8,656 research outputs found
When Nudges Are Forever: Inertia in the Swedish Premium Pension Plan
To inform economists and policy makers about whether the effects of nudges are persistent in one specific context, we study the choice architecture of the Swedish Premium Pension Plan. The data we study consist of all initial choices and subsequent rebalancing activities by the entire population of 7.3 million retirement savers in Sweden during the period 2000 to 2016. Based on our analysis of these data, we conclude that the effects of nudging in this case were surprisingly persistent and seem to last nearly two decades, if not forever
Electroweak Sudakov Corrections using Effective Field Theory
Electroweak Sudakov corrections of the form alpha^n log^m s/M_{W,Z}^2 are
summed using renormalization group evolution in soft-collinear effective theory
(SCET). Results are given for the scalar, vector and tensor form-factors for
fermion and scalar particles. The formalism for including massive gauge bosons
in SCET is developed.Comment: 5 page
Star Formation and Stellar Mass Assembly in Dark Matter Halos: From Giants to Dwarfs
The empirical model of Lu et al. 2014 is updated with recent data and used to
study galaxy star formation and assembly histories. At , the predicted
galaxy stellar mass functions are steep, and a significant amount of star
formation is hosted by low-mass haloes that may be missed in current
observations. Most of the stars in cluster centrals formed earlier than
but have been assembled much later. Milky Way mass galaxies have
had on-going star formation without significant mergers since , and
are thus free of significant (classic) bulges produced by major mergers. In
massive clusters, stars bound in galaxies and scattered in the halo form a
homogeneous population that is old and with solar metallicity. In contrast, in
Milky Way mass systems the two components form two distinct populations, with
halo stars being older and poorer in metals by a factor of . Dwarf
galaxies in haloes with have experienced a
star formation burst accompanied by major mergers at , followed by a
nearly constant star formation rate after . The early burst leaves a
significant old stellar population that is distributed in spheroids.Comment: 17 pages, 17 figure
Constraining the Star Formation Histories in Dark Matter Halos: I. Central Galaxies
Using the self-consistent modeling of the conditional stellar mass functions
across cosmic time by Yang et al. (2012), we make model predictions for the
star formation histories (SFHs) of {\it central} galaxies in halos of different
masses. The model requires the following two key ingredients: (i) mass assembly
histories of central and satellite galaxies, and (ii) local observational
constraints of the star formation rates of central galaxies as function of halo
mass. We obtain a universal fitting formula that describes the (median) SFH of
central galaxies as function of halo mass, galaxy stellar mass and redshift. We
use this model to make predictions for various aspects of the star formation
rates of central galaxies across cosmic time. Our main findings are the
following. (1) The specific star formation rate (SSFR) at high increases
rapidly with increasing redshift [] for halos of a given
mass and only slowly with halo mass () at a given , in
almost perfect agreement with the specific mass accretion rate of dark matter
halos. (2) The ratio between the star formation rate (SFR) in the main-branch
progenitor and the final stellar mass of a galaxy peaks roughly at a constant
value, , independent of halo mass or the
final stellar mass of the galaxy. However, the redshift at which the SFR peaks
increases rapidly with halo mass. (3) More than half of the stars in the
present-day Universe were formed in halos with 10^{11.1}\msunh < M_h <
10^{12.3}\msunh in the redshift range . (4) ... [abridged]Comment: 15 figures, 22 pages, Accepted for publication in Ap
The cross-correlation between galaxies of different luminosities and Colors
We study the cross-correlation between galaxies of different luminosities and
colors, using a sample selected from the SDSS Dr 4. Galaxies are divided into 6
samples according to luminosity, and each of these samples is divided into red
and blue subsamples. Projected auto-correlation and cross-correlation is
estimated for these subsample. At projected separations r_p > 1\mpch, all
correlation functions are roughly parallel, although the correlation amplitude
depends systematically on luminosity and color. On r_p < 1\mpch, the auto- and
cross-correlation functions of red galaxies are significantly enhanced relative
to the corresponding power laws obtained on larger scales. Such enhancement is
absent for blue galaxies and in the cross-correlation between red and blue
galaxies. We esimate the relative bias factor on scales r > 1\mpch for each
subsample using its auto-correlation function and cross-correlation functions.
The relative bias factors obtained from different methods are similar. For blue
galaxies the luminosity-dependence of the relative bias is strong over the
luminosity range probed (-23.0<M_r < -18.0),but for red galaxies the dependence
is weaker and becomes insignificant for luminosities below L^*. To examine
whether a significant stochastic/nonlinear component exists in the bias
relation, we study the ratio R_ij= W_{ii}W_{jj}/W_{ij}^2, where W_{ij} is the
projected correlation between subsample i and j. We find that the values of
R_ij are all consistent with 1 for all-all, red-red and blue-blue samples,
however significantly larger than 1 for red-blue samples. For faint red - faint
blue samples the values of R_{ij} are as high as ~ 2 on small scales r_p < 1
\mpch and decrease with increasing r_p.Comment: 25 pages, 18 figures, Accepted for publication in Ap
Long-term nitrogen addition decreases carbon leaching in a nitrogen-rich forest ecosystem
Dissolved organic carbon (DOC) plays a critical role in the carbon (C) cycle of forest soils, and has been recently connected with global increases in nitrogen (N) deposition. Most studies on effects of elevated N deposition on DOC have been carried out in N-limited temperate regions, with far fewer data available from N-rich ecosystems, especially in the context of chronically elevated N deposition. Furthermore, mechanisms for excess N-induced changes of DOC dynamics have been suggested to be different between the two kinds of ecosystems, because of the different ecosystem N status. The purpose of this study was to experimentally examine how long-term N addition affects DOC dynamics below the primary rooting zones (the upper 20cm soils) in typically N-rich lowland tropical forests. We have a primary assumption that long-term continuous N addition minimally affects DOC concentrations and effluxes in N-rich tropical forests. Experimental N addition was administered at the following levels: 0, 50, 100 and 150kgNha−1 yr−1, respectively. Results showed that seven years of N addition significantly decreased DOC concentrations in soil solution, and chemo-physical controls (solution acidity change and soil sorption) rather than biological controls may mainly account for the decreases, in contrast to other forests. We further found that N addition greatly decreased annual DOC effluxes from the primary rooting zone and increased water-extractable DOC in soils. Our results suggest that long-term N deposition could increase soil C sequestration in the upper soils by decreasing DOC efflux from that layer in N-rich ecosystems, a novel mechanism for continued accumulation of soil C in old-growth forests
The three-point correlation function of galaxies: comparing halo occupation models with observations
We present models for the three-point correlation function (3PCF) of both dark matter and galaxies. We show that models based on the halo model can reasonably match the dark-matter 3PCF obtained from high-resolution N-body simulations. On small scales (r≲ 0.5 h−1 Mpc) the 3PCF is sensitive to details regarding the density distributions of dark-matter haloes. On larger scales (r≳ 2.0 h−1 Mpc) the results are very sensitive to the abundance of the few most prominent haloes. Using the conditional luminosity function, we also construct models for the 3PCF of galaxies, which we test against large mock galaxy samples. The bias of the galaxy distribution with respect to the dark matter, and the finite number of galaxies that can be hosted by individual haloes, significantly reduce the normalized three-point correlation function with respect to that of dark matter. Contrary to the 3PCF of the dark matter, the galaxy 3PCF is much less sensitive to details regarding the spatial number density distribution of galaxies in individual haloes or to the abundance of the few most massive systems. Finally, we show that our model based on the conditional luminosity function is in good agreement with results obtained from the 2-degree Field Galaxy Redshift Survey. In particular, the model nicely reproduces the observational finding that the 3PCF for early-type galaxies is slightly higher than that of late-type galaxies, and that there is no significant dependence of the 3PCF on galaxy luminosit
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