118331890
Rotating black rings on Taub-NUT
A bstractIn this paper, we construct new solutions describing rotating black rings on Taub-NUT using the inverse-scattering method. These are five-dimensional vacuum spacetimes, generalising the Emparan-Reall and extremal Pomeransky-Sen’kov black rings to a Taub-NUT background space. When reduced to four dimensions in Kaluza-Klein theory, these solutions describe (possibly rotating) electrically charged black holes in superposition with a finitely separated magnetic monopole. Various properties of these solutions are studied, from both a five- and four-dimensional perspective.
118533298
Black holes on gravitational instantons
Abstract In this paper, we classify and construct five-dimensional black holes on gravitational instantons in vacuum Einstein gravity, with R × U ( 1 ) × U ( 1 ) isometry. These black holes have spatial backgrounds which are Ricci-flat gravitational instantons with U ( 1 ) × U ( 1 ) isometry, and are completely regular space–times outside the event horizon. Most of the known exact five-dimensional vacuum black-hole solutions can be classified within this scheme. Amongst the new space–times presented are static black holes on the Euclidean Kerr and Taub-bolt instantons. We also present a rotating black hole on the Eguchi–Hanson instanton.
119228842
A New AF gravitational instanton
Abstract It has long been conjectured that the Euclidean Schwarzschild and Euclidean Kerr instantons are the only non-trivial asymptotically flat (AF) gravitational instantons. In this Letter, we show that this conjecture is false by explicitly constructing a new two-parameter AF gravitational instanton with a U ( 1 ) × U ( 1 ) isometry group, using the inverse-scattering method. It has Euler number χ = 3 and Hirzebruch signature τ = 1 , and its global topology is C P 2 with a circle S 1 removed appropriately. Various other properties of this gravitational instanton are also discussed.
118210434
Rod-structure classification of gravitational instantons with U(1)×U(1) isometry
Abstract The rod-structure formalism has played an important role in the study of black holes in D = 4 and 5 dimensions with R × U ( 1 ) D − 3 isometry. In this paper, we apply this formalism to the study of four-dimensional gravitational instantons with U ( 1 ) × U ( 1 ) isometry, which could serve as spatial backgrounds for five-dimensional black holes. We first introduce a stronger version of the rod structure with the rod directions appropriately normalised, and show how the regularity conditions can be read off from it. Requiring the absence of conical and orbifold singularities will in general impose periodicity conditions on the coordinates, and we illustrate this by considering known gravitational instantons in this class. Some previous results regarding certain gravitational instantons are clarified in the process. Finally, we show how the rod-structure formalism is able to provide a classification of gravitational instantons, and speculate on the existence of possible new gravitational instantons.
55754943
A doubly rotating black ring with dipole charge
A bstractWe present a dipole-charged generalisation of the Pomeransky-Sen’kov black ring in five-dimensional Kaluza-Klein theory. It rotates in two independent directions, although one of the rotations has been tuned to achieve balance, so that the space-time does not contain any conical singularities. This solution was constructed using the inverse-scattering method in six-dimensional vacuum gravity. We then study various physical properties of this solution, with particular emphasis on the new features that the dipole charge introduces.
119301374
Balanced electric-magnetic dihole in Kaluza-Klein theory
A bstractWe present a four-dimensional double-black-hole (or dihole) solution in KaluzaKlein theory, describing a superposition of an electrically charged and a magnetically charged black hole. This system can be balanced for appropriately chosen parameters, and the resulting space-time is completely regular on and outside the event horizons. This solution was constructed using the inverse-scattering method in five-dimensional vacuum gravity, in which it describes a rotating black ring surrounding a static black hole on a Taub-NUT background space. Various properties of this solution are studied, from both a four- and five-dimensional perspective.
197471495
Charmonium, $D_s$ and $D_s^*$ from overlap fermion on DWF configurations
We take a new approach to determine the scale parameter $r_0$, the physical masses of strange and charm quarks through a global fit which incorporates continuum extrapolation, chiral extrapolation and quark mass interpolation to the lattice data. The charmonium and charm-strange meson spectrum are calculated with overlap valence quarks on $2+1$-flavor domain-wall fermion gauge configurations generated by the RBC and UKQCD Collaboration. We use the masses of $D_s$, $D_s^*$ and $J/\psi$ as inputs and obtain $m_c^{\overline{\rm MS}}(2\,{\rm GeV})=1.110(24)\,{\rm GeV}$, $m_s^{\overline{\rm MS}}(2\,{\rm GeV})=0.104(9)\,{\rm GeV}$ and $r_0=0.458(11)\,{\rm fm}$. Subsequently, the hyperfine-splitting of charmonium and $f_{D_s}$ are predicted to be $112(5)\,{\rm MeV}$ and $254(5)\,{\rm MeV}$, respectively.
16273589
Chemical composition of 90 F and G disk dwarfs
High resolution, high S/N spectra have been obtained for a sample of 90 F and G main-sequence disk stars covering the metallicity range 1:0 < (Fe/H) < +0:1, and have been analysed in a parallel way to the work of Edvardsson et al. (1993a) in order to re-inspect their re- sults and to reveal new information on the chemical evo- lution of the Galactic disk. Compared to Edvardsson et al. the present study in- cludes several improvements. Eective temperatures are based on the Alonso et al. (1996) calibration of color in- dices by the infrared flux method and surface gravities are calculated from Hipparcos parallaxes, which also allow more accurate ages to be calculated from a comparison of MV and Te with isochrones. In addition, more reli- able kinematical parameters are derived from Hipparcos distances and proper motions in combination with accu- rate radial velocities. Finally, a larger spectral coverage, 5600 8800 A, makes it possible to improve the abundance accuracy by studying more lines and to discuss several el- ements not included in the work of Edvardsson et al. The present paper provides the data and discusses some general results of the abundance survey. A group of stars in the metallicity range of 1:0 < (Fe/H) < 0:6 having a small mean Galactocentric distance in the stellar orbits, Rm < 7 kpc, are shown to be older than the other disk stars and probably belong to the thick disk. Excluding these stars, a slight decreasing trend of (Fe/H) with increasing Rm and age is found, but a large scatter in (Fe/H) (up to 0.5 dex) is present at a given age andRm. Abundance ratios with respect to Fe show, on the other hand, no signicant scatter at a given (Fe/H). The derived
118503079
Early Growth of Massive Black Holes in Quasars
Episodic activity of quasars is driving growth of supermassive black holes (SMBHs) via accretion of baryon gas. In this Letter, we develop a simple method to analyze the duty cycle of quasars up to the redshift -->z ~ 6 universe from luminosity functions (LFs). We find that the duty cycle below redshift -->z ~ 2 follows the cosmic history of star formation rate (SFR) density. Beyond -->z ~ 2, the evolutionary trends of the duty cycle are opposite to that of the cosmic SFR density history, implying the role of feedback from black hole activity. With the duty cycle, we get the net lifetime of quasars ( -->z ≤ 5) about ~109 yr. Based on the local SMBHs, the mean mass of SMBHs is obtained at any redshifts and their seeds are of -->105 M☉ at the reionization epoch ( -->zre) of the universe through the conservation of black hole number density in a comoving frame. We find that primordial black holes (~103 M☉) are able to grow up to the seeds via a moderate super-Eddington accretion of ~30 times the critical rate from -->z = 24 to -->zre. Highly super-Eddington accretion onto the primordial black holes is not necessary.
118576878
Evolution of the most massive galaxies to z= 0.6 – I. A new method for physical parameter estimation
We use principal component analysis (PCA) to estimate stellar masses, mean stellar ages, star formation histories (SFHs), dust extinctions and stellar velocity dispersions for a set of ∼290 000 galaxies with stellar masses greater than 1011 M⊙ and redshifts in the range 0.4 < z < 0.7 from the Baryon Oscillation Spectroscopic Survey (BOSS). We find that the fraction of galaxies with active star formation first declines with increasing stellar mass, but then flattens above a stellar mass of 1011.5 M⊙ at z∼ 0.6. This is in striking contrast to z∼ 0.1, where the fraction of galaxies with active star formation declines monotonically with stellar mass. At stellar masses of 1012 M⊙, therefore, the evolution in the fraction of star-forming galaxies from z∼ 0.6 to the present day reaches a factor of ∼10. When we stack the spectra of the most massive, star-forming galaxies at z∼ 0.6, we find that half of their [O iii] emission is produced by active galactic nuclei. The black holes in these galaxies are accreting on average at ∼0.01 the Eddington rate. To obtain these results, we use the stellar population synthesis models of Bruzual & Charlot to generate a library of model spectra with a broad range of SFHs, metallicities, dust extinctions and stellar velocity dispersions. The PCA is run on this library to identify its principal components over the rest-frame wavelength range 3700–5500 A. We demonstrate that linear combinations of these components can recover information equivalent to traditional spectral indices such as the 4000-A break strength and HδA, with greatly improved signal-to-noise ratio (S/N). In addition, the method is able to recover physical parameters such as stellar mass-to-light ratio, mean stellar age, velocity dispersion and dust extinction from the relatively low S/N BOSS spectra. We examine in detail the sensitivity of our stellar mass estimates to the input parameters in our model library, showing that almost all changes result in systematic differences in logM* of 0.1 dex or less. The biggest differences are obtained when using different population synthesis models – stellar masses derived using Maraston et al. models are systematically smaller by up to 0.12 dex at young ages.
15744505
Radio Luminosity, Black Hole Mass and Eddington Ratio for Quasars from the Sloan Digital Sky Survey
We investigate the MBH-O''.relation for radio-loud quasars with redshift z＜0.83 in Data Release 3 of the Sloan Digital Sky Survey (SDSS).The sample consists of 3772 quasars with better models of the H/~ and [O III] lines and available radio luminosity,including 306 radio-loud quasars,3466 radio-quiet quasars with measured radio luminosity or upper-limit of radio luminosity (181 radio-quiet quasars with measured radio luminosity).The virial supermassive black hole mass (MBH) is calculated from the broad H/line,and the host stellar velocity dispersion (σ*) is traced by the core [O III] gaseous velocity dispersion.The radio luminosity and radio loudness are derived from the FIRST catalog.Our results are as follows:(1) For radio-quiet quasars,we confirm that there is no obvious deviation from the MBH-O.relation defined for inactive galaxies when the uncertainties in MBH and the luminosity bias are concerned.(2) We find that the radio-loud quasars deviate more from the MBH-σ.relation than do the radio-quiet quasars.This deviation is only partly due to a possible cosmological evolution of the MBH-σ* relation and the luminosity bias.(3) The radioluminosity is proportional to M128+0.23-0.16 BH(LBol/LEdd)1.29+0.31-0.24 for radio-quiet quasars and to M3.10+0.6.-0.70(LBol.LEdd)4.18+1.40-1.10 for radio-loud quasars.The weaker dependence of the radio luminosity on the mass and the Eddington ratio for radio-loud quasars shows that other physical effects would account for their radio luminosities,such as the spin of the black hole.