Advancing space-based gravitational wave astronomy: Rapid parameter estimation via normalizing flows

Gravitational wave(GW) astronomy is witnessing a transformative shift from terrestrial to space-based detection, with missions like Taiji at the forefront. While the transition brings unprecedented opportunities for exploring massive black hole binaries(MBHBs), it also imposes complex challenges in data analysis, particularly in parameter estimation amidst confusion noise.Addressing this gap, we utilize scalable normalizing flow models to achieve rapid and accurate inference within the Taiji environment. Innovatively, our approach simplifies the data's complexity, employs a transformation mapping to overcome the year-period time-dependent response function, and unveils additional multimodality in the arrival time parameter. Our method estimates MBHBs several orders of magnitude faster than conventional techniques, maintaining high accuracy even in complex backgrounds. These findings significantly enhance the efficiency of GW data analysis, paving the way for rapid detection and alerting systems and enriching our ability to explore the universe through space-based GW observation.

Exploring the nature of black hole and gravity with an imminent merging binary of supermassive black holes

A supermassive binary black-hole candidate SDSS J1430+2303 reported recently motivates us to investigate an imminent binary of supermassive black holes as potential gravitational wave source, and the radiated gravitational waves at the end of the merger are shown to be in the band of space-borne detectors. We provide a general analysis on the required detecting sensitivity needed for probing such type gravitational wave sources and make a full discussion by considering two typically designed configurations of space-borne antennas. If a source is so close, it is possible to be detected with Taiji pathfinder-plus which is proposed to be an extension for the planned Taiji pathfinder by just adding an additional satellite to the initial two satellites. The gravitational wave detection on such kind of source enables us to explore the properties of supermassive black holes and the nature of gravity.

Editorial

The paradigm that our universe is dominated by non-luminous matter, i.e., dark matter, rather than ordinary baryonic matter, has been established since the 1980s. However, the nature of dark matter remains almost unknown. Many ongoing space experiments are aiming at uncovering the particle nature of dark matter via precise measurements of the flux of cosmic-ray particles, with a hope to find fingerprints that tiny annihilations or decays of dark matter may have left. Such experiments include PAMELA, Fermi-LAT, and AMS-02, all of them have made extraordinary discoveries. The DAMPE experiment is a new player in the game. The key component of the DAMPE detector is a calorimeter with both a large acceptance and a long radiation length, which makes it unique for dark matter research. For instance, DAMPE is capable of detecting a cosmic-ray electron with a maximum energy of-10 TeV.

Topology change and emergent scale symmetry in compact star matter via gravitational wave detection

Topological structure has been extensively studied and confirmed in highly correlated condensed matter physics. We explore the gravitational waves emitted from binary neutron star mergers using the pseudoconformal model for dense nuclear matter for compact stars. This model considers the topology change and the possible emergent scale symmetry and satisfies all the constraints from astrophysics. We find that the location of the topology change affects gravitational waves dramatically owing to its effect on the equation of state. In addition, the effect of this location on the waveforms of the gravitational waves is within the ability of the on-going and up-coming facilities for detecting gravitational waves, thus suggesting a possible way to measure the topology structure in nuclear physics.