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39 lines
1.0 KiB
ReStructuredText
39 lines
1.0 KiB
ReStructuredText
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.. index:: Green's functions
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.. module:: pytriqs.gf.local
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.. _green:
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Green's functions
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=================
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Green's functions are among the most important objects when dealing with
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many-body problems. TRIQS makes it easy for you to manipulate them. Before
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starting with some example, let us readily emphasize the essential notion
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that Green's functions have a **block** structure:
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.. math::
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G^a_{\alpha_a \beta_a} (\tau) = - \mathcal{T} <c^a_{\alpha_a}(\tau) c^{a \dagger}_{\beta_a} (0)>
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Here, :math:`a` labels a block, while :math:`\alpha_a, \beta_a` are indices
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**within** the block :math:`a`. In other words, there can be off-diagonal
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elements within a block but not between blocks. Whenever possible, one should
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take advantage of the symmetries of the problem under consideration and define
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blocks for the Green's functions.
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In this documentation, we will start with the block Green's function,
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and then proceed with the general Green's function and its block structure.
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.. toctree::
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:maxdepth: 2
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tutorial
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block
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transforms
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full
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