Miracle-dz/UniFAR-FTUs huggingface dataset:
RANKTEST: Stata module to test the rank of a matrix using the Kleibergen-Paap rk statistic

ranktest implements the Kleibergen-Paap (2006) rk test for the rank of a matrix. Tests of the rank of a matrix have many practical applications. For example, in econometrics the requirement for identification is the rank condition, which states that a particular matrix must be of full column rank. Another example from econometrics concerns cointegration in vector autoregressive (VAR) models; the Johansen trace test is a test of a rank of a particular matrix. The traditional test of the rank of a matrix for the standard (stationary) case is the Anderson (1951) canonical correlations test. If we denote one list of variables as Y and a second as Z, and we calculate the squared canonical correlations between Y and Z, the LM form of the Anderson test, where the null hypothesis is that the matrix of correlations or regression parameters B between Y and Z has rank(B)=r, is N times the sum of the r+1 largest squared canonical correlations. A large test statistic and rejection of the null indicates that the matrix has rank at least r+1. The Cragg-Donald (1993) statistic is a closely related Wald test for the rank of a matrix. Both the Anderson and Cragg-Donald tests require the assumption that the covariance matrix has a Kronecker form; when this is not so, e.g., when disturbances are heteroskedastic or autocorrelated, the test statistics are no longer valid. The Kleibergen-Paap (2006) rk statistic is a generalization of the Anderson canonical correlation rank test to the case of a non-Kronecker covariance matrix. The implementation in ranktest will calculate rk statistics that are robust to various forms of heteroskedasticity, autocorrelation, and clustering.
Subordinacy and spectral theory for infinite matrices

The notion of subordinacy, previously used as a tool in the spectral theory of ordinary differential operators, is extended and applied to solutions of three-term recurrence relations. The resulting asymptotic analysis yields a complete description of the spectral behaviour of infinite tridiagonal matrices, and provides a unified approach to the spectral theory of such operators, without detailed special assumptions
In-Medium Effects in the Holographic Quark-Gluon Plasma

We use the gauge/gravity duality to investigate various properties of strongly coupled gauge theories, which we interpret as models for the quark-gluon plasma (QGP). In particular, we use variants of the D3/D7 setup as an implementation of the top-down approach of connecting string theory with phenomenologically relevant gauge theories. We focus on the effects of finite temperature and finite density on fundamental matter in the holographic quark-gluon plasma, which we model as the 𝒩=2 hypermultiplet in addition to the 𝒩=4 gauge multiplet of supersymmetric Yang-Mills theory. We use a setup in which we can describe the holographic plasma at finite temperature and either baryon or isospin density and investigate the properties of the system from three different viewpoints. (i) We study meson spectra. Our observations at finite temperature and particle density are in qualitative agreement with phenomenological models and experimental observations. They agree with previous publications in the according limits. (ii) We study the temperature and density dependence of transport properties of fundamental matter in the QGP. In particular, we obtain diffusion coefficients. Furthermore, in a kinetic model we estimate the effects of the coupling strength on meson diffusion and therewith equilibration processes in the QGP. (iii) We observe the effects of finite temperature and density on the phase structure of fundamental matter in the holographic QGP. We trace out the phase transition lines of different phases in the phase diagram.
A closer look at a coronal loop rooted in a sunspot umbra

Extreme UV (EUV) and X-ray loops in the solar corona connect regions of enhanced magnetic activity, but they are not usually rooted in the dark umbrae of sunspots because the strong magnetic field found there suppresses convection. This means that the Poynting flux of magnetic energy into the upper atmosphere is not significant within the umbra as long as there are no light bridges or umbral dots. Here we report a rare observation of a coronal loop rooted in the dark umbra of a sunspot without any traces of light bridges or umbral dots. We used the slit-jaw images and spectroscopic data from IRIS and concentrate on the line profiles of O IV and Si IV that show persistent strong redshifted components in the loop rooted in the umbra. Using the ratios of O IV, we can estimate the density and thus investigate the mass flux. The coronal context and temperature diagnostics of these observations is provided through the EUV channels of AIA. The coronal loop, embedded within cooler downflows, hosts supersonic downflows. The speed of more than 100 km s$^{-1}$ is on the same order of magnitude in the transition region lines of O IV and Si IV, and is even seen at comparable speed in the chromospheric Mg II lines. At a projected distance of within $1"$ of the footpoint, we see a shock transition to smaller downflow speeds of about 15 km s$^{-1}$ being consistent with mass conservation across a stationary isothermal shock. We see no direct evidence for energy input into the loop because the loop is rooted in the dark uniform part of the umbra with no light bridges or umbral dots near by. Thus one might conclude that we are seeing a siphon flow driven from the footpoint at the other end of the loop. However, for a final result data of similar quality at the other footpoint are needed, but this is too far away to be covered by the IRIS field of view.
Rapid decay of storm time ring current due to pitch angle scattering in curved field line

[1] The storm time ring current sometimes exhibits rapid decay, as suggested from the Dst index, but the underlying mechanism is unknown. By means of a simulation with pitch angle scattering due to the field line curvature (FLC), together with the charge exchange and adiabatic loss cone loss, we investigated rapid decay of the storm time ring current for the large magnetic storm that occurred on 12 August 2000. When all three loss processes were included, the Dst (SYM-H) index showed rapid recovery with an e-folding time of ∼6 h. However, without FLC scattering, the simulated Dst (SYM-H) index showed a slower recovery with an e-folding time of ∼12 h. Overall flux of energetic neutral hydrogen with energy ≥ 39 keV was significantly reduced by the FLC scattering and is consistent with data from the high energy neutral analyzer (HENA) on board the IMAGE satellite. Power of precipitating protons showed a fairly good agreement with data from the far ultraviolet (FUV) imager on board IMAGE. These fairly good agreements with observations lead to the possible conclusion that the FLC scattering is a significant loss mechanism for the ring current ions, and the main oval of the proton aurora is likely a manifestation of the precipitating loss of the protons for this particular storm.
Parameterizing scalar-tensor theories for cosmological probes

We study the evolution of density perturbations for a class of f(R) models which closely mimic ΛCDM background cosmology. Using the quasi-static approximation, and the fact that these models are equivalent to scalar-tensor gravity, we write the modified Friedmann and cosmological perturbation equations in terms of the mass M of the scalar field. Using the perturbation equations, we then derive an analytic expression for the growth parameter γ in terms of M, and use our result to reconstruct the linear matter power spectrum. We find that the power spectrum at z ~ 0 is characterized by a tilt relative to its General Relativistic form, with increased power on small scales. We discuss how one has to modify the standard, constant γ prescription in order to study structure formation for this class of models. Since γ is now scale and time dependent, both the amplitude and transfer function associated with the linear matter power spectrum will be modified. We suggest a simple parameterization for the mass of the scalar field, which allows us to calculate the matter power spectrum for a broad class of f(R) models.
Horizons cannot save the Landscape

Solutions with anti-D3 branes in a Klebanov-Strassler geometry with positive charge dissolved in fluxes have a certain singularity corresponding to a diverging energy density of the RR and NS-NS three-form fluxes. There are many hopes and arguments for and against this singularity, and we attempt to settle the issue by examining whether this singularity can be cloaked by a regular event horizon. This is equivalent to the existence of asymptotically Klebanov-Tseytlin or Klebanov-Strassler black holes whose charge measured at the horizon has the opposite sign to the asymptotic charge. We find that no such KT solution exists. Furthermore, for a large class of KS black holes we considered, the charge at the horizon must also have the same sign as the asymptotic charge, and is completely determined by the temperature, the number of fractional branes and the gaugino masses of the dual gauge theory. Our result suggests that antibrane singularities in backgrounds with charge in the fluxes are unphysical, which in turn raises the question as to whether antibranes can be used to uplift AdS vacua to deSitter ones. Our results also point out to a possible instability mechanism for the antibranes.
Transient Relativistic Ejections and Stationary Core in XTE J1752-223

The Galactic X-ray transient XTE J1752−223 was shown to have properties of black hole binary candidates. As reported in our previous paper, we identified transient and decelerating ejecta in multi-epoch Very Long Baseline Interferometry (VLBI) observations with the European VLBI Network (EVN) and the NRAO Very Long Baseline Array (VLBA). Here we present new EVN and VLBA data in which a new transient ejection event and later a stationary component are identified. The latter is interpreted as a reappearance of the radio core/compact jet during the transition from soft to hard X-ray state. This component appears to be highly variable in brightness although effects of tropospheric instabilities might play a role too. We also re-analyse the earlier VLBI data and find that the transient ejecta closer to the core position has significantly higher proper motion, further strengthening the case for strongly decelerating ejecta on the scale of several hundred milliarcsecond, never observed in X-ray binaries before. Although the distance of the source is not well constrained, it is clear that these ejectas are at least mildly relativistic at the early stages. Moreover, we show the large scale environment of the transient from the Westerbork synthesis array data recorded in parallel during the EVN run.
Relativistic effects on tidal disruption kicks of solitary stars

Solitary stars that wander too close to their galactic centres can become tidally disrupted, if the tidal forces due to the supermassive black hole residing there overcome the self-gravity of the star. If the star is only partially disrupted, so that a fraction survives as a self-bound object, this remaining core will experience a net gain in specific orbital energy, which translates into a velocity 'kick' of up to similar to 10(3) km s(-1). In this paper, we present the result of smoothed particle hydrodynamics simulations of such partial disruptions, and analyse the velocity kick imparted on the surviving core. We compare gamma = 5/3 and gamma = 4/3 polytropes disrupted in both a Newtonian potential, and a generalized potential that reproduces most relativistic effects around a Schwarzschild black hole either exactly or to excellent precision. For the Newtonian case, we confirm the results of previous studies that the kick velocity of the surviving core is virtually independent of the ratio of the black hole to stellar mass, and is a function of the impact parameter beta alone, reaching at most the escape velocity of the original star. For a given beta, relativistic effects become increasingly important for larger black holemasses. In particular, we find that the kick velocity increases with the black hole mass, making larger kicks more common than in the Newtonian case, as low-beta encounters are statistically more likely than high-beta encounters. The analysis of the tidal tensor for the generalized potential shows that our results are robust lower limits on the true relativistic kick velocities, and are generally in very good agreement with the exact results.
Measurement of g-factors of ground and excited optical states of Er3+ in YLiF4 and LuLiF4 in zero dc magnetic field by photon echo method

New scheme of definition of g-factors as ground as excited optical states of a paramagnetic ion in zero external constant magnetic field has been proposed and experimentally realized in optical systems in which Zeeman Effect is manifested. A pulse of a weak magnetic field leads to occurrence of relative phase shifts of the excited dipoles and, as consequence, to modulation of a photon echo waveform if magnetic pulse (MP) overlaps in time with echo-pulse. The modulation periods of the waveform depend on polarization of the laser light, which excites the photon echo. The values of these periods for and laser light polarization have been measured and then the g-factors of the ground I15/2 and excited F9/2 states of the Er ion in the LuLiF4 and the YLiF4 matrices have been determined. Values of the g-factors have been compared with the known literary data.
PROPAGATION OF RELATIVISTIC, HYDRODYNAMIC, INTERMITTENT JETS IN A ROTATING, COLLAPSING GRB PROGENITOR STAR

The prompt emission of gamma-ray bursts (GRBs) is characterized by rapid variabilities, which may be a direct reflection of the unsteady central engine. We perform a series of axisymmetric 2.5-dimensional simulations to study the propagation of relativistic, hydrodynamic, intermittent jets through the envelope of a GRB progenitor star. A realistic rapidly rotating star is incorporated as the background of jet propagation, and the star is allowed to collapse due to the gravity of the central black hole. By modeling the intermittent jets with constant-luminosity pulses with equal on and off durations, we investigate how the half period, T, affects the jet dynamics. For relatively small T values (e.g., 0.2 s), the jet breakout time tbo depends on the opening angle of the jet, with narrower jets more penetrating and reaching the surface at shorter times. For T ≤ 1 s, the reverse shock (RS) crosses each pulse before the jet penetrates through the stellar envelope. As a result, after the breakout of the first group of pulses at tbo, several subsequent pulses vanish before penetrating the star, causing a quiescent gap. For larger half periods (T = 2.0 and 4.0 s), all the pulses can successfully penetrate through the envelope, since each pulse can propagate through the star before the RS crosses the shell. Our results may interpret the existence of a weak precursor in some long GRBs, given that the GRB central engine injects intermittent pulses with a half period T ≤ 1 s. The observational data seem to be consistent with such a possibility.
Short-term dynamical evolution of grand-design spirals in barred galaxies

We investigate the short-term dynamical evolution of stellar grand-design spiral arms in barred spiral galaxies using a three-dimensional (3D) $N$-body/hydrodynamic simulation. Similar to previous numerical simulations of unbarred, multiple-arm spirals, we find that grand-design spiral arms in barred galaxies are not stationary, but rather dynamic. This means that the amplitudes, pitch angles, and rotational frequencies of the spiral arms are not constant, but change within a few hundred million years (i.e. the typical rotational period of a galaxy). We also find that the clear grand-design spirals in barred galaxies appear it only when the spirals connect with the ends of the bar. Furthermore, we find that the short-term behaviour of spiral arms in the outer regions ($R>$ 1.5--2 bar radius) can be explained by the swing amplification theory and that the effects of the bar are not negligible in the inner regions ($R<$ 1.5--2 bar radius). These results suggest that, although grand-design spiral arms in barred galaxies are affected by the stellar bar, the grand-design spiral arms essentially originate not as bar-driven stationary density waves, but rather as self-excited dynamic patterns. We imply that a rigidly rotating grand-design spiral could not be a reasonable dynamical model for investigating gas flows and cloud formation even in barred spiral galaxies.
TRANSITION TO THE DISK DOMINANT STATE OF A NEW ULTRALUMINOUS X-RAY SOURCE IN M82

We report on the identification of a third, new ultraluminous X-ray source in the starburst galaxy M82. Previously, the source was observed at fluxes consistent with the high state of Galactic black hole binaries (BHBs). We observe fluxes up to (6.5 ± 0.3) × 1039 erg s−1 in the ultraluminous regime. When the source is not in the low/hard state, spectral fitting using a multicolor disk model shows that the disk luminosity varies as the disk inner temperature raised to the power 4.8 ± 0.9, consistent with the behavior of Galactic BHBs in the thermal dominant state. Fitting the spectrum with a multicolor disk model with general relativistic corrections suggests that the source harbors a rapidly spinning black hole with a mass less than 100 solar masses. A soft excess was found in the source spectrum that could be blackbody emission from a photosphere created by a massive outflow. The source also showed soft dips during a flare.
Type I Seesaw Mechanism, Lepton Flavour Violation and Higgs Decays

We review and update the current phenomenological constraints on minimal type I seesaw extensions of the Standard Model in which New Physics content can be probed at the electroweak scale. In this class of models, the flavour structure of the neutrino Yukawa couplings is determined by the requirement of reproducing neutrino oscillation data. The strongest constraints on the seesaw parameter space are imposed by the very recent upper limit on μ → eγ decay rate. Searches of non-standard Higgs boson decays into a light and a heavy neutrino may also provide and independent test of these seesaw scenarios.
Spectra of helium clusters with up to six atoms using soft-core potentials

In this paper, we investigate small clusters of helium atoms using the hyperspherical harmonic basis. We consider systems with $A=2,3,4,5,6$ atoms with an interparticle potential which does not present a strong repulsion at short distances. We use an attractive Gaussian potential that reproduces the values of the dimer binding energy, the atom-atom scattering length, and the effective range obtained with one of the widely used He-He interactions, the Aziz and Slaman potential, called LM2M2. In systems with more than two atoms, we consider a repulsive three-body force that, by construction, reproduces the trimer binding energy of the LM2M2 potential. With this model, consisting of the sum of a two- and three-body potential, we have calculated the spectrum of clusters formed by four, five, and six helium atoms. We have found that these systems present two bound states, one deep and one shallow, close to the threshold fixed by the energy of the $(A\ensuremath{-}1)$-atom system. Universal relations between the energies of the excited state of the $A$-atom system and the ground-state energy of the $(A\ensuremath{-}1)$-atom system are extracted, as well as the ratio between the ground state of the $A$-atom system and the ground-state energy of the trimer.
AGES OF MASSIVE GALAXIES AT 0.5 > z > 2.0 FROM 3D-HST REST-FRAME OPTICAL SPECTROSCOPY

We present low-resolution near-infrared stacked spectra from the 3D–HST survey up to z = 2.0 and fit them with commonly used stellar population synthesis models: BC03, FSPS10 (Flexible Stellar Population Synthesis), and FSPS-C3K. The accuracy of the grism redshifts allows the unambiguous detection of many emission and absorption features and thus a first systematic exploration of the rest-frame optical spectra of galaxies up to z = 2. We select massive galaxies ( log ( M * / M ⊙ ) > 10.8 ), we divide them into quiescent and star-forming via a rest-frame color–color technique, and we median-stack the samples in three redshift bins between z = 0.5 and z = 2.0. We find that stellar population models fit the observations well at wavelengths below the 6500 Å rest frame, but show systematic residuals at redder wavelengths. The FSPS-C3K model generally provides the best fits (evaluated with χ2red statistics) for quiescent galaxies, while BC03 performs the best for star-forming galaxies. The stellar ages of quiescent galaxies implied by the models, assuming solar metallicity, vary from 4 Gyr at z ∼ 0.75 to 1.5 Gyr at z ∼ 1.75, with an uncertainty of a factor of two caused by the unknown metallicity. On average, the stellar ages are half the age of the universe at these redshifts. We show that the inferred evolution of ages of quiescent galaxies is in agreement with fundamental plane measurements, assuming an 8 Gyr age for local galaxies. For star-forming galaxies, the inferred ages depend strongly on the stellar population model and the shape of the assumed star-formation history.
PERFECT STATE TRANSFER IN XX CHAINS INDUCED BY BOUNDARY MAGNETIC FIELDS

A recent numerical study of short chains found near-perfect quantum state transfer between the boundary sites of a spin-1/2 XX chain if a sufficiently strong magnetic field acts on these sites. We show that the phenomenon is based on a pair of states strongly localized at the boundaries of the system and provide a simple quantitative analytical explanation.
Quantifying Environmental and Line-of-sight Effects in Models of Strong Gravitational Lens Systems

Matter near a gravitational lens galaxy or projected along the line of sight (LOS) can affect strong lensing observables by more than contemporary measurement errors. We simulate lens fields with realistic three-dimensional mass configurations (self-consistently including voids), and then fit mock lensing observables with increasingly complex lens models to quantify biases and uncertainties associated with different ways of treating the lens environment (ENV) and LOS. We identify the combination of mass, projected offset, and redshift that determines the importance of a perturbing galaxy for lensing. Foreground structures have a stronger effect on the lens potential than background structures, due to nonlinear effects in the foreground and downweighting in the background. There is dramatic variation in the net strength of ENV/LOS effects across different lens fields; modeling fields individually yields stronger priors for H0 than ray tracing through N-body simulations. Models that ignore mass outside the lens yield poor fits and biased results. Adding external shear can account for tidal stretching from galaxies at redshifts , but it requires corrections for external convergence and cannot reproduce nonlinear effects from foreground galaxies. Using the tidal approximation is reasonable for most perturbers as long as nonlinear redshift effects are included. Even then, the scatter in H0 is limited by the lens profile degeneracy. Asymmetric image configurations produced by highly elliptical lens galaxies are less sensitive to the lens profile degeneracy, so they offer appealing targets for precision lensing analyses in future surveys like LSST and Euclid.
The outer stellar populations and environments of unusually H i-rich galaxies

We investigate the nature of HI-rich galaxies from the ALFALFA and GASS surveys, which are defined as galaxies in the top 10th percentile in atomic gas fraction at a given stellar mass. We analyze outer (R>1.5 Re) stellar populations for a subset of face-on systems using optical g-r versus r-z colour/colour diagrams. The results are compared with those from control samples that are defined without regard to atomic gas content, but are matched in redshift, stellar mass and structural parameters. HI-rich early-type (C>2.6) and late-type (C 10.5) HI-rich galaxies, regardless of type.