61 research outputs found
What the Timing of Millisecond Pulsars Can Teach us about Their Interior
The cores of compact stars reach the highest densities in nature and
therefore could consist of novel phases of matter. We demonstrate via a
detailed analysis of pulsar evolution that precise pulsar timing data can
constrain the star's composition, through unstable global oscillations
(r-modes) whose damping is determined by microscopic properties of the
interior. If not efficiently damped, these modes emit gravitational waves that
quickly spin down a millisecond pulsar. As a first application of this general
method, we find that ungapped interacting quark matter is consistent with both
the observed radio and x-ray data, whereas for ordinary nuclear matter some
additional enhanced damping mechanism is required.Comment: 6 pages, 5 figures, version to be published in PR
On the Infrared Behavior of Landau Gauge Yang-Mills Theory with a Fundamentally Charged Scalar Field
Recently it has been shown that infrared singularities of Landau gauge QCD
can confine static quarks via a linearly rising potential. We show that the
same mechanism can also provide a confining interaction between charged scalar
fields in the fundamental representation. This confirms that within this
scenario static confinement is a universal property of the gauge sector even
though it is formally represented in the functional equations of the matter
sector. The simplifications compared to the fermionic case make the scalar
system an ideal laboratory for a detailed analysis of the confinement mechanism
in numerical studies of the functional equations as well as in gauge-fixed
lattice simulations.Comment: 8 pages, PDFLaTe
Non-linear viscous saturation of r-modes
Pulsar spin frequencies and their time evolution are an important source of
information on compact stars and their internal composition. Oscillations of
the star can reduce the rotational energy via the emission of gravitational
waves. In particular unstable oscillation modes, like r-modes, are relevant
since their amplitude becomes large and can lead to a fast spin-down of young
stars if they are saturated by a non-linear saturation mechanism. We present a
novel mechanism based on the pronounced large-amplitude enhancement of the bulk
viscosity of dense matter. We show that the enhanced damping due to non-linear
bulk viscosity can saturate r-modes of neutron stars at amplitudes appropriate
for an efficient spin-down.Comment: 3 pages, contribution to the proceedings of the conference "Quark
Confinement and the Hadron Spectrum IX", August 30 - September 3, 2010,
Madrid; typos correcte
Low Energy Dynamics in Ultradegenerate QCD Matter
We study the low energy behavior of QCD Green functions in the limit that the
baryon chemical potential is much larger than the QCD scale parameter
. We show that there is a systematic low energy expansion in
powers of , where is the energy and is the
screening scale. This expansion is valid even if the effective quark-gluon
coupling is not small. The expansion is purely perturbative in the magnetic
regime . If the external momenta and energies satisfy , planar, abelian ladder diagrams involving the full quark
propagator have to be resummed but the corresponding Dyson-Schwinger equations
are closed.Comment: 4 pages, published versio
Impact of r-modes on the cooling of neutron stars
Studying the frequency and temperature evolution of a compact star can give
us valuable information about the microscopic properties of the matter inside
the star. In this paper we study the effect of dissipative reheating of a
neutron star due to r-mode oscillations on its temperature evolution. We find
that there is still an impact of an r-mode phase on the temperature long after
the star has left the instability region and the r-mode is damped completely.
With accurate temperature measurements it may be possible to detect this trace
of a previous r-mode phase in observed pulsars.Comment: 7 pages, 5 figures, Proceedings of QCD@work 2012 International
Workshop on QCD Theory and Experimen
Phase conversion dissipation in multicomponent compact stars
We propose a mechanism for the damping of density oscillations in
multicomponent compact stars. The mechanism is the periodic conversion between
different phases, i.e., the movement of the interface between them, induced by
pressure oscillations in the star. The damping grows nonlinearly with the
amplitude of the oscillation. We study in detail the case of r-modes in a
hybrid star with a sharp interface, and we find that this mechanism is powerful
enough to saturate the r-mode at very low saturation amplitude, of order
, and is therefore likely to be the dominant r-mode saturation
mechanism in hybrid stars with a sharp interface.Comment: 17 pages, 8 figures. Typos in Eq. (15), Eqs. (64)-(65) and Eqs.
(B4)-(B5) correcte
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