cssi/SciSciGPT-SciSciNet huggingface dataset:
Spin Echo Studies on Cellular Water

HIGH resolution nuclear magnetic resonance (NMR) studies on rat skeletal muscle have recently shown that cellular water produces an absorption line almost ten times as broad as the line width of pure water1. This suggests that these water molecules are at least partly bounded such that the proton correlation time is increased. Similar observations have also been made for deuterated water in skeletal muscle2 and for H2O in other tissues3–5. Our results further substantiate the notion that ordered water exists in biological tissue and rules out several criticisms of this interpretation.
Minimum Violation Control Synthesis on Cyber-Physical Systems under Attacks

Cyber-physical systems are conducting increasingly complex tasks, which are often modeled using formal languages such as temporal logic. The system's ability to perform the required tasks can be curtailed by malicious adversaries that mount intelligent attacks. At present, however, synthesis in the presence of such attacks has received limited research attention. In particular, the problem of synthesizing a controller when the required specifications cannot be satisfied completely due to adversarial attacks has not been studied. In this paper, we focus on the minimum violation control synthesis problem under linear temporal logic constraints of a stochastic finite state discrete-time system with the presence of an adversary. A minimum violation control strategy is one that satisfies the most important tasks defined by the user while violating the less important ones. We model the interaction between the controller and adversary using a concurrent Stackelberg game and present a nonlinear programming problem to formulate and solve for the optimal control policy. To reduce the computation effort, we develop a heuristic algorithm that solves the problem efficiently and demonstrate our proposed approach using a numerical case study.
Canonical endomorphism field on a Lie algebra

We show that every Lie algebra is equipped with a natural (1; 1)-variant tensor eld, the \canonical endomorphism eld", determined by the Lie structure, and satisfying a certain Nijenhuis bracket condition. This observation may be considered as complementary to the Kirillov-Kostant-Souriau theorem on symplectic geometry of coadjoint orbits. We show its relevance for classical mechanics, in particular for Lax equations. We show that the space of Lax vector elds is closed under Lie bracket and we introduce a new bracket for vector elds on a Lie algebra. This bracket de nes a new Lie structure on the space of vector elds.
NO HEAVY-ELEMENT DISPERSION IN THE GLOBULAR CLUSTER M92*

Although there have been recent claims that there is a large dispersion in the abundances of the heavy neutron capture elements in the old Galactic globular cluster M92, we show that the measured dispersion for the absolute abundances of four of the rare earth elements within a sample of 12 luminous red giants in M92 (≤0.07 dex) does not exceed the relevant sources of uncertainty. As expected from previous studies, the heavy elements show the signature of the r-process. Their abundance ratios are essentially identical to those of M30, another nearby globular cluster of similar metallicity.
Perfectoid multiplier/test ideals in regular rings and bounds on symbolic powers

Using perfectoid algebras we introduce a mixed characteristic analog of the multiplier ideal, respectively test ideal, from characteristic zero, respectively $$p > 0$$ , in the case of a regular ambient ring. We prove several properties about this ideal such as subadditivity. We then use these techniques to derive a uniform bound on the growth of symbolic powers of radical ideals in all excellent regular rings. The analogous result was shown in equal characteristic by Ein–Lazarsfeld–Smith and Hochster–Huneke.
The Distribution of Atomic Hydrogen around Two Irregular Galaxies

We present radio interferometric observations of two irregular galaxies that were candidates for having unusually extended H I emission. The galaxies, UGC 199 and DDO 26, otherwise appeared to be normal, low-luminosity systems with modest star formation rates. To a detection limit of (2–3) × 1019 cm-2 at a resolution of about 50'', however, the H I around neither galaxy is unusually extended compared with other irregular galaxies. The H I around UGC 199 appears as a regular, symmetric distribution with regular rotation and a maximum rotation speed of about 80 km s-1. By contrast, the H I around DDO 26 shows a concentration into two blobs with an arm in the outer parts to the northwest and some additional emission to the northwest of that. The kinematical major axis is approximately 75° from the H I and optical morphological axis, which is unusual for Im galaxies. In addition the velocity field in the outer parts of the galaxy is messy, and the velocity profiles at the two H I peaks are broad. We suggest that DDO 26 has been perturbed externally or may be two dwarfs in the process of merging.
Error analysis of moment-based modal wavefront sensing

The shape of a focus-modulated point spread function (PSF) is used as a quick visual assessment tool of aberration modes in the PSF. Further analysis in terms of shape moments can permit quantifying the modal coefficients with an accuracy comparable to that of typical wavefront sensors. In this Letter, the error of the moment-based wavefront sensing is analytically described in terms of the pixelation and photon/readout noise. All components highly depend on the (unknown) PSF shape but can be estimated from the measured PSF sampled at a reasonable spatial resolution and photon count. Numerical simulations verified that the models consistently predicted the behavior of the modal estimation error of the moment-based wavefront sensing.
RGB2LIDAR: Towards Solving Large-Scale Cross-Modal Visual Localization

We study an important, yet largely unexplored problem of large-scale cross-modal visual localization by matching ground RGB images to a geo-referenced aerial LIDAR 3D point cloud (rendered as depth images). Prior works were demonstrated on small datasets and did not lend themselves to scaling up for large-scale applications. To enable large-scale evaluation, we introduce a new dataset containing over 550K pairs (covering 143 km2 area) of RGB and aerial LIDAR depth images. We propose a novel joint embedding based method that effectively combines the appearance and semantic cues from both modalities to handle drastic cross-modal variations. Experiments on the proposed dataset show that our model achieves a strong result of a median rank of 5 in matching across a large test set of 50K location pairs collected from a 14km^2 area. This represents a significant advancement over prior works in performance and scale. We conclude with qualitative results to highlight the challenging nature of this task and the benefits of the proposed model. Our work provides a foundation for further research in cross-modal visual localization.
SIC-POVMs and Compatibility among Quantum States

An unexpected connection exists between compatibility criteria for quantum states and Symmetric Informationally Complete quantum measurements (SIC-POVMs). Beginning with Caves, Fuchs and Schack’s "Conditions for compatibility of quantum state assignments", I show that a qutrit SIC-POVM studied in other contexts enjoys additional interesting properties. Compatibility criteria provide a new way to understand the relationship between SIC-POVMs and mutually unbiased bases, as calculations in the SIC representation of quantum states make clear. This, in turn, illuminates the resources necessary for magic-state quantum computation, and why hidden-variable models fail to capture the vitality of quantum mechanics.
Perturbations and Quantum Relaxation

We investigate whether small perturbations can cause relaxation to quantum equilibrium over very long timescales. We consider in particular a two-dimensional harmonic oscillator, which can serve as a model of a field mode on expanding space. We assume an initial wave function with small perturbations to the ground state. We present evidence that the trajectories are highly confined so as to preclude relaxation to equilibrium even over very long timescales. Cosmological implications are briefly discussed.
The center of some braid groups and the Farrell cohomology of certain pure mapping class groups

In this paper we first show that many braid groups of low genus surfaces have their centers as direct factors. We then give a description of centralizers and normalizers of prime order elements in pure mapping class groups of surfaces with spherical quotients using automorphism groups of fundamental groups of the quotient surfaces. As an application, we use these to show that the p ‐primary part of the Farrell cohomology groups of certain mapping class groups are elementary abelian groups. At the end we compute the p ‐primary part of the Farrell cohomology of a few pure mapping class groups. 20F36, 20J06
Searching for the 3.5 keV Line in the Deep Fields with Chandra: the 10 Ms observations

In this paper we report a 3$\sigma$ detection of an emission line at $\sim$3.5 keV in the spectrum of the Cosmic X-ray Background using a total of $\sim$10 Ms Chandra observations towards the COSMOS Legacy and CDFS survey fields. The line is detected with an intensity is $8.8\ \pm\ {2.9}\times10^{-7}$ ph cm$^{-2}$s$^{-1}$. Based on our knowledge of $Chandra$, and the reported detection of the line by other instruments, an instrumental origin for the line remains unlikely. We cannot though rule out a statistical fluctuation and in that case the current data allows us to place a 3$\sigma$ upper limit at 0.8$\times$10$^{-6}$ ph cm$^{-2}$s$^{-1}$. We discuss the interpretation of this observed line in terms of the iron line background; S {\sc XVI} charge exchange as well as potentially from sterile neutrino decay. We note that our detection is consistent with previous measurements of this line toward the Galactic center, and can be modeled as the result of sterile neutrino decay from the Milky Way for the dark matter distribution modeled as an NFW profile. For this case, we estimate a mass m$_{\nu}\sim$7.01 keV and a mixing angle sin$^2$(2$\theta$)= 0.83--2.75 $\times 10^{-10}$. These derived values are in agreement with independent estimates from galaxy clusters; the Galactic center and M31.
The Host Galaxies of Gamma-ray Bursts. II. A Mass-metallicity Relation for Long-duration Gamma-ray Burst Host Galaxies

We present a statistically robust mass-metallicity relation for long-duration gamma-ray burst (LGRB) host galaxies at z < 1. By comparing the LGRB host mass-metallicity relation to samples representative of the general star-forming galaxy population, we conclude that LGRBs occur in host galaxies with lower metallicities than the general population, and that this trend extends to z ~ 1, with an average offset of –0.42 ± 0.18 from the M-Z relation for star-forming galaxies. Our sample in this work includes new spectroscopic data for six LGRB host galaxies obtained at the Keck and Magellan telescopes, as well as two new host galaxies from the literature. Combined with data from our previous work, this yields a total sample of six LGRB host galaxies at z < 0.3 and 10 host galaxies at 0.3 < z < 1. We have determined a number of interstellar medium properties for our host galaxies using optical emission-line diagnostics including metallicity, ionization parameter, young stellar population age, and star formation rate. Across our full sample of 16 LGRB hosts we find an average metallicity of log(O/H) + 12 = 8.4 ± 0.3. Notably, we also measure a comparatively high metallicity of log(O/H) + 12 = 8.83 ± 0.1 for the z = 0.296 host galaxy of GRB 050826. We also determine stellar masses (M ) for our LGRB host galaxy sample, finding a mean stellar mass of log(M /M ☉) = 9.25+0.19 –0.23.
First-principles multiway spectral partitioning of graphs

We consider the minimum-cut partitioning of a graph into more than two parts using spectral methods. While there exist well-established spectral algorithms for this problem that give good results, they have traditionally not been well motivated. Rather than being derived from first principles by minimizing graph cuts, they are typically presented without direct derivation and then proved after the fact to work. In this paper, we take a contrasting approach in which we start with a matrix formulation of the minimum cut problem and then show, via a relaxed optimization, how it can be mapped onto a spectral embedding defined by the leading eigenvectors of the graph Laplacian. The end result is an algorithm that is similar in spirit to, but different in detail from, previous spectral partitioning approaches. In tests of the algorithm we find that it outperforms previous approaches on certain particularly difficult partitioning problems.
States that “look the same” with respect to every basis in a mutually unbiased set

A complete set of mutually unbiased bases (MUBs) in a Hilbert space of dimension d defines a set of d + 1 orthogonal measurements. Relative to such a set, we define a MUB-balanced state to be a pure state for which the list of probabilities of the d outcomes of any of these measurements is independent of the choice of measurement, up to permutations. In this paper, we explicitly construct a MUB-balanced state for each prime power dimension d for which d = 3 (mod 4). These states have already been constructed by Appleby in unpublished notes, but our presentation here is different in that both the expression for the states themselves and the proof of MUB-balancedness are given in terms of the discrete Wigner function, rather than the density matrix or state vector. The discrete Wigner functions of these states are “rotationally symmetric” in a sense roughly analogous to the rotational symmetry of the energy eigenstates of a harmonic oscillator in the continuous two-dimensional phase space. Upon converting the Wigner function to a density matrix, we find that the states are expressible as real state vectors in the standard basis. We observe numerically that when d is large (and not a power of 3), a histogram of the components of such a state vector appears to form a semicircular distribution.
Measuring and modeling bipartite graphs with community structure

Network science is a powerful tool for analyzing complex systems in fields ranging from sociology to engineering to biology. This paper is focused on generative models of large-scale bipartite graphs, also known as two-way graphs or two-mode networks. We propose two generative models that can be easily tuned to reproduce the characteristics of real-world networks, not just qualitatively, but quantitatively. The characteristics we consider are the degree distributions and the metamorphosis coefficient. The metamorphosis coefficient, a bipartite analogue of the clustering coefficient, is the proportion of length-three paths that participate in length-four cycles. Having a high metamorphosis coefficient is a necessary condition for close-knit community structure. We define edge, node, and degreewise metamorphosis coefficients, enabling a more detailed understanding of the bipartite connectivity that is not explained by degree distribution alone. Our first model, bipartite Chung-Lu (CL), is able to reproduce real-world degree distributions, and our second model, bipartite block two-level Erdos-Renyi (BTER), reproduces both the degree distributions as well as the degreewise metamorphosis coefficients. We demonstrate the effectiveness of these models on several real-world data sets.
ON THE DISTRIBUTION OF PROTOSTAR MASSES

The distribution of protostar masses is studied for core-environment systems whose duration of infall follows a waiting-time distribution. Each core-environment system has a continuous density profile with no barrier to mass flow. The core is an isothermal sphere and the environment is a filament, a layer, or a uniform medium. The infall is terminated by gas dispersal due to outflows and turbulence. The distribution of infall durations is a declining exponential, the simplest waiting-time distribution. The resulting distribution of protostar masses closely resembles the initial mass function, provided the environment density is sufficiently high, and the distribution of initial core masses is sufficiently narrow. The high-mass tail of the mass function increases strongly with environment density and weakly with environment dimension. "Isolated" regions of low environment density form protostars of low mass from within the parent core. In contrast, "clustered" regions of high environment density form protostars of low mass from core gas, and protostars of high mass from core and environment gas.
An Analytic Model for Mass Transfer in Binaries with Arbitrary Eccentricity, with Applications to Triple-star Systems

Most studies of mass transfer in binary systems assume circular orbits at the onset of Roche lobe overflow. However, there are theoretical and observational indications that mass transfer could occur in eccentric orbits. In particular, eccentricity could be produced via sudden mass loss and velocity kicks during supernova explosions, or Lidov-Kozai (LK) oscillations in hierarchical triple systems, or, more generally, secular evolution in multiple-star systems. However, current analytic models of eccentric mass transfer are faced with the problem that they are only well defined in the limit of very high eccentricities, and break down for less eccentric and circular orbits. This provides a major obstacle to implementing such models in binary and higher-order population synthesis codes, which are useful tools for studying the long-term evolution of a large number of systems. Here, we present a new analytic model to describe the secular orbital evolution of binaries undergoing conservative mass transfer. The main improvement of our model is that the mass transfer rate is a smoothly varying function of orbital phase, rather than a delta function centered at periapsis. Consequently, our model is in principle valid for any eccentricity, thereby overcoming the main limitation of previous works. We implement our model in an easy-to-use and publicly available code that can be used as a basis for implementations of our model into population synthesis codes. We investigate the implications of our model in a number of applications with circular and eccentric binaries, and triples undergoing LK oscillations.
SPATIALLY RESOLVED CHEMISTRY IN NEARBY GALAXIES. II. THE NUCLEAR BAR IN MAFFEI 2

We present 2''-10'' imaging of 11 transitions from 9 molecular species across the nuclear bar in Maffei 2. The data were obtained with the BIMA and OVRO interferometers. The 10 detected transitions are compared with existing CO isotopologues, HCN, CS, and millimeter continuum data. Dramatic spatial variations among the mapped species are observed across the nuclear bar. A principal component analysis is performed to characterize correlations between the transitions, star formation, and molecular column density. The analysis reveals that HCN, HNC, HCO+, and 3 mm continuum are tightly correlated, indicating a direct connection to massive star formation. We find two main morphologically distinct chemical groups, CH3OH, SiO, and HNCO comprising the grain chemistry molecules, versus HCN, HNC, HCO+, and C2H, molecules strong in the presence of star formation. The grain chemistry molecules, HNCO, CH3OH, and SiO, trace hydrodynamical bar shocks. The near constancy of the HNCO/CH3OH, SiO/CH3OH, and SiO/HNCO ratios argues that shock properties are uniform across the nucleus. HCN/HCO+, HCN/HNC, HCN/CS, and HCN/CO ratios are explained primarily by variations in density. High HCO+/N2H+ ratios are correlated with the C2H line, suggesting that this ratio may be a powerful new dense photon-dominated region probe in external galaxies. C2H reveals a molecular outflow along the minor axis. The morphology and kinematics of the outflow are consistent with an outflow age of 6-7 Myr.
Searching for crystal-ice domains in amorphous ices

We employ classical molecular dynamics simulations to investigate the molecular-level structure of water during the isothermal compression of hexagonal ice ($\mathrm{I}h$) and low-density amorphous (LDA) ice at low temperatures. In both cases, the system transforms to high-density amorphous ice (HDA) via a first-order-like phase transition. We employ a sensitive local order metric (LOM) [F. Martelli et al., Phys. Rev. B 97, 064105 (2018)] that can discriminate among different crystalline and noncrystalline ice structures and is based on the positions of the oxygen atoms in the first- and/or second-hydration shell. Our results confirm that LDA and HDA are indeed amorphous, i.e., they lack polydispersed ice domains. Interestingly, HDA contains a small number of domains that are reminiscent of the unit cell of ice IV, although the hydrogen-bond network (HBN) of these domains differs from the HBN of ice IV. The presence of ice-IV-like domains provides some support to the hypothesis that HDA could be the result of a detour on the HBN rearrangement along the $\mathrm{I}h$-to-ice-IV pressure-induced transformation. Both nonequilibrium LDA-to-HDA and $\mathrm{I}h$-to-HDA transformations are two-step processes where a small distortion of the HBN first occurs at low pressures and then, a sudden, extensive rearrangement of hydrogen bonds at the corresponding transformation pressure follows. Interestingly, the $\mathrm{I}h$-to-HDA and LDA-to-HDA transformations occur when LDA and $\mathrm{I}h$ have similar local order, as quantified by the site-averaged LOMs. Since $\mathrm{I}h$ has a perfect tetrahedral HBN while LDA does not, it follows that higher pressures are needed to transform $\mathrm{I}h$ into HDA than that for the conversion of LDA to HDA. In correspondence with both first-order-like phase transitions, the samples are composed of a large HDA cluster that percolates within the $\mathrm{I}h/\mathrm{LDA}$ samples. Our results shed light on the debated structural properties of amorphous ices and indicate that the kinetics of the $\mathrm{I}h$-to-HDA and LDA-to-HDA transformations require an in-depth inspection of the underlying HBN. Such investigation is currently ongoing.
Feature Squeezing: Detecting Adversarial Examples in Deep Neural Networks.

Although deep neural networks (DNNs) have achieved great success in many tasks, they can often be fooled by \emph{adversarial examples} that are generated by adding small but purposeful distortions to natural examples. Previous studies to defend against adversarial examples mostly focused on refining the DNN models, but have either shown limited success or required expensive computation. We propose a new strategy, \emph{feature squeezing}, that can be used to harden DNN models by detecting adversarial examples. Feature squeezing reduces the search space available to an adversary by coalescing samples that correspond to many different feature vectors in the original space into a single sample. By comparing a DNN model's prediction on the original input with that on squeezed inputs, feature squeezing detects adversarial examples with high accuracy and few false positives. This paper explores two feature squeezing methods: reducing the color bit depth of each pixel and spatial smoothing. These simple strategies are inexpensive and complementary to other defenses, and can be combined in a joint detection framework to achieve high detection rates against state-of-the-art attacks.
The OSIRIS Lens-amplified Survey (OLAS). I. Dynamical Effects of Stellar Feedback in Low-mass Galaxies at z ∼ 2

Author(s): Hirtenstein, J; Jones, T; Wang, X; Wetzel, A; El-Badry, K; Hoag, A; Treu, T; Bradac, M; Morishita, T | Abstract: We introduce the OSIRIS Lens-Amplified Survey (OLAS), a kinematic survey of gravitationally lensed galaxies at cosmic noon taken with Keck adaptive optics. In this paper, we present spatially resolved spectroscopy and nebular emission kinematic maps for 17 star-forming galaxies with stellar masses 8 l log(M ∗/M o) l 9.8 and redshifts 1.2 l z l 2.3. OLAS is designed to probe the stellar mass (M ∗) and specific star formation rate (sSFR) range where simulations suggest that stellar feedback is most effective at driving gaseous outflows that create galaxy-wide potential fluctuations, which can generate dark matter cores. We compare our kinematic data with the trend among sSFR, M ∗, and Hα velocity dispersion, σ, from the Feedback In Realistic Environments (FIRE) simulations. Our observations reveal a correlation between sSFR and σ at fixed M ∗ that is similar to the trend predicted by simulations: feedback from star formation drives star-forming gas and newly formed stars into more dispersion-dominated orbits. The observed magnitude of this effect is in good agreement with the FIRE simulations, in which feedback alters the central density profiles of low-mass galaxies, converting dark matter cusps into cores over time. Our data support the scenario that stellar feedback drives gaseous outflows and potential fluctuations, which in turn drive dark matter core formation in dwarf galaxies.
A fast and efficient incremental approach toward dynamic community detection

Community detection is a discovery tool used by network scientists to analyze the structure of real-world networks. It seeks to identify natural divisions that may exist in the input networks that partition the vertices into coherent modules (or communities). While this problem space is rich with efficient algorithms and software, most of this literature caters to the static use-case where the underlying network does not change. However, many emerging real-world use-cases give rise to a need to incorporate dynamic graphs as inputs. In this paper, we present a fast and efficient incremental approach toward dynamic community detection. The key contribution is a generic technique called Δ-screening, which examines the most recent batch of changes made to an input graph and selects a subset of vertices to reevaluate for potential community (re)assignment. This technique can be incorporated into any of the community detection methods that use modularity as its objective function for clustering. For demonstration purposes, we incorporated the technique into two well-known community detection tools. Our experiments demonstrate that our new incremental approach is able to generate performance speedups without compromising on the output quality (despite its heuristic nature). For instance, on a real-world network with 63M temporal edges (over 12 time steps), our approach was able to complete in 1056 seconds, yielding a 3 × speedup over a baseline implementation. In addition to demonstrating the performance benefits, we also show how to use our approach to delineate appropriate intervals of temporal resolutions at which to analyze an input network.
(Dis)continuities of massless limits in spin-3/2-mediated interactions and cosmological supergravity

We extend to its spin-3/2 supersymmetric partner the very recent demonstration that the massless limit of massive spin-2 exchange amplitudes can be made continuous in background AdS spaces, in contrast to the known flat space discontinuities for both systems. In an AdS background, unlike spin-2 where the limit m→0 is the massless one, spin-3/2 “masslessness” requires m → √-Λ / 3, the supergravity value tuning the mass and cosmological constant that uniquely provides gauge invariance and two helicities. We find that continuity of the spin-3/2-mediated exchange amplitude can be regained in two “massless” limits m→0 and m → √-Λ/3; only the latter corresponds to cosmological supergravity.
Atmospheric Escape From TOI-700 d: Venus versus Earth Analogs

The recent discovery of an Earth-sized planet (TOI-700 d) in the habitable zone of an early-type M-dwarf by the Transiting Exoplanet Survey Satellite constitutes an important advance. In this Letter, we assess the feasibility of this planet to retain an atmosphere -- one of the chief ingredients for surface habitability -- over long timescales by employing state-of-the-art magnetohydrodynamic models to simulate the stellar wind and the associated rates of atmospheric escape. We take two major factors into consideration, namely, the planetary atmospheric composition and magnetic field. In all cases, we determine that the atmospheric ion escape rates are potentially a few orders of magnitude higher than the inner Solar system planets, but TOI-700 d is nevertheless capable of retaining a $1$ bar atmosphere over gigayear timescales for certain regions of the parameter space. The simulations show that the unmagnetized TOI-700 d with a 1 bar Earth-like atmosphere could be stripped away rather quickly ($<$ 1 gigayear), while the unmagnetized TOI-700 d with a 1 bar CO$_2$-dominated atmosphere could persist for many billions of years; we find that the magnetized Earth-like case falls in between these two scenarios. We also discuss the prospects for detecting radio emission of the planet (thereby constraining its magnetic field) and discerning the presence of an atmosphere.
Finitely based sets of 2-limited block-2-simple words

Let $${\mathfrak {A}}$$ be an alphabet and W be a set of words in the free monoid $${{\mathfrak {A}}}^*$$. Let S(W) denote the Rees quotient over the ideal of $${{\mathfrak {A}}}^*$$ consisting of all words that are not subwords of words in W. A set of words W is called finitely based if the monoid S(W) is finitely based. A word $$\mathbf{u}$$ is called 2-limited if each variable occurs in $$\mathbf{u}$$ at most twice. A block of a word $$\mathbf{u}$$ is a maximal subword of $$\mathbf{u}$$ that does not contain any linear variables. A word $$\mathbf{u}$$ is block-2-simple if each block of $$\mathbf{u}$$ involves at most two distinct variables. We provide an algorithm that recognizes finitely based sets of words among sets of 2-limited block-2-simple words. We also present new sufficient conditions under which a set of words is non-finitely based.
Switching ferromagnetic spins by an ultrafast laser pulse: Emergence of giant optical spin-orbit torque

Faster magnetic recording technology is indispensable to massive data storage and big data sciences. All-optical spin switching offers a possible solution, but at present it is limited to a handful of expensive and complex rare-earth ferrimagnets. The spin switching in more abundant ferromagnets may significantly expand the scope of all-optical spin switching. Here by studying 40000 ferromagnetic spins, we show that it is the optical spin-orbit torque that determines the course of spin switching in both ferromagnets and ferrimagnets. Spin switching occurs only if the effective spin angular momentum of each constituent in an alloy exceeds a critical value. Because of the strong exchange coupling, the spin switches much faster in ferromagnets than weakly coupled ferrimagnets. This establishes a paradigm for all-optical spin switching. The resultant magnetic field (65 T) is so big that it will significantly reduce high current in spintronics, thus representing the beginning of photospintronics.
Theoretical expectations for rare and forbidden tau decays

Given the experimental evidence for νμ − ντ oscillations, the existence of lepton flavor violation in τ decays is a theoretical certainty. In this brief review, I consider the connection between models of neutrino mass and the expected observability of some τ decays.
Relative Thom Spectra Via Operadic Kan Extensions

We show that a large number of Thom spectra, i.e. colimits of morphisms $BG\to BGL_1(\mathbb{S})$, can be obtained as iterated Thom spectra, i.e. colimits of morphisms $BG\to BGL_1(Mf)$ for some Thom spectrum $Mf$. This leads to a number of new relative Thom isomorphisms, e.g. $MU[6,\infty)\wedge_{MString} MU[6,\infty)\simeq MU[6,\infty)\wedge\mathbb{S}[B^3Spin]$. As an example of interest to chromatic homotopy theorists, we also show that Ravenel's $X(n)$ filtration of $MU$ is a tower of intermediate Thom spectra determined by a natural filtration of $BU$ by sub-bialagebras.
Mirage phenomena in superconducting quantum corrals

We investigate the local density of states and the order parameter structure inside an elliptic quantum corral on surfaces of isotropic and anisotropic superconductors. The Bogoliubov-de Gennes equations are solved in the presence of non-magnetic and magnetic impurities. We observe and discuss a variety of mirage and anti-mirage phenomena, which specifically reflect the nature of the superconducting pairing state.
Constraining the Speed of Sound inside Neutron Stars with Chiral Effective Field Theory Interactions and Observations

The dense matter equation of state (EOS) determines neutron star (NS) structure but can be calculated reliably only up to one to two times the nuclear saturation density, using accurate many-body methods that employ nuclear interactions from chiral effective field theory constrained by scattering data. In this work, we use physically motivated ansatzes for the speed of sound $c_S$ at high density to extend microscopic calculations of neutron-rich matter to the highest densities encountered in stable NS cores. We show how existing and expected astrophysical constraints on NS masses and radii from X-ray observations can constrain the speed of sound in the NS core. We confirm earlier expectations that $c_S$ is likely to violate the conformal limit of $c_S^2\leq c^2/3 $, possibly reaching values closer to the speed of light $c$ at a few times the nuclear saturation density, independent of the nuclear Hamiltonian. If QCD obeys the conformal limit, we conclude that the rapid increase of $c_S$ required to accommodate a $2 $ M$_\odot$ NS suggests a form of strongly interacting matter where a description in terms of nucleons will be unwieldy, even between one and two times the nuclear saturation density. For typical NSs with masses in the range $1.2-1.4~$ M$_\odot$, we find radii between $10$ and $14$ km, and the smallest possible radius of a $1.4$ M$_{\odot}$ NS consistent with constraints from nuclear physics and observations is $8.4$ km. We also discuss how future observations could constrain the EOS and guide theoretical developments in nuclear physics.
The Johnson Cokernel and the Enomoto-Satoh invariant

We study the cokernel of the Johnson homomorphism for the mapping class group of a surface with one boundary component. A graphical trace map simultaneously generalizing trace maps of Enomoto and Satoh and Conant, Kassabov and Vogtmann is given, and using technology from the author’s work with Kassabov and Vogtmann, this is is shown to detect a large family of representations which vastly generalizes series due to Morita and Enomoto and Satoh. The Enomoto‐Satoh trace is the rank-1 part of the new trace, and it is here that the new series of representations is found. The rank-2 part is also investigated, though a fuller investigation of the higher-rank case is deferred to another paper. 17B40; 20C15, 20F28
A quality improvement project to increase palliative care team involvement in pediatric oncology patients

Background Pediatric palliative care (PPC) for oncology patients improves quality of life and the likelihood of goal-concordant care. However, barriers to involvement exist. Objectives We aimed to increase days between PPC consult and death for patients with refractory cancer from a baseline median of 13.5 days to ≥30 days between March 2019 and March 2020. Methods Outcome measure was days from PPC consult to death; process measure was days from diagnosis to PPC consult. The project team surveyed oncologists to identify barriers. Plan-do-study-act cycles included establishing target diagnoses, offering education, standardizing documentation, and sending reminders. Results The 24-month baseline period included 30 patients who died and 25 newly diagnosed patients. The yearlong intervention period included six patients who died and 16 newly diagnosed patients. Interventions improved outcome and process measures. Targeted patients receiving PPC ≥30 days prior to death increased from 43% to 100%; median days from consult to death increased from 13.5 to 159.5. Targeted patients receiving PPC within 30 days of diagnosis increased from 28% to 63%; median days from diagnosis to consult decreased from 221.5 to 14. Of those without PPC consult ≤ 30 days after diagnosis, 17% had template documentation of the rationale. Conclusion Interventions utilized met the global aim, outcome, and process measures. Use of QI methodology empowered providers to involve PPC. Poor template use was a barrier to identifying further drivers. Future directions for this project relate to expanding the target list, creating long-term sustainability, formalizing standards, and surveying patients and families.
The theory of contractions of 2D 2nd order quantum superintegrable systems and its relation to the Askey scheme for hypergeometric orthogonal polynomials

We describe a contraction theory for 2nd order superintegrable systems, showing that all such systems in 2 dimensions are limiting cases of a single system: the generic 3-parameter potential on the 2-sphere, S9 in our listing. Analogously, all of the quadratic symmetry algebras of these systems can be obtained by a sequence of contractions starting from S9. By contracting function space realizations of irreducible representations of the S9 algebra (which give the structure equations for Racah/Wilson polynomials) to the other superintegrable systems one obtains the full Askey scheme of orthogonal hypergeometric polynomials.This relates the scheme directly to explicitly solvable quantum mechanical systems. Amazingly, all of these contractions of superintegrable systems with potential are uniquely induced by Wigner Lie algebra contractions of so(3, C) and e(2, C). The present paper concentrates on describing this intimate link between Lie algebra and superintegrable system contractions, with the detailed calculations presented elsewhere. Joint work with E. Kalnins, S. Post, E. Subag and R. Heinonen.
Seeking for toroidal event horizons from initially stationary BH configurations

We construct and evolve non-rotating vacuum initial data with a ring singularity, based on a simple extension of the standard Brill?Lindquist multiple BH initial data, and search for event horizons with spatial slices that are toroidal when the ring radius is sufficiently large. While evolutions of the ring singularity are not numerically feasible for large radii, we find some evidence, based on configurations of multiple BHs arranged in a ring, that this configuration leads to singular limit where the horizon width has zero size, possibly indicating the presence of a naked singularity, when the radius of the ring is sufficiently large. This is in agreement with previous studies that have found that there is no apparent horizon surrounding the ring singularity when the ring's radius is larger than about twice its mass.
Majorization: Here, There and Everywhere

The appearance of Marshall and Olkin’s 1979 book on inequalities with special emphasis on majorization generated a surge of interest in potential applications of majorization and Schur convexity in a broad spectrum of fields. After 25 years this continues to be the case. The present article presents a sampling of the diverse areas in which majorization has been found to be useful in the past 25 years.
A NEW X-RAY ANALYSIS OF THE OPEN CLUSTER BLANCO 1 USING WIDE-FIELD BVIc PHOTOMETRIC* AND PROPER MOTION SURVEYS

We perform a new analysis of the extant ROSAT and XMM-Newton X-ray surveys of the southern open cluster Blanco 1, utilizing new BVIc photometric and proper motion data sets. In our study, we match optical counterparts to 47 X-ray sources associated with Blanco 1 cluster members, six of which were listed in previous X-ray studies as cluster nonmembers. Our new catalog of optical counterparts to X-ray sources clearly traces out the Blanco 1 main sequence in a color-magnitude diagram, extending from early G to mid-M spectral types. Additionally, we derive new X-ray luminosities as well as ratios of X-ray to bolometric luminosities for confirmed cluster members. We compare these X-ray properties to other young open clusters, including the coeval Pleiades cluster, to investigate the relationship between age and X-ray activity. We find that stars in Blanco 1 generally exhibit X-ray properties similar to those of other open clusters, namely increasing Lx /L bol with reducing mass for earlier-type stars, and a saturation limit of Lx /L bol at a magnitude of 10–3 for stars with V – Ic 1.25. More generally, the X-ray detected stars in Blanco 1 have X-ray emission magnitudes that agree with the overall trends seen in the other young clusters. We observe that X-ray emission decays as a function of age and the rate of this decay is mass dependent. Specifically, for higher mass stars, the trend is Skumanich like (i.e., Lx /L bol age–1/2); however, as one goes to lower masses the magnitude of X-ray emission becomes less of a function of age. In fact, for the lowest mass stars (M-type), there is no observable reduction in X-ray production during the first ~1 Gyr of their lives. However, due to a lack of sensitivity to low X-ray fluxes, there may exist M-type stars that have less than saturated levels of X-ray flux which are not included in our study. In a direct comparison of Blanco 1 to the Pleiades open cluster, members of both clusters have similar X-ray characteristics; however, there does appear to be some discrepancies in the distribution of Lx /L bol as a function of color that may be related to scatter seen in the Pleiades CMD. Moreover, previous comparisons of this nature for Blanco 1 were not possible due to the reliance on photographic photometry. This is where the power of precise, homogeneous, and standardized CCD photometry allows for a high fidelity, detailed study of the X-ray properties of stars in Blanco 1, as well as a thorough comparison of Blanco 1 to other well-studied open clusters.
BOLOMETRIC AND UV LIGHT CURVES OF CORE-COLLAPSE SUPERNOVAE

The Swift UV-Optical Telescope (UVOT) has been observing core-collapse supernovae (CCSNe) of all subtypes in the UV and optical since 2005. Here we present 50 CCSNe observed with the Swift UVOT, analyzing their UV properties and behavior. Where we have multiple UV detections in all three UV filters (λ {sub c} = 1928-2600 A), we generate early time bolometric light curves, analyze the properties of these light curves and the UV contribution to them, and derive empirical corrections for the UV-flux contribution to optical-IR based bolometric light curves.
Solving Local Linear Systems with Boundary Conditions Using Heat Kernel Pagerank

We present an efficient algorithm for solving local linear systems with a boundary condition using the Green’s function of a connected induced subgraph related to the system. We introduce the method of using the Dirichlet heat kernel pagerank1 vector to approximate local solutions to linear systems in the graph Laplacian, satisfying given boundary conditions over a particular subset of vertices. With an efficient algorithm for approximating Dirichlet heat kernel pagerank, our Local Linear Solver algorithm computes an approximate local solution with multiplicative and additive error e by performing O(e−5s3log (s3e−1)log n) random walk steps, where n is the number of vertices in the full graph, and s is the size of the local system on the induced subgraph.
Parameter optimization in differential geometry based solvation models

Differential geometry (DG) based solvation models are a new class of variational implicit solvent approaches that are able to avoid unphysical solvent-solute boundary definitions and associated geometric singularities, and dynamically couple polar and non-polar interactions in a self-consistent framework. Our earlier study indicates that DG based non-polar solvation model outperforms other methods in non-polar solvation energy predictions. However, the DG based full solvation model has not shown its superiority in solvation analysis, due to its difficulty in parametrization, which must ensure the stability of the solution of strongly coupled nonlinear Laplace-Beltrami and Poisson-Boltzmann equations. In this work, we introduce new parameter learning algorithms based on perturbation and convex optimization theories to stabilize the numerical solution and thus achieve an optimal parametrization of the DG based solvation models. An interesting feature of the present DG based solvation model is that it provides accurate solvation free energy predictions for both polar and non-polar molecules in a unified formulation. Extensive numerical experiment demonstrates that the present DG based solvation model delivers some of the most accurate predictions of the solvation free energies for a large number of molecules.
The Dirac Sea

We give an alternate definition of the free Dirac field featuring an explicit construction of the Dirac sea. The treatment employs a semi-infinite wedge product of Hilbert spaces. We also show that the construction is equivalent to the standard Fock space construction.
Direct writing of heterostructures in single atomically precise graphene nanoribbons

Precision control of interfacial structures and electronic properties is the key to the realization of functional heterostructures. Here, utilizing the scanning tunneling microscope (STM) both as a manipulation and characterization tool, we demonstrate the fabrication of a heterostructure in a single atomically precise graphene nanoribbon (GNR) and report its electronic properties. The heterostructure is made of a seven-carbon-wide armchair GNR and a lower band gap intermediate ribbon synthesized bottom-up from a molecular precursor on an Au substrate. The short GNR segments are directly written in the ribbon with a STM tip to form atomic precision intraribbon heterostructures. Based on STM studies combined with density functional theory calculations, we show that the heterostructure has a type-I band alignment, with manifestations of quantum confinement and orbital hybridization. Our finding demonstrates a feasible strategy to create a double-barrier quantum dot structure with atomic precision for functionalities, such as negative differential resistance devices in GNR-based nanoelectronics.
Cup products, the Johnson homomorphism and surface bundles over surfaces with multiple fiberings

Let Σg→E→Σh be a surface bundle over a surface with monodromy representation ρ:π1Σh→ Mod(Σg) contained in the Torelli group ℐg. We express the cup product structure in H∗(E,ℤ) in terms of the Johnson homomorphism τ:ℐg→∧3(H1(Σg,ℤ))∕H1(Σg,ℤ). This is applied to the question of obtaining an upper bound on the maximal n such that p1:E→Σh1,…,pn:E→Σhn are fibering maps realizing E as the total space of a surface bundle over a surface in n distinct ways. We prove that any nontrivial surface bundle over a surface with monodromy contained in the Johnson kernel Kg fibers in a unique way.
Quark coalescence with quark number conservation and the effect on quark–hadron scaling

We develop a new formulation of the quark coalescence model by including the quark number conservation in order to describe the hadronization of the bulk of the quark–gluon plasma. The scalings between hadron and quark phase space distributions are shown to depend on the transverse momentum. For hard quarks, our general scalings reproduce the usual quadratic scaling relation for mesons and the cubic scaling relation for baryons. For softer quarks, however, the inclusion of the quark number conservation leads to a linear scaling for the hadron species that dominates the quark number of each flavor, while the scalings of non-dominant hadrons depend on the coalescence dynamics. For charm mesons, we find that the distribution of soft D mesons does not depend on the light quark distribution but the distribution of soft J/ψ mesons is inversely correlated to the light quark distribution.