XXth Oporto Meeting on Geometry, Topology and Physics
		19th to 22nd July 2012

Main Speakers

Talks 1:

Courses | Invited talks | talks | 1 | 2 | 3 |

Speaker	Talk
Chryssomalis Chryssomalakos (Instituto de Ciencias Nucleares UNAM, Mexico)	Operational Geometry on de Sitter Spacetime Abstract: Traditional geometry employs concepts like that of a point or a curve, the operational definition of which relies on the availability of classical point particles as probes. Such particles seem to not exist in nature, forcing us to consider here the efects of the use of realistic probes on the efective geometry of classical manifolds. As an example, we consider de Sitter spacetime, andemploy various composite probes to measure its sectional curvature " we compute the efects of the probes internal energy, spatial extension, and spin, on the measurement. Implications of our results for various approaches to quantum gravity are outlined.
Pedro Castelo Ferreira (Univ. of Lisbon, Lisbon, Portugal)	CFTD-branes description from 2+1D topological field theory Abstract: Are derived the world sheet D-branes vertex operators from the orbifolding of 2+1D topological massive gauge theories coupled to a dynamical scalar field. It is shown that the boundary conformal field theory states corresponding to D-branes are described by the vacuum states of the bulk theory and the brane tension is set by the bulk mass scales.
Simona-Luiza Druta-Romaniuc (Univ. "Alexandru Ioan Cuza" din Iasi, Romania)	Magnetic curves corresponding to Killing magnetic fields on 3D spaces Abstract: We find all the magnetic trajectories of the Killing magnetic fields on the three-dimensional Euclidian and Minkowksi spaces. While in the Euclidian case all the three vector fields corresponding to the canonical coordinates play the same role, in a three-dimensional Minkowksi space, only two of the mentioned vector fields play similar roles. So, in the second case is relevant to consider the Killing vector fields which are combinations of the three vector fields, with real coeficients, and to determine their associated magnetic curves.
Sebastian Guttenberg (CAMGSD and Instituto Superior Técnico, Lisbon, Portugal)	The quantum Siegel algebra Abstract: Siegel's algebra is the constraint algebra generated by the Virasoro constraints and the kappa-symmetry current of the Green Schwarz superstring. It was discussed in the literature mainly at classical level. In the context of the composite b-ghost of Berkovits' pure spinor string, these Siegel generators reappeared. The talk will present the Siegel algebra at quantum level (in terms of OPE's) with all its anomalies and discuss how these can be canceled and how it is related to Berkovits' b-ghost operators.