THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar: 

Exact vortex solutions in the extended CPN Skyrme-Faddeev model. 

Prof. Pawel Klimas

Departamento de Física – UFSC 

Abstract: 

The Skyrme-Faddeev model is a candidate for an effective classical model of the pure Yang-Mills theory in the low-energy (non-perturbative) limit. Its extended version possesses an integrable sector presenting an infinite number of local conservation laws, which are associated to the hidden symmetries of the zero curvature representation of the theory in loop space. In this sector one can construct some exact vortex solutions with waves traveling along them. 

Date: 20/September/2013 – (Friday) – Place: Sala 419 – Auditório do Bloco G – Time: 10:00

THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar:  

Colour-tuneable organic light-emitting transistors 

Prof. Heinz von Seggern

Electronic Materials, Technische Universität Darmstadt, 64287 Darmstadt, Germany. 

Abstract: 

The unique property of ambipolar organic light emitting field-effect transistors (OLETs) is the ability to position the light emission zone within the transistor channel through the applied biases. In this talk the basics of the ambipolar OLET will be discussed and two examples for colour conversion will be demonstrated. Both approaches take advantage of the ability of a controlled displacement of the recombination zone through the organic semiconductors. In the first approach two different acenes with different emission colours are employed in a parallel stack in a top-contact bottom-gate FET configuration. It will be demonstrated that due to thermionic emission of electrons at the source, light of one colour can be generated near the source contact even in hole accumulation. Due to the electrically controllable positioning the charge carrier recombination zone can be directed from the top acene layer to in the bottom acene layer. Thereby the emitted light can be continuously shifted by about 50 nm from green to red. A second approach takes advantage of the horizontal displacement of the recombination zone within the channel of the transistor. On top of the semi-transparent gate electrode of a F8BT transistor a colour conversion layer is deposited in a wedge-like shape partially covering the channel. In the ambipolar regime the charge carrier recombination takes place in the F8BT layer, and dependent on the position of the recombination zone either the emitted light of the F8BT layer or the partially absorbed and converted light from the colour conversion layer can be detected. The electroluminescence maximum of the emitted light can be shifted by about 30 nm. The physics and potential applications of such colour tuneable OLETs will be discussed. 

Date: 13/September/2013 – (Friday) – Place: Sala 419 – Auditório do Bloco G – Time: 10:00

THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar: 

 Quark matter under strong magnetic fields

Prof. Norberto Scoccola / Depto. de Fisica, Lab. TANDAR – Argentina

Abstract:

The phase structure of magnetized cold quark matter is analyzed in the framework of the two-flavor Nambu-Jona-Lasinio models paying special attention to its dependence on the model parameters as different values within the phenomenological allowed range are consid- ered. We first discuss the simpler chiral limit case, and then the more realistic situation of finite current masses. We show that in spite of the difference in the nature of some transi- tions, both cases are alike and exhibit a rather rich phase structure for a significant range of acceptable parameters. A simplification of the phase structure is obtained as parameters leading to larger values of the dressed quark mass in the vacuum are considered. Finally, we consider the so-called “inverse catalysis effect” showing that in some phases it implies an actual decrease of the order parameter as the magnetic field increases.

Date: 6/September/2013 – (Friday) – Place: Auditório do Bloco G – Sala 419 – Time: 10:00

The Physics Graduate Program invites everyone to: 

Qualifying Examination for Doctoral Thesis

Luiz Laércio Lopes 

Estrelas de Nêutrons no Regime da Simetria SU(3) 

Defense Committee: 

Prof. Dr. Marcus Emmanuel Benghi Pinto – (President) – FSC/UFSC

Prof. Dr. Norberto N. Scoccola – (Membro inglês) – Depto de Física – Lab. TANDAR

Prof. Dr. Sidney dos Santos Avancini – (Local member) – FSC/UFSC

Date: 6/September/2013 – Friday – Time: 2:00 pm – Place: Auditório do Bloco G – Sala 419