Characterizing Attention Cascades in WhatsApp Groups

An important political and social phenomena discussed in several countries, like India and Brazil, is the use of WhatsApp to spread false or misleading content. However, little is known about the information dissemination process in WhatsApp groups. Attention affects the dissemination of information in WhatsApp groups, determining what topics or subjects are more attractive to participants of a group. In this paper, we characterize and analyze how attention propagates among the participants of a WhatsApp group. An attention cascade begins when a user asserts a topic in a message to the group, which could include written text, photos, or links to articles online. Others then propagate the information by responding to it. We analyzed attention cascades in more than 1.7 million messages posted in 120 groups over one year. Our analysis focused on the structural and temporal evolution of attention cascades as well as on the behavior of users that participate in them. We found specific characteristics in cascades associated with groups that discuss political subjects and false information. For instance, we observe that cascades with false information tend to be deeper, reach more users, and last longer in political groups than in non-political groups.Comment: Accepted as a full paper at the 11th International ACM Web Science Conference (WebSci 2019). Please cite the WebSci versio

The maximum number of cliques in graphs without large matchings

Given two graphs $T$ and $F$, the maximum number of copies of $T$ in an $F$-free graph on $n$ vertices is denoted by $ex(n,T,F)$ and is called the Generalized Tur\'{a}n number. When $T=K_2$, it reduces to the classical Tur\'{a}n number $ex(n,F)$. In 1961, Erd\H{o}s and Gallai proved that $$ex(n,M_{k+1})=\max\left\{\binom{2k+1}{2}, \binom{k}{2}+k(n-k)\right\},$$ where $M_{k+1}$ is a matching of size $k+1$. In this note, we prove that for any $s\geq 2$, $$ex(n,K_s,M_{k+1})=\max\left\{\binom{2k+1}{s}, \binom{k}{s}+(n-k)\binom{k}{s-1}\right\}.$$Comment: Zoltan Furedi, Alexandr Kostochka and Ruth Luo's paper "A variation of a theorem by Posa" indicates an even shorter proo

Classical Amplitudes in Gravitational-Wave Physics

In this thesis, we study emission amplitudes for the class of nonlinear processes of tails, which are processes of order $G_N^2$, and represent the effect of scattering gravitational radiation off the static background curvature, including not only mass tails but also the "failed" tails due to the angular momentum of the source. As originally shown in our work, some of these amplitudes present anomalies, which are then properly understood and corrected with field theory tools which have straightforward counterpart in traditional methods. We also investigate the relation between emission and self-energy diagrams and, in particular, show that a correction to the anomalous self-energy diagrams is necessary to correctly account for conservative terms that arise from radiative processes. From this, we obtain the correct contribution to the conservative 5PN stemming from the electric quadrupole angular momentum failed tail, correcting previous results in the literature. Besides this, we also compute for the first time the conservative contributions from the angular momentum failed tail, for arbitrary multipole moments. Subsequently, we explore the natural higher-order extension (of order $G_N^3$) of the mass tails, called tails of tails, for generic electric and magnetic multipoles. As we will see, both long- and short-distance divergences are encountered, which are then properly understood and dealt with in terms of standard renormalization techniques. In this case, we are able to resum the logarithmic contributions through the integration of the renormalization group equation. Thus, in this thesis, we have extended the post-Newtonian perturbative expansion in the particularly thorny region of processes involving the mixture of radiative and potential modes.Comment: PhD thesis, 137 page

The Use of Digital Media for the Employer Brand Management in Hotels

Os colaboradores exercem um papel fulcral no sucesso da marca dos hotéis. Existe um número incontável de marcas de hotéis, cada uma com as suas características únicas, o que requer diferentes colaboradores para darem vida às suas promessas. Estes devem estar em sintonia com os valores e requisitos da marca do hotel de modo a poderem representá-la adequadamente durante a interação com os hóspedes. Os gestores devem comunicar corretamente as suas employer brands de modo a atrair os colaboradores desejados. As empresas enviam sinais sobre o seu posicionamento enquanto empregadoras sempre que utilizam um meio de comunicação online. Estas devem apresentar aos potencias candidatos informações claras e precisas de modo a permitir-lhes avaliar a sua afinidade com a empresa mesmo antes de se candidatarem. Assim, a hipótese de ocorrer um emparelhamento entre os colaboradores e os seus empregadores aumenta. Os gestores devem tomar especial atenção à forma como comunicam o seu posicionamento enquanto empregadores de modo a potencializar ativamente este emparelhamento. Neste estudo, explorou-se como dez das maiores redes hoteleiras do mundo utilizam os seus websites de recrutamento para apresentar o seu posicionamento enquanto empregadoras. Paralelamente, analisou-se como estas redes comunicam aos seus potenciais colaboradores, através de anúncios de trabalho, os valores da empresa e os benefícios que estas oferecem. Para tal, seguiu-se um design qualitativo e adotou-se uma abordagem abdutiva. O presente estudo demonstrou, por meio de uma template analysis, que as redes hoteleiras avaliadas gerem explicitamente as suas estratégias de employer branding com o intuito de atraírem apenas colaboradores que partilham os seus valores e objetivos. Também revelou que os hotéis que promovem um ambiente de trabalho socialmente diverso são potencialmente mais atrativos enquanto empregadores. Finalmente, apresentam-se recomendações sobre como os gestores de hotéis podem melhorar a comunicação das suas employer brands através dos meios digitais.A significant part of a hotel's brand success relies on its employees. There are many hotel brands, each with their unique characteristics, demanding employees who give life to their brand promises. To assure employees know how to represent it while interacting with guests, they must aline with company values and requirements. Managers must know how to communicate their employer brands to attract the right employees. Companies send signals about their employer positioning whenever they use online communication. Employers must offer potential candidates clear and precise information, allowing them to judge their fit within the company, even before applying for the job. By doing so, employers and employees increase their chance for a match. To actively enhance this match, managers should pay attention to how they communicate their employer positioning. This study explored how ten of the world’s largest hotel chains use their recruiting websites to present their employer positioning and communicate their values and employee value proposition on their job advertisements. A qualitative design, adopting an abductive approach, was used. Through a template analysis, this study found that these companies, while intending to attract employees who share similar values and objectives, are explicitly managing their employer branding strategies. Further, this study revealed that promoting a socially diverse work environment is a relevant aspect that helps a company attract employees. Managerial recommendations associated with how managers might improve their employer branding online communications are discussed in this paper

Hardship in international commercial contracts. A comparative analysis of the rules in transnational Commercial Law

Os contratos desempenham função imprescindível na economia moderna, estabelecendo expectativas de partes que desejam negociar. Estas partes devem ter autonomia para contratar, desde que respeitado o princípio da pacta sunt servanda. Por outro lado, pela racionalidade econômica dos agentes, eles buscarão a resolução do contrato (ou, pelo menos, sua renegociação) a partir do momento em que este deixar de se tornar vantajoso, o que pode ocorrer devido a acontecimentos supervenientes que frustrem a função econômica idealizada. Caso as partes não contratem essa alocação de riscos, é necessário buscar mecanismos que solucionem o problema. Várias normas internacionais buscaram tratar dessa questão, como a Convenção de Viena sobre Compra e Venda Internacional de Mercadorias (CISG), os Princípios UNIDROIT e os Princípios de Direito Contratual Europeu. Se, por um lado, os dois últimos tratam expressamente de casos de hardship, por outro lado a CISG possui somente uma cláusula genérica de exoneração que cria dúvidas quanto ao seu escopo de aplicação. Diante deste cenário plural, este artigo discute como interpretar situações de hardship em contratos comerciais internacionais sob este conjunto de normas, quais soluções são mais apropriadas para as necessidades do comércio e como estas normas internacionais interagem entre si para harmonizar o direito comercial internacional.Contracts have a vital role in modern economy, establishing parties’ expectations when contracting. Parties must have autonomy to enter into contracts, providing they respect the principle of pacta sunt servanda (sanctity of the contracts). On the other hand, due to their economic rationality, parties will often seek contract termination (or, at least, its renegotiation) once it is not profitable anymore, which can happen due to supervening events that frustrate the economic function of the contract. When these risks are not allocated in the contract, it is necessary to find mechanisms to solve the problem. Many international rules deal with the issue, such as the United Nations Convention on Contracts for the International Sale of Goods (CISG), the UNIDROIT Principles and the Principles of European Contract Law. If, on the one hand, the two latter expressly deal with hardship cases, on the other hand the CISG has only a generic clause of exoneration that creates doubts about its scope of application. Under this variegated framework, this paper discusses how to interpret hardship problems in international commercial contracts under this set of rules, which remedies are best suited for the needs of trade and how the international rules should interact to harmonize international commercial law

Quantum revival patterns from classical phase-space trajectories

A general semiclassical method in phase space based on the final value representation of the Wigner function is considered that bypasses caustics and the need to root-search for classical trajectories. We demonstrate its potential by applying the method to the Kerr Hamiltonian, for which the exact quantum evolution is punctuated by a sequence of intricate revival patterns. The structure of such revival patterns, lying far beyond the Ehrenfest time, is semiclassically reproduced and revealed as a consequence of constructive and destructive interferences of classical trajectories.Comment: 7 pages, 6 figure