T2.3: Prove that there exists a connected graph with degrees d₁ ≥ d₂ >> dn if and only if d1, d2,..., dn is graphic, d ≥ 1 and di≥2n2. That is, some graph having degree sequence with these conditions is connected. Hint - Do not attempt to directly prove this using Erdos-Gallai conditions. Instead work with a realization and show that 2-switches can be used to make a connected graph with the same degree sequence. Facts that can be useful: a component (i.e., connected) with n₁ vertices and at least n₁ edges has a cycle. Note also that a 2-switch using edges from different components of a forest will not necessarily reduce the number of components. Make sure that you justify that your proof has a 2-switch that does decrease the number of components.

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter3: Functions And Graphs
Section3.3: Lines
Problem 13E
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T2.3: Prove that there exists a connected graph with degrees d₁ ≥ d₂ >> dn if and only
if d1, d2,..., dn is graphic, d ≥ 1 and di≥2n2. That is, some graph having degree
sequence with these conditions is connected.
Hint - Do not attempt to directly prove this using Erdos-Gallai conditions. Instead work with a
realization and show that 2-switches can be used to make a connected graph with the same degree
sequence. Facts that can be useful: a component (i.e., connected) with n₁ vertices and at least
n₁ edges has a cycle. Note also that a 2-switch using edges from different components of a forest
will not necessarily reduce the number of components. Make sure that you justify that your proof
has a 2-switch that does decrease the number of components.
Transcribed Image Text:T2.3: Prove that there exists a connected graph with degrees d₁ ≥ d₂ >> dn if and only if d1, d2,..., dn is graphic, d ≥ 1 and di≥2n2. That is, some graph having degree sequence with these conditions is connected. Hint - Do not attempt to directly prove this using Erdos-Gallai conditions. Instead work with a realization and show that 2-switches can be used to make a connected graph with the same degree sequence. Facts that can be useful: a component (i.e., connected) with n₁ vertices and at least n₁ edges has a cycle. Note also that a 2-switch using edges from different components of a forest will not necessarily reduce the number of components. Make sure that you justify that your proof has a 2-switch that does decrease the number of components.
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