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Paper   IPM / M / 15369
School of Mathematics
  Title:   Zero divisor and unit elements with supports of size 4 in group algebras of torsion-free groups
  Author(s):  Alireza Abdollahi (Joint with F. Jafari)
  Status:   To Appear
  Journal: Comm. Algebra
  Supported by:  IPM
  Abstract:
Kaplansky Zero Divisor Conjecture states that if G is a torsion-free group and F is a field, then the group ring F½G contains no zero divisor and Kaplansky Unit Conjecture Q1 states that if G is a torsion-free group and F is a field, then F½G contains no non-trivial units. The support of an element a ¼ Px2G axx in F½G, denoted by suppða�?, is the set fx 2 Gjax 6¼ 0g. In this paper, we study possible zero divisors and units with supports of size 4 in group algebras of torsion-free groups. We prove that if a, b are non-zero elements in F½G for a possible torsion-free group G and an arbitrary field F such that jsuppða�?j ¼ 4 and ab ¼ 0, then jsuppðb�?j  7. In [J. Group Theory, 16 ð2013�?; no. 5, 667�??693], it is proved that if F ¼ F2 is the field with two elements, G is a torsion-free group and a; b 2 F2½G n f0g such that jsuppða�?j ¼ 4 and ab ¼ 0, then jsuppðb�?j  8. We improve the latter result to jsuppðb�?j  9. Also, concerning the Unit Conjecture, we prove that if ab ¼ 1 for some a; b 2 F½G and jsuppða�?j ¼ 4, then jsuppðb�?j  6.

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