cssi/SciSciGPT-SciSciNet huggingface dataset:
Spectroscopy and Photometry of Cataclysmic Variable Candidates from the Catalina Real Time Survey

The Catalina Real Time Survey (CRTS) has found over 500 cataclysmic variable (CV) candidates, most of which were previously unknown. We report here on follow-up spectroscopy of 36 of the brighter objects. Nearly all of the spectra are typical of CVs at minimum light. One object appears to be a flare star, while another has a spectrum consistent with a CV but lies, intriguingly, at the center of a small nebulosity. We measured orbital periods for eight of the CVs, and estimated distances for two based on the spectra of their secondary stars. In addition to the spectra, we obtained direct imaging for an overlapping sample of 37 objects, for which we give magnitudes and colors. Most of our new orbital periods are shortward of the so-called period gap from roughly 2 to 3 hr. By considering the cross-identifications between the Catalina objects and other catalogs such as the Sloan Digital Sky Survey, we argue that a large number of CVs remain uncataloged. By comparing the CRTS sample to lists of previously known CVs that CRTS does not recover, we find that the CRTS is biased toward large outburst amplitudes (and hence shorter orbital periods). We speculate that this is a consequence of the survey cadence.
Toward a broadband astro-comb: effects of nonlinear spectral broadening in optical fibers

We propose and analyze a new approach to generate a broadband astro-comb by spectral broadening of a narrowband astro-comb inside a highly nonlinear optical fiber. Numerical modeling shows that cascaded four-wave-mixing dramatically degrades the input comb’s side-mode suppression and causes side-mode amplitude asymmetry. These two detrimental effects can systematically shift the center-of-gravity of astro-comb spectral lines as measured by an astrophysical spectrograph with resolution ≈100,000; and thus lead to wavelength calibration inaccuracy and instability. Our simulations indicate that this performance penalty, as a result of nonlinear spectral broadening, can be compensated by using a filtering cavity configured for double-pass. As an explicit example, we present a design based on an Yb-fiber source comb (with 1 GHz repetition rate) that is filtered by double-passing through a low finesse cavity (finesse = 208), and subsequent spectrally broadened in a 2-cm, SF6-glass photonic crystal fiber. Spanning more than 300 nm with 16 GHz line spacing, the resulting astro-comb is predicted to provide 1 cm/s (~10 kHz) radial velocity calibration accuracy for an astrophysical spectrograph. Such extreme performance will be necessary for the search for and characterization of Earth-like extra-solar planets, and in direct measurements of the change of the rate of cosmological expansion.
Orientation of the Angular Momentum in Superfluid 3He-A in a Stretched Aerogel

Superfluid 3He-A in a fully characterized stretched aerogel, used in previous work by Pollanen et al., has been studied for parallel and perpendicular orientations of the magnetic field relative to the anisotropy axis of the aerogel. Consistently, we find that an equal spin pairing state (ESP) is stabilized down to the lowest temperature. From our pulsed NMR frequency shifts as a function of temperature and tip angle, the orientation of the orbital angular momentum $\hat{l}$ has been determined. The aerogel anisotropy introduced by uniaxial stretching tends to align $\hat{l}$ in the axial state parallel to the strain axis, consistent with the theory proposed by Sauls and contrary to Volovik’s prediction based on an impurity calculation of Rainer and Vuorio.
Uncertainty principles and Balian–Low type theorems in principal shift-invariant spaces

Abstract In this paper, we consider the time-frequency localization of the generator of a principal shift-invariant space on the real line which has additional shift-invariance. We prove that if a principal shift-invariant space on the real line is translation-invariant then any of its orthonormal (or Riesz) generators is non-integrable. However, for any n ⩾ 2 , there exist principal shift-invariant spaces on the real line that are also 1 n Z -invariant with an integrable orthonormal (or a Riesz) generator ϕ, but ϕ satisfies ∫ R | ϕ ( x ) | 2 | x | 1 + ϵ d x = ∞ for any ϵ > 0 and its Fourier transform ϕ ˆ cannot decay as fast as ( 1 + | ξ | ) − r for any r > 1 2 . Examples are constructed to demonstrate that the above decay properties for the orthonormal generator in the time domain and in the frequency domain are optimal.
Anomaly and a QCD-like phase diagram with massive bosonic baryons

We study a strongly coupled Z 2 lattice gauge theory with two flavors of quarks, invariant under an exact SU(2) × SU(2) × U A (1) × U B (1) symmetry which is the same as in QCD with two flavors of quarks without an anomaly. The model also contains a coupling that can be used to break the U A (1) symmetry and thus mimic the QCD anomaly. At low temperatures T and small baryon chemical potential μ B the model contains massless pions and massive bosonic baryons similar to QCD with an even number of colors. In this work we study the T − μ B phase diagram of the model and show that it contains three phases: (1) A chirally broken phase at low T and μ B , (2) a chirally symmetric baryon superfluid phase at low T and high μ B , and (3) a symmetric phase at high T. We find that the nature of the finite temperature chiral phase transition and in particular the location of the tricritical point that seperates the first order line from the second order line is affected significantly by the anomaly.
Cosmic Ray Acceleration by a Versatile Family of Galactic Wind Termination Shocks

There are two distinct breaks in the cosmic ray (CR) spectrum: the so-called "knee" around $3 \times 10^{15}$ eV and the so-called "ankle" around $10^{18}$ eV. Diffusive shock acceleration (DSA) at supernova remnant (SNR) shock fronts is thought to accelerate galactic CRs to energies below the knee, while an extragalactic origin is presumed for CRs with energies beyond the ankle. CRs with energies between $3 \times 10^{15}$ and $10^{18}$ eV, which we dub the "shin," have an unknown origin. It has been proposed that DSA at galactic wind termination shocks, rather than at SNR shocks, may accelerate CRs to these energies. This paper uses the galactic wind model of Bustard et al. (2016) to analyze whether galactic wind termination shocks may accelerate CRs to shin energies within a reasonable acceleration time and whether such CRs can subsequently diffuse back to the galaxy. We argue for acceleration times on the order of 100 Myrs rather than a few billion years, as assumed in some previous works, and we discuss prospects for magnetic field amplification at the shock front. Ultimately, we generously assume that the magnetic field is amplified to equipartition. This formalism allows us to obtain analytic formulae, applicable to any wind model, for CR acceleration. Even with generous assumptions, we find that very high wind velocities are required to set up the necessary conditions for acceleration beyond $10^{17}$ eV. We also estimate the luminosities of CRs accelerated by outflow termination shocks, including estimates for the Milky Way wind.
Performance guaranteed inertia emulation for diesel-wind system feed microgrid via model reference control

In this paper, a model reference control based inertia emulation strategy is proposed. Desired inertia can be precisely emulated through this control strategy so that guaranteed performance is ensured. A typical frequency response model with parametrical inertia is set to be the reference model. A measurement at a specific location delivers the information of disturbance acting on the diesel-wind system to the reference model. The objective is for the speed of the diesel-wind system to track the reference model. Since active power variation is dominantly governed by mechanical dynamics and modes, only mechanical dynamics and states, i.e., a swing-engine-governor system plus a reduced-order wind turbine generator, are involved in the feedback control design. The controller is implemented in a three-phase diesel-wind system feed microgrid. The results show exact synthetic inertia is emulated, leading to guaranteed performance and safety bounds.
Host Galaxies of Gamma-Ray Bursts

Host galaxies are an excellent means of probing the natal environments that generate gamma-ray bursts (GRBs). Recent work on the host galaxies of short-duration GRBs has offered new insights into the parent stellar populations and ages of their enigmatic progenitors. Similarly, surveys of long-duration GRB (LGRB) host environments and their ISM properties have produced intriguing new results with important implications for long GRB progenitor models. These host studies are also critical in evaluating the utility of LGRBs as potential tracers of star formation and metallicity at high redshifts. I will summarize the latest research on LGRB host galaxies, and discuss the resulting impact on our understanding of these events' progenitors, energetics, and cosmological applications.
Fault-tolerant architectures for superconducting qubits

In this short review, I draw attention to new developments in the theory of fault tolerance in quantum computation that may give concrete direction to future work in the development of superconducting qubit systems. The basics of quantum error-correction codes, which I will briefly review, have not significantly changed since their introduction 15 years ago. But an interesting picture has emerged of an efficient use of these codes that may put fault-tolerant operation within reach. It is now understood that two-dimensional surface codes, close relatives of the original toric code of Kitaev, can be adapted as shown by Raussendorf and Harrington to effectively perform logical gate operations in a very simple planar architecture, with error thresholds for fault-tolerant operation simulated to be 0.75%. This architecture uses topological ideas in its functioning, but it is not 'topological quantum computation'—there are no non-abelian anyons in sight. I offer some speculations on the crucial pieces of superconducting hardware that could be demonstrated in the next couple of years that would be clear stepping stones towards this surface-code architecture.
An invitation to higher gauge theory

In this easy introduction to higher gauge theory, we describe parallel transport for particles and strings in terms of 2-connections on 2-bundles. Just as ordinary gauge theory involves a gauge group, this generalization involves a gauge ‘2-group’. We focus on 6 examples. First, every abelian Lie group gives a Lie 2-group; the case of U(1) yields the theory of U(1) gerbes, which play an important role in string theory and multisymplectic geometry. Second, every group representation gives a Lie 2-group; the representation of the Lorentz group on 4d Minkowski spacetime gives the Poincare 2-group, which leads to a spin foam model for Minkowski spacetime. Third, taking the adjoint representation of any Lie group on its own Lie algebra gives a ‘tangent 2-group’, which serves as a gauge 2-group in 4d BF theory, which has topological gravity as a special case. Fourth, every Lie group has an ‘inner automorphism 2-group’, which serves as the gauge group in 4d BF theory with cosmological constant term. Fifth, every Lie group has an ‘automorphism 2-group’, which plays an important role in the theory of nonabelian gerbes. And sixth, every compact simple Lie group gives a ‘string 2-group’. We also touch upon higher structures such as the ‘gravity 3-group’, and the Lie 3-superalgebra that governs 11-dimensional supergravity.
Transient work function gating: A new photoemission regime

We present the theoretical basis for a new photoemission regime, transient work function gating (TWFG), which temporally and energetically gates photoemission and produces near-threshold photoelectrons with thermally limited emittance, percent-level quantum efficiency, and control over temporal coherence. The technique consists of actively gating the work function of a generalized photocathode using a non-ionizing long-wavelength optical field to produce an adiabatic modulation of the carrier density at their surface. We examine TWFG as a means to circumvent the long-standing trade-off between low emittance and high quantum efficiency, untethered to particle source or photocathode specifics. TWFG promises new opportunities in photoemission physics for next generation electron and accelerator-based x-ray photon sources.
Rigid constellations of closed Reeb orbits

We use Hamiltonian Floer theory to recover and generalize a classic rigidity theorem of Ekeland and Lasry. That theorem can be rephrased as an assertion about the existence of multiple closed Reeb orbits for certain tight contact forms on the sphere that are close, in a suitable sense, to the standard contact form. We first generalize this result to Reeb flows of contact forms on prequantization spaces that are suitably close to Boothby–Wang forms. We then establish, under an additional nondegeneracy assumption, the same rigidity phenomenon for Reeb flows on any closed contact manifold. A natural obstruction to obtaining sharp multiplicity results for closed Reeb orbits is the possible existence of fast closed orbits. To complement the existence results established here, we also show that the existence of such fast orbits cannot be precluded by any condition which is invariant under contactomorphisms, even for nearby contact forms.
Spatial contraction of the Poincaré group and Maxwell’s equations in the electric limit

Abstract The contraction of the Poincare group with respect to the space translations subgroup gives rise to a group that bears a certain duality relation to the Galilei group, that is, the contraction limit of the Poincare group with respect to the time translations subgroup. In view of this duality, we call the former the dual Galilei group. A rather remarkable feature of the dual Galilei group is that the time translations constitute a central subgroup. Therewith, in unitary irreducible representations (UIRs) of the group, the Hamiltonian appears as a Casimir operator proportional to the identity H = EI, with E (and a spin value s) uniquely characterizing the representation. Hence, a physical system characterized by a UIR of the dual Galilei group displays no non-trivial time evolution. Moreover, the combined U(1) gauge group and the dual Galilei group underlie a non-relativistic limit of Maxwell’s equations known as the electric limit. The analysis presented here shows that only electrostatics is possible for the electric limit, wholly in harmony with the trivial nature of time evolution governed by the dual Galilei group.
Topical collection: Testing the Kerr spacetime with gravitational-wave and electromagnetic observations

One of the Holy Grails of observational astronomy is to confirm the prediction that black holes in the Universe are described by the Kerr solution of Einstein’s field equations of general relativity. This Topical Collection provides a status report of theoretical and experimental progress towards confirming the “Kerr paradigm” through X-ray astronomy, gravitational lensing, stellar tidal disruption events, superradiance, and gravitational-wave observations of black hole binary mergers.
Noncommutative gauge theory, divergences and closed strings

We study the renormalization of non-commutative gauge theories with matter. As in the scalar field theory cases, there are logarithmic infrared divergences resulting from integrating out high momentum modes. In order to reproduce the correct infrared behaviour, the wilsonian effective action has to include certain ``closed string'' modes with prescribed couplings. In the case of quiver gauge theories, realized in string theory on orbifolds, we identify the required modes with a set of twisted sector fields. These closed string modes have exactly the prescribed couplings to correct the wilsonian effective action. This provides a concrete origin for the appearance of closed string modes in noncommutative field theories.
The Influence of Deuteration and Turbulent Diffusion on the Observed D/H Ratio

The influence of turbulent mixing on the chemistry of the interstellar medium (ISM) has so far received little attention. Previous studies of this effect have suggested that it might play an important role in mixing the various phases of the ISM. In this paper, we examine the potential effects of turbulent diffusion on the deuterium chemistry within molecular clouds. We find that such mixing acts to reduce the efficiency of deuteration in these clouds by increasing the ionization fraction and reducing freeze-out of heavy molecules. This leads to lower abundances for many deuterated species. We also examine the influence of turbulent mixing on the transition from atomic hydrogen to H_2 and from atomic deuterium to HD near the cloud edge. We find that including turbulent diffusion in our models serves to push these transitions deeper into the cloud and helps maintain a higher atomic fraction throughout the cloud envelope. Based on these findings, we propose a new process to account for the significant scatter in the observed atomic D/H ratio for galactic sightlines extending beyond the Local Bubble. Although several mechanisms have been put forward to explain this scatter, they are unable to fully account for the range in D/H values. We suggest a scenario in which turbulent mixing of atomic and molecular gas at the edges of molecular clouds causes the observed atomic D/H ratio to vary by a factor of ~2.
WIYN Open Cluster Study LXXX: HDI CCD UBVRI Photometry of the Old Open Cluster NGC 7142 and Comparison to M67

We present $UBVRI$ photometry of 8702 stars in a $0.5 ^\circ\times0.5 ^\circ$ field in the direction of NGC 7142, taken with the Half Degree Imager (HDI) at the WIYN 0.9-meter telescope, to improve knowledge of this cluster's basic parameters. Our photometry spans the ranges 10.6 - 20.4 mag in $U$, 10.6 - 22.0 mag in $B$, 10.0 - 21.8 mag in $V$, 9.2 - 20.7 mag in $R$, and 8.5 - 19.9 mag in $I$. Using color-color diagrams that employ all four color combinations that include $U$, versus $B-V$, we derive a reddening-metallicity relation for the cluster, with preferred values $E(B-V$) = 0.338 $\pm$ 0.031 mag for the left-edge fiducial of the main sequence and [Fe/H] = 0.0 $\pm$ 0.1 dex, where the Hyades cluster has been used as an unreddened reference cluster, the extinction relations of Cardelli have been employed, and the metallicity dependence of the Yonsei-Yale ($Y^2$) isochrones has been assumed. Comparison of our data to the $Y^2$ isochrones in multiple color-magnitude diagrams (CMDs) yields distance-metallicity and age-metallicity relations, with preferred values of $m-M\ =\ 12.65\ \pm\ 0.23$ mag and age = $4.0 ^{-0.7}_{+1.3}$ Gyr. Re-evaluation of the parameters of M67 using Stetson's $UBVI$ photometry yields [Fe/H] = -0.02 $\pm$ 0.05 dex, $E(B-V$) = 0.04 $\pm$ 0.01 mag, $m-M$ = 9.75 $\pm$ 0.03 mag, and age = 3.85 $\pm$ 0.17 Gyr; we thus find the metallicity and age of the two clusters to be indistinguishable. A semi-independent analysis adopting the parameters of M67 and shifting the fiducials of the two clusters in six CMDs until they match strongly corroborates the values listed above. The differences between our inferred parallaxes and the Gaia DR2 values are $87\ \pm\ 60$ $\mu$as for NGC 7142 and 48 $\pm$ 15 $\mu$as for M67, consistent with previous studies.
On the regularizability of the big bang singularity

The singularity for the big bang state can be represented using the generalized anisotropic Friedmann equation, resulting in a system of differential equations in a central force field. We study the regularizability of this singularity as a function of a parameter, the equation of state, w. We prove that for w > 1 it is regularizable only for w satisfying relative prime number conditions, and for w ≤ 1 it can always be regularized. This is done by using a McGehee transformation, usually applied in the three and four-body problems. This transformation blows up the singularity into an invariant manifold. The relationship of this result to other cosmological models is briefly discussed.
Image-based restoration of the concrete void system using 2D-to-3D unfolding technique

Abstract Hardened air void analysis provides essential information of concrete freeze–thaw durability based on the size and spacing of air voids in the material. As the physical freeze–thaw experiment is time-consuming and costly, the characteristics of concrete air voids are often deemed as a proxy of the freeze–thaw performance. This analysis is typically done by measuring the 2D air void intersections on polished samples, but the current interpretation of the 2D void characters does not accurately capture the 3D characteristic of the actual voids. To solve this problem, a 2D-to-3D unfolding technique from stereology can be used. However, the unfolding analysis is known to be sensitive to several factors, such as void population and size, along with a binning scheme, where improper unfolding can largely bias the prediction of the actual concrete void system. This study investigates the optimal strategy of unfolding analysis for concrete. The investigation is carried out on both idealized void systems to interrogate the influence of the critical factors individually and real concrete samples with varying levels of air entrainment to assess the concrete-specific impacts. The concrete void system is studied based on a stereological model emulating the intersected 3D air voids on the surface of polished concrete. The results highlight that, for unfolding concrete voids, logarithmic binning scheme is far more accurate to linear binning. The low unfolding error of the concrete samples indicates that the proposed methodology enables an accurate restoration of 3D void size distribution.
Small-Angle Scattering of X-Rays from Extragalactic Sources by Dust in Intervening Galaxies

Gamma-ray bursts are now known to be a cosmological population of objects, which are often accompanied by X-ray and optical afterglows. The total energy emitted in the afterglow can be similar to the energy radiated in the gamma-ray burst itself. If a galaxy containing a large column density of dust is near the line of sight to a gamma-ray burst, small-angle scattering of the X-rays due to diffraction by the dust grains will give rise to an X-ray echo of the afterglow. A measurement of the angular size of the echo at a certain time after the afterglow is observed yields a combination of the angular diameter distances to the scattering galaxy and the gamma-ray burst that can be used to constrain cosmological models in the same way as a time delay in a gravitational lens. The scattering galaxy will generally cause gravitational lensing as well, and this should modify the shape of the X-ray echo from a circular ring. The main difficulty in detecting this phenomenon is the very low flux expected for the echo. The flux can be increased when the gamma-ray burst is highly magnified by gravitational lensing, or when the deflecting galaxy is at low redshift. X-ray echoes of continuous (but variable) sources, such as quasars, may also be detectable with high-resolution instruments and would allow similar measurements.
Classical discrete time crystals

The spontaneous breaking of time-translation symmetry in periodically driven quantum systems leads to a new phase of matter: the discrete time crystal (DTC). This phase exhibits collective subharmonic oscillations that depend upon an interplay of non-equilibrium driving, many-body interactions and the breakdown of ergodicity. However, subharmonic responses are also a well-known feature of classical dynamical systems ranging from predator–prey models to Faraday waves and a.c.-driven charge density waves. This raises the question of whether these classical phenomena display the same rigidity characteristic of a quantum DTC. In this work, we explore this question in the context of periodically driven Hamiltonian dynamics coupled to a finite-temperature bath, which provides both friction and, crucially, noise. Focusing on one-dimensional chains, where in equilibrium any transition would be forbidden at finite temperature, we provide evidence that the combination of noise and interactions drives a sharp, first-order dynamical phase transition between a discrete time-translation invariant phase and an activated classical discrete time crystal (CDTC) in which time-translation symmetry is broken out to exponentially long timescales. Power-law correlations are present along a first-order line, which terminates at a critical point. We analyse the transition by mapping it to the locked-to-sliding transition of a d.c.-driven charge density wave. Finally, building upon results from the field of probabilistic cellular automata, we conjecture the existence of classical time crystals with true long-range order, where time-translation symmetry is broken out to infinite times. The phenomenon of many-body localization gives rise to entirely new phases of quantum matter when it is driven away from equilibrium. A numerical study now shows that one of these phases—the discrete time crystal—can also occur in a classical spin chain.
Describing screening in dense ionic fluids with a charge-frustrated Ising model.

Charge correlations in dense ionic fluids give rise to novel effects such as long-range screening and colloidal stabilization which are not predicted by the classic Debye–Huckel theory. We show that a Coulomb or charge-frustrated Ising model, which accounts for both long-range Coulomb and short-range molecular interactions, simply describes some of these ionic correlations. In particular, we obtain, at a mean field level and in simulations, a non-monotonic dependence of the screening length on the temperature. Using a combination of simulations and mean field theories, we study how the correlations in the various regimes are affected by the strength of the short ranged interactions.
X-Ray Source Population in the Elliptical Galaxy NGC 720 with Chandra

With a Chandra ACIS-S3 observation, we detect 42 X-ray point sources in the elliptical galaxy NGC 720, including a possible central source. Most of these sources will be low-mass X-ray binaries, and 12 are located within 2'' of globular cluster candidates. We investigate both the hardness ratios and combined spectra of the sources. They exhibit a distribution of X-ray colors similar to those seen in other early-type galaxies. We find that there is a population of highly absorbed sources located at large distances from the center of the galaxy. The overall spatial distribution of sources is consistent with the ellipticity and position angle of the galaxy, but the sources appear to form several arcs. NGC 720 contains nine ultraluminous sources (ULXs; LX ≥ 1039 ergs s-1). This number is more than have previously been detected in an early-type galaxy but similar to the number seen in the Antennae merger system. The ratio LULX/LB for NGC 720 is more than double the ratio for the S0 galaxy NGC 1553 and a factor of 7 higher than for the elliptical galaxy NGC 4697, although uncertainties in the distance and the source spectral properties could bring these ratios into agreement. The X-ray source luminosity function is also nearly as flat as those seen in disk and merger systems. The large number of ULXs in NGC 720 and its relatively flat X-ray luminosity function may provide evidence against the association of all ULXs with young stars. We also see a possible high-luminosity break in the luminosity function at 2 × 1039h ergs s-1.
Infra-red dynamics of D1-branes at the conifold

We study the infra-red dynamics of D1-branes at the conifold. We show using methods developed to study the infra-red dynamics of (4,4) theories, the infra-red degrees of freedom of the (2,2) theory of a single D1-brane at the conifold is that of a linear dilaton with background charge of √2 and a compact scalar. The gauge theory of N D1-branes at the conifold is used to formulate the matrix string in the conifold background.
Rejoinder: “On the Birnbaum Argument for the Strong Likelihood Principle”

I am honored and grateful to have so many interesting and challenging comments on my paper. I want to thank the discussants for their willingness to jump back into the thorny quagmire of Birnbaum’s argument. To a question raised in the paper “Does it matter?”, these discussions show the answer is yes. The enlightening connections to contemporary projects are especially valuable in galvanizing future efforts to address foundational issues in statistics. As long-standing as Birnbaum’s result has been, Birnbaum himself went through dramatic shifts in a short period of time following his famous (1962) result. More than of historical interest, these shifts provide a unique perspective on the current problem. Already in the rejoinder to Birnbaum (1962), he is worried about criticisms (by Pratt, 1962) pertaining to applying WCP to his constructed mathematical mixtures (what I call Birnbaumization), and hints at replacing WCP with another principle (Irrelevant Censoring). Then there is a gap until around 1968 at which point Birnbaum declares the SLP plausible “only in the simplest case, where the parameter space has but two” predesignated points [Birnbaum (1968), page 301]. He tells us in Birnbaum (1970a, page 1033) that he has pursued the matter thoroughly, leading to “rejection of both the likelihood concept and various proposed formalizations of prior information.” The basis for this shift is that the SLP permits interpretations that “can be seriously misleading with high probability” [Birnbaum (1968), page 301]. He puts forward the “confidence concept” (Conf) which takes from the Neyman–Pearson (N–P) approach “techniques for systematically appraising and bounding the probabilities (under respective hypotheses) of seriously misleading interpretations of data” while supplying it an evidential interpretation [Birnbaum (1970a), page 1033].
Physical Representation-Based Predicate Optimization for a Visual Analytics Database

Querying the content of images and video requires expensive content extraction methods. Modern extraction techniques are based on deep convolutional neural networks (CNNs) and can classify objects within images with astounding accuracy. Unfortunately, these methods are slow: processing a single image can take about 10 milliseconds on modern GPU-based hardware. As massive video libraries become ubiquitous, running a content-based query over millions of video frames is prohibitive. One promising approach to reduce the runtime cost of queries of visual content is to use a hierarchical model, such as a cascade, where simple cases are handled by an inexpensive classifier. Prior work has sought to design cascades that optimize the computational cost of inference by, for example, using smaller CNNs. However, we observe that there are critical factors besides the inference time that dramatically impact the overall query time. Notably, by treating the physical representation of the input image as part of our query optimization—that is, by including image transformations such as resolution scaling or color-depth reduction within the cascade—we can optimize data handling costs and enable drastically more efficient classifier cascades. In this paper, we propose TAHOMA, which generates and evaluates many potential classifier cascades that jointly optimize the CNN architecture and input data representation. Our experiments on a subset of ImageNet show that TAHOMA's input transformations speed up cascades by up to 35 times. We also find up to a 98x speedup over the ResNet50 classifier with no loss in accuracy and a 280x speedup if some accuracy is sacrificed.
Spatio-temporal pricing for ridesharing platforms

Ridesharing platforms match drivers and riders to trips, using dynamic prices to balance supply and demand. A challenge is to set prices that are appropriately smooth in space and time, so that drivers will choose to accept their dispatched trips, rather than drive to another area or wait for higher prices or a better trip. We work in a complete information, discrete time, multi-period, multi-location model, and introduce the Spatio-Temporal Pricing (STP) mechanism. The mechanism is incentive-aligned, in that it is a subgame-perfect equilibrium for drivers to always accept their trip dispatches. The mechanism is also welfare-optimal, envy-free, individually rational, budget balanced and core-selecting in equilibrium from any history onward. The proof of incentive alignment makes use of the M♯ concavity of minimum cost flow objectives. We also give an impossibility result, that there can be no dominant-strategy mechanism with the same economic properties. Simulation results suggest that the STP mechanism can achieve significantly higher social welfare than a myopic pricing mechanism.
The origins of the tools suppliers in the semiconductor industry

Technological progress in semiconductor chips plays a central role in enabling the Information Technology revolution. Continual technological progress in semiconductor chips, which has become popul...
Distributed Controllers for Human-Robot Locomotion: A Scalable Approach Based on Decomposition and Hybrid Zero Dynamics

This letter presents a formal foundation, based on decomposition, hybrid zero dynamics (HZD), and a scalable optimization, to develop distributed control algorithms for hybrid models of collaborative human-robot locomotion. The proposed approach considers a centralized controller and then decomposes the dynamics and feedback laws with a parameterization to synthesize local controllers. The Jacobian matrix of the Poincare map with local controllers is studied and compared to that with centralized ones. An optimization problem is then set up to tune the parameters of the local controllers for asymptotic stability. The proposed approach can significantly reduce the number of controller parameters to be optimized for the synthesis of distributed controllers. The analytical results are numerically evaluated with simulations of a multi-domain hybrid model with 19 degrees of freedom for stable amputee locomotion with a powered knee-ankle prosthetic leg.
Time-domain terahertz spectroscopy in high magnetic fields

There are a variety of elementary and collective terahertz-frequency excitations in condensed matter whose magnetic field dependence contains significant insight into the states and dynamics of the electrons involved. Often, determining the frequency, temperature, and magnetic field dependence of the optical conductivity tensor, especially in high magnetic fields, can clarify the microscopic physics behind complex many-body behaviors of solids. While there are advanced terahertz spectroscopy techniques as well as high magnetic field generation techniques available, a combination of the two has only been realized relatively recently. Here, we review the current state of terahertz time-domain spectroscopy (THz-TDS) experiments in high magnetic fields. We start with an overview of time-domain terahertz detection schemes with a special focus on how they have been incorporated into optically accessible high-field magnets. Advantages and disadvantages of different types of magnets in performing THz-TDS experiments are also discussed. Finally, we highlight some of the new fascinating physical phenomena that have been revealed by THz-TDS in high magnetic fields.
Hair of Astrophysical Black Holes

The “no hair” theorem is not formally applicable for black holes formed from collapse of a rotating neutron star. Rotating neutron stars can self-produce particles via vacuum breakdown forming a highly conducting plasma magnetosphere such that magnetic field lines are effectively “frozen-in” the star both before and during collapse. In the limit of no resistivity, this introduces a topological constraint which prohibits the magnetic field from sliding off the newly-formed event horizon. As a result, during collapse of a neutron star into a black hole, the latter conserves the number of magnetic flux tubes \(N_B = e \varPhi _\infty /( \pi c \hbar )\), where \(\varPhi _\infty \) is the initial magnetic flux through the hemispheres of the progenitor and out to infinity. The black hole’s magnetosphere subsequently relaxes to the split monopole magnetic field geometry with self-generated currents outside the event horizon. The dissipation of the resulting equatorial current sheet leads to a slow loss of the anchored flux tubes, a process that makes the black hole bald on long resistive time scales rather than the short light-crossing time scales expected from the vacuum “no-hair” theorem.
Assessing Discourse Relations in Language Generation from GPT-2.

Recent advances in NLP have been attributed to the emergence of large-scale pre-trained language models. GPT-2, in particular, is suited for generation tasks given its left-to-right language modeling objective, yet the linguistic quality of its generated text has largely remain unexplored. Our work takes a step in understanding GPT-2's outputs in terms of discourse coherence. We perform a comprehensive study on the validity of explicit discourse relations in GPT-2's outputs under both organic generation and fine-tuned scenarios. Results show GPT-2 does not always generate text containing valid discourse relations; nevertheless, its text is more aligned with human expectation in the fine-tuned scenario. We propose a decoupled strategy to mitigate these problems and highlight the importance of explicitly modeling discourse information.
Autotuning Search Space for Loop Transformations

One of the challenges for optimizing compilers is to predict whether applying an optimization will improve its execution speed. Programmers may override the compiler's profitability heuristic using optimization directives such as pragmas in the source code. Machine learning in the form of autotuning can assist users in finding the best optimizations for each platform. In this paper we propose a loop transformation search space that takes the form of a tree, in contrast to previous approaches that usually use vector spaces to represent loop optimization configurations. We implemented a simple autotuner exploring the search space and applied it to a selected set of PolyBench kernels. While the autotuner is capable of representing every possible sequence of loop transformations and their relations, the results motivate the use of better search strategies such as Monte Carlo tree search to find sophisticated loop transformations such as multilevel tiling.
Which Elections Can Be Lost

The concept of electoral competition is relevant to a variety of research agendas in political science, yet the question of how to measure electoral competition has received little direct attention. We revisit the distinction proposed by Giovanni Sartori between competition as a structure or rule of the game and competitiveness as an outcome of that game and argue that to understand which elections can be lost (and therefore when parties and leaders are potentially threatened by electoral accountability), scholars may be better off considering the full range of elections where competition is allowed. We provide a data set of all national elections between 1945 and 2006 and a measure of whether each election event is structured such that the competition is possible. We outline the pitfalls of other measures used by scholars to define the potential for electoral competition and show that such methods can lead to biased or incomplete findings. The new global data on elections and the minimal conditions necessary for electoral competition are introduced, followed by an empirical illustration of the differences between the proposed measure of competition and existing methods used to infer the existence of competition.
Limited participation and consumption-saving puzzles: A simple explanation and the role of insurance $

In this paper, we show that the existence of a large, negative wealth shock and insufficient insurance against such a shock could explain both the limited stock market participation puzzle and the low-consumption–high-savings puzzle. We then conduct an empirical analysis on the relation between household portfolio choices and access to private insurance and various types of government safety nets. The empirical results demonstrate that a lack of insurance against large, negative wealth shocks is positively correlated with lower participation rates and higher saving rates. Overall, the evidence suggests an important role of insurance in household investment and savings decisions.
Shock tube design for high intensity blast waves for laboratory testing of armor and combat materiel

Abstract Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from ∼1 MPa to ∼5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods are experimentally investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral priming section which supports a deflagration to detonation transition. This approach increases the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (near Friedlander waveform). The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increases the peak pressure from 1.17 MPa to 2.25 MPa. A 103 mm driving section is used to increase peak pressure to 2.64 MPa. The third method, adding solid fuel to the driving section with the oxy-acetylene, results in a peak pressure increasing to 1.70 MPa.
Reconciling Equal Protection and Federal Indian Law

Copyright ? 2010 California Law Review, Inc. California Law Review, Inc. (CLR) is a California nonprofit corporation. CLR and the authors are solely responsible for the content of their publications. t Professor of Law, University of Connecticut School of Law. This Article is inspired and guided by Professor Frickey's scholarship and support, just as I have been and will continue to be throughout my career. It nevertheless reflects my distinctive interests and understanding of the law, and I expect that Professor Frickey would have challenged and even disagreed with some of its approach and arguments. Despite this, I dedicate it to him with my deepest thanks and admiration, and hope that it contributes to our shared goal of creating normatively and institutionally grounded frameworks for federal Indian law and policy. On a more personal note, Phil was not only a great scholar, but a truly good man. His generosity to colleagues and aspiring academics was unmatched, and will always be a model to me. I was lucky to know him, and am so sad that we lost him so soon.
The Effects of Generalized Trust and Civic Cooperation on the Big N Presence and Audit Fees Across the Globe

SUMMARY We examine the impact of country-level generalized trust and civic cooperation (i.e., societal trust) on Big N auditor choice and audit fees. Because higher societal trust countries are ass...
Financial Market Segmentation, Stock Market Volatility and the Role of Monetary Policy

We explore the role of monetary policy in a world of segmented nancial markets, where the agents who trade stocks encounter nancial income risk although the rest do not. In such an economy, we ask the question of how the monetary authority operates when it aims to maximize total welfare. We nd that optimal monetary policy has the novel role of sharing the nancial market risk traders face, among all agents in the economy. This nding holds for any concave utility function and is not sensitive to the degree of market segmentation. When risk is shared perfectly in this way, consumption is equalized between the two groups, and agents, if given the choice, would be indierent between participating or not in the nancial markets. We also explore the implications that this policy has for the volatility of stock prices and of ination, when compared to the policies of constant money supply, ination targeting and nominal interest rate pegging. We nd that optimal monetary policy is not necessarily associated either with minimal stock price volatility or with minimal ination volatility.
Truth, Justice, and the American Constitution

In Freedom's Law, Professor Ronald Dworkin asserts that the constitutional provisions that protect individual rights embody moral principles, thus requiring interpreters to conduct a "moral reading" of the Constitution. Professor Dorf argues that Dworkin does not always persuade that his moral readings of particular clauses are correct, but that Dworkin does set forth a potentially powerful method for interpreting the entire Constitution. Dorf draws upon Dworkin's previous writings to show that the moral reading is best understood as an application of Dworkin's view of law as integrity. Under that view, a judge decides a case by choosing the interpretation that best fits the whole of our legal tradition, with principles of political morality playing an important role in this process. Dorf considers Dworkin's claim that the moral reading produces right answers even in hard cases in light of the postmodern critique of ultimate truth, as exemplified by Professor Dennis Patterson's Law and Truth. Although Dorf finds a metaphysical difference between the postmodern view and law as integrity, he maintains that the two theories yield the same interpretive method. Dorf questions the utility of Dworkin's specific applications of the moral reading in cases involving individual rights because Dworkin's arguments appear unlikely to persuade readers who do not share his views on contested moral issues such as abortion or the right to die. In those areas where disagreement does not so clearly rest on differences about first principles, however, the moral reading is more compelling. Dworkin's justification for the moral reading supports extending its use to all constitutional interpretation. The moral reading, Dorf concludes, has great potential in areas that Freedom's Law does not explore.
One Privilege to Rule Them All - Some Post-Sarbanes-Oxley and Other Reflections on a Federally Codified Attorney-Client Privilege

This article builds on my previous work, Federalizing Privilege, further elaborating why Congress should federalize the law of the attorney-client privilege. This proposed uniform, preemptive protection for client confidences would apply in every proceeding in federal and state court, and in arbitration hearings, agency adjudications, and legislative proceedings. As a second-best alternative, Congress should codify attorney-client privilege law for all federal question and federal criminal cases, as well as non-judicial proceedings involving federal matters. This piece bolsters claims made in Federalizing Privilege in two ways. It responds to a number of concerns about codification, explaining why a codified attorney-client privilege will not inappropriately inhibit doctrinal development, will avoid the pitfalls of the federal rule-making process, and is the best approach to achieving an appropriate balance between competing policies. It also discusses recent developments that further evince the need for national privilege reform, most notably, the shift in the regulatory landscape embodied in the Sarbanes-Oxley Act of 2002. In addition, the article examines how other recent developments, including increased prosecutorial aggressiveness, are producing creeping, piecemeal, and often unmonitored erosions of the privilege. Voluntary changes to such prosecutorial practices -- which are both piecemeal and tenuous -- are insufficient responses to a problem needing a holistic solution.