Non-Abelian (p,q) Strings in the Warped Deformed Conifold

We calculate the tension of $(p,q)$-strings in the warped deformed conifold using the non-Abelian DBI action. In the large flux limit, we find exact agreement with the recent expression obtained by Firouzjahi, Leblond and Henry-Tye up to and including order $1/M^2$ terms if $q$ is also taken to be large. Furthermore using the finite $q$ prescription for the symmetrised trace operation we anticipate the most general expression for the tension valid for any $(p,q)$. We find that even in this instance, corrections to the tension scale as $1/M^2$ which is not consistent with simple Casimir scaling.Comment: 18 pages, Latex, 1 figure; Added a discussion of the case when the warp factor parameter $b\neq 1$ and typos correcte

A exposição das vinhas mediterrâneas ao ozono troposférico: uma abordagem de modelação

The main objective of this Thesis is to develop and evaluate a modeling system capable of simulating in detail the exposure and uptake of ambient ozone (O₃) by vineyards in Mediterranean environments. It also aims to contribute to the state of the art on the influence of climate in viticulture in the context of climate change. The selected study area was the Douro Demarcated Region (DDR) in Portugal. The assessment on climate change potential impact was based on WRF downscaled ERA-Interim and MPI-ESM-LR global simulations forced with a RCP8.5 GHG emission scenario, for recent-past (1986–2005) and future periods (2046–2065, 2081–2100). For the evaluation of phytotoxic risk due to ozone, a validation of a simulation with the WRF-CHIMERE system was carried out. This simulation covered a grapevine growing season from April to September 2017. In the same period, a field campaign was carried out, including measurements of ambient ozone, phenology, and leaf gas-exchange and water relations for the grapevine along representative vineyards of the study area. The field campaign indicated that the phytotoxicity threshold for ambient O₃ (40 ppb) was reached in all stages of grapevine development, including a sensitive period such as flowering. Regarding ambient O₃ exposure standards, the measured May-Jun AOT40, 8 ppm-h, exceeded the long-term objective for the protection of vegetation, 3 ppm-h, and was close to that established as a general annual standard by the 2002/03 and 2008/50 European Directives, 9 ppm-h. The validated ambient ozone simulations by the WRF-CHIMERE system also indicated that grapevine-specific thresholds for Jun-Sep AOT40 could be exceeded, mainly in the drier, warmer Douro Superior eastern subregion. On the other hand, the standard based on the phytotoxic ozone dose introduced into the plant, POD, also indicated risk of phytotoxicity, this time mostly located in the Baixo and Cima Corgo western DDR subregions. The POD risk had a lesser extension when adjusted to the physiological behavior of local grapevine varieties, mainly due to the inclusion of the plant water stress effect throughout the region. It has also been possible to relate the WRF-ERA recent-past climate simulations with vintage yield and quality in the DDR. The mid-term and long term WRF-MPI climate scenarios revealed shifts to warmer and drier conditions not remaining within the ranges for quality and production. Important conclusions of this work are the relevance of including phenological and physiological parametrizations of local grapevine varieties to refine standards related with ozone phytotoxic risk and climate change. A current limitation is the lack of valid O₃ exposure and dose-effect relationships for the grapevine.O principal objectivo desta Tese consiste no desenvolvimento e validação de um sistema de modelação capaz de simular em detalhe a exposição e a absorção do ozono (O₃) ambiental pelas vinhas em ambientes mediterrânicos. Visa também contribuir para o estado da arte sobre a influência do clima na viticultura no contexto das alterações climáticas. A área de estudo seleccionada foi a Região Demarcada do Douro (DDR), em Portugal. A avaliação do impacto potencial das alterações climáticas baseou-se no refinamento da resolução das simulações globais de ERA-Interim e MPI-ESMLR, forçadas com um cenário de emissão de GEE RCP8.5 para períodos recentes (1986-2005) e futuros (2046-2065, 2081-2100), recorrendo ao modelo WRF. Para a avaliação do risco fitotóxico devido ao ozono, foi efetuada uma validação de uma simulação do sistema WRF-CHIMERE. Esta simulação abrangeu um período de crescimento para as vinhas entre Abril e Setembro de 2017. No mesmo período, foi realizada uma campanha experimental, incluindo medições do ozono ambiente, fenologia, troca de gases foliares e relações de água, ao longo de vinhas representativas da área de estudo. A campanha indicou que o limiar de fitotoxicidade para O₃ ambiental (40 ppb) foi atingido em todas as fases de desenvolvimento das vinhas, incluindo um período sensível como a floração. Em relação aos padrões de exposição ambiental ao O₃, o indicador AOT40 entre Maio-Junho, 8 ppm-h, excedeu o objetivo a longo prazo para a proteção da vegetação, 3 ppm-h, e aproximou-se do estabelecido como norma geral anual pelas Diretivas Europeias 2002/03 e 2008/50, 9 ppm-h. As simulações de ozono ambiente, validadas pelo sistema WRF-CHIMERE, também indicaram que os limiares específicos para as vinhas, para AOT40 entre Junho-Setembro, podiam ser excedidos, principalmente na sub-região mais seca e quente mais oriental da DDR, o Douro Superior. Por outro lado, o padrão baseado na dose de ozono fitotóxico introduzida na planta, POD, indicou também risco de fitotoxicidade, principalmente nas sub-regiões ocidentais da DDR, o Baixo Corgo e o Cima Corgo. O risco indicado pelo POD teve uma menor extensão quando ajustado ao comportamento fisiológico das castas de videira locais, sobretudo devido à inclusão do efeito de stress hídrico das plantas em toda a região. Os resultados das simulações climáticas WRFERA para o período recente revelaram também uma relação coerente com o rendimento e qualidade da vinha na DDR em clima presente. Os cenários climáticos de médio e longo prazo do WRF-MPI indicaram uma tendência para condições mais quentes e secas, que propiciarão valores de produção e de qualidade inferiores aos recomendados. Conclusões importantes deste trabalho são a relevância de incluir parametrizações fenológicas e fisiológicas das castas de videira locais para refinar as normas relacionadas com o risco fitotóxico do ozono e as alterações climáticas. Uma limitação atual é a falta de relações exposição ou dose-efeito válidas para o O₃ e as vinhas.Programa Doutoral em Ciências e Engenharia do Ambient

Spectroscopy of the near-nuclear regions of Cygnus A: estimating the mass of the supermassive black hole

We use a combination of high spatial resolution optical and near-IR spectroscopic data to make a detailed study of the kinematics of the NLR gas in the near-nuclear regions of the powerful, FRII radio galaxy Cygnus A (z=0.0560), with the overall goal of placing limits on the mass of any supermassive black hole in the core. Our K-band infrared observations (0.75 arcsec seeing) -- taken with NIRSPEC on the Keck II telescope -- show a smooth rotation pattern across the nucleus in the Paschen alpha and H_2 emission lines along a slit position (PA180) close to perpendicular to the radio axis, however, there is no evidence for such rotation along the radio axis (PA105). Higher spatial resolution observations of the [OIII]5007 emission line -- taken with STIS on the Hubble Space Telescope (HST) -- confirm the general rotation pattern of the gas in the direction perpendicular to the radio axis, and provide evidence for steep velocity gradients within a radius of 0.1 arcsec of the core. The circular velocities measured from both the Keck and HST data lead to an estimate of the mass of the supermassive black hole of 2.5+/-0.7x10^9 solar masses. For the host galaxy properties of Cygnus A, this mass is consistent with the global correlations between black hole mass and host galaxy properties deduced for non-active galaxies. Therefore, despite the extreme power of its radio source and the quasar-like luminosity of its AGN, the black hole in Cygnus A is not unusually massive considering theluminosity of its host galaxy. Indeed, the estimated mass of the black hole in Cygnus A is similar to that inferred for the supermassive black hole in the FRI radio galaxy M87, despite the fact that the AGN and radio jets of Cygnus A are 2 -- 3 orders of magnitude more powerful.Comment: 17 pages, 12 figure

Chasing Brane Inflation in String-Theory

We investigate the embedding of brane anti-brane inflation into a concrete type IIB string theory compactification with all moduli fixed. Specifically, we are considering a D3-brane, whose position represents the inflaton $\phi$, in a warped conifold throat in the presence of supersymmetrically embedded D7-branes and an anti D3-brane localized at the tip of the warped conifold cone. After presenting the moduli stabilization analysis for a general D7-brane embedding, we concentrate on two explicit models, the Ouyang and the Kuperstein embeddings. We analyze whether the forces, induced by moduli stabilization and acting on the D3-brane, might cancel by fine-tuning such as to leave us with the original Coulomb attraction of the anti D3-brane as the driving force for inflation. For a large class of D7-brane embeddings we obtain a negative result. Cancelations are possible only for very small intervals of $\phi$ around an inflection point but not globally. For the most part of its motion the inflaton then feels a steep, non slow-roll potential. We study the inflationary dynamics induced by this potential.Comment: 34 pages, 4 figures. Final version published in JCA

Membrane Instantons and de Sitter Vacua

We investigate membrane instanton effects in type IIA strings compactified on rigid Calabi-Yau manifolds. These effects contribute to the low-energy effective action of the universal hypermultiplet. In the absence of additional fivebrane instantons, the quaternionic geometry of this hypermultiplet is determined by solutions of the three-dimensional Toda equation. We construct solutions describing membrane instantons, and find perfect agreement with the string theory prediction. In the context of flux compactifications we discuss how membrane instantons contribute to the scalar potential and the stabilization of moduli. Finally, we demonstrate the existence of meta-stable de Sitter vacua.Comment: v3: minor clarifications, JHEP version, 38 page

Analysis of climate change indices in relation to wine production: a case study in the Douro region (Portugal)

Climate change is of major relevance to wine production as most of the wine-growing regions of the world, in particular the Douro region, are located within relatively narrow latitudinal bands with average growing season temperatures limited to 13–21◦C. This study focuses on the incidence of climate variables and indices that are relevant both for climate change detection and for grape production with particular emphasis on extreme events (e.g. cold waves, storms, heat waves). Dynamical downscaling ofMPI-ESM-LR global data forced with RCP8.5 climatic scenario is performed with the Weather Research and Forecast (WRF) model to a regional scale including the Douro valley of Portugal for recent-past (1986–2005) and future periods (2046– 2065; 2081–2100). The number, duration and intensity of events are superimposed over critical phenological phases of the vine (dormancy, bud burst, flowering, v´eraison, and maturity) in order to assess their positive or negative implications on wine production in the region. An assessment on the statistical significance of climatic indices, their differences between the recent-past and the future scenarios and the potential impact on wine production is performed. Preliminary results indicate increased climatic stress on the Douro region wine production and increased vulnerability of its vine varieties. These results will provide evidence for future strategies aimed to preserve the high-quality wines in the region and their typicality in a sustainable way.The authors wish to thank the financial support of the DOUROZONE project (PTDC/AAG-MAA/3335/2014; POCI- 01-0145-FEDER-016778) through the Project 3599 – Promoting the scientific production and the technological development, and thematic networks (3599-PPCDT) and through FEDER.info:eu-repo/semantics/publishedVersio

Stable and Metastable Cosmic Strings in Heterotic M-Theory

We address the question of finding stable and metastable cosmic strings in quasi-realistic heterotic M-theory compactifications with stabilized moduli. According to Polchinski's conjecture, the only stable strings in the absence of massless fields are Aharonov-Bohm strings. Such strings could potentially be created in heterotic compactifications as bound states of open membranes, five-branes wrapped on four-cycles and solitonic strings. However, in generic compactifications, the process of moduli stabilization can conflict production of Aharanov-Bohm strings. In this case, heterotic cosmic strings will have to be unstable under breakage on monopoles. We estimate the monopole masses and find that they are big enough so that the strings can be metastable with a sufficiently long lifetime. On the other hand, if we allow one or more axions to remain massless at low energies, stable global strings can be produced.Comment: LaTeX, 26 pages, 1 figure, subsection added, references adde

String Necklaces and Primordial Black Holes from Type IIB Strings

We consider a model of static cosmic string loops in type IIB string theory, where the strings wrap cycles within the internal space. The strings are not topologically stabilised, however the presence of a lifting potential traps the windings giving rise to kinky cycloops. We find that PBH formation occurs at early times in a small window, whilst at late times we observe the formation of dark matter relics in the scaling regime. This is in stark contrast to previous predictions based on field theoretic models. We also consider the PBH contribution to the mass density of the universe, and use the experimental data to impose bounds on the string theory parameters.Comment: 45 pages, 9 figures, LaTeX; published versio

Precision Measurement of The Most Distant Spectroscopically Confirmed Supernova Ia with the Hubble Space Telescope

We report the discovery of a redshift 1.71 supernova in the GOODS North field. The Hubble Space Telescope (HST) ACS spectrum has almost negligible contamination from the host or neighboring galaxies. Although the rest frame sampled range is too blue to include any Si ii line, a principal component analysis allows us to confirm it as a Type Ia supernova with 92% confidence. A recent serendipitous archival HST WFC3 grism spectrum contributed a key element of the confirmation by giving a host-galaxy redshift of 1.713 +/- 0.007. In addition to being the most distant SN Ia with spectroscopic confirmation, this is the most distant Ia with a precision color measurement. We present the ACS WFC and NICMOS 2 photometry and ACS and WFC3 spectroscopy. Our derived supernova distance is in agreement with the prediction of LambdaCDM.Comment: 13 pages, 6 figures, published in ApJ with updated analysi

Grapevine bioclimatic indices in relation to climate change: a case study in the Portuguese Douro Demarcated Region

Climate change is of major relevance to wine production as most of the wine-growing regions of the world, in particular the Douro region, are located within relatively narrow latitudinal bands with average growing season temperatures limited to 13-21ºC. This study focuses on the temporal variability of three grapevine bioclimatic indices, which are commonly used as part of the Geoviticulture Multicriteria Climatic Classification System (MCC) to classify the climate of wine producing regions worldwide. Dynamical downscaling of MPI-ESM-LR global data forced with RCP8.5 climatic scenario is performed with the Weather Research and Forecast (WRF) model to a regional scale including the Douro valley of Portugal for recent-past (1986-2005) and future periods (2046-2065; 2081-2100). Results indicate significant shifts towards warmer and dryer conditions during the growing season and higher night temperatures during the grape ripening period. An assessment on the statistical significance of the differences between the recent-past and the future scenarios and the potential impact on wine production in the study area is performed. These results will provide evidence for future strategies aimed to preserve the high-quality wines in the region and their typicality in a sustainable way.The authors wish to thank the financial support of the DOUROZONE project (PTDC/AAG-MAA/3335/2014; POCI- 01-0145-FEDER-016778) through the Project 3599 – Promoting the scientific production and the technological development, and thematic networks (3599-PPCDT) and through FEDER, and the national funds from FCT – Science and Technology Portuguese Foundation for the doc grant of C. Silveira (SFRH/BD/112343/2015).info:eu-repo/semantics/publishedVersio