Research Repository

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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), doi:10.1103/PhysRevD.96.103535. ISSN 2470-0010

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

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, doi:10.1103/PhysRevD.96.023526. ISSN 2470-0010

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

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), doi:10.1103/PhysRevD.94.116017. ISSN 2470-0010

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

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), doi:10.1103/PhysRevD.93.123503. ISSN 1550-7998

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

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, doi:10.1103/PhysRevD.93.043534. ISSN 1550-7998

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

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), doi:10.1103/PhysRevD.93.043521. ISSN 1550-7998

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

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), doi:10.1103/PhysRevD.91.025022. ISSN 2470-0010

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

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), doi:10.1088/1475-7516/2014/06/062. ISSN 1475-7516

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

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), doi:10.1103/PhysRevD.89.063503. ISSN 2470-0010

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