cssi/SciSciGPT-SciSciNet huggingface dataset:
An Attacker Modeling Framework for the Assessment of Cyber-Physical Systems Security

Characterizing attacker behavior with respect to Cyber-Physical Systems is important to assuring the security posture and resilience of these systems. Classical cyber vulnerability assessment approaches rely on the knowledge and experience of cyber-security experts to conduct security analyses and can be inconsistent where the experts’ knowledge and experience are lacking. This paper proposes a flexible attacker modeling framework that aids in the security analysis process by simulating a diverse set of attacker behaviors to predict attack progression and provide consistent system vulnerability analysis. The model proposes an expanded architecture of vulnerability databases to maximize its effectiveness and consistency in detecting CPS vulnerabilities while being compatible with existing vulnerability databases. The model has the power to be implemented and simulated against an actual or virtual CPS. Execution of the attacker model is demonstrated against a simulated industrial control system architecture, resulting in a probabilistic prediction of attacker behavior.
Averaging causal estimators in high dimensions

There has been increasing interest in recent years in the development of approaches to estimate causal effects when the number of potential confounders is prohibitively large. This growth in interest has led to a number of potential estimators one could use in this setting. Each of these estimators has different operating characteristics, and it is unlikely that one estimator will outperform all others across all possible scenarios. Coupling this with the fact that an analyst can never know which approach is best for their particular data, we propose a synthetic estimator that averages over a set of candidate estimators. Averaging is widely used in statistics for problems such as prediction, where there are many possible models, and averaging can improve performance and increase robustness to using incorrect models. We show that these ideas carry over into the estimation of causal effects in high-dimensional scenarios. We show theoretically that averaging provides robustness against choosing a bad model, and show empirically via simulation that the averaging estimator performs quite well, and in most cases nearly as well as the best among all possible candidate estimators. Finally, we illustrate these ideas in an environmental wide association study and see that averaging provides the largest benefit in the more difficult scenarios that have large numbers of confounders.
Isolator-Free Integration of C-Band InAs-InP Quantum Dash Buried Heterostructure Lasers with Silicon Waveguides

An InAs-on-InP quantum dash buried heterostructure laser and silicon chip optimized for mutual integration by direct facet-to-facet coupling have achieved −1.2 dB coupling efficiency, with coupled laser RIN of −150 dB/Hz and 152 kHz linewidth.
A Compact Gated-Synapse Model for Neuromorphic Circuits

This work reports a compact behavioral model for gated-synaptic memory. The model is developed in Verilog-A for easy integration into computer-aided design of neuromorphic circuits using emerging memory. The model encompasses various forms of gated synapses within a single framework and is not restricted to only a single type. The behavioral theory of the model is described in detail along with a full list of the default parameter settings. The model includes parameters, such as a device’s ideal set time, threshold voltage, general evolution of the conductance with respect to time, decay of the device’s state, etc. Finally, the model’s validity is shown via extensive simulation and fitting to experimentally reported data on published gated-synapses.
Characterization of Met25 as a color associated genetic marker in Yarrowia lipolytica.

Abstract Yarrowia lipolytica offers an ideal host for biosynthesis of high value natural products and oleochemicals through metabolic engineering despite being restricted to a limited number of selective markers, and counter-selection achieved primarily with URA3. In this work, we investigate MET25, a locus encoding sulfide housekeeping gene within the cell, to be exploited as a standard genetic marker. Divalent lead supplemented in media induces lead sulfide (PbS) aggregation in MET25-deficient cells such that deficient cells grow brown/black, and cells with functional copies of MET25 grow white. Loss of MET25 did not induce strict auxotrophic requirements for methionine in Y. lipolytica, indicating MET25 deficiency could be rescued by alternative pathways. Plasmid and chromosomal-based complementation of MET25 in the met25 deficient cells on a double layer agar plate with nutrient gradients demonstrates delayed phenotype (white morphology) restoration, indicating post-transcriptional feedback regulation of methionine biosynthesis in this yeast. MET25 deficient Y. lipolytica could be used as an efficient whole-cell lead sensor with detection limit as low as 10 ​ppm of lead in drinking water. We further tested whether MET25 deficiency can be exploited to confer resistance to methyl-mercury through chemical neutralization and detoxification. Kinetic growth curves of wild type and MET25-deficient cells were obtained under varying concentrations of methylmercury and cellular toxicity to methyl mercury was calculated from the Hill equation. Our results indicate that methylmecury may not be used as the counter-selectable marker due to insignificant changes of growth fitness. This work demonstrates the utility of using MET25 as a sensitive lead sensor and the challenges of using MET25 as a counter-selectable genetic marker, as well as the complex regulation of methionine biosynthesis in Y. lipolyitca, which may shed lights for us to develop valuable biotechnological applications centering around the sulfur house-keeping metabolism of the nonconventional yeast.
Domain Generalizer: A Few-shot Meta Learning Framework for Domain Generalization in Medical Imaging

Deep learning models perform best when tested on target (test) data domains whose distribution is similar to the set of source (train) domains. However, model generalization can be hindered when there is significant difference in the underlying statistics between the target and source domains. In this work, we adapt a domain generalization method based on a model-agnostic meta-learning framework [1] to biomedical imaging. The method learns a domain-agnostic feature representation to improve generalization of models to the unseen test distribution. The method can be used for any imaging task, as it does not depend on the underlying model architecture. We validate the approach through a computed tomography (CT) vertebrae segmentation task across healthy and pathological cases on three datasets. Next, we employ few-shot learning, i.e. training the generalized model using very few examples from the unseen domain, to quickly adapt the model to new unseen data distribution. Our results suggest that the method could help generalize models across different medical centers, image acquisition protocols, anatomies, different regions in a given scan, healthy and diseased populations across varied imaging modalities.
Accelerating Grasp Exploration by Leveraging Learned Priors

The ability of robots to grasp novel objects has industry applications in e-commerce order fulfillment and home service. Data-driven grasping policies have achieved success in learning general strategies for grasping arbitrary objects. However, these approaches can fail to grasp objects which have complex geometry or are significantly outside of the training distribution. We present a Thompson sampling algorithm that learns to grasp a given object with unknown geometry using online experience. The algorithm leverages learned priors from the Dexterity Network robot grasp planner to guide grasp exploration and provide probabilistic estimates of grasp success for each stable pose of the novel object. We find that seeding the policy with the Dex-Net prior allows it to more efficiently find robust grasps on these objects. Experiments suggest that the best learned policy attains an average total reward 64.5% higher than a greedy baseline and achieves within 5.7% of an oracle baseline when evaluated over 300, 000 training runs across a set of 3000 object poses.
An analysis of observation length requirements for machine understanding of human behaviors from spoken language

Abstract The task of quantifying human behavior by observing interaction cues is an important and useful one across a range of domains in psychological research and practice. Machine learning-based approaches typically perform this task by first estimating behavior based on cues within an observation window, such as a fixed number of words, and then aggregating the behavior over all the windows in that interaction. The length of this window directly impacts the accuracy of estimation by controlling the amount of information being used. The exact link between window length and accuracy, however, has not been well studied, especially in spoken language. In this paper, we investigate this link and present an analysis framework that determines appropriate window lengths for the task of behavior estimation. Our proposed framework utilizes a two-pronged evaluation approach: (a) extrinsic similarity between machine predictions and human expert annotations, and (b) intrinsic consistency between intra-machine and intra-human behavior relations. We apply our analysis to real-life conversations that are annotated for a large and diverse set of behavior codes and examine the relation between the nature of a behavior and how long it should be observed. We find that behaviors describing negative and positive affect can be accurately estimated from short to medium-length expressions whereas behaviors related to problem-solving and dysphoria require much longer observations and are difficult to quantify from language alone. These findings are found to be generally consistent across different behavior modeling approaches.
Ongoing speciation within the diatom Fragilariopsis kerguelensis in the Southern Ocean

While the identification of microbial eukaryotes using metabarcoding tools is now widespread, additional data are needed to confirm molecular observations, to mark the difference between species and population variants, and to better understand the biogeography of microbial eukaryotes. In this issue of Molecular Ecology, Postel et al not only use three molecular approaches to identify subgroups of Fragilariopsis kerguelensis but also use morphology and physiology to better understand the relationship between the three genotypes. They revealed that (a) the three genotypes of the diatom F. kerguelensis show negligible gene flux; (b) two of the genotypes are geographically isolated with different physiology but still able to crossbreed; and (c) the remaining genotype is omnipresent but reproductively isolated.
Ultrasensitive small molecule fluorogenic probe for human heparanase

Heparanase (HPA) is a critical enzyme involved in the remodeling of the extracellular matrix (ECM), and its elevated expression has been linked with diseases such as various types of cancer and inflammation. The detection of heparanase enzymatic activity holds tremendous value in the study of the cellular microenvironment, and search of molecular therapeutics targeting heparanase, however, no structurally defined probes are available for the detection of heparanase activity. Here we present the development of the first ultrasensitive fluorogenic small-molecule probe for heparanase enzymatic activity via tuning the electronic effect of the substrate. The probe exhibits a 756-fold fluorescence turn-on response in the presence of human heparanase, allowing one-step detection of heparanase activity in real-time with a picomolar detection limit. The high sensitivity and robustness of the probe are exemplified in a high-throughput screening assay for heparanase inhibitors.
Coil-stretch-like transition of elastic sheets in extensional flows.

The conformation of a long linear polymer dissolved in fluid and exposed to an extensional flow is well-known to exhibit a “coil–stretch” transition, which for sufficiently long chains can lead to bistability. The present work reports computations indicating that an analogous “compact–stretched” transition arises in the dynamics of a thin elastic sheet. Sheets of nominally circular, square or rectangular shape are simulated in planar and biaxial flows using a finite element method for the sheet conformations and a regularized Stokeslet method for the fluid flow. If a neo-Hookean constitutive model is used for the sheet elasticity, the sheets will stretch without bound once a critical extension rate, as characterized nondimensionally by a capillary number, is exceeded. Nonlinear elasticity, represented with the Yeoh model, arrests the stretching, leading to a highly-stretched steady state once the critical capillary number is exceeded. For all shapes and in both planar and biaxial extension, a parameter regime exists in which both weakly stretched (compact) and strongly stretched states can be found, depending on initial conditions. I.e. this parameter regime displays bistability. As in the long-chain polymer case, the bistable behavior arises from the hydrodynamic interaction between distant elements of the sheet, and vanishes if these interactions are artificially screened by use of a Brinkman model for the fluid motion. While the sheets can transiently display wrinkled shapes, all final shapes in planar and biaxial extension are planar.
New Results on Routing via Matchings on Graphs

In this paper we present some new complexity results on the routing time of a graph under the routing via matching model. This is a parallel routing model which was introduced by Alon et al. [1]. The model can be viewed as a communication scheme on a distributed network. The nodes in the network can communicate via matchings (a step), where a node exchanges data (pebbles) with its matched partner. Let G be a connected graph with vertices labeled from \(\{1,...,n\}\) and the destination vertices of the pebbles are given by a permutation \(\pi \). The problem is to find a minimum step routing scheme for the input permutation \(\pi \). This is denoted as the routing time \(rt(G,\pi )\) of G given \(\pi \). In this paper we characterize the complexity of some known problems under the routing via matching model and discuss their relationship to graph connectivity and clique number. We also introduce some new problems in this domain, which may be of independent interest.
A neglected issue: The sexual side-effects of current treatments for breast cancer.

All current treatments for breast cancer can result in serious sexual impairments, but this important aspect of cancer care has been largely neglected. This paper contains a brief summary of breast cancer treatments and their potential sexual side effects. The remedies which are available at this time are also discussed. This material is presented to encourage professionals to become more aware of and more attentive to the sexual needs of their cancer patients.
The compactness locus of a geometric functor and the formal construction of the Adams isomorphism

We introduce the compactness locus of a geometric functor between rigidly-compactly generated tensor-triangulated categories, and describe it for several examples arising in equivariant homotopy theory and algebraic geometry. It is a subset of the tensor-triangular spectrum of the target category which, crudely speaking, measures the failure of the functor to satisfy Grothendieck-Neeman duality (or equivalently, to admit a left adjoint). We prove that any geometric functor --- even one which does not admit a left adjoint --- gives rise to a Wirthmuller isomorphism once one passes to a colocalization of the target category determined by the compactness locus. When applied to the inflation functor in equivariant stable homotopy theory, this produces the Adams isomorphism.
Fractional virasoro algebras

We show that it is possible to construct a Virasoro algebra as a central extension of the fractional Witt algebra generated by non-local operators of the form, $L_n^a\equiv\left(\frac{\partial f}{\partial z}\right)^a$ where $a\in {\mathbb R}$. The Virasoro algebra is explicitly of the form, \beq [L^a_m,L_n^a]=A_{m,n}L^a_{m+n}+\delta_{m,n}h(n)cZ^a \eeq where $c$ is the central charge (not necessarily a constant), $Z^a$ is in the center of the algebra and $h(n)$ obeys a recursion relation related to the coefficients $A_{m,n}$. In fact, we show that all central extensions which respect the special structure developed here which we term a multimodule Lie-Algebra, are of this form. This result provides a mathematical foundation for non-local conformal field theories, in particular recent proposals in condensed matter in which the current has an anomalous dimension.
Baryon Spin and Magnetic Moments in Relativistic Chiral Quark Models

The spin and flavor fractions of constituent quarks in the baryon octet are obtained from their lowest order chiral fluctuations involving Goldstone bosons. SU(3) breaking suggested by the mass difference between the strange and up, down quarks is included, as are relativistic effects by means of a light-cone quark model for the proton, and the gluon contribution from the axial anomaly in the singlet channel. Magnetic moments from the Karl-Sehgal formulas are analyzed in this framework as well.
Impact of Dual Slope Path Loss on User Association in HetNets

Intelligent load balancing is essential to fully realize the benefits of dense heterogeneous networks. Current techniques have largely been studied with single slope path loss models, though multi-slope models are known to more closely match real deployments. This paper develops insight into the performance of biasing and uplink/downlink decoupling for user association in HetNets with dual slope path loss models. It is shown that dual slope path loss models change the tradeoffs inherent in biasing and reduce gains from both biasing and uplink/downlink decoupling. The results show that with the dual slope path loss models, the bias maximizing the median rate is not optimal for other users, e.g., edge users. Furthermore, optimal downlink biasing is shown to realize most of the gains from downlink-uplink decoupling. Moreover, the user association gains in dense networks are observed to be quite sensitive to the path loss exponent beyond the critical distance in a dual slope model.
Distribution Spaces and a New Construction of Stochastic Processes Associated with the Grassmann Algebra

We associate with the Grassmann algebra a topological algebra of distributions, which allows the study of processes analogous to the corresponding free stochastic processes with stationary increments, as well as their derivatives.
Extending the applicability of Redfield theories into highly non-Markovian regimes

We present a new, computationally inexpensive method for the calculation of reduced density matrix dynamics for systems with a potentially large number of subsystem degrees of freedom coupled to a generic bath. The approach consists of propagation of weak-coupling Redfield-like equations for the high-frequency bath degrees of freedom only, while the low-frequency bath modes are dynamically arrested but statistically sampled. We examine the improvements afforded by this approximation by comparing with exact results for the spin-boson model over a wide range of parameter space. We further generalize the method to multi-site models and compare with exact results for a model of the Fenna–Matthews–Olson complex. The results from the method are found to dramatically improve Redfield dynamics in highly non-Markovian regimes, at a similar computational cost. Relaxation of the mode-freezing approximation via classical (Ehrenfest) evolution of the low-frequency modes results in a dynamical hybrid method. We find that this Redfield-based dynamical hybrid approach, which is computationally more expensive than bare Redfield dynamics, yields only a marginal improvement over the simpler approximation of complete mode arrest.
Transiting Planets with LSST. III. Detection Rate per Year of Operation

The Large Synoptic Survey Telescope (LSST) will generate light curves for approximately 1 billion stars. Our previous work has demonstrated that, by the end of the LSST 10-year mission, large numbers of transiting exoplanetary systems could be recovered using the LSST "deep-drilling" cadence. Here, we extend our previous work to examine how the recoverability of transiting planets over a range of orbital periods and radii evolves per year of LSST operation. As specific example systems, we consider hot Jupiters orbiting solar-type stars and hot Neptunes orbiting K-dwarfs at distances from Earth of several kpc, as well as super-Earths orbiting nearby low-mass M-dwarfs. The detection of transiting planets increases steadily with the accumulation of data over time, generally becoming large (10%) after 4–6 years of operation. However, we also find that short-period (2 days) hot Jupiters orbiting G-dwarfs and hot Neptunes orbiting K-dwarfs can already be discovered within the first 1–2 years of LSST operation.
Stability in the cohomology of the space of complex irreducible polynomials in several variables

We prove that the space of complex irreducible polynomials of degree $d$ in $n$ variables satisfies two forms of homological stability: first, its cohomology stabilizes as $d$ increases, and second, its compactly supported cohomology stabilizes as $n$ increases. Our topological results are inspired by counting results over finite fields due to Carlitz and Hyde.
Enabling massive deep neural networks with the GraphBLAS

Deep Neural Networks (DNNs) have emerged as a core tool for machine learning. The computations performed during DNN training and inference are dominated by operations on the weight matrices describing the DNN. As DNNs incorporate more stages and more nodes per stage, these weight matrices may be required to be sparse because of memory limitations. The GraphBLAS.org math library standard was developed to provide high performance manipulation of sparse weight matrices and input/output vectors. For sufficiently sparse matrices, a sparse matrix library requires significantly less memory than the corresponding dense matrix implementation. This paper provides a brief description of the mathematics underlying the GraphBLAS. In addition, the equations of a typical DNN are rewritten in a form designed to use the GraphBLAS. An implementation of the DNN is given using a preliminary GraphBLAS C library. The performance of the GraphBLAS implementation is measured relative to a standard dense linear algebra library implementation. For various sizes of DNN weight matrices, it is shown that the GraphBLAS sparse implementation outperforms a BLAS dense implementation as the weight matrix becomes sparser.
F-theorem without supersymmetry

The conjectured F-theorem for three-dimensional field theories states that the finite part of the free energy on S 3 decreases along RG trajectories and is stationary at the fixed points. In previous work various successful tests of this proposal were carried out for theories with $ \mathcal{N} = 2 $ supersymmetry. In this paper we perform more general tests that do not rely on supersymmetry. We study perturbatively the RG flows produced by weakly relevant operators and show that the free energy decreases monotonically. We also consider large N field theories perturbed by relevant double trace operators, free massive field theories, and some non-Abelian gauge theories. In all cases the free energy in the IR is smaller than in the UV, consistent with the F-theorem. We discuss other odd-dimensional Euclidean theories on S d and provide evidence that (−1)(d−1)/2 log|Z| decreases along RG flow; in the particular case d = 1 this is the well-known g-theorem.
Shapes of polynomial Julia sets

Any Jordan curve in the complex plane can be approximated arbitrarily well in the Hausdorff topology by Julia sets of polynomials. Finite collections of disjoint Jordan domains can be approximated by the basins of attraction of rational maps.
Heterotic plane wave matrix models and giant gluons

In this paper we define and study a matrix model describing the M-theory plane wave background with a single Horava-Witten domain wall. In the limit of infinite μ, the matrix model action becomes quadratic and we can identify the matrix hamiltonian with a regularized hamiltonian for hemispherical membranes that carry fermionic degrees of freedom on their boundaries. The number of fermionic degrees of freedom must be sixteen; this condition arises naturally in the framework of the matrix model. We can also prove the exact E 8 symmetry of the spectrum around the membrane vacua at infinite μ, which arises as a current algebra at level one just as in the heterotic string. We also find the full E 8 gauge multiplet as well as the multiple-gluon states, carried by collections of hemispherical membranes. Finally we discuss the dual description of the hemispherical membranes in terms of spherical fivebranes immersed in the domain wall; we identify the correct vacuum of the matrix model and make some preliminary remarks about comparison with the (1,0) superconformal field theory.
Extensions and applications of the Bohm criterion

The generalized Bohm criterion is revisited in the context of incorporating kinetic effects of the electron and ion distribution functions into the theory. The underlying assumptions and results of two different approaches are compared: the conventional 'kinetic Bohm criterion' and a fluid-moment hierarchy approach. The former is based on the asymptotic limit of an infinitely thin sheath (λD/l = 0), whereas the latter is based on a perturbative expansion of a sheath that is thin compared to the plasma (λD/l 1). Here λD is the Debye length, which characterizes the sheath length scale, and l is a measure of the plasma or presheath length scale. The consequences of these assumptions are discussed in terms of how they restrict the class of distribution functions to which the resulting criteria can be applied. Two examples are considered to provide concrete comparisons between the two approaches. The first is a Tonks–Langmuir model including a warm ion source (Robertson 2009 Phys. Plasmas 16 103503). This highlights a substantial difference between the conventional kinetic theory, which predicts slow ions dominate at the sheath edge, and the fluid moment approach, which predicts slow ions have little influence. The second example considers planar electrostatic probes biased near the plasma potential using model equations and particle-in-cell simulations. This demonstrates a situation where electron kinetic effects alter the Bohm criterion, leading to a subsonic ion flow at the sheath edge.
Learning Adaptive Language Interfaces through Decomposition

Our goal is to create an interactive natural language interface that efficiently and reliably learns from users to complete tasks in simulated robotics settings. We introduce a neural semantic parsing system that learns new high-level abstractions through decomposition: users interactively teach the system by breaking down high-level utterances describing novel behavior into low-level steps that it can understand. Unfortunately, existing methods either rely on grammars which parse sentences with limited flexibility, or neural sequence-to-sequence models that do not learn efficiently or reliably from individual examples. Our approach bridges this gap, demonstrating the flexibility of modern neural systems, as well as the one-shot reliable generalization of grammar-based methods. Our crowdsourced interactive experiments suggest that over time, users complete complex tasks more efficiently while using our system by leveraging what they just taught. At the same time, getting users to trust the system enough to be incentivized to teach high-level utterances is still an ongoing challenge. We end with a discussion of some of the obstacles we need to overcome to fully realize the potential of the interactive paradigm.
VerdictDB: Universalizing Approximate Query Processing

Despite 25 years of research in academia, approximate query processing (AQP) has had little industrial adoption. One of the major causes of this slow adoption is the reluctance of traditional vendors to make radical changes to their legacy codebases, and the preoccupation of newer vendors (e.g., SQL-on-Hadoop products) with implementing standard features. Additionally, the few AQP engines that are available are each tied to a specific platform and require users to completely abandon their existing databases---an unrealistic expectation given the infancy of the AQP technology. Therefore, we argue that a universal solution is needed: a database-agnostic approximation engine that will widen the reach of this emerging technology across various platforms. Our proposal, called VerdictDB, uses a middleware architecture that requires no changes to the backend database, and thus, can work with all off-the-shelf engines. Operating at the driver-level, VerdictDB intercepts analytical queries issued to the database and rewrites them into another query that, if executed by any standard relational engine, will yield sufficient information for computing an approximate answer. VerdictDB uses the returned result set to compute an approximate answer and error estimates, which are then passed on to the user or application. However, lack of access to the query execution layer introduces significant challenges in terms of generality, correctness, and efficiency. This paper shows how VerdictDB overcomes these challenges and delivers up to 171× speedup (18.45× on average) for a variety of existing engines, such as Impala, Spark SQL, and Amazon Redshift, while incurring less than 2.6% relative error. VerdictDB is open-sourced under Apache License.
KICKSTARTING REIONIZATION WITH THE FIRST BLACK HOLES: THE EFFECTS OF SECOND-ORDER PERTURBATION THEORY IN PRE-REIONIZATION VOLUMES

We explore structure formation in the dark ages (z ~ 30-6) using two well-known methods for initializing cosmological N-body simulations. Overall, both the Zel'dovich approximation and second-order Lagrangian perturbation theory (2LPT) are known to produce accurate present-day dark matter halo mass functions. However, since the 2LPT method drives more rapid evolution of dense regions, it increases the occurrence of rare massive objects—an effect that is most pronounced at high redshift. We find that 2LPT produces more halos that could harbor Population III stars and their black hole remnants, and they produce them earlier. Although the differences between the 2LPT and Zel'dovich approximation mass functions are nearly erased by z = 6, this small boost to the number and mass of black holes more than doubles the reionized volume of the early universe. We discuss the implications for reionization and massive black hole growth.
Path sets in one-sided symbolic dynamics

Abstract Path sets are spaces of one-sided infinite symbol sequences associated to pointed graphs ( G , v 0 ) , which are edge-labeled directed graphs with a distinguished vertex v 0 . Such sets arise naturally as address labels in geometric fractal constructions and in other contexts. The resulting set of symbol sequences need not be closed under the one-sided shift. This paper establishes basic properties of the structure and symbolic dynamics of path sets, and shows that they are a strict generalization of one-sided sofic shifts.
A theorem on multiplicative cell attachments with an application to Ravenel’s X ( n ) spectra

We show that the homotopy groups of a connective $$\mathbb {E}_k$$ -ring spectrum with an $$\mathbb {E}_k$$ -cell attached along a class $$\alpha $$ in degree n are isomorphic to the homotopy groups of the cofiber of the self-map associated to $$\alpha $$ through degree 2n. Using this, we prove that the $$2n-1$$ st homotopy groups of Ravenel’s X(n) spectra are cyclic for all n. This further implies that, after localizing at a prime, $$X(n+1)$$ is homotopically unique as the $$\mathbb {E}_1-X(n)$$ -algebra with homotopy groups in degree $$2n-1$$ killed by an $$\mathbb {E}_1$$ -cell. Lastly, we prove analogous theorems for a sequence of $$\mathbb {E}_k$$ -ring Thom spectra, for each odd k, which are formally similar to Ravenel’s X(n) spectra and whose colimit is also MU.
Response Functions for a Granular Fluid

The response of an isolated granular fluid to small perturbations of the hydrodynamic fields is considered. The corresponding linear response functions are identified in terms of a formal solution to the Liouville equation including the effects of the cooling reference state. These functions are evaluated exactly in the asymptotic long wavelength limit and shown to represent hydrodynamic modes. More generally, the linear granular Navier-Stokes equations for the response functions and related Langevin equations are obtained from an extension of Mori’s identity. The resulting Green-Kubo expressions for transport coefficients are compared and contrasted with those for a molecular fluid. Next the response functions are described in terms of an effective dynamics in the single particle phase space. A closed linear kinetic equation is obtained formally in terms of a linear two particle functional. This closure is evaluated for two examples: a short time Markovian approximation, and a low density expansion on length and time scales of the mean free time and mean free path. The former is a generalization of the revised Enskog kinetic theory to include velocity correlations. The latter is an extension of the Boltzmann equation to include the effects of recollisions (rings) among the particles.
Detection of Extraplanar Diffuse Ionized Gas in M83

We present the first kinematic study of extraplanar diffuse ionized gas (eDIG) in the nearby, face-on disk galaxy M83 using optical emission-line spectroscopy from the Robert Stobie Spectrograph on the Southern African Large Telescope. We use a Markov Chain Monte Carlo method to decompose the [NII]$\lambda\lambda$6548, 6583, H$\alpha$, and [SII]$\lambda\lambda$6717, 6731 emission lines into HII region and diffuse ionized gas emission. Extraplanar, diffuse gas is distinguished by its emission-line ratios ([NII]$\lambda$6583/H$\alpha \gtrsim 1.0$) and its rotational velocity lag with respect to the disk ($\Delta v = -24$ km/s in projection). With interesting implications for isotropy, the velocity dispersion of the diffuse gas, $\sigma = 96$ km/s, is a factor of a few higher in M83 than in the Milky Way and nearby, edge-on disk galaxies. The turbulent pressure gradient is sufficient to support the eDIG layer in dynamical equilibrium at an electron scale height of $h_{z} = 1$ kpc. However, this dynamical equilibrium model must be finely tuned to reproduce the rotational velocity lag. There is evidence of local bulk flows near star-forming regions in the disk, suggesting that the dynamical state of the gas may be intermediate between a dynamical equilibrium and a galactic fountain flow. As one of the first efforts to study eDIG kinematics in a face-on galaxy, this study demonstrates the feasibility of characterizing the radial distribution, bulk velocities, and vertical velocity dispersions in low-inclination systems.
Hubble Space Telescope Imaging of the Ultracompact Blue Dwarf Galaxy HS 0822+3542: An Assembling Galaxy in a Local Void?

We present deep U-band, narrow V-band, and I-band images and photometry of the ultracompact blue dwarf galaxy HS 0822+3542 obtained with the Advanced Camera for Surveys/High Resolution Channel of the Hubble Space Telescope. This object is also extremely metal-poor [12 + log(O/H) = 7.45] and resides in a nearby void. The images resolve it into two physically separate components that were previously described as star clusters in a single galaxy. The primary component is only ~100 pc in maximum extent and consists of a starburst region surrounded by a ringlike structure of relatively redder stars. The secondary component is ~50 pc in size and lies at a projected distance of ~80 pc away from the primary, and is also actively star-forming. We estimate masses of ~107 and ~106 M☉ for the two components based on their luminosities, with an associated dynamical timescale for the system of a few megayears. This timescale and the structure of the components suggest that a collision between them triggered their starbursts. The spectral energy distributions of both components can be fitted by the combination of a recent (a few megayears old) starburst and an evolved (several gigayears old) underlying stellar population, similar to larger blue compact dwarf galaxies. This indicates that despite its metal deficiency, the object is not forming its first generation of stars. However, the small sizes and masses of the two components suggest that HS 0822+3542 represents a dwarf galaxy in the process of assembling from clumps of stars intermediate in size between globular clusters and objects previously classified as galaxies. Its relatively high ratio of neutral gas mass to stellar mass (~1) and high specific star formation rate, log(SFR/M☉) -9.2, also suggest that it is still converting much of its gas to stars.
Test map characterizations of local properties of fundamental groups

Local properties of the fundamental group of a path-connected topological space can pose obstructions to the applicability of covering space theory. A generalized covering map is a generalization o...
On the relative Galois module structure of rings of integers in tame extensions

Let $F$ be a number field with ring of integers $O_F$ and let $G$ be a finite group. We describe an approach to the study of the set of realisable classes in the locally free class group $Cl(O_FG)$ of $O_FG$ that involves applying the work of the second-named author in the context of relative algebraic $K$ theory. When $G$ is of odd order, we show (subject to certain conditions) that the set of realisable classes is a subgroup of $Cl(O_FG)$. This may be viewed as being a partial analogue of a classical theorem of Shafarevich on the inverse Galois problem for soluble groups in the setting of Galois module theory.
Inverse scattering transform for two-level systems with nonzero background

We formulate the inverse scattering transform for the scalar Maxwell-Bloch system of equations describing the resonant interaction of light and active optical media in the case when the light intensity does not vanish at infinity. We show that pure background states in general do not exist with a nonzero background field. We then use the formalism to compute explicitly the soliton solutions of this system. We discuss the initial population of atoms and show that the pure soliton solutions do not correspond to a pure state initially. We obtain a representation for the soliton solutions in determinant form and explicitly write down the one-soliton solutions. We next derive periodic solutions and rational solutions from the one-soliton solutions. We then analyze the properties of these solutions, including discussion of the sharp-line and small-amplitude limits, and thereafter show that the two limits do not commute. Finally, we investigate the behavior of general solutions, showing that solutions are stable (i.e., the radiative parts of solutions decay) only when initially atoms in the ground state dominate, i.e., initial population inversion is negative.We formulate the inverse scattering transform for the scalar Maxwell-Bloch system of equations describing the resonant interaction of light and active optical media in the case when the light intensity does not vanish at infinity. We show that pure background states in general do not exist with a nonzero background field. We then use the formalism to compute explicitly the soliton solutions of this system. We discuss the initial population of atoms and show that the pure soliton solutions do not correspond to a pure state initially. We obtain a representation for the soliton solutions in determinant form and explicitly write down the one-soliton solutions. We next derive periodic solutions and rational solutions from the one-soliton solutions. We then analyze the properties of these solutions, including discussion of the sharp-line and small-amplitude limits, and thereafter show that the two limits do not commute. Finally, we investigate the behavior of general solutions, showing that solutions are stable...
Photochemical Oxygen in Non-1-bar CO2 Atmospheres of Terrestrial Exoplanets

Atmospheric chemistry models have shown that molecular oxygen can build up in CO_2-dominated atmospheres on potentially habitable exoplanets without input of life. Existing models typically assume a surface pressure of 1 bar. Here we present model scenarios of CO_2-dominated atmospheres with the surface pressure ranging from 0.1 to 10 bars, while keeping the surface temperature at 288 K. We use a one-dimensional photochemistry model to calculate the abundance of O_2 and other key species, for outgassing rates ranging from a Venus-like volcanic activity up to 20 times Earth-like activity. The model maintains the redox balance of the atmosphere and the ocean, and includes the pressure dependency of outgassing on the surface pressure. Our calculations show that the surface pressure is a controlling parameter in the photochemical stability and oxygen buildup of CO_2-dominated atmospheres. The mixing ratio of O_2 monotonically decreases as the surface pressure increases at very high outgassing rates, whereas it increases as the surface pressure increases at lower-than-Earth outgassing rates. Abiotic O_2 can only build up to the detectable level, defined as 10^(−3) in volume mixing ratio, in 10-bar atmospheres with the Venus-like volcanic activity rate and the reduced outgassing rate of H_2 due to the high surface pressure. Our results support the search for biological activities and habitability via atmospheric O_2 on terrestrial planets in the habitable zone of Sun-like stars.
Reduction of cosmological data for the detection of time-varying dark energy density

We present a method for reducing cosmological data to constraints on the amplitudes of modes of the dark energy density as a function of redshift. The modes are chosen so that (1) one of them has constant density and (2) the others are non-zero only if there is time-variation in the dark energy density and (3) the amplitude errors for the time-varying modes are uncorrelated with each other. We apply our method to various combinations of three-year WMAP data, baryon acoustic oscillation data, the 'Gold' supernova data set, and the Supernova Legacy Survey data set. We find no significant evidence for a time-varying dark energy density or for non-zero mean curvature. Although by some measure the limits on four of the time-varying mode amplitudes are quite tight, they are consistent with the expectation that the dark energy density does not vary on timescales shorter than a Hubble time. Since we do not expect detectable time variation in these modes, our results should be viewed as a systematic error test which the data have passed. We discuss a procedure to identify modes with maximal signal-to-noise ratio.
Graph similarity drives zeolite diffusionless transformations and intergrowth.

Predicting and directing polymorphic transformations is a critical challenge in zeolite synthesis1–3. Interzeolite transformations enable selective crystallization4–7, but are often too complex to be designed by comparing crystal structures. Here, computational and theoretical tools are combined to both exhaustively data mine polymorphic transformations reported in the literature and analyse and explain interzeolite relations. It was found that crystallographic building units are weak predictors of topology interconversion and insufficient to explain intergrowth. By introducing a supercell-invariant metric that compares crystal structures using graph theory, we show that diffusionless (topotactic and reconstructive) transformations occur only between graph-similar pairs. Furthermore, all the known instances of intergrowth occur between either structurally similar or graph similar frameworks. We identify promising pairs to realize diffusionless transformations and intergrowth, with hundreds of low-distance pairs identified among known zeolites, and thousands of hypothetical frameworks connected to known zeolite counterparts. The theory may enable the understanding and control of zeolite polymorphism. Zeolites are industrially useful catalysts, but their synthesis is poorly understood and many predicted structures remain unsynthesized. Machine learning and graph theory are used respectively to mine the literature on zeolite transformations and to predict similar zeolite pairs that may easily be transformed into each other.
Dynamical Formation of Close Binaries in Globular Clusters: Cataclysmic Variables

We answer the long-standing question of which production mechanism is responsible for the cataclysmic variables (CVs) in globular clusters. Arguments have been given that range from mostly primordial presence to a significant contribution of later dynamical formation in close stellar encounters. We conclude, based on a thorough analysis of a homogeneous Chandra data set, that the majority of CVs in dense globular clusters have a dynamical origin.
The Centrally Symmetric V-States for Active Scalar Equations. Two-Dimensional Euler with Cut-Off

We consider the family of active scalar equations on the plane and study the dynamics of two centrally symmetric patches. We focus on the two-dimensional Euler equation written in the vorticity form and consider its truncated version. For this model, a non-linear and non-local evolution equation is studied and a family of stationary solutions \({\{y(x,\lambda)\}, x\in [-1,1], \lambda\in (0,\lambda_0)}\) is found. For these functions, we have \({y(x,\lambda)\in C^\infty(-1,1)}\) and \({\|y(x,\lambda)-|x|\|_{C[-1,1]}\to 0, \,\,\lambda\to 0}\) . The relation to the V-states observed numerically in Wu et al. (J Comput Phys 53:1–42, 1984), Cerretelli and Williamson (J Fluid Mech 493:219–229, 2003) is discussed.
Gauge Fixing Identity in the Background Field Method of QCD in Pure Gauge

In this paper we derive a gauge fixing identity by varying the covariant gauge fixing term in in the background field method of QCD in pure gauge. Using this gauge fixing identity, we establish a relation between in QCD and in background field method of QCD in pure gauge. We show the validity of this gauge fixing identity, in general noncovariant and general Coulomb gauge fixings respectively. This gauge fixing identity is used to prove factorization theorem in QCD at high energy colliders and in nonequilibrium QCD at high energy heavy-ion colliders.
The Einstein–Podolsky–Rosen State Maximally Violates Bell's Inequalities

In their well-known argument against the completeness of quantum theory, Einstein, Podolsky, and Rosen (EPR) made use of a state that strictly correlates the positions and momenta of two particles. We prove the existence and uniqueness of the EPR state as a normalized, positive linear functional of the Weyl algebra for two degrees of freedom. We then show that the EPR state maximally violates Bell's inequalities.