Abstract
SHEEP is an algebraic system written by I. Frick [1,2] that is specialized for manipulating components of tensors. On top of this language another system has been built treating a new data type "indicial formula" representing formulas containing tensors or spinors with symbolic (letter) indices. Such formulas can be used in two ways:
1. There are routines for manipulating indicial formulas, such as evaluation, differentiation, simplification using symmetries, substitution of products and sums, etc.
Also scalar sums can be efficiently substituted, e.g. sin2x+cos2x−1=>0
2. There is a compiler which for any indicial formula generates a corresponding program that actually performs the contractions etc. indicated in the formula. Thus the components of a tensor can be computed as soon as an indicial formula for its computation has been typed.
Terminology adopted from [6]
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References
Frick, I 1977 "The Computer Algebra System SHEEP, what it can and cannot do in General Relativity".
Frick, I 1977 "SHEEP, users guide", preprint. Inst. of Theor. Physics, Univ. of Stockholm.
Hörnfeldt, L 1976 NIGSAM:11 "A Tensor Compiler".
Hörnfeldt, L 1977 NIGSAM:12 "Indicial and componentwise tensor calculus with computer"
Hörnfeldt, L 1978 Manual
Bogen R. and Pavelle R. "Indicial Tensor Manipulation on MACSYMA" Lett. Math. Phys. 1977
Pereira, M J. Math. Phys., Vol. 15, No. 3, March 1974
Schouten, J A "Ricci-Calculus" Springer-Verlag
Anderson, J. N.Y. Private communication
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© 1979 Springer-Verlag Berlin Heidelberg
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Hörnfeldt, L. (1979). A system for automatic generation of tensor algorithms and indicial tensor calculus, including substitution of sums. In: Ng, E.W. (eds) Symbolic and Algebraic Computation. EUROSAM 1979. Lecture Notes in Computer Science, vol 72. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-09519-5_80
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DOI: https://doi.org/10.1007/3-540-09519-5_80
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