Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Iterative methods for shifted positive definite linear systems and time
  discretization of the heat equation   In earlier work we have studied a method for discretization in time of a
parabolic problem which consists in representing the exact solution as an
integral in the complex plane and then applying a quadrature formula to this
integral. In application to a spatially semidiscrete finite element version of
the parabolic problem, at each quadrature point one then needs to solve a
linear algebraic system having a positive definite matrix with a complex shift,
and in this paper we study iterative methods for such systems. We first
consider the basic and a preconditioned version of the Richardson algorithm,
and then a conjugate gradient method as well as a preconditioned version
thereof.

25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph