# A small cosmological constant from Abelian symmetry breaking

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**A small cosmological constant from Abelian symmetry breaking.** / Tasinato, Gianmassimo.

Research output: Contribution to journal › Article › peer-review

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*Classical and Quantum Gravity*, vol. 31, no. 22. https://doi.org/10.1088/0264-9381/31/22/225004

### APA

*Classical and Quantum Gravity*,

*31*(22). https://doi.org/10.1088/0264-9381/31/22/225004

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TY - JOUR

T1 - A small cosmological constant from Abelian symmetry breaking

AU - Tasinato, Gianmassimo

PY - 2014/11/21

Y1 - 2014/11/21

N2 - We investigate some cosmological consequences of a vector–tensor theory where an Abelian symmetry in the vector sector is slightly broken by a mass term and by ghost-free derivative self-interactions. When studying cosmological expansion in the presence of large bare cosmological constant Λcc, we find that the theory admits branches of de Sitter solutions in which the scale of the Hubble parameter is inversely proportional to a power of Λcc. Hence, a large value of Λcc leads to a small size for the Hubble scale. In an appropriate limit, in which the symmetry breaking parameters are small, the theory recovers the Abelian symmetry plus an additional Galileon symmetry acting on the longitudinal vector polarization. The approximate Galileon symmetry can make the structure of this theory stable at the energy scales we are interested in. We also analyze the dynamics of linearized cosmological fluctuations around the de Sitter solutions, showing that no manifest instabilities arise, and that the transverse vector polarizations become massless around these configurations.

AB - We investigate some cosmological consequences of a vector–tensor theory where an Abelian symmetry in the vector sector is slightly broken by a mass term and by ghost-free derivative self-interactions. When studying cosmological expansion in the presence of large bare cosmological constant Λcc, we find that the theory admits branches of de Sitter solutions in which the scale of the Hubble parameter is inversely proportional to a power of Λcc. Hence, a large value of Λcc leads to a small size for the Hubble scale. In an appropriate limit, in which the symmetry breaking parameters are small, the theory recovers the Abelian symmetry plus an additional Galileon symmetry acting on the longitudinal vector polarization. The approximate Galileon symmetry can make the structure of this theory stable at the energy scales we are interested in. We also analyze the dynamics of linearized cosmological fluctuations around the de Sitter solutions, showing that no manifest instabilities arise, and that the transverse vector polarizations become massless around these configurations.

KW - cosmology

KW - alternative theories of gravity

KW - cosmological perturbations

KW - RCUK

KW - STFC

KW - ST/H005498/1

U2 - 10.1088/0264-9381/31/22/225004

DO - 10.1088/0264-9381/31/22/225004

M3 - Article

VL - 31

JO - Classical and Quantum Gravity

JF - Classical and Quantum Gravity

SN - 0264-9381

IS - 22

ER -

ID: 2953842