122607999
From binary black hole simulation to triple black hole simulation
Black hole systems are among the most promising sources for a gravitational wave detection project. Now, China is planning to construct a space-based laser interferometric detector as a follow-on mission of LISA in the near future. Aiming to provide some theoretical support to this detection project on the numerical relativity side, we focus on black hole systems simulation in this work. Considering the globular galaxy, multiple black hole systems also likely to exist in our universe and play a role as a source for the gravitational wave detector we are considering. We will give a progress report in this paper on our black hole system simulation. More specifically, we will present triple black hole simulation together with binary black hole simulation. On triple black hole simulations, one novel perturbational method is proposed.
120027918
SPIN EXPANSION FOR HEAD-ON COLLISION OF TWO BLACK HOLES
The spin expansion technique proposed in [L. Boyel, M. Kesden and S. Nissanke, Phys. Rev. Lett.100 (2008) 151101] is very powerful to analyze the relation between the initial state of binary black hole and the final state of the merged black hole. But this technique needs orbital angular momentum to determine the third direction of a triad. Without this triad we cannot get the decomposed components of the involved quantities, and the spin expansion breaks down. The head-on collision of two black holes, whose orbital angular momentum vanishes, falls into this case. In this paper we propose a new method to construct a triad for spin expansion technique. With this new method, we get the same set of equations as in the above-mentioned paper. Furthermore, we use numerical simulations to illustrate the validity of our new method for the head-on collision of two black holes.
122890389
GMF model dependence of correlations between BL Lacs and ultra high energy cosmic rays
Some studies suggested that there exists a correlation between locations of BL Lacertae objects (BL Lacs) and arrival directions of ultra high energy cosmic rays (UHECRs). Especially by assuming the primary particles charged +1 and using a galactic magnetic field (GMF) model to calculate deflections of the UHECRs, the significance of correlation can be improved. A new GMF model is constructed by incorporating all progresses in the GMF measurements in recent years and use it to a thorough study of the deflections of the UHECRs measured by the AGASA experiment. Compared with other models, the GFM model dependence of the correlation between the LTHECRs and the selected BL Lacs is studied. It turns out that only specific one of those GMF models makes the correlation significant, even if the GMF models are not very different. The UHECR deflections are also different depending on which GMF model is used. It indicates that the significance of the correlation, suggested in those studies, is strongly depending on GMF models. Great improvement in statistics may help to suppress the sensitivity to GMF models. (C) 2007 Elsevier B.V. All rights reserved.
121925364
SEARCH FOR 10 TEV GAMMA-RAY EMISSION FROM ACTIVE GALACTIC NUCLEI WITH THE TIBET AIR SHOWER ARRAY
121086320
Cosmic Ray Experiments in the Era of LHC
Many uncertainties in cosmic ray experiments will be eliminated with more measurements about interaction between nucleons in the Large Hadron Collider (LHC) experiment. Cosmic ray experiments will enter an era marked by the high precision of measurements carried out by combining multipurpose instruments on very large scales. They have been putting strict constraints on models of cosmic ray acceleration at sources and propagation through the universe. Measurements of electrons, all kinds of nuclei, even gamma rays and neutrinos will enhance the opportunity of breakthrough in solving the mystery of origin of cosmic rays or even finding the source of the dark matter. A fundamental problem in cosmic ray experiments is the energy scale of ground based experiments for ultra high energy cosmic rays. A unique and straightforward approach is to match the energy spectra of nuclei measured by space or balloon borne experiments with what measured by ground based detectors at high altitudes and propagate the scale up ...
18990615
Scaling properties of hadron production in the Ising model for quark-hadron phase transition
Earlier study of quark-hadron phase transition in the Ginzberg-Landau theory is reexamined in the Ising model, so that spatial fluctuations during the transition can be taken into account. Although the dimension of the physical system is 2, as will be argued, bothd=2 andd=4 Ising systems are studied, the latter being theoretically closer to the Ginzberg-Landau theory. The normalized factorial momentsFq are used to quantify multiplicity fluctuations, and the scaling exponentν is used to characterize the scaling properties. It is found by simulation on the Ising lattice thatν becomes a function of the temperatureT nearTc. The average value ofν over a range ofT<Tc agrees with the value of 1.3 derived analytically from the Ginzberg-Landau theory. Thus the implications of the mean-field theory are not invalidated by either the introduction of spatial fluctuations or the restriction to a 2D system.
17094516
Energy estimation of UHE cosmic rays using the atmospheric fluorescence technique
Abstract We use the CORSIKA air shower simulation program to review the method for assigning energies to ultra-high energy cosmic rays viewed with the air fluorescence technique. This technique uses the atmosphere as a calorimeter, and we determine the corrections that must be made to the calorimetric energy to yield the primary cosmic-ray energy.