Quark stars their influence on Astroparticle Physics.pdf

a r X i v : 0 8 0 8 .1 6 5 2 v 1 [ a s t r o - p h ] 1 2 A u g 2 0 0 8 Quark stars: their influence on Astroparticle Physics Sanjay K. Ghosh Department of Physics, Bose Institute, 93/1, A.P.C. Road, Kolkata 700 009, India. and Centre for Astroparticle Physics Space Science, Bose Institute, Block EN, Sector V, Salt Lake, Kolkata - 700 091, India Abstract We discuss some of the recent developments in the quark star physics along with the consequences of possible hadron to quark phase transition at high density scenario of neutron stars and their implica- tions on the Astroparticle Physics. 1 Introduction The underlying quark structure of hadrons suggets the possibility of a quark- hadron phase transition at extreme conditions of high tempereature and/or density. Since a compact object like neutron star (NS) provide the natural scenario of high density, the suggestion for the existence of quark core inside such massive compact objects was put forward by Ivanenko and Kurdge- laidze (1969). The existence of 3-flavour quark star or strange star (QS), made up of u, d and s quarks, was suggested by Itoh (1970). In general, the two flavour matter can not be more stable compared to nucleonic mat- ter. The presence of s quarks, along with u and d quarks, provides an additional fermi well which would result in the lowering of the energy of the 3- flavour quark matter or strange quark matter (SQM) compared to 2- flavour quark matter. Since s quark has larger mass, the situation would 1 be more favourable at higher densities. Such possibilities were recognized by Bodmer (1971) and led Witten (1984) to conjecture that SQM may be the true ground state of strongly interacting matter at high densities. Since then, this field has become an active area of research. The possibilty of a quark -hadron phase transition in the early universe (high temperature and small chemical potential) scenario and attempts to produce such a matter in the laboratory through heavy ion collision r