All Outputs (77)

Simulations of Cold Electroweak Baryogenesis: hypercharge U(1) and the creation of helical magnetic fields (2017)
Journal Article
Mou, Z.-G., Saffin, P. M., & Tranberg, A. (2017). Simulations of Cold Electroweak Baryogenesis: hypercharge U(1) and the creation of helical magnetic fields. Journal of High Energy Physics, 2017(6), https://doi.org/10.1007/JHEP06%282017%29075

We perform numerical simulations of Cold Electroweak Baryogenesis, including for the first time in the Bosonic sector the full electroweak gauge group SU(2)×U(1) and CP-violation. We find that the maximum generated baryon asymmetry is reduced by a fa... Read More about Simulations of Cold Electroweak Baryogenesis: hypercharge U(1) and the creation of helical magnetic fields.

Highly excited strings I: Generating function (2017)
Journal Article
Skliros, D. P., Copeland, E. J., & Saffin, P. M. (in press). Highly excited strings I: Generating function. Nuclear Physics B, https://doi.org/10.1016/j.nuclphysb.2016.12.022

This is the first of a series of detailed papers on string amplitudes with highly excited strings (HES). In the present paper we construct a generating function for string amplitudes with generic HES vertex operators using a fixed-loop momentum forma... Read More about Highly excited strings I: Generating function.

Disformally self-tuning gravity (2016)
Journal Article
Emond, W. T., & Saffin, P. M. (in press). Disformally self-tuning gravity. Journal of High Energy Physics, 2016(3), https://doi.org/10.1007/JHEP03%282016%29161

We extend a previous self-tuning analysis of the most general scalar-tensor theory of gravity in four dimensions with second order field equations by considering a generalized coupling to the matter sector. Through allowing a disformal coupling to ma... Read More about Disformally self-tuning gravity.

The Parametrized Post-Newtonian-Vainshteinian formalism (2015)
Journal Article
Avilez-Lopez, A., Padilla, A., Saffin, P. M., & Skordis, C. (2015). The Parametrized Post-Newtonian-Vainshteinian formalism. Journal of Cosmology and Astroparticle Physics, 2015(6), Article 044. https://doi.org/10.1088/1475-7516/2015/06/044

Light degrees of freedom that modify gravity on cosmological scales must be "screened" on solar system scales in order to be compatible with data. The Vainshtein mechanism achieves this through a breakdown of classical perturbation theory, as large i... Read More about The Parametrized Post-Newtonian-Vainshteinian formalism.

Cold Baryogenesis from first principles in the two-Higgs doublet model with fermions (2015)
Journal Article
Mou, Z.-G., Saffin, P. M., & Tranberg, A. (2015). Cold Baryogenesis from first principles in the two-Higgs doublet model with fermions. Journal of High Energy Physics, 2015, https://doi.org/10.1007/JHEP06%282015%29163

We present a first-principles numerical computation of the baryon asymmetry in electroweak-scale baryogenesis. For the scenario of Cold Baryogenesis, we consider a one fermion-family reduced CP-violating two Higgs-doublet model, including a classical... Read More about Cold Baryogenesis from first principles in the two-Higgs doublet model with fermions.

Unitarity and the Vainshtein mechanism (2015)
Journal Article
Kaloper, N., Padilla, A., Saffin, P. M., & Stefanyszyn, D. (2015). Unitarity and the Vainshtein mechanism. Physical Review D, 91(4), https://doi.org/10.1103/PhysRevD.91.045017

We investigate low energy limits of massive gauge theories that feature the Vainshtein mechanism, focussing on the effects of the UV modes that are integrated out. It turns out that the Goldstone sectors are significantly influenced by the effects fr... Read More about Unitarity and the Vainshtein mechanism.

Charge-swapping q balls (2014)
Journal Article
Copeland, E. J., Saffin, P. M., & Zhou, S. Y. (2014). Charge-swapping q balls. Physical Review Letters, 113(23), https://doi.org/10.1103/PhysRevLett.113.231603

© 2014 American Physical Society. Q balls are nontopological solitonic solutions to a wide class of field theories that possess global symmetries. Here we show that in these same theories there also exists a tower of novel composite Q-ball solutions... Read More about Charge-swapping q balls.

Oscillon lifetime in the presence of quantum fluctuations (2014)
Journal Article
Saffin, P. M., Tognarelli, P., & Tranberg, A. (2014). Oscillon lifetime in the presence of quantum fluctuations. Journal of High Energy Physics, 2014(8), Article 125. https://doi.org/10.1007/JHEP08%282014%29125

We consider the stability of oscillons in 2+1 space-time dimensions, in the presence of quantum fluctuations. Taking the oscillon to be the inhomogeneous mean field of a self-interacting quantum scalar field, we compare its classical evolution to the... Read More about Oscillon lifetime in the presence of quantum fluctuations.

Ensemble fermions for electroweak dynamics and the fermion preheating temperature (2013)
Journal Article
Mou, Z.-G., Tranberg, A., & Saffin, P. M. (2013). Ensemble fermions for electroweak dynamics and the fermion preheating temperature. Journal of High Energy Physics, 2013(11), https://doi.org/10.1007/JHEP11%282013%29097

We refine the implementation of ensemble fermions for the electroweak sector of the Standard Model, introduced previously. We consider the behavior of different observables as the size of the ensemble is increased and show that the dynamics converges... Read More about Ensemble fermions for electroweak dynamics and the fermion preheating temperature.

Gravitational waves from oscillon preheating (2013)
Journal Article
Zhou, S.-Y., Copeland, E. J., Easther, R., Finkel, H., Mou, Z.-G., & Saffin, P. M. (2013). Gravitational waves from oscillon preheating. Journal of High Energy Physics, 2013, Article 26. https://doi.org/10.1007/JHEP10%282013%29026

Oscillons are long-lived, localized excitations of nonlinear scalar fields which may be copiously produced during preheating after inflation, leading to a possible oscillon-dominated phase in the early Universe. For example, this can happen after axi... Read More about Gravitational waves from oscillon preheating.

Adiabatic and isocurvature perturbation projections in multi-field inflation (2013)
Journal Article
Gordon, C., & Saffin, P. M. (2013). Adiabatic and isocurvature perturbation projections in multi-field inflation. Journal of Cosmology and Astroparticle Physics, 2013(8), Article 021. https://doi.org/10.1088/1475-7516/2013/08/021

Current data are in good agreement with the predictions of single field inflation. However, the hemispherical asymmetry seen in the cosmic microwave background data, may hint at a potential problem. Generalizing to multi-field models may provide one... Read More about Adiabatic and isocurvature perturbation projections in multi-field inflation.

Duality and decay of macroscopic F-strings (2013)
Journal Article
Skliros, D. P., Copeland, E. J., & Saffin, P. M. (2013). Duality and decay of macroscopic F-strings. Physical Review Letters, 111(4), Article 041601. https://doi.org/10.1103/PhysRevLett.111.041601

We study the decay of fundamental string loops of arbitrary size L/min(n,m)≫√α′, labeled by (n, m; λn, ¯λm), where n, m correspond to left- and right-mover harmonics and λn, ¯λm to polarization tensors, and find that a description in terms of the rec... Read More about Duality and decay of macroscopic F-strings.

The covariance of multi-field perturbations, pseudo-susy and fNL (2012)
Journal Article
Saffin, P. M. (2012). The covariance of multi-field perturbations, pseudo-susy and fNL. Journal of Cosmology and Astroparticle Physics, 2012(9), Article 002. https://doi.org/10.1088/1475-7516/2012/09/002

We reconsider cosmological perturbation theory for multi-component scalars, enforcing covariance in field-space, and ensuring that phyical observations are independent of field re-definitions. We use the formalism to clarify some issues in the litera... Read More about The covariance of multi-field perturbations, pseudo-susy and fNL.

Classical duals, Legendre transforms and the Vainshtein mechanism (2012)
Journal Article
Padilla, A., & Saffin, P. M. (2012). Classical duals, Legendre transforms and the Vainshtein mechanism. Journal of High Energy Physics, 2012(7), Article 122. https://doi.org/10.1007/JHEP07%282012%29122

We show how to generalize the classical duals found by Gabadadze {et al} to a very large class of self-interacting theories. This enables one to adopt a perturbative description beyond the scale at which classical perturbation theory breaks down in t... Read More about Classical duals, Legendre transforms and the Vainshtein mechanism.

Self-tuning and the derivation of a class of scalar-tensor theories (2012)
Journal Article
Charmousis, C., Copeland, E. J., Padilla, A., & Saffin, P. M. (2012). Self-tuning and the derivation of a class of scalar-tensor theories. Physical Review D, 85(10), Article 104040. https://doi.org/10.1103/PhysRevD.85.104040

We have recently proposed a special class of scalar tensor theories known as the Fab Four. These arose from attempts to analyse the cosmological constant problem within the context of Horndeski's most general scalar tensor theory. The Fab Four togeth... Read More about Self-tuning and the derivation of a class of scalar-tensor theories.

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.