Title: Probing dark matter with pulsar experiments

Time: 10:00 am, Friday, October 30th, 2026

Location: Large meeting room（三楼大会议室）, the 3rd floor, Astronomy building, Xujiahui

Abstract: Pulsars, which are very rapidly spinning neutron stars, can be instrumental in solving the puzzle, which has perplexed the minds of the scientific community for almost a century – dark matter (DM). In the talk I will explain how different DM candidates can be searched for in pulsar observables. The ultralight scalar field DM (also known as "fuzzy" DM), consisting of bosons with extremely low masses of 10^−22 eV, solves some of the problems of the conventional cold DM hypothesis. It was shown by Khmelnitsky and Rubakov (2014) that such DM in the Milky Way induces oscillating gravitational potentials, leaving characteristic imprints in the time of arrivals of radio pulses from pulsars. In addition (Ivanov et al 2019, Castillo et al. 2022), the coupling of axion-like particles to photons alters the polarization properties of light, i.e. the plane of polarization of linearly polarized beam propagating through the axion field starts to oscillate with typical frequencies of 10^-8 – 10^-5 Hz. Searches for these two effects were performed in the data of the European Pulsar Timing Array (EPTA), and stringent constraints on the DM density and coupling constant between photons and axion-like particles have been set. In addition, traces of QCD axions with masses of around ~ micro-eV can be searched for with the spectroscopic observations of pulsars. A novel approach to search for QCD axions in binary pulsars and its application on simulated data will be introduced. Production of Primordial black holes (PBHs) is coupled with the scalar-induced gravitational waves in the early Universe, which can be searched for in the data of PTAs. In this talk I am going to explain how the observed gravitational wave spectrum in PTA band can be can recalculated in the spectrum of primordial curvature perturbations in model-independent manner.  A special focus is given to systematics and artifacts in pulsar data that can mimic the signal of interest and possible methods to avoid the existing biases.

Speaker: Dr. Nataliya Porayko is a Staff Scientist in the "Fundamental Physics in Radio Astronomy" research department at the Max Planck Institute for Radio Astronomy in Bonn, Germany. She leads the Research Group **COMPULSE** ("Chasing Obscure Matter with PULSar Experiments"), which focuses on searching for dark matter using pulsar observations. She obtained her PhD degree at the University of Bonn in Germany. Subsequently, she conducted postdoctoral research at the University of Milano-Bicocca in Italy. Her research primarily uses pulsar timing and polarimetry data—particularly from the European Pulsar Timing Array (EPTA)—to search for signatures of ultralight scalar field dark matter and axion-like particles. Her broader work also involves studying pulsar scintillation and the ionized interstellar medium, often utilizing data from the LOw-Frequency ARray (LOFAR).