ShantanuT01/DACTYL-Pretraining huggingface dataset:
Spectrophotometric distances to stars observed by large spectroscopic surveys offer a crucial complement to parallax distances that remain very important also after the future Gaia data releases. Here we present a probabilistic approach to modeling spectroscopic information for a subset of 4,000 main sequence stars with good parallaxes ($\sigma_\varpi/\varpi<0.1$) from the LAMOST $\times$ TGAS $\times$ 2MASS cross-match, yielding a precise spectroscopic distance estimator with uncertainties of $\sim$6% for single stars. Unlike previous approaches to this problem, we explicitly account for the individual parallax uncertainties in the model building and fully incorporate the fraction of near-equal binaries of main sequence stars, which would lead to biased distance estimates if neglected. Using this model, we estimate the distance for all (150,000) main sequence stars from LAMOST Data Release 5, without parallax information. As an application, we compute their orbital actions, where our more precise distances result in 5 times smaller action uncertainties. This illustrates how future studies of the Milky Way's orbital structure can benefit from using our model. For the fainter and more distant stars of most current spectroscopic surveys, an approach such as the one presented in this work will deliver better distances than Gaia Data Release 2.
We discuss the lift of certain D6-antiD6-brane systems to M-theory. These are purely gravitational configurations with a bolt singularity. When reduced along a trivial circle, and for large bolt radius, the bolt is related to a non-supersymmetric orbifold type of singularity where some closed string tachyons are expected in the twisted sectors. This is a kind of open-closed string duality that relates open string tachyons on one side and localised tachyons in the other. We consider the evolution of the system of branes from M-theory point of view. This evolution gives rise to a brane-antibrane annihilation on the brane side. On the gravity side, the evolution is related to a reduction of the order of the orbifold and to a contraction of the bolt to a nut or flat space if the system has non-vanishing or vanishing charge, respectively. We also consider the inverse process of reducing a non-supersymmetric orbifold to a D6-brane system. For $C^2/Z_N\times Z_M$, the reduced system is a fractional D6-brane at an orbifold singularity $C/Z_M$.
Quantum statistical distributions for the partons provide a fair description of deep inelastic scattering data at $Q^2 = 3$ and $10 (GeV/c)^2$. The study of the polarized structure functions seems to suggest an alternative possible solution of the {\it spin crisis} based on the Pauli principle. In this scheme, in fact, the defects of the Gottfried sum rule and Ellis--Jaffe sum rule for proton, result strongly connected. This possibility finds particular evidence from the phenomenological observation that the relation $\Delta u = 2 \tilde{F} + u - d -1$ seems well satisfied by parton distributions.
Using the spectroscopies based upon x-ray absorption, we have studied the structural and magnetic properties of Zn$_{1-x}$Co$_{x}$O films ($x$ = 0.1 and 0.25) produced by reactive magnetron sputtering. These films show ferromagnetism with a Curie temperature $T_{\mathrm{C}}$ above room temperature in bulk magnetization measurements. Our results show that the Co atoms are in a divalent state and in tetrahedral coordination, thus substituting Zn in the wurtzite-type structure of ZnO. However, x-ray magnetic circular dichroism at the Co \textit{L}$_{2,3}$ edges reveals that the Co 3\textit{d} sublattice is paramagnetic at all temperatures down to 2 K, both at the surface and in the bulk of the films. The Co 3\textit{d} magnetic moment at room temperature is considerably smaller than that inferred from bulk magnetisation measurements, suggesting that the Co 3\textit{d} electrons are not directly at the origin of the observed ferromagnetism.
We show the vanishing viscosity limit to entropy shocks for the fractal Burgers equation in one space dimension. More precisely, we quantify the rate of convergence of the inviscid limit in $L^2$ for large initial perturbations around the entropy shock on any bounded time interval. This is the first result on the inviscid limit to entropy shock for the fractal Burgers equation with the quantified convergence, for large initial perturbations.
We study the globular cluster (GC) system of the dust-lane elliptical galaxy NGC 6702, using B, V and I-band photometric observations carried out at the Keck telescope. This galaxy has a spectroscopic age of ~2Gyrs suggesting recent star-formation. We find strong evidence for a bimodal GC colour distribution, with the blue peak having a colour similar to that of the Galactic halo GCs. Assuming that the blue GCs are indeed old and metal-poor, we estimate an age of 2-5Gyrs and supersolar metallicity for the red GC subpopulation. Despite the large uncertainties, this is in reasonable agreement with the spectroscopic galaxy age. Additionally, we estimate a specific frequency of S_{N}=2.3\pm1.1 for NGC 6702. We predict that passive evolution of NGC 6702 will further increase its specific frequency to S_{N}~2.7 within 10Gyrs, in closer agreement to that of typical present-day ellipticals. We also discuss evidence that the merger/accretion event that took place a few Gyrs ago involved a high gas fraction.
We prove the multiplicative property of localized Chern characters. As a direct consequence, a localized Chern character gives rise to a ring homomorphism from the K-group of periodic complexes to the bivariant Chow cohomology group. As an application, we prove the functoriality of Kiem-Li's cosection-localized intersection homomorphisms.
Let $C$ be a smooth curve in $\PP^2$ given by an equation F=0 of degree $d$. In this paper we consider elementary transformations of linear pfaffian representations of $C$. Elementary transformations can be interpreted as actions on a rank 2 vector bundle on $C$ with canonical determinant and no sections, which corresponds to the cokernel of a pfaffian representation. Every two pfaffian representations of $C$ can be bridged by a finite sequence of elementary transformations. Pfaffian representations and elementary transformations are constructed explicitly. For a smooth quartic, applications to Aronhold bundles and theta characteristics are given.
Recent XMM-Newton observations of the B2 type star rho Oph A indicated a periodicity of 1.205d, which was ascribed to rotational modulation. Since variability of X-ray emission in massive stars is frequently the signature of a magnetic field, we investigated whether the presence of a magnetic field can indeed be invoked to explain the observed X-ray peculiarity. Two FORS2 spectropolarimetric observations in different rotation phases revealed the presence of a negative (<B_z>_all=-419+-101G) and positive (<B_z>_all=538+-69G) longitudinal magnetic field, respectively. We estimate a lower limit for the dipole strength as B_d = 1.9+-0.2kG. Our calculations of the Kepler and Alfven radii imply the presence of a centrifugally supported, magnetically confined plasma around rho Oph A. The study of the spectral variability indicates a behaviour similar to that observed in typical magnetic early-type Bp stars.
The study of substructures in random objects has a long history, beginning with Erd\H{o}s and R\'enyi's work on subgraphs of random graphs. We study the existence of certain substructures in random subsets of vector spaces over finite fields. First we provide a general framework which can be applied to establish coarse threshold results and prove a limiting Poisson distribution at the threshold scale. To illustrate our framework we apply our results to $k$-term arithmetic progressions, sums, right triangles, parallelograms and affine planes. We also find coarse thresholds for the property that a random subset of a finite vector space is sum-free, or is a Sidon set.
We show that the quenched complexity of saddles of the spherical pure $p$-spin model agrees with the annealed complexity when both are positive. Precisely, we show that the second moment of the number of critical values of a given finite index in a given interval has twice the growth rate of the first moment.
In this paper, we study the $(k,l)$-stable vector bundles over non-singular projective curve $X$ of genus $g\geq 2,$ its relation with stability and Segre invariants. For rank 2 and 3, we give an explicit description and relation of $(k,l)$-stability and Brill-Noether loci.
We study scenarii linked with the Swiss cheese picture in dimension three obtained when two random walks are forced to meet often, or when one random walk is forced to squeeze its range. In the case of two random walks, we show that they most likely meet in a region of optimal density. In the case of one random walk, we show that a small range is reached by a strategy uniform in time. Both results rely on an original inequality estimating the cost of visiting sparse sites, and in the case of one random walk on the precise Large Deviation Principle of van den Berg, Bolthausen and den Hollander, including their sharp estimates of the rate functions in the neighborhood of the origin
Let F be a number field, p a prime number. We construct the (multi-variable) p-adic L-function of an automorphic representation of $GL_2(A_F)$ (with certain conditions at places above p and $\infty$), which interpolates the complex L-function at the central critical point. We use this construction to prove that the p-adic L-function of a modular elliptic curve E over F has vanishing order greater or equal to the number of primes above p at which E has split multiplicative reduction, as predicted by the exceptional zero conjecture.   This is a generalization of analogous results by Spie{\ss} (arXiv:1207.2289) over totally real fields.
Under the assumption of Abelian dominance in QCD, we have shown that chiral condensate is locally present around each QCD monopole. The essence is that either of charge or chirality of a quark is not conserved, when the low energy massless quark collides with QCD monopole. In reality, the charge is conserved so that the chirality is not conserved. Reviewing the presence of the local chiral condensate, we show by using chiral anomaly that chiral non symmetric quark pair production takes place when a quark is putted in a vacuum with monopole condensation, while chiral symmetric pair production takes place in a vacuum with no monopole condensation. Our results strongly indicate that the chiral symmetry is broken by the monopole condensation.
We analyze the simplest problem of electrochemical relaxation in more than one dimension - the response of an uncharged, ideally polarizable metallic sphere (or cylinder) in a symmetric, binary electrolyte to a uniform electric field. In order to go beyond the circuit approximation for thin double layers, our analysis is based on the Poisson-Nernst-Planck (PNP) equations of dilute solution theory. Unlike most previous studies, however, we focus on the nonlinear regime, where the applied voltage across the conductor is larger than the thermal voltage. In such strong electric fields, the classical model predicts that the double layer adsorbs enough ions to produce bulk concentration gradients and surface conduction. Our analysis begins with a general derivation of surface conservation laws in the thin double-layer limit, which provide effective boundary conditions on the quasi-neutral bulk. We solve the resulting nonlinear partial differential equations numerically for strong fields and also perform a time-dependent asymptotic analysis for weaker fields, where bulk diffusion and surface conduction arise as first-order corrections. We also derive various dimensionless parameters comparing surface to bulk transport processes, which generalize the Bikerman-Dukhin number. Our results have basic relevance for double-layer charging dynamics and nonlinear electrokinetics in the ubiquitous PNP approximation.
We present an alternative proof for the existence of solutions of stochastic functional differential equations satisfying a global Lipschitz condition. The proof is based on an approximation scheme in which the continuous path dependence does not go up to the present: there is a memory gap. Strong convergence is obtained by closing the gap. Such approximation is particularly useful when extending stochastic models with discrete delay to models with continuous full finite memory.
We discuss one of the most interesting phenomena exhibited by baby skyrmions -- breaking of rotational symmetry. The topics we will deal with here include the appearance of rotational symmetry breaking in the static solutions of baby Skyrme models, both in flat as well as in curved spaces, the zero-temperature crystalline structure of baby skyrmions, and finally, the appearance of spontaneous breaking of rotational symmetry in rotating baby skyrmions.
Iron perovskites CaFeO_3 and La_{0.33}Sr_{0.67}FeO_3 show charge disproportionation, resulting in charge-ordered states with Fe^{3+}:Fe^{5+} =1:1 and =2:1, respectively. We have made photoemission and unrestricted Hartree-Fock band-structure calculation of CaFeO_3 and compared it with La_{0.33}Sr_{0.67}FeO_3. With decreasing temperature, a gradual decrease of the spectral weight near the Fermi level occurred in CaFeO_3 as in La_{0.33}Sr_{0.67}FeO_3 although lattice distortion occurs only in CaFeO_3. Hartree-Fock calculations have indicated that both the breathing and tilting distortions are necessary to induce the charge disproportionation in CaFeO_3, while no lattice distortion is necessary for the charge disproportionation in La_{0.33}Sr_{0.67}FeO_3.
We present predictions for charged hadron production and Lambda polarization in p-p and p-Pb collisions at the LHC using the saturation inspired DHJ model for the dipole cross section in the extended geometric scaling region.
We introduce a general class of combinatorial objects, which we call \emph{multi-complexes}, which simultaneously generalizes graphs, multigraphs, hypergraphs and simplicial and delta complexes. We introduce a natural algebra of multi-complexes which is defined as the algebra which has a formal basis $\mathcal{C}$ of all isomorphism types of multi-complexes, and multiplication is to take the disjoint union. This is a Hopf algebra with an operation encoding the dissasembly information for such objects, and extends the Hopf algebra of graphs. In our main result, we explicitly describe here the structure of this Hopf algebra of multi-complexes $H$. We find an explicit basis $\mathcal{B}$ of the space of primitives, which is of combinatorial relevance: it is such that each multi-complex is a polynomial with non-negative integer coefficients of the elements of $\mathcal{B}$, and each $b\in\mathcal{B}$ is a polynomial with integer coefficients in $\mathcal{C}$. Using this, we find the cancellation and grouping free formula for the antipode. The coefficients appearing in all these polynomials are, up to signs, numbers counting multiplicities of sub-multi-complexes in a multi-complex. We also explicitly illustrate how our results specialize to the graph Hopf algebra, and observe how they specialize to results in all of the above mentioned particular cases. We also investigate applications of these results to the graph reconstruction conjectures, and rederive some results in the literature on these questions.
GRB spectra appear non-thermal, but recent observations of a few bursts with Fermi GBM have confirmed previous indications from BATSE of the presence of an underlying thermal component. Photospheric emission is indeed expected when the relativistic outflow emerging from the central engine becomes transparent to its own radiation, with a quasi-blackbody spectrum in absence of additional sub-photospheric dissipation. However, its intensity strongly depends on the acceleration mechanism - thermal or magnetic - of the flow. We aim to compute the thermal and non-thermal emissions produced by an outflow with a variable Lorentz factor, where the power injected at the origin is partially thermal (fraction epsilon_th) and partially magnetic (fraction 1-epsilon_th). The thermal emission is produced at the photosphere, and the non-thermal emission in the optically thin regime. Apart from the value of epsilon_th, we want to test how the other model parameters affect the observed ratio of the thermal to non-thermal emission. If the non-thermal emission is made by internal shocks, we self-consistently obtained the light curves and spectra of the thermal and non-thermal components for any distribution of the Lorentz factor in the flow. If the non-thermal emission results from magnetic reconnection we were unable to produce a light curve and could only compare the respective non-thermal and thermal spectra. In the different considered cases, we varied the model parameters to see when the thermal component in the light curve and/or spectrum is likely to show up or, on the contrary, to be hidden. We finally compared our results to the proposed evidence for the presence of a thermal component in GRB spectra. Focussing on GRB 090902B and GRB 10072B, we showed how these observations can be used to constrain the nature and acceleration mechanism of GRB outflows.
Electric field fluctuations play a major role in dissociation reactions in liquid water and determine its vibrational spectroscopic response. Here, we study the statistics of electric fields in liquid water using molecular dynamics computer simulations with a particular focus on the strong but rare fields that drive dissociation. Our simulations indicate that the important contributions to the electric field acting on OH bonds stem from water molecules less than 7 {\AA} away. Long-ranged contributions play a minor role.
In this paper, we study generic non-local NJL models for four-dimensional QCD in the limit of a large number of colours. We diagonalise, through a Bogoliubov-type transformation, the Hamiltonian of the model completely in terms of the compound operators creating/annihilating mesons - bound states of dressed quarks and antiquarks - and demonstrate a one-to-one correspondence between the Bogoliubov diagonalisation condition and the Bethe-Salpeter equation for bound states. We conclude that, in the leading order in N_C, the nontrivial contents of the theory is entirely encoded in the chiral angle - the solution to the mass-gap equation for dressed quarks. As a consequence, we extend the statement of existence of excited solutions to the mass-gap equation, called vacuum replicas, beyond the BCS level and prescribe a new index to the mesonic operators - the label of the vacuum state in which the corresponding meson is created.
In a recent work [D. K. Burgarth et al., Nat. Commun. 5, 5173 (2014)] it was shown that a series of frequent measurements can project the dynamics of a quantum system onto a subspace in which the dynamics can be more complex. In this subspace even full controllability can be achieved, although the controllability over the system before the projection is very poor since the control Hamiltonians commute with each other. We can also think of the opposite: any Hamiltonians of a quantum system, which are in general noncommutative with each other, can be made commutative by embedding them in an extended Hilbert space, and thus the dynamics in the extended space becomes trivial and simple. This idea of making noncommutative Hamiltonians commutative is called "Hamiltonian purification." The original noncommutative Hamiltonians are recovered by projecting the system back onto the original Hilbert space through frequent measurements. Here we generalize this idea to open-system dynamics by presenting a simple construction to make Lindbladians, as well as Hamiltonians, commutative on a larger space with an auxiliary system. We show that the original dynamics can be recovered through frequently measuring the auxiliary system in a non-selective way. Moreover, we provide a universal pair of Lindbladians which describes an "accessible" open quantum system for generic system sizes. This allows us to conclude that through a series of frequent non-selective measurements a nonaccessible open quantum system generally becomes accessible. This sheds further light on the role of measurement backaction on the control of quantum systems.
The Lagrange description of an ideal fluid gives rise in a natural way to a gauge potential and a Poisson structure that are classical precursors of analogous noncommuting entities. With this observation we are led to construct gauge-covariant coordinate transformations on a noncommuting space. Also we recognize the Seiberg-Witten map from noncommuting to commuting variables as the quantum correspondent of the Lagrange to Euler map in fluid mechanics.
We show how trinification models based on the gauge group $SU(3)_C \times SU(3)_L \times SU(3)_R$ realized near the TeV scale can provide naturally a variety of dark matter (DM) candidates. These models contain a discrete $T$ parity which may remain unbroken even after spontaneous symmetry breaking. The lightest $T$-odd particle, which could be a fermion, a scalar, or a gauge boson, can constitute the dark matter of the universe. This framework naturally admits a doublet-singlet fermionic DM, a singlet scalar DM, or a vector boson DM. Here we develop the vector boson DM scenario wherein the DM couples off-diagonally with the usual fermions and vector-like fermions present in the theory. We show consistency of this framework with dark matter relic abundance and direct detection limits as well as LHC constraints. We derive upper limits of 900 GeV on the vector gauge boson DM mass and 4.5 TeV on the vector-like quarks and lepton masses. We also show the consistency of spontaneous gauge symmetry breaking down to Standard Model times an extra $U(1)$ while preserving the $T$-parity.
Context. The two nuclei of the starburst galaxy Arp220 contain multiple compact radio sources previously identified as radio supernovae or supernova remnants. Aims. In order to search for an embedded radio AGN, or other possible exotic objects, we have carried out a program of VLBI monitoring at 6 cm over three epochs each separated by four months. Methods. Combining the new data with existing data at 6 cm and 18 cm (spanning 4 and 12 years respectively) we are able to characterise source flux density variability on a range of time-scales. Additionally we analyse the variability of sources in shape and position. Results. We detect rapid (< 4 months) variability in three sources (W7, W26 and W29). These sources show possible superluminal motion (> 4c) of jet-like features near rapidly varying almost stationary components. These enigmatic sources might be associated with an AGN or a highly beamed microquasar (i.e. microblazar). Other hypotheses include that the apparent variability is intrinsic and is produced by neutron star powered central components within a supernova remnant, by a sequence of several supernovae within super star clusters, or is extrinsic and is produced by Galactic interstellar scintillation of very compact non-varying objects. Conclusions. A microquasar/microblazar origin seems to be the best explanation for the nature of the variable sources in Arp220.
We consider the currents flowing in a solid-state interferometer under the effect of both an Aharonov-Bohm phase and a bias potential. Expressions are obtained for these currents, allowing for electronic or electron-boson interactions, which may take place solely on a quantum dot placed on one of the interferometer arms. The boson system can be out of equilibrium. The results are used to obtain the transport current through the interferometer, and the current circulating around it under the effect of the Aharonov-Bohm flux. The modifications of both currents, brought about by coupling the quantum dot to an incoherent sonic or electromagnetic source, are then analyzed. By choosing the appropriate range of the boson source intensity and its frequency, the magnitude of the interference-related terms of both currents can be controlled.