Welcome to the homepage of Dr. Xu, Renxin


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Personal Statements

Research Interests: Particle astrophysics (e.g., for pulsars, see below)

  1. I am interested in the physics in extraterrestrial extreme-environments. Pulsar is one of the excellent examples with such extremeness, which can be mainly classified into:
    • Rotation-powered pulsars
    • Accretion-powered pulsars
      • Accretion-powered X-ray pulsars
      • X-ray bursters
    • Magnetism-powered (?) pulsars (Magnetars?)
      • Soft gamma ray repeaters
      • Anomalous X-ray pulsars

    Let's listen to the Vela pulsar (the sound of Vela) in radio band ... You are also invited going to the page of Pular Group at PKU.

  2. We currently believe, according to various observations, that pulsars are celestial bodies which are distinguished by their compactness (typically about 1.4 solar mass, but only about 10 km radius). What's the real nature of pulsar? Unfortunately/fortunately, this remains unknown, being related to the nature of non-perturbative QCD (quantum chromo-dynamics). Historically, in 1930s, Lev Landau speculated that dense matter at supra-nuclear density in stellar cores could be considered as gigantic nuclei (the prototype of standard model of neutron star). A gigantic nucleus should be neutron-rich (renamed neutron star thus) via neutronization. However, we propose a very different point of view: the rump left behind after a supernova could be a strangeon star (after strangeonization). Nucleon is the constituent of a nucleus, while strangeon is named as the constituent of a gigantic nucleus if 3-flavor symmetry (u, d and s) restores there. There are then two models at least:
  3. the former develops in hadron degrees of freedom, while the latter is relevant to quark degrees (and especially the strangeness). Can we find hard observational evidence to rule out that pulsars are neutron stars or strangeon stars? This is certainly one of the big questions in the coming years.
  4. A brief introduction to my major research could be found at:

    Strange matter in the Universe: the many faces

    4U 1746-37: a candidate of quark-cluster star? (English version)

Publications

Here are some selected papers. A complete set will be available in the future.

Books:

    Particle Astrophysics translated by Xiaoyu Lai, Guoyin Chen and Renxin Xu

Welcome to FPS series of meeting, and to the conferences which you may also be interested in:

FPS Pulsar Symposium 6 (FPS6; 2017.6.28-30. Proceedings)

KIAA-WAP II: Cosmic Rays in a New Era (APh_II; 2017.8.17-19)

Quarks and Compact Stars (QCS2017; 2017.2.20-22)

FAST Pulsar Symposium 5 (FPS5; 2016.7.5-8. Proceedings)

Compact stars in the QCD phase diagram (5) (2016.5.23-27)

KIAA Workshop on Astroparticle Physics (APh; 2015.9.28-29)

FAST Pulsar Symposium 4 (FPS4; 2015.7.3-5. Proceedings)

Quarks and Compact Stars (QCS2014; 2014.10.20-22. Proceedings)

Compact stars in the QCD phase diagram (4) (2014.9.26-30)

FAST Pulsar Symposium 3 (FPS3; 2014.7.2-4. Proceedings)

FAST Pulsar Symposium 2 (FPS2; 2013.7.1-3. Proceedings)

Compact stars in the QCD phase diagram (3) (2012.12.12-15)

Neutron Stars and Pulsars: Challenges and Opportunities after 80 Years (IAUS291; 2012.8.20-24)

FAST Pulsar Symposium 1 (FPS1; 2012.8.13-16. Proceedings)

Compact stars in the QCD phase diagram (2) (2009.5.20-24)

CCAST Workshop on dense matter and neutron stars (2003.10.20-24)

Teaching

I am teaching three courses these years, two (Astrophysics & Atomic physics) for undergraduates and one (Physics of compact stars) for graduates. The book "Introduction to Astrophysics" was written during my teaching of astrophysics.

The schedule of the Astrophysics course (one semester)

The schedule of the Atomic-physics course (one semester)