Phase diagram of two dimensional electron gas in a perpendicular magnetic field around Landau level filling factors \nu=1 and \nu=3

The measured melting curve $T_{m}(\nu)$ between the crystal and liquid phases is analyzed using thermodynamics to extract the change of magnetization $\Delta M$ as a function of the Landau level filling factor \ $\nu,$ near $\nu=1$. \ An explanation of $\Delta M$($\nu)$ is proposed \ in terms of Skyrmions. \ Near $\nu=3$, a Wigner crystal is the most probable solid phase, experiments excluding Skyrmions.Comment: 5 pages, 4 figure

Anlaytic mean-field Hall crystal solution at nu=1/3: composite fermion like sub-bands and correlation effects

An analytic solution of the Hartree-Fock problem for a 2DEG at filling 1/3 and half an electron per unit cell is presented. The Coulomb interaction dynamically breaks the first Landau level in three narrow sub-bands, one of which is fully occupied and the other empty, as in the composite fermion model. The localized orbitals associated to the Bloch like single electron wavefunctions are nearly static, resembling the angular momentum eigenstates within a Landau level for non-interacting fermions. Strong correlations are expected owing to the large charge density overlap between neighboring plaquettes. A numerical evaluation brings the cohesive energy close to that of the best present day models. It is also found that correlations are long range, requiring over 50 particles spread over a finite sample to approach convergence. Since presently allowed exact calculations are far from this number, the question of how relevant the considered wave-function is for the description of the ground state of the 2DEG system remains open.Comment: 24 pages, 4 figures, content exposed in the: Symposium Quantum Hall Effect: "Past, Present and Future", Sttutgart, Germany, 2-5 July 2003 and in the Third Stig Lundquist Conference on Advancing Frontiers of Condensed Matter Physics 11-15 August 2003, ICTP, Trieste Ital

Interaction and imitation in a world of Quixotes and Sanchos

Producción CientíficaThis paper studies a two-population evolutionary game in a new setting in between a symmetric and an asymmetric evolutionary model. It distinguishes two types of agents: Sanchos, whose payoffs are defined by a prisoner’s dilemma game, and Quixotes, whose payoffs are defined by a snowdrift game. Considering an imitative revision protocol, a revising agent is paired with someone from his own population or the other population. When matched, they observe payoffs, but not identities. Thus, agents in one population interact and imitate agents from their own population and from the other population. In this setting we prove that a unique mixed-strategy asymptotically stable fixed point of the evolutionary dynamics exists. Taking as an example the compliance with social norms, and depending on the parameters, two type of equilibrium are possible, one with full compliance among Quixotes and partial compliance among Sanchos, or another with partial compliance among Quixotes and defection among Sanchos. In the former type, Sanchos comply above their Nash equilibrium (as they imitate compliant Quixotes). In the latter type, Quixotes comply below their Nash equilibrium (as they imitate defecting Sanchos)

The Hartree-Fock state for the 2DEG at filling factor 1/2 revisited: analytic solution, dynamics and correlation energy

The CDW Hartree-Fock state at half filling and half electron per unit cell is examined. Firstly, an exact solution in terms of Bloch-like states is presented. Using this solution we discuss the dynamics near half filling and show the mass to diverge logarithmically as this filling is approached. We also show how a uniform density state may be constructed from a linear combination of two degenerate solutions. Finally we show the second order correction to the energy to be an order of magnitude larger than that for competing CDW solutions with one electron per unit cell.Comment: 14 pages, no figures, extended acknowledgements, two new references include

Compliance with Social Norms as an Evolutionary Stable Equilibrium

Producción CientíficaThis paper studies a two-population evolutionary game in a new setting in between a symmetric and an asymmetric evolutionary model. It distinguishes two types of agents: Sanchos, whose payoffs are defined by a prisoner’s dilemma game, and Quixotes, whose payoffs are defined by a snowdrift game. Considering an imita- tive revision protocol, a revising agent is paired with someone from his own popula- tion or the other population. When matched, they observe payoffs, but not identities. Thus, agents in one population interact and imitate agents from their own population and from the other population. In this setting we prove that a unique mixed-strategy asymptotically stable fixed point of the evolutionary dynamics exists. Taking as an example the compliance with social norms, and depending on the parameters, two type of equilibrium are possible, one with full compliance among Quixotes and par- tial compliance among Sanchos, or another with partial compliance among Quixotes and defection among Sanchos. In the former type, Sanchos comply above their Nash equilibrium (as they imitate compliant Quixotes). In the latter type, Quixotes comply below their Nash equilibrium (as they imitate defecting Sanchos).This study was funded by the Spanish Government (projects ECO2014- 52343-P and ECO2017-82227-P), as well as financial aid from Junta de Castilla y León (projects VA024P17 and VA105G18), co-financed by FEDER funds

Relação entre transporte aéreo e turismo em Moçambique

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2012.O desenvolvimento do mercado aéreo iniciado nos Estados Unidos e mais tarde estendido para a Europa impulsionou a projeção internacional da aviação civil e do turismo, fazendo com que os destinos turísticos longínquos dos principais centros emissores fossem cada vez mais difundidos e procurados. Em Moçambique as dinâmicas do transporte aéreo e do turismo têm sido objeto de análise, primordialmente pelo setor privado que, busca promover mecanismos para que o transporte aéreo tenha, cada vez mais, um impacto positivo na atividade turística nacional. Esta situação vem sendo observada desde a criação do Ministério do Turismo no ano 2000. É nesta perspectiva que o presente trabalho tem como objetivo geral verificar se o transporte aéreo impulsiona ou representa um obstáculo ao turismo Moçambique. Para o efeito, a metodologia adotada incluiu análise de dados secundários sobre o contexto – antecedentes, marcos legais, transformações e atualidades sobre turismo e transporte aéreo em Moçambique; coleta de informações junto a informantes-chave de ambos os setores por meio de formulário aplicado pelo autor; o uso das ferramentas Análise SWOT para captar a percepção dos informantes sobre a relação entre transporte aéreo e turismo e Escala de Likert para analisar a opinião dos informantes em relação aos princípios balizadores de regulação de transporte aéreo no contexto nacional. Embora haja uma evolução normativa, a análise dos dados evidencia que a relação entre os setores de transporte aéreo e turismo em Moçambique ainda é descrita, com maior peso, por pontos fracos e que, em função da falta de coordenação multisetorial, do protecionismo à companhia aérea de bandeira nacional e da falta de cumprimento da maioria dos princípios balizadores de regulação, o transporte aéreo representa um obstáculo ao desenvolvimento do turismo. _______________________________________________________________________________________ ABSTRACTThe development of the airline industry started in the United States and later extended to Europe boosted the projection of international civil aviation and tourism, making tourism destinations far from major centers issuers were even more pervasive and demand. In Mozambique the dynamics of air transport and tourism have been the object of analysis, primarily by the private sector that seeks to promote mechanisms for air transport has, increasingly, a positive impact on domestic tourism. This situation has been observed since the creation of the Ministry of Tourism in 2000. From this perspective, this study aims to verify that the general aviation drives or represent an obstacle to tourism Mozambique. For this purpose, the methodology included analysis of secondary data about the context - history, legal, processing, and updates on tourism and air transport in Mozambique, collecting information from key informants from both sectors through questionnaire applied by author, using the tools SWOT analysis to capture the informants 'perceptions about the relationship between air transport and tourism and Likert Scale to assess the informants' opinion a guide to the principles of regulation of air transport in the national context. Although there are normative development, data analysis shows that the relationship between the sectors of air transport and tourism in Mozambique is still described, with greater weight, for weaknesses and that, due to the lack of coordinated multi-sectoral protectionism to the company national flag carrier and the lack of enforcement of a guide for most of the principles of regulation, air transport represents an obstacle to tourism development

Optimal pollution standards and non-compliance in a dynamic framework

In this paper we present a Stackelberg differential game to study the dynamic interaction between a polluting firm and a regulator who sets pollution limits overtime. At each time, the firm settles emissions taking into account the fine for non-compliance, and balances current costs of investments in a capital stock which allows for future emission reductions. We show that the optimal effective pollution limit path, which is the pollution level above which the fine is truly imposed, decreases overtime, inducing a rise in capital stock and a decrease in both emissions and the level of non-compliance. If the effective pollution limit coincides with the pollution limit set by the regulator, we generally find a bounded value of the severity of the fine that maximizes social welfare. If the effective pollution limit is larger than the pollution limit set by the regulator due to fine discounts in exchange for firm’s investment in capital, the effect of a more severe fine depends on the magnitude of this discount. In the limiting scenario with a sufficiently large severity of the fine, emissions coincide with the effective pollution limit and no penalties are levied, since the firm shows adequate adaptation progress through capital investment