cssi/SciSciGPT-SciSciNet huggingface dataset:
Millimeter-wave spectroscopy and mapping of quasar hosts, and the status of ULIRGS as Quasar 2s

Abstract It is becoming possible to detect high redshift quasars in various molecular lines, and to show by mapping lensed objects that the strong dust and molecular emission arises in warm dense ∼ 100 pc-scale “tori.” The properties of ULIRGS, at least those with AGN-like narrow line regions, are very similar, as expected in the hidden quasar hypothesis. Several of the latter are in fact confirmed as “Quasar 2s” by spectropolarimetry. I argue against claims that the source of the majority of the luminosity has been determined in any ULIRG or Scuba sources.
A superconducting focal plane array for ultraviolet, optical, and near-infrared astrophysics

Microwave Kinetic Inductance Detectors, or MKIDs, have proven to be a powerful cryogenic detector technology due to their sensitivity and the ease with which they can be multiplexed into large arrays. A MKID is an energy sensor based on a photon-variable superconducting inductance in a lithographed microresonator, and is capable of functioning as a photon detector across the electromagnetic spectrum as well as a particle detector. Here we describe the first successful effort to create a photon-counting, energy-resolving ultraviolet, optical, and near infrared MKID focal plane array. These new Optical Lumped Element (OLE) MKID arrays have significant advantages over semiconductor detectors like charge coupled devices (CCDs). They can count individual photons with essentially no false counts and determine the energy and arrival time of every photon with good quantum efficiency. Their physical pixel size and maximum count rate is well matched with large telescopes. These capabilities enable powerful new astrophysical instruments usable from the ground and space. MKIDs could eventually supplant semiconductor detectors for most astronomical instrumentation, and will be useful for other disciplines such as quantum optics and biological imaging.
Relativistic motion in a constant electromagnetic field

For a relativistic charged particle moving in a constant electromagnetic field, its velocity 4-vector has been well studied. However, despite the fact that both the electromagnetic field and the equations of motion are purely real, the resulting 4-velocity is seemingly due to a complex electromagnetic field. This work shows that this is not due to some complex formalism used (such as Clifford algebra) but is intrinsically due to the fact that the o(3,1) Lie algebra of the Lorentz group is equivalent to two commuting complex su(2) algebras. Expressing the complex su(2) generators in terms of the boost and rotation operators then naturally introduces a complex electromagnetic field. This work solves the equation of motion not as a matrix equation, but as an operator evolution equation in terms of the generators of the Lorentz group. The factorization of the real evolution operator into two commuting complex evolution operators then directly gives the time evolution of the velocity 4-vector without any reference to an intermediate field.
Probabilistic Inversions for Time–Distance Helioseismology

Time–distance helioseismology is a set of powerful tools to study localized features below the Sun’s surface. Inverse methods are needed to robustly interpret time–distance measurements, with many examples in the literature. However, techniques that utilize a more statistical approach to inferences, and that are broadly used in the astronomical community, are less-commonly found in helioseismology. This article aims to introduce a potentially powerful inversion scheme based on Bayesian probability theory and Monte Carlo sampling that is suitable for local helioseismology. We first describe the probabilistic method and how it is conceptually different from standard inversions used in local helioseismology. Several example calculations are carried out to compare and contrast the setup of the problems and the results that are obtained. The examples focus on two important phenomena that are currently outstanding issues in helioseismology: meridional circulation and supergranulation. Numerical models are used to compute synthetic observations, providing the added benefit of knowing the solution against which the results can be tested. For demonstration purposes, the problems are formulated in two and three dimensions, using both ray- and Born-theoretical approaches. The results seem to indicate that the probabilistic inversions not only find a better solution with much more realistic estimation of the uncertainties, but they also provide a broader view of the range of solutions possible for any given model, making the interpretation of the inversion more quantitative in nature. The probabilistic inversions are also easy to set up for a broad range of problems, and they can take advantage of software that is publicly available. Unlike the progress being made in fundamental measurement schemes in local helioseismology that image the far side of the Sun, or have detected signatures of global Rossby waves, among many others, inversions of those measurements have had significantly less success. Such statistical methods may help overcome some of these barriers to move the field forward.
Colliding in the Shadows of Giants: Planetesimal Collisions during the Growth and Migration of Gas Giants

Giant planet migration is an important phenomenon in the evolution of planetary systems. Recent works have shown that giant planet growth and migration can shape the asteroid belt, but these works have not considered interactions between planetesimals. We have calculated the evolution of planetesimal disks, including planetesimal-planetesimal collisions, during gas giant growth and migration. The numbers, locations, and impact velocities of these collisions depend on the specific growth and migration path. We find that giant planet growth alone has little effect on impact velocities, and most of the planetesimals scattered by growing giants do not undergo collisions with each other during the growth period. In contrast, we find that giant planet migration induces large numbers of high velocity collisions between planetesimals. These impacts have sufficient velocities to cause shock-induced vaporization for both water ice and silicate components of planetesimals, and to cause catastrophic disruption of the bodies. New bodies may form from impact debris. Collisional evolution reduces the efficiency of planetesimal implantation into the asteroid belt via giant planet growth and migration. A small fraction of the largest planetesimals implanted into the asteroid belt would have been processed via collisions. We identify important consequences of planetesimal collisions that have not been considered in planet accretion models. The prevalence of high velocity collisions during giant planet migration, and their potential links to the properties of meteorites, and the formation of chondrules, makes impact vaporization a critically important phenomenon. The consequences of vaporizing planetesimal constituents require further detailed study. New collision outcome models for impacts within the nebula, and models for new planetesimal formation are needed.
Fiber detection for state surfaces

Every Kauffman state of a link diagram D.K/ naturally defines a state surface S whose boundary is K . For a homogeneous state , we show that K is a fibered link with fiber surface S if and only if an associated graph G0 is a tree. As a corollary, it follows that for an adequate knot or link, the second and next-to-last coefficients of the Jones polynomial are the obstructions to certain state surfaces being fibers for K .
Positive scalar curvature with skeleton singularities

We study positive scalar curvature on the regular part of Riemannian manifolds with singular, uniformly Euclidean ( $$L^\infty $$ ) metrics that consolidate Gromov’s scalar curvature polyhedral comparison theory and edge metrics that appear in the study of Einstein manifolds. We show that, in all dimensions, edge singularities with cone angles $$\le 2\pi $$ along codimension-2 submanifolds do not affect the Yamabe type. In three dimensions, we prove the same for more general singular sets, which are allowed to stratify along 1-skeletons, exhibiting edge singularities (angles $$\le 2\pi $$ ) and arbitrary $$L^\infty $$ isolated point singularities. We derive, as an application of our techniques, Positive Mass Theorems for asymptotically flat manifolds with analogous singularities.
Inceptive Event Time-Surfaces for Object Classification Using Neuromorphic Cameras.

This paper presents a novel fusion of low-level approaches for dimensionality reduction into an effective approach for high-level objects in neuromorphic camera data called Inceptive Event Time-Surfaces (IETS). IETSs overcome several limitations of conventional time-surfaces by increasing robustness to noise, promoting spatial consistency, and improving the temporal localization of (moving) edges. Combining IETS with transfer learning improves state-of-the-art performance on the challenging problem of object classification utilizing event camera data.
Explicit representations of 3-dimensional Sklyanin algebras associated to a point of order 2

The representation theory of a 3-dimensional Sklyanin algebra $S$ depends on its (noncommutative projective algebro-) geometric data: an elliptic curve $E$ in $\mathbb{P}^2$, and an automorphism $\sigma$ of $E$ given by translation by a point. Indeed, by a result of Artin-Tate-van den Bergh, we have that $S$ is module-finite over its center if and only if $\sigma$ has finite order. In this case, all irreducible representations of $S$ are finite-dimensional and of at most dimension $|\sigma|$. In this work, we provide an algorithm in Maple to directly compute all irreducible representations of $S$ associated to $\sigma$ of order 2, up to equivalence. Using this algorithm, we compute and list these representations. To illustrate how the algorithm developed in this paper can be applied to other algebras, we use it to recover well-known results about irreducible representations of the skew polynomial ring $\mathbb{C}_{-1}[x,y]$.
Automatic Machine Translation Evaluation in Many Languages via Zero-Shot Paraphrasing

We frame the task of machine translation evaluation as one of scoring machine translation output with a sequence-to-sequence paraphraser, conditioned on a human reference. We propose training the paraphraser as a multilingual NMT system, treating paraphrasing as a zero-shot translation task (e.g., Czech to Czech). This results in the paraphraser’s output mode being centered around a copy of the input sequence, which represents the best case scenario where the MT system output matches a human reference. Our method is simple and intuitive, and does not require human judgements for training. Our single model (trained in 39 languages) outperforms or statistically ties with all prior metrics on the WMT 2019 segment-level shared metrics task in all languages (excluding Gujarati where the model had no training data). We also explore using our model for the task of quality estimation as a metric—conditioning on the source instead of the reference—and find that it significantly outperforms every submission to the WMT 2019 shared task on quality estimation in every language pair.
Quantum field theory with no zero-point energy

Traditional quantum field theory can lead to enormous zero-point energy, which markedly disagrees with experiment. Unfortunately, this situation is built into conventional canonical quantization procedures. For identical classical theories, an alternative quantization procedure, called affine field quantization, leads to the desirable feature of having a vanishing zero-point energy. This procedure has been applied to renormalizable and nonrenormalizable covariant scalar fields, fermion fields, as well as general relativity. Simpler models are offered as an introduction to affine field quantization.
ESCAPE, ACCRETION, OR STAR FORMATION? THE COMPETING DEPLETERS OF GAS IN THE QUASAR MARKARIAN 231

We report on high resolution CO(1–0), CS(2–1), and 3 mm continuum Combined Array for Research in Millimeter Astronomy (CARMA) observations of the molecular outflow host and nearest quasar Markarian 231. We use the CS(2–1) measurements to derive a dense gas mass within Mrk 231 of 1.8 ± 0.3 x 10^(10) M⊙, consistent with previous measurements. The CS(2–1) data also seem to indicate that the molecular disk of Mrk 231 is forming stars at about normal efficiency. The high resolution CARMA observations were able to resolve the CO(1–0) outflow into two distinct lobes, allowing for a size estimate to be made and further constraining the molecular outflow dynamical time, further constraining the molecular gas escape rate. We find that 15% of the molecular gas within the Mrk 231 outflow actually exceeds the escape velocity in the central kiloparsec. Assuming that molecular gas is not constantly being accelerated, we find the depletion timescale of molecular gas in Mrk 231 to be 49 Myr, rather than 32 Myr, more consistent with the poststarburst stellar population observed in the system.
Cap products in string topology

Chas and Sullivan showed that the homology of the free loop space LM of an oriented closed smooth manifold M admits the structure of a Batalin‐Vilkovisky (BV) algebra equipped with an associative product (loop product) and a Lie bracket (loop bracket). We show that the cap product is compatible with the above two products in the loop homology. Namely, the cap product with cohomology classes coming from M via the circle action acts as derivations on the loop product as well as on the loop bracket. We show that Poisson identities and Jacobi identities hold for the cap product action, turning H .M/ H .LM/ into a BV algebra. Finally, we describe cap products in terms of the BV algebra structure in the loop homology. 55P35, 55P35
Ultraviolet Imaging Observations of the cD Galaxy in Abell 1795: Further Evidence for Massive Star Formation in a Cooling Flow

We present images from the Ultraviolet Imaging Telescope (UIT) of the Abell 1795 cluster of galaxies. We compare the cD galaxy morphology and photometry of these data with those from existing archival and published data. The addition of a far-UV color helps us to construct and test star formation model scenarios for the sources of UV emission. Models of star formation with rates in the range ~5-20 M☉ yr-1 indicate that the best-fitting models are those with continuous star formation or a recent (~4 Myr old) burst superimposed on an old population. The presence of dust in the galaxy, dramatically revealed by Hubble Space Telescope images, complicates the interpretation of UV data. However, we find that the broadband UV/optical colors of this cD galaxy can be reasonably matched by models using a Galactic form for the extinction law with EB-V = 0.14. We also briefly discuss other objects in the large UIT field of view.
Glueball Spectroscopy in Regge Phenomenology

We show that linear Regge trajectories for mesons and glueballs, and the cubic mass spectrum associated with them, determine a relation between the masses of the ρ meson and the scalar glueball, \(M(0^{ + + } ) = 3/\sqrt 2 M(\rho )\), which implies \(M(0^{ + + } ) = 1650_ \pm 10\) MeV. We also discuss relations between the masses of the scalar, tensor and 3-- glueballs, \(M(2^{ + + } ) = \sqrt 2 M(0^{ + + } ),{\text{ }}M(3^{ - - } ) = 2M(0^{ + + } )\), which imply \(M(2^{ + + } ) = 2290_ \pm {\text{ }}15{\text{ MeV, }}M(3^{ - - } ) = 3240_ \pm {\text{ }}20\) MeV.
Possible Infrared Counterparts to the Soft Gamma-Ray Repeater SGR 1806–20

We report the discovery of possible infrared counterparts to SGR 1806-20. We use archival Chandra observations to determine the location of SGR 1806-20 to less than 1'' accuracy. We then locate two infrared objects within this error circle in K-band (2.2 μm) images of this field. Based on the X-ray absorption toward SGR 1806-20 and the extinction toward the nearby star cluster, we discuss the likelihood of association for the possible counterparts and the implications for SGR 1806-20's physical properties and origins.
A generalized muon trajectory estimation algorithm with energy loss for application to muon tomography

This work presents a generalized muon trajectory estimation algorithm to estimate the path of a muon in either uniform or nonuniform media. The use of cosmic ray muons in nuclear nonproliferation and safeguard verification applications has recently gained attention due to the non-intrusive and passive nature of the inspection, penetrating capabilities, as well as recent advances in detectors that measure position and direction of the individual muons before and after traversing the imaged object. However, muon image reconstruction techniques are limited in resolution due to low muon flux and the effects of multiple Coulomb scattering (MCS). Current reconstruction algorithms, e.g., point of closest approach (PoCA) or straight-line path (SLP), rely on overly simple assumptions for muon path estimation through the imaged object. For robust muon tomography, efficient and flexible physics-based algorithms are needed to model the MCS process and accurately estimate the most probable trajectory of a muon as it traverses an object. In the present work, the use of a Bayesian framework and a Gaussian approximation of MCS is explored for estimation of the most likely path of a cosmic ray muon traversing uniform or nonuniform media and undergoing MCS. The algorithm's precision is compared to Monte Carlo simulated muon trajectories. It was found that the algorithm is expected to be able to predict muon tracks to less than 1.5 mm root mean square (RMS) for 0.5 GeV muons and 0.25 mm RMS for 3 GeV muons, a 50% improvement compared to SLP and 15% improvement when compared to PoCA. Further, a 30% increase in useful muon flux was observed relative to PoCA. Muon track prediction improved for higher muon energies or smaller penetration depth where energy loss is not significant. The effect of energy loss due to ionization is investigated, and a linear energy loss relation that is easy to use is proposed.
Green Valley Galaxies

The “green valley” is a wide region separating the blue and the red peaks in the ultraviolet-optical color magnitude diagram, first revealed using GALEX UV photometry. The term was coined by Christopher Martin (Caltech), in 2005. Green valley highlights the discriminating power of UV to very low relative levels of ongoing star formation, to which the optical colors, including u−r, are insensitive. It corresponds to massive galaxies below the star-forming, “main” sequence, and therefore represents a critical tool for the study of the quenching of star formation and its possible resurgence in otherwise quiescent galaxies. This article reviews the results pertaining to (predominantly disk) morphology, structure, environment, dust content and gas properties of green valley galaxies in the local universe. Their relationship to AGN is also discussed. Attention is given to biases emerging from defining the “green valley” using optical colors. We review various evolutionary scenarios and we present evidence for a new one, the quasi-static view of the green valley, in which the majority (but not all) of galaxies currently in the green valley were only partially quenched in the distant past and now participate in a slow cosmic decline of star formation, which also drives down the activity on the main sequence, presumably as a result of the dwindling accretion/cooling onto galaxy disks. This emerging synthetic picture is based on the findings from Fang et al. (2012), Salim et al. (2012) and Martin et al. (2007), as well as other results.
WHY OPTIMAL STATES RECRUIT FEWER REACTIONS IN METABOLIC NETWORKS

The metabolic network of a living cell involves several hundreds or thousands of interconnected biochemical reactions. Previous research has shown that under realistic conditions only a fraction of these reactions is concurrently active in any given cell. This is partially determined by nutrient availability, but is also strongly dependent on the metabolic function and network structure. Here, we establish rigorous bounds showing that the fraction of active reactions is smaller (rather than larger) in metabolic networks evolved or engineered to optimize a specific metabolic task, and we show that this is largely determined by the presence of thermodynamically irreversible reactions in the network. We also show that the inactivation of a certain number of reactions determined by irreversibility can generate a cascade of secondary reaction inactivations that propagates through the network. The mathematical results are complemented with numerical simulations of the metabolic networks of the bacterium Escherichia coli and of human cells, which show, counterintuitively, that even the maximization of the total reaction flux in the network leads to a reduced number of active reactions.
THE HST/ACS+WFC3 SURVEY FOR LYMAN LIMIT SYSTEMS. II. SCIENCE

We present the first science results from our Hubble Space Telescope survey for Lyman limit absorption systems (LLS) using the low dispersion spectroscopic modes of the Advanced Camera for Surveys and the Wide Field Camera 3. Through an analysis of 71 quasars, we determine the incidence frequency of LLS per unit redshift and per unit path length, l(z) and l(X), respectively, over the redshift range 1 < z < 2.6, and find a weighted mean of l(X) =0.29 ± 0.05 for 2.0 < z < 2.5 through a joint analysis of our sample and that of Ribaudo et al. Through stacked spectrum analysis, we determine a median (mean) value of the mean free path to ionizing radiation at z = 2.4 of λ912 mfp = 243(252) h –1 72 Mpc, with an error on the mean value of ±43 h –1 72 Mpc. We also re-evaluate the estimates of λ912 mfp from Prochaska et al. and place constraints on the evolution of λ912 mfp with redshift, including an estimate of the "breakthrough" redshift of z = 1.6. Consistent with results at higher z, we find that a significant fraction of the opacity for absorption of ionizing photons comes from systems with N H I ≤1017.5 cm–2 with a value for the total Lyman opacity of τLyman eff = 0.40 ± 0.15. Finally, we determine that at minimum, a 5-parameter (4 power law) model is needed to describe the column density distribution function f(N H I , X) at z ~ 2.4, find that f(N H I , X) undergoes no significant change in shape between z ~ 2.4 and z ~ 3.7, and provide our best fit model for f(N H I , X).
Effective generation and twisted weak positivity of direct images

We study pushforwards of log pluricanonical bundles on projective log canonical pairs (Y,Δ) over the complex numbers, partially answering a Fujita-type conjecture due to Popa and Schnell in the log canonical setting. We show two effective global generation results. First, when Y surjects onto a projective variety, we show a quadratic bound for generic generation for twists by big and nef line bundles. Second, when Y is fibered over a smooth projective variety, we show a linear bound for twists by ample line bundles. These results additionally give effective nonvanishing statements. We also prove an effective weak positivity statement for log pluricanonical bundles in this setting, which may be of independent interest. In each context we indicate over which loci positivity holds. Finally, using the description of such loci, we show an effective vanishing theorem for pushforwards of certain log-sheaves under smooth morphisms.
Accelerating Training of Transformer-Based Language Models with Progressive Layer Dropping

Recently, Transformer-based language models have demonstrated remarkable performance across many NLP domains. However, the unsupervised pre-training step of these models suffers from unbearable overall computational expenses. Current methods for accelerating the pre-training either rely on massive parallelism with advanced hardware or are not applicable to language modeling. In this work, we propose a method based on progressive layer dropping that speeds the training of Transformer-based language models, not at the cost of excessive hardware resources but from model architecture change and training technique boosted efficiency. Extensive experiments on BERT show that the proposed method achieves a 24% time reduction on average per sample and allows the pre-training to be 2.5X faster than the baseline to get a similar accuracy on downstream tasks. While being faster, our pre-trained models are equipped with strong knowledge transferability, achieving a 1.1 point higher GLUE score than the baseline when pre-trained with the same number of samples.
Optimal control and coordination of connected and automated vehicles at urban traffic intersections

We address the problem of coordinating online a continuous flow of connected and automated vehicles (CAVs) crossing two adjacent intersections in an urban area. We present a decentralized optimal control framework whose solution yields for each vehicle the optimal acceleration/deceleration at any time in the sense of minimizing fuel consumption. The solution, when it exists, allows the vehicles to cross the intersections without the use of traffic lights, without creating congestion on the connecting road, and under the hard safety constraint of collision avoidance. The effectiveness of the proposed solution is validated through simulation considering two intersections located in downtown Boston, and it is shown that coordination of CAVs can reduce significantly both fuel consumption and travel time.
Quenched limit theorems for Fourier transforms and periodogram

In this paper, we study the quenched central limit theorem for the discrete Fourier transform. We show that the Fourier transform of a stationary ergodic process, suitable centered and normalized, satisfies the quenched CLT conditioned by the past sigma algebra. For functions of Markov chains with stationary transitions, this means that the CLT holds with respect to the law of the chain started at a point for almost all starting points. It is necessary to emphasize that no assumption of irreducibility with respect to a measure or other regularity conditions are imposed for this result. We also discuss necessary and sufficient conditions for the validity of quenched CLT without centering. The results are highly relevant for the study of the periodogram of a Markov process with stationary transitions which does not start from equilibrium. The proofs are based of a nice blend of harmonic analysis, theory of stationary processes, martingale approximation and ergodic theory.
A HIGHLY ECCENTRIC 3.9 MILLISECOND BINARY PULSAR IN THE GLOBULAR CLUSTER NGC 6652

We present the Robert C. Byrd Green Bank Telescope discovery of the highly eccentric binary millisecond pulsar PSR J1835-3259A in the Fermi Large Area Telescope-detected globular cluster NGC 6652. Timing over one orbit yields the pulse period 3.89 ms, orbital period 9.25 days, eccentricity ∼ 0.95, and an unusually high companion mass of 0.74 assuming a 1.4 pulsar. We caution that the lack of data near periastron prevents a precise measurement of the eccentricity, and that further timing is necessary to constrain this and the other orbital parameters. From tidal considerations, we find that the companion must be a compact object. This system likely formed through an exchange encounter in the dense cluster environment. Our initial timing results predict the measurements of at least two post-Keplerian parameters with long-term phase-connected timing: the rate of periastron advance ∼ yr−1, requiring 1 year of phase connection; and the Einstein delay ∼ 10 ms, requiring 2–3 years of timing. For an orbital inclination , a measurement of is also likely. PSR J1835-3259A thus provides an opportunity to measure the neutron star mass with high precision, to probe the cluster environment, and, depending on the nature of the companion, to investigate the limits of general relativity.
HYDRODYNAMIC SIMULATION OF NON-THERMAL PRESSURE PROFILES OF GALAXY CLUSTERS

Cosmological constraints from X-ray and microwave observations of galaxy clusters are subjected to systematic uncertainties. Non-thermal pressure support due to internal gas motions in galaxy clusters is one of the major sources of astrophysical uncertainties. Using a mass-limited sample of galaxy clusters from a high-resolution hydrodynamical cosmological simulation, we characterize the non-thermal pressure fraction profile and study its dependence on redshift, mass, and mass accretion rate. We find that the non-thermal pressure fraction profile is universal across redshift when galaxy cluster radii are defined with respect to the mean matter density of the universe instead of the commonly used critical density. We also find that the non-thermal pressure is predominantly radial, and the gas velocity anisotropy profile exhibits strong universality when galaxy cluster radii are defined with respect to the mean matter density of the universe. However, we find that the non-thermal pressure fraction is strongly dependent on the mass accretion rate of the galaxy cluster. We provide fitting formulae for the universal non-thermal pressure fraction and velocity anisotropy profiles of gas in galaxy clusters, which should be useful in modeling astrophysical uncertainties pertinent to using galaxy clusters as cosmological probes.
Dynamical projective curvature in gravitation

By using a projective connection over the space of two-dimensional affine connections, we are able to show that the metric interaction of Polyakov two-dimensional gravity with a coadjoint element arises naturally through the projective Ricci tensor. Through the curvature invariants of Thomas and Whitehead, we are able to define an action that could describe dynamics to the projective connection. We discuss implications of the projective connection in higher dimensions as related to gravitation.
Emergent kink stability of a magnetized plasma jet injected into a transverse background magnetic field

We report experimental results on the injection of a magnetized plasma jet into a transverse background magnetic field in the HelCat linear plasma device at the University of New Mexico [M. Gilmore et al., J. Plasma Phys. 81(1), 345810104 (2015)]. After the plasma jet leaves the plasma-gun muzzle, a tension force arising from an increasing curvature of the background magnetic field induces in the jet a sheared axial-flow gradient above the theoretical kink-stabilization threshold. We observe that this emergent sheared axial flow stabilizes the n = 1 kink mode in the jet, whereas a kink instability is observed in the jet when there is no background magnetic field present.
Density-matrix based numerical methods for discovering order and correlations in interacting systems

We review recently introduced numerical methods for the unbiased detection of the order parameter and/or dominant correlations in many-body interacting systems, by using reduced density matrices. Most of the paper is devoted to the 'quasi-degenerate density matrix' (QDDM) which is rooted in Anderson's observation that the degenerate symmetry-broken states valid in the thermodynamic limit are manifested in finite systems as a set of low-energy 'quasi-degenerate' states (in addition to the ground state). This method, its original form due to Furukawa et al (2006 Phys. Rev. Lett. 96 047211), is given a number of improvements here, above all the extension from two-fold symmetry breaking to arbitrary cases. This is applied to two test cases: (1) interacting spinless hardcore bosons on the triangular lattice and (2) a spin-1/2 antiferromagnetic system at the percolation threshold. In addition, we survey a different method called the 'correlation density matrix', which detects (possibly long-range) correlations only from the ground state, but using the reduced density matrix from a cluster consisting of two spatially separated regions.
Detection of X-Ray Emission from Gravitationally Lensed Submillimeter Sources in the Field of Abell 370

We report the detection by Chandra of SMM J02399-0134 and SMM J02399-0136, two distant (z = 1.06 and z = 2.81, respectively) submillimeter sources gravitationally magnified by the galaxy cluster Abell 370. These are high-significance (>7 σ) X-ray detections of the high-redshift submillimeter source population. The X-ray positions are coincident with the optical positions to within 1''. The X-ray spectra, while of low signal-to-noise ratio, are quite hard. Absorbed power-law models with fixed photon indices of Γ = 2.0 imply local absorbing columns greater than 2 × 1023 cm-2 and unabsorbed luminosities greater than 1044 ergs s-1 in both sources. These results imply that nuclear activity is responsible for the bulk of the luminosity in SMM J02399-0134 and for at least 20% of the luminosity of SMM J02399-0136, consistent with previous optical observations. We also place an upper limit on the X-ray flux of a third submillimeter source, SMM J02400-0134. Considered together with previously published Chandra upper limits on the X-ray flux from submillimeter sources, our results imply that 20% of submillimeter sources exhibit X-ray emission from active galactic nuclei (with 90% confidence), consistent with expectations of their contribution to the diffuse X-ray background.
Minimal genera of open 4-manifolds

We study exotic smoothings of open 4–manifolds using the minimal-genus function and its analog for end homology. While traditional techniques in open 4–manifold smoothing theory give no control of minimal genera, we make progress by using the adjunction inequality for Stein surfaces. Smoothings can be constructed with much more control of these genus functions than the compact setting seems to allow. As an application, we expand the range of 4–manifolds known to have exotic smoothings (up to diffeomorphism). For example, every 2–handlebody interior (possibly infinite or nonorientable) has an exotic smoothing, and “most” have infinitely many, or sometimes uncountably many, distinguished by the genus function and admitting Stein structures when orientable. Manifolds with 3–homology are also accessible. We investigate topological submanifolds of smooth 4–manifolds. Every domain of holomorphy (Stein open subset) in ℂ2 is topologically isotopic to uncountably many other diffeomorphism types of domains of holomorphy with the same genus functions, or with varying but controlled genus functions.
D(NA)-branes

We engineer a configuration of branes in type IIB string theory whose mechanical structure is that of a DNA molecule. We obtain it by considering a T-dual description of the quantum Hall soliton. Using a probe analysis, we investigate the dynamics of the system and show that it is stable against radial perturbations. We exercise a certain amount of restraint in discussing applications to biophysics.
How beaming of gravitational waves compares to the beaming of electromagnetic waves: impacts to gravitational wave detection

We focus on understanding the beaming of gravitational radiation from gamma ray bursts (GRBs) by approximating GRBs as linearly accelerated point masses. For accelerated point masses, it is known that gravitational radiation is beamed isotropicly at high speeds, and beamed along the polar axis at low speeds. Aside from this knowledge, there has been very little work done on beaming of gravitational radiation from GRBs, and the impact beaming could have on gravitational wave (GW) detection. We determine the following: (1) the observation angle at which the most power is emitted as a function of speed, (2) the maximum ratio of power radiated away as a function of speed, and (3) the angular distribution of power ratios at relativistic and non-relativistic speeds. Additionally the dependence of the beaming of GW radiation on speed is essentially the opposite of the beaming of electromagnetic (EM) radiation from GRBs. So we investigate why this is the case by calculating the angular EM radiation distribution from a linear electric quadrupole, and compare this distribution to the angular gravitational radiation distribution from a GRB.
A Hybrid Approach to Secure Function Evaluation using SGX

A protocol for two-party secure function evaluation (2P-SFE) aims to allow the parties to learn the output of function f of their private inputs, while leaking nothing more. In a sense, such a protocol realizes a trusted oracle that computes f and returns the result to both parties. There have been tremendous strides in efficiency over the past ten years, yet 2P-SFE protocols remain impractical for most real-time, online computations, particularly on modestly provisioned devices. Intel's Software Guard Extensions (SGX) provides hardware-protected execution environments, called enclaves, that may be viewed as trusted computation oracles. While SGX provides native CPU speed for secure computation, previous side-channel and micro-architecture attacks have demonstrated how security guarantees of enclaves can be compromised. In this paper, we explore a balanced approach to 2P-SFE on SGX-enabled processors by constructing a protocol for evaluating f relative to a partitioning of f. This approach alleviates the burden of trust on the enclave by allowing the protocol designer to choose which components should be evaluated within the enclave, and which via standard cryptographic techniques. We describe SGX-enabled SFE protocols (modeling the enclave as an oracle), and formalize the strongest-possible notion of 2P-SFE for our setting. We prove our protocol meets this notion when properly realized. We implement the protocol and apply it to two practical problems: privacy-preserving queries to a database, and a version of Dijkstra's algorithm for privacy-preserving navigation. Our evaluation shows that our SGX-enabled SFE scheme enjoys a 38x increase in performance over garbled-circuit-based SFE. Finally, we justify modeling of the enclave as an oracle by implementing protections against known side-channels.
Dimer model: Full asymptotic expansion of the partition function

We give a complete rigorous proof of the full asymptotic expansion of the partition function of the dimer model on a square lattice on a torus for general weights zh, zv of the dimer model and arbitrary dimensions of the lattice m, n. We assume m is even and we show that the asymptotic expansion depends on the parity of n. We review and extend the results of Ivashkevich et al. [J. Phys. A: Math. Gen. 35, 5543 (2002)] on the full asymptotic expansion of the partition function of the dimer model, and we give a rigorous estimate of the error term in the asymptotic expansion of the partition function.
A spacetime derivation of the Lorentzian OPE inversion formula

Caron-Huot has recently given an interesting formula that determines OPE data in a conformal field theory in terms of a weighted integral of the four-point function over a Lorentzian region of cross-ratio space. We give a new derivation of this formula based on Wick rotation in spacetime rather than cross-ratio space. The derivation is simple in two dimensions but more involved in higher dimensions. We also derive a Lorentzian inversion formula in one dimension that sheds light on previous observations about the chaos regime in the SYK model.
Using multiscale norms to quantify mixing and transport

Mixing is relevant to many areas of science and engineering, including the pharmaceutical and food industries, oceanography, atmospheric sciences and civil engineering. In all these situations one goal is to quantify and often then to improve the degree of homogenization of a substance being stirred, referred to as a passive scalar or tracer. A classical measure of mixing is the variance of the concentration of the scalar, which is the L2 norm of a mean-zero concentration field. Recently, other norms have been used to quantify mixing, in particular the mix-norm as well as negative Sobolev norms. These norms have the advantage that unlike variance they decay even in the absence of diffusion, and their decay corresponds to the flow being mixing in the sense of ergodic theory. General Sobolev norms weigh scalar gradients differently, and are known as multiscale norms for mixing. We review the applications of such norms to mixing and transport, and show how they can be used to optimize the stirring and mixing of a decaying passive scalar. We then review recent work on the less-studied case of a continuously replenished scalar field?the source?sink problem. In that case the flows that optimally reduce the norms are associated with transport rather than mixing: they push sources onto sinks, and vice versa.
Crack Growth Behavior in NiTi Shape Memory Alloys Under Mode-I Isothermal Loading: Effect of Stress State

Fracture behavior in nickel-titanium (NiTi) shape memory alloys (SMAs) subjected to mode-I, isothermal loading is studied using finite element analysis (FEA). Compact tension (CT) SMA specimen is modeled in Abaqus finite element suite and crack growth under displacement boundary condition is investigated for plane strain and plane stress conditions. Parameters for the SMA material constitutive law implemented in the finite element setup are acquired from characterization tests conducted on near-equiatomic NiTi SMA. Virtual crack closure technique (VCCT) is implemented where crack is assumed to extend when the energy release rate at the crack-tip becomes equal to the experimentally obtained material-specific critical value. Load-displacement curves and mechanical fields near the crack-tip in plane strain and plane stress cases are examined. Moreover, a discussion with respect to the crack resistance R-curves calculated using the load-displacement response for plane strain and plane stress conditions is presented.
Embedding Groups into Distributive Subsets of the Monoid of Binary Operations

Let X be a set and Bin(X) the set of all binary operations on X. We say that a subset of Bin(X) is a distributive set of operations if all pairs of elements are right distributive. J.Przytycki posed the question of which groups can be realized as distributive sets. The initial guess that any group may be embedded into Bin(X) for some X was complicated by an observation that if a binary operation is idempotent (a*a=a), then it commutes with every element of S. The first noncommutative subgroup of Bin(X), the symmetric group on three elements, was found in October of 2011 by Y.Berman. We show that any group can be embedded in Bin(X) for X=G (as a set). We also discuss minimality of embeddings observing that, in particular, X with six elements is the smallest set such that Bin(X) contains a non-abelian subgroup.
Are dyons the preons of the knot model

We consider the possibility that the preons defined by the SLq(2) extension of the Standard Model may be identified with Schwinger dyons. The SLq(2) extension is here presented as a model that may ...
Conjugacy for Homogeneous Ordered Graphs

We show that for any countable homogeneous ordered graph G, the conjugacy problem for automorphisms of G is Borel complete. In fact we establish that each such G satisfies a strong extension property called ABAP, which implies that the isomorphism relation on substructures of G is Borel reducible to the conjugacy relation on automorphisms of G.
The Nature of Turbulence in the Outer Regions of Protoplanetary Disks

We carry out a series of local, shearing box simulations of the outer regions of protoplanetary disks, where ambipolar diffusion is important due to low ionization levels, to better characterize the nature of turbulence and angular momentum transport in these disks. These simulations are divided into two groups, one with far ultraviolet (FUV) ionization included, and one without FUV. In both cases, we explore a large range in diffusivity values. We find that in the simulations without FUV, the properties of the turbulence are similar to the unstratified simulations of Bai & Stone (2011); for a given diffusivity, the MRI can still be present so long as the magnetic field is sufficiently weak. Furthermore, the dynamics of the mid-plane in these simulations are primarily controlled by the MRI. In the FUV simulations on the other hand, the MRI-active FUV layers transport strong toroidal magnetic flux to the mid-plane, which shuts off the MRI. Instead, angular momentum transport at the mid-plane is dominated by laminar magnetic fields, resulting in lower levels of turbulent Maxwell stress compared to the no-FUV simulations. Finally, we perform a temporal correlation analysis on the FUV simulations, confirming our result that the dynamics in the mid-plane region is strongly controlled by the FUV-ionized layers.
Petri map for rank two bundles with canonical determinant

We prove the Bertram–Feinberg–Mukai conjecture for a generic curve C of genus g and a semistable vector bundle E of rank two and determinant K on C, namely we prove the injectivity of the Petri-canonical map S2(H0(E))→H0(S2(E)).
Norms of quantum Gaussian multi-mode channels

We compute the S^p→S^p norm of a general Gaussian gauge-covariant multi-mode channel for any 1 ≤ p < ∞, where S^p is a Schatten space. As a consequence, we verify the Gaussian optimizer conjecture and the multiplicativity conjecture in these cases.
Tightening the Lieb-Robinson bound in locally-interacting systems

Limits on the speed of information spreading in many-body systems are strengthened by accounting for previously ignored features, in some cases demonstrating finite speed limits where none were known
Higher spin ANEC and the space of CFTs

We study the positivity properties of the leading Regge trajectory in higher-dimensional, unitary, conformal field theories (CFTs). These conditions correspond to higher spin generalizations of the averaged null energy condition (ANEC). By studying higher spin ANEC, we will derive new bounds on the dimensions of charged, spinning operators and prove that if the Hofman-Maldacena bounds are saturated, then the theory has a higher spin symmetry. We also derive new, general bounds on CFTs, with an emphasis on theories whose spectrum is close to that of a generalized free field theory. As an example, we consider the Ising CFT and show how the OPE structure of the leading Regge trajectory is constrained by causality. Finally, we use the analytic bootstrap to perform additional checks, in a large class of CFTs, that higher spin ANEC is obeyed at large and finite spin. In the process, we calculate corrections to large spin OPE coefficients to one-loop and higher in holographic CFTs.
Chameleon gravity and satellite geodesy

We consider the possibility of the detection of a chameleon effect by an earth orbiting satellite such as LAGEOS, and possible constraints that might be placed on chameleon model parameters. Approximate constraints presented here result from using a simple monopole approximation for the gravitational field of the earth, along with results from the Khoury-Weltman chameleon model, solar system constraints obtained from the Cassini mission, and parameter bounds obtained from the LAGEOS satellite. It is furthermore suggested that a comparison of ground-based and space-based multipole moments of the geopotential could reveal a possible chameleon effect.
Full-wave feasibility study of anti-radar diagnostic of magnetic field based on O-X mode conversion and oblique reflectometry imaging

An innovative millimeter wave diagnostic is proposed to measure the local magnetic field and edge current as a function of the minor radius in the tokamak pedestal region. The idea is to identify the direction of minimum reflectivity at the O-mode cutoff layer. Correspondingly, the transmissivity due to O-X mode conversion is maximum. That direction, and the angular map of reflectivity around it, contains information on the magnetic field vector B at the cutoff layer. Probing the plasma with different wave frequencies provides the radial profile of B. Full-wave finite-element simulations are presented here in 2D slab geometry. Modeling confirms the existence of a minimum in reflectivity that depends on the magnetic field at the cutoff, as expected from mode conversion physics, giving confidence in the feasibility of the diagnostic. The proposed reflectometric approach is expected to yield superior signal-to-noise ratio and to access wider ranges of density and magnetic field, compared with related radiome...