scholarly journals Super-Hawking radiation

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Ricardo Z. Ferreira ◽  
Carlo Heissenberg
Keyword(s):  
Emission Spectrum ◽  
Cosmic String ◽  
Azimuthal Angle ◽  
Conformal Factor ◽  
Effective Area ◽  
Total Power ◽  
Emission Rates ◽  
Null Infinity ◽  
The North ◽  
Angular Momentum State

Abstract We discuss modifications to the Hawking spectrum that arise when the asymptotic states are supertranslated or superrotated. For supertranslations we find nontrivial off-diagonal phases in the two-point correlator although the emission spectrum is eventually left unchanged, as previously pointed out in the literature. In contrast, superrotations give rise to modifications which manifest themselves in the emission spectrum and depend nontrivially on the associated conformal factor at future null infinity. We study Lorentz boosts and a class of superrotations whose conformal factors do not depend on the azimuthal angle on the celestial sphere and whose singularities at the north and south poles have been associated to the presence of a cosmic string. In spite of such singularities, superrotations still lead to finite spectral emission rates of particles and energy which display a distinctive power-law behavior at high frequencies for each angular momentum state. The integrated particle emission rate and emitted power, on the contrary, while finite for boosts, do exhibit ultraviolet divergences for superrotations, between logarithmic and quadratic. Such divergences can be ascribed to modes with support along the cosmic string. In the logarithimic case, corresponding to a superrotation which covers the sphere twice, the total power emitted still presents the Stefan-Boltzmann form but with an effective area which diverges logarithmically in the ultraviolet.

scholarly journals Measuring the local dark matter density with LAMOST DR5 and Gaia DR2

2020 ◽  
Vol 495 (4) ◽  
pp. 4828-4844 ◽  
Author(s):  
Rui Guo ◽  
Chao Liu ◽  
Shude Mao ◽  
Xiang-Xiang Xue ◽  
R J Long ◽  
...  
Keyword(s):  
Dark Matter ◽  
Azimuthal Angle ◽  
Matter Density ◽  
Dwarf Stars ◽  
Dark Matter Density ◽  
The North ◽  
Vertical Data ◽  
Data Release ◽  
The Difference ◽  
North And South

ABSTRACT We apply the vertical Jeans equation to the kinematics of Milky Way stars in the solar neighbourhood to measure the local dark matter density. More than 90 000 G- and K-type dwarf stars are selected from the cross-matched sample of LAMOST (Large Sky Area Multi-Object Fibre Spectroscopic Telescope) fifth data release and Gaia second data release for our analyses. The mass models applied consist of a single exponential stellar disc, a razor thin gas disc, and a constant dark matter density. We first consider the simplified vertical Jeans equation that ignores the tilt term and assumes a flat rotation curve. Under a Gaussian prior on the total stellar surface density, the local dark matter density inferred from Markov chain Monte Carlo simulations is $0.0133_{-0.0022}^{+0.0024}\ {\rm M}_{\odot }\, {\rm pc}^{-3}$. The local dark matter densities for subsamples in an azimuthal angle range of −10° < ϕ < 5° are consistent within their 1σ errors. However, the northern and southern subsamples show a large discrepancy due to plateaux in the northern and southern vertical velocity dispersion profiles. These plateaux may be the cause of the different estimates of the dark matter density between the north and south. Taking the tilt term into account has little effect on the parameter estimations and does not explain the north and south asymmetry. Taking half of the difference of σz profiles as unknown systematic errors, we then obtain consistent measurements for the northern and southern subsamples. We discuss the influence of the vertical data range, the scale height of the tracer population, the vertical distribution of stars, and the sample size on the uncertainty of the determination of the local dark matter density.

scholarly journals Observed acidification trends in North Atlantic water masses

2012 ◽  
Vol 9 (12) ◽  
pp. 5217-5230 ◽  
Author(s):  
M. Vázquez-Rodríguez ◽  
F. F. Pérez ◽  
A. Velo ◽  
A. F. Ríos ◽  
H. Mercier
Keyword(s):  
North Atlantic ◽  
Surface Waters ◽  
Sea Water ◽  
Deep Convection ◽  
Atlantic Water ◽  
Atmospheric Co2 ◽  
Emission Rates ◽  
The North ◽  
Iceland Basin ◽  
The North Atlantic

Abstract. The lack of observational pH data has made it difficult to assess recent rates of ocean acidification, particularly in the high latitudes. Here we present a time series that spans over 27 yr (1981–2008) of high-quality carbon system measurements in the North Atlantic, which comprises fourteen cruises and covers the important water mass formation areas of the Irminger and Iceland Basins. We provide direct quantification of acidification rates in upper and intermediate North Atlantic waters. The highest rates were associated with surface waters and with Labrador Sea Water (LSW). The Subarctic Intermediate and Subpolar Mode Waters (SAIW and SPMW) showed acidification rates of −0.0019 ± 0.0001 and −0.0012 ± 0.0002 yr−1, respectively. The deep convection activity in the North Atlantic Subpolar Gyre injects surface waters loaded with anthropogenic CO2 into lower layers, provoking the remarkable acidification rate observed for LSW in the Iceland Basin (−0.0016 ± 0.0002 yr−1). An extrapolation of the observed linear acidification trends suggests that the pH of LSW could drop 0.45 units with respect to pre-industrial levels by the time atmospheric CO2 concentrations reach ~775 ppm. Under circulation conditions and evolution of CO2 emission rates similar to those of the last three decades, by the time atmospheric CO2 reaches 550 ppm, an aragonite undersaturation state could be reached in the cLSW of the Iceland Basin, earlier than surface SPMW.

Particle tunneling in a quantum corrected spacetime

2015 ◽  
Vol 30 (02) ◽  
pp. 1550007
Author(s):  
Cheng-Zhou Liu ◽  
Qiao-Jun Cao
Keyword(s):  
Black Hole ◽  
Emission Spectrum ◽  
Tunneling Probability ◽  
Quantum Corrections ◽  
Emission Rates ◽  
Unitary Theory ◽  
Before And After ◽  
Trajectory Method ◽  
Trajectory Equation ◽  
Simpler Method

Particle tunneling from a quantum corrected black hole in the gravity's rainbow was investigated by the radial trajectory method of the tunneling framework. Using the thermodynamic property of the event horizon, a simpler method for calculating the tunneling probability was shown. In this method, the Painleve coordinate transformation of spacetime and the radial trajectory equation of the tunneling particles used in the previous radial trajectory method was not used. Using the simpler method, the tunneling probability of outgoing particles, regardless of whether they are massless or massive, were calculated in a unified way. The emission rates were related to the changes of the black hole entropies before and after the emission. This implies that the emission spectrum agrees with the underling unitary theory. In addition, the Bekenstein–Hawking area for the modified black hole was established and the emission spectrum with quantum corrections was discussed.

Simplified Method for Elastic Distortional Buckling Stress of Cold-Formed Thin-Wall Steel Members

2012 ◽  
Vol 166-169 ◽  
pp. 3391-3398
Author(s):  
Yang Zhao ◽  
Wei Ming Yan ◽  
Cheng Yu
Keyword(s):  
Technical Specification ◽  
Effective Area ◽  
Thin Wall ◽  
Steel Buildings ◽  
Distortional Buckling ◽  
The North ◽  
Buckling Stress ◽  
Steel Members ◽  
Calculation Results ◽  
Similar Computation

For the distortional buckling of cold-formed thin-wall steel members, the Direct Strength Method (DSM) is a recently adopted design approach by foreign standard, and Chinese professional standard Technical specification for low-rise cold-formed thin-wall steel buildings present the calculation formulas based on the Effective Area Method (EAM) .The key of both methods is the elastic distortional buckling stress .At present, the calculation methods about it are over conservative .Compare the calculation results of method in AISI S100with the one calculated by software CUFSM ,for C and Z sections in bending and axial compression loading respectively in the North American Specifications for Cold-Formed Steel Structural Members (AISI S100). This paper presents revised simplified methods for calculating the elastic distortional buckling stress. The new methods yield more accurate results but similar computation cost compared to the existing methods.

scholarly journals Atmospheric trends of the halon gases from polar firn air

2005 ◽  
Vol 5 (1) ◽  
pp. 937-960 ◽  
Author(s):  
C. E. Reeves ◽  
W. T. Sturges ◽  
G. A. Sturrock ◽  
K. Preston ◽  
D. E. Oram ◽  
...  
Keyword(s):  
Ice Core ◽  
Atmospheric Model ◽  
Polar Regions ◽  
Emission Rates ◽  
Depth Profiles ◽  
Devon Island ◽  
The North ◽  
Global Emission ◽  
Core Project ◽  
Atmospheric Concentrations

Abstract. Four halons (H-1301, H-1211, H-2402 and H-1202) have been measured in air samples collected from polar firn from Dome Concordia (Dome C), Antarctica, from Devon Island, Canada and the North Greenland Ice Core Project (NGRIP) site, Greenland. H-2402 and H-1202 are reported for the first time in firn air. The depth profiles show the concentrations of all four halons to be zero at the base of the firn thus demonstrating their entirely anthropogenic origin. This is the first evidence of this for H-2402 and H-1202. A 2-D atmospheric model was run to produce historical trends in the atmospheric concentrations at the firn sites, which were then input into a firn diffusion model to produce concentration depth profiles for comparison with the measurements. The firn measurements provide constraints on the atmospheric concentrations in both hemispheres which allow the global emission rates and their latitudinal distribution in the atmospheric model to be evaluated. Global emission trends previously determined from measurements at Cape Grim are found to be consistent with the firn data. Further emissions of H-1202 in recent years (late 1980s onwards) are likely to have come from latitudes mostly south of 40° N, but emissions prior to that may have come from further north. Emissions of H-1211 may also have shifted to latitudes south of 40° N during the late 1980s. The firn data is used to derive atmospheric trends in total organic bromine in the form of halons for both polar regions.

scholarly journals Simulations of Sulfate-Nitrate-Ammonium (SNA) aerosols during the extreme haze events over Northern China in October 2014

2016 ◽  
Author(s):  
Dan Chen ◽  
Zhiquan Liu ◽  
Jerome Fast ◽  
Junmei Ban
Keyword(s):  
Relative Humidity ◽  
Observational Data ◽  
Heterogeneous Reaction ◽  
Northern China ◽  
Reaction Rates ◽  
Heterogeneous Reactions ◽  
Formation Mechanisms ◽  
Emission Rates ◽  
Oxidation Rates ◽  
The North

Abstract. Extreme haze events have occurred frequently over China in recent years. Although many studies have investigated the formation mechanisms associated with PM2.5 for heavily polluted regions in China based on observational data, adequately predicting peak PM2.5 concentrations is still challenging for regional air quality models. In this study, we evaluate the performance of one configuration of the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) and use the model to investigate the sensitivity of heterogeneous reactions on simulated peak sulfate, nitrate, and ammonium concentrations in the vicinity of Beijing during four extreme haze episodes in October 2014 over the North China Plain. The highest observed PM2.5 concentration of 469 μg m-3 occurred in Beijing. Comparisons with observations show that the model reproduced the temporal variability in PM2.5 with the highest PM2.5 values on polluted days (defined as days in which observed PM2.5 is greater than 75 μg m-3), but predictions of sulfate, nitrate, and ammonium were too low on days with the highest observed concentrations. Observational data indicate that the sulfur/nitric oxidation rates are strongly correlated with relative humidity during periods of peak PM2.5; however, the model failed to reproduce the highest PM2.5 concentrations due to missing heterogeneous reactions. As the parameterizations of those reactions is not well established yet, estimates of SO2-to-H2SO4 and NO2/NO3-to-HNO3 reaction rates that depend on relative humidity were applied which improved the simulation of sulfate, nitrate, and ammonium enhancement on polluted days in terms of both concentrations and partitioning among those species. Sensitivity simulations showed that the extremely high heterogeneous reaction rates and also higher emission rates than those reported in the emission inventory were likely important factors contributing to those peak PM2.5 simulations.

scholarly journals ESTIMATION OF BVOC EMISSIONS IN GUANGZHOU AND ITS SPATIAL-TEMPORAL VARIATIONS: PRELIMINARY RESULTS FROM GLOBEIS

2018 ◽  
Vol XLII-3/W5 ◽  
pp. 33-38
Author(s):  
L. Li ◽  
Y. Wang ◽  
Y. Zheng ◽  
T. Chen
Keyword(s):  
Land Cover ◽  
Meteorological Data ◽  
Seasonal Pattern ◽  
Temporal Variations ◽  
Emission Rates ◽  
Area Index ◽  
Land Cover Types ◽  
The North ◽  
Result Show ◽  
High Emission

<p><strong>Abstract.</strong> Biogenic VOC emissions greatly exceed anthropogenic emissions and are regarded as significant precursors to secondary organic aerosol (SOA) and ozone. Using the Global Biosphere Emission and Interactions System (GloBEIS) model, 1<span class="thinspace"></span>&amp;times;<span class="thinspace"></span>1<span class="thinspace"></span>km gridded and hourly BVOC emissions in Guangzhou were estimated for the year of 2012. This study used satellite-retrieved land cover data, cloud product and leaf area index (LAI), observed meteorological data and local emission rates for land cover types in South China. The result show that the total BVOC emission in Guangzhou, 2012 was 4.39<span class="thinspace"></span>kt and the average area emission was 5.93<span class="thinspace"></span>t/(km<sup>2</sup>&amp;sdot;a), of which isoprene contributed about 55.7% (2.44<span class="thinspace"></span>kt)), monoterpenes about 11.9% (0.52<span class="thinspace"></span>kt) and OVOC about 32.4% (1.42<span class="thinspace"></span>kt). Emission factors of land cover types and correction parameters including LAI, wind speed and relative humidity have great effects on the estimation results of the model. BVOC emissions in Guangzhou exhibit a marked monthly and seasonal pattern with the peak emission in July to August and the lowest emission in January and are mainly distributed in the east-western of Conghua, the north of Zengcheng and the border of Huadu and Conghua, mostly covered by evergreen broadleaf forest with high emission factor, while areas of BVOC emission below 50<span class="thinspace"></span>kg/(km<sup>2</sup>&amp;sdot;a) are distributed in highly urbanized areas like Tianhe, Yuexiu, Liwan and Haizhu district.</p>

scholarly journals Evidence of cosmic strings by the observation of the alignment of quasar polarization axes on Mpc scale

2018 ◽  
Vol 27 (09) ◽  
pp. 1850094 ◽  
Author(s):  
Reinoud Jan Slagter
Keyword(s):  
Symmetry Breaking ◽  
Gauge Field ◽  
Cosmic String ◽  
Axial Symmetry ◽  
Approximation Scheme ◽  
Azimuthal Angle ◽  
Goldstone Boson ◽  
Second Order ◽  
Compact Objects ◽  
Warp Factor

The recently found alignment of the polarization axes (PA) of quasars in large quasar groups (LQGs) on Mpc scales can be explained by general relativistic cosmic string networks. By considering the cosmic string as a result of spontaneous symmetry breaking of the gauged U(1) abelian Higgs model with topological charge [Formula: see text], many stability features of [Formula: see text]-vortex solutions of superconductivity can be taken over. Decay of the high multiplicity ([Formula: see text]) super-conducting vortex into a lattice of [Formula: see text] vortices of unit magnetic flux is energetically favorable. The temporarily broken axial symmetry will leave an imprint of a preferred azimuthal-angle on the lattice. The stability of the lattice depends critically on the parameters of the model, especially when gravity comes into play. In order to handle the strong nonlinear behavior of the time-dependent coupled field equations of gravity and the scalar-gauge field, we will use a high-frequency approximation scheme to second order on a warped 5D axially symmetric spacetime with the scalar-gauge field residing on the brane. We consider different winding numbers for the subsequent orders of perturbations of the scalar field. A profound contribution to the energy–momentum tensor comes from the bulk spacetime and can be understood as “dark”-energy. The cosmic string becomes super-massive by the contribution of the 5D Weyl tensor on the brane and the stored azimuthal preferences will not fade away. During the recovery to axial symmetry, gravitational and electro-magnetic radiation will be released. The perturbative appearance of a nonzero energy–momentum component [Formula: see text] can be compared with the phenomenon of bifurcation along the Maclaurin–Jacobi sequence of equilibrium ellipsoids of self-gravitating compact objects, signaling the onset of secular instabilities. There is a kind of similarity with the Goldstone-boson modes of spontaneously broken symmetries of continuous groups. The recovery of the SO(2) symmetry from the equatorial eccentricity takes place on a time-scale comparable with the emission of gravitational waves. The emergent azimuthal-angle dependency in our model can be used to explain the aligned PA in LQGs on Mpc scales. Spin axis direction perpendicular to the major axes of LQGs when the richness decreases can be explained as a second-order effect in our approximation scheme by the higher multiplicity terms. The preferred directions are modulo [Formula: see text], with [Formula: see text] being an integer dependent on the [Formula: see text]th order of approximation. When more data of quasars of high redshift becomes available, one could prove that the alignment emerged after the symmetry breaking scale and must have a cosmological origin. The effect of the warp factor on the second-order perturbations could also be an indication of the existence of extra large dimensions.

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