67,393 research outputs found
Supernatural Supersymmetry: Phenomenological Implications of Anomaly-Mediated Supersymmetry Breaking
We discuss the phenomenology of supersymmetric models in which supersymmetry
breaking terms are induced by the super-Weyl anomaly. Such a scenario is
envisioned to arise when supersymmetry breaking takes place in another world,
i.e., on another brane. We review the anomaly-mediated framework and study in
detail the minimal anomaly-mediated model parametrized by only 3+1 parameters:
M_aux, m_0, \tan\beta, and sign(\mu). The renormalization group equations
exhibit a novel "focus point" (as opposed to fixed point) behavior, which
allows squark and slepton masses to be far above their usual naturalness
bounds. We present the superparticle spectrum and highlight several
implications for high energy colliders. Three lightest supersymmetric particle
(LSP) candidates exist: the Wino, the stau, and the tau sneutrino. For the Wino
LSP scenario, light Wino triplets with the smallest possible mass splittings
are preferred; such Winos are within reach of Run II Tevatron searches.
Finally, we study a variety of sensitive low energy probes, including b -> s
gamma, the anomalous magnetic moment of the muon, and the electric dipole
moments of the electron and neutron.Comment: 32 pages, 17 figure
Considerations in the Interpretation of Cosmological Anomalies
Anomalies drive scientific discovery -- they are associated with the cutting
edge of the research frontier, and thus typically exploit data in the low
signal-to-noise regime. In astronomy, the prevalence of systematics --- both
"known unknowns" and "unknown unknowns" --- combined with increasingly large
datasets, the widespread use of ad hoc estimators for anomaly detection, and
the "look-elsewhere" effect, can lead to spurious false detections. In this
informal note, I argue that anomaly detection leading to discoveries of new
physics requires a combination of physical understanding, careful experimental
design to avoid confirmation bias, and self-consistent statistical methods.
These points are illustrated with several concrete examples from cosmology.Comment: An informal summary of an invited talk given at the IAU symposium
"Statistical Challenges in 21st Century Cosmology", accepted in the
Proceedings IAU Symposium No. 306, 2014 (A.F. Heavens, J.-L. Starck, A.
Krone-Martins eds.). 7 pages, 1 figure. Comments welcom
Associations between stratospheric variability and tropospheric blocking
There is widely believed to be a link between stratospheric flow variability and stationary, persistent “blocking” weather systems, but the precise nature of this link has proved elusive. Using data from the ERA-40 Reanalysis and an atmospheric general circulation model (GCM) with a well-resolved stratosphere (HadGAM), it is shown that there are in fact several different highly significant associations, with blocking in different regions being related to different patterns of stratospheric variability. This is true in both hemispheres and in both data sets. The associations in HadGAM are shown to be very similar to those in ERA-40, although the model has a tendency to underestimate both European blocking and the wave number 2 stratospheric variability to which this is related. Although the focus is on stratospheric variability in general, several of the blocking links are seen to occur in association with the major stratospheric sudden warmings. In general, the direction of influence appears to be upward, as blocking anomalies are shown to modify the planetary stationary waves, leading to an upward propagation of wave activity into the stratosphere. However, significant correlations are also apparent with the zonal mean flow in the stratosphere leading the occurrence of blocking at high latitudes. Finally, the underestimation of blocking is an enduring problem in GCMs, and an example has recently been given in which improving the resolution of the stratosphere improved the representation of blocking. Here, however, another example is given, in which increasing the stratospheric resolution unfortunately does not lead to an improvement in blocking
Role based behavior analysis
Tese de mestrado, Segurança Informática, Universidade de Lisboa, Faculdade de Ciências, 2009Nos nossos dias, o sucesso de uma empresa depende da sua agilidade e capacidade de se adaptar a condições que se alteram rapidamente. Dois requisitos para esse sucesso são trabalhadores proactivos e uma infra-estrutura ágil de Tecnologias de Informacão/Sistemas de Informação (TI/SI) que os consiga suportar. No entanto, isto nem sempre sucede. Os requisitos dos utilizadores ao nível da rede podem nao ser completamente conhecidos, o que causa atrasos nas mudanças de local e reorganizações. Além disso, se não houver um conhecimento preciso dos requisitos, a infraestrutura de TI/SI poderá ser utilizada de forma ineficiente, com excessos em algumas áreas e deficiências noutras. Finalmente, incentivar a proactividade não implica acesso completo e sem restrições, uma vez que pode deixar os sistemas vulneráveis a ameaças externas e internas. O objectivo do trabalho descrito nesta tese é desenvolver um sistema que consiga caracterizar o comportamento dos utilizadores do ponto de vista da rede. Propomos uma arquitectura de sistema modular para extrair informação de fluxos de rede etiquetados. O processo é iniciado com a criação de perfis de utilizador a partir da sua informação de fluxos de rede. Depois, perfis com características semelhantes são agrupados automaticamente, originando perfis de grupo. Finalmente, os perfis individuais são comprados com os perfis de grupo, e os que diferem significativamente são marcados como anomalias para análise detalhada posterior. Considerando esta arquitectura, propomos um modelo para descrever o comportamento de rede dos utilizadores e dos grupos. Propomos ainda métodos de visualização que permitem inspeccionar rapidamente toda a informação contida no modelo. O sistema e modelo foram avaliados utilizando um conjunto de dados reais obtidos de um operador de telecomunicações. Os resultados confirmam que os grupos projectam com precisão comportamento semelhante. Além disso, as anomalias foram as esperadas, considerando a população subjacente. Com a informação que este sistema consegue extrair dos dados em bruto, as necessidades de rede dos utilizadores podem sem supridas mais eficazmente, os utilizadores suspeitos são assinalados para posterior análise, conferindo uma vantagem competitiva a qualquer empresa que use este sistema.In our days, the success of a corporation hinges on its agility and ability to adapt to fast changing conditions. Proactive workers and an agile IT/IS infrastructure that can support them is a requirement for this success. Unfortunately, this is not always the case. The user’s network requirements may not be fully understood, which slows down relocation and reorganization. Also, if there is no grasp on the real requirements, the IT/IS infrastructure may not be efficiently used, with waste in some areas and deficiencies in others. Finally, enabling proactivity does not mean full unrestricted access, since this may leave the systems vulnerable to outsider and insider threats. The purpose of the work described on this thesis is to develop a system that can characterize user network behavior. We propose a modular system architecture to extract information from tagged network flows. The system process begins by creating user profiles from their network flows’ information. Then, similar profiles are automatically grouped into clusters, creating role profiles. Finally, the individual profiles are compared against the roles, and the ones that differ significantly are flagged as anomalies for further inspection. Considering this architecture, we propose a model to describe user and role network behavior. We also propose visualization methods to quickly inspect all the information contained in the model. The system and model were evaluated using a real dataset from a large telecommunications operator. The results confirm that the roles accurately map similar behavior. The anomaly results were also expected, considering the underlying population. With the knowledge that the system can extract from the raw data, the users network needs can be better fulfilled, the anomalous users flagged for inspection, giving an edge in agility for any company that uses it
On the void explanation of the Cold Spot
The integrated Sachs-Wolfe (ISW) contribution induced on the cosmic microwave
background by the presence of a supervoid as the one detected by Szapudi et al.
(2015) is reviewed in this letter in order to check whether it could explain
the Cold Spot (CS) anomaly. Two different models, previously used for the same
purpose, are considered to describe the matter density profile of the void: a
top hat function and a compensated profile produced by a Gaussian potential.
The analysis shows that, even enabling ellipticity changes or different values
for the dark-energy equation of state parameter , the ISW contribution
due to the presence of the void does not reproduce the properties of the CS.
Finally, the probability of alignment between the void and the CS is also
questioned as an argument in favor of a physical connection between these two
phenomena
Tropical Pacific influences on the North Atlantic thermohaline circulation
Most global climate models simulate a weakening of the North Atlantic Thermohaline Circulation (THC) in response to enhanced greenhouse warming. Both surface warming and freshening in high latitudes, the so-called sinking region, contribute to the weakening of the THC. Some models simulate even a complete breakdown of the THC at sufficiently strong forcing. Here results from a state-of-the-art global climate model are presented that does not simulate a weakening of the THC in response to greenhouse warming. Large-scale air-sea interactions in the tropics, similar to those operating during present-day El Niños, lead to anomalously high salinities in the tropical Atlantic. These are advected into the sinking region, thereby increasing the surface density and compensating the effects of the local warming and freshening. The results of the model study are corroborated by the analysis of observations
transition form factors
Using a continuum approach to the hadron bound-state problem, we calculate
transition form factors on the
entire domain of spacelike momenta, for comparison with existing experiments
and in anticipation of new precision data from next-generation
colliders. One novel feature is a model for the contribution to the
Bethe-Salpeter kernel deriving from the non-Abelian anomaly, an element which
is crucial for any computation of properties. The study
also delivers predictions for the amplitudes that describe the light- and
strange-quark distributions within the . Our results compare
favourably with available data. Important to this at large- is a sound
understanding of QCD evolution, which has a visible impact on the
in particular. Our analysis also provides some insights into the properties of
mesons and associated observable manifestations of the
non-Abelian anomaly.Comment: 16 pages, 7 figures, 3 table
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