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Percolating cosmic string networks from kination (2024)
Journal Article
Conlon, J. P., Copeland, E. J., Hardy, E., & González, N. S. (2024). Percolating cosmic string networks from kination. Physical Review D, 110(8), Article 083537. https://doi.org/10.1103/physrevd.110.083537

We describe a new mechanism, whose ingredients are realized in string compactifications, for the formation of cosmic (super)string networks. Oscillating string loops grow when their tension 𝜇 decreases with time. If 2𝐻 +˙𝜇/𝜇 <0, where 𝐻 is the Hubble...

Gravitational wave emission from a cosmic string loop: Global case (2024)
Journal Article
Baeza-Ballesteros, J., Copeland, E. J., Figueroa, D. G., & Lizarraga, J. (2024). Gravitational wave emission from a cosmic string loop: Global case. Physical Review D, 110(4), Article 043522. https://doi.org/10.1103/physrevd.110.043522

We study the simultaneous decay of global string loops into scalar particles (massless and massive modes) and gravitational waves (GWs). Using field-theory simulations in flat space-time of isolated loops with initial length ∼80–1700 times their cor... Read More about Gravitational wave emission from a cosmic string loop: Global case.

Primordial black holes and stochastic inflation beyond slow roll. Part I. Noise matrix elements (2023)
Journal Article
Mishra, S. S., Copeland, E. J., & Green, A. M. (2023). Primordial black holes and stochastic inflation beyond slow roll. Part I. Noise matrix elements. Journal of Cosmology and Astroparticle Physics, 2023(September 2023), Article 005. https://doi.org/10.1088/1475-7516/2023/09/005

Primordial Black Holes (PBHs) may form in the early Universe, from the grav-itational collapse of large density perturbations, generated by large quantum fluctuations during inflation. Since PBHs form from rare over-densities, their abundance is sens... Read More about Primordial black holes and stochastic inflation beyond slow roll. Part I. Noise matrix elements.

Primordial black holes and stochastic inflation beyond slow roll. Part I. Noise matrix elements (2023)
Journal Article
Mishra, S. S., Copeland, E. J., & Green, A. M. (2023). Primordial black holes and stochastic inflation beyond slow roll. Part I. Noise matrix elements. Journal of Cosmology and Astroparticle Physics, 2023(09), Article 005. https://doi.org/10.1088/1475-7516/2023/09/005

Primordial Black Holes (PBHs) may form in the early Universe, from the gravitational collapse of large density perturbations, generated by large quantum fluctuations during inflation. Since PBHs form from rare over-densities, their abundance is sensi... Read More about Primordial black holes and stochastic inflation beyond slow roll. Part I. Noise matrix elements.

CMB constraints on monodromy inflation at strong coupling (2022)
Journal Article
Copeland, E. J., Cunillera, F., Moss, A., & Padilla, A. (2022). CMB constraints on monodromy inflation at strong coupling. Journal of Cosmology and Astroparticle Physics, 2022(09), Article 080. https://doi.org/10.1088/1475-7516/2022/09/080

We carry out a thorough numerical examination of field theory monodromy inflation at strong coupling. We perform an MCMC analysis using a Gaussian likelihood, fitting multiparameter models using CMB constraints on the spectral index and the tensor to... Read More about CMB constraints on monodromy inflation at strong coupling.

Generalised scalar-tensor theories and self-tuning (2022)
Journal Article
Copeland, E. J., Ghataore, S., Niedermann, F., & Padilla, A. (2022). Generalised scalar-tensor theories and self-tuning. Journal of Cosmology and Astroparticle Physics, 2022(3), Article 004. https://doi.org/10.1088/1475-7516/2022/03/004

We explore a family of generalised scalar-tensor theories that exhibit self-tuning to low scale anti de Sitter vacua, even in the presence of a large cosmological constant. We are able to examine the linearised fluctuations about these vacua and comp... Read More about Generalised scalar-tensor theories and self-tuning.

Fifth forces and broken scale symmetries in the Jordan frame (2022)
Journal Article
Copeland, E. J., Millington, P., & Sevillano Muñoz, S. (2022). Fifth forces and broken scale symmetries in the Jordan frame. Journal of Cosmology and Astroparticle Physics, 2022(02), Article 016. https://doi.org/10.1088/1475-7516/2022/02/016

We study the origin of fifth forces in scalar-tensor theories of gravity in the so-called Jordan frame, where the modifications to the gravitational sector are manifest. We focus on theories of Brans-Dicke type in which an additional scalar field is... Read More about Fifth forces and broken scale symmetries in the Jordan frame.

Effect of high harmonic loops on gravitational wave bounds from cosmic strings (2021)
Journal Article
Pazouli, D., Palapanidis, K., Avgoustidis, A., & Copeland, E. J. (2021). Effect of high harmonic loops on gravitational wave bounds from cosmic strings. Physical Review D, 104(12), Article 123505. https://doi.org/10.1103/PhysRevD.104.123505

Based on a binary tree model for the self-intersection of cosmic string loops containing high harmonics we estimate the number of self-intersections of the parent and daughter loops and the associated cusp production to determine the most likely numb... Read More about Effect of high harmonic loops on gravitational wave bounds from cosmic strings.

Dark energy loopholes some time after GW170817 (2020)
Journal Article
Bordin, L., Copeland, E. J., & Padilla, A. (2020). Dark energy loopholes some time after GW170817. Journal of Cosmology and Astroparticle Physics, 2020(11), Article 063. https://doi.org/10.1088/1475-7516/2020/11/063

We revisit the constraints on scalar tensor theories of modified gravity following the purge of GW170817. We pay particular attention to dynamical loopholes where the anomalous speed of propagation of the gravitational wave can vanish on-shell, when... Read More about Dark energy loopholes some time after GW170817.