1. Black Hole Echology Qingwen Wang Supervisor : Niayesh Afshordi
Perimeter Institute & University of Waterloo |CosPA
Black Hole Echology
Qingwen Wang
Supervisor :
Niayesh Afshordi

2. Content
Introduction
Echology
Template
Superradiance
Outlook

3. Introduction
Did LIGO confirm existence of event horizons? Not necessarily!
Delayed Echoes from
near-horizon structures
Cardoso, Hopper, Macedo, Palenzuela, Pani 2016

4. Abedi, Dykaar&Afshordi 16,17
Introduction
Abedi, Dykaar&Afshordi 16,17

5. Introduction Motivated by Quantum gravity models Information paradox:
Fuzzball, firewall etc.
Cosmology constant problem:
Gravitational aether theory.

6. Introduction Truncate original template
Repeat with some reflection rate
Search for max SNR
Claimed 2.5σ evidence for echoes in LIGO public data
LIGO template for GW and max SNR template for the echoes
Abedi, Dykaar & Afshordi 16,17

7. Echology Let’s instead solve the (linear) Einstein equations with wall
Simply repeat event

8. Echology : Soft wall
“ Shape ” Reflectivity needed if want detective signal

9. Echology : Nonlinear effect
Redshifted signal damps slower

10. Single echo fits to Complex Gaussian
Echo template
Single echo fits to Complex Gaussian

11. Echo template

12. Superradiance in Time domain
the higher spin, the earlier effect
⚠️ not real case for other spin than 0.67

13. Superradiance in Frequency domain
Soft walls add-up superradiance
Perfect walls kill superradiance
Superradiance in Frequency domain

14. Outlook: Data Fitting Connor’s work for event150914
My template starting with second echo
Matches with Jahed’s work

15. Outlook: Physical boundary in Kerr
Using now: Energy flux reflection and unchanged phase
Looking for: Physical one from some models
Difficulty: Mixed
Outlook: Physical boundary in Kerr
Eg. Empty BH model Saravani, Afshordi and Robert 2012

16. Thanks
Questions ?