<p id="mathjaxlink" class="pcenter"><a href="chap3_mj.html">[MathJax on]</a></p>
<p><a id="X78FC7902804CED8E" name="X78FC7902804CED8E"></a></p>
<div class="ChapSects"><a href="chap3.html#X78FC7902804CED8E">3 <span class="Heading">Mappings of many-object structures</span></a>
<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap3.html#X82F856A086B93832">3.1 <span class="Heading">Homomorphisms of magmas with objects</span></a>
</span>
<div class="ContSSBlock">
<span class="ContSS"><br /><span class="nocss"> </span><a href="chap3.html#X86E00FEA7FF38FEA">3.1-1 MagmaWithObjectsHomomorphism</a></span>
</div></div>
<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap3.html#X7C4D1AEE80D41A35">3.2 <span class="Heading">Homomorphisms of semigroups and monoids with objects</span></a>
</span>
</div>
<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap3.html#X795C8DE37AED7B44">3.3 <span class="Heading">Homomorphisms to more than one piece</span></a>
</span>
<div class="ContSSBlock">
<span class="ContSS"><br /><span class="nocss"> </span><a href="chap3.html#X7AE44D9485EB50F1">3.3-1 HomomorphismByUnion</a></span>
<span class="ContSS"><br /><span class="nocss"> </span><a href="chap3.html#X7C053B0379DDCE13">3.3-2 IsInjectiveOnObjects</a></span>
</div></div>
<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap3.html#X7B9D71BB7BAEFAAA">3.4 <span class="Heading">Mappings defined by a function</span></a>
</span>
<div class="ContSSBlock">
<span class="ContSS"><br /><span class="nocss"> </span><a href="chap3.html#X81B64F9A855D265F">3.4-1 MappingWithObjectsByFunction</a></span>
</div></div>
</div>
<h3>3 <span class="Heading">Mappings of many-object structures</span></h3>
<p>A <em>homomorphism</em> <span class="SimpleMath">f</span> from a magma with objects <span class="SimpleMath">M</span> to a magma with objects <span class="SimpleMath">N</span> consists of</p>
<ul>
<li><p>a map <span class="SimpleMath">f_O</span> from the objects of <span class="SimpleMath">M</span> to those of <span class="SimpleMath">N</span>,</p>
</li>
<li><p>a map <span class="SimpleMath">f_A</span> from the arrows of <span class="SimpleMath">M</span> to those of <span class="SimpleMath">N</span>.</p>
</li>
</ul>
<p>The map <span class="SimpleMath">f_A</span> is required to be compatible with the tail and head maps and to preserve multiplication:</p>
<p class="pcenter">
f_A(a : u \to v) * f_A(b : v \to w) ~=~ f_A(a*b : u \to w)
</p>
<p>with tail <span class="SimpleMath">f_O(u)</span> and head <span class="SimpleMath">f_O(w)</span>.</p>
<p>When the underlying magma of <span class="SimpleMath">M</span> is a monoid or group, the map <spanclass="SimpleMath">f_A</span> is required to preserve identities and inverses.</p>
<p>The simplest construction gives a homomorphism <span class="SimpleMath">M -> N</span> with both <span class="SimpleMath">M</span> and <span class="SimpleMath">N</span> connected. It is implemented as <code class="code">IsMappingToSinglePieceRep</code> with attributes <code class="code">Source</code>, <code class="code">Range</code> and <code class="code">MappingToSinglePieceData</code>. The operation requires the following information:</p>
<ul>
<li><p>a magma homomorphism <code class="code">hom</code> from the underlying magma of <span class="SimpleMath">M</span> to the underlying magma of <span class="SimpleMath">N</span>,</p>
</li>
<li><p>a list <code class="code">imobs</code> of the images of the objects of <span class="SimpleMath">M</span>.</p>
</li>
</ul>
<p>In the first example we construct endomappings of <code class="code">m</code> and <code class="code">M78</code>.</p>
<p>A homomorphism <em>to</em> a connected magma with objects may have a source with several pieces, and so is a union of homomorphisms <em>from</em> single pieces.</p>
<div class="func"><table class="func" width="100%"><tr><td class="tdleft"><code class="func">‣ HomomorphismByUnion</code>( <var class="Arg">src</var>, <var class="Arg">rng</var>, <var class="Arg">homs</var> )</td><td class="tdright">( operation )</td></tr></table></div>
<p>When <span class="SimpleMath">f : M -> N</span> and <span class="SimpleMath">N</span> has more than one connected component, then <span class="SimpleMath">M</span> also has more than one component and <span class="SimpleMath">f</span> is a union of homomorphisms, one for each piece in the range.</p>
<p>See section <a href="chap5.html#X795C8DE37AED7B44"><span class="RefLink">5.5</span></a> for the equivalent operation with groupoids.</p>
¤ Die Informationen auf dieser Webseite wurden
nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit,
noch Qualität der bereit gestellten Informationen zugesichert.0.50Bemerkung:
(vorverarbeitet)
¤
Die Informationen auf dieser Webseite wurden
nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit,
noch Qualität der bereit gestellten Informationen zugesichert.
Bemerkung:
Die farbliche Syntaxdarstellung ist noch experimentell.