Equation of State Parameters for Stringy Particles in Cosmology with Dark Energy

We construct the strong energy conditions (SECs) for both massive and massless stringy particles in the higher dimensional cosmology (HDC) with dark energy Λ. Exploiting these conditions we find the equation of state (EOS) parameters w ≥ −(D −4)/D for both the massive and massless stringy particles in D dimensional cosmology. We elucidate the relations between the EOS parameter in the HDCwithdarkenergy and that of Hawking-Penrose limit for the massive and massless point particles in the D = 3+1dimensions. Weevaluate the EOS parameters in terms of the contributions from the point particle property, dark energy, and extended object degrees of freedom, respectively. We also investigate the weak energy condition (WEC) and dominant energy condition for the massive and massless stringy particles in the HDC, and those for the massive and massless point particles in the D =3+1dimensions,respectively. We show that the Dark Energy Spectroscopic Instrument (DESI) data satisfies the WEC in the HDC. The high temperature asymptotic behavior of a dilaton-Einstein-Gauss-Bonnet scenario is also shown to be consistent with the corresponding WECs obtained in the HDC.