cssi/SciSciGPT-SciSciNet huggingface dataset:
Super-CMB fluctuations and the Hubble tension

Abstract We study the covariance in the angular power spectrum estimates of CMB fluctuations when the primordial fluctuations are non-Gaussian. The non-Gaussian covariance comes from a nonzero connected four-point correlation function – or the trispectrum in Fourier space – and can be large when long-wavelength (super-CMB) modes are strongly coupled to short-wavelength modes. The effect of such non-Gaussian covariance can be modeled through additional freedom in the theoretical CMB angular power spectrum and can lead to different inferred values of the standard cosmological parameters relative to those in Λ CDM. Taking the collapsed limit of the primordial trispectrum in the quasi-single field inflation model as an example, we study how the six standard Λ CDM parameters shift when two additional parameters describing the trispectrum are allowed. The reduced statistical significance of the Hubble tension in the extended model allows us to combine the Planck temperature data and the type Ia supernovae data from Panstarrs with the distance-ladder measurement of the Hubble constant. This combination of data shows strong evidence for a primordial trispectrum-induced non-Gaussian covariance, with a likelihood improvement of Δ χ 2 ≈ − 15 (with two additional parameters) relative to Λ CDM.
Steady-state Planet Migration by the Kozai-Lidov Mechanism in Stellar Binaries

We study the steady-state orbital distributions of giant planets migrating through the combination of the Kozai-Lidov (KL) mechanism due to a stellar companion and friction due to tides raised on the planet by the host star. We run a large set of Monte Carlo simulations that describe the secular evolution of a star-planet-star triple system including the effects from general relativistic precession, stellar and planetary spin evolution, and tides. Our simulations show that KL migration produces Hot Jupiters (HJs) with semi-major axes that are generally smaller than in the observations and they can only explain the observations if the following are both true: (1) tidal dissipation at high eccentricities is at least ~150 times more efficient than the upper limit inferred from the Jupiter-Io interaction; (2) highly eccentric planets get tidally disrupted at distances 0.015 AU. Based on the occurrence rate and semi-major axis distribution of HJs, we find that KL migration in stellar binaries can produce at most ~20% of the observed HJs. Almost no intermediate-period (semi-major axis ~0.1 -2 AU) planets are formed by this mechanism—migrating planets spend most of their lifetimes undergoing KL oscillations at large orbital separations (>2 AU) or as HJs.
Real-time Quadrotor Navigation Through Planning in Depth Space in Unstructured Environments*

This paper addresses the problem of real-time vision-based autonomous obstacle avoidance in unstructured environments for quadrotor UAVs. We assume that our UAV is equipped with a forward facing stereo camera as the only sensor to perceive the world around it. Moreover, all the computations are performed onboard. Feasible trajectory generation in this kind of problems requires rapid collision checks along with efficient planning algorithms. We propose a trajectory generation approach in the depth image space, which refers to the environment information as depicted by the depth images. In order to predict the collision in a look ahead robot trajectory, we create depth images from the sequence of robot poses along the path. We compare these images with the depth images of the actual world sensed through the forward facing stereo camera. We aim at generating fuel optimal trajectories inside the depth image space. In case of a predicted collision, a switching strategy is used to aggressively deviate the quadrotor away from the obstacle. For this purpose we use two closed loop motion primitives based on Linear Quadratic Regulator (LQR) objective functions. The proposed approach is validated through simulation and hardware experiments.
Chiral EFT based nuclear forces: achievements and challenges

During the past two decades, chiral effective field theory has become a popular tool to derive nuclear forces from first principles. Two-nucleon interactions have been worked out up to sixth order of chiral perturbation theory and three-nucleon forces up to fifth order. Applications of some of these forces have been conducted in nuclear few- and many-body systems—with a certain degree of success. But in spite of these achievements, we are still faced with great challenges. Among them is the issue of a proper uncertainty quantification of predictions obtained when applying these forces in ab initio calculations of nuclear structure and reactions. A related problem is the order by order convergence of the chiral expansion. We start this review with a pedagogical introduction and then present the current status of the field of chiral nuclear forces. This is followed by a discussion of representative examples for the application of chiral two- and three-body forces in the nuclear many-body system including convergence issues.
On the absolute continuity of p-harmonic measure and surface measure in Reifenberg flat domains

In this paper, we study the set of absolute continuity of p-harmonic measure, $\mu$, and $(n-1)-$dimensional Hausdorff measure, $\mathcal{H}^{n-1}$, on locally flat domains in $\mathbb{R}^{n}$, $n\geq 2$. We prove that for fixed $p$ with $2 0=\mathcal{H}^{n-1}(K)$ where $\mu$ is the p-harmonic measure associated to a positive weak solution to p-Laplace equation in $\Omega$ with continuous boundary value zero on $\partial\Omega$. We also show that there exists such a domain for which the same result holds when $p$ is fixed with $2-\eta 0$ provided that $n\geq 3$. This work is a generalization of a recent result of Azzam, Mourgoglou, and Tolsa when the measure $\mu$ is harmonic measure at $x$, $\omega=\omega^{x}$, associated to the Laplace equation, i.e when $p=2$.
The analytic solution for the power series expansion of Heun function

Abstract The Heun function generalizes all well-known special functions such as Spheroidal Wave, Lame, Mathieu, and hypergeometric 2 F 1 , 1 F 1 and 0 F 1 functions. Heun functions are applicable to diverse areas such as theory of black holes, lattice systems in statistical mechanics, solution of the Schrodinger equation of quantum mechanics, and addition of three quantum spins. In this paper I will apply three term recurrence formula (Y.S. Choun, arXiv:1303.0806 , 2013) to the power series expansion in closed forms of Heun function (infinite series and polynomial) including all higher terms of A n ’s. Section 3 contains my analysis on applying the power series expansions of Heun function to a recent paper (R.S. Maier, Math. Comp. 33 (2007) 811–843). Due to space restriction final equations for the 192 Heun functions are not included in the paper, but feel free to contact me for the final solutions. Section 4 contains two additional examples using the power series expansions of Heun function. This paper is 3rd out of 10 in series “Special functions and three term recurrence formula (3TRF)”. See Section 5 for all the papers in the series. The previous paper in series deals with three term recurrence formula (3TRF). The next paper in the series describes the integral forms of Heun function and its asymptotic behaviors analytically.
Spectroscopic Constants and Vibrational Frequencies for l-C3H+ and Isotopologues from Highly-Accurate Quartic Force Fields: The Detection of l-C3H+ in the Horsehead Nebula PDR Questioned

Very recently, molecular rotational transitions observed in the photon-dominated region of the Horsehead nebula have been attributed to l-C3H+. In an effort to corroborate this finding, we employed state-of-the art and proven high-accuracy quantum chemical techniques to compute spectroscopic constants for this cation and its isotopologues. Even though the B rotational constant from the fit of the observed spectrum and our computations agree to within 20 MHz, a typical level of accuracy, the D rotational constant differs by more than 40%, while the H rotational constant differs by three orders of magnitude. With the likely errors in the rotational transition energies resulting from this difference in D on the order of 1 MHz for the lowest observed transition (J = 4 yields 3) and growing as J increases, the assignment of the observed rotational lines from the Horsehead nebula to l-C3H+ is questionable.
Constructing a Flexible Likelihood Function for Spectroscopic Inference

We present a modular, extensible likelihood framework for spectroscopic inference based on synthetic model spectra. The subtraction of an imperfect model from a continuously sampled spectrum introduces covariance between adjacent datapoints (pixels) into the residual spectrum. For the high signal-to-noise data with large spectral range that is commonly employed in stellar astrophysics, that covariant structure can lead to dramatically underestimated parameter uncertainties (and, in some cases, biases). We construct a likelihood function that accounts for the structure of the covariance matrix, utilizing the machinery of Gaussian process kernels. This framework specifically address the common problem of mismatches in model spectral line strengths (with respect to data) due to intrinsic model imperfections (e.g., in the atomic/molecular databases or opacity prescriptions) by developing a novel local covariance kernel formalism that identifies and self-consistently downweights pathological spectral line "outliers." By fitting many spectra in a hierarchical manner, these local kernels provide a mechanism to learn about and build data-driven corrections to synthetic spectral libraries. An open-source software implementation of this approach is available at this http URL, including a sophisticated probabilistic scheme for spectral interpolation when using model libraries that are sparsely sampled in the stellar parameters. We demonstrate some salient features of the framework by fitting the high resolution $V$-band spectrum of WASP-14, an F5 dwarf with a transiting exoplanet, and the moderate resolution $K$-band spectrum of Gliese 51, an M5 field dwarf.
Scl in free products

We study stable commutator length (scl) in free products via surface maps into a wedge of spaces. We prove that scl is piecewise rational linear if it vanishes on each factor of the free product, generalizing a theorem of Danny Calegari. We further prove that the property of isometric embedding with respect to scl is preserved under taking free products. The method of proof gives a way to compute scl in free products which lets us generalize and derive in a new way several well-known formulas. Finally we show independently and in a new approach that scl in free products of cyclic groups behaves in a piecewise quasirational way when the word is fixed but the orders of factors vary, previously proved by Timothy Susse, settling a conjecture of Alden Walker.
The Equivariant Generating Hypothesis

This conjecture was introduced by Freyd in 1965 [4] and remains open today. Recent work has examined analogous statements in algebraic categories that share many properties of the homotopy category of spectra, such as the derived category of a ring (see Hovey et al [7] or Lockridge [10]) or the stable module category of a finite group (see Benson et al [1] or Carlson et al [2]). Here we examine the analogous conjecture for the homotopy category of G –equivariant spectra for a compact Lie group G .
On Some Electroconvection Models

We consider a model of electroconvection motivated by studies of the motion of a two-dimensional annular suspended smectic film under the influence of an electric potential maintained at the boundary by two electrodes. We prove that this electroconvection model has global in time unique smooth solutions.
The Warm Ionized Medium in the Milky Way and Other Galaxies

There are now observations of several emission lines from the warm ionized medium (WIM or, equivalently, the diffuse ionized gas) of the local interstellar medium, from the Perseus arm in the Milky Way, and also in several other galaxies. Interesting features of these observations include the great strength of [N II] λ6563 (~Hα in some cases) and the fact that [S II] λ6717/[N II] λ6583 is almost the same (~0.6-0.7) in all locations and objects. Other line ratios (e.g., [O III] λ5007/Hβ) vary considerably. This paper presents simple photoionization models that reproduce the observed spectra, providing extra heating beyond that supplied by photoionization is assumed. The same extra heating was used for models of all stellar temperatures being combined together, although it could easily depend on T*. With observed gas-phase abundances (not solar), the line ratios in the Local arm at b = 0° are fitted with no extra heating and S/H = 13 ppm, as opposed to solar (~20 ppm). Local gas observed at b = -35° requires extra heating of about Γ-25 = 0.75, where Γ-25 is the extra heating in units of 10-25 ergs H-1 s-1. In the Perseus arm there are similar results: little extra heating is required at |z| = 500 pc, and Γ-25 = 3.0 is needed at |z| = 1.2 kpc. To fit the observations, the gas-phase composition in the Perseus arm must be reduced as required by the Galactic abundance gradient observed for H II regions. The requirements for NGC 891 (the best observed other galaxy) at |z| = 1 kpc and 2 kpc are similar to the Perseus arm: little or no extra heating near the plane (1 kpc in this case) and Γ-25 ~ 3 at |z| = 2 kpc. In NGC 891 there is also an increase of λ5007/Hα with |z| that can only come about if most of the ionizing radiation is supplied by very hot stars (type O4: T* ~ 50,000 K). Either their radiation must propagate from the plane to high |z| through very little intervening matter, or else the stars are located at high |z|. The total power requirement of the extra heating is 15% of the power to photoionize the WIM without extra heating. Extra heating enhances [O II] λ3727/Hβ. Figure 1 shows that there is a spread in the predicted values, but the ratio can serve as a useful diagnostic of extra heating. The [S III] λλ9065, 9531 lines (see Fig. 2) are not useful in diagnosing extra heating.
Smooth embeddings with stein surface images

A simple characterization is given of open subsets of a complex surface that smoothly perturb to Stein open subsets. As applications, complex 2-space C^2 contains domains of holomorphy (Stein open subsets) that are exotic R^4's, and others homotopy equivalent to the 2-sphere but cut out by smooth, compact 3-manifolds. Pseudoconvex embeddings of Brieskorn spheres and other 3-manifolds into complex surfaces are constructed, as are pseudoconcave holomorphic fillings (with disagreeing contact and boundary orientations). Pseudoconcave complex structures on Milnor fibers are found. A byproduct of this construction is a simple polynomial expression for the signature of the (p,q,npq-1) Milnor fiber. Akbulut corks in complex surfaces can always be chosen to be pseudoconvex or pseudoconcave submanifods. The main theorem is expressed via Stein handlebodies (possibly infinite), which are defined holomorphically in all dimensions by extending Stein theory to manifolds with noncompact boundary.
Computing aggregate properties of preimages for 2D cellular automata

Computing properties of the set of precursors of a given configuration is a common problem underlying many important questions about cellular automata. Unfortunately, such computations quickly become intractable in dimension greater than one. This paper presents an algorithm—incremental aggregation—that can compute aggregate properties of the set of precursors exponentially faster than naive approaches. The incremental aggregation algorithm is demonstrated on two problems from the two-dimensional binary Game of Life cellular automaton: precursor count distributions and higher-order mean field theory coefficients. In both cases, incremental aggregation allows us to obtain new results that were previously beyond reach.
Spectrum generating conformal and quasiconformal U-duality groups, supergravity and spherical vectors

After reviewing the algebraic structures that underlie the geometries of N = 2 Maxwell-Einstein supergravity theories (MESGT) with symmetric scalar manifolds in five and four dimensions, we give a unified realization of their three dimensional U-duality groups as spectrum generating quasiconformal groups. They are F 4(4),E 6(2),E 7(−5),E 8(−24) and SO(n+2, 4). Our formulation is covariant with respect to U-duality symmetry groups of corresponding five dimensional supergravity theories, which are SL(3,\( \mathbb{R} \)), SL(3,\( \mathbb{C} \)), SU*(6), E 6(−26) and SO(n − 1, 1) × SO(1, 1), respectively. We determine the spherical vectors of quasiconformal realizations of all these groups twisted by a unitary character ν. We present their quadratic Casimir operators and determine their values in terms of ν and the number n V of vector fields of the respective 5D supergravity. For ν = −(n V + 2) + iρ the quasiconformal action induces unitary representations belonging to the principal series. For special discrete values of ν it leads to unitary representations belonging to the quaternionic discrete series. Our results lay the algebraic groundwork for constructing explicitly the quaternionic discrete series unitary representations. For rank 2 cases, SU(2, 1) and G 2(2), corresponding to simple N = 2 supergravity in four and five dimensions, respectively, this program was carried out in arXiv:0707.1669 and applied to quantum attractor flows.
How Would Surround Vehicles Move? A Unified Framework for Maneuver Classification and Motion Prediction

Reliable prediction of surround vehicle motion is a critical requirement for path planning for autonomous vehicles. In this paper, we propose a unified framework for surround vehicle maneuver classification and motion prediction that exploits multiple cues, namely, the estimated motion of vehicles, an understanding of typical motion patterns of freeway traffic and intervehicle interaction. We report our results in terms of maneuver classification accuracy and mean and median absolute error of predicted trajectories against the ground truth for real traffic data collected using vehicle mounted sensors on freeways. An ablative analysis is performed to analyze the relative importance of each cue for trajectory prediction. Additionally, an analysis of execution time for the components of the framework is presented. Finally, we present multiple case studies analyzing the outputs of our model for complex traffic scenarios.
Modular polynomials via isogeny volcanoes

We present a new algorithm to compute the classical modular polynomial l in the rings Z(X;Y ) and (Z=mZ)(X;Y ), for a prime l and any positive integer m. Our approach uses the graph of l-isogenies to eciently compute l mod p for many primes p of a suitable form, and then applies the Chinese Remainder Theorem (CRT). Under the Generalized Riemann Hypoth- esis (GRH), we achieve an expected running time of O(l 3 (logl) 3 log logl), and compute l mod m using O(l 2 (logl) 2 +l 2 logm) space. We have used the new algorithm to compute l with l over 5000, and l mod m with l over 20000. We also consider several modular functions g for which g is smaller than l, allowing us to handle l over 60000.
Integrable open spin chains in defect conformal field theory

We demonstrate that the one-loop dilatation generator for the scalar sector of a certain perturbation of = 4 Super Yang-Mills with fundamentals is the hamiltonian of an integrable spin chain with open boundary conditions. The theory is a supersymmetric defect conformal field theory (dCFT) with the fundamentals in hypermultiplets confined to a codimension one defect. We obtain a -matrix satisfying a suitably generalized form of the boundary Yang-Baxter equation, study the Bethe ansatz equations, and demonstrate how Dirichlet and Neumann boundary conditions arise in field theory, and match to existing results in the plane wave limit.
How big are the smallest drops of quark-gluon plasma?

Using holographic duality, we present results for both head-on and off-center collisions of Gaussian shock waves in strongly coupled $$ \mathcal{N}=4 $$ supersymmetric Yang-Mills theory. The shock waves superficially resemble Lorentz contracted colliding protons. The collisions results in the formation of a plasma whose evolution is well described by viscous hydrodynamics. The size of the produced droplet is R ∼ 1/T eff where T eff is the effective temperature, which is the characteristic microscopic scale in strongly coupled plasma. These results demonstrate the applicability of hydrodynamics to microscopically small systems and bolster the notion that hydrodynamics can be applied to heavy-light ion collisions as well as some proton-proton collisions.
Accurate closed-form trajectories of light around a Kerr black hole using asymptotic approximants

Highly accurate closed-form expressions that describe the full trajectory of photons propagating in the equatorial plane of a Kerr black hole are obtained using asymptotic approximants. This work extends a prior study of the overall bending angle for photons (Barlow et al 2017 Class. Quantum Grav. 34 135017). The expressions obtained provide accurate trajectory predictions for arbitrary spin and impact parameters, and provide significant time advantages compared with numerical evaluation of the elliptic integrals that describe photon trajectories. To construct approximants, asymptotic expansions for photon deflection are required in various limits. To this end, complete expansions are derived for the azimuthal angle as a function of radial distance from the black hole in the far-distance and closest-approach (pericenter) limits, and new coefficients are reported for the bending angle in the weak-field limit (large impact parameter).
Theory of Double Ladder Lumped Circuits With Degenerate Band Edge

A conventional periodic LC ladder circuit forms a transmission line that has a regular band edge between a passband and a stopband. Here for the first time, we develop the theory of simple yet unconventional double ladder circuit that exhibits a special degeneracy condition referred to as a degenerate band edge (DBE). The degeneracy occurs when four independent eigenstates coalesce into a single eigenstate at the DBE frequency. In addition to possible practical applications, this circuit may provide insight into DBE behavior that is not clear in more complex systems. We show that double ladder resonators exhibit unusual behavior of the loaded quality factor near the DBE, leading to a stable resonance frequency against load variations. These two properties in the proposed circuit are superior to the analogous properties in single ladder circuits. Our proposed analysis leads to analytic expressions for all circuit quantities thus providing insight into the very complex behavior near degeneracy points in periodic circuits. Interestingly, here we show for the first time That a DBE is obtained with unit cells that are symmetric along the propagation direction. The proposed theory of double ladders presented here has potential applications in filters, couplers, oscillators, and pulse shaping networks.
Quantitatively ranking incorrect responses to multiple-choice questions using item response theory

Using relative correctness of incorrect responses on multiple-choice assessments to gain more information about student understanding.
Cosmic Acceleration, Dark Energy and Fundamental Physics

A web of interlocking observations has established that the expansion of the Universe is speeding up and not slowing, revealing the presence of some form of repulsive gravity. Within the context of...
Measuring spiral arm torques: Results for M100

Spiral arms, if they are massive, exert gravitational torques that transport angular momentum radially within galactic disks. These torques depend not on the pattern speed or permanence of the arms but only on the nonaxisymmetric mass distribution. Hence the torques can be measured from photometry. We demonstrate this using $gri$ CCD data for M100 (NGC 4321). Since we find consistency among the three bands, we believe that dust and young stars in the arms do not seriously bias our results. If the present epoch is representative, the timescale for redistribution of angular momentum in M100 is $5-10$ Gyr, the main uncertainty being the mass-to-light ratio of the disk.
Electron transparent graphene windows for environmental scanning electron microscopy in liquids and dense gases

Due to its ultrahigh electron transmissivity in a wide electron energy range, molecular impermeability, high electrical conductivity and excellent mechanical stiffness, suspended graphene membranes appear to be a nearly ideal window material for in situ (in vivo) environmental electron microscopy of nano- and mesoscopic objects (including bio-medical samples) immersed in liquids and/or in dense gaseous media. In this paper, taking advantage of a small modification of the graphene transfer protocol onto metallic and SiN supporting orifices, reusable environmental cells with exchangeable graphene windows have been designed. Using colloidal gold nanoparticles (50 nm) dispersed in water as model objects for scanning electron microscopy in liquids as proof of concept, different conditions for imaging through the graphene membrane were tested. Limiting factors for electron microscopy in liquids, such as electron beam induced water radiolysis and damage of the graphene membrane at high electron doses, are discussed.
Dark Energy Constraints from the CTIO Lensing Survey

We perform a cosmological parameter analysis of the 75 deg2 CTIO lensing survey in conjunction with cosmic microwave background (CMB) and Type Ia supernovae data. For ΛCDM cosmologies, we find that the amplitude of the power spectrum at low redshift is given by σ8 = 0.81 (95% confidence level), where the error bound includes both statistical and systematic errors. The total of all systematic errors is smaller than the statistical errors, but they do make up a significant fraction of the error budget. We find that weak lensing improves the constraints on dark energy as well. The (constant) dark energy equation of state parameter, w, is measured to be -0.89 (95% c.l.). Marginalizing over a constant w slightly changes the estimate of σ8 to 0.79 (95% c.l.). We also investigate variable w cosmologies but find that the constraints weaken considerably; next-generation surveys are needed to obtain meaningful constraints on the possible time evolution of dark energy.
The elusive memristor: properties of basic electrical circuits

We present an introduction to and a tutorial on the properties of the recently discovered ideal circuit element, a memristor. By definition, a memristor M relates the charge q and the magnetic flux in a circuit and complements a resistor R, a capacitor C and an inductor L as an ingredient of ideal electrical circuits. The properties of these three elements and their circuits are a part of the standard curricula. The existence of the memristor as the fourth ideal circuit element was predicted in 1971 based on symmetry arguments, but was clearly experimentally demonstrated just last year. We present the properties of a single memristor, memristors in series and parallel, as well as ideal memristor–capacitor (MC), memristor–inductor (ML) and memristor–capacitor–inductor (MCL) circuits. We find that the memristor has hysteretic current–voltage characteristics. We show that the ideal MC (ML) circuit undergoes non-exponential charge (current) decay with two time scales and that by switching the polarity of the capacitor, an ideal MCL circuit can be tuned from overdamped to underdamped. We present simple models which show that these unusual properties are closely related to the memristor's internal dynamics. This tutorial complements the pedagogy of ideal circuit elements (R, C and L) and the properties of their circuits, and is aimed at undergraduate physics and electrical engineering students.
New Substellar Discoveries from Kepler and K2: Is There a Brown Dwarf Desert?

We present the discoveries of a brown dwarf and a low mass star from the Kepler and K2 missions. The newly discovered brown dwarf is EPIC 212036875b and the low mass star is KOI-607b. EPIC 212036875b has a mass of $ M_{b}=52.3\pm 1.9M_J$, a radius of $ R_{b}=0.874\pm 0.017R_J$, and orbits its host star in $ P=5.169885 \pm 0.000027$ days. Its host star is a late F-type star with $ M_\star=1.288\pm 0.065M_\odot$, $ R_\star=1.498\pm 0.025R_\odot$, and $ T_{\rm eff}=6238 \pm 60$K. KOI-607b has a mass of $ M_{b}=95.1\pm 3.4M_J$, a radius of $ R_{b}=1.089\pm 0.089R_J$, and an orbital period of $ P=5.89399148 \pm 0.00000060$ days. The primary star in the KOI-607 system is a G dwarf with $ M_\star=0.993\pm 0.052M_\odot$, $ R_\star=0.915\pm 0.031R_\odot$, and $ T_{\rm eff} = 5418\pm 87$K. We also revisit a brown dwarf, CWW 89Ab, that was previously published by Nowak et al. 2017 (under the designation EPIC 219388192b). CWW 89Ab is one of two known transiting brown dwarfs associated with a star cluster, which illustrates the need for more brown dwarfs with accurate masses and radii and reliable age determinations to test theoretical models. We find that the newly discovered brown dwarf, EPIC 212036875b, falls in the middle of the so-called "brown dwarf desert", indicating that EPIC 212036875b is either a particularly rare object, or the brown dwarf desert may not be so dry after all.
THE INITIATION AND PROPAGATION OF HELIUM DETONATIONS IN WHITE DWARF ENVELOPES

Detonations in helium-rich envelopes surrounding white dwarfs have garnered attention as triggers of faint thermonuclear “.Ia” supernovae and double detonation Type Ia supernovae. However, recent studies have found that the minimum size of a hotspot that can lead to a helium detonation is comparable to, or even larger than, the white dwarf’s pressure scale height, casting doubt on the successful ignition of helium detonations in these systems. In this paper, we examine the previously neglected effects of C/O pollution and a full nuclear reaction network, and we consider hotspots with spatially constant pressure in addition to constant density hotspots. We find that the inclusion of these effects significantly decreases the minimum hotspot size for helium-rich detonation ignition, making detonations far more plausible during turbulent shell convection or during double white dwarf mergers. The increase in burning rate also decreases the minimum shell mass in which a helium detonation can successfully propagate and alters the composition of the shell’s burning products. The ashes of these low-mass shells consist primarily of silicon, calcium, and unburned helium and metals and may explain the high-velocity spectral features observed in most Type Ia supernovae.
Robust Spectral Compressed Sensing via Structured Matrix Completion

This paper explores the problem of spectral compressed sensing, which aims to recover a spectrally sparse signal from a small random subset of its n time domain samples. The signal of interest is assumed to be a superposition of r multidimensional complex sinusoids, while the underlying frequencies can assume any continuous values in the normalized frequency domain. Conventional compressed sensing paradigms suffer from the basis mismatch issue when imposing a discrete dictionary on the Fourier representation. To address this issue, we develop a novel algorithm, called enhanced matrix completion (EMaC), based on structured matrix completion that does not require prior knowledge of the model order. The algorithm starts by arranging the data into a low-rank enhanced form exhibiting multifold Hankel structure, and then attempts recovery via nuclear norm minimization. Under mild incoherence conditions, EMaC allows perfect recovery as soon as the number of samples exceeds the order of r log 4 n, and is stable against bounded noise. Even if a constant portion of samples are corrupted with arbitrary magnitude, EMaC still allows exact recovery, provided that the sample complexity exceeds the order of r 2 log 3 n. Along the way, our results demonstrate the power of convex relaxation in completing a low-rank multifold Hankel or Toeplitz matrix from minimal observed entries. The performance of our algorithm and its applicability to super resolution are further validated by numerical experiments.
Macro-Fiscal Implications of Climate Change: The Case of Djibouti

This paper reviews the significant macro-fiscal challenges posed by climate change in Djibouti and the costs of mitigation and adaptation policies. The paper concludes that Djibouti is susceptible to climate change and related costs are potentially large. Investing now in adaptation and mitigation has large benefits in terms of reducing the related costs in the future. Reforms to generate the fiscal space are therefore needed and investment for mitigation and adaptation to climate change should be built into the long-term fiscal projections. Finally, concerted international efforts and stepping up regional cooperation could help moderate climate-related macro-fiscal risks.
Performance Limits of Differential Power Processing

This paper explores performance limits of differential power processing (DPP) for large-scale modular dc energy systems with stochastic loads. An analytical stochastic model is developed to estimate the average power loss of a DPP topology under probabilistic load distributions. A scaling factor $\mathcal{S}$ (•) is introduced to describe how power loss scales as the system size or load power variance increases. The average power losses of several example DPP topologies are analyzed and compared against conventional dc-dc converters given the same total switch die area and magnetic volume. The performance limits for various DPP topologies are derived and verified by Monte-Carlo simulations in SPICE, and the results indicate that the ac-coupled DPP converter stands out from all the representative DPP topologies discussed here in terms of the lowest power loss. The paper provides an analytical framework to evaluate the performance of different DPP topologies in a methodical way, offering insights for the design of DPP systems with large-scale stochastic loads.
Severe Corrosion of Carbon Steel in Oil Field Produced Water Can Be Linked to Methanogenic Archaea Containing a Special Type of [NiFe] Hydrogenase.

ABSTRACT Methanogenic archaea have long been implicated in microbially influenced corrosion (MIC) of oil and gas infrastructure, yet a first understanding of the underlying molecular mechanisms has only recently emerged. We surveyed pipeline-associated microbiomes from geographically distinct oil field facilities and found methanogens to account for 0.2 to 9.3% of the 16S rRNA gene sequencing reads. Neither the type nor the abundance of the detected methanogens was correlated with the perceived severity of MIC in these pipelines. Using fluids from one pipeline, MIC was reproduced in the laboratory, both under stagnant conditions and in customized corrosion reactors simulating pipeline flow. High corrosion rates (up to 2.43 mm Fe0 · yr−1) with macroscopic, localized corrosion features were attributed to lithotrophic, mesophilic microbial activity. Other laboratory tests with the same waters yielded negligible corrosion rates ( 0.15 mm Fe0 · yr−1) biofilms. The micH gene, on the other hand, was absent in noncorrosive biofilms, despite an abundance of methanogens. Reconstruction of a nearly complete Methanococcus maripaludis genome from a highly corrosive mixed biofilm revealed micH and associated genes in nearly identical genetic configuration to that in strain OS7, thereby supporting our hypothesis that the encoded molecular mechanism contributed to corrosion. Lastly, the proposed MIC biomarker was detected in multiple oil fields, indicating a geographically widespread involvement of this [NiFe] hydrogenase in MIC. IMPORTANCE Microorganisms can deteriorate built environments, which is particularly problematic in the case of pipelines transporting hydrocarbons to industrial end users. MIC is notoriously difficult to detect and monitor and, as a consequence, is a particularly difficult corrosion mechanism to manage. Despite the advent of molecular tools and improved microbial monitoring strategies for oil and gas operations, specific underlying MIC mechanisms in pipelines remain largely enigmatic. Emerging mechanistic understanding of methanogenic MIC derived from pure culture work allowed us to develop a qPCR assay that distinguishes technically problematic from benign methanogens in a West African oil field. Detection of the same gene in geographically diverse samples from North America hints at the widespread applicability of this assay. The research presented here offers a step toward a mechanistic understanding of biocorrosion in oil fields and introduces a binary marker for (methanogenic) MIC that can find application in corrosion management programs in industrial settings.
The Ultimately Large Telescope: What Kind of Facility Do We Need to Detect Population III Stars?

The launch of the James Webb Space Telescope will open up a new window for observations at the highest redshifts, reaching out to z~15. However, even with this new facility, the first stars will remain out of reach, as they are born in small minihalos with luminosities too faint to be detected even by the longest exposure times. In this paper, we investigate the basic properties of the Ultimately Large Telescope, a facility that can detect Population III star formation regions at high redshift. Observations will take place in the near-infrared and therefore a moon-based facility is proposed. An instrument needs to reach magnitudes as faint as 39mag$_\mathrm{AB}$, corresponding to a primary mirror size of about 100m in diameter. Assuming JWST NIRCam filters, we estimate that Pop III sources will have unique signatures in a colour-colour space and can be identified unambiguously.
Causality and passivity: From electromagnetism and network theory to metamaterials

Abstract In this review, we take an extensive look at the role that the principles of causality and passivity have played in various areas of physics and engineering, including in the modern field of metamaterials. The aim is not to provide a comprehensive list of references as that number would be in the thousands, but to review the major results and contributions which have animated these areas and to provide a unified framework which could be useful in understanding the developments in different fields. Towards these goals, we chart the early history of the field through its dual beginnings in the analysis of the Sellmeier equation and in Hilbert transforms, giving rise to the far reaching dispersion relations in the early works of Sokhotskii, Plemelj, Kramers, Kronig, and Titchmarsh. However, these early relations constitute a limited result as they only apply to a restricted class of transfer functions. To understand how this restriction can be lifted, we take a quick detour into the distributional analysis of Schwartz, and discuss the dispersion relations in the context of distribution theory. This approach expands the reach of the dispersion analysis to distributional transfer functions and also to those functions which exhibit polynomial growth properties. To generalize the results even further to tensorial transfer functions, we consider the concept of passivity — originally studied in the theory of electrical networks. We clarify why passivity implies causality and present generalized dispersion relations applicable to transfer functions which are distributional, tensorial, and possibly exhibiting polynomial growth. Subsequently, as special cases, we present examples of dispersion relations from several areas of physics including electromagnetism, acoustics, seismology, reflectance measurements, and scattering theory. We discuss sum rules which follow from the infinite integral dispersion relations and also how these integrals may be simplified either by truncating them under appropriate assumptions or by replacing them with derivative relations. These derivative relations, termed derivative analyticity relations, form the basis of the so called nearly-local approximations of the dispersion relations which are extensively employed in many fields including acoustics. Finally, we review the clever applications of ideas from causality and passivity to the recent field of metamaterials. In many ways, these ideas have provided limits to what can be achieved in metamaterial property design and metamaterial device performance.
OXTR rs53576 Variation with Breast and Nipple Pain in Breastfeeding Women.

Abstract Background Thirty percent of women who seek professional breastfeeding support require assistance with ongoing breast and nipple pain and
Self-adjointness of perturbed bi-Laplacians on infinite graphs

Abstract We give a sufficient condition for the essential self-adjointness of a perturbation of the square of the magnetic Laplacian on an infinite weighted graph. The main result is applicable to graphs whose degree function is not necessarily bounded. The result allows perturbations that are not necessarily bounded from below by a constant.
Gagliardo-Nirenberg, Trudinger-Moser and Morrey inequalities on Dirichlet spaces

Abstract With a view towards Riemannian or sub-Riemannian manifolds, RCD metric spaces and specially fractals, this paper proves Sobolev embedding theorems in the general framework of Dirichlet spaces. Under suitable assumptions that are verified in a variety of settings, we obtain the whole family of Gagliardo-Nirenberg and Trudinger-Moser inequalities with optimal exponents. These turn out to depend not only on the Hausdorff and walk dimensions of the space but also on other invariants. In addition, we prove Morrey type inequalities and apply them to study the infimum of the exponents that ensure continuity of Sobolev functions. The results are illustrated in the case of fractals with the Vicsek set, whereas several conjectures are made for general nested fractals and the Sierpinski carpet.
The Impacts of the Affordable Care Act: How Reasonable Are the Projections?

The Patient Protection and Affordable Care Act (ACA) is the most comprehensive reform of the U.S. medical system in at least 45 years. The ACA transforms the non-group insurance market in the United States, mandates that most residents have health insurance, signifi cantly expands public insurance and subsidizes private insurance coverage, raises revenues from a variety of new taxes, and reduces and reorganizes spending under the nation’s largest health insurance plan, Medicare. Projecting the impacts of such fundamental reform to the health care system is fraught with diffi culty. But such projections were required for the legislative process, and were delivered by the Congressional Budget Offi ce (CBO). This paper discusses the projected impact of the ACA in more detail, and describes evidence that sheds light upon the accuracy of the projections. It begins by reviewing in broad detail the structure of the ACA, and then reviews evidence from a key case study that informs our understanding of the ACA’s impacts: a comparable health reform that was carried out in Massachusetts four years earlier. The paper discusses the key results from that earlier reform and what they might imply for the impacts of the ACA. The paper ends with a discussion of the projected impacts of the ACA and offers some observations on those estimates.
Vulnerability-Aware Resilient Networks: Software Diversity-Based Network Adaptation

By leveraging the principle of software polyculture to ensure security in a network, we propose a vulnerability-based software diversity metric to determine how a network topology can be adapted to minimize security vulnerability while maintaining maximum network connectivity. Our proposed metric estimates the software diversity of the node using the vulnerabilities of software packages installed on nearby nodes on attack paths reachable to the node. Our software diversity-based adaptation (SDA) scheme employs the diversity of each node for edge adaptations. These adaptations include the removal of edges that expose high security vulnerability as well as the potential addition of edges between certain nodes with low vulnerabilities associated with them. To validate the proposed SDA scheme, we conduct extensive experiments comparing our approach with counterpart baseline schemes in real networks. Our simulation results demonstrate that SDA outperforms these existing counterparts. We discuss insights into these findings in terms of the effectiveness and efficiency of the proposed SDA scheme under three real network topologies with vastly different network densities.
Survey of Machine Learning Accelerators

New machine learning accelerators are being announced and released each month for a variety of applications from speech recognition, video object detection, assisted driving, and many data center applications. This paper updates the survey of of AI accelerators and processors from last year's IEEE-HPEC paper. This paper collects and summarizes the current accelerators that have been publicly announced with performance and power consumption numbers. The performance and power values are plotted on a scatter graph and a number of dimensions and observations from the trends on this plot are discussed and analyzed. For instance, there are interesting trends in the plot regarding power consumption, numerical precision, and inference versus training. This year, there are many more announced accelerators that are implemented with many more architectures and technologies from vector engines, dataflow engines, neuromorphic designs, flash-based analog memory processing, and photonic-based processing.
Advances in Inference and Representation for Simultaneous Localization and Mapping

Simultaneous localization and mapping (SLAM) is the process of constructing a global model of an environment from local observations of it; this is a foundational capability for mobile robots, supp...
Nonuniqueness of Weak Solutions for the Transport Equation at Critical Space Regularity

We consider the linear transport equations driven by an incompressible flow in dimensions $$d\ge 3$$ . For divergence-free vector fields $$u \in L^1_t W^{1,q}$$ , the celebrated DiPerna-Lions theory of the renormalized solutions established the uniqueness of the weak solution in the class $$L^\infty _t L^p$$ when $$\frac{1}{p} + \frac{1}{q} \le 1$$ . For such vector fields, we show that in the regime $$\frac{1}{p} + \frac{1}{q} > 1$$ , weak solutions are not unique in the class $$ L^1_t L^p$$ . One crucial ingredient in the proof is the use of both temporal intermittency and oscillation in the convex integration scheme.
Dictators as Founding Fathers? The Role of Constitutions Under Autocracy

This article advances a theory of why autocratic coalitions adopt constitutions. We argue that autocratic rulers adopt constitutions in the nascent stages of an autocratic coalition taking power, when uncertainty about leader intentions is high. Constitutions can serve to consolidate a new distribution of power, allowing a launching organization (LO) to codify and defend their rights. Autocratic coalitions that adopt constitutions should therefore last longer in power than those that do not. Using new data compiled on constitutions created under autocracy in Latin America from 1950 to 2002, we show that autocratic coalitions who adopt and operate under constitutions extend their survival. This result holds after controlling for the presence of other autocratic institutions, country fixed effects, and after using an instrumental variables strategy to address reverse causation. A case study of Mexico details the mechanism by which this relationship between constitutions and stability occurs.