6,578 research outputs found
Because We Smile: Jonathan Swift\u27s Enthusiastic Magnifying Glass
Jonathan Swift (1667-1745) was intellectually before his time. His insights into the human condition reveal a belief in the not-hopeless corruption of humanity. To capture this state of the human condition, he used two key symbols: wind and machine. These two symbols represent the two sides of the dialectical argument into which Swift forces his readers. What guide should direct humanity-enthusiasm and emotional stimulation (wind) or reason and objective systems (the machine)? Preoccupied with these two ideas, Swift uses his scatological satires to level all of humanity. Swift forces his readers onto their knees in the mud and mire and only after moving them toward repenting of all vain pride does Swift allow his audience the redemption of laughter
Eigenvector Sky Subtraction
We develop a new method for estimating and removing the spectrum of the sky
from deep spectroscopic observations; our method does not rely on simultaneous
measurement of the sky spectrum with the object spectrum. The technique is
based on the iterative subtraction of continuum estimates and Eigenvector sky
models derived from Singular Value Decompositions (SVD) of sky spectra, and sky
spectra residuals. Using simulated data derived from small telescope
observations we demonstrate that the method is effective for faint objects on
large telescopes. We discuss simple methods to combine our new technique with
the simultaneous measurement of sky to obtain sky subtraction very near the
Poisson limit.Comment: Accepted for publication in The Astrophysical Journal (Letters) 2000
March 7. Includes one extra figure which did not fit in a lette
Merging binary black holes formed through chemically homogeneous evolution in short-period stellar binaries
We explore a newly proposed channel to create binary black holes of stellar
origin. This scenario applies to massive, tight binaries where mixing induced
by rotation and tides transports the products of hydrogen burning throughout
the stellar envelopes. This slowly enriches the entire star with helium,
preventing the build-up of an internal chemical gradient. The stars remain
compact as they evolve nearly chemically homogeneously, eventually forming two
black holes, which, we estimate, typically merge 4--11 Gyr after formation.
Like other proposed channels, this evolutionary pathway suffers from
significant theoretical uncertainties, but could be constrained in the near
future by data from advanced ground-based gravitational-wave detectors. We
perform Monte Carlo simulations of the expected merger rate over cosmic time to
explore the implications and uncertainties. Our default model for this channel
yields a local binary black hole merger rate of about Gpc yr
at redshift , peaking at twice this rate at . This means that this
channel is competitive, in terms of expected rates, with the conventional
formation scenarios that involve a common-envelope phase during isolated binary
evolution or dynamical interaction in a dense cluster. The events from this
channel may be distinguished by the preference for nearly equal-mass components
and high masses, with typical total masses between 50 and 110
. Unlike the conventional isolated binary evolution scenario
that involves shrinkage of the orbit during a common-envelope phase, short time
delays are unlikely for this channel, implying that we do not expect mergers at
high redshift.Comment: Minor update to match the version published in MNRAS; 15 pages 10
figure
Quantum Key Distribution (QKD) and Commodity Security Protocols: Introduction and Integration
We present an overview of quantum key distribution (QKD), a secure key
exchange method based on the quantum laws of physics rather than computational
complexity. We also provide an overview of the two most widely used commodity
security protocols, IPsec and TLS. Pursuing a key exchange model, we propose
how QKD could be integrated into these security applications. For such a QKD
integration we propose a support layer that provides a set of common QKD
services between the QKD protocol and the security applicationsComment: 12Page
Merger rates of double neutron stars and stellar origin black holes: The Impact of Initial Conditions on Binary Evolution Predictions
The initial mass function (IMF), binary fraction and distributions of binary
parameters (mass ratios, separations and eccentricities) are indispensable
input for simulations of stellar populations. It is often claimed that these
are poorly constrained significantly affecting evolutionary predictions.
Recently, dedicated observing campaigns provided new constraints on the initial
conditions for massive stars. Findings include a larger close binary fraction
and a stronger preference for very tight systems. We investigate the impact on
the predicted merger rates of neutron stars and black holes.
Despite the changes with previous assumptions, we only find an increase of
less than a factor 2 (insignificant compared with evolutionary uncertainties of
typically a factor 10-100). We further show that the uncertainties in the new
initial binary properties do not significantly affect (within a factor of 2)
our predictions of double compact object merger rates. An exception is the
uncertainty in IMF (variations by a factor of 6 up and down). No significant
changes in the distributions of final component masses, mass ratios, chirp
masses and delay times are found.
We conclude that the predictions are, for practical purposes, robust against
uncertainties in the initial conditions concerning binary parameters with
exception of the IMF. This eliminates an important layer of the many uncertain
assumptions affecting the predictions of merger detection rates with the
gravitational wave detectors aLIGO/aVirgo.Comment: Accepted for publication in Ap
Has the Stability and Growth Pact Impeded Political Budget Cycles in the European Union?
This paper examines whether there is a political budget cycle (PBC) in countries in the euro area. Using a multivariate model for the period 1999-2004 and various election indicators we find strong evidence that the Stability and Growth Pact has not restricted fiscal policy makers in the euro area in pursuing expansionary policies before elections. In an election-year – but not in the year prior to the election – the budget deficit increases. This result is in line with third generation PBC models, which are based on moral hazard. We also find a significant but small partisan effect on fiscal policy outcomes.fiscal policy, political budget cycle, Stability and Growth Pact
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