cssi/SciSciGPT-SciSciNet huggingface dataset:
A novel calibration framework for survival analysis when a binary covariate is measured at sparse time points

The goals in clinical and cohort studies often include evaluation of the association of a time-dependent binary treatment or exposure with a survival outcome. Recently, several impactful studies targeted the association between initiation of aspirin and survival following colorectal cancer (CRC) diagnosis. The value of this exposure is zero at baseline and may change its value to one at some time point. Estimating this association is complicated by having only intermittent measurements on aspirin-taking. Commonly used methods can lead to substantial bias. We present a class of calibration models for the distribution of the time of status change of the binary covariate. Estimates obtained from these models are then incorporated into the proportional hazard partial likelihood in a natural way. We develop non-parametric, semiparametric, and parametric calibration models, and derive asymptotic theory for the methods that we implement in the aspirin and CRC study. We further develop a risk-set calibration approach that is more useful in settings in which the association between the binary covariate and survival is strong.
Harnessing Smoothness to Accelerate Distributed Optimization

There has been a growing effort in studying the distributed optimization problem over a network. The objective is to optimize a global function formed by a sum of local functions, using only local computation and communication. The literature has developed consensus-based distributed (sub)gradient descent (DGD) methods and has shown that they have the same convergence rate $O(\frac{\log t}{\sqrt{t}})$ as the centralized (sub)gradient methods (CGD), when the function is convex but possibly nonsmooth. However, when the function is convex and smooth, under the framework of DGD, it is unclear how to harness the smoothness to obtain a faster convergence rate comparable to CGD's convergence rate. In this paper, we propose a distributed algorithm that, despite using the same amount of communication per iteration as DGD, can effectively harnesses the function smoothness and converge to the optimum with a rate of $O(\frac{1}{t})$ . If the objective function is further strongly convex, our algorithm has a linear convergence rate. Both rates match the convergence rate of CGD. The key step in our algorithm is a novel gradient estimation scheme that uses history information to achieve fast and accurate estimation of the average gradient. To motivate the necessity of history information, we also show that it is impossible for a class of distributed algorithms like DGD to achieve a linear convergence rate without using history information even if the objective function is strongly convex and smooth.
Ubiquitous Event Mining to Enhance Personal Health

Advances in user interfaces, pattern recognition, and ubiquitous computing continue to pave the way for better navigation towards our health goals. Quantitative methods which can guide us towards our personal health goals will help us optimize our daily life actions, and environmental exposures. Ubiquitous computing is essential for monitoring these factors and actuating timely interventions in all relevant circumstances. We need to combine the events recognized by different ubiquitous systems and derive actionable causal relationships from an event ledger. Understanding of user habits and health should be teleported between applications rather than these systems working in silos, allowing systems to find the optimal guidance medium for required interventions. We propose a method through which applications and devices can enhance the user experience by leveraging event relationships, leading the way to more relevant, useful, and, most importantly, pleasurable health guidance experience.
TOO MANY, TOO FEW, OR JUST RIGHT? THE PREDICTED NUMBER AND DISTRIBUTION OF MILKY WAY DWARF GALAXIES

We predict the spatial distribution and number of Milky Way dwarf galaxies to be discovered in the Dark Energy Survey (DES) and Large Synoptic Survey Telescope (LSST) surveys, by completeness correcting the observed Sloan Digital Sky Survey dwarf population. We apply most massive in the past, earliest forming, and earliest infall toy models to a set of dark matter-only simulated Milky Way/M31 halo pairs from the Exploring the Local Volume In Simulations project. Inclusive of all toy models and simulations, at 90% confidence we predict a total of 37-114 L ≳ 10{sup 3} L {sub ☉} dwarfs and 131-782 L ≲ 10{sup 3} L {sub ☉} dwarfs within 300 kpc. These numbers of L ≳ 10{sup 3} L {sub ☉} dwarfs are dramatically lower than previous predictions, owing primarily to our use of updated detection limits and the decreasing number of SDSS dwarfs discovered per sky area. For an effective r {sub limit} of 25.8 mag, we predict 3-13 L ≳ 10{sup 3} L {sub ☉} and 9-99 L ≲ 10{sup 3} L {sub ☉} dwarfs for DES, and 18-53 L ≳ 10{sup 3} L {sub ☉} and 53-307 L ≲ 10{sup 3} L {sub ☉} dwarfs for LSST. We alsomore » show that the observed spatial distribution of Milky Way dwarfs in the LSST-era will discriminate between the earliest infall and other simplified models for how dwarf galaxies populate dark matter subhalos.« less
A Flavorful Factoring of the Strong CP Problem

Motivated by the intimate connection between the strong CP problem and the flavor structure of the Standard Model, we present a flavor model that revives and extends the classic mu = 0 solution to the strong CP problem. QCD is embedded into a SU(3)1 × SU(3)2 × SU(3)3 gauge group, with each generation of quarks charged under the respective SU(3). The non-zero value of the up-quark Yukawa coupling (along with the strange quark and bottom-quark Yukawas) is generated by contributions from small instantons at a new scale M ≫ ΛQCD. The Higgsing of SU(3)3 → SU(3)c allows dimension-5 operators that generate the Standard Model flavor structure and can be completed in a simple renormalizable theory. The smallness of the third generation mixing angles can naturally emerge in this picture, and is connected to the smallness of threshold corrections to $$ \overline{\theta} $$ . Remarkably, $$ \overline{\theta} $$ is essentially fixed by the measured quark masses and mixings, and is estimated to be close to the current experimental bound and well within reach of the next generation of neutron and proton EDM experiments.
Large N matrices from a nonlocal spin system

Large N matrices underpin the best understood models of emergent spacetime. We suggest that large N matrices can themselves be emergent from simple quantum mechanical spin models with finite dimensional Hilbert spaces. We exhibit the emergence of large N matrices in a nonlocal statistical physics model of order N2 Ising spins. The spin partition function is shown to admit a large N saddle described by a matrix integral, which we solve. The matrix saddle is dominant at high temperatures, metastable at intermediate temperatures and ceases to exist below a critical order one temperature. The matrix saddle is disordered in a sense we make precise and competes with ordered low energy states. We verify our analytic results by Monte Carlo simulation of the spin system.
Status and Future Perspectives for Lattice Gauge Theory Calculations to the Exascale and Beyond

In this and a set of companion white papers, the USQCD Collaboration lays out a program of science and computing for lattice gauge theory. These white papers describe how calculation using Lattice QCD (and other gauge theories) can aid the interpretation of ongoing and upcoming experiments in particle and nuclear physics, as well as inspire new ones.
Fast spin dynamics algorithms for classical spin systems

We have proposed new algorithms for the numerical integration of the equations of motion for classical spin systems. In close analogy to symplectic integrators for Hamiltonian equations of motion used in Molecular Dynamics, these algorithms are based on the Suzuki-Trotter decomposition of exponential operators and unlike more commonly used algorithms exactly conserve spin length and, in special cases, energy. Using higher order decompositions we investigate integration schemes of up to fourth order and compare them to a well-established fourth order predictor-corrector method. We demonstrate that these methods can be used with much larger time steps than the predictor-corrector method and thus may lead to a substantial speedup of computer simulations of the dynamical behavior of magnetic materials.
Model-based iterative reconstruction for flat-panel cone-beam CT with focal spot blur, detector blur, and correlated noise.

While model-based reconstruction methods have been successfully applied to flat-panel cone-beam CT (FP-CBCT) systems, typical implementations ignore both spatial correlations in the projection data as well as system blurs due to the detector and focal spot in the x-ray source. In this work, we develop a forward model for flat-panel-based systems that includes blur and noise correlation associated with finite focal spot size and an indirect detector (e.g. scintillator). This forward model is used to develop a staged reconstruction framework where projection data are deconvolved and log-transformed, followed by a generalized least-squares reconstruction that utilizes a non-diagonal statistical weighting to account for the correlation that arises from the acquisition and data processing chain. We investigate the performance of this novel reconstruction approach in both simulated data and in CBCT test-bench data. In comparison to traditional filtered backprojection and model-based methods that ignore noise correlation, the proposed approach yields a superior noise-resolution tradeoff. For example, for a system with 0.34 mm FWHM scintillator blur and 0.70 FWHM focal spot blur, using the correlated noise model instead of an uncorrelated noise model increased resolution by 42% (with variance matched at 6.9 × 10(-8) mm(-2)). While this advantage holds across a wide range of systems with differing blur characteristics, the improvements are greatest for systems where source blur is larger than detector blur.
D-branes as unstable lumps in bosonic open string field theory

We construct Dp-branes in bosonic string theory as unstable lumps in a truncated string field theory of open strings on a D25-brane. We find that the lowest level truncation gives good quantitative agreement with the predicted D-brane tension and low-lying spectrum of the D-brane for sufficiently large p and study the effect of the next level corrections for p = 24. We show that a U(1) gauge field zero mode on the D-brane arises through a mechanism reminiscent of the Randall-Sundrum mechanism for gravity.
Reconciling the Diversity and Uniformity of Galactic Rotation Curves with Self-Interacting Dark Matter

Author(s): Ren, T; Kwa, A; Kaplinghat, M; Yu, HB | Abstract: Galactic rotation curves exhibit diverse behavior in the inner regions while obeying an organizing principle; i.e., they can be approximately described by a radial acceleration relation or the modified Newtonian dynamics phenomenology. We analyze the rotation curve data from the SPARC sample and explicitly demonstrate that both the diversity and uniformity are naturally reproduced in a hierarchical structure formation model with the addition of dark matter self-interactions. The required concentrations of the dark matter halos are fully consistent with the concentration-mass relation predicted by the Planck cosmological model. The inferred stellar mass-to-light (3.6 μm) ratios scatter around 0.5 Mâ™/Lâ™, as expected from population synthesis models, leading to a tight radial acceleration relation and a baryonic Tully-Fisher relation. The inferred stellar-halo mass relation is consistent with the expectations from abundance matching. These results provide compelling arguments in favor of the idea that the inner halos of galaxies are thermalized due to dark matter self-interactions.
UNCONVENTIONAL BOSE–EINSTEIN CONDENSATIONS BEYOND THE "NO-NODE" THEOREM

Feynman's "no-node" theorem states that the conventional many-body ground state wavefunctions of bosons in the coordinate representation are positive definite. This implies that time-reversal symmetry cannot be spontaneously broken. In this article, we review our progress in studying a class of new states of unconventional Bose–Einstein condensations beyond this paradigm. These states can either be the long-lived metastable states of ultracold bosons in high orbital bands in optical lattices as a result of the "orbital Hund's rule" interaction, or the ground states of spinful bosons with spin-orbit coupling linearly dependent on momentum. In both cases, Feynman's argument does not apply. The resultant many-body wavefunctions are complex-valued and thus break time-reversal symmetry spontaneously. Exotic phenomena in these states include the Bose–Einstein condensation at nonzero momentum, the ordering of orbital angular momentum moments, the half-quantum vortex, and the spin texture of skyrmions.
Zeta functions of the Dirac operator on quantum graphs

We construct spectral zeta functions for the Dirac operator on metric graphs. We start with the case of a rose graph, a graph with a single vertex where every edge is a loop. The technique is then developed to cover any finite graph with general energy independent matching conditions at the vertices. The regularized spectral determinant of the Dirac operator is also obtained as the derivative of the zeta function at a special value. In each case the zeta function is formulated using a contour integral method, which extends results obtained for Laplace and Schrodinger operators on graphs.
Tilting Mutation of Weakly Symmetric Algebras and Stable Equivalence

We consider tilting mutations of a weakly symmetric algebra at a subset of simple modules, as recently introduced by T. Aihara. These mutations are defined as the endomorphism rings of certain tilting complexes of length 1. Starting from a weakly symmetric algebra A, presented by a quiver with relations, we give a detailed description of the quiver and relations of the algebra obtained by mutating at a single loopless vertex of the quiver of A. In this form the mutation procedure appears similar to, although significantly more complicated than, the mutation procedure of Derksen, Weyman and Zelevinsky for quivers with potentials. By definition, weakly symmetric algebras connected by a sequence of tilting mutations are derived equivalent, and hence stably equivalent. The second aim of this article is to study these stable equivalences via a result of Okuyama describing the images of the simple modules. As an application we answer a question of Asashiba on the derived Picard groups of a class of self-injective algebras of finite representation type. We conclude by introducing a mutation procedure for maximal systems of orthogonal bricks in a triangulated category, which is motivated by the effect that a tilting mutation has on the set of simple modules in the stable category.
Test of the unitary coupled-cluster variational quantum eigensolver for a simple strongly correlated condensed-matter system

The variational quantum eigensolver has been proposed as a low-depth quantum circuit that can be employed to examine strongly correlated systems on today’s noisy intermediate-scale quantum computer...
A new duality between $ \mathcal{N} $ = 8 superconformal field theories in three dimensions

We propose a new duality between two 3d $$ \mathcal{N} $$ = 8 superconformal Chern-Simons-matter theories: the U(3)1 × U(3)−1 ABJM theory and a theory consisting of the product between the (SU(2)3 × SU(2)− 3)/ℤ2 BLG theory and a free $$ \mathcal{N} $$ = 8 theory of eight real scalars and eight Majorana fermions. As evidence supporting this duality, we show that the moduli spaces, superconformal indices, S3 partition functions, and certain OPE coefficients of BPS operators in the two theories agree.
Kerr-Newman black holes with string corrections

We study $\mathcal{N}=2$ supergravity with higher-derivative corrections that preserve the $\mathcal{N}=2$ supersymmetry and show that Kerr-Newman black holes are solutions to these theories. Modifications of the black hole entropy due to the higher derivatives are universal and apply even in the BPS and Schwarzschild limits. Our solutions and their entropy are greatly simplified by supersymmetry of the theory even though the black holes generally do not preserve any of the supersymmetry.
The Exoplanet Census: A General Method Applied to Kepler

We develop a general method to fit the planetary distribution function (PLDF) to exoplanet survey data. This maximum likelihood method accommodates more than one planet per star and any number of planet or target star properties. Application to Kepler data relies on estimates of the efficiency of discovering transits around Solar type stars by Howard et al. (2011). These estimates are shown to agree with theoretical predictions for an ideal transit survey. Using announced Kepler planet candidates, we fit the PLDF as a joint powerlaw in planet radius, down to 0.5R⊕, and orbital period, up to 50 days. The estimated number of planets per star in this sample is ∼ 0.7 —1.4, where the broad range covers systematic uncertainties in the detection efficiency. To analyze trends in the PLDF we consider four planet samples, divided between shorter and longer periods at 7 days and between large and small radii at 3 R⊕. At longer periods, the size distribution of the small planets, with index α ≃ −1.2 ± 0.2 steepens to α ≃ −2.0 ± 0.2 for the larger planet sample. For shorter periods, the opposite is seen: smaller planets follow a steep powerlaw, α ≃ −1.9 ± 0.2 that is much shallower, α ≃ −0.7 ± 0.2 at large radii. The observed deficit of intermediate-sized planets at the shortest periods may arise from the evaporation and sublimation of Neptune and Saturn-like planets. If the trend and explanation hold, it would be spectacular observational confirmation of the core accretion and migration hypotheses, and allow refinement of these theories. Subject headings: Methods: statistical — Planetary Systems — Planets and satellites: detection — Planets and satellites: dynamical evolution and stability — Planets and satellites: formation — Stars: statistics
What do models learn from question answering datasets

While models have reached superhuman performance on popular question answering (QA) datasets such as SQuAD, they have yet to outperform humans on the task of question answering itself. In this paper, we investigate if models are learning reading comprehension from QA datasets by evaluating BERT-based models across five datasets. We evaluate models on their generalizability to out-of-domain examples, responses to missing or incorrect data, and ability to handle question variations. We find that no single dataset is robust to all of our experiments and identify shortcomings in both datasets and evaluation methods. Following our analysis, we make recommendations for building future QA datasets that better evaluate the task of question answering through reading comprehension. We also release code to convert QA datasets to a shared format for easier experimentation at https://github.com/amazon-research/qa-dataset-converter
Expanding the Compute-and-Forward Framework: Unequal Powers, Signal Levels, and Multiple Linear Combinations

The compute-and-forward framework permits each receiver in a Gaussian network to directly decode a linear combination of the transmitted messages. The resulting linear combinations can then be employed as an end-to-end communication strategy for relaying, interference alignment, and other applications. Recent efforts have demonstrated the advantages of employing unequal powers at the transmitters and decoding more than one linear combination at each receiver. However, neither of these techniques fit naturally within the original formulation of compute-and-forward. This paper proposes an expanded compute-and-forward framework that incorporates both of these possibilities and permits an intuitive interpretation in terms of signal levels. Within this framework, recent achievability and optimality results are unified and generalized.
Gaze-in-wild: A dataset for studying eye and head coordination in everyday activities.

The study of gaze behavior has primarily been constrained to controlled environments in which the head is fixed. Consequently, little effort has been invested in the development of algorithms for the categorization of gaze events (e.g. fixations, pursuits, saccade, gaze shifts) while the head is free, and thus contributes to the velocity signals upon which classification algorithms typically operate. Our approach was to collect a novel, naturalistic, and multimodal dataset of eye + head movements when subjects performed everyday tasks while wearing a mobile eye tracker equipped with an inertial measurement unit and a 3D stereo camera. This Gaze-in-the-Wild dataset (GW) includes eye + head rotational velocities (deg/s), infrared eye images and scene imagery (RGB + D). A portion was labelled by coders into gaze motion events with a mutual agreement of 0.74 sample based Cohen’s κ. This labelled data was used to train and evaluate two machine learning algorithms, Random Forest and a Recurrent Neural Network model, for gaze event classification. Assessment involved the application of established and novel event based performance metrics. Classifiers achieve ~87% human performance in detecting fixations and saccades but fall short (50%) on detecting pursuit movements. Moreover, pursuit classification is far worse in the absence of head movement information. A subsequent analysis of feature significance in our best performing model revealed that classification can be done using only the magnitudes of eye and head movements, potentially removing the need for calibration between the head and eye tracking systems. The GW dataset, trained classifiers and evaluation metrics will be made publicly available with the intention of facilitating growth in the emerging area of head-free gaze event classification.
The structure of the consecutive pattern poset

The consecutive pattern poset is the infinite partially ordered set of all permutations where � � � ifhas a subsequence of adjacent entries in the same relative order as the entries of �. We study the structure of the intervals in this poset from topological, poset-theoretic, and enumerative perspectives. In particular, we prove that all intervals are rank-unimodal and strongly Sperner, and we characterize disconnected and shellable intervals. We also show that most intervals are not shellable and have Mobius function equal to zero.
Characterizing Online Vandalism: A Rational Choice Perspective

What factors influence the decision to vandalize? Although the harm is clear, the benefit to the vandal is less clear. In many cases, the thing being damaged may itself be something the vandal uses or enjoys. Vandalism holds communicative value: perhaps to the vandal themselves, to some audience at whom the vandalism is aimed, and to the general public. Viewing vandals as rational community participants despite their antinormative behavior offers the possibility of engaging with or countering their choices in novel ways. Rational choice theory (RCT) as applied in value expectancy theory (VET) offers a strategy for characterizing behaviors in a framework of rational choices, and begins with the supposition that subject to some weighting of personal preferences and constraints, individuals maximize their own utility by committing acts of vandalism. This study applies the framework of RCT and VET to gain insight into vandals’ preferences and constraints. Using a mixed-methods analysis of Wikipedia, I combine social computing and criminological perspectives on vandalism to propose an ontology of vandalism for online content communities. I use this ontology to categorize 141 instances of vandalism and find that the character of vandalistic acts varies by vandals’ relative identifiability, policy history with Wikipedia, and the effort required to vandalize.
Ohmic Heating of Asteroids around Magnetic Stars

We consider the impact of electromagnetic induction and Ohmic heating on a conducting planetary object that orbits a magnetic star. Power dissipated as heat saps orbital energy. If this heat is trapped by an insulating crust or mantle, interior temperatures increase substantially. We provide a quantitative description of this behavior and discuss the astrophysical scenarios in which it might occur. Magnetic fields around some main-sequence stars and white dwarfs are strong enough to cause the decay of close-in orbits of asteroids and dwarf planets, drawing them through the Roche limit on Myr time scales. We confirm that Ohmic heating around neutron stars is driven by the rotation of the stellar magnetic dipole, not orbital dynamics. In any case, heating can raise interior temperatures of asteroids or dwarf planets on close-in orbits to well above liquidus. Hot material escaping to the surface may lead to volcanic ejections that can obscure the host star (as in the light curve of KIC 8462852) and pollute its atmosphere (as observed with metal-rich white dwarfs). We speculate that mixing of a volatile-rich mantle or crust with material from an induction-heated core may lead to an explosion that could destroy the asteroid prior to tidal break-up.
NOISE AND BELL'S INEQUALITY

To many, the idea of the EPR paradox and the possibility of local hidden variables were dismissed by the Bell inequality, although the central points of this argument have been around since the advent of quantum mechanics. Yet, there remains considerable evidence that this inequality can be violated even by classical systems. The question really is whether or not strongly correlated classical fields will also violate Bell's inequality. In a previous paper, it was shown that this was the case. Here, we ask the question as to just how much correlation in the classical waves is required to violate the inequality.
TAUT FOLIATIONS IN KNOT COMPLEMENTS

A transversely orientable codimension-one foliation F of a 3-manifold M is called taut [Gabai 1991] if every leaf of F intersects some closed transverse curve. The existence of a taut foliation in a 3-manifold M provides much interesting topological information about both M and objects embedded in M. If a closed 3-manifold M contains a taut foliation, either M is finitely covered by S 2 S 1 or M is irreducible [Novikov 1965; Reeb 1952; Rosenberg 1968]. If a closed 3-manifold M contains a taut foliation, then its fundamental group is infinite [Haefliger 1962; Novikov 1965; Gabai and Oertel 1989] and acts nontrivially on interesting 1-dimensional objects (see, for example, [Thurston 1998; Calegari and Dunfield 2003; Palmeira 1978; Roberts et al. 2003]), and its universal cover is R 3 [Palmeira 1978]. Taut foliations can be perturbed to interesting contact structures [Eliashberg and Thurston 1998; Kazez and Roberts 2014] and hence can be used to obtain Heegaard‐Floer information [Ozsvath and Szabo 2004b]. In this paper we seek to add to the understanding of the existence of taut foliations by describing a new construction of taut foliations. Let k be a nontrivial knot in S 3 . In his proof of the Property R conjecture, Gabai [1987b] showed that the knot exterior MD S 3 n int N.k/ has a taut foliation whose restriction to the torus@ M is a collection of circles of slope 0. Thus a zero frame Dehn surgery on k yields a closed 3-manifold that admits a taut foliation obtained by adding disks along the boundary circles of the taut foliation of M. In this paper, we extend Gabai’s theorem from zero frame surgery to any slope in an interval that contains 0. Although we restrict attention to knots in S 3 , the approach described in this paper applies more generally to manifolds.M;@ M/ with boundary a nonempty
Constraining the inflationary equation of state

We explore possible constraints on the inflationary equation state: p = wρ. While w must be close to -1 for those modes that contribute to the observed power spectrum, for those modes currently out of experimental reach, the constraints on w are much weaker, with only w < −1/3 as an a priori requirement. We find, however, that limits on the reheat temperature and the inflationary energy scale constrain w further, though there is still ample parameter space for a vastly different (accelerating) equation of state between the end of quasi-de Sitter inflation and the beginning of the radiation-dominated era. In the event that such an epoch of acceleration could be observed, we review the consequences for the primordial power spectrum.
A Short Proof of Stability of Topological Order under Local Perturbations

Recently, the stability of certain topological phases of matter under weak perturbations was proven. Here, we present a short, alternate proof of the same result. We consider models of topological quantum order for which the unperturbed Hamiltonian H 0 can be written as a sum of local pairwise commuting projectors on a D-dimensional lattice. We consider a perturbed Hamiltonian H = H 0 + V involving a generic perturbation V that can be written as a sum of short-range bounded-norm interactions. We prove that if the strength of V is below a constant threshold value then H has well-defined spectral bands originating from the low-lying eigenvalues of H 0. These bands are separated from the rest of the spectrum and from each other by a constant gap. The width of the band originating from the smallest eigenvalue of H 0 decays faster than any power of the lattice size.
Sub-Milliarcsecond Precision of Pulsar Motions: Using In-Beam Calibrators with the VLBA

We present Very Long Baseline Array (VLBA) phase-referenced measurements of the parallax and proper motion of two pulsars, B0919+06 and B1857-26. Sub-milliarcsecond positional accuracy was obtained by simultaneously observing a weak calibrator source within the 40' field of view of the VLBA at 1.5 GHz. We discuss the merits of using weak close calibrator sources for Very Long Baseline Interferometry (VLBI) observations at low frequencies, and we outline a method of observation and data reduction for these type of measurements. For the pulsar B0919+06 we measure a parallax of 0.31 ± 0.14 mas. The accuracy of the proper motions is ≈0.5 mas yr-1, an order of magnitude improvement over most previous determinations.
Handling leakage with subsystem codes

Leakage is a particularly damaging error that occurs when a qubit state falls out of its two-level computational subspace. Compared to independent depolarizing noise, leaked qubits may produce many more configurations of harmful correlated errors during error-correction. In this work, we investigate different local codes in the low-error regime of a leakage gate error model. When restricting to bare-ancilla extraction, we observe that subsystem codes are good candidates for handling leakage, as their locality can limit damaging correlated errors. As a case study, we compare subspace surface codes to the subsystem surface codes introduced by Bravyi et al. In contrast to depolarizing noise, subsystem surface codes outperform same-distance subspace surface codes below error rates as high as ≤ 7.5 x 10alt;supagt;-4alt;/supagt; while offering better per-qubit distance protection. Furthermore, we show that at low to intermediate distances, Bacon-Shor codes offer better per-qubit error protection against leakage in an ion-trap motivated error model below error rates as high as ≤ 1.2 x 10alt;supagt;-3alt;/supagt;. For restricted leakage models, this advantage can be extended to higher distances by relaxing to unverified two-qubit cat state extraction in the surface code. These results highlight an intrinsic benefit of subsystem code locality to error-corrective performance.
Contracting the Facebook API

In recent years, there has been an explosive growth in the popularity of online social networks such as Facebook. In a new twist, third party developers are now able to create their own web applications which plug into Facebook and work with Facebook’s “social” data, enabling the entire Facebook user base of more than 400 million active users to use such applications. These client applications can contain subtle errors that can be hard to debug if they misuse the Facebook API. In this paper we present an experience report on applying Microsoft’s new code contract system for the .NET framework to the Facebook API. We wrote contracts for several classes in the Facebook API wrapper which allows Microsoft .NET developers to implement Facebook applications. We evaluated the usefulness of these contracts during implementation of a new Facebook application. Our experience indicates that having code contracts provides a better and quicker software development experience.
Lower bounds on the mix norm of passive scalars advected by incompressible enstrophy-constrained flows

Consider a diffusion-free passive scalar θ being mixed by an incompressible flow u on the torus . Our aim is to study how well this scalar can be mixed under an enstrophy constraint on the advecting velocity field. Our main result shows that the mix-norm is bounded below by an exponential function of time. The exponential decay rate we obtain is not universal and depends on the size of the support of the initial data. We also perform numerical simulations and confirm that the numerically observed decay rate scales similarly to the rigorous lower bound, at least for a significant initial period of time. The main idea behind our proof is to use the recent work of Crippa and De Lellis (2008 J. Reine Angew. Math. 616 15–46) making progress towards the resolution of Bressan's rearrangement cost conjecture.
Pareto-Optimal Data Compression for Binary Classification Tasks

The goal of lossy data compression is to reduce the storage cost of a data set X while retaining as much information as possible about something (Y) that you care about. For example, what aspects of an image X contain the most information about whether it depicts a cat? Mathematically, this corresponds to finding a mapping X → Z ≡ f ( X ) that maximizes the mutual information I ( Z , Y ) while the entropy H ( Z ) is kept below some fixed threshold. We present a new method for mapping out the Pareto frontier for classification tasks, reflecting the tradeoff between retained entropy and class information. We first show how a random variable X (an image, say) drawn from a class Y ∈ { 1 , … , n } can be distilled into a vector W = f ( X ) ∈ R n - 1 losslessly, so that I ( W , Y ) = I ( X , Y ) ; for example, for a binary classification task of cats and dogs, each image X is mapped into a single real number W retaining all information that helps distinguish cats from dogs. For the n = 2 case of binary classification, we then show how W can be further compressed into a discrete variable Z = g β ( W ) ∈ { 1 , … , m β } by binning W into m β bins, in such a way that varying the parameter β sweeps out the full Pareto frontier, solving a generalization of the discrete information bottleneck (DIB) problem. We argue that the most interesting points on this frontier are "corners" maximizing I ( Z , Y ) for a fixed number of bins m = 2 , 3 , … which can conveniently be found without multiobjective optimization. We apply this method to the CIFAR-10, MNIST and Fashion-MNIST datasets, illustrating how it can be interpreted as an information-theoretically optimal image clustering algorithm. We find that these Pareto frontiers are not concave, and that recently reported DIB phase transitions correspond to transitions between these corners, changing the number of clusters.
DISCOVERY OF RUBIDIUM, CADMIUM, AND GERMANIUM EMISSION LINES IN THE NEAR-INFRARED SPECTRA OF PLANETARY NEBULAE

We identify [Rb iv] 1.5973 and [Cd iv] 1.7204 μm emission lines in high-resolution (R = 40,000) near-infrared spectra of the planetary nebulae (PNe) NGC 7027 and IC 5117, obtained with the Immersion GRating INfrared Spectrometer (IGRINS) on the 2.7 m telescope at McDonald Observatory. We also identify [Ge vi] 2.1930 μm in NGC 7027. Alternate identifications for these features are ruled out based on the absence of other multiplet members and/or transitions with the same upper levels. Ge, Rb, and Cd can be enriched in PNe by s-process nucleosynthesis during the asymptotic giant branch stage of evolution. To determine ionic abundances, we calculate [Rb iv] collision strengths and use approximations for those of [Cd iv] and [Ge vi]. Our identification of [Rb iv] 1.5973 μm is supported by the agreement between Rb3+/H+ abundances found from this line and the 5759.55 A feature in NGC 7027. Elemental Rb, Cd, and Ge abundances are derived with ionization corrections based on similarities in ionization potential ranges between the detected ions and O and Ne ionization states. Our analysis indicates abundances 2–4 times solar for Rb and Cd in both nebulae. Ge is subsolar in NGC 7027, but its abundance is uncertain due to the large and uncertain ionization correction. The general consistency of the measured relative s-process enrichments with predictions from models appropriate for these PNe (2.0–2.5 M⊙, [Fe/H] = −0.37) demonstrates the potential of using PN compositions to test s-process nucleosynthesis models.
Three-dimensional Simulations of Spherical Accretion Flows with Small-Scale Magnetic Fields

Spherical (nonrotating) accretion flows with small-scale magnetic fields have been investigated using three-dimensional, time-dependent MHD simulations. These simulations have been designed to model high-resolution (quasi-) steady accretion flows in a wedge computational domain that represents a small fraction of the full spherical domain. Subsonic and supersonic (superfast-magnetosonic) accretion flows have been considered. Two accretion regimes have been studied: conservative, or radiatively inefficient; and nonconservative, in which the heat released in magnetic reconnections is completely lost. The flows in both regimes are turbulent. They show flattened radial density profiles and reduction of the accretion velocities and mass accretion rates in comparison with hydrodynamic Bondi flows. In the conservative regime, the turbulence is more intensive and supported mostly by thermal convection. In the nonconservative regime, the turbulence is less intensive and supported by magnetic buoyancy and various magnetic interactions. We have concluded that steady, supersonic spherical accretion cannot develop in the presence of small-scale magnetic fields.
Splashback Shells of Cold Dark Matter Halos

The density field in the outskirts of dark matter halos is discontinuous as a result of a caustic formed by matter at its first apocenter after infall. In this paper, we present an algorithm to identify the "splashback shell" formed by these apocenters in individual simulated halos using only a single snapshot of the density field. We implement this algorithm in the code Shellfish (SHELL Finding In Spheroidal Halos) and demonstrate that the code identifies splashback shells correctly and measures their properties with an accuracy of for halos with more than 50,000 particles and mass accretion rates of . Using Shellfish, we present the first estimates for several basic properties of individual splashback shells, such as radius, , mass, and overdensity, and provide fits to the distribution of these quantities as functions of , , and We confirm previous findings that decreases with increasing , but we show that, independent of accretion rate, it also decreases with increasing . We also study the 3D structures of these shells and find that they generally have non-ellipsoidal oval shapes. We find that splashback radii estimated by Shellfish are 20%–30% larger than those estimated in previous studies from stacked density profiles at high accretion rates. We demonstrate that the latter are biased low owing to the contribution of high-mass subhalos to these profiles, and we show that using the median instead of mean density in each radial bin mitigates the effect of substructure on density profiles and removes the bias.
Second order hydrodynamic coefficients from 3-point stress tensor correlators via AdS/CFT

We study second order relativistic viscous hydrodynamics in 4-dimensional conformal field theories. We derive Kubo-type relations for second order hydrodynamic coefficients in terms of 3-point stress tensor retarded correlators. For $ \mathcal{N} = 4 $ super Yang-Mills theory at strong coupling and at finite temperature we compute these stress tensor 3-point correlators, using AdS/CFT, by evaluating real-time cubic Witten diagrams in the AdS-Schwarzschild background. The small momentum expansion of the 3-point correlators in terms of first and second order hydrodynamic coefficients is matched with the AdS result. We arrive at the same expressions for the hydrodynamic coefficients which multiply terms quadratic in the shear and vorticity tensors in the hydrodynamic expansion of the stress tensor as did Bhattacharyya, Hubeny, Minwalla and Rangamani [1]. Our method extends the results of Baier et al [2], and allows for a unified treatment of hydrodynamic coefficients, which are extracted from 2-, and now, 3-point retarded stress tensor correlators in the AdS-Schwarzschild background.
Learning Spectral Templates for Photometric Redshift Estimation from Broadband Photometry

Estimating redshifts from broadband photometry is often limited by how accurately we can map the colors of galaxies to an underlying spectral template. Current techniques utilize spectrophotometric samples of galaxies or spectra derived from spectral synthesis models. Both of these approaches have their limitations, either the sample sizes are small and often not representative of the diversity of galaxy colors or the model colors can be biased (often as a function of wavelength) which introduces systematics in the derived redshifts. In this paper we learn the underlying spectral energy distributions from an ensemble of $\sim$100K galaxies with measured redshifts and colors. We show that we are able to reconstruct emission and absorption lines at a significantly higher resolution than the broadband filters used to measure the photometry for a sample of 20 spectral templates. We find that our training algorithm reduces the fraction of outliers in the derived photometric redshifts by up to 28%, bias up to 91%, and scatter up to 25%, when compared to estimates using a standard set of spectral templates. We discuss the current limitations of this approach and its applicability for recovering the underlying properties of galaxies. Our derived templates and the code used to produce these results are publicly available in a dedicated Github repository: this https URL.
Fracton phases of matter

Fractons are a new type of quasiparticle which are immobile in isolation, but can often move by forming bound states. Fractons are found in a variety of physical settings, such as spin liquids and elasticity theory, and exhibit unusual phenomenology, such as gravitational physics and localization. The past several years have seen a surge of interest in these exotic particles, which have come to the forefront of modern condensed matter theory. In this review, we provide a broad treatment of fractons, ranging from pedagogical introductory material to discussions of recent advances in the field. We begin by demonstrating how the fracton phenomenon naturally arises as a consequence of higher moment conservation laws, often accompanied by the emergence of tensor gauge theories. We then provide a survey of fracton phases in spin models, along with the various tools used to characterize them, such as the foliation framework. We discuss in detail the manifestation of fracton physics in elasticity theory, as well as the connections of fractons with localization and gravitation. Finally, we provide an overview of some recently proposed platforms for fracton physics, such as Majorana islands and hole-doped antiferromagnets. We conclude with some open questions and an outlook on the field.
Characterization of LSST CCDs using realistic images, before first light

The 3.2 gigapixel LSST camera, an array of 189 thick fully-depleted CCDs, will repeatedly image the southern sky and accomplish a wide variety of science goals. However, its trove of tens of billions of object images implies stringent requirements on systematic biases imprinted during shift-and-stare CCD observation. In order to correct for these biases which, without correction, violate requirements on weak lensing precision, we investigate CCD systematics using both simulations of charge transport as well as with a unique bench-top optical system matched to the LSST’s fast f/1.2 beam. By illuminating single CCDs with realistic scenes of stars and galaxies and then analyzing these images with the LSST data management pipelines, we can characterize the survey’s imaging performance well before the camera’s first light. We present measurements of several CCD systematics under varying conditions in the laboratory, including the brightness-dependent broadening of star and galaxy images, charge transport anomalies in the silicon bulk as well as the edges, and serial deferred charge. Alongside these measurements, we also present the development and testing of physics-based models which inform corrections or mitigation strategies for these systematics. Optimization of the CCD survey operation under a variety of realistic observational conditions, including systematic effects from the optics, clocking, sky brightness, and image analysis, will be critical to achieve the LSST’s goals of precision astronomy and cosmology.
Influence of Cohesive Energy and Chain Stiffness on Polymer Glass Formation

The generalized entropy theory is applied to assess the joint influence of the microscopic cohesive energy and chain stiffness on glass formation in polymer melts using a minimal model containing a single bending energy and a single (monomer averaged) nearest neighbor van der Waals energy. The analysis focuses on the combined impact of the microscopic cohesive energy and chain stiffness on the magnitudes of the isobaric fragility parameter mP and the glass transition temperature Tg. The computations imply that polymers with rigid structures and weak nearest neighbor interactions are the most fragile, while Tg becomes larger when the chains are stiffer and/or nearest neighbor interactions are stronger. Two simple fitting formulas summarize the computations describing the dependence of mP and Tg on the microscopic cohesive and bending energies. The consideration of the combined influence of the microscopic cohesive and bending energies leads to the identification of some important design concepts, such as i...
Romans supergravity from five-dimensional holograms

We study five-dimensional superconformal field theories and their holographic dual, matter-coupled Romans supergravity. On the one hand, some recently derived formulae allow us to extract the central charges from deformations of the supersymmetric five-sphere partition function, whose large N expansion can be computed using matrix model techniques. On the other hand, the conformal and flavor central charges can be extracted from the six-dimensional supergravity action, by carefully analyzing its embedding into type I’ string theory. The results match on the two sides of the holographic duality. Our results also provide analytic evidence for the symmetry enhancement in five-dimensional superconformal field theories.
The LS category of the product of lens spaces

It is known that degree-one maps f W M !N between manifolds tend to have domain more complex than their image. The Lusternik–Schnirelmann category is a numerical invariant that measures the complexity of a space. Thus, Rudyak’s conjecture that cat M cat N for a degree-one map f W M !N is quite natural. Rudyak (see also the book by Cornea, Lupton, Opera and Tanre [7, page 65]) obtained some partial results supporting the conjecture. In particular, he proved the following: