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Cosmology with the Laser Interferometer Space Antenna (2023)
Journal Article
Auclair, P., Bacon, D., Baker, T., Barreiro, T., Bartolo, N., Belgacem, E., …Zhdanov, V. I. (2023). Cosmology with the Laser Interferometer Space Antenna. Living Reviews in Relativity, 26, Article 5. https://doi.org/10.1007/s41114-023-00045-2

The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and... Read More about Cosmology with the Laser Interferometer Space Antenna.

Clockwork cosmology (2023)
Journal Article
Wood, K., Saffin, P. M., & Avgoustidis, A. (2023). Clockwork cosmology. Journal of Cosmology and Astroparticle Physics, 2023(07), Article 062. https://doi.org/10.1088/1475-7516/2023/07/062

The higher order generalisation of the clockwork mechanism to gravitational interactions provides a means to generate an exponentially suppressed coupling to matter from a fundamental theory of multiple interacting gravitons, without introducing larg... Read More about Clockwork cosmology.

Deconstructing higher order clockwork gravity (2021)
Journal Article
Avgoustidis, A., Niedermann, F., Padilla, A., & Saffin, P. M. (2021). Deconstructing higher order clockwork gravity. Physical Review D, 103(12), Article 124007. https://doi.org/10.1103/physrevd.103.124007

We consider the higher order clockwork theory of gravitational interactions, whereby a number of gravitons are coupled together with TeV strength, but nevertheless generate a Planck scale coupling to matter without the need for a dilaton. It is shown... Read More about Deconstructing higher order clockwork gravity.

Euclid: Forecast constraints on the cosmic distance duality relation with complementary external probes (2020)
Journal Article
Martinelli, M., Martins, C., Nesseris, S., Sapone, D., Tutusaus, I., Avgoustidis, A., …Zacchei, A. (2020). Euclid: Forecast constraints on the cosmic distance duality relation with complementary external probes. Astronomy and Astrophysics, 644, Article A80. https://doi.org/10.1051/0004-6361/202039078

In metric theories of gravity with photon number conservation, the luminosity and angular diameter distances are related via the Etherington relation, also known as the distance-duality relation (DDR). A violation of this relation would rule out the... Read More about Euclid: Forecast constraints on the cosmic distance duality relation with complementary external probes.

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.

Cosmological evolution of semilocal string networks (2019)
Journal Article
Achúcarro, A., Avgoustidis, A., López-Eiguren, A., Martins, C. J. A. P., & Urrestilla, J. (2019). Cosmological evolution of semilocal string networks. Philosophical Transactions A: Mathematical, Physical and Engineering Sciences, 377(2161), 1-11. https://doi.org/10.1098/rsta.2019.0004

Semilocal strings—a particular limit of electroweak strings—are an interesting example of a stable non-topological defect whose properties resemble those of their topological cousins, the Abrikosov–Nielsen–Olesen vortices. There is, however, one impo... Read More about Cosmological evolution of semilocal string networks.

Early dark energy constraints on growing neutrino quintessence cosmologies (2019)
Journal Article
Noble Chamings, F., Avgoustidis, A., Copeland, E. J., Green, A. M., & Li, B. (2019). Early dark energy constraints on growing neutrino quintessence cosmologies. Physical Review D, 100(4), https://doi.org/10.1103/physrevd.100.043525

We investigate cosmological models in which dynamical dark energy consists of a scalar field whose present-day value is controlled by a coupling to the neutrino sector. The behavior of the scalar field depends on three functions: a kinetic function,... Read More about Early dark energy constraints on growing neutrino quintessence cosmologies.

Dynamics of junctions and the multitension velocity-dependent one-scale model (2019)
Journal Article
Rybak, I., Avgoustidis, A., & Martins, C. (2019). Dynamics of junctions and the multitension velocity-dependent one-scale model. Physical Review D, 99(6), Article 063516. https://doi.org/10.1103/physrevd.99.063516

The dynamics of string junctions and their influence on the evolution of cosmic superstring networks are studied in full detail. We review kinematic constraints for colliding strings in a Friedmann-Lemaître-Robertson-Walker background and obtain the... Read More about Dynamics of junctions and the multitension velocity-dependent one-scale model.

Collisions of cosmic strings with chiral currents (2018)
Journal Article
Rybak, I., Avgoustidis, A., & Martins, C. (2018). Collisions of cosmic strings with chiral currents. Physical Review D, 98(6), Article 15. https://doi.org/10.1103/physrevd.98.063519

We present an analytic study of cosmic superconducting chiral string collisions in Minkowski space, applying the kinematic constraints that arise from the relevant generalization of the Nambu-Goto action. In particular, we revisit the solution for ch... Read More about Collisions of cosmic strings with chiral currents.

Semi-analytic calculation of cosmic microwave background anisotropies from wiggly and superconducting cosmic strings (2017)
Journal Article
Rybak, I. Y., Avgoustidis, A., & Martins, C. (2017). Semi-analytic calculation of cosmic microwave background anisotropies from wiggly and superconducting cosmic strings. Physical Review D, 96(10), Article 103535. https://doi.org/10.1103/PhysRevD.96.103535

We study how the presence of world-sheet currents affects the evolution of cosmic string networks, and their impact on predictions for the cosmic microwave background (CMB) anisotropies generated by these networks. We provide a general description of... Read More about Semi-analytic calculation of cosmic microwave background anisotropies from wiggly and superconducting cosmic strings.

Evolution of semilocal string networks: II. Velocity estimators (2017)
Journal Article
Lopez-Eiguren, A., Urrestilla, J., Achúcarro, A., Avgoustidis, A., & Martins, C. (2017). Evolution of semilocal string networks: II. Velocity estimators. Physical Review D, 96, Article 023526. https://doi.org/10.1103/PhysRevD.96.023526

We continue a comprehensive numerical study of semilocal string networks and their cosmological evolution. These can be thought of as hybrid networks comprised of (non-topological) string segments, whose core structure is similar to that of Abelian H... Read More about Evolution of semilocal string networks: II. Velocity estimators.

Stretching and Kibble scaling regimes for Hubble-damped defect networks (2016)
Journal Article
Martins, C., Rybak, I. Y., Avgoustidis, A., & Shellard, E. (2016). Stretching and Kibble scaling regimes for Hubble-damped defect networks. Physical Review D, 94(11), Article 116017. https://doi.org/10.1103/PhysRevD.94.116017

The cosmological evolution of topological defect networks can broadly be divided into two stages. At early times they are friction dominated due to particle scattering and therefore nonrelativistic and may either be conformally stretched or evolve in... Read More about Stretching and Kibble scaling regimes for Hubble-damped defect networks.

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.

Extending the velocity-dependent one-scale model for domain walls (2016)
Journal Article
Martins, C., Rybak, I. Y., Avgoustidis, A., & Shellard, E. (2016). Extending the velocity-dependent one-scale model for domain walls. Physical Review D - Particles, Fields, Gravitation and Cosmology, 93(4), Article 043534. https://doi.org/10.1103/PhysRevD.93.043534

We report on an extensive study of the evolution of domain wall networks in Friedmann-Lemaˆıtre- Robertson-Walker universes by means of the largest currently available field-theory simulations. These simulations were done in 40963 boxes and for a ran... Read More about Extending the velocity-dependent one-scale model for domain walls.

Sub-percent constraints on cosmological temperature evolution (2016)
Journal Article
Avgoustidis, A., Genova-Santos, R. .., Luzzi, G., & Martins, C. (2016). Sub-percent constraints on cosmological temperature evolution. Physical Review D - Particles, Fields, Gravitation and Cosmology, 93(4), Article 043521. https://doi.org/10.1103/PhysRevD.93.043521

The redshift dependence of the cosmic microwave background temperature is one of the key cosmological observables. In the standard cosmological model one has T (z) = T0(1 + z), where T0 is the present-day temperature. Deviations from this behavior wo... Read More about Sub-percent constraints on cosmological temperature evolution.

Zipping and unzipping in string networks: dynamics of Y-junctions (2015)
Journal Article
Avgoustidis, A., Pourtsidou, A., & Sakellariadou, M. (2015). Zipping and unzipping in string networks: dynamics of Y-junctions. Physical Review D, 91(2), Article 025022. https://doi.org/10.1103/PhysRevD.91.025022

We study, within the Nambu-Goto approximation, the stability of massive string junctions under the influence of the tensions of three strings joining together in a Y-type configuration. The relative angle β between the strings at the junction is in g... Read More about Zipping and unzipping in string networks: dynamics of Y-junctions.

Is the universe transparent? (2015)
Journal Article
Liao, K., Avgoustidis, A., & Li, Z. (2015). Is the universe transparent?. Physical Review D, 92(12), Article 123539. https://doi.org/10.1103/PhysRevD.92.123539

We present our study on cosmic opacity, which relates to changes in photon number as photons travel from the source to the observer. Cosmic opacity may be caused by absorption or scattering due to matter in the Universe, or by extragalactic magnetic... Read More about Is the universe transparent?.

Cosmological effects of scalar-photon couplings: dark energy and varying-α models (2014)
Journal Article
Avgoustidis, A., Martins, C., Monteiro, A., Vielzeuf, P., & Luzzi, G. (2014). Cosmological effects of scalar-photon couplings: dark energy and varying-α models. Journal of Cosmology and Astroparticle Physics, 2014(6), https://doi.org/10.1088/1475-7516/2014/06/062

We study cosmological models involving scalar fields coupled to radiation and discuss their effect on the redshift evolution of the cosmic microwave background temperature, focusing on links with varying fundamental constants and dynamical dark energ... Read More about Cosmological effects of scalar-photon couplings: dark energy and varying-α models.

Evolution of semilocal string networks: large-scale properties (2014)
Journal Article
Achúcarro, A., Avgoustidis, A., Leite, A., Lopez-Eiguren, A., Martins, C., Nunes, A., & Urrestilla, J. (2014). Evolution of semilocal string networks: large-scale properties. Physical Review D, 89(6), Article 063503. https://doi.org/10.1103/PhysRevD.89.063503

We report on a detailed numerical study of the evolution of semilocal string networks, based on the largest and most accurate field theory simulations of these objects to date. We focus on the large-scale network properties, confirming earlier indica... Read More about Evolution of semilocal string networks: large-scale properties.