Frequency response of space-based interferometric gravitational-wave detectors

Gravitational waves are perturbations of the metric of space-time. Six polarizations are possible, although general relativity predicts that only two such polarizations, tensor plus and tensor cross are present for gravitational waves. We give the analytical formulas for the antenna response functions for the six polarizations which are valid for any equal-arm interferometric gravitational-wave detectors without optical cavities in the arms.The response function averaged over the source direction and polarization angle decreases at high frequencies which deteriorates the signal-to-noise ratio registered in the detector. At high frequencies, the averaged response functions for the tensor and breathing modes fall of as $1/f^2$, the averaged response function for the longitudinal mode falls off as $1/f$ and the averaged response function for the vector mode falls off as $\ln(f)/f^2$.Comment: V3: minor corrections. PRD in pres

A Social Force Model for Adjusting Sensing Ranges in Multiple Sensing Agent Systems

In previous work of multiple sensing agent systems (MSASs), they mainly adjust the sensing ranges of agents by centralized heuristics; and the whole adjustment process is controlled in centralized manner. However, such method may not fit for the characteristics of MSASs where the agents are distributed and decide their activities autonomously. To solve such problem, this paper introduces the social force model for adjusting the sensing ranges of multiple sensing agents, which can make the agents adjust their sensing ranges autonomously according to their social forces to other agents and the sensing objects. Based on the social force model, the coverage and optimization models are presented for both point-type and area-type objects. The presented model can produce appropriate social forces among the sensing agents and objects in MSASs; thereby the system observability and lifetime can be improved

Source localizations with the network of space-based gravitational wave detectors

The sky localization of the gravitational wave (GW) source is an important scientific objective for GW observations. A network of space-based GW detectors dramatically improves the sky localization accuracy compared with an individual detector not only in the inspiral stage but also in the ringdown stage. It is interesting to explore what plays an important role in the improvement. We find that the angle between the detector planes dominates the improvement, and the time delay is the next important factor. A detector network can dramatically improve the source localization for short signals and long signals with most contributions to the signal-to-noise ratio (SNR) coming from a small part of the signal in a short time, and the more SNR contributed by smaller parts, the better improvement by the network. We also find the effects of the arm length in the transfer function and higher harmonics are negligible for source localization with the detector network.Comment: 14 pages, 8 figures, 2 tables. Phys. Rev. D accepted. Comments are welcome! arXiv admin note: text overlap with arXiv:2105.1127

The Holographic dark energy reexamined

We have reexamined the holographic dark energy model by considering the spatial curvature. We have refined the model parameter and observed that the holographic dark energy model does not behave as phantom model. Comparing the holographic dark energy model to the supernova observation alone, we found that the closed universe is favored. Combining with the Wilkinson Microwave Anisotropy Probe (WMAP) data, we obtained the reasonable value of the spatial curvature of our universe.Comment: divided into sections, add one figure, some typos corrected, references added, Accepted for publication in PRD; v3: some typos corrected, title change

Testing alternative theories of gravity with space-based gravitational wave detectors

We use gravitational waves (GWs) from binary black holes (BBHs) and neutron stars inspiraling into intermediate-mass black holes to evaluate how accurately the future space-based GW detectors such as LISA, Taiji and TianQin and their combined networks can determine source parameters and constrain alternative theories of gravity. We find that, compared with single detector, the detector network can greatly improve the estimation errors of source parameters, especially the sky localization, but the improvement of the constraint on the graviton mass $m_g$ and the Brans-Dicke coupling constant $\omega_{BD}$ is small. We also consider possible scalar modes existed in alternative theories of gravity and we find the inclusion of the scalar mode has little effect on the constraints on source parameters, $m_g$, and $\omega_{BD}$ and the parametrized amplitude $A_B$ of scalar modes are small. For the constraint on the graviton mass, we consider both the effects in the GW phase and the transfer function due to the mass of graviton. With the network of LISA, Taiji and TianQin, we get the lower bound on the graviton Compton wavelength $\lambda_g\gtrsim 1.24 \times 10^{20}$ m for BBHs with masses $(10^6+10^7)M_\odot$, and $A_B< 5.7\times 10^{-4}$ for BBHs with masses $(1+2)\times 10^5M_\odot$; $\omega_{BD}>6.11\times10^{6}$ for neutron star-black hole binary with masses $(1.4+400)M_{\odot}$.Comment: 21 pages, 3 figures, 4 tables. Typos corrected and references updated. Published in PR