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At least 793 records · Page 44
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DOE OSTI2014

What happens to Petrov classification, on horizons of axisymmetric dirty black holes

We consider axisymmetric stationary dirty black holes with regular non-extremal or extremal horizons, and compute their on-horizon Petrov types. The Petrov type (PT) in the frame of the observer crossing the horizon can be different from that formally obtained in the usual (but singular in the horizon limit) frame of an observer on a circular orbit. We call this entity the boosted Petrov type (BPT), as the corresponding frame is obtained by a singular boost from the regular one. The PT off-horizon can be more general than PT on-horizon and that can be more general than the BPT on horizon. This is valid for all regular metrics, irrespective of the extremality of the horizon. We analyze and classify the possible relations between the three characteristics and discuss the nature and features of the underlying singular boost. The three Petrov types can be the same only for space-times of PT D and O off-horizon. The mutual alignment of principal null directions and the generator in the vicinity of the horizon is studied in detail. As an example, we also analyze a special class of metrics with utra-extremal horizons (for which the regularity conditions look different from the general case) and compare their off-horizon and on-horizon algebraic structure in both frames.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

On exact statistics and classification of ergodic systems of integer dimension

We describe classes of ergodic dynamical systems for which some statistical properties are known exactly. These systems have integer dimension, are not globally dissipative, and are defined by a probability density and a two-form. This definition generalizes the construction of Hamiltonian systems by a Hamiltonian and a symplectic form. Some low dimensional examples are given, as well as a discretized field theory with a large number of degrees of freedom and a local nearest neighbor interaction. We also evaluate unequal-time correlations of these systems without direct numerical simulation, by Padé approximants of a short-time expansion. We briefly speculate on the possibility of constructing chaotic dynamical systems with non-integer dimension and exactly known statistics. In this case there is no probability density, suggesting an alternative construction in terms of a Hopf characteristic function and a two-form.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Classification of Hamilton-Jacobi separation in orthogonal coordinates with diagonal curvature

We find all orthogonal metrics where the geodesic Hamilton-Jacobi equation separates and the Riemann curvature tensor satisfies a certain equation (called the diagonal curvature condition). All orthogonal metrics of constant curvature satisfy the diagonal curvature condition. The metrics we find either correspond to a Benenti system or are warped product metrics where the induced metric on the base manifold corresponds to a Benenti system. Furthermore, we show that most metrics we find are characterized by concircular tensors; these metrics, called Kalnins-Eisenhart-Miller metrics, have an intrinsic characterization which can be used to obtain them on a given space. In conjunction with other results, we show that the metrics we found constitute all separable metrics for Riemannian spaces of constant curvature and de Sitter space.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

SU(4) based classification of four-level systems and their semiclassical solution

We present a systematic method to classify the four-level system using SU(4) symmetry as the basis group. It is shown that this symmetry allows three dipole transitions which eventually leads to six possible configurations of the four-level system. Using a dressed atom approach, the semi-classical version of each configuration is exactly solved under rotating wave approximation and the symmetry among the Rabi oscillation among various models is studied.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Mineral classification map using MF and SAM techniques: A case study in the Nohwa Island, Korea

The purpose of this study is to map pyprophyllite distribution at surface of the Nohwa deposit, Korea by using Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) data. For this, combined Spectral Angle Mapper (SAM), and Matched Filtering (MF) technique based on mathematical algorithm was applied. The regional distribution of high-grade and low-grade pyrophyllite in the Nohwa deposit area could be differentiated by this method. The results of this study show that ASTER data analysis using combination of SAM and MF techniques will assist in exploration of pyrophyllite at the exposed surface.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Reconstruction of chaotic saddles by classification of unstable periodic orbits: Kuramoto-Sivashinsky equation

The unstable periodic orbits (UPOs) embedded in a chaotic attractor after an attractor merging crisis (MC) are classified into three subsets, and employed to reconstruct chaotic saddles in the Kuramoto-Sivashinsky equation. It is shown that in the post-MC regime, the two chaotic saddles evolved from the two coexisting chaotic attractors before crisis can be reconstructed from the UPOs embedded in the pre-MC chaotic attractors. The reconstruction also involves the detection of the mediating UPO responsible for the crisis, and the UPOs created after crisis that fill the gap regions of the chaotic saddles. We show that the gap UPOs originate from saddle-node, period-doubling, and pitchfork bifurcations inside the periodic windows in the post-MC chaotic region of the bifurcation diagram. The chaotic attractor in the post-MC regime is found to be the closure of gap UPOs.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Classification of Lagrangian fibrations

This paper classifies Lagrangian fibrations over surfaces with compact total spaces up to fibrewise symplectomorphism identical on the base. Bibliography: 15 titles.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2011

Classification of Ricci-flat metrics on the cotangent bundles of compact rank-one symmetric spaces

All complete Ricci-flat Kaehler G-invariant metrics (g,J,{Omega}) on the cotangent bundle of a compact rank-one symmetric space G/K, dim G/K>=3 (with the fixed Kaehler form, the canonical symplectic structure {Omega}), are classified. It is proved that the set of equivalence classes of such metrics can be parametrized by positive numbers. The representative of each class is constructed by using explicit expressions. An alternative description of these structures based on the Kaehler reduction procedure is proposed. We show also that the complete Ricci-flat Kaehler metrics, constructed by Stenzel, are diffeomorphic to these ones. Bibliography: 26 titles.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2014

Topological classification of systems of Kovalevskaya-Yehia type

All the Fomenko-Zieschang invariants are calculated for the Kovalevskaya-Yehia problem, for all noncritical values of the parameters g and λ, by constructing admissible systems of coordinates and determining the mutual disposition of the basis cycles. The family of Kovalevskaya-Yehia systems contains 29 pairwise Liouville non-equivalent foliations. These foliations include those that are equivalent to previously known foliations, which arose in the integrable cases of Kovalevskaya and of Kovalevskaya-Yehia for g = 0, in the Zhukovskiı case, and in the Goryachev-Chaplygin-Sretenskiı case. Eleven new foliations are included in the 29 foliations, new in the sense that they are not Liouville equivalent to any foliations discovered earlier which arose in the known integrable cases of the rigid body. The topological type of the Liouville foliation for the family of Kovalevskaya-Yehia systems stabilizes at large values of the energy H, and this 'high-energy' system is roughly Liouville equivalent, at one of the energy levels, to the Goryachev-Chaplygin-Sretenskiı integrable case, which is already known. Bibliography: 29 titles.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2014

A topological classification of the Chaplygin systems in the dynamics of a rigid body in a fluid

The paper is concerned with the topological analysis of the Chaplygin integrable case in the dynamics of a rigid body in a fluid. A full list of the topological types of Chaplygin systems in their dependence on the energy level is compiled on the basis of the Fomenko-Zieschang theory. An effective description of the topology of the Liouville foliation in terms of natural coordinate variables is also presented, which opens a direct way to calculating topological invariants. It turns out that on all nonsingular energy levels Chaplygin systems are Liouville equivalent to the well-known Euler case in the dynamics of a rigid body with fixed point. Bibliography: 23 titles.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2012

THE CLASSIFICATION OF KEPLER B-STAR VARIABLES

The light curves of 252 B-star candidates in the Kepler database are analyzed in a similar fashion to that done by Balona et al. to further characterize B-star variability, increase the sample of variable B stars for future study, and to identify stars whose power spectra include particularly interesting features such as frequency groupings. Stars are classified as either constant light emitters, {beta} Cep stars, slowly pulsating B stars (SPBs), hybrid pulsators, binaries or stars whose light curves are dominated by rotation (Bin/Rot), hot subdwarfs, or white dwarfs. One-hundred stars in our sample were found to be either light constants or to be variable at a level of less than 0.02 mmag. We increase the number of candidate B-star variables found in the Kepler database by Balona et al. in the following fashion: {beta} Cep stars from 0 to 10, SPBs from eight to 54, hybrid pulsators from seven to 21, and Bin/Rot stars from 23 to 82. For comparison purposes, approximately 51 SPBs and six hybrids had been known prior to 2007. The number of {beta} Cep stars known prior to 2004 was 93. A secondary result of this study is the identification of an additional 11 pulsating white dwarf candidates, four of which possess frequency groupings.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

SPECTRAL CLASSIFICATION OF GALAXIES AT 0.5 {<=} z {<=} 1 IN THE CDFS: THE ARTIFICIAL NEURAL NETWORK APPROACH

The aim of this work is to combine spectral energy distribution (SED) fitting with artificial neural network techniques to assign spectral characteristics to a sample of galaxies at 0.5 < z < 1. The sample is selected from the spectroscopic campaign of the ESO/GOODS-South field, with 142 sources having photometric data from the GOODS-MUSIC catalog covering bands between {approx}0.4 and 24 {mu}m in 10-13 filters. We use the CIGALE code to fit photometric data to Maraston's synthesis spectra to derive mass, specific star formation rate, and age, as well as the best SED of the galaxies. We use the spectral models presented by Kinney et al. as targets in the wavelength interval {approx}1200-7500 A. Then a series of neural networks are trained, with average performance {approx}90%, to classify the best SED in a supervised manner. We consider the effects of the prominent features of the best SED on the performance of the trained networks and also test networks on the galaxy spectra of Coleman et al., which have a lower resolution than the target models. In this way, we conclude that the trained networks take into account all the features of the spectra simultaneously. Using the method, 105 out of 142 galaxies of the sample are classified with high significance. The locus of the classified galaxies in the three graphs of the physical parameters of mass, age, and specific star formation rate appears consistent with the morphological characteristics of the galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

A NEW DISCRIMINATOR FOR GAMMA-RAY BURST CLASSIFICATION: THE E{sub peak}-FLUENCE ENERGY RATIO

Using the derived gamma-ray burst (GRB) E{sub peak} and fluences from the complete BATSE 5B Spectral Catalog, we study the ensemble characteristics of the E{sub peak}-fluence relation for GRBs. This relation appears to be a physically meaningful and insightful fundamental discriminator between long and short bursts. We discuss the results of the lower limit test of the E{sub peak}-E{sub iso} relations in the E{sub peak}-fluence plane for Burst And Transient Source Experiment bursts with no observed redshift. Our results confirm the presence of two GRB classes as well as heavily suggesting two different GRB progenitor types.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

THE SPECTROSCOPIC CLASSIFICATION AND EXPLOSION PROPERTIES OF SN 2009nz ASSOCIATED WITH GRB 091127 AT z = 0.490

We present spectroscopic observations of GRB 091127 (z = 0.490) at the peak of the putative associated supernova SN 2009nz. Subtracting a late-time spectrum of the host galaxy, we isolate the contribution of SN 2009nz and uncover broad features typical of nearby gamma-ray-burst-supernovae (GRB-SNe). This establishes unambiguously that GRB 091127 was accompanied by a broad-lined Type Ic SN, and links a cosmological long burst with a standard energy release (E{sub {gamma},iso} Almost-Equal-To 1.1 Multiplication-Sign 10{sup 52} erg) to a massive star progenitor. The spectrum of SN 2009nz closely resembles that of SN 2006aj, with SN 2003dh also providing an acceptable match, but has significantly narrower features than SNe 1998bw and 2010bh, indicative of a lower expansion velocity. The photospheric velocity inferred from the Si II {lambda}6355 absorption feature, v{sub ph} Almost-Equal-To 17, 000 km s{sup -1}, is indeed closer to that of SNe 2006aj and 2003dh than to the other GRB-SNe. Combining the measured velocity with the light curve peak brightness and width, we estimate the following nominal (maximal) explosion parameters: M{sub Ni} Almost-Equal-To 0.35 (0.6) M{sub Sun }, E{sub K} Almost-Equal-To 2.3 Multiplication-Sign 10{sup 51} (8.4 Multiplication-Sign 10{sup 51}) erg, and M{sub ej} Almost-Equal-To 1.4 (3.5) M{sub Sun }, similar to those of SN 2006aj. These properties indicate that SN 2009nz follows a trend of lower M{sub Ni} for GRB-SNe with lower E{sub K} and M{sub ej}. Equally important, since GRB 091127 is a typical cosmological burst, the similarity of SN 2009nz to SN 2006aj either casts doubt on the claim that XRF 060218/SN 2006aj was powered by a neutron star or indicates that the nature of the central engine is encoded in the SN properties but not in the prompt emission. Future spectra of GRB-SNe at z {approx}> 0.3 will shed light on the full dispersion of SN properties for standard long GRBs, on the relation between SNe associated with sub-energetic and standard GRBs, and on a potential dispersion in the associated SN types.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

REVISION OF SOLAR SPICULE CLASSIFICATION

Solar spicules are the fundamental magnetic structures in the chromosphere and may play a key role in channeling the chromosphere and corona. Recently, it was suggested by De Pontieu et al. that there were two types of spicules with very different dynamic properties, which were detected by the space-time plot technique in the Ca II H line (3968 A) wavelength from Hinode/Solar Optical Telescope observations. A 'Type I' spicule with a 3-7-minute lifetime undergoes a cycle of upward and downward motions; by contrast, a 'Type II' spicule fades away within dozens of seconds without a descending phase. We are motivated by the fact that for a spicule with complicated three-dimensional motion the space-time plot, which is made through a slit on a fixed position, could not match the spicule behavior all the time and might lose its real life story. By revisiting the same data sets, we identify and trace 105 and 102 spicules in the quiet Sun (QS) and coronal hole (CH), respectively, and obtain their statistical dynamic properties. First, we have not found a single convincing example of 'Type II' spicules. Second, more than 60% of the identified spicules in each region show a complete cycle, i.e., the majority are 'Type I' spicules. Third, the lifetimes of the spicules in the QS and CH are 148 s and 112 s, respectively, but there is no fundamental lifetime difference between the spicules in the QS and CH reported earlier. Therefore, the suggestion of coronal heating by 'Type II' spicules should be taken with caution.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

A CLASSIFICATION OF H II REGIONS BASED ON OXYGEN AND HELIUM LINES: THE CASES OF TOL 2146-391 AND TOL 0357-3915

We present long-slit spectrophotometry of two H II galaxies: TOL 2146-391 and TOL 0357-3915. We performed a detailed analysis that involves abundance determinations relaxing the assumption of homogeneous temperature. The temperature inhomogeneity values, t{sup 2}, were obtained through two methods: (1) comparing abundances from oxygen recombination lines to abundances from collisionally excited lines and (2) by using the line intensity ratios of a set of He I lines together with the HELIO10 program. We find that the HELIO10 program is a good alternative to obtain a t{sup 2} value in photoionized regions where recombination lines of heavy elements are not available. We have plotted 27 high- and low-metallicity H II regions in an oxygen degree of ionization versus t{sup 2} diagram; we find areas populated by H II regions and areas void of them; the physical characteristics of each area are discussed. In addition, an average t{sup 2} value can be determined for the objects in each area. We propose to use this (t{sup 2}) value for the cases where a direct measurement of t{sup 2} cannot be determined.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

The classification of magnetohydrodynamic regimes of thermonuclear combustion

Physical properties of magnetohydrodynamic (MHD) reaction fronts are studied as functions of the thermodynamic conditions, and the strength and orientation of the magnetic field in the unburned matter through which the fronts propagate. We determine the conditions for the existence of the various types of MHD reaction fronts and the character of the changes in physical quantities across these reaction fronts. The analysis is carried out in general for a perfect gas equation of state and a constant energy release, and then extended to thermonuclear reaction fronts in degenerate carbon-oxygen mixtures and degenerate helium in conditions typical of Type Ia supernova explosions. We find that as unburned matter enters perpendicular to a reaction front, the release of energy through burning generates shear velocity in the reacting gas that, depending on the type of reaction front, strengthens or weakens the magnetic field. In addition, we find that the steady-state propagation of a reaction front is impossible for certain ranges of magnetic field direction. Our results provide insight into the phenomena of MHD thermonuclear combustion that is relevant to the interpretation of future simulations of SN Ia explosions that have magnetic fields systematically incorporated.

79 ASTRONOMY AND ASTROPHYSICS↗