Repositório RCAAP

Este artigo é uma introdução a variedades simplécticas tóricas para não especialistas, começando com uma breve síntese de variedades simplécticas e acções hamiltonianas. As variedades simplécticas tóricas formam já um tema extenso, ao qual a modesta lista de referências abaixo não faz justiça – o objectivo deste texto não é ser exaustivo ou justo, mas simplesmente deixar entrever o que são estes espaços e a razão pela qual o leitor poderá querer adicioná-los ao seu repertório de objectos geométricos.

Recentemente, os autores provaram em [15, 16] que as funções constantes são os únicos maximizantes reais da desigualdade L2 -> L6 de extensão de Fourier na 2-esfera. Isto é um caso particular de [16, Teorema 1.1], cuja prova contém vários dos métodos e ideias-chave. Neste artigo, descrevemos a prova deste caso particular, e apresentamos algumas generalizações e problemas em aberto.

Neste texto revemos dois resultados na teoria das representações de álgebras de dimensão finita nos quais a quantidade de um certo tipo de estruturas está intimamente ligado ao tamanho dessas mesmas estruturas. Mais concretamente, discutimos os seguintes factos: (1) uma álgebra de dimensão finita admite apenas um número finito de módulos indecomponíveis a menos de isomorfismo se e só se todos os módulos indecomponíveis são de dimensão finita; (2) a categoria de módulos de uma álgebra de dimensão finita admite apenas um número finito de classes de torsão se e só se todas as classes de torsão são geradas por módulos de dimensão finita.

We introduce the notion of a cut cellular surface (CCS), being a surface with boundary, which is cut in a specified way to be represented in the plane, and is composed of 0-, 1- and 2-cells. We obtain invariants of CCS’s under Pachner-like moves on the cellular structure, by counting colourings of the 1-cells with elements of a finite group, subject to a “flat- ness” condition for each 2-cell. These invariants are also described in a TQFT setting, which is not the same as the usual 2-dimensional TQFT framework. We study the properties of functions which arise in this con- text, associated to the disk, the cylinder and the pants surface, and derive general properties of these functions from topology, including properties which come from invariance under the Hatcher-Thurston moves on pants decompositions.

Faz-se uma curta introdução à teoria dos sistemas lineares em grafos. Descreve-se o Teorema de Riemann–Roch num grafo. Estuda-se o conceito de gonalidade de um grafo e, em particular, calcula-se a gonalidade de um grafo bipartido completo.

Neste artigo descreve-se a actividade política conhecida de António Aniceto Monteiro e apontam-se as razões que o levaram a dois exílios.

A Regra Geral de Gonçalo Trancoso

Os leitores são convidados a enviar, para eventual publicação, soluções, comentários, propostas de problemas, etc. Essa correspondência deve ser enviada para a SPM, ao cuidado do editor desta secção. Há livros da Gradiva para sortear entre as soluções recebidas em cada número. Relembremos o problema do número anterior.

Notícias

Dada uma equação às diferenças linear e homogénea, de coeficientes constantes, começamos por construir uma função contínua interpolatória da respectiva solução.Tal função é posteriormente usada para definir uma função paramétrica, com valores em R2, que designamos por ‘retrato de fase’. Embora com algum abuso de linguagem, a definição que propomos para retrato de fase de uma equação às diferenças revela-se interessante para efeitos de estudo da dinâmica das soluções de equações às diferenças, tal como acontece com sistemas de equações diferenciais onde os denominados retratos de fase constituem uma técnica bem conhecida. Como ilustração, apresentam-se alguns exemplos de construção da referida função interpolatória bem como de retratos de fase associados a certas equações às diferenças de segunda ordem, em particular equações ligadas a sucessões do tipo Fibonacci.

Nesta breve continuação de um artigo anterior, relembramos a noção de uma superfície celular recortada (CCS), sendo uma superfície com fronteira, que é cortada de uma maneira especificada para ser representada no plano, e é composta de 0-, 1- e 2-células. Obtemos invariantes de CCS sob transformações semelhantes às de Pachner na estrutura celular, contando as colorações das 1- e 2-células com elementos de um 2-grupo finito, sujeito a uma condição de “planicidade falsa” para cada 2-célula. Essas invariantes, que estendem as invariantes de Yetter para esta classe de superfícies, também são descritas numa configuração de TQFT. Um resultado do artigo anterior relativo à fração de comutação de um grupo é generalizado para o contexto de 2-grupos.

The objective of this study is to analyze the determinants of the performance of Portuguese firms, which is very important for the efficient management of any organization. In this context, we consider a sample of non-financial firms listed on Euronext Lisbon between 2010 and 2015, and the panel data methodology is used. It is investigated whether some factors influence the firms’ performance, measuring this through the variables ROA, and Tobin’s Q. Overall, the results show that liquidity, leverage and market-to book influence firm performance. When we use Tobin's Q as a market measure, gross domestic product also appears as a variable explaining the performance of Portuguese companies.

The main goal of this study is to analyze the evolution of the magnitude and relevance of impairment losses on account receivables at Euronext Lisbon companies, given the recent financial crisis that has devastated our country. The study follows a longitudinal approach, based on the direct collection and content analysis of consolidated financial statements of the Euronext Lisbon listed companies, from 2005 to 2014.From the empirical study, we’ve concluded that the impairments on accounts receivable have a greater magnitude as well as greater relevance in the financial statements during crisis periods. We also concluded that the smaller companies recognize more impairments when compared to the biggest ones. We also found big bath practice indications, because it was mainly in the worst financial performance years that the recognition of impairment losses on receivables affected negatively the companies’ results.

This study presents a review of the literature related to comprehensive income, identifying opportunities for future research. For this purpose, is addressed the genesis of the concept, the evolution of its reporting and the empirical evidence about its usefulness. The concept of comprehensive income is presented in a historical perspective, discussing its importance as a performance indicator. The evolution of the comprehensive income reporting is described based on the rules issued by two accounting standard setters with worldwide influence: the FASB (Financial Accounting Standards Board) and IASB (International Accounting Standards Board). The usefulness of comprehensive income is addressed in empirical terms, based on its materiality, value relevance, predictive value and volatility.

This paper aims to identify the main determinants of leverage on Portuguese Small and Medium Enterprises (SME), as well as their behaviour to financial prosperity and recession. Applying the panel data methodology, we analyse a sample of 1,444 SME for the period between 2004 and 2012. The results show a positive relationship between tangibility of assets, the firms’ size, the growth rate of the asset and the business risk, and the level of indebtedness of the company. We find also a negative relationship between profitability, the tax advantages non-resultant from debt and the firms’ cycle of life, and the indebtedness level. Finally, the results show that the financial crisis influences negatively the levels of indebtedness of Portuguese companies, a result of rationing and enhancement of bank credit.

This study was motivated by the need to characterize scientific research on the "Mental Accounting" construct in the period 1900 to 2015. Mental Accounting is a branch of Accounting science that aims at guiding individuals to make financial decisions as successful enterprises. Discussion of this topic is usually based on the Perspective Theory. The main objective of this study is to describe and to analyze the progress of Accounting research in the Mental Accounting area in the mentioned period, based on an approach of content analysis. The results confirm the need for Accounting research in the Mental Accounting area, although in recent years a gradual progress and greater interest in it is seen. However, despite being considered a promising area, it is still little explored in the literature. We also note that the consumer and his purchasing decisions are priority issues, with focus on the main concept of Mental Accounting in this area, namely the "Loss Aversion" As a suggestion for future works we propose the investigation of other issues related to the Mental Accounting construct, with the aim of expanding the approaches to the issue.

The organizations that are within Social Economy, very State dependent have the financial perspective amongst their biggest issues. With the financial down flow, their survival is very much at stake. Several authors are in favor of applying concepts of relational marketing within nonprofit organizations (OSFL in Portuguese). In fact, they appear as a response to the need of fundraising and customer loyalty on behalf of the donor companies and long-term relationship. However, it is important to ascertain the level of the existing relationship between these two sectors as well as social responsibility induced motivations in companies that reside in Aveiro. This project is based on the actual literature and although the scarcity of the existing literature regarding relational marketing in nonprofit organizations, it aims to generate knowledge around this specific theme and answer to questions such as success factors in the dual relationship companies - nonprofit organizations the way that communication promotes fund raising and customer loyalty. Accordingly, this project fits the descriptive study case criteria, and for that matter the study will use a qualitative approach and a nonprobabilistic convenient sampling method using semi-structured interviews. The investigation evolves three studies with three samples, in a total of 24 respondents, namely 8 from nonprofit organizations and 16 companies. The main results of this study are: Study 1: nonprofit organizations appeal more frequently to small and medium companies because they are more easily reached and closer to the community; the supplying companies of the nonprofit organizations are the first to be contacted by these; as well as poor developed relationships and communication with the companies Study 2: Companies tend to collaborate punctual and informally and they do so in a philanthropic motivational way, valuing non-material benefits. In the case of small and medium companies, personal contacts assume special importance in the placement of donations. Study 3: Credibility, corporate imaging and mission and values alignment constitute relational facts of success.

Adwords allows companies to deliver relevant ads to consumers who are already on the search stage of the buying funnel. As the use of search engines increases and the search costs decrease, it is becoming increasingly mandatory for companies to use this technology. The goal of this research is to understand the factors that contribute to the success of an Adwords campaign for small and medium enterprises by undergoing three research phases. During the first phase we did a secondary research to summarize the reasons to adopt this type of advertising, its benefits, and the best course of action both strategically and in terms of measurement to small and medium enterprises. On the second phase we did a qualitative research through interviews to 8 Adwords managers in order to understand which factors influence their management decisions in a Adwords campaign. In the third phase we did a quantitative analysis based on a questionnaire inquiry answered by 144 Adwords campaign managers. We concluded that many Adwords managers lack theoretical knowledge in this type of advertising, that theoretical knowledge affects management decisions and the results of an Adwords campaign and that not all strategies defined in specialized literature about the matter have the expected impact on the results of an Adwords campaign. At the end of this dissertation we present the main conclusions, limitations and recommendations for further studies.

Auditors, in order to increase the effectiveness and efficiency of audit procedures and, consequently, their performance, had to adopt certain technological tools to support auditing. They are able to monitor the volume, variety and complexity of the data to be audited, and the speed with which they are produced, as a result of the dematerialization of the processes and the digital transformation that today's companies face. The main objective of this dissertation is to highlight the changes in the auditing procedures caused by the introduction of the technological tools to support the Audit, namely in the effectiveness and efficiency of the procedures. In addition, the work aims to also understand the tasks in which these tools are used, identifying the advantages of its adoption and exploring its current use by auditors. In order to respond to these objectives, a questionnaire survey was conducted to the Official Chartered Accountants (ROC) of Portugal. The main conclusions show that there is a great variety of technological tools used by ROCs in Portugal, the most used being Microsoft Excel. This tool facilitates the analysis work and preparation of audit procedures. It is also concluded that ROCs are generally satisfied with the contribution of the use of these tools to the effectiveness and efficiency of audit procedures, and this is more meaningful in the procedures "Risk Identification and Assessment", "Audit Work Papers" And "Data Analysis". They also consider that the tools they use are prepared to keep pace with the new trends and challenges imposed on the Audit.

O nº15 da série IV da Revista Estudos apresenta várias temáticas que, situadas no âmbito das Finanças e das Finanças Empresariais, da Contabilidade Mental e, nomeadamente, do comportamento do consumidor, realçam a natureza multidisciplinar do conhecimento pedagógico e científico que nos comprometemos a divulgar – aquele que se tem vindo a desenvolver dentro e fora dos muros do ISCA e da Universidade de Aveiro. (...)