## Title: *Forecast for cosmological parameter estimation with gravitational-wave standard sirens*
## Reporter: Yong Zhou
| 6.3 | 10.00 AM | 6420 | Yota Watanabe |
## Title: *The Ostrogradsky instability can be overcome by quantum physics*
## Reporter: Yota Watanabe
## Abstract
In this talk, I will introduce an article using GW standard sirens to forecast cosmological parameter from LISA-Taiji network.
Higher-derivative interactions are of interest to model theories of inflation or quantum gravity, such as Riemann tensor squared, Horndeski theory, or its extensions. When an energy exceeds the scale which suppresses the higher derivatives, a ghost mode may appear unless some coupling constants are fine-tuned. It is widely stated in the literature that it is problematic to have the Ostrogradsky instability, i.e., that the Hamiltonian is unbounded from below. On the contrary, in this journal club, I will introduce the references which take a quantum effect into account and state that a problem to consider should be a backward propagation in time.
## References
-[Arxiv:2101.11882](https://arxiv.org/abs/2101.11882)*Forecast for cosmological parameter estimation with gravitational-wave standard sirens from the LISA-Taiji network* by *Ling-Feng Wang et al*
-[Arxiv:2010.14732](https://arxiv.org/abs/2010.14732)*Hubble parameter estimation via dark sirens with the LISA-Taiji network* by *Renjie Wang et al*
-[Arxiv:2002.03603](https://arxiv.org/abs/2002.03603)*The LISA-Taiji network* by *Wen-Hong Ruan et al*
-[Arxiv:2105.00898](https://arxiv.org/abs/2105.00898)*The Ostrogradsky instability can be overcome by quantum physics* by John F Donoghue, Gabriel Menezes*
-[Arxiv:1908.04170](https://arxiv.org/abs/1908.04170)*The arrow of causality and quantum gravity* by *John F. Donoghue, Gabriel Menezes*
## Title: *The Late Time Physics May Not Solve the Hubble Tension*
## Reporter: Wang-wei Yu
## Abstract
In this seminar, I will introduce some progress of our work. We consider a nonlinear electrodynamics black holes with charged scalar hair model. Firstly, a non-local conserved charge is established by using equation of motion. Then, with the conserved charge and assumption of smoothness, we prove a theorem about inner Cauchy horizon. The theorem is independent of the form of scalar potential and nonlinear electrodynamics. Finally, We take the Born-Infeld black hole as a example to investigate the interior dynamics. Kasner behavior and scalar oscillation will be discussed mainly.
In this seminar, I will introduce some others' work about how to solve the Hubble tension. I will explain why the late time physics may not slove the Hubble tension. Besides this, I will share a recent paper about Sensitivity of the Hubble Constant Determination to Cepheid Color Calibration.
