ShantanuT01/DACTYL-Pretraining huggingface dataset:
We describe a new method to search for metal-poor candidates from the Hamburg/ESO objective-prism survey (HES) based on identifying stars with apparently strong CH G-band strengths for their colors. The hypothesis we exploit is that large over-abundances of carbon are common among metal-poor stars. The selection was made by considering two line indices in the 4300A region, applied directly to the low-resolution prism spectra. This work also extends a previously published method by adding bright sources to the sample. The spectra of these stars suffer from saturation effects, compromising the index calculations and leading to an undersampling of the brighter candidates. Visual inspection and classification of the spectra from the HES plates yielded a list of 5,288 new metal-poor candidates, which are presently being used as targets for medium-resolution spectroscopic follow-up. Estimates of the stellar atmospheric parameters, as well as carbon abundances, are now available for 117 of the first candidates, based on follow-up medium-resolution spectra obtained with the SOAR 4.1m and Gemini 8m telescopes. We demonstrate that our new method improves the metal-poor star fractions found by our pilot study by up to a factor of three in the same magnitude range, as compared with our pilot study based on only one CH G-band index. Our selection scheme obtained roughly a 40% success rate for identification of stars with [Fe/H] < -1.0; the primary contaminant is late-type stars with near solar abundances and, often, emission line cores that filled in the CaII K line on the prism spectrum. Because the selection is based on carbon, we greatly increase the numbers of known CEMP stars from the HES with intermediate metallicities -2.0 < [Fe/H] < -1.0, which previous survey efforts undersampled. There are eight newly discovered stars with [Fe/H] < -3.0 in our sample, including two with [Fe/H] < -3.5.
We experimentally verify hitherto untested theoretical predictions about the thermoelectric properties of Kondo correlated quantum dots (QDs). The specific conditions required for this study are obtained by using QDs epitaxially grown in nanowires, combined with a recently developed method for controlling and measuring temperature differences at the nanoscale. This makes it possible to obtain data of very high quality both below and above the Kondo temperature, and allows a quantitative comparison with theoretical predictions. Specifically, we verify that Kondo correlations can induce a polarity change of the thermoelectric current, which can be reversed either by increasing the temperature or by applying a magnetic field.
We theoretically study the effect of magnetic moir\'e superlattice on the topological surface states by introducing a continuum model of Dirac electrons with a single Dirac cone moving in the time-reversal symmetry breaking periodic pontential. The Zeeman-type moir\'e potentials generically gap out the moir\'e surface Dirac cones and give rise to isolated flat Chern minibands with Chern number $\pm1$. This result provides a promising platform for realizing the time-reversal breaking correlated topological phases. In a $C_6$ periodic potential, when the scalar $U_0$ and Zeeman $\Delta_1$ moir\'e potential strengths are equal to each other, we find that energetically the first three bands of $\Gamma$-valley moir\'e surface electrons are non-degenerate and realize i) an $s$-orbital model on a honeycomb lattice, ii) a degenerate $p_x,p_y$-orbitals model on a honeycomb lattice, and iii) a hybridized $sd^2$-orbital model on a kagome lattice, where moir\'e surface Dirac cones in these bands emerge. When $U_0\neq\Delta_1$, the difference between the two moir\'e potential serves as an effective spin-orbit coupling and opens a topological gap in the emergent moir\'e surface Dirac cones.
The formation of blue stragglers is still not completely understood, particularly the relationship between formation environment and mechanism. We use a large, homogeneous sample of blue stragglers in the cores of 57 globular clusters to investigate the relationships between blue straggler populations and their environments. We use a consistent definition of "blue straggler" based on position in the color-magnitude diagram, and normalize the population relative to the number of red giant branch stars in the core. We find that the previously determined anti-correlation between blue straggler frequency and total cluster mass is present in the purely core population. We find some weak correlations with central velocity dispersion and with half-mass relaxation time. The blue straggler frequency does not show any trend with any other cluster parameter. Even though collisions may be expected to be a dominant blue straggler formation process in globular cluster cores, we find no correlation between the frequency of blue stragglers and the collision rate in the core. We also investigated the blue straggler luminosity function shape, and found no relationship between any cluster parameter and the distribution of blue stragglers in the color-magnitude diagram. Our results are inconsistent with some recent models of blue straggler formation that include collisional formation mechanisms, and may suggest that almost all observed blue stragglers are formed in binary systems.
We consider the random walk loop soup on the discrete half-plane and study the percolation problem, i.e. the existence of an infinite cluster of loops. We show that the critical value of the intensity is equal to 1/2. The absence of percolation at intensity 1/2 was shown in a previous work. We also show that in the supercritical regime, one can keep only the loops up to some large enough upper bound on the diameter and still have percolation.
Let $\mathbb{R}^n$ be the n-dimensional Euclidean space with $O$ as the origin. Let $\wedge$ be a lattice of determinant $1$ such that there is a sphere $|X|<R$ which contains no point of $\wedge$ other than $O$ and has $n$ linearly independent points of $\wedge$ on its boundary. A well known conjecture in the geometry of numbers asserts that any closed sphere in $\mathbb{R}^n $ of radius $ \sqrt{n/4}$ contains a point of $\wedge$. This is known to be true for $n\leq 8$. Here we prove a more general conjecture of Woods for $n=9$ from which this conjecture follows in $\mathbb{R}^9$. Together with a result of C. T. McMullen (2005), the long standing conjecture of Minkowski follows for $n=9$.
The 2-body system of a superconducting sphere levitated in the magnetic field generated by a persistent current in a superconducting ring, can possibly convert gravitational waves into electromagnetic waves, and vice versa. Faraday's law of induction implies that the time-varying distance between the sphere and the ring caused by the tidal force of an incident gravitational wave induces time-varying electrical currents, which are the source of an electromagnetic wave at the same frequency as the incident gravitational wave. At sufficiently low temperatures, the internal degrees of freedom of the superconductors are frozen out because of the superconducting energy gap, and only external degrees of freedom, which are coupled to the radiation fields, remain. Hence this wave-conversion process is loss-free and therefore efficient, and by time-reversal symmetry, so is the reverse process. A Hertz-like experiment at microwave frequencies should therefore be practical to perform. This would open up observations of the gravitational-wave analog of the Cosmic Microwave Background from the extremely early Big Bang, and also communications directly through the interior of the Earth.
Time dynamics of isolated many-body quantum systems has long been an elusive subject. Very recently, however, meaningful experimental studies of the problem have finally become possible, stimulating theoretical interest as well. Progress in this field is perhaps most urgently needed in the foundations of quantum statistical mechanics. This is so because in generic isolated systems, one expects nonequilibrium dynamics on its own to result in thermalization: a relaxation to states where the values of macroscopic quantities are stationary, universal with respect to widely differing initial conditions, and predictable through the time-tested recipe of statistical mechanics. However, it is not obvious what feature of many-body quantum mechanics makes quantum thermalization possible, in a sense analogous to that in which dynamical chaos makes classical thermalization possible. For example, dynamical chaos itself cannot occur in an isolated quantum system, where time evolution is linear and the spectrum is discrete. Underscoring that new rules could apply in this case, some recent studies even suggested that statistical mechanics may give wrong predictions for the outcomes of relaxation in such systems. Here we demonstrate that an isolated generic quantum many-body system does in fact relax to a state well-described by the standard statistical mechanical prescription. Moreover, we show that time evolution itself plays a merely auxiliary role in relaxation and that thermalization happens instead at the level of individual eigenstates, as first proposed by J.M. Deutsch and M. Srednicki. A striking consequence of this eigenstate thermalization scenario is that the knowledge of a single many-body eigenstate suffices to compute thermal averages-any eigenstate in the microcanonical energy window will do, as they all give the same result.
We study and derive identities for the multi-variate independence polynomials from the perspective of heaps theory. Using the inversion formula and the combinatorics of partially commutative algebras we show how the multi-variate version of Godsil type identity as well as the fundamental identity can be obtained from weight preserving bijections. Finally, we obtain a new multi-variate identity involving connected bipartite subgraphs similar to the Christoffel-Darboux type identities obtained by Bencs.
We investigate the possible total radiated energy produced by a binary black hole system containing non-vanishing total angular momentum. For the scenearios considered we find that the total radiated energy does not exceed 1%. Additionally we explore the gravitational radiation field and the variation of angular momentum in the process.
The possibility of distinguishing of scalar field models of dark energy with different Lagrangians and time variable equation of state parameter by available observational data is analyzed. The multicomponent cosmological models with the scalar field with either Klein-Gordon or Dirac-Born-Infeld Lagrangians as dark energy and the monotonic decreasing and increasing equation of state parameters are considered. It is concluded that scalar field models of dark energy with decreasing and increasing EoS parameters should be distinguishable at the accuracy level of forthcoming observational data. The Lagrangians of scalar fields could be distinguished by expected observational data (Planck, SDSS etc.) in the case of decreasing EoS parameter, but are practically indistinguishable in the case of increasing one.
The X-ray source 1RXS J180431.1-273932 has been proposed as a new member of the symbiotic X-ray binary (SyXB) class of systems, which are composed of a late-type giant that loses matter to an extremely compact object, most likely a neutron star. In this paper, we present an optical campaign of imaging plus spectroscopy on selected candidate counterparts of this object. We also reanalyzed the available archival X-ray data collected with XMM-Newton. We find that the brightest optical source inside the 90% X-ray positional error circle is spectroscopically identified as a magnetic cataclysmic variable (CV), most likely of intermediate polar type, through the detection of prominent Balmer, He I, He II, and Bowen blend emissions. On either spectroscopic or statistical grounds, we discard as counterparts of the X-ray source the other optical objects in the XMM-Newton error circle. A red giant star of spectral type M5 III is found lying just outside the X-ray position: we consider this latter object as a fore-/background one and likewise rule it out as a counterpart of 1RXS J180431.1-273932. The description of the X-ray spectrum of the source using a bremsstrahlung plus black-body model gives temperatures of around 40 keV and around 0.1 keV for these two components, respectively. We estimate a distance of about 450 pc and a 0.2-10 keV X-ray luminosity of about 1.7e32 erg/s for this system and, using the information obtained from the X-ray spectral analysis, a mass of about 0.8 solar masses for the accreting white dwarf (WD). We also confirm an X-ray periodicity of 494 s for this source, which we interpret as the spin period of the WD. In summary, 1RXS J180431.1-273932 is identified as a magnetic CV and its SyXB nature is excluded.
We apply the coadjoint orbit technique to the group of area preserving diffeomorphisms (APD) of a 2D manifold, particularly to the APD of the semi-infinite cylinder which is identified with $w_{\infty}$. The geometrical action obtained is relevant to both $w$ gravity and 2D turbulence. For the latter we describe the hamiltonian, which appears to be given by the Schwinger mass term, and discuss some possible developments within our approach. Next we show that the set of highest weight orbits of $w_{\infty}$ splits into subsets, each of which consists of highest weight orbits of $\bar{w}_N$ for a given N. We specify the general APD geometric action to an orbit of $\bar{w}_N$ and describe an appropriate set of observables, thus getting an action and observables for $\bar{w}_N$ gravity. We compute also the Ricci form on the $\bar{w}_N$ orbits, what gives us the critical central charge of the $\bar{w}_N$ string, which appears to be the same as the one of the $W_N$ string.
The results of monitoring the optical polarization and the gamma-ray flux for the radio-loud narrow-line Seyfert 1 galaxy is reported. We have detected a weak correlation between the gamma-ray variability and the optical variability. However, these observations do not provide conclusive evidence that the emissions are due to a relativistic jet oriented close to the line-of-sight to the observer.
Earlier work by Diaconis and Saloff-Coste gives a spectral criterion for a maximum separation cutoff to occur for birth and death chains. Ding, Lubetzky and Peres gave a related criterion for a maximum total variation cutoff to occur in the same setting. Here, we provide complementary results which allow us to compute the cutoff times and windows in a variety of examples.
We consider a field $F$ and positive integers $n$, $m$, such that $m$ is not divisible by $\mathrm{Char}(F)$ and is prime to $n!$. The absolute Galois group $G_F$ acts on the group $\mathbb{U}_n(\mathbb{Z}/m)$ of all $(n+1)\times(n+1)$ unipotent upper-triangular matrices over $\mathbb{Z}/m$ cyclotomically. Given $0,1\neq z\in F$ and an arbitrary list $w$ of $n$ Kummer elements $(z)_F$, $(1-z)_F$ in $H^1(G_F,\mu_m)$, we construct in a canonical way a quotient $\mathbb{U}_w$ of $\mathbb{U}_n(\mathbb{Z}/m)$ and a cohomology element $\rho^z$ in $H^1(G_F,\mathbb{U}_w)$ whose projection to the superdiagonal is the prescribed list. This extends results by Wickelgren, and in the case $n=2$ recovers the Steinberg relation in Galois cohomology, proved by Tate.
In the optical Stern-Gerlach effect the two branches in which the incoming atomic packet splits up can display interference pattern outside the cavity when a field measurement is made which erases the which-way information on the quantum paths the system can follow. On the contrary, the mere possibility to acquire this information causes a decoherence effect which cancels out the interference pattern. A phase space analysis is also carried out to investigate on the negativity of the Wigner function and on the connection between its covariance matrix and the distinguishability of the quantum paths.
I provide an incomplete inventory of the astronomical variability that will be found by next-generation time-domain astronomical surveys. These phenomena span the distance range from near-Earth satellites to the farthest Gamma Ray Bursts. The surveys that detect these transients will issue alerts to the greater astronomical community; this decision process must be extremely robust to avoid a slew of ``false'' alerts, and to maintain the community's trust in the surveys. I review the functionality required of both the surveys and the telescope networks that will be following them up, and the role of VOEvents in this process. Finally, I offer some ideas about object and event classification, which will be explored more thoroughly by other articles in these proceedings.
We study regular graphs whose distance-$2$ graph or distance-$1$-or-$2$ graph is strongly regular. We provide a characterization of such graphs $\Gamma$ (among regular graphs with few distinct eigenvalues) in terms of the spectrum and the mean number of vertices at maximal distance $d$ from every vertex, where $d+1$ is the number of different eigenvalues of $\Gamma$. This can be seen as a another version of the so-called spectral excess theorem, which characterizes in a similar way those regular graphs that are distance-regular.
We propose a generalized Jaynes-Cummings model that includes but is not limited to an extensive collection of experimental and theoretical proposals from the literature. It covers nonlinear boson terms, nonlinear dispersive and multi-boson exchange interaction. Our model features an underlying Lie graded algebra symmetry reminiscent to supersymmetric quantum mechanics. This allows us to propose a diagonalization scheme and calculate its analytic time evolution. In consequence, we are able to construct closed forms for relevant observables and explore the dynamics of particular realizations of our model independent of their complexity. As an practical example, we show the evolution of the population inversion and the boson quadratures for an initial state consisting of the qubit in the ground state interacting with a coherent field for a selection of cases including the standard JC model with Stark shift, Kerr-like terms, intensity dependent coupling, multi-boson exchange and algebraic deformations.
We study quark flavor violating interactions mediated by the Higgs boson $h$. We consider observables involving a third generation quark, of both the up and the down quark sectors, like $h\rightarrow bs$ and $t\rightarrow ch$. Using an effective field theory approach we systematically list all the possible tree-level ultraviolet completions, which comprise models with vector-like quarks and/or extra scalars. We provide upper bounds on the flavor violating transitions allowed by current limits stemming from low energy processes, such as meson mixing and $b \rightarrow s \gamma$. We find that scenarios with vector-like quarks always have very suppressed flavor-violating transitions, while a general two Higgs doublet model may have a sizeable rate. To study the latter case in detail, we perform a full numerical simulation taking into account all relevant theoretical and phenomenological constraints. Our results show that ${\rm BR}(t\rightarrow ch)$ [${\rm BR}(h\rightarrow bs)$] are still allowed at the subpercent [percent] level, which are being [may be] explored at the LHC [future colliders]. Finally, we have found that the mild mass-splitting discrepancy with respect to the SM in the $B_s$ meson system can be accommodated in the Two-Higgs-Doublet Model. If confirmed, it yields the prediction ${\rm BR}(h\rightarrow bs)\simeq 10^{-4}$, if the new contribution to the mass-splitting is dominated by tree-level Higgs boson exchange.
We study two empirical process of special structure: firstly, the centred multiplier process indexed by a class $F$, $f \to \left|\sum_{i=1}^N (\xi_i f(X_i) - \E \xi f)\right|$, where the i.i.d. multipliers $(\xi_i)_{i=1}^N$ need not be independent of $(X_i)_{i=1}^N$, and secondly, $(f,h) \to \left|\sum_{i=1}^N (f(X_i)h(X_i)-\E f h) \right|$, the centred product process indexed by the classes $F$ and $H$.   We use chaining methods to obtain high probability upper bounds on the suprema of the two processes using a natural variation of Talagrand's $\gamma$-functionals.
The present paper is devoted to the study of backward stochastic differential equations with mean reflection formulated by Briand et al. [7]. We investigate the solvability of a generalized mean reflected BSDE, whose driver also depends on the distribution of the solution term $Y$. Using a fixed-point argument, BMO martingale theory and the $\theta$-method, we establish the existence and uniqueness result for such BSDEs in several typical situations, including the case where the driver is quadratic with bounded or unbounded terminal condition.
Let $\Omega$ be a domain in $\mathbb{R}^d$, $d\geq 2$, and $1<p<\infty$. Fix $V\in L_{\mathrm{loc}}^\infty(\Omega)$. Consider the functional $Q$ and its G\^{a}teaux derivative $Q^\prime$ given by $$Q(u):= \frac{1}{p}\int_\Omega. (|\nabla u|^p+V|u|^p) \dx, Q^\prime (u):= -\nabla\cdot(|\nabla u|^{p-2}\nabla u)+V|u|^{p-2} u.$$ In this paper we discuss a few aspects of relations between functional-analytic properties of the functional $Q$ and properties of positive solutions of the equation $Q^\prime (u)=0$.
We have calculated the next-to-leading order perturbative QCD corrections to the photon energy spectrum in radiative Upsilon decays. The higher-order corrections significantly modify the shape of the spectrum, in particular at large photon energies, and thereby reduce the discrepancy between experimental data and previous leading-order predictions. The next-to-leading order calculation of the photon energy spectrum allows a more reliable determination of the strong coupling constant from radiative Upsilon decays by restricting the analysis to the region of the energy spectrum that can be described by NLO perturbation theory.
The emission line spectra of cyanoacetylene and methanol reveal chemical and physical heterogeneity on very small (< 0.1 pc) scales toward the peak in cyanopolyyne emission in the Taurus Molecular Cloud, TMC-1 (CP). We generate grids of homogeneous chemical models using a three-phase rate equation approach to obtain all time-dependent abundances spanning the physical conditions determined from molecular tracers of compact and extended regions of emission along this line of sight. Each time-dependent abundance is characterized by one of four features: a maximum/minimum, a monotonic increase/decrease, oscillatory behavior, or inertness. We similarly classify the time-dependent agreement between modeled and observed abundances by calculating both the root-mean-square logarithm difference and root-mean-square deviation between the modeled and observed abundances at every point in our grid models for three groups of molecules: (i) a composite group of all species present in both the observations and our chemical network G, (ii) the cyanopolyynes C = {HC$_3$N, HC$_5$N, HC$_7$N, HC$_9$N}, and (iii) the oxygen-containing organic species methanol and acetaldehyde S = {CH$_3$OH, CH$_3$CHO}. We discuss how the Bayesian uncertainties in the observed abundances constrain solutions within the grids of chemical models. The calculated best fit times at each grid point for each group are tabulated to reveal the minimum solution space of the grid models and the effects the Bayesian uncertainties have on the grid model solutions. The results of this approach separate the effect different physical conditions and model-free parameters have on reproducing accurately the abundances of different groups of observed molecular species.
Recently, the Strichartz estimates for the damped wave equation was obtained by the first author except for the wave endpoint case. In the present paper, we give the Strichartz estimate in the wave endpoint case. We slightly modify the argument of Keel--Tao. Moreover, we apply the endpoint Strichartz estimate to the unconditional uniqueness for the energy critical nonlinear damped wave equation. This problem seems not to be solvable as the perturbation of the wave equation.