arXiv Machine Learning By Bashir Zeimarani, Alireza Khatib, Somayeh Mousavinasr, Carlos Maur\'icio Serodio Figueiredo

PixSim: a calibrated open-source simulator of instant-payment fraud, recovery and interdiction under analyst capacity constraints

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PixSim is an open‑source simulator that models Brazil’s Pix instant‑payment system, incorporating irreversible settlement, a regulated recovery mechanism (MED), downstream fund dispersal, and capacity‑constrained analyst review. Calibrated to Banco Central do Brasil data, the model reproduces the 2025 recovery rate within 0.006 and its decomposition within 0.02, and projects future performance under various policy scenarios. Benchmark tests show how staffing levels, alert expiry rules, and scorer quality affect recovery outcomes and false‑block harm.

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