12,439 research outputs found
Analysts' Conflict of Interest and Biases in Earnings Forecasts
Analysts' earnings forecasts are influenced by their desire to win investment banking clients. We hypothesize that the equity bull market of the 1990s, along with the boom in investment banking business, exacerbated analysts' conflict of interest and their incentives to adjust strategically forecasts to avoid earnings disappointments. We document shifts in the distribution of earnings surprises, the market's response to surprises and forecast revisions, and in the predictability of non-negative surprises. Further confirmation is based on subsamples where conflicts of interest are more pronounced, including growth stocks and stocks with consecutive non-negative surprises; however shifts are less notable in international markets.
Stochastic Cluster Series expansion for quantum spin systems
In this paper we develop a cluster-variant of the Stochastic Series expansion
method (SCSE). For certain systems with longer-range interactions the SCSE is
considerably more efficient than the standard implementation of the Stochastic
Series Expansion (SSE), at low temperatures. As an application of this method
we calculated the T=0-conductance for a linear chain with a (diagonal) next
nearest neighbor interaction.Comment: 5 pages, 7 figure
Earnings Quality and Stock Returns
An exclusive focus on bottom-line income misses important information about the quality of earnings. Accruals (the difference between accounting earnings and cash flow) are reliably, negatively associated with future stock returns. Earnings increases that are accompanied by high accruals, suggesting low-quality earnings, are associated with poor future returns. We explore various hypotheses -- earnings manipulation, extrapolative biases about future growth, and under-reaction to business conditions -- to explain accruals' predictive power. Distinctions between the hypotheses are based on evidence from operating performance, the behavior of individual accrual items, and discretionary versus nondiscretionary components of accruals.
Dirac Quantization of Two-Dimensional Dilaton Gravity Minimally Coupled to N Massless Scalar Fields
It is shown that the Callan-Giddings-Harvey-Strominger theory on the cylinder
can be consistently quantized (using Dirac's approach) without imposing any
constraints on the sign of the gravitational coupling constant or the sign (or
value) of the cosmological constant. The quantum constraints in terms of the
original geometrical variables are also derived
The 2D analogue of the Reissner-Nordstrom solution
A two-dimensional (2D) dilaton gravity model, whose static solutions have the
same features of the Reissner-Nordstrom solutions, is obtained from the
dimensional reduction of a four-dimensional (4D) string effective action
invariant under S-duality transformations. The black hole solutions of the 2D
model and their relationship with those of the 4D theory are discussed.Comment: 5 pages, Plain-Tex, no figure
Monodisperse self-assembly in a model with protein-like interactions
We study the self-assembly behaviour of patchy particles with `protein-like'
interactions that can be considered as a minimal model for the assembly of
viral capsids and other shell-like protein complexes. We thoroughly explore the
thermodynamics and dynamics of self assembly as a function of the parameters of
the model and find robust assembly of all target structures considered. Optimal
assembly occurs in the region of parameter space where a free energy barrier
regulates the rate of nucleation, thus preventing the premature exhaustion of
the supply of monomers that can lead to the formation of incomplete shells. The
interactions also need to be specific enough to prevent the assembly of
malformed shells, but whilst maintaining kinetic accessibility. Free-energy
landscapes computed for our model have a funnel-like topography guiding the
system to form the target structure, and show that the torsional component of
the interparticle interactions prevents the formation of disordered aggregates
that would otherwise act as kinetic traps.Comment: 11 pages; 10 figure
Exosuit-induced improvements in walking after stroke: comprehensive analysis on gait energetics and biomechanics
Outstanding Poster Presentation Finalis
Bounds on Cross-sections and Lifetimes for Dark Matter Annihilation and Decay into Charged Leptons from Gamma-ray Observations of Dwarf Galaxies
We provide conservative bounds on the dark matter cross-section and lifetime
from final state radiation produced by annihilation or decay into charged
leptons, either directly or via an intermediate particle . Our analysis
utilizes the experimental gamma-ray flux upper limits from four Milky Way dwarf
satellites: HESS observations of Sagittarius and VERITAS observations of Draco,
Ursa Minor, and Willman 1. Using 90% confidence level lower limits on the
integrals over the dark matter distributions, we find that these constraints
are largely unable to rule out dark matter annihilations or decays as an
explanation of the PAMELA and ATIC/PPB-BETS excesses. However, if there is an
additional Sommerfeld enhancement in dwarfs, which have a velocity dispersion
~10 to 20 times lower than that of the local Galactic halo, then the
cross-sections for dark matter annihilating through 's required to
explain the excesses are very close to the cross-section upper bounds from
Willman 1. Dark matter annihilation directly into 's is also marginally
ruled out by Willman 1 as an explanation of the excesses, and the required
cross-section is only a factor of a few below the upper bound from Draco.
Finally, we make predictions for the gamma-ray flux expected from the dwarf
galaxy Segue 1 for the Fermi Gamma-ray Space Telescope. We find that for a
sizeable fraction of the parameter space in which dark matter annihilation into
charged leptons explains the PAMELA excess, Fermi has good prospects for
detecting a gamma-ray signal from Segue 1 after one year of observation.Comment: 11 pages, 4 figures. References added. Final published versio
A multicomponent model of the infrared emission from Comet Halley
A model based on a mixture of coated silicates and amorphous carbon grains produces a good spectral match to the available Halley data and is consistent with the compositional and morphological information derived from interplanetary dust particle studies and Halley flyby data. The dark appearance of comets may be due to carbonaceous coatings on the dominant (by mass) silicates. The lack of a 10 micrometer feature may be due to the presence of large silicate grains. The optical properties of pure materials apparently are not representative of cometary materials. The determination of the optical properties of additional silicates and carbonaceous materials would clearly be of use
- …