A spectral gap is a positive separation between designated parts of the spectrum of a linear operator. For the power method, the relevant gap separates the modulus of the dominant eigenvalue from the other eigenvalue moduli.
The spectral gap is a concept used in various fields such as mathematics, physics, and particularly in quantum mechanics and condensed matter physics. It refers to the difference between the lowest energy levels of a system, particularly the lowest eigenvalue or ground state energy and the next lowest eigenvalue or excited state energy.
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