Departamento de Física

Em 2010, quando Geim e Novoselov ganharam o Nobel, mostraram que, dentro da rede do grafeno, os eletrons se comportam como particulas sem massa - fermions de Dirac - podendo se movimentar a velocidade proximas a velocidade da luz dentro deste material. Esta propriedade atraiu a atencao da comunidade cientifica para a importância desse material. O grafeno e formado por uma rede hexagonal de carbono com hibridizacao sp2. Com espessura de um atomo, e considerado um material bidimensional. Uma das tecnicas de obtencao do grafeno e a deposicao quimica em fase vapor (chemical vapor deposition - CVD), com a qual obtemos grafeno quase que perfeitamente cristalino em monocamada. Este grafeno pode ser utilizado em aplicacoes na eletronica orgânica por manter a sua alta mobilidade eletronica. Uma desvantagem do uso do grafeno para transistores de efeito de campo (FETs) e que eles nao podem ser desligados, pois o grafeno e um semicondutor de GAP zero. Um jeito de resolver este problema e a aber...

We introduce and study a pure gauge Abelian theory in 2 + 1D in which massive quantum vortex states do exist in the spectrum of excitations. This theory can be mapped in a three-dimensional gas of point particles with a logarithmic interaction, in the grand-canonical ensemble. We claim that this theory is the 2 + 1D analog of the sine–Gordon, the massive vortices being the counterparts of sine–Gordon solitons. We show that a symmetry breaking, order parameter, similar to the vacuum expectation value of a Higgs field does exist.

We introduce and study a pure gauge Abelian theory in 2 + 1D in which massive quantum vortex states do exist in the spectrum of excitations. This theory can be mapped in a three-dimensional gas of point particles with a logarithmic interaction, in the grand-canonical ensemble. We claim that this theory is the 2 + 1D analog of the sine–Gordon, the massive vortices being the counterparts of sine–Gordon solitons. We show that a symmetry breaking, order parameter, similar to the vacuum expectation value of a Higgs field does exist.

Hydrodynamic turbulence is studied as a constrained system from the point of view of metafluid dynamics. We present a Lagrangian description for this new theory of turbulence inspired from the analogy with electromagnetism. Consequently it is a gauge theory. This new approach to the study of turbulence tends to renew the optimism to solve the difficult problem of turbulence. As a constrained system, turbulence is studied in the Dirac and Faddeev-Jackiw formalisms giving the Dirac brackets. An important result is that we show these brackets are the same in and out of the inertial range, giving the way to quantize turbulence.

In this work we show that we can obtain dual equivalent actions following the symplectic formalism with the introduction of extra variables which enlarge the phase space. We show that the results are equal as the one obtained with the recently developed gauging iterative Noether dualization method. We believe that, with the arbitrariness property of the zero mode, the symplectic embedding method is more profound since it can reveal a whole family of dual equivalent actions. We illustrate the method demonstrating that the gauge-invariance of the electromagnetic Maxwell Lagrangian broken by the introduction of an explicit mass term and a topological term can be restored to obtain the dual equivalent and gauge-invariant version of the theory.

The Wyman solution depends on two parameters, the mass M and the scalar charge Σ. If one fixes M to a positive value, say M0, and lets Σ2 take values along the real line, we show that this solution exhibits a type of critical behavior, in analogy with the nonstatic massless scalar field solutions. For Σ2>0 the space-times have naked singularities, for Σ2=0 one has a Schwarzschild black hole of mass M0 and finally for −M02⩽Σ2<0 one has “wormhole-like” solutions. We also show that the Wyman solution is not self-similar, i.e., it does not admit a homothetic Killing vector.

Improving the beginning steps of a previous work, we settle the dual embedding method (DEM) as an alternative and efficient method for obtaining dual equivalent actions also in D = 3. We show that we can obtain dual equivalent actions which were previously obtained in the literature using the gauging iterative Noether dualization method (NDM). We believe that, with the arbitrariness property of the zero mode, the DEM is more profound since it can reveal a whole family of dual equivalent actions. The result confirms the one obtained previously which is important since it has the same structure that appears in the Abelian Higgs model with an anomalous magnetic interaction.