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I will talk about whether there is criticality in periodically driven systems. The motivation is based on the work done in [Phys. Rev. Lett. 122, 110602 (2019)]. This paper uses an RG approach and finds that criticality is absent in periodically driven open systems. This is interpreted as a second order phase transition becoming first order because of the drive. I will talk about dynamical classical system described by the φ4 theory with O(N) symmetry. I have included fluctuations in the presence of the periodic drive and calculated the corrections to the mass up to an infinite loop order within the Hartree approach. In the presence of a sufficiently strong periodic drive, I obtain multiple solutions for the correlation length [(mass)^(−1/2)]. One of them diverges at the transition but the other remains finite and hence, we conclude that the drive can indeed suppress criticality in these systems. In order to make further progress, I apply Hartree approximation to the φ6 theory, which is known to exhibits a first order phase transition. Multiple solutions for the correlation length emerge in a way that is very similar to the periodically driven system. This indicates that the transition can be changed from second to first order by the periodic drive.

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Nikhil Sharma
Seminar Room 0.03, ETP
Contact: not specified