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  1. We calculate STM signatures of correlated ground-states at integer filling of the magic angle twisted bilayer graphene narrow bands. First, we compute the fully-interacting TBG spectral function at ±4 electrons/moiré unit cell and show that it can be used to experimentally validate the strong-coupling approach. Although variation exists in the data, we find experimental evidence for the strong-coupling regime. For all other integer fillings of the flat bands, we consider the spatial features of the corresponding spectral functions of many states in the large degenerate ground-state manifold, and assess the possibility of Kekulé distortion (KD) emerging at the graphene latticemore »scale. Remarkably, we find that coupling the two opposite graphene valleys in the intervalley-coherent (IVC) TBG insulators does not always result in KD. As an example, we show that the K-IVC state and its nonchiral U(4) rotations do not exhibit any KD, while T-IVC does. We analyze 14 different many-body correlated states and show that their combined STM/Chern number signal can be used to uniquely determine the nature of the many-body ground-state. Their STM signal and features are obtained over a large range of energies and model parameters.« less
    Free, publicly-accessible full text available June 6, 2023
  2. This paper proposes long-term reliability management for spatial multitasking GPU architectures. Specifically, we focus on electromigration (EM)-induced long-term failure of the GPU's power delivery network. A distributed power delivery network model at functional unit granularity is developed and used for our EM analysis of GPU architectures. We use a recently proposed physics-based EM reliability model and consider the EM-induced time-to-failure at the GPU system level as a reliability resource. For GPU scheduling, we mainly focus on spatial multitasking, which allows GPU computing resources to be partitioned among multiple applications. We find that the existing reliability-agnostic thread block scheduler for spatialmore »multitasking is effective in achieving high GPU utilization, but poor reliability. We develop and implement a long-term reliability-aware thread block scheduler in GPGPU-Sim, and compare it against existing reliability-agnostic scheduler. We evaluate several use cases of spatial multitasking and find that our proposed scheduler achieves up to 30\% improvement in long-term reliability.« less
  3. Abstract We report the results of the first joint observation of the KAGRA detector with GEO 600. KAGRA is a cryogenic and underground gravitational-wave detector consisting of a laser interferometer with 3 km arms, located in Kamioka, Gifu, Japan. GEO 600 is a British–German laser interferometer with 600 m arms, located near Hannover, Germany. GEO 600 and KAGRA performed a joint observing run from April 7 to 20, 2020. We present the results of the joint analysis of the GEO–KAGRA data for transient gravitational-wave signals, including the coalescence of neutron-star binaries and generic unmodeled transients. We also perform dedicated searches for binary coalescence signals and generic transientsmore »associated with gamma-ray burst events observed during the joint run. No gravitational-wave events were identified. We evaluate the minimum detectable amplitude for various types of transient signals and the spacetime volume for which the network is sensitive to binary neutron-star coalescences. We also place lower limits on the distances to the gamma-ray bursts analyzed based on the non-detection of an associated gravitational-wave signal for several signal models, including binary coalescences. These analyses demonstrate the feasibility and utility of KAGRA as a member of the global gravitational-wave detector network.« less
    Free, publicly-accessible full text available June 1, 2023
  4. Free, publicly-accessible full text available May 1, 2023