### Conveners

#### Cosmology and Gravitational Waves: Session 1

- Sugumi Kanno ()

#### Cosmology and Gravitational Waves: Session 2

- Koji Ishiwata (Kanazawa University)

#### Cosmology and Gravitational Waves: Session 3

- Sugumi Kanno ()

We study emission processes of gravitational waves (GWs) from string axions with various masses. First, we clarify the conditions of the onset of violent parametric amplification of inhomogeneous axions. Then, we investigate the fate of the instability with lattice simulations. We analyze GW production processes due to the axion dynamics and find the pre-oscillon formation stage is important...

The first-order electroweak phase transition in the early universe could occur in multiple steps leading to specific multi-peaked signatures in the primordial gravitational wave (GW) spectrum. In this talk we argue that these signatures are generic phenomena in multi-scalar extensions of the Standard Model. In a simple example of such an extension, we study the emergence of reoccurring and...

In this talk, we consider the standard model extension with a dark sector with the $U(1)_X$ Abelian gauge symmetry, which is spontaneously broken by dark Higgs mechanism. We discuss patterns of the electroweak phase transition and detectability of gravitational waves (GWs) when strongly first order phase transition occurs. We find the collider bounds exclude a part of parameter space that...

Cosmic strings are generic cosmological predictions of many extensions of the Standard Model

of particle physics, such as a U(1)′ symmetry breaking phase transition in the early universe.

Unlike other topological defects, cosmic strings can reach a scaling

regime that maintains a small fixed fraction of the total energy density of the universe from a

very early epoch...

For a realistic scenario of inflationary primordial black holes (PBHs), a highly blue-tilted power spectrum of primordial perturbations is required. In the axion-like curvaton model, which is base on the supersymmetric axion model, such a spectrum is achieved. I will show that PBHs formed in this model can explain the massive black holes implied by the LIGO gravitational wave (GW) events....

A Chern-Simons coupling with a gauge field is common in axion inflation. It is well known that this coupling leads to interesting phenomenology via the resonant production of helical gauge fields; e.g., gravitational wave, magnetogenesis, leptogenesis, etc. In this talk, we extend the previous analysis to the case where chiral fermions are charged under this gauge field which couples with the...

We discuss a possibility that our electroweak vacuum is absolutely stable even if the top Yukawa coupling is larger than the critical value. Such a scenario can be realized without introducing new particles if we adopt a renormalization prescription which respects the asymptotic scale invariance at the quantum level. Instead, the theory becomes non-renormalizable and the perturbative unitarity...

The geometric phase (Pancharatnam-Berry phase) results from the geometrical properties of the parameter space of the Hamiltonian. In this paper, we show that the non-adiabatic Berry phase can generate the effective chemical potential, which can bias the matter and the antimatter number densities without introducing the derivative coupling of the field. Our scenario is consistent with

the...

In spite of the vast literature on the subject of first order Electroweak Phase Transitions (EWPT), which can provide the necessary conditions for generating the Baryon Asymmetry in the Universe, fermion-induced EWPTs still remain a rather uncharted territory. In this talk, we consider a simple fermionic extension of the Standard Model (SM) involving one $SU(2)_L$ doublet and two singlet...

Cosmological domain walls have been widely studied in numerical lattice simulations in the past. The main effort was to understand the dynamics of domain walls in the case of spontaneous breaking of global discrete symmetries which are often present in supersymmetric theories. It was found that networks formed by cosmological domain walls are (meta)stable if vacua between which walls...

In this talk, we propose a novel scenario which simultaneously explains O(10)M? primordial black holes (PBHs) in the minimally supersymmetric standard model. Gravitational waves (GWs) events detected by LIGO-Virgo collaboration suggest an existence of black holes as heavy as 30Msol?. In our scenario, as seeds of the PBHs, we make use of the baryon number perturbations which are induced by the...

We consider D-term hybrid inflation in the framework of

superconformal supergravity. In part of the parameter space,

inflation continues for subcritical inflaton field value.

Consequently, a new type of inflation emerges, which gives

predictions for the scalar spectral index and the tensor-to-scalar

ratio that are consistent with the Planck 2015 results. The

potential in the...

The striking discovery that the expansion of the Universe is not slowing down but accelerating has turned into one of the main mysteries in Cosmology. Large observational campaigns are being developed to seed light on this and other problems. I will briefly review this effort and then discuss The Dark Energy Survey (DES) : a state-of-the-art large-scale galaxy survey designed to understand,...