3,200 research outputs found
Exploiting Metric Structure for Efficient Private Query Release
We consider the problem of privately answering queries defined on databases
which are collections of points belonging to some metric space. We give simple,
computationally efficient algorithms for answering distance queries defined
over an arbitrary metric. Distance queries are specified by points in the
metric space, and ask for the average distance from the query point to the
points contained in the database, according to the specified metric. Our
algorithms run efficiently in the database size and the dimension of the space,
and operate in both the online query release setting, and the offline setting
in which they must in polynomial time generate a fixed data structure which can
answer all queries of interest. This represents one of the first subclasses of
linear queries for which efficient algorithms are known for the private query
release problem, circumventing known hardness results for generic linear
queries
Chains of N=2, D=4 heterotic/type II duals
We report on a search for heterotic strings that are dual candidates of
type II compactifications on Calabi-Yau threefolds described as
fibrations. We find many new heterotic duals by using standard orbifold
techniques. The associated type II compactifications fall into chains in which
the proposed duals are heterotic compactifications related one another by a
sequential Higgs mechanism. This breaking in the heterotic side typically
involves the sequence , while in the type II side the weights of the complex hypersurfaces and the
structure of the quotient singularities also follow specific patterns.Comment: Latex, 21 pages, 2 table
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