Comparing strange and nonstrange quark stars within resummed QCD at NLO

We employ the renormalization group optimized perturbation theory (RGOPT) resummation method to evaluate the equation of state (EoS) for strange (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msub><a:mi>N</a:mi><a:mi>f</a:mi></a:msub><a:mo>=</a:mo><a:mn>2</a:mn><a:mo>+</a:mo><a:mn>1</a:mn></a:math>) and nonstrange (<c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:msub><c:mi>N</c:mi><c:mi>f</c:mi></c:msub><c:mo>=</c:mo><c:mn>2</c:mn></c:math>) cold quark matter at next-to-leading order. This allows us to obtain the mass-radius relation for pure quark stars and compare the results with the predictions from perturbative QCD (pQCD) at next-to-next-to-leading order. Choosing the renormalization scale to generate maximum star masses of order <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>M</e:mi><e:mo>=</e:mo><e:mn>2</e:mn><e:mo>−</e:mo><e:mn>2.6</e:mn><e:msub><e:mi>M</e:mi><e:mo stretchy="false">⊙</e:mo></e:msub></e:math>, we show that the RGOPT can produce mass-radius curves compatible with the masses and radii of some recently observed pulsars, regardless of their strangeness content. The scale values required to produce the desired maximum masses are higher in the strange scenario since the EoS is softer in this case. The possible reasons for such behavior are discussed. Our results also show that, as expected, the RGOPT predictions for the relevant observables are less sensitive to scale variations than those furnished by pQCD.