ShantanuT01/DACTYL-Pretraining huggingface dataset:
The Janis-Newman algorithm is an old but very powerful tool to generate rotating solutions from static ones through a set of complex coordinate transformations. Several solutions have been derived in this way, including solutions with gauge fields. However, the transformation of the latter was so far always postulated as an ad hoc result. In this paper we propose a generalization of the procedure, extending it to the transformation of the gauge field. We also present a simplification of the algorithm due to G. Giampieri. We illustrate our prescription on the Kerr-Newman solution.
We report the observation of a very high energy \gamma-ray source, whose position is coincident with HESS J1841-055. This source has been observed for 4.5 years by the ARGO-YBJ experiment from November 2007 to July 2012. Its emission is detected with a statistical significance of 5.3 standard deviations. Parameterizing the source shape with a two-dimensional Gaussian function we estimate an extension \sigma=(0.40(+0.32,-0.22}) degree, consistent with the HESS measurement. The observed energy spectrum is dN/dE =(9.0-+1.6) x 10^{-13}(E/5 TeV)^{-2.32-+0.23} photons cm^{-2} s^{-1} TeV^{-1}, in the energy range 0.9-50 TeV. The integral \gamma-ray flux above 1 TeV is 1.3-+0.4 Crab units, which is 3.2-+1.0 times the flux derived by HESS. The differences in the flux determination between HESS and ARGO-YBJ, and possible counterparts at other wavelengths are discussed.
It has been shown that the non-sinusoidal character oscillations appear in the transmitted, reflected and absorbed light fluxes when light pulses irradiate a semiconductor quantum well (QW), containing a set of a large number of the equidistant energy levels of electronic excitations. The oscillation amplitude is comparable to the flux values for the short pulses, duration of which \gamma_l^{-1} \leq \hbar/\Delta E. A damping echo of the exciting pulse appears through the time intervals 2\pi\hbar/\Delta E in the case of the very short light pulses \gamma_l^{-1}\ll \hbar/\Delta E. Symmetrical and asymmetrical pulses with a sharp front have been considered. Our theory is applicable for the narrow QWs in a strong magnetic field, when the equidistant energy levels correspond to the electron-hole pairs with different Landau quantum numbers.
Recently, from the new Spitzer Photometry and Accurate Rotation Curves (SPARC) data, McGaugh et al. (2016) reported a tight Radial Acceleration Relation (RAR) between the observed total acceleration and the acceleration produced by baryons in spiral galaxies. The relation can be fitted by different functions. However, these functions can be discerned if we express the data in the form of halo acceleration relation (HAR). The data reveals a maximum in the halo acceleration. We examined NFW (cusp) and Burkert (core) profiles in the context of dark matter and different parameter families of the interpolating function in the framework of Modified Newtonian Dynamics (MOND).
We are interested in a kinetic equation intended to describe the interaction of particles with their environment. The environment is modeled by a collection of local vibrational degrees of freedom. We establish the existence of weak solutions for a wide class of initial data and external forces. We also identify a relevant regime which allows us to derive, quite surprisingly, the attractive Vlasov--Poisson system from the coupled Vlasov-Wave equations.
Using the machinery from the theory of Calabi-Yau differential equations, we find formulas for $1/\pi^2$ of hypergeometric and non-hypergeometric types.
We have built an information engine that can transport a bead in a desired direction by using favorable fluctuations from the thermal bath. However, in its original formulation, the information engine generates a fluctuating velocity and cannot control the position of the bead. Here, we introduce a feedback algorithm that can control the bead's position, to follow a desired trajectory. The bead can track the path if the maximum desired velocity is below the engine's maximum average velocity. Measuring the range of frequency that the feedback algorithm can track, we find a bandwidth that is slightly lower than the corner frequency of the bead in the trap.
We present results of deep integral field spectroscopy observations using high resolution optical (4150-7200 A) VIMOS VLT spectra, of NGC 4696, the dominant galaxy in the Centaurus cluster (Abell 3526). After the Virgo cluster, this is the second nearest (z=0.0104) example of a cool core cluster. NGC 4696 is surrounded by a vast, luminous H alpha emission line nebula (L = 2.2 \times 10^40 ergs per second). We explore the origin and excitation of the emission-line filaments and find their origin consistent with being drawn out, under rising radio bubbles, into the intracluster medium as in other similar systems. Contrary to previous observations we do not observe evidence for shock excitation of the outer filaments. Our optical spectra are consistent with the recent particle heating excitation mechanism of Ferland et al.
I investigate an analytical model of galaxy clusters based on the assumption that the intracluster medium plasma is polytropic and is in hydrostatic equilibrium. The Einasto profile is adopted as a model for the spatial-density distribution of dark matter halos. This model has sufficient degrees of freedom to simultaneously fit X-ray surface brightness and temperature profiles, with five parameters to describe the global cluster properties and three additional parameters to describe the cluster's cool-core feature. The model is tested with Chandra X-ray data for seven galaxy clusters, including three polytropic clusters and four cool-core clusters. It is found that the model accurately reproduces the X-ray data over most of the radial range. For all galaxy clusters, the data allows to show that the model is essentially as good as that of Vikhlinin et al and Bulbul et al, as inferred by the reduced $\chi^2$.
We consider a random walker whose motion is tethered around a focal point. We use two models that exhibit the same spatial dependence in the steady state but widely different dynamics. In one case, the walker is subject to a deterministic bias towards the focal point, while in the other case, it resets its position to the focal point at random times. The deterministic tendency of the biased walker makes the forays away from the focal point more unlikely when compared to the random nature of the returns of the resetting walker. This difference has consequences on the spatio-temporal dynamics at intermediate times. To show the differences in the two models, we analyze their probability distribution and their dynamics in presence and absence of partially or fully absorbing traps. We derive analytically various quantities: (i) mean first-passage times to one target, where we recover results obtained earlier by a different technique, (ii) splitting probabilities to either of two targets as well as survival probabilities when one or either target is partially absorbing. The interplay between confinement, diffusion and absorbing traps produces interesting non-monotonic effects in various quantities, all potentially accessible in experiments. The formalism developed here may have a diverse range of applications, from study of animals roaming within home ranges and of electronic excitations moving in organic crystals to developing efficient search algorithms for locating targets in a crowded environment.
In a first step, we establish the existence (and sometimes the uniqueness) of solutions for a large class of quadratic backward stochastic differential equations (QBSDEs) with continuous generator and a merely square integrable terminal condition. Our approach is different from those existing in the literature. Although we are focused on QBSDEs, our existence result also covers the BSDEs with linear growth, keeping $\xi$ square integrable in both cases. As byproduct, the existence of viscosity solutions is established for a class of quadratic partial differential equations (QPDEs) with a square integrable terminal datum. In a second step, we consider QBSDEs with measurable generator for which we establish a Krylov's type a priori estimate for the solutions. We then deduce an It\^o--Krylov's change of variable formula. This allows us to establish various existence and uniqueness results for classes of QBSDEs with square integrable terminal condition and sometimes a merely measurable generator. Our results show, in particular, that neither the existence of exponential moments of the terminal datum nor the continuity of the generator are necessary to the existence and/or uniqueness of solutions for quadratic BSDEs. Some comparison theorems are also established for solutions of a class of QBSDEs.
In this paper, we have presented the impact of the gate leakage through thin gate dielectrics (SiO2 and high-\k{appa} gate dielectric) on the subthreshold characteristics of the tunnel field effect transistors (TFET) for a low operating voltage of 0.5 V. Using calibrated two-dimensional simulations it is shown that even for such a low operating voltage, the gate leakage substantially degrades several subthreshold parameters of the TFET such as the off-state current, minimum subthreshold swing and average subthreshold swing. While the drain-offset as well as the short-gate are effective methods for reducing the gate leakage, we show that if the gate tunneling leakage is not considered, even for these two methods, the overall TFET off-state current will be significantly underestimated. Our results demonstrate the need to carefully account for the gate leakage in the design of TFETs just as it is done for the conventional nanoscale MOSFETs.
We explore via linearized perturbation theory the Gregory-Laflamme instability of the black string solutions of Einstein's equations with negative cosmological constant recently discussed in literature. Our results indicate that the black strings whose conformal infinity is the product of time and $S^{d-3}\times S^1$ are stable for large enough values of the event horizon radius. All topological black strings are also classically stable. We argue that this provides an explicit realization of the Gubser-Mitra conjecture.
We analyze the properties of the quasi-one-dimensional triangle lattice emphasizing the occurrence of flat bands and band touching via the tuning of the lattice hopping parameters and on-site energies. The spectral properties of the infinite system will be compared with the transmission through a finite piece of the lattice with attached semi-infinite leads. Furthermore, we investigate the adiabatic pumping properties of such a system: depending on the transmission through the lattice, this results in nonzero integer charge transfers or transfers that increase linearly with the lattice size.
We investigate the impact of astrophysical systematics on cosmic shear cosmological parameter constraints from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), and the concordance with cosmic microwave background measurements by Planck. We present updated CFHTLenS cosmic shear tomography measurements extended to degree scales using a covariance calibrated by a new suite of N-body simulations. We analyze these measurements with a new model fitting pipeline, accounting for key systematic uncertainties arising from intrinsic galaxy alignments, baryonic effects in the nonlinear matter power spectrum, and photometric redshift uncertainties. We examine the impact of the systematic degrees of freedom on the cosmological parameter constraints, both independently and jointly. When the systematic uncertainties are considered independently, the intrinsic alignment amplitude is the only degree of freedom that is substantially preferred by the data. When the systematic uncertainties are considered jointly, there is no consistently strong preference in favor of the more complex models. We quantify the level of concordance between the CFHTLenS and Planck datasets by employing two distinct data concordance tests, grounded in Bayesian evidence and information theory. We find that the two data concordance tests largely agree with one another, and that the level of concordance between the CFHTLenS and Planck datasets is sensitive to the exact details of the systematic uncertainties included in our analysis, ranging from decisive discordance to substantial concordance as the treatment of the systematic uncertainties becomes more conservative. The least conservative scenario is the one most favored by the cosmic shear data, but it is also the one that shows the greatest degree of discordance with Planck. The data and analysis code are public at https://github.com/sjoudaki/cfhtlens_revisited
As one candidate of the higher dimensional black holes, the 5D Ricci-flat black string is considered in this paper. By means of a non-trivial potential $V_{n}$, the quasi-normal modes of a massless scalar field around this black string space is studied. By using the classical third order WKB approximation, we analyse carefully the evolution of frequencies in two aspects, one is the induced cosmological constant $\Lambda$ and the other is the quantum number $n$. The massless scalar field decays more slowly because of the existences of the fifth dimension and the induced cosmological constant. If extra dimension has in fact existed near black hole, those quasi-normal frequencies may have some indication on it.
We show that indefinite theta series on cones converge and provide an explicit modular completion. Our completion rests on a convolution of the Gaussian with a piecewise constant function supported on the cone. Our main innovation is to formulate this convolution in terms of euclidean geometry as opposed to hyperbolic geometry. This change of perspective allows us to establish essential asymptotic estimates without further difficulty.
We consider a model of fragmentation of sheet by cracks that move with a velocity in preferred direction, but undergo random transverse displacements as they move. There is a non-zero probability of crack-splitting, and the split cracks move independently. If two cracks meet, they merge, and move as a single crack. In the steady state, there is non-zero density of cracks, and the sheet left behind by the moving cracks is broken into a large number of fragments of different sizes. The evolution operator for this model reduces to the Hamiltonian of quantum XY spin chain, which is exactly integrable. This allows us to determine the steady state, and also the distribution of sizes of fragments.
We study fully nonlinear elliptic equations such as \[ F(D^2u) = u^p, \quad p>1, \] in $\R^n$ or in exterior domains, where $F$ is any uniformly elliptic, positively homogeneous operator. We show that there exists a critical exponent, depending on the homogeneity of the fundamental solution of $F$, that sharply characterizes the range of $p>1$ for which there exist positive supersolutions or solutions in any exterior domain. Our result generalizes theorems of Bidaut-V\'eron \cite{B} as well as Cutri and Leoni \cite{CL}, who found critical exponents for supersolutions in the whole space $\R^n$, in case $-F$ is Laplace's operator and Pucci's operator, respectively. The arguments we present are new and rely only on the scaling properties of the equation and the maximum principle.
We study the clustering of matter in the intergalactic medium from the Lyman-alpha forests seen in the spectra of pairs or groups of z ~ 2 quasars observed with FORS2 and UVES at the VLT-UT2 Kueyen ESO telescope. The sample consists of five pairs with separations 0.6, 1, 2.1, 2.6 and 4.4 arcmin and a group of four quasars with separations from 2 up to 10 arcmin. This unprecedented data set allows us to measure the transverse flux correlation function for a range of angular scales. Correlations are clearly detectable at separations smaller than 3 arcmin. The shape and correlation length of the transverse correlation function on these scales is in good agreement with those expected from absorption by the photoionized warm intergalactic medium associated with the filamentary and sheet-like structures predicted in CDM-like models for structure formation. At larger separation no significant correlation is detected. Assuming that the absorbing structures are randomly orientated with respect to the line of sight, the comparison of transverse and longitudinal correlation lengths constrains the cosmological parameters (as a modified version of the Alcock & Paczy\'nski test). The present sample is too small to get significant constraints. Using N-body simulations, we investigate the possibility to constrain Ol from future larger samples of QSO pairs with similar separations. The observation of a sample of 30 pairs at 2, 4.5 and 7.5 arcmin should constrain the value of Ol at +- 15 % (2 sigma level). We further use the observed spectra of the group of four quasars, to search for underdense regions in the intergalactic medium. We find a quasi-spherical structure of reduced absorption with radius 12.5 h^{-1} Mpc which we identify as an underdense region.
The current paper establishes the global well-posedness issue for the full viscous MHD equations in the axisymmetric setting. Global solutions are obtained in critical Besov spaces uniformly to the viscosity when the resistivity is fixed in the spirit of \cite{AKH,Hassainia,hz0}. Furthermore, strong convergence in the resolution spaces with a rate of convergence is also studied.
Here I review the transverse momentum distributions of identified hadrons produced in Au-Au collisions at RHIC and Pb-Pb collisions at LHC in the framework of recombination model. Minijets play an important role in generating shower partons in the intermediate $p_T$ region. At LHC, the resultant soft shower partons are even found to dominate over the thermal partons in the non-strange sector. The azimuthal anisotropy of the produced hadrons could also be explained as the consequence of the effects of minijets. Harmonic analysis of the $\phi$ dependence leads to $v_n(p_T, b)$ that can be well produced without reference to flow.
Here we report successful synthesis of single crystalline magnetic Weyl semimetal Co3Sn2S2. The synthesized crystal is characterized through various tools viz. X-ray diffraction, field emission electron microscopy and X-ray photoelectron spectroscopy. A clear ferromagnetic transition is observed in magnetization and heat capacity at around 175K, which is further verified through electrical transport measurements. Hysteresis is observed in R-T measurements in cooling and warming cycle, showing the presence of first order phase transition and charge ordering in the synthesized sample. The synthesized Co3Sn2S2 exhibits high magnetoresistance of around 230% at 2K. The transport phenomenon in synthesized Co3Sn2S2 appears to have contributions from topological surface states at low temperature below say 70 K, and above that the same is found to be strongly dependent on its bulk magnetic state. Magnetoconductivity data at low fields of up to plus minus 1T (Tesla) is fitted with Hikami Larkin Nagaoka model, which shows the presence of weak antilocalization effect in synthesized Co3Sn2S2 crystal at low temperatures below 30K.
Supervised hashing methods are widely-used for nearest neighbor search in computer vision applications. Most state-of-the-art supervised hashing approaches employ batch-learners. Unfortunately, batch-learning strategies can be inefficient when confronted with large training datasets. Moreover, with batch-learners, it is unclear how to adapt the hash functions as a dataset continues to grow and diversify over time. Yet, in many practical scenarios the dataset grows and diversifies; thus, both the hash functions and the indexing must swiftly accommodate these changes. To address these issues, we propose an online hashing method that is amenable to changes and expansions of the datasets. Since it is an online algorithm, our approach offers linear complexity with the dataset size. Our solution is supervised, in that we incorporate available label information to preserve the semantic neighborhood. Such an adaptive hashing method is attractive; but it requires recomputing the hash table as the hash functions are updated. If the frequency of update is high, then recomputing the hash table entries may cause inefficiencies in the system, especially for large indexes. Thus, we also propose a framework to reduce hash table updates. We compare our method to state-of-the-art solutions on two benchmarks and demonstrate significant improvements over previous work.
We present the distance matrix evolution for different types of networks: exponential, scale-free and classical random ones. Statistical properties of these matrices are discussed as well as topological features of the networks. Numerical data on the degree and distance distributions are compared with theoretical predictions.
We make a first attempt to find dwarf galaxies in eight \Fermi-LAT extended, unassociated, source fields using \Gaia\ DR2. We probe previously unexplored heliocentric distances of $d<20$~kpc with an extreme-deconvolution (XD) technique. We find no signature of a dwarf galaxy in any of these fields despite \Gaia's excellent astrometric accuracy. We estimate our detection limits by applying the XD method to mock data, obtaining a conservative limit on the stellar mass of $M_* < 10^4$~M$_{\sun}$ for $d < 20$\, kpc. Such a low stellar mass implies either a low-mass subhalo, or a massive stripped-down subhalo. We use an analytic model for stripped subhalos to argue that, given the sizes and fluxes of the \Fermi-LAT sources, we can reject the hypothesis that they owe to dark matter annihilation.
We consider the Dirac cones and higher-order topological phases in quasi-continuous media of classical waves (e.g., photonic and sonic crystals). Using sonic crystals as prototype examples, we revisit some of the known systems in the study of topological acoustics. We show the emergence of various Dirac cones and higher-order topological band gaps in the same motherboard by tuning the geometry of the system. We provide a pedagogical review of the underlying physics and methodology via the bulk-edge-corner correspondence, symmetry-based indicators, Wannier representations, filling anomaly, and fractional corner charges. In particular, the theory of the Dirac cones and the higher-order topology are put in the same framework. These examples and the underlying physics principles can be inspiring and useful in the future study of higher-order topological metamaterials.
Recently, it has been determined that there are 242 Wilf classes of triples of 4-letter permutation patterns by showing that there are 32 non-singleton Wilf classes. Moreover, the generating function for each triple lying in a non-singleton Wilf class has been explicitly determined. In this paper, toward the goal of enumerating avoiders for the singleton Wilf classes, we obtain the generating function for all but one of the triples containing 1324. (The exceptional triple is conjectured to be intractable.) Our methods are both combinatorial and analytic, including generating trees, recurrence relations, and decompositions by left-right maxima. Sometimes this leads to an algebraic equation for the generating function, sometimes to a functional equation or a multi-index recurrence amenable to the kernel method.
For any given algebra of local observables in Minkowski space an associated scaling algebra is constructed on which renormalization group (scaling) transformations act in a canonical manner. The method can be carried over to arbitrary spacetime manifolds and provides a framework for the systematic analysis of the short distance properties of local quantum field theories. It is shown that every theory has a (possibly non-unique) scaling limit which can be classified according to its classical or quantum nature. Dilation invariant theories are stable under the action of the renormalization group. Within this framework the problem of wedge (Bisognano-Wichmann) duality in the scaling limit is discussed and some of its physical implications are outlined.