### Conveners

#### Beyond I

- Yi Wang (afternoon) ()
- Chunshan Lin (morning) ()

### Description

Monday session

Detection of gravitational wave signals from mergers of black holes and neutron stars is one the most important discoveries of this century. I shall briefly present the phenomenon of gravitational radiation as predicted by Einstein's general relativity. I shall describe gravitational wave detectors and

methods of analyzing gravitational wave data. I shall review the observations made during...

I will discuss efficiency factors for the production of gravitational waves through bubble collisions and plasma-related sources in strong phase transitions, and the conditions under which the bubble collisions can contribute significantly to the signal. I will also show that generically the sound-wave period is much shorter than a Hubble time leading to a reduction of GW signal produced by...

Exotic compact objects (ECOs) produce the same initial event detected by LIGO-Virgo collabo-ration as classical black holes (BHs), but various quantum gravity models feature the different following echoes. In particular, we investigate the echoes from the fluctuation-dissipation theorem [1, 2], which changes the dispersion relationship near the (would-be) horizon and results in a Boltzmann...

A rather minimal possibility is that dark matter consists of the gauge bosons of a spontaneously broken symmetry. I will discuss the possibility of detecting the gravitational waves produced by the phase transition associated with such breaking. Concretely, I will focus on the scenario based on an 𝑆𝑈(2)_D group and argue that it is a case study for the sensitivity of future gravitational wave...

The Wilsonian renormalization group (RG) requires Euclidean signature. The conformal factor of the metric then has a wrong-sign kinetic term, which has a profound effect on its RG properties. In particular around the Gaussian fixed point, it supports a Hilbert space of renormalizable interactions involving arbitrarily high powers of the gravitational fluctuations. These interactions are...

In this talk I will briefly introduce the present understanding about the cosmic acceleration at present from the perspective of phenomenological study. I will review the latest observational status of the late-time cosmic acceleration and then depict how to do the model building of dynamical dark energy. Afterwards, I will also give an introduction to a type of torsional based modified...

If the Standard Model vacuum is metastable, bubbles that form expand and convert the entire vacuum into a true vacuum state incompatible with observations. It is sometimes argued, however, that true vacuum bubbles forming during inflation are 'inflated away' and thus pose no danger to the present day universe, even if they form. I will argue that this point of view is incorrect - while the...

Within the framework of $\Lambda$CDM, the local determination of the Hubble constant disagrees -- at the 4.4$\sigma$ level -- with that inferred from the very accurate CMB observations by the Planck satellite. This clearly motivates the study of extensions of the standard cosmological model that could reduce such tension. Proposed extensions of $\Lambda$CDM that reduce this so-called Hubble...