### Conveners

#### Parallel: Cosmology 1

- Ki-Young Choi (Sungkyunkwan University)

Numerous physically well-motivated early universe models predict mild oscillations in the primordial spectra. We present our recent research on finding hints of primordial features in the CMB. First, we use and develop a free-form reconstruction technique on the CMB power spectrum to obtain a form of primordial power spectrum which fits both the temperature and polarisation data well. The...

The cosmological collider program is to find a new massive particle from non-Gaussianity of the curvature perturbation. In this work, we study the effects of a massive field with a "continuous" spectrum on the non-Gaussianity. This kind of continuous spectrum is motivated by several extra dimensional models. We find that in contrast to the usual case without the continuous spectrum, the...

Primordial black holes (PBH) have recently emerged as very interesting candidates for the cold dark matter in the universe. We study the generation of PBHs in a single field model of inflation with an inflection point in the inflaton potential. We found that PBHs can be produced in our scenario in the asteroid-mass window with a nearly monochromatic mass fraction which can account for the...

Gravitational lensing deflects the paths of photons, altering the statistics of cosmic backgrounds and distorting their information content. We take the Cosmic Infrared Background (CIB), which provides a wealth of information about galaxy formation and evolution, as an example to probe the effect of gravitational lensing on non-Gaussian statistics. Using the Websky simulations, we first...

This work investigates the possibility that our inflation originates from a composite theory. Taking an 𝑆𝑈(𝑁𝑐) gauge theory with 𝑁𝑓 fermions in the fundamental representation, we consider an effective chiral Lagrangian involving a dilaton and pions. The walking dynamics of the theory constrain the potential specifics. We identify the dilaton as the inflaton, which resembles a hybrid inflation...

In view of the improving measurements of the tensor-to-scalar ratio, hybrid inflation remains a suitable mechanism to achieve low-scale inflation. However, as originally proposed, hybrid inflation with a single waterfall field gives rise to a hierarchy problem, also known as the 𝜂 problem. In this work, we consider an extension to the original model in which twin waterfall fields, related by a...

Primordial black holes (PBH) have recently emerged as very interesting candidates for the cold dark matter in the universe. We study the generation of PBHs in a single field model of inflation with an inflection point in the inflaton potential. We found that PBHs can be produced in our scenario in the asteroid-mass window with a nearly monochromatic mass fraction which can account for the...

Numerous physically well-motivated early universe models predict mild oscillations in the primordial spectra. We present our recent research on finding hints of primordial features in the CMB. First, we use and develop a free-form reconstruction technique on the CMB power spectrum to obtain a form of primordial power spectrum which fits both the temperature and polarisation data well. The...