cssi/SciSciGPT-SciSciNet huggingface dataset:
On the complexity of constructing pseudorandom functions (especially when they don't exist).

We study the complexity of black-box constructions of pseudorandom functions (PRF) from one-way functions (OWF) that are secure against non-uniform adversaries. We show that if OWF do not exist, then given as an oracle any (inefficient) hard-toinvert function, one can compute a PRF in polynomial time with only k(n) oracle queries, for any k(n) = ω(1) (e.g. k(n) = log∗ n). Combining this with the fact that OWF imply PRF, we show that unconditionally there exists a (pathological) construction of PRF from OWF making at most k(n) queries. This result shows a limitation of a certain class of techniques for proving efficiency lower bounds on the construction of PRF from OWF. Our result builds on the work of Reingold, Trevisan, and Vadhan (TCC ’04), who show that when OWF do not exist there is a pseudorandom generator (PRG) construction that makes only one oracle query to the hard-to-invert function. Our proof combines theirs with the Nisan-Wigderson generator (JCSS ’94), and with a recent technique by Berman and Haitner (TCC ’12). Working in the same context (i.e. when OWF do not exist), we also construct a poly-time PRG with arbitrary polynomial stretch that makes non-adaptive queries to an (inefficient) one-bit-stretch oracle PRG. This contrasts with the well-known adaptive stretch-increasing construction due to Goldreich and Micali. Both above constructions simply apply an affine function (parity or its complement) to the query answers. We complement this by showing that if the post-processing is restricted to only taking projections then non-adaptive constructions of PRF, or even linear-stretch PRG, can be ruled out. Both authors were supported by by NSF grant CCF-0845003. UCLA, enmiles@cs.ucla.edu. Research performed while a student at Northeastern University. Northeastern University, viola@ccs.neu.edu
Sunday Sounds: Preserving the Radio Ministry of Brooklyn’s Bethany Baptist Church

This article discusses the importance of preserving radio broadcasts from traditionally under-documented groups, in this case the Sunday sermons from an African American Baptist church in Brooklyn ...
A Smooth Robustness Measure of Signal Temporal Logic for Symbolic Control

Recent years have seen an increasing use of Signal Temporal Logic (STL) as a formal specification language for symbolic control, due to its expressiveness and closeness to natural language. Furthermore, STL specifications can be encoded as cost functions using STL's robust semantics, transforming the synthesis problem into an optimization problem. Unfortunately, these cost functions are non-smooth and non-convex, and exact solutions using mixed-integer programming do not scale well. Recent work has focused on using smooth approximations of robustness, which enable faster gradient-based methods to find local maxima, at the expense of soundness and/or completeness. We propose a novel robustness approximation that is smooth everywhere, sound, and asymptotically complete. Our approach combines the benefits of existing approximations, while enabling an explicit tradeoff between conservativeness and completeness.
Pulsed RF schemes for tearing mode stabilization

The RF stabilization of tearing modes with current condensation has the potential to increase stabilization efficiency and loosen power localization requirements. Such benefits stem from the cooperative feedback between the RF deposition and the resulting island temperature perturbation governed by diffusion. A self-consistent treatment of the damping of an rf ray as it traverses the island shows that low damping scenarios can require unfavorably high powers to overcome initial power leakage and effectively capitalize on the nonlinear effect. In this work, it is demonstrated that for such regimes, modulated stabilization schemes can achieve significant improvements in heating and current drive contributions to stabilization for the same average power as a continuous wave scheme. The impact of modulation frequency and duty cycle on the performance is explored, the results of which suggest modulation strategies in which the pulsing periods are kept on the order of a diffusive time.
Tunable nanophotonics enabled by chalcogenide phase-change materials

Nanophotonics has garnered intensive attention due to its unique capabilities in molding the flow of light in the subwavelength regime. Metasurfaces (MSs) and photonic integrated circuits (PICs) enable the realization of mass-producible, cost-effective, and highly efficient flat optical components for imaging, sensing, and communications. In order to enable nanophotonics with multi-purpose functionalities, chalcogenide phase-change materials (PCMs) have been introduced as a promising platform for tunable and reconfigurable nanophotonic frameworks. Integration of non-volatile chalcogenide PCMs with unique properties such as drastic optical contrasts, fast switching speeds, and long-term stability grants substantial reconfiguration to the more conventional static nanophotonic platforms. In this review, we discuss state-of-the-art developments as well as emerging trends in tunable MSs and PICs using chalcogenide PCMs. We outline the unique material properties, structural transformation, electro-optic, and thermo-optic effects of well-established classes of chalcogenide PCMs. The emerging deep learning-based approaches for the optimization of reconfigurable MSs and the analysis of light-matter interactions are also discussed. The review is concluded by discussing existing challenges in the realization of adjustable nanophotonics and a perspective on the possible developments in this promising area.
A Survey on Ethereum Systems Security: Vulnerabilities, Attacks, and Defenses

Blockchain technology is believed by many to be a game changer in many application domains. While the first generation of blockchain technology (i.e., Blockchain 1.0) is almost exclusively used for cryptocurrency, the second generation (i.e., Blockchain 2.0), as represented by Ethereum, is an open and decentralized platform enabling a new paradigm of computing—Decentralized Applications (DApps) running on top of blockchains. The rich applications and semantics of DApps inevitably introduce many security vulnerabilities, which have no counterparts in pure cryptocurrency systems like Bitcoin. Since Ethereum is a new, yet complex, system, it is imperative to have a systematic and comprehensive understanding on its security from a holistic perspective, which was previously unavailable in the literature. To the best of our knowledge, the present survey, which can also be used as a tutorial, fills this void. We systematize three aspects of Ethereum systems security: vulnerabilities, attacks, and defenses. We draw insights into vulnerability root causes, attack consequences, and defense capabilities, which shed light on future research directions.
Neural Syntactic Preordering for Controlled Paraphrase Generation

Paraphrasing natural language sentences is a multifaceted process: it might involve replacing individual words or short phrases, local rearrangement of content, or high-level restructuring like topicalization or passivization. Past approaches struggle to cover this space of paraphrase possibilities in an interpretable manner. Our work, inspired by pre-ordering literature in machine translation, uses syntactic transformations to softly “reorder” the source sentence and guide our neural paraphrasing model. First, given an input sentence, we derive a set of feasible syntactic rearrangements using an encoder-decoder model. This model operates over a partially lexical, partially syntactic view of the sentence and can reorder big chunks. Next, we use each proposed rearrangement to produce a sequence of position embeddings, which encourages our final encoder-decoder paraphrase model to attend to the source words in a particular order. Our evaluation, both automatic and human, shows that the proposed system retains the quality of the baseline approaches while giving a substantial increase in the diversity of the generated paraphrases.
Embedding the Heisenberg group into a bounded-dimensional Euclidean space with optimal distortion

Let H:=(100R10RR1) denote the Heisenberg group with the usual Carnot–Caratheodory metric d. It is known (since the work of Pansu and Semmes) that the metric space (H,d) cannot be embedded in a bilipschitz fashion into a Hilbert space; however, from a general theorem of Assouad, for any 0<e≤1/2, the snowflaked metric space (H,d1−e) embeds into an infinite-dimensional Hilbert space with distortion O(e−1/2). This distortion bound was shown by Austin, Naor, and Tessera to be sharp for the Heisenberg group H. Assouad's argument allows l2 to be replaced by RD(e) for some dimension D(e) dependent on e. Naor and Neiman showed that D could be taken independent of e, at the cost of worsening the bound on the distortion to O(e−1−cD), where cD→0 as D→∞. In this paper we show that one can in fact retain the optimal distortion bound O(e−1/2) and still embed into a bounded-dimensional space RD, answering a question of Naor and Neiman. As a corollary, the discrete ball of radius R≥2 in Γ:=(100Z10ZZ1) can be embedded into a bounded-dimensional space RD with the optimal distortion bound of O(log1/2R).
On the cohomology of integral p-adic unipotent radicals

Let G be a reductive split p-adic group and let U be the unipotent radical of a Borel subgroup. We study the cohomology with trivial Zp-coefficients of the profinite nilpotent group N=U(OF) and its...
Exponential Stability of Primal-Dual Gradient Dynamics with Non-Strong Convexity.

This paper studies the exponential stability of the primal-dual gradient dynamics (PDGD) for solving convex optimization problems where constraints are in the form of Ax + By = d and the objective is min x , y f (x) + g(y) with strongly convex smooth f but only convex smooth g. We show that when g is a quadratic function or when g and matrix B together satisfy an inequality condition, the PDGD can achieve global exponential stability given that matrix A is of full row rank. These results indicate that the PDGD is locally exponentially stable with respect to any convex smooth g under a regularity condition. Two quadratic Lyapunov functions are designed to prove the exponential stability. Lastly, numerical experiments further complement the theoretical analysis.
Halpern Iteration for Near-Optimal and Parameter-Free Monotone Inclusion and Strong Solutions to Variational Inequalities

We leverage the connections between nonexpansive maps, monotone Lipschitz operators, and proximal mappings to obtain near-optimal (i.e., optimal up to poly-log factors in terms of iteration complexity) and parameter-free methods for solving monotone inclusion problems. These results immediately translate into near-optimal guarantees for approximating strong solutions to variational inequality problems, approximating convex-concave min-max optimization problems, and minimizing the norm of the gradient in min-max optimization problems. Our analysis is based on a novel and simple potential-based proof of convergence of Halpern iteration, a classical iteration for finding fixed points of nonexpansive maps. Additionally, we provide a series of algorithmic reductions that highlight connections between different problem classes and lead to lower bounds that certify near-optimality of the studied methods.
Short-run environmental effects of COVID-19: Evidence from forest fires

The outbreak of the 2019 novel coronavirus disease (COVID-19) has raised questions about changes in economic production and subsequent effects on the environment. This article employs satellite data on real-time active fire locations in Nepal to evaluate the short-term environmental effects of COVID-19. Using plausibly exogenous variation in the number of reported COVID-19 cases across the country, this study finds that the incidence of COVID-19 led to a strong negative effect on the incidence of human-induced forest fires. Results indicate that an additional reported case of COVID-19 resulted in a 4.54% decrease in the number of forest fire incidents and a 11.36% reduction in fire radiative power associated with these events. Findings also show that districts with smaller areas of community-managed forests per capita experienced a 8.11% decrease in the number of forest fire incidents. Restrictions on movement of people across districts in response to the pandemic likely reduced the incidence of forest fire events in Nepal. These short-run estimates of environmental benefits, which do not account for negative consequences of the virus outbreak on health and labor market outcomes, partially offset the social cost of pandemics in the developing world.
Merqury: reference-free quality, completeness, and phasing assessment for genome assemblies

Recent long-read assemblies often exceed the quality and completeness of available reference genomes, making validation challenging. Here we present Merqury, a novel tool for reference-free assembly evaluation based on efficient k-mer set operations. By comparing k-mers in a de novo assembly to those found in unassembled high-accuracy reads, Merqury estimates base-level accuracy and completeness. For trios, Merqury can also evaluate haplotype-specific accuracy, completeness, phase block continuity, and switch errors. Multiple visualizations, such as k-mer spectrum plots, can be generated for evaluation. We demonstrate on both human and plant genomes that Merqury is a fast and robust method for assembly validation.
Optimal Reduced-order Modeling of Bipedal Locomotion

State-of-the-art approaches to legged locomotion are widely dependent on the use of models like the linear inverted pendulum (LIP) and the spring-loaded inverted pendulum (SLIP), popular because their simplicity enables a wide array of tools for planning, control, and analysis. However, they inevitably limit the ability to execute complex tasks or agile maneuvers. In this work, we aim to automatically synthesize models that remain low-dimensional but retain the capabilities of the high-dimensional system. For example, if one were to restore a small degree of complexity to LIP, SLIP, or a similar model, our approach discovers the form of that additional complexity which optimizes performance. In this paper, we define a class of reduced-order models and provide an algorithm for optimization within this class. To demonstrate our method, we optimize models for walking at a range of speeds and ground inclines, for both a five-link model and the Cassie bipedal robot.
COVID-19 infections and outcomes in a live registry of heart failure patients across an integrated health care system.

Background Patients with comorbid conditions have a higher risk of mortality with SARS-CoV-2 (COVID-19) infection, but the impact on heart failure patients living near a disease hotspot is unknown. Therefore, we sought to characterize the prevalence and outcomes of COVID-19 in a live registry of heart failure patients across an integrated health care system in Connecticut. Methods In this retrospective analysis, the Yale Heart Failure Registry (NCT04237701) that includes 26,703 patients with heart failure across a 6-hospital integrated health care system in Connecticut was queried on April 16th, 2020 for all patients tested for COVID-19. Sociodemographic and geospatial data as well as, clinical management, respiratory failure, and patient mortality were obtained via the real-time registry. Data on COVID-19 specific care was extracted by retrospective chart review. Results COVID-19 testing was performed on 900 symptomatic patients, comprising 3.4% of the Yale Heart Failure Registry (N = 26,703). Overall, 206 (23%) were COVID- 19+. As compared to COVID-19-, these patients were more likely to be older, black, have hypertension, coronary artery disease, and were less likely to be on renin angiotensin blockers (P<0.05, all). COVID-19- patients tended to be more diffusely spread across the state whereas COVID-19+ were largely clustered around urban centers. 20% of COVID-19+ patients died, and age was associated with increased risk of death [OR 1.92 95% CI (1.33–2.78); P<0.001]. Among COVID-19+ patients who were ≥85 years of age rates of hospitalization were 87%, rates of death 36%, and continuing hospitalization 62% at time of manuscript preparation. Conclusions In this real-world snapshot of COVID-19 infection among a large cohort of heart failure patients, we found that a small proportion had undergone testing. Patients found to be COVID-19+ tended to be black with multiple comorbidities and clustered around lower socioeconomic status communities. Elderly COVID-19+ patients were very likely to be admitted to the hospital and experience high rates of mortality.
Covid-19 Crisis Communications: The Challenge for Environmental Organizations

Abstract During the early stages of the Covid-19 pandemic, U.S. environmental organizations and U.S. chapters of international environmental organizations grappled with a broad set of challenges, including when and what to communicate to supporters. In the winter and early spring of 2020, environmental organizations became crisis communicators, confronted by time pressures and the limited attention spans of audiences beset by the pandemic. Crafting communications that are concise and factual, compassionate, that instill confidence, and that evince organizational competence are important facets of crisis communications. However, environmental organizations faced the additional challenge of ensuring that their own priorities were presented clearly and persuasively amidst the flood of pandemic-related information. Responding to the Covid-19 pandemic, and preparation for future pandemics, force environmental organizations to amend their crisis communications to underscore their relevance to crises and their role in problem-solving.
Managerial Political Spending Choice and Earnings Management

This study investigates whether and how the CEOs’ political spending choice is associated with their earnings management behavior. Using a sample of 8,502 firm-year observations from S&P 500 firms ...
Designing accurate emulators for scientific processes using calibration-driven deep models.

Predictive models that accurately emulate complex scientific processes can achieve speed-ups over numerical simulators or experiments and at the same time provide surrogates for improving the subsequent analysis. Consequently, there is a recent surge in utilizing modern machine learning methods to build data-driven emulators. In this work, we study an often overlooked, yet important, problem of choosing loss functions while designing such emulators. Popular choices such as the mean squared error or the mean absolute error are based on a symmetric noise assumption and can be unsuitable for heterogeneous data or asymmetric noise distributions. We propose Learn-by-Calibrating, a novel deep learning approach based on interval calibration for designing emulators that can effectively recover the inherent noise structure without any explicit priors. Using a large suite of use-cases, we demonstrate the efficacy of our approach in providing high-quality emulators, when compared to widely-adopted loss function choices, even in small-data regimes. The success of machine learning for scientific discovery normally depends on how well the inherent assumptions match the problem in hand. Here, Thiagarajan et al. alleviate this constraint by allowing the change of optimization criterion in a data-driven approach to emulate complex scientific processes.
Optical clocks based on molecular vibrations as probes of variation of the proton-to-electron mass ratio

Some new physics models of quantum gravity or dark matter predict drifts or oscillations of the fundamental constants. A relatively simple model relates molecular vibrations to the proton-to-electron mass ratio $\mu$. Many vibrational transitions are at optical frequencies with prospects for use as highly accurate optical clocks. We give a brief summary of new physics models that lead to changes in $\mu$ and the current limits on drifts and oscillation amplitudes. After an overview of laboratory procedures, we give examples of molecules with experiments currently in development or underway. These experiments' projected systematic and statistical uncertainties make them leading candidates in next-generation searches for time-variation of $\mu$.
General messenger Higgs mediation

We present a general formalism for analyzing supersymmetric models where the Higgs sector directly couples to the messengers of supersymmetry breaking. Such Higgs-messenger interactions are strongly motivated by the discovery of a Higgs boson near 125 GeV, but they also raise the specter of the μ/B μ and $ {A \left/ {{m_H^2}} \right.} $ problems. Using our formalism, we identify new avenues to solving these problems through strong dynamics in the messenger sector or hidden sector. Although our formalism is entirely general, we show how it reproduces familiar results in two simplifying limits: one where the hidden sector consists of a single spurion, and the other where it is approximately superconformal. In the latter limit, our formalism generalizes and clarifies the scenario of hidden sector sequestering, which we show can solve both the μ/B μ and $ {A \left/ {{m_H^2}} \right.} $ problems uniformly.
Working principles of doping-well structures for high-mobility two-dimensional electron systems

Suppressing electron scattering is essential to achieve high-mobility two-dimensional electron systems (2DESs) that are clean enough to probe exotic interaction-driven phenomena. In heterostructures it is common practice to utilize modulation doping, where the ionized dopants are physically separated from the 2DES channel. The doping-well structure augments modulation doping by providing additional screening for all types of charged impurities in the vicinity of the 2DES, which is necessary to achieve record-breaking samples. Despite its prevalence in the design of ultrahigh-mobility 2DESs, the working principles of the doping-well structure have not been reported. Here we elaborate on the mechanics of electron transfer from doping wells to the 2DES, focusing on GaAs/AlGaAs samples grown by molecular beam epitaxy. Based on this understanding we demonstrate how structural parameters in the doping well can be varied to tune the properties of the 2DES.
Theory of AC quantum transport with fully electrodynamic coupling

With the continued scaling of microelectronic devices along with the growing demand of high-speed wireless telecommunications technologies, there is increasing need for high-frequency device modeling techniques that accurately capture the quantum mechanical nature of charge transport in nanoscale devices along with the dynamic fields that are generated. In an effort to fill this gap, we develop a simulation methodology that self-consistently couples AC non-equilibrium Green functions with the full solution of Maxwell’s equations in the frequency domain. We apply this technique to simulate radiation from a quantum-confined, quarter-wave, monopole antenna where the length L is equal to one quarter of the wavelength, $$\lambda _0$$ . Classically, such an antenna would have a narrower, more directed radiation pattern compared to one with $$L \ll \lambda _0$$ , but we find that a quantum quarter-wave antenna has no directivity gain compared to the classical solution. We observe that the quantized wave function within the antenna significantly alters the charge and current density distribution along the length of the wire, which in turn modifies the far-field radiation pattern from the antenna. These results show that high-frequency radiation from quantum systems can be markedly different from classical expectations. Our method, therefore, will enable accurate modeling of the next generation of high-speed nanoscale electronic devices.
Statistical Inference for Online Decision Making via Stochastic Gradient Descent

Online decision making aims to learn the optimal decision rule by making personalized decisions and updating the decision rule recursively. It has become easier than before with the help of big dat...
Assumed Density Filtering Q-learning.

While off-policy temporal difference (TD) methods have widely been used in reinforcement learning due to their efficiency and simple implementation, their Bayesian counterparts have not been utilized as frequently. One reason is that the non-linear max operation in the Bellman optimality equation makes it difficult to define conjugate distributions over the value functions. In this paper, we introduce a novel Bayesian approach to off-policy TD methods, called as ADFQ, which updates beliefs on state-action values, Q, through an online Bayesian inference method known as Assumed Density Filtering. We formulate an efficient closed-form solution for the value update by approximately estimating analytic parameters of the posterior of the Q-beliefs. Uncertainty measures in the beliefs not only are used in exploration but also provide a natural regularization for the value update considering all next available actions. ADFQ converges to Q-learning as the uncertainty measures of the Q-beliefs decrease and improves common drawbacks of other Bayesian RL algorithms such as computational complexity. We extend ADFQ with a neural network. Our empirical results demonstrate that ADFQ outperforms comparable algorithms on various Atari 2600 games, with drastic improvements in highly stochastic domains or domains with a large action space.
Dense binary PG(t − 1,2)-free matroids have critical number t − 1 or t

The critical threshold of a (simple binary) matroid N is the infimum over all ρ such that any N-free matroid M with |M|>ρ2r(M)|M|>ρ2r(M) has bounded critical number. In this paper, we resolve two conjectures of Geelen and Nelson, showing that the critical threshold of the projective geometry PG(t−1,2)PG(t−1,2) is 1−3⋅2−t1−3⋅2−t. We do so by proving the following stronger statement: if M is PG(t−1,2)PG(t−1,2)-free with |M|>(1−3⋅2−t)2r(M)|M|>(1−3⋅2−t)2r(M), then the critical number of M is t−1t−1 or t. Together with earlier results of Geelen and Nelson [9] and Govaerts and Storme [11], this completes the classification of dense PG(t−1,2)PG(t−1,2)-free matroids.
Monotonicity of degrees of generalized Alexander polynomials of groups and 3-manifolds

We investigate the behavior of the higher-order degrees, . As a result, we show that these generalized degrees give obstructions to the deficiency of a group being positive and obstructions to a finitely presented group being the fundamental group of a compact, orientable 3-manifold.
THERMOPOWER OF SnTe FROM BOLTZMANN TRANSPORT CALCULATIONS

The doping and temperature dependent thermopower of SnTe is calculated from the first principles band structure using Boltzmann transport theory. We find that the p-type thermopower is inferior to PbTe consistent with experimental observations, but that the n-type thermopower is substantially more favorable.
Energy landscapes for the self-assembly of supramolecular polyhedra

We develop a mathematical model for the energy landscape of polyhedral supramolecular cages recently synthesized by self-assembly (Sun et al. in Science 328:1144–1147, 2010). Our model includes two essential features of the experiment: (1) geometry of the organic ligands and metallic ions; and (2) combinatorics. The molecular geometry is used to introduce an energy that favors square-planar vertices (modeling $$\mathrm {Pd}^{2+}$$ ions) and bent edges with one of two preferred opening angles (modeling boomerang-shaped ligands of two types). The combinatorics of the model involve two-colorings of edges of polyhedra with four-valent vertices. The set of such two-colorings, quotiented by the octahedral symmetry group, has a natural graph structure and is called the combinatorial configuration space. The energy landscape of our model is the energy of each state in the combinatorial configuration space. The challenge in the computation of the energy landscape is a combinatorial explosion in the number of two-colorings of edges. We describe sampling methods based on the symmetries of the configurations and connectivity of the configuration graph. When the two preferred opening angles encompass the geometrically ideal angle, the energy landscape exhibits a very low-energy minimum for the most symmetric configuration at equal mixing of the two angles, even when the average opening angle does not match the ideal angle.
ADJOINT FUNCTORS ON THE DERIVED CATEGORY OF MOTIVES

We show that the subcategory of mixed Tate motives in Voevodsky’s derived category of motives is not closed under infinite products. In fact, the infinite product is not mixed Tate. More generally, the inclusions of several subcategories of motives do not have left or right adjoints. The proofs use the failure of finite generation for Chow groups in various contexts. In the positive direction, we show that for any scheme of finite type over a field whose motive is mixed Tate, the Chow groups are finitely generated.
Truncated Heegaard Floer homology and knot concordance invariants

We construct a sequence of smooth concordance invariants νn(K) defined using truncated Heegaard Floer homology. The invariants generalize the concordance invariants ν of Ozsvath and Szabo and ν+ of Hom and Wu. We exhibit an example in which the gap between two consecutive elements in the sequence νn can be arbitrarily large. We also prove that the sequence νn contains more concordance information than τ, ν, ν′, ν+ and ν+′.
Efficient race detection with futures

This paper addresses the problem of provably efficient and practically good on-the-fly determinacy race detection in task parallel programs that use futures. Prior works on determinacy race detection have mostly focused on either task parallel programs that follow a series-parallel dependence structure or ones with unrestricted use of futures that generate arbitrary dependences. In this work, we consider a restricted use of futures and show that we can detect races more efficiently than with general use of futures. Specifically, we present two algorithms: MultiBags and MultiBags+. MultiBags targets programs that use futures in a restricted fashion and runs in time O(T1α(m, n)), where T1 is the sequential running time of the program, α is the inverse Ackermann's function, m is the total number of memory accesses, n is the dynamic count of places at which parallelism is created. Since α is a very slowly growing function (upper bounded by 4 for all practical purposes), it can be treated as a close-to-constant overhead. MultiBags+ is an extension of MultiBags that target programs with general use of futures. It runs in time O((T1 + k2)α(m, n)) where T1, α, m and n are defined as before, and k is the number of future operations in the computation. We implemented both algorithms and empirically demonstrate their efficiency.
A Model for Vortex Nucleation in the Ginzburg–Landau Equations

This paper studies questions related to the dynamic transition between local and global minimizers in the Ginzburg–Landau theory of superconductivity. We derive a heuristic equation governing the dynamics of vortices that are close to the boundary, and of dipoles with small inter-vortex separation. We consider a small random perturbation of this equation and study the asymptotic regime under which vortices nucleate.
Using think-aloud interviews to characterize model-based reasoning in electronics for a laboratory course assessment

A description of the types of thinking that upper division physics students employ while interpreting the output signal of a circuit functioning far outside its recommended operation range.
Kiloparsec-scale Simulations of Star Formation in Disk Galaxies. I. The Unmagnetized and Zero-feedback Limit

We present hydrodynamic simulations of the evolution of self-gravitating dense gas on scales of 1 kpc down to parsec in a galactic disk, designed to study dense clump formation from giant molecular clouds (GMCs). These structures are expected to be the precursors to star clusters and this process may be the rate limiting step controlling star formation rates in galactic systems as described by the Kennicutt-Schmidt relation. We follow the thermal evolution of the gas down to ~5 K using extinction-dependent heating and cooling functions. We do not yet include magnetic fields or localized stellar feedback, so the evolution of the GMCs and clumps is determined solely by self-gravity balanced by thermal and turbulent pressure support and the large-scale galactic shear. While cloud structures and densities change significantly during the simulation, GMC virial parameters remain mostly above unity for timescales exceeding the free-fall time of GMCs indicating that energy from galactic shear and large-scale cloud motions continuously cascades down to and within the GMCs. We implement star formation at a slow, inefficient rate of 2% per local free-fall time, but even this yields global star formation rates that are about two orders of magnitude larger than the observed Kennicutt-Schmidt relation due to overproduction of dense gas clumps. We expect a combination of magnetic support and localized stellar feedback is required to inhibit dense clump formation to ~1% of the rate that results from the nonmagnetic, zero-feedback limit.
Non-Hermitian Fermion Mapping for One-Component Plasma

The two-dimensional, one-component logarithmic Coulomb gas is mapped onto a non-Hermitian fermionic field theory. At β = 2, the field theory is free. Correlation functions are calculated and a perturbation theory is discussed for extending to other β. A phase transition is found at the mean-field level at large β. Some results are extended to spaces of constant negative curvature.
On Borwein's conjectures for planar uniform random walks

Let $ p_n(x)=\int_0^\infty J_0(xt)[J_0(t)]^n xt\,\mathrm{d}\, t$ be Kluyver's probability density for $n$-step uniform random walks in the Euclidean plane. Through connection to a similar problem in 2-dimensional quantum field theory, we evaluate the third-order derivative $ p_5'''(0^{+})$ in closed form, thereby giving a new proof for a conjecture of J. M. Borwein. By further analogies to Feynman diagrams in quantum field theory, we demonstrate that $ p_n(x),0\leq x\leq 1$ admits a uniformly convergent Maclaurin expansion for all odd integers $ n\geq5$, thus settling another conjecture of Borwein.
Leveraging unstructured data to detect emerging reliability issues

Unstructured data refers to information that does not have a predefined data model or is not organized in a predefined manner [1]. Loosely speaking, unstructured data refers to text data that is generated by humans. In aftersales service businesses, there are two main sources of unstructured data: customer complaints, which generally describe symptoms, and technician comments, which outline diagnostics and treatment information. A legitimate customer complaint can eventually be tracked to a failure or a claim. However, there is a delay between the time of a customer complaint and the time of a failure or a claim. A proactive strategy aimed at analyzing customer complaints for symptoms can help service providers detect reliability problems in advance and initiate corrective actions such as recalls. This paper introduces essential text mining concepts in the context of reliability analysis and a method to detect emerging reliability issues. The application of the method is illustrated using a case study.
An Empirical Fitting Method to Type Ia Supernova Light Curves. III. A Three-Parameter Relationship: Peak Magnitude, Rise Time, and Photospheric Velocity

We examine the relationship between three parameters of Type Ia supernovae (SNe Ia): peak magnitude, rise time, and photospheric velocity at the time of peak brightness. The peak magnitude is corrected for extinction using an estimate determined from MLCS2k2 fitting. The rise time is measured from the well-observed B-band light curve with the first detection at least 1 mag fainter than the peak magnitude, and the photospheric velocity is measured from the strong absorption feature of Si ii λ6355 at the time of peak brightness. We model the relationship among these three parameters using an expanding fireball with two assumptions: (a) the optical emission is approximately that of a blackbody, and (b) the photospheric temperatures of all SNe Ia are the same at the time of peak brightness. We compare the precision of the distance residuals inferred using this physically motivated model against those from the empirical Phillips relation and the MLCS2k2 method for 47 low-redshift SNe Ia (0.005 < z < 0.04) and find comparable scatter. However, SNe Ia in our sample with higher velocities are inferred to be intrinsically fainter. Eliminating the high-velocity SNe and applying a more stringent extinction cut to obtain a "low-v golden sample" of 22 SNe, we obtain significantly reduced scatter of 0.108 ± 0.018 mag in the new relation, better than those of the Phillips relation and the MLCS2k2 method. For 250 km s−1 of residual peculiar motions, we find 68% and 95% upper limits on the intrinsic scatter of 0.07 and 0.10 mag, respectively.
Demonstration of Efficient Nonreciprocity in a Microwave Optomechanical Circuit

Nonreciprocal devices, in which electrical or optical signals travel in one direction only, are essential for telecommunication and quantum applications, but they are often both lossy and bulky to implement. A prototype device demonstrates nonreciprocity in a microwave optomechanical circuit that allows for dynamic isolation control while avoiding the need for large magnetic fields.
Green function of the Poisson equation: D = 2, 3, 4

We study the Green function of the Poisson equation in two, three and four dimensions. The solution g of the equation , where and are D-dimensional position vectors, is customarily expanded into radial and angular coordinates. For the two-dimensional case (D = 2), we find a subtle interplay of the necessarily introduced scale L with the radial component of zero magnetic quantum number. For D = 3, the well-known expressions are briefly recalled; this is done in order to highlight the analogy with the four-dimensional case, where we uncover analogies of the four-dimensional spherical harmonics with the familiar three-dimensional case. Remarks on the SO(4) symmetry of the hydrogen atom complete the investigations.
Majorana braiding in realistic nanowire Y-junctions and tuning forks

Majorana fermions are predicted to arise in networks of semiconductor nanowires, where their nonabelian statistics may be exploited to perform logic operations necessary for a (topological) quantum computer. In this paper, the authors numerically simulate a topological braiding operation in devices with Y-junction and tuning fork geometries, using an experimentally motivated nanowire model. Their results demonstrate that such devices have an optimal geometry for braiding, and suggest that performing a successful braiding operation lies within experimental reach.
Experimental Observation of Nonreciprocal Waves in a Resonant Metamaterial Beam

Structures hosting nonreciprocal (one-way) wave propagation are of key interest in signal processing, sensing, and civil infrastructure, yet experimental realization has so far relied on adaptive materials and external stimulation, which require significant power and are not scalable beyond lab prototypes. This work presents an elastic metamaterial that exploits stiffness variations in an array of geometrically phase-shifted resonators to achieve a nonreciprocal tilt of dispersion modes within dynamic modulation regimes. The ability to induce asymmetric vibrational modes in a scalable, energy-efficient manner has direct implications for numerous applications.
High Resolution Observations of Chromospheric Jets in Sunspot Umbra

Recent observations of a sunspot's umbra have suggested that it may be finely structured on a subarcsecond scale representing a mix of hot and cool plasma elements. In this study, we report the first detailed observations of umbral spikes, which are cool jet-like structures seen in the chromosphere of an umbra. The spikes are cone-shaped features with a typical height of 0.5-1.0 Mm and a width of about 0.1 Mm. Their lifetime ranges from 2 to 3 minutes and they tend to re-appear at the same location. The spikes are not associated with photospheric umbral dots and they instead tend to occur above the darkest parts of the umbra where magnetic fields are strongest. The spikes exhibit up and down oscillatory motions and their spectral evolution suggests that they might be driven by upward propagating shocks generated by photospheric oscillations. It is worth noting that triggering of the running penumbral waves seems to occur during the interval when the spikes reach their maximum height.
Discriminants and the monoid of quadratic rings

We consider the natural monoid structure on the set of quadratic rings over an arbitrary base scheme and characterize this monoid in terms of discriminants. Quadratic field extensions K of Q are characterized by their discriminants. Indeed, there is a bijection { Separable quadratic algebras over Q up to isomorphism } ∼ −→ Q×/Q×2 Q[ √ d] = Q[x]/(x − d) 7→ dQ×2 where a separable quadratic algebra over Q is either a quadratic field extension or the algebra Q[ √ 1] ' Q×Q of discriminant 1. In particular, the set of isomorphism classes of separable quadratic extensions of Q can be given the structure of an elementary abelian 2-group, with identity element the class of Q×Q: we have simply Q[ √ d1] ∗Q[ √ d2] = Q[ √ d1d2] up to isomorphism. If d1, d2, d1d2 ∈ Q× \ Q×2 then Q( √ d1d2) sits as the third quadratic subfield of the compositum Q( √ d1, √ d2):
Multiphysics model of chemical aging in frictional contacts

An increase of static friction during stationary contacts of two solids due to interfacial chemical bonding has been reported in multiple experiments. However, the physics underlying such frictional aging is still not fully understood because it involves multiple physical and chemical effects coupled with each other, making direct interpretation of experimental results difficult. Here, we develop a multiphysics chemical aging model that combines contact mechanics, mechanochemistry, and interfacial chemical reaction kinetics. Our model predicts that aging is proportional to normal loads in a low-load regime and becomes nonlinear at higher loads. We also discovered a nonmonotonic temperature dependence of aging with a peak near room temperature. In addition, our simulations provide insights into contributions from specific physical/chemical effects on the overall aging. Our model shows quantitative agreement with available single-asperity experiments on silica-silica interfaces, and it provides a framework for building a chemical aging model for other material systems with arbitrary types of physical and chemical effects involved.
Monstrous string-string duality

Abstract We analyze the general class of supersymmetry preserving orbifolds of strong/weak Type IIA/heterotic dual pairs in six dimensions and below. A unified treatment is given by considering compactification to two space-time dimensions and constructing orbifolds by subgroups of the Fischer-Greiss monster, utilizing the moonshine results of Conway and Norton. Duality requires nontrivial Ramond-Ramond fluxes on the Type IIA side which are localized at the fixed points. Further orbifolding by (−1) F L gives examples of new four-dimensional N = 2 type IIA vacua which are not conformal field theory backgrounds.
Concordance of Bing Doubles and Boundary Genus

Cha and Kim proved that if a knot K is not algebraically slice, then no iterated Bing double of K is concordant to the unlink. We prove that if K has nontrivial signature ! , then the n‐iterated Bing double of K is not concordant to any boundary link with boundary surfaces of genus less than 2 n" 1 ! . The same result holds with ! replaced by 2" ,t wice the Ozsv´´ ok not concordance invariant.
Luminosities and Space Densities of Short Gamma-Ray Bursts

Using the Euclidean value of V/Vmax as a cosmological distance indicator, we derive the isotropic-equivalent characteristic peak luminosity of gamma-ray bursts both longer and shorter than 2 s. The short bursts have essentially the same characteristic peak luminosity of 0.6 × 1051 ergs (0.064 s)-1 as do the long bursts. This may apply also to bursts with durations less than 0.25 s. The local space density of short bursts is around 3 times lower than that of long bursts.
Surgeries on periodic links and homology of periodic 3-manifolds

We show that a closed orientable 3-manifold M admits an action of Zp with fixed point set S 1 iff M can be obtained as the result of surgery on a p-periodic framed link L and Zp acts freely on the components of L. We prove a similar theorem for free Zp-actions. As an interesting application, we prove the following, rather unexpected result: for any M as above and for any odd prime p, H1(M, Zp) 6 Zp. We also prove a similar criterion of 2-periodicity for rational homology 3-spheres. In the early 1960’s both Wallace [Wa] and Lickorish [Li] proved that every closed, connected, orientable 3-manifold may be obtained by surgery on a framed link in S 3 . Thus, link diagrams may be used to depict manifolds. Every manifold has infinitely many different framed link descriptions. However, in 1970’s Kirby [K] showed that two framed links determine the same 3-manifold iff they are related by a finite sequence of two specific types of moves. This calculus of framed links, together with the earlier results, gives a classification of 3-manifolds in terms of equivalence classes of framed links. The framed link representation of 3-manifolds has proven to be extremely useful. For instance, most of the new 3-manifold invariants originating from famous Witten’s paper [Wi] are based on the framed link approach. Therefore, it is always very useful to have some kind of correspondence between certain classes of 3-manifolds and some classes of framed links. One example of such correspondence is the classical relationship between the lens spaces and the chain-link diagrams (see, for instance, [Ro]). This result, in
NOVAE EJECTA AS DISCRETE ADIABATICALLY EXPANDING GLOBULES

Available data for novae show that the X-ray and visible spectral regions correlate with each other as they evolve. Large differences in ionization exist simultaneously in the two wavelength regimes, and a straightforward model is proposed that explains the characteristics observed in both spectral regimes. Its key features are (1) ejected blobs of very high density gas from the white dwarf (WD) that expand to create within each clump a wide range of emitting density, ionization, and velocity, and (2) a more homogeneous circumbinary envelope of gas that is produced by secondary star mass loss. The relative mass loss rates from the two stars determine whether the He/N or the Fe II visible spectrum predominates during decline, when hard X-rays are detected, and when the WD can be detected as a super soft X-ray source.