8,110 research outputs found
When Should Sellers Use Auctions?
A bidding process can be organized so that offers are submitted simultaneously or sequentially. In the latter case, potential buyers can condition their behavior on previous entrants' decisions. The relative performance of these mechanisms is investigated when entry is costly and selective, meaning that potential buyers with higher values are more likely to participate. A simple sequential mechanism can give both buyers and sellers significantly higher payoffs than the commonly used simultaneous bid auction. The findings are illustrated with parameters estimated from simultaneous entry USFS timber auctions where our estimates predict that the sequential mechanism would increase revenue and efficiency.
Lakshmi Planum: A distinctive highland volcanic province
Lakshmi Planum, a broad smooth plain located in western Ishtar Terra and containing two large oval depressions (Colette and Sacajawea), has been interpreted as a highland plain of volcanic origin. Lakshmi is situated 3 to 5 km above the mean planetary radius and is surrounded on all sides by bands of mountains interpreted to be of compressional tectonic origin. Four primary characteristics distinguish Lakshmi from other volcanic regions known on the planet, such as Beta Regio: (1) high altitude, (2) plateau-like nature, (3) the presence of very large, low volcanic constructs with distinctive central calderas, and (4) its compressional tectonic surroundings. Building on the previous work of Pronin, the objective is to establish the detailed nature of the volcanic deposits on Lakshmi, interpret eruption styles and conditions, sketch out an eruption history, and determine the relationship between volcanism and the tectonic environment of the region
On the size of approximately convex sets in normed spaces
Let X be a normed space. A subset A of X is approximately convex if
for all and where is
the distance of to . Let \Co(A) be the convex hull and \diam(A) the
diameter of . We prove that every -dimensional normed space contains
approximately convex sets with \mathcal{H}(A,\Co(A))\ge \log_2n-1 and
\diam(A) \le C\sqrt n(\ln n)^2, where denotes the Hausdorff
distance. These estimates are reasonably sharp. For every , we construct
worst possible approximately convex sets in such that
\mathcal{H}(A,\Co(A))=\diam(A)=D. Several results pertaining to the
Hyers-Ulam stability theorem are also proved.Comment: 32 pages. See also http://www.math.sc.edu/~howard
Extremal Approximately Convex Functions and Estimating the Size of Convex Hulls
A real valued function defined on a convex is anemconvex function iff
it satisfies A thorough study of
approximately convex functions is made. The principal results are a sharp
universal upper bound for lower semi-continuous approximately convex functions
that vanish on the vertices of a simplex and an explicit description of the
unique largest bounded approximately convex function~ vanishing on the
vertices of a simplex.
A set in a normed space is an approximately convex set iff for all
the distance of the midpoint to is . The bounds
on approximately convex functions are used to show that in with the
Euclidean norm, for any approximately convex set , any point of the
convex hull of is at a distance of at most
from . Examples are given to show
this is the sharp bound. Bounds for general norms on are also given.Comment: 39 pages. See also http://www.math.sc.edu/~howard
Update of MRST parton distributions.
We discuss the latest update of the MRST parton distributions in response
to the most recent data. We discuss the areas where there are hints
of difficulties in the global fit, and compare to some other updated sets of
parton distributions, particularly CTEQ6. We briefly discuss the issue of
uncertainties associated with partons
MRST global fit update.
We discuss the impact of the most recent data on the MRST global analysis -
in particular the new high-ET jet data and their implications for the gluon and
the new small x structure function data. In the light of these new data we also
consider the uncertainty in predictions for physical quantities depending on parton
distributions, concentrating on the W cross-section at hadron colliders
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