THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar:
“Cosmological implications of the Yang-Mills vacuum and Dark Energy”
ROMAN PASECHNIK – Lund University
Abstract:
In my talk I will discuss important implications of the Yang-Mills (in particular, QCD) vacuum dynamics in Cosmology. Such important aspects as compensation of non-perturbative vacua at large distances, de-Sitter solutions of Einstein-Yang-Mills equations with homogeneous SU(2) condensate accounting for the vacuum polarisation, possibility for Cosmic Inflation driven by the Yang-Mills condensate and generation of Dark Energy as a gravitational correction to the QCD ground state energy will be discussed in some basic details.
Date: 24/July/2015 – (friday) – Place: Sala 212 – Auditório do Departamento de Física– Time: 10h15min
THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar:
Vignettes from the world of liquid crystals
Peter Palffy-Muhoray
Liquid Crystal Institute, Kent State University – USA
Abstract:
Liquid crystals, discovered some 125 years ago, are orientationally ordered soft materials. Although they have received considerable attention – much of it due to their potential for applications in display devices – they continue to astonish, puzzle and delight. In this talk, I will describe some unusual phenomena in liquid crystalline systems which originate in orientational order. I will discuss ideas about the underlying physics, and indicate some intriguing problems that remain unsolved.
Date: 15/July/2015 – (wednesday) – Place: Sala 212 – Auditório do Departamento de Física– Time: 10h15min
THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar:
Gravitational lensing
Gena S. Bisnovatyi-Kogan
Space Research Institute, Russian Academy of Sciences,
Russia and National Research Nuclear University MEPhI, Moscow, Russia
Abstract:
After some historical remarks, we consider observational data on the gravitational lensing, different types of lensing: strong, weak, and microlensing, discovery of planets around distant stars by microlensing. We consider lensing with large deviation angles, when light passes close to the gravitational radius of the lens, and formation of weak relativistic rings. In the last part we consideran influence of plasma on the gravitational lensing. When a gravitating body is surrounded by a plasma, the lensing angle depends on the frequency of the electromagnetic wave, due to dispersion properties of plasma, in presence of a plasma inhomogeneity, and due to a gravity. The second effect leads, even in a uniform plasma, to a difference of the gravitational photon deflection angle from the vacuum case, and to its dependence on the photon frequency. Both effects are taken into account. Dependence of the lensing angle on the photon frequency in a homogeneous plasma resembles the properties of a refractive prism spectrometer, which strongest action is for longest radio waves. We have shown that the gravitational effect could be detected in the case of a hot gas in the gravitational field of a galaxy cluster.
Date: 26/July/2015 – (friday) – Place: Sala 212 – Auditório do Departamento de Física– Time: 10h15min
THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar:
Cópias de Gribov e Confinamento
Prof. Dr. Marcelo Santos Guimarães – UERJ
Abstract:
A quantização de teorias de calibre não-abelianas sofre com problemas de ambiguidades no procedimento de fixação de calibre, caracterizados pelo aparecimento de modos-zero no operador de Faddeev-Popov no regime de baixas energias da teoria. Esses modos-zero dão origem às cópias de Gribov, que corresponde a existência de configurações equivalentes dos campos mesmo após a fixação de calibre. Essa falha no procedimento de fixação de calibre no regime não-perturbativo sinaliza a necessidade de uma análise mais cuidadosa da teoria em baixas energias e, de fato, foi mostrado que as cópias de Gribov estão relacionadas com as propriedades confinantes das teorias de calibre. Neste trabalho serão discutidas as relações gerais entre as cópias de Gribov e confinamento. Muitos resultados sobre os efeitos das cópias de Gribov na física de baixas energias das teorias de calibre serão apresentadas. A tentativa de eliminar consistentemente as cópias é feita restringindo-se as configurações de campos na formulação de integral funcional para a chamada região de Gribov. Esta restrição fornece uma teoria efetiva descrevendo a dinâmica os campos de calibre em baixas energias: a teoria de Gribov-Zwanziger. A construção e as propriedades gerais dessa teoria serão discutidas. A mesma construção pode ser aplicada à campos de calibre em interação com campos de matéria. Neste contexto, a estrutura de fases do sistema Yang-Mills-Higgs pode ser analisada do ponto de vista do fenômeno de Gribov. A influência das cópias de Gribov em teorias supersimétricas também será discutida.
Date: 19/June/2015 – (friday) – Place: Sala 212 – Auditório do Departamento de Física– Time: 10h15min
