# Relative Projectivity and Transferability for Partial Lattices

Relative Projectivity and Transferability for Partial Lattices A partial lattice P is ideal-projective, with respect to a class C $\mathcal {C}$ of lattices, if for every K ∈ C $K\in \mathcal {C}$ and every homomorphism φ of partial lattices from P to the ideal lattice of K, there are arbitrarily large choice functions f:P→K for φ that are also homomorphisms of partial lattices. This extends the traditional concept of (sharp) transferability of a lattice with respect to C $\mathcal {C}$ . We prove the following: (1) A finite lattice P, belonging to a variety V $\mathcal {V}$ , is sharply transferable with respect to V $\mathcal {V}$ iff it is projective with respect to V $\mathcal {V}$ and weakly distributive lattice homomorphisms, iff it is ideal-projective with respect to V $\mathcal {V}$ , (2) Every finite distributive lattice is sharply transferable with respect to the class R mod $\mathcal {R}_{\text {mod}}$ of all relatively complemented modular lattices, (3) The gluing D 4 of two squares, the top of one being identified with the bottom of the other one, is sharply transferable with respect to a variety V $\mathcal {V}$ iff V $\mathcal {V}$ is contained in the variety ℳ ω $\mathcal {M}_{\omega }$ generated by all lattices of length 2, (4) D 4 is projective, but not ideal-projective, with respect to R mod $\mathcal {R}_{\text {mod}}$ , (5) D 4 is transferable, but not sharply transferable, with respect to the variety ℳ $\mathcal {M}$ of all modular lattices. This solves a 1978 problem of G. Grätzer, (6) We construct a modular lattice whose canonical embedding into its ideal lattice is not pure. This solves a 1974 problem of E. Nelson. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Order Springer Journals

# Relative Projectivity and Transferability for Partial Lattices

, Volume 35 (1) – Dec 15, 2016
22 pages

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Publisher
Springer Journals
Copyright
Copyright © 2016 by Springer Science+Business Media Dordrecht
Subject
Mathematics; Geometry; Number Theory
ISSN
0167-8094
eISSN
1572-9273
D.O.I.
10.1007/s11083-016-9421-0
Publisher site
See Article on Publisher Site

### Abstract

A partial lattice P is ideal-projective, with respect to a class C $\mathcal {C}$ of lattices, if for every K ∈ C $K\in \mathcal {C}$ and every homomorphism φ of partial lattices from P to the ideal lattice of K, there are arbitrarily large choice functions f:P→K for φ that are also homomorphisms of partial lattices. This extends the traditional concept of (sharp) transferability of a lattice with respect to C $\mathcal {C}$ . We prove the following: (1) A finite lattice P, belonging to a variety V $\mathcal {V}$ , is sharply transferable with respect to V $\mathcal {V}$ iff it is projective with respect to V $\mathcal {V}$ and weakly distributive lattice homomorphisms, iff it is ideal-projective with respect to V $\mathcal {V}$ , (2) Every finite distributive lattice is sharply transferable with respect to the class R mod $\mathcal {R}_{\text {mod}}$ of all relatively complemented modular lattices, (3) The gluing D 4 of two squares, the top of one being identified with the bottom of the other one, is sharply transferable with respect to a variety V $\mathcal {V}$ iff V $\mathcal {V}$ is contained in the variety ℳ ω $\mathcal {M}_{\omega }$ generated by all lattices of length 2, (4) D 4 is projective, but not ideal-projective, with respect to R mod $\mathcal {R}_{\text {mod}}$ , (5) D 4 is transferable, but not sharply transferable, with respect to the variety ℳ $\mathcal {M}$ of all modular lattices. This solves a 1978 problem of G. Grätzer, (6) We construct a modular lattice whose canonical embedding into its ideal lattice is not pure. This solves a 1974 problem of E. Nelson.

### Journal

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Published: Dec 15, 2016

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