Privacy and Fairness in Recommender Systems via Adversarial Training of User Representations

Latent factor models for recommender systems represent users and items as low dimensional vectors. Privacy risks of such systems have previously been studied mostly in the context of recovery of personal information in the form of usage records from the training data. However, the user representations themselves may be used together with external data to recover private user information such as gender and age. In this paper we show that user vectors calculated by a common recommender system can be exploited in this way. We propose the privacy-adversarial framework to eliminate such leakage of private information, and study the trade-off between recommender performance and leakage both theoretically and empirically using a benchmark dataset. An advantage of the proposed method is that it also helps guarantee fairness of results, since all implicit knowledge of a set of attributes is scrubbed from the representations used by the model, and thus can't enter into the decision making. We discuss further applications of this method towards the generation of deeper and more insightful recommendations.Comment: International Conference on Pattern Recognition and Method

H2O contents and hydrogen isotopic composition of apatite crystals from L, LL5-6 ordinary chondrites.

第3回極域科学シンポジウム/第35回南極隕石シンポジウム 11月30日（金） 国立国語研究所 2階講

Gauged compact Q-balls and Q-shells in a multi-component CPNCP^N model

We study a multicomponent $CP^N$ model's scalar electrodynamics. The model contains Q-balls/shells, which are non-topological compact solitons with time dependency $e^{i\omega t}$. Two coupled $CP^N$ models can decouple locally if one of their $CP^N$ fields takes the vacuum value. Because of the compacton nature of solutions, Q-shells can shelter another compact Q-ball or Q-shell within their hollow region. Even if compactons do not overlap, they can interact through the electromagnetic field. We investigate how the size of multi-compacton formations is affected by electric charge. We are interested in structures with non-zero or zero total net charge.Comment: 23 pages, 8 figure

An efficient numerical quadrature for the calculation of the potential energy of wavefunctions expressed in the Daubechies wavelet basis

An efficient numerical quadrature is proposed for the approximate calculation of the potential energy in the context of pseudo potential electronic structure calculations with Daubechies wavelet and scaling function basis sets. Our quadrature is also applicable in the case of adaptive spatial resolution. Our theoretical error estimates are confirmed by numerical test calculations of the ground state energy and wave function of the harmonic oscillator in one dimension with and without adaptive resolution. As a byproduct we derive a filter, which, upon application on the scaling function coefficients of a smooth function, renders the approximate grid values of this function. This also allows for a fast calculation of the charge density from the wave function.Comment: 35 pages, 9 figures. Submitted to: Journal of Computational Physic