Tight Combinatorial Generalization Bounds for Threshold Conjunction Rules

Abstract. We propose a combinatorial technique for obtaining tight data dependent generalization bounds based on a splitting and connec-tivity graph (SC-graph) of the set of classifiers. We apply this approach to a parametric set of conjunctive rules and propose an algorithm for effective SC-bound computation. Experiments on 6 data sets from the UCI ML Repository show that SC-bound helps to learn more reliable rule-based classifiers as compositions of less overfitted rules

Tides in colliding galaxies

Long tails and streams of stars are the most noticeable upshots of galaxy collisions. Their origin as gravitational, tidal, disturbances has however been recognized only less than fifty years ago and more than ten years after their first observations. This Review describes how the idea of galactic tides emerged, in particular thanks to the advances in numerical simulations, from the first ones that included tens of particles to the most sophisticated ones with tens of millions of them and state-of-the-art hydrodynamical prescriptions. Theoretical aspects pertaining to the formation of tidal tails are then presented. The third part of the review turns to observations and underlines the need for collecting deep multi-wavelength data to tackle the variety of physical processes exhibited by collisional debris. Tidal tails are not just stellar structures, but turn out to contain all the components usually found in galactic disks, in particular atomic / molecular gas and dust. They host star-forming complexes and are able to form star-clusters or even second-generation dwarf galaxies. The final part of the review discusses what tidal tails can tell us (or not) about the structure and content of present-day galaxies, including their dark components, and explains how tidal tails may be used to probe the past evolution of galaxies and their mass assembly history. On-going deep wide-field surveys disclose many new low-surface brightness structures in the nearby Universe, offering great opportunities for attempting galactic archeology with tidal tails.Comment: 46 pages, 13 figures, Review to be published in "Tidal effects in Astronomy and Astrophysics", Lecture Notes in Physics. Comments are most welcom

Advances in Global and Local Helioseismology: an Introductory Review

Helioseismology studies the structure and dynamics of the Sun's interior by observing oscillations on the surface. These studies provide information about the physical processes that control the evolution and magnetic activity of the Sun. In recent years, helioseismology has made substantial progress towards the understanding of the physics of solar oscillations and the physical processes inside the Sun, thanks to observational, theoretical and modeling efforts. In addition to the global seismology of the Sun based on measurements of global oscillation modes, a new field of local helioseismology, which studies oscillation travel times and local frequency shifts, has been developed. It is capable of providing 3D images of the subsurface structures and flows. The basic principles, recent advances and perspectives of global and local helioseismology are reviewed in this article.Comment: 86 pages, 46 figures; "Pulsation of the Sun and Stars", Lecture Notes in Physics, Vol. 832, Rozelot, Jean-Pierre; Neiner, Coralie (Eds.), 201

ЦИФРОВАЯ ЛИНГВИСТИЧЕСКАЯ МИГРАТОЛОГИЯ И МОНИТОРИНГ ПОТЕНЦИАЛЬНО ОПАСНЫХ ТЕКСТОВ О МИГРАЦИИ

The modern opposition of "friend and foe" is maximally manifested in the news migration discourse, where texts appear as potentially dangerous for the society of the receiving country. The authors consider migration processes through the prism of digital linguistic migration, which allows us to see the bifurcation points of changing attitudes towards migrants and migration in different countries. As a result of geopolitical transformations, new waves of migration arise, presenting migration as a pandemic, raising the problems of intercultural communication, language adaptation and the integration of migrants and refugees in the global rank. There is no doubt that this phenomenon determines ethno-linguistic and sociopolitical life both in the regions and in the countries that are somehow involved in migration. Analysis of potentially dangerous types of media and social media discourse is precisely the subject area where such formalization is possible. This requires an interdisciplinary approach involving specialists in linguistics, sociology, cultural studies, psychology, mathematics, computer science and Digital Humanities. Powerful geopolitical transformations are causing new waves of migration of such force that it acts as a pandemic. As a result of these processes of humanitarian migration issues (intercultural communication, ethno-psycholinguistics norms, linguistic adaptation/ re-adaptation, integration of migrants and refugees) global sound. Migration itself determines the ethnolinguistic and socio-political "portrait" of a particular locus.Современная оппозиция «друг и враг» максимально проявляется в новостном дискурсе о миграции, где тексты представляются потенциально опасными для общества принимающей страны. Авторы рассматривают миграционные процессы через призму цифровой лингвистической миграции, что позволяет нам увидеть точки бифуркации изменения отношения к мигрантам и миграции в разных странах. В результате геополитических преобразований возникают новые волны миграции, представляющие миграцию в качестве пандемии, поднимающие проблемы межкультурного общения, языковой адаптации и интеграции мигрантов и беженцев в глобальный ранг. Нет сомнений в том, что это явление определяет этнолингвистическую и социально-политическую жизнь как в регионах, так и в странах, так или иначе вовлеченных в миграцию. Анализ потенциально опасных типов медиа и дискурса в социальных сетях является как раз предметной областью, где такая формализация возможна. Это требует междисциплинарного подхода с привлечением специалистов в области лингвистики, социологии, культурологии, психологии, математики, информатики и цифровых гуманитарных наук. Мощные геополитические преобразования вызывают новые волны миграции такой силы, что она действует как пандемия. В результате этих процессов проблемы гуманитарной миграции (межкультурная коммуникация, этнопсихолингвистические нормы, лингвистическая адаптация / реадаптация, интеграция мигрантов и беженцев) приобретают глобальный характер. Сама миграция определяет этнолингвистический и социально-политический «портрет» определенного локуса

Homophily Evolution in Online Networks: Who Is a Good Friend and When?

Homophily is considered by network scientists as one of the major mechanisms of social network formation. However, the role of dynamic homophily in the network growth process has not been investigated in detail yet. In this paper, we estimate the role of homophily by various attributes at different stages of online network formation process. We consider the process of online friendship formation in the Vkontakte social networking site among first-year students at a Russian university. We reveal that at the beginning of the network formation a similarity in gender and score in entrance exams plays the key role, while by the end of network establishment period the role of the same group affiliation becomes more important. We explain the results with the tendency of students to follow different strategies to control the information flow in their social environment

Homophily Evolution in Online Networks: Who Is a Good Friend and When?

Homophily is considered by network scientists as one of the major mechanisms of social network formation. However, the role of dynamic homophily in the network growth process has not been investigated in detail yet. In this paper, we estimate the role of homophily by various attributes at different stages of online network formation process. We consider the process of online friendship formation in the Vkontakte social networking site among first-year students at a Russian university. We reveal that at the beginning of the network formation a similarity in gender and score in entrance exams plays the key role, while by the end of network establishment period the role of the same group affiliation becomes more important. We explain the results with the tendency of students to follow different strategies to control the information flow in their social environment