cssi/SciSciGPT-SciSciNet huggingface dataset:
Dynamic Regulation of JAK-STAT Signaling Through the Prolactin Receptor Predicted by Computational Modeling

The expansion of insulin-producing beta cells during pregnancy is critical to maintain glucose homeostasis in the face of increasing insulin resistance. Prolactin receptor (PRLR) signaling is one of the primary mediators of beta cell expansion during pregnancy, and loss of PRLR signaling results in reduced beta cell mass and gestational diabetes. Harnessing the proliferative potential of prolactin signaling to expand beta cell mass outside of the context of pregnancy requires quantitative understanding of the signaling at the molecular level. A mechanistic computational model was constructed to describe prolactin-mediated JAK-STAT signaling in pancreatic beta cells. The effect of different regulatory modules was explored through ensemble modeling. A Bayesian approach for likelihood estimation was used to fit the model to experimental data from the literature. Including receptor upregulation, with either inhibition by SOCS proteins, receptor internalization, or both, allowed the model to match experimental results for INS-1 cells treated with prolactin. The model predicts that faster dimerization and nuclear import rates of STAT5B compared to STAT5A can explain the higher STAT5B nuclear translocation. The model was used to predict the dose response of STAT5B translocation in rat primary beta cells treated with prolactin and reveal possible strategies to modulate STAT5 signaling. JAK-STAT signaling must be tightly controlled to obtain the biphasic response in STAT5 activation seen experimentally. Receptor up-regulation, combined with SOCS inhibition, receptor internalization, or both is required to match experimental data. Modulating reactions upstream in the signaling can enhance STAT5 activation to increase beta cell survival.
A weak Weyl’s law on compact metric measure spaces

The well known Weyl’s Law (Weyl’s asymptotic formula) gives an approximation to the number $${\mathcal {N}}_{\omega }$$ of eigenvalues (counted with multiplicities) on a large interval $$[0, \omega ]$$ of the Laplace–Beltrami operator on a compact Riemannian manifold $$\mathbf{M}$$ . In this paper we prove a kind of a weak version of the Weyl’s law on certain compact metric measure spaces $$\mathbf{X}$$ which are equipped with a self-adjoint non-negative operator $${\mathcal {L}}$$ acting in $$L_{2}(\mathbf{X})$$ . Roughly speaking, we show that if a certain Poincare inequality holds then $${\mathcal {N}}_{\omega }$$ is controlled by the cardinality of an appropriate cover $${\mathcal {B}}_{\omega ^{-1/2}}=\{B(x_{j},\omega ^{-1/2})\},\quad x_{j}\in \mathbf{X},$$ of $$\mathbf{X}$$ by balls of radius $$\omega ^{-1/2}$$ . Moreover, an opposite inequality holds if the heat kernel that corresponds to $${\mathcal {L}}$$ satisfies short time Gaussian estimates. It is known that in the case of the so-called strongly local regular with a complete intrinsic metric Dirichlet spaces the Poincare inequality holds iff the corresponding heat kernel satisfies short time Gaussian estimates. Thus for such spaces one obtains that $${\mathcal {N}}_{\omega }$$ is essentially equivalent to the cardinality of a cover $${\mathcal {B}}_{\omega ^{-1/2}}$$ .
Role of SARS-CoV-2 in Altering the RNA-Binding Protein and miRNA-Directed Post-Transcriptional Regulatory Networks in Humans

The outbreak of a novel coronavirus SARS-CoV-2 responsible for the COVID-19 pandemic has caused a worldwide public health emergency. Due to the constantly evolving nature of the coronaviruses, SARS-CoV-2-mediated alterations on post-transcriptional gene regulations across human tissues remain elusive. In this study, we analyzed publicly available genomic datasets to systematically dissect the crosstalk and dysregulation of the human post-transcriptional regulatory networks governed by RNA-binding proteins (RBPs) and micro-RNAs (miRs) due to SARS-CoV-2 infection. We uncovered that 13 out of 29 SARS-CoV-2-encoded proteins directly interacted with 51 human RBPs, of which the majority of them were abundantly expressed in gonadal tissues and immune cells. We further performed a functional analysis of differentially expressed genes in mock-treated versus SARS-CoV-2-infected lung cells that revealed enrichment for the immune response, cytokine-mediated signaling, and metabolism-associated genes. This study also characterized the alternative splicing events in SARS-CoV-2-infected cells compared to the control, demonstrating that skipped exons and mutually exclusive exons were the most abundant events that potentially contributed to differential outcomes in response to the viral infection. A motif enrichment analysis on the RNA genomic sequence of SARS-CoV-2 clearly revealed the enrichment for RBPs such as SRSFs, PCBPs, ELAVs, and HNRNPs, suggesting the sponging of RBPs by the SARS-CoV-2 genome. A similar analysis to study the interactions of miRs with SARS-CoV-2 revealed functionally important miRs that were highly expressed in immune cells, suggesting that these interactions may contribute to the progression of the viral infection and modulate the host immune response across other human tissues. Given the need to understand the interactions of SARS-CoV-2 with key post-transcriptional regulators in the human genome, this study provided a systematic computational analysis to dissect the role of dysregulated post-transcriptional regulatory networks controlled by RBPs and miRs across tissue types during a SARS-CoV-2 infection.
Capacitive-Mediated Strong Coupling in Terahertz Plasmonic Metafilms

We report terahertz metafilms designed to strongly couple hybridized lattice and fundamental dipole modes to form polaritons. By altering the metafilm's capacitance, the coupling strength of the dipole-lattice coupling is tuned from weak to strong.
Ford Multi-AV Seasonal Dataset:

This article presents a challenging multi-agent seasonal dataset collected by a fleet of Ford autonomous vehicles (AVs) at different days and times during 2017–2018. The vehicles traversed an avera...
Video game level repair via mixed integer linear programming

Recent advancements in procedural content generation via machine learning enable the generation of video-game levels that are aesthetically similar to human-authored examples. However, the generated levels are often unplayable without additional editing. We propose a “generate-then-repair” framework for automatic generation of playable levels adhering to specific styles. The framework constructs levels using a generative adversarial network (GAN) trained with human-authored examples and repairs them using a mixed-integer linear program (MIP) with playability constraints. A key component of the framework is computing minimum cost edits between the GAN generated level and the solution of the MIP solver, which we cast as a minimum cost network flow problem. Results show that the proposed framework generates a diverse range of playable levels, that capture the spatial relationships between objects exhibited in the human-authored levels.
What is the effect of pharmacological treatment for attention-deficit/hyperactivity disorder in children with comorbid tic disorders? A Cochrane Review summary with commentary

Objective: The Covid-19 related pandemic has negatively impacted NHS service provision We investigated its effect on specialist paediatric neuro-rehabilitation services in England and Wales Methods: A questionnaire was sent to UK National Neuro-rehabilitation network members by survey monkey app Questions explored: (1) centre details;(2) Covid-19 impact;(3) mitigation strategies;(4) recovery planning Results: 19 centres responded, including 17 Regional Neuroscience Centres;one stand-alone neurorehabilitation unit;one community-based specialist unit 18 reported Covid-19 had had a significant impact on service provision Six reported the impact was wholly negative;9 mainly negative, with some positive aspects;3 mainly positive, with some negative aspects;one was unsure 16 reported having fewer neurorehabilitation beds than pre-Covid-19;in 2, >80% were closed;2, 61-80%;3, 41-60%;7, 21-40% and 2, <20% Six indicated they were unable to accept internal or external referrals;3 only in exceptional circumstances 7 centres offer full rehabilitation to existing inpatients;11 only restricted rehabilitation 14 had discharged inpatients early;8 provided outpatient therapy post-discharge, 6 could not Two-thirds of centres transferred patients out at the start of the crisis, 9 to another neurorehabilitation unit and 3 to district hospitals Outpatient services were closed in 5 centres;operating fully (2);on a limited basis (8);on an increased basis due to reduced inpatient work (2) No community teams were offering normal services 9 centres were concerned about service restoration in the short term;12 in the medium term;10 in the long term Only 5 reported having a neurorehabilitation recovery plan Conclusion: Results highlight importance of developing robust neurorehabilitation service recovery plans to prevent children with acquired disability being further disadvantaged
On the inverse scattering from anisotropic periodic layers and transmission eigenvalues

This paper is concerned with the inverse scattering and the transmission eigenvalues for anisotropic periodic layers. For the inverse scattering problem, we study the Factorization method for shape...
Rare variants association testing for a binary outcome when pooling individual level data from heterogeneous studies.

Whole genome sequencing (WGS) and whole exome sequencing studies are used to test the association of rare genetic variants with health traits. Many existing WGS efforts now aggregate data from heterogeneous groups, for example, combining sets of individuals of European and African ancestries. We here investigate the statistical implications on rare variant association testing with a binary trait when combining together heterogeneous studies, defined as studies with potentially different disease proportion and different frequency of variant carriers. We study and compare in simulations the Type 1 error control and power of the naive score test, the saddlepoint approximation to the score test, and the BinomiRare test in a range of settings, focusing on low numbers of variant carriers. We show that Type 1 error control and power patterns depend on both the number of carriers of the rare allele and on disease prevalence in each of the studies. We develop recommendations for association analysis of rare genetic variants. (1) The Score test is preferred when the case proportion in the sample is 50%. (2) Do not down-sample controls to balance case-control ratio, because it reduces power. Rather, use a test that controls the Type 1 error. (3) Conduct stratified analysis in parallel with combined analysis. Aggregated testing may have lower power when the variant effect size differs between strata.
Late development of navigationally-relevant motion processing in the occipital place area

Human adults flawlessly and effortlessly navigate boundaries and obstacles in the immediately visible environment, a process we refer to as "visually guided navigation." Neuroimaging work in adults suggests this ability involves the occipital place area (OPA) [1, 2]-a scene-selective region in the dorsal stream that selectively represents information necessary for visually guided navigation [3-9]. Despite progress in understanding the neural basis of visually guided navigation, however, little is known about how this system develops. Is navigationally relevant information processing present in the first few years of life? Or does this information processing only develop after many years of experience? Although a handful of studies have found selective responses to scenes (relative to objects) in OPA in childhood [10-13], no study has explored how more specific navigationally relevant information processing emerges in this region. Here, we do just that by measuring OPA responses to first-person perspective motion information-a proxy for the visual experience of actually navigating the immediate environment-using fMRI in 5- and 8-year-old children. We found that, although OPA already responded more to scenes than objects by age 5, responses to first-person perspective motion were not yet detectable at this same age and rather only emerged by age 8. This protracted development was specific to first-person perspective motion through scenes, not motion on faces or objects, and was not found in other scene-selective regions (the parahippocampal place area or retrosplenial complex) or a motion-selective region (MT). These findings therefore suggest that navigationally relevant information processing in OPA undergoes prolonged development across childhood.
Non-Left-Orderable Surgeries on 1-Bridge Braids

Boyer, Gordon and Watson have conjectured that an irreducible rational homology 3-sphere is an L-space if and only if its fundamental group is not left-orderable. Since Dehn surgeries on knots in S...
The Impact of the "Muslim Ban" Executive Order on Healthcare Utilization in Minneapolis-St. Paul, Minnesota

Abstract Objective Determine whether the 2017 “Muslim Ban” Executive Order impacted healthcare utilization by people born in Order-targeted nations living in the United States. Methods We conducted a retrospective cohort study of people living in Minneapolis-St. Paul, MN in 2016-2017 who were: 1) born in Order-targeted nations, 2) born in Muslim-majority nations not listed in the Order, and 3) born in the United States and non-Latinx. Primary outcomes were: 1) primary care visits, 2) missed primary care appointments, 3) primary care diagnoses for stress-responsive conditions, 4) emergency department visits, and 5) emergency department visits for stress-responsive diagnoses. We evaluated visit trends before and after Order issuance using linear regression and differences between study groups using a difference-in-difference analyses. Results In early 2016, primary care visits and stress-responsive diagnoses increased among individuals from Muslim majority nations. Following the Order, there was an immediate increase in emergency department visits among individuals from Order-targeted nations. Conclusions Increases in healthcare utilization among people born in Muslim majority countries before and after the “Muslim Ban” likely reflect elevated cumulative stress including the impact of the Order.
Collisions of Dark Matter Axion Stars with Astrophysical Sources

If QCD axions form a large fraction of the total mass of dark matter, then axion stars could be very abundant in galaxies. As a result, collisions with each other, and with other astrophysical bodies, can occur. We calculate the rate and analyze the consequences of three classes of collisions, those occurring between a dilute axion star and: another dilute axion star, an ordinary star, or a neutron star. In all cases we attempt to quantify the most important astrophysical uncertainties; we also pay particular attention to scenarios in which collisions lead to collapse of otherwise stable axion stars, and possible subsequent decay through number changing interactions. Collisions between two axion stars can occur with a high total rate, but the low relative velocity required for collapse to occur leads to a very low total rate of collapses. On the other hand, collisions between an axion star and an ordinary star have a large rate, Γ⊙ ∼ 3000 collisions/year/galaxy, and for sufficiently heavy axion stars, it is plausible that most or all such collisions lead to collapse. We identify in this case a parameter space which has a stable region and a region in which collision triggers collapse, which depend on the axion number (N ) in the axion star, and a ratio of mass to radius cubed characterizing the ordinary star (M s /R 3 ). Finally, we revisit the calculation of collision rates between axion stars and neutron stars, improving on previous estimates by taking cylindrical symmetry of the neutron star distribution into account. Collapse and subsequent decay through collision processes, if occurring with a significant rate, can affect dark matter phenomenology and the axion star mass distribution.
Quickest online selection of an increasing subsequence of specified size

Given a sequence of independent random variables with a common continuous distribution, we consider the online decision problem where one seeks to minimize the expected value of the time that is needed to complete the selection of a monotone increasing subsequence of a prespecified length n. This problem is dual to some online decision problems that have been considered earlier, and this dual problem has some notable advantages. In particular, the recursions and equations of optimality lead with relative ease to asymptotic formulas for mean and variance of the minimal selection time. © 2016 Wiley Periodicals, Inc. Random Struct. Alg., 2016
A Low-order Model of Water Vapor, Clouds, and Thermal Emission for Tidally Locked Terrestrial Planets

In the spirit of minimal modeling of complex systems, we develop an idealized two-column model to investigate the climate of tidally locked terrestrial planets with Earth-like atmospheres in the habitable zone of M-dwarf stars. The model is able to approximate the fundamental features of the climate obtained from three-dimensional (3D) atmospheric general circulation model (GCM) simulations. One important reason for the two-column model's success is that it reproduces the high cloud albedo of the GCM simulations, which reduces the planet's temperature and delays the onset of a runaway greenhouse state. The two-column model also clearly illustrates a secondary mechanism for determining the climate: the nightside acts as a "radiator fin" through which infrared energy can be lost to space easily. This radiator fin is maintained by a temperature inversion and dry air on the nightside, and plays a similar role to the subtropics on modern Earth. Since one-dimensional radiative-convective models cannot capture the effects of the cloud albedo and radiator fin, they are systematically biased toward a narrower habitable zone. We also show that cloud parameters are the most important in the two-column model for determining the day-night thermal emission contrast, which decreases and eventually reverses as the stellar flux increases. This reversal is important because it could be detected by future extrasolar planet characterization missions, which would suggest that the planet has Earth-like water clouds and is potentially habitable.
Gas Accretion via Lyman Limit Systems

In cosmological simulations, a large fraction of the partial Lyman limit systems (pLLSs; \(16\lesssim \log N_{\text{HI}} 2) redshifts. Here I discuss unambiguous evidence for metal-poor gas at all z probed by the pLLSs and LLSs. At z < 1, all the pLLSs and LLSs so far studied are located in the CGM of galaxies with projected distances \(\lesssim\) 100–200 kpc. Regardless of the exact origin of the low-metallicity pLLSs/LLSs, there is a significant mass of cool, dense, low-metallicity gas in the CGM that may be available as fuel for continuing star formation in galaxies over cosmic time. As such, the metal-poor pLLSs and LLSs are currently among the best observational evidence of cold, metal-poor gas accretion onto galaxies.
Joint compute and forward for the two way relay channel with spatially coupled LDPC codes

We consider the design and analysis of coding schemes for the binary input two way relay channel with erasure noise. We focus on reliable physical layer network coding as described in [1] in which the relay performs perfect error correction prior to forwarding messages. The best known achievable rates for this problem can be achieved through either decode and forward or compute and forward relaying. We consider a decoding paradigm called joint compute and forward which we numerically show can achieve the best of these rates with a single encoder and decoder. This is accomplished by deriving the exact performance of a message passing decoder based on joint compute and forward for spatially coupled LDPC ensembles.
Hot particles attract in a cold bath

Active particles in a passive medium is a ubiquitous motif in biology. A novel long-range attractive force between highly diffusive ``hot'' particles in a less diffusive ``cold'' bath is reported. The interaction range of hot particles in a cold bath can be more than 10 times the particle radius.
Matchings, coverings, and Castelnuovo-Mumford regularity

We show that the co-chordal cover number of a graph $G$ gives an upper bound for the Castelnuovo-Mumford regularity of the associated edge ideal. Several known combinatorial upper bounds of regularity for edge ideals are then easy consequences of covering results from graph theory, and we derive new upper bounds by looking at additional covering results.
Hidden nonassociative structure in supersymmetric quantum mechanics

It is shown that the Hamilton equations in supersymmetric quantum mechanics can be presented in nonassociative form, where the Hamiltonian is decomposed into two nonassociative factors.
On the Discrepancy between Density Estimation and Sequence Generation

Many sequence-to-sequence generation tasks, including machine translation and text-to-speech, can be posed as estimating the density of the output y given the input x: p(y|x). Given this interpretation, it is natural to evaluate sequence-to-sequence models using conditional log-likelihood on a test set. However, the goal of sequence-to-sequence generation (or structured prediction) is to find the best output yˆ given an input x, and each task has its own downstream metric R that scores a model output by comparing against a set of references y*: R(yˆ, y* | x). While we hope that a model that excels in density estimation also performs well on the downstream metric, the exact correlation has not been studied for sequence generation tasks. In this paper, by comparing several density estimators on five machine translation tasks, we find that the correlation between rankings of models based on log-likelihood and BLEU varies significantly depending on the range of the model families being compared. First, log-likelihood is highly correlated with BLEU when we consider models within the same family (e.g. autoregressive models, or latent variable models with the same parameterization of the prior). However, we observe no correlation between rankings of models across different families: (1) among non-autoregressive latent variable models, a flexible prior distribution is better at density estimation but gives worse generation quality than a simple prior, and (2) autoregressive models offer the best translation performance overall, while latent variable models with a normalizing flow prior give the highest held-out log-likelihood across all datasets. Therefore, we recommend using a simple prior for the latent variable non-autoregressive model when fast generation speed is desired.
Introduction to the absolute brightness and number statistics in spontaneous parametric down-conversion

As a tutorial, we examine the absolute brightness and number statistics of photon pairs generated in Spontaneous Parametric Down-Conversion (SPDC) from first principles. In doing so, we demonstrate how the diverse implementations of SPDC can be understood through a single common framework, and use this to derive straightforward formulas for the biphoton generation rate (pairs per second) in a variety of different circumstances. In particular, we consider the common cases of both collimated and focused gaussian pump beams in a bulk nonlinear crystal, as well as in nonlinear waveguides and micro-ring resonators. Furthermore, we examine the number statistics of down-converted light using a non-perturbative approximation (the multi-mode squeezed vacuum), to provide quantitative formulas for the relative likelihood of multi-pair production events, and explore how the quantum state of the pump affects the subsequent statistics of the downconverted light. Following this, we consider the limits of the undepleted pump approximation, and conclude by performing experiments to test the effectiveness of our theoretical predictions for the biphoton generation rate in a variety of different sources.
TESTS OF THE STANDARD MODEL USING MUON POLARIZATION ASYMMETRIES IN KAON DECAYS

We have examined the physics and the experimental feasibility of studying various kaon decay processes in which the polarization of a muon in the final state is measured. Valuable information on CP violation, the quark mixing (CKM) matrix, and new physics can be obtained from such measurements. We have considered muon polarization in KL→μ+μ- and K→πμ+μ- decays. Although the effects are small, or difficult to measure because of the small branching ratios involved, these studies could provide clean measurements of the CKM parameters. The experimental difficulty appears comparable to the observation of . New sources of physics, involving nonstandard CP violation, could produce effects observable in these measurements. Limits from new results on the neutron and electron electric dipole moment, and in neutral kaon decays, do not eliminate certain models that could contribute to the signal. A detailed examination of muon polarization out of the decay plane in K+→μ+π0ν and K+→μ+νγ decays also appears to be of interest. With current kaon beams and detector techniques, it is possible to measure the T-violating polarization for K+→μ+π0ν and with uncertainties approaching ~10-4. This level of sensitivity would provide an interesting probe of new physics.
Conjugate gradient-based soft-output detection and precoding in massive MIMO systems

Massive multiple-input multiple-output (MIMO) promises improved spectral efficiency, coverage, and range, compared to conventional (small-scale) MIMO wireless systems. Unfortunately, these benefits come at the cost of significantly increased computational complexity, especially for systems with realistic antenna configurations. To reduce the complexity of data detection (in the uplink) and precoding (in the downlink) in massive MIMO systems, we propose to use conjugate gradient (CG) methods. While precoding using CG is rather straightforward, soft-output minimum mean-square error (MMSE) detection requires the computation of the post-equalization signal-to-interference-and-noise-ratio (SINR). To enable CG for soft-output detection, we propose a novel way of computing the SINR directly within the CG algorithm at low complexity. We investigate the performance/complexity trade-offs associated with CG-based soft-output detection and precoding, and we compare it to existing exact and approximate methods. Our results reveal that the proposed algorithm is able to outperform existing methods for massive MIMO systems with realistic antenna configurations.
Nuclear expansion and symmetry energy of hot nuclei

The decrease in the symmetry energy of hot nuclei populated in 58Ni + 58Ni, 58Fe + 58Ni and 58Fe + 58Fe reactions at beam energies of 30, 40 and 47 MeV/nucleon, as a function of excitation energy is studied. It is observed that this decrease is mainly a consequence of increasing expansion or decreasing density rather than the increasing temperature. The results are in good agreement with the recently reported microscopic calculation based on the Thomas–Fermi approach. An empirical relation to study the symmetry energy of finite nuclei in various mass regions is proposed.
Edge-insensitive magnetism and half metallicity in graphene nanoribbons.

Realizing magnetism in graphene nanostructures is a decade-long challenge. The magnetic edge state and half metallicity in zigzag graphene nanoribbons are particularly promising [Y.-W. Son, et al., Nature 444, 347 (2006)]. However, its experimental realization has been hindered by the stringent requirement of the mono-hydrogenated zigzag edge. Using first-principle calculations, we predict that free-carrier doping can overcome this challenge and realize ferromagnetism and half-metallicity in narrow graphene nanoribbons of general types of edge structures. This magnetism exists within the density range of gate-doping experiments (~10lsupg13l/supg cmlsupg-2l/supg) and has large spin polarization energy up to 17 meV per carrier, which induces a Zeeman splitting equivalent to an external magnetic field of a few hundred Tesla. Finally, we trace the formation mechanics of this edge-insensitive magnetism to the quantum confinement of the electronic state near the band edge and reveal the scaling law of magnetism versus the ribbon width. Our findings suggest that combining doping with quantum confinement could be a general tool to realize transition-metal-free magnetism in light-element nanostructures.
Operation of a Superconducting Nanowire in Two Detection Modes: KID and SPD

We present the performance of a superconducting nanowire that can be operated in two detection modes: (i) as a kinetic inductance detector (KID) or (ii) as a single-photon detector (SPD). Two superconducting nanowires developed for use as single-photon detectors (SNSPDs) are embedded as the inductive (L) component in resonant inductor/capacitor (LC) circuits coupled to a microwave transmission line. The capacitors are low loss commercial chip capacitors and limit the internal quality factor of the resonators to approximately $$Q_i = 170$$ . The resonator quality factor, $$Q_r \simeq 23$$ , is dominated by the coupling to the feedline and limits the detection bandwidth to on the order of 1 MHz. When operated in KID mode, the detectors are AC biased with tones at their resonant frequencies of 45.85 and 91.81 MHz. In the low-bias, standard KID mode, a single photon produces a hot spot that does not turn an entire section of the line normal but only increases the kinetic inductance. In the high-bias, critical KID mode, a photon event turns a section of the line normal and the resonance is destroyed until the normal region is dissipated. When operated as an SPD in Geiger mode, the resonators are DC biased through cryogenic bias tees and each photon produces a sharp voltage step followed by a ringdown signal at the resonant frequency of the detector which is converted to a standard pulse with an envelope detector. We show that AC biasing in the critical KID mode is inferior to the sensitivity achieved in DC-biased SPD mode due to the small fraction of time spent near the critical current with an AC bias.
Fast Calculation of the Lomb-Scargle Periodogram Using Graphics Processing Units

I introduce a new code for fast calculation of the Lomb-Scargle periodogram that leverages the computing power of graphics processing units (GPUs). After establishing a background to the newly emergent field of GPU computing, I discuss the code design and narrate key parts of its source. Benchmarking calculations indicate no significant differences in accuracy compared to an equivalent CPU-based code. However, the differences in performance are pronounced; running on a low-end GPU, the code can match eight CPU cores, and on a high-end GPU it is faster by a factor approaching 30. Applications of the code include analysis of long photometric time series obtained by ongoing satellite missions and upcoming ground-based monitoring facilities, and Monte Carlo simulation of periodogram statistical properties.
On the Spin-down of Intermittent Pulsars

Magnetospheres of pulsars are thought to be filled with plasma, and variations in plasma supply can affect both pulsar emission properties and spin-down rates. A number of recently discovered "intermittent" pulsars switch between two distinct states: an "on," radio-loud state, and an "off," radio-quiet state. Spin-down rates in the two states differ by a large factor, ~1.5-2.5, which is not easily understood in the context of current models. In this Letter, we present self-consistent numerical solutions of "on" and "off" states of intermittent pulsar magnetospheres. We model the "on" state as a nearly ideal force-free magnetosphere with abundant magnetospheric plasma supply. The lack of radio emission in the "off" state is associated with plasma supply disruption that results in lower plasma density on the open field lines. We model the "off" state using nearly vacuum conditions on the open field lines and nearly ideal force-free conditions on the closed field lines, where plasma can remain trapped even in the absence of pair production. The toroidal advection of plasma in the closed zone in the "off" state causes spin-downs that are a factor of ~2 higher than vacuum values, and we naturally obtain a range of spin-down ratios between the "on" and "off" states, ~1.2-2.9, which corresponds to a likely range of pulsar inclination angles of 30°-90°. We consider the implications of our model to a number of poorly understood but possibly related pulsar phenomena, including nulling, timing noise, and rotating radio transients.
Shake genus and slice genus

An important difference between high-dimensional smooth manifolds and smooth 4–manifolds that in a 4–manifold it is not always possible to represent every middle-dimensional homology class with a smoothly embedded sphere. This is true even among the simplest 4–manifolds: X0(K) obtained by attaching an 0–framed 2–handle to the 4–ball along a knot K in S3. The 0–shake genus of K records the minimal genus among all smooth embedded surfaces representing a generator of the second homology of X0(K) and is clearly bounded above by the slice genus of K. We prove that slice genus is not an invariant of X0(K), and thereby provide infinitely many examples of knots with 0–shake genus strictly less than slice genus. This resolves Problem 1.41 of Kirby’s 1997 problem list. As corollaries we show that Rasmussen’s s invariant is not a 0–trace invariant and we give examples, via the satellite operation, of bijective maps on the smooth concordance group which fix the identity but do not preserve slice genus. These corollaries resolve some questions from a conference at the Max Planck Institute, Bonn (2016).
Modulation theory of quantum tunneling into a Calogero-Sutherland fluid.

Quantum hydrodynamics of interacting electrons with a parabolic single-particle spectrum is studied using the Calogero-Sutherland model. The effective action and modulation equations, describing the evolution of periodic excitations in the fluid, are derived. Applications to the problem of a single-electron tunneling into the FQHE edge state are discussed.
Hedetniemi's conjecture is asymptotically false

Abstract Extending a recent breakthrough of Shitov, we prove that the chromatic number of the tensor product of two graphs can be a constant factor smaller than the minimum chromatic number of the two graphs. More precisely, we prove that there exists an absolute constant δ > 0 such that for all c sufficiently large, there exist graphs G and H with chromatic number at least ( 1 + δ ) c for which χ ( G × H ) ≤ c .
Independent Policy Gradient Methods for Competitive Reinforcement Learning

We obtain global, non-asymptotic convergence guarantees for independent learning algorithms in competitive reinforcement learning settings with two agents (i.e., zero-sum stochastic games). We consider an episodic setting where in each episode, each player independently selects a policy and observes only their own actions and rewards, along with the state. We show that if both players run policy gradient methods in tandem, their policies will converge to a min-max equilibrium of the game, as long as their learning rates follow a two-timescale rule (which is necessary). To the best of our knowledge, this constitutes the first finite-sample convergence result for independent policy gradient methods in competitive RL; prior work has largely focused on centralized, coordinated procedures for equilibrium computation.
Revisiting the Temperature of the Diffuse ISM with CHESS Sounding Rocket Observations

Measuring the temperature and abundance patterns of clouds in the interstellar medium (ISM) provides an observational basis for models of the physical conditions within the clouds, which play an important role in studies of star and planet formation. The Colorado High-resolution Echelle Stellar Spectrograph is a far-ultraviolet rocket-borne instrument designed to study the atomic-to-molecular transitions within diffuse molecular and translucent cloud regions. The final two flights of the instrument observed β^1 Scorpii (β Sco) and γ Arae. We present flight results of interstellar molecular hydrogen excitation on the sightlines, including measurements of the column densities and temperatures. These results are compared to previous values that were measured using the damping wings of low J'' H_2 absorption features. For β Sco, we find that the derived column density of the J'' = 1 rotational level differs by a factor of 2–3 when compared to the previous observations. We discuss the discrepancies between the two measurements and show that the source of the difference is due to the opacity of higher rotational levels contributing to the J'' = 1 absorption wing, increasing the inferred column density in the previous work. We extend this analysis to 9 Copernicus and 13 Far-Ultraviolet Spectroscopic Explorer spectra to explore the interdependence of the column densities of different rotational levels and how the H_2 kinetic temperature is influenced by these relationships. We find a revised average gas kinetic temperature of the diffuse molecular ISM of T_(01) = 68 ± 13 K, 12% lower than the value found previously.
TabulaROSA: Tabular Operating System Architecture for Massively Parallel Heterogeneous Compute Engines

The rise in computing hardware choices is driving a reevaluation of operating systems. The traditional role of an operating system controlling the execution of its own hardware is evolving toward a model whereby the controlling processor is distinct from the compute engines that are performing most of the computations. In this context, an operating system can be viewed as software that brokers and tracks the resources of the compute engines and is akin to a database management system. To explore the idea of using a database in an operating system role, this work defines key operating system functions in terms of rigorous mathematical semantics (associative array algebra) that are directly translatable into database operations. These operations possess a number of mathematical properties that are ideal for parallel operating systems by guaranteeing correctness over a wide range of parallel operations. The resulting operating system equations provide a mathematical specification for a Tabular Operating System Architecture (TabulaROSA) that can be implemented on any platform. Simulations of forking in TabularROSA are performed using an associative array implementation and compared to Linux on a 32,000+ core supercomputer. Using over 262,000 forkers managing over 68,000,000,000 processes, the simulations show that TabulaROSA has the potential to perform operating system functions on a massively parallel scale. The TabulaROSA simulations show 20x higher performance as compared to Linux while managing 2000x more processes in fully searchable tables.
Scaling of the splash threshold for low-viscosity fluids

The ambient gas pressure is determined for the onset of splashing of low-viscosity liquid drops on smooth dry surfaces as we change the control parameters: drop impact velocity, drop radius, viscosity, surface tension, density, and gas molecular weight. This threshold pressure indicates that there are two distinct regimes when drop impact velocity is varied. By rescaling data using functions of only three dimensionless numbers, the commonly used Reynolds and Weber numbers, as well as the ratio of drop radius to gas mean free path, all data is collapsed to a single curve that encompasses both regimes.
Canonical bases of quantum Schubert cells and their symmetries

The goal of this work is to provide an elementary construction of the canonical basis $$\mathbf B(w)$$ in each quantum Schubert cell $$U_q(w)$$ and to establish its invariance under modified Lusztig’s symmetries. To that effect, we obtain a direct characterization of the upper global basis $$\mathbf {B}^{up}$$ in terms of a suitable bilinear form and show that $$\mathbf B(w)$$ is contained in $$\mathbf {B}^{up}$$ and its large part is preserved by modified Lusztig’s symmetries.
The analytic class number formula for 1-dimensional affine schemes

We derive an analytic class number formula valid for an order in a product of $S$-integers in global fields, or equivalently for reduced finite-type affine schemes of pure dimension $1$ over $\mathbb{Z}$.
Composition of massive giant planets

The two current models for giant planet formation are core accretion and disk instability. We discuss the core masses and overall planetary enrichment in heavy elements predicted by the two formation models, and show that both models could lead to a large range of final compositions. For example, both can form giant planets with nearly stellar compositions. However, low-mass giant planets, enriched in heavy elements compared to their host stars, are more easily explained by the core accretion model. The final structure of the planets, i.e., the distribution of heavy elements, is not firmly constrained in either formation model.
Semiconcave Functions in Alexandrov???s Geometry

The following is a compilation of some techniques in Alexandrov’s geometry which are directly connected to convexity.
Integral canonical models for automorphic vector bundles of abelian type

We define and construct integral canonical models for automorphic vector bundles over Shimura varieties of abelian type. More precisely, we first build on Kisin’s work to construct integral canonical models over OE[1∕N] for Shimura varieties of abelian type with hyperspecial level at all primes not dividing N compatible with Kisin’s construction. We then define a notion of an integral canonical model for the standard principal bundles lying over Shimura varieties and proceed to construct them in the abelian type case. With these in hand, one immediately also gets integral models for automorphic vector bundles.
SCALING OF VON NEUMANN ENTROPY AT THE ANDERSON TRANSITION

Extensive body of work has shown that for the model of a non-interacting electron in a random potential there is a quantum critical point for dimensions greater than two — a metal–insulator transition. This model also plays an important role in the plateau-to-plateu transition in the integer quantum Hall effect, which is also correctly captured by a scaling theory. Yet, in neither of these cases the ground state energy shows any non-analyticity as a function of a suitable tuning parameter, typically considered to be a hallmark of a quantum phase transition, similar to the non-analyticity of the free energy in a classical phase transition. Here we show that von Neumann entropy (entanglement entropy) is non-analytic at these phase transitions and can track the fundamental changes in the internal correlations of the ground state wave function. In particular, it summarizes the spatially wildly fluctuating intensities of the wave function close to the criticality of the Anderson transition. It is likely that all quantum phase transitions can be similarly described.
GYROSCOPIC PUMPING OF LARGE-SCALE FLOWS IN STELLAR INTERIORS AND APPLICATION TO LITHIUM-DIP STARS

The maintenance of large-scale differential rotation in stellar convective regions by rotationally influenced convective stresses also drives large-scale meridional flows by angular-momentum conservation. This process is an example of "gyroscopic pumping" and has recently been studied in detail in the solar context. An important question concerns the extent to which these gyroscopically pumped meridional flows penetrate into nearby stably stratified (radiative) regions, since they could potentially be an important source of non-local mixing. Here, we present an extensive study of the gyroscopic pumping mechanism, using a combination of analytical calculations and numerical simulations both in Cartesian geometry and in spherical geometry. The various methods, when compared with one another, provide physical insight into the process itself, as well as increasingly sophisticated means of estimating the gyroscopic pumping rate. As an example of application, we investigate the effects of this large-scale mixing process on the surface abundances of the light elements Li and Be for stars in the mass range 1.3-1.5 M ☉ (the so-called Li-dip stars). We find that gyroscopic pumping is a very efficient mechanism for circulating material between the surface and the deep interior, so much in fact that it overestimates Li and Be depletion by orders of magnitude for stars on the hot side of the dip. However, when the diffusion of chemical species back into the surface convection zone is taken into account, a good fit with observed surface abundances of Li and Be as a function of stellar mass in the Hyades cluster can be found for reasonable choices of model parameters.
Improved decay of conical averages of the Fourier transform

An improved lower bound is given for the decay of conical averages of Fourier transforms of measures, for cones of dimension $d \geq 4$. The proof uses a weighted version of the broad restriction inequality, a narrow decoupling inequality for the cone, and some techniques of Du and Zhang originally developed for the Schrodinger equation.
Capture-formed Binaries via Encounters with Massive Protostars

Most massive stars are found in the center of dense clusters and have a companion fraction much higher than their lower mass siblings; the massive stars of the Trapezium core in Orion have ~1.5 companions each. This high multiplicity could be a consequence of formation via a capture scenario, or it could be due to fragmentation of the cores that form the massive stars. During stellar formation circumstellar disks appear to be nearly ubiquitous. Their large radii compared to stellar sizes increase the interaction radius significantly, suggesting that disk interactions with neighboring stars could assist in capturing binary companions. This mechanism has been studied for stars of approximately solar mass and found to be inefficient. In this paper we present simulations of interactions between a 22 M☉ star-disk system and less massive impactors in order to study the disk-assisted capture formation of binaries in a regime suited to massive stars. The formation of binaries by capture is found to be much more efficient for massive capturers. We discuss the effects of a mass-dependent velocity dispersion and mass segregation on the capture rates and consider the long-term survival of the resulting binaries in a dense cluster.
Split Grothendieck rings of rooted trees and skew shapes via monoid representations

We study commutative ring structures on the integral span of rooted trees and n-dimensional skew shapes. The multiplication in these rings arises from the smash product operation on monoid representations in pointed sets. We interpret these as Grothendieck rings of indecomposable monoid representations over F1 — the “field” of one element. We also study the base-change homomorphism from 〈t〉-modules to k[t]-modules for a field k containing all roots of unity, and interpret the result in terms of Jordan decompositions of adjacency matrices of certain graphs.
The Banks–Zaks expansion in perturbative QCD: An update

The recent QCD calculations of the five-loop β-function and of Re+e− to O(αs4) provide one more term in the Banks–Zaks (BZ) expansion in (161 2 − nf). There is no longer any hope that the expansion could extend, even crudely, to low nf. Above nf ∼ 9, however, the results appear to be reasonably consistent from order to order.
Cyclotomic structure in the topological Hochschild homology of $DX$

Let X be a finite CW complex, and let DX be its dual in the category of spectra. We demonstrate that the Poincare/Koszul duality between THH(DX) and the free loop space Σ+∞LX is in fact a genuinely S1–equivariant duality that preserves the Cn–fixed points. Our proof uses an elementary but surprisingly useful rigidity theorem for the geometric fixed point functor ΦG of orthogonal G–spectra.