arXiv subjects

Ian R. Vernon

Publications and source records attributed to Ian R. Vernon.

4 recordsLinked to original sources

arXiv2005

Graviton Emission into Non-Z_2 Symmetric Brane World Spacetimes

The equations for the evolution of a homogeneous brane world that emits gravitons at early times, and into a non-Z_2 symmetric bulk, are derived using an AdS-Vaidya spacetime approximation. The behaviour of the black hole mass parameters either side of the brane is analysed, and it is found that in general graviton emission leads to a decrease in the non-Z_2 symmetry. However, the behaviour of the dark radiation term in the Friedmann equation is more complex: it is shown that this term can increase or decrease due to the non-Z_2 symmetry, and can become negative in some cases, leading to H=0 and the brane universe collapsing. Constraints on the initial (nonzero) sizes of the mass parameters are therefore derived.

hep-th↗

arXiv2004

Bulk black holes radiating in non-Z_2 brane-world spacetimes

In this paper we present a general asymmetric brane model involving arbitrary energy transport to and from an embedded 4-D FRW universe. We derive a locally defined mass function for the 5D spacetime and describe its time evolution on the brane. We then specialise our model to the two cases of graviton production in the early universe and radiating black holes in the bulk.

hep-th↗

arXiv2004

Exact Evolution of the Complete Non-Linear Cosmological Radion

The cosmological two brane model is discussed in detail. An elegant method for deriving the generalised non-linear equations for the interbrane distance is presented. These equations are used to identify equilibrium positions of the radion, and are then linearised in order to determine the nature of these equilibrium solutions. Numerical methods are then employed to determine the complete behaviour of the (unstabilised) cosmological radion for a variety of interesting cases, including radiation and matter dominated non-Z_2 symmetric branes. The implications to theories involving brane collisions are then discussed.

hep-ph↗

arXiv2001

Cosmological Phase Transitions in a Brane World

In brane world scenarios the Friedmann equation is modified, resulting in an increased expansion at early times. This has important effects on cosmological phase transitions which we investigate, elucidating significant differences to the standard case. First order phase transitions require a higher nucleation rate to complete; baryogenesis and particle abundances could be suppressed. Topological defect evolution is also affected, though the current defect densities are largely unchanged. In particular, the increased expansion does not solve the usual monopole and domain wall problems.

hep-ph↗