scholarly journals Remarks on Distance Based Topological Indices for ℓ-Apex Trees

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 802
Author(s):  
Martin Knor ◽  
Muhammad Imran ◽  
Muhammad Kamran Jamil ◽  
Riste Škrekovski

A graph G is called an ℓ-apex tree if there exist a vertex subset A ⊂ V ( G ) with cardinality ℓ such that G − A is a tree and there is no other subset of smaller cardinality with this property. In the paper, we investigate extremal values of several monotonic distance-based topological indices for this class of graphs, namely generalized Wiener index, and consequently for the Wiener index and the Harary index, and also for some newer indices as connective eccentricity index, generalized degree distance, and others. For the one extreme value we obtain that the extremal graph is a join of a tree and a clique. Regarding the other extreme value, which turns out to be a harder problem, we obtain results for ℓ = 1 and pose some open questions for higher ℓ. Symmetry has always played an important role in Graph Theory, in recent years, this role has increased significantly in several branches of this field, including topological indices of graphs.

2020 ◽  
Vol 12 (02) ◽  
pp. 2050015
Author(s):  
Hanlin Chen ◽  
Renfang Wu

Let [Formula: see text] be a topological index of a graph. If [Formula: see text] (or [Formula: see text], respectively) for each edge [Formula: see text], then [Formula: see text] is monotonically decreasing (or increasing, respectively) with the addition of edges. In this paper, by a unified approach, we determine the extremal values of some monotonic topological indices, including the Wiener index, the hyper-Wiener index, the Harary index, the connective eccentricity index, the eccentricity distance sum, among all connected bipartite graphs with a given number of cut edges, and characterize the corresponding extremal graphs, respectively.


2007 ◽  
Vol 72 (1) ◽  
pp. 171-206 ◽  
Author(s):  
Denis R. Hirschfeldt ◽  
Richard A. Shore

AbstractWe investigate the complexity of various combinatorial theorems about linear and partial orders, from the points of view of computability theory and reverse mathematics. We focus in particular on the principles ADS (Ascending or Descending Sequence), which states that every infinite linear order has either an infinite descending sequence or an infinite ascending sequence, and CAC (Chain-AntiChain), which states that every infinite partial order has either an infinite chain or an infinite antichain. It is wellknown that Ramsey's Theorem for pairs () splits into a stable version () and a cohesive principle (COH). We show that the same is true of ADS and CAC, and that in their cases the stable versions are strictly weaker than the full ones (which is not known to be the case for and ). We also analyze the relationships between these principles and other systems and principles previously studied by reverse mathematics, such as WKL0, DNR, and BΣ2. We show, for instance, that WKL0 is incomparable with all of the systems we study. We also prove computability-theoretic and conservation results for them. Among these results are a strengthening of the fact, proved by Cholak, Jockusch, and Slaman, that COH is -conservative over the base system RCA0. We also prove that CAC does not imply DNR which, combined with a recent result of Hirschfeldt, Jockusch. Kjos-Hanssen, Lempp, and Slaman, shows that CAC does not imply (and so does not imply ). This answers a question of Cholak, Jockusch, and Slaman.Our proofs suggest that the essential distinction between ADS and CAC on the one hand and on the other is that the colorings needed for our analysis are in some way transitive. We formalize this intuition as the notions of transitive and semitransitive colorings and show that the existence of homogeneous sets for such colorings is equivalent to ADS and CAC, respectively. We finish with several open questions.


2018 ◽  
Vol 6 (1) ◽  
pp. 146
Author(s):  
Thomas Frölich ◽  
F F Bevier ◽  
Alicja Babakhani ◽  
Hannah H Chisholm ◽  
Peter Henningsen ◽  
...  

To address subjectivity, as a generally rooted phenomenon, other ways of visualisation must be applied than in conventional objectivistic approaches. Using ‘trees’ as operational metaphors, as employed in Arthur Cayley’s ‘theory of the analytical forms called trees’, one rooted ‘tree’ must be set beneath the other and, if such ‘trees’ are combined, the resulting ‘forest’ is nevertheless made up of individual ‘trees’ and not of a deconstructed mix of ‘roots’, ‘branches’, ‘leaves’ or further categories, each understood as addressable both jointly and individually. The reasons for why we have chosen a graph theory and corresponding discrete mathematics as an approach and application are set out in this first of our three articles. It combines two approaches that, in combination, are quite uncommon and which are therefore not immediately familiar to all readers. But as simple as it is to imagine a tree, or a forest, it is equally simple to imagine a child blowing soap bubbles with the aid of a blow ring. A little more challenging, perhaps, is the additional idea of arranging such blow rings in series, transforming the size of the soap bubble in one ring after the other. To finally combine both pictures, the one of trees and the other of blow rings, goes beyond simple imagination, especially when we prolong the imagined blow ring becoming a tunnel, with a specific inner shape. The inner shape of the blow ring and its expansion as a tunnel are understood as determined by discrete qualities, each forming an internal continuity, depicted as a scale, with the scales combined in the form of a glyph plot. The different positions on these scales determine their length and if the endpoints of the spines are connected with an enveloping line then this corresponds to the free space left open in the tunnel to go through it. Using so many visualisation techniques at once is testing. Nevertheless, this is what we propose here and to facilitate such a visualisation within the imagination, we do it step by step. As the intended result of this ‘juggling of three balls’, as it were, we end up with a concept of how living beings elaborate their principal structure to enable controlled outside-inside communication.


Author(s):  
Stefano De Falco

A dichotomy often frequent in the context of geographic studies concerns the dualism between propagation and induction models-based phenomena, inherent in variables and factors characterizing contiguous areas, and research relating to homogeneity between geographically not closed areas. In the wake of the latter research, this contribution proposes a model that exploits the potential of graph theory for the evaluation of common dynamics relating to non-contiguous areas. The assumption underlying the model envisages configuring the reality being studied in terms of a network whose nodes and branches are respectively representative of entities distant from each other and of their related affinities. The proposed approach focuses on some Italian industrial districts. The value of the proposed approach is twofold, on the one hand regarding the specific industrial district topic with both scientific and practical implications, and on the other hand it aims to provide a method that can be replicated in similar scenarios in which it is interesting to evaluate the similarity between neighboring areas analytically.


2016 ◽  
Vol 2 (1) ◽  
pp. 87-103
Author(s):  
Michael Schmitz

AbstractIn this paper I first introduce Tomasello’s notion of thought and his account of its emergence and development through differentiation, arguing that it calls into question the theory bias of the philosophical tradition on thought as well as its frequent atomism. I then raise some worries that he may be overextending the concept of thought, arguing that we should recognize an area of intentionality intermediate between action and perception on the one hand and thought on the other. After that I argue that the co-operative nature of humans is reflected in the very structure of their intentionality and thought: in co-operative modes such as the mode of joint attention and action and the we-mode, they experience and represent others as co-subjects of joint relations to situations in the world rather than as mere objects. In conclusion, I briefly comment on what Tomasello refers to as one of two big open questions in the theory of collective intentionality, namely that of the irreducibility of jointness.


Author(s):  
Paul Schor

This chapter reviews developments from 1940 to 2000. Among these is the increased awareness of the census. On the one hand, the Census Bureau itself published for every census an administrative history (called Procedural History) of the census; on the other hand, sociology and political science adopted the goal and, since the 1960s, have focused considerable attention on categories of race and ethnicity, especially the so-called “ethnoracial pentagon”—the five major categories defined by the federal administration as those which government agencies should utilize. In 1980, the creation of an “Ancestry” category reflected the evolution toward more open questions, giving more room for the perceptions that people had of themselves. The 2000 census, after long negotiations, approved the recognition of multiracial families by offering, for the first time, the possibility of checking off more than one race on the schedule.


2020 ◽  
Vol 10 (7) ◽  
pp. 113 ◽  
Author(s):  
Ines Testoni ◽  
Lorenza Palazzo ◽  
Ciro De Vincenzo ◽  
Michael Alexander Wieser

The censorship of death-related issues is widespread in contemporary Western culture because the boundary between death and life is substantially managed in medical areas. In the context of Italian educational initiatives, to remove this limitation, 215 high school students in Southern Italy were educated on death through conventional and informal lessons. The students answered a questionnaire with open questions to survey their emotional and reflective experiences. Their answers were qualitatively, thematically analysed to explore how the representation of death can follow a death education course, and if this experience can be managed without harmful effects. The students’ answers narrated how the course reduced their anxiety linked to these themes, on the one hand improving communication between peers by making it more authentic and empathic and, on the other, providing alternative perspectives on life. Indeed, the project offered an opportunity to discuss something strongly heartfelt but rarely faced, and the survey confirmed that the research objectives were fully achieved.


2020 ◽  
Vol 12 (04) ◽  
pp. 2050041
Author(s):  
Mesfin Masre ◽  
Samuel Asefa Fufa ◽  
Tomáš Vetrík

Binary and [Formula: see text]-ary trees have extensive applications, particularly in computer science and chemistry. We present exact values of all important distance-based indices for complete [Formula: see text]-ary trees. We solve recurrence relations to obtain the value of the most well-known index called the Wiener index. New methods are used to express the other indices (the degree distance, the eccentric distance sum, the Gutman index, the edge-Wiener index, the hyper-Wiener index and the edge-hyper-Wiener index) as well. Values of distance-based indices for complete binary trees are corollaries of the main results.


2020 ◽  
Vol 39 (5) ◽  
pp. 6033-6046
Author(s):  
Shriram Kalathian ◽  
Sujatha Ramalingam ◽  
Sundareswaran Raman ◽  
Narasimman Srinivasan

A fuzzy graph is one of the versatile application tools in the field of mathematics, which allows the user to easily describe the fuzzy relation between any objects. The nature of fuzziness is favorable for any environment, which supports to predict the problem and solving it. Fuzzy graphs are beneficial to give more precision and flexibility to the system as compared to the classical model (i.e.,) crisp theory. A topological index is a numerical quantity for the structural graph of the molecule and it can be represented through Graph theory. Moreover, its application not only in the field of chemistry can also be applied in areas including computer science, networking, etc. A lot of topological indices are available in chemical-graph theory and H. Wiener proposed the first index to estimate the boiling point of alkanes called ‘Wiener index’. Many topological indices exist only in the crisp but it’s new to the fuzzy graph environment. The main aim of this paper is to define the topological indices in fuzzy graphs. Here, indices defined in fuzzy graphs are Modified Wiener index, Hyper Wiener index, Schultz index, Gutman index, Zagreb indices, Harmonic index, and Randić index with illustrations. Bounds for some of the indices are proved. The algorithms for distance matrix and MWI are shown. Finally, the application of these indices is discussed.


Variation Principles in Dynamics and in the Electromagnetic Field.—In the dynamics of a material system the name "action" is given to two different quantities. One of these is S = Ʃ r ∫ q'' r q1 s p r dq r = Ʃ r ∫ t'' t ' p r q r dt , q r , p , being the co-ordinate and momentum associated with the r th degree of freedom, and the integral being extended from one definite set of values of the q r 's, to another. The other is A = ∫ t'' t ' (Ʃ r ) p r q r —H) dt , where H (except in special circumstances) is in conservative systems the total energy, and the integral is taken between two definite times t ' and t ''. Corresponding to S and to A, there are two distinct principles of "least action." Among the group of imaginary systems produced by varying the p r and q r under specified conditions in each case, on the one hand the S and on the other the A, of the "natural" system which obeys the laws of dynamics, possesses an extreme value.


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