A general method for finding extremal states of Hamiltonian dynamical systems, with applications to perfect fluids

In addition to the Hamiltonian functional itself, non-canonical Hamiltonian dynamical systems generally possess integral invariants known as ‘Casimir functionals’. In the case of the Euler equations for a perfect fluid, the Casimir functionals correspond to the vortex topology, whose invariance derives from the particle-relabelling symmetry of the underlying Lagrangian equations of motion. In a recent paper, Vallis, Carnevale & Young (1989) have presented algorithms for finding steady states of the Euler equations that represent extrema of energy subject to given vortex topology, and are therefore stable. The purpose of this note is to point out a very general method for modifying any Hamiltonian dynamical system into an algorithm that is analogous to those of Vallis etal. in that it will systematically increase or decrease the energy of the system while preserving all of the Casimir invariants. By incorporating momentum into the extremization procedure, the algorithm is able to find steadily-translating as well as steady stable states. The method is applied to a variety of perfect-fluid systems, including Euler flow as well as compressible and incompressible stratified flow.

Surface chemistry of alanine on Cu{111}: Adsorption geometry and temperature dependence

Adsorption of l-alanine on the Cu{111} single crystal surface was investigated as a model system for interactions between small chiral modifier molecules and close-packed metal surfaces. Synchrotron-based X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy are used to determine the chemical state, bond coordination and out-of-plane orientation of the molecule on the surface. Alanine adsorbs in its anionic form at room temperature, whilst at low temperature the overlayer consists of anionic and zwitterionic molecules. NEXAFS spectra exhibit a strong angular dependence of the π ⁎ resonance associated with the carboxylate group, which allows determining the tilt angle of this group with respect to the surface plane (48° ± 2°) at room temperature. Low-energy electron diffraction (LEED) shows a p(2√13x2√13)R13° superstructure with only one domain, which breaks the mirror symmetry of the substrate and, thus, induces global chirality to the surface. Temperature-programmed XPS (TP-XPS) and temperature-programmed desorption (TPD) experiments indicate that the zwitterionic form converts into the anionic species (alaninate) at 293 K. The latter desorbs/decomposes between 435 K and 445 K.

Crystal growth and magnetic properties of tin selenide-doped europium Sn(1-x)Eu(x)Se

The growth and magnetic properties of Tin Selenide (SnSe) doped with Eu(2+) Sn(1-x)Eu(x)Se (x=2.5%) were investigated. Q-band (34 GHz) electron paramagnetic resonance measurements show that the site symmetry of Eu(2+) at 4.2 K is orthorhombic and the Lande factor was determined to be g=1.99 +/- 0.01. The exchange coupling between nearest-neighbor (NN) Eu(2+) ions was estimated from magnetization and magnetic-susceptibility measurements using a model that takes into account the magnetic contributions of single ions, pairs and triplets. The exchange interaction between Eu(2+) nearest neighbors was found to be antiferromagnetic with an estimated average value of J(p)/k(B) =-0.18 +/- 0.03 K. (C) 2009 Elsevier B.V. All rights reserved.

Magnetic fabric and zircon U-Pb geochronology of the Itaoca pluton: Implications for the Brasiliano deformation of the southern Ribeira Belt (SE Brazil)

The Itaoca pluton consists of porphyritic monzogranite that intruded the upper crust into low-grade metasedimentary rocks of the Apiai Dornain (Ribeira Belt). Anisotropy of magnetic susceptibility and zircon U-Pb (Shrimp) geochronology were combined to determine pluton emplacement mechanisms and its chronology relative to the collision structures of the Paranapiacaba (Brasiliano II) orogenic system. Magnetic susceptibility ranges between 4 and 38 x 10(-3) SI, and thermomagnetic measurements indicate multidomain magnetite is the main carrier of anisotropy. The pluton shows an ""onion-skin"" structure roughly elongated to the northeast with its hinge zone including kilometer-wide roof-pendants. Magnetic lineations are variable in orientation in consistency with the dominant oblate symmetry of the magnetic fabric. A distinct NE-trending point-maxima, however, indicates the mean lineation is parallel to the stretching direction of the transpressive deformation that affected the regional host rocks. Prismatic zircon from the monzogranite, both in the core and in the finely-zoned margins, yielded an age of 623 +/- 10 Ma. These results suggest the magmatic fabric recorded the earlier strain increments of the regional shear deformation. It may correspond to the transition from continental arc to collision tectonics of the southern Ribeira Belt. (C) 2008 Elsevier Ltd. All rights reserved.

The impact of foreign direct investment and openness on Vietnamese economy

This thesis examines the impact of foreign direct investment (FDI) on Vietnamese economy based on Partial Adjustment Model and time series data from 1976 to 2004. FDI is shown to have not only short run but also long run effect on gross domestic product (GDP) of Vietnam. However, elasticity of GDP with respect to FDI is small and it will take many years to fully manifest itself. The impact of trade openness on GDP has also been examined and it is shown to be stronger than that of FDI. The paper offers a number of explanations and discusses briefly suggestions in order to increase the contribution of FDI to Vietnam’s economic development.

The impact of big-boxes on local retail : What happens when IKEA comes to town?

The development of large discount retailers, or big-boxes as they are sometimes referred to, are often subject to heated debate and their entry on a market is greeted with either great enthusiasm or dread. For instance, the world’s largest retailer Wal-Mart (Forbes 2014) has a number of anti- and pro-groups dedicated to its being and the event of a Wal-Mart entry tends to be met with protests and campaigns (Decamme 2013) but also welcomed by, for instance, consumers (Davis & DeBonis 2013). Also in Sweden, the entry of a big box is a hot topic and before IKEA’s opening i Borlänge 2013, the first in Sweden in more than five years, great expectations were mixed with worry (Västerbottens-Kuriren 2011).The presence of large scale discount retailers is not, however, a novel phenomenon but a part of a long-term change in retailing that has taken place globally over the past couple of decades (Taylor & Smalling, 2005). As noted by Dawson (2006), the trend in Europe has over the past few decades gone towards an increasing concentration of large firms along with a decrease of smaller firms.This trend is also detectable in the Swedish retail industry. Over the past decade, the retailing industry in Sweden has increased by around 190 Billion SEK, and its share of GDP has risen from 2,7% to 2,9%, while the number of employees have increased from 200 000 to 250 000 (HUI 2013). This growth, however, has not been distributed evenly but rather it has been oriented mainly towards out-of-town retail clusters. Parallel to this development, the number of large retailers has risen at the expense of market shares of smaller independent firms (Rämme et al 2010). Thereby, the presence of large scale retailers is simply part of a changing retail landscape.The effects of this development, where large scale retailing agents relocate shopping to out-of-town shopping areas, have been heavily debated. On the one hand, the big-boxes are accused of displacing independent small retail businesses in the city-centers and the residential areas, resulting in, to some extent, reduced employment opportunities and less availability for the consumers - especially the elderly (Ljungberg et al 2006). In addition, as access to shopping now tends to require some sort of a motorized vehicle, environmental aspects to the discussion have emerged. Ultimately these types of concerns have resulted in calls for regulations against this development (Olsson 2010). On the other hand, the proponents of the new shopping landscape argue that this evolution implies productivity gains, the benefits of lower prices and an increased variety of products (Maican & Orth 2012). Moreover it is argued that it leads to, for instance, better services (such as longer opening hours) and a creative destruction transformation pressure on retailers, which brings about a renewal of city-centerIIretail and services, increasing their attractivity (Bergström 2010). The belief in benefits of a big box entry can be exemplified by the attractivity of IKEA, and the fact that municipalities are prepared to commit to expenses amounting up to hundreds of millions in order to attract the entry of this big-box. Borlänge municipality, for instance, agreed to expenses of about 350 million SEK in order to secure the entry of IKEA, which opened in 2013 (Blomgren 2009).Against this backdrop, the overall effects of large discount retailers become important: Are the economic benefits enough to warrant subsidies or are there, on the contrary, some very compelling grounds for regulations against these types of establishments? In other words; how is overall retail in a region where a store like IKEA enters affected? And how are local retail firms affected?In order to answer these questions, the purpose of this thesis is to study how entry of a big-box retailer affects the entry region. The object of this study is IKEA - one of the world’s largest retailers, with 345 stores, active in over 40 countries and with profits of about 3.3 billion (IKEA 2013; IKEA 2014). By studying the effects of IKEA-entry, both on an aggregated level and on firm level, this thesis intends to find indications of how large discount retail establishments in general can be expected to affect the economic development both in a region overall, but also on the local firm level, something which is of interest to both policymakers as well as the retailing industry in general.The first paper examines the effects of IKEA on retail revenues and employment in the municipalities that IKEA chose to enter between 2000 and 2011; Gothenburg, Haparanda, Kalmar and Karlstad. By means of a matching method we first identify non-entry municipalities that have a similar probability of IKEA entry as the true entry municipalities. Then, using these non-entry municipalities as a control group, the causal effects of IKEA entry can be estimated using a treatment-control approach. We also extend the analysis to examine the spatial impact of IKEA by estimating the effects on retail in neighboring municipalities. It is found that a new IKEA store increases revenues in durable goods trade with 20% in the entry municipality and the number of employees with 17%. Only small, and in most cases statistically insignificant, negative effects were found in neighboring municipalities.It appears that there is a positive net effect on durables retail sales and employment in the entry municipality. However, the analysis is based on data on an aggregated municipality level and thereby it remains unclear if and how the effects vary within the entry municipalities. In addition, the data used in the first study includes the sales and employment of IKEA itself, which could account for the majority of the increases in employment and retail. Thereby the potential spillover effects on incumbent retailers in the entry municipalities cannot be discerned in the first study.IIITo examine effects of IKEA entry on incumbent retail firms, the second paper in this thesis analyses how IKEA entry affects the revenues and employment of local retail firms in three municipalities; Haparanda, Kalmar and Karlstad, which experienced entry by IKEA between 2000 and 2010. In this second study, we exclude Gothenburg due to the fact that big-box entry appears to have weaker effects in metropolitan areas (as indicated by Artz & Stone 2006). By excluding Gothenburg we aim to reduce the geographical heterogeneity in our study. We obtain control municipalities that are as similar as possible to the three entry municipalities using the same method as in the previous study, but including a slightly different set of variables in the selection equation. Using similar retail firms in the control municipalities as our comparison group, we estimate the impact of IKEA entry on revenues and employment for retail firms located at varying distances from the IKEA entry site.The results generated in this study imply that entry by IKEA increases revenues in incumbent retail firms by, on average, 11% in the entry municipalities. In addition, we do not find any significant impact on retail revenues in the city centers of the entry municipalities. However, we do find that retail firms within 1 km of the IKEA experience increases in revenues of about 26%, which indicates large spillover effects in the area nearby the entry site. As expected, this impact decreases as we expand the buffer zone: firms located between 0-2 km experiences a 14% increase and firms in 2-5 km experiences an increase of 10%. We do not find any significant impacts on retail employment.

Vector Theory of Spontaneous Lorentz Violation

Classical electromagnetism predicts two massless propagating modes, which are known as the two polarizations of the photon. On the other hand, if the Lorentz symmetry of classical electromagnetism is spontaneously broken, the new theory will still have two massless Nambu-Goldstone modes resembling the photon. If the Lorentz symmetry is broken by a bumblebee potential that allows for excitations out of the minimum, then massive modes arise. Furthermore, in curved spacetime, such massive modes will be created through a process other than the usual Higgs mechanism because of the dependence of the bumblebee potential on both the vector field and the metric tensor. Also, it is found that these massive modes do not propagate due to the extra constraints.

Public debt indexation and denomination, the case of Brazil: a comment

In this work I analyze the model proposed by Goldfajn (2000) to study the choice of the denomination of the public debt. The main purpose of the analysis is pointing out possible reasons why new empirical evidence provided by Bevilaqua, Garcia and Nechio (2004), regarding a more recent time period, Önds a lower empirical support to the model. I also provide a measure of the overestimation of the welfare gains of hedging the debt led by the simpliÖed time frame of the model. Assuming a time-preference parameter of 0.9, for instance, welfare gains associated with a hedge to the debt that reduces to a half a once-for-all 20%-of-GDP shock to government spending run around 1.43% of GDP under the no-tax-smoothing structure of the model. Under a Ramsey allocation, though, welfare gains amount to just around 0.05% of GDP.

What happens after the central bank of Brazil increases the target interbank rate by 1%?

I start presenting an explicit solution to Taylorís (2001) model, in order to illustrate the link between the target interest rate and the overnight interest rate prevailing in the economy. Next, I use Vector Auto Regressions to shed some light on the evolution of key macroeconomic variables after the Central Bank of Brazil increases the target interest rate by 1%. Point estimates show a four-year accumulated output loss ranging from 0:04% (whole sample, 1980 : 1-2004 : 2; quarterly data) to 0:25% (Post-Real data only) with a Örst-year peak output response between 0:04% and 1:0%; respectively. Prices decline between 2% and 4% in a 4-year horizon. The accumulated output response is found to be between 3:5 and 6 times higher after the Real Plan than when the whole sample is considered. The 95% confidence bands obtained using bias-corrected bootstrap always include the null output response when the whole sample is used, but not when the data is restricted to the Post-Real period. Innovations to interest rates explain between 4:9% (whole sample) and 9:2% (post-Real sample) of the forecast error of GDP.

The effect of social security, demography and technology on retirement

This article investigates the causes in the reduction of labor force participation of the old. We argue that the changes in social security policy, in technology and in demography may account for most of the changes in retirement over the second part of the last century in the U.S. economy. We develop a dynamic general equilibrium model with endogenous retirement that embeds social security legislation. The model is able to match very closely the increase in the retirement rate of males aged 65 and older. It also quanti es the isolated impact on retirement and on the solvency of the social security system of the di¤erent factors. The model suggests that technological and demographic changes had a strong in uence on retirement, so that it would have increased signi cantly even if the social security rules had not changed. However, as the latter became much more generous in the past, changes in social security policy can account not only for a sizeable part of the expansion of retirement, but also for the most of the observed increase in the social security expenses as a share of GDP.

The effect of social security, demography and technology on retirement

This article investigates the causes in the reduction of labor force participation of the old. We argue that the changes in social security policy, in technology and in demography may account for most of the changes in retirement over the second part of the last century in the U.S. economy. We develop a dynamic general equilibrium model with endogenous retirement that embeds social security legislation. The model is able to match very closely the increase in the retirement rate of males aged 65 and older. It also quanti es the isolated impact on retirement and on the solvency of the social security system of the di¤erent factors. The model suggests that technological and demographic changes had a strong in uence on retirement, so that it would have increased signi cantly even if the social security rules had not changed. However, as the latter became much more generous in the past, changes in social security policy can account not only for a sizeable part of the expansion of retirement, but also for the most of the observed increase in the social security expenses as a share of GDP.

What happens after the Central Bank of Brazil increases the target interbank rate by 1%?

In this paper I use Taylor's (2001) model and Vector Auto Regressions to shed some light on the evolution of some key macroeconomic variables after the Central Bank of Brazil, through the COPOM, increases the target interest rate by 1%. From a quantitative perspective, the best estimate from the empírical analysis, obtained with a 1994 : 2 - 2004 : 2 subsample of the data, is that GDP goes through an accumulated decline, over the next four years, around 0.08%. Innovations to interest rates explain around 9.2% of the forecast erro r of GDP.

Comments on public debt indexation and denomination, the case of Brazil

In this work I analyze the model proposed by Goldfajn (2000) to study the choice of the denomination of the public debt. Some potential shortcmomings of the mo dei in explaining the data are discussed. Measures of the overestimation of the welfare gains of reducing distortions from taxation, under the model's simplified time frame, are also provided. Assuming a time-preference parameter of 0.9, for instance, welfare gains associated with a hedge to the debt that reduces to half a once-for-all 20o/o-of-GDP shock to governemnt spending run around 1.43% of GDP under the no-tax-smoothing structure of the model. Under a Ramsey allocation, though, welfare gains amount to just around 0.05% of GDP.

A restatement of the welafare costs of inflation. The wast of scarce resources in the manufacturing , banking and household sectors

Lucas (2000) estimates that the US welfare costs of inflation are around 1% of GDP. This measurement is consistent with a speci…c distorting channel in terms of the Bailey triangle under the demand for monetary base schedule (outside money): the displacement of resources from the production of consumption goods to the household transaction time à la Baumol. Here, we consider also several new types of distortions in the manufacturing and banking industries. Our new evidences show that both banks and firms demand special occupational employments to avoid the inflation tax. We de…ne the concept of ”the foat labor”: The occupational employments that are aflected by the in‡ation rates. More administrative workers are hired relatively to the bluecollar workers for producing consumption goods. This new phenomenon makes the manufacturing industry more roundabout. To take into account this new stylized fact and others, we redo at same time both ”The model 5: A Banking Sector -2” formulated by Lucas (1993) and ”The Competitive Banking System” proposed by Yoshino (1993). This modelling allows us to characterize better the new types of misallocations. We …nd that the maximum value of the resources wasted by the US economy happened in the years 1980-81, after the 2nd oil shock. In these years, we estimate the excess resources that are allocated for every speci…c distorting channel: i) The US commercial banks spent additional resources of around 2% of GDP; ii) For the purpose of the firm foating time were used between 2.4% and 4.1% of GDP); and iii) For the household transaction time were allocated between 3.1% and 4.5 % of GDP. The Bailey triangle under the demand for the monetary base schedule represented around 1% of GDP, which is consistent with Lucas (2000). We estimate that the US total welfare costs of in‡ation were around 10% of GDP in terms of the consumption goods foregone. The big di¤erence between our results and Lucas (2000) are mainly due to the Harberger triangle in the market for loans (inside money) which makes part of the household transaction time, of the …rm ‡oat labor and of the distortion in the banking industry. This triangle arises due to the widening interest rates spread in the presence of a distorting inflation tax and under a fractionally reserve system. The Harberger triangle can represent 80% of the total welfare costs of inflation while the remaining percentage is split almost equally between the Bailey triangle and the resources used for the bank services. Finally, we formulate several theorems in terms of the optimal nonneutral monetary policy so as to compare with the classical monetary theory.

Morphological and Structural changes of CaxSr1-xTiO3 Powders Obtained by the Microwave-Assisted Hydrothermal Method

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