1. No category

How to detect the Quark-Gluon Plasma with Telescopes
M. Hanauske
Institut f¨
ur Theoretische Physik, J. W. Goethe–Universit¨
at, D-60054 Frankfurt, Germany
Abstract
The appearance of the QCD - phase transition (QPT) at
low temperatures and high densities will change the properties of neutron stars (NS). Whether this change will be
visible with telescopes and gravitational wave antennas depends strongly on the equation of state (eos) of hadronic
and quark matter and on the construction of the phase
transition (PT).
1.8
Introduction
If the onset of the QPT at low temperatures is below
≈ 5ρ0 , ρ0 := 0.15 fm−3 a PT is going to happen in the
interior of NS. The accepted underlying theory of strong
interactions, QCD, is however not solvable in the nonperturbative regime. So far numerical solutions of QCD on a
finite space-time lattice are unable to describe infinite nuclear matter at low temperatures and high densities. As an
alternative approach several effective models of hadronic
and quark interactions have been proposed. By choosing
different models (and/or parameter sets inside the models) for the hadronic and quark phase, the composition
of particles inside the stars, the eos and as a result, the
properties of the stars will change. The construction of
the QPT between the models should be done by a Gibbsconstruction, having two independent chemical potentials
(µB , µQ ). However the Gibbs-construction can be modified due to surface tension and coulomb effects. Such effects would shift the PT to be more ”maxwell-like”, having
an almost constant pressure during the mixed phase. The
star properties depend strongly on the onset of the PT and
especially if it begins before or after the appearance of hyperonic particles in the hadronic phase (ρB ≈ 2.5ρ0 ). Depending on the eos the properties of the stars will change;
but finally just one eos will have been realized in nature.
2
Properties of Compact Stars
Depending on the used model the following varieties of
compact stars (CS) are possible:
NS: no PT, solely hadrons; hybrid stars (HS): PT; naked
quark stars (QS):no PT, solely quarks and exotic stars
(like stars with kaon condensation or strongly bound
hyperon stars (HyS)). In Fig.1 the star properties are
plotted for three hybrid models (NLZY-B180(Gibbs-PT),
NLZY-B175(Maxwell-PT) [3] and CH-NJL-2SC(2 GibbsPT) [4]), a naked quark model (NJL (ξ = 0) [2]) and a
hybrid and naked hyperon star model [1]. Some of the
hybrid models show a twin star behavior, where the third
sequence of HS is separated from the second one by a unstable region (green part of the curves). Such a twin star
behavior is unusual in hybrid models using Gibbs-PT; in
hybrid models using maxwell-PT twins appear quite often.
Because of their selfboundness at ’low’ energy densities,
the QS and HyS have lower radii than the NS and HS.
@@
R
9
8
3
2
RS
1.6
[4]
[1]
[1]
1.4
1.2
M
1
RS =@2 M RS
1
[2]
0.8
[3]
0.6
0.4
R1 = 8
4
6
10
8
12
10
12
14
14
16
18
R
Figure 1: Mass M [M ] and radius R [km] for hybrid,
quark and hyperon stars. The Schwarzschild radius RS =
2 M , the absolute threshold for stable stars (R = 9/8 RS ),
the photon surface (R = 3/2 RS ) and R∞ =const lines.
3
Astrophysical Observables for the QGP
NS are usually bigger than QS and third sequence HS.
Telescope are able to measure the radiation radius R∞
from thermal radiating stars. The measure of two different radii of stars having the same mass would proof the
existence of a twin and therefore of a strong PT. QS can
rotate faster than NS whereas in HS a spin up effect can occur. Single quadrupodeformed CS will emit gravitational
waves with twice their rotation frequency. During a twin
star collapse energy is emitted by neutrinos, high energetic
photons and gravitational waves. Mergers of two NS and
two QS will emit different gravitational waves profiles.
Acknowledgments
I thank the Gesellschaft f¨
ur Schwerionenforschungforschung for their financial support. I also gratefully acknowledge the Saha Institute for Nuclear Physics (Kolkata,
India) for their hospitality and the DAAD/DST for
their financial support during the days of writing this
report. I thank all authors for their work, Prof.Dr.
D.Bandyopadhyay for fruitful discussions and HD Dr.
J.Schaffner for his comments on this report.
References
[1] J. Schaffner-Bielich, M. Hanauske, H. St¨ocker, and W.
Greiner, Phys. Rev. Lett.88(2002) 171101
[2] M.Hanauske,
D.Zschiesche,
S.Schramm et.al.,
http://wave.xray.mpg.de/conferences/xeus-workshop
[3] I. N. Mishustin, M. Hanauske, A. Bhattacharyya, L.
M. Satarov, et.al., Phys. Lett. B552(2003)
[4] Igor Shovkovy, Matthias Hanauske and Mei Huang,
Phys. Rev. D66(2003)