Boundary versus bulk behavior of time-dependent correlation functions in one-dimensional quantum systems

We study the influence of reflective boundaries on time-dependent responses of one-dimensional quantum fluids at zero temperature beyond the low-energy approximation. Our analysis is based on an extension of effective mobile impurity models for nonlinear Luttinger liquids to the case of open boundary conditions. For integrable models, we show that boundary autocorrelations oscillate as a function of time with the same frequency as the corresponding bulk autocorrelations. This frequency can be identified as the band edge of elementary excitations. The amplitude of the oscillations decays as a power law with distinct exponents at the boundary and in the bulk, but boundary and bulk exponents are determined by the same coupling constant in the mobile impurity model. For nonintegrable models, we argue that the power-law decay of the oscillations is generic for autocorrelations in the bulk, but turns into an exponential decay at the boundary. Moreover, there is in general a nonuniversal shift of the boundary frequency in comparison with the band edge of bulk excitations. The predictions of our effective field theory are compared with numerical results obtained by time-dependent density matrix renormalization group (tDMRG) for both integrable and nonintegrable critical spin-$S$ chains with $S=1/2$, $1$ and $3/2$.Comment: 20 pages, 12 figure

Non-equilibrium Statistical Mechanics of Anharmonic Crystals with Self-consistent Stochastic Reservoirs

We consider a d-dimensional crystal with an arbitrary harmonic interaction and an anharmonic on-site potential, with stochastic Langevin heat bath at each site. We develop an integral formalism for the correlation functions that is suitable for the study of their relaxation (time decay) as well as their behavior in space. Furthermore, in a perturbative analysis, for the one-dimensional system with weak coupling between the sites and small quartic anharmonicity, we investigate the steady state and show that the Fourier's law holds. We also obtain an expression for the thermal conductivity (for arbitrary next-neighbor interactions) and give the temperature profile in the steady state

Flight-to-quality and contagion in the european sovereign debt crisis: the cases of Portugal and Greece

This work aims to analyze the co-movements between the Portuguese, Greek, Irish and German government bond markets after the subprime crisis (2007 to 2013). Additionally, it aims to test the existence of contagion between the Portuguese, Greece and Irish bond markets, and to explore the phenomenon of flight-to-quality from the Portuguese and Greek bond markets to the German market. The analysis is undertaken using a DCC-IGARCH model with daily data for the 10 year yields government bonds. Results suggest the existence of contagion between the Greek and the Portuguese markets, and to a lesser extent between the Irish and the Portuguese markets. The correlation between the Portuguese and Greek yields at the end of the analyzed period indicates the non-existence of decoupling between the two countries. During most of the identified crisis periods, flight-to-quality flows are evident from the Portuguese and Greek bond markets to the German market.FC

Magnetically-controlled impurities in quantum wires with strong Rashba coupling

We investigate the effect of strong spin-orbit interaction on the electronic transport through non-magnetic impurities in one-dimensional systems. When a perpendicular magnetic field is applied, the electron spin polarization becomes momentum-dependent and spin-flip scattering appears, to first order in the applied field, in addition to the usual potential scattering. We analyze a situation in which, by tuning the Fermi level and the Rashba coupling, the magnetic field can suppress the potential scattering. This mechanism should give rise to a significant negative magnetoresistance in the limit of large barriers.Comment: 4 pages, 2 figure

Ciclo biológico e estragos associados a monosteira, Monosteira unicostata (Mulsant & Rey, 1852), em amendoeira, no Planalto Mirandês

A monosteira, Monostelro unicostata (Mulsant & Rey, 1852), e considerada uma praga importante da amendoeira. Contudo, em Portugal, são escassos os conhecimentos acerca da sua biologia e dos estragos que ocasiona. Neste sentido, com o presente trabalho pretendeu-se par um lado estudar o cicio biológico do insecto em amendoeira no Planalto Mirandês, e por outro lado proceder a uma avaliação dos estraagos causados pela praga. O trabalho decorreu em 2007 e 2008 num amendoal localizado em Vilarinho dos Galegos (Mogadouro) onde, com periodicidade semanal ou quinzenal, se procedeu a recolha de 20 folhas em 20 árvores para observação (i) da existência de ovos, ninfas e adultos de monosteira e (ii) do numero de folhas com estragos visíveis. Paralelamente, e com periodicidade aproximadamente quinzenal foi realizada a técnica de pancadas em 25 arvores escolhidas aleatoriamente na parcela para quantificação dos adultos da praga

A mosca-da-azeitona, Bactrocera oleae (Gmelin), no Planalto Mirandês: ciclo biológico e importância económica.

Em Portugal o olival para produção de azeitona de mesa representa 4.0% da superfície olivícola. Trás-os-Montes concentra aproximadamente metade da área nacional e mais de 55% da produção. Um dos principais entraves a produção diz respeito aos prejuízos de natureza quantitativa e qualitativa. provocados peles inimigos da cultura. Entre estes inimigos assume particular relevo a mosca-da-azeitona, Bactrocera oleae (Gmelin) que constitui a praga chave da cultura no conjunto dos países da bacia do Mediterrâneo. Com 0 presente estudo pretendeu-se contribuir para o conhecimento do cicio biológico da mosca-da-azeitona, Bactrocera oleae (Gmelin), e sua importância económica em azeitona de mesa na região do Planalto Mirandês

Effects of omega-3 fatty acids on arterial stiffness in patients with hypertension: a randomized pilot study.

BackgroundOmega-3 fatty acids prevent cardiovascular disease (CVD) events in patients with myocardial infarction or heart failure. Benefits in patients without overt CVD have not been demonstrated, though most studies did not use treatment doses (3.36 g) of omega-3 fatty acids. Arterial stiffness measured by pulse wave velocity (PWV) predicts CVD events independent of standard risk factors. However, no therapy has been shown to reduce PWV in a blood pressure-independent manner. We assessed the effects of esterified omega-3 fatty acids on PWV and serum markers of inflammation among patients with hypertension.Design and methodsWe performed a prospective, randomized; double-blinded pilot study of omega-3 fatty acids among 62 patients in an urban, safety net hospital. Patients received 3.36 g of omega-3 fatty acids vs. matched placebo daily for 3-months. The principal outcome measure was change in brachial-ankle PWV. Serum inflammatory markers associated with CVD risk were also assessed.ResultsThe majority (71 %) were of Latino ethnicity. After 3-months, mean change in arterial PWV among omega-3 and placebo groups was -97 cm/s vs. -33 cm/s respectively (p = 0.36 for difference, after multivariate adjustment for baseline age, systolic blood pressure, and serum adiponectin). Non-significant reductions in lipoprotein-associated phospholipase A2 (LpPLA2) mass and high sensitivity C-reactive protein (hsCRP) relative to placebo were also observed (p = 0.08, and 0.21, respectively).ConclusionHigh-dose omega-3 fatty acids did not reduce arterial PWV or markers of inflammation among patients within a Latino-predominant population with hypertension.Clinical trial registrationNCT00935766 , registered July 8 2009

Flight-to-quality and contagion in the European sovereign debt crisis: The cases of Portugal and Greece

Purpose: The purpose of this paper is to analyze the co-movements between the Portuguese, Greek, Irish and German government bond markets after the subprime crisis (2007 to 2013), with a special focus on the European sovereign debt crisis. It aims to assess the existence of contagion between the Portuguese, Greece and Irish bond markets and to explore the phenomenon of flight-to-quality from the Portuguese and Greek bond markets to the German market. Design/methodology/approach: The analysis is undertaken using a DCC-GARCH model with daily data for 10-year yield government bonds. The change in correlation from the stable periods to the crisis periods is used to identify contagion or flight-to-quality. Findings: Results suggest that there was contagion between the Greek and Portuguese markets, and to a lesser extent between the Irish and Portuguese markets. During most of the identified crisis periods, there are evident flight-to-quality flows from the Portuguese and Greek bond markets to the German market. Originality/value: This paper contributes to the literature by applying the methodology DCC-GARCH to several crisis episodes for the analysis of contagion and flight-to-quality during the European sovereign debt crisis.info:eu-repo/semantics/acceptedVersio