cssi/SciSciGPT-SciSciNet huggingface dataset:
TIDAL INTERACTIONS IN MERGING WHITE DWARF BINARIES

The recently discovered system J0651 is the tightest known detached white dwarf (WD) binary. Since it has not yet initiated Roche-lobe overflow, it provides a relatively clean environment for testing our understanding of tidal interactions. I investigate the tidal heating of each WD, parameterized in terms of its tidal Q parameter. Assuming that the heating can be radiated efficiently, the current luminosities are consistent with Q 1 ≈ 7 × 1010 and Q 2 ≈ 2 × 107, for the He and C/O WDs, respectively. Conversely, if the observed luminosities are merely from the cooling of the WDs, these estimated values of Q represent the upper limits. A large Q 1 for the He WD means its spin velocity will be slower than that expected if it was tidally locked, which, since the binary is eclipsing, may be measurable via the Rossiter-McLaughlin effect. After one year, gravitational wave emission shifts the time of eclipses by 5.5 s, but tidal interactions cause the orbit to shrink more rapidly, changing the time by up to an additional 0.3 s after a year. Future eclipse timing measurements may therefore infer the degree of tidal locking.
The Picard rank conjecture for the Hurwitz spaces of degree up to five

We prove that the rational Picard group of the simple Hurwitz space Hd,g is trivial for d up to five. We also relate the rational Picard groups of the Hurwitz spaces to the rational Picard groups of the Severi varieties of nodal curves on Hirzebruch surfaces. 0 Introduction LetHd,g be the simple Hurwitz space which parametrizes isomorphism classes of simply branched covers of P1 of degree d and genus g. AlthoughHd,g has been studied classically, many fundamental questions about its geometry are still unanswered. The goal of this paper is to address one such question, the question of its Picard group. It is conjectured (for example, [DE96]) that the rational Picard group PicQ(Hd,g) is trivial. We call this the Picard rank conjecture for Hd,g. Our main result is a proof of this conjecture for d ≤ 5. Theorem A. The rational Picard group ofHd,g is trivial for d ≤ 5. In the main text, Theorem A is divided into the case of degree 3 (Proposition 3.3), degree 4 (Proposition 4.10), and degree 5 (Proposition 5.4). The Picard rank conjecture was known for d = 2 and 3. For d = 2, it was proved by Cornalba and Harris [CH88, Lemma 4.5], and for d = 3 by Stankova-Frenkel [SF00, § 12.2]. In these cases, now there are more refined results about the Picard group of the moduli stacks; see [Cor07] for d = 2 and [BV12] for d = 3. The conjecture is also known for d > 2g− 2. In this range, the map Hd,g →Mg is a fibration, whereMg is the moduli space of smooth curves of genus g. An analysis of this fibration shows that PicQ(Hd,g) = 0 if and only if PicQ(Mg) ∼= Q (see, for example, [Moc95] or [DE96, § 3]). Thus, the conjecture for d > 2g− 2 follows from Harer’s theorem [Har83]. We briefly explain the rationale behind the conjecture. Let us blur the distinction between the coarse moduli spaces and the fine moduli stacks. This is harmless, since we are concerned with the rational Picard group. Let us also take d ≥ 4 (the discussion holds for d = 2, 3 with minor modifications). Let Hd,g be the partial compactification ofHd,g where C is allowed to be nodal, but
Temporal Localization of Fine-Grained Actions in Videos by Domain Transfer from Web Images

We address the problem of fine-grained action localization from temporally untrimmed web videos. We assume that only weak video-level annotations are available for training. The goal is to use these weak labels to identify temporal segments corresponding to the actions, and learn models that generalize to unconstrained web videos. We find that web images queried by action names serve as well-localized highlights for many actions, but are noisily labeled. To solve this problem, we propose a simple yet effective method that takes weak video labels and noisy image labels as input, and generates localized action frames as output. This is achieved by cross-domain transfer between video frames and web images, using pre-trained deep convolutional neural networks. We then use the localized action frames to train action recognition models with long short-term memory networks. We collect a fine-grained sports action data set FGA-240 of more than 130,000 YouTube videos. It has 240 fine-grained actions under 85 sports activities. Convincing results are shown on the FGA-240 data set, as well as the THUMOS 2014 localization data set with untrimmed training videos.
A POPULATION OF RELIC INTERMEDIATE-MASS BLACK HOLES IN THE HALO OF THE MILKY WAY

If 'seed' central black holes were common in the subgalactic building blocks that merged to form present-day massive galaxies, then relic intermediate-mass black holes (IMBHs) should be present in the Galactic bulge and halo. We use a particle tagging technique to dynamically populate the N-body Via Lactea II high-resolution simulation with black holes, and assess the size, properties, and detectability of the leftover population. The method assigns a black hole to the most tightly bound central particle of each subhalo at infall according to an extrapolation of the M {sub BH}-σ{sub *} relation, and self-consistently follows the accretion and disruption of Milky Way progenitor dwarfs and their holes in a cosmological 'live' host from high redshift to today. We show that, depending on the minimum stellar velocity dispersion, σ {sub m}, below which central black holes are assumed to be increasingly rare, as many as ∼2000 (σ {sub m} = 3 km s{sup –1}) or as few as ∼70 (σ {sub m} = 12 km s{sup –1}) IMBHs may be left wandering in the halo of the Milky Way today. The fraction of IMBHs forced from their hosts by gravitational recoil is ≲ 20%. We identify two main Galactic subpopulations,more » 'naked' IMBHs, whose host subhalos were totally destroyed after infall, and 'clothed' IMBHs residing in dark matter satellites that survived tidal stripping. Naked IMBHs typically constitute 40%-50% of the total and are more centrally concentrated. We show that, in the σ {sub m} = 12 km s{sup –1} scenario, the clusters of tightly bound stars that should accompany naked IMBHs would be fainter than m{sub V} = 16 mag, spatially resolvable, and have proper motions of 0.1-10 mas yr{sup –1}. Their detection may provide an observational tool to constrain the formation history of massive black holes in the early universe.« less
SCATTERED NEBULAR LIGHT IN THE EXTENDED ORION NEBULA

We have combined 327.5 MHz radio observations and optical spectroscopy to study conditions in the Extended Orion Nebula (EON). We see a steady progression of characteristics with increasing distance from the dominant photoionizing star ?1Ori C. This progression includes a decrease in the F(H?)/F(H?) ratio, an increase in the relative strength of scattered stellar continuum, decrease in electron density determined from the [S II] doublet, and increase in the ratio of emission measures derived from the H? line and the 327.5?MHz radio continuum. We conclude that beyond about 5' south of ?1Ori C that scattered light from the much brighter central Huygens region of the nebula significantly contaminates local emission. This strengthens earlier arguments that wavelength and model-dependent scattering of emission-line radiation imposes a fundamental limit on our ability to determine the physical conditions and abundances in this and arguably other similar Galactic Nebulae. The implications for the study of extragalactic H II regions are even more severe. We confirm the result of an earlier study that at least the eastern boundary of the EON is dominated by scattered light from the Huygens region.
Derivatives of knots and second-order signatures

We define a set of “second-order” L–signature invariants for any algebraically slice knot. These obstruct a knot’s being a slice knot and generalize Casson–Gordon invariants, which we consider to be “first-order signatures”. As one application we prove: If K is a genus one slice knot then, on any genus one Seifert surface † , there exists a homologically essential simple closed curve J of self-linking zero, which has vanishing zero-th order signature and a vanishing first-order signature. This extends theorems of Cooper and Gilmer. We introduce a geometric notion, that of a derivative of a knot with respect to a metabolizer. We also introduce a new relation, generalizing homology cobordism, called null-bordism.
EXTRACTING RADIAL VELOCITIES OF A- AND B-TYPE STARS FROM ECHELLE SPECTROGRAPH CALIBRATION SPECTRA

We present a technique to extract radial velocity (RV) measurements from echelle spectrograph observations of rapidly rotating stars (V sin i ≳ 50 kms^(−1)). This type of measurement is difficult because the line widths of such stars are often comparable to the width of a single echelle order. To compensate for the scarcity of lines and Doppler information content, we have developed a process that forward-models the observations, fitting the RV shift of the star for all echelle orders simultaneously with the echelle blaze function. We use our technique to extract RV measurements from a sample of rapidly rotating A- and B-type stars used as calibrator stars observed by the California Planet Survey observations. We measure absolute RVs with a precision ranging from 0.5–2.0 kms^(−1) per epoch for more than 100 A- and B-type stars. In our sample of 10 well-sampled stars with RV scatter in excess of their measurement uncertainties, three of these are single-lined binaries with long observational baselines. From this subsample, we present detections of two previously unknown spectroscopic binaries and one known astrometric system. Our technique will be useful in measuring or placing upper limits on the masses of sub-stellar companions discovered by wide-field transit surveys, and conducting future spectroscopic binarity surveys and Galactic space-motion studies of massive and/or young, rapidly rotating stars.
HD 16771: A lithium-rich giant in the red-clump stage

Aims. We report the discovery of a young lithium rich giant, HD 16771, in the core-helium burning phase that does not seem to fit existing proposals of Li synthesis near the luminosity function bump or during He-core flash. We aim to understand the nature of Li enrichment in the atmosphere of HD 16771 by exploring various Li enhancement scenarios.Methods. We have collected high-resolution echelle spectra of HD 16771 and derived stellar parameters and chemical abundances for 27 elements by either line equivalent widths or synthetic spectrum analyses.Results. HD 16771 is a Li-rich (log ϵ (Li) = + 2.67 ± 0.10 dex) intermediate mass giant star (M = 2.4 ± 0.1 M ⊙ ) with age ~ 0.76 ± 0.13 Gyr and located at the red giant clump. Kinematics and chemical compositions are consistent with HD 16771 being a member of the Galactic thin disk population. The non-detection of 6 Li ( C/13 C = 12 ± 2), and the slow rotation (v sin i = 2.8 km s-1 ) all suggest that lithium might have been synthesized in this star. On the contrary, HD 16771 with a mass of 2.4 M ⊙ has no chance of encountering luminosity function bump and He-core flash where the possibility of fast deep-mixing for Li enrichment in K giants has been suggested previously.Conclusions. Based of the evolutionary status of this star, we discuss the possibility that 7 Li synthesis in HD 16771 is triggered by the engulfment of close-in planet(s) during the RGB phase.
GRB 991216 Joins the Jet Set: Discovery and Monitoring of Its Optical Afterglow

The optical light curve of the energetic γ-ray burst GRB 991216 is consistent with jetlike behavior in which a power-law decay steepens from t-1.22±0.04 at early times to t-1.53±0.05 in a gradual transition at around 2 days. The derivation of the late-time decay slope takes into account the constant contribution of a host or intervening galaxy, which was measured 110 days after the event at R = 24.56 ± 0.14, although the light curve deviates from a single power law whether or not a constant term is included. The early-time spectral energy distribution of the afterglow can be described as Fν ∝ ν-0.74±0.05 or flatter between optical and X-ray, which, together with the slow initial decay, is characteristic of standard adiabatic evolution in a uniformly dense medium. Assuming that a reported absorption-line redshift of 1.02 is correct, the apparent isotropic energy of 6.7 × 1053 ergs is reduced by a factor of ≈200 in the jet model, and the initial half-opening angle is ≈6°. GRB 991216 is the third good example of a jetlike afterglow (following GRB 990123 and GRB 990510), supporting a trend in which the apparently most energetic γ-ray events have the narrowest collimation and a uniform interstellar medium environment. This, plus the absence of evidence for supernovae associated with jetlike afterglows, suggests that these events may originate from a progenitor in which angular momentum plays an important role but a massive stellar envelope or wind does not, e.g., in the coalescence of a compact binary.
Vanadium Transitions in the Spectrum of Arcturus

We derive a new abundance for vanadium in the bright, mildly metal-poor red giant Arcturus. This star has an excellent high-resolution spectral atlas and well-understood atmospheric parameters, and it displays a rich set of neutral vanadium lines that are available for abundance extraction. We employ a newly recorded set of laboratory FTS spectra to investigate any potential discrepancies in previously reported V I log(gf) values near 900 nm. These new spectra support our earlier laboratory transition data and the calibration method utilized in that study. We then perform a synthetic spectrum analysis of weak V I features in Arcturus, deriving log {\epsilon}(V) = 3.54 $\pm$ 0.01 ({\sigma} = 0.04) from 55 lines. There are no significant abundance trends with wavelength, line strength, or lower excitation energy.
THE FAINT END OF THE CLUSTER-GALAXY LUMINOSITY FUNCTION AT HIGH REDSHIFT

We measure the faint-end slope of the galaxy luminosity function (LF) for cluster galaxies at 1 < z < 1.5 using Spitzer IRAC data. We investigate whether this slope, {alpha}, differs from that of the field LF at these redshifts, and with the cluster LF at low redshifts. The latter is of particular interest as low-luminosity galaxies are expected to undergo significant evolution. We use seven high-redshift spectroscopically confirmed galaxy clusters drawn from the IRAC Shallow Cluster Survey to measure the cluster-galaxy LF down to depths of M* + 3 (3.6 {mu}m) and M* + 2.5 (4.5 {mu}m). The summed LF at our median cluster redshift (z = 1.35) is well fit by a Schechter distribution with {alpha}{sub 3.6{mu}m} = -0.97 {+-} 0.14 and {alpha}{sub 4.5{mu}m} = -0.91 {+-} 0.28, consistent with a flat faint-end slope and is in agreement with measurements of the field LF in similar bands at these redshifts. A comparison to {alpha} in low-redshift clusters finds no statistically significant evidence of evolution. Combined with past studies which show that M* is passively evolving out to z {approx} 1.3, this means that the shape of the cluster LF is largely in place by z {approx} 1.3. Thismore » suggests that the processes that govern the buildup of the mass of low-mass cluster galaxies have no net effect on the faint-end slope of the cluster LF at z {approx}< 1.3.« less
Analysis and optimization of weighted ensemble sampling

We give a mathematical framework for weighted ensemble (WE) sampling, a binning and resampling technique for efficiently computing probabilities in molecular dynamics. We prove that WE sampling is unbiased in a very general setting that includes adaptive binning. We show that when WE is used for stationary calculations in tandem with a coarse model, the coarse model can be used to optimize the allocation of replicas in the bins.
A comparison principle for functions of a uniformly random subspace

This note demonstrates that it is possible to bound the expectation of an arbitrary norm of a random matrix drawn from the Stiefel manifold in terms of the expected norm of a standard Gaussian matrix with the same dimensions. A related comparison holds for any convex function of a random matrix drawn from the Stiefel manifold. For certain norms, a reversed inequality is also valid.
Imprints of Molecular Clouds in Radio Continuum Images

We show radio continuum images of several molecular complexes in the inner Galaxy and report the presence of dark features that coincide with dense molecular clouds. Unlike infrared dark clouds, these features which we call radio dark clouds are produced by a deficiency in radio continuum emission from molecular clouds that are embedded in a bath of UV radiation field or synchrotron emitting cosmic-ray particles. The contribution of the continuum emission along different path lengths results in dark features that trace embedded molecular clouds. The new technique of identifying cold clouds can place constraints on the depth and the magnetic field of molecular clouds when compared to those of the surrounding hot plasma radiating at radio wavelengths. The study of five molecular complexes in the inner Galaxy, Sgr A, Sgr B2, radio Arc, the Snake filament, and G359.75-0.13 demonstrates an anti-correlation between the distributions of radio continuum and molecular line and dust emission. Radio dark clouds are identified in Green Bank Telescope maps and Very Large Array images taken with uniform sampling of uv coverage. The level at which the continuum flux is suppressed in these sources suggests that the depth of the molecular cloud is similar to the size of the continuum emission within a factor of two. These examples suggest that high-resolution, high-dynamic-range continuum images can be powerful probes of interacting molecular clouds with massive stars and supernova remnants in regions where the kinematic distance estimates are ambiguous as well as in the nuclei of active galaxies.
A new lattice action for studying topological charge

Abstract We propose a new lattice action for non-abelian gauge theories, which will reduce short-range lattice artifacts in the computation of the topological susceptibility. The standard Wilson action is replaced by the Wilson action of a gauge covariant interpolation of the original fields to a finer lattice. If the latter is fine enough, the action of all configurations with non-zero topological charge will satisfy the necessary bound for the scaling of the topological susceptibility. As a simpler example we consider the O (3) σ-model in two dimensions, where a numerical analysis of discretized continuum instantons indicates that a finer lattice with half the lattice spacing of the original is enough to satisfy the continuum bound.
Constraining the Potential Liquid Water Environment at Gale Crater, Mars

The Mars Science Laboratory (MSL) Rover Environmental Monitoring Station (REMS) has now made continuous in situ meteorological measurements for several Martian years at Gale crater, Mars. Of importance in the search for liquid formation are REMS' measurements of ground temperature and in-air measurements of temperature and relative humidity, which is with respect to ice. Such data can constrain the surface and subsurface stability of brines. Here we use updated calibrations to REMS data and consistent relative humidity comparisons (i.e., with respect to liquid versus with respect to ice) to investigate the potential formation of surface and subsurface liquids throughout MSL's traverse. We specifically study the potential for the deliquescence of calcium perchlorate. Our data analysis suggests that surface brine formation is not favored within the first 1648 sols as there are only two times (sols 1232 and 1311) when humidity-temperature conditions were within error consistent with a liquid phase. On the other hand, modeling of the subsurface environment would support brine production in the shallow subsurface. Indeed, we find that the shallow subsurface for terrains with low thermal inertia (Γ ≲ 300 J m-2 K-1 s-1/2) may be occasionally favorable to brine formation through deliquescence. Terrains with Γ ≲ 175 J m-2 K-1 s-1/2 and albedos of ≳0.25 are the most apt to subsurface brine formation. Should brines form, they would occur around Ls 100°. Their predicted properties would not meet the Special nor Uncertain Region requirements, as such they would not be potential habitable environments to life as we know it.
Cosmological reconstruction from galaxy light: neural network based light-matter connection

We present a method to reconstruct the initial conditions of the universe using observed galaxy positions and luminosities under the assumption that the luminosities can be calibrated with weak lensing to give the mean halo mass. Our method relies on following the gradients of forward model and since the standard way to identify halos is non-differentiable and results in a discrete sample of objects, we propose a framework to model the halo position and mass field starting from the non-linear matter field using Neural Networks (NN), which are differentiable, yet can produce very pointlike maps. We evaluate the performance of our model with multiple metrics and find that our model is more than 95% correlated with the halo-mass fields up to k~ 0.7 h/Mpc, and significantly reduces the stochasticity over the Poisson shot noise. We develop a data likelihood model that takes our modeling error and intrinsic scatter in the halo mass-light relation into account and show that a displaced log-normal model is a good approximation to it. We optimize over the corresponding loss function to reconstruct the initial density field of the dark matter starting from the halo mass field. To speed up and improve the convergence, we develop an annealing procedure for several parameters in the loss function, such as smoothing the likelihood starting with large smoothing and gradually decreasing it. We apply the method to halo number densities of = 2.5× 10−4 − 10−3(h/Mpc)3, typical of current and future redshift surveys, and recover a Gaussian initial density field, mapping all the higher order information in the data into the power spectrum of the linear reconstructed field. We show that our reconstruction improves over the standard reconstruction. For baryonic acoustic oscillations (BAO) the gains are relatively modest because BAO is dominated by large scales where standard reconstruction suffices. We improve upon it by ~ 15–20% in terms of error on BAO peak as estimated by Fisher analysis at z=0. We expect larger gains will be achieved when applying this method to the broadband linear power spectrum reconstruction on smaller scales.
THE EFFECTS OF DOUBLY IONIZED CHEMISTRY ON SH+ AND S+2 ABUNDANCES IN X-RAY-DOMINATED REGIONS

Recent laboratory measurements for the S+2 + H2 reaction find a total rate coefficient significantly larger than previously used in theoretical models of X-ray-dominated regions (XDRs). While the branching ratio of the products is unknown, one energetically possible route leads to the SH+ molecule, a known XDR diagnostic. In this work, we study the effects of S+2 on the formation of SH+ and the destruction of S+2 in XDRs. We find that the predicted SH+ column density for molecular gas surrounding an active galactic nucleus (AGN) increases by as much as 2 dex. As long as the branching ratio for S+2 + H2 → SH+ + H+ exceeds a few percent, doubly ionized chemistry will be the dominant pathway to SH+, which then initiates the formation of other sulfur-bearing molecules. We also find that the high rate of S+2 + H2 efficiently destroys S+2 once H2 forms, while the S+2 abundance remains high in the H0 region. We discuss the possible consequences of S+2 in the H0 region on mid-infrared diagnostics. The enhanced SH+ abundance has important implications in the study of XDRs, while our conclusions for S+2 could potentially affect the interpretation of Spitzer and SOFIA observations.
Triadic Measures on Graphs: The Power of Wedge Sampling

Graphs are used to model interactions in a variety of contexts, and there is a growing need to quickly assess the structure of a graph. Some of the most useful graph metrics, especially those measuring social cohesion, are based on triangles. Despite the importance of these triadic measures, associated algorithms can be extremely expensive. We discuss the method of wedge sampling. This versatile technique allows for the fast and accurate approximation of all current variants of clustering coefficients and enables rapid uniform sampling of the triangles of a graph. Our methods come with provable and practical time-approximation tradeoffs for all computations. We provide extensive results that show our methods are orders of magnitude faster than the stateof-the-art, while providing nearly the accuracy of full enumeration. Our results will enable more wide-scale adoption of triadic measures for analysis of extremely large graphs, as demonstrated on several real-world examples.
Segmenting Root Systems in X-Ray Computed Tomography Images Using Level Sets

The segmentation of plant roots from soil and other growing media in X-ray computed tomography images is needed to effectively study the root system architecture without excavation. However, segmentation is a challenging problem in this context because the root and non-root regions share similar features. In this paper, we describe a method based on level sets and specifically adapted for this segmentation problem. In particular, we deal with the issues of using a level sets approach on large image volumes for root segmentation, and track active regions of the front using an occupancy grid. This method allows for straightforward modifications to a narrow-band algorithm such that excessive forward and backward movements of the front can be avoided, distance map computations in a narrow band context can be done in linear time through modification of Meijster et al.'s distance transform algorithm, and regions of the image volume are iteratively used to estimate distributions for root versus non-root classes. Results are shown of three plant species of different maturity levels, grown in three different media. Our method compares favorably to a state-of-the-art method for root segmentation in X-ray CT image volumes.
The {\mathbb{Z}_2}-Orbifold of the {\mathcal{W}_3}-Algebra

The Zamolodchikov \({\mathcal{W}_3}\)-algebra \({\mathcal{W}^c_3}\) with central charge c has full automorphism group \({\mathbb{Z}_2}\). It was conjectured in the physics literature over 20 years ago that the orbifold \({(\mathcal{W}^c_3)^{\mathbb{Z}_2}}\) is of type \({\mathcal{W}(2,6,8,10,12)}\) for generic values of c. We prove this conjecture for all \({c \neq \frac{559 \pm 7 \sqrt{76657}}{95}}\), and we show that for these two values, the orbifold is of type \({\mathcal{W}(2,6,8,10,12,14)}\). This paper is part of a larger program of studying orbifolds and cosets of vertex algebras that depend continuously on a parameter. Minimal strong generating sets for orbifolds and cosets are often easy to find for generic values of the parameter, but determining which values are generic is a difficult problem. In the example of \({(\mathcal{W}^c_3)^{\mathbb{Z}_2}}\), we solve this problem using tools from algebraic geometry.
Automated reporting of GUI design violations for mobile apps

The inception of a mobile app often takes form of a mock-up of the Graphical User Interface (GUI), represented as a static image delineating the proper layout and style of GUI widgets that satisfy requirements. Following this initial mock-up, the design artifacts are then handed off to developers whose goal is to accurately implement these GUIs and the desired functionality in code. Given the sizable abstraction gap between mock-ups and code, developers often introduce mistakes related to the GUI that can negatively impact an app's success in highly competitive marketplaces. Moreover, such mistakes are common in the evolutionary context of rapidly changing apps. This leads to the time-consuming and laborious task of design teams verifying that each screen of an app was implemented according to intended design specifications. This paper introduces a novel, automated approach for verifying whether the GUI of a mobile app was implemented according to its intended design. Our approach resolves GUI-related information from both implemented apps and mock-ups and uses computer vision techniques to identify common errors in the implementations of mobile GUIs. We implemented this approach for Android in a tool called GVT and carried out both a controlled empirical evaluation with open-source apps as well as an industrial evaluation with designers and developers from Huawei. The results show that GVT solves an important, difficult, and highly practical problem with remarkable efficiency and accuracy and is both useful and scalable from the point of view of industrial designers and developers. The tool is currently used by over one-thousand industrial designers and developers at Huawei to improve the quality of their mobile apps.
2D materials in electro-optic modulation: energy efficiency, electrostatics, mode overlap, material transfer and integration

Here we discuss the physics of electro-optic modulators deploying 2D materials. We include a scaling laws analysis and show how energy-efficiency and speed change for three underlying cavity systems as a function of critical device length scaling. A key result is that the energy-per-bit of the modulator is proportional to the volume of the device, thus making the case for submicron-scale modulators possible deploying a plasmonic optical mode. We then show how Graphene’s Pauli-blocking modulation mechanism is sensitive to the device operation temperature, whereby a reduction of the temperature enables a 10× reduction in modulator energy efficiency. Furthermore, we show how the high-index tunability of graphene is able to compensate for the small optical overlap factor of 2D-based material modulators, which is unlike classical silicon-based dispersion devices. Lastly, we demonstrate a novel method towards a 2D material printer suitable for cross-contamination free and on-demand printing. The latter paves the way to integrate 2D materials seamlessly into taped-out photonic chips.
GENERAL RELATIVITY AS AN ÆTHER THEORY

Most early twentieth century relativists — Lorentz, Einstein, Eddington, for examples — claimed that general relativity was merely a theory of the aether. We shall confirm this claim by deriving the Einstein equations using aether theory. We shall use a combination of Lorentz's and Kelvin's conception of the aether. Our derivation of the Einstein equations will not use the vanishing of the covariant divergence of the stress–energy tensor, but instead equate the Ricci tensor to the sum of the usual stress–energy tensor and a stress–energy tensor for the aether, a tensor based on Kelvin's aether theory. A crucial first step is generalizing the Cartan formalism of Newtonian gravity to allow spatial curvature, as conjectured by Gauss and Riemann. In essence, we shall show that the Einstein equations are a special case of Newtonian gravity coupled to a particular type of luminiferous aether. Our derivation of general relativity is simple, and it emphasizes how inevitable general relativity is, given the truth of Newtonian gravity and the Maxwell equations.
Learning-Based Application-Agnostic 3D NoC Design for Heterogeneous Manycore Systems

The rising use of deep learning and other big-data algorithms has led to an increasing demand for hardware platforms that are computationally powerful, yet energy-efficient. Due to the amount of data parallelism in these algorithms, high-performance three-dimensional (3D) manycore platforms that incorporate both CPUs and GPUs present a promising direction. However, as systems use heterogeneity (e.g., a combination of CPUs, GPUs, and accelerators) to improve performance and efficiency, it becomes more pertinent to address the distinct and likely conflicting communication requirements (e.g., CPU memory access latency or GPU network throughput) that arise from such heterogeneity. Unfortunately, it is difficult to quickly explore the hardware design space and choose appropriate tradeoffs between these heterogeneous requirements. To address these challenges, we propose the design of a 3D Network-on-Chip (NoC) for heterogeneous manycore platforms that considers the appropriate design objectives for a 3D heterogeneous system and explores various tradeoffs using an efficient machine learning (ML)-based multi-objective optimization (MOO) technique. The proposed design space exploration considers the various requirements of its heterogeneous components and generates a set of 3D NoC architectures that efficiently trades off these design objectives. Our findings show that by jointly considering these requirements (latency, throughput, temperature, and energy), we can achieve 9.6 percent better Energy-Delay Product on average at nearly iso-temperature conditions when compared to a thermally-optimized design for 3D heterogeneous NoCs. More importantly, our results suggest that our 3D NoCs optimized for a few applications can be generalized for unknown applications as well. Our results show that these generalized 3D NoCs only incur a 1.8 percent (36-tile system) and 1.1 percent (64-tile system) average performance loss compared to application-specific NoCs.
DRASIC: Distributed Recurrent Autoencoder for Scalable Image Compression

We propose a new architecture for distributed image compression from a group of distributed data sources. The work is motivated by practical needs of data-driven codec design, low power consumption, robustness, and data privacy. The proposed architecture, which we refer to as Distributed Recurrent Autoencoder for Scalable Image Compression (DRASIC), is able to train distributed encoders and one joint decoder on correlated data sources. Its compression capability is much better than the method of training codecs separately. Meanwhile, the performance of our distributed system with 10 distributed sources is only within 2 dB peak signal-to-noise ratio (PSNR) of the performance of a single codec trained with all data sources. We experiment distributed sources with different correlations and show how our data-driven methodology well matches the Slepian-Wolf Theorem in Distributed Source Coding (DSC). To the best of our knowledge, this is the first data-driven DSC framework for general distributed code design with deep learning.
The Impact of Interpixel Capacitance in CMOS Detectors on PSF Shapes and Implications for WFIRST

Unlike optical CCDs, near-infrared detectors, which are based on CMOS hybrid readout technology, typically suffer from electrical crosstalk between the pixels. The interpixel capacitance (IPC) responsible for the crosstalk affects the point-spread function (PSF) of the telescope, increasing the size and modifying the shape of all objects in the images while correlating the Poisson noise. Upcoming weak lensing surveys that use these detectors, such as WFIRST, place stringent requirements on the PSF size and shape (and the level at which these are known), which in turn must be translated into requirements on IPC. To facilitate this process, we present a first study of the effect of IPC on WFIRST PSF sizes and shapes. Realistic PSFs are forward-simulated from physical principles for each WFIRST bandpass. We explore how the PSF size and shape depends on the range of IPC coupling with pixels that are connected along an edge or corner; for the expected level of IPC in WFIRST, IPC increases the PSF sizes by ~5%. We present a linear fitting formula that describes the uncertainty in the PSF size or shape due to uncertainty in the IPC, which could arise for example due to unknown time evolution of IPC as the detectors age or due to spatial variation of IPC across the detector. We also study of the effect of a small anisotropy in the IPC, which further modifies the PSF shapes. Our results are a first, critical step in determining the hardware and characterization requirements for the detectors used in the WFIRST survey.
Environmental structure and competitive scoring advantages in team competitions

In most professional sports, playing field structure is kept neutral so that scoring imbalances may be attributed to differences in team skill. It thus remains unknown what impact environmental heterogeneities can have on scoring dynamics or competitive advantages. Applying a novel generative model of scoring dynamics to roughly 10 million team competitions drawn from an online game, we quantify the relationship between the structure within a competition and its scoring dynamics, while controlling the impact of chance. Despite wide structural variations, we observe a common three-phase pattern in the tempo of events. Tempo and balance are highly predictable from a competition's structural features alone and teams exploit environmental heterogeneities for sustained competitive advantage. Surprisingly, the most balanced competitions are associated with specific environmental heterogeneities, not from equally skilled teams. These results shed new light on the design principles of balanced competition, and illustrate the potential of online game data for investigating social dynamics and competition.
Noncommutative spheres and the AdS/CFT correspondence

We present direct arguments for non-commutativity of spheres in the AdS/CFT correspondence. The discussion is based on results for the SN orbifold SCFT. Concentrating on three point correlations (at finite N) we exhibit a comparison with correlations on a non-commutative sphere. In this manner an essential signature of non-commutativity is identified giving further support for the original proposal of hep-th/9902059.
Local Well-Posedness for the Motion of a Compressible, Self-Gravitating Liquid with Free Surface Boundary

We establish the local well-posedness for the free boundary problem for the compressible Euler equations describing the motion of liquid under the influence of Newtonian self-gravity. We do this by solving a tangentially-smoothed version of Euler’s equations in Lagrangian coordinates which satisfies uniform energy estimates as the smoothing parameter goes to zero. The main technical tools are delicate energy estimates and optimal elliptic estimates in terms of boundary regularity, for the Dirichlet problem and Green’s function.
The Novikov conjecture

We give a survey on recent development of the Novikov conjecture and its applications to topological rigidity and non-rigidity. .
Riemannian Geometry on Quantum Spaces

An algebraic formulation of Riemannian geometry on quantum spaces is presented, where Riemannian metric, distance, Laplacian, connection, and curvature have their counterparts. This description is also extended to complex manifolds. Examples include the quantum sphere, the complex quantum projective space and the two-sheeted space.
Estimating average treatment effects with a double-index propensity score

We consider estimating average treatment effects (ATE) of a binary treatment in observational data when data-driven variable selection is needed to select relevant covariates from a moderately large number of available covariates X . To leverage covariates among X predictive of the outcome for efficiency gain while using regularization to fit a parametric propensity score (PS) model, we consider a dimension reduction of X based on fitting both working PS and outcome models using adaptive LASSO. A novel PS estimator, the Double-index Propensity Score (DiPS), is proposed, in which the treatment status is smoothed over the linear predictors for X from both the initial working models. The ATE is estimated by using the DiPS in a normalized inverse probability weighting estimator, which is found to maintain double robustness and also local semiparametric efficiency with a fixed number of covariates p. Under misspecification of working models, the smoothing step leads to gains in efficiency and robustness over traditional doubly robust estimators. These results are extended to the case where p diverges with sample size and working models are sparse. Simulations show the benefits of the approach in finite samples. We illustrate the method by estimating the ATE of statins on colorectal cancer risk in an electronic medical record study and the effect of smoking on C-reactive protein in the Framingham Offspring Study.
Multiscale preferential sweeping of particles settling in turbulence

In a seminal article, Maxey (J. Fluid Mech., vol. 174, 1987, pp. 441–465) presented a theoretical analysis showing that enhanced particle settling speeds in turbulence occur through the preferential sweeping mechanism, which depends on the preferential sampling of the fluid velocity gradient field by the inertial particles. However, recent direct numerical simulation (DNS) results in Ireland et al. (J. Fluid Mech., vol. 796, 2016b, pp. 659–711) show that even in a portion of the parameter space where this preferential sampling is absent, the particles nevertheless exhibit enhanced settling velocities. Further, there are several outstanding questions concerning the role of different turbulent flow scales on the enhanced settling, and the role of the Taylor Reynolds number . The results also show that as the Stokes settling velocity of the particles is increased, the flow scales of the turbulence responsible for enhancing the particle settling speed become larger. Finally, we explored the multiscale nature of the preferential sweeping mechanism by considering how particles preferentially sample the fluid velocity gradients coarse grained at various scales. The results show that while rapidly settling particles do not preferentially sample the fluid velocity gradients, they do preferentially sample the fluid velocity gradients coarse grained at scales outside of the dissipation range. This explains the findings of Ireland et al., and further illustrates the truly multiscale nature of the mechanism generating enhanced particle settling speeds in turbulence.
Geometric limits of knot complements

We prove that any complete hyperbolic 3-manifold with finitely generated fundamental group, with a single topological end, and which embeds into is the geometric limit of a sequence of hyperbolic knot complements in . In particular, we derive the existence of hyperbolic knot complements that contain balls of arbitrarily large radius. We also show that a complete hyperbolic 3-manifold with two convex cocompact ends cannot be a geometric limit of knot complements in .
On landmark selection and sampling in high-dimensional data analysis

In recent years, the spectral analysis of appropriately defined kernel matrices has emerged as a principled way to extract the low-dimensional structure often prevalent in high-dimensional data. Here, we provide an introduction to spectral methods for linear and nonlinear dimension reduction, emphasizing ways to overcome the computational limitations currently faced by practitioners with massive datasets. In particular, a data subsampling or landmark selection process is often employed to construct a kernel based on partial information, followed by an approximate spectral analysis termed the Nystrom extension. We provide a quantitative framework to analyse this procedure, and use it to demonstrate algorithmic performance bounds on a range of practical approaches designed to optimize the landmark selection process. We compare the practical implications of these bounds by way of real-world examples drawn from the field of computer vision, whereby low-dimensional manifold structure is shown to emerge from high-dimensional video data streams.
Learning Sparse Prototypes for Text Generation

Prototype-driven text generation uses non-parametric models that first choose from a library of sentence "prototypes" and then modify the prototype to generate the output text. While effective, these methods are inefficient at test time as a result of needing to store and index the entire training corpus. Further, existing methods often require heuristics to identify which prototypes to reference at training time. In this paper, we propose a novel generative model that automatically learns a sparse prototype support set that, nonetheless, achieves strong language modeling performance. This is achieved by (1) imposing a sparsity-inducing prior on the prototype selection distribution, and (2) utilizing amortized variational inference to learn a prototype retrieval function. In experiments, our model outperforms previous prototype-driven language models while achieving up to a 1000x memory reduction, as well as a 1000x speed-up at test time. More interestingly, we show that the learned prototypes are able to capture semantics and syntax at different granularity as we vary the sparsity of prototype selection, and that certain sentence attributes can be controlled by specifying the prototype for generation.
Constraints on Effective Constitutive Parameters of Certain Bianisotropic Laminated Composite Materials

Abstract When the electrically thin unit cell of a laminated composite material is made of two bianisotropic sheets whose constitutive properties in the thickness direction are decoupled from the constitutive properties in the interfacial planes, the laminated composite material can be homogenized into a material, not all of whose constitutive parameters are independent of each other. This nonindependence of the constitutive dyadics of the constituent materials and the homogenized composite material is captured by two simple constraints, which may not hold if even one of the two constituent materials has more complicated constitutive properties than stated above.
Magneto-structural transformations via a solid-state nudged elastic band method: Application to iron under pressure

We extend the solid-state nudged elastic band method to handle a non-conserved order parameter, in particular, magnetization, that couples to volume and leads to many observed effects in magnetic systems. We apply this formalism to the well-studied magneto-volume collapse during the pressure-induced transformation in iron—from ferromagnetic body-centered cubic (bcc) austenite to hexagonal close-packed (hcp) martensite. We find a bcc-hcp equilibrium coexistence pressure of 8.4 GPa, with the transition-state enthalpy of 156 meV/Fe at this pressure. A discontinuity in magnetization and coherent stress occurs at the transition state, which has a form of a cusp on the potential-energy surface (yet all the atomic and cell degrees of freedom are continuous); the calculated pressure jump of 25 GPa is related to the observed 25 GPa spread in measured coexistence pressures arising from martensitic and coherency stresses in samples. Our results agree with experiments, but necessarily differ from those arising from drag and restricted parametrization methods having improperly constrained or uncontrolled degrees of freedom.
Lorentz Symmetry and Matter-Gravity Couplings

In spite of the many high-sensitivity investigations of Lorentz violation performed in the context of the fermion sector of the minimal StandardModel Extension (SME) in Minkowski spacetime, only about half of the coefficients for Lorentz violation in that sector have been investigated experimentally. Reference 3 establishes a methodology for obtaining sensitivities to some of these open parameters by considering gravitational couplings in the fermions sector of the SME, extending pure gravity work. Of particular interest are the aμ coefficients for baryons and charged leptons, which are unobservable in principle in Minkowski spacetime, but could be relatively large due to gravitational countershading. The first half of Ref. 3 develops the necessary theoretical results for the analysis of Lorentz violation in matter-gravity couplings. Those results are summarized in Sec. 2 below, while Sec. 3 summarizes the experimental predictions provided in the second half of that work.
Homogeneous coordinate rings and mirror symmetry for toric varieties

In this paper we give some evidence for M Kontsevich’s homological mirror symmetry conjecture [13] in the context of toric varieties. Recall that a smooth complete toric variety is given by a simplicial rational polyhedral fan  such that jj D R and all maximal cones are non-singular (Fulton [10, Section 2.1]). The convex hull of the primitive vertices of the 1–cones of  is a convex polytope which we denote by P , containing the origin as an interior point, and may be thought of as the Newton polytope of a Laurent polynomial W W .C/ ! C. This Laurent polynomial is the Landau–Ginzburg mirror of X .