#  Seminar: John Cardy (UC Berkeley & All Souls College, Oxford): "TTbar deformation of 2d quantum field theory and modular forms" 

 



####  calendar\_today Date and Time 

 **April 4, 2023** 

 09:30AM - 09:30AM EDT 

####  pin\_drop Location 

 **https://harvard.zoom.us/j/779283357?pwd=MitXVm1pYUlJVzZqT3lwV2pCT1ZUQT09**  



 

 



 

 **![John Cardy](/sites/g/files/omnuum6611/files/styles/hwp_1_1__360x360_scale/public/mathpicture/files/john_cardy.jpg?itok=WuoRC07z) 

 

  
Speaker:** John Cardy (University of California, Berkeley, & All Souls College, Oxford)  
**Title:** The TTbar deformation of 2d quantum field theory and modular forms  
**Abstract:** "TTbar" deformed 2d quantum field theory is a non-local theory in which Minkowski space is deformed in a state-dependent but consistent manner. For a massive theory this is equivalent to each particle acquiring a width proportional to its mass in its rest frame, giving rise to simple CDD factors dressing the $S$--matrix, but for deformed conformal field theories the spectrum becomes quite complicated, and the question of modular invariance of the torus partition function is non-trivial. I will show that this leads to a theory of TTbar deformed modular forms in general. Maass forms turn out to play an important role as eigenforms of the deformation.

 

 

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