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	<updated>2026-08-31T23:04:11Z</updated>
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	<entry>
		<id>https://diffgeom.subwiki.org/w/index.php?title=Tensor_product_of_metric_connections_is_metric&amp;diff=2113</id>
		<title>Tensor product of metric connections is metric</title>
		<link rel="alternate" type="text/html" href="https://diffgeom.subwiki.org/w/index.php?title=Tensor_product_of_metric_connections_is_metric&amp;diff=2113"/>
		<updated>2015-09-22T15:18:42Z</updated>

		<summary type="html">&lt;p&gt;Asafs: /* Proof */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;==Statement==&lt;br /&gt;
&lt;br /&gt;
A [[differential manifold]] &amp;lt;math&amp;gt;M&amp;lt;/math&amp;gt;. Two [[fact about::metric bundle]]s &amp;lt;math&amp;gt;(E,g)&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;(E&#039;,g&#039;)&amp;lt;/math&amp;gt; (i.e., &amp;lt;math&amp;gt;E,E&#039;&amp;lt;/math&amp;gt; are [[vector bundle]]s and &amp;lt;math&amp;gt;g,g&#039;&amp;lt;/math&amp;gt; are [[Riemannian metric]]s or [[pseudo-Riemannian metric]]s on these). &amp;lt;math&amp;gt;\nabla, \nabla&#039;&amp;lt;/math&amp;gt; are [[fact about::metric connection]]s on &amp;lt;math&amp;gt;(E,g)&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;(E&#039;,g&#039;)&amp;lt;/math&amp;gt; respectively. Then, the [[fact about::tensor product of connections]] &amp;lt;math&amp;gt;\nabla \otimes \nabla&#039;&amp;lt;/math&amp;gt; is a metric connection on &amp;lt;math&amp;gt;(E \otimes E&#039;,g \otimes g&#039;)&amp;lt;/math&amp;gt;.&lt;br /&gt;
&lt;br /&gt;
==Proof==&lt;br /&gt;
&lt;br /&gt;
==Related facts==&lt;br /&gt;
&lt;br /&gt;
* [[Tensor product of flat connections is flat]]&lt;/div&gt;</summary>
		<author><name>Asafs</name></author>
	</entry>
	<entry>
		<id>https://diffgeom.subwiki.org/w/index.php?title=Tensor_product_of_metric_connections_is_metric&amp;diff=2112</id>
		<title>Tensor product of metric connections is metric</title>
		<link rel="alternate" type="text/html" href="https://diffgeom.subwiki.org/w/index.php?title=Tensor_product_of_metric_connections_is_metric&amp;diff=2112"/>
		<updated>2015-09-22T10:04:15Z</updated>

		<summary type="html">&lt;p&gt;Asafs: /* Proof */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;==Statement==&lt;br /&gt;
&lt;br /&gt;
A [[differential manifold]] &amp;lt;math&amp;gt;M&amp;lt;/math&amp;gt;. Two [[fact about::metric bundle]]s &amp;lt;math&amp;gt;(E,g)&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;(E&#039;,g&#039;)&amp;lt;/math&amp;gt; (i.e., &amp;lt;math&amp;gt;E,E&#039;&amp;lt;/math&amp;gt; are [[vector bundle]]s and &amp;lt;math&amp;gt;g,g&#039;&amp;lt;/math&amp;gt; are [[Riemannian metric]]s or [[pseudo-Riemannian metric]]s on these). &amp;lt;math&amp;gt;\nabla, \nabla&#039;&amp;lt;/math&amp;gt; are [[fact about::metric connection]]s on &amp;lt;math&amp;gt;(E,g)&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;(E&#039;,g&#039;)&amp;lt;/math&amp;gt; respectively. Then, the [[fact about::tensor product of connections]] &amp;lt;math&amp;gt;\nabla \otimes \nabla&#039;&amp;lt;/math&amp;gt; is a metric connection on &amp;lt;math&amp;gt;(E \otimes E&#039;,g \otimes g&#039;)&amp;lt;/math&amp;gt;.&lt;br /&gt;
&lt;br /&gt;
==Proof==&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
A [[differential manifold]] &amp;lt;math&amp;gt;M&amp;lt;/math&amp;gt;. Two [[fact about::metric bundle]]s &amp;lt;math&amp;gt;(E,g)&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;(E&#039;,g&#039;)&amp;lt;/math&amp;gt; (i.e., &amp;lt;math&amp;gt;E,E&#039;&amp;lt;/math&amp;gt; are [[vector bundle]]s and &amp;lt;math&amp;gt;g,g&#039;&amp;lt;/math&amp;gt; are [[Riemannian metric]]s or [[pseudo-Riemannian metric]]s on these). &amp;lt;math&amp;gt;\nabla, \nabla&#039;&amp;lt;/math&amp;gt; are [[fact about::metric connection]]s on &amp;lt;math&amp;gt;(E,g)&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;(E&#039;,g&#039;)&amp;lt;/math&amp;gt; respectively. Then, the [[fact about::tensor product of connections]] &amp;lt;math&amp;gt;\nabla \otimes \nabla&#039;&amp;lt;/math&amp;gt; is a metric connection on &amp;lt;math&amp;gt;(E \otimes E&#039;,g \otimes g&#039;)&amp;lt;/math&amp;gt;.&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
Let &amp;lt;math&amp;gt;X,Y \in \Ga(E), X&#039;,Y&#039; \in \Ga(E&#039;)&amp;lt;/math&amp;gt;. Then $\til X \some{def} X \otimes X&#039; \in \Ga(E \otimes E&#039;), \til Y \some{def} Y \otimes Y&#039; \in \Ga(E \otimes E&#039;)$. Let $Z \in \Ga(\TM)$. We just expand the two expressions which are needed to be shown equal:&lt;br /&gt;
&lt;br /&gt;
==Related facts==&lt;br /&gt;
&lt;br /&gt;
* [[Tensor product of flat connections is flat]]&lt;/div&gt;</summary>
		<author><name>Asafs</name></author>
	</entry>
	<entry>
		<id>https://diffgeom.subwiki.org/w/index.php?title=Tensor_product_of_metric_connections_is_metric&amp;diff=2111</id>
		<title>Tensor product of metric connections is metric</title>
		<link rel="alternate" type="text/html" href="https://diffgeom.subwiki.org/w/index.php?title=Tensor_product_of_metric_connections_is_metric&amp;diff=2111"/>
		<updated>2015-09-22T10:03:09Z</updated>

		<summary type="html">&lt;p&gt;Asafs: /* Proof */&lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;==Statement==&lt;br /&gt;
&lt;br /&gt;
A [[differential manifold]] &amp;lt;math&amp;gt;M&amp;lt;/math&amp;gt;. Two [[fact about::metric bundle]]s &amp;lt;math&amp;gt;(E,g)&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;(E&#039;,g&#039;)&amp;lt;/math&amp;gt; (i.e., &amp;lt;math&amp;gt;E,E&#039;&amp;lt;/math&amp;gt; are [[vector bundle]]s and &amp;lt;math&amp;gt;g,g&#039;&amp;lt;/math&amp;gt; are [[Riemannian metric]]s or [[pseudo-Riemannian metric]]s on these). &amp;lt;math&amp;gt;\nabla, \nabla&#039;&amp;lt;/math&amp;gt; are [[fact about::metric connection]]s on &amp;lt;math&amp;gt;(E,g)&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;(E&#039;,g&#039;)&amp;lt;/math&amp;gt; respectively. Then, the [[fact about::tensor product of connections]] &amp;lt;math&amp;gt;\nabla \otimes \nabla&#039;&amp;lt;/math&amp;gt; is a metric connection on &amp;lt;math&amp;gt;(E \otimes E&#039;,g \otimes g&#039;)&amp;lt;/math&amp;gt;.&lt;br /&gt;
&lt;br /&gt;
==Proof==&lt;br /&gt;
&lt;br /&gt;
Let $X,Y \in \Ga(E), X&#039;,Y&#039; \in \Ga(E&#039;)$. Then $\til X \some{def} X \otimes X&#039; \in \Ga(E \otimes E&#039;), \til Y \some{def} Y \otimes Y&#039; \in \Ga(E \otimes E&#039;)$. Let $Z \in \Ga(\TM)$. We just expand the two expressions which are needed to be shown equal:&lt;br /&gt;
&lt;br /&gt;
==Related facts==&lt;br /&gt;
&lt;br /&gt;
* [[Tensor product of flat connections is flat]]&lt;/div&gt;</summary>
		<author><name>Asafs</name></author>
	</entry>
	<entry>
		<id>https://diffgeom.subwiki.org/w/index.php?title=Tensor_product_of_metric_connections_is_metric&amp;diff=2110</id>
		<title>Tensor product of metric connections is metric</title>
		<link rel="alternate" type="text/html" href="https://diffgeom.subwiki.org/w/index.php?title=Tensor_product_of_metric_connections_is_metric&amp;diff=2110"/>
		<updated>2015-09-22T10:00:47Z</updated>

		<summary type="html">&lt;p&gt;Asafs: &lt;/p&gt;
&lt;hr /&gt;
&lt;div&gt;==Statement==&lt;br /&gt;
&lt;br /&gt;
A [[differential manifold]] &amp;lt;math&amp;gt;M&amp;lt;/math&amp;gt;. Two [[fact about::metric bundle]]s &amp;lt;math&amp;gt;(E,g)&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;(E&#039;,g&#039;)&amp;lt;/math&amp;gt; (i.e., &amp;lt;math&amp;gt;E,E&#039;&amp;lt;/math&amp;gt; are [[vector bundle]]s and &amp;lt;math&amp;gt;g,g&#039;&amp;lt;/math&amp;gt; are [[Riemannian metric]]s or [[pseudo-Riemannian metric]]s on these). &amp;lt;math&amp;gt;\nabla, \nabla&#039;&amp;lt;/math&amp;gt; are [[fact about::metric connection]]s on &amp;lt;math&amp;gt;(E,g)&amp;lt;/math&amp;gt; and &amp;lt;math&amp;gt;(E&#039;,g&#039;)&amp;lt;/math&amp;gt; respectively. Then, the [[fact about::tensor product of connections]] &amp;lt;math&amp;gt;\nabla \otimes \nabla&#039;&amp;lt;/math&amp;gt; is a metric connection on &amp;lt;math&amp;gt;(E \otimes E&#039;,g \otimes g&#039;)&amp;lt;/math&amp;gt;.&lt;br /&gt;
&lt;br /&gt;
==Proof==&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
&lt;br /&gt;
==Related facts==&lt;br /&gt;
&lt;br /&gt;
* [[Tensor product of flat connections is flat]]&lt;/div&gt;</summary>
		<author><name>Asafs</name></author>
	</entry>
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