Equivalence between supersymmetric self-dual and Maxwell-Chern-Simons models coupled to a matter spinor superfield

We study the duality of the supersymmetric self-dual and Maxwell-Chern-Simons theories coupled to a fermionic matter superfield, using a master action. This approach evades the difficulties inherent to the quartic couplings that appear when matter is represented by a scalar superfield. The price is that the spinorial matter superfield represents a unusual supersymmetric multiplet, whose main physical properties we also discuss. (C) 2009 Elsevier B.V. All rights reserved.

Terror Management Theory and Belief in an Afterlife

Research has shown that belief in an afterlife, a form of symbolic immortality, can alleviate the negative emotions associated with one’s mortality (Deschesne et. al, 2003). We found this aspect of TMT particularly interesting, but lacking any substantial research. Therefore, we set out to determine if belief in an afterlife could diminish the effects of mortality salience. As far as we know, our study is the first to use a pre-screening process to determine participants’ prior beliefs. One prediction might be that those who believe in an afterlife will be less affected by the effects of mortality salience.

Bias and size effects of price-comparison search engines : theory and experimental evidence

We analyze the impact on consumer prices of the size and bias of price comparison search engines. In the context of a model related to Burdett and Judd (1983) and Varian (1980), we develop and test experimentally several theoretical predictions. The experimental results confirm the model’s predictions regarding the impact of the number of firms, and the type of bias of the search engine, but reject the model’s predictions regarding changes in the size of the index. The explanatory power of an econometric model for the price distributions is significantly improved when variables accounting for risk attitudes are introduced.

Existence and asymptotic behaviour for the parabolic-parabolic Keller-Segel system with singular data

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Short-wave instabilities in the Benjamin-Bona-Mahoney-Peregrine equation: theory and numerics

In this paper we discuss the nonlinear propagation of waves of short wavelength in dispersive systems. We propose a family of equations that is likely to describe the asymptotic behaviour of a large class of systems. We then restrict our attention to the analysis of the simplest nonlinear short-wave dynamics given by U-0 xi tau, = U-0 - 3(U-0)(2). We integrate numerically this equation for periodic and non-periodic boundary conditions, and we find that short waves may exist only if the amplitude of the initial profile is not too large.

QUARK MEAN-FIELD THEORY AND CONSISTENCY WITH NUCLEAR-MATTER

1/N(c) expansion in QCD (with N(c) the number of colors) suggests using a potential from meson sector (e.g., Richardson) for baryons. For light quarks a sigma-field has to be introduced to ensure chiral symmetry breaking (chi-SB). It is found that nuclear matter properties can be used to pin down the chi-SB modeling. All masses, M(N), m-sigma, m-omega, are found to scale with density. The equations are solved self-consistently.

Quantum equivalence between the self-dual and the Maxwell-Chern-Simons models nonlinearly coupled to U(1) scalar fields

The use of master actions to prove duality at quantum level becomes cumbersome if one of the dual fields interacts nonlinearly with other fields. This is the case of the theory considered here consisting of U(1) scalar fields coupled to a self-dual field through a linear and a quadratic term in the self-dual field. Integrating perturbatively over the scalar fields and deriving effective actions for the self-dual and the gauge field we are able to consistently neglect awkward extra terms generated via master action and establish quantum duality up to cubic terms in the coupling constant. The duality holds for the partition function and some correlation functions. The absence of ghosts imposes restrictions on the coupling with the scalar fields.

Note on the nonuniqueness of the massive Fierz-Pauli theory and spectator fields

It is possible to show that there are three independent families of models describing a massive spin-2 particle via a rank-2 tensor. One of them contains the massive Fierz-Pauli model, the only case described by a symmetric tensor. The three families have different local symmetries in the massless limit and can not be interconnected by any local field redefinition. We show here, however, that they can be related with the help of a decoupled and nondynamic (spectator) field. The spectator field may be either an antisymmetric tensor B μν=-Bνμ, a vector Aμ or a scalar field φ, corresponding to each of the three families. The addition of the extra field allows us to formulate master actions which interpolate between the symmetric Fierz-Pauli theory and the other models. We argue that massive gravity models based on the Fierz-Pauli theory are not expected to be equivalent to possible local self-interacting theories built up on top of the two new families of massive spin-2 models. The approach used here may be useful to investigate dual (nonsymmetric) formulations of higher-spin particles. © 2013 American Physical Society.

Some aspects of self-duality and generalised BPS theories

If a scalar eld theory in (1+1) dimensions possesses soliton solutions obeying rst order BPS equations, then, in general, it is possible to nd an in nite number of related eld theories with BPS solitons which obey closely related BPS equations. We point out that this fact may be understood as a simple consequence of an appropriately generalised notion of self-duality. We show that this self-duality framework enables us to generalize to higher dimensions the construction of new solitons from already known solutions. By performing simple eld transformations our procedure allows us to relate solitons with di erent topological properties. We present several interesting examples of such solitons in two and three dimensions.

Quantum Correlations in Field Theory and Integrable Systems

In this thesis we will investigate some properties of one-dimensional quantum systems. From a theoretical point of view quantum models in one dimension are particularly interesting because they are strongly interacting, since particles cannot avoid each other in their motion, and you we can never ignore collisions. Yet, integrable models often generate new and non-trivial solutions, which could not be found perturbatively. In this dissertation we shall focus on two important aspects of integrable one- dimensional models: Their entanglement properties at equilibrium and their dynamical correlators after a quantum quench. The first part of the thesis will be therefore devoted to the study of the entanglement entropy in one- dimensional integrable systems, with a special focus on the XYZ spin-1/2 chain, which, in addition to being integrable, is also an interacting model. We will derive its Renyi entropies in the thermodynamic limit and its behaviour in different phases and for different values of the mass-gap will be analysed. In the second part of the thesis we will instead study the dynamics of correlators after a quantum quench , which represent a powerful tool to measure how perturbations and signals propagate through a quantum chain. The emphasis will be on the Transverse Field Ising Chain and the O(3) non-linear sigma model, which will be both studied by means of a semi-classical approach. Moreover in the last chapter we will demonstrate a general result about the dynamics of correlation functions of local observables after a quantum quench in integrable systems. In particular we will show that if there are not long-range interactions in the final Hamiltonian, then the dynamics of the model (non equal- time correlations) is described by the same statistical ensemble that describes its statical properties (equal-time correlations).

The Role of the Family in Shaping Self-Concept and Cognitive Styles in Hungary

The project studied the perception of parenting styles and their relation to self-development, cognitive styles, and individualisation in adolescence. Typical parenting styles of mothers and fathers were studied in five different maternal and paternal parenting backgrounds: warm authoritarian, warm democratic, cold neglectful, cold authoritarian, and neutral. Perception of different styles of parenting (for fathers: authority, 'maintaining distance' behaviour, reciprocity, enhancing self-reliance; for mothers: authority, unpredictable behaviour, mutual trust, achievement orientation, and enhancing self-reliance) were analysed in each group using the newly developed Hungarian Parenting Questionnaire (Sallay & Munnich, 1999). This questionnaire has a theoretical basis in the ideas of Harvey (1966, 1967), where the socialisation process is combined with self-development. This categorisation of paternal and maternal parenting backgrounds enabled Sallay to explore and describe in detail how diverse parenting styles contribute to self-development, the development of cognitive complexity, and individualisation. The results show that diverse parenting by mothers and fathers produces differing impacts in nuclear and divorced families and for males and females, taking into consideration such self-components as physical, active, psychological (capabilities, personality, emotions, roles, preferences), social and reflective selves. Cognitive self-complexity varied according to parenting styles and genders: maternal and paternal parenting proved to have the most significant impact on self-complexity in a warm, democratic family. With respect to individualistic tendencies, adolescent boys were most individualistic in a cold, neglectful paternal background in nuclear families as compared to other paternal and maternal family backgrounds and to females.

The Influence of Self-efficacy and Compensatory Health Behavior in Bicycle Helmet Use

Individuals show compensatory health behavior (e.g. safer cycling without helmet) to compensate for risky behavior. Compensatory health behavior is facilitated by high self-efficacy. A total of 134 cyclists with different helmet wearing frequencies (occasionally (OH) or never helmet (NH)) were asked to fill out a questionnaire on their compensatory health behavior when cycling without a helmet and on their general self-efficacy. An interaction between self-efficacy and use of a helmet on compensatory health behavior was found. OH-users with high self-efficacy showed more compensatory health behavior than OH-users with low self-efficacy. This effect was not present in NH-users. We assume that OH-users engage in compensatory health behavior, whereas NH-users remain unprotected by behavioral adaptation. These persons are vulnerable and may require specific attention in preventive actions.

Principal-Agent Theory and the World Trade Organization: Complex Agency and ‘Missing Delegation’

This paper analyses the World Trade Organization within a principal-agent framework. The concept of complex agency is introduced to focus on the variety of actors that comprise an international organization. Special attention is paid to the relationship between contracting parties’ representatives and the Secretariat. In the empirical part, the paper analyses the role of the Secretariat in assisting negotiations and presents evidence of declining influence. It is shown how principal-agent theory can contribute to addressing this ‘puzzle of missing delegation’. The paper concludes with a cautionary note as to the ‘location’ of international organizations’ emerging pathologies and calls for additional research to address the relationship between material and social sources to explain behaviour of the key actors within the complex agency.