ShantanuT01/DACTYL-Pretraining huggingface dataset:
We demonstrate how the metallicities of red supergiant (RSG) stars can be measured from quantitative spectroscopy down to resolutions of ~3000 in the J-band. We have obtained high resolution spectra on a sample of the RSG population of h and chi Persei, a double cluster in the solar neighborhood. We show that careful application of the MARCS model atmospheres returns measurements of Z consistent with solar metallicity. Using two grids of synthetic spectra--one in pure LTE and one with NLTE calculations for the most important diagnostic lines--we measure Z = +0.04 +/- 0.10 (LTE) and Z = -0.04 +/- 0.08 (NLTE) for the sample of eleven RSGs in the cluster. We degrade the spectral resolution of our observations and find that those values remain consistent down to resolutions of less than R of 3000. Using measurements of effective temperatures we compare our results with stellar evolution theory and find good agreement. We construct a synthetic cluster spectrum and find that analyzing this composite spectrum with single-star RSG models returns an accurate metallicity. We conclude that the RSGs make ideal targets in the near infrared for measuring the metallicities of star forming galaxies out to 7-10 Mpc and up to ten times farther by observing the integrated light of unresolved super star clusters.
The unusual 2-stage spin flop transition in BaCu2Si2O7 is studied by single-crystal neutron diffraction. The magnetic structures of the various spin-flop phases are determined. The results appear to be inconsistent with the previously proposed theoretical explanation of the 2-stage transition.
By using the Pekeris approximation, the Duffin-Kemmer-Petiau (DKP) equation is investigated for a vector deformed Woods-Saxon (dWS) potential. The parametric Nikiforov-Uvarov (NU) method is used in calculations. The approximate energy eigenvalue equation and the corresponding wave function spinor components are calculated for any total angular momentum J in closed form. The exact energy equation and wave function spinor components are also given for the J=0 case. We use a set of parameter values to obtain the numerical values for the energy states with various values of quantum levels (n,J) and potential's deformation constant q and width R.
DY Cen has shown a steady fading of its visual light by about 1 magnitude in the last 40 years suggesting a secular increase in its effective temperature. We have conducted non-LTE and LTE abundance analyses to determine the star's effective temperature, surface gravity, and chemical composition using high-resolution spectra obtained over two decades. The derived stellar parameters for three epochs suggest that DY Cen has evolved at a constant luminosity and has become hotter by about 5000 K in 23 years. We show that the derived abundances remain unchanged for the three epochs. The derived abundances of the key elements, including F and Ne, are as observed for the extreme helium stars resulting from a merger of an He white dwarf with a C-O white dwarf. Thus, DY Cen by chemical composition appears to be also a product of a merger of two white dwarfs. This appearance seems to be at odds with the recent suggestion that DY Cen is a single-lined spectroscopic binary.
The thermal evolution of neutron stars (NSs) is investigated by coupling with the evolution of $\textit{r}$-mode instability that is described by a second order model.The heating effect due to shear viscous damping of the $\textit{r}$-modes enables us to understand the high temperature of two young pulsars (i.e., PSR B0531+21 and RX J0822-4300) in the framework of the simple $npe$ NS model, without superfluidity or exotic particles.Moreover, the light curves predicted by the model within an acceptable parameter regime may probably cover all of the young and middle-aged pulsars in the $\lg T_s^{\infty}-\lg t$ panel, and an artificially strong $p$ superfluidity invoked in some early works is not needed here. Additionally, by considering the radiative viscous damping of the $\textit{r}$-modes, a surprising extra cooling effect is found, which can even exceed the heating effect sometimes although plays an ignorable role in the thermal history.
We investigate the crystal properties of CdTe nanowires overgrown with HgTe. Scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) confirm, that the growth results in a high ensemble uniformity and that the individual heterostructures are single-crystalline, respectively. We use high-resolution X-ray diffraction (HRXRD) to investigate strain, caused by the small lattice mismatch between the two materials. We find that both CdTe and HgTe show changes in lattice constant compared to the respective bulk lattice constants. The measurements reveal a complex strain pattern with signatures of both uniaxial and shear strains present in the overgrown nanowires.
In this paper we study nonlocal equations driven by the fractional powers of hypoelliptic operators in the form $$\mathscr K u = \mathscr A u - \partial_t u \overset{def}{=} \operatorname{tr}(Q \nabla^2 u) + <BX,\nabla u> - \partial_t u,$$ introduced by H\"ormander in his 1967 hypoellipticity paper. We show that the nonlocal operators $(-\mathscr K)^s$ and $(-\mathscr A)^s$ can be realized as the Dirichlet-to-Neumann map of doubly-degenerate extension problems. We solve such problems in $L^\infty$, and in $L^p$ for $1\leq p<\infty$ when $\operatorname{tr}(B)\geq 0$. In forthcoming works we use such calculus to establish some new Sobolev and isoperimetric inequalities.
We introduce a canonical form for reduced bases of integral closures of discrete valuation rings, and we describe an algorithm for computing a basis in reduced normal form. This normal form has the same applications as the Hermite normal form: identification of isomorphic objects, construction of global bases by patching local ones, etc. but in addition the bases are reduced, which is a crutial property for several important applications. Except for very particular cases, a basis in Hermite normal form cannot be reduced.
The critical fluctuations in a mesoscopic superconducting ring are studied within the Ginzburg-Landau approach. The nonlocal conductivity as well as the specific heat are calculated as functions of the magnetic flux $\Phi$ through the ring. At $\Phi=\Phi_0/2$ two low-energy eigenstates become degenerate and near this point the behavior of fluctuations-dependent quantities change dramatically: both the zero Fourier component $\sigma_0$ of the fluctuation conductivity and the specific heat become non-monotonic functions of $|\Phi-\Phi_0/2|$ with rather special resonant structure.
We construct the non uniform AdS black string solution with a perturbation theory in six dimensions, focusing on the backreacting second order correction. The backreactions at second order give the first relevant corrections to the thermodynamical quantities. Our results show that for configurations with horizon radius and length in the extradimension small compared to the AdS radius, the properties of the non uniform black string are similar to the locally asymptotically flat case. For black strings with small horizon radial coordinate but large length in the extradimension, the thermodynamical properties of the solutions are affected by the AdS curvature.
We present a complete classification, at the classical level, of the observables of topological Yang-Mills theories with an extended shift supersymmetry of N generators, in any space-time dimension. The observables are defined as the Yang-Mills BRST cohomology classes of shift supersymmetry invariants. These cohomology classes turn out to be solutions of an N-extension of Witten's equivariant cohomology. This work generalizes results known in the case of shift supersymmetry with a single generator.
Let n > 2 and let d < (n+1)/2. We prove that for a general hypersurface X of degree d in P^n, all the genus 0 Kontsevich moduli spaces M_{0,n}(X,e) are irreducible, reduced, local complete intersection stacks of the expected dimension.
4D Higgs field is identified with the extra-dimensional component of gauge potentials in the gauge-Higgs unification scenario. $SO(5) \times U(1)$ gauge-Higgs EW unification in the Randall-Sundrum warped space is successful at low energies. The Higgs field appears as an Aharonov-Bohm phase $\theta_H$ in the fifth dimension. Its mass is generated at the quantum level and is finite. The model yields almost the same phenomenology as the standard model for $\theta_H < 0.1$, and predicts $Z'$ bosons around 6 - 10 TeV with very broad widths. The scenario is genelarized to $SO(11)$ gauge-Higgs grand unification. Fermions are introduced in the spinor and vector representations of $SO(11)$. Proton decay is naturally forbidden.
As part of a survey of HI 21-cm emission in the Southern Milky Way, we have detected two large shells in the interstellar neutral hydrogen near l=279 deg. The center velocities are +36 and +59 km/s, which puts the shells at kinematic distances of 7 and 10 kpc. The larger shell is about 610 pc in diameter and very empty, with density contrast of at least 15 between the middle and the shell walls. It has expansion velocity of about 20 km/s and swept up mass of several million solar masses. The energy indicated by the expansion may be as high as 2.4 X 10^53 ergs. We estimate its age to be 15 to 20 million years. The smaller shell has diameter of about 400 pc, expansion velocity about 10 km/s and swept up mass of about 10^6 solar masses.   Morphologically both regions appear to be shells, with high density regions mostly surrounding the voids, although the first appears to have channels of low density which connect with the halo above and below the HI layer. They lie on the edge of the Carina arm, which suggests that they may be expanding horizontally into the interarm region as well as vertically out of the disk. If this interpretation is correct, this is the first detection of an HI chimney which has blown out of both sides of the disk.
Gravitational waves contain tail effects that are due to the backscattering of linear waves in the curved space-time geometry around the source. The knowledge as well as the accuracy of the two-body inspiraling post-Newtonian (PN) dynamics and of the gravitational-wave signal has been recently improved, notably by computing the spin-orbit (SO) terms induced by tail effects in the gravitational-wave energy flux at the 3PN order. Here we sketch this derivation, which yields the phasing formula including SO tail effects through the same 3PN order. Those results can be employed to improve the accuracy of analytical templates aimed at describing the whole process of inspiral, merger, and ringdown.
The one-dimensional planar magnonic crystals are usually fabricated as a sequence of stripes intentionally or accidentally separated by non-magnetic spacers. The influence of spacers on shaping the spin wave spectra is complex and still not completely clarified. We performed the detailed numerical studies of the one-dimensional single- and bi-component magnonic crystals comprised of a periodic array of thin ferromagnetic stripes separated by non-magnetic spacers. We showed that the dynamic dipolar interactions between the stripes mediated by non-magnetic spacer, even ultra-narrow, significantly shift up the frequency of the ferromagnetic resonance and simultaneously reduce the spin wave group velocity, which is manifested by the flattening of the magnonic band. We attributed these changes in the spectra to the modifications of dipolar pinning and shape anisotropy both dependent on the width of the spacers and the thickness of the stripes, as well as to the dynamical magnetic volume charges formed due to inhomogeneous spin wave amplitude.
Young brown dwarfs and directly-imaged exoplanets have enticingly similar photometric and spectroscopic characteristics, indicating that their cool, low gravity atmospheres should be studied in concert. Similarities between the peculiar shaped H band, near and mid-IR photometry as well as location on color magnitude diagrams provide important clues about how to extract physical properties of planets from current brown dwarf observations. In this proceeding we discuss systems newly assigned to 10-150 Myr nearby moving groups, highlight the diversity of this uniform age-calibrated brown dwarf sample, and reflect on their implication for understanding current and future planetary data.
Let $ p_n(x) $ be a random polynomial of degree $n$ and $\{Z^{(n)}_j\}_{j=1}^n$ and $\{X^{n, k}_j\}_{j=1}^{n-k}, k<n$, be the zeros of $p_n$ and $p_n^{(k)}$, the $k$th derivative of $p_n$, respectively. We show that if the linear statistics $\frac{1}{a_n} \left[ f\left( \frac {Z^{(n)}_1}{b_n} \right)+ \cdots + f \left(\frac {Z^{(n)}_n}{b_n} \right) \right]$ associated with $\{Z^{(n)}_j\}$ has a limit as $n\to\infty$ at some mode of convergence, the linear statistics associated with $\{X^{n, k}_j\}$ converges to the same limit at the same mode. Similar statement also holds for the centered linear statistics associated with the zeros of $p_n$ and $p_n^{(k)}$, provided the zeros $\{Z^{(n)}_j\}$ and the sequences $\{a_n\}$ and $\{b_n\}$ of positive numbers satisfy some mild conditions.
The recently discovered nonlinear Hall effect (NHE) in a few non-interacting systems provides a novel mechanism to generate second harmonic electrical Hall signals under time-reversal-symmetric conditions. Here, we introduce a new approach to engineering NHE by using twisted moir\'e structures. We find that the twisted WSe$_2$ bilayer exhibits a NHE when tuning the Fermi level to the moir\'e flat bands. Near half-filling of the first moir\'e band, the nonlinear Hall signal shows a sharp peak with the generation efficiency at least two orders of magnitude larger than those in previous experiments. We propose that the giant NHE and diverging generation efficiency originate from a mass-diverging type continuous Mott transition, which is evidenced by resistivity measurements. This work demonstrates not only how interaction effects can couple to Berry curvature dipoles to produce novel quantum phenomena, but also what NHE measurements can provide for developing a new tool to study the quantum criticality.
State-of-the-art methods in generative representation learning yield semantic disentanglement, but typically do not consider physical scene parameters, such as geometry, albedo, lighting, or camera. We posit that inverse rendering, a way to reverse the rendering process to recover scene parameters from an image, can also be used to learn physically disentangled representations of scenes without supervision. In this paper, we show the utility of inverse rendering in learning representations that yield improved accuracy on downstream clustering, linear classification, and segmentation tasks with the help of our novel Leave-One-Out, Cycle Contrastive loss (LOOCC), which improves disentanglement of scene parameters and robustness to out-of-distribution lighting and viewpoints. We perform a comparison of our method with other generative representation learning methods across a variety of downstream tasks, including face attribute classification, emotion recognition, identification, face segmentation, and car classification. Our physically disentangled representations yield higher accuracy than semantically disentangled alternatives across all tasks and by as much as 18%. We hope that this work will motivate future research in applying advances in inverse rendering and 3D understanding to representation learning.
The dynamics of the one-dimensional random transverse Ising model with both nearest-neighbor (NN) and next-nearest-neighbor (NNN) interactions is studied in the high-temperature limit by the method of recurrence relations. Both the time-dependent transverse correlation function and the corresponding spectral density are calculated for two typical disordered states. We find that for the bimodal disorder the dynamics of the system undergoes a crossover from a collective-mode behavior to a central-peak one and for the Gaussian disorder the dynamics is complex. For both cases, it is found that the central-peak behavior becomes more obvious and the collective-mode behavior becomes weaker as $K_{i}$ increase, especially when $K_{i}>J_{i}/2$ ($J_{i}$ and $K_{i}$ are exchange couplings of the NN and NNN interactions, respectively). However, the effects are small when the NNN interactions are weak ($K_{i}<J_{i}/2$).
Certain classes of higher dimensional models suggest that the Casimir Effect is a candidate for the cosmological constant. In this paper we demonstrate that a sufficiently advanced civilization could, in principal, manipulate the radius of the extra dimension to locally adjust the value of the cosmological constant. This adjustment could be tuned to generate an expansion/contraction of spacetime around a spacecraft creating an exotic form of field-propulsion. Due to the fact that spacetime expansion itself is not restricted by relativity, a faster-than-light 'warp drive' could be created. Calculations of the energy requirements of such a drive are performed and an 'ultimate' speed limit, based on the Planckian limits on the size of the extra dimensions is found.
We study supercritical branching processes under the influence of an i.i.d. emigration component. We provide conditions, under which the lifetime of the process is finite respectively has a finite expectation. A new version of the Kesten-Stigum theorem is obtained and the extinction probability for a large initial population size is related to the tail behaviour of the emigration.
We present the studies of magnetic properties of Ge/1-x/Cr/x/Te diluted magnetic semiconductor with changeable chemical composition 0.016 \leq x \leq 0.061. A spin-glass state (at T \leq 35 K) for x = 0.016 and 0.025 and a ferromagnetic phase (at T < 60 K) for x \geq 0.030 are observed. The long range carrier-mediated magnetic interactions are found to be responsible for the observed magnetic ordering for x < 0.045, while for x \geq 0.045 the spinodal decomposition of Cr ions leads to a maximum and decrease of the Curie temperature, TC, with increasing x. The calculations based on spin waves model are able to reproduce the observed magnetic properties at a homogeneous limit of Cr alloying, e.g. x < 0.04, and prove that carrier mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction is responsible for the observed magnetic states. The value of the Cr-hole exchange integral, Jpd, estimated via fitting of the experimental results with the theoretical model, is in the limits 0.77...0.88 eV.
We prove a central limit theorem for $\log|\zeta(1/2+it)|$ with respect to the measure $|\zeta^{(m)}(1/2+it)|^{2k}dt$ ($k,m\in\mathbb N$), assuming RH and the asymptotic formula for twisted and shifted integral moments of zeta. Under the same hypotheses, we also study a shifted case, looking at the measure $|\zeta(1/2+it+i\alpha)|^{2k}dt$, with $\alpha\in(-1,1)$. Finally we prove unconditionally the analogue result in the random matrix theory context.
Investigations of the spin dynamics of the geometrically frustrated pyrochlore (Tb_pY_{1-p})_2Ti_2O_7, using muon spin relaxation and neutron spin echo, as a function of magnetic coverage p, have been carried out. Our major finding is that paramagnetic fluctuations prevail as T->0 for all values of p, and that they are sensitive to dilution, indicating a cooperative spin motion. However, the percolation threshold p_c is not a critical point for the fluctuations. We also find that the low temperatures spectral density has a 1/f behavior, and that dilution slows down the spin fluctuations.
Utilizing sp3d5s* tight-binding band structure and wave functions for electrons and holes we show that acoustic phonon limited hole mobility in [110] grown silicon nanowires (SiNWs) is greater than electron mobility. The room temperature acoustically limited hole mobility for the SiNWs considered can be as high as 2500 cm2/Vs, which is nearly three times larger than the bulk acoustically limited silicon hole mobility. It is also shown that the electron and hole mobility for [110] grown SiNWs exceed that of similar diameter [100] SiNWs, with nearly two orders of magnitude difference for hole mobility. Since small diameter SiNWs have been seen to grow primarily along [110] direction, results strongly suggest that these SiNWs may be useful in future electronics. Our results are also relevant to recent experiments measuring SiNW mobility.
In a pilot project to study the relationship between star formation and molecular gas properties in nearby normal early-type galaxies, we used the IRAM 30m telescope to observe the 13CO(J=1-0), 13CO(J=2-1), HCN(J=1-0) and HCO+(J=1-0) line emission in the four galaxies of the SAURON sample with the strongest 12CO emission. We report the detection of 13CO emission in all four SAURON sources and HCN emission in three sources, while no HCO+ emission was found to our detection limits in any of the four galaxies. We find that the 13CO/12CO ratios of three SAURON galaxies are somewhat higher than those in galaxies of different Hubble types. The HCN/12CO and HCN/13CO ratios of all four SAURON galaxies resemble those of nearby Seyfert and dwarf galaxies with normal star formation rates, rather than those of starburst galaxies. The HCN/HCO+ ratio is found to be relatively high (i.e., >1) in the three SAURON galaxies with detected HCN emission, mimicking the behaviour in other star-forming galaxies but being higher than in starburst galaxies. When compared to most galaxies, it thus appears that 13CO is enhanced (relative to 12CO) in three out of four SAURON galaxies and HCO+ is weak (relative to HCN) in three out of three galaxies.   All three galaxies detected in HCN follow the standard HCN-infrared luminosity and dense gas fraction-star formation efficiency correlations. As already suggested by 12CO observations, when traced by infrared radiation, star formation in the three SAURON galaxies thus appears to follow the same physical laws as in galaxies of different Hubble types. The star formation rate and fraction of dense molecular gas however do not reach the high values found in nearby starburst galaxies, but rather resemble those of nearby normal star-forming galaxies.
We consider the azimuthal asymmetries in semi-inclusive deep inelastic leptoproduction arising due to both perturbative and nonperturbative effects at HERMES energies and show that the $k_T^2/Q^2$ order corrections to $< \cos\phi >$ and $< \cos2\phi >$ are significant. We also reconsider the results of perturbative effects for $< \cos\phi >$ at large momentum transfers \cite{A1} using the more recent sets of scale-dependent distribution and fragmentation functions, which bring up to $18{%}$ difference in $< \cos\phi >$. In the same approach we calculate the $< \cos2\phi >$ as well.
We consider a velocity tracking problem for the Navier-Stokes equations in a 2D-bounded domain. The control acts on the boundary through a injection-suction device and the flow is allowed to slip against the surface wall. We study the well-posedness of the state equations, linearized state equations and adjoint equations. In addition, we show the existence of an optimal solution and establish the first order optimality condition.