All Outputs (41)

An étude on global vacuum energy sequester (2017)
Journal Article
D’Amico, G., Kaloper, N., Padilla, A., Stefanyszyn, D., Westphal, A., & Zahariade, G. (2017). An étude on global vacuum energy sequester. Journal of High Energy Physics, 2017(9), Article 74. https://doi.org/10.1007/JHEP09%282017%29074

Recently two of the authors proposed a mechanism of vacuum energy sequester as a means of protecting the observable cosmological constant from quantum radiative corrections. The original proposal was based on using global Lagrange multipliers, but la... Read More about An étude on global vacuum energy sequester.

Probing scalar effective field theories with the soft limits of scattering amplitudes (2017)
Journal Article
Padilla, A., Stefanyszyn, D., & Wilson, T. (2017). Probing scalar effective field theories with the soft limits of scattering amplitudes. Journal of High Energy Physics, 2017(4), https://doi.org/10.1007/JHEP04%282017%29015

We investigate the soft behaviour of scalar effective field theories (EFTs) when there is a number of distinct derivative power counting parameters, ?1 < ?2 < . . . < ?Q. We clarify the notion of an enhanced soft limit and use these to extend the sco... Read More about Probing scalar effective field theories with the soft limits of scattering amplitudes.

Vacuum energy sequestering and graviton loops (2017)
Journal Article
Kaloper, N., & Padilla, A. (2017). Vacuum energy sequestering and graviton loops. Physical Review Letters, 118(6), Article 061303. https://doi.org/10.1103/PhysRevLett.118.061303

We recently formulated a local mechanism of vacuum energy sequester. This mechanism automatically removes all matter loop contributions to vacuum energy from the stress energy tensor which sources the curvature. Here we adapt the local vacuum energy... Read More about Vacuum energy sequestering and graviton loops.

Sequestering effects on and of vacuum decay (2016)
Journal Article
Kaloper, N., Padilla, A., & Stefanyszyn, D. (2016). Sequestering effects on and of vacuum decay. Physical Review D, 94(2), Article 25022. https://doi.org/10.1103/PhysRevD.94.025022

We consider phase transitions and their contributions to vacuum energy in the manifestly local theory of vacuum energy sequestering. We demonstrate that the absence of instabilities imposes constraints on the couplings of gravitating and nongravitati... Read More about Sequestering effects on and of vacuum decay.

How to avoid a swift kick in the chameleons (2016)
Journal Article
Padilla, A., Platts, E., Stefanyszyn, D., Walters, A., Weltman, A., & Wilson, T. (2016). How to avoid a swift kick in the chameleons. Journal of Cosmology and Astroparticle Physics, 2016, Article 58. https://doi.org/10.1088/1475-7516/2016/03/058

Recently, it was argued that the conformal coupling of the chameleon to matter fields created an issue for early universe cosmology. As standard model degrees of freedom become non-relativistic in the early universe, the chameleon is attracted toward... Read More about How to avoid a swift kick in the chameleons.

Manifestly Local Theory of Vacuum Energy Sequestering (2016)
Journal Article
Kaloper, N., Padilla, A., Stefanyszyn, D., & Zahariade, G. (2016). Manifestly Local Theory of Vacuum Energy Sequestering. Physical Review Letters, 116(5), Article 051302. https://doi.org/10.1103/PhysRevLett.116.051302

© 2016 American Physical Society. We present a manifestly local, diffeomorphism invariant, and locally Poincaré invariant formulation of vacuum energy sequestering. In this theory, quantum vacuum energy generated by matter loops is canceled by auxili... Read More about Manifestly Local Theory of Vacuum Energy Sequestering.

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.

Sequestration of vacuum energy and the end of the universe (2015)
Journal Article
Kaloper, N., & Padilla, A. (2015). Sequestration of vacuum energy and the end of the universe. Physical Review Letters, 114(10), https://doi.org/10.1103/PhysRevLett.114.101302

Recently, we proposed a mechanism for sequestering the standard model vacuum energy that predicts that the Universe will collapse. Here we present a simple mechanism for bringing about this collapse, employing a scalar field whose potential is linear... Read More about Sequestration of vacuum energy and the end of the universe.

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.

Vacuum energy sequestering: The framework and its cosmological consequences (2014)
Journal Article
Kaloper, N., & Padilla, A. (2014). Vacuum energy sequestering: The framework and its cosmological consequences. Physical Review D - Particles, Fields, Gravitation and Cosmology, 90(8), https://doi.org/10.1103/physrevd.90.084023

Recently we suggested a reformulation of general relativity which completely sequesters from gravity all of the vacuum energy from a protected matter sector, assumed to contain the standard model. Here we elaborate further on the mechanism, presentin... Read More about Vacuum energy sequestering: The framework and its cosmological consequences.

Sequestering the standard model vacuum energy (2014)
Journal Article
Kaloper, N., & Padilla, A. (2014). Sequestering the standard model vacuum energy. Physical Review Letters, 112(9), Article 091304. https://doi.org/10.1103/PhysRevLett.112.091304

We propose a very simple reformulation of general relativity, which completely sequesters from gravity all of the vacuum energy from a matter sector, including all loop corrections and renders all contributions from phase transitions automatically sm... Read More about Sequestering the standard model vacuum energy.

The cosmology of the Fab-Four (2012)
Journal Article
Copeland, E. J., Padilla, A., & Saffin, P. M. (2012). The cosmology of the Fab-Four. Journal of Cosmology and Astroparticle Physics, 2012(12), Article 026. https://doi.org/10.1088/1475-7516/2012/12/026

We have recently proposed a novel self tuning mechanism to alleviate the famous cosmological constant problem, based on the general scalar tensor theory proposed by Horndeski. The self-tuning model ends up consisting of four geometric terms in the ac... Read More about The cosmology of the Fab-Four.

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.

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.

Multi-Galileons, solitons, and Derrick’s theorem (2011)
Journal Article
Padilla, A., Saffin, P. M., & Zhou, S. (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. (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. (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.

Strong coupling in Ho?ava gravity (2009)
Journal Article
Charmousis, C., Niz, G., Padilla, A., & Saffin, P. M. (2009). Strong coupling in Ho?ava 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 Ho?ava gravity.

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.