Conveners
Cosmic Strings: Block 1
- Batool Imtiaz (University of Science and Technology of China)
- Reinoud Slagter (ASFYON, Astronomisch Fysisch Onderzoek Nederland)
Description
Cosmic strings (CS's) are topological defects formed at the GUT symmetry breaking scale in the Einstein-U(1) scalar- gauge field model. This model shows a surprising resemblance with superconductivity and the relativistic Nielsen-Olesen quantized magnetic flux vortex solution. In the standard model of particle physics this scalar-gauge field is responsible for the spontaneously broken symmetry (Higgs mechanism). So one could say that this quantum field with the Mexican hat potential has lived up to its reputation. In cosmological context, the confined regions of the false vacuum of the scalar field form a locus of trapped energy, i.e., a CS. The mass and dimension of a CS is largely determined by the energy scale at which the phase transition takes place.
It is believed that in the FLRW model a scale-invariant cosmic string-network is formed. Observational bounds, however, predict a negligible contribution of CS's to large-scale inhomogeneities such as the angular distribution in the CMB radiation. A renewed interest occurred when it was realized that CS's could be produced within the framework of superstring theory inspired cosmological models, i.e., brane-world models. Supersymmetric GUT's can even demand the existence of CS. These super-massive CS's could be produced when the universe underwent phase transitions at energies much higher than the GUT scale, so their gravitational impact increases. Although evidence of CS are not yet found, new observational windows are opened by these super-massive CS's.
In this parallel session one can present cosmic string-related subjects, such as observational results on CS, gravitational waves and CS, vortex solutions and GRT, cosmic strings and higher dimensional models.
We consider the possible existence of gravitationally bound stringlike objects in the framework of the generalized hybrid metric-Palatini gravity theory, in which the gravitational action is represented by an arbitrary function of the Ricci and of the Palatini scalars, respectively. The theory admits an equivalent scalar-tensor representation in terms of two independent scalar fields. Assuming...
There has been observational evidence about spin axes of quasars in large quasar groups correlated over hundreds of Mpc. This is seen in the radio spectrum as well as in the optical range. There is not yet a satisfactory explanation of this "spooky" alignment.
This alignment cannot be explained by mutual interaction at the time that quasars manifest themselves optically. A cosmological...
Gravitational wave astronomy opens up a new window of exploration in fundamental physics. The recent analysis by the NANOGrav collaboration based on the 12.5-year pulsar-timing data set has shown evidence for a common red process which is compatible with a stochastic background of gravitational waves. In this talk, we will discuss the interpretation of this signal in terms of physics beyond...
In this work, we study 5-dimensional braneworld scenarios in the scalar-tensor representation of the generalized hybrid metric-Palatini gravitational theory. We start by considering a model for a brane supported purely by the gravitational scalar fields of the theory and then consider other distinct cases where the models are also supported by an additional matter scalar field. We investigate...
