234 research outputs found
Some special Kahler metrics on SL(2,C) and their holomorphic quantization
The group SU(2)*SU(2) acts naturally on SL(2,C) by simultaneous right and
left multiplication. We study the Kahler metrics invariant under this action
using global Kahler potentials. The volume growth and various curvature
quantities are then explicitly computable. Examples include metrics of
positive, negative and zero Ricci curvature, and the 1-lump metric of the
CP^1-model on a sphere.
We then look at the holomorphic quantization of these metrics, where some
physically satisfactory results on the dimension of the Hilbert space can be
obtained. These give rise to an interesting geometrical conjecture, regarding
the dimension of this space for general Stein manifolds in the semi-classical
limit.Comment: 28 pages, no figure
Moduli of vortices and Grassmann manifolds
We use the framework of Quot schemes to give a novel description of the
moduli spaces of stable n-pairs, also interpreted as gauged vortices on a
closed Riemann surface with target Mat(r x n, C), where n >= r. We then show
that these moduli spaces embed canonically into certain Grassmann manifolds,
and thus obtain natural Kaehler metrics of Fubini-Study type; these spaces are
smooth at least in the local case r=n. For abelian local vortices we prove
that, if a certain "quantization" condition is satisfied, the embedding can be
chosen in such a way that the induced Fubini-Study structure realizes the
Kaehler class of the usual L^2 metric of gauged vortices.Comment: 22 pages, LaTeX. Final version: last section removed, typos
corrected, two references added; to appear in Commun. Math. Phy
Editorial: Cancer Nanotheranostics: What Have We Learned So Far?
According to the National Cancer Institute, in 2015 an estimated of 1.7 million new cases of cancer will be diagnosed only in the United States and around 600, 000 people will die from the disease. The most common type of cancer is breast cancer, with more than 234, 000 new cases expected in the United States in 2015. The next most common cancers are prostate cancer and lung cancer.After a quarter of century of rapid technological advances, research has revealed the complexity of cancer, a disease intimately related to the dynamic transformation of the genome. These transformations trigger a range of modification to cell processes and molecular events that initiate and promote tumor genesis and progression, then local invasion and metastasis, i.e., the hallmarks of cancer development. These alterations may cause a wide scope of “diseases” that share similar molecular patterns that cause transformation and malignancy. Each of this stepwise evolution of the initial molecular event drives abnormal growth and loss of differentiation that ultimately causes tissue and organ failure. The initial molecular event may lay within the erroneous expression of a given gene, epigenetic modification and/or sporadic mutations occurring on genomic DNA during the life span of organisms. Each and every one of these molecular events may be evaluated and used as diagnostics biomarker and therapeutic target. For example, therapy action may target a mutated gene and silence its expression so as to avoid erroneous protein expression that mutates cell function. However, the full understanding of the molecular onset of this disease is still far from achieved and the search for mechanisms of treatment will follow closely..
Um modelo de caracterização e avaliação ecológica para o planeamento e gestão
Decorrem actualmente na Universidade de Évora diversos projectos de investigação visando o desenvolvimento de metodologias de caracterização
e avaliação ecológica com vista ao planeamento e gestão do território. Tais
projectos, desenvolvidos a escalas complementares (1:10 000; 1:25 000 e
1:100 000), pretendem via a constituir um quadro metodológico inovador
integrando num único plano de caracterização e avaliação, o plano dos
sistemas de uso e o plano dos sistemas ecológicos espaciais.
A necessidade de um tal sistema integrado justifica-se pela carência de um
referencial de caracterização e avaliação do território com vista à articulação
od sprocesos de gestão e à promoção dos objectivos de Conservação da
Natureza. Com efeito, a necessidade de assegurar a preservação da
biodiversidade da globalidade do território impõe uma abordagem à gestaõ
do uso deste que assegure que o nível de fragmentação, de conectividade
residual, e de complementaridade funcional asseguram as condições para a
sustentação viável de meta-populações das espécie-objectivo.
Para atingir tal objectivo importa conhecer e conseguir articular nos
processos de simulação e gestão, as necessidades, processos e funções
dos diferentes usos antrópicos de uma dada região e as necessidades
processos, funções e condicionantes espaciais dos diferentes sistemas
ecológicos susceptiveis de ocorrerem nessa região ou locais. Interessa
igualmente identificat a forma como essa articulação se processa e a sua
hierarquização escalar e funcional
Quantum lump dynamics on the two-sphere
It is well known that the low-energy classical dynamics of solitons of
Bogomol'nyi type is well approximated by geodesic motion in M_n, the moduli
space of static n-solitons. There is an obvious quantization of this dynamics
wherein the wavefunction evolves according to the Hamiltonian H_0 equal to
(half) the Laplacian on M_n. Born-Oppenheimer reduction of analogous mechanical
systems suggests, however, that this simple Hamiltonian should receive
corrections including k, the scalar curvature of M_n, and C, the n-soliton
Casimir energy, which are usually difficult to compute, and whose effect on the
energy spectrum is unknown. This paper analyzes the spectra of H_0 and two
corrections to it suggested by work of Moss and Shiiki, namely H_1=H_0+k/4 and
H_2=H_1+C, in the simple but nontrivial case of a single CP^1 lump moving on
the two-sphere. Here M_1=TSO(3), a noncompact kaehler 6-manifold invariant
under an SO(3)xSO(3) action, whose geometry is well understood. The symmetry
gives rise to two conserved angular momenta, spin and isospin. A hidden
isometry of M_1 is found which implies that all three energy spectra are
symmetric under spin-isospin interchange. The Casimir energy is found exactly
on the zero section of TSO(3), and approximated numerically on the rest of M_1.
The lowest 19 eigenvalues of H_i are found for i=0,1,2, and their spin-isospin
and parity compared. The curvature corrections in H_1 lead to a qualitatively
unchanged low-level spectrum while the Casimir energy in H_2 leads to
significant changes. The scaling behaviour of the spectra under changes in the
radii of the domain and target spheres is analyzed, and it is found that the
disparity between the spectra of H_1 and H_2 is reduced when the target sphere
is made smaller.Comment: 35 pages, 3 figure
Non-abelian vortices on compact Riemann surfaces
We consider the vortex equations for a U(n) gauge field coupled to a Higgs
field with values on the n times n square matrices. It is known that when these
equations are defined on a compact Riemann surface, their moduli space of
solutions is closely related to a moduli space of tau-stable holomorphic
n-pairs on that surface. Using this fact and a local factorization result for
the Higgs matrix, we show that the vortex solutions are entirely characterized
by (1) the location in the surface of the zeros of the determinant of the Higgs
matrix and (2) by the choice of a vortex internal structure at each of these
zeros. We describe explicitly the vortex internal spaces and show that they are
compact and connected spaces.Comment: 17 pages; v2: typos corrected, as will appear in CM
Density Perturbations in the Brans-Dicke Theory
We analyse the fate of density perturbation in the Brans-Dicke Theory, giving
a general classification of the solutions of the perturbed equations when the
scale factor of the background evolves as a power law. We study with details
the cases of vacuum, inflation, radiation and incoherent matter. We find, for
the a negative Brans-Dicke parameter, a significant amplification of
perturbations.Comment: 26 pages, latex fil
A regional survey of emerging hot climate conditions in Portugal and the new challenge to animal housing
Portugal, located in the South-western Europe, is characterised by a Mediterranean climate with hot
and dry summer.
According to data from Portuguese IM (Instituto de Meteorologia) during the last decade, summer
temperatures tend to be higher, and several heat waves have occurred, with temperatures above 40
oC. During summer, days with high temperatures and heat waves are becoming more and more
common in Portugal. The past four summers have been among the hottest ever registered.
These frequently high temperatures can cause problems in intensive animal production. In most
cases, the livestock buildings are not prepared for animal production under high temperatures and
most of them do not have environmental control equipments adequate to control indoor
environment under such conditions.
From a geographical point of view, and examining climatic data, we find two regions (Alentejo and
Trás-os-Montes) where high temperatures are more usual and summer tend to be hot. In these two
regions, livestock is quite relevant and have a great significance to the regional economy.
Two locations were chosen in these regions to register and analyse air temperature in order to
identify the occurrence of hot climate conditions; and to evaluate its influence on the inside animal
housing climate
Twisting gauged non-linear sigma-models
We consider gauged sigma-models from a Riemann surface into a Kaehler and
hamiltonian G-manifold X. The supersymmetric N=2 theory can always be twisted
to produce a gauged A-model. This model localizes to the moduli space of
solutions of the vortex equations and computes the Hamiltonian Gromov-Witten
invariants. When the target is equivariantly Calabi-Yau, i.e. when its first
G-equivariant Chern class vanishes, the supersymmetric theory can also be
twisted into a gauged B-model. This model localizes to the Kaehler quotient
X//G.Comment: 33 pages; v2: small additions, published versio
VINHOS QUE PENSAM - parte I/III GESTÃO DO VIGOR VEGETATIVO DA VINHA A PARTIR DE SENSORES ATIVOS MUTIESPECTRAIS PRÓXIMOS
Costumo dizer que o projeto “Vinhos
que pensam” nasceu de um aperto
de mão entre a equipa de Agricultura
de Precisão da Universidade
de Évora e a Fundação Eugénio de
Almeida, nasceu sem financiamento
próprio mas com uma visão muito
clara de criar valor social na área da
vitivinicultura Alentejana. Passados 6
anos, julgamos que o conhecimento
produzido é relevante para a atividade
e gestão vitivinícola Alentejana,
no entanto, novas perguntas surgem
todos os anos e dessa forma somos
alimentados na motivação de prosseguir
com este projeto, ao qual, outras
entidades e vontades se vão agora
também associando.
A Agrobótica, muito recentemente,
desafiou-nos a apresentar os resultados
mais relevantes do projeto
“Vinhos que pensam” e com o maior
prazer lhe dissemos que sim, no entanto,
colocou-se-nos um problema,
os resultados mais relevantes, muito
dificilmente caberiam num único artigo,
como tal, decidimos dividir tais resultados em três artigos, este primeiro
mais virado para os aspetos da gestão
do vigor da vegetação da vinha; o segundo
mais virado para os sensores
geoelétricos do solo e sua aplicação na gestão e estudo do solo; e por fim,
um terceiro mais virado para aspetos
da nutrição das plantas considerando
a interação solo/planta e a utilização
dos sensores multiespectrais
- …