Prepared for submission to JHEP INR-TH-2017-002 Exact solutions and critical chaos in dilaton gravity with a boundary Maxim Fitkevicha;b Dmitry Levkova Yegor Zenkevich1c;d;e aInstitute for Nuclear Research of the Russian Academy of Sciences, 60th October An- niversary Prospect 7a, Moscow 117312, Russia bMoscow Institute of Physics and Technology, Institutskii per. 9, Dolgoprudny 141700, Moscow Region, Russia cDipartimento di Fisica, Universit`adi Milano-Bicocca, Piazza della Scienza 3, I-20126 Milano, Italy dINFN, sezione di Milano-Bicocca, I-20126 Milano, Italy eNational Research Nuclear University MEPhI, Moscow 115409, Russia E-mail:
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[email protected] Abstract: We consider (1 + 1)-dimensional dilaton gravity with a reflecting dy- namical boundary. The boundary cuts off the region of strong coupling and makes our model causally similar to the spherically-symmetric sector of multidimensional gravity. We demonstrate that this model is exactly solvable at the classical level and possesses an on-shell SL(2; R) symmetry. After introducing general classical solution of the model, we study a large subset of soliton solutions. The latter describe reflec- tion of matter waves off the boundary at low energies and formation of black holes at energies above critical. They can be related to the eigenstates of the auxiliary inte- grable system, the Gaudin spin chain. We argue that despite being exactly solvable, the model in the critical regime, i.e. at the verge of black hole formation, displays arXiv:1702.02576v2 [hep-th] 17 Apr 2017 dynamical instabilities specific to chaotic systems. We believe that this model will be useful for studying black holes and gravitational scattering.