ShantanuT01/DACTYL-Pretraining huggingface dataset:
Camera fingerprints are precious tools for a number of image forensics tasks. A well-known example is the photo response non-uniformity (PRNU) noise pattern, a powerful device fingerprint. Here, to address the image forgery localization problem, we rely on noiseprint, a recently proposed CNN-based camera model fingerprint. The CNN is trained to minimize the distance between same-model patches, and maximize the distance otherwise. As a result, the noiseprint accounts for model-related artifacts just like the PRNU accounts for device-related non-uniformities. However, unlike the PRNU, it is only mildly affected by residuals of high-level scene content. The experiments show that the proposed noiseprint-based forgery localization method improves over the PRNU-based reference.
High-energy gamma rays of interstellar origin are produced by the interaction of cosmic-ray (CR) particles with the diffuse gas and radiation fields in the Galaxy. The main features of this emission are well understood and are reproduced by existing CR propagation models employing 2D Galactocentric cylindrically symmetrical geometry. However, the high-quality data from instruments like the Fermi Large Area Telescope reveal significant deviations from the model predictions on few to tens of degree scales indicating the need to include the details of the Galactic spiral structure and thus require 3D spatial modelling. In this paper the high-energy interstellar emissions from the Galaxy are calculated using the new release of the GALPROP code employing 3D spatial models for the CR source and interstellar radiation field (ISRF) densities. Three models for the spatial distribution of CR sources are used that are differentiated by their relative proportion of input luminosity attributed to the smooth disc or spiral arms. Two ISRF models are developed based on stellar and dust spatial density distributions taken from the literature that reproduce local near- to far-infrared observations. The interstellar emission models that include arms and bulges for the CR source and ISRF densities provide plausible physical interpretations for features found in the residual maps from high-energy gamma-ray data analysis. The 3D models for CR and ISRF densities provide a more realistic basis that can be used for the interpretation of the non-thermal interstellar emissions from the Galaxy.
Theoretical study of anomalous decay mode tau -> omega3pinu is presented.
In 1940 Fisher famously showed that if there exists a non-trivial $(v,k,\lambda)$-design then $\lambda(v-1) \geq k(k-1)$. Subsequently Bose gave an elegant alternative proof of Fisher's result. Here, we show that the idea behind Bose's proof can be generalised to obtain new bounds on the number of blocks in $(v,k,\lambda)$-coverings and -packings with $\lambda(v-1)<k(k-1)$.
Spirals and helices are common motifs of long-range order in magnetic solids, and they may also be organized into more complex emergent structures such as magnetic skyrmions and vortices. A new type of spiral state, the spiral spin-liquid, in which spins fluctuate collectively as spirals, has recently been predicted to exist. Here, using neutron scattering techniques, we experimentally prove the existence of a spiral spin-liquid in MnSc$_2$S$_4$ by directly observing the 'spiral surface' - a continuous surface of spiral propagation vectors in reciprocal space. We elucidate the multi-step ordering behavior of the spiral spin-liquid, and discover a vortex-like triple-q phase on application of a magnetic field. Our results prove the effectiveness of the $J_1$-$J_2$ Hamiltonian on the diamond lattice as a model for the spiral spin-liquid state in MnSc$_2$S$_4$, and also demonstrate a new way to realize a magnetic vortex lattice.
I illustrate a general formalism based upon the subtraction method for the calculation of next-to-leading order QCD cross sections for any number of jets in any type of hard collisions. I discuss the implementation of this formalism in a numerical program which generates partonic kinematical configurations with an appropriate weight, thus allowing the definition of arbitrary jet algorithms and cuts matching the experimental setup at the last step of the computation. I present results obtained with computer codes which calculate one-jet and two-jet inclusive quantities in photon-hadron and hadron-hadron collisions.
We report on how nanocrystal size affects the critical behavior of the rare-earth metal Gd near the ferromagnetic-to-paramagnetic phase transition. The asymptotic critical behavior of the coarse-grained polycrystalline sample (with an average crystallite size of $L \cong \unit[100]{\mu m}$) is that of a (pure) \textsl{uniaxial dipolar} ferromagnet, as is the case with single-crystal Gd, albeit the width of the asymptotic critical region (ACR) is reduced. As the grain size approaches $\sim \unit[30]{nm}$, the ACR is so narrow that it could not be accessed in the present experiments. Inaccessibly narrow ACR for $L \sim \unit[30]{nm}$ and the continuous increase in the width of ACR as $L$ decreases from $\unit[16]{nm}$ to $\unit[9.5]{nm}$ basically reflects a crossover to the \textsl{random uniaxial dipolar} fixed point caused by the quenched random-exchange disorder prevalent at the internal interfaces (grain boundaries).
We construct a new class of asymptotically (a)dS black hole solutions of Einstein-Yang-Mills massive gravity in the presence of Born-Infeld nonlinear electrodynamics. The obtained solutions possess a Coulomb electric charge, massive term and a non-abelian hair as well. We calculate the conserved and thermodynamic quantities, and investigate the validity of the first law of thermodynamics. Also, we investigate thermal stability conditions by using the sign of heat capacity through canonical ensemble. Next, we consider the cosmological constant as a thermodynamical pressure and study the van der Waals like phase transition of black holes in the extended phase space thermodynamics. Our results indicate the existence of a phase transition which is affected by the parameters of theory. Finally, we consider a massless scalar perturbation in the background of asymptotically adS solutions and calculate the quasinormal modes by employing the pseudospectral method. The imaginary part of quasinormal frequencies is the time scale of a thermal state (in the conformal field theory) for the approach to thermal equilibrium.
We study theoretically fusion of the light proton-rich exotic nuclei $^{17}$F and $^8$B at near-barrier energies in order to investigate the possible role of breakup processes on their fusion cross sections. To this end, coupled channel calculations are performed considering the couplings to the breakup channels of these projectiles. In case of $^{17}$F, the coupling arising out of the inelastic excitation from the ground state to the bound excited state and its couplings to the continuum have also been taken into consideration. It is found that the inelastic excitation/breakup of $^{17}$F affect the fusion cross sections very nominally even for a heavy target like Pb. On the other hand, calculations for fusion of the one-proton halo nucleus $^8$B on a Pb target show a significant suppression of the complete fusion cross section above the Coulomb barrier. This is due to the larger breakup probability of $^8$B as compared to that of $^{17}$F. However, even for $^8$B, there is little change in the complete fusion cross sections as compared to the no-coupling case at sub-barrier energies.
Let $F_{\wp}$ be a finite extension of $\mathbb{Q}_p$. By considering partially de Rham families, we establish a Colmez-Greenberg-Stevens formula (on Fontaine-Mazur $\mathcal{L}$-invariants) for (general) $2$-dimensional semi-stable non-crystalline $\mathrm{Gal}(\overline{\mathbb{Q}_p}/F_{\wp})$-representations. As an application, we prove local-global compatibility results for completed cohomology of quaternion Shimura curves, and in particular the equality of Fontaine-Mazur $\mathcal{L}$-invariants and Breuil's $\mathcal{L}$-invariants, in critical case.
We present a detailed analysis of a H$_2$-rich, extremely strong intervening Damped Ly-$\alpha$ Absorption system (DLA) at $z_{\rm abs}=2.786$ towards the quasar J$\,$0843+0221, observed with the Ultraviolet and Visual Echelle Spectrograph on the Very Large Telescope. The total column density of molecular (resp. atomic) hydrogen is $\log N$(H$_2$)=$21.21\pm0.02$ (resp. $\log N$(H$\,$I)=$21.82\pm0.11$), making it to be the first case in quasar absorption lines studies with H$_2$ column density as high as what is seen in $^{13}$CO-selected clouds in the Milky-Way.   We find that this system has one of the lowest metallicity detected among H$_2$-bearing DLAs, with $\rm [Zn/H]=-1.52^{+0.08}_{-0.10}$. This can be the reason for the marked differences compared to systems with similar H$_2$ column densities in the local Universe: $(i)$ the kinetic temperature, $T\sim$120~K, derived from the $J=0,1$ H$_2$ rotational levels is at least twice higher than expected; $(ii)$ there is little dust extinction with A$_V < 0.1$; $(iii)$ no CO molecules are detected, putting a constraint on the $X_{\rm CO}$ factor $X_{\rm CO}> 2\times 10^{23} $ cm$^{-2}$/(km/s\,K), in the very low metallicity gas. Low CO and high H$_2$ contents indicate that this system represents "CO-dark/faint" gas.   We investigate the physical conditions in the H$_2$-bearing gas using the fine-structure levels of C$\,$I, C$\,$II, Si$\,$II and the rotational levels of HD and H$_2$. We find the number density to be about $n \sim 260-380\,$cm$^{-3}$, implying a high thermal pressure of $(3-5) \times 10^4\,$cm$^{-3}\,$K. We further identify a trend of increasing pressure with increasing total hydrogen column density. This independently supports the suggestion that extremely strong DLAs (with $\log\,$N(H) $\sim 22$) probe high-z galaxies at low impact parameters.
We present the Lambda Adaptive Multi-Band Deblending Algorithm in R (LAMBDAR), a novel code for calculating matched aperture photometry across images that are neither pixel- nor PSF-matched, using prior aperture definitions derived from high resolution optical imaging. The development of this program is motivated by the desire for consistent photometry and uncertainties across large ranges of photometric imaging, for use in calculating spectral energy distributions. We describe the program, specifically key features required for robust determination of panchromatic photometry: propagation of apertures to images with arbitrary resolution, local background estimation, aperture normalisation, uncertainty determination and propagation, and object deblending. Using simulated images, we demonstrate that the program is able to recover accurate photometric measurements in both high-resolution, low-confusion, and low-resolution, high-confusion, regimes. We apply the program to the 21-band photometric dataset from the Galaxy And Mass Assembly (GAMA) Panchromatic Data Release (PDR; Driver et al. 2016), which contains imaging spanning the far-UV to the far-IR. We compare photometry derived from LAMBDAR with that presented in Driver et al. (2016), finding broad agreement between the datasets. Nonetheless, we demonstrate that the photometry from LAMBDAR is superior to that from the GAMA PDR, as determined by a reduction in the outlier rate and intrinsic scatter of colours in the LAMBDAR dataset. We similarly find a decrease in the outlier rate of stellar masses and star formation rates using LAMBDAR photometry. Finally, we note an exceptional increase in the number of UV and mid-IR sources able to be constrained, which is accompanied by a significant increase in the mid-IR colour-colour parameter-space able to be explored.
Compact groups of galaxies recently have been discovered in association with several strong gravitational lens systems. These groups provide additional convergence to the lensing potential and thus affect the value of H_0 derived from the systems. Lens system time delays are now being measured with uncertainties of only a few percent or better. Additionally, vast improvements are being made in incorporating observational constraints such as Einstein ring structures and stellar velocity dispersions into the lens models. These advances are reducing the uncertainties on H_0 to levels at which the the effects of associated galaxy groups may contribute significantly to the overall error budget. We describe a dedicated multiwavelength program, using Keck, HST, and Chandra, to find such groups and measure their properties. We present, as a case study, results obtained from observations of the CLASS lens system B1608+656 and discuss the implications for the value of H_0 derived from this system.
Magnetostriction and thermal expansion of the spin-ladder compound piperidinium copper bromide (C$_5$H$_{12}$N)$_2$CuBr$_4$ are analyzed in detail. We find perfect agreement between experiments and the theory of a two-leg spin ladder Hamiltonian for more than a decade in temperature and in a wide range of magnetic fields. Relating the magnetostriction along different crystallographic directions to two static spin-spin correlation functions, which we compute with Quantum Monte Carlo, allows us to reconstruct the magnetoelastic couplings of (C$_5$H$_{12}$N)$_2$CuBr$_4$. We especially focus on the quantum critical behavior near the two critical magnetic fields $H_{c1}$ and $H_{c2}$, which is characterized by strong singularities rooted in the low dimensionality of the critical spin-system. Extending our discussion in Lorenz et al [Phys. Rev. Lett., 100, 067208 (2008)], we show explicitly that the thermal expansion near the upper critical field $H_{c2}$ is quantitatively described by a parameter-free theory of one-dimensional, non-relativistic Fermions. We also point out that there exists a singular quantum critical correction to the elastic moduli. This correction is proportional to the magnetic susceptibility $\chi$ which diverges as $\chi \sim 1/\sqrt{T}$ at the critical fields and thus leads to a strong softening of the crystal.
In this paper, we relate the competition number of a graph to its edge clique cover number by presenting a tight inequality $k(G) \ge \theta_e(G)-|V(G)|+\widetilde{k}(G)$ where $\theta_e(G)$, $k(G)$, and $\widetilde{k}(G)$ are the edge clique cover number, the competition number, and the co-competition number of a graph $G$, respectively. By utilizing this inequality and a notion of competition-effective edge clique cover, we obtain some meaningful results on competition numbers of planar graphs.
We show that a class of spacetimes introduced by Fayyazuddin and Smith to describe intersecting M5-branes admit a generalized Kahler calibration. Equipped with this understanding, we are able to construct spacetimes corresponding to further classes of calibrated $p$-brane world-volume solitons. We note that these classes of spacetimes also describe the fields of $p$-branes wrapping certain supersymmetric cycles of Calabi-Yau manifolds.
In this thesis, I investigate the molecular electronic properties of molecular junctions formed from single molecules. I started my thesis by discusses the main theoretical methods using in this work density functional theory and the green function formalism of electron transport. These two techniques are used to study the charge transport through dicarboxylic acid terminated alkanes in chapter 4, with graphene gold nanogap electrodes. The results are then compared with those using symmetric gold electrodes and reveal that there is a difference between the two situations due to the difference in Fermi energies relative to the frontier orbitals of the molecules. Furthermore, the electrical conductance in the asymmetric junction is higher than that in the symmetric junction, which suggests that graphene offers superior electrode performance when utilizing carboxylic acid anchor groups. In chapter 5, I study affected of the saturated chain conductance by adding oxygen to the chain. Comparisons between my electronic structure calculations on oligoether chains and previous work on alkanes show that the conductance of oligoether is lower than that of alkane chains with the same length. I found that the beta tunneling factor per methyl unit of the alkanes is lower than the beta factor of oligoether. In the final chapter, molecular dynamic simulations are used to examine the molecular assembly of two candidate molecules for graphene-based molecular electronics, one with one pyrene anchor, Pyrene PEGn exTTF, PPT, and the other with three pyrene anchors, tri pyrene derivative, TPPT, on a disordered graphene surface. PPT is seen to form flat structures whilst TPPT is seen to form semicircular cone like micelle structures on the graphene surface. In the presence of water, the PPT tends to aggregate whereas the TPPT micelle expands.
Using the Gaussian R\'enyi-2 entropy, we analyse the behaviour of two different aspects of quantum correlations (entanglement and quantum discord) in two optomechanical subsystems (optical and mechanical). We work in the resolved sideband and weak coupling regimes. In experimentally accessible parameters, we show that it is possible to create entanglement and quantum discord in the considered subsystems by quantum fluctuations transfer from either light to light or light to matter. We find that both mechanical and optical entanglement are strongly sensitive to thermal noises. In particular, we find that the mechanical one is more affected by thermal effects than that optical. Finally, we reveal that under thermal noises, the discord associated with the entangled state decays aggressively, whereas the discord of the separable state (quantumness of correlations) exhibits a freezing behaviour, seeming to be captured over a wide range of temperature.
We investigate the stability of a neutrino-dominated accretion flow (NDAF), which is expected to be formed in the gravitational collapse of a massive star or the merger of a neutron star binary, based on the variable-$\alpha$ prescription. Recent magnetohydrodynamic (MHD) simulations shows that the viscosity parameter $\alpha$ is proportional to the power of the magnetic Prandtl number ${\rm Pm}=\nu/\eta$, where $\nu$ and $\eta$ are the kinematic viscosity and electric resistivity of the fluid, respectively. In the inner region of a hyperaccretion flow, the viscosity and resistivity are carried by mildly, relativistically degenerated electrons. We fit the dependence of the magnetic Prandtl number on density and temperature by a simple analytic form, and derive the condition for an NDAF to be dynamically unstable. As demonstrations we perform simple one-dimensional simulations of NDAFs with the variable-$\alpha$ and show that the mass accretion becomes highly time-variable in the unstable branch. This mechanism may account for the rapid variability observed in the prompt emission of gamma-ray bursts (GRBs). The mass ejection from a hyperaccretion flow due to viscous heating, which makes a kilonova/macronova emission in the merger of a neutron star binary, is also briefly discussed.
Several computer codes based on phenomenological models are being developed with the aim of obtaining fission observables, such as neutron and gamma multiplicities and product yields. Key points in these calculations, which are handled differently by the various codes, are the sharing of the total excitation energy between the fragments and the generation of angular momenta. After the initial states of the fragments is set, the de-excitation through the emission of neutrons and photons can be model. However, many models also include tunable parameters that are used to make the calculations conform with literature data. As a result, it could be possible to obtain good agreement with experimental results even with questionable assumptions on the initial conditions. To test the assumptions made by different fission models the code DE$\ell$FIN has been developed. DE$\ell$FIN starts with the fission fragments as generated by the models and calculates the average neutron emission as a function of mass in a transparent and coherent way using the nuclear reaction code TALYS. Hence, the probabilities of neutron emission in competition with $\gamma$ de-excitation comes from parameters of the TALYS code that have not been optimised. The results are then compared looking at general trends and at the difference to what is obtained with the stand-alone versions of the codes. In this study, the output of DE$\ell$FIN for five of the most commonly used fission codes is compared to the results of the stand-alone versions, and to experimental data, for the reactions $^{235}$U(n$_{\mathrm{th}}$,f), $^{239}$Pu(n$_{\mathrm{th}}$,f) and $^{252}$Cf(sf).
The impulsive phase of solar flares is a time of rapid energy deposition and heating in the lower solar atmosphere, leading to changes in the temperature and density structure of the region. We use an O V density diagnostic formed of the 192 to 248 line ratio, provided by Hinode EIS, to determine the density of flare footpoint plasma, at O V formation temperatures of 250,000 K, giving a constraint on the properties of the heated transition region. Hinode EIS rasters from 2 small flare events in December 2007 were used. Raster images were co-aligned to identify and establish the footpoint pixels, multiple-component Gaussian line fitting of the spectra was carried out to isolate the diagnostic pair, and the density was calculated for several footpoint areas. The assumptions of equilibrium ionization and optically thin radiation for the O V lines were found to be acceptable. Properties of the electron distribution, for one event, were deduced from earlier RHESSI hard X-ray observations and used to calculate the plasma heating rate, delivered by an electron beam adopting collisional thick-target assumptions, for 2 model atmospheres. Electron number densities of at least log n = 12.3 cm-3 were measured during the flare impulsive phase, far higher than previously expected. For one footpoint, the radiative loss rate for this plasma was found to exceed that which can be delivered by an electron beam implied by the RHESSI data. However, when assuming a completely ionised target atmosphere the heating rate exceeded the losses. A chromospheric thickness of 70-700 km was found to be required to balance a conductive input to the O V-emitting region with radiative losses. The analysis shows that for heating by collisional electrons, it is difficult, or impossible to raise the temperature of the chromosphere to explain the observed densities without assuming a completely ionised atmosphere.
We study the dynamics caused by transport of transverse magnetization in one dimensional transverse Ising chain at zero temperature. We observe that a class of initial states having product structure in fermionic momentum-space and satisfying certain criteria, produce spatial variation in transverse magnetization. Starting from such a state, we obtain the transverse magnetization analytically and then observe its dynamics in presence of a homogeneous constant field $\Gamma$. In contradiction with general expectation, whatever be the strength of the field, the magnetization of the system does not become homogeneous even after infinite time. At each site, the dynamics is associated with oscillations having two different timescales. The envelope of the larger timescale oscillation decays algebraically with an exponent which is invariant for all such special initial states. The frequency of this oscillation varies differently with external field in ordered and disordered phases. The local magnetization after infinite time also characterizes the quantum phase transition.
We propose a novel parametrization of the four-point vertex function in the one-loop one-particle irreducible renormalization group (RG) scheme for fermions. It is based on a decomposition of the effective two-fermion interaction into fermion bilinears that interact via exchange bosons. Besides being more efficient than previous N-patch schemes, this parametrization also reduces the ambiguity of introducing boson fields. We apply this parametrization to the two-dimensional (t,t')-Hubbard model using a novel $\Omega$-frequency regularization.