ShantanuT01/DACTYL-Pretraining huggingface dataset:
Aims. We examined the characteristics of isolated intermediate drift bursts (IMDs) and their morphologies on dynamic spectra, in particular the positioning of emission and absorption ridges and the repetition rate of fiber groups. These were compared with a model in order to determine the conditions under which the IMDs appear and exhibit the above characteristics. Methods. We analyzed sixteen metric type IV events with embedded IMDs. The events were recorded with the Artemis-JLS/SAO high resolution (10 ms cadence) receiver in the 270-450MHz range with a frequency resolution of 1.4 MHz. We developed cross- and autocorrelation techniques to measure the duration, spectral width, and frequency drift of fiber bursts in 47 IMD groups. We also developed a semi-automatic algorithm to track fibers on dynamic spectra. Results. We distinguish six morphological groups of fibers, based on the relative position of the emission and absorption ridges. These included fibers with emission or absorption ridges only, fibers with the absorption ridge at lower or higher frequency than the emission, or with two absorption ridges above and below the emission or with two emission ridges were separated by an absorption ridge. Some borderline cases of IMDs with very high drift rate (~0.30 s-1) or very narrow total bandwidth (~8 MHz) were recorded; among them a group of rope-like IMDs with fast repetition rate and relatively narrow total frequency extent. The whistler hypothesis leads to reasonable magnetic field (~4.6 G), but the Alfven-wave hypothesis requires much higher field. We estimated the ratio of the whistler to the cyclotron frequency, x, to be ~ 0.3 to 0.6 and the average frequency scale along the loop of ~220Mm. We present empirical relations between fiber burst parameters and discuss their possible origin.
In order for the core Fundamental Plane (cFP) to endure, small ellipticals must not survive mergers with giant ellipticals, despite the fact the small secondary galaxy can be as much as a million times more dense than the primary. However, our previous set of experiments has shown that, for purely stellar galaxies, the secondary does in fact survive mergers with primaries up to 100 times more massive. In this paper, we demonstrate the effect that a massive central black hole has on mergers of cFP galaxies. Our results indicate that the addition of a massive central singularity inside the primary galaxy provides strong enough tidal forces to destroy dense cFP companions when the secondary's orbital decay is sufficiently elongated. The destruction of the secondary acts to preserve the original low central density profile of the primary in the giant merger remnant, which allows the remnant to remain on the cFP. On more circular orbits, though, the secondary is only disrupted near the end of the merger, and the degree to which the secondary particles disperse depends on the amount of orbital energy left in the merger. Hence, there are some mergers for which the cFP is not preserved in our experiments. We find that if the secondary is not dispersed, it forms a spinning stellar disk with a central density that forces the merger remnant off the cFP.
In this paper we give a comprehensive treatment of a two-penalty boundary obstacle problem for a divergence form elliptic operator, motivated by applications to fluid dynamics and thermics. Specifically, we prove existence, uniqueness and optimal regularity of solutions, and establish structural properties of the free boundary. The proofs are based on tailor-made monotonicity formulas of Almgren, Weiss, and Monneau-type, combined with the classical theory of oblique derivative problems.
We report the results of flux and spectral variability studies of all seven {\it Nuclear Spectroscopic Telescope Array (NuSTAR)} observations of TeV $\gamma-$ray emitting blazar Markarian (or Mrk) 501. We found strong evidence of intraday variability in 3-79 keV X-ray light curves (LCs) of Mrk 501 during four out of these seven observations. We examined spectral variability using a model-independent hardness-ratio analysis and found a general "harder-when-brighter" behaviour in two observations. We also investigated the nature of 3-79 keV X-ray spectra of TeV blazar Mrk 501 and found that five out of seven spectra are well described by the curved log-parabola models with photon indices (at 10 keV) $\alpha \sim$ 2.12-2.32 and a curvature $\beta \sim$ 0.15-0.28. The two other spectra are somewhat better represented by simple power-law models with photon indices 2.70 and 2.75. We briefly discuss available physical models to explain our results.
Even though composite fermions in the fractional quantum Hall liquid are well established, it is not yet known up to what energies they remain intact. We probe the high-energy spectrum of the 1/3 liquid directly by resonant inelastic light scattering, and report the observation of a large number of new collective modes. Supported by our theoretical calculations, we associate these with transitions across two or more composite fermions levels. The formation of quasiparticle levels up to high energies is direct evidence for the robustness of topological order in the fractional quantum Hall effect.
The concentration - virial mass relation is a well-defined trend that reflects the formation of structure in an expanding Universe. Numerical simulations reveal a marked correlation that depends on the collapse time of dark matter halos and their subsequent assembly history. However, observational constraints are mostly limited to the massive end via X-ray emission of the hot diffuse gas in clusters. An alternative approach, based on gravitational lensing over galaxy scales, revealed an intriguingly high concentration at Milky Way-sized halos. This letter focuses on the robustness of these results by adopting a bootstrapping approach that combines stellar and lensing mass profiles. We also apply the identical methodology to simulated halos from EAGLE to assess any systematic. We bypass several shortcomings of ensemble type lens reconstruction and conclude that the mismatch between observed and simulated concentration-to-virial-mass relations are robust, and need to be explained either invoking a lensing-related sample selection bias, or a careful investigation of the evolution of concentration with assembly history. For reference, at a halo mass of $10^{12} M_\odot$, the concentration of observed lenses is $c_{12}\sim 40\pm 5$, whereas simulations give $c_{12}\sim 15\pm1$.
The computation of transport coefficients, even in linear response, is a major challenge for theoretical methods that rely on analytic continuation of correlations functions obtained numerically in Matsubara space. While maximum entropy methods can be used for certain correlation functions, this is not possible in general, important examples being the Seebeck, Hall, Nernst and Reggi-Leduc coefficients. Indeed, positivity of the spectral weight on the positive real-frequency axis is not guaranteed in these cases. The spectral weight can even be complex in the presence of broken time-reversal symmetry. Various workarounds, such as the neglect of vertex corrections or the study of the infinite frequency or Kelvin limits have been proposed. Here, we show that one can define auxiliary response functions that allow to extract the desired real-frequency susceptibilities from maximum entropy methods in the most general multiorbital cases with no particular symmetry. As a benchmark case, we study the longitudinal thermoelectric response and corresponding Onsager coefficient in the single-band two-dimensional Hubbard model treated with dynamical mean-field theory (DMFT) and continuous-time quantum Monte Carlo (CTQMC). We thereby extend to transport coefficients the maximum entropy analytic continuation with auxiliary functions (MaxEntAux method), developed for the study of the superconducting pairing dynamics of correlated materials.
The paper is about an arithmetic problem in $\F_2[x]$. We give \emph{admissible} (necessary) conditions satisfied by a set of odd prime divisors of perfect polynomials over $\F_2$. This allows us to prove a new characterization of \emph{all} known perfect polynomials, and to open a way of finding more of them (if they exist).
We study a branching random walk on $\r$ with an absorbing barrier. The position of the barrier depends on the generation. In each generation, only the individuals born below the barrier survive and reproduce. Given a reproduction law, Biggins et al. \cite{BLSW91} determined whether a linear barrier allows the process to survive. In this paper, we refine their result: in the boundary case in which the speed of the barrier matches the speed of the minimal position of a particle in a given generation, we add a second order term $a n^{1/3}$ to the position of the barrier for the $n^\mathrm{th}$ generation and find an explicit critical value $a_c$ such that the process dies when $aa_c$. We also obtain the rate of extinction when $a < a_c$ and a lower bound on the surviving population when $a > a_c$.
The historic LHC discovery of the 125 GeV particle with properties that closely resemble the Standard Model (SM) Higgs boson verifies our understanding of electroweak symmetry breaking, but solidifies the need for a resolution to the hierarchy problem. Many extensions of the SM that address the hierarchy problem contain a non-minimal Higgs sector. Therefore, as a benchmark alternative to the SM Higgs mechanism, we study a general 2 Higgs doublet model (2HDM-G) framework for evaluating future sensitivity to Higgs couplings. We study how well it can be distinguished from the SM Higgs boson by future measurements at LHC14, ILC (250, 500,1000 GeV) and a Muon Collider (125 GeV). Additionally, our study bears on singlet Higgs extensions of two Higgs doublet models through predicted coupling relationships.
We study electron transport through a small metallic island in the perturbative regime. Using a recently developed diagrammatic technique, we calculate the occupation of the island as well as the conductance through the transistor in forth order in the tunneling matrix elements, a process referred to as cotunneling. Our formulation does not require the introduction of a cut-off. At resonance we find significant modifications of previous theories and good agreement with recent experiments.
We consider a generalized two-color Polya urn (black and withe balls) first introduced by Hill, Lane, Sudderth where the urn composition evolves as follows: let $\pi:\left[0,1\right]\rightarrow\left[0,1\right]$, and denote by $x_{n}$ the fraction of black balls after step $n$, then at step $n+1$ a black ball is added with probability $\pi\left(x_{n}\right)$ and a white ball is added with probability $1-\pi\left(x_{n}\right)$. Originally introduced to mimic attachment under imperfect information, this model has found applications in many fields, ranging from Market Share modeling to polymer physics and biology. In this work we discuss large deviations for a wide class of continuous urn functions $\pi$. In particular, we prove that this process satisfies a Sample-Path Large Deviations principle, also providing a variational representation for the rate function. Then, we derive a variational representation for the limit $\phi\left(s\right)=\lim_{n\rightarrow\infty}{\textstyle \frac{1}{n}}\log\mathbb{P}\left(\left\{ nx_{n}=\left\lfloor sn\right\rfloor \right\} \right),\, s\in\left[0,1\right]$, where $nx_{n}$ is the number of black balls at time $n$, and use it to give some insight on the shape of $\phi\left(s\right)$. Under suitable assumptions on $\pi$ we are able to identify the optimal trajectory. We also find a non-linear Cauchy problem for the Cumulant Generating Function and provide an explicit analysis for some selected examples. In particular we discuss the linear case, which embeds the Bagchi-Pal Model, giving the exact implicit expression for $\phi$ in terms of the Cumulant Generating Function.
General characterizations of ergodic Markov chains have been developed in considerable detail. In this paper, we study the transience for discrete-time Markov chains on general state spaces, including the geometric transience and algebraic transience. Criteria are presented through establishing the drift condition and considering the first return time. As an application, we give explicit criteria for the random walk on the half line and the skip-free chain on nonnegative integers.
It has recently been discovered that some, if not all, classical novae emit GeV gamma-rays during outburst. Despite using an unreliable method to determine its distance, previous work showed that nova V1324 Sco was the most gamma-ray luminous of all gamma-ray-detected novae. We present here a different, more robust, method to determine the reddening and distance to V1324 Sco using high-resolution optical spectroscopy. Using two independent methods we derived a reddening of E(B-V) = 1.16 +/- 0.12 and a distance rD > 6.5 kpc. This distance is >40% greater than previously estimated, meaning that V1324 Sco has an even higher gamma-ray luminosity than previously calculated. We also use periodic modulations in the brightness, interpreted as the orbital period, in conjunction with pre-outburst photometric limits to show that a main-sequence companion is strongly favored.
The exact critical Casimir amplitude is derived for anisotropic systems within the $d=2$ Ising universality class by combining conformal field theory (CFT) with anisotropic $\varphi^4$ theory. Explicit results are presented for the general anisotropic scalar $\varphi^4$ model and for the fully anisotropic triangular-lattice Ising model in finite rectangular and infinite strip geometries with periodic boundary conditions (PBC). These results demonstrate the validity of multiparameter universality for confined anisotropic systems and the nonuniversality of the critical Casimir amplitude. We find an unexpected complex form of self-similarity of the anisotropy effects near the instability where weak anisotropy breaks down. This can be traced back to the property of modular invariance of isotropic CFT for $d=2$. More generally, for $d>2$ we predict the existence of self-similar structures of the finite-size scaling functions of $O(n)$-symmetric systems with planar anisotropies and PBC both in the critical region for $ n \geq 1$ as well as in the Goldstone-dominated low-temperature region for $ n \geq 2$.
Chandra observations toward the nearby molecular cloud MBM12 show unexpectedly strong and nearly equal foreground O VIII and O VII emission. As the observed portion of MBM12 is optically thick at these energies, the emission lines must be formed nearby, coming either from the Local Bubble (LB) or charge exchange with ions from the Sun. Equilibrium models for the LB predict stronger O VII than O VIII, so these results suggest that the LB is far from equilibrium or a substantial portion of O VIII is from another source, such as charge exchange within the Solar system. Despite the likely contamination, we can combine our results with other EUV and X-ray observations to reject LB models which posit a cool recombining plasma as the source of LB X-rays.
In this review article we present the calculation of the splitting rate in flat space of a macroscopic fundamental string either intersecting at a generic angle a Dp-brane or lying on it. The result is then applied, in the context of the string/gauge theory correspondence, to the study of exclusive decay rates of large spin mesons into mesons. As examples, we discuss the cases of N=4 SYM with a small number of flavors, and of QCD-like theories in the quenched approximation. In the latter context, explicit analytic formulas are given for decay rates of mesons formed either by heavy quarks or by massless quarks.
We present a multigrid algorithm for self consistent solution of the Kohn-Sham equations in real space. The entire problem is discretized on a real space mesh with a high order finite difference representation. The resulting self consistent equations are solved on a heirarchy of grids of increasing resolution with a nonlinear Full Approximation Scheme, Full Multigrid algorithm. The self consistency is effected by updates of the Poisson equation and the exchange correlation potential at the end of each eigenfunction correction cycle. The algorithm leads to highly efficient solution of the equations, whereby the ground state electron distribution is obtained in only two or three self consistency iterations on the finest scale.
We establish a structure theorem on the arc space of a $k$-scheme of finite type. More precisely, we show that the arc space is locally for the pro-smooth toplogy a product of an infinite dimensional affine space and of a non-noetherian scheme, stratified by $k$-schemes of finite type, that glues the different formal completions of the arc space. This statement globalizes Drinfeld-Grinberg-Kazhdan's theorem and proves a conjecture of Kollar and Nemethi. Then, we use this theorem to construct a derived category of constructible sheaves, stable by six operations and we show a finiteness result for the cohomology.
We construct explicit representations of the Heisenberg-Weyl algebra [P,M]=1 in terms of ladder operators acting in the space of Sheffer-type polynomials. Thus we establish a link between the monomiality principle and the umbral calculus. We use certain operator identities which allow one to evaluate explicitly special boson matrix elements between the coherent states. This yields a general demonstration of boson normal ordering of operator functions linear in either creation or annihilation operators. We indicate possible applications of these methods in other fields.
The thermal Casimir effect in ideal metal rectangular boxes is considered using the method of zeta functional regularization. The renormalization procedure is suggested which provides the finite expression for the Casimir free energy in any restricted quantization volume. This expression satisfies the classical limit at high temperature and leads to zero thermal Casimir force for systems with infinite characteristic dimensions. In the case of two parallel ideal metal planes the results, as derived previously using thermal quantum field theory in Matsubara formulation and other methods, are reproduced starting from the obtained expression. It is shown that for rectangular boxes the temperature-dependent contribution to the electromagnetic Casimir force can be both positive and negative depending on side lengths. The numerical computations of the scalar and electromagnetic Casimir free energy and force are performed for cubes
Nitrogen is an important element in various fields of stellar and Galactic astronomy, and the solar nitrogen abundance is crucial as a yardstick for comparing different objects in the cosmos. In order to obtain a precise and accurate value for this abundance, we carried out N i line formation calculations in a 3D radiative-hydrodynamic STAGGER model solar atmosphere, in full 3D non-local thermodynamic equilibrium (non-LTE), using a model atom that includes physically-motivated descriptions for the inelastic collisions of N i with free electrons and with neutral hydrogen. We selected five N i lines of high excitation energy to study in detail, based on their strengths and on their being relatively free of blends. We found that these lines are slightly strengthened from non-LTE photon losses and from 3D granulation effects, resulting in negative abundance corrections of around $-0.01$ dex and $-0.04$ dex respectively. Our advocated solar nitrogen abundance is $\log\epsilon_{\mathrm{N}} = 7.77$, with the systematic $1\sigma$ uncertainty estimated to be $0.05$ dex. This result is consistent with earlier studies after correcting for differences in line selections and equivalent widths.
Thin films of the half doped manganite Pr0.5Ca0.5MnO3 were grown on (100) oriented MgO substrates by pulsed laser deposition technique. In order to study the effect of strain on the magnetic field induced charge order melting, films of different thicknesses were prepared and their properties were studied by x-ray diffraction, electrical resistivity and magnetoresistance measurements. A field induced charge order melting is observed for films with very small thicknesses. The charge order transition temperature and the magnetic filed induced charge order melting are observed to depend on the nature of strain that is experienced by the film.
In the spirit of Lehmer's speculation that Ramanujan's tau-function never vanishes, it is natural to ask whether any given integer $\alpha$ is a value of $\tau(n)$. For odd $\alpha$, Murty, Murty, and Shorey proved that $\tau(n)\neq \alpha$ for sufficiently large $n$. Several recent papers have identified explicit examples of odd $\alpha$ which are not tau-values. Here we apply these results (most notably the recent work of Bennett, Gherga, Patel, and Siksek) to offer the first examples of even integers that are not tau-values. Namely, for primes $\ell$ we find that $$ \tau(n)\not \in \{ \pm 2\ell \ : \ 3\leq \ell< 100\} \cup \{\pm 2\ell^2 \ : \ 3\leq \ell <100\} \cup \{\pm 2\ell^3 \ : \ 3\leq \ell<100\ {\text {\rm with $\ell\neq 59$}}\}.$$ Moreover, we obtain such results for infinitely many powers of each prime $3\leq \ell<100$. As an example, for $\ell=97$ we prove that $$\tau(n)\not \in \{ 2\cdot 97^j \ : \ 1\leq j\not \equiv 0\pmod{44}\}\cup \{-2\cdot 97^j \ : \ j\geq 1\}.$$ The method of proof applies mutatis mutandis to newforms with residually reducible mod 2 Galois representation and is easily adapted to generic newforms with integer coefficients.
Image restoration is an important and challenging task in computer vision. Reverting a filtered image to its original image is helpful in various computer vision tasks. We employ a nonlinear activation function free network (NAFNet) for a fast and lightweight model and add a color attention module that extracts useful color information for better accuracy. We propose an accurate, fast, lightweight network with multi-scale and color attention for Instagram filter removal (CAIR). Experiment results show that the proposed CAIR outperforms existing Instagram filter removal networks in fast and lightweight ways, about 11$\times$ faster and 2.4$\times$ lighter while exceeding 3.69 dB PSNR on IFFI dataset. CAIR can successfully remove the Instagram filter with high quality and restore color information in qualitative results. The source code and pretrained weights are available at \url{https://github.com/HnV-Lab/CAIR}.
Supported by the use of a regular scalar field we find a black hole solution in the Einstein-Gauss-Bonnet model. From the obtained solution we can recover the Schwarzschild black hole as in other works. Later, by implementing the odd parity perturbations method we study the stability of the linearized equations of motion of the model, we find the explicit form of the Regge-Wheeler potential and we explore the condition of vanishing perturbations at the horizon of the black hole. We test the stability of the obtained solution by checking the positivity condition of the Regge-Wheeler potential. Finally, we show that the stability of model depends on the value of a parameter introduced in the profile for the scalar field.
Let $\mathcal{H}$ be a class of given graphs. A graph $G$ is said to be $\mathcal{H}$-free if $G$ contains no induced copies of $H$ for any $H \in \mathcal{H}$. In this article, we characterize all pairs $\{R,S\}$ of graphs such that every connected $\{R,S\}$-free graph has the same edge-connectivity and minimum degree.