scholarly journals A note on the potential function of an arbitrary graph H

Filomat ◽  
2020 ◽  
Vol 34 (11) ◽  
pp. 3759-3766
Author(s):  
Jianhua Yin ◽  
Guangming Li
Keyword(s):  
Potential Function ◽  
Upper Bound ◽  
Degree Sequence ◽  
Arbitrary Graph ◽  
Induced Subgraph ◽  
Graphic Sequence ◽  
Increasing Function

Given a graph H, a graphic sequence ? is potentially H-graphic if there is a realization of ? containing H as a subgraph. In 1991, Erd?s et al. introduced the following problem: determine the minimum even integer ?(H,n) such that each n-term graphic sequence with sum at least ?(H,n) is potentially H-graphic. This problem can be viewed as a ?potential? degree sequence relaxation of the Tur?n problems. Let H be an arbitrary graph of order k. Ferrara et al. [Combinatorica, 36(2016)687-702] established an upper bound on ?(H,n): if ? = ?(n) is an increasing function that tends to infinity with n, then there exists an N = N(?,H) such that ?(H,n)? ?~(H)n + ?(n) for any n ? N, where ?~(H) is a parameter only depending on the graph H. Recently, Yin [European J. Combin., 85(2020)103061] obtained a new upper bound on ?(H,n): there exists an M = M(k,?(H)) such that ?(H,n) ? ?~(H)n + k2-3k+4 for any n ? M. In this paper, we investigate the precise behavior of ?(H,n) for arbitrary H with ?~?(H)+1(H < ?~(H) or??(H)+1(H) ? 2, where ??(H)+1(H) = min{?F)|F is an induced subgraph of H and |V(F)|= ?(H) + 1} and ?~?(H)+1(H) = 2(k-?(H)-1)+??(H)+1(H)-1. Moreover, we also show that ?(H,n) = (k-?(H)-1)(2n-k+?(H))+2 for those H so that ??(H)+1(H) = 1,?~?(H)+1(H)=~?~(H),?~p(H) < ?~(H) for ?(H) + 2 ? p ? k and there is an F < H with |V(F)| = ?(H) + 1 and ?(F) = (12,0?(H)-1).

PARTIAL RESULT ON HADWIGER'S CONJECTURE

2010 ◽  
Vol 02 (03) ◽  
pp. 413-423 ◽  
Author(s):  
ZI-XIA SONG
Keyword(s):  
Degree Sequence ◽  
Simple Graph ◽  
Partial Result ◽  
Degree Sequences ◽  
Induced Subgraph ◽  
Graphic Sequence ◽  
Hadwiger's Conjecture ◽  
Hadwiger’S Conjecture

Let D = (d1, d2, …, dn) be a graphic sequence with 0 ≤ d1 ≤ d2 ≤ ⋯ ≤ dn. Any simple graph G with D its degree sequence is called a realization of D. Let R[D] denote the set of all realizations of D. We say that D is H-free if no graph in R[D] contains H as an induced subgraph. In this paper, we prove that Hadwiger's Conjecture is true for graphs whose degree sequences are claw-free or [Formula: see text]-free.

scholarly journals New Results on Degree Sequences of Uniform Hypergraphs

10.37236/3414 ◽  
2013 ◽  
Vol 20 (4) ◽  
Author(s):  
Sarah Behrens ◽  
Catherine Erbes ◽  
Michael Ferrara ◽  
Stephen G. Hartke ◽  
Benjamin Reiniger ◽  
...  
Keyword(s):  
Efficient Algorithm ◽  
Necessary Conditions ◽  
Degree Sequence ◽  
Sufficient Conditions ◽  
Degree Sequences ◽  
Uniform Hypergraph ◽  
Graphic Sequence ◽  
Uniform Hypergraphs ◽  
Open Question

A sequence of nonnegative integers is $k$-graphic if it is the degree sequence of a $k$-uniform hypergraph. The only known characterization of $k$-graphic sequences is due to Dewdney in 1975. As this characterization does not yield an efficient algorithm, it is a fundamental open question to determine a more practical characterization. While several necessary conditions appear in the literature, there are few conditions that imply a sequence is $k$-graphic. In light of this, we present sharp sufficient conditions for $k$-graphicality based on a sequence's length and degree sum.Kocay and Li gave a family of edge exchanges (an extension of 2-switches) that could be used to transform one realization of a 3-graphic sequence into any other realization. We extend their result to $k$-graphic sequences for all $k \geq 3$. Finally we give several applications of edge exchanges in hypergraphs, including generalizing a result of Busch et al. on packing graphic sequences.

scholarly journals On Komlós’ tiling theorem in random graphs

2019 ◽  
Vol 29 (1) ◽  
pp. 113-127
Author(s):  
Rajko Nenadov ◽  
Nemanja Škorić
Keyword(s):  
Chromatic Number ◽  
Random Graph ◽  
Random Graphs ◽  
Upper Bound ◽  
Minimum Degree ◽  
Arbitrary Graph ◽  
Spanning Subgraph ◽  
Delta G ◽  
Image Position ◽  
Vertex Disjoint

AbstractGiven graphs G and H, a family of vertex-disjoint copies of H in G is called an H-tiling. Conlon, Gowers, Samotij and Schacht showed that for a given graph H and a constant γ>0, there exists C>0 such that if $p \ge C{n^{ - 1/{m_2}(H)}}$ , then asymptotically almost surely every spanning subgraph G of the random graph 𝒢(n, p) with minimum degree at least $\delta (G) \ge (1 - \frac{1}{{{\chi _{{\rm{cr}}}}(H)}} + \gamma )np$ contains an H-tiling that covers all but at most γn vertices. Here, χcr(H) denotes the critical chromatic number, a parameter introduced by Komlós, and m2(H) is the 2-density of H. We show that this theorem can be bootstrapped to obtain an H-tiling covering all but at most $\gamma {(C/p)^{{m_2}(H)}}$ vertices, which is strictly smaller when $p \ge C{n^{ - 1/{m_2}(H)}}$ . In the case where H = K3, this answers the question of Balogh, Lee and Samotij. Furthermore, for an arbitrary graph H we give an upper bound on p for which some leftover is unavoidable and a bound on the size of a largest H -tiling for p below this value.

scholarly journals A Note on the Warmth of Random Graphs with Given Expected Degrees

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
Yilun Shang
Keyword(s):  
Statistical Mechanics ◽  
Chromatic Number ◽  
Random Graph ◽  
Lower Bounds ◽  
Random Graphs ◽  
Upper Bound ◽  
Degree Sequence ◽  
Graph Model ◽  
Upper And Lower Bounds ◽  
Random Graph Model

We consider the random graph modelG(w)for a given expected degree sequencew=(w1,w2,…,wn). Warmth, introduced by Brightwell and Winkler in the context of combinatorial statistical mechanics, is a graph parameter related to lower bounds of chromatic number. We present new upper and lower bounds on warmth ofG(w). In particular, the minimum expected degree turns out to be an upper bound of warmth when it tends to infinity and the maximum expected degreem=O(nα)with0<α<1/2.

scholarly journals HAMILTONICITY OF CAMOUFLAGE GRAPHS

2021 ◽  
Vol 5 (10) ◽  
Author(s):  
Sowmiya K
Keyword(s):  
Planar Graphs ◽  
Degree Sequence ◽  
Simple Graph ◽  
Hamilton Path ◽  
Graphic Sequence ◽  
Vertex Transitive ◽  
Connected Vertex

This paper examines the Hamiltonicity of graphs having some hidden behaviours of some other graphs in it. The well-known mathematician Barnette introduced the open conjecture which becomes a theorem by restricting our attention to the class of graphs which is 3-regular, 3- connected, bipartite, planar graphs having odd number of vertices in its partition be proved as a Hamiltonian. Consequently the result proved in this paper stated that “Every connected vertex-transitive simple graph has a Hamilton path” shows a significant improvement over the previous efforts by L.Babai and L.Lovasz who put forth this conjecture. And we characterize a graphic sequence which is forcibly Hamiltonian if every simple graph with degree sequence is Hamiltonian. Thus we discussed about the concealed graphs which are proven to be Hamiltonian.

scholarly journals Certain Bounds of Regularity of Elimination Ideals on Operations of Graphs

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Zongming Lv ◽  
Muhammad Junaid Ali Junjua ◽  
Muhammad Tajammal Tahir ◽  
Khurram Shabbir
Keyword(s):  
Upper Bound ◽  
Degree Sequence ◽  
Borel Type

Elimination ideals are regarded as a special type of Borel type ideals, obtained from degree sequence of a graph, introduced by Anwar and Khalid. In this paper, we compute graphical degree stabilities of K n ∨ C m and K n ∗ C m by using the DVE method. We further compute sharp upper bound for Castelnuovo–Mumford regularity of elimination ideals associated to these families of graphs.

scholarly journals A New Upper Bound Based on Vertex Partitioning for the Maximum K-plex Problem

2021 ◽  
Author(s):  
Hua Jiang ◽  
Dongming Zhu ◽  
Zhichao Xie ◽  
Shaowen Yao ◽  
Zhang-Hua Fu
Keyword(s):  
Branch And Bound ◽  
Upper Bound ◽  
Undirected Graph ◽  
State Of The Art ◽  
Search Space ◽  
Exact Algorithms ◽  
Induced Subgraph ◽  
Massive Graphs ◽  
Vertex Set ◽  
Number Of Branches

Given an undirected graph, the Maximum k-plex Problem (MKP) is to find a largest induced subgraph in which each vertex has at most k−1 non-adjacent vertices. The problem arises in social network analysis and has found applications in many important areas employing graph-based data mining. Existing exact algorithms usually implement a branch-and-bound approach that requires a tight upper bound to reduce the search space. In this paper, we propose a new upper bound for MKP, which is a partitioning of the candidate vertex set with respect to the constructing solution. We implement a new branch-and-bound algorithm that employs the upper bound to reduce the number of branches. Experimental results show that the upper bound is very effective in reducing the search space. The new algorithm outperforms the state-of-the-art algorithms significantly on real-world massive graphs, DIMACS graphs and random graphs.

Induced Turán Numbers

2017 ◽  
Vol 27 (2) ◽  
pp. 274-288 ◽  
Author(s):  
PO-SHEN LOH ◽  
MICHAEL TAIT ◽  
CRAIG TIMMONS ◽  
RODRIGO M. ZHOU
Keyword(s):  
Upper Bound ◽  
Independent Interest ◽  
Forbidden Subgraphs ◽  
Free Graph ◽  
Induced Subgraph ◽  
Vertex Graph ◽  
Recent Theorem ◽  
Fixed Order ◽  
Turán Theorem ◽  
Asymptotic Upper Bound

The classical Kővári–Sós–Turán theorem states that ifGis ann-vertex graph with no copy ofKs,tas a subgraph, then the number of edges inGis at mostO(n2−1/s). We prove that if one forbidsKs,tas aninducedsubgraph, and also forbidsanyfixed graphHas a (not necessarily induced) subgraph, the same asymptotic upper bound still holds, with different constant factors. This introduces a non-trivial angle from which to generalize Turán theory to induced forbidden subgraphs, which this paper explores. Along the way, we derive a non-trivial upper bound on the number of cliques of fixed order in aKr-free graph with no induced copy ofKs,t. This result is an induced analogue of a recent theorem of Alon and Shikhelman and is of independent interest.

An approximate solution of the integral equation of renewal theory

1985 ◽  
Vol 22 (04) ◽  
pp. 926-931 ◽  
Author(s):  
Z. Șeyda Deligönül
Keyword(s):  
Integral Equation ◽  
Approximate Solution ◽  
Upper Bound ◽  
Hazard Function ◽  
Renewal Theory ◽  
New Method ◽  
Renewal Function ◽  
Increasing Function

In this study, an approximation to the solution of the renewal integral equation is constructed. Performance of the new method is evaluated and it is shown that the approximation provides an upper bound for the renewal function when the hazard function is a non-increasing function of time.

scholarly journals Braess's paradox and power-law nonlinearities in networks

1993 ◽  
Vol 35 (1) ◽  
pp. 1-22 ◽  
Author(s):  
Bruce Calvert ◽  
Grant Keady
Keyword(s):  
Water Supply ◽  
Potential Function ◽  
Power Law ◽  
Equilibrium Flow ◽  
Pipe Network ◽  
Pipe Networks ◽  
Braess’S Paradox ◽  
Supply Pipe ◽  
The Difference ◽  
Increasing Function

AbstractWe study flows in physical networks with a potential function defined over the nodes and a flow defined over the arcs. The networks have the further property that the flow on an arc a is a given increasing function of the difference in potential between its initial and terminal node. An example is the equilibrium flow in water-supply pipe networks where the potential is the head and the Hazen-Williams rule gives the flow as a numerical factor ka times the head difference to a power s > 0 (and s ≅ 0.54). In the pipe-network problem with Hazen-Williams nonlinearities, having the same s > 0 on each arc, given the consumptions and supplies, the power usage is a decreasing function of the conductivity factors ka. There is also a converse to this. Approximately stated, it is: if every relationship between flow and head difference is not a power law, with the same s on each arc, given at least 6 pipes, one can arrange (lengths of) them so that Braess's paradox occurs, i.e. one can increase the conductivity of an individual pipe yet require more power to maintain the same consumptions.

Sign in / Sign up

Export Citation Format

Share Document