Relic Abundances and the Boltzmann Equation

I discuss the validity of the quantum Boltzmann equation for the calculation of WIMP relic densities.Comment: 5 pages, no figures; talk given at Dark Matter 2000; an important reference is added in the revised versio

Protecting the SWAP\sqrt{SWAP} operation from general and residual errors by continuous dynamical decoupling

We study the occurrence of errors in a continuously decoupled two-qubit state during a $\sqrt{SWAP}$ quantum operation under decoherence. We consider a realization of this quantum gate based on the Heisenberg exchange interaction, which alone suffices for achieving universal quantum computation. Furthermore, we introduce a continuous-dynamical-decoupling scheme that commutes with the Heisenberg Hamiltonian to protect it from the amplitude damping and dephasing errors caused by the system-environment interaction. We consider two error-protection settings. One protects the qubits from both amplitude damping and dephasing errors. The other features the amplitude damping as a residual error and protects the qubits from dephasing errors only. In both settings, we investigate the interaction of qubits with common and independent environments separately. We study how errors affect the entanglement and fidelity for different environmental spectral densities.Comment: Extended version of arXiv:1005.1666. To appear in PR

EDUCAÇÃO SEXUAL NA ESCOLA – CONTEXTOS PARA A MUDANÇA

A educação sexual é hoje uma das áreas de intervenção prioritária no nosso País e ocupa um lugar de interesse no âmbito das políticas educativas e de saúde pública na União Europeia. Diversos estudos têm sido desenvolvidos abordando a problemática da sexualidade na adolescência( 1,2,3,4), os quais constatam a precocidade do início das relações sexuais entre os adolescentes, a inexistência de um parceiro sexual regular e a reduzida utilização sistemática do preservativo nas situações de risco acrescido. Perante este panorama tornam-se relevantes as intervenções de educação sexual dirigidas aos indivíduos nesta fase da vida. Até porque é inquestionável o papel crucial que a sexualidade desempenha no crescimento e desenvolvimento do adolescente, no relacionamento interpessoal, no respeito, na comunicação, na autoestima, na assertividade e na autoconfiança. Face ao exposto optou-se pela metodologia de investigação ação. Na fase diagnóstica procedeu-se à aplicação de um conjunto de instrumentos dos quais destacamos o questionário: avaliação de atitudes dos professores face á Educação sexual (QAAPES)(5); conceções e práticas face à Educação sexual – versão para professores(6). Os resultados apresentados reportam-se apenas à primeira fase do processo. Os mesmos permitiram-nos constatar o reconhecimento da educação sexual na escola como uma necessidade explícita. Na opinião dos professores esta diz respeito a todos os professores e deve ser abordada preferencialmente na componente letiva. Para estes a principal finalidade da educação sexual é desenvolver as competências dos alunos para que consigam viver a sua sexualidade de uma forma mais saudável

Imaging 3D seismic velocity along the seismogenic zone of Algarve region (southern Portugal)

The present seismic tomographic study is focused around Algarve region, in South of Portugal. To locate the seismic events and find the local velocity structure of epicentral area, the P and S arrival times at 38 stations are used. The data used in this study were obtained during the Algarve campaign which worked from January/2006 to July/2007. The preliminary estimate of origin times and hypocentral coordinates are determined by the Hy- poinverse program. Linearized inversion procedure was applied to comprise the following two steps: 1) finding the minimum 1D velocity model using Velest and 2) simultaneous relocation of hypocenters and determination of local velocity structure. The velocity model we have reached is a 10 layer model which gave the lowest RMS, after several runnings of eight different velocity models that we used “a priori”. The model parameterization assumes a continuous velocity field between 4.5 km/s and 7.0 km/s until 30 km depth. The earth structure is represented in 3D by velocity at discrete points, and velocity at any intervening point is determined by linear interpolation among the surrounding eight grid points. A preliminary analysis of the resolution capabilities of the dataset, based on the Derivative Weight Sum (DWS) distribution, shows that the velocity structure is better resolved in the West part of the region between the surface to15 km. The resulting tomographic image has a prominent low-velocity anomaly that shows a maximum decrease in P-wave velocity in the first 12 kms in the studied region. We also identified the occurrence of local seismic events of reduced magnitude not catalogued, in the neighbourhood of Almodôvar (low Alentejo). The spatial distribution of epicentres defines a NE-SW direction that coincides with the strike of the mapped geological faults of the region and issued from photo-interpretation. Is still expectable to refine the seismicity of the region of Almodôvar and establish more rigorously its role in the seismotectonic picture of the region. This work is expected to produce a more detailed knowledge of the structure of the crust over the region of Algarve, being able to identify seismogenic zones, potentially generators of significant seismic events and also the identification of zones of active faults

Validation of the Lower Tagus Valley velocity and structural model using ambient noise broadband measurements

Along his history the Lower Tagus Valley (LTV) region was shaken by several earthquakes, some of them were produced in large ruptures of offshore structures located southwest of the Portuguese coastline, among these we the Lisbon earthquake of 1 November 1755; other moderates earthquakes were produced by local sources such as the 1344, 1531 and the 1909 Benavente earthquake. In order to promote an improved assessment of the seismic hazard in this region, we propose the introduction of realistic methods on the prediction of ground motion produced by moderate to large earthquakes in LTV. This process involves the establishment of a structural 3D model based on all the available geophysical and geotechnical data on the area (seismic, gravimetric, deep wells and geological outcrops) and the determination of wave propagation from a finite difference method: by applying the E3D program [1,2]. To confirm this model we use broadband ambient noise measurements collected in two profiles with azimuth perpendicular to the basin axis and we applied the horizontal to vertical (H/V) spectral ratio method [3] to the recordings in order to estimate the amplification of the basin. The H/V curves obtained reveals the existence of two low frequency peaks centered on 0.2 a 1 Hz frequencies[4]. These peaks are strongly related with the thickness of Cenozoic and alluvial sediments. By inversion of the H/V curve, we obtain a more detailed velocity model for the region where the profile were determined, which is in good agreement with borehole data and other results obtained with magnetic and seismic reflection methods

Committed emissions from existing energy infrastructure jeopardize 1.5 °C climate target.

Net anthropogenic emissions of carbon dioxide (CO2) must approach zero by mid-century (2050) in order to stabilize the global mean temperature at the level targeted by international efforts1-5. Yet continued expansion of fossil-fuel-burning energy infrastructure implies already 'committed' future CO2 emissions6-13. Here we use detailed datasets of existing fossil-fuel energy infrastructure in 2018 to estimate regional and sectoral patterns of committed CO2 emissions, the sensitivity of such emissions to assumed operating lifetimes and schedules, and the economic value of the associated infrastructure. We estimate that, if operated as historically, existing infrastructure will cumulatively emit about 658 gigatonnes of CO2 (with a range of 226 to 1,479 gigatonnes CO2, depending on the lifetimes and utilization rates assumed). More than half of these emissions are predicted to come from the electricity sector; infrastructure in China, the USA and the 28 member states of the European Union represents approximately 41 per cent, 9 per cent and 7 per cent of the total, respectively. If built, proposed power plants (planned, permitted or under construction) would emit roughly an extra 188 (range 37-427) gigatonnes CO2. Committed emissions from existing and proposed energy infrastructure (about 846 gigatonnes CO2) thus represent more than the entire carbon budget that remains if mean warming is to be limited to 1.5 degrees Celsius (°C) with a probability of 66 to 50 per cent (420-580 gigatonnes CO2)5, and perhaps two-thirds of the remaining carbon budget if mean warming is to be limited to less than 2 °C (1,170-1,500 gigatonnes CO2)5. The remaining carbon budget estimates are varied and nuanced14,15, and depend on the climate target and the availability of large-scale negative emissions16. Nevertheless, our estimates suggest that little or no new CO2-emitting infrastructure can be commissioned, and that existing infrastructure may need to be retired early (or be retrofitted with carbon capture and storage technology) in order to meet the Paris Agreement climate goals17. Given the asset value per tonne of committed emissions, we suggest that the most cost-effective premature infrastructure retirements will be in the electricity and industry sectors, if non-emitting alternatives are available and affordable4,18

Improving the Knowledge on Seismogenic Sources in the Lower Tagus Valley for Seismic Hazard Purposes

The Lower Tagus Valley, that includes the metropolitan area of Lisbon, has been struck by several earthquakes which produced significant material damage and loss of lives. Their exact location remains unknown. Our goal is to shed some light into the seismogenic sources in the area using seismic reflection and geological data. In areas with no seismic coverage, potential-field data interpretation was carried out. Seismicity was overlaid to the potential seismogenic structures and high-resolution data was acquired in order to confirm which structures have been active into the Quaternary. Three major fault-zones affecting the Neogene were identified: V. F. Xira, Samora-Alcochete and Pinhal Novo. For the first fault, strong evidences suggest it is active. The other two fault-zones and other structures previously unknown can be correlated with several epicentres. Empirical relationships between maximum moment magnitude and fault area indicate that MW > 6.5 earthquakes can be expected for the larger structures

Finite quantum environments as thermostats: an analysis based on the Hilbert space average method

We consider discrete quantum systems coupled to finite environments which may possibly consist of only one particle in contrast to the standard baths which usually consist of continua of oscillators, spins, etc. We find that such finite environments may, nevertheless, act as thermostats, i.e., equilibrate the system though not necessarily in the way predicted by standard open system techniques. Thus, we apply a novel technique called the Hilbert space Average Method (HAM) and verify its results numerically.Comment: 12 pages, 10 figure

Dissipative Field Theory with Caldeira-Leggett Method and its Application to Disoriented Chiral Condensation

The effective field theory including the dissipative effect is developed based on the Caldeira-Leggett theory at the classical level. After the integration of the small field fluctuations considered as the field radiation, the integro-differential field equation is given and shown to include the dissipative effects. In that derivation, special cares should be taken for the boundary condition of the integration. Application to the linear sigma model is given, and the decay process of the chiral condensate is calculated with it, both analytically in the linear approximation and numerically. With these results, we discuss the stability of chiral condensates within the quenched approximation.Comment: 16pages, ReV-Te