5,582 research outputs found
Dynamics of generalized tachyon field
We investigate the dynamics of generalized tachyon field in FRW spacetime. We
obtain the autonomous dynamical system for the general case. Because the
general autonomous dynamical system cannot be solved analytically, we discuss
two cases in detail: and . We find the critical points and
study their stability. At these critical points, we also consider the stability
of the generalized tachyon field, which is as important as the stability of
critical points. The possible final states of the universe are discussed.Comment: 9 pages, 5 figures, published versio
Generalized Delayed Feedback Model with Post-Click Information in Recommender Systems
Predicting conversion rate (e.g., the probability that a user will purchase
an item) is a fundamental problem in machine learning based recommender
systems. However, accurate conversion labels are revealed after a long delay,
which harms the timeliness of recommender systems. Previous literature
concentrates on utilizing early conversions to mitigate such a delayed feedback
problem. In this paper, we show that post-click user behaviors are also
informative to conversion rate prediction and can be used to improve
timeliness. We propose a generalized delayed feedback model (GDFM) that unifies
both post-click behaviors and early conversions as stochastic post-click
information, which could be utilized to train GDFM in a streaming manner
efficiently. Based on GDFM, we further establish a novel perspective that the
performance gap introduced by delayed feedback can be attributed to a temporal
gap and a sampling gap. Inspired by our analysis, we propose to measure the
quality of post-click information with a combination of temporal distance and
sample complexity. The training objective is re-weighted accordingly to
highlight informative and timely signals. We validate our analysis on public
datasets, and experimental performance confirms the effectiveness of our
method.Comment: NeurIPS'2
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