cssi/SciSciGPT-SciSciNet huggingface dataset:
Random walks on the mapping class group

We show that a random walk on the mapping class group of an orientable surface gives rise to a pseudo-Anosov element with asymptotic probability one. Our methods apply to many subgroups of the mapping class group, including the Torelli group.
Using conceptual metaphor and functional grammar to explore how language used in physics affects student learning

This paper introduces a theory about the role of language in learning physics. The theory is developed in the context of physics students and physicists talking and writing about the subject of quantum mechanics. We found that physicists' language encodes different varieties of analogical models through the use of grammar and conceptual metaphor. We hypothesize that students categorize concepts into ontological categories based on the grammatical structure of physicists' language. We also hypothesize that students overextend and misapply conceptual metaphors in physicists' speech and writing. Using our theory, we will show how, in some cases, we can explain student difficulties in quantum mechanics as difficulties with language.
How Recent is Cosmic Acceleration

Possibly the most peculiar expectation of the standard fine-tuned cosmological paradigm is that cosmic acceleration is to only be a very recent (z<1) phenomenon, with the universe being required to be decelerating at all higher redshifts. Detailed exploration of the Hubble plot out to z=2 or so will not just provide an absolute test of this expectation but will also allow for testing of conformal gravity, a non fine-tuned alternate cosmological theory which provides equally good fitting to the current z<1 Hubble plot data while requiring the universe to be accelerating at higher z instead. With both standard and conformal gravity being found to be compatible with a very recently reported z=1.7 data point, additional data points will thus be needed to determine whether the universe is accelerating or decelerating above z=1.
Linearly Polarized Remote-Edge Luminescence in GaSe Nanoslabs

Layered two-dimensional materials present an appealing platform for integrating optoelectronic devices with nanoscale lasers. The authors exploit the anisotropic optical properties and unique optical-selection rules of gallium selenide to generate linearly polarized luminescence at the remote edges of slabs of 200 or more layers. These results reveal the carrier spin dynamics in GaSe, and nanoscale slabs of this layered, polar semiconductor are compatible with standard fabrication processes---two requirements for spintronic technology.
Compound Real Wishart and q-Wishart Matrices

We introduce a family of matrices with noncommutative entries that generalize the classical real Wishart matrices. With the help of the Brauer product, we derive a nonasymptotic expression for the moments of traces of monomials in such matrices; the expression is quite similar to the formula derived in [9, Theorem 2.1; Asymptotic normality for traces of polynomials in independent complex Wishart matrices; Probability Theory and Related fields, 140, 2008] for independent complex Wishart matrices.We then analyze the fluctuations about the Marchenko-Pastur law. We show that after centering by the mean, traces of real symmetric polynomials in q-Wishart matrices converge in distribution, and we identify the asymptotic law as the normal law when q = 1, and as the semicircle law when q = 0.
Weak Solutions to the Navier–Stokes Inequality with Arbitrary Energy Profiles

In a recent paper, Buckmaster and Vicol (Ann Math (2) 189(1):101–144, 2019) used the method of convex integration to construct weak solutions u to the 3D incompressible Navier–Stokes equations such that $$\Vert u(t) \Vert _{L^2} =e(t)$$ for a given non-negative and smooth energy profile $$e:[0,T]\rightarrow \mathbb {R}$$. However, it is not known whether it is possible to extend this method to construct nonunique suitable weak solutions (that is weak solutions satisfying the strong energy inequality (SEI) and the local energy inequality (LEI)), Leray–Hopf weak solutions (that is weak solutions satisfying the SEI), or at least to exclude energy profiles that are not nonincreasing. In this paper we are concerned with weak solutions to the Navier–Stokes inequality on $$\mathbb {R}^3$$, that is vector fields that satisfy both the SEI and the LEI (but not necessarily solve the Navier–Stokes equations). Given $$T>0$$ and a nonincreasing energy profile $$e:[0,T] \rightarrow [0,\infty )$$ we construct weak solution to the Navier–Stokes inequality that are localised in space and whose energy profile $$\Vert u(t)\Vert _{L^2 (\mathbb {R}^3 )}$$ stays arbitrarily close to e(t) for all $$t\in [0,T]$$. Our method applies only to nonincreasing energy profiles. The relevance of such solutions is that, despite not satisfying the Navier–Stokes equations, they satisfy the partial regularity theory of Caffarelli et al. (Commun Pure Appl Math 35(6):771–831, 1982). In fact, Scheffer’s constructions of weak solutions to the Navier–Stokes inequality with blow-ups (Commun Math Phys 101(1):47–85, 1985; Commun Math Phys 110(4): 525–551, 1987) show that the Caffarelli, Kohn & Nirenberg’s theory is sharp for such solutions. Our approach gives an indication of a number of ideas used by Scheffer. Moreover, it can be used to obtain a stronger result than Scheffer’s. Namely, we obtain weak solutions to the Navier–Stokes inequality with both blow-up and a prescribed energy profile.
Exact and approximate methods for proving unrealizability of syntax-guided synthesis problems

We consider the problem of automatically establishing that a given syntax-guided-synthesis (SyGuS) problem is unrealizable (i.e., has no solution). We formulate the problem of proving that a SyGuS problem is unrealizable over a finite set of examples as one of solving a set of equations: the solution yields an overapproximation of the set of possible outputs that any term in the search space can produce on the given examples. If none of the possible outputs agrees with all of the examples, our technique has proven that the given SyGuS problem is unrealizable. We then present an algorithm for exactly solving the set of equations that result from SyGuS problems over linear integer arithmetic (LIA) and LIA with conditionals (CLIA), thereby showing that LIA and CLIA SyGuS problems over finitely many examples are decidable. We implement the proposed technique and algorithms in a tool called Nay. Nay can prove unrealizability for 70/132 existing SyGuS benchmarks, with running times comparable to those of the state-of-the-art tool Nope. Moreover, Nay can solve 11 benchmarks that Nope cannot solve.
Student epistemological framing on paper-based assessments

Physics instructors often think of assessment as occurring after instruction, however, students get information from assessments that influence their understandings of how they should engage in physics learning.
Log canonical singularities are Du Bois

A recurring difficulty in the Minimal Model Program (MMP) is that while log terminal singularities are quite well behaved (for instance, they are rational), log canonical singularities are much more complicated; they need not even be CohenMacaulay. The aim of this paper is to prove that, as conjectured in [Kol92, 1.13], log canonical singularities are Du Bois. The concept of Du Bois singularities, abbreviated as DB, was introduced by Steenbrink in [Ste83] as a weakening of rationality. It is not clear how to define Du Bois singularities in positive characteristic, so we work over a field of characteristic 0 throughout the paper. The precise definition is rather involved, see (1.10), but our main applications rely only on the following consequence:
Contact interactions and resonance-like physics at present and future colliders from unparticles

High scale conformal physics can lead to unusual unparticle stuff at our low energies. In this paper we discuss how the exchange of unparticles between Standard Model fields can lead to new contact interaction physics as well as a pseudoresonance-like structure, an unresonance, that might be observable at the Tevatron or LHC in the Drell-Yan channel. The specific signatures of this scenario are quite unique and can be used to easily identify this new physics given sufficient integrated luminosity.
Implementing and assessing computational modeling in introductory mechanics

Students taking introductory physics are rarely exposed to computational modeling. In a one-semester large lecture introductory calculus-based mechanics course at Georgia Tech, students learned to solve physics problems using the VPython programming environment. During the term, 1357 students in this course solved a suite of 14 computational modeling homework questions delivered using an online commercial course management system. Their proficiency with computational modeling was evaluated with a proctored assignment involving a novel central force problem. The majority of students (60.4%) successfully completed the evaluation. Analysis of erroneous student-submitted programs indicated that a small set of student errors explained why most programs failed. We discuss the design and implementation of the computational modeling homework and evaluation, the results from the evaluation, and the implications for computational instruction in introductory science, technology, engineering, and mathematics (STEM) courses.
A Striking Confluence Between Theory and Observations of High-Mass X-ray Binary Pulsars.

We analyse the most powerful X-ray outbursts from neutron stars in ten Magellanic high-mass X-ray binaries and three pulsating ultraluminous X-ray sources. Most of the outbursts rise to L(sub max) which is about the level of the Eddington luminosity, while the rest and more powerful outbursts also appear to recognize that limit when their emissions are assumed to be anisotropic and beamed toward our direction. We use the measurements of pulsar spin periods P(sub S) and their derivatives P˙(sub S) to calculate the X-ray luminosities L(sub p) in their faintest accreting (“propeller”) states. In four cases with unknown P˙(sub S), we use the lowest observed X-ray luminosities, which only adds to the heterogeneity of the sample. Then we calculate the ratios L(sub p)/L(sub max) and we obtain an outstanding confluence of theory and observations from which we conclude that work done on both fronts is accurate and the results are trustworthy: sources known to reside on the lowest Magellanic propeller line are all located on/near that line, whereas other sources jump higher and reach higher-lying propeller lines. These jumps can be interpreted in only one way, higher-lying pulsars have stronger surface magnetic fields in agreement with empirical results in which P˙(sub S) and L(sub p) values were not used.
Cosmological Tests of Gravity

Modications of general relativity provide an alternative explanation to dark energy for the observed acceleration of the universe. We review recent developments in modied gravity theories, focusing on higher dimensional approaches and chameleon/f(R) theories. We classify these models in terms of the screening mechanisms that enable such theories to approach general relativity on small scales (and thus satisfy solar system constraints). We describe general features of the modied Friedman equation in such theories. The second half of this review describes experimental tests of gravity in light of the new theoretical approaches. We summarize the high precision tests of gravity on laboratory and solar system scales. We describe in some detail tests on astrophysical scales ranging from kpc (galaxy scales) to Gpc (large-scale structure). These tests rely on the growth and inter-relationship of perturbations in the metric potentials, density and velocity elds which can be measured using gravitational lensing, galaxy cluster abundances, galaxy clustering and the Integrated Sachs-Wolfe eect.
Decomposition Algorithms for Solving NP-hard Problems on a Quantum Annealer

NP-hard problems such as the maximum clique or minimum vertex cover problems, two of Karp’s 21 NP-hard problems, have several applications in computational chemistry, biochemistry and computer network security. Adiabatic quantum annealers can search for the optimum value of such NP-hard optimization problems, given the problem can be embedded on their hardware. However, this is often not possible due to certain limitations of the hardware connectivity structure of the annealer. This paper studies a general framework for a decomposition algorithm for NP-hard graph problems aiming to identify an optimal set of vertices. Our generic algorithm allows us to recursively divide an instance until the generated subproblems can be embedded on the quantum annealer hardware and subsequently solved. The framework is applied to the maximum clique and minimum vertex cover problems, and we propose several pruning and reduction techniques to speed up the recursive decomposition. The performance of both algorithms is assessed in a detailed simulation study.
The Isgur-Wise limit on the lattice

Abstract We construct the Isgur-Wise limit of QCD in a form appropriate to lattice gauge theory techniques. The formulation permits a calculation of heavy quark processes even when the momentum transfers are much larger than the inverse lattice spacing. Applications include semi-leptonic heavy quark decay and scattering processes, including the computation of the nonperturbative part of the Isgur-Wise universal function.
Three-body forces produced by a similarity renormalization group transformation in a simple model

Abstract A simple class of unitary renormalization group transformations that force Hamiltonians towards a band-diagonal form produce few-body interactions in which low- and high-energy states are decoupled, which can greatly simplify many-body calculations. One such transformation has been applied to phenomenological and effective field theory nucleon–nucleon interactions with success, but further progress requires consistent treatment of at least the three-nucleon interaction. In this paper we demonstrate in an extremely simple model how these renormalization group transformations consistently evolve two- and three-body interactions towards band-diagonal form, and introduce a diagrammatic approach that generalizes to the realistic nuclear problem.
Comment on Experiments Related to the Aharonov–Bohm Phase Shift

Recent experiments undertaken by Caprez, Barwick, and Batelaan should clarify the connections between classical and quantum theories in connection with the Aharonov–Bohm phase shift. It is pointed out that resistive aspects for the solenoid current carriers play a role in the classical but not the quantum analysis for the phase shift. The observed absence of a classical lag effect for a macroscopic solenoid does not yet rule out the possibility of a lag explanation of the observed phase shift for a microscopic solenoid.
Thermodynamic Relations among Isotropic Material Properties in Conditions of Plane Shear Stress

We present new general relationships among the material properties of an isotropic material kept in homogeneous stress conditions with hydrostatic pressure and plane shear. The derivation is not limited to the proximity of the zero shear-stress and -strain condition, which allows us to identify the relationship between adiabatic and isothermal shear compliances (inverse of the moduli of rigidity) along with new links, among others, between isobaric and isochoric shear thermal expansion coefficients and heat capacities at constant stress and constant shear strain. Such relationships are important for a variety of applications, including the determination of constitutive equations, the characterization of nanomaterials, and the identification of properties related to earthquakes precursors and complex media (e.g., soil) behavior. The results may be useful to investigate the behavior of materials during phase transitions involving shear or in non-homogeneous conditions within a local thermodynamic equilibrium framework.
Holographic brownian motion in magnetic environments

Using the gauge/gravity correspondence, we study the dynamics of a heavy quark in two strongly-coupled systems at finite temperature: Super-Yang-Mills in the presence of a magnetic field and non-commutative Super-Yang-Mills. In the former, our results agree qualitatively with the expected behavior from weakly-coupled theories. In the latter, we propose a Langevin equation that accounts for the effects of non-commutativity and we find new interesting features. The equation resembles the structure of Brownian motion in the presence of a magnetic field and implies that the fluctuations along non-commutative directions are correlated. Moreover, our results show that the viscosity is smaller than the commutative case and that the diffusion properties of the quark are unaffected by non-commutativity. Finally, we compute the random force autocorrelator and verify that the fluctuation-dissipation theorem holds in the presence of non-commutativity.
The J-flow on Kähler surfaces: a boundary case

We study the J-flow on Kahler surfaces when the Kahler class lies on the boundary of the open cone for which global smooth convergence holds and satisfies a nonnegativity condition. We obtain a C0 estimate and show that the J-flow converges smoothly to a singular Kahler metric away from a finite number of curves of negative self-intersection on the surface. We discuss an application to the Mabuchi energy functional on Kahler surfaces with ample canonical bundle.
XMM-Newton and Chandra Observations of the Unidentified Fermi-LAT Source 3FGL J1016.5–6034: A Young Pulsar with a Nebula?

We report the discovery of a bright X-ray source in the XMM-Newton and Chandra X-ray Observatory (CXO) images of the unidentified Fermi-LAT source 3FGL J1016.5-6034. The XMM-Newton spectrum of the source is well fit by an absorbed blackbody+power-law model with a temperature, $kT=0.20\pm0.02$ keV, and photon index $\Gamma=1.8\pm0.1$. The CXO resolves the same source into a point source (CXOU J101546.0-602939) and a surrounding compact nebula seen up to about $30''$ from the point source. The CXO spectrum of the nebula can be described by an absorbed power-law with $\Gamma=1.7\pm0.3$ and is partly responsible for the non-thermal emission observed in the XMM-Newton spectrum. The XMM-Newton images also reveal faint extended emission on arcminute scales. These properties strongly suggest that the X-ray source and the accompanying extended emission are a newly discovered young pulsar with a pulsar wind nebula. We also analyze $\sim10$ years of Fermi-LAT data and find that the improved LAT source localization is consistent with the position of CXOU J101546.0-602939.
A Fermi golden rule for quantum graphs

We present a Fermi golden rule giving rates of decay of states obtained by perturbing embedded eigenvalues of a quantum graph. To illustrate the procedure in a notationally simpler setting, we first describe a Fermi golden rule for boundary value problems on surfaces with constant curvature cusps. We also provide a resonance existence result which is uniform on compact sets of energies and metric graphs. The results are illustrated by numerical experiments.
AN INCREASE in the MASS of PLANETARY SYSTEMS AROUND LOWER-MASS STARS

Trends in the planet population with host star mass provide an avenue to constrain planet formation theories. We derive the planet radius distribution function for Kepler stars of different spectral types, sampling a range in host star masses. We find that M dwarf stars have 3.5 times more small planets (1.0–2.8 R⨁) than main-sequence FGK stars, but two times fewer Neptune-sized and larger (>2.8 R⨁) planets. We find no systematic trend in the planet size distribution between spectral types F, G, and K to explain the increasing occurrence rates. Taking into account the mass–radius relationship and heavy-element mass of observed exoplanets, and assuming those are independent of spectral type, we derive the inventory of the heavy-element mass locked up in exoplanets at short orbits. The overall higher planet occurrence rates around M stars are not consistent with the redistribution of the same mass into more, smaller planets. At the orbital periods and planet radii where Kepler observations are complete for all spectral types, the average heavy-element mass locked up in exoplanets increases roughly inversely with stellar mass from 4 M⨁ in F stars to 5 M⨁ in G and K stars to 7 M⨁ in M stars. This trend stands in stark contrast with observed protoplanetary disk masses that decrease toward lower mass stars, and provides a challenge for current planet formation models. Neither models of in situ formation nor migration of fully formed planets are consistent with these results. Instead, these results are indicative of large-scale inward migration of planetary building blocks—either through type-I migration or radial drift of dust grains—that is more efficient for lower mass stars, but does not result in significantly larger or smaller planets.
Modeling Survival in model-based Reinforcement Learning

Although recent model-free reinforcement learning algorithms have been shown to be capable of mastering complicated decision-making tasks, the sample complexity of these methods has remained a hurdle to utilizing them in many real-world applications. In this regard, model-based reinforcement learning proposes some remedies. Yet, inherently, model-based methods are more computationally expensive and susceptible to sub-optimality. One reason is that model-generated data are always less accurate than real data, and this often leads to inaccurate transition and reward function models. With the aim to mitigate this problem, this work presents the notion of survival by discussing cases in which the agent’s goal is to survive and its analogy to maximizing the expected rewards. To that end, a substitute model for the reward function approximator is introduced that learns to avoid terminal states rather than to maximize accumulated rewards from safe states. Focusing on terminal states, as a small fraction of state-space, reduces the training effort drastically. Next, a model-based reinforcement learning method is proposed (Survive) to train an agent to avoid dangerous states through a safety map model built upon temporal credit assignment in the vicinity of terminal states. Finally, the performance of the presented algorithm is investigated, along with a comparison between the proposed and current methods.
LOW MACH NUMBER MODELING OF CONVECTION IN HELIUM SHELLS ON SUB-CHANDRASEKHAR WHITE DWARFS. I. METHODOLOGY

We assess the robustness of a low Mach number hydrodynamics algorithm for modeling helium shell convection on the surface of a white dwarf in the context of the sub-Chandrasekhar model for Type Ia supernovae. We use the low Mach number stellar hydrodynamics code, MAESTRO, to perform three-dimensional, spatially adaptive simulations of convection leading up to the point of the ignition of a burning front. We show that the low Mach number hydrodynamics model provides a robust description of the system.
Suspending superconducting qubits by silicon micromachining

We present a method for relieving aluminum 3D transmon qubits from a silicon substrate using micromachining. Our technique is a high yield, one-step deep reactive ion etch that requires no additional fabrication processes and results in the suspension of the junction area and edges of the aluminum film. The drastic change in the device geometry affects both the dielectric and the flux noise environment experienced by the qubit. In particular, the participation ratios of various dielectric interfaces are significantly modified, and suspended qubits exhibited longer T1's than non-suspended ones. We also find that the suspension increases the flux noise experienced by tunable SQUID-based qubits.
EXTREME-ULTRAVIOLET AND X-RAY OBSERVATIONS OF COMET LOVEJOY (C/2011 W3) IN THE LOWER CORONA

We present an analysis of extreme-ultraviolet and soft X-ray emission detected toward Comet Lovejoy (C/2011 W3) during its post-perihelion traverse of the solar corona on 2011 December 16. Observations were recorded by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory and the X-Ray Telescope (XRT) aboard Hinode. A single set of contemporaneous images is explored in detail, along with prefatory consideration for time evolution using only the 171?? data. For each of the eight passbands, we characterize the emission and derive outgassing rates where applicable. As material sublimates from the nucleus and is immersed in coronal plasma, it rapidly ionizes through charge states seldom seen in this environment. The AIA data show four stages of oxygen ionization (O III-O VI) along with C IV, while XRT likely captured emission from O VII, a line typical of the corona. With a nucleus of at least several hundred meters upon approach to a perihelion that brought the comet to within 0.2 R ? of the photosphere, Lovejoy was the most significant sungrazer in recent history. Correspondingly high outgassing rates on the order of 1032.5 oxygen atoms per second are estimated. Assuming that the neutral oxygen comes from water, this translates to a mass-loss rate of ~9.5 ? 109?g?s?1, and based only on the 171?? observations, we find a total mass loss of ~1013 g over the AIA egress. Additional and supporting analyses include a differential emission measure to characterize the coronal environment, consideration for the opening angle, and a comparison of the emission's leading edge with the expected position of the nucleus.
TORQUE ENHANCEMENT, SPIN EQUILIBRIUM, AND JET POWER FROM DISK-INDUCED OPENING OF PULSAR MAGNETIC FIELDS

The interaction of a rotating star's magnetic field with a surrounding plasma disk lies at the heart of many questions posed by neutron stars in X-ray binaries. We consider the opening of stellar magnetic flux due to differential rotation along field lines coupling the star and disk, using a simple model for the disk-opened flux, the torques exerted on the star by the magnetosphere, and the power extracted by the electromagnetic wind. We examine the conditions under which the system enters an equilibrium spin state, in which the accretion torque is instantaneously balanced by the pulsar wind torque alone. For magnetic moments, spin frequencies, and accretion rates relevant to accreting millisecond pulsars, the spin-down torque from this enhanced pulsar wind can be substantially larger than that predicted by existing models of the disk-magnetosphere interaction, and is in principle capable of maintaining spin equilibrium at frequencies less than 1 kHz. We speculate that this mechanism may account for the non-detection of frequency increases during outbursts of SAX J1808.4-3658 and XTE J1814-338, and may be generally responsible for preventing spin-up to sub-millisecond periods. If the pulsar wind is collimated by the surrounding environment, the resulting jet can satisfy the power requirements of the highly relativistic outflows from Cir X-1 and Sco X-1. In this framework, the jet power scales relatively weakly with accretion rate, L_j ~ Mdot^{4/7}, and would be suppressed at high accretion rates only if the stellar magnetic moment is sufficiently low.
Surgery on nullhomologous tori and simply connected 4‐manifolds with b+ = 1

For 5 ≤ k ≤ 8, we show that an infinite family of exotic smooth structures on CP 2 #kCP 2 can be obtained by 1/n-surgeries on a single embedded nullhomologous torus in a manifold R k which is homeomorphic to CP 2 #kCP 2 .
Are sex robots enough

Nancy Jecker’s essay Nothing to be Ashamed of: Sex Robots for Older Adults with Disabilities 1 presents a provocative application of the capabilities approach. Her ethical argument for providing access to sex robots for older adults with disabilities proceeds in five parts: 1. Older adults frequently suffer disabilities that impair sexual functioning. 2. The ability to function sexually is linked to central human capabilities, including: the ability to generate a personally meaningful life narrative; be physically, mentally and emotionally healthy; experience bodily integrity; feel and express a range of human emotions; affiliate deeply with others; and reflect on and choose a plan for their life. 3. Society should take reasonable steps to support these human capabilities at a minimal threshold as part of a broader duty to respect human dignity. 4. Providing access to sex robots comprises part of reasonable efforts to support the six capabilities at a minimal threshold. 5. Therefore, society ought to make reasonable efforts to ensure access to sex robots for older adults with disabilities that impair sexual functioning. I am sympathetic to this line of reasoning, having proposed a series of legal reforms that would facilitate sexual expression among older adults with cognitive impairments as well.2 3 …
Gotta Catch'Em All: Using Honeypots to Catch Adversarial Attacks on Neural Networks

Deep neural networks (DNN) are known to be vulnerable to adversarial attacks. Numerous efforts either try to patch weaknesses in trained models, or try to make it difficult or costly to compute adversarial examples that exploit them. In our work, we explore a new "honeypot" approach to protect DNN models. We intentionally inject trapdoors, honeypot weaknesses in the classification manifold that attract attackers searching for adversarial examples. Attackers' optimization algorithms gravitate towards trapdoors, leading them to produce attacks similar to trapdoors in the feature space. Our defense then identifies attacks by comparing neuron activation signatures of inputs to those of trapdoors. In this paper, we introduce trapdoors and describe an implementation of a trapdoor-enabled defense. First, we analytically prove that trapdoors shape the computation of adversarial attacks so that attack inputs will have feature representations very similar to those of trapdoors. Second, we experimentally show that trapdoor-protected models can detect, with high accuracy, adversarial examples generated by state-of-the-art attacks (PGD, optimization-based CW, Elastic Net, BPDA), with negligible impact on normal classification. These results generalize across classification domains, including image, facial, and traffic-sign recognition. We also present significant results measuring trapdoors' robustness against customized adaptive attacks (countermeasures).
Hidden sector monopole dark matter with matter domination

The thermal freeze-out mechanism for relic dark matter heavier than O(10 − 100 TeV) requires cross-sections that violate perturbative unitarity. Yet the existence of dark matter heavier than these scales is certainly plausible from a particle physics perspective, pointing to the need for a non-thermal cosmological history for such theories. Topological dark matter is a well-motivated scenario of this kind. Here the hidden-sector dark matter can be produced in abundance through the Kibble-Zurek mechanism describing the non-equilibrium dynamics of defects produced in a second order phase transition. We revisit the original topological dark matter scenario, focusing on hidden-sector magnetic monopoles, and consider more general cosmological histories. We find that a monopole mass of order (1–105) PeV is generic for the thermal histories considered here, if monopoles are to entirely reproduce the current abundance of dark matter. In particular, in a scenario involving an early era of matter domination, the monopole number density is always less than or equal to that in a pure radiation dominated equivalent provided a certain condition on critical exponents is satisfied. This results in a larger monopole mass needed to account for a fixed relic abundance in such cosmologies.
On polytopes and generalizations of the KLT relations

We combine the technology of the theory of polytopes and twisted intersection theory to derive a large class of double copy relations that generalize the classical relations due to Kawai, Lewellen and Tye (KLT). To do this, we first study a generalization of the scattering equations of Cachazo, He and Yuan. While the scattering equations were defined on ℳ0, n — the moduli space of marked Riemann spheres — the new scattering equations are defined on polytopes known as accordiohedra, realized as hyperplane arrangements. These polytopes encode as patterns of intersection the scattering amplitudes of generic scalar theories. The twisted period relations of such intersection numbers provide a vast generalization of the KLT relations. Differential forms dual to the bounded chambers of the hyperplane arrangements furnish a natural generalization of the Bern-Carrasco-Johansson (BCJ) basis, the number of which can be determined by counting the number of solutions of the generalized scattering equations. In this work the focus is on a generalization of the BCJ expansion to generic scalar theories, although we use the labels KLT and BCJ interchangeably.
Dominos in hedgehog domains

We introduce a new class of discrete approximations of planar domains that we call "hedgehog domains". In particular, this class of approximations contains two-step Aztec diamonds and similar shapes. We show that fluctuations of the height function of a random dimer tiling on hedgehog discretizations of a planar domain converge in the scaling limit to the Gaussian Free Field with Dirichlet boundary conditions. Interestingly enough, in this case the dimer model coupling function satisfies the same Riemann-type boundary conditions as fermionic observables in the Ising model. In addition, using the same factorization of the double-dimer model coupling function as in [17], we show that in the case of approximations by hedgehog domains the expectation of the double-dimer height function is harmonic in the scaling limit.
NASA Thermionic-Conversion program

Technological processes in out-of-core thermionic energy conversion are described. The emphasis was on high temperature electrode materials and system engineering of converter geometries to produce practical power densities.
Artificial Cognition for Human-robot Interaction

Human-robot interaction can increase the challenges of artificial intelligence. Many domains of AI and its effect is laid down, which is mainly called for their integration, modelling of human cognition and human, collecting and representing knowledge, use of this knowledge in human level, maintaining decision making processes and providing these decisions towards physical action eligible to and in coordination with humans. A huge number of AI technologies are abstracted from task planning to theory of mind building, from visual processing to symbolic reasoning and from reactive control to action recognition and learning. Specific human-robot interaction is focused on this case. Multi-model and situated communication can support human-robot collaborative task achievement. Present study deals with the process of using artificial intelligence (AI) for human-robot interaction.
An Ontological Map for Meaningful Use of Healthcare Information Systems (MUHIS)

An ontological map of meaningful use of healthcare information systems (MUHIS) is the visualization of its requirements and practices using an ontology. We map (a) the Stages 1and 2 meaningful use requirements set by the Centers for Medicaid & Medicare Services (CMS) for Electronic Health Records (EHR), and (b) the current literature on meaningful use, to derive the ontological map of the requirements and practices respectively. The map is fragmented and incomplete. The results will focus attention on the gaps (a) in the requirements, (b) in practices, and (c) between requirements and practices, and highlight the bright, light, blank, and blind spots in MUHIS. These gaps should be (a) bridged if they are important, (b) ignored if they are unimportant, or (c) reconsidered if they have been overlooked. Feedback based on incremental ontological maps over time will help to continuously improve MUHIS.
The New Housing Segregation: The Jim Crow Effects of Crime-Free Housing Ordinances

America is profoundly segregated along racial lines. We attend separate schools, live in separate neighborhoods, attend different churches, and shop at different stores. This rigid racial segregation results in social, economic, and resource inequality, with White communities of opportunity on the one hand, and many communities of color without access to quality schools, jobs, transportation, or health care on the other. Many people view this as an unfortunate fact of life, or as a relic of legal systems long-since overturned, and beyond the reach of current legal process. But this is not true. On the contrary, the law continues to play a profound role in creating and legitimizing patterns of racial segregation all across America. Crime-free housing ordinances are one of the most salient examples of the role law plays in producing and sustaining racial segregation today. They are, in this respect, a critical mechanism for effectuating the new housing segregation. Crime-free housing ordinances are local laws that either encourage or require private landlords to evict or exclude tenants who have had varying levels of contact with the criminal legal system. Though formally race neutral, these laws facilitate racial segregation in a number of significant ways. This is the first law review article to explain precisely how they do so. The Article contends that crime-free housing ordinances enable racial segregation by importing the racial biases, racial logics, and racial disparities of the criminal legal system into private housing markets. While scholars have examined the important role local laws played in effectuating racial inequality, they have not paid attention to crime-free housing ordinances. In addition to foregrounding how crime-free housing ordinances reinforce and perpetuate racially segregated communities, this Article proposes an intervention: a “segregative effects” claim, an underutilized cause of action under the Fair Housing Act of 1968, to challenge this segregative impact. While this intervention would not end the pervasive nature of housing segregation across the United States, it could eliminate at least one of the causes of this persistent problem: a body of law whose formal race neutrality has obscured its racially segregative effects.
Blockholder Ownership and Corporate Control: The Role of Liquidity

Employing an instrumental variable approach based on the regulatory change of tick sizes, I examine the link between the liquidity of a firm's equity and activism by large shareholders. I find that liquidity increases the likelihood of block formation. Blockholders of more liquid securities take smaller stakes that do not precommit them to monitor. I find evidence that the threat of exit from a block can discipline managers and that this threat is more effective when liquidity is higher. While liquidity increases exit from existing blocks, I find no evidence that share illiquidity that forces blockholders to actively monitor.
Recent Monetary Policy in the U.S.: Risk Management of Asset Bubbles

Abstract Recently Chairman Greenspan (2003 and 2004) has discussed a risk management approach to the implementation of monetary policy. This paper explores the economic environment of the 1990s and the policy dilemmas the Fed faced given the stock boom from the mid to late 1990s to after the bust in 2000-2001. Drawing on Greenspan's comments about conducting monetary policy in the real world of risk and uncertainty, the paper assesses why US monetary policy was neutral with respect to the stock market boom.
Reconciling Differences in Federal and Private Sector Pay Comparisons

Many comparisons of federal and private sector pay have found large federal pay premiums. Those studies have focused on individuals with similar pay-related characteristics, such as education and experience. Comparisons conducted by the federal government for purposes of determining the pay raises of federal white collar employees, however, find large federal pay disadvantages. Those comparisons focus on similar jobs. This article offers one possible explanation for the differences in results.
Democracy and environmental quality

We develop and estimate an econometric model of the relationship between several local and global air pollutants and economic development while allowing for critical aspects of the socio-political-economic regime of a State. We obtain empirical support for our hypothesis that democracy and its associated freedoms provide the conduit through which agents can exercise their preferences for environmental quality more effectively than under an autocratic regime, thus leading to decreased concentrations or emissions of pollution. However, additional factors such as income inequality, age distribution, education, and urbanization may mitigate or exacerbate the net effect of the type of political regime on pollution, depending on the underlying societal preferences and the weights assigned to those preferences by the State.
Executive Weapons to Combat Infection of the Art Market

We all know that criminal proceedings implicate heightened constitutional protections in comparison to civil proceedings. Many of us also have at least heard of civil forfeiture, somewhat of a hybrid of criminal and civil process that has its roots in this country in the first session of Congress. A civil forfeiture proceeding is filed directly against a piece of real or personal property on the premise that its association with criminal activity has tainted it such that it is subject to forfeiture. In 1996, in Bennis v. Michigan, the Supreme Court ruled that the seizure of property, even one‘s residence, when the property owner had no knowledge of, and did not consent to, the illegal use of the property, was not prohibited by the Due Process or Takings Clauses, which drew widespread criticism from legal academia. Congress responded to Bennis by enacting the Civil Asset Forfeiture Recovery Act of 2000 (CAFRA), which raised the government‘s burden of proof in many civil forfeiture actions filed after 2000 from probable cause to preponderance of the evidence and codified a widely, but not universally, applicable innocent owner defense.
Nonparametric Tests for Treatment Effect Heterogeneity

Abstract In this paper we develop two nonparametric tests of treatment effect heterogeneity. The first test is for the null hypothesis that the treatment has a zero average effect for all subpopulations defined by covariates. The second test is for the null hypothesis that the average effect conditional on the covariates is identical for all subpopulations, that is, that there is no heterogeneity in average treatment effects by covariates. We derive tests that are straightforward to implement and illustrate the use of these tests on data from two sets of experimental evaluations of the effects of welfare-to-work programs.
Illiquidity and stock returns: cross-section and time-series effects $

This paper shows that over time, expected market illiquidity positively affects ex ante stock excess return, suggesting that expected stock excess return partly represents an illiquidity premium. This complements the cross-sectional positive return–illiquidity relationship. Also, stock returns are negatively related over time to contemporaneous unexpected illiquidity. The illiquidity measure here is the average across stocks of the daily ratio of absolute stock return to dollar volume, which is easily obtained from daily stock data for long time series in most stock markets. Illiquidity affects more strongly small firm stocks, thus explaining time series variations in their premiums over time. r 2002 Elsevier Science B.V. All rights reserved. JEL classificaion: G12
Start-up financing

Entrepreneurs raise money for start-ups by acquiring debt, selling stock, mixing the two, and crowdfunding. This chapter explains the pros and cons of those start-up financing options. Start-ups must repay debt on time, which is hard for them to do before they start making profits. Stock investors collect repayment only when the start-up is acquired or goes public, but entrepreneurs cede some control of the start-up to stockholders. Hybrid options like convertible debt provide a temporary solution to some of financing problems. Crowdfunding is a new way to fundraise through peer-to-peer networks, but it works well only for a few types of start-ups. Entrepreneurs should perform careful analysis before choosing a fundraising option because fundraising has long-term consequences for start-ups.
Cleaning the gears: Counter-cyclical asset trading with financial transactions taxes

Abstract This paper analyzes the effect of financial transactions taxes (FTT) and idiosyncratic income risk on counter-cyclical asset trading. The model is in the class of DSGE models with incomplete markets. The paper is able demonstrate the potential welfare loss from the imposition of FTT on agents through two factors: higher coefficient of variation of consumption and higher incidence of constrained credit. The paper is also able to demonstrate the effect of FTTs on the market through three factors: significantly lower trading volume, higher variance in unencumbered markets, higher volume in unencumbered markets.
A framework for assessing comprehensive income risk exposure over varying time horizons

This paper develops a novel, intertemporal approach to assessing comprehensive income risk exposure. While a large body of accounting and policy literature focuses on quality and reliability attributes, the present study employs the premise that fair value and comprehensive income are perfectly measured at all times. In this framework, the context-sensitive impacts of comprehensive income volatility stem from the structure and dynamics of the value generation process rather than variations in measurement quality. These impacts occur concurrently with measurement related effects, but are treated as conceptually distinct. The results illustrate how factors such as risk horizon, trading frequency, and portfolio composition can affect the severity of risk exposure over time. Applied to patterns of unrealized fair-value changes in US bank available-for-sale portfolios, the model significantly improves on the most widely accepted convention for multiperiod risk aggregation (the so-called square-root-of-time or “sqrt(t)” rule). The proposed approach has direct application to value-at-risk and stress-test methods estimates that use horizon-dependent volatilities as inputs. From a financial reporting standpoint, the proposed framework affirms the utility of the “mixed measurement” accounting model and supports multifaceted or “dual presentation” approaches to financial statements.
Indoor Air Pollution and Children’s Health: Net Benefits from Stove and Behavioral Interventions in Rural China

Indoor air pollution (IAP) from cooking and heating stoves is a major cause of acute respiratory infections (ARI) and a serious health risk in developing countries. This paper examines improvements in respiratory health for children five and under in rural China resulting from stove and behavioural interventions to reduce IAP. The analysis uses data from a World Bank/Government of China project completed in 2006, whereby a large number of rural households from four provinces in China were subject to different combinations of stove improvement and behavioural interventions to reduce IAP levels and exposure. Difference-in-difference and matching models show that both stove and behavioural interventions were effective in reducing the incidence of ARI, although the latter are more cost effective.
Adaptation and central banking

What or who governs central bank decisions? Most considerations focus on motivations. Instead, we consider the extent to which specific behaviors have adaptive value in the context of central banking. From that perspective, poor decisions are not the product of poor motivations. They are, instead, a product of the poor institutions within which central bank decision makers operate.