events that is based on the image centered ray-shooting approach of Bennett & Rhie. It has been used to model a wide variety of binary and triple lens systems, but it is designed to efficiently model high-magnification planetary microlensing events, because these high-magnification events are, by far, the most challenging events to model. It is designed to be efficient enough to handle complicated microlensing events, which include more than two lens masses and lens orbital motion. This method uses a polar coordinate integration grid with a smaller grid spacing in the radial direction than in the angular direction, and it employs an integration scheme specifically designed to handle limb-darkened sources. I present tests that show that these features achieve second-order accuracy for the light curves of a number of high-magnification planetary events. They improve the precision of the calculations by a factor of >100 compared to first-order integration schemes with the same grid spacing in both directions (for a fixed number of grid points). This method also includes a χ2 minimization method, based on the Metropolis algorithm, that allows the jump function to vary in a way that allows quick convergence to χ2 minima. Finally, I introduce a global parameter space search strategy that allows a blind search of parameter space for light curve models without requiring χ2 minimization over a large grid of fixed parameters. Instead, the parameter space is explored on a grid of initial conditions for a set of χ2 minimizations using the full parameter space. While this method may be somewhat faster than methods that find the χ2 minima over a large grid of parameters, I argue that the main strength of this method is for events with the signals of multiple planets, where a much higher dimensional parameter space must be explored to find the correct light curve model.
Efficient isolation of protoplasts from rice calli with pause points and its application in transient gene expression and genome editing assays

An efficient in vivo transient transfection system using protoplasts is an important tool to study gene expression, metabolic pathways, and multiple mutagenesis parameters in plants. Although rice protoplasts can be isolated from germinated seedlings or cell suspension culture, preparation of those donor tissues can be inefficient, time-consuming, and laborious. Additionally, the lengthy process of protoplast isolation and transfection needs to be completed in a single day. Here we report a protocol for the isolation of protoplasts directly from rice calli, without using seedlings or suspension culture. The method is developed to employ discretionary pause points during protoplast isolation and before transfection. Protoplasts maintained within a sucrose cushion partway through isolation, for completion on a subsequent day, per the first pause point, are referred to as S protoplasts. Fully isolated protoplasts maintained in MMG solution for transfection on a subsequent day, per the second pause point, are referred to as M protoplasts. Both S and M protoplasts, 1 day after initiation of protoplast isolation, had minimal loss of viability and transfection efficiency compared to protoplasts 0 days after isolation. S protoplast viability decreases at a lower rate over time than that of M protoplasts and can be used with added flexibility for transient transfection assays and time-course experiments. The protoplasts produced by this method are competent for transfection of both plasmids and ribonucleoproteins (RNPs). Cas9 RNPs were used to demonstrate the utility of these protoplasts to assay genome editing in vivo. The current study describes a highly effective and accessible method to isolate protoplasts from callus tissue induced from rice seeds. This method utilizes donor materials that are resource-efficient and easy to propagate, permits convenience via pause points, and allows for flexible transfection days after protoplast isolation. It provides an advantageous and useful platform for a variety of in vivo transient transfection studies in rice.
The Stellar Population and Star Clusters in the Unusual Local Group Galaxy IC 10

We present an analysis of Hubble Space Telescope U, V, I, and Hα images of the peculiar Local Group irregular galaxy IC 10. The images are used to determine the nature of the stellar products in a portion of the recent starburst in this galaxy. We identified 13 stellar associations and clusters, two of which are probably old (≥350 Myr) and the rest of which are young (4-30 Myr) and presumably formed in the starburst. We found the following: (1) The slope of the stellar initial mass function (IMF) for 6.3-18 M☉ stars formed in the starburst lies between two limiting cases: a value of -1.9 ± 0.4 under the assumption of coevality over the past 13 Myr and of -0.9 ± 0.3 under the assumption of constant star formation over the past 40 Myr for Z = 0.004 (-2.1 ± 0.4 and -1.0 ± 0.04, respectively, for Z = 0.008). Thus, most likely, the IMF of the intermediate-mass stars is not very unusual. The slope of the IMF for the underlying galaxy population under the assumption of constant star formation is -2.6 ± 0.3 for 4.8-18 M☉ stars assuming Z = 0.004 (-2.3 ± 0.3 for Z = 0.008) and is unusually steep. (2) The lower stellar mass limit in the starburst is ≤6.3 M☉. This constraint is less than some predictions of what lower stellar mass limits might be in starbursts but higher than others. (3) There are two modest-sized Hα shells (~50 pc diameter) that easily could have been produced in the past few Myr by the clusters they encircle. (4) The dominant mode of star formation in the starburst has been that of a scaled-up OB association. This mode, with a few compact clusters sprinkled in, is similar to the star formation that took place in Constellation III in the LMC, as well as that in the blue compact dwarfs I Zw 18 and VII Zw 403. The starburst in this part of IC 10 has not produced a superstar cluster. We also compare the high WC/WN ratio to evolutionary models and discuss possible explanations. The high ratio can be reproduced if there were small, well-synchronized (Δτ ≤ 1 Myr), but widely scattered, pockets of secondary star formation 3-4 Myr ago.
Discriminating Accretion States via Rotational Symmetry in Simulated Polarimetric Images of M87

In April 2017, the Event Horizon Telescope observed the shadow of the supermassive black hole at the core of the elliptical galaxy Messier 87. While the original image was constructed from measurements of the total intensity, full polarimetric data were also collected, and linear polarimetric images are expected in the near future. We propose a modal image decomposition of the linear polarization field into basis functions with varying azimuthal dependence of the electric vector position angle. We apply this decomposition to images of ray traced general relativistic magnetohydrodynamics simulations of the Messier 87 accretion disk. For simulated images that are physically consistent with previous observations, the magnitude of the coefficient associated with rotational symmetry, $\beta_2$, is a useful discriminator between accretion states. We find that at 20 $\mu$as resolution, $|\beta_2|$ is greater than 0.2 only for models of disks with horizon-scale magnetic pressures large enough to disrupt steady accretion. We also find that images with a more radially directed electric vector position angle correspond to models with higher black hole spin. Our analysis demonstrates the utility of the proposed decomposition as a diagnostic framework to improve constraints on theoretical models.
Color octet contribution in exclusive P-wave charmonium decay

Abstract Recent advances in our understanding of the higher-wave quarkonia have generated much interests in quarkonium physics. However most are devoted to inclusive decays and productions. Experimental data of several two-body exclusive decay channels of P-wave charmonia such as ππ and pp are available and some have recently been re-measured by the BES collaboration. It is not clear from the outset that color octet is needed for these exclusive channels. Indeed only color singlet has been used in the past and reasonable agreement with data was found. Contrary to these old results, we provide theoretical arguments for the inclusion of color octet and perform explicit calculations to back this up.
Osteoporotic and neoplastic compression fracture classification on longitudinal CT

Classification of vertebral compression fractures (VCF) having osteoporotic or neoplastic origin is fundamental to the planning of treatment. We developed a fracture classification system by acquiring quantitative morphologic and bone density determinants of fracture progression through the use of automated measurements from longitudinal studies. A total of 250 CT studies were acquired for the task, each having previously identified VCFs with osteoporosis or neoplasm. Thirty-six features for each identified VCF were computed and classified using a committee of support vector machines. Ten-fold cross validation on 695 identified fractured vertebrae showed classification accuracies of 0.812, 0.665, and 0.820 for the measured, longitudinal, and combined feature sets respectively.
On the general structure of mathematical models for physical systems

It is proposed that the mathematical models for any physical systems that are based in first principles, such as conservation laws or balance principles, have some common elements, namely, a space of kinematical states, a space of dynamical states, a constitutive law that associates dynamical states with kinematical states, as well as a duality principle. The equations of motion or statics then come about from, on the one hand, specifying the integrability of the kinematical state, and on the other hand, specifying a statement that is dual to it for the dynamical states. Examples are given from various fundamental physical systems.
Automatic estimation of flux distributions of astrophysical source populations

AbstractIn astrophysics a common goal is to infer the ux distribution of populations of scienti callyinteresting objects such as pulsars or supernovae. In practice, inference for the ux distributionis often conducted using the cumulative distribution of the number of sources detected at agiven sensitivity. The resulting \log(N >S) log(S)" relationship can be used to compareand evaluate theoretical models for source populations and their evolution. Under restrictiveassumptions the relationship should be linear. In practice, however, when simple theoreticalmodels fail, it is common for astrophysicists to use pre-speci ed piecewise linear models. Thispaper proposes a methodology for estimating both the number and locations of \breakpoints"in astrophysical source populations that extends beyond existing work in this eld.An important component of the proposed methodology is a new Interwoven EM Algorithmthat computes parameter estimates. It is shown that in simple settings such estimates areasymptotically consistent despite the complex nature of the parameter space. Through simula-tion studies it is demonstrated that the proposed methodology is capable of accurately detectingstructural breaks in a variety of parameter con gurations. This paper concludes with an appli-cation of our methodology to the Chandra Deep Field North (CDFN) dataset.Keywords: Broken power law, CDFN X-ray survey, Interwoven EM algorithm, Likelihood com-putations, logN logS, Pareto distribution
Local kernel canonical correlation analysis with application to virtual drug screening

Drug discovery is the process of identifying compounds which have potentially meaningful biological activity. A major challenge that arises is that the number of compounds to search over can be quite large, sometimes numbering in the millions, making experimental testing intractable. For this reason computational methods are employed to filter out those compounds which do not exhibit strong biological activity. This filtering step, also called virtual screening reduces the search space, allowing for the remaining compounds to be experimentally tested. In this paper we propose several novel approaches to the problem of virtual screening based on Canonical Correlation Analysis (CCA) and on a kernel-based extension. Spectral learning ideas motivate our proposed new method called Indefinite Kernel CCA (IKCCA). We show the strong performance of this approach both for a toy problem as well as using real world data with dramatic improvements in predictive accuracy of virtual screening over an existing methodology.
Microlocal analysis of forced waves

We use radial estimates for pseudodifferential operators to describe long-time evolution of solutions to iut−Pu=f, where P is a self-adjoint zeroth-order pseudodifferential operator satisfying hyperbolic dynamical assumptions and where f is smooth. This is motivated by recent results of Colin de Verdiere and Saint-Raymond (2019) concerning a microlocal model of internal waves in stratified fluids.
Torsion, TQFT, and Seiberg{Witten invariants of 3{manifolds

We prove a conjecture of Hutchings and Lee relating the Seiberg{Witten invariants of a closed 3{manifold X with b1 1 to an invariant that \counts" gradient flow lines|including closed orbits|of a circle-valued Morse function on the manifold. The proof is based on a method described by Donaldson for computing the Seiberg{Witten invariants of 3{manifolds by making use of a \topological quantum eld theory," which makes the calculation completely explicit. We also realize a version of the Seiberg{Witten invariant of X as the intersection number of a pair of totally real submanifolds of a product of vortex moduli spaces on a Riemann surface constructed from geometric data on X . The analogy with recent work of Ozsv ath and Szab o suggests a generalization of a conjecture of Salamon, who has proposed a model for the Seiberg{Witten{ Floer homology of X in the case that Xis a mapping torus.
Multiscale Spatial Density Smoothing: An Application to Large-Scale Radiological Survey and Anomaly Detection

ABSTRACTWe consider the problem of estimating a spatially varying density function, motivated by problems that arise in large-scale radiological survey and anomaly detection. In this context, the density functions to be estimated are the background gamma-ray energy spectra at sites spread across a large geographical area, such as nuclear production and waste-storage sites, military bases, medical facilities, university campuses, or the downtown of a city. Several challenges combine to make this a difficult problem. First, the spectral density at any given spatial location may have both smooth and nonsmooth features. Second, the spatial correlation in these density functions is neither stationary nor locally isotropic. Finally, at some spatial locations, there are very little data. We present a method called multiscale spatial density smoothing that successfully addresses these challenges. The method is based on recursive dyadic partition of the sample space, and therefore shares much in common with other ...
Twisted Boundary Conditions and Matching to the Effective Four-Dimensional Theory

Nontrivial twisted boundary conditions associated with extra compact dimensions can produce an ambiguity in the value of the four-dimensional coupling constants of the renormalizable interactions of the twisted fields' zero-modes. Resolving this indeterminacy would require a knowledge of the exact form of the higher dimensional action including the coefficients of higher-dimensional operators. For the case of moderately sized extra dimensions, the uncertainty in the coupling constants can be of order one and may lead to modifications in the stability of the model.
Holographic systematics of D-brane inflation

We provide a systematic treatment of possible corrections to the inflaton potential for D-brane inflation in the warped deformed conifold. We consider the D3-brane potential in the presence of the most general possible corrections to the throat geometry sourced by coupling to the bulk of a compact Calabi-Yau space. This corresponds to the potential on the Coulomb branch of the dual gauge theory, in the presence of arbitrary perturbations of the Lagrangian. The leading contributions arise from perturbations by the most relevant operators that do not destroy the throat geometry. We find a generic contribution from a non-chiral operator of dimension Δ = 2 associated with a global symmetry current, resulting in a negative contribution to the inflaton mass-squared. If the Calabi-Yau preserves certain discrete symmetries, this is the dominant correction to the inflaton potential, and fine-tuning of the inflaton mass is possible. In the absence of such discrete symmetries, the dominant contribution comes from a chiral operator with Δ = 3/2, corresponding to a 3/2 term in the inflaton potential. The resulting inflationary models are phenomenologically similar to the inflection point scenarios arising from specific D7-brane embeddings, but occur under far more general circumstances. Our strategy extends immediately to other warped geometries, given sufficient knowledge of the Kaluza-Klein spectrum.
A bound on massive higher spin particles

According to common lore, massive elementary higher spin particles lead to inconsistencies when coupled to gravity. However, this scenario was not completely ruled out by previous arguments. In this paper, we show that in a theory where the low energy dynamics of the gravitons are governed by the Einstein-Hilbert action, any finite number of massive elementary particles with spin more than two cannot interact with gravitons, even classically, in a way that preserves causality. This is achieved in flat spacetime by studying eikonal scattering of higher spin particles in more than three spacetime dimensions. Our argument is insensitive to the physics above the effective cut-off scale and closes certain loopholes in previous arguments. Furthermore, it applies to higher spin particles even if they do not contribute to tree-level graviton scattering as a consequence of being charged under a global symmetry such as ℤ2. We derive analogous bounds in anti-de Sitter space-time from analyticity properties of correlators of the dual CFT in the Regge limit. We also argue that an infinite tower of fine-tuned higher spin particles can still be consistent with causality. However, they necessarily affect the dynamics of gravitons at an energy scale comparable to the mass of the lightest higher spin particle. Finally, we apply the bound in de Sitter to impose restrictions on the structure of three-point functions in the squeezed limit of the scalar curvature perturbation produced during inflation.
Mapping the Similarities of Spectra: Global and Locally-biased Approaches to SDSS Galaxy Data

We present a novel approach to studying the diversity of galaxies. It is based on a novel spectral graph technique, that of locally-biased semi-supervised eigenvectors. Our method introduces new coordinates that summarize an entire spectrum, similar to but going well beyond the widely used Principal Component Analysis (PCA). Unlike PCA, however, this technique does not assume that the Euclidean distance between galaxy spectra is a good global measure of similarity. Instead, we relax that condition to only the most similar spectra, and we show that doing so yields more reliable results for many astronomical questions of interest. The global variant of our approach can identify very finely numerous astronomical phenomena of interest. The locally-biased variants of our basic approach enable us to explore subtle trends around a set of chosen objects. The power of the method is demonstrated in the Sloan Digital Sky Survey Main Galaxy Sample, by illustrating that the derived spectral coordinates carry an unprecedented amount of information.
Hysteresis Patterns of Watershed Nitrogen Retention and Loss Over the Past 50 years in United States Hydrological Basins

Author(s): Newcomer, ME; Bouskill, NJ; Wainwright, H; Maavara, T; Arora, B; Siirila-Woodburn, ER; Dwivedi, D; Williams, KH; Steefel, C; Hubbard, SS | Abstract: Patterns of watershed nitrogen (N) retention and loss are shaped by how watershed biogeochemical processes retain, biogeochemically transform, and lose incoming atmospheric deposition of N. Loss patterns represented by concentration, discharge, and their associated stream exports are important indicators of integrated watershed N retention behaviors. We examined continental United States (CONUS) scale N deposition (e.g., wet and dry atmospheric deposition), vegetation trends, and stream trends as potential indicators of watershed N-saturation and retention conditions, and how watershed N retention and losses vary over space and time. By synthesizing changes and modalities in watershed nitrogen loss patterns based on stream data from 2200 U.S. watersheds over a 50nyears record, our work revealed two patterns of watershed N-retention and loss. One was a hysteresis pattern that reflects the integrated influence of hydrology, atmospheric inputs, land-use, stream temperature, elevation, and vegetation. The other pattern was a one-way transition to a new state. We found that regions with increasing atmospheric deposition and increasing vegetation health/biomass patterns have the highest N-retention capacity, become increasingly N-saturated over time, and are associated with the strongest declines in stream N exports—a pattern, that is, consistent across all land cover categories. We provide a conceptual model, validated at an unprecedented scale across the CONUS that links instream nitrogen signals to upstream mechanistic landscape processes. Our work can aid in the future interpretation of in-stream concentrations of DOC and DIN as indicators of watershed N-retention status and integrators of watershed hydrobiogeochemical processes.
The algebraic crossing number and the braid index of knots and links

It has been conjectured that the algebraic crossing number of a link is uniquely determined in minimal braid representation. This conjecture is true for many classes of knots and links. The Morton-Franks-Williams inequality gives a lower bound for braid index. And sharpness of the inequality on a knot type implies the truth of the conjecture for the knot type. We prove that there are infinitely many examples of knots and links for which the inequality is not sharp but the conjecture is still true. We also show that if the conjecture is true for K and L, then it is also true for the (p,q)-cable of K and for the connect sum of K and L.
The Likely Near-Infrared Counterpart to the Anomalous X-Ray Pulsar 1E 1048.1–5937*

We report our discovery of the likely near-infrared counterpart to the anomalous X-ray pulsar (AXP) 1E 1048.1-5937, using observations from the 6.5 m Baade (Magellan I) telescope in Chile. We derived a precise position for the X-ray source using archival data from the Chandra X-Ray Observatory. This position is inconsistent with a position reported earlier from XMM-Newton, but we show that the originally reported XMM-Newton position suffered from attitude reconstruction problems. Only two of the infrared objects in a 17'' ? 17'' field containing the target have unusual colors, and one of these has colors consistent with those of the identified counterparts of two other AXPs. The latter object is also the only source detected within the 06 Chandra error circle, and we identify it as the counterpart to 1E 1048.1-5937. This is the first AXP counterpart detected in multiple infrared bands, with magnitudes J = 21.7(3), H = 20.8(3), and K = 19.4(3). There is marginal evidence for spectral flattening at longer wavelengths.
Ricci Curvature, Isoperimetry and a Non-additive Entropy

Searching for the dynamical foundations of Havrda-Charvat/Daroczy/ Cressie-Read/Tsallis non-additive entropy, we come across a covariant quantity called, alternatively, a generalized Ricci curvature, an N-Ricci curvature or a Bakry-Emery-Ricci curvature in the configuration/phase space of a system. We explore some of the implications of this tensor and its associated curvature and present a connection with the non-additive entropy under investigation. We present an isoperimetric interpretation of the non-extensive parameter and comment on further features of the system that can be probed through this tensor.
PS2: managing the next step in the Pan-STARRS wide field survey system

The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) is unique among the existing or planned major ground-based optical survey systems as the only "distributed aperture" system. The concept of increasing system etendue by replicating small telescopes and digital cameras presents both management opportunities and challenges. The focus in this paper is on management lessons learned from PS1, and how those have been used to form the management plan for PS2. The management plan components emphasized here include technical development, financial and schedule planning, and critical path and risk management. Finally, the status and schedule for PS2 are presented.
Can Graph Neural Networks Count Substructures

The ability to detect and count certain substructures in graphs is important for solving many tasks on graph-structured data, especially in the contexts of computational chemistry and biology as well as social network analysis. Inspired by this, we propose to study the expressive power of graph neural networks (GNNs) via their ability to count attributed graph substructures, extending recent works that examine their power in graph isomorphism testing and function approximation. We distinguish between two types of substructure counting: induced-subgraph-count and subgraph-count, and establish both positive and negative answers for popular GNN architectures. Specifically, we prove that Message Passing Neural Networks (MPNNs), 2-Weisfeiler-Lehman (2-WL) and 2-Invariant Graph Networks (2-IGNs) cannot perform induced-subgraph-count of substructures consisting of 3 or more nodes, while they can perform subgraph-count of star-shaped substructures. As an intermediary step, we prove that 2-WL and 2-IGNs are equivalent in distinguishing non-isomorphic graphs, partly answering an open problem raised in Maron et al. (2019). We also prove positive results for k-WL and k-IGNs as well as negative results for k-WL with a finite number of iterations. We then conduct experiments that support the theoretical results for MPNNs and 2-IGNs. Moreover, motivated by substructure counting and inspired by Murphy et al. (2019), we propose the Local Relational Pooling model and demonstrate that it is not only effective for substructure counting but also able to achieve competitive performance on molecular prediction tasks.
Actinide-rich and Actinide-poor r-process-enhanced Metal-poor Stars Do Not Require Separate r-process Progenitors

The astrophysical production site of the heaviest elements in the universe remains a mystery. Incorporating heavy element signatures of metal-poor, $r$-process enhanced stars into theoretical studies of $r$-process production can offer crucial constraints on the origin of heavy elements. In this study, we introduce and apply the "Actinide-Dilution with Matching" model to a variety of stellar groups ranging from actinide-deficient to actinide-enhanced to empirically characterize $r$-process ejecta mass as a function of electron fraction. We find that actinide-boost stars do not indicate the need for a unique and separate $r$-process progenitor. Rather, small variations of neutron richness within the same type of $r$-process event can account for all observed levels of actinide enhancements. The very low-$Y_e$, fission-cycling ejecta of an $r$-process event need only constitute 10-30% of the total ejecta mass to accommodate most actinide abundances of metal-poor stars. We find that our empirical $Y_e$ distributions of ejecta are similar to those inferred from studies of GW170817 mass ejecta ratios, which is consistent with neutron-star mergers being a source of the heavy elements in metal-poor, $r$-process enhanced stars.
The Planetary Nebula Luminosity Function (PNLF): Contamination from Supernova Remnants

The planetary nebula luminosity function (PNLF) has been used as an extragalactic distance indicator since the 1980's, but there are still unsolved problems associated with its use. One of the most serious involves PNLF distances beyond ~ 10 Mpc, which tend to be slightly smaller than those of other methods. We consider the implications of previous spectroscopic investigations that found that several of the brightest planetary nebula (PN) candidates in M74 are actually compact supernova remnants (SNRs). Using narrow-band imaging data from the KPNO 4-m telescope, we measure the [O III] $\lambda$5007 and H$\alpha$ fluxes of all the known SNRs in M31 and M33, and test whether those objects could be misidentified as bright PNe at distances beyond ~ 10 Mpc. Our results suggest that compact SNRs are not an important source of contamination in photometric surveys for extragalactic PNe.
Solar and stellar activity: diagnostics and indices

We summarize the fifty-year concerted effort to place the "activity" of the Sun in the context of the stars. As a working definition of solar activity in the context of stars, we adopt those globally-observable variations on time scales below thermal time scales, of � 10 5 yr for the convection zone. So defined, activity is dominated by magnetic-field evolution, including the 22-year Hale cycle, the typical time it takes for the quasi-periodic reversal in which the global magnetic-field takes place. This is accompanied by sunspot variations with 11 year periods, known since the time of Schwabe, as well as faster variations due to rotation of active regions and flaring. "Diagnostics and indices" are terms given to the indirect signatures of varying magnetic- fields, including the photometric (broad-band) variations associated with the sunspot cycle, and variations of the accompanying heated plasma in higher layers of stellar atmospheres seen at special optical wavelengths, and UV and X-ray wavelengths. Our attention is also focussed on the theme of the Symposium by examining evidence for deep and extended minima of stars, and placing the 70-year long solar Maunder Minimum into a stellar context.
An analytic scaling relation for the maximum tokamak elongation against n = 0 MHD resistive wall modes

A highly elongated plasma is desirable in order to increase plasma pressure and energy confinement to maximize fusion power output. However, there is a limit to the maximum achievable elongation which is set by vertical instabilities driven by the n = 0 MHD mode. This limit can be increased by optimizing several parameters characterizing the plasma and the wall. The purpose of our study is to explore how and to what extent this can be done. Specifically, we extend many earlier calculations of the n = 0 mode and numerically determine scaling relations for the maximum elongation as a function of dimensionless parameters describing (1) the plasma profile ( and l i ), (2) the plasma shape ( and δ), (3) the wall radius (b/a) and (4) most importantly the feedback system capability parameter . These numerical calculations rely on a new formulation of n = 0 MHD theory we recently developed (Freidberg et al 2015 J. Plasma Phys. 81 515810607, Lee et al 2015 J. Plasma Phys. 81 515810608) that reduces the 2D stability problem into a 1D problem. This method includes all the physics of the ideal MHD axisymmetric instability while reducing the computation time significantly, so that many parameters can be explored during the optimization process. The scaling relations we present include the effects of the optimal triangularity and the finite aspect ratio on the maximum elongation, and can be useful for determining optimized plasma shapes in current experiments and future tokamak designs.
Thermalization, Freeze-out, and Noise: Deciphering Experimental Quantum Annealers

Quantum annealing might be very useful for finding answers\dots{}but to which questions? A mechanistic understanding of how quantum annealers behave is crucial to identifying the tasks for which they are well suited. This study contrasts two annealers operating at different temperatures, to clarify the roles that thermal processes and analog errors play in their performance. Regrettably, the results show that present-day quantum annealers do $n\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}t$ function reliably as classical Boltzmann samplers. The insight from these experiments carries considerable implications for the design of future annealers, and the prospects for using them in machine learning and beyond.
Effects of cutoff functions of Tersoff potentials on molecular dynamics simulations of thermal transport

Past molecular dynamics studies of thermal transport have predominantly used Stillinger–Weber potentials. As materials continuously shrink, their properties increasingly depend on defect and surface effects. Unfortunately, Stillinger–Weber potentials are best used for diamond-cubic-like bulk crystals. They cannot represent the energies of many metastable phases, nor can they accurately predict the energetics of defective and surface regions. To study nanostructured materials, where these regions can dominate thermal transport, the accuracy of Tersoff potentials in representing these structures is more desirable. Based upon an analysis of thermal transport in a GaN system, we demonstrate that the cutoff function of the existing Tersoff potentials may lead to problems in determining the thermal conductivity. To remedy this issue, improved cutoff schemes are proposed and evaluated.
Massive Spin-2 Scattering and Asymptotic Superluminality

We place model-independent constraints on theories of massive spin-2 particles by considering the positivity of the phase shift in eikonal scattering. The phase shift is an asymptotic S-matrix observable, related to the time delay/advance experienced by a particle during scattering. Demanding the absence of a time advance leads to constraints on the cubic vertices present in the theory. We find that, in theories with massive spin-2 particles, requiring no time advance means that either: (i) the cubic vertices must appear as a particular linear combination of the Einstein-Hilbert cubic vertex and an h 3 potential term or (ii) new degrees of freedom or strong coupling must enter at parametrically the mass of the massive spin-2 field. These conclusions have implications for a variety of situations. Applied to theories of large-N QCD, this indicates that any spectrum with an isolated massive spin-2 at the bottom must have these particular cubic self-couplings. Applied to de Rham-Gabadadze-Tolley massive gravity, the constraint is in accord with results obtained from a shockwave calculation: of the two free dimensionless parameters in the theory there is a one parameter line consistent with a subluminal phase shift.
An infinite family of links with critical bridge spheres

A closed orientable splitting surface in an oriented 3–manifold is a topologically minimal surface of index n if its associated disk complex is ( n − 2 ) –connected but not ( n − 1 ) –connected. A critical surface is a topologically minimal surface of index 2. In this paper, we use an equivalent combinatorial definition of critical surfaces to construct the first known critical bridge spheres for nontrivial links.
Molecular Tagging Velocimetry in Superfluid Helium-4: Progress, Issues, and Future Development

Helium-4 in the superfluid phase (He II) is a two-fluid system that exhibits fascinating quantum hydrodynamics with important scientific and engineering applications. However, the lack of high-precision flow measurement tools in He II has impeded the progress in understanding and utilizing its hydrodynamics. In recent years, there have been extensive efforts in developing quantitative flow visualization techniques applicable to He II. In particular, a powerful molecular tagging velocimetry (MTV) technique, based on tracking thin lines of $$\hbox {He}^*_2$$ excimer molecules created via femtosecond laser-field ionization in helium, has been developed in our laboratory. This technique allows unambiguous measurement of the normal fluid velocity field in the two-fluid system. Nevertheless, there are two limitations to this technique: (1) only the velocity component perpendicular to the tracer line can be measured; and (2) there is an inherent error in determining the perpendicular velocity. In this paper, we discuss how these issues can be resolved by advancing the MTV technique. We also discuss two novel schemes for tagging and producing $$\hbox {He}^*_2$$ tracers. The first method allows the creation of a tagged $$\hbox {He}^*_2$$ tracer line without the use of an expensive femtosecond laser. The second method enables full-space velocity field measurement through tracking small clouds of $$\hbox {He}^*_2$$ molecules created via neutron- $$^3\hbox {He}$$ absorption reactions in He II.
Cyclic posets and triangulation clusters

Triangulated categories coming from cyclic posets were originally introduced by the authors in a previous paper as a generalization of the constructions of various triangulated categories with cluster structures. We give an overview, and then analyze “triangulation clusters” which are those corresponding to topological triangulations of the 2-disk. Locally finite nontriangulation clusters give topological triangulations of the “cactus space” associated to the “cactus cyclic poset”.
When wanting closure reduces patients’ patience

Abstract What makes patients impatient? We find that people both make impatient health decisions and experience impatience when waiting for healthcare partially because they are eager to achieve psychological closure on their goals. Across five preregistered studies (N = 1806), we first document an increased preference for a worse health device (Study 1) and more painful treatment (Study 2) when they allow for earlier goal closure, even though they would not provide remedy sooner. We next find that because the desire to achieve closure increases with proximity to a goal, the experience of impatience increases closer to the completion of a medical checkup (Studies 3–5). We discuss the implications of people’s desire to reach goal closure on the pursuit of both health habits and health care.
Proximity-based proteomics reveals the thylakoid lumen proteome in the cyanobacterium Synechococcus sp. PCC 7002

Cyanobacteria possess unique intracellular organization. Many proteomic studies have examined different features of cyanobacteria to learn about the intracellular structures and their respective functions. While these studies have made great progress in understanding cyanobacterial physiology, the conventional fractionation methods used to purify cellular structures have limitations; specifically, certain regions of cells cannot be purified with existing fractionation methods. Proximity-based proteomics techniques were developed to overcome the limitations of biochemical fractionation for proteomics. Proximity-based proteomics relies on spatiotemporal protein labeling followed by mass spectrometry of the labeled proteins to determine the proteome of the region of interest. We performed proximity-based proteomics in the cyanobacterium Synechococcus sp. PCC 7002 with the APEX2 enzyme, an engineered ascorbate peroxidase. We determined the proteome of the thylakoid lumen, a region of the cell that has remained challenging to study with existing methods, using a translational fusion between APEX2 and PsbU, a lumenal subunit of photosystem II. Our results demonstrate the power of APEX2 as a tool to study the cell biology of intracellular features and processes, including photosystem II assembly in cyanobacteria, with enhanced spatiotemporal resolution.
Isomorphisms of graded path algebras

We prove that if two path algebras with homogeneous relations are isomorphic as algebras, then they are isomorphic as graded path algebras. This extends a result by Bell and Zhang in the connected case.
Learning Hamiltonian Monte Carlo in R

Hamiltonian Monte Carlo (HMC) is a powerful tool for Bayesian computation. In comparison with the traditional Metropolis–Hastings algorithm, HMC offers greater computational efficiency, especially ...