



Name: 
Surbhi Khetrapal 

Address: 
Centre for High Energy Physics 


Indian Institute of Science 


560012 Bangalore 


INDIA 

Office: 
CHEP B214 

PhD Thesis Focus: 
Study of time dependent phenomenon in AdSCFT 


(expected completion in 2018) 

Phone: 
+918022933147 

EMail: 
surbhi (at) chep.iisc.ernet.in 



RESEARCH SUMMARY


1. Local quenches and quantum chaos from higher spin perturbations. Study of local quenches in 2d CFT at largec by operators carrying higher spin charge. Viewing such states as solutions in ChernSimons theory, representing infalling massive particles with spinthree charge in the BTZ background, we use the Wilson line prescription to compute the single interval entanglement entropy and scrambling time following the quench. We show that the EE correlator deep in the quenched regime and its expansion for small quench widths overlaps with Regge limit for chaos of the outoftime ordered correlator. We find that the scrambling time for the twosided mutual information between two intervals in the thermofield double state increases with increasing spinthree charge. For larger values of the charge, the scrambling time is shorter than for pure gravity and controlled by the spinthree Lyapunov exponent, 4π/β.


2. Universal corrections to entanglement entropy of local quantum quenches. Study of the time evolution of single interval Rényi and entanglement entropies following local quantum quenches in 2d CFTs at finite temperature for which the locally excited states have a finite temporal width ε. We show that, for local quenches produced by the action of a conformal primary field, the time dependence of Rényi and entanglement entropies at order ε^{2} is universal. It is determined by the expectation value of the stress tensor in the replica geometry. Furthermore, we find universal time dependent correction at order μ^{2} ε^{2} in CFTs admitting a higher spin symmetry and deformed by higher spin chemical potential μ.


3. Thermalisation of Green functions and quasinormal modes. A new method is developed to study the thermalization of retarded Green function in CFTs holographically dual to thin shell AdS Vaidya space times. The method relies on using the information of all time derivatives of the Green function at the shell and then evolving it for later times, where the time derivatives of the Green function at the shell are given in terms of a recursion formula. Using this method analytic results for short time thermalization of the Green function are obtained, and to obtain its long time behaviour, this method is implemented numerically. 
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