iTHEMS Weekly News Letter

Research News

Modeling the insides of a neutron star -- Improvements to a model for the inside of a neutron star make it applicable to neutron star mergers thumbnail
Dr. Tetsuo Hatsuda thumbnail
Dr. Shun Furusawa thumbnail
Prof. Gordon Baym thumbnail

Modeling the insides of a neutron star -- Improvements to a model for the inside of a neutron star make it applicable to neutron star mergers


RIKEN astrophysicists have developed an improved model for the interior structure of neutron stars that agrees well with observations. Unlike previous models, it can be extended to consider what happens when two neutron stars merge.

The collapsed remnants of giant stars, neutron stars are fascinating objects. They are a mere 20−30 kilometers in diameter but are nearly 400,000–600,000 times more massive than the Earth, which makes them incredibly dense.

Neutron stars are not uniform agglomerations of neutrons—like the astrophysical equivalent of a giant atomic nucleus containing only neutrons. Rather they have an onion-like structure. Theorists have been busy trying to model this internal structure based on quantum mechanics and data from observations.

Seminar Report

Boosting the lensing study for DM properties with machine learning techniques


Strong lensing of the galaxy, which can be seen as arc-like features, is a powerful probe of the small-scale DM halos. The populations of small-scale DM halo give us hints about its particle properties. We need to manage huge parameter spaces (e.g. redshift distribution of the source galaxies, lensing galaxies, mass functions of perturbing subhalos and so on) to determine the subhalo signatures from the strong-lensing image data using likelihood ratio test. The machine-learning based techniques of the reduced likelihood ratio estimator enable us to derive the parameters of subhalo mass function, which are key quantities to access the nature of DM, in an efficient way. The importance of this technique increases for the coming era of large-sized lensing image data. In the near future, we should probe the parameters of the subhalo mass function hence the DM properties from galaxy-galaxy lensing. Furthermore, the method is so flexible that encourages us to consider much wider applications in DM search.

Upcoming Events


iTHEMS Math Seminar

Index of the Wilson-Dirac operator revisited: a discrete version of Dirac operator on a finite lattice

February 25 at 16:00 - 18:10, 2020

Dr. Mikio Furuta (Professor, The University of Tokyo)

Venue: Seminar Room #160, 1F Main Research Building, RIKEN

Event Official Language: English

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