All Outputs (72)

Strong coupling in Hořava gravity (2009)
Journal Article
Charmousis, C., Niz, G., Padilla, A., & Saffin, P. M. (2009). Strong coupling in Hořava gravity. Journal of High Energy Physics, 2009(8), https://doi.org/10.1088/1126-6708/2009/08/070

By studying perturbations about the vacuum, we show that Horava gravity suffers from two different strong coupling problems, extending all the way into the deep infra-red. The first of these is associated with the principle of detailed balance and ex... Read More about Strong coupling in Hořava gravity.

Cosmological constraints on f(G) dark energy models (2009)
Journal Article
Zhou, S.-Y., Copeland, E. J., & Saffin, P. M. (2009). Cosmological constraints on f(G) dark energy models. Journal of Cosmology and Astroparticle Physics, 2009(7), https://doi.org/10.1088/1475-7516/2009/07/009

Modified gravity theories with the Gauss-Bonnet term G=R2−4RμνRμν+RμνρσRμνρσ have recently gained a lot of attention as a possible explanation of dark energy. We perform a thorough phase space analysis on the so-called f(G) models, where f(G) is some... Read More about Cosmological constraints on f(G) dark energy models.

The evolution of conifolds (2008)
Journal Article
Butcher, N. A., & Saffin, P. M. (2008). The evolution of conifolds. Journal of High Energy Physics, 2008(12), https://doi.org/10.1088/1126-6708/2008/12/012

We simulate the gravitational dynamics of the conifold geometries (resolved and deformed) involved in the description of certain compact spacetimes. As the cycles of the conifold collapse towards a singular geometry we find that a horizon develops, s... Read More about The evolution of conifolds.

Some stationary properties of a Q-ball in arbitrary space dimensions (2008)
Journal Article
Tsumagari, M. I., Copeland, E. J., & Saffin, P. M. (2008). Some stationary properties of a Q-ball in arbitrary space dimensions. Physical Review D, 78(6), https://doi.org/10.1103/PhysRevD.78.065021

Introducing new physically motivated ansaetze, we explore both analytically and numerically the classical and absolute stabilities of a single Q-ball in an arbitrary number of spatial dimensions D, working in both the thin and thick wall limits.

Transmission of an inhomogeneous state via resonant tunnelling (2008)
Journal Article
Saffin, P. M., Padilla, A., & Copeland, E. J. (2008). Transmission of an inhomogeneous state via resonant tunnelling. Journal of High Energy Physics, 2008(9), https://doi.org/10.1088/1126-6708/2008/09/055

We recently investigated the nature of resonant tunnelling in standard scalar Quantum Field Theory, uncovering the conditions required for resonance. It was shown that whereas the homogeneous false vacuum may decay via bubble nucleation, it may not d... Read More about Transmission of an inhomogeneous state via resonant tunnelling.

Cosmic string Y-junctions: a comparison between field theoretic and Nambu-Goto dynamics (2008)
Journal Article
Bevis, N., & Saffin, P. M. (2008). Cosmic string Y-junctions: a comparison between field theoretic and Nambu-Goto dynamics. Physical Review D, 78(2), https://doi.org/10.1103/PhysRevD.78.023503

We explore the formation of cosmic string Y-junctions when strings of two different types collide, which has recently become important since string theory can yield cosmic strings of distinct types. Using a model containing two types of local U(1) st... Read More about Cosmic string Y-junctions: a comparison between field theoretic and Nambu-Goto dynamics.

The fermion spectrum in braneworld collisions (2007)
Journal Article
Saffin, P. M., & Tranberg, A. (2007). The fermion spectrum in braneworld collisions. Journal of High Energy Physics, 2007(12), https://doi.org/10.1088/1126-6708/2007/12/053

In braneworld collisions fermions originally localised on one brane can be transferred to another brane, or to a space-time boundary. By modelling branes as scalar field kinks we bounce them off boundaries and study resulting effects according to a b... Read More about The fermion spectrum in braneworld collisions.

Singular manifolds, topology change and the dynamics of compactification (2007)
Journal Article
Butcher, N. A., & Saffin, P. M. (2007). Singular manifolds, topology change and the dynamics of compactification. Journal of High Energy Physics, 2007(11), https://doi.org/10.1088/1126-6708/2007/11/062

We investigate the dynamics of the geometric transitions associated to compactified spacetimes. By including the dynamics of gravity we are able to follow the evolution of collapsing cycles as they attempt to undergo a topology changing transition. R... Read More about Singular manifolds, topology change and the dynamics of compactification.

Particle transfer in braneworld collisions (2007)
Journal Article
Saffin, P. M., & Tranberg, A. (2007). Particle transfer in braneworld collisions. Journal of High Energy Physics, 2007(8), https://doi.org/10.1088/1126-6708/2007/08/072

We study the behaviour of fermions localized on moving kinks as these collide with either antikinks or spacetime boundaries. We numerically solve for the evolution of the scalar kinks and the bound (i.e. localized) fermion modes, and calculate the nu... Read More about Particle transfer in braneworld collisions.

Oscillons and quasi-breathers in D+1 dimensions (2007)
Journal Article
Saffin, P. M., & Tranberg, A. (2007). Oscillons and quasi-breathers in D+1 dimensions. Journal of High Energy Physics, 2007(1), https://doi.org/10.1088/1126-6708/2007/01/030

We study oscillons in D+1 space-time dimensions using a spherically symmetric ansatz. From Gaussian initial conditions, these evolve by emitting radiation, approaching quasi-breathers'', near-periodic solutions to the equations of motion. Using a tru... Read More about Oscillons and quasi-breathers in D+1 dimensions.

Scaling solutions and geodesics in moduli space (2006)
Journal Article
Karthauser, J., & Saffin, P. M. (2006). Scaling solutions and geodesics in moduli space. Classical and Quantum Gravity, 23(14), https://doi.org/10.1088/0264-9381/23/14/004

In this paper we consider cosmological scaling solutions in general relativity coupled to scalar fields with a non-trivial moduli space metric. We discover that the scaling property of the cosmology is synonymous with the scalar fields tracing out a... Read More about Scaling solutions and geodesics in moduli space.

The Dynamics of coset dimensional reduction (2006)
Journal Article
Karthauser, J. L., & Saffin, P. M. (2006). The Dynamics of coset dimensional reduction. Physical Review D, 73(8), https://doi.org/10.1103/PhysRevD.73.084027

The evolution of multiple scalar fields in cosmology has been much studied, particularly when the potential is formed from a series of exponentials. For a certain subclass of such systems it is possible to get `assisted` behaviour, where the presence... Read More about The Dynamics of coset dimensional reduction.