Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A remark on Ricci flow of left invariant metrics   We prove that the Ricci flow equation for left invariant metrics on Lie
groups reduces to a first order ordinary differential equation for a map $Q :
(-a,a) \to UT$, where $UT$ is the group of upper triangular matrices. We
decompose the matrix $R_{ij}$ of Ricci tensor coordinates with respect to an
orthonormal frame field $E_{i}$ into a sum $\overset{1}{R}_{ij} +
\overset{2}{R}_{ij} + \overset{3}{R}_{ij} + \overset{4}{R}_{ij}$ such that, for
any $E_{i'} = U^i_{i'} E_i$ with $||U^i_{i'}|| \in O(n)$,
$\overset{\alpha}{R}_{i'j'} = U_{i'}^i \overset{\alpha}{R}_{ij} U^j_{j'}$. This
allows us to specify several cases when the differential equation can be
simplified. As an example we consider three-dimensional unimodular Lie groups.

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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
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The categories of this paper are: cmp-lg
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The categories of this paper are: chao-dyn
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The categories of this paper are: dg-ga
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The categories of this paper are: solv-int
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The categories of this paper are: alg-geom
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The categories of this paper are: ao-sci