196 research outputs found
Making Decisions that Reduce Discriminatory Impacts
As machine learning algorithms move into realworld settings, it is crucial to ensure they are
aligned with societal values. There has been
much work on one aspect of this, namely the
discriminatory prediction problem: How can
we reduce discrimination in the predictions themselves? While an important question, solutions to
this problem only apply in a restricted setting, as
we have full control over the predictions. Often
we care about the non-discrimination of quantities we do not have full control over. Thus, we
describe another key aspect of this challenge, the
discriminatory impact problem: How can we
reduce discrimination arising from the real-world
impact of decisions? To address this, we describe
causal methods that model the relevant parts of
the real-world system in which the decisions are
made. Unlike previous approaches, these models not only allow us to map the causal pathway
of a single decision, but also to model the effect
of interference–how the impact on an individual
depends on decisions made about other people.
Often, the goal of decision policies is to maximize a beneficial impact overall. To reduce the
discrimination of these benefits, we devise a constraint inspired by recent work in counterfactual
fairness (Kusner et al., 2017), and give an efficient
procedure to solve the constrained optimization
problem. We demonstrate our approach with an
example: how to increase students taking college
entrance exams in New York City public schools
Causal Effect Inference for Structured Treatments
We address the estimation of conditional average treatment effects (CATEs) for structured treatments (e.g., graphs, images, texts). Given a weak condition on the effect, we propose the generalized Robinson decomposition, which (i) isolates the causal estimand (reducing regularization bias), (ii) allows one to plug in arbitrary models for learning, and (iii) possesses a quasi-oracle convergence guarantee under mild assumptions. In experiments with small-world and molecular graphs we demonstrate that our approach outperforms prior work in CATE estimation
Words are Malleable: Computing Semantic Shifts in Political and Media Discourse
Recently, researchers started to pay attention to the detection of temporal
shifts in the meaning of words. However, most (if not all) of these approaches
restricted their efforts to uncovering change over time, thus neglecting other
valuable dimensions such as social or political variability. We propose an
approach for detecting semantic shifts between different viewpoints--broadly
defined as a set of texts that share a specific metadata feature, which can be
a time-period, but also a social entity such as a political party. For each
viewpoint, we learn a semantic space in which each word is represented as a low
dimensional neural embedded vector. The challenge is to compare the meaning of
a word in one space to its meaning in another space and measure the size of the
semantic shifts. We compare the effectiveness of a measure based on optimal
transformations between the two spaces with a measure based on the similarity
of the neighbors of the word in the respective spaces. Our experiments
demonstrate that the combination of these two performs best. We show that the
semantic shifts not only occur over time, but also along different viewpoints
in a short period of time. For evaluation, we demonstrate how this approach
captures meaningful semantic shifts and can help improve other tasks such as
the contrastive viewpoint summarization and ideology detection (measured as
classification accuracy) in political texts. We also show that the two laws of
semantic change which were empirically shown to hold for temporal shifts also
hold for shifts across viewpoints. These laws state that frequent words are
less likely to shift meaning while words with many senses are more likely to do
so.Comment: In Proceedings of the 26th ACM International on Conference on
Information and Knowledge Management (CIKM2017
A Geometric Theory of Diblock Copolymer Phases
We analyze the energetics of sphere-like micellar phases in diblock
copolymers in terms of well-studied, geometric quantities for their lattices.
We argue that the A15 lattice with Pm3n symmetry should be favored as the
blocks become more symmetric and corroborate this through a self-consistent
field theory. Because phases with columnar or bicontinuous topologies
intervene, the A15 phase, though metastable, is not an equilibrium phase of
symmetric diblocks. We investigate the phase diagram of branched diblocks and
find thatthe A15 phase is stable.Comment: 4 pages, RevTeX, 3 eps figures include
Coplanar k-unduloids are nondegenerate
We prove each embedded, constant mean curvature (CMC) surface in Euclidean
space with genus zero and finitely many coplanar ends is nondegenerate: there
is no nontrivial square-integrable solution to the Jacobi equation, the
linearization of the CMC condition. This implies that the moduli space of such
coplanar surfaces is a real-analytic manifold and that a neighborhood of these
in the full CMC moduli space is itself a manifold. Nondegeneracy further
implies (infinitesimal and local) rigidity in the sense that the asymptotes map
is an analytic immersion on these spaces, and also that the coplanar
classifying map is an analytic diffeomorphism.Comment: 19 pages, no figures; improvements to expositio
Neural Networks for Information Retrieval
Machine learning plays a role in many aspects of modern IR systems, and deep
learning is applied in all of them. The fast pace of modern-day research has
given rise to many different approaches for many different IR problems. The
amount of information available can be overwhelming both for junior students
and for experienced researchers looking for new research topics and directions.
Additionally, it is interesting to see what key insights into IR problems the
new technologies are able to give us. The aim of this full-day tutorial is to
give a clear overview of current tried-and-trusted neural methods in IR and how
they benefit IR research. It covers key architectures, as well as the most
promising future directions.Comment: Overview of full-day tutorial at SIGIR 201
Bogomol'nyi Decomposition for Vesicles of Arbitrary Genus
We apply the Bogomol'nyi technique, which is usually invoked in the study of
solitons or models with topological invariants, to the case of elastic energy
of vesicles. We show that spontaneous bending contribution caused by any
deformation from metastable bending shapes falls in two distinct topological
sets: shapes of spherical topology and shapes of non-spherical topology
experience respectively a deviatoric bending contribution a la Fischer and a
mean curvature bending contribution a la Helfrich. In other words, topology may
be considered to describe bending phenomena. Besides, we calculate the bending
energy per genus and the bending closure energy regardless of the shape of the
vesicle. As an illustration we briefly consider geometrical frustration
phenomena experienced by magnetically coated vesicles.Comment: 8 pages, 1 figure; LaTeX2e + IOPar
Fairness in Algorithmic Decision Making: An Excursion Through the Lens of Causality
As virtually all aspects of our lives are increasingly impacted by
algorithmic decision making systems, it is incumbent upon us as a society to
ensure such systems do not become instruments of unfair discrimination on the
basis of gender, race, ethnicity, religion, etc. We consider the problem of
determining whether the decisions made by such systems are discriminatory,
through the lens of causal models. We introduce two definitions of group
fairness grounded in causality: fair on average causal effect (FACE), and fair
on average causal effect on the treated (FACT). We use the Rubin-Neyman
potential outcomes framework for the analysis of cause-effect relationships to
robustly estimate FACE and FACT. We demonstrate the effectiveness of our
proposed approach on synthetic data. Our analyses of two real-world data sets,
the Adult income data set from the UCI repository (with gender as the protected
attribute), and the NYC Stop and Frisk data set (with race as the protected
attribute), show that the evidence of discrimination obtained by FACE and FACT,
or lack thereof, is often in agreement with the findings from other studies. We
further show that FACT, being somewhat more nuanced compared to FACE, can yield
findings of discrimination that differ from those obtained using FACE.Comment: 7 pages, 2 figures, 2 tables.To appear in Proceedings of the
International Conference on World Wide Web (WWW), 201
Simulations of Two-Dimensional Melting on the Surface of a Sphere
We have simulated a system of classical particles confined on the surface of
a sphere interacting with a repulsive potential. The same system
simulated on a plane with periodic boundary conditions has van der Waals loops
in pressure-density plots which are usually interpreted as evidence for a first
order melting transition, but on the sphere such loops are absent.
We also investigated the structure factor and from the width of the first
peak as a function of density we can show that the growth of the correlation
length is consistent with KTHNY theory. This suggests that simulations of two
dimensional melting phenomena are best performed on the surface of a sphere.Comment: 4 eps figure
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