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Understanding the suppression of structure formation from dark matter-dark energy momentum coupling (2020)
Journal Article
Chamings, F. N., Avgoustidis, A., Copeland, E. J., Green, A. M., & Pourtsidou, A. (2020). Understanding the suppression of structure formation from dark matter-dark energy momentum coupling. Physical Review D, 101(4), https://doi.org/10.1103/physrevd.101.043531

Models in which scalar field dark energy interacts with dark matter via a pure momentum coupling have previously been found to potentially ease the structure formation tension between early-and late-universe observations. In this article we explore t... Read More about Understanding the suppression of structure formation from dark matter-dark energy momentum coupling.

Inflation in loop quantum cosmology (2019)
Journal Article
Bhardwaj, A., Copeland, E. J., & Louko, J. (2019). Inflation in loop quantum cosmology. Physical Review D, 99(6), Article 063520. https://doi.org/10.1103/physrevd.99.063520

We develop a consistent analytic approach to determine the conditions under which slow-roll inflation can arise when the inflaton is the same scalar field that is responsible for the bounce in loop quantum cosmology (LQC). We find that the requiremen... Read More about Inflation in loop quantum cosmology.

Dark Energy after GW170817 Revisited (2019)
Journal Article
Copeland, E. J., Kopp, M., Padilla, A., Saffin, P. M., & Skordis, C. (2019). Dark Energy after GW170817 Revisited. Physical Review Letters, 122(6), Article 061301. https://doi.org/10.1103/physrevlett.122.061301

We revisit the status of scalar-tensor theories with applications to dark energy in the aftermath of the gravitational wave signal GW170817 and its optical counterpart GRB170817A. At the level of the cosmological background, we identify a class of th... Read More about Dark Energy after GW170817 Revisited.

Dynamical systems applied to cosmology: dark energy and modified gravity (2018)
Journal Article
Bahamonde, S., Böhmer, C. G., Carloni, S., Copeland, E. J., Fang, W., & Tamanini, N. (2018). Dynamical systems applied to cosmology: dark energy and modified gravity. Physics Reports, 775-777, 1-122. https://doi.org/10.1016/j.physrep.2018.09.001

The Nobel Prize winning confirmation in 1998 of the accelerated expansion of our Universe put into sharp focus the need of a consistent theoretical model to explain the origin of this acceleration. As a result over the past two decades there has been... Read More about Dynamical systems applied to cosmology: dark energy and modified gravity.

Gravitational waves from asymmetric oscillon dynamics? (2018)
Journal Article
Amin, M. A., Braden, J., Copeland, E. J., Giblin, J. T., Solorio, C., Weiner, Z. J., & Zhou, S.-Y. (2018). Gravitational waves from asymmetric oscillon dynamics?. Physical Review D, 98(2), 1-6. https://doi.org/10.1103/physrevd.98.024040

It has been recently suggested that oscillons produced in the early universe from certain asymmetric potentials continue to emit gravitational waves for a number of e-folds of expansion after their formation, leading to potentially detectable gravita... Read More about Gravitational waves from asymmetric oscillon dynamics?.

The shape dependence of chameleon screening (2018)
Journal Article
Burrage, C., Copeland, E. J., Moss, A., & Stevenson, J. A. (2018). The shape dependence of chameleon screening. Journal of Cosmology and Astroparticle Physics, 2018(1), https://doi.org/10.1088/1475-7516/2018/01/056

Chameleon scalar fields can screen their associated fifth forces from detection by changing their mass with the local density. These models are an archetypal example of a screening mechanism, and have become an important target for both cosmological... Read More about The shape dependence of chameleon screening.

Radiative screening of fifth forces (2016)
Journal Article
Burrage, C., Copeland, E. J., & Millington, P. (2016). Radiative screening of fifth forces. Physical Review Letters, 117(21), Article 211102. https://doi.org/10.1103/PhysRevLett.117.211102

© 2016 American Physical Society. We describe a symmetron model in which the screening of fifth forces arises at the one-loop level through the Coleman-Weinberg mechanism of spontaneous symmetry breaking. We show that such a theory can avoid current... Read More about Radiative screening of fifth forces.

A proposed experimental search for chameleons using asymmetric parallel plates (2016)
Journal Article
Burrage, C., Copeland, E. J., & Stevenson, J. A. (2016). A proposed experimental search for chameleons using asymmetric parallel plates. Journal of Cosmology and Astroparticle Physics, 2016(8), https://doi.org/10.1088/1475-7516/2016/08/070

Light scalar fields coupled to matter are a common consequence of theories of dark energy and attempts to solve the cosmological constant problem. The chameleon screening mechanism is commonly invoked in order to suppress the fifth forces mediated by... Read More about A proposed experimental search for chameleons using asymmetric parallel plates.

CMB constraints on cosmic strings and superstrings (2016)
Journal Article
Charnock, T., Avgoustidis, A., Copeland, E. J., & Moss, A. (2016). CMB constraints on cosmic strings and superstrings. Physical Review D - Particles, Fields, Gravitation and Cosmology, 93(12), Article 123503. https://doi.org/10.1103/PhysRevD.93.123503

We present the first complete MCMC analysis of cosmological models with evolving cosmic (super)string networks, using the Unconnected Segment Model in the unequal-time correlator formalism. For ordinary cosmic string networks, we derive joint constra... Read More about CMB constraints on cosmic strings and superstrings.