73,614 research outputs found
Weak magnetism phenomena in heavy-fermion superconductors: selected SR studies
The behavior of the so-called weak moment antiferromagnetic states, observed
in the heavy-fermion superconductors UPt and URuSi, is discussed in
view of recent SR results obtained as function of control parameters like
chemical substitution and external pressure. In UPt, the Pd substitution
for Pt reveals the dynamical character of the weak moment order. On the other
hand, SR measurements performed on samples in which Th substitutes U
suggest that crystallographic disorder on the magnetic sites deeply affects the
fluctuation timescale. In URuSi, a phase separation between the
so-called hidden order state, present at ambient pressure, and an
antiferromagnetic state, occurring under pressure, is observed. In view of the
pressure-temperature phase diagram obtained by SR, it is deduced that the
respective order parameters have different symmetries.Comment: To appear in: J. Phys.: Cond. Matte
Inferring Networks of Substitutable and Complementary Products
In a modern recommender system, it is important to understand how products
relate to each other. For example, while a user is looking for mobile phones,
it might make sense to recommend other phones, but once they buy a phone, we
might instead want to recommend batteries, cases, or chargers. These two types
of recommendations are referred to as substitutes and complements: substitutes
are products that can be purchased instead of each other, while complements are
products that can be purchased in addition to each other.
Here we develop a method to infer networks of substitutable and complementary
products. We formulate this as a supervised link prediction task, where we
learn the semantics of substitutes and complements from data associated with
products. The primary source of data we use is the text of product reviews,
though our method also makes use of features such as ratings, specifications,
prices, and brands. Methodologically, we build topic models that are trained to
automatically discover topics from text that are successful at predicting and
explaining such relationships. Experimentally, we evaluate our system on the
Amazon product catalog, a large dataset consisting of 9 million products, 237
million links, and 144 million reviews.Comment: 12 pages, 6 figure
Adding a Stick to the Carrot? The Interaction of Bonuses and Fines
In this paper we report on a principal-agent experiment where the principal can choose whether to rely on an unenforcable bonus contract or to combine the bonus contract with a fine if the agent’s effort falls below a minimum standard. We show that most principals do not use the fine and that the pure bonus contract is more efficient than the combined contract. Our experiment suggests that principals who are less fair are more likely to choose a combined contract and less likely to actually pay the announced bonus. This offers a new explanation for why explicit and implicit incentives are substitutes rather than complements
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