Miracle-dz/UniFAR-FTUs huggingface dataset:
Exceptional reductions

Starting from basic identities of the group E8, we perform progressive reductions, namely decompositions with respect to the maximal and symmetric embeddings of E7 × SU(2) and then of E6 × U(1). This procedure provides a systematic approach to the basic identities involving invariant primitive tensor structures of various irreps of finite-dimensional exceptional Lie groups. We derive novel identities for E7 and E6, highlighting the E8 origin of some well-known ones. In order to elucidate the connections of this formalism to four-dimensional Maxwell–Einstein supergravity theories based on symmetric scalar manifolds (and related to irreducible Euclidean Jordan algebras, the unique exception being the triality-symmetric stu model), we then derive a fundamental identity involving the unique rank-4 symmetric invariant tensor of the 0-brane charge symplectic irrep of U-duality groups, with potential applications in the quantization of the charge orbits of supergravity theories, as well as in the study of multi-center black hole solutions therein.
Effect of valence fluctuations on the ground state properties of SmB6

SmB6 is a prototypical valence fluctuating material revealing properties of a narrow-gap semiconductor down to temperatures of a few Kelvin [1-4]. Paradoxically, at lowest temperatures it exhibits metallic-like conductivity, which is moreover smaller than the Mott's minimum metallic conductivity [1-3]. This fundamental discrepancy between theory and experiment is a subject of long-standing controversy precluding to conclude whether ground state of SmB6 is metallic, or insulating. According to latest research this anomalous conductivity behaviour has been attributed either to a conducting channel due to the existence of topologically protected surface states [5-7], or to the mechanism of valence-fluctuation induced hopping transport [8]. Unfortunately, in spite of half a century of intensive research in the field, convincing conclusion about the nature of the ground state in SmB6 is still missing. Here we show that valence-fluctuation caused uncertainty of impurity energies in the impurity band of SmB6 leads to a presence of occupied and unoccupied states above and below Fermi level, respectively, even in the ground state of SmB6, thus revealing that the subsystem of localized charge carriers in the ground state cannot be described by an energy distribution function for T = 0 K. This fundamental conclusion adds another reason for absence of resistivity divergence in SmB6 at lowest temperatures, and sheds new light on interpretation of experimental data obtained for SmB6 (and similar systems) near absolute zero. We believe that presented results will stimulate further studies aimed to understand nature of the ground state not only in valence fluctuating semiconductors, but also in many other systems having dynamical ground state.
ON THE IONIZATION OF LUMINOUS WMAP SOURCES IN THE GALAXY: CONSTRAINTS FROM He RECOMBINATION LINE OBSERVATIONS WITH THE GBT

Murray & Raham used the Wilkinson Microwave Anisotropy Probe (WMAP) free–free foreground emission map to identify diffuse ionized regions (DIRs) in the Galaxy. It has been found that the 18 most luminous WMAP sources produce more than half of the total ionizing luminosity of the Galaxy. We observed radio recombination lines (RRLs) toward the luminous WMAP source G49.75−0.45 with the Green Bank Telescope near 1.4 GHz. Hydrogen RRL is detected toward the source but no helium line is detected, implying that . This limit puts severe constraint on the ionizing spectrum. The total ionizing luminosity of G49 (3.05 × 1051 s−1) is ∼2.8 times the luminosity of all radio H ii regions within this DIR and this is generally the case for other WMAP sources. Murray & Rahman propose that the additional ionization is due to massive clusters (∼7.5 × 103 M☉ for G49) embedded in the WMAP sources. Such clusters should produce enough photons with energy ⩾24.6 eV to fully ionize helium in the DIR. Our observations rule out a simple model with G49 ionized by a massive cluster. We also considered “leaky” H ii region models for the ionization of the DIR, suggested by Lockman and Anantharamaiah, but these models also cannot explain our observations. We estimate that the helium ionizing photons need to be attenuated by ≳10 times to explain the observations. If selective absorption of He ionizing photons by dust is causing this additional attenuation, then the ratio of dust absorption cross sections for He and H ionizing photons should be ≳6.
Quasi-Periodic and Fractal Polymers: Energy Structure and Carrier Transfer

We study the energy structure and the coherent transfer of an extra electron or hole along aperiodic polymers made of N monomers, with fixed boundaries, using B-DNA as our prototype system. We use a Tight-Binding wire model, where a site is a monomer (e.g., in DNA, a base pair). We consider quasi-periodic (Fibonacci, Thue–Morse, Double-Period, Rudin–Shapiro) and fractal (Cantor Set, Asymmetric Cantor Set) polymers made of the same monomer (I polymers) or made of different monomers (D polymers). For all types of such polymers, we calculate the highest occupied molecular orbital (HOMO) eigenspectrum and the lowest unoccupied molecular orbital (LUMO) eigenspectrum, the HOMO–LUMO gap and the density of states. We examine the mean over time probability to find the carrier at each monomer, the frequency content of carrier transfer (Fourier spectra, weighted mean frequency of each monomer, total weighted mean frequency of the polymer), and the pure mean transfer rate k. Our results reveal that there is a correspondence between the degree of structural complexity and the transfer properties. I polymers are more favorable for charge transfer than D polymers. We compare k(N) of quasi-periodic and fractal sequences with that of periodic sequences (including homopolymers) as well as with randomly shuffled sequences. Finally, we discuss aspects of experimental results on charge transfer rates in DNA with respect to our coherent pure mean transfer rates.
Globular cluster clustering and tidal features around ultra-compact dwarf galaxies in the halo of NGC 1399

We present a novel approach to constrain the formation channels of ultra-compact dwarf galaxies (UCDs). They most probably are an inhomogeneous class of objects, composed of remnants of tidally stripped dwarf elliptical galaxies and star clusters that occupy the high mass end of the globular cluster luminosity function. We use three methods to unravel their nature: 1) we analyzed their surface brightness profiles; 2) we carried out a direct search for tidal features around UCDs; and 3) we compared the spatial distribution of GCs and UCDs in the halo of their host galaxy. Based on FORS2 observations under excellent seeing conditions, we studied the detailed structural composition of a large sample of 97 UCDs in the halo of NGC 1399, the central galaxy of the Fornax cluster, by analyzing their surface brightness profiles. We found that 13 of the UCDs were resolved above the resolution limit of 23 pc and we derived their structural parameters fitting a single Sérsic function. When decomposing their profiles into composite King and Sérsic profiles, we find evidence for faint stellar envelopes at μ =∼ 26 mag arcsec−2, surrounding the UCDs up to an extension of 90 pc in radius. We also show new evidence for faint asymmetric structures and tidal tail-like features surrounding several of these UCDs, a possible tracer of their origin and assembly history within their host galaxy halos. In particular, we present evidence for the first discovery of a significant tidal tail with an extension of ∼350 pc around UCD-FORS 2. Finally, we studied the local overdensities in the spatial distribution of globular clusters within the halo of NGC 1399 out to 110 kpc to see if they are related to the positions of the UCDs. We found a local overabundance of globular clusters on a scale of ≤1 kpc around UCDs, when we compared it to the distribution of globulars from the host galaxy. This effect is strongest for the metal-poor blue GCs. We discuss how likely it is that these clustered globulars were originally associated with the UCD, either as globular cluster systems of a nucleated dwarf galaxy that was stripped down to its nucleus, or as a surviving member of a merged super star cluster complex.
The Revival of (0,2) Linear Sigma Models

Compactifications of the heterotic string are a viable route to phenomenologically realistic vacua and interesting new mathematics. While supergravity aspects of heterotic compactifications are largely well-understood their worldsheet description remains largely unexplored. We review recent work in developing linear sigma model techniques aimed at elucidating the underlying worldsheet description.
Confinements regulate capillary instabilities of fluid threads

We study the breakup of confined fluid threads at low flow rates to understand instability mechanisms. To determine the critical conditions between the earlier quasi-stable necking stage and the later unstable collapse stage, simulations and experiments are designed to operate at an extremely low flow rate. The critical mean radii at the neck centres are identified by the stop-flow method for elementary microfluidic configurations. Two distinct origins of capillary instabilities are revealed for different confinement situations. One is the gradient of capillary pressure induced by the confinements of geometry and external flow, whereas the other is the competition between the capillary pressure and internal pressure determined by the confinements.
Direct assessment of Kolmogorov's first refined similarity hypothesis

Using volumetric velocity data from a turbulent laboratory water flow and numerical simulations of homogeneous, isotropic turbulence, we present a direct experimental and numerical assessment of Kolmogorov's first refined similarity hypothesis based on three-dimensional measurements of the local energy dissipation rate $\epsilon_r$ measured at dissipative scales $r$. We focus on the properties of the stochastic variables $V_L = \Delta u(r)/(r \epsilon_r)^{1/3}$ and $V_T = \Delta v(r)/(r\epsilon_r)^{1/3}$, where $\Delta u(r)$ and $\Delta v(r)$ are longitudinal and transverse velocity increments. Over one order of magnitude of scales $r$ within the dissipative range, the distributions of $V_L$ and $V_T$ from both experiment and simulation collapse when parameterised by a suitably defined local Reynolds number, providing the first conclusive experimental evidence in support of the first refined similarity hypothesis and its universality.
Neutrino luminosities and heat capacities of neutron stars in analytic form

We derive analytic approximations for the neutrino luminosities and the heat capacities of neutron stars with isothernal nucleon cores as functions of the mass and radius of stars. The neutrino luminosities are approximated for the three basic neutrino emission mechanisms, and the heat capacities for the five basic combinations of the partial heat capacities. The approximations are valid for for a wide class of equations of state of dense nucleonmatter. The results significantly simplify the theoretical interpretation of observations of cooling neutron stars as well as of quasistationary thermal states of neutron stars in X-ray transients. For illustration, we present an analysis of the neutrino cooling functions of nine isolated neutron stars taking into account the effects of their magnetic fields and of the presence of light elements in their heat blanketing envelopes. These results allow one to investigate the superfluid properties of neutron star cores.
2001 QR322 – an update on Neptune’s first unstable Trojan companion

The Neptune Trojans are the most recent addition to the panoply of Solar system small body populations. The orbit of the first discovered member, 2001 QR322, was investigated shortly after its discovery, based on early observations of the object, and it was found to be dynamically stable on timescales comparable to the age of the Solar system. As further observations were obtained of the object over the following years, the best-fit solution for its orbit changed. We therefore carried out a new study of 2001 QR322’s orbit in 2010, finding that it lay on the boundary between dynamically stable and unstable regions in Neptune’s Trojan cloud, and concluding that further observations were needed to determine the true stability of the object’s orbit. Here we follow up on that earlier work, and present the preliminary results of a dynamical study using an updated fit to 2001 QR322’s orbit. Despite the improved precision with which the orbit of 2001 QR322 is known, we find that the best-fit solution remains balanced on a knife-edge, lying between the same regions of stability and instability noted in our earlier work. In the future, we intend to carry out new observations that should hopefully refine the orbit to an extent that its true nature can finally be disentangled.
Radiative Grain Alignment in Protoplanetary Disks: Implications for Polarimetric Observations

We apply the theory of radiative torque (RAT) alignment for studying protoplanetary disks around a T-Tauri star and perform 3D radiative transfer calculations to provide the expected maps of polarized radiation to be compared with observations, such as with ALMA. We revisit the issue of grain alignment for large grains expected in the protoplanetary disks and find that mm-sized grains at the midplane do not align with the magnetic field since the Larmor precession timescale for such large grains becomes longer than the gaseous damping timescale. Hence, for these grains the RAT theory predicts that the alignment axis is determined by the grain precession with respect to the radiative flux. As a result, we expect that the polarization will be in the azimuthal direction for a face-on disk. It is also shown that if dust grains have superparamagnetic inclusions, magnetic field alignment is possible for (sub-)micron grains at the surface layer of disks, and this can be tested by mid-infrared polarimetric observations.
Dynamics of geometric and entropic quantifiers of correlations in open quantum systems

We extend the Hilbert-Schmidt (square norm) distance, previously used to define the geometric quantum discord, to define also geometric quantifiers of total and classical correlations. We then compare the dynamics of geometric and entropic quantifiers of the different kinds of correlations in a non-Markovian open two-qubit system under local dephasing. We find that qualitative differences occur only for quantum discords. This is taken to imply that geometric and entropic discords are not, in general, equivalent in describing the dynamics of quantum correlations. We then show that also geometric and entropic quantifiers of total correlations present qualitative disagreements in the state space. This aspect indicates that the differences found for quantum discord are not attributable to a different separation, introduced by each measure, between the quantum and classical parts of correlations. Finally, we find that the Hilbert-Schmidt distance formally coincides with a symmetrized form of linear relative entropy.
Landau–Zener transitions in a semiconductor quantum dot

We study the transitions between neighboring energy levels in a quasi-one-dimensional semiconductor quantum dot with two interacting electrons in it, when it is subject to a linearly time-dependent electric field. We analyze the applicability of a simple two-level Landau–Zener model to describe the evolution of the probability amplitudes in this realistic system. We show that the Landau–Zener model works very well when it is viewed in the adiabatic basis, but it is not as robust in the diabatic basis.
An animated realistic head with vocal tract for the finite element simulation of vowel /a/

Three-dimensional (3D) acoustic models can accurately simulate the voice production mechanism. These models require detailed 3D vocal tract geometries through which sound waves propagate. A few open source databases typically based on magnetic resonance imaging (MRI) are already available in literature. However, the 3D geometries they contain are mainly focused on the vocal tract and remove the head, which limits the computational domain of the simulations. This work develops a unified model consisting of an MRI-based vocal tract geometry set in a realistic head. The head is generated from scratch based on anatomical data of another subject, and contains different layers that add an organic appearance to the character. It is then not only designed to allow accurate finite element simulations of vowels, but more importantly, it can also be animated to add a realistic visual layer to the generated sound. This is expected to help in the dissemination of results and also to open potential applications in the audiovisual and animation sector. This paper shows the first results of the model focusing on the vowel /a/.
Examination of Trapping Effects on Single-Event Transients in GaN HEMTs

The effect of various trapping centers on single-event transients (SETs) in GaN high-electron-mobility transistors (HEMTs) is examined via calibrated technology computer-aided design (TCAD) simulations. A single-channel, Schottky-gate HEMT computational model is developed and validated with static characteristics and single-photon absorption laser data. Simulations of SETs show that a 2-D electron gas (2-DEG) enhancement effect occurs, which leads to additional collected charge above the generated charge. The origins of this effect are examined and shown to result from an increase in the occupation rate of the surface donor traps as the influx of charge is developed in the charge track. Variations in trap characteristics are then introduced, and their effect on internal charge collection processes is examined. It is further shown that the SET response is dominated by the properties of the surface donor traps (i.e., energy level and density) such that the SET drain current closely follows the transient decay of occupation rate back to the original dc level.
Quantum geometry with a nondegenerate vacuum: a toy model

Motivated by a recent proposal (by Koslowski-Sahlmann) of a kinematical representation in Loop Quantum Gravity (LQG) with a nondegenerate vacuum metric, we construct a polymer quantization of the parametrised massless scalar field theory on a Minkowskian cylinder. The dif- feomorphism covariant kinematics is based on states which carry a continuous label corresponding to smooth embedding geometries, in addition to the discrete embedding and matter labels. The physical state space, obtained through group averaging procedure, is nonseparable. A physical state in this theory can be interpreted as a quantum spacetime, which is composed of discrete strips and supercedes the classical continuum. We find that the conformal group is broken in the quantum theory, and consists of all Poincare translations. These features are remarkably different compared to the case without a smooth embedding. Finally, we analyse the length operator whose spectrum is shown to be a sum of contributions from the continuous and discrete embedding geometries, being in perfect analogy with the spectra of geometrical operators in LQG with a nondegenerate vacuum geometry.
SPECTRAL INDEX AS A FUNCTION OF MASS ACCRETION RATE IN BLACK HOLE SOURCES: MONTE CARLO SIMULATIONS AND AN ANALYTICAL DESCRIPTION

We present herein a theoretical study of correlations between spectral indexes of X-ray emergent spectra and mass accretion rate () in black hole (BH) sources, which provide a definitive signature for BHs. It has been firmly established, using the Rossi X-ray Timing Explorer (RXTE) in numerous BH observations during hard-soft state spectral evolution, that the photon index of X-ray spectra increases when increases and, moreover, the index saturates at high values of . In this paper, we present theoretical arguments that the observationally established index saturation effect versus mass accretion rate is a signature of the bulk (converging) flow onto the BH. Also, we demonstrate that the index saturation value depends on the plasma temperature of converging flow. We self-consistently calculate the Compton cloud (CC) plasma temperature as a function of mass accretion rate using the energy balance between energy dissipation and Compton cooling. We explain the observable phenomenon, index– correlations using a Monte Carlo simulation of radiative processes in the innermost part (CC) of a BH source and we account for the Comptonization processes in the presence of thermal and bulk motions, as basic types of plasma motion. We show that, when increases, BH sources evolve to high and very soft states (HSS and VSS, respectively), in which the strong blackbody(BB)-like and steep power-law components are formed in the resulting X-ray spectrum. The simultaneous detections of these two components strongly depends on sensitivity of high-energy instruments, given that the relative contribution of the hard power-law tail in the resulting VSS spectrum can be very low, which is why, to date RXTE observations of the VSS X-ray spectrum have been characterized by the presence of the strong BB-like component only. We also predict specific patterns for high-energy e-fold (cutoff) energy (Efold) evolution with for thermal and dynamical (bulk) Comptonization cases. For the former case, Efold monotonically decreases with , in the latter case, the Efold decrease is followed by its increase at high values of . The observational evolution of Efold versus can be another test for the presence of a converging flow effect in the formation of the resulting spectra in the close vicinity of BHs.
Spectroscopy of Dwarf Stars Around the North Celestial Pole

New space missions (e.g., NASA-TESS and ESA-PLATO) will perform an in-depth analysis of bright stars in large fields of the celestial sphere searching for extraterrestrial planets and investigating their host-stars. Asteroseismic observations will search for exoplanet-hosting stars with solar-like oscillations. In order to achieve all the goals, a full characterization of the stellar objects is important. However, accurate atmospheric parameters are available for less than 30% of bright dwarf stars of the solar neighborhood. In this study we observed high-resolution (R = 60,000) spectra for all bright (V < 8 mag) and cooler than F5 spectral class dwarf stars in the northern-most field of the celestial sphere with radius of 20° from the α(2000) = 161. °03 and δ(2000) = 86. °60 that is a center of one of the preliminary ESO-PLATO fields. Spectroscopic atmospheric parameters were determined for 140 slowly rotating stars, for 73% of them for the first time. The majority (83%) of the investigated stars are in the TESS object lists and all of them are in the preliminary PLATO field. Our results have no systematic differences when compared with other recent studies. We have 119 stars in common with the Geneva–Copenhagen Survey, where stellar parameters were determined photometrically, and find a 14 ± 125 K difference in effective temperatures, 0.01 ± 0.16 in log g, and −0.02 ± 0.09 dex in metallicities. Comparing our results for 39 stars with previous high-resolution spectral determinations, we find only a 7 ± 73 K difference in effective temperatures, 0.02 ± 0.09 in log g, and −0.02 ± 0.09 dex in metallicities. We also determined basic kinematic and orbital parameters for this sample of stars. From the kinematical point of view, almost all our stars belong to the thin disk substructure of the Milky Way. The derived galactocentric metallicity gradient is −0.066 ± 0.024 dex kpc−1 (2.5σ significance) and the vertical metallicity gradient is −0.102 ± 0.099 dex kpc−1 (1σ significance) that comply with the latest inside-out thin disk formation models, including those with stellar migration taken into account.