Seminar session on geometry and relativity

Seminar session on geometry and relativity

Sala de seminários do CMAT - building 6 room 3.08 |

Wed, 06/14/2023 - 12:00


Participation is free but please send an email to and state whether you would like to joins us for lunch at Restaurante Panorâmico. Deadline for registration: 5th June.

All are welcome! 


Tentative programme 

11:30: Abdelghani Zeghib (CNRS-ENS, Lyon, France)

Title: Kundt Spacetimes

Abstract: To any pseudo-Riemannian metric one associates the set of its scalar curvature invariants. One may ask if  this system of functions fully determines the metric. In particular, (locally)homogeneous pseudo-Riemannian spaces have all their scalar curvature invariants constant. One then asks if the converse is true? It turns out that in the Lorentz case, this constancy does not imply local homogeneity, but rather leads to a Kundt structure which is a kind of "geometric" foliation.  

12:30: Lunch

14:30: Michael Bradley (University of Umea, Sweden)

Title: Perturbations of a class of LRS Cosmologies for a general energy-momentum tensor with applications to dissipative fluids

Abstract:  First order perturbations of homogeneous and hypersurface orthogonal LRS (Locally Rotationally Symmetric) class II cosmologies are considered in the framework of the 1+1+2 covariant decomposition of spacetime. The study, which is for a general energy-momentum tensor, extends some previous works where matter was assumed to be a perfect fluid. Through a harmonic decomposition, the system of equations is transformed to evolution equations in time and algebraic constraints. This result is then applied to dissipative one-component fluids, and on using the simplified acausal Eckart theory the system is reduced to two closed subsystems governed by four and eight harmonic coefficients, respectively. The system is also seen to close in a simplified causal theory. Finally, it is shown, within the Eckart theory, how vorticity can be generated from viscosity.

15:30: Philip Semrén (University of Umea, Sweden)

Title: Electromagnetic, gravitational, and plasma related perturbations on a class of locally rotationally symmetric cosmologies. 

Abstract: This talk will be about some additional applications of the general equations shown in the presentation by Prof. Bradley, which describe perturbations on certain locally rotationally symmetric cosmologies. The main application that we will talk about is the case when the cosmological fluid is considered to be a plasma coupled to an electromagnetic field. This scenario can, for instance, be used to study the evolution, and potentially the amplification, of primordial magnetic fields. Finally, we will conclude with some potential topics that could be interesting to investigate further.



Organization: Ana Cristina Ferreira, João Oliveira e Maria Piedade Ramos.