1. To find strange star with FAST http://vega.bac.pku.edu.cn/rxxu R. X. Xu Renxin Xu ( 徐仁新 ) School of Physics, Peking University ( ) Frontiers in Radio Astronomy and FAST Early Sciences Symposium July 29, 2015; Guiyang, China To Find Evidence for Quark-cluster Star with FAST

2. “… The successful use of Yang-Mills theory to describe the strong interactions of elementary particles depends on a subtle quantum mechanical property called the "mass gap": the quantum particles have positive masses, even though the classical waves travel at the speed of light. …” FAST is helpful to understand the strong interaction, being related to one of the Millennium Problems. As in the case of Navier-Stokes Equation, we do have a framework for strong interaction, the QCD Lagrangian: although asymptotic, but non-perturbative in low-E scale. Mathematical difficulty of NQCD provides opportunity for FAST to drop hints about NQCD!

3. Summary What is a Quark-cluster Star? How to find with FAST? Conclusions To find strange star with FAST http://vega.bac.pku.edu.cn/rxxu R. X. Xu

4. Quark-cluster star is nucleus-like object: differences and similarities proton neutron Self-bound: by strong int. l ~ fm: electrons outsidel > λ e : electrons inside 2-flavour symmetry: isospin 3-flavour symmetry: strangeness light clusters: p(uud), n(udd) heavy clusters: 6(H), 9, 12, 18 a < λ c : classical particle a ~ λ c : quantum effects quantum gas/liquidsolid condensed matter at low-T What is a Quark-cluster Star? 3-flavour quark-cluster A quark-luster star is of condensed matter of 3-f clusters.

5. Different models of pulsar’s nature in the market conventional Neutron Star light flavour symmetry: Strange Star What is a Quark-cluster Star? To find strange star with FAST http://vega.bac.pku.edu.cn/rxxu R. X. Xu

6. Summary What is a Quark-cluster Star? How to find with FAST? Conclusions To find strange star with FAST http://vega.bac.pku.edu.cn/rxxu R. X. Xu

7. Xu (Modern Physics Letters A, 2008) 1 How to find with FAST?

8. To find evidence with FAST by  PSR mass measurements (M)  PSR moment of inertia measurements (I)  Discovering fastest spinning PSRs (P)  Magnetospheric activity (pulse-profile) To find strange star with FAST http://vega.bac.pku.edu.cn/rxxu R. X. Xu

9. Watts et al. (2015) Hyperon puzzle? Quark-confinement? in this quark-cluster star model How to find with FAST?_ M

10. To find strange star with FAST http://vega.bac.pku.edu.cn/rxxu R. X. Xu Maximum mass Maximum mass detected  0.6 1.4 ~ ? (~3.2) 1.3 1.4 ~ 2.0 ? (~2.2) What’s the real mass spectrum? deep massive

11. Message from PRE X-ray bursts: low-mass? Photospheric radius expansion in 4U 1746-37 Constraints by PRE bursts of 4U 1746-37, on the assumption that the touchdown flux corresponded to L Edd, and the obscure effect is included. Li et al. (ApJ, 2015) How to find with FAST?_ M To find strange star with FAST http://vega.bac.pku.edu.cn/rxxu R. X. Xu

12. R, but to measure I via spin-orbit coupling… + J S L S2S2 S1S1 2-body in Newtonian gravity2-body in Einstein gravity The two-body problem in GR:  Analytical approach (post-Minkowskian, post-Newtonian, matching of asymptotic expansions)  Numerical Relativity Three routes to measure I by pulsar timing (Kramer & Wex, 2009): for highly relativistic binaries …  Correction to the advance of periastron,   Non-linear time evolution of the longitude of periastron if the spin is inclined with respect to J  Two derivatives, x, once again leading to an estimate of I sin ..  How to find with FAST?_ I

13. P is limited by mass shedding & r-mode inst… Spin figure: Alessandro Patruno Spin of self-bound on surface may not limited by mass shedding: NS  sub-Keplerian QcS  super-Keplerian? The GW-induced rotation- mode instability depends on the viscosity of matter, thus the EoS. Higher sensitivity of FAST will give the first opportunity to undertake a deep survey for fast pulsars, for even sub-ms pulsars! How to find with FAST?_ P To find strange star with FAST http://vega.bac.pku.edu.cn/rxxu R. X. Xu

14. How to find with FAST?_ pulse Magnetospheric activity depends on surface… To find strange star with FAST http://vega.bac.pku.edu.cn/rxxu R. X. Xu

15. Summary What is a Quark-cluster Star? How to find with FAST? Conclusions To find strange star with FAST http://vega.bac.pku.edu.cn/rxxu R. X. Xu

16. Conclusions Besides testing gravity and detecting GW waves, pulsars provide a unique test-ground for the fundamental strong interaction (QCD). We are expecting FAST to improve our knowledge about M and I, the lower-ends of P and drifting subpulses. These observations are surely related to the EoS of cold dense matter, and may finally find clear evidence for quark- cluster star. THANKS! To find strange star with FAST http://vega.bac.pku.edu.cn/rxxu R. X. Xu