All Outputs (62)

Dynamical simulations of electroweak baryogenesis with fermions (2012)
Journal Article
Saffin, P. M., & Tranberg, A. (2012). Dynamical simulations of electroweak baryogenesis with fermions. Journal of High Energy Physics, 2012(2), Article 102. https://doi.org/10.1007/JHEP02%282012%29102

We perform real-time numerical lattice simulations of a one-family version of the Standard Model. We model the quantum fermions using the ensemble method and treat the bosonic scalar and non-abelian gauge fields classically. Our main interest is elec... Read More about Dynamical simulations of electroweak baryogenesis with fermions.

General second-order scalar-tensor theory and self-tuning (2012)
Journal Article
Charmousis, C., Copeland, E. J., Saffin, P. M., & Padilla, A. (2012). General second-order scalar-tensor theory and self-tuning. Physical Review Letters, 108(5), Article 051101. https://doi.org/10.1103/PhysRevLett.108.051101

Starting from the most general scalar-tensor theory with second order field equations in four dimensions, we establish the unique action that will allow for the existence of a consistent self-tuning mechanism on FLRW backgrounds, and show how it can... Read More about General second-order scalar-tensor theory and self-tuning.

Reducing heterotic M-theory to five dimensional supergravity on a manifold with boundary (2011)
Journal Article
Moss, I. G., Omotani, J. T., & Saffin, P. M. (2011). Reducing heterotic M-theory to five dimensional supergravity on a manifold with boundary. Journal of High Energy Physics, 2011(10), https://doi.org/10.1007/JHEP10%282011%29088

This paper constructs the reduction of heterotic M-theory in eleven dimensions to a supergravity model on a manifold with boundary in five dimensions using a Calabi-Yau three-fold. New results are presented for the boundary terms in the action and fo... Read More about Reducing heterotic M-theory to five dimensional supergravity on a manifold with boundary.

Colliding branes and big crunches (2011)
Journal Article
Omotani, J., Saffin, P. M., & Louko, J. (2011). Colliding branes and big crunches. Physical Review D, 84(6), Article 063526. https://doi.org/10.1103/PhysRevD.84.063526

We examine the global structure of colliding domain walls in AdS spacetime and come to the conclusion that singularities forming from such collisions are of the big-crunch type rather than that of a black brane.

Real-time fermions for baryogenesis simulations (2011)
Journal Article
Saffin, P. M., & Tranberg, A. (2011). Real-time fermions for baryogenesis simulations. Journal of High Energy Physics, 2011(7), https://doi.org/10.1007/JHEP07%282011%29066

We study how to numerically simulate quantum fermions out of thermal equilibrium, in the context of electroweak baryogenesis. We find that by combining the lattice implementation of Aarts and Smit [1] with the "low cost" fermions of Borsanyi and Hind... Read More about Real-time fermions for baryogenesis simulations.

Multi-Galileons, solitons, and Derrick’s theorem (2011)
Journal Article
Padilla, A., Saffin, P. M., & Zhou, S.-Y. (2011). Multi-Galileons, solitons, and Derrick’s theorem. Physical Review D, 83(4), https://doi.org/10.1103/PhysRevD.83.045009

The field theory Galilean symmetry, which was introduced in the context of modified gravity, gives a neat way to construct Lorentz-covariant theories of a scalar field, such that the equations of motion contain at most second-order derivatives. Here... Read More about Multi-Galileons, solitons, and Derrick’s theorem.

Bi-galileon theory II: phenomenology (2011)
Journal Article
Padilla, A., Saffin, P. M., & Zhou, S.-Y. (2011). Bi-galileon theory II: phenomenology. Journal of High Energy Physics, 2011(1), https://doi.org/10.1007/JHEP01%282011%29099

We continue to introduce bi-galileon theory, the generalisation of the single galileon model introduced by Nicolis et al. The theory contains two coupled scalar fields and is described by a Lagrangian that is invariant under Galilean shifts in those... Read More about Bi-galileon theory II: phenomenology.

Bi-galileon theory I: motivation and formulation (2010)
Journal Article
Padilla, A., Saffin, P. M., & Zhou, S.-Y. (2010). Bi-galileon theory I: motivation and formulation. Journal of High Energy Physics, 2010(12), https://doi.org/10.1007/JHEP12%282010%29031

We introduce bi-galileon theory, the generalisation of the single galileon model introduced by Nicolis et al. The theory contains two coupled scalar fields and is described by a Lagrangian that is invariant under Galilean shifts in those fields. This... Read More about Bi-galileon theory I: motivation and formulation.

The gravitational dynamics of warped throats (2010)
Journal Article
Butcher, N. A., & Saffin, P. M. (in press). The gravitational dynamics of warped throats. Journal of High Energy Physics, 2010(6), https://doi.org/10.1007/JHEP06%282010%29044

We investigate the time evolution due to gravitational dynamics of a particular spacetime commonly used in brane-cosmology and string compactifications, namely the Klebanov-Strassler geometry, which is achieved by adding a perturbation to the momentu... Read More about The gravitational dynamics of warped throats.

Evolution and stability of cosmic string loops with Y-junctions (2009)
Journal Article
Bevis, N., Copeland, E. J., Martin, P.-Y., Niz, G., Pourtsidou, A., Saffin, P. M., & Steer, D. (2009). Evolution and stability of cosmic string loops with Y-junctions. Physical Review D, 80(12), https://doi.org/10.1103/PhysRevD.80.125030

We study the evolution of non-periodic cosmic string loops containing Y-junctions, such as may form during the evolution of a network of (p,q) cosmic superstrings. We set up and solve the Nambu-Goto equations of motion for a loop with junctions, focu... Read More about Evolution and stability of cosmic string loops with Y-junctions.

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 t... Read More about Oscillons and quasi-breathers in D+1 dimensions.