A simple XY model for cascade transfer
 Date
 January 20 (Thu) at 13:30  15:00, 2022 (JST)
 Speaker

 Tomohiro Tanogami (Ph.D. Student / JSPS Research Fellow DC, Graduate School of Science, Kyoto University)
 Venue
 via Zoom
 Language
 English
Cascade transfer is the phenomenon that an inviscid conserved quantity, such as energy or enstrophy, is transferred conservatively from large (small) to small (large) scales. As a consequence of this cascade transfer, the distribution of the transferred quantity obeys a universal scaling law independent of the details of large (small) scales. For example, in the energy cascade in fluid turbulence, the energy spectrum follows Kolmogorov's power law [1]. Such behavior is observed even in systems different from ordinary fluids, such as quantum fluid, elastic body, and spin systems. Here, we aim to establish the concept of a universality class for cascade transfer. As a first step toward this end, we propose a simple model representing one universality class [2]. In doing so, we regard cascade transfer as a cooperative phenomenon of unidirectional transport across scales and ask how it emerges from spatially local interactions. The constructed model is a modified XY model with amplitude fluctuations, in which the spin is regarded as the “velocity” of a turbulent field in d dimensions. We show that the model exhibits an inverse energy cascade with the nonKolmogorov energy spectrum. We also discuss the relation to spin turbulence [3,4] and atmospheric turbulence [5].
*If you would like to participate, please contact Hidetoshi Taya.
References
 U. Frisch, Turbulence, Cambridge university press (1995)
 T. Tanogami and S.i. Sasa, A Simple XY Model for Cascade Transfer, (2021), arXiv: 2106.11670
 M. Tsubota, Y. Aoki, and K. Fujimoto, Spinglasslike behavior in the spin turbulence of spinor BoseEinstein condensates, Phys. Rev. A 88, 061601 (2013), doi: 10.1103/PhysRevA.88.061601
 J. F. RodriguezNieva, Turbulent relaxation after a quench in the Heisenberg model, (2020), arXiv: 2009.11883
 G. D. Nastrom, K. S. Gage, and W. H. Jasperson, Kinetic energy spectrum of largeand mesoscale atmospheric processes, Nature volume 310, pages 36–38 (1984), doi: 10.1038/310036a0