- 'G.J. Qiao'
title: 'What if pulsars are born as strange stars?'
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pulsars, neutron stars, elementary particles, supernovae

Introduction
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Soon after the discovery of neutrons, the idea of neutron star was proposed[@l32bz34]. The discoveries of radio pulsars and some other accretion-powered X-ray sources indicate that there do exist in nature certain objects with mass $M\sim M_\odot$, and radius $R\sim
10$ km. They were commonly regarded as neutron stars until the idea of strange star was proposed[@w84; @afo86; @hzr86]. The basic idea of the strange star conjecture is that, strange quark matter (SQM), which is simply composed of an approximately equal portion of up, down, and strange quarks and a few electrons to balance the non-neutral charges, might be more stable than the normal nuclear matters. According to the lattice quantum chromodynamics (QCD), a new state of strong interaction matter, the so-called quark-gluon plasma (QGP), will appear when the temperature of the matter achieves as high as $\sim150-200$ MeV or the density of the matter achieves several times of $\rho_0$, where $\rho_0 
\sim 3\times10^{14}$g/cm$^3$ is the nuclear density. SQM is just one kind of such QGPs. Though we can not tell whether SQM is the lowest state of hadronic 