cssi/SciSciGPT-SciSciNet huggingface dataset:
NOISE-SUSTAINED CONVECTIVE INSTABILITY IN A MAGNETIZED TAYLOR-COUETTE FLOW

The helical magnetorotational instability of the magnetized Taylor-Couette flow is studied numerically in a finite cylinder. A distant upstream insulating boundary is shown to stabilize the convective instability entirely while reducing the growth rate of the absolute instability. The reduction is less severe with greater height. After we model the boundary conditions properly, the wave patterns observed in the experiment turn out to be a noise-sustained convective instability. After the source of the noise resulting from unstable Ekman and Stewartson layers is switched off, a slowly decaying inertial oscillation is observed in the simulation. We reach the conclusion that the experiments completed to date have not yet reached the regime of absolute instability.
Robust Faster-Than-Nyquist PDM-mQAM Systems With Tomlinson-Harashima Precoding

A training-based channel estimation algorithm is proposed for the faster-than-Nyquist polarization division multiplexed m-ary quadrature amplitude modulation (m = 4, 16, 64) systems with Tomlinson-Harashima precoding (THP). This is robust to the convergence failure phenomenon suffered by the existing algorithm, yet remaining format-transparent. Simulation results show that the proposed algorithm requires a reduced optical signal-to-noise ratio to achieve a certain bit error rate in the presence of first-order polarization mode dispersion and phase noise introduced by the laser linewidth.
Partial and spectral-viscosity models for geophysical flows

Two models based on the hydrostatic primitive equations are proposed. The first model is the primitive equations with partial viscosity only, and is oriented towards large-scale wave structures in the ocean and atmosphere. The second model is the viscous primitive equations with spectral eddy viscosity, and is oriented towards turbulent geophysical flows. For both models, the existence and uniqueness of global strong solutions are established. For the second model, the convergence of the solutions to the solutions of the classical primitive equations as eddy viscosity parameters tend to zero is also established.
Prediction of antiferromagnetism in barium chromium phosphide confirmed after synthesis

We have carried out density-functional theory (DFT) calculations for the chromium pnictide BaCr2P2, which is structurally analogous to BaFe2As2, a parent compound for iron-pnictide superconductors. Evolutionary methods combined with DFT predict that the chromium analog has the same crystal structure as the latter. DFT also predicts Neel antiferromagnetic order on the chromium sites. Comparison with a simple electron-hopping model over a square lattice of chromium atoms suggests that it is due to residual nesting of the Fermi surfaces. We have confirmed the DFT predictions directly after the successful synthesis of polycrystalline samples of BaCr2P2. X-ray diffraction recovers the predicted crystal structure to high accuracy, while magnetic susceptibility and specific-heat measurements are consistent with a transition to an antiferromagnetically ordered state below [Formula: see text] K.
An Ultraviolet Survey of Low-redshift Partial Lyman-limit Systems with the HST Cosmic Origins Spectrograph

We present an ultraviolet spectroscopic survey of strong H I absorbers in the intergalactic medium, probing their evolution over the last 6-7 Gyr at redshifts $0.24 \leq z \leq 0.84$. We measure column densities $N_{\rm HI} \,( {\rm cm}^{-2})$ from the pattern of Lyman-series absorption lines and flux decrement at the Lyman limit (LL) when available. We analyzed 220 H I absorbers in ultraviolet spectra of 102 active galactic nuclei (AGN) taken by the Cosmic Origins Spectrograph aboard the Hubble Space Telescope with G130M/G160M gratings (1134-1795 \AA). For 158 absorbers with $\log N_{\rm HI} \geq 15$, the mean frequency is $d {\cal N}/dz = 4.95 \pm 0.39$ over pathlength $\Delta z = 31.94$ ($0.24 \leq z \leq 0.84)$. We identify 8 Lyman Limit Systems (LLS, $\log N_{\rm HI} \geq 17.2$) and 54 partial systems (pLLS) with $16.0 \leq \log N_{\rm HI} < 17.2$. Toward 159 AGN between $0.01 < z_{\rm abs} < 0.84$ with $\Delta z \approx 48$, we find four damped Ly$\alpha$ absorbers (DLA) with $(d {\cal N}/dz)_{\rm DLA} = 0.083^{+0.066}_{-0.040}$ at $\langle z \rangle = 0.18$. The mean LLS frequency between $z = 0.24-0.48$ is $(d {\cal N}/dz)_{\rm LLS} = 0.36^{+0.20}_{-0.13}$ fitted to $N(z) = (0.25^{+0.13}_{-0.09})(1+z)^{1.14}$. For 54 pLLS we find $(d {\cal N}/dz)_{\rm pLLS} = 1.69\pm0.23$ at $\langle z \rangle = 0.39$, a frequency consistent with gaseous halo sizes $R \approx 100 h^{-1}~{\rm kpc}$ for ($0.3-3L^*$) galaxies. A maximum-likelihood analysis yields a distribution $f(N,z) = C_0 N^{-\beta} (1+z)^{\gamma}$ with $\beta = 1.48 \pm 0.05$ and $\gamma = 1.14^{+0.88}_{-0.89}$ for $15 \leq \log N_{\rm HI} \leq 17.5$. The far-UV opacity gradient is $d \tau_{\rm eff} / dz \approx (0.444)(1+z)^{1.14}$ over the range $15 \leq \log N_{\rm HI} \leq 17$, implying mean LyC optical depth $\tau_{\rm eff} \approx 0.3-0.5$ toward sources at $z = 1-2$.
Graphene Formed on SiC Under Various Environments: Comparison of Si-Face and C-Face

The morphology of graphene on SiC {0 0 0 1} surfaces formed in various environments including ultra-high vacuum, 1 atm of argon and 10−6–10−4 Torr of disilane is studied by atomic force microscopy, low-energy electron microscopy and Raman spectroscopy. The graphene is formed by heating the surface to 1100–1600 °C, which causes preferential sublimation of the Si atoms. The argon atmosphere or the background of disilane decreases the sublimation rate so that a higher graphitization temperature is required, thus improving the morphology of the films. For the (0 0 0 1) surface, large areas of monolayer-thick graphene are formed in this way, with the size of these areas depending on the miscut of the sample. Results on the surface are more complex. This surface graphitizes at a lower temperature than for the (0 0 0 1) surface and consequently the growth is more three-dimensional. In an atmosphere of argon the morphology becomes even worse, with the surface displaying markedly inhomogeneous nucleation, an effect attributed to unintentional oxidation of the surface during graphitization. Use of a disilane environment for the surface is found to produce improved morphology, with relatively large areas of monolayer-thick graphene.
Mixed Dark Matter in Left-Right Symmetric Models

Motivated by the recently reported diboson and dijet excesses in Run 1 data at ATLAS and CMS, we explore models of mixed dark matter in left-right symmetric theories. In this study, we calculate the relic abundance and the elastic scattering cross section with nuclei for a number of dark matter candidates that appear within the fermionic multiplets of left-right symmetric models. In contrast to the case of pure multiplets, WIMP-nucleon scattering proceeds at tree-level, and hence the projected reach of future direct detection experiments such as LUX-ZEPLIN and XENON1T will cover large regions of parameter space for TeV-scale thermal dark matter. Decays of the heavy charged W 0 boson to particles in the dark sector can potentially shift the right-handed gauge coupling to larger values when xed to the rate of the Run 1 excesses, moving towards the theoretically attractive scenario, gR = gL. This region of parameter space may be probed by future collider searches for new Higgs bosons or electroweak fermions.
Truncated quantum Drinfeld Hecke algebras and Hochschild cohomology

We consider deformations of quantum exterior algebras extended by finite groups. Among these deformations are a class of algebras which we call truncated quantum Drinfeld Hecke algebras in view of their relation to classical Drinfeld Hecke algebras. We give the necessary and sufficient conditions for which these algebras occur, using Bergman’s Diamond Lemma. We compute the relevant Hochschild cohomology to make explicit the connection between Hochschild cohomology and truncated quantum Drinfeld Hecke algebras. To demonstrate the variance of the allowed algebras, we compute both classical type examples and demonstrate an example that does not arise as a factor algebra of a quantum Drinfeld Hecke algebra.
Time-Symmetric Boundary Conditions and Quantum Foundations

Despite the widely-held premise that initial boundary conditions (BCs) corresponding to measurements/interactions can fully specify a physical subsystem, a literal reading of Hamilton’s principle would imply that both initial and final BCs are required (or more generally, a BC on a closed hypersurface in spacetime). Such a time-symmetric perspective of BCs, as applied to classical fields, leads to interesting parallels with quantum theory. This paper will map out some of the consequences of this counter-intuitive premise, as applied to covariant classical fields. The most notable result is the contextuality of fields constrained in this manner, naturally bypassing the usual arguments against so-called “realistic” interpretations of quantum phenomena.
Long string scattering in c = 1 string theory

We study the scattering of long strings in c = 1 string theory, both in the worldsheet description and in the non-singlet sector of the dual matrix quantum mechanics. From the worldsheet perspective, the scattering amplitudes of long strings are obtained from a decoupling limit of open strings amplitudes on FZZT branes, which we compute by integrating Virasoro conformal blocks along with structure constants of boundary Liouville theory. In particular, we study the tree level amplitudes of (1) a long string decaying by emitting a closed string, and (2) the scattering of a pair of long strings. We show that they are indeed well defined as limits of open string amplitudes, and that our results are in striking numerical agreement with computations in the adjoint and bi-adjoint sectors of the dual matrix model (based on proposals of Maldacena and solutions due to Fidkowski), thereby providing strong evidence of the duality.
A New Recipe for Obtaining Central Volume Densities of Prestellar Cores from Size Measurements

We propose a simple analytical method for estimating the central volume density of prestellar molecular cloud cores from their column density profiles. Prestellar cores feature a flat central part of the column density and volume density profiles of the same size indicating the existence of a uniform-density inner region. The size of this region is set by the thermal pressure force which depends only on the central volume density and temperature of the core, and can provide a direct measurement of the central volume density. Thus, a simple length measurement can immediately yield a central density estimate independent of any dynamical model for the core and without the need for fitting. Using the radius at which the column density is 90% of the central value as an estimate of the size of the flat inner part of the column density profile yields an estimate of the central volume density within a factor of two for well-resolved cores.
TYPE II-P SUPERNOVAE AS STANDARD CANDLES: THE SDSS-II SAMPLE REVISITED

We revisit the observed correlation between the H{beta} and Fe II velocities for Type II-P supernovae (SNe II-P) using 28 optical spectra of 13 SNe II-P and demonstrate that it is well modeled by a linear relation with a dispersion of about 300 km s{sup -1}. Using this correlation, we re-analyze the publicly available sample of SNe II-P compiled by D'Andrea et al. and find a Hubble diagram with an intrinsic scatter of 11% in distance, which is nearly as tight as that measured before their sample is added to the existing set. The larger scatter reported in their work is found to be systematic, and most of it can be alleviated by measuring the H{beta} rather than Fe II velocities, due to the low signal-to-noise ratios and early epochs at which many of the optical spectra were obtained. Their sample, while supporting the mounting evidence that SNe II-P are good cosmic rulers, is biased toward intrinsically brighter objects and is not a suitable set to improve upon SN II-P correlation parameters. This will await a dedicated survey.
Spectral Characteristics of the Unitary Critical Almost-Mathieu Operator

We discuss spectral characteristics of a one-dimensional quantum walk whose coins are distributed quasi-periodically. The unitary update rule of this quantum walk shares many spectral characteristics with the critical Almost-Mathieu Operator; however, it possesses a feature not present in the Almost-Mathieu Operator, namely singularity of the associated cocycles (this feature is, however, present in the so-called Extended Harper’s Model). We show that this operator has empty absolutely continuous spectrum and that the Lyapunov exponent vanishes on the spectrum; hence, this model exhibits Cantor spectrum of zero Lebesgue measure for all irrational frequencies and arbitrary phase, which in physics is known as Hofstadter’s butterfly. In fact, we will show something stronger, namely, that all spectral parameters in the spectrum are of critical type, in the language of Avila’s global theory of analytic quasiperiodic cocycles. We further prove that it has empty point spectrum for each irrational frequency and away from a frequency-dependent set of phases having Lebesgue measure zero. The key ingredients in our proofs are an adaptation of Avila’s Global Theory to the present setting, self-duality via the Fourier transform, and a Johnson-type theorem for singular dynamically defined CMV matrices which characterizes their spectra as the set of spectral parameters at which the associated cocycles fail to admit a dominated splitting.
Fairway: a way to build fair ML software

Machine learning software is increasingly being used to make decisions that affect people's lives. But sometimes, the core part of this software (the learned model), behaves in a biased manner that gives undue advantages to a specific group of people (where those groups are determined by sex, race, etc.). This "algorithmic discrimination" in the AI software systems has become a matter of serious concern in the machine learning and software engineering community. There have been works done to find "algorithmic bias" or "ethical bias" in the software system. Once the bias is detected in the AI software system, the mitigation of bias is extremely important. In this work, we a)explain how ground-truth bias in training data affects machine learning model fairness and how to find that bias in AI software,b)propose a method Fairway which combines pre-processing and in-processing approach to remove ethical bias from training data and trained model. Our results show that we can find bias and mitigate bias in a learned model, without much damaging the predictive performance of that model. We propose that (1) testing for bias and (2) bias mitigation should be a routine part of the machine learning software development life cycle. Fairway offers much support for these two purposes.
A Unique Theory of Gravity and Matter

Abstract The author has previously suggested that the ground state for 4-dimensional quantumgravity can be represented as a condensation of non-linear gravitons connected by Dirac strings.In this note we suggest that the low-lying excitations of this state can be described by a quasi-topological action of the form ∫d 13 z F4∧F5∧F4 , corresponding to a trilinear coupling of solitonic 8-branes and 7-branes. It is shownthat when the excitations associated with F5 are neglected, the effective action can beinterpreted as a theory of conformal gravity in four dimensions. This in turn suggests that ordinarygravity as well supersymmetric matter and phenomenological gauge symmetries arise from thespontaneous breaking of topological invariance. The possibly deep mathematical significance ofthis theory is also noted. 1999 Elsevier Science Ltd.
Many-electron effects on optical absorption spectra of strained graphene

We use the first-principles GW + Bethe–Salpeter equation approach to study the electronic structure and optical absorption spectra of uniaxial strained graphene. Applied strain induces an anisotropic Fermi velocity and tilts the axis of the Dirac cone. As a result, the optical response of strained graphene is dramatically changed; the optical absorption is anisotropic; the characteristic single optical absorption peak of pristine graphene is split into two peaks with enhanced excitonic effects. Within the infrared regime, the optical absorbance of uniaxial strained graphene is no longer a constant because of the broken symmetry and anisotropic excitonic effects. Within the visible-light regime, we observe a prominent optical absorption peak due to an enhanced red shift by electron–hole interactions, enabling us to change the visible color and transparency of stretched graphene. Finally, we also reveal enhanced excitonic effects within the ultraviolet regime, where a few nearly bound excitons are identified.
The simplicial boundary of a CAT(0) cube complex

For a CAT(0) cube complex X , we define a simplicial flag complex @4X , called the simplicial boundary, which is a natural setting for studying nonhyperbolic behavior of X . We compare @4X to the Roller, visual and Tits boundaries of X , give conditions under which the natural CAT(1) metric on @4X makes it isometric to the Tits boundary, and prove a more general statement relating the simplicial and Tits boundaries. The simplicial boundary @4X allows us to interpolate between studying geodesic rays in X and the geometry of its contact graph X , which is known to be quasi-isometric to a tree, and we characterize essential cube complexes for which the contact graph is bounded. Using related techniques, we study divergence of combinatorial geodesics in X using @4X . Finally, we rephrase the rank-rigidity theorem of Caprace and Sageev in terms of group actions on X and @4X and state characterizations of cubulated groups with linear divergence in terms of X and @4X .
PBW deformations of Artin–Schelter regular algebras

We consider properties and extensions of PBW deformations of Artin–Schelter regular algebras. PBW deformations in global dimension two are classified and the geometry associated to the homogenizations of these algebras is exploited to prove that all simple modules are one-dimensional in the non-PI case. It is shown that this property is maintained under tensor products and certain skew polynomial extensions.
Chess players' fame versus their merit.

We investigate a pool of international chess title holders born between 1901 and 1943. Using Elo ratings, we compute for every player his expected score in a game with a randomly selected player from the pool. We use this figure as the player’s merit. We measure players’ fame as the number of Google hits. The correlation between fame and merit is 0.38. At the same time, the correlation between the logarithm of fame and merit is 0.61. This suggests that fame grows exponentially with merit.
Molecular Clouds: Internal Properties, Turbulence, Star Formation and Feedback

All stars are born in molecular clouds, and most in giant molecular clouds (GMCs), which thus set the star formation activity of galaxies. We first review their observed properties, including measures of mass surface density, �, and thus mass, M. We discuss cloud dynamics, concluding most GMCs are gravitationally bound. Star formation is highly clustered within GMCs, but overall is very inefficient. We compare properties of star-forming clumps with those of young stellar clusters (YSCs). The high central densities of YSCs may result via dynamical evolution of already-formed stars during and after star cluster formation. We discuss theoretical models of GMC evolution, especially addressing how turbulence is maintained, and emphasizing the importance of GMC collisions. We describe how feedback limits total star formation effi- ciency, ǫ, in clumps. A turbulent and clumpy medium allows higher ǫ, permitting formation of bound clusters even when escape speeds are less than the ionized gas sound speed.
The flavor-locked flavorful two Higgs doublet model

We propose a new framework to generate the Standard Model (SM) quark flavor hierarchies in the context of two Higgs doublet models (2HDM). The ‘flavorful’ 2HDM couples the SM-like Higgs doublet exclusively to the third quark generation, while the first two generations couple exclusively to an additional source of electroweak symmetry breaking, potentially generating striking collider signatures. We synthesize the flavorful 2HDM with the ‘flavor-locking’ mechanism, that dynamically generates large quark mass hierarchies through a flavor-blind portal to distinct flavon and hierarchon sectors: dynamical alignment of the flavons allows a unique hierarchon to control the respective quark masses. We further develop the theoretical construction of this mechanism, and show that in the context of a flavorful 2HDM-type setup, it can automatically achieve realistic flavor structures: the CKM matrix is automatically hierarchical with |Vcb| and |Vub| generically of the observed size. Exotic contributions to meson oscillation observables may also be generated, that may accommodate current data mildly better than the SM itself.
Advanced Physical-Layer Technologies in VHF Data Link Communications

The VHF band has been widely used for aviation voice communication using analog communication systems for decades. However, due to fast increasing transportation and high usage of VHF channels, the band is becoming much more crowded, and use of analog waveforms will likely not maintain the required performance and quality of service in the future. Therefore, digital communication systems have been considered and studied due to their larger spectral efficiency. Notably, digital systems proposed for VHF are broadband VHF (B-VHF) using multi carrier-code division multiple access (MC-CDMA), and VHF data link modes 2 and 3 (VDL2/3) using differential 8-state phase shift keying (D8PSK) modulation. Compared to B-VHF, VDL2/3 has received more attention due to its simplicity and more constant amplitude waveform, yielding lower peak-to-average power ratio (PAPR) and hence better energy efficiency. Recently, advanced VHF digital link (A-VDL) was proposed for VHF [1]. This scheme enables use same platform as VDL except for the physical layer processing, including modulation. The proposed A-VDL, following digital video broadcasting satellite second-generation (DVB-S2) standard, uses amplitude and phase-shift keying (APSK) modulation with higher modulation order than VDL, hence providing higher spectral efficiency than VDL. Compared to the widely used quadrature amplitude modulation (QAM), APSK is more resistant to amplifier amplitude and phase distortions. Thus, APSK has become of interest for satellite communications, as well as VHF communications in A-VDL. In this paper, we investigate other advanced technologies such as channel encoding techniques used in DVB-S2, low-density parity-check (LDPC) codes, more efficient standardized voice encoders, as well as better pulse shaping filters than the classical square-root raised-cosine (SRRC) filter used in VDL and A-VDL. Via simulations and analysis, we compare the proposed scheme's link margin, PAPR, and spectral efficiency compared to VDL and A-VDL, which both use Reed Solomon (RS) encoding. In addition, as another way of generating the same VDL waveforms (or possibly other single-carrier aeronautical band waveforms), we investigate the single-carrier type waveform used in cellular LTE and 5G uplink communication links: the discrete Fourier transform-spread OFDM (DFT-s-OFDM), and discuss how we can take advantage of using the same LTE and 5G hardware resources.
Searching for Standard Model adjoint scalars with diboson resonance signatures

We explore the phenomenology of scalar fields in the adjoint representation of SM gauge groups. We write a general set of dimension 5 effective operators in which SM adjoint scalars couple to pairs of standard model bosons. Using these effective operators, we explore new possible decay channels of a scalar color octet into a gluon and a Z boson, another gluon, or a photon. We recast several analyses from Run I of the LHC to find constraints on an a scalar octet decaying into these channels, and we project the discovery potential of color octets in our gluon+photon channel for the 14 TeV run of LHC.
Electromagnetically induced transparency at a chiral exceptional point

Electromagnetically induced transparency, as a quantum interference effect to eliminate optical absorption in an opaque medium, has found extensive applications in slow-light generation, optical storage, frequency conversion, optical quantum memory and enhanced nonlinear interactions at the few-photon level in all kinds of systems. Recently, there has been great interest in exceptional points, a type of spectral singularity that could be reached by tuning various parameters in open systems, to render unusual features to the physical systems, such as optical states with chirality. Here we theoretically and experimentally study transparency and absorption modulated by chiral optical states at exceptional points in an indirectly coupled resonator system. By tuning one resonator to an exceptional point, transparency or absorption occurs depending on the chirality of the eigenstate. Our results demonstrate a new strategy to manipulate the light flow and the spectra of a photonic resonator system by exploiting a discrete optical state associated with a specific chirality at an exceptional point as a unique control bit. Such an approach is compatible with the state control utilized in quantum gate operation and may open up new avenues for controlling slow light using optical states for optical quantum memory and computing. The optical analogue of electromagnetically induced transparency and absorption can be modulated by chiral optical states at an exceptional point, which is shown in a system of indirectly coupled microresonators.
Data-space inversion using a recurrent autoencoder for time-series parameterization

Data-space inversion (DSI) and related procedures represent a family of methods applicable for data assimilation in subsurface flow settings. These methods differ from usual model-based techniques in that they provide only posterior predictions for quantities (time series) of interest, not posterior models with calibrated parameters. DSI methods require a large number (O(500–1000)) of flow simulations to first be performed on prior geological realizations. Given observed data, posterior predictions for time series of interest, such as well injection or production rates, can then be generated directly. DSI operates in a Bayesian setting and provides posterior samples of the data vector. In this work, we develop and evaluate a new approach for data parameterization in DSI. Parameterization is useful in DSI as it reduces the number of variables to determine in the inversion, and it maintains the physical character of the data variables. The new parameterization uses a recurrent autoencoder (RAE) for dimension reduction, and a long short-term memory (LSTM) recurrent neural network architecture to represent flow-rate time series. The RAE-based parameterization is combined with an ensemble smoother with multiple data assimilation (ESMDA) for posterior data sample generation. Results are presented for two- and three-phase flows in a 2D channelized system and a 3D multi-Gaussian model. The new DSI RAE procedure, along with several existing DSI treatments, is assessed through detailed comparison to reference rejection sampling (RS) results. The new DSI methodology is shown to consistently outperform existing approaches, in terms of statistical (P10–P90 interval and Mahalanobis distance) agreement with RS results. The method is also shown to accurately capture derived quantities which are computed from variables considered directly in DSI. This requires correlation and covariance between variables to be properly captured, and accuracy in these relationships is demonstrated. The RAE-based parameterization developed here is clearly useful in DSI, and it may also find application in other subsurface flow problems.
Molecular cluster perturbation theory. I. Formalism

We present second-order molecular cluster perturbation theory (MCPT(2)), a linear scaling methodology to calculate arbitrarily large systems with explicit calculation of individual wave functions in a coupled-cluster framework. This new MCPT(2) framework uses coupled-cluster perturbation theory and an expansion in terms of molecular dimer interactions to obtain molecular wave functions that are infinite order in both the electronic fluctuation operator and all possible dimer (and products of dimers) interactions. The MCPT(2) framework has been implemented in the new SIA/Aces4 parallel architecture, making use of the advanced dynamic memory control and fine-grained parallelism to perform very large explicit molecular cluster calculations. To illustrate the power of this method, we have computed energy shifts, lattice site dipole moments, and harmonic vibrational frequencies via explicit calculation of the bulk system for the polar and non-polar polymorphs of solid hydrogen fluoride. The explicit lattice si...
First Interferometric Observations of Molecular Gas in a Polar Ring: The Helix Galaxy NGC 2685

We have detected four giant molecular cloud associations (sizes ≤66 ≈ 430 pc) in the western and eastern regions of the polar ring in NGC 2685 (the Helix galaxy) using the Owens Valley Radio Observatory millimeter interferometer. Emission from molecular gas is found close to the brightest Hα and H I peaks in the polar ring and is confirmed by new IRAM 30 m single-dish observations. The CO and H I line velocities are very similar, providing additional kinematic confirmation that the CO emission emerges from the polar ring. For the first time, the total molecular mass within a polar ring is determined [M ~ (8-11) × 106 M☉, using the standard Galactic conversion factor]. We detect about M ~ 4.4 × 106 M☉ in the nuclear region with the single dish. Our upper limit derived from the interferometric data is lower (M ≤ 0.7 × 106 M☉), suggesting that the molecular gas is distributed in an extended (≥1.3 kpc) diffuse disk. These new values are an order of magnitude lower than in previous reports. The total amount of molecular gas and the atomic gas content of the polar ring are consistent with formation due to accretion of a small gas-rich object, such as a dwarf irregular. The properties of the NGC 2685 system suggest that the polar ring and the host galaxy have been in a stable configuration for a considerable time (a few gigayears). The second (outer) H I ring within the disk of NGC 2685 is very likely at the outer Lindblad resonance of the ~11 kpc long stellar bar.
Ultraviolet, Optical, and Near-IR Microwave Kinetic Inductance Detector Materials Developments

We have fabricated 2024 pixel microwave kinetic inductance detector (MKID) arrays in the ultraviolet/optical/ near-IR (UVOIR) regime that are currently in use in astronomical instruments. In order to make MKIDs desirable for novel instruments, larger arrays with nearly perfect yield need to be fabricated. As array size increases, however, the percent yield often decreases due to frequency collisions in the readout. The per-pixel performance must also be improved, namely, the energy resolution. We are investigating ways to reduce frequency collisions and to improve the per-pixel performance of our devices through new superconducting material systems and fabrication techniques. There are two main routes that we are currently exploring. First, we are attempting to create more uniform titanium nitride films through the use of atomic layer deposition rather than the more traditional sputtering method. In addition, we are experimenting with completely new material systems for MKIDs, such as platinum silicide.
MULTIPLE AUTHORS DETECTION: A QUANTITATIVE ANALYSIS OF DREAM OF THE RED CHAMBER

Inspired by the authorship controversy of Dream of the Red Chamber and the application of machine learning in the study of literary stylometry, we develop a rigorous new method for the mathematical analysis of authorship by testing for a so-called chrono-divide in writing styles. Our method incorporates some of the latest advances in the study of authorship attribution, particularly techniques from support vector machines. By introducing the notion of relative frequency as a feature ranking metric, our method proves to be highly effective and robust. Applying our method to the Cheng–Gao version of Dream of the Red Chamber has led to convincing if not irrefutable evidence that the first 80 chapters and the last 40 chapters of the book were written by two different authors. Furthermore, our analysis has unexpectedly provided strong support to the hypothesis that Chapter 67 was not the work of Cao Xueqin either. We have also tested our method to the other three Great Classical Novels in Chinese. As expected no chrono-divides have been found. This provides further evidence of the robustness of our method.
The linking-unlinking game

Combinatorial two-player games have recently been applied to knot theory. Examples of this include the knotting-unknotting game and the region unknotting game, both of which are played on knot shadows. These are turn-based games played by two players, where each player has a separate goal to achieve in order to win the game. In this paper, we introduce the linking-unlinking game which is played on two-component link shadows. We then present winning strategies for the linking-unlinking game played on all shadows of two-component rational tangle closures and played on a large family of general two-component link shadows.
Star Formation for Predictive Primordial Galaxy Formation

The elegance of inflationary cosmology and cosmological perturbation theory ends with the formation of the first stars and galaxies, the initial sources of light that launched the phenomenologically rich process of cosmic reionization. Here we review the current understanding of early star formation, emphasizing unsolved problems and technical challenges. We begin with the first generation of stars to form after the Big Bang and trace how they influenced subsequent star formation. The onset of chemical enrichment coincided with a sharp increase in the overall physical complexity of star forming systems. Ab-initio computational treatments are just now entering the domain of the predictive and are establishing contact with local observations of the relics of this ancient epoch.
Inversion Charge Boost and Transient Steep-Slope Induced by Free-Charge-Polarization Mismatch in a Ferroelectric-Metal–Oxide–Semiconductor Capacitor

In this paper, the transient behavior of a ferroelectric (FE)-metal–oxide–semiconductor (MOS) capacitor is theoretically investigated with a series resistor. It is shown that compared with a conventional high-k dielectric MOS capacitor, a significant inversion charge boost can be achieved by an FE MOS capacitor due to a transient steep subthreshold swing (SS) driven by the free-charge-polarization mismatch. It is also shown that the observation of transient steep SS in the experiment significantly depends not only on the measurement time but also on the viscosity coefficient under Landau’s mean field theory, which in general represents the average FE time response associated with the domain nucleation and propagation. Therefore, this paper not only establishes a theoretical framework that describes the physical origin behind the inversion charge-boost in an FE MOS capacitor but also shows that the key feature of depolarization effect on an FE MOS capacitor in the steady state should be the inversion charge boost, rather than the steep SS (e.g., sub-60 mV/decade at room temperature), which cannot be experimentally observed as the measurement time is much longer than the intrinsic FE response. Finally, from the effect of viscosity coefficient on inversion charge boost, we outline the required material targets for the FE response in field-effect transistors to be applicable for next-generation high-speed and low-power digital switches.
Equivalence of Szegedy’s and coined quantum walks

Szegedy’s quantum walk is a quantization of a classical random walk or Markov chain, where the walk occurs on the edges of the bipartite double cover of the original graph. To search, one can simply quantize a Markov chain with absorbing vertices. Recently, Santos proposed two alternative search algorithms that instead utilize the sign-flip oracle in Grover’s algorithm rather than absorbing vertices. In this paper, we show that these two algorithms are exactly equivalent to two algorithms involving coined quantum walks, which are walks on the vertices of the original graph with an internal degree of freedom. The first scheme is equivalent to a coined quantum walk with one walk step per query of Grover’s oracle, and the second is equivalent to a coined quantum walk with two walk steps per query of Grover’s oracle. These equivalences lie outside the previously known equivalence of Szegedy’s quantum walk with absorbing vertices and the coined quantum walk with the negative identity operator as the coin for marked vertices, whose precise relationships we also investigate.
A compactness theorem for Fueter sections

We prove that a sequence of Fueter sections of a bundle of compact hyperkahler manifolds $\mathfrak X$ over a $3$-manifold $M$ with bounded energy converges (after passing to a subsequence) outside a $1$-dimensional closed rectifiable subset $S \subset M$. The non-compactness along $S$ has two sources: (1) Bubbling-off of holomorphic spheres in the fibres of $\mathfrak X$ transverse to a subset $\Gamma \subset S$, whose tangent directions satisfy strong rigidity properties. (2) The formation of non-removable singularities in a set of $\mathcal H^1$-measure zero. Our analysis is based on the ideas and techniques that Lin developed for harmonic maps. These methods also apply to Fueter sections on 4-dimensional manifolds; we discuss the corresponding compactness theorem in an appendix. We hope that the work in this paper will provide a first step towards extending the hyperkahler Floer theory developed by Hohloch-Noetzl-Salamon to general target spaces. Moreover, we expect that this work will find applications in gauge theory in higher dimensions.
Heat Diffusion with Frozen Boundary

Consider “frozen random walk” on $$\mathbb {Z}$$ : n particles start at the origin. At any discrete time, the leftmost and rightmost $$\lfloor {\frac{n}{4}}\rfloor $$ particles are “frozen” and do not move. The rest of the particles in the “bulk” independently jump to the left and right uniformly. The goal of this note is to understand the limit of this process under scaling of mass and time. To this end we study the following deterministic mass splitting process: start with mass 1 at the origin. At each step the extreme quarter mass on each side is “frozen”. The remaining “free” mass in the center evolves according to the discrete heat equation. We establish diffusive behavior of this mass evolution and identify the scaling limit under the assumption of its existence. It is natural to expect the limit to be a truncated Gaussian. A naive guess for the truncation point might be the 1 / 4 quantile points on either side of the origin. We show that this is not the case and it is in fact determined by the evolution of the second moment of the mass distribution.
Three-Point Functions of Quarter BPS Operators in N = 4 SYM

In a recent paper by Ryzhov [1], ¼-BPS chiral primaries were constructed in the fully interacting four dimensional = 4 Super-Yang-Mills theory with gauge group SU(N). These operators are annihilated by four supercharges, and at order g2 have protected scaling dimension and normalization. Here, we compute three-point functions involving these ¼-BPS operators along with ½-BPS operators. The combinatorics of the problem is rather involved, and we consider the following special cases: (1) correlators ½½BPS of two ½-BPS primaries with an arbitrary chiral primary; (2) certain classes of ½¼¼ and ¼¼¼ three-point functions; (3) three-point functions involving the Δ ≤ 7 operators found in [1]; (4) ½¼¼ correlators with the special ¼ made of single and double trace operators only. The analysis in cases (1)--(3) is valid for general N, while (4) is a large-N approximation. Order g2 corrections to all three-point functions considered in this paper are found to vanish. In the AdS/CFT correspondence, ¼-BPS chiral primaries are dual to threshold bound states of elementary supergravity excitations. We present a supergravity discussion of two- and three-point correlators involving these bound states.
Transport Measurements of Surface Electrons in 200-nm-Deep Helium-Filled Microchannels Above Amorphous Metallic Electrodes

We report transport measurements of electrons on helium in a microchannel device where the channels are 200 nm deep and $$3\,\mu \hbox {m}$$ wide. The channels are fabricated above amorphous metallic $$\hbox {Ta}_{40}\hbox {W}_{40}\hbox {Si}_{20}$$ , which has surface roughness below 1 nm and minimal variations in work function across the surface due to the absence of polycrystalline grains. We are able to set the electron density in the channels using a ground plane. We estimate a mobility of $${300}\,\hbox {cm}^2/\hbox {V}\,\hbox {s}$$ and electron densities as high as $$2.56\times 10^{9}\,\hbox {cm}^{-2}$$ . We demonstrate control of the transport using a barrier which enables pinch-off at a central microchannel connecting two reservoirs. The conductance through the central microchannel is measured to be 10 nS for an electron density of $$1.58\times 10^{9}\,\text {cm}^{-2}$$ . Our work extends transport measurements of surface electrons to thin helium films in microchannel devices above metallic substrates.
Improving Beckner's bound via Hermite functions

We obtain an improvement of the Beckner inequality ∥f∥22 −∥f∥p2 ≤ (2 − p)∥∇f∥22 valid for p ∈ [1,2] and the Gaussian measure. Our improvement is essential for the intermediate case p ∈ (1,2), and moreover, we find the natural extension of the inequality for any real p.
Free Motion of a Dirac Particle with a Minimum Uncertainty in Position

In this paper, we present a covariant, relativistic noncommutative algebra which includes two small deformation parameters. Using this algebra, we obtain a generalized uncertainty principle which predicts a minimal observable length in measurement of space-time distances. Then, we introduce a new representation for coordinate and momentum operators which leads to a generalized Dirac equation. The solutions of the generalized Dirac equation for a free particle will be explicitly obtained. We also obtain the modified fermionic propagator for a free Dirac particle.
Characterization of Errors in Interferometry with Entangled Atoms

Key ingredients for achieving atomic interferometers close to the Heisenberg limit are identified, providing a clear path towards the design of ultra-precise inertial sensors
Submatrix deconfinement and small black holes in AdS

Large N gauged multi-matrix quantum mechanical models usually have a first order Hagedorn transition, related to deconfinement. In this transition the change of the energy and entropy is of order N 2 at the critical temperature. This paper studies the microcanonical ensemble of the model at intermediate energies 1 ≪ E ≪ N 2 in the coexistence region for the first order phase transition. Evidence is provided for a partial deconfinement phase where submatrix degrees of freedom for a U(M) subgroup of U(N), with M ≪ N have an excitation energy of order M 2 and are effectively phase separated from the other degrees of freedom. These results also provide a simple example of the Susskind-Horowitz-Polchinski correspondence principle where a transition from a long string to a black hole is smooth. Implications for the dual configurations of small black holes in AdS are discussed.
Squashed entanglement and approximate private states

The squashed entanglement is a fundamental entanglement measure in quantum information theory, finding application as an upper bound on the distillable secret key or distillable entanglement of a quantum state or a quantum channel. This paper simplifies proofs that the squashed entanglement is an upper bound on distillable key for finite-dimensional quantum systems and solidifies such proofs for infinite-dimensional quantum systems. More specifically, this paper establishes that the logarithm of the dimension of the key system (call it $$\log _{2}K$$log2K) in an $$\varepsilon $$ź-approximate private state is bounded from above by the squashed entanglement of that state plus a term that depends only $$\varepsilon $$ź and $$\log _{2}K$$log2K. Importantly, the extra term does not depend on the dimension of the shield systems of the private state. The result holds for the bipartite squashed entanglement, and an extension of this result is established for two different flavors of the multipartite squashed entanglement.
Spin-Torque Sensors for Energy Efficient High-Speed Long Interconnects

In this paper, we propose a spin-torque (ST)-based sensing scheme that can enable energy efficient multibit long distance interconnect architectures. Current-mode interconnects have recently been proposed to overcome the performance degradations associated with conventional voltage-mode copper interconnects. However, the performance of current-mode interconnects are limited by analog current sensing transceivers and equalization circuits. As a solution, we propose the use of ST-based receivers that use magnetic tunnel junctions and simple digital components for current-to-voltage conversion, and do not require analog transceivers. We incorporate spin-Hall metal in our design to achieve high-speed sensing. We show both single and multibit operations that reveal major benefits at higher speeds. Our simulation results show that the proposed technique consumes only 3.93–4.72 fJ/b/mm energy while operating at 1–2 Gb/s, which is considerably better than existing charge-based interconnects. In addition, voltage-controlled magnetic anisotropy (VCMA) can reduce the required current at the sensor. With the inclusion of VCMA, the energy consumption can be further reduced to 2.02–4.02 fJ/b/mm.
ORBIT PARAMETRIZATIONS FOR K3 SURFACES

We study moduli spaces of lattice-polarized K3 surfaces in terms of orbits of representations of algebraic groups. In particular, over an algebraically closed field of characteristic 0, we show that in many cases, the nondegenerate orbits of a representation are in bijection with K3 surfaces (up to suitable equivalence) whose Neron–Severi lattice contains a given lattice. An immediate consequence is that the corresponding moduli spaces of these lattice-polarized K3 surfaces are all unirational. Our constructions also produce many fixed-point-free automorphisms of positive entropy on K3 surfaces in various families associated to these representations, giving a natural extension of recent work of Oguiso.
Nonexistence of nnsc fill-ins with large mean curvature

In this note we show that a closed Riemannian manifold does not admit a fill-in with nonnegative scalar curvature if the mean curvature is point-wise large. Similar result also holds for fill-ins with a negative scalar curvature lower bound.