cssi/SciSciGPT-SciSciNet huggingface dataset:
Scaling behavior of circular colliders dominated by synchrotron radiation

The scaling formulas in this paper — many of which involve approximation — apply primarily to electron colliders like CEPC or FCC-ee. The more abstract “radiation dominated” phrase in the title is intended to encourage use of the formulas — though admittedly less precisely — to proton colliders like SPPC, for which synchrotron radiation begins to dominate the design in spite of the large proton mass. Optimizing a facility having an electron–positron Higgs factory, followed decades later by a p, p collider in the same tunnel, is a formidable task. The CEPC design study constitutes an initial “constrained parameter” collider design. Here the constrained parameters include tunnel circumference, cell lengths, phase advance per cell, etc. This approach is valuable, if the constrained parameters are self-consistent and close to optimal. Jumping directly to detailed design makes it possible to develop reliable, objective cost estimates on a rapid time scale. A scaling law formulation is intended to contribute to a “ground-up” stage in the design of future circular colliders. In this more abstract approach, scaling formulas can be used to investigate ways in which the design can be better optimized. Equally important, by solving the lattice matching equations in closed form, as contrasted with running computer programs such as MAD, one can obtain better intuition concerning the fundamental parametric dependencies. The ground-up approach is made especially appropriate by the seemingly impossible task of simultaneous optimization of tunnel circumference for both electrons and protons. The fact that both colliders will be radiation dominated actually simplifies the simultaneous optimization task. All GeV scale electron accelerators are “synchrotron radiation dominated”, meaning that all beam distributions evolve within a fraction of a second to an equilibrium state in which “heating” due to radiation fluctuations is canceled by the “cooling” in RF cavities that restore the lost energy. To the contrary, until now, the large proton to electron mass ratio has caused synchrotron radiation to be negligible in proton accelerators. The LHC beam energy has still been low enough that synchrotron radiation has little effect on beam dynamics; but the thermodynamic penalty in cooling the superconducting magnets has still made it essential for the radiated power not to be dissipated at liquid helium temperatures. Achieving this has been a significant challenge. For the next generation p, p collider this will be even more true. Furthermore, the radiation will effect beam distributions on time scales measured in minutes, for example causing the beams to be flattened, wider than they are high. In this regime scaling relations previously valid only for electrons will be applicable also to protons.
Probing the birth of super star clusters: Implications for massive star formation

Super star clusters are one of the most extreme star forming environments in the universe, and the most massive and dense of these may be proto globular clusters. Like individual massive stars, the earliest stages of super star cluster evolution are deeply obscured, and therefore our knowledge about their birth environments is currently very incomplete. However, the study of natal super star clusters has become somewhat of a cottage industry in recent years, and the sample of such objects has been growing rapidly with high-quality long-wavelength data now available from a number of observatories. The natal super star clusters identified in thermal-infrared and radio observations represent the youngest stage of massive star cluster evolution yet observed. Their properties appear to be similar to those of ultracompact h II regions in the milky way, but scaled up in total mass and luminosity. I will overview what we think we know about these objects based on existing observations, discuss their relationship to ultracompact h II regions, present new models of their spectral energy distributions based on 3-d simulations, and outline some of the most significant gaps in our current understanding.
Tired of Topic Models? Clusters of Pretrained Word Embeddings Make for Fast and Good Topics too!

Topic models are a useful analysis tool to uncover the underlying themes within document collections. The dominant approach is to use probabilistic topic models that posit a generative story, but in this paper we propose an alternative way to obtain topics: clustering pre-trained word embeddings while incorporating document information for weighted clustering and reranking top words. We provide benchmarks for the combination of different word embeddings and clustering algorithms, and analyse their performance under dimensionality reduction with PCA. The best performing combination for our approach performs as well as classical topic models, but with lower runtime and computational complexity.
Rheoscopic fluids in a post-Kalliroscope world

In rheoscopic flow visualization, the working fluid is seeded with small reflective flakes that align preferentially in the flow due to their anisotropy. This leads to directed light scattering, which can be exploited to distinguish qualitatively different regions of the flow. For the past four decades, the gold standard in rheoscopic flow visualization has been Kalliroscope, a commercial product consisting of crystalline guanine particles. Recently, however, worldwide production of crystalline guanine has dropped precipitously, leading the Kalliroscope Corporation to halt production in 2014. Here, we present a short survey of alternative rheoscopic flow visualization techniques and introduce an inexpensive rheoscopic fluid based on stearic acid crystals extracted from shaving cream, which has a performance similar to, and in certain respects superior to, Kalliroscope.
A RADIO TELESCOPE SEARCH FOR AXIONS

The axion is a hypothetical elementary particle and a cold dark matter candidate. It could dominate the potential wells of most astrophysical objects. Axions spontaneously decay into nearly monochromatic microwave photons. We present results from a radio telescope search for these axion decay photons of mass ma = 298-363 μeV in Local Group dwarf galaxies. We report a limit on the axion-to-two-photon coupling constant gaγγ > 1.0 × 10-9 GeV-1.
Mathematical Modeling of Arterial Blood Pressure Using Photo- Plethysmography Signal in Breath-hold Maneuver

recent research has shown that each apnea episode results in a significant rise of the beat-to-beat blood pressure followed by a drop to the pre-episode levels when patient resumes normal breathing. While the physiological implications of these repetitive and significant oscillations are still unknown, it is of interest to quantify them. Since current array of instruments deployed for polysomnography studies does not include beat-to-beat measurement of blood pressure, but includes oximetry which can supply pulsatile photoplethysmography (PPG) signal, in addition to percent oxygen saturation. Hence, we have investigated a new method for continuous estimation of systolic (SBP), diastolic (DBP), and mean (MBP) blood pressure waveforms from PPG. Peaks and troughs of PPG waveform are used as input to a 5th order autoregressive moving average model to construct estimates of SBP, DBP, and MBP waveforms. Since breath hold maneuvers are shown to faithfully simulate apnea episodes, we evaluated the performance of the proposed method in 7 subjects (4 F; $32 \pm 4$ yrs., BMI $24.57 \pm 3.87$ kg/m2) in supine position doing 5 breath holding maneuvers with 90s of normal breathing between them. The modeling error ranges were (all units are in mmHg $) 0.88 \pm 4.87$ to $- 2.19 \pm 5.73($ SBP); $0.29 \pm 2.39$ to $- 0.97 \pm 3.83($ DBP); and $- 0.42 \pm 2.64$ to $- 1.17 \pm 3.82($ MBP). The cross validation error ranges were $0.28 \pm 6.45$ to $- 1.74 \pm 6.55($ SBP); $0.09 \pm 3.37$ to $0.97 \pm 3.67($ DBP); and $0.33 \pm 4.34$ to $- 0.87 \pm 4.42($ MBP). The overall level of estimation error, as measured by the root mean squared of the model residuals, was less than 7 mmHg.
The Local Group as an Astrophysical Laboratory for Massive Star Feedback

The feedback effects of massive stars on their galactic and intergalactic environments can dominate evolutionary processes in galaxies and affect cosmic structure in the Universe. Only the Local Group offers the spatial resolution to quantitatively study feedback processes on a variety of scales. Lyman continuum radiation from hot, luminous stars ionizes HII regions and is believed to dominate production of the warm component of the interstellar medium (ISM). Some of this radiation apparently escapes from galaxies into the intergalactic environment. Supernovae and strong stellar winds generate shell structures such as supernova remnants, stellar wind bubbles, and superbubbles around OB associations. Hot (10^6 K) gas is generated within these shells, and is believed to be the origin of the hot component of the ISM. Superbubble activity thus is likely to dominate the ISM structure, kinematics, and phase balance in star-forming galaxies. Galactic superwinds in starburst galaxies enable the escape of mass, ionizing radiation, and heavy elements. Although many important issues remain to be resolved, there is little doubt that feedback processes plays a fundamental role in energy cycles on scales ranging from individual stars to cosmic structure. This contribution reviews studies of radiative and mechanical feedback in the Local Group.
Using Local Experiences for Global Motion Planning

Sampling-based planners are effective in many real-world applications such as robotics manipulation, navigation, and even protein modeling. However, it is often challenging to generate a collision-free path in environments where key areas are hard to sample. In the absence of any prior information, sampling-based planners are forced to explore uniformly or heuristically, which can lead to degraded performance. One way to improve performance is to use prior knowledge of environments to adapt the sampling strategy to the problem at hand. In this work, we decompose the workspace into local primitives, memorizing local experiences by these primitives in the form of local samplers, and store them in a database. We synthesize an efficient global sampler by retrieving local experiences relevant to the given situation. Our method transfers knowledge effectively between diverse environments that share local primitives and speeds up the performance dramatically. Our results show, in terms of solution time, an improvement of multiple orders of magnitude in two traditionally challenging high-dimensional problems compared to state-of-the-art approaches.
QUENCHING OF HIGHLY ROTATIONALLY EXCITED HCl IN COLLISIONS WITH He

We report rotational quenching cross sections and rate coefficients of HCl due to collisions with He. The close-coupling method and the coupled-states approximation are applied in quantum-mechanical scattering calculations of state-to-state cross sections for HCl with initial rotational levels up to j = 20 for kinetic energies from 10?5 to 15,000?cm?1. State-to-state rate coefficients for temperatures between 0.1 and 3000?K are also presented. Comparison of the present rate coefficients with previous results reported in the literature for lowly excited rotational levels shows reasonable agreement. Small differences are attributed to the differences in the interaction potential energy surfaces. The uncertainty in the computed cross sections and rate coefficients is estimated by varying the potential well depth. Applications of current results to astrophysical systems are also briefly discussed.
Information-Based Physics: An Observer-Centric Foundation.

It is generally believed that physical laws, reflecting an inherent order in the universe, are ordained by nature. However, in modern physics the observer plays a central role raising questions about how an observer-centric physics can result in laws apparently worthy of a universal nature-centric physics. Over the last decade, we have found that the consistent apt quantification of algebraic and order-theoretic structures results in calculi that possess constraint equations taking the form of what are often considered to be physical laws. I review recent derivations of the formal relations among relevant variables central to special relativity, probability theory and quantum mechanics in this context by considering a problem where two observers form consistent descriptions of and make optimal inferences about a free particle that simply influences them. I show that this approach to describing such a particle based only on available information leads to the mathematics of relativistic quantum mechanics as...
Coassembly is a homotopy limit map

We prove a claim by Williams that the coassembly map is a homotopy limit map. As an application, we show that the homotopy limit map for the coarse version of equivariant A-theory agrees with the coassembly map for bivariant A-theory that appears in the statement of the topological Riemann–Roch theorem.
DERIVATION OF STOCHASTIC ACCELERATION MODEL CHARACTERISTICS FOR SOLAR FLARES FROM RHESSI HARD X-RAY OBSERVATIONS

The model of stochastic acceleration of particles by turbulence has been successful in explaining many observed features of solar flares. Here, we demonstrate a new method to obtain the accelerated electron spectrum and important acceleration model parameters from the high-resolution hard X-ray (HXR) observations provided by RHESSI. In our model, electrons accelerated at or very near the loop top (LT) produce thin target bremsstrahlung emission there and then escape downward producing thick target emission at the loop footpoints (FPs). Based on the electron flux spectral images obtained by the regularized spectral inversion of the RHESSI count visibilities, we derive several important parameters for the acceleration model. We apply this procedure to the 2003 November 3 solar flare, which shows an LT source up to 100-150 keV in HXR with a relatively flat spectrum in addition to two FP sources. The results imply the presence of strong scattering and a high density of turbulence energy with a steep spectrum in the acceleration region.
Efficient Clustering for Stretched Mixtures: Landscape and Optimality

This paper considers a canonical clustering problem where one receives unlabeled samples drawn from a balanced mixture of two elliptical distributions and aims for a classifier to estimate the labels. Many popular methods including PCA and k-means require individual components of the mixture to be somewhat spherical, and perform poorly when they are stretched. To overcome this issue, we propose a non-convex program seeking for an affine transform to turn the data into a one-dimensional point cloud concentrating around -1 and 1, after which clustering becomes easy. Our theoretical contributions are two-fold: (1) we show that the non-convex loss function exhibits desirable landscape properties as long as the sample size exceeds some constant multiple of the dimension, and (2) we leverage this to prove that an efficient first-order algorithm achieves near-optimal statistical precision even without good initialization. We also propose a general methodology for multi-class clustering tasks with flexible choices of feature transforms and loss objectives.
Experimental Characterization of Magnetic Materials for the Magnetic Shielding of Cryomodules in Particle Accelerators

The magnetic properties of two important passive magnetic shielding materials (A4K and Amumetal) for accelerator applications, subjected to various processing and heat treatment conditions are studied comprehensively over a wide range of temperatures: from cryogenic to room temperature. We analyze the effect of processing on the extent of degradation of the magnetic properties of both materials and investigate the possibility of restoring these properties by reannealing.
Laser‐Assisted Chemical Modification of Monolayer Transition Metal Dichalcogenides

Laser-assisted chemical modification is demonstrated on ultra-thin transition-metal dichalcogenides (TMDs), locally replacing selenium by sulfur atoms. The photo-conversion process takes place in a controlled reactive gas environment and the heterogeneous reaction rates are monitored via in situ real-time Raman and photoluminescence spectroscopies. The spatially localized photo-conversion resulted in a heterogeneous TMD structure, with chemically distinct domains, where the initial high crystalline quality of the film is not affected during the process. This has been further confirmed via transmission electron microscopy as well as Raman and Photoluminescence spatial maps. Our study demonstrates the potential of laser-assisted chemical conversion for on-demand synthesis of heterogeneous two-dimensional materials with applications in nanodevices.
The M-Theory S-Matrix From ABJM: Beyond 11D Supergravity

We show that by studying the flat spacetime limit of the Mellin amplitude associated with the four-point correlation function of scalar operators in the stress tensor multiplet of ABJM theory, one can produce the momentum expansion of the M-theory four-graviton S-matrix elements. Using CFT data previously obtained from the supersymmetric localization method, we carry out this procedure explicitly to the second nontrivial order in the momentum expansion, and recover precisely the known R4 contribution to the scattering amplitude of super-gravitons in M-theory in eleven dimensions.
SUPERNOVA-TRIGGERED MOLECULAR CLOUD CORE COLLAPSE AND THE RAYLEIGH-TAYLOR FINGERS THAT POLLUTED THE SOLAR NEBULA

A supernova is a likely source of short-lived radioisotopes (SLRIs) that were present during the formation of the earliest solar system solids. A suitably thin and dense supernova shock wave may be capable of triggering the self-gravitational collapse of a molecular cloud core while simultaneously injecting SLRIs. Axisymmetric hydrodynamics models have shown that this injection occurs through a number of Rayleigh-Taylor (RT) rings. Here we use the FLASH adaptive mesh refinement hydrodynamics code to calculate the first fully three-dimensional (3D) models of the triggering and injection process. The axisymmetric RT rings become RT fingers in 3D. While ~100 RT fingers appear early in the 3D models, only a few RT fingers are likely to impact the densest portion of the collapsing cloud core. These few RT fingers must then be the source of any SLRI spatial heterogeneity in the solar nebula inferred from isotopic analyses of chondritic meteorites. The models show that SLRI injection efficiencies from a supernova several parsecs away fall at the lower end of the range estimated for matching SLRI abundances, perhaps putting them more into agreement with recent reassessments of the level of 60Fe present in the solar nebula.
MVG Mechanism: Differential Privacy under Matrix-Valued Query

Differential privacy mechanism design has traditionally been tailored for a scalar-valued query function. Although many mechanisms such as the Laplace and Gaussian mechanisms can be extended to a matrix-valued query function by adding i.i.d. noise to each element of the matrix, this method is often suboptimal as it forfeits an opportunity to exploit the structural characteristics typically associated with matrix analysis. To address this challenge, we propose a novel differential privacy mechanism called the Matrix-Variate Gaussian (MVG) mechanism, which adds a matrix-valued noise drawn from a matrix-variate Gaussian distribution, and we rigorously prove that the MVG mechanism preserves (e,δ)-differential privacy. Furthermore, we introduce the concept of directional noise made possible by the design of the MVG mechanism. Directional noise allows the impact of the noise on the utility of the matrix-valued query function to be moderated. Finally, we experimentally demonstrate the performance of our mechanism using three matrix-valued queries on three privacy-sensitive datasets. We find that the MVG mechanism can notably outperforms four previous state-of-the-art approaches, and provides comparable utility to the non-private baseline.
Few-particle vortex cluster equilibria in Bose–Einstein condensates: existence and stability

Motivated by recent experimental and theoretical studies of few-particle vortex clusters in Bose–Einstein condensates, we consider the ordinary differential equations of motion and systematically examine settings for up to N = 6 vortices. We analyze the existence of corresponding stationary state configurations and also consider their spectral stability properties. We compare our particle model results with the predictions of the full partial differential equation system. Whenever possible, we propose generalizations of these results in the context of clusters of N vortices. Some of these we can theoretically establish, especially for the N-vortex polygons, while others we state as conjectures, e.g. for the N-vortex line equilibrium.
Improved Bounds for the Ramsey Number of Tight Cycles Versus Cliques

The 3-uniform tight cycle Cs 3 has vertex set and edge set {{i, i + 1, i + 2}: i ∈ }. We prove that for every s ≢ 0 (mod 3) with s ⩾ 16 or s ∈ {8, 11, 14} there is a cs > 0 such that the 3-uniform hypergraph Ramsey number r(Cs 3, Kn 3) satisfies \begin{equation*} r(C_s^3, K_n^3)< 2^{c_s n \log n}.\ \end{equation*} This answers in a strong form a question of the author and Rodl, who asked for an upper bound of the form for each fixed s ⩾ 4, where es → 0 as s → ∞ and n is sufficiently large. The result is nearly tight as the lower bound is known to be exponential in n.
Spectra of Semi-Infinite Quantum Graph Tubes

The spectrum of a semi-infinite quantum graph tube with square period cells is analyzed. The structure is obtained by rolling up a doubly periodic quantum graph into a tube along a period vector and then retaining only a semi-infinite half of the tube. The eigenfunctions associated to the spectrum of the half-tube involve all Floquet modes of the full tube. This requires solving the complex dispersion relation \({D(\lambda,k_1,k_2)=0}\) with \({(k_1,k_2)\in(\mathbb{C}/2\pi\mathbb{Z})^2}\) subject to the constraint \({a k_1 + b k_2 \equiv 0}\) (mod \({2\pi}\)), where a and b are integers. The number of Floquet modes for a given \({\lambda\in\mathbb{R}}\) is \({2\max\left\{ a, b \right\}}\). Rightward and leftward modes are determined according to an indefinite energy flux form. The spectrum may contain eigenvalues that depend on the boundary conditions, and some eigenvalues may be embedded in the continuous spectrum.
Two regime cooling in flow induced by a spark discharge

Cooling of the flow induced by a spark plasma discharge is found to occur at two different rates: an initially fast cooling regime followed by a slow cooling regime. Convective cooling in the fast regime contributes to 30--50% of the total cooling and occurs within the first millisecond of the induced flow.
Decay of the Boltzmann Equation with the Specular Boundary Condition in Non-convex Cylindrical Domains

The basic question about the existence, uniqueness, and stability of the Boltzmann equation in general non-convex domains with the specular reflection boundary condition has been widely open. In this paper, we consider cylindrical domains whose cross section is generally non-convex analytic bounded planar domain. We establish a global well-posedness and asymptotic stability of the Boltzmann equation with the specular reflection boundary condition. Our method consists of the delicate construction of $${\epsilon}$$ -tubular neighborhoods of billiard trajectories which bounce infinitely many times or hit the boundary tangentially at some moment, and sharp estimates of the size of such neighborhoods.
Orbital order driven quantum criticality

Charge, spin, and orbital degrees of freedom underlie the physics of transition metal compounds. Much work has revealed quantum critical points associated with spin and charge degrees of freedom in many of these systems. Here we illustrate that the simplest models that embody the orbital degrees of freedom —the two- and three-dimensional quantum orbital compass models— exhibit an exact quantum critical behavior on diluted square and cubic lattices (with doping δ=1/4 and δ=1/2, respectively). This raises the possibility of quantum critical points triggered by the degradation of orbital order upon doping (or applying pressure to) such transition metal systems. We prove the existence of an orbital spin glass in several related systems in which the orbital couplings are made non-uniform. Moreover, a new orbital Larmor precession (i.e., a periodic change in the orbital state) is predicted when uniaxial pressure is applied.
Wireless localization for mmWave networks in urban environments

Millimeter wave (mmWave) technology is expected to be a major component of 5G wireless networks. Ultra-wide bandwidths of mmWave signals and the possibility of utilizing large number of antennas at the transmitter and the receiver allow accurate identification of multipath components in temporal and angular domains, making mmWave systems advantageous for localization applications. In this paper, we analyze the performance of a two-step mmWave localization approach that can utilize time-of-arrival, angle-of-arrival, and angle-of-departure from multiple nodes in an urban environment with both line-of-sight (LOS) and non-LOS (NLOS) links. Networks with/without radio-environmental mapping (REM) are considered, where a network with REM is able to localize nearby scatterers. Estimation of a UE location is challenging due to large numbers of local optima in the likelihood function. To address this problem, a gradient-assisted particle filter (GAPF) estimator is proposed to accurately estimate a user equipment (UE) location as well as the locations of nearby scatterers. Monte-Carlo simulations show that the GAPF estimator performance matches the Cramer-Rao bound (CRB). The estimator is also used to create a REM. It is seen that significant localization gains can be achieved by increasing beam directionality or by utilizing REM.
The application of cloud computing to the creation of image mosaics and management of their provenance

We have used the Montage image mosaic engine to investigate the cost and performance of processing images on the Amazon EC2 cloud, and to inform the requirements that higher-level products impose on provenance management technologies. We will present a detailed comparison of the performance of Montage on the cloud and on the Abe high performance cluster at the National Center for Supercomputing Applications (NCSA). Because Montage generates many intermediate products, we have used it to understand the science requirements that higher-level products impose on provenance management technologies. We describe experiments with provenance management technologies such as the "Provenance Aware Service Oriented Architecture" (PASOA).
W*-rigidity for the von Neumann algebras of products of hyperbolic groups

We show that if \({\Gamma = \Gamma_1\times\dotsb\times \Gamma_n}\) is a product of \({{\rm n} \geq 2}\) non-elementary ICC hyperbolic groups then any discrete group \({\Lambda}\) which is \({W^*}\)-equivalent to \({\Gamma}\) decomposes as a direct product of n ICC groups and does not decompose as a direct product of k ICC groups when \({{\rm n} \not= {\rm k}}\). This gives a group-level strengthening of Ozawa and Popa’s unique prime decomposition theorem by removing all assumptions on the group \({\Lambda}\). This result in combination with Margulis’ normal subgroup theorem allows us to give examples of lattices in the same Lie group which do not generate stably equivalent II1 factors.
Is dark matter fact or fantasy? — Clues from the data

We discuss arguments both in favor of and against dark matter. With the repeated failure of experiment to date to detect dark matter we discuss what could be done instead, and to this end look for ...
New kinetic terms for massive gravity and multi-gravity: a no-go in vielbein form

We reconsider the possibility of a class of new kinetic terms in the first order (vielbein) formulation of massive gravity and multi-gravity. We find that new degrees of freedom emerge which are not associated with the Boulware–Deser ghost and are intrinsic to the vielbein formulation. These new degrees of freedom are associated with the Lorentz transformations which encode the additional variables contained in the vielbein over the metric. Although they are not guaranteed to be ghostly, they are nevertheless infinitely strongly coupled on Minkowski spacetime and are not part of the spin-2 multiplet. Hence their existence implies the uniqueness of the Einstein–Hilbert term as the kinetic term for a massive graviton.
Calculating Time Eigenvalues of the Neutron Transport Equation with Dynamic Mode Decomposition

A novel method to compute time eigenvalues of neutron transport problems is presented based on solutions to the time-dependent transport equation. Using these solutions, we use the dynamic mode dec...
Landmark diffusion maps (L-dMaps): Accelerated manifold learning out-of-sample extension

Abstract Diffusion maps are a nonlinear manifold learning technique based on harmonic analysis of a diffusion process over the data. Out-of-sample extensions with computational complexity O ( N ) , where N is the number of points comprising the manifold, frustrate applications to online learning applications requiring rapid embedding of high-dimensional data streams. We propose landmark diffusion maps (L-dMaps) to reduce the complexity to O ( M ) , where M ≪ N is the number of landmark points selected using pruned spanning trees or k-medoids. Offering ( N / M ) speedups in out-of-sample extension, L-dMaps enable the application of diffusion maps to high-volume and/or high-velocity streaming data. We illustrate our approach on three datasets: the Swiss roll, molecular simulations of a C24H50 polymer chain, and biomolecular simulations of alanine dipeptide. We demonstrate up to 50-fold speedups in out-of-sample extension for the molecular systems with less than 4% errors in manifold reconstruction fidelity relative to calculations over the full dataset.
First principles study of hBN-AlN short-period superlattice heterostructures

We report a theoretical study of the structural, electronic, and optical properties of hBN-AlN superlattice (SL) heterostructures using a first-principles approach based on standard and hybrid density functional theory. We consider a short-period (L < 10 nm) SL and find that its properties depend strongly on the AlN layer thickness LAlN. For LAlN≲1 nm, AlN stabilizes into the hexagonal phase and the SL displays insulating behavior with type II interface band alignment and optical gaps as small as 5.2 eV. The wurtzite phase is formed for thicker AlN layers. In these cases, built-in electric fields lead to the formation of polarization compensating charges as well as two-dimensional conductive behavior for electronic transport along interfaces. We also find defect-like states localized at interfaces which are optically active in the visible range.
Effective field theory of relativistic quantum hall systems

Motivated by the observation of the fractional quantum Hall effect in graphene, we consider the effective field theory of relativistic quantum Hall states. We find that, beside the Chern-Simons term, the effective action also contains a term of topological nature, which couples the electromagnetic field with a topologically conserved current of 2 + 1 dimensional relativistic fluid. In contrast to the Chern-Simons term, the new term involves the spacetime metric in a nontrivial way. We extract the predictions of the effective theory for linear electromagnetic and gravitational responses. For fractional quantum Hall states at the zeroth Landau level, additional holomorphic constraints allow one to express the results in terms of two dimensionless constants of topological nature.
KECK SPECTROSCOPY OF z> 1 FIELD SPHEROIDALS: DYNAMICAL CONSTRAINTS ON THE GROWTH RATE OF RED "NUGGETS"

We present deep Keck spectroscopy for 17 morphologically selected field spheroidals in the redshift range 1.05 10^(11) M_☉) grew in size over 0 M_(dyn) > 10^(10) M_☉) did not grow significantly. These trends are consistent with a picture in which more massive spheroidals formed at higher redshift via "wetter" mergers involving greater dissipation. To examine growth under the favored "dry" merger hypothesis, we also examine size growth at a fixed velocity dispersion. This test, uniquely possible with our dynamical data, allows us to consider the effects of "progenitor bias." Above our completeness limit (σ > 200 km s^(–1)), we find size growth consistent with that inferred for the mass-selected sample, thus ruling out strong progenitor bias. To maintain continuity in the growth of massive galaxies over the past 10 Gyr, our new results imply that size evolution over 1.3 2 are truly massive and compact.
PatDNN: Achieving Real-Time DNN Execution on Mobile Devices with Pattern-based Weight Pruning

With the emergence of a spectrum of high-end mobile devices, many applications that formerly required desktop-level computation capability are being transferred to these devices. However, executing Deep Neural Networks (DNNs) inference is still challenging considering the high computation and storage demands, specifically, if real-time performance with high accuracy is needed. Weight pruning of DNNs is proposed, but existing schemes represent two extremes in the design space: non-structured pruning is fine-grained, accurate, but not hardware friendly; structured pruning is coarse-grained, hardware-efficient, but with higher accuracy loss. In this paper, we advance the state-of-the-art by introducing a new dimension, fine-grained pruning patterns inside the coarse-grained structures, revealing a previously unknown point in the design space. With the higher accuracy enabled by fine-grained pruning patterns, the unique insight is to use the compiler to re-gain and guarantee high hardware efficiency. In other words, our method achieves the best of both worlds, and is desirable across theory/algorithm, compiler, and hardware levels. The proposed PatDNN is an end-to-end framework to efficiently execute DNN on mobile devices with the help of a novel model compression technique---pattern-based pruning based on an extended ADMM solution framework---and a set of thorough architecture-aware compiler/code generation-based optimizations, i.e., filter kernel reordering, compressed weight storage, register load redundancy elimination, and parameter auto-tuning. Evaluation results demonstrate that PatDNN outperforms three state-of-the-art end-to-end DNN frameworks, TensorFlow Lite, TVM, and Alibaba Mobile Neural Network with speedup up to 44.5X, 11.4X, and 7.1X, respectively, with no accuracy compromise. Real-time inference of representative large-scale DNNs (e.g., VGG-16, ResNet-50) can be achieved using mobile devices.
Resonance projectors and asymptotics for r -normally hyperbolic trapped sets

We prove an asymptotic formula for the number of scattering resonances in a strip near the real axis when the trapped set is r-normally hyperbolic with r large and a pinching condition on the normal expansion rates holds. Our dynamical assumptions are stable under smooth perturbations and motivated by the setting of black holes. The key tool is a Fourier integral operator which microlocally projects onto the resonant states in the strip. In addition to Weyl law, this operator provides new information about microlocal concentration of resonant states.
Nature abhors a circle

The loss of orbital energy and angular momentum to gravitational waves produced in a binary inspiral forces the orbital eccentricity to adiabatically evolve and oscillate. For comparable-mass binaries, the osculating eccentricity is thought to decrease monotonically in the inspiral. Contrary to this, we here show that, once the osculating eccentricity is small enough, radiation reaction forces it to grow secularly before the binary reaches the last stable orbit. We explore this behavior, its physical interpretation and consequences, and its potential impact on future gravitational wave observations.
HIERARCHICAL GALAXY GROWTH AND SCATTER IN THE STELLAR MASS–HALO MASS RELATION

The relation between galaxies and dark matter halos reflects the combined effects of many distinct physical processes. Observations indicate that the $z=0$ stellar mass-halo mass (SMHM) relation has remarkably small scatter in stellar mass at fixed halo mass ($\lesssim$ 0.2 dex) with little dependence on halo mass. We investigate the origins of this scatter by combining N-body simulations with observational constraints on the SMHM relation. We find that at the group and cluster scale ($M_{\rm vir}>10^{14}{M_\odot}$) the scatter due purely to hierarchical assembly is $\approx0.16$ dex, which is comparable to recent direct observational estimates. At lower masses, mass buildup since $z\approx2$ is driven largely by in-situ growth. We include a model for the in-situ buildup of stellar mass and find that an intrinsic scatter in this growth channel of $0.2$ dex produces a relation between scatter and halo mass that is consistent with observations from $10^{12}{M_\odot}<M_{\rm vir}<10^{14.75}{M_\odot}$. The approximately constant scatter across a wide range of halo masses at $z=0$ thus appears to be a coincidence as it is determined largely by in-situ growth at low masses and by hierarchical assembly at high masses. These results indicate that the scatter in the SMHM relation can provide unique insight into the regularity of the galaxy formation process.
Limits of Risk Predictability in a Cascading Alternating Renewal Process Model.

Most risk analysis models systematically underestimate the probability and impact of catastrophic events (e.g., economic crises, natural disasters, and terrorism) by not taking into account interconnectivity and interdependence of risks. To address this weakness, we propose the Cascading Alternating Renewal Process (CARP) to forecast interconnected global risks. However, assessments of the model’s prediction precision are limited by lack of sufficient ground truth data. Here, we establish prediction precision as a function of input data size by using alternative long ground truth data generated by simulations of the CARP model with known parameters. We illustrate the approach on a model of fires in artificial cities assembled from basic city blocks with diverse housing. The results confirm that parameter recovery variance exhibits power law decay as a function of the length of available ground truth data. Using CARP, we also demonstrate estimation using a disparate dataset that also has dependencies: real-world prediction precision for the global risk model based on the World Economic Forum Global Risk Report. We conclude that the CARP model is an efficient method for predicting catastrophic cascading events with potential applications to emerging local and global interconnected risks.
HIERARCHICAL STAR FORMATION IN THE MILKY WAY DISK

Hierarchical star formation leads to a progressive decrease in the clustering of star clusters both in terms of spatial scale and age. Consistently, statistical analysis of the positions and ages of clusters in the Milky Way disk strongly suggests that a correlation between the duration of star formation in a region and its size does exist. The average age difference between pairs of open clusters increases with their separation as the ~0.16 power. In contrast, for the Large Magellanic Cloud, Efremov & Elmegreen found that the age difference scales with the ~0.35 power of the region size. This discrepancy may be tentatively interpreted as an argument in support of intrinsically shorter (faster) star formation timescales in smaller galaxies. However, if both the effects of cluster dissolution and incompleteness are taken into consideration, the average age difference between cluster pairs in the Galaxy increases with their separation as the ~0.4 power. This result implies that the characteristic timescale for coherent, clustered-mode star formation is nearly 1 Myr. Therefore, the overall consequence of ignoring the effect of cluster dissolution is to overestimate the star formation timescale. On the other hand, in the Galactic disk and for young clusters separated by less than three times the characteristic cluster tidal radius (10 pc), the average age difference is 16 Myr, which suggests common origin. A close pair classification scheme is introduced and a list of 11 binary cluster candidates with physical separation less than 30 pc is compiled. Two of these pairs are likely primordial: ASCC 18/ASCC 21 and NGC 3293/NGC 3324. A triple cluster candidate in a highly hierarchical configuration is also identified: NGC 1981/NGC 1976/Collinder 70 in Orion. We find that binary cluster candidates seem to show a tendency to have components of different size—evidence for dynamical interaction.
Dark matter, dark radiation and gravitational waves from mirror Higgs parity

An exact parity replicates the Standard Model giving a Mirror Standard Model, SM ↔ SM′. This “Higgs Parity” and the mirror electroweak symmetry are spontaneously broken by the mirror Higgs, 〈H′〉 = v′ ≫ 〈H〉, yielding the Standard Model Higgs as a Pseudo-Nambu-Goldstone Boson of an approximate SU (4) symmetry, with a quartic coupling λSM(v′) ∼ 10−3. Mirror electromagnetism is unbroken and dark matter is composed of e′ and $$ {\overline{e}}^{\prime } $$ . Direct detection may be possible via the kinetic mixing portal, and in unified theories this rate is correlated with the proton decay rate. With a high reheat temperature after inflation, the et dark matter abundance is determined by freeze-out followed by dilution from decays of mirror neutrinos, ν′ → lH . Remarkably, this requires v′ ∼ (108–1010) GeV, predicting a Higgs mass of 123 ± 3 GeV at 1σ and a Standard Model neutrino mass of (10−2–10−1) eV, consistent with observed neutrino masses. The mirror QCD sector exhibits a first order phase transition producing gravitational waves that may be detected by future observations. Mirror glueballs decay to mirror photons giving dark radiation with ∆Neff ∼ 0.03–0.4. With a low reheat temperature after inflation, the e′ dark matter abundance is determined by freeze-in from the SM sector by either the Higgs or kinetic mixing portal.
The Quantum Mechanical Arrows of Time

The familiar textbook quantum mechanics of laboratory measurements incorporates a quantum mechanical arrow of time—the direction in time in which state vector reduction operates. This arrow is usually assumed to coincide with the direction of the thermodynamic arrow of the quasiclassical realm of everyday experience. But in the more general context of cosmology we seek an explanation of all observed arrows, and the relations between them, in terms of the conditions that specify our particular universe. This paper investigates quantum mechanical and thermodynamic arrows in a time-neutral formulation of quantum mechanics for a number of model cosmologies in fixed background spacetimes. We find that a general universe may not have well defined arrows of either kind. When arrows are emergent they need not point in the same direction over the whole of spacetime. Rather they may be local, pointing in different directions in different spacetime regions. Local arrows can therefore be consistent with global time symmetry. [Editors note: for a video of the talk given by Prof. Hartle at the Aharonov-80 conference in 2012 at Chapman University, see quantum.chapman.edu/talk-15.]
Atomic Transition Probabilities for UV and Blue Lines of Fe II and Abundance Determinations in the Photospheres of the Sun and Metal-poor Star HD 84937

We report new branching fractions for 121 UV lines from the low-lying odd-parity levels of Fe II belonging to the z6Do, z6Fo, z6Po, z4Fo, z4Do and z4Po terms of the 3d6(5D)4p configuration. These lines range in wavelength from 2250 - 3280 {\AA} and originate in levels ranging in energy from 38459 - 47626 cm-1. In addition, we report branching fractions for 10 weak blue lines connecting to the z4Do term which range in wavelength from 4173 - 4584 {\AA}. The BFs are combined with radiative lifetimes from the literature to determine transition probabilities and log(gf) values. Comparison is made to selected experimental and theoretical data from the literature. Our new data are applied to iron abundance determinations in the Sun and in metal-poor star HD 84937. For the Sun, eight blue lines yield log {\epsilon}(Fe) = 7.46 +/- 0.03, in agreement with standard solar abundance estimates. For HD 84937 the observable wavelength range extends to the vacuum UV ({\lambda} >= 2327 {\AA}), and from 75 lines we derive log {\epsilon}(Fe) = 5.26 +/- 0.01 ({\sigma} = 0.07), near to the metallicity estimates of past HD 84937 studies.
Regularization of the light-cone gauge gluon propagator singularities using sub-gauge conditions

Perturbative QCD calculations in the light-cone gauge have long suffered from the ambiguity associated with the regularization of the poles in the gluon propagator. In this work we study sub-gauge conditions within the light-cone gauge corresponding to several known ways of regulating the gluon propagator. Using the functional integral calculation of the gluon propagator, we rederive the known sub-gauge conditions for the θ-function gauges and identify the sub-gauge condition for the principal value (PV) regularization of the gluon propagator’s light-cone poles. The obtained sub-gauge condition for the PV case is further verified by a sample calculation of the classical Yang-Mills field of two collinear ultrarelativistic point color charges. Our method does not allow one to construct a sub-gauge condition corresponding to the well-known Mandelstam-Leibbrandt prescription for regulating the gluon propagator poles.
Semi-adsorption-controlled growth window for half-Heusler FeVSb epitaxial films

The electronic, magnetic, thermoelectric, and topological properties of Heusler compounds (composition $XYZ$ or ${X}_{2}YZ$) are highly sensitive to stoichiometry and defects. Here we establish the existence and experimentally map the bounds of a semi-adsorption-controlled growth window for semiconducting half-Heusler FeVSb films, grown by molecular beam epitaxy (MBE). We show that due to the high volatility of Sb, the Sb stoichiometry is self-limiting for a finite range of growth temperatures and Sb fluxes, similar to the growth of III-V semiconductors such as GaSb and GaAs. Films grown within this window are nearly structurally indistinguishable by x-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED). The highest electron mobility and lowest background carrier density are obtained towards the Sb-rich bound of the window, suggesting that Sb vacancies may be a common defect. Similar semi-adsorption-controlled bounds are expected for other ternary intermetallics that contain a volatile species $Z=${Sb, As, Bi}, e.g., CoTiSb, LuPtSb, GdPtBi, and NiMnSb. However, outstanding challenges remain in controlling the remaining Fe/V ($X/Y$) transition metal stoichiometry.