A development of the malcev s description for torsion free abelian groups
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A development of the Malcev´s description for torsion free abelian groups. Alexander Fomin Mathematics in the contemporary world Vologda, 2013, October 8. Finitely presented modules over the ring U. U =  p Z p where Z p is the ring of p-adic integers introduced by Kurt Hensel in 1900.

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A development of the Malcev´s description for torsion free abelian groups

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A development of the malcev s description for torsion free abelian groups

A development of the Malcev´s description for torsion free abelian groups

Alexander Fomin

Mathematics in the contemporary world

Vologda, 2013, October 8


Finitely presented modules over the ring u

Finitely presented modules over the ring U

U=pZp

where Zpis the ring of p-adic integers introduced by Kurt Hensel in 1900.

Um UkM0


Category sequences

Category “Sequences”

An object of the category S is a finite sequence m1,…,mn of elements of a finitely presented U-module M.

Morphisms {a1,…,an} {b1,…,bk} are pairs (φ,T), where

φ : <a1,…,an>U <b1,…,bk>U is a U-module homomorphism and T is a matrix with integer entries such that

(φ a1,…, φ an)= (b1,…,bk)T


Category tffr

Category TFFR

  • Objects are torsion free abelian groups of finite rank with marked bases.

  • Morphisms are homomorphisms such that the corresponding matrix is of integer entries.


Category qd

Category QD

  • Objects are quotient divisible groups with marked bases introduced by Beaumont-Pierce in 1961 and generalized by Fomin-Wickless in 1998.

  • Morphisms are homomorphisms such that the corresponding matrix is of integer entries


The main theorem

The main Theorem

  • Each of three following objects determines uniquely two other objects:

  • 1. A sequence of the category S,

  • 2. A torsion free group of the category TFFR,

  • 3. A quotient divisible group of the categoty QD.


A development of the malcev s description for torsion free abelian groups

(2) (3)

TFFR QD

It is a duality of two categories introduced by Wickless and Fomin in 1998.


Malcev s description 1938

Malcev´s description (1938)

  • (1) (2)

  • (m1,…,mn) A

  • It is a duality of two categories S and TFFR which is a development of the Malcev´s description (1938)


A development of the malcev s description for torsion free abelian groups

(1) (3)

  • S QD

  • It is an equivalence of two categories S and QD which presents a generalization of the Kurosh´s Theorem (1937).


A development of the malcev s description for torsion free abelian groups

Derry

Malcev

Kurosh

prim

t.f.f.r.

q.d.,1998


Example 1

Example 1

  • (S) The sequence of zeros 0,0,…,0.

  • (TFFR) The group is free.

  • (QD) The group is divisible.


Example 2

Example 2

  • (S) The sequence m1,…,mn is a free basis of a free U-module M=m1U+…+ mnU

  • (TFFR) The group is divisible.

  • (QD) The group is free


Example 3

Example 3

  • (S) The sequence consists of p-adic integers and it is linearly independent over Z.

  • (TFFR) The group is strongly indecomposable and it has the following property: every subgroup of infinite index is free.

  • (QD) The group is a pure subgroup of Zp.


Example 4

Example 4

  • (S) the sequence is linearly independent over Z.

  • (TFFR) The group is coreduced (it doesn´t contain nonzero free direct summands).

  • (QD) The group is reduced.


Example 5

Example 5

  • (S)The sequence is linearly independent overU.

  • (TFFR)The group is completely decomposable into a direct sum of rank-1 torsion free groups.

  • (QD) The group is completely decomposable into a direct sum of rank-1 quotient divisible mixed groups.


Example 6

Example 6

  • (S)The sequence is almost linearly independent overU.

  • (TFFR)The group is almost completely decomposable into a direct sum of rank-1 torsion free groups.

  • (QD) The group is completely decomposable into a direct sum of rank-1 quotient divisible mixed groups.


Thank you

Thank you

For your attention


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