His development of multiscale representations as a generalization of renormalization group addressed the limitations of calculus and statistics in the study of nonlinear and network system dependencies on collective behaviors.
[3] Bar-Yam is the president of Cambridge, Massachusetts-based NECSI, an independent research institution and think tank dedicated to the study of complex systems and its applications to solving real-world problems.
NECSI's faculty, co-faculty, and affiliates represent a wide range of scientific disciplines, and have included Jerome Kagan, Thomas Schelling, and Nassim Nicholas Taleb.
Bar-Yam has advised many policymaking and regulatory bodies on various topics, including: the Pentagon's Chairman Action Group on global social unrest and the crises in Egypt and Syria; the National Security Council and the National Counter Terrorism Council on global strategy; the Chief of Naval Operations Strategic Studies Group on military force transformation; the Centers for Disease Control and Prevention on delivery of prevention services and control of hospital infections; Congressman Barney Frank (as chairman of the House Financial Services Committee) on market regulation and the financial crisis.
[3] Pandemics are a natural field of study for complex systems scientists, as many of the main insights of the discipline—including network theory, nonlinearity, chaos, emergent properties, adaptation, and non-ergodicity—can be directly brought to bear on the analysis of infectious diseases and their spread.
Bar-Yam has studied pandemics since the early 2000s, in concert with NECSI's stated mission to foster collaboration among different disciplines (e.g. mathematics and epidemiology) and to apply theoretical work to problems in the real world.
His research has emphasized the role of increasing global travel in pandemics; community monitoring of symptoms as potentially superior to conventional testing, tracking, and tracing techniques; and specific guidelines for individuals, policymakers, healthcare workers, and businesses to slow the spread of infectious diseases.
[13][15] On January 26, 2020, one week after the first case of COVID-19 disease in the United States was reported, Bar-Yam co-authored a note with Nassim Nicholas Taleb and Joseph Norman.
The note outlined several principles in connection with the novel coronavirus outbreak, and argued that policy responses should follow a precautionary approach, including drastically constraining human mobility patterns as soon and as swiftly as possible.
Those recommendations included a lockdown, separate quarantine facilities for mild and moderate COVID-19 cases to prevent transmission within households, mask wearing in shared spaces, travel restrictions, improved safety of essential services, increased testing, health guidelines to prevent mild cases from becoming severe, and increased support for hospitals and healthcare workers.
On May 12, 2020, CNN.com published an opinion piece by Bar-Yam, in which he argued against the premature opening of states, and urged individual citizens to continue strict restrictions on their movement and contact with others.
[2] On November 26, 2021, Bar-Yam suggested solely on the basis of a simple linear extrapolation that the omicron variant might have eight times the fatality rate of the wild-type virus.