Graph independence number (Caro-Wei) estimate without probabilistic argument?












2














A short introduction: The independence number $alpha(G)$ of a graph $G$ is the cardinality of the largest independent vertex set. Independent vertex set is made only of vertices with no edges between them.



enter image description here



For example, the set shown above has $alpha(G)=3$ because in set ${A,C,E}$ all vertices are independent and it's impossible to construct a set with four independent elements.



I have stumbled upon a theorem of Caro and Wei who independently provided the following estimate for the lower bound:



$$alpha(G)gesum_{i=1}^{n}frac1{d_i+1}tag{1}$$



My naive attempts to prove the statement fell short so I started to look for a proof elsewhere. Despite the fact that this famous result of Caro and Wei was quoted in many places (Google returned thousands of pages on the first try), it was not easy to find a full proof. This one turned out be my personal favorite (copied from here):



enter image description here



All other proofs that I have found so far are more or less just a copy of it, most often with fewer words. Another copy can be found on MSE (please note that this post is not a copy of the same question).



The proof starts with some combinatorics and then jumps to probabilities and expectations. It's perfectly readable and I have enjoyed it immensely but...



Imagine that you have to explain the theorem to someone (like my son) who is very good at combinatorics but has zero experience with probabilities and expectations.



My question is: Is there a proof of (1) that is not based on a probabilistic argument? Can we replace the probabilistic part of the proof with something that is "more basic", if you understand what I mean. My attemts to find such proof were unsuccessful.










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  • 1




    I'm trying to understand this paper on algorithmic proof of the result: core.ac.uk/download/pdf/82699691.pdf
    – mathnoob
    Nov 28 '18 at 17:02
















2














A short introduction: The independence number $alpha(G)$ of a graph $G$ is the cardinality of the largest independent vertex set. Independent vertex set is made only of vertices with no edges between them.



enter image description here



For example, the set shown above has $alpha(G)=3$ because in set ${A,C,E}$ all vertices are independent and it's impossible to construct a set with four independent elements.



I have stumbled upon a theorem of Caro and Wei who independently provided the following estimate for the lower bound:



$$alpha(G)gesum_{i=1}^{n}frac1{d_i+1}tag{1}$$



My naive attempts to prove the statement fell short so I started to look for a proof elsewhere. Despite the fact that this famous result of Caro and Wei was quoted in many places (Google returned thousands of pages on the first try), it was not easy to find a full proof. This one turned out be my personal favorite (copied from here):



enter image description here



All other proofs that I have found so far are more or less just a copy of it, most often with fewer words. Another copy can be found on MSE (please note that this post is not a copy of the same question).



The proof starts with some combinatorics and then jumps to probabilities and expectations. It's perfectly readable and I have enjoyed it immensely but...



Imagine that you have to explain the theorem to someone (like my son) who is very good at combinatorics but has zero experience with probabilities and expectations.



My question is: Is there a proof of (1) that is not based on a probabilistic argument? Can we replace the probabilistic part of the proof with something that is "more basic", if you understand what I mean. My attemts to find such proof were unsuccessful.










share|cite|improve this question


















  • 1




    I'm trying to understand this paper on algorithmic proof of the result: core.ac.uk/download/pdf/82699691.pdf
    – mathnoob
    Nov 28 '18 at 17:02














2












2








2


1





A short introduction: The independence number $alpha(G)$ of a graph $G$ is the cardinality of the largest independent vertex set. Independent vertex set is made only of vertices with no edges between them.



enter image description here



For example, the set shown above has $alpha(G)=3$ because in set ${A,C,E}$ all vertices are independent and it's impossible to construct a set with four independent elements.



I have stumbled upon a theorem of Caro and Wei who independently provided the following estimate for the lower bound:



$$alpha(G)gesum_{i=1}^{n}frac1{d_i+1}tag{1}$$



My naive attempts to prove the statement fell short so I started to look for a proof elsewhere. Despite the fact that this famous result of Caro and Wei was quoted in many places (Google returned thousands of pages on the first try), it was not easy to find a full proof. This one turned out be my personal favorite (copied from here):



enter image description here



All other proofs that I have found so far are more or less just a copy of it, most often with fewer words. Another copy can be found on MSE (please note that this post is not a copy of the same question).



The proof starts with some combinatorics and then jumps to probabilities and expectations. It's perfectly readable and I have enjoyed it immensely but...



Imagine that you have to explain the theorem to someone (like my son) who is very good at combinatorics but has zero experience with probabilities and expectations.



My question is: Is there a proof of (1) that is not based on a probabilistic argument? Can we replace the probabilistic part of the proof with something that is "more basic", if you understand what I mean. My attemts to find such proof were unsuccessful.










share|cite|improve this question













A short introduction: The independence number $alpha(G)$ of a graph $G$ is the cardinality of the largest independent vertex set. Independent vertex set is made only of vertices with no edges between them.



enter image description here



For example, the set shown above has $alpha(G)=3$ because in set ${A,C,E}$ all vertices are independent and it's impossible to construct a set with four independent elements.



I have stumbled upon a theorem of Caro and Wei who independently provided the following estimate for the lower bound:



$$alpha(G)gesum_{i=1}^{n}frac1{d_i+1}tag{1}$$



My naive attempts to prove the statement fell short so I started to look for a proof elsewhere. Despite the fact that this famous result of Caro and Wei was quoted in many places (Google returned thousands of pages on the first try), it was not easy to find a full proof. This one turned out be my personal favorite (copied from here):



enter image description here



All other proofs that I have found so far are more or less just a copy of it, most often with fewer words. Another copy can be found on MSE (please note that this post is not a copy of the same question).



The proof starts with some combinatorics and then jumps to probabilities and expectations. It's perfectly readable and I have enjoyed it immensely but...



Imagine that you have to explain the theorem to someone (like my son) who is very good at combinatorics but has zero experience with probabilities and expectations.



My question is: Is there a proof of (1) that is not based on a probabilistic argument? Can we replace the probabilistic part of the proof with something that is "more basic", if you understand what I mean. My attemts to find such proof were unsuccessful.







graph-theory alternative-proof






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asked Nov 27 '18 at 10:16









OldboyOldboy

7,1691832




7,1691832








  • 1




    I'm trying to understand this paper on algorithmic proof of the result: core.ac.uk/download/pdf/82699691.pdf
    – mathnoob
    Nov 28 '18 at 17:02














  • 1




    I'm trying to understand this paper on algorithmic proof of the result: core.ac.uk/download/pdf/82699691.pdf
    – mathnoob
    Nov 28 '18 at 17:02








1




1




I'm trying to understand this paper on algorithmic proof of the result: core.ac.uk/download/pdf/82699691.pdf
– mathnoob
Nov 28 '18 at 17:02




I'm trying to understand this paper on algorithmic proof of the result: core.ac.uk/download/pdf/82699691.pdf
– mathnoob
Nov 28 '18 at 17:02










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