cssi/SciSciGPT-SciSciNet huggingface dataset:
Deciding memory safety for single-pass heap-manipulating programs

We investigate the decidability of automatic program verification for programs that manipulate heaps, and in particular, decision procedures for proving memory safety for them. We extend recent work that identified a decidable subclass of uninterpreted programs to a class of alias-aware programs that can update maps. We apply this theory to develop verification algorithms for memory safety— determining if a heap-manipulating program that allocates and frees memory locations and manipulates heap pointers does not dereference an unallocated memory location. We show that this problem is decidable when the initial allocated heap forms a forest data-structure and when programs are streaming-coherent, which intuitively restricts programs to make a single pass over a data-structure. Our experimental evaluation on a set of library routines that manipulate forest data-structures shows that common single-pass algorithms on data-structures often fall in the decidable class, and that our decision procedure is efficient in verifying them.
The Evolution and Properties of Rotating Massive Star Populations

We investigate the integrated properties of massive (>10 Msun), rotating, single-star stellar populations for a variety of initial rotation rates (v/vcrit=0.0, 0.2, 0.4, 0.5, and 0.6). We couple the new MESA Isochrone and Stellar Tracks (MIST) models to the Flexible Stellar Population Synthesis (FSPS) package, extending the stellar population synthesis models to include the contributions from very massive stars (>100 Msun), which can be significant in the first ~4 Myr after a starburst. These models predict ionizing luminosities that are consistent with recent observations of young nuclear star clusters. We also construct composite stellar populations assuming a distribution of initial rotation rates. Even in low-metallicity environments where rotation has a significant effect on the evolution of massive stars, we find that stellar population models require a significant contribution from fast-rotating (v/vcrit>0.4) stars in order to sustain the production of ionizing photons beyond a few Myr following a starburst. These results have potentially important implications for cosmic reionization by massive stars and the interpretation of nebular emission lines in high-redshift star-forming galaxies.
On-Orbit Sensitivity Evolution of the EUV Imaging Spectrometer on Hinode

Since its launch on 22 September 2006, the EUV Imaging Spectrometer onboard the Hinode satellite has exhibited a gradual decay in sensitivity. Using spectroheliograms taken in the Fe viii 185.21 A and Si vii 275.35 A emission lines in quiet regions near Sun center we characterize that decay. For the period from December 2006 to March 2012, the decline in the sensitivity can be characterized as an exponential decay with an average time constant of 7358±1030 days (20.2±2.8 years). Emission lines formed at temperatures ≳ 106.1 K in the quiet Sun data exhibit solar-cycle effects.
What Determines the X-Ray Intensity and Duration of a Solar Flare?

Solar flares are observed and classified according to their intensity measured with the GOES X-ray Sensors. We show that the duration of a flare, as measured by the full width at half maximum (FWHM) in GOES is not related to the size of the flare as measured by GOES intensity. The durations of X-class flares range from a few minutes to a few hours, and the same is true of M- and C-class flares. In this work, we therefore examine the statistical relationships between the basic properties of flares -- temperature, emission measure, energy, etc. -- in comparison to both their size and duration. We find that the size of the flare is directly related to all of these basic properties, as previously found by many authors. The duration is not so clear. When examining the whole data set, the duration appears to be independent of all of these properties. In larger flares, however, there are direct correlations between the GOES FWHM and magnetic reconnection flux and ribbon area. We discuss the possible explanations, finding that this discrepancy may be due to large uncertainties in small flares, though we cannot rule out the possibility that the driving physical processes are different in smaller flares than larger ones. We discuss the implications of this result and how it relates to the magnetic reconnection process that releases energy in flares.
Optimal noise-canceling shortcuts to adiabaticity: application to noisy Majorana-based gates

Adiabatic braiding of Majorana zero modes can be used for topologically protected quantum information processing. While extremely robust to many environmental perturbations, these systems are vulnerable to noise with high-frequency components. Ironically, slower processes needed for adiabaticity allow more noise-induced excitations to accumulate, resulting in an antiadiabatic behavior that limits the precision of Majorana gates if some noise is present. In a recent publication (2017 Phys. Rev. B 96 075158), fast optimal protocols were proposed as a shortcut for implementing the same unitary operation as the adiabatic braiding in a low-energy effective model. These shortcuts sacrifice topological protection in the absence of noise but provide performance gains and remarkable robustness to noise due to the shorter evolution time. Nevertheless, gates optimized for vanishing noise are suboptimal in the presence of noise. If we know the noise strength beforehand, can we design protocols optimized for the existing unavoidable noise, which will effectively correct the noise-induced errors? We address this question in the present paper, focusing on the same low-energy effective model. We find such optimal protocols using simulated-annealing Monte Carlo simulations. The numerically found pulse shapes, which we fully characterize, are in agreement with Pontryagin's minimum principle, which allows us to arbitrarily improve the approximate numerical results (due to discretization and imperfect convergence) and obtain numerically exact optimal protocols. The protocols are bang–bang (sequence of sudden quenches) for vanishing noise, but contain continuous segments in the presence of multiplicative noise due to the nonlinearity of the master equation governing the evolution. We find that such noise-optimized protocols completely eliminate the above-mentioned antiadiabatic behavior. The final error corresponding to these optimal protocols monotonically decreases with the total time (in three different regimes). A liner fit to 1/τ indicates extrapolation of the cost function to finite value in the limit. However, quadratic and cubic fits are more suggestive of the cost function extrapolating to zero in the limit of infinite time. Our results set the precision limit of the device as a function of the noise strength and total time.
Analytical solutions for weak black hole kicks

The black hole is modelled by a combined gravitational potential of the bulge, disk and halo and is subjected to an initial weak kick. The resulting differential equations are set up, and shown to possess analytical solutions. The effects of black hole accretion and dynamical friction are also incorporated into this analytical framework. The resultant frequencies and amplitudes are computed, and are compared with the ones obtained from numerical simulations. Within the valid range of parameters of the analytical model, the two sets of results are shown to be in reasonable agreement. It is shown that this model reproduces the linear dependence of the amplitude on the initial kick velocity, and the constant of proportionality is close to that obtained from the simulations. The analytical treatment presented is quite general, and its applications to other areas are also indicated.
Foldable cubical complexes of nonpositive curvature

We study finite foldable cubical complexes of nonpositive cur- vature (in the sense of A.D. Alexandrov). We show that such a complex X admits a graph of spaces decomposition. It is also shown that when dim X = 3, X contains a closed rank one geodesic in the 1-skeleton unless the universal cover of X is isometric to the product of two CAT(0) cubical complexes. AMS Classification 20F65, 20F67; 53C20
Spectral and Modal Properties of a Mid-IR Spherical Microlaser

Whispering gallery mode (WGM) lasers are wellknown for their small sizes, low thresholds, and narrow linewidths, and have been the subject of research and development for more than two decades. However most of the initial reports and studies have focused on near-IR and visible WGM microlasers. Recent advances in the synthesis, doping, and processing of high quality mid-IR transparent glasses have provided the means to extend the wavelengths of these microlasers to the mid-IR range. In this paper, we present a detailed characterization of a compact and low-cost mid-IR spherical WGM microlaser based on heavily doped Er:ZBLAN glass operating near 2.7 μm with an estimated linewidth less than 1.1 MHz. We describe experimental results on observed singlemode and multimode spectra, thermal tuning, and polarization characteristics of such microlasers. Using a simple analysis of spherical microresonator modes and including considerations of pump and laser mode overlap we provide guidelines for optimized microlaser design.
Interpolation for restricted tangent bundles of general curves

Let q1,q2,…,qn∈ℙr be a general collection of points, and (C,p1,p2,…,pn) a general marked curve of genus g. We determine when there exists a nondegenerate degree-d map f:C→ℙr such that f(pi)=qi for all i. This is a consequence of our main theorem, which states that the restricted tangent bundle f∗Tℙr of a general curve of genus g, equipped with a general degree-d map f to ℙr, satisfies the property of interpolation, i.e., that for a general effective divisor D of any degree on C, either H0(f∗Tℙr(−D))=0 or H1(f∗Tℙr(−D))=0. We also prove an analogous theorem for the twist f∗Tℙr(−1).
Yukawa Bound States of a Large Number of Fermions

We consider the bound state problem for a field theory that contains a Dirac fermion x that Yukawa couples to a (light) scalar field o. We are interested in bound states with a large number N of x particles. A Fermi gas model is used to numerically determine the dependence of the radius R of these bound states on N and also the dependence of the binding energy on N. Since scalar interactions with relativistic x's are suppressed two regimes emerge. For modest values of N the state is composed of non-relativistic x particles. In this regime as N increases R decreases. Eventually the core region becomes relativistic and the size of the state starts to increase as N increases. As a result, for fixed Yukawa coupling and x mass, there is a minimum sized state that occurs roughly at the value of N where the core region first becomes relativistic. As an application to dark matter, our analysis offers the possibility of having a supermassive thermal DM candidate. We also compute an elastic scattering form factor that can be relevant for direct detection if the dark matter is composed of such x particles.
Generalized hindsight for reinforcement learning

One of the key reasons for the high sample complexity in reinforcement learning (RL) is the inability to transfer knowledge from one task to another. In standard multi-task RL settings, low-reward data collected while trying to solve one task provides little to no signal for solving that particular task and is hence effectively wasted. However, we argue that this data, which is uninformative for one task, is likely a rich source of information for other tasks. To leverage this insight and efficiently reuse data, we present Generalized Hindsight: an approximate inverse reinforcement learning technique for relabeling behaviors with the right tasks. Intuitively, given a behavior generated under one task, Generalized Hindsight returns a different task that the behavior is better suited for. Then, the behavior is relabeled with this new task before being used by an off-policy RL optimizer. Compared to standard relabeling techniques, Generalized Hindsight provides a substantially more efficient reuse of samples, which we empirically demonstrate on a suite of multi-task navigation and manipulation tasks. Videos and code can be accessed here: this https URL.
Relativistic Hydrodynamic Attractors with Broken Symmetries: Non-Conformal and Non-Homogeneous

Standard textbooks will state that hydrodynamics requires near-equilibrium to be applicable. Recently, however, out-of-equilibrium attractor solutions for hydrodynamics have been found in kinetic theory and holography in systems with a high degree of symmetry, suggesting the possibility of a genuine out-of-equilibrium formulation of hydrodynamics. This work demonstrates that attractor solutions also occur in non-conformal kinetic theory and spatially non-homogeneous systems, potentially having important implications for the interpretation of experimental data in heavy-ion and proton-proton collisions and relativistic fluid dynamics as a whole.
Efficient active learning of sparse halfspaces with arbitrary bounded noise

We study active learning of homogeneous $s$-sparse halfspaces in $\mathbb{R}^d$ under label noise. Even in the presence of mild label noise this is a challenging problem and only recently have label complexity bounds of the form $\tilde{\mathcal{O}} (s \cdot \mathrm{polylog}(d, \frac{1}{\epsilon}) )$ been established in \cite{zhang2018efficient} for computationally efficient algorithms under the broad class of isotropic log-concave distributions. In contrast, under high levels of label noise, the label complexity bounds achieved by computationally efficient algorithms are much worse. When the label noise satisfies the {\em Massart} condition \cite{massart2006risk}, i.e., each label is flipped with probability at most $\eta$ for a parameter $\eta \in \big[0, \frac12\big)$, state-of-the-art result \cite{awasthi2016learning} provides a computationally efficient active learning algorithm under isotropic log-concave distributions with label complexity $\tilde{\mathcal{O}}(s^{\mathrm{poly}({1/(1-2\eta)})} \mathrm{poly}(\ln d, \frac{1}{\epsilon}) )$, which is label-efficient only when the noise rate $\eta$ is a constant. In this work, we substantially improve on it by designing a polynomial time algorithm for active learning of $s$-sparse halfspaces under bounded noise and isotropic log-concave distributions, with a label complexity of $\tilde{\mathcal{O}}\Big(\frac{s}{(1-2\eta)^4} \mathrm{polylog} (d, \frac 1 \epsilon) \Big)$. This is the first efficient algorithm with label complexity polynomial in $\frac{1}{1-2\eta}$ in this setting, which is label-efficient even for $\eta$ arbitrarily close to $\frac12$. Our guarantees also immediately translate to new state-of-the-art label complexity results for full-dimensional active and passive halfspace learning under arbitrary bounded noise and isotropic log-concave distributions.
Field theory models for tachyon and gauge field string dynamics

In hep-th/0008227, the unstable lump solution of 3 theory was shown to have a spectrum governed by the solvable Schroedinger equation with the l = 3 reflectionless potential and was used as a model for tachyon condensation in string theory. In this paper we study in detail an l→∞ scalar field theory model whose lump solution mimics remarkably the string theory setup: the original field theory tachyon and the lump tachyon have the same mass, the spectrum of the lump consists of equally spaced infinite levels, there is no continuous spectrum, and nothing survives after tachyon condensation. We also find exact solutions for lumps with codimension ≥ 2, and show that that their tensions satisfy (1/2π)(Tp/Tp+1) = e/√(2π) ≈ 1.08. We incorporate gauge fixed couplings to a U(1) gauge field which preserve solvability and result in massless gauge fields on the lump.
Annulus amplitudes and ZZ branes in minimal string theory

We study the annulus amplitudes of (p,q) minimal string theory. Focusing on the ZZ-FZZT annulus amplitude as a target-space probe of the ZZ brane, we use it to confirm that the ZZ branes are localized in the strong-coupling region. Along the way we learn that the ZZ-FZZT open strings are fermions, even though our theory is bosonic! We also provide a geometrical interpretation of the annulus amplitudes in terms of the Riemann surface p,q that emerges from the FZZT branes. The ZZ-FZZT annulus amplitude measures the deformation of p,q due to the presence of background ZZ branes; each kind of ZZ-brane deforms only one A-period of the surface. Finally, we use the annulus amplitudes to argue that the ZZ branes can be regarded as ``wrong-branch tachyons which violate the bound α<Q/2.
On-shell electroweak sector and the Higgs mechanism

We describe a new approach towards the development of an entirely on-shell description of the bosonic electroweak sector of the Standard Model and the Higgs mechanism. We write down on-shell three particle amplitudes consistent with Poincare invariance and little group covariance. Tree-level, four particle amplitudes are determined by demanding consistent factorization on all poles and correct UV behaviour. We present expressions for these 2 → 2 scattering amplitudes using massive spinor helicity variables. We show that on-shell consistency conditions suffice to derive relations between the masses of the W ±, Z , the Weinberg angle and the couplings. This provides a completely on-shell description of the Higgs mechanism without any reference to the vacuum expectation value of the Higgs field.
Electrostatic and whistler instabilities excited by an electron beam

The electron beam-plasma system is ubiquitous in the space plasma environment. Here, using a Darwin particle-in-cell method, the excitation of electrostatic and whistler instabilities by a gyrating electron beam is studied in support of recent laboratory experiments. It is assumed that the total plasma frequency (ωpe) is larger than the electron cyclotron frequency (Ωe). The fast-growing electrostatic beam-mode waves saturate in a few plasma oscillations by slowing down and relaxing the electron beam parallel to the background magnetic field. Upon their saturation, the finite amplitude electrostatic beam-mode waves can resonate with the tail of the background thermal electrons and accelerate them to the beam parallel velocity. The slower-growing whistler waves are excited in primarily two resonance modes: (a) through Landau resonance due to the inverted slope of the beam electrons in the parallel velocity and (b) through cyclotron resonance by scattering electrons to both lower pitch angles and smaller en...
Finer metagenomic reconstruction via biodiversity optimization

When analyzing communities of microorganisms from their sequenced DNA, an important task is taxonomic profiling: enumerating the presence and relative abundance of all organisms, or merely of all taxa, contained in the sample. This task can be tackled via compressive-sensing-based approaches, which favor communities featuring the fewest organisms among those consistent with the observed DNA data. Despite their successes, these parsimonious approaches sometimes conflict with biological realism by overlooking organism similarities. Here, we leverage a recently developed notion of biological diversity that simultaneously accounts for organism similarities and retains the optimization strategy underlying compressive-sensing-based approaches. We demonstrate that minimizing biological diversity still produces sparse taxonomic profiles and we experimentally validate superiority to existing compressive-sensing-based approaches. Despite showing that the objective function is almost never convex and often concave, generally yielding NP-hard problems, we exhibit ways of representing organism similarities for which minimizing diversity can be performed via a sequence of linear programs guaranteed to decrease diversity. Better yet, when biological similarity is quantified by k-mer co-occurrence (a popular notion in bioinformatics), minimizing diversity actually reduces to one linear program that can utilize multiple k-mer sizes to enhance performance. In proof-of-concept experiments, we verify that the latter procedure can lead to significant gains when taxonomically profiling a metagenomic sample, both in terms of reconstruction accuracy and computational performance. Reproducible code is available at https://github.com/dkoslicki/MinimizeBiologicalDiversity.
SABER: A Systems Approach to Blur Estimation and Reduction in X-Ray Imaging

Blur in X-ray radiographs not only reduces the sharpness of image edges but also reduces the overall contrast. The effective blur in a radiograph is the combined effect of blur from multiple sources such as the detector panel, X-ray source spot, and system motion. In this paper, we use a systems approach to model the point spread function (PSF) of the effective radiographic blur as the convolution of multiple PSFs, where each PSF models one of the various sources of blur. In particular, we model the combined contribution of X-ray source and detector blurs while assuming negligible contribution from other forms of blur. Then, we present a numerical optimization algorithm for estimating the source and detector PSFs from multiple radiographs acquired at different X-ray source to object (SOD) and object to detector distances (ODD). Finally, we computationally reduce blur in radiographs using deblurring algorithms that use the estimated PSFs from the previous step. Our approach to estimate and reduce blur is called SABER, which is an acronym for systems approach to blur estimation and reduction.
Monopoles in 2 + 1-Dimensional Conformal Field Theories with Global U(1) Symmetry

In 2 + 1-dimensional conformal field theories with a global U(1) symmetry, monopoles can be introduced through a background gauge field that couples to the U(1) conserved current. We use the state-operator correspondence to calculate scaling dimensions of such monopole insertions. We obtain the next-to-leading term in the 1/N b expansion of the Wilson-Fisher fixed point in the theory of N b complex bosons.
Merging Black Holes in the Low-mass and High-mass Gaps from 2 + 2 Quadruple Systems

The origin of the black hole (BH) binary mergers observed by LIGO-Virgo is still uncertain, as are the boundaries of the stellar BH mass function. Stellar evolution models predict a dearth of BHs both at masses $\gtrsim 50$ M$_\odot$ and $\lesssim 5$ M$_\odot$, thus leaving low- and high-mass gaps in the BH mass function. A natural way to form BHs of these masses is through mergers of neutron stars (NSs; for the low-mass gap) or lower-mass BHs (for the high-mass gap); the low- or high-mass-gap BH produced as a merger product can then be detected by LIGO-Virgo if it merges again with a new companion. We show that the evolution of a 2+2 quadruple system can naturally lead to BH mergers with component masses in the low- or high-mass gaps. In our scenario, the BH in the mass gap originates from the merger of two NSs, or two BHs, in one of the two binaries and the merger product is imparted a recoil kick (from anisotropic gravitational wave emission), which triggers its interaction with the other binary component of the quadruple system. The outcome of this three-body interaction is usually a new eccentric compact binary containing the BH in the mass gap, which can then merge again. The merger rate is $\sim 10^{-7} - 10^{-2}$ Gpc$^{-3}$ yr$^{-1}$ and $\sim 10^{-3} - 10^{-2}$ Gpc$^{-3}$ yr$^{-1}$ for BHs in the low-mass and high-mass gap, respectively. As the sensitivity of gravitational wave detectors improves, tighter constraints will soon be placed on the stellar BH mass function.
SUPRATHERMAL ELECTRONS IN THE SOLAR CORONA: CAN NONLOCAL TRANSPORT EXPLAIN HELIOSPHERIC CHARGE STATES?

There have been several ideas proposed to explain how the Sun's corona is heated and how the solar wind is accelerated. Some models assume that open magnetic field lines are heated by Alfven waves driven by photospheric motions and dissipated after undergoing a turbulent cascade. Other models posit that much of the solar wind's mass and energy is injected via magnetic reconnection from closed coronal loops. The latter idea is motivated by observations of reconnecting jets and also by similarities of ion composition between closed loops and the slow wind. Wave/turbulence models have also succeeded in reproducing observed trends in ion composition signatures versus wind speed. However, the absolute values of the charge-state ratios predicted by those models tended to be too low in comparison with observations. This Letter refines these predictions by taking better account of weak Coulomb collisions for coronal electrons, whose thermodynamic properties determine the ion charge states in the low corona. A perturbative description of nonlocal electron transport is applied to an existing set of wave/turbulence models. The resulting electron velocity distributions in the low corona exhibit mild suprathermal tails characterized by "kappa" exponents between 10 and 25. These suprathermal electrons are found to be sufficiently energetic to enhance the charge states of oxygen ions, while maintaining the same relative trend with wind speed that was found when the distribution was assumed to be Maxwellian. The updated wave/turbulence models are in excellent agreement with solar wind ion composition measurements.
Spatiotemporal Analysis of Nonaffine Displacements in Disordered Solids Sheared Across the Yielding Point

The time evolution and spatial correlations of nonaffine displacements in deformed amorphous solids are investigated using molecular dynamics simulations. The three-dimensional model glass is represented via the binary mixture, which is slowly annealed well below the glass transition temperature and then sheared at a constant strain rate. It is shown that with increasing strain, the typical size of clusters of atoms with large nonaffine displacements increases, and these clusters remain spatially homogeneously distributed, until the yielding point when mobile atoms become localized within a system-spanning shear band. Furthermore, the yielding transition is associated with an abrupt change in the spatial correlation of nonaffine displacements, which varies from exponential to power-law decay. We also find that the height of the first peak in the pair correlation function of small atoms exhibits a distinct increase at the yielding strain. These results are discussed in relation to the yielding transition in amorphous materials under cyclic loading.
Complex-temperature properties of the Ising model on 2D heteropolygonal lattices

Using exact results, we determine the complex-temperature phase diagrams of the 2D Ising model on three regular heteropolygonal lattices, (3.6.3.6) (kagome), (3.122) and (4.82) (bathroom tile), where the notation denotes the regular n-sided polygons adjacent to each vertex. We also work out the exact complex-temperature singularities of the spontaneous magnetization. A comparison with the properties on the square, triangular, and hexagonal lattices is given. In particular, we find the first case where, even for isotropic spin-spin exchange couplings, the non-trivial non-analyticities of the free energy of the Ising model lie in a two-dimensional, rather than one-dimensional, algebraic variety in the z=e-2K plane.
Sub-microsecond x-ray imaging using hole-collecting Schottky type CdTe with charge-integrating pixel array detectors

CdTe is increasingly being used as the x-ray sensing material in imaging pixel array detectors for x-rays, generally above 20 keV, where silicon sensors become unacceptably transparent. Unfortunately CdTe suffers from polarization, which can alter the response of the material over time and with accumulated dose. Most prior studies used long integration times or CdTe that was not of the hole-collecting Schottky type. We investigated the temporal response of hole-collecting Schottky type CdTe sensors on timescales ranging from tens of nanoseconds to several seconds. We found that the material shows signal persistence on the timescale of hundreds of milliseconds attributed to the detrapping of a shallow trap, and additional persistence on sub-microsecond timescales after polarization. The results show that this type of CdTe can be used for time resolved studies down to approximately 100 ns. However quantitative interpretation of the signal requires careful attention to bias voltages, polarization and exposure history.
A brief comparison between available bio-printing methods

The scarcity of organs for transplant has led to large waiting lists of very sick patients. In drug development, the time required for human trials greatly increases the time to market. Drug companies are searching for alternative environments where the in ���� vivo conditions can be closely replicated. Both these problems could be addressed by manufacturing artificial human tissue. Recently, researchers in tissue engineering have developed tissue generation methods based on 3-D printing to fabricate artificial human tissue. Broadly, these methods could be classified as laser-assisted and laser free. The former have very fine spatial resolutions (10s of μm) but suffer from slow speed ( < 102 drops per second). The later have lower spatial resolutions (100s of μ m) but are very fast (up to 5 x 103 drops per second). In this paper we review state-of-the-art methods in each of these classes and provide a comparison based on reported resolution, printing speed, cell density and cell viability.
Anisotropic mesh adaptation for 3D anisotropic diffusion problems with application to fractured reservoir simulation

Anisotropic mesh adaptation is studied for linear finite element solution of 3D anisotropic diffusion problems. The 𝕄-uniform mesh approach is used, where an anisotropic adaptive mesh is generated as a uniform one in the metric specified by a tensor. In addition to mesh adaptation, preservation of the maximum principle is also studied. Some new sufficient conditions for maximum principle preservation are developed, and a mesh quality measure is defined to server as a good indicator. Four different metric tensors are investigated: one is the identity matrix, one focuses on minimizing an error bound, another one on preservation of the maximum principle, while the fourth combines both. Numerical examples show that these metric tensors serve their purposes. Particularly, the fourth leads to meshes that improve the satisfaction of the maximum principle by the finite element solution while concentrating elements in regions where the error is large. Application of the anisotropic mesh adaptation to fractured reservoir simulation in petroleum engineering is also investigated, where unphysical solutions can occur and mesh adaptation can help improving the satisfaction of the maximum principle.
Entanglement entropy of random fractional quantum Hall systems

The entanglement entropy of the ν=1/3 and ν=5/2 quantum Hall states in the presence of short-range random disorder has been calculated using direct diagonalization. A microscopic model of electron–electron interaction is used and spin-polarized electrons are confined to a single Landau level and interact with long-range Coulomb interaction. In the case of very weak disorder, the values of topological entanglement entropy are roughly consistent with the expected theoretical results. By considering a broad range of disorder strengths, entanglement entropy was studied in an effort to detect quantum phase transitions. In particular, there is a signature of the transition as the function of the disorder strength for the ν=5/2 state. Prospects of using the density matrix renormalization group to compute the entanglement entropy for larger system sizes are discussed.
Local mixing on abelian covers of hyperbolic surfaces with cusps

We prove the local mixing theorem for geodesic flows on abelian covers finite volume hyperbolic surfaces with cusps, which is a continuation of the work of Oh-Pan. We also describe applications to counting problems and the prime geodesic theorem.
Laser-pulse and electron-bunch plasma wakefield accelerator

Propagation distances of intense laser pulses and high-charge electron beams through the plasma are, respectively, limited by diffraction and self-deceleration. This imposes severe constraints on the performance of the two major advanced accelerator concepts: laser and plasma wakefield accelerators. Using numerical simulations, we demonstrate that when the two beams copropagate in the plasma, they can interact synergistically and extend each other's travel distances. The key interactions responsible for the synergy are found to be laser channeling by the electron bunch, and direct laser acceleration of the bunch electrons by the laser pulse. Remarkably, the amount of energy transferred from the laser pulse to the plasma can be increased by several times by the guiding electron bunch despite its small energy content. Implications of such synergistic interactions for the high-gradient acceleration of externally injected witness charges are discussed, and a new concept of a laser-pulse and electron-bunch plasma accelerator is formulated.
Unifying Deep Local and Global Features for Image Search

Image retrieval is the problem of searching an image database for items that are similar to a query image. To address this task, two main types of image representations have been studied: global and local image features. In this work, our key contribution is to unify global and local features into a single deep model, enabling accurate retrieval with efficient feature extraction. We refer to the new model as DELG, standing for DEep Local and Global features. We leverage lessons from recent feature learning work and propose a model that combines generalized mean pooling for global features and attentive selection for local features. The entire network can be learned end-to-end by carefully balancing the gradient flow between two heads – requiring only image-level labels. We also introduce an autoencoder-based dimensionality reduction technique for local features, which is integrated into the model, improving training efficiency and matching performance. Comprehensive experiments show that our model achieves state-of-the-art image retrieval on the Revisited Oxford and Paris datasets, and state-of-the-art single-model instance-level recognition on the Google Landmarks dataset v2. Code and models are available at https://github.com/tensorflow/models/tree/master/research/delf.
Ciliary neuropeptidergic signaling dynamically regulates excitatory synapses in postnatal neocortical pyramidal neurons.

Primary cilia are compartmentalized sensory organelles present on the majority of neurons in the mammalian brain throughout adulthood. Recent evidence suggests that cilia regulate multiple aspects of neuronal development, including the maintenance of neuronal connectivity. However, whether ciliary signals can dynamically modulate postnatal circuit excitability is unknown. Here we show that acute cell-autonomous knockdown of ciliary signaling rapidly strengthens glutamatergic inputs onto cultured rat neocortical pyramidal neurons, and increases spontaneous firing. This increased excitability occurs without changes to passive neuronal properties or intrinsic excitability. Further, the neuropeptide receptor somatostatin receptor 3 (SSTR3) is localized nearly exclusively to excitatory neuron cilia both in vivo and in culture, and pharmacological manipulation of SSTR3 signaling bidirectionally modulates excitatory synaptic inputs onto these neurons. Our results indicate that ciliary neuropeptidergic signaling dynamically modulates excitatory synapses, and suggest that defects in this regulation may underlie a subset of behavioral and cognitive disorders associated with ciliopathies.
Nonparametric tests of the causal null with non-discrete exposures

In many scientific studies, it is of interest to determine whether an exposure has a causal effect on an outcome. In observational studies, this is a challenging task due to the presence of confoun...
Engineering Supramolecular Organizing Centers for Optogenetic Control of Innate Immune Responses

The spatiotemporal organization of oligomeric protein complexes, such as the supramolecular organizing centers (SMOCs) made of MyDDosome and MAVSome, is essential for transcriptional activation of host inflammatory responses and immunometabolism. Light-inducible assembly of MyDDosome and MAVSome is presented herein to induce activation of nuclear factor-kB and type-I interferons. Engineering of SMOCs and the downstream transcription factor permits programmable and customized innate immune operations in a light-dependent manner. These synthetic molecular tools will likely enable optical and user-defined modulation of innate immunity at a high spatiotemporal resolution to facilitate mechanistic studies of distinct modes of innate immune activations and potential intervention of immune disorders and cancer.
Guilt of the Meat-Eating Consumer: When Animal Anthropomorphism Leads to Healthy Meat Dish Choices

Despite increasing concerns about animal welfare and the general prevalence of meat-eating practices, little attention has been paid in the consumer behavior literature to understanding consumer guilt around meat consumption. This research fills this void by exploring how consumers behave when animals are anthropomorphized, which can cause moral concerns to arise regarding the harm inflicted upon animals. We found that animal anthropomorphism can reduce meat consumption when consumers already have a low commitment to eating meat. However, the majority of consumers do not reduce their meat consumption in the face of animal anthropomorphism. Instead, they choose healthier meat dishes over less healthy but tastier meat dishes because the health benefits of meat consumption provide a strong excuse for eating meat, thereby dissipating their guilt about animal suffering. We demonstrate that guilt reduction is the underlying process mechanism and that the humane treatment of meat animals, which alleviates guilt about animal suffering, attenuates the effect of animal anthropomorphism on the choice of healthy meat dishes.
Double-Containment Coil With Enhanced Winding Mounting for Transcranial Magnetic Stimulation With Reduced Acoustic Noise

Objective: This work aims to reduce the acoustic noise level of transcranial magnetic stimulation (TMS) coils. TMS requires high currents (several thousand amperes) to be pulsed through the coil, which generates a loud acoustic impulse whose peak sound pressure level (SPL) can exceed 130 dB(Z). This sound poses a risk to hearing and elicits unwanted neural activation of auditory brain circuits. Methods: We propose a new double-containment coil with enhanced winding mounting (DCC), which utilizes acoustic impedance mismatch to contain and dissipate the impulsive sound within an air-tight outer casing. The coil winding is potted into a rigid block, which is mounted to the outer casing through the block´s acoustic nodes that are subject to minimum vibration during the pulse. The rest of the winding block is isolated from the casing by an air gap, and the sound is absorbed by polyester fiber panels within the casing. The casing thickness under the winding center is minimized to maximize the electric field output. Results: Compared to commercial figure-of-eight TMS coils, the DCC prototype has 18–41 dB(Z) lower peak SPL at matched stimulation strength, whilst providing 28% higher maximum stimulation strength than equally focal coils. Conclusion: The DCC design greatly reduces the acoustic noise of TMS while increasing the achievable stimulation strength. Significance: The acoustic noise reduction from our coil design is comparable to that provided by typical hearing protection devices. This coil design approach can enhance hearing safety and reduce auditory co-activations in the brain and other detrimental effects of TMS sound.
New Data Structures for Orthogonal Range Reporting and Range Minima Queries

In this paper we present new data structures for two extensively studied variants of the orthogonal range searching problem. First, we describe a data structure that supports two-dimensional orthogonal range minima queries in $O(n)$ space and $O(\log^{\varepsilon} n)$ time, where $n$ is the number of points in the data structure and $\varepsilon$ is an arbitrarily small positive constant. Previously known linear-space solutions for this problem require $O(\log^{1+\varepsilon} n)$ (Chazelle, 1988) or $O(\log n\log \log n)$ time (Farzan et al., 2012). A modification of our data structure uses space $O(n\log \log n)$ and supports range minima queries in time $O(\log \log n)$. Both results can be extended to support three-dimensional five-sided reporting queries. Next, we turn to the four-dimensional orthogonal range reporting problem and present a data structure that answers queries in optimal $O(\log n/\log \log n + k)$ time, where $k$ is the number of points in the answer. This is the first data structure that achieves the optimal query time for this problem. Our results are obtained by exploiting the properties of three-dimensional shallow cuttings.
Distributed Branch Points and the Shape of Elastic Surfaces with Constant Negative Curvature

We develop a theory for distributed branch points and investigate their role in determining the shape and influencing the mechanics of thin hyperbolic objects. We show that branch points are the natural topological defects in hyperbolic sheets, they carry a topological index which gives them a degree of robustness, and they can influence the overall morphology of a hyperbolic surface without concentrating energy. We develop a discrete differential geometric approach to study the deformations of hyperbolic objects with distributed branch points. We present evidence that the maximum curvature of surfaces with geodesic radius R containing branch points grow sub-exponentially, $$O(e^{c\sqrt{R}})$$ in contrast to the exponential growth $$O(e^{c' R})$$ for surfaces without branch points. We argue that, to optimize norms of the curvature, i.e., the bending energy, distributed branch points are energetically preferred in sufficiently large pseudospherical surfaces. Further, they are distributed so that they lead to fractal-like recursive buckling patterns.
Adaptive mesh refinement on moving quadrilateral grids

This paper describes an adaptive mesh refinement algorithm for unsteady gas dynamics. The algorithm is based on an unsplit, second-order Godunov integration scheme for logically-rectangular moving quadrilateral grids. The integration scheme is conservative and provides a robust, high resolution discretization of the equations of gas dynamics for problems with strong nonlinearities. The integration scheme is coupled to a local adaptive mesh refinement algorithm that dynamically adjusts the location of refined grid patches to preserve the accuracy of the solution, preserving conservation at interfaces between coarse and fine grids while adjusting the geometry of the fine grids so that grid lines remain smooth under refinement. Numerical results are presented illustrating the performance of the algorithm. 5 refs., 3 figs.
Private Sequential Learning

Can we learn privately and efficiently through sequential interactions? A private learning model is formulated to study an intrinsic tradeoff between privacy and query complexity in sequential lear...
Purposeful Internationalization: A Common-Good Approach of Global Engagement

Internationalization strategies are becoming pervasive within HEIs, but a common thread that aligns diverse international activities with the essence of each institution’s public good mission is missing. Some Institutions enact an approach that challenges the current mainstream Anglo-American construct of internationalization while contributing to a greater public good.
Cohomological Invariants in Positive Characteristic

We determine the mod p cohomological invariants for several affine group schemes G in chararacteristic p. These are invariants of G-torsors with values in etale motivic cohomology, or equivalently in Kato's version of Galois cohomology based on differential forms. In particular, we find the mod 2 cohomological invariants for the symmetric groups and the orthogonal groups in characteristic 2, which Serre computed in characteristic not 2. We also determine all operations on the mod p etale motivic cohomology of fields, extending Vial's computations of the operations on the mod p Milnor K-theory of fields.
Neuroscience and the Child Welfare System

A growing body of research by neuroscientists demonstrates that a child’s early life experiences and environment literally shape the child’s brain architecture, with lifelong consequences that are very difficult to reverse. Children’s relationships with their primary caregivers are at the core of this brain development, but when this relationship is severely deficient, the developing child’s brain is deeply affected. This research has not gained sufficient recognition in policy debates about the child welfare system because much of the work is complex and hard for non-neuroscientists to decipher with nuance. This essay brings a family law scholar’s perspective to understanding the possibilities and limitations of drawing on this still-emerging science in the development of child welfare policy.
Why firm access to the bond market differs over the business cycle: A theory and some evidence

Abstract This paper presents a theory of firm access to the bond market in which information gathering agencies are valuable but alter the relative cost of bond financing across firms and over the business cycle. The theory builds on the assumption that information frictions prevent these agencies from rating firms correctly all of the time. As a result, the cost of bond financing becomes dependent on the state of the economy and the “quality” of the signal provided by these agencies’ ratings. In addition, when the mix of bond issuers becomes riskier, as happens in recessions, bond financing becomes more expensive for mid-quality firms. Bond financing may even become more expensive to all firms, in which case mid-quality firms will be affected the most. The analysis of the bonds issued in the last two decades by American firms shows that split ratings, our proxy for the “quality” of the rating agencies’ signal, do not affect the relative cost of bond financing across firms in expansions, but they do increase the relative cost of this funding source for mid-credit quality issuers in recessions.
A Right to Reach an Audience: An Approach to Intermediary Bias on the Internet

Some of the thorniest problems of communications law and policy were supposed to have been solved by the Internet. The issue of who can speak, or access the means of speech, was said to have been solved by the arrival of ubiquitous, relatively cheap access to the Internet. The problem of media concentration was supposed to have been solved now that so many more speakers could contribute. Like “First Amendment manna from heaven,” the Internet thus seemed to offer a solution to the vexing communications policy problems of scarcity, diversity, and access.
The Right to Abandon

The common law prohibits the abandonment of real property. Perhaps it is surprising, therefore, that the following are true: (1) the common law generally permits the abandonment of chattel property, (2) the common law promotes the transfer of real property via adverse possession, and (3) the civil law is widely believed to permit the abandonment of real property. Because the literature on abandonment is disappointingly sparse, these three peculiarities have escaped sustained scholarly analysis and criticism. This Article aims to provide a comprehensive analysis of the law of abandonment. After engaging in such an analysis, this Article finds that the common law’s flat prohibition on the abandonment of corporeal interests in real property is misguided. Legal rules prohibiting abandonment ought to be replaced with a more permissive regime in which both the value of the underlying resource and the steps that the abandoning owner takes to ensure that would-be claimants are alerted to the resource’s availability are what matters. Furthermore, the law of abandonment ought to be harmonized for real property and chattels. Finally, this Article criticizes the