96 research outputs found
The QCD Equation of State - From Nuclear Physics to Perturbation Theory
In this talk, we briefly review the current understanding of the behavior of
the QCD equation of state throughout the phase diagram. Special emphasis is
given to regions of phenomenological interest, and a number of important open
questions as well as directions of ongoing research are pointed out. These
include in particular the region of low temperatures and (moderately) high
densities, where at the moment we have extremely few first principles tools
available.Comment: Invited talk at the workshop Excited QCD 2011, Lec Houches, Feb.
20-25, 2011. 6 pages, no figure
Scalar and Pseudoscalar Correlators in Yang-Mills Theory
Correlation functions of the FF and F\tilde{F} operators in hot SU(3)
Yang-Mills theory have recently been studied both on the lattice and in
perturbation theory, and the results subsequently compared to the strong
coupling limit of large-N_c N=4 Super Yang-Mills theory, available through the
AdS/CFT correspondence. Here, we review the perturbative calculations, covering
both Euclidean spatial correlators and the UV limit of spectral densities, and
comment on the emerging physical picture as well as on possible extensions of
the present studies.Comment: 3 pages, 2 figures. To appear in the proceedings of The IX
International Conference on Quark Confinement and the Hadron Spectrum,
Madrid, Spain, 30 August - 3 September 201
Neutron star structure from QCD
In this review article, we argue that our current understanding of the
thermodynamic properties of cold QCD matter, originating from first principles
calculations at high and low densities, can be used to efficiently constrain
the macroscopic properties of neutron stars. In particular, we demonstrate that
combining state-of-the-art results from Chiral Effective Theory and
perturbative QCD with the current bounds on neutron star masses, the Equation
of State of neutron star matter can be obtained to an accuracy better than 30%
at all densities.Comment: Invited contribution to the EPJA Topical Issue "Exotic Matter in
Neutron Stars"; 10 pages, 13 figure
The Pressure of QCD at Finite Temperature and Quark Number Density
This paper is a slightly modified version of the introductory part of a
doctoral dissertation that contained also three original articles,
hep-ph/0212283, hep-ph/0305183 and hep-ph/0311323. Our purpose is to review the
history and present status of finite-temperature perturbation theory as applied
to the context of determining the equilibrium properties of quark-gluon plasma,
most notably the pressure of QCD at finite temperatures and quark chemical
potentials. We first introduce the general formalism of finite-temperature
field theory and perturbation theory, then follow through the evaluation of the
pressure order by order, and finally proceed to analyze the most recent, order
g^6ln(g) results by comparing the perturbative predictions with lattice data.
In the appendix we provide a somewhat pedagogical introduction to the most
important computational techniques used in the perturbative framework, namely
the analytic evaluation of multi-loop vacuum diagrams both in full QCD and in
its three-dimensional high-T effective theories.Comment: 65 pages, 21 figures; introductory part of a PhD thesi
Cool Quark Matter
We generalize the state-of-the-art perturbative equation of state of cold quark matter to nonzero temperatures, needed in the description of neutron star mergers and core collapse processes. The new result is accurate to O(g(5)) in the gauge coupling, and is based on a novel framework for dealing with the infrared sensitive soft field modes of the theory. The zero Matsubara mode sector is treated via a dimensionally reduced effective theory, while the soft nonzero modes are resummed using the hard thermal loop approximation. This combination of known effective descriptions offers unprecedented access to small but nonzero temperatures, both in and out of beta equilibrium.Peer reviewe
Quark Matter Equation of State from Perturbative QCD
In this proceedings contribution, we discuss recent developments in the perturbative determination of the Equation of State of dense quark matter, relevant for the microscopic description of neutron star cores. First, we introduce the current state of the art in the problem, both at zero and small temperatures, and then present results from two recent perturbative studies that pave the way towards extending the EoS to higher orders in perturbation theory.Peer reviewe
Neutron stars and stellar mergers as a laboratory for dense QCD matter
Neutron star observations, including direct mass and radius measurements as well as the analysis of gravitational wave signals emitted by stellar mergers, provide valuable and unique insights into the properties of strongly interacting matter at high densities. In this proceedings contribution, I review recent efforts to systematically constrain the equation of state (EoS) of dense nuclear and quark matter using a combination of ab initio particle and nuclear physics calculations and astrophysical data. In particular, I discuss the constraints that the gravitational wave observation GW170817 has placed on the EoS, and comment on the future prospects of improving the accuracy, to which this quantity is known.Peer reviewe
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