Hausdorff partial metric











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Using a metric on a metric space $(X,d)$ we can define Hausdorff metric $h$ on the set of all compact subsets of $(X,d)$,say $K(X)$. I am able to show that $h$ is indeed a metric. Suppose instead of metric $d$ on $X$ we had a partial metric $p$ on $X$. If we analogously define Hausdorff partial metric, say $h_p$, similar to the definition of $h$, will $h_p$ be a partial metric non $K(X)$?



Edit



Let $Xne emptyset$. A partial metric on $X$ is a function $p:Xtimes X to mathbb{R}^+$ satisfying



a)$p(x,y)=p(y,x)$ (symmetry)



b)$0le p(x,x) =p(x,y)= p(y,y)$ then $x=y$ (equality)



c)$p(x,x)le p(x,y)$ (small self distances)



d)$p(x,z)le p(x,y)+p(y,z)-p(y,y)$ (triangle inequality)



for all $x,y,zin X.$



Why partial metric is useful?



Some research articles state that, partial metric is useful in modeling partially defined information as comes in computer science.



Definition



$$h_p(A,B)=sup_{ain A}inf_{bin B} p(a,b)$$



$K(X)$: set of all compact subsets in the partial metric space $(X,p)$



Question



Is $h_p$ a partial metric on $K(X)$?










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  • define partial metric, and why is that notion useful at all?
    – Henno Brandsma
    Nov 17 at 9:18










  • @HennoBrandsma On partial metric spaces: dcs.warwick.ac.uk/pmetric/index.html
    – supremum
    Nov 17 at 10:28

















up vote
0
down vote

favorite












Using a metric on a metric space $(X,d)$ we can define Hausdorff metric $h$ on the set of all compact subsets of $(X,d)$,say $K(X)$. I am able to show that $h$ is indeed a metric. Suppose instead of metric $d$ on $X$ we had a partial metric $p$ on $X$. If we analogously define Hausdorff partial metric, say $h_p$, similar to the definition of $h$, will $h_p$ be a partial metric non $K(X)$?



Edit



Let $Xne emptyset$. A partial metric on $X$ is a function $p:Xtimes X to mathbb{R}^+$ satisfying



a)$p(x,y)=p(y,x)$ (symmetry)



b)$0le p(x,x) =p(x,y)= p(y,y)$ then $x=y$ (equality)



c)$p(x,x)le p(x,y)$ (small self distances)



d)$p(x,z)le p(x,y)+p(y,z)-p(y,y)$ (triangle inequality)



for all $x,y,zin X.$



Why partial metric is useful?



Some research articles state that, partial metric is useful in modeling partially defined information as comes in computer science.



Definition



$$h_p(A,B)=sup_{ain A}inf_{bin B} p(a,b)$$



$K(X)$: set of all compact subsets in the partial metric space $(X,p)$



Question



Is $h_p$ a partial metric on $K(X)$?










share|cite|improve this question
























  • define partial metric, and why is that notion useful at all?
    – Henno Brandsma
    Nov 17 at 9:18










  • @HennoBrandsma On partial metric spaces: dcs.warwick.ac.uk/pmetric/index.html
    – supremum
    Nov 17 at 10:28















up vote
0
down vote

favorite









up vote
0
down vote

favorite











Using a metric on a metric space $(X,d)$ we can define Hausdorff metric $h$ on the set of all compact subsets of $(X,d)$,say $K(X)$. I am able to show that $h$ is indeed a metric. Suppose instead of metric $d$ on $X$ we had a partial metric $p$ on $X$. If we analogously define Hausdorff partial metric, say $h_p$, similar to the definition of $h$, will $h_p$ be a partial metric non $K(X)$?



Edit



Let $Xne emptyset$. A partial metric on $X$ is a function $p:Xtimes X to mathbb{R}^+$ satisfying



a)$p(x,y)=p(y,x)$ (symmetry)



b)$0le p(x,x) =p(x,y)= p(y,y)$ then $x=y$ (equality)



c)$p(x,x)le p(x,y)$ (small self distances)



d)$p(x,z)le p(x,y)+p(y,z)-p(y,y)$ (triangle inequality)



for all $x,y,zin X.$



Why partial metric is useful?



Some research articles state that, partial metric is useful in modeling partially defined information as comes in computer science.



Definition



$$h_p(A,B)=sup_{ain A}inf_{bin B} p(a,b)$$



$K(X)$: set of all compact subsets in the partial metric space $(X,p)$



Question



Is $h_p$ a partial metric on $K(X)$?










share|cite|improve this question















Using a metric on a metric space $(X,d)$ we can define Hausdorff metric $h$ on the set of all compact subsets of $(X,d)$,say $K(X)$. I am able to show that $h$ is indeed a metric. Suppose instead of metric $d$ on $X$ we had a partial metric $p$ on $X$. If we analogously define Hausdorff partial metric, say $h_p$, similar to the definition of $h$, will $h_p$ be a partial metric non $K(X)$?



Edit



Let $Xne emptyset$. A partial metric on $X$ is a function $p:Xtimes X to mathbb{R}^+$ satisfying



a)$p(x,y)=p(y,x)$ (symmetry)



b)$0le p(x,x) =p(x,y)= p(y,y)$ then $x=y$ (equality)



c)$p(x,x)le p(x,y)$ (small self distances)



d)$p(x,z)le p(x,y)+p(y,z)-p(y,y)$ (triangle inequality)



for all $x,y,zin X.$



Why partial metric is useful?



Some research articles state that, partial metric is useful in modeling partially defined information as comes in computer science.



Definition



$$h_p(A,B)=sup_{ain A}inf_{bin B} p(a,b)$$



$K(X)$: set of all compact subsets in the partial metric space $(X,p)$



Question



Is $h_p$ a partial metric on $K(X)$?







general-topology metric-spaces compactness fractals hausdorff-distance






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edited Nov 17 at 10:09

























asked Nov 17 at 7:54









supremum

1,2001719




1,2001719












  • define partial metric, and why is that notion useful at all?
    – Henno Brandsma
    Nov 17 at 9:18










  • @HennoBrandsma On partial metric spaces: dcs.warwick.ac.uk/pmetric/index.html
    – supremum
    Nov 17 at 10:28




















  • define partial metric, and why is that notion useful at all?
    – Henno Brandsma
    Nov 17 at 9:18










  • @HennoBrandsma On partial metric spaces: dcs.warwick.ac.uk/pmetric/index.html
    – supremum
    Nov 17 at 10:28


















define partial metric, and why is that notion useful at all?
– Henno Brandsma
Nov 17 at 9:18




define partial metric, and why is that notion useful at all?
– Henno Brandsma
Nov 17 at 9:18












@HennoBrandsma On partial metric spaces: dcs.warwick.ac.uk/pmetric/index.html
– supremum
Nov 17 at 10:28






@HennoBrandsma On partial metric spaces: dcs.warwick.ac.uk/pmetric/index.html
– supremum
Nov 17 at 10:28

















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