near-fields - MathStructures

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=====Near-fields=====

Abbreviation: **NFld**
====Definition====
A \emph{near-field} is a [[near-rings with identity]] $\mathbf{N}=\langle N,+,-,0,\cdot,1
\rangle $ such that


$\mathbf{N}$ is non-trivial:  $0\ne 1$


every non-zero element has a multiplicative inverse:  $x\ne 0\Longrightarrow \exists y 
(x\cdot y=1)$

Remark: 
The inverse of $x$ is unique, and is usually denoted by $x^{-1}$.


==Morphisms==
Let $\mathbf{M}$ and $\mathbf{N}$ be near-fields. A morphism from $\mathbf{M}$
to $\mathbf{N}$ is a function $h:M\rightarrow N$ that is a homomorphism: 

$h(x+y)=h(x)+h(y)$, $h(x\cdot y)=h(x)\cdot h(y)$

Remark: 
It follows that $h(0)=0$ and $h(-x)=-h(x)$.

====Examples====
Example 1: 

====Basic results====
$0$ is a zero for $\cdot$: $0\cdot x=0$ and $x\cdot 0=0$.

====Properties====
^[[Classtype]]  |first-order |
^[[Equational theory]]  | |
^[[Quasiequational theory]]  | |
^[[First-order theory]]  | |
^[[Locally finite]]  |no |
^[[Residual size]]  |unbounded |
^[[Congruence distributive]]  | |
^[[Congruence modular]]  |yes |
^[[Congruence n-permutable]]  |yes, $n=2$ |
^[[Congruence regular]]  |yes |
^[[Congruence uniform]]  |yes |
^[[Congruence extension property]]  | |
^[[Definable principal congruences]]  | |
^[[Equationally def. pr. cong.]]  | |
^[[Amalgamation property]]  | |
^[[Strong amalgamation property]]  | |
^[[Epimorphisms are surjective]]  | |
====Finite members====

$\begin{array}{lr}
f(1)= &1\\
f(2)= &\\
f(3)= &\\
f(4)= &\\
f(5)= &\\
f(6)= &\\
\end{array}$

====Subclasses====
[[Fields]] 

====Superclasses====
[[Near-rings with identity]] 


====References====

[(Ln19xx>
)]

Trace: • partial_semigroups • bck-algebras • flew-algebras • tense_algebras • intuitionistic_linear_logic_algebras • algebraic_lattices • multiplicative_semilattices • commutative_bck-algebras • weakly_associative_lattices • semirings