\section*{Acknowledgment}
We acknowledge useful conversations with Bela Bauer, Vadim Oganesyan, Vipin Varma, Sung-Sik Lee, Tom Faulkner, and
Steve Shenker who introduced us to the concept of shredded horizons.  We acknowledge support by SciDAC-DOE grant DE-FG02-12ER46875 (BKC and XY) as well as DOE DE-SC0020165 (BKC) during part of this work. DP acknowledges support from the Charles E. Kaufman foundation and NSF PIRE-1743717.  We thank the Aspen Center for Physics (DP and BKC) and the Galileo Galilei Institute (BKC) for their hospitality.
This research is part of the Blue Waters sustained petascale computing project, which is supported by the National Science Foundation (awards OCI-0725070 and ACI-1238993) and the State of Illinois. Blue Waters is a joint effort of the University of Illinois at Urbana Champaign and its National Center for Supercomputing Applications. 

