Physics Colloquium: Quantum critical points and the sign problem

Physics Colloquium
Quantum critical points and the sign problem

Dr. Rubem Mondaini
Assistant Professor
Beijing Computational Science Research Center (CSRC)

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I plan to show in this talk that the SP in determinant quantum Monte Carlo (DQMC) is quantitatively linked to quantum critical behavior.

Abstract:
Solving quantum many-body problems exposes the challenges that numerical simulations in classical computers face in exploring quantum matter. One of these is presented by the "sign problem" (SP), which is a fundamental limitation to the investigation of strongly correlated materials in condensed matter physics, solving quantum chromodynamics at finite baryon density, and computational studies of nuclear matter, for example. In short, widely employed importance sampling techniques, when extended to the quantum realm, often lead to "negative probabilities" that hamper the simulations. It is usually argued that the SP is not intrinsic to the physics of particular Hamiltonians, since the details of how it onsets, and its eventual occurrence, can be altered by the choice of algorithm or many-particle basis. Despite that, I plan to show in this talk that the SP in determinant quantum Monte Carlo (DQMC) is quantitatively linked to quantum critical behavior. This demonstration is done via simulations of a number of fundamental models of condensed matter physics, all of whose critical properties are relatively well understood. The possible generalization to transitions which are yet under debate will also be discussed.

Speaker Bio:
Rubem obtained his PhD in Physics at the Federal University of Rio de Janeiro (2012), where his main line of research encompasses the following subjects: Strongly Correlated/Quantum many-body systems in and out-of-equilibrium, with specific interests in Magnetic Multilayers, Transport Properties in Many-Body Systems, Disorder in Graphene, Superconductivity in Cuprates, Thermalization and Many-Body Localization. After postdoc positions at the Pennsylvania State University and the University of California, Davis, he moved to China, where, currently, holds a tenure-track faculty position as Assistant Professor at the Beijing Computational Science Research Center (CSRC).

Intended Audience:
Beginners, undergraduates, graduates, experts. Those with interest in the topic.

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