Miracle-dz/UniFAR-FTUs huggingface dataset:
Polar metals as electrodes to suppress the critical-thickness limit in ferroelectric nanocapacitors

Enhancing the performance of nanoscale ferroelectric (FE) field-effect transistors and FE capacitors for memory devices and logic relies on miniaturizing the metal electrode/ferroelectric area and reducing the thickness of the insulator. Although size reductions improve data retention, deliver lower voltage threshold switching, and increase areal density, they also degrade the functional electric polarization. There is a critical, nanometer length $t_\mathrm{FE}^*$ below which the polarization disappears owing to depolarizing field effects. Here we show how to overcome the critical thickness limit imposed on ferroelectricity by utilizing electrodes formed from a novel class of materials known as polar metals. Electronic structure calculations on symmetric polar-metal electrode/FE capacitor structures demonstrate that electric polarizations can persist to the sub-nanometer scale with $t_\mathrm{FE}^*\rightarrow0$ when a component of the polar axis in the electrode is perpendicular to the electrode/insulator interface. Our results reveal the importance of interfacial dipolar coherency in sustaining the polarization, which provides a platform for atomic scale structure-based design of functions that deteriorate in reduced dimensions.
MEMS-based frequency modulation of fiber ring laser

Fiber lasers are gaining wide attention nowadays due to their high stability, high reliability, low cost and compactness. Frequency modulation of the laser system has many applications such as wavelength tuning, active mode locking, generation of optical frequency combs and fiber sensors in general. In this work, we report frequency modulation of fiber ring laser system using transmission-type corner cube in-plane MEMS phase modulator fabricated by DRIE technology on an SOI substrate. The fiber-coupled MEMS-based phase modulator is inserted in a multilongitudinal mode fiber ring laser, which has a free spectral range of 345 kHz. By varying the applied voltage on the MEMS device, a wide range of the frequency modulation index can be achieved.
Empirical Modeling of the Redshift Evolution of the [ N II ] /Hα Ratio for Galaxy Redshift Surveys

We present an empirical parameterization of the [N ii]/Hα flux ratio as a function of stellar mass and redshift valid at 0 < z < 2.7 and 8.5 < log ( M / M ⊙ ) < 11.0 . This description can (i) easily be applied to simulations for modeling [N ii]λ6584 line emission, (ii) deblend [N ii] and Hα in current low-resolution grism and narrow-band observations to derive intrinsic Hα fluxes, and (iii) reliably forecast the number counts of Hα emission-line galaxies for future surveys, such as those planned for Euclid and the Wide Field Infrared Survey Telescope (WFIRST). Our model combines the evolution of the locus on the Baldwin, Phillips & Terlevich (BPT) diagram measured in spectroscopic data out to z ∼ 2.5 with the strong dependence of [N ii]/Hα on stellar mass and [O iii]/Hβ observed in local galaxy samples. We find large variations in the [N ii]/Hα flux ratio at a fixed redshift due to its dependency on stellar mass; hence, the assumption of a constant [N ii] flux contamination fraction can lead to a significant under- or overestimate of Hα luminosities. Specifically, measurements of the intrinsic Hα luminosity function derived from current low-resolution grism spectroscopy assuming a constant 29% contamination of [N ii] can be overestimated by factors of ∼8 at log ( L ) > 43.0 for galaxies at redshifts z ∼ 1.5. This has implications for the prediction of Hα emitters for Euclid and WFIRST. We also study the impact of blended Hα and [N ii] on the accuracy of measured spectroscopic redshifts.
DETECTING COLLISIONS AND FINDING CONTACT DURATIONS IN EXPERIMENTAL GRANULAR FLOW

1PhD student, Dept. of Civil and Environmental Engineering, Saitama University (255 Shimo Okubo, Sakura ku, Saitama, Japan) E-mail: s05d2057@mail.saitama-u.acjp 2Member of JSCE, Assoc. Professor, Dept. of Civil and Environmental Engineering, Saitama University (255 Shimo Okubo, Sakura ku, Saitama, Japan) E-mail: iwa@mail.saitama-u.ac. jp 3Member of JSCE, Professor, Dept. of Civil and Environmental Engineering, Saitama University (255 Shimo Okubo, Sakura ku, Saitama, Japan) E-mail: m-oda@mail.saitama-u.ac. jp
An accurate linear model for redshift space distortions in the void–galaxy correlation function

Redshift space distortions within voids provide a unique method to test for environmental dependence of the growth rate of structures in low density regions, where effects of modified gravity theories might be important. We derive a linear theory model for the redshift space void-galaxy correlation that is valid at all pair separations, including deep within the void, and use this to obtain expressions for the monopole $\xi^s_0$ and quadrupole $\xi^s_2$ contributions. Our derivation highlights terms that have previously been neglected but are important within the void interior. As a result our model differs from previous works and predicts new physical effects, including a change in the sign of the quadrupole term within the void radius. We show how the model can be generalised to include a velocity dispersion. We compare our model predictions to measurements of the correlation function using mock void and galaxy catalogues modelled after the BOSS CMASS galaxy sample using the Big MultiDark $N$-body simulation, and show that the linear model with dispersion provides an excellent fit to the data at all scales, $0\leq s\leq120\;h^{-1}$Mpc. While the RSD model matches simulations, the linear bias approximation does not hold within voids, and care is needed in fitting for the growth rate. We show that fits to the redshift space correlation recover the growth rate $f(z=0.52)$ to a precision of $2.7\%$ using the simulation volume of $(2.5\;h^{-1}\mathrm{Gpc})^3$.
On the spreading of quantum walks starting from local and delocalized states

We investigate the ballistic spreading behavior of the one-dimensional discrete time quantum walks whose time evolution is driven by any balanced quantum coin. We obtain closed-form expressions for the long-time variance of position of quantum walks starting from any initial qubit (spin-$1/2$ particle) and position states following a delta-like (local), Gaussian and uniform probability distributions. By averaging over all spin states, we find out that the average variance of a quantum walk starting from a local state is independent of the quantum coin, while from Gaussian and uniform states it depends on the sum of relative phases between spin states given by the quantum coin, being non-dispersive for a Fourier walk and large initial dispersion. We also perform numerical simulations of the average probability distribution and variance along the time to compare them with our analytical results.
Supernovae feedback propagation: the role of turbulence

Modelling the propagation of supernova (SN) bubbles, in terms of energy, momentum, and spatial extent, is critical for simulations of galaxy evolution which do not capture these scales. To date, small-scale models of SN feedback predict that the evolution of above-mentioned quantities can be solely parametrized by average quantities of the surrounding gas, such as density. However, most of these studies neglect the turbulent motions of this medium. In this paper, we study the propagation and evolution of SNe in turbulent environments. We confirm that the time evolution of injected energy and momentum can be characterized by the average density. However, the details of the density structure of the interstellar medium play a crucial role in the spatial extent of the bubble, even at a given average density. We demonstrate that spherically symmetric models of SN bubbles do not model well their spatial extent, and therefore cannot not be used to design sub-grid models of SNe feedback at galactic and cosmological scales. (Less)
Low-frequency electromagnetic oscillations of the Earth-ionosphere cavity

The observational and theoretical work on the low-frequency electromagnetic oscillations of the earth-ionosphere cavity, known as the Schumann resonances, is reviewed. Additional theoretical considerations are introduced to allow the models to incorporate the asymmetries of the actual cavity. These models are used to explain the observed variations of the power and of the apparent frequency of the resonant modes. The theoretical studies show that the structure of the low D or C region of the ionosphere is critical to these resonances, and the observed frequencies must rule out certain proposed ionospheric models. The perturbations of the cavity are also studied, and comparisons are made between different types of perturbations. The resonance data from July 9, 1962, are used to confirm the tremendous extent of the ionospheric perturbations caused by the Starfish high-altitude nuclear explosion. The possible effects of natural perturbations are also examined.
RANDOM MATRIX THEORY AND CHIRAL SYMMETRY IN QCD

▪ Abstract Random matrix theory is a powerful way to describe universal correlations of eigenvalues of complex systems. It also may serve as a schematic model for disorder in quantum systems. In this review, we discuss both types of applications of chiral random matrix theory to the QCD partition function. We show that constraints imposed by chiral symmetry and its spontaneous breaking determine the structure of low-energy effective partition functions for the Dirac spectrum. We thus derive exact results for the low-lying eigenvalues of the QCD Dirac operator. We argue that the statistical properties of these eigenvalues are universal and can be described by a random matrix theory with the global symmetries of the QCD partition function. The total number of such eigenvalues increases with the square root of the Euclidean four-volume. The spectral density for larger eigenvalues (but still well below a typical hadronic mass scale) also follows from the same low-energy effective partition function. The valid.
Determination of the Total c ¯ c Production Cross Section in 340 GeV /c Σ − -Nucleus Interactions

The production of charmed particles by Σ − of 340 GeV /c momentum was studied in the hyperon beam experiment WA89 at the CERN-SPS, using the Ω -spectrometer. In two data-taking periods in 1993 and 1994 an integrated luminosity of 1600 µ b − 1 on copper and carbon targets was recorded. From the reconstruction of 930 ± 90 charm particle decays in 10 decay channels production cross sections for D, D, D − s and Λ +c were determined in the region x F > 0. Assuming an A 1 dependence of the cross section on the nucleon number, we calculate a total c ¯ c production cross section of σ cc ( x F > 0) = 5 . 3 ± 0 . 4 ( stat ) ± 1 . 0 ( syst ) + 1 . 0 (Ξ c ) µ b per nucleon. The last term is an upper limit on the unknown contribution from charmed-strange baryon production.
The shape-alignment relation in Λ cold dark matter cosmic structures

In this paper, we study the supercluster-cluster morphological properties using one of the largest (2 × 512 3 ) smoothed particle hydrodynamics (SPH)+N-body simulations of large- scale structure formation in acold dark matter (�CDM) model, based on the publicly available code GADGET . W efind that filamentary (prolate-like) shapes are the dominant su- percluster and cluster dark matter halo morphological feature, in agreement with previous studies. However, the baryonic gas component of the clusters is predominantly spherical. We investigate the alignment between cluster haloes (using either their dark matter or their bary- onic components) and their parent supercluster major-axis orientation, finding that clusters show such a preferential alignment. Combining the shape and the alignment statistics, we also find that the amplitude of supercluster-cluster alignment increases, although weakly, with supercluster filamentariness.
Tension of organizing filaments of scroll waves

We consider the asymptotic theory for the dynamics of organizing filaments of three-dimensional scroll waves. For a generic autowave medium where two dimensional vortices do not meander, we show that some of the coefficients of the evolution equation are always zero. This simpler evolution equation predicts a monotonic change of the total filament length with time, independently of initial conditions. Whether the filament will shrink or expand is determined by a single coefficient, the filament tension, that depends on the medium parameters. We illustrate the behaviour of scroll wave filaments with positive and negative tension by numerical experiments. In particular, we show that in the case of negative filament tension, the straight filament is unstable, and its evolution may lead to a multiplication of vortices.
Radio-frequency impedance measurements using a tunnel-diode oscillator technique

A resonant method based on a tunnel-diode oscillator for precision measurements of relative impedance changes in materials is described. The system consists of an effective self-resonant LC tank circuit driven by a forward-biased tunnel diode operating in its negative resistance region. Samples under investigation are placed in the core of an inductive coil and impedance changes are determined directly from the measured shift in resonance frequency. A customized low temperature insert is used to integrate this experiment with a commercial Model 6000 Physical Property Measurement System (Quantum Design). Test measurements on a manganese-based perovskite sample exhibiting colossal magnetoresistance indicate that this method is well suited to study the magnetoimpedance in these materials.
Suppression of weak localization and enhancement of noise by tunneling in semiclassical chaotic transport

We add simple tunneling effects and ray splitting into the recent trajectory-based semiclassical theory of quantum chaotic transport. We use this to derive the weak-localization correction to conductance and the shot noise for a quantum chaotic cavity (billiard) coupled to $n$ leads via tunnel barriers. We derive results for arbitrary tunneling rates and arbitrary (positive) Ehrenfest time ${\ensuremath{\tau}}_{E}$. For all Ehrenfest times, we show that the shot noise is enhanced by the tunneling, while the weak localization is suppressed. In the opaque barrier limit (small tunneling rates with large lead widths, such that the Drude conductance remains finite), the weak localization goes to zero linearly with the tunneling rate, while the Fano factor of the shot noise remains finite but becomes independent of the Ehrenfest time. The crossover from random matrix theory behavior $({\ensuremath{\tau}}_{E}=0)$ to classical behavior $({\ensuremath{\tau}}_{E}=\ensuremath{\infty})$ goes exponentially with the ratio of the Ehrenfest time to the paired-path survival time. The paired-path survival time varies between the dwell time (in the transparent barrier limit) and half the dwell time (in the opaque barrier limit). Finally, our method enables us to see the physical origin of the suppression of weak localization; it is due to the fact that tunnel barriers ``smear'' the coherent-backscattering peak over reflection and transmission modes.
Dark matter in the inner parts of barred galaxies : The data

This paper presents surface photometry ( B, V, I, J, H, K) and Ha rotation curves of 27 isolated spiral galaxies. The final goal is to obtain the mass distribution of a sample of isolated spiral galaxies in order to model their gas kinematics. This is then compared to the observed rotation curve, to determine the necessity of a dark halo in the inner parts (Perez et al. 2004, AA Marquez & Moles 1999, AA Baggett et al. 1998, AJ, 116, 1626). Regarding the Kormendy relation ( Kormendy 1977, ApJ, 218, 333), in agreement with de Jong, no correlation between the bulge effective radius and its surface brightness is found, possibly due to the small range of bulge magnitudes covered. We find a smaller scatter in the structural relations when compared to non-isolated samples in agreement with Marquez & Moles ( 1999). Finally, a correlation between the disk scale-length and the bar size is observed, possibly reflecting the rapid growth of a bar.
Assessing the impact of bulk and shear viscosities on large scale structure formation

It is analyzed the effects of both bulk and shear viscosities on the perturbations, relevant for structure formation in late time cosmology. It is shown that shear viscosity can be as effective as the bulk viscosity on suppressing the growth of perturbations and delaying the nonlinear regime. A statistical analysis of the shear and bulk viscous effects is performed and some constraints on these viscous effects are given.
MACHOs in a Flattened Halo

If massive compact halo objects (MACHOs) are detected in ongoing searches, then τ SMC /τ LMC , the ratio of the optical depths toward the Small and Large Magellanic Clouds, will be a robust indicator of the flattening of the Galactic dark matter halo. For a spherical halo, τ SMC /τ LMC is about 1.45, independent of details of the shape of the Galactic rotation curve, the assumed mass of the Galactic disk and spheroid, and the truncation distance (if any) of the dark halo. For an E6 halo (axis ratio c/a=0.4), the ratio of optical depths is τ SMC /τ LMC ∼0.95 again independent of assumptions about Galactic parameters
An Optical Emission Line Survey of Large Planetary Nebulae

Accurate emission line fluxes from planetary nebulae (PNe) provide important constraints on the nature of the final phases of stellar evolution. Large, evolved PNe may trace the latest stages of PN evolution, where material from the AGB wind is returned to the interstellar medium. However, the low surface brightness and spatially extended emission of large PNe have made accurate measurements of line fluxes difficult with traditional long-slit spectroscopic techniques. Furthermore, distinguishing these nebulae from H II regions, supernova remnants, or interstellar gas ionized by a hot, evolved stellar core can be challenging. Here, we report on an ongoing survey of large Galactic PNe ($r > 5^\prime$) with the Wisconsin H-Alpha Mapper (WHAM), a Fabry-Perot spectrograph designed to detect faint diffuse optical emission lines with high sensitivity and spectral resolution. Our sample includes newly revealed $H\alpha$ enhancements from the AAO/UKST and WHAM $H\alpha$ surveys of Parker et al. and Haffner et al. We present accurate emission line fluxes of $H\alpha$, [N II]$\lambda$6583, and [O III]$\lambda$5007, and compare our data to other measurements. We use the emission line ratios and kinematics of the ionized gas to assess, or in some cases reassess, the identification of some nebulae.
Earth Similarity Index and Habitability Studies of Exoplanets

Study of exoplanets has been of considerable interest for Astronomers, Planetary Scientists and Astrobiologists. Analysis of huge planetary data from space missions such as CoRoT and Kepler is directed ultimately at finding a planet similar to Earth- the Earth's twin, and looking for potential habitability. The Earth Similarity Index (ESI) is defined to find the similarity with Earth, which ranges from 1 (Earth) to 0 (totally dissimilar to Earth). ESI can be computed using four physical parameters of a planet, namely radius, density, escape velocity and surface temperature. The surface temperature entering surface ESI is a non-observable quantity and what we know is only equilibrium temperature of exoplanets. We have established a relation between surface and equilibrium temperatures using the data available for the solar system objects to address the difficulty in determining surface temperature. From the ESI analysis, we have found 20 Earth-like exoplanets with ESI value above 0.8, which is set as the threshold. We are also interested in Mars-like planets to search for planets that may host the extreme life For example, methane-specific extremophile life form metabolism, for which a new approach, called Mars Similarity Index (MSI) is introduced. MSI is defined in the range between 1 (present Mars) and 0 (dissimilar to present Mars) and uses the same physical parameters as that of ESI. We introduced another new approach to study the potential habitability of exoplanets based on Cobb-Douglas Function, multi-parametric function. This did not yield any encouraging results.
Records of Auroral Candidates and Sunspots in Rikkokushi, Chronicles of Ancient Japan from Early 7th Century to 887

In this article, we present the results of the surveys on sunspots and auroral candidates in Rikkokushi, Japanese Official Histories from the early 7th century to 887 to review the solar and auroral activities. In total, we found one sunspot record and 13 auroral candidates in Rikkokushi. We then examine the records of the sunspots and auroral candidates, compare the auroral candidates with the lunar phase to estimate the reliability of the auroral candidates, and compare the records of the sunspots and auroral candidates with the contemporary total solar irradiance reconstructed from radioisotope data. We also identify the locations of the observational sites to review possible equatorward expansion of auroral oval. These discussions suggest a major gap of auroral candidates from the late 7th to early 9th century, which includes the minimum number of candidates reconstructed from the radioisotope data, a similar tendency as the distributions of sunspot records in contemporary China, and a relatively high magnetic latitude with a higher potential for observing aurorae more frequently than at present.
Estimating model bias over the complete nuclide chart with sparse Gaussian processes at the example of INCL/ABLA and double-differential neutron spectra

Predictions of nuclear models guide the design of nuclear facilities to ensure their safe and efficient operation. Because nuclear models often do not perfectly reproduce available experimental data, decisions based on their predictions may not be optimal. Awareness about systematic deviations between models and experimental data helps to alleviate this problem. This paper shows how a sparse approximation to Gaussian processes can be used to estimate the model bias over the complete nuclide chart at the example of inclusive double-differential neutron spectra for incident protons above 100\,MeV. A powerful feature of the presented approach is the ability to predict the model bias for energies, angles, and isotopes where data are missing. The number of experimental data points that can be taken into account is at least in the order of magnitude of~$10^4$ thanks to the sparse approximation. The approach is applied to the Li\`ege Intranuclear Cascade Model (INCL) coupled to the evaporation code ABLA. The results suggest that sparse Gaussian process regression is a viable candidate to perform global and quantitative assessments of models. Limitations of a philosophical nature of this (and any other) approach are also discussed.