2,912 research outputs found
P-Cygni Type Lya from Starburst Galaxies
P-Cygni type Lya profiles exhibited in nearly half of starburst galaxies,
both nearby and high-z, are believed to be formed by an expanding supershell
surrounding a star-forming region. We apply the Monte Carlo code which was
developed previously for static and plane-parallel medium to calculate the Lya
line transfer in a supershell of neutral hydrogen which are expanding radially
in a spherical bulk flow. We consider typical cases that the supershell has the
Lya line-centre optical depth of , a radial expansion
velocity of \tau_0$ and V_exp of the
supershell. We discuss the effects of dust extinction and the implication of
our works in relation to recent spectroscopic observations of starburst
galaxies.Comment: 15 pages, 6 figures, submitted to MNRA
Rotation Correction Method Using Depth-Value Symmetry of Human Skeletal Joints for Single RGB-D Camera System
Most red-green-blue and depth (RGB-D) motion-recognition technologies employ both depth and RGB cameras to recognize a user\u27s body. However, motion-recognition solutions using a single RGB-D camera struggle with rotation recognition depending on the device-user distance and field-of-view. This paper proposes a near-real-time rotational-coordinate-correction method that rectifies a depth error unique Microsoft Kinect by using the symmetry of the depth coordinates of the human body. The proposed method is most effective within 2 m, a key range in which the unique depth error of Kinect occurs, and is anticipated to be utilized in applications requiring low cost and fast installation. It could also be useful in areas such as media art that involve unspecified users because it does not require a learning phase. Experimental results indicate that the proposed method has an accuracy of 85.38%, which is approximately 12% higher than that of the reference installation method
Massless Rotating Spacetimes in Four-Dimensional Horava Gravity
We study a particular exact solution for rotating spacetimes in
four-dimensional Horava gravity, which has been proposed as a renormalizable
gravity model without the ghost problem. We show that the massless Kerr
spacetime or the massless Kerr-(A)dS spacetime in Einstein gravity is an exact
solution in four-dimensional Horava for an arbitrary IR Lorentz-violation
parameter lambda, but with an appropriate cosmological constant. In particular,
for the massless topological Kerr-AdS black hole solution with the hyperbolic
horizon topology or the massless Kerr-dS cosmological solution with the
spherical horizon topology, there exist the ergosphere and the non-vanishing
Hawking temperature, which imply the existence of negative mass black holes as
well as positive mass spacetimes, by losing its mass from the massless ones via
the Hawking radiation or Penrose process in the ergosphere.Comment: 10 pages, 3 figure
Generic features of the cosmological evolution of density parameters
The evolution of various energy components with dark energy was examined. Recently many non-standard gravity models were suggested to explain the current observational data showing an accelerating phase since the recent past. All suggested models should mimic ÎCDM somehow, especially from the near past to the current epoch. However, most of them do not try to explain or predict what happens if their model were extended to the far past and/or the past. In this paper we want to address this point by analyzing the critical points of the evolution equations and their stability. Standard ÎCDM gives three critical points, radiation dominated, matter dominated, and cosmological constant dominated. Furthermore, the radiation-dominated point corresponds to the past stable point, the matterdominated point to the saddle point, and the cosmological-constantâdominated point to the future stable point. This means that this model predicts that the universe
starts from radiation domination then passes through a matter-dominated era and finally evolves into a cosmological-constantâdominated era, that is, the future de Sitter phase. We applied these creteria to few f(R) gravity models to determine viable parameter ranges
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