cssi/SciSciGPT-SciSciNet huggingface dataset:
The case for mixed dark matter from sterile neutrinos

Sterile neutrinos are SU(2) singlets that mix with active neutrinos via a mass matrix, its diagonalization leads to mass eigenstates that couple via standard model vertices. We study the cosmological production of heavy neutrinos via standard model charged and neutral current vertices under a minimal set of assumptions: i) the mass basis contains a hierarchy of heavy neutrinos, ii) these have very small mixing angles with the active (flavor) neutrinos, iii) standard model particles, including light (active-like) neutrinos are in thermal equilibrium. If kinematically allowed, the same weak interaction processes that produce active-like neutrinos also produce the heavier species. We introduce the quantum kinetic equations that describe their production, freeze out and decay and discuss the various processes that lead to their production in a wide range of temperatures assessing their feasibility as dark matter candidates. The final distribution function at freeze-out is a mixture of the result of the various production processes. We identify processes in which finite temperature collective excitations may lead to the production of the heavy species. As a specific example, we consider the production of heavy neutrinos in the mass range Mh 140 MeV from pion decay shortly after the QCD crossover including finite temperature corrections to the pion form factors and mass. We consider the different decay channels that allow for the production of heavy neutrinos showing that their frozen distribution functions exhibit effects from ``kinematic entanglement'' and argue for their viability as mixed dark matter candidates. We discuss abundance, phase space density and stability constraints and argue that heavy neutrinos with lifetime τ> 1/H0 freeze out of local thermal equilibrium, and conjecture that those with lifetimes τ 1/H0 may undergo cascade decay into lighter DM candidates and/or inject non-LTE neutrinos into the cosmic neutrino background. We provide a comparison with non-resonant production via active-sterile mixing.
KIC 8462852: THE INFRARED FLUX

We analyzed the warm Spitzer/IRAC data of KIC 8462852. We found no evidence of infrared excess at 3.6 μm and a small excess of 0.43 ± 0.18 mJy at 4.5 μm below the 3σ threshold necessary to claim a detection. The lack of strong infrared excess 2 years after the events responsible for the unusual light curve observed by Kepler further disfavors the scenarios involving a catastrophic collision in a KIC 8462852 asteroid belt, a giant impact disrupting a planet in the system or a population of dust-enshrouded planetesimals. The scenario invoking the fragmentation of a family of comets on a highly elliptical orbit is instead consistent with the lack of strong infrared excess found by our analysis.
A New Look at Type-III Bursts and Their Use as Coronal Diagnostics

We present meter-wave solar radio spectra of the highest spectro–temporal resolution achieved to date. The observations, obtained with the first station of the Long Wavelength Array (LWA1), show unprecedented detail of solar emissions across a wide bandwidth during a Type-III/IIIb storm. Our flux calibration demonstrates that the LWA1 can detect Type-III bursts much weaker than 1 SFU, much lower than previous observations, and that the distribution of fluxes in these bursts varies with frequency. The high sensitivity and low noise in the data provide strong constraints to models of this type of plasma emission, providing evidence against the idea that Type-IIIb striae are generated from electrons trapped in Langmuir-wave sidebands. The continuous generation of electron beams in the corona revealed by the high density Type-III storm is evidence for ubiquitous magnetic reconnection in the lower corona. Such an abundance of reconnection events not only contributes to the total coronal energy budget, but also provides an engine by which to form the populations of seed particles responsible for proton-rich solar energetic-particle events. An active region (AR) with such levels of reconnection and the accompanying Type-III/IIIb storms is proposed here to be associated with an increase of SEP production if a CME erupts. The data’s constraints on existing theories of Type-IIIb production are used to make an association of the observed Type-IIIb storm to specific electron-beam paths with increased inhomogeneities in density, temperature, and/or turbulence. This scenario ties in the observed timing of Type-III and -IIIb storms, constrained theories of Type-III and -IIIb emission, and the ability of the emitting AR to produce a strong SEP event. The result requires but a single observable to cement these ideas, the statistical correlation of Type-III/IIIb activity with SEP-productive AR.
Magnetic component of quark-gluon plasma

We describe recent developments of the 'magnetic scenario' of sQGP. We show that at T = (0.8-1.3)T c there is a dense plasma of monopoles, capable of supporting metastable flux tubes. Their existence allows us to quantitatively explain the non-trivial T-dependence of the static QQ potential energy calculated on the lattice. By molecular dynamics simulation we derived transport properties (shear viscosity and diffusion constant) and showed that the best liquid is given by most symmetric plasma, with 50%-50% of electric and magnetic charges. The results are close to those of the 'perfect liquid' observed at RHIC.
Accelerated evolution of convective simulations

A mechanism for rapidly achieving thermal relaxation in high-$P\phantom{\rule{0}{0ex}}e$ convective simulations is studied in the context of Rayleigh-B\'enard convection. It achieves statistically similar states to standard timestepping and saves up to an order of magnitude in computational time for the problems studied.
Measure concentration and the weak Pinsker property

Let \((X,\mu)\) be a standard probability space. An automorphism \(T\) of \((X,\mu)\) has the weak Pinsker property if for every \(\varepsilon > 0\) it has a splitting into a direct product of a Bernoulli shift and an automorphism of entropy less than \(\varepsilon \). This property was introduced by Thouvenot, who asked whether it holds for all ergodic automorphisms.
A city-scale IoT-enabled ridesharing platform

The advent of on-demand mobility systems is expected to have a tremendous potential on the wellness of transportation users in cities. Yet such positive effects are reached when the systems under c...
Comprehensive Census and Complete Characterization of Nearby Debris Disk Stars

Debris disks are intimately linked to planetary system evolution since the rocky material surrounding the host stars is believed to be due to secondary generation from the collisions of planetesimals. With the conclusion and lack of future large scale infrared excess survey missions, it is time to summarize the history of using excess emission in the infrared as a tracer of debris and exploit all available data as well as provide a comprehensive study of the parameters of these important objects. We have compiled a catalog of infrared excess stars from peer-reviewed articles and performed an extensive search for new debris disks by cross-correlating the Tycho-2 and AllWISE catalogs. This study will conclude following the thorough examination of each debris disk star's parameters obtained through high-resolution spectroscopy at various facilities which is currently ongoing. We will maintain a webpage ( www.debrisdisks.org ) devoted to these infrared excess sources and provide various resources related to our catalog creation, SED fitting, and data reduction.
Spectroscopic Confirmation of the Dwarf Galaxies Hydra II and Pisces II and the Globular Cluster Laevens 1

We present Keck/DEIMOS spectroscopy of stars in the recently discovered Milky Way satellites Hydra II, Pisces II, and Laevens 1. We measured a velocity dispersion of 5.4^(+3.6)_(-2.4) km s^(−1) for Pisces II, but we did not resolve the velocity dispersions of Hydra II or Laevens 1. We marginally resolved the metallicity dispersions of Hydra II and Pisces II but not Laevens 1. Furthermore, Hydra II and Pisces II obey the luminosity–metallicity relation for Milky Way dwarf galaxies (〈[Fe/H] 〉 = -2.02 ± 0.08 and -2.45 ± 0.07, respectively), whereas Laevens 1 does not (〈[Fe/H]〉= -1.68 ± 0.05). The kinematic and chemical properties suggest that Hydra II and Pisces II are dwarf galaxies, and Laevens 1 is a globular cluster. We determined that two of the previously observed blue stars near the center of Laevens 1 are not members of the cluster. A third blue star has ambiguous membership. Hydra II has a radial velocity 〈ν_(helio) 〉 = 303.1 ± 1.4 km s^(−1), similar to the leading arm of the Magellanic stream. The mass-to-light ratio for Pisces II is 370^(+310)_(-240) M⊙/L⊙. It is not among the most dark matter-dominated dwarf galaxies, but it is still worthy of inclusion in the search for gamma-rays from dark matter self-annihilation.
A proof of Milnor conjecture in dimension 3

We present a proof of Milnor conjecture in dimension 3 based on Cheeger-Colding theory on limit spaces of manifolds with Ricci curvature bounded below. It is different from [Liu] that relies on minimal surface theory.
Global aspects of abelian duality in dimension three

In three dimensions, an abelian gauge field is related by duality to a free, periodic scalar field. Though usually considered on $$ {\mathrm{\mathbb{R}}}^3 $$ , this duality can be extended to a general three-manifold M , in which case topological features of M become important. Here I comment upon several of these features as related to the partition function on M. In a companion article, I discuss similarly the algebra of operators on a surface of genus g.
Effects of Large-Scale Convection on p-Mode Frequencies

We describe an approach for finding the eigenfrequencies of solar acoustic modes (p-modes) in a convective envelope in the Wentzel-Kramers-Brillouin limit. This approximation restricts us to examining the effects of fluid motions that are large compared with the mode wavelength but allows us to treat the three-dimensional mode as a localized ray. The method of adiabatic switching is then used to investigate the frequency shifts resulting from simple perturbations to a polytropic model of the convection zone as well as from two basic models of a convective cell. We find that although solely depth-dependent perturbations can give frequency shifts that are first order in the strength of the perturbation, models of convective cells generate downward frequency shifts that are second order in the perturbation strength. These results may have implications for resolving the differences between eigenfrequencies derived from solar models and those found from helioseismic observations.
Site percolation on lattices with low average coordination numbers

We present a study of site and bond percolation on periodic lattices with (on average) fewer than three nearest neighbors per site. We have studied this issue in two contexts: by simulating oxides with a mixture of 2-coordinated and higher-coordinated sites and by mapping site-bond percolation results onto a site model with mixed coordination number. Our results show that a conjectured power-law relationship between coordination number and site percolation threshold holds approximately if the coordination number is defined as the average number of connections available between high-coordinated sites and suggest that the conjectured power-law relationship reflects a real phenomenon requiring further study. The solution may be to modify the power-law relationship to be an implicit formula for percolation threshold, one that takes into account aspects of the lattice beyond spatial dimension and average coordination number.
Earthquake Catalog-Based Machine Learning Identification of Laboratory Fault States and the Effects of Magnitude of Completeness

Machine learning regression can predict macroscopic fault properties such as shear stress, friction, and time to failure using continuous records of fault zone acoustic emissions. Here we show that a similar approach is successful using event catalogs derived from the continuous data. Our methods are applicable to catalogs of arbitrary scale and magnitude of completeness. We investigate how machine learning regression from an event catalog of laboratory earthquakes performs as a function of the catalog magnitude of completeness. We find that strong model performance requires a sufficiently low magnitude of completeness, and below this magnitude of completeness model performance saturates.
Positive feedback produces broad distributions in maximum activation attained within a narrow time window in stochastic biochemical reactions.

How do single cell fate decisions induced by activation of key signaling proteins above threshold concentrations within a time interval are affected by stochastic fluctuations in biochemical reactions? We address this question using minimal models of stochastic chemical reactions commonly found in cell signaling and gene regulatory systems. Employing exact solutions and semi-analytical methods we calculate distributions of the maximum value (N) of activated species concentrations (Pmax(N)) and the time (t) taken to reach the maximum value (Pmax(t)) within a time interval in the minimal models. We find, the presence of positive feedback interactions make Pmax(N) more spread out with a higher “peakedness” in Pmax(t). Thus positive feedback interactions may help single cells to respond sensitively to a stimulus when cell decision processes require upregulation of activated forms of key proteins to a threshold number within a time window.
The IR-resummed Effective Field Theory of Large Scale Structures

We present a new method to resum the effect of large scale motions in the Effective Field Theory of Large Scale Structures. Because the linear power spectrum in ΛCDM is not scale free the effects of the large scale flows are enhanced. Although previous EFT calculations of the equal-time density power spectrum at one and two loops showed a remarkable agreement with numerical results, they also showed a 2% residual which appeared related to the BAO oscillations. We show that this was indeed the case, explain the physical origin and show how a Lagrangian based calculation removes this differences. We propose a simple method to upgrade existing Eulerian calculations to effectively make them Lagrangian and compare the new results with existing fits to numerical simulations. Our new two-loop results agrees with numerical results up to k~ 0.6 h Mpc−1 to within 1% with no oscillatory residuals. We also compute power spectra involving momentum which is significantly more affected by the large scale flows. We show how keeping track of these velocities significantly enhances the UV reach of the momentum power spectrum in addition to removing the BAO related residuals. We compute predictions for the real space correlation function around the BAO scale and investigate its sensitivity to the EFT parameters and the details of the resummation technique.
Anomaly conditions for non-Abelian finite family symmetries

Assuming that finite family symmetries are gauged, we derive discrete anomaly conditions for various non-Abelian groups. We thus provide new constraints for flavor model building, in which discrete non-Abelian symmetries are employed to explain the tri-bimaximal mixing pattern in the lepton sector.
Symmetries and charges of general relativity at null boundaries

We study general relativity at a null boundary using the covariant phase space formalism. We define a covariant phase space and compute the algebra of symmetries at the null boundary by considering the boundary-preserving diffeomorphisms that preserve this phase space. This algebra is the semi-direct sum of diffeomorphisms on the two sphere and a nonabelian algebra of supertranslations that has some similarities to supertranslations at null infinity. By using the general prescription developed by Wald and Zoupas, we derive the localized charges of this algebra at cross sections of the null surface as well as the associated fluxes. Our analysis is covariant and applies to general non-stationary null surfaces. We also derive the global charges that generate the symmetries for event horizons, and show that these obey the same algebra as the linearized diffeomorphisms, without any central extension. Our results show that supertranslations play an important role not just at null infinity but at all null boundaries, including non-stationary event horizons. They should facilitate further investigations of whether horizon symmetries and conservation laws in black hole spacetimes play a role in the information loss problem, as suggested by Hawking, Perry, and Strominger.
Direct estimation of information divergence using nearest neighbor ratios

We propose a direct estimation method for Renyi and f-divergence measures based on a new graph theoretical interpretation. Suppose that we are given two sample sets X and Y, respectively with N and M samples, where η := M/N is a constant value. Considering the k-nearest neighbor (k-NN) graph of Y in the joint data set (X, Y), we show that the average powered ratio of the number of X points to the number of Y points among all k-NN points is proportional to Renyi divergence of X and Y densities. A similar method can also be used to estimate f-divergence measures. We derive bias and variance rates, and show that for the class of γ-Holder smooth functions, the estimator achieves the MSE rate of O(N−2γ/(γ+d)). Furthermore, by using a weighted ensemble estimation technique, for density functions with continuous and bounded derivatives of up to the order d, and some extra conditions at the support set boundary, we derive an ensemble estimator that achieves the parametric MSE rate of O(1/N). Our estimator requires no boundary correction, and remarkably, the boundary issues do not show up. Our approach is also more computationally tractable than other competing estimators, which makes them appealing in many practical applications.
Asymptotic minimax risk of predictive density estimation for non-parametric regression

We consider the problem of estimating the predictive density of future observations from a non-parametric regression model. The density estimators are evaluated under Kullback–Leibler divergence and our focus is on establishing the exact asymptotics of minimax risk in the case of Gaussian errors. We derive the convergence rate and constant for minimax risk among Bayesian predictive densities under Gaussian priors and we show that this minimax risk is asymptotically equivalent to that among all density estimators.
Testing Determinantal Point Processes

Determinantal point processes (DPPs) are popular probabilistic models of diversity. In this paper, we investigate DPPs from a new perspective: property testing of distributions. Given sample access to an unknown distribution $q$ over the subsets of a ground set, we aim to distinguish whether $q$ is a DPP distribution, or $\epsilon$-far from all DPP distributions in $\ell_1$-distance. In this work, we propose the first algorithm for testing DPPs. Furthermore, we establish a matching lower bound on the sample complexity of DPP testing. This lower bound also extends to showing a new hardness result for the problem of testing the more general class of log-submodular distributions.
Symplectic large- N theory of topological heavy-fermion semiconductors

I present a theory of topological heavy-fermion semiconductors based on the large-N symplectic representation for the electron spin. The theory is exact in the limit when the number of spin flavors N = 2k is infinite. I find that both weak and strong topological insulating phases exist for k < 3. Furthermore, for k ≥ 3 the weak topological insulating state is fully suppressed while only strong topological and trivial insulator states survive. In addition, using the mean-field theory results, I consider the tunneling into topologically trivial and non-trivial phases of a generic heavy-fermion insulators by calculating the differential tunneling conductance. The implications of the presented results for the existing heavy-fermion semiconductors are discussed.
Nonparametric methods for doubly robust estimation of continuous treatment effects

Summary Continuous treatments (e.g. doses) arise often in practice, but many available causal effect estimators are limited by either requiring parametric models for the effect curve, or by not allowing doubly robust covariate adjustment. We develop a novel kernel smoothing approach that requires only mild smoothness assumptions on the effect curve and still allows for misspecification of either the treatment density or outcome regression. We derive asymptotic properties and give a procedure for data-driven bandwidth selection. The methods are illustrated via simulation and in a study of the effect of nurse staffing on hospital readmissions penalties.
Kernel Decompositions for Schur Functions on the Polydisk

A certain kernel (sometimes called the Pick kernel) associated to Schur functions on the disk is always positive semi-definite. A generalization of this fact is well-known for Schur functions on the polydisk. In this article, we show that the “Pick kernel” on the polydisk has a great deal of structure beyond being positive semi-definite. It can always be split into two kernels possessing certain shift invariance properties.
Minimizing properties of critical points of quasi-local energy

In relativity, the energy of a moving particle depends on the observer, and the rest mass is the minimal energy seen among all observers. The Wang–Yau quasi-local mass for a surface in spacetime introduced in Wang and Yau (Phys Rev Lett 102(2):021101, 2009 ; Commun Math Phys 288(3):919–942, 2009) is defined by minimizing quasi-local energy associated with admissible isometric embeddings of the surface into the Minkowski space. A critical point of the quasi-local energy is an isometric embedding satisfying the Euler–Lagrange equation. In this article, we prove results regarding both local and global minimizing properties of critical points of the Wang–Yau quasi-local energy. In particular, under a condition on the mean curvature vector we show a critical point minimizes the quasi-local energy locally. The same condition also implies that the critical point is globally minimizing among all axially symmetric embedding provided the image of the associated isometric embedding lies in a totally geodesic Euclidean 3-space.
Station-Keeping Requirements for Constellations of Free-Flying Collectors Used for Astronomical Imaging in Space

The accuracy requirements on station-keeping for constellations of free-flying collectors that are coupled as (future) imaging arrays in space for astrophysics applications are examined. The basic imaging element of these arrays is the two-element interferometer. Accurate knowledge of two quantities is required: the "projected baseline length," which is the distance between the two interferometer elements projected on the plane transverse to the line of sight to the target, and the "optical path difference," which is the difference in the distances from that transverse plane to the beam combiner. Rules of thumb are determined for the typical accuracy required on these parameters. The requirement on the projected baseline length is a "knowledge" requirement and depends on the angular size of the targets of interest. It is generally at a level of half a meter for typical stellar targets, decreasing to perhaps a few centimeters only for the widest attainable fields of view. The requirement on the optical path difference is a "control" requirement and is much tighter, depending on the bandwidth of the signal. It is at a level of half a wavelength for narrow (few percent) signal bands, decreasing to ≈0.2 λ for the broadest bandwidths expected to be useful. Translation of these requirements into engineering requirements on station-keeping accuracy depends on the specific details of the collector constellation geometry. Several examples are provided to guide future application of the criteria presented here. Some implications for the design of such collector constellations and for the methods used to transform the information acquired into images are discussed.
Efficient distributed estimation of inverse covariance matrices

In distributed systems, communication is a major concern due to issues such as its vulnerability or efficiency. In this paper, we are interested in estimating sparse inverse covariance matrices when samples are distributed into different machines. We address communication efficiency by proposing a method where, in a single round of communication, each machine transfers a small subset of the entries of the inverse covariance matrix. We show that, with this efficient distributed method, the error rates can be comparable with estimation in a non-distributed setting, and correct model selection is still possible. Practical performance is shown through simulations.
New opportunities with spectro-interferometry and spectro-astrometry

Latest-generation spectro-interferometric instruments combine a milliarcsecond angular resolution with spectral capabilities, resulting in an immensely increased information content. Here, I present methodological work and results that illustrate the fundamentally new scientific insights provided by spectro-interferometry with very high spectral dispersion or in multiple line transitions (Brackett and Pfund lines). In addition, I discuss some pitfalls in the interpretation of spectro-interferometric data. In the context of our recent studies on the classical Be stars β CMi and ζ Tau, I present the first position-velocity diagram obtained with optical interferometry and provide a physical interpretation for a phase inversion, which has in the meantime been observed for several classical Be-stars. In the course of our study on the Herbig B[e] star V921 Sco, we combined, for the first time, spectro-interferometry and spectro-astrometry, providing a powerful and resource-efficient way to constrain the spatial distribution as well as the kinematics of the circumstellar gas with an unprecedented velocity resolution up to R = λ/Δλ = 100,000. Finally, I discuss our phase sign calibration procedure, which has allowed us to calibrate AMBER differential phases and closure phases for all spectral modes, and derive from the gained experience science-driven requirements for future instrumentation projects.
D-brane actions

Abstract Effective world-brane actions for solitons of ten-dimensional type IIA and IIB superstring theory are derived using the formulation of solitons as Dirichlet branes. The one-brane actions are used to recover predictions of SL(2, Z ) strong-weak coupling duality. The two-brane action, which contains a hidden eleventh target-space coordinate, is shown to be the eleven-dimensional supermembrane action. It can be thought of as the membrane action of “M-theory”.
VoroTop: Voronoi cell topology visualization and analysis toolkit

This paper introduces a new open-source software program called VoroTop, which uses Voronoi topology to analyze local structure in atomic systems. Strengths of this approach include its abilities to analyze high-temperature systems and to characterize complex structure such as grain boundaries. This approach enables the automated analysis of systems and mechanisms previously not possible.
Length spectra and strata of flat metrics

In this paper we consider strata of flat metrics coming from quadratic differentials (semi-translation structures) on surfaces of finite type. We provide a necessary and sufficient condition for a set of simple closed curves to be spectrally rigid over a stratum with enough complexity, extending a result of Duchin–Leininger–Rafi. Specifically, for any stratum with more zeroes than the genus, the $$\Sigma $$ -length-spectrum of a set of simple closed curves $$\Sigma $$ determines the flat metric in the stratum if and only if $$\Sigma $$ is dense in the projective measured foliation space. We also prove that flat metrics in any stratum are locally determined by the $$\Sigma $$ -length-spectrum of a finite set of closed curves $$\Sigma $$ .
Pattern equivariant cohomology and theorems of Kesten and Oren

In 1966 Harry Kesten settled the Erd\H os-Szusz conjecture on the local discrepancy of irrational rotations. His proof made heavy use of continued fractions and Diophantine analysis. In this paper we give a purely topological proof Kesten's theorem (and Oren's generalization of it) using the pattern equivariant cohomology of aperiodic tiling spaces.
Radio Pulses along the Galactic Plane

We have surveyed 68 deg2 along the Galactic plane for single, dispersed radio pulses. Each of 3027 independent pointings was observed for 68 s using the Arecibo telescope at 430 MHz. Spectra were collected at intervals of 0.5 ms and examined for pulses with duration 0.5-8 ms. Such single-pulse analysis is the most sensitive method of detecting highly scattered or highly dispersed signals from pulsars with large pulse-to-pulse intensity variations. A total of 36 individual pulses from five previously known pulsars were detected, along with a single pulse not associated with a previously known source. Follow-up observations discovered a pulsar, PSR J1918+08, from which the pulse originated. This pulsar has a period of 2.130 s and a dispersion measure of 30 pc cm-3, and it has been seen to emit single pulses with strength up to 8 times the average.
Spectral characterization of non-Gaussian quantum noise: Keldysh approach and application to photon shot noise

This work provides a universal characterization of nonclassical, non-Gaussian environmental fluctuations in the frequency domain, based on the Keldysh approach to quantum noise characterization. The authors also present a calculation of frequency-resolved third cumulant, i.e., quantum bispectrum, of a nontrivial quantum bath. They show that the quantum bispectrum reveals that quantum fluctuations can break detailed balance.
Granular impact model as an energy-depth relation

Velocity-squared drag forces are common in describing an object moving through a granular material. The resulting force law is a nonlinear differential equation, and closed-form solutions of the dynamics are typically obtained by making simplifying assumptions. Here, we consider a generalized version of such a force law which has been used in many studies of granular impact. We show that recasting the force law into an equation for the kinetic energy vs. depth, K(z), yields a linear differential equation, and thus general closed-form solutions for the velocity vs. depth. This approach also has several advantages in fitting such models to experimental data, which we demonstrate by applying it to data from 2D impact experiments. We also present new experimental results for this model, including shape and depth dependence of the velocity-squared drag force.
Quantum Annealing for Constrained Optimization

Quantum computers can perform certain tasks much faster than classical computers. An example is $q\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}m$ $a\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}g$, an operation that permits the exploration of energy landscapes to find global minima $i.e.$, optimal solutions) for problems that are classically intractable. This permits simultaneous exploration of enormous computational spaces, as is necessary for complex problems in economics, network design, and nonlinear control. The authors show how suitably engineered quantum annealers can efficiently guide and focus the quantum wave function towards the solutions of constrained optimization problems.
The rotation problem

Any reasonable form of quantum gravity can explain (by phase interference) why, on a large scale, inertial frames seem not to rotate relative to the average matter distribution in the universe without the need for absolute space, finely tuned initial conditions, or without giving up independent degrees of freedom for the gravitational field. A simple saddlepoint approximation to a path-integral calculation for a perfect fluid cosmology shows that only cosmologies with an average present relative rotation rate smaller than about $$T^*H^2 \approx 10^{-71}$$ radians per year could contribute significantly to a measurement of relative rotation rate in our universe, where $$T^*\approx 10^{-51}$$ years is the Planck time and $$H \approx 10^{-10}$$ $$\hbox {yr}^{-1}$$ is the present value of the Hubble parameter. A more detailed calculation (taking into account that with vorticity flow lines are not normal to surfaces of constant global time, and approximating the action to second order in the mean square vorticity) shows that the saddlepoint at zero vorticity is isolated and that only cosmologies with an average present relative rotation rate smaller than about $$T^*H^2 a_1^{1/2} \approx 10^{-73}$$ radians per year could contribute significantly to a measurement of relative rotation rate in our universe, where $$a_1 \approx 10^{-4}$$ is the value of the cosmological scale factor at the time when matter became more significant than radiation in the cosmological expansion. Including inflation with 60 e-foldings in the calculation of the action further restricts relative rotation rate to be smaller than $$\approx 10^{-74}$$ radians per year. These calculations are consistent with measurements indicating a present relative rotation rate less than about $$10^{-20}$$ radians per year. The observed lack of relative rotation may be evidence for the existence of quantum gravity.
AN XMM-NEWTON SURVEY OF THE SOFT X-RAY BACKGROUND. III. THE GALACTIC HALO X-RAY EMISSION

We present measurements of the Galactic halo's X-ray emission for 110 XMM-Newton sight lines selected to minimize contamination from solar wind charge exchange emission. We detect emission from few million degree gas on ~4/5 of our sight lines. The temperature is fairly uniform (median = 2.22 ? 106 K, interquartile range = 0.63 ? 106 K), while the emission measure and intrinsic 0.5-2.0 keV surface brightness vary by over an order of magnitude (~(0.4-7) ? 10?3 cm?6 pc and ~(0.5-7) ? 10?12 erg cm?2 s?1 deg?2, respectively, with median detections of 1.9 ? 10?3 cm?6 pc and 1.5 ? 10?12 erg cm?2 s?1 deg?2, respectively). The high-latitude sky contains a patchy distribution of few million degree gas. This gas exhibits a general increase in emission measure toward the inner Galaxy in the southern Galactic hemisphere. However, there is no tendency for our observed emission measures to decrease with increasing Galactic latitude, contrary to what is expected for a disk-like halo morphology. The measured temperatures, brightnesses, and spatial distributions of the gas can be used to place constraints on models for the dominant heating sources of the halo. We provide some discussion of such heating sources, but defer comparisons between the observations and detailed models to a later paper.
Deep learning with cinematic rendering: fine-tuning deep neural networks using photorealistic medical images

Deep learning has emerged as a powerful artificial intelligence tool to interpret medical images for a growing variety of applications. However, the paucity of medical imaging data with high-quality annotations that is necessary for training such methods ultimately limits their performance. Medical data is challenging to acquire due to privacy issues, shortage of experts available for annotation, limited representation of rare conditions and cost. This problem has previously been addressed by using synthetically generated data. However, networks trained on synthetic data often fail to generalize to real data. Cinematic rendering simulates the propagation and interaction of light passing through tissue models reconstructed from CT data, enabling the generation of photorealistic images. In this paper, we present one of the first applications of cinematic rendering in deep learning, in which we propose to fine-tune synthetic data-driven networks using cinematically rendered CT data for the task of monocular depth estimation in endoscopy. Our experiments demonstrate that: (a) convolutional neural networks (CNNs) trained on synthetic data and fine-tuned on photorealistic cinematically rendered data adapt better to real medical images and demonstrate more robust performance when compared to networks with no fine-tuning, (b) these fine-tuned networks require less training data to converge to an optimal solution, and (c) fine-tuning with data from a variety of photorealistic rendering conditions of the same scene prevents the network from learning patient-specific information and aids in generalizability of the model. Our empirical evaluation demonstrates that networks fine-tuned with cinematically rendered data predict depth with 56.87% less error for rendered endoscopy images and 27.49% less error for real porcine colon endoscopy images.
Entropy, Extremality, Euclidean Variations, and the Equations of Motion

We study the Euclidean gravitational path integral computing the Renyi entropy and analyze its behavior under small variations. We argue that, in Einstein gravity, the extremality condition can be understood from the variational principle at the level of the action, without having to solve explicitly the equations of motion. This set-up is then generalized to arbitrary theories of gravity, where we show that the respective entanglement entropy functional needs to be extremized. We also extend this result to all orders in Newton’s constant G N , providing a derivation of quantum extremality. Understanding quantum extremality for mixtures of states provides a generalization of the dual of the boundary modular Hamiltonian which is given by the bulk modular Hamiltonian plus the area operator, evaluated on the so-called modular extremal surface. This gives a bulk prescription for computing the relative entropies to all orders in G N . We also comment on how these ideas can be used to derive an integrated version of the equations of motion, linearized around arbitrary states.
Tuning the molecular weight distribution from atom transfer radical polymerization using deep reinforcement learning

We devise a novel technique to control the shape of polymer molecular weight distributions (MWDs) in atom transfer radical polymerization (ATRP). This technique makes use of recent advances in both simulation-based, model-free reinforcement learning (RL) and the numerical simulation of ATRP. A simulation of ATRP is built that allows an RL controller to add chemical reagents throughout the course of the reaction. The RL controller incorporates fully-connected and convolutional neural network architectures and bases its decision upon the current status of the ATRP reaction. The initial, untrained, controller leads to ending MWDs with large variability, allowing the RL algorithm to explore a large search space. When trained using an actor-critic algorithm, the RL controller is able to discover and optimize control policies that lead to a variety of target MWDs. The target MWDs include Gaussians of various width, and more diverse shapes such as bimodal distributions. The learned control policies are robust and transfer to similar but not identical ATRP reaction settings, even under the presence of simulated noise. We believe this work is a proof-of-concept for employing modern artificial intelligence techniques in the synthesis of new functional polymer materials.
CLASSICAL ABSORPTION IN SMALL METAL PARTICLES AND THIN FILMS

We study the electric dipole absorption in small metal particles and thin films in a longitudinal electric field. In diffusive approximation, we give both the phenomenological and microscopic derivations with the account for Thomas–Fermi screening and Drude relaxation.
A Revised Characterization of the WFPC2 CTE Loss

Charge transfer loss on the Wide Field Planetary Camera 2 (WFPC2) onboard the Hubble Space Telescope is a primary source of uncertainty in stellar photometry obtained with this camera. This effect, discovered shortly after the camera was installed, has grown over time and can dim stars by several tenths of a magnitude (or even more, in particularly bad cases). The impact of CTE loss on WFPC2 stellar photometry was characterized by several studies between 1998 and 2000, but has received diminished attention since ACS became HST's primary imager. After the failure of ACS in January 2007, WFPC2 once again became the primary imaging instrument on board HST, restoring the importance of ensuring accurate CTE corrections. This paper reexamines the CTE loss of WFPC2, with three significant changes over previous studies. First, the present study considers calibration data obtained through 2007, thus increasing the confidence in the reliability of the CTE corrections when applied to recent observations. Second, the change in CTE loss during readout is accounted for analytically. Finally, a reanalysis of the CTE dependencies on counts, background, and observation date was made. The resulting correction is significantly more accurate than that provided in the WFPC2 Instrument Handbook (Dolphin 2002 and updates through 2004), resulting in photometry that can be enhanced by over 5% in certain circumstances.
Frame Dependence of the Electric Field Spectrum of Solar Wind Turbulence

We present the first survey of electric field data using the ARTEMIS spacecraft in the solar wind to study inertial range turbulence. It was found that the average perpendicular spectral index of the electric field depends on the frame of measurement. In the spacecraft frame it is –5/3, which matches the magnetic field due to the large solar wind speed in Lorentz transformation. In the mean solar wind frame, the electric field is primarily due to the perpendicular velocity fluctuations and has a spectral index slightly shallower than –3/2, which is close to the scaling of the velocity. These results are an independent confirmation of the difference in scaling between the velocity and magnetic field, which is not currently well understood. The spectral index of the compressive fluctuations was also measured and found to be close to –5/3, suggesting that they are not only passive to the velocity but may also interact nonlinearly with the magnetic field.
A Robust and Tunable Add–Drop Filter Using Whispering Gallery Mode Microtoroid Resonator

We fabricated and theoretically investigated an add-drop filter (ADF) using an on-chip whispering gallery mode (WGM) microtoroid resonator with ultrahigh-quality factor (Q) side coupled to two taper fibers, forming the bus and drop waveguides. The new device design incorporates silica side walls close to the microresonators which not only enable placing the coupling fibers on the same plane with respect to the microtoroid resonator but also provides mechanical stability, leading to an ADF with high drop efficiency and improved robustness to environmental perturbations. We show that this new device can be thermally tuned to drop desired wavelengths from the bus without significantly affecting the drop efficiency, which is around 57%.
Malicious Overtones: Hunting Data Theft in the Frequency Domain with One-class Learning

A method for detecting electronic data theft from computer networks is described, capable of recognizing patterns of remote exfiltration occurring over days to weeks. Normal traffic flow data, in the form of a host’s ingress and egress bytes over time, is used to train an ensemble of one-class learners. The detection ensemble is modular, with individual classifiers trained on different traffic features thought to characterize malicious data transfers. We select features that model the egress to ingress byte balance over time, periodicity, short timescale irregularity, and density of the traffic. The features are most efficiently modeled in the frequency domain, which has the added benefit that variable duration flows are transformed to a fixed-size feature vector, and by sampling the frequency space appropriately, long-duration flows can be tested. When trained on days or weeks worth of traffic from individual hosts, our ensemble achieves a low false-positive rate (
Adaptive Transform Domain Image Super-Resolution via Orthogonally Regularized Deep Networks

Deep learning methods, in particular, trained convolutional neural networks (CNNs) have recently been shown to produce compelling results for single image super-resolution (SR). Invariably, a CNN is learned to map the low resolution (LR) image to its corresponding high resolution (HR) version in the spatial domain. We propose a novel network structure for learning the SR mapping function in an image transform domain, specifically the discrete cosine transform (DCT). As the first contribution, we show that DCT can be integrated into the network structure as a convolutional DCT (CDCT) layer. With the CDCT layer, we construct the DCT deep SR (DCT-DSR) network. We further extend the DCT-DSR to allow the CDCT layer to become trainable (i.e., optimizable) . Because this layer represents an image transform, we enforce pairwise orthogonality constraints and newly formulated complexity order constraints on the individual basis functions/filters. This orthogonally regularized deep SR network (ORDSR) simplifies the SR task by taking advantage of image transform domain while adapting the design of transform basis to the training image set. The experimental results show ORDSR achieves state-of-the-art SR image quality with fewer parameters than most of the deep CNN methods. A particular success of ORDSR is in overcoming the artifacts introduced by bicubic interpolation. A key burden of deep SR has been identified as the requirement of generous training LR and HR image pairs; ORSDR exhibits a much more graceful degradation as training size is reduced with significant benefits in the regime of limited training. Analysis of memory and computation requirements confirms that ORDSR can allow for a more efficient network with faster inference.
A SYSTEMATIC SURVEY OF HIGH-TEMPERATURE EMISSION IN SOLAR ACTIVE REGIONS

The recent analysis of observations taken with the EUV Imaging Spectrometer and X-Ray Telescope instruments on Hinode suggests that well-constrained measurements of the temperature distribution in solar active regions can finally be made. Such measurements are critical for constraining theories of coronal heating. Past analysis, however, has suffered from limited sample sizes and large uncertainties at temperatures between 5 and 10 MK. Here we present a systematic study of the differential emission measure distribution in 15 active region cores. We focus on measurements in the 'inter-moss' region, that is, the region between the loop footpoints, where the observations are easier to interpret. To reduce the uncertainties at the highest temperatures we present a new method for isolating the Fe XVIII emission in the AIA/SDO 94 A channel. The resulting differential emission measure distributions confirm our previous analysis showing that the temperature distribution in an active region core is often strongly peaked near 4 MK. We characterize the properties of the emission distribution as a function of the total unsigned magnetic flux. We find that the amount of high-temperature emission in the active region core is correlated with the total unsigned magnetic flux, while the emission at lower temperatures, in contrast,more » is inversely related. These results provide compelling evidence that high-temperature active region emission is often close to equilibrium, although weaker active regions may be dominated by evolving million degree loops in the core.« less
General Navier–Stokes-like momentum and mass-energy equations

Abstract A new system of general Navier–Stokes-like equations is proposed to model electromagnetic flow utilizing analogues of hydrodynamic conservation equations. Such equations are intended to provide a different perspective and, potentially, a better understanding of electromagnetic mass, energy and momentum behaviour. Under such a new framework additional insights into electromagnetism could be gained. To that end, we propose a system of momentum and mass-energy conservation equations coupled through both momentum density and velocity vectors.