ShantanuT01/DACTYL-Pretraining huggingface dataset:
We discuss the potential to constrain the small-$x$ PDFs using the exclusive production of heavy vector mesons. The calculation of $J/\psi$ and $\Upsilon$ photoproduction at NLO in collinear factorisation is described. The different behaviour of the NLO corrections for $J/\psi$ and $\Upsilon$ is highlighted and we outline what might be expected from the inclusion of these processes in a PDF fit.
We consider the additive martingale $W_t(\lambda)$ and the derivative martingale $\partial W_t(\lambda)$ for one-dimensional supercritical super-Brownian motions with general branching mechanism. In the critical case $\lambda=\lambda_0$, we prove that $\sqrt{t}W_t(\lambda_0)$ converges in probability to a positive limit, which is a constant multiple of the almost sure limit $\partial W_\infty(\lambda_0)$ of the derivative martingale $\partial W_t(\lambda_0)$. We also prove that, on the survival event, $\limsup_{t\to\infty}\sqrt{t}W_t(\lambda_0)=\infty$ almost surely.
We report on an electrical detection method of ultrasensitive carbon nanotube mechanical resonators. The noise floor of the detection method is reduced using a RLC resonator and an amplifier based on a high electron mobility transistor cooled at 4.2 K. This allows us to resolve the resonance frequency of nanotube resonators with an unprecedented quality. We show that the noise of the resonance frequency measured at 4.2 K is limited by the resonator itself, and not by the imprecision of the measurement. The Allan deviation reaches ~10^-5 at 125 ms integration time. When comparing the integration time dependence of the Allan deviation to a power law, the exponent approaches ~1/4. The Allan deviation might be limited by the diffusion of particles over the surface of the nanotube. Our work holds promise for mass spectrometry and surface science experiments based on mechanical nano-resonators.
We have used a combination of resonant magnetic x-ray scattering (RMXS) and x-ray absorption spectroscopy (XAS) to investigate the properties of the doped spin-orbital Mott insulator Sr2Ir(1-x)Rh(x)O4 (0.07 < x < 0.70). We show that Sr2Ir(1-x)Rh(x)O4 represents a unique model system for the study of dilute magnetism in the presence of strong spin-orbit coupling, and provide evidence of a doping-induced change in magnetic structure and a suppression of magnetic order at x_c ~ 0.17. We demonstrate that Rh-doping introduces Rh3+/Ir5+ ions which effectively hole-dope this material. We propose that the magnetic phase diagram for this material can be understood in terms of a novel spin-orbital percolation picture.
We have fabricated PbTiO$_{3}$/SrRuO$_{3}$ superlattices with ultra-thin SrRuO$_{3}$ layers. Due to the superlattice geometry, the samples show a large anisotropy in their electrical resistivity, which can be controlled by changing the thickness of the PbTiO$_{3}$ layers. Therefore, along the ferroelectric direction, SrRuO$_{3}$ layers can act as dielectric, rather than metallic, elements. We show that, by reducing the concentration of PbTiO$_{3}$, an increasingly important effect of polarization asymmetry due to compositional inversion symmetry breaking occurs. The results are significant as they represent a new class of ferroelectric superlattices, with a rich and complex phase diagram. By expanding our set of materials we are able to introduce new behaviors that can only occur when one of the materials is not a perovskite titanate. Here, compositional inversion symmetry breaking in bi-color superlattices, due to the combined variation of A and B site ions within the superlattice, is demonstrated using a combination of experimental measurements and first principles density functional theory.
Reference frames are of special importance in physics. They are usually considered to be idealized entities. However, in most situations, e.g. in laboratories, physical processes are described within reference frames constituted by physical systems. As new technological developments make it possible to demonstrate quantum properties of complex objects an interesting conceptual problem arises: Could one use states of quantum systems to define reference frames? Recently such a framework has been introduced in [F. Giacomini, E. Castro-Ruiz, and \v{C}. Brukner, Nat Commun 10, 494 (2019)]. One of its consequences is the fact that quantum correlations depend on a physical state of an observers reference frame. The aim of this work is to examine the dynamical aspect of this phenomena and show that the same is true for correlations established during an evolution of a composite systems. Therefore, decoherence process is also relative: For some observers the reduced evolution of subsystems is unitary, whereas for others not. I also discuss implications of this results for modern developments of decoherence theory: Quantum Darwinism and Spectrum Broadcast Structures.
Various spin observables (analyzing powers and spin-correlation parameters) in $pd$ elastic scattering at $T_p = 800-1000$ MeV are analyzed within the framework of the refined Glauber model. The theoretical model uses as input spin-dependent $NN$ amplitudes obtained from the most recent partial-wave analysis and also takes into account the deuteron $D$ wave and charge-exchange effects. Predictions of the refined Glauber model are compared with the existing experimental data. Reasonable agreement between the theoretical calculations and experimental data at low momentum transfers $|t| \lesssim 0.2$ (GeV/$c)^2$ is found for all observables considered. Moderate discrepancies found in this region are shown to be likely due to uncertainties in the input $NN$ amplitudes. Qualitative agreement at higher momentum transfers is also found for most observables except the tensor ones with mixed $x$ and $z$ polarization components. Possible reasons for observed deviations of the model calculations from the data at $|t| > 0.2$ (GeV/$c)^2$ are discussed.
We recognize that the skin lesion diagnosis is an essential and challenging sub-task in Image classification, in which the Fisher vector (FV) encoding algorithm and deep convolutional neural network (DCNN) are two of the most successful techniques. Since the joint use of FV and DCNN has demonstrated proven success, the joint techniques could have discriminatory power on skin lesion diagnosis as well. To this hypothesis, we propose the aggregation algorithm for skin lesion diagnosis that utilize the residual network to extract the local features and the Fisher vector method to aggregate the local features to image-level representation. We applied our algorithm on the International Skin Imaging Collaboration 2018 (ISIC2018) challenge and only focus on the third task, i.e., the disease classification.
The present work is an endeavour to connect the properties of tiny nearly massless objects with those of some of the most massive ones, the compact stars.   Since 1996 there is major influx of X-ray and $\gamma$ ray data from binary stars, one or both of which are compact objects that are difficult to explain as neutron stars since they contain a mass M in too small a radius R . The suggestion has been put forward that these are strange quark stars (SS) explainable in a simple model with chiral symmetry restoration (CSR) for the quarks and the M, R and other properties like QPOs (quasi periodic oscillations) in their X-ray power spectrum.   It would be nice if this astrophysical data could shed some light on fundamental properties of quarks obeying QCD. One can relate the strong coupling constant of QCD, $\alpha_s$ to the quark mass through the Dyson-Schwinger gap equation using the real time formalism of Dolan and Jackiw. This enables us to obtain the density dependence of $\alpha_s$ from the simple CSR referred to above. This way fundamental physics, difficult to extract from other models like for example lattice QCD, can be constrained from present-day compact star data and may be put back to modelling the dense quark phase of early universe.
We calculate the high energy neutrino spectrum from gamma-ray bursts where the emission arises in a dissipative jet photosphere determined by either baryonically or magnetically dominated dynamics, and compare these neutrino spectra to those obtained in conventional internal shock models. We also calculate the diffuse neutrino spectra based on these models, which appear compatible with the current IceCube 40+59 constraints. While a re-analysis based on the models discussed here and the data from the full array would be needed, it appears that only those models with the most extreme parameters are close to being constrained at present. A multi-year operation of the full IceCube and perhaps a next generation of large volume neutrino detectors may be required in order to distinguish between the various models discussed.
We built a multi-wavelength dataset for galaxies from the Local Volume HI Survey (LVHIS), which comprises 82 galaxies. We also select a sub-sample of ten large galaxies for investigating properties in the galactic outskirts. The LVHIS sample covers nearly four orders of magnitude in stellar mass and two orders of magnitude in HI mass fraction (fHI). The radial distribution of HI gas with respect to the stellar disc is correlated with fHI but with a large scatter. We confirm the previously found correlations between the total HI mass and star formation rate (SFR), and between HI surface densities and SFR surface densities beyond R25. However, the former correlation becomes much weaker when the average surface densities rather than total mass or rate are considered, and the latter correlation also becomes much weaker when the effect of stellar mass is removed or controlled. Hence the link between SFR and HI is intrinsically weak in these regions, consistent with what was found on kpc scales in the galactic inner regions. We find a strong correlation between the SFR surface density and the stellar mass surface density, which is consistent with the star formation models where the gas is in quasi-equilibrium with the mid-plane pressure. We find no evidence for HI warps to be linked with decreasing star forming efficiencies.
Second order phase transitions are universally driven by an order parameter which becomes trivial at the critical point. At the same time, collective excitations which involve the amplitude of the order parameter develop a gap which smoothly closes to zero at criticality. We develop analytical techniques to study this "Higgs" mode in holographic systems which undergo a continuous phase transition at finite temperature and chemical potential. This allows us to study the linear response of the system at energy scales of the order of the gap. We express the Green's functions of scalar operators in terms of thermodynamic quantities and a single transport coefficient which we fix in terms of black hole horizon data.
We construct the most general chirally-invariant Lagrangian for mesons in the presence of external sources coupled to the tensor current \bar{\psi}\sigma_{\mu\nu}\psi. In order to have only even terms in the chiral expansion, we consider the new source of O(p^2). With this choice, we build the even-parity effective Lagrangian up to the p^6-order (NLO). While there are only 4 new terms at the p^4-order, at p^6-order we find 78 terms for n_f=2 and 113 terms for n_f=3. We provide a detailed discussion on the different mechanisms that ensure that our final set of operators is complete and non-redundant. We also examine the odd-parity sector, to conclude that the first operators appear at the p^8-order (NNLO).
The Paper actually concerns a toy model, not physical Casimir cavities made of conducting plates, but the results are taken implicitly to apply in general. We question on general physical grounds one basic assumption and the results of a renormalization procedure. Then, for physical systems, i) considering condensed matter theory/experiments, we find strong evidence against the conclusive claims concerning a putative and dominating surface energy present individually on the plates, and ii) we propose two experiments with physical Casimir cavities to show in detail that the results of the renormalization in this case look somewhat paradoxical. In any case the proposed experiments appear to be feasible and thus it could be tested if the putative self-energies of the plates are indeed there in a physical Casimir cavity, or if the toy model of the Paper has by contrast no connection with physical reality. However at the moment the authors are not legitimate to issue as conclusive claims statements like- refute the claim sometimes attributed to Feynman that virtual photons do not gravitate -
We study the angular correlation function of speckle patterns that result from multiple scattering of photons by cold atomic clouds. We show that this correlation function becomes larger than the value given by Rayleigh law for classical scatterers. These large intensity fluctuations constitute a new mesoscopic interference effect specific to atom-photon interactions, that could not be observed in other systems such as weakly disordered metals. We provide a complete description of this behavior and expressions that allow for a quantitative comparison with experiments.
Three decades ago the first convincing evidence of microbial fossils in carbonaceous chondrites was discovered and reported by Hans Dieter Pflug and his collaborators. In addition to morphology, other data, notably laser mass spectroscopy, confirmed the identification of such structures as putative bacterial fossils. Balloon-borne cryosampling of the stratosphere enables recovery of fragile cometary dust aggregates with their structure and carbonaceous matter largely intact. Scanning electron microscope studies of texture and morphology of particles in the Cardiff collection, together with Energy Dispersive X-ray identifications, show two main types of putative bio-fossils - firstly organic-walled hollow spheres around 10 microns across, secondly siliceous diatom skeletons similar to those found in carbonaceous chondrites and terrestrial sedimentary rocks and termed "acritarchs". Since carbonaceous chondrites (particularly Type 1 chondrites) are thought to be extinct comets the data reviewed in this article provide strong support for theories of cometary panspermia.
The central result of this paper is an analytic duality relation for real-valued L\'evy processes killed upon exiting a half-line. By Nagasawa's theorem, this yields a remarkable time-reversal identity involving the L\'evy process conditioned to stay positive. As examples of applications, we construct a version of the L\'evy process indexed by the entire real line and started from $-\infty$ which enjoys a natural spatial-stationarity property, and point out that the latter leads to a natural Lamperti-type representation for self-similar Markov processes in $(0,\infty)$ started from the entrance point 0+.
H2O+ has been observed in its ortho- and para- states toward the massive star forming core Sgr B2(M), located close to the Galactic center. The observations show absorption in all spiral arm clouds between the Sun and Sgr B2. The average o/p ratio of H2O+ in most velocity intervals is 4.8, which corresponds to a nuclear spin temperature of 21 K. The relationship of this spin temperature to the formation temperature and current physical temperature of the gas hosting H2O+ is discussed, but no firm conclusion is reached. In the velocity interval 0 to 60 km/s, an ortho/para ratio of below unity is found, but if this is due to an artifact of contamination by other species or real is not clear.
We study the phase diagram of the triangular-lattice $Q$-state Potts model in the real $(Q,v)$-plane, where $v=e^J-1$ is the temperature variable. Our first goal is to provide an obviously missing feature of this diagram: the position of the antiferromagnetic critical curve. This curve turns out to possess a bifurcation point with two branches emerging from it, entailing important consequences for the global phase diagram. We have obtained accurate numerical estimates for the position of this curve by combining the transfer-matrix approach for strip graphs with toroidal boundary conditions and the recent method of critical polynomials. The second goal of this work is to study the corresponding $A_{p-1}$ RSOS model on the torus, for integer $p=4,5,\ldots,8$. We clarify its relation to the corresponding Potts model, in particular concerning the role of boundary conditions. For certain values of $p$, we identify several new critical points and regimes for the RSOS model and we initiate the study of the flows between the corresponding field theories.
We derive the fraction of substructure in the Galactic halo using a sample of over 10,000 spectroscopically-confirmed halo giant stars from the LAMOST spectroscopic survey. By observing 100 synthetic models along each line of sight with the LAMOST selection function in that sky area, we statistically characterize the expected halo populations. We define as SHARDS (Stellar Halo Accretion Related Debris Structures) any stars in >3-sigma excesses above the model predictions. We find that at least 10% of the Milky Way halo stars from LAMOST are part of SHARDS. By running our algorithm on smooth halos observed with the LAMOST selection function, we show that the LAMOST data contain excess substructure over all Galactocentric radii R_GC < 40 kpc, beyond what is expected due to statistical fluctuations and incomplete sampling of a smooth halo. The level of substructure is consistent with the fraction of stars in SHARDS in model halos created entirely from accreted satellites. This work illustrates the potential of vast spectroscopic surveys with high filling factors over large sky areas to recreate the merging history of the Milky Way.
We study the threshold $\theta$ contact process on $\mathbb{Z}^d$ with infection parameter $\lambda$. We show that the critical point $\lambda_{\mathrm{c}}$, defined as the threshold for survival starting from every site occupied, vanishes as $d\to\infty$. This implies that the threshold $\theta$ voter model on $\mathbb{Z}^d$ has a nondegenerate extremal invariant measure, when $d$ is large.
In this paper we combine archival and proprietary XMM-Newton observations (about 5deg^2) that overlap with the Sloan Digital Sky Survey to explore the nature of the moderate-z X-ray population. We focus on X-ray sources with optically red colours (g-r>0.4), which we argue are important for understanding the origin of the X-ray background. Firstly, these systems constitute a significant fraction, about 2/3, of the z<1 X-ray population to the limit f(2-8keV)~2e-14cgs. Secondly, their luminosity function under evolution of the form ~(1+z)^3 suggests that they could be responsible for about 17 per cent of the diffuse X-ray background to z=1. Thirdly, their stacked X-ray spectrum in the range 1-8keV is consistent with a power-law distribution with Gamma~1.4 (without fitting intrinsic absorption), i.e. similar to the diffuse X-ray background. We find that the optically red X-ray population comprises a mixed bag of objects, both obscured (N_H>1e22 cm^{-2}) and unobscured (N_H<1e22 cm^{-2}), with a wide range of X-ray luminosities up L_X~1e44cgs. We argue that dilution of the AGN light by the host galaxy may play a role in shaping the continuum optical emission of this population. Finally, we explore a possible association of these sources and the moderate-z red (J-Ks>2mag) AGNs identified in the Two Micron All Sky Survey (2MASS). The median N_H of the red X-ray sources studied here is ~1e21cm^{-2}, lower than that found for the 2MASS AGNs, suggesting different populations.
HAGAR is a system of seven Non-imaging Atmospheric Cherenkov Telescopes located at Hanle in the Ladakh region of the Indian Himalayas at an altitude of 4270 meters {\it amsl}. Since 2008, we have observed the Crab Nebula to assess the performance of the HAGAR telescopes. We describe the analysis technique for the estimation of $\gamma$-ray signal amidst cosmic ray background. The consolidated results spanning nine years of the Crab nebula observations show long term performance of the HAGAR telescopes. Based on about 219 hours of data, we report the detection of $\gamma$-rays from the Crab Nebula at a significance level of about 20$\sigma$, corresponding to a time averaged flux of (1.64$\pm$0.09) $\times10^{-10}$ photons cm$^{-2}$ sec$^{-1}$ above 230 GeV. Also, we perform a detailed study of possible systematic effects in our analysis method on data taken with the HAGAR telescopes.
Sutter et al. have responded to the criticisms we made of their cosmic void catalogue in our recent paper presenting an alternative catalogue (Nadathur & Hotchkiss 2013). Unfortunately, their response contains several statements which are incorrect, as we point out in this note.
We write down and solve a closed set of Schwinger-Dyson equations for the two-matrix model in the large $N$ limit. Our elementary method yields exact solutions for correlation functions involving angular degrees of freedom whose calculation was impossible with previously known techniques. The result sustains the hope that more complicated matrix models important for lattice string theory and QCD may also be solvable despite the problem of the angular integrations. As an application of our method we briefly discuss the calculation of wavefunctions with general matter boundary conditions for the Ising model coupled to $2D$ quantum gravity. Some novel insights into the relationship between lattice and continuum boundary conditions are obtained.
Compensated isocurvature perturbations (CIPs) are modes in which the baryon and dark matter density fluctuations cancel. They arise in the curvaton scenario as well as some models of baryogenesis. While they leave no observable effects on the cosmic microwave background (CMB) at linear order, they do spatially modulate two-point CMB statistics and can be reconstructed in a manner similar to gravitational lensing. Due to the similarity between the effects of CMB lensing and CIPs, lensing contributes nearly Gaussian random noise to the CIP estimator that approximately doubles the reconstruction noise power. Additionally, the cross correlation between lensing and the integrated Sachs-Wolfe (ISW) effect generates a correlation between the CIP estimator and the temperature field even in the absence of a correlated CIP signal. For cosmic-variance limited temperature measurements out to multipoles $l \leq 2500$, subtracting a fixed lensing bias degrades the detection threshold for CIPs by a factor of $1.3$, whether or not they are correlated with the adiabatic mode.
A comparative study of the liquid-drop model (LDM) type expansions of energy $E$ and compression modulus $K_A$ is made within the energy density formalism using Skyrme interactions. As compared to the energy expansion, it is found that, in the pure bulk mode of density vibration, the LDM expansion of $K_A$ shows an anomalous convergence behaviour due to {\it pair \ effect}. A least squares fit analysis is done to estimate the minimum error, one would expect even with synthetic data due to the inherent nature of the LDM expansion of $K_A$ as well as the narrow range of accessible mass number $A$, in the values of the various coefficients. The dependence of the higher-order coefficients like curvature and Gauss curvature on the coupling $\beta_c$ between the bulk and surface parts of the monopole vibrations is analytically studied. It is shown that the $K_A -$ expansion including the dynamical effect ( $A-$ dependence of $\beta_c$ ) shows an `up-turn' behaviour below mass number about 120, suggesting the inapplicability of the LDM expansion of $K_A$ over this mass region.
In this paper we show that a uniruled manifold with a split tangent bundle admits almost holomorphic fibrations that are related to the splitting. We analyse these fibrations in detail in several special cases, this yields new results about the integrability of the direct factors and the universal covering of the manifold.