1. Low-energy Low-energy effective string theory effective string theory in primordial gravitational wave in primordial gravitational wave 朴云松 University of CAS USTC-ICTS ， 2015.4.23

2. 一、动机 二、我们的工作 三、讨论 Based on 1501.06345, PRD, with Yong Cai and Yu-Tong Wang

3. The paradigm of early universe: inflation (alternatives ?)

4. Planck 2015 results

5. As a laboratory inflation sub-Planck scale LHC ?

6. 1 、 Primordial scalar perturbation Planck 限制, 原初的 “ 污染 ” 源多 2 、 Primordial gravitational wave 目前只有上限, 没有原初的 “ 污染 ” 源

7. inflationary lab string theory primordial gravitational wave can be non-trivial? inflationary gravitational wave BICEP2/Keck and Planck 2015

8. the low-energy effective action of heterotic string is Metsaev,Tseytlin, Nucl.Phys.B293, 385 (1987) 一个例子：

9. 二、 我们的工作

10. The primordial GW The effect is negligible, if and Beyond GR the effective Planck scale the propagating speed

11. The change of speed may be non-trivial. Gasperini,Veneziano 2002

12. The effect of non-trivial change of speed The equation is

13. the mode is in Bunch-Davis state Initially, this sets Inflation background

14. The perturbation is, and are determined by the matching conditions. Inflation background

15. The result of primordial GWs is that of slow-roll inflation The character scale

16. Detail of the GWs However, the oscillation appear for is inflationary-like

17. The oscillation can be attributed to other mechanism? 1 、 is oscillating, hardly implemented. 2 、 The production of particles, only a bump-like behavior. Gary Shiu et.al 1405.0346

18. Transfer to B-mode polarization spectrum l=2,65

20. is the optical depth

21. 三、 Discussion

22. The assumptions: 1 、 Inflation is the paradigm of early universe. 2 、 The higher-order derivative terms in superstring theory is significant. alter The conclusion: The oscillating GWs is imprinted in CMB B-mode polarization. Hope r>0.01.

23. The physics of oscillation The low-energy effective action of superstring alters the initial state of mode The Bunch-Davis state only for mode but for mode Note: initial state is not altered by

24. r =0.05+lense By Yu-Tong Wang The outlook:

25. Tegmark, ApJ 464, L35 1996 WMAP 3-year 2006 Planck 2015 The history of CMB TT spectrum observations

26. Thank You !