Concise Encyclopedia of Supersymmetry

2004 Edition
| Editors: Steven Duplij, Warren Siegel, Jonathan Bagger

Exterior Algebra

  • Steven Duplij
  • Warren Siegel
  • Cosmas Zachos
  • Euro Spallucci
  • Władysław Marcinek
  • Marco De Andrade
  • Ion Vancea
  • Joachim Kupsch
  • Hitoshi Murakami
  • Steven Duplij
  • Lev Gendenshtein
  • Dimitry Leites
  • Władysław Marcinek
  • Stanislav Klimenko
  • Igor Nikitin
  • Victor Rivelles
  • Theodore Voronov
Reference work entry
DOI: https://doi.org/10.1007/1-4020-4522-0_184

In super case there are two possible definitions leading to nonisomorphic algebras (which are, however, isomorphic as vector spaces).

First definition. For a ℤ2- graded vector space V = V0V1 define Λ (V): = T(V)/I, where T(V) is the tensor algebra of V and the ideal I is generated by Open image in new window for all v, wV (tilde stands for parity). There is a natural ℤ-grading (degree) inherited from T(V). There is also a natural ℤ2-grading (parity). The natural inclusion V→ Λ (V) is even (preserves parity) and maps elements of V to Λ1 (V). The algebra Λ (V) is not commutative as a ℤ2- graded algebra ; multiplication in it satisfies the condition Open image in new window for all elements v ∈ Λ k (V) and w∈ Λ l (V). Notice that degree and parity are independent. For a purely even V, parity is trivial (all elements of Λ (V) are even), and signs are due only to the degree of respective elements.

Second definition. For V = V0V1 consider the space with reversed parity π V, elements of which are denoted π v, where vV (the canonical isomorphism (π V0 = V1, (π V)1 = V0 is written as the multiplication by an odd symbol π). Define E(V): = SV) = TV)/J, where the ideal J is generated by Open image in new window for all v, wV. By definition, the algebra E(V) is commutative (in ℤ2-graded sense). The natural monomorphism VE(V), v ↦ π v, is odd (reverses parity). As well as for Λ (V), there is a natural ℤ-grading (degree), and the elements of V are mapped to E1(V) = π V. Degree and parity are independent, except for a purely even or a purely odd V. For a purely even vector space V = V0, the algebras Λ (V) and E(V) are isomorphic as algebras (not as ℤ2- graded algebras , because in this case parity is trivial for Λ (V) and coincides with degree modulo 2 for E(V)). This is the classical exterior algebra . In general, the algebras Λ (V) and E(V) are not isomorphic. However, in every degree k, there is an isomorphism of vector spaces Λ k (V)≅ E k (V). The parity of this isomorphism is k mod 2. If we forget about ℤ2-gradings and use the classical notions of exterior and symmetric algebras, then Λ k (V)≅ E k (V)≅ ⊕i+j = kΛ i (V0)⊗ S j (V1). The difference in the multiplication laws in Λ (V) and E(V) is in the different commutation relation between (the images of) elements of V of opposite parity: in the case of Λ (V) their transposition gives the minus sign, and in the case of E(V) they strictly commute (no sign). The algebra E(V) has the advantage of being (super) commutative, so working with it seems more convenient (cf., however, [3].) The construction of E(V) was suggested by Bernstein and Leites [2]. Elements of E(V) can be regarded as polynomial functions on the superspace π V*. Here π V* is considered not as ℤ2- graded vector space , but as the corresponding supermanifold . (Elements of E1(V) = π V are linear functions on π V*.) Thus, E(V) can be naturally completed to Ê(V): = CV*). The defining relations of the algebra Λ (V) are satisfied by the operators e(v) of the “exterior multiplication” by the elements of V on the space of Open image in new window [5].

Bibliography

  1. F. A. Berezin. Introduction to algebra and analysis with anticommuting variables, Moscow Moscow State University Press, 1983.Google Scholar
  2. J. N. Bernstein, D. A. Leites Funct. Anal. Pril., 11 (1977) 70.CrossRefGoogle Scholar
  3. P. Deligne, in: Quantum Fields and Strings: A course for mathematicians. American Mathematical Society, Institute for Advanced Study, 1999.Google Scholar
  4. Yu. I. Manin. Gauge fields and complex geometry, Moscow, Nauka, 1984.Google Scholar
  5. T. Voronov. Dual forms on supermanifolds and Cartan calculus. Manchester Centre for Pure Mathematics, preprint 1999/9 math.DG/9912192.Google Scholar

Copyright information

© Kluwer Academic Publishers 2004

Authors and Affiliations

  • Steven Duplij
  • Warren Siegel
  • Cosmas Zachos
  • Euro Spallucci
  • Władysław Marcinek
  • Marco De Andrade
  • Ion Vancea
  • Joachim Kupsch
  • Hitoshi Murakami
  • Steven Duplij
  • Lev Gendenshtein
  • Dimitry Leites
  • Władysław Marcinek
  • Stanislav Klimenko
  • Igor Nikitin
  • Victor Rivelles
  • Theodore Voronov

There are no affiliations available