### Conveners

#### Parallel: Cosmology 3

- Masahide Yamaguchi (IBS-CTPU)

The motion of cosmic strings in the universe leads to the generation of wakes behind them. We study magnetized wakes of cosmic strings moving in the post recombination plasma. We show that magnetic reconnection can occur in the post shock region. Since the width of the cosmic string wake is very small, the reconnection occurs over a very short length scale. The reconnection leads to a large...

Possible implementations of perturbative quantum gravity for scalar tensor models are discussed. In particular, the perturbative approach generates new non-minimal couplings between a scalar field and gravity, and provides a way to calculate the one-loop scalar field effective potential. A brief overview of the perturbative approach is given. We show how the theory generates non-minimal...

We perform the calculation for tree-level ultraviolet unitarity violation scales for scalar-R^2 inflation models by including an additional R^2|Φ|^2-type term. Due to certain constraints, we resort to the Einstein frame for our calculations, where we separate our analysis between metric and Palatini formulations. We follow recent works in this line that debunk the naive predictions for...

I will introduce the effective field theory (EFT) of the cuscuton. The cuscuton has the intriguing property that when present in a theory it does not propagate any scalar degrees of freedom, but only the two gravitational ones. Even more interestingly, it appears in several places in cosmology, such as in modified gravity, varying speed of light theories, and it has been shown to be the...

We introduce the gauged quintessence model, in which the dark energy field (quintessence) has a $U(1)$ gauge symmetry. This is a kind of realization of interacting quintessence model and the first quintessence model under a gauge symmetry. We identify the radial part of the complex scalar as the dark energy field (quintessence), while the angular part is the longitudinal component of a new...

We study the dark gauge boson in the gauged quintessence model. The gauged quintessence is the dark energy field under a gauge symmetry, and therefore its mass varies as the quintessence scalar value changes. The change of the dark gauge boson mass brings interesting consequences. The evolution of the universe is sensitively affected by the mass-varying dark gauge boson. We study various...