ShantanuT01/DACTYL-Pretraining huggingface dataset:
The Fermi Gamma-ray Space Telescope is producing the most detailed inventory of the gamma-ray sky to date. Despite tremendous achievements approximately 25% of all Fermi extragalactic sources in the Second Fermi LAT Catalogue (2FGL) are listed as active galactic nuclei (AGN) of uncertain type. Typically, these are suspected blazar candidates without a conclusive optical spectrum or lacking spectroscopic observations. Here, we explore the use of machine-learning algorithms - Random Forests and Support Vector Machines - to predict specific AGN subclass based on observed gamma-ray spectral properties. After training and testing on identified/associated AGN from the 2FGL we find that 235 out of 269 AGN of uncertain type have properties compatible with gamma-ray BL Lacs and flat-spectrum radio quasars with accuracy rates of 85%. Additionally, direct comparison of our results with class predictions made after following the infrared colour-colour space of Massaro et al. (2012) show that the agreement rate is over four-fifths for 54 overlapping sources, providing independent cross validation. These results can help tailor follow-up spectroscopic programs and inform future pointed surveys with ground-based Cherenkov telescopes.
The IMACS Cluster Building Survey (ICBS) provides spectra of ~2200 galaxies 0.31<z<0.54 in 5 rich clusters (R <= 5 Mpc) and the field. Infalling, dynamically cold groups with tens of members account for approximately half of the supercluster population, contributing to a growth in cluster mass of ~100% by today. The ICBS spectra distinguish non-starforming (PAS) and poststarburst (PSB) from starforming galaxies -- continuously starforming (CSF) or starbursts, (SBH or SBO), identified by anomalously strong H-delta absorption or [O II] emission. For the infalling cluster groups and similar field groups, we find a correlation between PAS+PSB fraction and group mass, indicating substantial "preprocessing" through quenching mechanisms that can turn starforming galaxies into passive galaxies without the unique environment of rich clusters. SBH + SBO starburst galaxies are common, and they maintain an approximately constant ratio (SBH+SBO)/CSF ~ 25% in all environments -- from field, to groups, to rich clusters. Similarly, while PSB galaxies strongly favor denser environments, PSB/PAS ~ 10-20% for all environments. This result, and their timescale tau < 500 Myr, indicates that starbursts are not signatures of a quenching mechanism that produces the majority of passive galaxies. We suggest instead that starbursts and poststarbursts signal minor mergers and accretions, in starforming and passive galaxies, respectively, and that the principal mechanisms for producing passive systems are (1) early major mergers, for elliptical galaxies, and (2) later, less violent processes -- such as starvation and tidal stripping, for S0 galaxies.
Massive black holes (MBHs) in galactic nuclei are believed to be surrounded by a high density stellar cluster, whose mass is mostly in hard-to-detect faint stars and compact remnants. Such dark cusps dominate the dynamics near the MBH: a dark cusp in the Galactic center (GC) of the Milky Way would strongly affect orbital tests of General Relativity there; on cosmic scales, dark cusps set the rates of gravitational wave emission events from compact remnants that spiral into MBHs, and they modify the rates of tidal disruption events, to list only some implications. A recently discovered long-period massive young binary (P_12 <~ 1 yr, M_12 ~ O(100 M_sun), T_12 ~ 6x10^6 yr), only ~0.1 pc from the Galactic MBH (Pfuhl et al 2013), sets a lower bound on the 2-body relaxation timescale there, min t_rlx ~ (P_12/M_12)^(2/3)T_12 ~ 10^7 yr, and correspondingly, an upper bound on the stellar number density, max n ~ few x 10^8/<M_star^2> 1/pc^3, based on the binary's survival against evaporation by the dark cusp. However, a conservative dynamical estimate, the drain limit, implies t_rlx > O(10^8) yr. Such massive binaries are thus too short-lived and tightly bound to constrain a dense relaxed dark cusp. We explore here in detail the use of longer-period, less massive and longer-lived binaries (P_12 ~ few yr, M_12 ~ 2-4 M_sun, T_12 ~ 10^8-10^10 yr), presently just below the detection threshold, for probing the dark cusp, and develop the framework for translating their future detections among the giants in the GC into dynamical constraints.
We show that the conjectural construction proposed by Bayer, Bertram, Macr\'i and Toda gives rise to Bridgeland stability conditions for a principally polarized abelian three-fold with Picard rank one by proving that tilt stable objects satisfy the strong Bogomolov-Gieseker type inequality. This is done by showing any Fourier-Mukai transform gives an equivalence of abelian categories which are double tilts of coherent sheaves.
The physical systems with ferromagnetism and "bad" metallicity hosting unusual transport properties are playgrounds of novel quantum phenomena. Recently EuTi$_{1-x}$Nb$_x$O$_3$ emerged as a ferromagnetic system where non-trivial temperature dependent transport properties are observed due to coexistence and competition of various magnetic and non-magnetic scattering processes. In the ferromagnetic state, the resistivity shows a $T^2$ temperature dependence possibly due to electron-magnon scattering and above the Curie temperature $T_c$, the dependence changes to $T^{3/2}$ behaviour indicating a correlation between transport and magnetic properties. In this paper, we show that the transport spin-polarization in EuTi$_{1-x}$Nb$_x$O$_3$, a low Curie temperature ferromagnet, is as high ($\sim 40\%$) as that in some of the metallic ferromagnets with high Curie temperatures. In addition, owing to the low Curie temperature of EuTi$_{1-x}$Nb$_x$O$_3$, the temperature ($T$) dependence of $P_t$ could be measured systematically up to $T_c$ which revealed a proportionate relationship with magnetization $M_s$ vs. $T$. This indicates that such proportionality is far more universally valid than the ferromagnets with ideal parabolic bands. Furthermore, our band structure calculations not only helped understand the origin of such high spin polarization in EuTi$_{1-x}$Nb$_x$O$_3$ but also provided a route to estimate the Hubbard $U$ parameter in complex metallic ferromagnets in general using experimental inputs.
Using Mellin-Barnes integrals we give a method to compute a relevant subgroup of the monodromy group of an A-hypergeometric system of differential equations. Presumably this group is the full monodromy group of the system.   This article is a major rewrite of an article posted 2 years ago.
We treat the problem of completing the moduli space for roots of line bundles on curves. Special attention is devoted to higher spin curves within the universal Picard scheme. Two new different constructions, both using line bundles on nodal curves as boundary points, are carried out and compared with pre-existing ones.
Point sources exhibit low threshold electron emission due to local field enhancement at the tip. The development and implementation of tip emitters have been hampered by the need to position them sufficiently apart to achieve field enhancement, limiting the number of emission sites and therefore the overall current. Here we report low threshold field (< 0.1V/um) emission of multiple electron beams from atomically thin edges of reduced graphene oxide (rGO). Field emission microscopy (FEM) measurements show evidence for interference from emission sites that are separated by a few nanometers, suggesting that the emitted electron beams may be coherent. Based on our high-resolution transmission electron microscopy, infrared spectroscopy and simulation results, field emission from the rGO edge is attributed to a stable and unique aggregation of oxygen groups in the form of cyclic edge ethers. Such closely spaced electron beams from rGO offer prospects for novel applications and understanding the physics of linear electron sources.
The recent detection by the Fermi gamma-ray space telescope of high-energy gamma-rays from the radio galaxy NGC 1275 makes the observation of the very high energy (VHE: E > 100 GeV) part of its broadband spectrum particularly interesting, especially for the understanding of active galactic nuclei (AGN) with misaligned multi-structured jets. The radio galaxy NGC 1275 was recently observed by VERITAS at energies above 100 GeV for about 8 hours. No VHE gamma-ray emission was detected by VERITAS from NGC 1275. A 99% confidence level upper limit of 2.1% of the Crab Nebula flux level is obtained at the decorrelation energy of approximately 340 GeV, corresponding to 19% of the power-law extrapolation of the Fermi Large Area Telescope (LAT) result.
Euclid, WFIRST, and HETDEX will make emission-line selected galaxies the largest observed constituent in the $z > 1$ universe. However, we only have a limited understanding of the physical properties of galaxies selected via their Ly$\alpha$ or rest-frame optical emission lines. To begin addressing this problem, we present the basic properties of $\sim 2,000$ AEGIS, COSMOS, GOODS-N, GOODS-S, and UDS galaxies identified in the redshift range $1.90 < z < 2.35$ via their [O II], H$\beta$, and [O III] emission lines. For these $z \sim 2$ galaxies, [O III] is generally much brighter than [O II] and H$\beta$, with typical rest-frame equivalent widths of several hundred Angstroms. Moreover, these strong emission-line systems span an extremely wide range of stellar mass ($\sim 3$ dex), star-formation rate ($\sim 2$ dex), and [O III] luminosity ($\sim 2$ dex). Comparing the distributions of these properties to those of continuum selected galaxies, we find that emission-line galaxies have systematically lower stellar masses and lower optical/UV dust attenuations. These measurements lay the groundwork for an extensive comparison between these rest-frame optical emission-line galaxies and Ly$\alpha$ emitters identified in the HETDEX survey.
A procedure suggested by Vvedensky for obtaining continuum equations as the coarse-grained limit of discrete models is applied to the restricted solid-on-solid model with both adsorption and desorption. Using an expansion of the master equation, discrete Langevin equations are derived; these agree quantitatively with direct simulation of the model. From these, a continuum differential equation is derived, and the model is found to exhibit either Edwards-Wilkinson or Kardar-Parisi-Zhang exponents, as expected from symmetry arguments. The coefficients of the resulting continuum equation remain well-defined in the coarse-grained limit.
Removing the background in ID Card images is a real challenge for remote verification systems because many of the re-digitalised images present cluttered backgrounds, poor illumination conditions, distortion and occlusions. The background in ID Card images confuses the classifiers and the text extraction. Due to the lack of available images for research, this field represents an open problem in computer vision today. This work proposes a method for removing the background using semantic segmentation of ID Cards. In the end, images captured in the wild from the real operation, using a manually labelled dataset consisting of 45,007 images, with five types of ID Cards from three countries (Chile, Argentina and Mexico), including typical presentation attack scenarios, were used. This method can help to improve the following stages in a regular identity verification or document tampering detection system. Two Deep Learning approaches were explored, based on MobileUNet and DenseNet10. The best results were obtained using MobileUNet, with 6.5 million parameters. A Chilean ID Card's mean Intersection Over Union (IoU) was 0.9926 on a private test dataset of 4,988 images. The best results for the fused multi-country dataset of ID Card images from Chile, Argentina and Mexico reached an IoU of 0.9911. The proposed methods are lightweight enough to be used in real-time operation on mobile devices.
We present an adaptation of Voronoi theory for imaginary quadratic number fields of class number greater than 1. This includes a characterisation of extreme Hermitian forms which is analogous to the classic characterisation of extreme quadratic forms as well as a version of Voronoi's famous algorithm which may be used to enumerate all perfect Hermitian forms for a given imaginary quadratic number field in dimensions 2 and 3. We also present an application of the algorithm which allows to determine generators of the general linear group of an $\O_K$-lattice.
Our target is to learn visual correspondence from unlabeled videos. We develop LIIR, a locality-aware inter-and intra-video reconstruction framework that fills in three missing pieces, i.e., instance discrimination, location awareness, and spatial compactness, of self-supervised correspondence learning puzzle. First, instead of most existing efforts focusing on intra-video self-supervision only, we exploit cross video affinities as extra negative samples within a unified, inter-and intra-video reconstruction scheme. This enables instance discriminative representation learning by contrasting desired intra-video pixel association against negative inter-video correspondence. Second, we merge position information into correspondence matching, and design a position shifting strategy to remove the side-effect of position encoding during inter-video affinity computation, making our LIIR location-sensitive. Third, to make full use of the spatial continuity nature of video data, we impose a compactness-based constraint on correspondence matching, yielding more sparse and reliable solutions. The learned representation surpasses self-supervised state-of-the-arts on label propagation tasks including objects, semantic parts, and keypoints.
In a more general electroweak theory, there could be Higgs particles that are odd under $CP$, and also Higgs-like particles which are not eigenstates of $CP$. We discuss distributions which for the Bjorken process are sensitive to the $CP$ parity. Correlations among momenta of the initial electron and final-state fermions yield this kind of information. We discuss also observables which may demonstrate presence of $CP$ violation and identify a phase shift $\delta$ which is a measure of the strength of $CP$ violation in the Higgs-vector-vector coupling, and which can be measured directly in the decay distribution. We present Monte Carlo data on the expected efficiency, and conclude that it is relatively easy to determine whether the produced particle is even or odd under $CP$. However, observation of any $CP$ violation would require a very large amount of data.
We show that the system where $CP^1$ model coupled to Hopf term can reveal fractional spin in a collective coordinate quantization scheme, provided one makes a transition to physically inequivalent sector within a same solitonic sector characterized by a nonvanishing topological number
Generation of polarization-entangled photons from quantum dots via the biexciton-exciton recombination cascade is complicated by the presence of an energy spitting between the intermediate excitonic levels, which severely degrades the quality of the entangled photon source. In this paper we present a novel, conceptually simple and straightforward proposal for restoring the entanglement of said source by applying a cascade of time-dependent operations on the emitted photons. This is in striking contrast with the techniques usually employed, that act on the quantum emitter itself in order to remove the fine structure splitting at its root. The feasibility of the implementation with current technology is discussed, and the robustness of the proposed compensation scheme with respect to imperfections of the experimental apparatus is evaluated via a series of Monte Carlo simulations.
In this note, we present a counterexample to a conjecture of Rozoy and Thiagarajan from 1991 (called also the nice labeling problem) asserting that any (coherent) event structure with finite degree admits a labeling with a finite number of labels, or equivalently, that there exists a function $f: \mathbb{N} \mapsto \mathbb{N}$ such that an event structure with degree $\le n$ admits a labeling with at most $f(n)$ labels. Our counterexample is based on the Burling's construction from 1965 of 3-dimensional box hypergraphs with clique number 2 and arbitrarily large chromatic numbers and the bijection between domains of event structures and median graphs established by Barth\'elemy and Constantin in 1993.
We demonstrate a new method for the calculation of inelastic scattering cross-section, which in contrary to the Regge-based methods takes into account the energy momentum conservation law. By virtue of this method it was shown that the main contribution to integral expressing inelastic scattering cross-sections comes not from the multi-Regge domain. In particular this leads to the fact that accounting of longitudinal momenta contribution to virtualities is sufficient and results in the new mechanism of cross-section growth. The necessity of taking into account the large number of interference contributions is shown and the approximate method for this purpose is developed. By considering the interference contributions from a single fitting constant achieved a qualitative agreement of the total and inelastic cross sections with experimental data.
Graph states have been used to construct quantum error correction codes for independent errors. Hypergraph states generalize graph states, and symmetric hypergraph states have been shown to allow for the correction of correlated errors. In this paper, it is shown that symmetric hypergraph states are not useful for the correction of independent errors, at least for up to 30 qubits. Furthermore, error correction for error models with protected qubits is explored. A class of known graph codes for this scenario is generalized to hypergraph codes.
For nonsingular projective 3-folds $X$ (of general type) whose geometric genus $p_g=h^0(X, K_X)$ is $\geq 5$, the birationality of the fourth canonical map $\varphi_{4,X}=\Phi_{|4K_X|}$ was characterized by D.-Q. Zhang and the first author in 2008. This paper aims at characterizing the birationality of $\varphi_{4,X}$ for those $X$ with $p_g=4$.
We present the resummed predictions for inclusive cross section for the production of Higgs boson at next-to-next-to leading logarithmic ($\rm \overline {NNLL}$) accuracy taking into account both soft-virtual ($\rm SV$) and next-to SV ($\rm NSV$) threshold logarithms. We derive the $N$-dependent coefficients and the $N$-independent constants in Mellin-$N$ space for our study. Using the minimal prescription we perform the inverse Mellin transformation and match it with the corresponding fixed order results. We report in detail the numerical impact of $N$-independent part of resummed result and explore the ambiguity involved in exponentiating them. By studying the K factors at different logarithmic accuracy, we find that the perturbative expansion shows better convergence improving the reliability of the prediction at $\rm NNLO + \overline{NNLL}$ accuracy. For instance, the cross-section at $\rm NNLO + \overline{NNLL}$ accuracy reduces by $3.15\%$ as compared to the $\rm NNLO$ result for the central scale $\mu_R = \mu_F = m_H/2$ at 13 TeV LHC. We also observe that the resummed $\rm SV + NSV$ result improves the renormalisation scale uncertainty at every order in perturbation theory. The uncertainty from the renormalisation scale $\mu_R$ ranges between $(+8.85\% ,-10.12\%)$ at $\rm NNLO$ whereas it goes down to $(+6.54\% , - 8.32\%)$ at $\rm NNLO + \overline{NNLL}$ accuracy. However, the factorisation scale uncertainty is worsened by the inclusion of these NSV logarithms hinting the importance of resummation beyond $\rm NSV$ terms. We also present our predictions for $\rm SV + NSV$ resummed result at different collider energies.
We consider a Z' model where the Z' boson couples only to up and top quarks. As a simple setup, one can consider a family-dependent $U(1)'$ symmetry, under which only right-handed up-type quarks are charged. After symmetry breaking, the right-handed quarks mix with each other and top flavor-changing neutral currents (FCNCs) mediated by the Z' boson can be generated at tree level. We take into account several processes to probe the top FCNCs, and find that the same sign top quark pair production or the triple top quark production is the most capable of testing the top FCNCs. We also consider a few non-FCNC processes to probe the Z' boson, for example, dijet production at the LHC.
We present results of deep echelle spectrophotometry of eight Galactic HII regions located at Galactocentric distances between 6.3 and 10.4 kpc. The data have been taken with the Very Large Telescope (VLT) Ultraviolet Echelle Spectrograph (UVES) in the 3100 to 10360 A range. We have derived C++ and O++ abundances from recombination lines for all the objects, as well as O+ abundances from this kind of lines for three of the nebulae. The intensity of recombination lines is almost independent of the assumed electron temperature as well as of the possible presence of spatial temperature variations or fluctuations inside the nebulae. These data allow the determination of the gas-phase C and O abundance gradients of the Galactic disk, of paramount importance for chemical evolution models. This is the first time the C gradient is derived from such a large number of HII regions and for such a wide range of Galactocentric distances. Abundance gradients are found of the form $\Delta$log(O/H) = -0.044$\pm$0.010 dex kpc^-1, $\Delta$log(C/H) = -0.103$\pm$0.018 dex kpc^-1, and $\Delta$log(C/O) = -0.058$\pm$0.018 dex kpc^-1.
Recently there is huge interest in graph theory and intensive study on computing integer powers of matrices. In this paper, we investigate relationships between one type of graph and well-known Fibonacci sequence. In this content, we consider the adjacency matrix of one type of graph with 2k (k=1,2,...) vertices. It is also known that for any positive integer r, the (i,j)th entry of A^{r} (A is the adjacency matrix of the graph) is just the number of walks from vertex i to vertex j, that use exactly k edges.
In this paper, we study the well-posedness for a coupled PDE/ODE system describing the interaction of several massive point vortices moving within a vorticity backgound in a 2D ideal incompressible fluid. The points are driven by the velocity induced by the background vorticity, by the other vortices, and by a Kutta-Joukowski-type lift force creating an additional gyroscopic effect. This system reduces to the so-called vortex-wave system, introduced by Marchioro and Pulvirenti, when the point vortices are massless. On the one hand, we establish existence of a weak solution before the first collision. We show moreover that the background vorticity is transported by the flow associated to the total velocity field. On the other hand, we establish uniqueness in the case where the vorticity is initially constant in a neighborhood of the points vortices. When all the densities of the point vortices have the same sign, no collision occurs in finite time and our results are then global in time. Our proofs strongly rely on the definition of a suitable energy functional.
In a given graph $G$, a set $S$ of vertices with an assignment of colors is a {\sf defining set of the vertex coloring of $G$}, if there exists a unique extension of the colors of $S$ to a $\Cchi(G)$-coloring of the vertices of $G$. A defining set with minimum cardinality is called a {\sf smallest defining set} (of vertex coloring) and its cardinality, the {\sf defining number}, is denoted by $d(G, \Cchi)$. Let $ d(n, r, \Cchi = k)$ be the smallest defining number of all $r$-regular $k$-chromatic graphs with $n$ vertices. Mahmoodian et. al \cite{rkgraph} proved that, for a given $k$ and for all $n \geq 3k$, if $r \geq 2(k-1)$ then $d(n, r, \Cchi = k)=k-1$. In this paper we show that for a given $k$ and for all $n < 3k$ and $r\geq 2(k-1)$, $d(n, r, \Cchi=k)=k-1$.