ShantanuT01/DACTYL-Pretraining huggingface dataset:
Even in the absence of resolved flares, the corona is heated to several million degrees. However, despite its importance for the structure, dynamics, and evolution of the solar atmosphere, the origin of this heating remains poorly understood. Several observational and theoretical considerations suggest that the heating is driven by small, impulsive energy bursts which could be Parker-style "nanoflares" (Parker 1988) that arise via reconnection within the tangled and twisted coronal magnetic field. The classical "smoking gun" (Klimchuk 2009; Cargill et al. 2013) for impulsive heating is the direct detection of widespread hot plasma (T > 6 MK) with a low emission measure. In recent years there has been great progress in the development of Transition Edge Sensor (TES) X-ray microcalorimeters that make them more ideal for studying the Sun. When combined with grazing-incidence focusing optics, they provide direct spectroscopic imaging over a broad energy band (0.5 to 10 keV) combined with extremely impressive energy resolution in small pixels, as low as 0.7 eV (FWHM) at 1.5 keV (Lee 2015), and 1.56 eV (FWHM) at 6 keV (Smith 2012), two orders of magnitude better than the current best traditional solid state photon-counting spectrometers. Decisive observations of the hot plasma associated with nanoflare models of coronal heating can be provided by new solar microcalorimeters. These measurements will cover the most important part of the coronal spectrum for searching for the nanoflare-related hot plasma and will characterize how much nanoflares can heat the corona both in active regions and the quiet Sun. Finally, microcalorimeters will enable to study all of this as a function of time and space in each pixel simultaneously a capability never before available.
Several models of quantum open systems are known at present to violate, according to principles of the standard quantum theory of open systems, the second law of thermodynamics. Here, a new and rather trivial model of another type is suggested describing mechanism that violates, according to the same principles, the zeroth and the second laws of thermodynamics simultaneously. Up to a technically minor modification, the model resembles some models already known, solved by standard means, and properly understood. Universal validity of two basic principles of thermodynamics in strictly quantum situations is thus simultaneously called in question.
In math.AG/0108089, math.AG/0212090 and math.AG/0308247 we gave numerical conditions which ensure that an equisingular family is irreducible respectively T-smooth. Combining results by Greuel, Lossen and Shustin and an idea from math.AG/9802009 we give in the present paper series of examples of families of irreducible curves on surfaces in projective three-space with only ordinary multiple points which are reducible and where at least one component does not have the expected dimension. The examples show that for families of curves with ordinary multiple points the conditions for T-smoothness in math.AG/0308247 have the right asymptotics.
Finite state machines (FSMs) are a theoretically and practically important model of computation. We propose a general, thermodynamically consistent model of FSMs and characterise the resource requirements of these machines. We model FSMs as time-inhomogeneous Markov chains. The computation is driven by instantaneous manipulations of the energy levels of the states. We calculate the entropy production of the machine, its error probability, and the time required to complete one update step. We find that a sequence of generalised bit-setting operations is sufficient to implement any FSM.
We consider identifying codes in binary Hamming spaces F^n, i.e., in binary hypercubes. The concept of identifying codes was introduced by Karpovsky, Chakrabarty and Levitin in 1998. Currently, the subject forms a topic of its own with several possible applications, for example, to sensor networks.   Let C be a subset of F^n. For any subset X of F^n, denote by I_r(X)=I_r(C;X) the set of elements of C within distance r from at least one x in X. Now C is called an (r,<= l)-identifying code if the sets I_r(X) are distinct for all subsets X of size at most l. We estimate the smallest size of such codes with fixed l and r/n converging to some number rho in (0,1). We further show the existence of such a code of size O(n^{3/2}) for every fixed l and r slightly less than n/2, and give for l=2 an explicit construction of small such codes for r the integer part of n/2-1 (the largest possible value).
We demonstrate the existence of a congruence class bias in the distribution of supersingular primes on average for elliptic curves over $\Q$. For example, we show that on average there are twice as many supersingular primes congruent to 2 mod 3 as there are congruent to 1 mod 3. Our result is obtained using the averaging approach of Fouvry-Murty along with ideas of David-Pappalardi.
Let $G$ be a simple connected graph. For any two vertices $u$ and $v$, let $d(u,v)$ denote the distance between $u$ and $v$ in $G$. A radio-$k$-labeling of $G$ for a fixed positive integer $k$ is a function $f$ which assigns to each vertex a non-negative integer label such that for every two vertices $u$ and $ v $ in $G$, $|f(u)-f(v)| \geq k - d(u,v) +1$. The span of $f$ is the difference between the largest and smallest labels of $f(V)$. The radio-$k$-number of a graph $G$, denoted by $rn_k(G)$, is the smallest span among all radio-$k$-labelings admitted by $G$. A cycle $C_n$ has diameter $d=\lfloor n/2 \rfloor$. In this paper, we combine a lower bound approach with cyclic group structure to determine the value of $ rn_k(C_n)$ for $k \geq n-3$. For $d \leq k < n-3$, we obtain the values of $rn_k(C_n)$ when $n$ and $k$ have the same parity, and prove partial results when $n$ and $k$ have different parities. Our results extend the known values of $rn_d (C_n)$ and $rn_{d+1} (C_n)$ shown by Liu and Zhu, and by Karst, Langowitz, Oehrlein and Troxell, respectively.
This file, provided as bibliographical information, contains the table of contents and editors' foreword from the proceedings of the July 1996 Warwick EuroConference on Algebraic Geometry.
We obtain spinning boson star solutions and hairy black holes with synchronised hair in the Einstein-Klein-Gordon model, wherein the scalar field is massive, complex and with a non-minimal coupling to the Ricci scalar. The existence of these hairy black holes in this model provides yet another manifestation of the universality of the synchronisation mechanism to endow spinning black holes with hair. We study the variation of the physical properties of the boson stars and hairy black holes with the coupling parameter between the scalar field and the curvature, showing that they are, qualitatively, identical to those in the minimally coupled case. By discussing the conformal transformation to the Einstein frame, we argue that the solutions herein provide new rotating boson star and hairy black hole solutions in the minimally coupled theory, with a particular potential, and that no spherically symmetric hairy black hole solutions exist in the non-minimally coupled theory, under a condition of conformal regularity.
The chemical compositions of stars from the Asymptotic Giant Branch are still poorly known due to the low temperatures of their atmospheres and therefore the presence of many molecular transitions hampering the analysis of atomic lines. One way to overcome this difficulty is by the study of lines in regions free from molecular contamination. We have chosen some of those regions to study the chemical abundance of the S-type star GZ Peg. Stellar parameters are derived from spectroscopic analysis and a metallicity of -0.77 dex is found. Chemical abundances of 8 elements are reported and an enhancement of s-process elements is inferred, typical to that of an S-type star.
The fundamental gates of linear optics quantum computation are realized by using single photons sources, linear optics and photon counters. Success of these gates is conditioned on the pattern of photons detected without using feedback. Here it is shown that the maximum probability of success of these gates is typically strictly less than 1. For the one-mode non-linear sign shift, the probability of success is bounded by 1/2. For the conditional sign shift of two modes, this probability is bounded by 3/4. These bounds are still substantially larger than the highest probabilities shown to be achievable so far, which are 1/4 and 2/27, respectively.
We present bipartite Bell-type inequalities which allow the two partners to use some non-local resource. Such inequality can only be violated if the parties use a resource which is more non-local than the one permitted by the inequality. We introduce a family of N-inputs non-local machines, which are generalizations of the well-known PR-box. Then we construct Bell-type inequalities that cannot be violated by strategies that use one these new machines. Finally we discuss implications for the simulation of quantum states.
Quantum electrodynamics theory of the resonance Raman scattering is developed for an atom in a close proximity to a carbon nanotube. The theory predicts a dramatic enhancement of the Raman intensity in the strong atomic coupling regime to nanotube plasmon near-fields. This resonance scattering is a manifestation of the general electromagnetic surface enhanced Raman scattering effect, and can be used in designing efficient nanotube based optical sensing substrates for single atom detection, precision spontaneous emission control, and manipulation.
We give a sufficient condition for the existence of the harmonic measure from infinity of transient random walks on weighted graphs. In particular, this condition is verified by the random conductance model on $\Z^d$, $d\geq 3$, when the conductances are i.i.d. and the bonds with positive conductance percolate. The harmonic measure from infinity also exists for random walks on supercritical clusters of $\Z^2$. This is proved using results of Barlow (2004).
Recent X-ray observations of blue-shifted absorption lines revealed an existence of the extremely fast disk winds with outflow velocities of ~0.1-0.3c. Such fast outflows would have a large impact on the coevolution of black holes and host galaxies since they are expected to carry a large amount of kinetic energy. One of the common characteristics of these fast winds is a strong time variability of the absorption feature. To investigate this variability, we have developed a new X-ray spectral model of the disk winds, which is generated by 3-dimensional Monte Carlo radiation transfer simulations on the assumption of the realistic wind geometry. By applying our wind model to the multi-epoch X-ray data of an archetypal wind source PDS 456, we find the variability in the absorption line is explained by a change of the wind outflowing angle without any large variability in the mass outflow rate of the wind. This result indicates that the fast disk winds are stable and that local hydrodynamic instabilities produce a large time variability of the absorption line. Moreover, we also apply our wind model to the disk-line source 1H 0707-495. The characteristic Fe-K feature in this source is successfully reproduced our disk wind model for all the observations.
Inspired by one--dimensional light--particle systems, the dynamics of a non-Hamiltonian system with long--range forces is investigated. While the molecular dynamics does not reach an equilibrium state, it may be approximated in the thermodynamic limit by a Vlasov equation that does possess stable stationary solutions. This implies that on a macroscopic scale, the molecular dynamics evolves on a slow timescale that diverges with the system size. At the single-particle level, the evolution is driven by incoherent interaction between the particles, which may be effectively modeled by a noise, leading to a Brownian-like dynamics of the momentum. Because this self-generated diffusion process depends on the particle distribution, the associated Fokker-Planck equation is nonlinear, and a subdiffusive behavior of the momentum fluctuation emerges, in agreement with numerics.
We compare the observed peaked iron abundance profiles for a small sample of groups and clusters with the predictions of a simple model involving the metal ejection from the brightest galaxy and the subsequent diffusion of metals by stochastic gas motions. Extending the analysis of Rebusco et al. (2005) we found that for 5 out of 8 objects in the sample an effective diffusion coefficient of the order of $10^{29}$ cm$^{2}$ s$^{-1}$ is needed. For AWM4, Centaurus and AWM7 the results are different suggesting substantial intermittence in the process of metal spreading across the cluster. There is no obvious dependence of the diffusion coefficient on the mass of the system.   We also estimated the characteristic velocities and the spatial scales of the gas motions needed to balance the cooling losses by the dissipation of the same gas motions. A comparison of the derived spatial scales and the sizes of observed radio bubbles inflated in the ICM by a central active galactic nucleus (AGN) suggests that the AGN/ICM interaction makes an important (if not a dominant) contribution to the gas motions in the cluster cores.
If $\mu_m$ and $d_m$ denote, respectively, the $m$-th largest Laplacian eigenvalue and the $m$-th largest vertex degree of a graph, then $\mu_m \geqslant d_m-m+2$. This inequality was conjectured by Guo in 2007 and proved by Brouwer and Haemers in 2008. Brouwer and Haemers gave several examples of graphs achieving equality, but a complete characterisation was not given. In this paper we consider the problem of characterising graphs satisfying $\mu_m = d_m-m+2$. In particular we give a full classification of graphs with $\mu_m = d_m-m+2 \leqslant 1$.
We present a detailed spatial analysis of stellar populations based on long-slit optical spectra in a sample of eight luminous early-type galaxies selected from nearby sparse groups and pairs, three of them may be interacting with a galaxy of similar mass. We have measured luminosity-weighted averages of age, [M/H], [Fe/H], and [$\alpha$/Fe] to add empirical data relative to the influence of galaxy mass, environment, interaction, and AGN feedback in their formation and evolution. The stellar population of the individual galaxies were determined through the stellar population synthesis code STARLIGHT using semi-empirical simple stellar population models. Radial variations of luminosity-weighted means of age, [M/H], [Fe/H], and [$\alpha$/Fe] were measured up to half of the effective radius of each galaxy. We found trends between these values and the nuclear stellar velocity dispersion. There are also relations between the metallicity/age gradients and the velocity dispersion. Contributions of 1-4 Gyr old stellar populations were found in IC5328 and NGC6758 as well as 4-8 Gyr old ones in NGC5812. Extended gas is present in IC5328, NGC1052, NGC1209, and NGC6758, and the presence of a LINER is identified in all these galaxies. The regions up to one effective radius of all galaxies are dominated by $\alpha$-enhanced metal-rich old stellar populations likely due to rapid star formation episodes that induced efficient chemical enrichment. On average, the age and [$\alpha$/Fe] gradients are null and the [M/H] gradients are negative, although discordant cases were found. We found no correlation between the stellar population properties and the LINER presence as well as between the stellar properties and environment or gravitational interaction, suggesting that the influence of progenitor mass can-not be discarded in the formation and evolution of early-type galaxies.
Let $k$ be an uncountable algebraically closed field of characteristic $0$, and let $X$ be a smooth projective connected variety of dimension $2p$, appropriately embedded into $\mathbb P^m$ over $k$. Let $Y$ be a hyperplane section of $X$, and let $A^p(Y)$ and $A^{p+1}(X)$ be the groups of algebraically trivial algebraic cycles of codimension $p$ and $p+1$ modulo rational equivalence on $Y$ and $X$ respectively. Assume that, whenever $Y$ is smooth, the group $A^p(Y)$ is regularly parametrized by an abelian variety $A$ and coincides with the subgroup of degree $0$ classes in the Chow group $CH^p(Y)$. In the paper we prove that the kernel of the push-forward homomorphism from $A^p(Y)$ to $A^{p+1}(X)$ is the union of a countable collection of shifts of a certain abelian subvariety $A_0$ inside $A$. For a very general section $Y$ either $A_0=0$ or $A_0$ coincides with an abelian subvariety $A_1$ in $A$ whose tangent space is the group of vanishing cycles $H^{2p-1}(Y)_{\rm van}$. Then we apply these general results to sections of a smooth cubic fourfold in $\mathbb P^5$.
Standard Convolutional Neural Networks (CNNs) can be easily fooled by images with small quasi-imperceptible artificial perturbations. As alternatives to CNNs, the recently proposed Capsule Networks (CapsNets) are shown to be more robust to white-box attacks than CNNs under popular attack protocols. Besides, the class-conditional reconstruction part of CapsNets is also used to detect adversarial examples. In this work, we investigate the adversarial robustness of CapsNets, especially how the inner workings of CapsNets change when the output capsules are attacked. The first observation is that adversarial examples misled CapsNets by manipulating the votes from primary capsules. Another observation is the high computational cost, when we directly apply multi-step attack methods designed for CNNs to attack CapsNets, due to the computationally expensive routing mechanism. Motivated by these two observations, we propose a novel vote attack where we attack votes of CapsNets directly. Our vote attack is not only effective but also efficient by circumventing the routing process. Furthermore, we integrate our vote attack into the detection-aware attack paradigm, which can successfully bypass the class-conditional reconstruction based detection method. Extensive experiments demonstrate the superior attack performance of our vote attack on CapsNets.
We argue that the most conservative geometric extension of Einstein gravity describing both positive and negative mass sources and observers is bimetric gravity and contains two copies of standard model matter which interact only gravitationally. Matter fields related to one of the metrics then appear dark from the point of view of an observer defined by the other metric, and so may provide a potential explanation for the dark universe. In this framework we consider the most general form of linearized field equations compatible with physically and mathematically well-motivated assumptions. Using gauge-invariant linear perturbation theory, we prove a no-go theorem ruling out all bimetric gravity theories that, in the Newtonian limit, lead to precisely opposite forces on positive and negative test masses.
Recently, Babson and Steingrimsson have introduced generalised permutation patterns that allow the requirement that two adjacent letters in a pattern must be adjacent in the permutation. We consider pattern avoidance for such patterns, and give a complete solution for the number of permutations avoiding any single pattern of length three with exactly one adjacent pair of letters. We also give some results for the number of permutations avoiding two different patterns. Relations are exhibited to several well studied combinatorial structures, such as set partitions, Dyck paths, Motzkin paths, and involutions. Furthermore, a new class of set partitions, called monotone partitions, is defined and shown to be in one-to-one correspondence with non-overlapping partitions.
The electronic band structure of CeAgSb$_{2}$ has been calculated using the self-consistent full potential nonorthogonal local orbital minimum basis scheme based on the density functional theory. We investigated the electronic structure with the spin-orbit interaction and on-site Coulomb potential for the Ce-derived 4f orbitals to obtain the correctly ground state of CeAgSb$_{2}$.
We study the three-dimensional Hasegawa-Mima model of turbulent magnetized plasma with horizontal viscous terms and a weak vertical dissipative term. In particular, we establish the global existence and uniqueness of strong solutions for this model.
Detection of small objects in large swaths of imagery is one of the primary problems in satellite imagery analytics. While object detection in ground-based imagery has benefited from research into new deep learning approaches, transitioning such technology to overhead imagery is nontrivial. Among the challenges is the sheer number of pixels and geographic extent per image: a single DigitalGlobe satellite image encompasses >64 km2 and over 250 million pixels. Another challenge is that objects of interest are minuscule (often only ~10 pixels in extent), which complicates traditional computer vision techniques. To address these issues, we propose a pipeline (You Only Look Twice, or YOLT) that evaluates satellite images of arbitrary size at a rate of >0.5 km2/s. The proposed approach can rapidly detect objects of vastly different scales with relatively little training data over multiple sensors. We evaluate large test images at native resolution, and yield scores of F1 > 0.8 for vehicle localization. We further explore resolution and object size requirements by systematically testing the pipeline at decreasing resolution, and conclude that objects only ~5 pixels in size can still be localized with high confidence. Code is available at https://github.com/CosmiQ/yolt.
We give a full description of the algebraic structures of the Bose-Mesner algebra and Terwilliger algebra of the wreath product of one-class association schemes.
It is proved that for any cohomology theory A in the sense of [PS] and any essentially k-smooth semi-local X the Cousin complex is exact. As a consequence we prove that for any integer n the Nisnevich sheaf A^n_Nis, associated with the presheaf U |--> A^n(U), is strictly homotopy invariant.   Particularly, for any presheaf of S^1-spectra E on the category of k-smooth schemes its Nisnevich sheves of stable A1-homotopy groups are strictly homotopy invariant.   The ground field k is arbitrary. We do not use Gabber's presentation lemma. Instead, we use the machinery of nice triples as invented in [PSV] and developed further in [P3]. This recovers a known inaccuracy in Morel's arguments in [M].   The machinery of nice triples is inspired by the Voevodsky machinery of standard triples.
In the ROSAT era of the mid-1990's, the problems facing deep X-ray surveys could be largely solved with 10 m class telescopes. In the first decade of this new millennium, with X-ray telescopes such as the Chandra X-ray Observatory and XMM-Newton in operation, deep X-ray surveys are challenging 10 m telescopes. For example, in the Chandra Deep Field surveys, approximately 30% of the X-ray sources have optical counterparts fainter than R=25 (I=24).   This paper reviews current progress with 6-10 m class telescopes in following up sources discovered in deep X-ray surveys, including results from several X-ray surveys which have depended on telescopes such as Keck, VLT and HET. Topics include the prospects for detecting extreme redshift (z>6) quasars and the first detections of normal and starburst galaxies at cosmologically interesting distances in the X-ray band.   X-ray astronomy can significantly bolster the science case for the next generation of large aperture (30-100 m) ground-based telescopes and has already provided targets for these large telescopes through the Chandra and XMM-Newton surveys. The next generation of X-ray telescopes will continue to challenge large optical telescopes; this review concludes with a discussion of prospects from new X-ray missions coming into operation on a 5-30 year timescale.