The cone $mathbb R_+^n$ of all vectors in $mathbb R^n$

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In a paper I've been studying it says:




Let $x$ in the cone $mathbb R_+^n$ of all vectors in $mathbb R^n$ with nonnnegative components ($ninmathbb N$)




Somebody tell me what does it means, please? $mathbb R_+^n$ should be $[0,infty)timesdotstimes [0,infty)$ ($n$ times), but I don't understand why the cone $mathbb R_+^n$. Maybe the cone $mathbb R_+^n$ is different from $[0,infty)timesdotstimes [0,infty)$?







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    up vote
    1
    down vote

    favorite












    In a paper I've been studying it says:




    Let $x$ in the cone $mathbb R_+^n$ of all vectors in $mathbb R^n$ with nonnnegative components ($ninmathbb N$)




    Somebody tell me what does it means, please? $mathbb R_+^n$ should be $[0,infty)timesdotstimes [0,infty)$ ($n$ times), but I don't understand why the cone $mathbb R_+^n$. Maybe the cone $mathbb R_+^n$ is different from $[0,infty)timesdotstimes [0,infty)$?







    share|cite|improve this question





















      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      In a paper I've been studying it says:




      Let $x$ in the cone $mathbb R_+^n$ of all vectors in $mathbb R^n$ with nonnnegative components ($ninmathbb N$)




      Somebody tell me what does it means, please? $mathbb R_+^n$ should be $[0,infty)timesdotstimes [0,infty)$ ($n$ times), but I don't understand why the cone $mathbb R_+^n$. Maybe the cone $mathbb R_+^n$ is different from $[0,infty)timesdotstimes [0,infty)$?







      share|cite|improve this question











      In a paper I've been studying it says:




      Let $x$ in the cone $mathbb R_+^n$ of all vectors in $mathbb R^n$ with nonnnegative components ($ninmathbb N$)




      Somebody tell me what does it means, please? $mathbb R_+^n$ should be $[0,infty)timesdotstimes [0,infty)$ ($n$ times), but I don't understand why the cone $mathbb R_+^n$. Maybe the cone $mathbb R_+^n$ is different from $[0,infty)timesdotstimes [0,infty)$?









      share|cite|improve this question










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      asked Jul 25 at 8:15









      Mark

      3,56051746




      3,56051746




















          4 Answers
          4






          active

          oldest

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          up vote
          4
          down vote



          accepted










          A cone is a set $CsubseteqBbb R^n$ with $xin Cimpliesalpha xin C$ for all $alphage0$. The name is motivated by the usualy geometric cones, but $Bbb R^n_+ := [0,infty)^n$ satisfies this too.



          See this picture of different cones in $Bbb R^3$, two are familiar, and the right most one is $Bbb R^n_+$.



          enter image description here






          share|cite|improve this answer




























            up vote
            1
            down vote













            A cone $C$ is a set in a vector space with two propertes: $x+y in C$ whenever $x,y in C$ and $tx in C$ whenever $xin C$ and $t geq 0$. Since $[0,infty ) times [0,infty ) times ...[0,infty ) $ has these properties it is a cone.






            share|cite|improve this answer





















            • Are you sure about $x+y in C$ ? This seems to belong to the definition of a convex cone instead, not necessarily a cone.
              – nicomezi
              Jul 25 at 8:24











            • @Kavi: $ x+y in C$ is not required !
              – Fred
              Jul 25 at 8:25










            • @nicomezi Some authors add it to the definition because all they gonna do is discuss convex cones. However, I think the preferred definition of only cone should not contain it.
              – M. Winter
              Jul 25 at 8:26

















            up vote
            1
            down vote













            A subset $A$ of a vector space $X$ on a field $K$ with a notion of positivity is said to be a cone if, for all $x in A$, $lambda>0$, we have $lambda x in A$.



            The infite version of the cone you probably have in mind satisfies this property if the vertex, or apex, is at the origin.






            share|cite|improve this answer




























              up vote
              1
              down vote













              Yes, we have $mathbb R_+^n= [0,infty)timesdotstimes [0,infty)$.



              If $C ne emptyset$ is a subset of $mathbb R^n$, then $C$ is called a cone if $x in C$ and $t ge 0$ imply that $tx in C$.



              Hence $mathbb R_+^n$ is a cone in $mathbb R^n$






              share|cite|improve this answer





















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                4 Answers
                4






                active

                oldest

                votes








                4 Answers
                4






                active

                oldest

                votes









                active

                oldest

                votes






                active

                oldest

                votes








                up vote
                4
                down vote



                accepted










                A cone is a set $CsubseteqBbb R^n$ with $xin Cimpliesalpha xin C$ for all $alphage0$. The name is motivated by the usualy geometric cones, but $Bbb R^n_+ := [0,infty)^n$ satisfies this too.



                See this picture of different cones in $Bbb R^3$, two are familiar, and the right most one is $Bbb R^n_+$.



                enter image description here






                share|cite|improve this answer

























                  up vote
                  4
                  down vote



                  accepted










                  A cone is a set $CsubseteqBbb R^n$ with $xin Cimpliesalpha xin C$ for all $alphage0$. The name is motivated by the usualy geometric cones, but $Bbb R^n_+ := [0,infty)^n$ satisfies this too.



                  See this picture of different cones in $Bbb R^3$, two are familiar, and the right most one is $Bbb R^n_+$.



                  enter image description here






                  share|cite|improve this answer























                    up vote
                    4
                    down vote



                    accepted







                    up vote
                    4
                    down vote



                    accepted






                    A cone is a set $CsubseteqBbb R^n$ with $xin Cimpliesalpha xin C$ for all $alphage0$. The name is motivated by the usualy geometric cones, but $Bbb R^n_+ := [0,infty)^n$ satisfies this too.



                    See this picture of different cones in $Bbb R^3$, two are familiar, and the right most one is $Bbb R^n_+$.



                    enter image description here






                    share|cite|improve this answer













                    A cone is a set $CsubseteqBbb R^n$ with $xin Cimpliesalpha xin C$ for all $alphage0$. The name is motivated by the usualy geometric cones, but $Bbb R^n_+ := [0,infty)^n$ satisfies this too.



                    See this picture of different cones in $Bbb R^3$, two are familiar, and the right most one is $Bbb R^n_+$.



                    enter image description here







                    share|cite|improve this answer













                    share|cite|improve this answer



                    share|cite|improve this answer











                    answered Jul 25 at 8:29









                    M. Winter

                    17.6k62764




                    17.6k62764




















                        up vote
                        1
                        down vote













                        A cone $C$ is a set in a vector space with two propertes: $x+y in C$ whenever $x,y in C$ and $tx in C$ whenever $xin C$ and $t geq 0$. Since $[0,infty ) times [0,infty ) times ...[0,infty ) $ has these properties it is a cone.






                        share|cite|improve this answer





















                        • Are you sure about $x+y in C$ ? This seems to belong to the definition of a convex cone instead, not necessarily a cone.
                          – nicomezi
                          Jul 25 at 8:24











                        • @Kavi: $ x+y in C$ is not required !
                          – Fred
                          Jul 25 at 8:25










                        • @nicomezi Some authors add it to the definition because all they gonna do is discuss convex cones. However, I think the preferred definition of only cone should not contain it.
                          – M. Winter
                          Jul 25 at 8:26














                        up vote
                        1
                        down vote













                        A cone $C$ is a set in a vector space with two propertes: $x+y in C$ whenever $x,y in C$ and $tx in C$ whenever $xin C$ and $t geq 0$. Since $[0,infty ) times [0,infty ) times ...[0,infty ) $ has these properties it is a cone.






                        share|cite|improve this answer





















                        • Are you sure about $x+y in C$ ? This seems to belong to the definition of a convex cone instead, not necessarily a cone.
                          – nicomezi
                          Jul 25 at 8:24











                        • @Kavi: $ x+y in C$ is not required !
                          – Fred
                          Jul 25 at 8:25










                        • @nicomezi Some authors add it to the definition because all they gonna do is discuss convex cones. However, I think the preferred definition of only cone should not contain it.
                          – M. Winter
                          Jul 25 at 8:26












                        up vote
                        1
                        down vote










                        up vote
                        1
                        down vote









                        A cone $C$ is a set in a vector space with two propertes: $x+y in C$ whenever $x,y in C$ and $tx in C$ whenever $xin C$ and $t geq 0$. Since $[0,infty ) times [0,infty ) times ...[0,infty ) $ has these properties it is a cone.






                        share|cite|improve this answer













                        A cone $C$ is a set in a vector space with two propertes: $x+y in C$ whenever $x,y in C$ and $tx in C$ whenever $xin C$ and $t geq 0$. Since $[0,infty ) times [0,infty ) times ...[0,infty ) $ has these properties it is a cone.







                        share|cite|improve this answer













                        share|cite|improve this answer



                        share|cite|improve this answer











                        answered Jul 25 at 8:23









                        Kavi Rama Murthy

                        20.1k2829




                        20.1k2829











                        • Are you sure about $x+y in C$ ? This seems to belong to the definition of a convex cone instead, not necessarily a cone.
                          – nicomezi
                          Jul 25 at 8:24











                        • @Kavi: $ x+y in C$ is not required !
                          – Fred
                          Jul 25 at 8:25










                        • @nicomezi Some authors add it to the definition because all they gonna do is discuss convex cones. However, I think the preferred definition of only cone should not contain it.
                          – M. Winter
                          Jul 25 at 8:26
















                        • Are you sure about $x+y in C$ ? This seems to belong to the definition of a convex cone instead, not necessarily a cone.
                          – nicomezi
                          Jul 25 at 8:24











                        • @Kavi: $ x+y in C$ is not required !
                          – Fred
                          Jul 25 at 8:25










                        • @nicomezi Some authors add it to the definition because all they gonna do is discuss convex cones. However, I think the preferred definition of only cone should not contain it.
                          – M. Winter
                          Jul 25 at 8:26















                        Are you sure about $x+y in C$ ? This seems to belong to the definition of a convex cone instead, not necessarily a cone.
                        – nicomezi
                        Jul 25 at 8:24





                        Are you sure about $x+y in C$ ? This seems to belong to the definition of a convex cone instead, not necessarily a cone.
                        – nicomezi
                        Jul 25 at 8:24













                        @Kavi: $ x+y in C$ is not required !
                        – Fred
                        Jul 25 at 8:25




                        @Kavi: $ x+y in C$ is not required !
                        – Fred
                        Jul 25 at 8:25












                        @nicomezi Some authors add it to the definition because all they gonna do is discuss convex cones. However, I think the preferred definition of only cone should not contain it.
                        – M. Winter
                        Jul 25 at 8:26




                        @nicomezi Some authors add it to the definition because all they gonna do is discuss convex cones. However, I think the preferred definition of only cone should not contain it.
                        – M. Winter
                        Jul 25 at 8:26










                        up vote
                        1
                        down vote













                        A subset $A$ of a vector space $X$ on a field $K$ with a notion of positivity is said to be a cone if, for all $x in A$, $lambda>0$, we have $lambda x in A$.



                        The infite version of the cone you probably have in mind satisfies this property if the vertex, or apex, is at the origin.






                        share|cite|improve this answer

























                          up vote
                          1
                          down vote













                          A subset $A$ of a vector space $X$ on a field $K$ with a notion of positivity is said to be a cone if, for all $x in A$, $lambda>0$, we have $lambda x in A$.



                          The infite version of the cone you probably have in mind satisfies this property if the vertex, or apex, is at the origin.






                          share|cite|improve this answer























                            up vote
                            1
                            down vote










                            up vote
                            1
                            down vote









                            A subset $A$ of a vector space $X$ on a field $K$ with a notion of positivity is said to be a cone if, for all $x in A$, $lambda>0$, we have $lambda x in A$.



                            The infite version of the cone you probably have in mind satisfies this property if the vertex, or apex, is at the origin.






                            share|cite|improve this answer













                            A subset $A$ of a vector space $X$ on a field $K$ with a notion of positivity is said to be a cone if, for all $x in A$, $lambda>0$, we have $lambda x in A$.



                            The infite version of the cone you probably have in mind satisfies this property if the vertex, or apex, is at the origin.







                            share|cite|improve this answer













                            share|cite|improve this answer



                            share|cite|improve this answer











                            answered Jul 25 at 8:23









                            nicomezi

                            3,4121819




                            3,4121819




















                                up vote
                                1
                                down vote













                                Yes, we have $mathbb R_+^n= [0,infty)timesdotstimes [0,infty)$.



                                If $C ne emptyset$ is a subset of $mathbb R^n$, then $C$ is called a cone if $x in C$ and $t ge 0$ imply that $tx in C$.



                                Hence $mathbb R_+^n$ is a cone in $mathbb R^n$






                                share|cite|improve this answer

























                                  up vote
                                  1
                                  down vote













                                  Yes, we have $mathbb R_+^n= [0,infty)timesdotstimes [0,infty)$.



                                  If $C ne emptyset$ is a subset of $mathbb R^n$, then $C$ is called a cone if $x in C$ and $t ge 0$ imply that $tx in C$.



                                  Hence $mathbb R_+^n$ is a cone in $mathbb R^n$






                                  share|cite|improve this answer























                                    up vote
                                    1
                                    down vote










                                    up vote
                                    1
                                    down vote









                                    Yes, we have $mathbb R_+^n= [0,infty)timesdotstimes [0,infty)$.



                                    If $C ne emptyset$ is a subset of $mathbb R^n$, then $C$ is called a cone if $x in C$ and $t ge 0$ imply that $tx in C$.



                                    Hence $mathbb R_+^n$ is a cone in $mathbb R^n$






                                    share|cite|improve this answer













                                    Yes, we have $mathbb R_+^n= [0,infty)timesdotstimes [0,infty)$.



                                    If $C ne emptyset$ is a subset of $mathbb R^n$, then $C$ is called a cone if $x in C$ and $t ge 0$ imply that $tx in C$.



                                    Hence $mathbb R_+^n$ is a cone in $mathbb R^n$







                                    share|cite|improve this answer













                                    share|cite|improve this answer



                                    share|cite|improve this answer











                                    answered Jul 25 at 8:24









                                    Fred

                                    37.2k1237




                                    37.2k1237






















                                         

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