Colóquios

Scattering Amplitudes and Classical Observables | Colóquio DFMA

Data: 
sexta-feira, 24 Novembro, 2023 - 16:00 até 17:00
Palestrante: 
Prof. Gabriel Santos Menezes
Resumo: 

Resumo: Scattering experiments play a key role in the understanding of the fundamental aspects of nature. In this respect, scattering amplitudes have a paramount physical significance through their contribution in the calculation of scattering cross-sections, the primary observables in this context. On the other hand, amplitudes have also been applied successfully to assess features of general-relativistic problems. In this talk I will review some basic techniques which are important in the modern research on scattering amplitudes as well as discussing some current trends and future perspectives, with a particular focus on the black-hole binary dynamics and classical observables.

What can we learn from the full (three-dimensional) kinematic dipole? | Colóquios DFMA

Data: 
sexta-feira, 10 Novembro, 2023 - 16:00 até 17:00
Palestrante: 
Dra. Caroline Guandalin
Resumo: 

Resumo: Recent studies of our motion with respect to the distribution of matter on large scales have found discrepancies in our peculiar velocity with respect to results obtained from the cosmic microwave background (CMB). These findings raise questions about the Cosmological Principle, a fundamental concept that suggests our velocity should be the same in both the CMB and matter reference frames. In this talk, I will explore the quasar luminosity function (QLF), which describes how quasars are distributed in terms of distance and brightness, and how different QLF models impact the strength of the kinematic dipole. I will also discuss how ignoring the dipole evolution over time leads to different results for our peculiar velocity. Finally, I will explain how this time evolution may provide opportunities to constrain cosmological parameters, with a particular focus on dark energy.

Cosmology with gravitational lensing of the Cosmic Microwave Background | Colóquios DFMA

Data: 
sexta-feira, 27 Outubro, 2023 - 16:00 até 17:00
Palestrante: 
Prof. Louis Legrand
Resumo: 

Resumo:
 
The Cosmic Microwave Background (CMB) is the most distant light that we can observe today. Since its emission roughly 380.000 years after the Big Bang it crossed all the Universe while coming to us. During their travel, the photons of the CMB have been deflected by the matter they crossed along their path, an effect called gravitational lensing. This deflection field of the CMB is a powerful observable, proportional to the integral of the matter distribution up to the early Universe. I will introduce how we can reconstruct this lensing field from CMB observations. I will then demonstrate how CMB lensing can put tight constraints on the content of the Universe, on the sum of the neutrino masses, and help us discover cosmic inflation. Lastly, I will introduce a new CMB lensing estimator, which will reconstruct optimally the lensing field for the next generation of CMB surveys. 

 

"Dipoles" | Colóquio DFMA

Data: 
terça-feira, 11 Julho, 2023 - 17:00 até 18:00
Palestrante: 
Prof. Dr. Enrico Bertuzzo - FISMAT IFUSP
Resumo: 

Resumo: Electric and magnetic dipoles play an important role in classical electromagnetism and quantum mechanics. They are even more significant in quantum field theory, since the first successful loop prediction of QED is precisely the anomalous (dipole) magnetic moment of the electron. More broadly, dipole operators frequently appear in theories beyond the standard model, where they can be probed using different techniques. In this colloquium, I will first summarize the important role that dipoles play in classical electromagnetism, quantum mechanics and quantum field theory; I will then describe two examples of theories beyond the Standard Model in which dipole operators are important for the phenomenology: "sterile dipoles" and "dark dipoles".

"Transição espectral do tipo Anderson em modelos esparsos multidimensionais: novos rumos e diretrizes | Colóquio DFMA"

Data: 
terça-feira, 27 Junho, 2023 - 17:00 até 18:00
Palestrante: 
Prof. Dr. Domingos Humberto Urbano Marchetti - FGE IFUSP
Resumo: 

Resumo: Proposto por Anderson em 1959 para descrever a mobilidade de elétrons em uma rede cristalina na presença de impurezas (contexto Físico: semicondutores, por exemplo, Si dopados com P), o modelo de Anderson é descrito por uma Hamiltoniana Hω = ∆ + V ω em l2 (Zd) onde ∆ é o Laplaciano discreto e V ω é um potencial aleatório (para cada sítio nV ω (n) é uma variável aleatória independente e igualmente distribuída F(x) = µ ( : Vω (n) ≤ x}) com um parâmetro v que controla a desordem. Anderson conjecturou a existência de um valor crítico 0 < vc < ∞ tal que, para v ≥ vo espectro de Hω é puro ponto (p.p.), µ quase certamente, e para v < vc medida espectral de Hω contém duas componentes separadas pela chamada fronteira de mobilidade (“mobility edges”) λ±: se λ ∈ [λ, λ+] o espectro de Hω  é puramente absolutamente contínuo (a.c.) e puro ponto no complemento, trazendo à Física dos materiais o importante e novo fenômeno de localização. Nossa atenção restringe-se aos últimos desenvolvimentos relativos a elusiva existência de espectro a.c., estabelecida em 1998 por A. Klein para o modelo de Anderson na rede de Bethe. Daremos nesta apresentaçãênfase as ideias e resultados empregados na trabalho em colaboração com W. F. Wreszinski sobre uma transição do tipo Anderson em uma classe de modelos esparsos em d ≥ 2

Páginas

Desenvolvido por IFUSP