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1. chinaXiv:202101.00003 [pdf]

On dark matter

Xian-Qiao Yu
Subjects: Physics >> The Physics of Elementary Particles and Fields

In this article, I shall propose a new model of dark matter, in which I introduce a neutral primordial axial-vector field, which is a new field beyond the standard model. All the standard model elementary particles are produced spontaneously from this field in the Big Bang epoch of the universe and then these produced elementary particles decayed or annihilated in the well-known standard model interactions. The relic of the primordial axial-vector field appears in a form of vacuum energy can not only give naturally the correct abundance of dark matter in the present universe, but provide a natural solution to the cosmological constant problem as well. Some possible experiments for testing the new theory of dark matter are also suggested in this article.

submitted time 2021-03-29 Hits1773Downloads378 Comment 0

2. chinaXiv:201609.01022 [pdf]

Versatile Directional Searches for Gravitational Waves with Pulsar Timing Arrays

D. R. Madison(1; 2); X.-J. Zhu(3; 4); G. Hobbs; W. Coles; R. M. Shannon(4; 6); J. Wang; C. Tiburzi(8; 9; 10; 11); R. N. Manchester; M. Bailes; N. D. R. Bhat; S. Burke-Spolaor; S.Dai; J. Dempsey; M. Keith
Subjects: Physics >> Nuclear Physics

By regularly monitoring the most stable millisecond pulsars over many years, pulsar timing arrays (PTAs) are positioned to detect and study correlations in the timing behaviour of those pulsars. Gravitational waves (GWs) from supermassive black hole binaries (SMBHBs) are an exciting potentially detectable source of such correlations. We describe a straight-forward technique by which a PTA can be "phased-up" to form time series of the two polarisation modes of GWs coming from a particular direction of the sky. Our technique requires no assumptions regarding the time-domain behaviour of a GW signal. This method has already been used to place stringent bounds on GWs from individual SMBHBs in circular orbits. Here, we describe the methodology and demonstrate the versatility of the technique in searches for a wide variety of GW signals including bursts with unmodeled waveforms. Using the first six years of data from the Parkes Pulsar Timing Array, we conduct an all-sky search for a detectable excess of GW power from any direction. For the lines of sight to several nearby massive galaxy clusters, we carry out a more detailed search for GW bursts with memory, which are distinct signatures of SMBHB mergers. In all cases, we find that the data are consistent with noise.

submitted time 2016-09-14 Hits910Downloads487 Comment 0

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