ShantanuT01/DACTYL-Pretraining huggingface dataset:
Methods. We used different galaxy classification techniques: human labeling, multi-photometry diagrams, Naive Bayes, Logistic Regression, Support Vector Machine, Random Forest, k-Nearest Neighbors, and k-fold validation. Results. We present results of a binary automated morphological classification of galaxies conducted by human labeling, multiphotometry, and supervised Machine Learning methods. We applied its to the sample of galaxies from the SDSS DR9 with 0.02 < z < 0.1 and 24m < Mr < 19.4m. To study the classifier, we used absolute magnitudes: Mu, Mg, Mr , Mi, Mz, Mu-Mr , Mg-Mi, Mu-Mg, Mr-Mz, and inverse concentration index to the center R50/R90. Using the Support vector machine classifier and the data on color indices, absolute magnitudes, inverse concentration index of galaxies with visual morphological types, we were able to classify 316 031 galaxies from the SDSS DR9 with unknown morphological types. Conclusions. The methods of Support Vector Machine and Random Forest with Scikit-learn machine learning in Python provide the highest accuracy for the binary galaxy morphological classification: 96.4% correctly classified (96.1% early E and 96.9% late L types) and 95.5% correctly classified (96.7% early E and 92.8% late L types), respectively. Applying the Support Vector Machine for the sample of 316 031 galaxies from the SDSS DR9 at z < 0.1, we found 141 211 E and 174 820 L types among them.
Using a physically motivated stress energy tensor, we prove weak and strong monotonicity formulas for solutions to the semilinear elliptic system $\Delta u=\nabla W(u)$ with $W$ nonnegative. In particular, we extend a recent two dimensional result to all dimensions.
A special type of immigration associated with measure-valued branching processes is formulated by using skew convolution semigroups. We give characterization for a general inhomogeneous skew convolution semigroup in terms of probability entrance laws. The related immigration process is constructed by summing up measure-valued paths in the Kuznetsov process determined by an entrance rule. The behavior of the Kuznetsov process is then studied, which provides insights into trajectory structures of the immigration process. Some well-known results on excessive measures are formulated in terms of stationary immigration processes.
The calculation of the magnetic moment of the deuteron in the framework of the Bethe--Salpeter approach is performed. The relativistic corrections are calculated analytically and estimated numerically. It is shown that the main contributions are due to partial waves with positive energies and $P$--waves. A comparison with the non-relativistic schemes of calculations including mesonic exchange currents is made.
We study an asymmetric form of two-mode entangled coherent state (ECS), where the two local amplitudes have different values, for testing the Bell-Clauser-Horne-Shimony-Holt (Bell-CHSH) inequality. We find that the asymmetric ECSs have obvious advantages over the symmetric form of ECSs in testing the Bell-CHSH inequality. We further study an asymmetric strategy in distributing an ECS over a lossy environment and find that such a scheme can significantly increase violation of the inequality.
We study supersymmetric contributions to correlation coefficients that characterize the spectral shape and angular distribution for polarized muon- and beta-decays. In the minimal supersymmetric Standard Model (MSSM), one-loop box graphs containing superpartners can give rise to non-(V-A)x(V-A) four fermion operators in the presence of left-right or flavor mixing between sfermions. We analyze the present phenomenological constraints on such mixing and determine the range of allowed contributions to the weak decay correlation coefficients. We discuss the prospective implications for future muon- and beta-decay experiments, and argue that they may provide unique probes of left-right mixing in the first generation scalar fermion sector.
In this paper, we will describe the mathematical foundation of topological Landau-Ginzburg (LG) models coupled to gravity at genus 0 in terms of primitive forms. We also discuss the mirror symmetry for Calabi-Yau manifolds and CP^1 in our context. We will show that the mirror partner of CP^1 is the theory of primitive form associated to f=z+qz^{-1}.
The Ernst method of removing nodal singularities from the charged C-metric representing uniformly accelerated black holes with mass $m$, charge $q$ and acceleration $A$ by "adding" an electric field $E$ is generalized. Utilizing the new form of the C-metric found recently, Ernst's simple "equilibrium" condition $mA=qE$ valid for small accelerations is generalized for arbitrary $A$. The nodal singularity is removed also in the case of accelerating and rotating charged black holes, and the corresponding equilibrium condition is determined.
The process of baryon production in K p collisions at high energies is considered in the framework of the Quark-Gluon String Model. The contribution of the string-junction mechanism to the strange baryon production is analysed. The results of numerical calculations are in reasonable agreement with the data on inclusive spectra of p, Lambda, bar{Lambda}, and on the bar{Lambda}/Lambda asymmetry. The predictions for Xi and Omega baryons are presented.
We present the general expression of helicity amplitudes for generic multi-body particle decays characterised by multiple decay chains. This is achieved by addressing for the first time the issue of the matching of final particle spin states among different decay chains in full generality for generic multi-body decays, proposing a method able to match the exact definition of spin states relative to the decaying particle ones. We stress the importance of our result by showing that one of the matching method used in the literature is incorrect, leading to amplitude models violating rotational invariance. The results presented are therefore relevant for performing numerous amplitude analysis, notably those searching for exotic structures like pentaquarks.
Neutron star magnetic fields may have polar caps (PC) that are offset from the dipole axis, through field-line sweepback near the light cylinder or non-symmetric currents within the star. The effects of such offsets on electron-positron pair cascades are investigated, using simple models of dipole magnetic fields with small distortions that shift the PCs by different amounts or directions. Using a Monte Carlo pair cascade simulation, we explore the changes in the pair spectrum, multiplicity and energy flux across the PC, as well as the trends in pair flux and pair energy flux with spin-down luminosity, L_{sd}. We also give an estimate of the distribution of heating flux from returning positrons on the PC for different offsets. We find that even modest offsets can produce significant increases in pair multiplicity, especially for pulsars that are near or beyond the pair death lines for centered PCs, primarily because of higher accelerating fields. Pair spectra cover several decades in energy, with the spectral range of millisecond pulsars (MSPs) two orders of magnitude higher than for normal pulsars, and PC offsets allow significant extension of all spectra to lower pair energies. We find that the total PC pair luminosity L_{pair} is proportional to L_{sd}, with L_{pair} ~ 10^{-3} L_{sd} for normal pulsars and L_{pair} ~ 10^{-2} L_{sd} for MSPs. Remarkably, the total PC heating luminosity for even large offsets increases by less than a factor of two, even though the PC area increases by much larger factors, because most of the heating occurs near the magnetic axis.
Given a bipartite quantum system represented by a tensor product of two Hilbert spaces, we give an elementary argument showing that if either component space is infinite-dimensional, then the set of nonseparable density operators is trace-norm dense in the set of all density operators (and the separable density operators nowhere dense). This result complements recent detailed investigations of separability, which show that when both component Hilbert spaces are finite-dimensional, there is a separable neighborhood (perhaps very small for large dimensions) of the maximally mixed state.
Gamma-ray bursts (GRBs) are believed to originate from ultra-relativistic winds/fireballs to avoid the "compactness problem". However, the most energetic photons in GRBs may still suffer from $\gamma-\gamma$ absorption leading to electron/positron pair production in the winds/fireballs. We show here that in a wide range of model parameters, the resulting pairs may dominate those electrons associated with baryons. Later on, the pairs would be carried into a reverse shock so that a shocked pair-rich fireball may produce a strong flash at lower frequencies, i.e. in the IR band, in contrast with optical/UV emission from a pair-poor fireball. The IR emission would show a 5/2 spectral index due to strong self-absorption. Rapid responses to GRB triggers in the IR band would detect such strong flashes. The future detections of many IR flashes will infer that the rarity of prompt optical/UV emissions is in fact due to dust obscuration in the star formation regions.
We report the observation of an antipolar phase in cubic GaNb$_4$S$_8$ driven by an unconventional microscopic mechanism, the cooperative Jahn-Teller effect of Nb$_4$S$_4$ molecular clusters. The assignment of the antipolar nature is based on sudden changes in the crystal structure and a strong drop of the dielectric constant at $T_\mathrm{JT}=31$\,K, also indicating the first-order nature of the transition. In addition, we found that local symmetry lowering precedes long-range orbital ordering, implying the presence of a dynamic Jahn-Teller effect in the cubic phase above $T_\mathrm{JT}$. Based on the variety of structural polymorphs reported in lacunar spinels, also including ferroelectric phases, we argue that GaNb$_4$S$_8$ may be transformable to a ferroelectric state, which would further classify the observed antipolar phase as antiferrolectric.
In the framework of the Schwinger boson representation for the su(2)-algebra, the closed form is derived for the total spin eigenstates which result from the coupling of n su(2)-spins. In order to demonstrate its usefulness, the orthogonal set for the so(5)-algebra, which is reduced to four su(2)-spin systems, is obtained.
Oscillatory magnetoresistance measurements on graphene have revealed a wealth of novel physics. These phenomena are typically studied at low currents. At high currents, electrons are driven far from equilibrium with the atomic lattice vibrations so that their kinetic energy can exceed the thermal energy of the phonons. Here, we report three non-equilibrium phenomena in monolayer graphene at high currents: (i) a "Doppler-like" shift and splitting of the frequencies of the transverse acoustic (TA) phonons emitted when the electrons undergo inter-Landau level (LL) transitions; (ii) an intra-LL Mach effect with the emission of TA phonons when the electrons approach supersonic speed, and (iii) the onset of elastic inter-LL transitions at a critical carrier drift velocity, analogous to the superfluid Landau velocity. All three quantum phenomena can be unified in a single resonance equation. They offer avenues for research on out-of-equilibrium phenomena in other two-dimensional fermion systems.
We derive formulas for the Coulomb matrix within the full-potential linearized augmented-plane-wave (FLAPW) method. The Coulomb matrix is a central ingredient in implementations of many-body perturbation theory, such as the Hartree-Fock and GW approximations for the electronic self-energy or the random-phase approximation for the dielectric function. It is represented in the mixed product basis, which combines numerical muffin-tin functions and interstitial plane waves that are here expanded with the Rayleigh formula. The resulting algorithm is very efficient in terms of both computational cost and accuracy and is superior to an implementation with the Fourier transform of the step function. In order to allow an analytic treatment of the divergence at k=0 in reciprocal space, we expand the Coulomb matrix analytically around this point without resorting to a projection onto plane waves. We then apply a basis transformation that diagonalizes the Coulomb matrix and confines the divergence to a single eigenvalue. At the same time, response matrices like the dielectric function separate into head, wings, and body with the same mathematical properties as in a plane-wave basis. As an illustration we apply the formulas to electron-energy-loss spectra for nickel at different k vectors including k=0. The convergence of the spectra towards the result at k=0 is clearly seen. Our treatment also allows to include transitions from core states that give rise to a shallow peak at high energies and lead to good agreement with experiment.
Electromechanical coupling through piezoelectric polymer chains allows the emission of organic molecules in active nanowires to be tuned. This effect is evidenced by highly bendable arrays of counter-ion dye-doped nanowires made of a poly(vinylidenefluoride) copolymer. A reversible redshift of the dye emission is found upon the application of dynamic stress during highly accurate bending experiments. By density functional theory calculations it is found that these photophysical properties are associated with mechanical stresses applied to electrostatically interacting molecular systems, namely to counterion-mediated states that involve light-emitting molecules as well as charged regions of piezoelectric polymer chains. These systems are an electrostatic class of supramolecular functional stress-sensitive units, which might impart new functionalities in hybrid molecular nanosystems and anisotropic nanostructures for sensing devices and soft robotics.
The nucleosynthesis yields from neutrino-induced spallation of 4He are calculated in case of penetration of some 4He into the carbon-oxygen-neon shell. The neutrino contribution to creation of the weak r-process component becomes noticeable in case 4He is dragged down at radii R < 10^9 cm.
A coherent state representation for the electrons of ordered antiferromagnets is used to derive effective Hamiltonians for the dynamics of holes in such systems. By an appropriate choice of these states, the constraint of forbidden double occupancy can be implemented rigorously. Using these coherent states, one arrives at a path integral representation of the partition function of the systems, from which the effective Hamiltonians can be read off. We apply this method to the t-J model on the square lattice and on the triangular lattice. In the former case, we reproduce the well-known fermion-boson Hamiltonian for a hole in a collinear antiferromagnet. We demonstrate that our method also works for non-collinear antiferromagnets by calculating the spectrum of a hole in the triangular antiferromagnet in the self-consistent Born approximation and by comparing it with numerically exact results.
We investigate the narrow-line region (NLR) of two radio-quiet QSOs, PG1012+008 and PG1307+085, using high signal-to-noise spatially resolved long-slit spectra obtained with FORS1 at the Very Large Telescope. Although the emission is dominated by the point-spread function of the nuclear source, we are able to detect extended NLR emission out to several kpc scales in both QSOs by subtracting the scaled central spectrum from outer spectra. In contrast to the nuclear spectrum, which shows a prominent blue wing and a broad line profile of the [O III] line, the extended emission reveals no clear signs of large scale outflows. Exploiting the wide wavelength range, we determine the radial change of the gas properties in the NLR, i.e., gas temperature, density, and ionization parameter, and compare them with those of Seyfert galaxies and type-II QSOs. The QSOs have higher nuclear temperature and lower electron density than Seyferts, but show no significant difference compared to type-II QSOs, while the ionization parameter decreases with radial distance, similar to the case of Seyfert galaxies. For PG1012+008, we determine the stellar velocity dispersion of the host galaxy. Combined with the black hole mass, we find that the luminous radio-quiet QSO follows the local M_BH-sigma* relation of active galactic nuclei.
This paper studies the asymptotic behavior of the Green function of a multidimensional random walk killed when leaving a convex cone with smooth boundary. Our results imply uniqueness, up to a multiplicative factor, of the positive harmonic function for the killed random walk.
To investigate the initial process of Joule heating in semiconductors microscopically and quantitatively, we developed a theoretical framework for the ab initio evaluation of the carrier energy relaxation in semiconductors under a high electric field using a combination of the two-temperature model and the Boltzmann equation. We employed the method for bulk silicon as a typical example. Consequently, we found a remarkable difference in the energy relaxation processes of the electron and hole carriers. The longitudinal acoustic and optical phonons at the zone boundary contribute to the energy relaxation of electron carriers, whereas they contribute negligibly to that of the hole carriers. In addition, at the band edge, the energy relaxation rate is maximized for the electron carriers, whereas it is suppressed for the hole carriers. These differences stem from the presence/absence of intervalley scattering processes and isotropic/anisotropic band structures in electrons and holes. Our results lay the foundation for controlling the thermal generation in semiconductors by material design.
Collision-induced absorption (CIA) from molecular hydrogen is a dominant opacity source in the atmosphere of cool white dwarfs. It results in a significant flux depletion in the near-IR and IR parts of their spectra. Because of the extreme conditions of helium-rich atmospheres (where the density can be as high as a few g/cm$^3$), this opacity source is expected to undergo strong pressure distortion and the currently used opacities have not been validated at such extreme conditions. To check the distortion of the CIA opacity we applied state-of-the-art ab initio methods of computational quantum chemistry to simulate the CIA opacity at high densities. The results show that the CIA profiles are significantly distorted above densities of $0.1\,{\rm g/cm}^3$ in a way that is not captured by the existing models. The roto-translational band is enhanced and shifted to higher frequencies as an effect of the decrease of the interatomic separation of the H$_2$ molecule. The vibrational band is blueward shifted and split into $Q_R$ and $Q_P$ branches, separated by a pronounced interference dip. Its intensity is also substantially reduced. The distortions result in a shift of the maximum of the absorption from $2.3\,\mu{\rm m}$ to $3-7 \mu{\rm m}$, which could potentially explain the spectra of some very cool, helium-rich white dwarfs.
We numerically investigate the spectral statistics of pseudo-energies for the unitary network operator U of the Chalker--Coddington network. The shape of the level spacing distribution as well the scaling of its moments is compared to known results for quantum Hall systems. We also discuss the influence of multifractality on the tail of the spacing distribution.
The early Cosmology driven by a single scalar field, both massless and massive, in the context of Eddington-inspired Born-Infeld gravity, is explored. We show the existence of nonsingular solutions of bouncing and loitering type (depending on the sign of the gravitational theory's parameter, $\epsilon$) replacing the Big Bang singularity, and discuss their properties. In addition, in the massive case we find some new features of the cosmological evolution depending on the value of the mass parameter, including asymmetries in the expansion/contraction phases, or a continuous transition between a contracting phase to an expanding one via an intermediate loitering phase. We also provide a combined analysis of cosmic chronometers, standard candles, BAO, and CMB data to constrain the model, finding that for roughly $\vert \epsilon \vert \lesssim 5\cdot 10^{-8} \text{ m}^2$ the model is compatible with the latest observations while successfully removing the Big Bang singularity. This bound is several orders of magnitude stronger than the most stringent constraints currently available in the literature
A new approach to identify the independent amplitudes along with their partial wave multipole expansions, for photo and electro-production is suggested,which is generally applicable to mesons with arbitrary spin-parity. These amplitudes facilitate direct identification of different resonance contributions.
Based on precise Coulomb wave functions (CWFs), we attempt to calculate the fusion cross sections of light nuclei in a complex spherical square-well nuclear potential (i.e., optical potential model). Comparing with experimental benchmark cross section data, we can calibrate optical potential parameters associated with D+D, D+T, D+3He, p+D, p+6Li and p+7Li fusion reactions. Surprisingly, we find that our calculated optical potential parameters are quite different from those of many previous results (e.g., Phys. Rev. C. 61 (2000) 024610, Nucl. Phys. A 986 (2019) 98, etc.), in which approximate Coulomb wave functions (ACWFs) with only retaining the leading terms are exploited for the continuity conditions at the radius of nuclear potential. Furthermore, with the obtained optical potential parameters, we compare the fusion cross sections and astrophysical S-factors with that formulated from ACWFs approach, and also find apparent deviations especially for the fusion reactions with resonance peaks such as D+T and D+3He fusion reactions. We then calculate the phase diagrams of the fusion cross sections with respect to the optical potential parameters and demonstrate several narrow shape resonance belts. It implies that a small deviation of ACWFs from the exact CWFs at nuclear radius might lead to fall off the resonance regimes and therefore causes the big difference on the optical parameters as well as the cross sections.
We present an experimental study of higher-dimensional quantum key distribution protocols based on mutually unbiased bases, implemented by means of photons carrying orbital angular momentum. We perform (d+1) mutually unbiased measurements in a classical prepare and measure scheme and on a pair of entangled photons for dimensions ranging from d = 2 to 5. In our analysis, we pay attention to the detection efficiency and photon pair creation probability. As security measures, we determine from experimental data the average error rate, the mutual information shared between the sender and receiver and the secret key generation rate per photon. We demonstrate that increasing the dimension leads to an increased information capacity as well as higher key generation rates per photon up to a dimension of d = 4.