1. Introduction :

Cosmological models play a vital role

in the understanding of the universe around us.

The present day universe appears, an astronomical consideration, to be

of the friedmann-Robertson- Walker (FRW) type.

That is the standard FRW Cosmological model which prescribes a homogeneous

and Isotropic distribution for its matter content, has been quite successful in

describing the present state of the universe. Recently higher dimensional space

time is an active field of research in the attempts to unify gravity with other

gauge interaction 30. The concept of extra dimensions is relevant in

cosmology particularly at the early universe-theoretically the present 4D stage

of the universe might have been preceded by a multidimensional phase. In fact

there exist solutions of Einstein’s equations such that, as time evolves, the

standard dimensions expand while extra space shrinks to planckian dimension

beyond our ability to detect with the currently available experimental

facilities (Chatterjee 31, 32 and Chatterjee et al 9. It is encouraging to

note that both the concept of higher dimensional space time and string theory

assumed added importance in the domain of the early universe.

The concept of string theory was

developed to describe events of the early stage of the evolution of the

universe. The general relativistic treatment of strings was initiated by

Stachel 33 and Letelier 34. The gravitational effects of cosmic strings

have been extensively discussed by vilenkin 35. Gott 36 in general relativity. Relativistic string models in the context of

Bianchi space time have been obtained by Krori et. al. 37. Banerjee and Bhuj 38, Tikekar and Patel 39.

In this study, I will attach strange

quark matter to string cloud. It is

plausible to attach strange quark matter to the string cloud. Because, one of such transitions during the

phase transitions of the universe could be Quark Glucon Plasma (OGP) – hardon

gas (called quark-hardon phase transition) when cosmic temperature was T » 200

Mev. The possibility of the existence of quark matter dates back to early

seventies. Bodmer 12 and Witten 13

proposed two ways of formation of strange matter. The quark-hadrom phase

transition in the early universe and conversion of neutron stars into strange

ones at ultrahigh densities. In the

theories of strong interaction quark bag models suppose that breaking of

physical vacuum takes place inside hadrons.

As a result vacuum energy densities inside and outside a hadron become

essentially different and the vacuum pressure on the bag wall equilibrates the

pressure of quarks matter is true, then some of neutrons stars could actually

be strange stars, built entirely of strange matter 14, 15.

Typically, strange quark matter is

modeled with an equation of state based on the phenomenological bag model of

quark matter, in which quark confinement is described by an energy term

proportional to the volume. In this model, quarks are though as degenerate

Fermi gales, which exist only in a region of space endowed with a vacuum energy

density BC (called as the bag constant). Also, in the framework of this model the

quark matter is composed of mass less u, d quarks, massive s quarks and

electrons.

In the simplified version of the bag

model, it is assumed that quarks are mass less and non interacting. So, we have quark pressure.

Pq = . (1)

Where

rq is

me quark energy density

The total energy density is

r = rq + Bc

.(2)

But

the total pressure is

P = Pq

– Bc (3)

In

this paper, I have solved Einstein’s field equations for Five dimensional

Bianchi type-III, Space- time with strange quark matter attached to the string

cloud.