135 research outputs found
Multiwinner Voting with Fairness Constraints
Multiwinner voting rules are used to select a small representative subset of
candidates or items from a larger set given the preferences of voters. However,
if candidates have sensitive attributes such as gender or ethnicity (when
selecting a committee), or specified types such as political leaning (when
selecting a subset of news items), an algorithm that chooses a subset by
optimizing a multiwinner voting rule may be unbalanced in its selection -- it
may under or over represent a particular gender or political orientation in the
examples above. We introduce an algorithmic framework for multiwinner voting
problems when there is an additional requirement that the selected subset
should be "fair" with respect to a given set of attributes. Our framework
provides the flexibility to (1) specify fairness with respect to multiple,
non-disjoint attributes (e.g., ethnicity and gender) and (2) specify a score
function. We study the computational complexity of this constrained multiwinner
voting problem for monotone and submodular score functions and present several
approximation algorithms and matching hardness of approximation results for
various attribute group structure and types of score functions. We also present
simulations that suggest that adding fairness constraints may not affect the
scores significantly when compared to the unconstrained case.Comment: The conference version of this paper appears in IJCAI-ECAI 201
Nambu--Jona-Lasinio model in a parallel electromagnetic field
We explore the features of the and chiral symmetry breaking of the
Nambu--Jona-Lasinio model without the Kobayashi-Maskawa-'t Hooft determinant
term in the presence of a parallel electromagnetic field. We show that the
electromagnetic chiral anomaly can induce both finite neutral pion condensate
and isospin-singlet pseudo-scalar condensate and thus modifies the
chiral symmetry breaking pattern. In order to characterize the strength of the
symmetry breaking, we evaluate the susceptibility associated with the
charge. The result shows that the susceptibility contributed from the
chiral anomaly is consistent with the behavior of the corresponding
condensate. The spectra of the mesonic excitations are also studied
The Multi-shop Ski Rental Problem
We consider the {\em multi-shop ski rental} problem. This problem generalizes
the classic ski rental problem to a multi-shop setting, in which each shop has
different prices for renting and purchasing a pair of skis, and a
\emph{consumer} has to make decisions on when and where to buy. We are
interested in the {\em optimal online (competitive-ratio minimizing) mixed
strategy} from the consumer's perspective. For our problem in its basic form,
we obtain exciting closed-form solutions and a linear time algorithm for
computing them. We further demonstrate the generality of our approach by
investigating three extensions of our basic problem, namely ones that consider
costs incurred by entering a shop or switching to another shop. Our solutions
to these problems suggest that the consumer must assign positive probability in
\emph{exactly one} shop at any buying time. Our results apply to many
real-world applications, ranging from cost management in \texttt{IaaS} cloud to
scheduling in distributed computing
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