Engineering

Collaborating to better understand metal degradation

Southwest Research Institute and The University of Texas at San Antonio are working together to understand the susceptibility of additively manufactured materials to hydrogen embrittlement, a common problem that can lead ...

Energy & Green Tech

How do lithium-ion batteries work?

The smartphone era is only just over a decade old, but the pocket-sized computers at the heart of that societal transformation are only really possible because of another technology: lithium-ion batteries.

Perturbation theory (quantum mechanics)

In quantum mechanics, perturbation theory is a set of approximation schemes directly related to mathematical perturbation for describing a complicated quantum system in terms of a simpler one. The idea is to start with a simple system for which a mathematical solution is known, and add an additional "perturbing" Hamiltonian representing a weak disturbance to the system. If the disturbance is not too large, the various physical quantities associated with the perturbed system (e.g. its energy levels and eigenstates) can, from considerations of continuity, be expressed as 'corrections' to those of the simple system. These corrections, being 'small' compared to the size of the quantities themselves, can be calculated using approximate methods such as asymptotic series. We can therefore study the complicated system based on our knowledge of the simpler one.

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