1,596 research outputs found
The impact of fiscal policy on economic activity over the business cycle - evidence from a threshold VAR analysis
Does the state of the business cycle matter for the effects of fiscal policy shocks on GDP? This study analyses quarterly German data from 1976 to 2009 in a threshold SVAR, expanding the SVAR approach by Blanchard and Perotti (2002). In a linear benchmark SVAR, the analysis finds that hiking spending yields a short-term fiscal multiplier of around 0.70, while the fiscal multiplier resulting from an increase in taxes and social security contributions is -0.66. In addition, the threshold model derives fundamentally new insights on the effects of shocks, depending on when in the business cycle they occur, their size and their direction. Most importantly, fiscal spending multipliers are much larger in times of a negative output gap but have only a very limited effect in times of a positive output gap. Discretionary revenue policies, on the other hand, have a generally more limited impact. Our findings have important implications for the optimal fiscal policy mix over different stages of the business cycle. Various robustness checks, including a different threshold specification, do not influence these implications substantially. --fiscal policy,business cycle,nonlinear analysis,fiscal multipliers
Evidence of Rocky Planetesimals Orbiting Two Hyades Stars
The Hyades is the nearest open cluster, relatively young and containing
numerous A-type stars; its known age, distance, and metallicity make it an
ideal site to study planetary systems around 2-3 Msun stars at an epoch similar
to the late heavy bombardment. Hubble Space Telescope far-ultraviolet
spectroscopy strongly suggests ongoing, external metal pollution in two remnant
Hyads. For ongoing accretion in both stars, the polluting material has
log[n(Si)/n(C)] > 0.2, is more carbon deficient than chondritic meteorites, and
is thus rocky. These data are consistent with a picture where rocky
planetesimals and small planets have formed in the Hyades around two
main-sequence A-type stars, whose white dwarf descendants bear the scars. These
detections via metal pollution are shown to be equivalent to infrared excesses
of Lir/L* ~ 1e-6 in the terrestrial zone of the stars.Comment: 7 pages, 3 figures, 2 tables, accepted to MNRA
Determination of S17(0) from published data
The experimental landscape for the 7Be+p radiative capture reaction is
rapidly changing as new high precision data become available. We present an
evaluation of existing data, detailing the treatment of systematic errors and
discrepancies, and show how they constrain the astrophysical S factor (S17),
independent of any nuclear structure model. With theoretical models robustly
determining the behavior of the sub-threshold pole, the extrapolation error can
be reduced and a constraint placed on the slope of S17. Using only radiative
capture data, we find S17(0) = 20.7 +/- 0.6 (stat) +/- 1.0 (syst) eV b if data
sets are completely independent, while if data sets are completely correlated
we find S17(0) = 21.4 +/- 0.5 (stat) +/- 1.4 (syst) eV b. The truth likely lies
somewhere in between these two limits. Although we employ a formalism capable
of treating discrepant data, we note that the central value of the S factor is
dominated by the recent high precision data of Junghans et al., which imply a
substantially higher value than other radiative capture and indirect
measurements. Therefore we conclude that further progress will require new high
precision data with a detailed error budget.Comment: 10 pages, 1 figure published versio
Gemini spectra of 12000K white dwarf stars
We report signal-to-noise ratio SNR ~ 100 optical spectra for four DA white
dwarf stars acquired with the GMOS spectrograph of the 8m Gemini north
telescope. These stars have 18<g<19 and are around Teff ~ 12000 K, were the
hydrogen lines are close to maximum. Our purpose is to test if the effective
temperatures and surface gravities derived from the relatively low
signal-to-noise ratio ( ~ 21) optical spectra acquired by the Sloan
Digital Sky Survey through model atmosphere fitting are trustworthy. Our
spectra range from 3800A to 6000A, therefore including H beta to H9. The H8
line was only marginally present in the SDSS spectra, but is crucial to
determine the gravity. When we compare the values published by Kleinman et al.
(2004) and Eisenstein et al. (2006) with our line-profile (LPT) fits, the
average differences are: Delta Teff ~ 320 K, systematically lower in SDSS, and
Delta log g ~ 0.24 dex, systematically larger in SDSS. The correlation between
gravity and effective temperature can only be broken at wavelengths bluer than
3800 A. The uncertainties in Teff are 60% larger, and in log g larger by a
factor of 4, than the Kleinman et al. (2004) and Eisenstein et al. (2006)
internal uncertainties.Comment: 11 pages and 8 figure
The astrophysical reaction 8Li(n,gamma)9Li from measurements by reverse kinematics
We study the breakup of 9Li projectiles in high energy (28.5 MeV/u)
collisions with heavy nuclear targets (208Pb). The wave functions are
calculated using a single-particle model for 9Li, and a simple optical
potential model for the scattering part. A good agreement with measured data is
obtained with insignificant E2 contribution.Comment: 4 pages, 3 figure
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