4,936 research outputs found
The role of mass, equation of state and superfluid reservoir in large pulsar glitches
Observations of pulsar glitches may provide insights on the internal physics
of neutron stars and recent studies show how it is in principle possible to
constrain pulsar masses with timing observations. The reliability of these
estimates depend on the current uncertainties about the structure of neutron
stars and on our ability to model the dynamics of the superfluid neutrons in
the internal layers. We assume a simplified model for the rotational dynamics
of a neutron star and estimate an upper bound to the mass of 25 pulsars from
their largest glitch and average activity: the aim is to understand to which
extent the mass constraints are sensitive to the choice of the unknown
structural properties of neutron stars, like the extension of the superfluid
region and the equation of state. Reasonable values, within the range measured
for neutron star masses, are obtained only if the superfluid domain extends for
at least a small region inside the outer core, which is compatible with
calculations of the neutron S-wave pairing gap. Moreover, the mass constraints
stabilise when the superfluid domain extends to densities over nuclear
saturation, irrespective of the equation of state tested.Comment: 11 pages, 6 figure
A universal formula for the relativistic correction to the mutual friction coupling time-scale in neutron stars
Vortex-mediated mutual friction governs the coupling between the superfluid
and normal components in neutron star interiors. By, for example, comparing
precise timing observations of pulsar glitches with theoretical predictions it
is possible to constrain the physics in the interior of the star, but to do so
an accurate model of the mutual friction coupling in general relativity is
needed. We derive such a model directly from Carter's multifluid formalism, and
study the vortex structure and coupling time-scale between the components in a
relativistic star. We calculate how general relativity modifies the shape and
the density of the quantized vortices and show that, in the quasi-Schwarzschild
coordinates, they can be approximated as straight lines for realistic neutron
star configurations. Finally, we present a simple universal formula (given as a
function of the stellar compactness alone) for the relativistic correction to
the glitch rise-time, which is valid under the assumption that the superfluid
reservoir is in a thin shell in the crust or in the outer core. This universal
relation can be easily employed to correct, a posteriori, any Newtonian
estimate for the coupling time-scale, without any additional computational
expense.Comment: 20 pages, 7 figure
Antitrust risk in EU manufacturing: A sector-level ranking. Bruegel Working Paper 2014/07, July 2014
The object of this paper is twofold: to provide a broad descriptive analysis of the risk of collusive
behaviour throughout Europe in the manufacturing sector; and to identify those manufacturing sectors
in which the European Commission has been more active in the past in its capacity of antitrust
authority
The doping effect of Italian feed-in tariffs on the PV market
In less than six years, Italy has become one of the leading markets for PV power plants and one of the countries in the world with the largest number of installations and installed peak power. Such a quick and large growth is due to a series of feed-in tariff schemes that have been uncapped until 2012. As a
matter of fact, any size or any number of PV power plants could be installed during a period of three years.
Since the feed-in tariffs are not paid by national taxes but are charged on the electricity bills, Italian energy users are now due to pay each year a surcharge of 9 billion euros on their energy bills.
This paper aims at discussing this development by highlighting the benefits but also some significant
drawbacks that the application of uncontrolled feed-in tariffs has produced
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