119160554
THE ARGO-YBJ EXPERIMENT PROGRESSES AND FUTURE EXTENSION
Gamma ray source detection above 30 TeV is an encouraging approach for finding galactic cosmic ray origins. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100 GeV. To target the goals, the ARGO-YBJ experiment has been established. Significant progresses have been made in the experiment. A large air shower detector array in an area of 1 km2 is proposed to boost the sensitivity. Hybrid detections with multi-techniques will allow a good discrimination between different types of primary particles, including photons and protons, thus enable an energy spectrum measurement for individual species. Fluorescence light detector array will extend the spectrum measurement to 100 PeV and higher where the second knee is located. An energy scale determined by balloon experiments at 10 TeV will be propagated to ultra high energy cosmic ray experiments.
118436059
The Correlated Multi-color Optical Variations of BL Lac Object S5 0716+714
S5 0716+714 is a well-studied BL Lac object in the sky. Verifying the existence of correlations among the flux variations in different bands serves as an important tool to investigate the emission processes. To examine the possible existence of a lag between variations in different optical bands on this source, we employ a discrete correlation function analysis on the light curves. In order to obtain statistically meaningful values for the cross-correlation time lags and their related uncertainties, we perform Monte Carlo simulations called 'flux redistribution/random subset selection'. Our analysis confirms that the variations in different optical light curves are strongly correlated. The time lags show a hint of the variations in high frequency band leading those in low frequency band of the order of a few minutes.
117043052
SEARCH FOR 10 TeV BURST-LIKE EVENTS COINCIDENT WITH THE BATSE BURSTS USING THE TIBET AIR SHOWER ARRAY
118587418
Testing Lorentz invariance with the ultrahigh energy cosmic ray spectrum
The Greisen-Zatsepin-Kuzmin cutoff predicted at the ultrahigh energy cosmic ray spectrum has been observed by the HiRes and Auger experiments. The results put severe constraints on the effect of Lorentz invariance violation (LIV), which has been introduced to explain the absence of the Greisen-Zatsepin-Kuzmin cutoff indicated in the AGASA data. Assuming a homogeneous source distribution with a single power-law spectrum, we calculate the ultrahigh energy cosmic ray spectrum observed on the Earth by taking photopion production, e(+)e(-) pair production, and the adiabatic energy loss into account. The effect of LIV is also taken into account in the calculation. By fitting the HiRes monocular spectra and the Auger combined spectra, we show that the LIV parameter is constrained to xi=-0.8(-0.5)(+3.2)x10(-23) and 0.0(-0.4)(+1.0)x10(-23), respectively, which is very consistent with strict Lorentz invariance up to the highest energy.
123646598
Progress in Very High Energy Neutrino Astronomic Experiments
In this review, I will report progress in UHE neutrino search using existing experiments and status of constructing detectors. Physics relevant to UHE neutrinos are updated as well.
121925364
SEARCH FOR 10 TEV GAMMA-RAY EMISSION FROM ACTIVE GALACTIC NUCLEI WITH THE TIBET AIR SHOWER ARRAY
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.
122996811
Newman-Penrose constants of the Kerr-Newman metric
The Newman-Unti formalism of the Kerr-Newman metric near future null infinity is developed, with which the Newman-Penrose constants for both the gravitational and electromagnetic fields of the Kerr-Newman metric are computed and shown to be zero. The multipole structure near future null infinity in the sense of Janis-Newman of the Kerr-Newman metric is then further studied. It is found that up to the ${2}^{4}$-pole, modulo a constant dependent upon the order of the pole, these multipole moments agree with those of Geroch-Hansen multipole moments defined at spatial infinity.
119264530
Numerical stability of the Z4c formulation of general relativity
We study numerical stability of different approaches to the discretization of a conformal decomposition of the Z4 formulation of general relativity. We demonstrate that in the linear, constant coefficient regime a novel discretization for tensors is formally numerically stable with a method of lines time-integrator. We then perform a full set of apples with apples tests on the non-linear system, and thus present numerical evidence that both the new and standard discretizations are, in some sense, numerically stable in the non-linear regime. The results of the Z4c numerical tests are compared with those of BSSNOK evolutions. We typically do not employ the Z4c constraint damping scheme and find that in the robust stability and gauge wave tests the Z4c evolutions result in lower constraint violation at the same resolution as the BSSNOK evolutions. In the gauge wave tests we find that the Z4c evolutions maintain the desired convergence factor over many more light-crossing times than the BSSNOK tests. The difference in the remaining tests is marginal.
119209594
Constructing EOB dynamics with numerical energy flux for intermediate-mass-ratio inspirals
A new scheme for computing dynamical evolutions and gravitational radiations for intermediatemass-ratio inspirals (IMRIs) based on an effective one-body (EOB) dynamics plus Teukolsky perturbation theory is built in this paper. In the EOB framework, the dynamics essentially affects the resulted gravitational waveform for binary compact star system. This dynamics includes two parts. One is the conservative part which comes from effective one-body reduction. The other part is the gravitational back reaction which contributes to the shrinking process of the inspiral of binary compact star system. Previous works used analytical waveform to construct this back reaction term. Since the analytical form is based on post-Newtonian expansion, the consistency of this term is always checked by numerical energy flux. Here we directly use numerical energy flux by solving the Teukolsky equation via the frequency-domain method to construct this back reaction term. And the conservative correction to the leading order terms in mass-ratio is included in the deformed-Kerr metric and the EOB Hamiltonian. We try to use this method to simulate not only quasi-circular adiabatic inspiral but also the nonadiabatic plunge phase. For several different spinning black holes, we demonstrate and compare the resulted dynamical evolutions and gravitational waveforms.
118380186
Numerical evolution of multiple black holes with accurate initial data
We present numerical evolutions of three equal-mass black holes using the moving puncture approach. We calculate puncture initial data for three black holes solving the constraint equations by means of a high-order multigrid elliptic solver. Using these initial data, we show the results for three black hole evolutions with sixth-order waveform convergence. We compare results obtained with the BAM and AMSS- N C KU codes with previous results. The approximate analytic solution to the Hamiltonian constraint used in previous simulations of three black holes leads to different dynamics and waveforms. We present some numerical experiments showing the evolution of four black holes and the resulting gravitational waveform.