Overview
Comment:Update README.md: Section headers, links, etc.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | master | trunk
Files: files | file ages | folders
SHA3-256: 74b66b89f996f7246c128dfc60a8623f87c2c9874f04470b2597c70434acd58a
User & Date: trnsz@pobox.com on 2021-03-02 17:32:01
Other Links: manifest | tags
Context
2021-03-02
17:36:29
README.md: Comment out Chisel mirror until sync'd check-in: a3f811a8e7 user: trnsz@pobox.com tags: master, trunk
17:32:01
Update README.md: Section headers, links, etc. check-in: 74b66b89f9 user: trnsz@pobox.com tags: master, trunk
2021-03-01
10:35:17
multi: Update to PR autoresponder, add SECURITY.md check-in: 97f0d9c57e user: jeff@gridfinity.com tags: master, trunk
Changes

Modified README.md from [10f18bcc98] to [a5e0a6df5a].

1
2
3
4




5
6
7
8
9
10
11
12




13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29











30
31
32
33


34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49


50
51
52
53
54

55


56
57


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78

79
80
81
82
83
84




+
+
+
+








+
+
+
+

















+
+
+
+
+
+
+
+
+
+
+




+
+
















+
+





+
-
+
+


+
+
# **GRG**

## Computer Algebra System for Differential Geometry, Gravitation and Field Theory

----

## Introduction

The computer algebra system **GRG** is designed to make calculation in differential geometry and field theory as simple and natural as possible. **GRG** is based on the computer algebra system **REDUCE** but **GRG** has its own simple input language whose commands resemble short English phrases.

**GRG** understands tensors, spinors, vectors, differential forms and knows all standard operations with these quantities. Input form for mathematical expressions is very close to traditional mathematical notation including Einstein summation rule. **GRG** knows covariant properties of the objects: one can easily raise and lower indices, compute covariant and Lie derivatives, perform coordinate and frame transformations etc. **GRG** works in any dimension and allows one to represent tensor quantities with respect to holonomic, orthogonal and even any other arbitrary frame.

One of the key features of **GRG** is that it knows a large number of built-in usual field-theoretical and geometrical quantities and formulas for their computation providing ready solutions to many standard problems.

Another unique feature of **GRG** is that it can export results of calculations into other computer algebra system such as *Maple*, *Mathematica*, *Macsyma* or ***REDUCE*** in order to use these systems to proceed with analysis of the data. The *LaTeX* output format is supported as well. **GRG** is compatible with the **REDUCE** graphics shells providing nice book-quality output with Greek letters, integral signs, etc.

----

## Features

The main built-in **GRG** capabilities are:

- Connection, torsion and nonmetricity.
- Curvature.
- Spinorial formalism.
- Irreducible decomposition of the curvature, torsion, and nonmetricity in any dimension.
- Einstein equations.
- Scalar field with minimal and non-minimal interaction.
- Electromagnetic field.
- Yang-Mills field.
- Dirac spinor field.
- Geodesic equation.
- Null congruences and optical scalars.
- Kinematics for time-like congruences.
- Ideal and spin fluid.
- Newman-Penrose formalism.
- Gravitational equations for the theory with arbitrary gravitational Lagrangian in Riemann and Riemann-Cartan spaces.

----

## Availability

- [**GRG Homepage**](https://reduce-algebra.sourceforge.io/grg32/grg32.php)
- [GitHub Mirror](https://github.com/reduce-algebra/grg/)
- [SourceHut Mirror](https://git.sr.ht/~trn/grg/)
- [Chisel Mirror](https://chiselapp.com/user/reduce-algebra/repository/grg/)

----

## Documentation

- [User Manual and Reference Guide](https://github.com/reduce-algebra/grg/tree/master/doc)

----

## Author

```text
Vadim V. Zhytnikov
Physics Department, Faculty of Mathematics,
Moscow State Pedagogical University,
Davydovskii per. 4, Moscow 107140, Russia

Telephone (Home): (095) 188-16-11

E-mail: vvzhy@td.lpi.ac.ru

E-mail: grg@curie.phy.ncu.edu.tw
        Subject: for Zhytnikov
```

----

## License

- **GRG** is free of charge. See [LICENSE](https://github.com/reduce-algebra/grg/blob/master/LICENSE) for full details.

----
## Upstream

## Homepage

- [GRG Homepage](https://reduce-algebra.sourceforge.io/grg32/grg32.php)

----


GRG for REDUCE
GRG Homepage | GitHub Mirror | SourceHut Mirror | NotABug Mirror | Chisel Mirror | Chisel RSS ]