ShantanuT01/DACTYL-Pretraining huggingface dataset:
(Abridged) The color and luminosity distribution of horizontal branch (HB) stars in globular clusters are sensitive probes of their original helium abundances. However, recent analyses based on visual and near-ultraviolet (UV) CMDs have provided conflicting results. To clarify the situation, we address the optimum ranges of applicability (in terms of the $T_{eff}$ range covered by the HB stars) for visual and near-UV CMDs, as far as application of this HB $Y$ test goes. We consider both Stromgren and Hubble Space Telescope (HST) bandpasses. Our results indicate that the distributions of HB stars in the y vs (b-y) plane can be a reliable indicator of the He content in cool blue HB (BHB) stars, particularly when a differential comparison between blue and red HB stars is carried out in the range $T_{eff}<8300$K. Conversely, we demonstrate that CMDs using the F336W filter have a much less straightforward interpretation at the cool end of the BHB, as the distributions of HB stars in the F336W vs (F336W-F555W) plane are affected by a triple degeneracy effect. In other words, the position of an HB star is exactly the same, for a given chemical composition, for multiple combinations of the parameters $Y$, $M_{HB}$, and age along the HB evolutionary track. Other HST UV filters do not appear to be as severely affected by this degeneracy effect, to which visual bandpasses are also immune. We do find, on the other hand, that such near-UV CMDs can be extremely useful for the hottest stars along the cool BHB end. Based on a reanalysis of the distribution of HB stars in the y vs (b-y) plane, we find that the coolest among the BHB stars in M3 are likely enhanced in helium by $\Delta Y\approx 0.01$, compared with the red HB stars in the same cluster. Using near-UV HST photometry we find evidence of a progressive increase in $Y$ with increasing temperature, reaching $\Delta Y=0.02$ at $T_{eff}=10900$K.
We use Kohn-Sham spin-density-functional theory to study the statistics of ground-state spin and the spacing between conductance peaks in the Coulomb blockade regime for both 2D isolated and realistic quantum dots. We make a systematic investigation of the effects of electron-electron interaction strength and electron number on both the peak spacing and spin distributions. A direct comparison between the distributions from isolated and realistic dots shows that, despite the difference in the boundary conditions and confining potential, the statistical properties are qualitatively the same. Strong even/odd pairing in the peak spacing distribution is observed only in the weak e-e interaction regime and vanishes for moderate interactions. The probability of high spin ground states increases for stronger e-e interaction and seems to saturate around $r_s \sim 4$. The saturated value is larger than previous theoretical predictions. Both spin and conductance peak spacing distributions show substantial variation as the electron number increases, not saturating until $N \sim 150$. To interpret our numerical results, we analyze the spin distribution in the even $N$ case using a simple two-level model.
We present a theoretical and experimental analysis of the transverse monopole mode of a fast rotating Bose-Einstein condensate. The condensate's rotation frequency is similar to the trapping frequency and the effective confinement is only ensured by a weak quartic potential. We show that the non-harmonic character of the potential has a clear influence on the mode frequency, thus making the monopole mode a precise tool for the investigation of the fast rotation regime.
We demonstrate microwave manipulation of the spin states of electrically injected spin-polarized electrons in silicon. Although the silicon channel is bounded by ferromagnetic metal films, we show that moderate microwave power can be applied to the devices without altering the device operation significantly. Resonant microwave irradiation is used to induce spin rotation of spin-polarized electrons as they travel across a silicon channel, and the resultant spin polarization is subsequently detected by a ferromagnetic Schottky barrier spin detector. These results demonstrate the potential for combining advanced electron spin resonance techniques to complement the study of semiconductor spintronic devices beyond standard magnetotransport measurements.
I show that the claims in Phys. Rev. Lett. 98, 257602 by Betouras et al concerning YMn2O5 are incorect.
The cosmological constant $\Lambda$ modifies certain properties of large astrophysical rotating configurations with ellipsoidal geometries, provided the objects are not too compact. Assuming an equilibrium configuration and so using the tensor virial equation with $\Lambda$ we explore several equilibrium properties of homogeneous rotating ellipsoids. One shows that the bifurcation point, which in the oblate case distinguishes the Maclaurin ellipsoid from the Jacobi ellipsoid, is sensitive to the cosmological constant. Adding to that, the cosmological constant allows triaxial configurations of equilibrium rotating the minor axis as solutions of the virial equations. The significance of the result lies in the fact that minor axis rotation is indeed found in nature. Being impossible for the oblate case, it is permissible for prolate geometries, with $\Lambda$ zero and positive. For the triaxial case, however, an equilibrium solution is found only for non-zero positive $\Lambda$. Finally, we solve the tensor virial equation for the angular velocity and display special effects of the cosmological constant there.
The hadronic vacuum polarization function $\Pi_h$ for two light flavors is computed on the entire domain of spacelike and timelike momenta using a framework of Dyson-Schwinger equations. The analytical continuation of the function $\Pi_h$ is based on the utilization of the Gauge Technique with the entry of QCD Green's functions determined from generalized quark spectral functions. For the first time, the light quark spectral functions are extracted from the solution of the gap equation for the quark propagator. The scale is set up by the phenomena of dynamical chiral symmetry breaking, which is a striking feature of low energy QCD.
We introduce a regularization-free approach for the wellposedness of the classic Cahn-Hilliard equation with logarithmic potentials.
Gaia is a space mission currently measuring the five astrometric parameters as well as spectrophotometry of at least 1 billion stars to G = 20.7 mag with unprecedented precision. The sixth parameter in phase space (radial velocity) is also measured thanks to medium-resolution spectroscopy being obtained for the 150 million brightest stars. During the commissioning phase, two fields, one around each ecliptic pole, have been repeatedly observed to assess and to improve the overall satellite performances as well as the associated reduction and analysis software. A ground-based photometric and spectroscopic survey was therefore initiated in 2007, and is still running in order to gather as much information as possible about the stars in these fields. This work is of particular interest to the validation of the Radial Velocity Spectrometer (RVS) outputs. The paper presents the radial velocity measurements performed for the Southern targets in the 12 - 17 R magnitude range on high- to mid-resolution spectra obtained with the GIRAFFE and UVES spectrographs.
A simple method to obtain a canonical partition function for one dimensional lattice gas model is presented. The simplification is based upon rewriting a sum over all possible configurations to a sum over numbers of clusters in the system.
Heavy-ion collisions can be simulated by means of comprehensive approaches, to include the many different reaction mechanisms which may contribute. QMD models and their relativistic extensions are examples of these approaches based on Monte Carlo techniques. In this paper are shown some results obtained by coupling a new QMD code, which describes the fast stage of ion-ion collisions, to the evaporation /fission/Fermi break-up and photon de-excitation routines present in the FLUKA multipurpose Monte Carlo transport and interaction code. In particular, we compare the predicted neutron spectra to available experimental data from thin and thick target irradiations. We show also some predictions of particle and charged fragment fluences for the interaction of C and Fe ions with a thick PMMA target, which may be useful to assess the risk of side-effects in the hadron therapy of tumours.
For a reaction network with species set $\mathscr{S}$, a log-parametrized (LP) set is a non-empty set of the form $E(P, x^*) = \{x \in \mathbb{R}^\mathscr{S}_> \mid \log x - \log x^* \in P^\perp\}$ where $P$ (called the LP set's flux subspace) is a subspace of $\mathbb{R}^\mathscr{S}$, $x^*$ (called the LP set's reference point) is a given element of $\mathbb{R}^\mathscr{S}_>$, and $P^\perp$ (called the LP set's parameter subspace) is the orthogonal complement of $P$. A network with kinetics $K$ is a positive equilibria LP (PLP) system if its set of positive equilibria is an LP set. Analogously, it is a complex balanced equilibria LP (CLP) system if its set of complex balanced equilibria is an LP set. An LP kinetic system is a PLP or CLP system. This paper studies concentration robustness of a species on subsets of equilibria. We present the "species hyperplane criterion", a necessary and sufficient condition for absolute concentration robustness (ACR) for a species of a PLP system. An analogous criterion holds for balanced concentration robustness (BCR) for species of a CLP system. These criteria also lead to interesting necessary properties of LP systems with concentration robustness. Furthermore, we show that PLP and CLP power law systems with Shinar-Feinberg reaction pairs in species $X$ in a linkage class have ACR and BCR in $X$, respectively. This leads to a broadening of the "low deficiency building blocks" framework to include LP systems of Shinar-Feinberg type with arbitrary deficiency. Finally, we apply our results to species concentration robustness in LP systems with poly-PL kinetics.
We study a finite Larmor radius model used to describe the ions distributions in the core of a toka-mak plasma, that consist in a gyro-kinetic transport equation, coupled with an electro-neutrality equation. Since the last equation do not provide enough regularity on the electric potential, we introduce a simple linear collision operator adapted to the finite Larmor radius approximation. Next we study the two-dimensional dynamics in the direction perpendicular to the magnetic field and prove thanks to the smoothing effects of the collisions and of the gyro-average the global existence of solutions, as well as short time uniqueness and stability.
Interstellar space hosts nanometre- to micron-sized dust grains. The carbonaceous-rich component of these grain populations emits in infrared bands, observed remotely for decades with telescopes and satellites. They are a key ingredient of astrochemical dust evolution. The precise carriers for most of these bands are still unknown and not well reproduced in the laboratory. In this work, we show the high-energy mechanochemical synthesis of disordered aromatic and aliphatic analogues provides interstellar relevant dust particles. The mechanochemical milling of carbon-based solids under a hydrogen atmosphere produces particles with a spectroscopic match to astrophysical observations of aromatic infrared band (AIB) emission. The H/C ratio for the analogues that best reproduce these astronomical infrared observations lies in the 5$\pm$2% range. This value is much lower than diffuse interstellar hydrogenated amorphous carbons, another Galactic dust grain component observed in absorption, and it most probably provides a constraint on the hydrogenation degree of the most aromatic carbonaceous dust grain carriers. A broad band, observed in AIBs, in the 7.4-8.3 $\mu$m range is correlated to the hydrogen content, and thus the structural evolution in the analogues produced. The mechanochemical process can be seen as an experimental reactor to stimulate local energetic chemical reactions. It introduces bond disorder and hydrogen chemical attachment on the produced defects, with an effect similar to the interstellar space very localised chemical reactions with solids. From the vantage point of astrophysics, these laboratory interstellar dust analogues will be used to predict dust grain evolution under simulated interstellar conditions, including harsh radiative environments. Such interstellar analogues offer an opportunity to derive a global view on the cycling of matter in other star forming systems.
The symmetry operators generating the hidden $\mathbb{Z}_2$ symmetry of the asymmetric quantum Rabi model (AQRM) at bias $\epsilon \in \frac{1}{2}\mathbb{Z}$ have recently been constructed by V. V. Mangazeev et al. [J. Phys. A: Math. Theor. 54 12LT01 (2021)]. We start with this result to determine symmetry operators for the $N$-qubit generalisation of the AQRM, also known as the biased Dicke model, at special biases. We also prove for general $N$ that the symmetry operators, which commute with the Hamiltonian of the biased Dicke model, generate a $\mathbb{Z}_2$ symmetry.
I review some aspects of $K$ and $B$ physics both in the context of the standard model and in some cases in a scenario which is rather different from the standard model. I discuss, in particular, where we are likely to see deviations from the standard model in the near future before new colliders are built.
We obtain a new lower bound on the size of value set f(F_p) of a sparse polynomial f in F_p[X] over a finite field of p elements when p is prime. This bound is uniform with respect of the degree and depends on some natural arithmetic properties of the degrees of the monomial terms of f and the number of these terms. Our result is stronger than those which canted be extracted from the bounds on multiplicities of individual values in f(F_p).
We present Plateau de Bure Interferometer observations of far infra-red emission lines in BRI 0952-0115, a lensed quasar at z=4.4 powered by a super-massive black hole (M_BH=2x10^9 M_sun). In this source, the resolved map of the [CII] emission at 158 micron allows us to reveal the presence of a companion galaxy, located at \sim 10 kpc from the quasar, undetected in optical observations. From the CO(5-4) emission line properties we infer a stellar mass M*<2.2x10^10 M_sun, which is significantly smaller than the one found in local galaxies hosting black holes with similar masses (M* \sim 10^12 M_sun). The detection of the [NII] emission at 205 micron suggests that the metallicity in BRI 0952-0115 is consistent with solar, implying that the chemical evolution has progressed very rapidly in this system. We also present PdBI observations of the [CII] emission line in SDSSJ1148+5251, one of the most distant quasar known, at z=6.4. We detect broad wings in the [CII] emission line, indicative of gas which is outflowing from the host galaxy. In particular, the extent of the wings, and the size of the [CII] emitting region associated to them, are indicative of a quasar-driven massive outflow with the highest outflow rate ever found (dM/dt>3500 M_sun/yr).
We give the supergravity duals of commutative and noncommutative non-abelian gauge theories with N=2 in 2+1 dimensions. The moduli space on the Coulomb branch of these theories is studied using supergravity.
The iterated Crank-Nicholson method has become a popular algorithm in numerical relativity. We show that one should carry out exactly two iterations and no more. While the limit of an infinite number of iterations is the standard Crank-Nicholson method, it can in fact be worse to do more than two iterations, and it never helps. We explain how this paradoxical result arises.
Carbon nanotubes are the focus of considerable research efforts due to their fascinating physical properties. They provide an excellent model system for the study of one dimensional materials and molecular electronics. The chirality of nanotubes can lead to very different electronic behaviours, either metallic or semiconducting. Their electronic spectrum consists of a series of Van Hove singularities defining a bandgap for semiconducting tubes and molecular orbitals at the corresponding energies. A promising way to tune the nanotubes electronic properties for future applications is to use doping by heteroatoms. Here we report on experimental investigation of the role of many-body interactions in nanotube bandgaps, the visualization in direct space of the molecular orbitals of nanotubes and the properties of nitrogen doped nanotubes using scanning tunneling microscopy and transmission electron microscopy as well as electron energy loss spectroscopy.
We explore the possibility of subsequent star formation after a first star forms in a Pop III object, by focusing on the radiation hydrodynamic (RHD) feedback brought by ionizing photons as well as H2 dissociating photons. For the purpose, we perform three-dimensional RHD simulations, where the radiative transfer of ionizing photons and H2 dissociating photons from a first star is self-consistently coupled with hydrodynamics based on a smoothed particle hydrodynamics method. As a result, it is shown that density peaks above a threshold density can keep collapsing owing to the shielding of H2 dissociating radiation by an H2 shell formed ahead of a D-type ionization front. But, below the threshold density, an M-type ionization front accompanied by a shock propagates, and density peaks are radiation hydrodynamically evaporated by the shock. The threshold density is dependent on the distance from a source star, which is $\approx 10^2 cm^{-3}$ for the source distance of 30pc. Taking into consideration that the extent of a Pop III object is $\approx 100$pc and density peaks within it have the density of $10^{2-4}$cm$^{-3}$, it is concluded that the secondary star formation is allowed in the broad regions in a Pop III object.
We study the critical behavior of the $d=3$ Ising model with bond randomness through extensive Monte Carlo simulations and finite-size scaling techniques. Our results indicate that the critical behavior of the random-bond model is governed by the same universality class as the site- and bond-diluted models, clearly distinct from that of the pure model, thus providing a complete set of universality in disordered systems.
Previous studies have demonstrated that putatively single nitrogen-type Wolf-Rayet stars (WN stars) without known companions are X-ray sources. However, almost all WN star X-ray detections so far have been of earlier WN2 - WN6 spectral subtypes. Later WN7 - WN9 subtypes (also known as WNL stars) have proved more difficult to detect, an important exception being WR 79a (WN9ha). We present here new X-ray detections of the WNL stars WR 16 (WN8h) and WR 78 (WN7h). These new results, when combined with previous detections, demonstrate that X-ray emission is present in WN stars across the full range of spectral types, including later WNL stars. The two WN8 stars observed to date (WR 16 and WR 40) show unusually low X-ray luminosities (Lx) compared to other WN stars, and it is noteworthy that they also have the lowest terminal wind speeds (v_infty). Existing X-ray detections of about a dozen WN stars reveal a trend of increasing Lx with wind luminosity Lwind = (1/2) M_dot v_infty^2, suggesting that wind kinetic energy may play a key role in establishing X-ray luminosity levels in WN stars.
The oxygen abundances in the \HII regions of a sample of low surface brightness (LSB) disk galaxies are presented. In general, LSB galaxies are found to be metal poor ($Z < {1 \over 3} Z\solar$). Indeed, some LSB galaxies rival the lowest abundance extragalactic objects known. These low metallicities indicate that LSB galaxies evolve slowly, forming relatively few stars over a Hubble time.   The low metallicities of LSB galaxies occur even though many are comparable in size and mass to the prominent spirals which define the Hubble sequence. As well as being low in surface brightness, these galaxies tend to be isolated. This suggests that surface mass density and environment are more relevant to galaxy evolution than gross size.   Despite the low surface brightness of the disks, massive ($M > 60 M\solar$) stars are inferred to be present and no abnormality of the IMF is indicated. Many low excitation \HII regions exist at low metallicity in LSB galaxies, and the ionization parameter is not tightly correlated with metallicity. However, there does seem to be a significant envelope of maximum ionization at a given metallicity.
We study families $\Phi$ of coverings which are faithful for the Hausdorff dimension calculation on a given set $E$ (i. e., special relatively narrow families of coverings leading to the classical Hausdorff dimension of an arbitrary subset of $E$) and which are natural generalizations of comparable net-coverings. They are shown to be very useful for the determination or estimation of the Hausdorff dimension of sets and probability measures.   We give general necessary and sufficient conditions for a covering family to be faithful and new techniques for proving faithfulness/non-faithfulness for the family of cylinders generated by expansions of real numbers. Motivated by applications in the multifractal analysis of infinite Bernoulli convolutions, we study in details the Cantor series expansion and prove necessary and sufficient conditions for the corresponding net-coverings to be faithful. To the best of our knowledge this is the first known sharp condition of the faithfulness for a class of covering families containing both faithful and non-faithful ones.   Applying our results, we characterize fine fractal properties of probability measures with independent digits of the Cantor series expansion and show that a class of faithful net-coverings essentially wider that the class of comparable ones. We construct, in particular, rather simple examples of faithful families $\mathcal{A}$ of net-coverings which are "extremely non-comparable" to the Hausdorff measure.
We show that the transverse double spin asymmetry (DSA) in the Drell-Yan process contributed only from the Sivers functions can be picked out by the weighting function $\frac{Q_T}{M^2}(\cos(\phi-\phi_{S_1})\cos(\phi-\phi_{S_2})+3\sin(\phi-\phi_{S_1})\sin(\phi-\phi_{S_2}))$. The asymmetry is proportional to the product of two Sivers functions from each hadron $f_{1T}^{\perp(1)}\times f_{1T}^{\perp (1)}$. Using two sets of Sivers functions extracted from the semi-inclusive deeply elastic scattering data at HERMES, we estimate this asymmetry in the $p^\uparrow\bar{p}^\uparrow$ Drell-Yan process which is possible to be performed in HESR at GSI. The prediction of DSA in the Drell-Yan process contributed by the function $g_{1T}(x,\Vec k_T^2)$, which can be extracted by the weighting function $\frac{Q_T}{M^2}(3\cos(\phi-\phi_{S_1})\cos(\phi-\phi_{S_2})+\sin(\phi-\phi_{S_1})\sin(\phi-\phi_{S_2}))$, is also given at GSI.
Some models of the expanding Universe predict that the astrometric proper motion of distant radio sources embedded in space-time are non-zero as radial distance from observer to the source grows. Systematic effects due to this proper motion can even increase with distance making possible to measure them with high precision astrometric techniques like VLBI. We analyzed a large set of geodetic VLBI data spanning from 1979 till 2008 to estimate the dipole and the quadrupole harmonics in the expansion of the vector field of the proper motions of quasars in the sky. We estimated the vector spherical harmonics (three parameters for the dipole and ten - for the quadrupole systematic) directly from the VLBI group delays without intermediate calculation of the individual proper motion. The estimates have been obtained separately for different red shift zones. It was shown that the dipole harmonic does not vary significantly, whereas the amplitude of the quadrupole gradually increases with the red shift. This quadrupole pattern can be interpreted either as an anisotropic Hubble expansion, or as an indication of the primordial gravitational waves in the early Universe. However, more prosaic explanations may also be possible.