18,795 research outputs found
Efficient computation of hashes
The sequential computation of hashes at the core of many distributed storage systems and found, for example, in grid services can hinder efficiency in service quality and even pose security challenges that can only be addressed by the use of parallel hash tree modes. The main contributions of this paper are, first, the identification of several efficiency and security challenges posed by the use of sequential hash computation based on the Merkle-Damgard engine. In addition, alternatives for the parallel computation of hash trees are discussed, and a prototype for a new parallel implementation of the Keccak function, the SHA-3 winner, is introduced
Gravitational waves from single neutron stars: an advanced detector era survey
With the doors beginning to swing open on the new gravitational wave
astronomy, this review provides an up-to-date survey of the most important
physical mechanisms that could lead to emission of potentially detectable
gravitational radiation from isolated and accreting neutron stars. In
particular we discuss the gravitational wave-driven instability and
asteroseismology formalism of the f- and r-modes, the different ways that a
neutron star could form and sustain a non-axisymmetric quadrupolar "mountain"
deformation, the excitation of oscillations during magnetar flares and the
possible gravitational wave signature of pulsar glitches. We focus on progress
made in the recent years in each topic, make a fresh assessment of the
gravitational wave detectability of each mechanism and, finally, highlight key
problems and desiderata for future work.Comment: 39 pages, 12 figures, 2 tables. Chapter of the book "Physics and
Astrophysics of Neutron Stars", NewCompStar COST Action 1304. Minor
corrections to match published versio
Nuclear Equation of State from Observations of Short Gamma-Ray Burst Remnants
The favoured progenitor model for short -ray bursts (SGRBs) is the
merger of two neutron stars that triggers an explosion with a burst of
collimated -rays. Following the initial prompt emission, some SGRBs
exhibit a plateau phase in their -ray light curves that indicates additional
energy injection from a central engine, believed to be a rapidly rotating,
highly magnetised neutron star. The collapse of this `protomagnetar' to a black
hole is likely to be responsible for a steep decay in -ray flux observed at
the end of the plateau. In this letter, we show that these observations can be
used to effectively constrain the equation of state of dense matter. In
particular, we show that the known distribution of masses in binary neutron
star systems, together with fits to the -ray light curves, provide
constraints that exclude the softest and stiffest plausible equations of state.
We further illustrate how a future gravitational wave observation with Advanced
LIGO/Virgo can place tight constraints on the equation of state, by adding into
the picture a measurement of the chirp mass of the SGRB progenitor.Comment: accepted for publication in Phys. Rev.
- …