6,010 research outputs found
Surprising comparative properties of monetary models : results from a new model database
In this paper we investigate the comparative properties of empirically-estimated monetary models of the U.S. economy using a new database of models designed for such investigations. We focus on three representative models due to Christiano, Eichenbaum, Evans (2005), Smets and Wouters (2007) and Taylor (1993a). Although these models differ in terms of structure, estimation method, sample period, and data vintage, we find surprisingly similar economic impacts of unanticipated changes in the federal funds rate. However, optimized monetary policy rules differ across models and lack robustness. Model averaging offers an effective strategy for improving the robustness of policy rules
Surprising comparative properties of monetary models: results from a new data base
In this paper we investigate the comparative properties of empirically-estimated monetary models of the U.S. economy. We make use of a new data base of models designed for such investigations. We focus on three representative models: the Christiano, Eichenbaum, Evans (2005) model, the Smets and Wouters (2007) model, and the Taylor (1993a) model. Although the three models differ in terms of structure, estimation method, sample period, and data vintage, we find surprisingly similar economic impacts of unanticipated changes in the federal funds rate. However, the optimal monetary policy responses to other sources of economic fluctuations are widely different in the different models. We show that simple optimal policy rules that respond to the growth rate of output and smooth the interest rate are not robust. In contrast, policy rules with no interest rate smoothing and no response to the growth rate, as distinct from the level, of output are more robust. Robustness can be improved further by optimizing rules with respect to the average loss across the three models
The effectiveness of subsidies revisited: Accounting for wage and employment effects in business R&D
The present paper investigates the effectiveness of public subsidies to business enterprise research in a panel of OECD countries. We contribute to the literature by explicitly distinguishing between effects of a subsidy on R&D employment and expenditure, thereby accounting for a potential increase in scientists’ wages. The results indicate that subsidies are effective in generating additional research. We find that an increase in the direct subsidy rate of one percentage point leads to at least 1% more business R&D employment in the long run. Expenditure for business research increases by roughly 20-30% more than employment. We take this as evidence that subsidies also raise scientists’ wages. In addition, we find that there exists significant crowding out of private research through university research. Research performed in public non-university institutions seems to have no effect on private research. --
The First Supernova Explosions in the Universe
We investigate the supernova explosions that end the lives of massive
Population III stars in low-mass minihalos (M~10^6 M_sun) at redshifts z~20.
Employing the smoothed particle hydrodynamics method, we carry out numerical
simulations in a cosmological set-up of pair-instability supernovae with
explosion energies of E_SN=10^51 and 10^53 ergs. We find that the more
energetic explosion leads to the complete disruption of the gas in the
minihalo, whereas the lower explosion energy leaves much of the halo intact.
The higher energy supernova expels > 90% of the stellar metals into a region ~1
kpc across over a timescale of 3-5 Myr. Due to this burst-like initial star
formation episode, a large fraction of the universe could have been endowed
with a metallicity floor, Z_min>10^-4 Z_sun, already at z>15.Comment: Published in ApJ Letter
Broken windows revisited: the role of neighborhoods and individual characteristics in reaction to disorder cues
RG transport theory for open quantum systems: Charge fluctuations in multilevel quantum dots in and out of equilibrium
We present the real-time renormalization group (RTRG) method as a method to
describe the stationary state current through generic multi-level quantum dots
with a complex setup in nonequilibrium. The employed approach consists of a
very rudiment approximation for the RG equations which neglects all vertex
corrections while it provides a means to compute the effective dot Liouvillian
self-consistently. Being based on a weak-coupling expansion in the tunneling
between dot and reservoirs, the RTRG approach turns out to reliably describe
charge fluctuations in and out of equilibrium for arbitrary coupling strength,
even at zero temperature. We confirm this in the linear response regime with a
benchmark against highly-accurate numerically renormalization group data in the
exemplary case of three-level quantum dots. For small to intermediate bias
voltages and weak Coulomb interactions, we find an excellent agreement between
RTRG and functional renormalization group data, which can be expected to be
accurate in this regime. As a consequence, we advertise the presented RTRG
approach as an efficient and versatile tool to describe charge fluctuations
theoretically in quantum dot systems
Asymmetric Cosets
The aim of this work is to present a general theory of coset models G/H in
which different left and right actions of H on G are gauged. Our main results
include a formula for their modular invariant partition function, the
construction of a large set of boundary states and a general description of the
corresponding brane geometries. The paper concludes with some explicit
applications to the base of the conifold and to the time-dependent Nappi-Witten
background.Comment: 34 pages, LaTeX, 8 figures, 1 table, v2: references added, v3: typos
correcte
Neighbouring residue effects on the ^(15)N chemical shifts of some aliphatic dipeptides
The ^(15)N chemical shifts of a number of simple aliphatic dipeptides have been determined in a aqueous solution and while the amine nitrogen shift is independent of the nature of the neighbouring residue, the peptide nitrogen shift shows a marked dependence upon the nature of the adjacent amino-acid
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