120 research outputs found

    New bounds on the signed total domination number of graphs

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    In this paper, we study the signed total domination number in graphs and present new sharp lower and upper bounds for this parameter. For example by making use of the classic theorem of Turan, we present a sharp lower bound on this parameter for graphs with no complete graph of order r+1 as a subgraph. Also, we prove that n-2(s-s') is an upper bound on the signed total domination number of any tree of order n with s support vertices and s' support vertives of degree two. Moreover, we characterize all trees attainig this bound.Comment: This paper contains 11 pages and one figur

    On the inverse signed total domination number in graphs

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    In this paper, we study the inverse signed total domination number in graphs and present new lower and upper bounds on this parameter. For example by making use of the classic theorem of Turan (1941), we present a sharp upper bound for graphs with no induced complete subgraph of order greater than two. Also, we bound this parameter for a tree in terms of its order and the number of leaves and characterize all trees attaining this bound

    Energy Gap from Step Structure of the Analytically Inverted Non-Additive Kinetic Potential

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    The bandgap constitutes a challenging problem in density functional theory (DFT) methodologies. It is known that the energy gap values calculated by common DFT approaches are underestimated. The bandgap was also found to be related to the derivative discontinuity (DD) of the exchange-correlation potential in the Kohn-Sham formulation of DFT. Several reports have shown that DD appears as a step on the potential curve. The step structure is a mandatory structure for aligning the KS energy levels in the ionization potentials in a dissociated molecule in both fragments and is a function of electron localisation. Reproducing the step in the DFT framework gives the charge transfer process and the correct energy gap and describes the source of dissociation. This step phenomenon has not yet been studied in the non-additive kinetic potential vNAD[ρA,ρB](r)v^{\text{NAD}}[\rho_A,\rho_B](\textbf{r}), a key quantity used in embedding theories. While vNAD[ρA,ρB](r)v^{\text{NAD}}[\rho_A,\rho_B](\textbf{r}) is known to be difficult to approximate, in this work, we explain how an accurate energy gap can be produced from the analytically inverted vNAD[ρA,ρB](r)v^{\text{NAD}}[\rho_A,\rho_B](\textbf{r}), even if we use the input densities calculated by the local and semi-local functionals. We used the precisely calculated vNAD[ρA,ρB](r)v^{\text{NAD}}[\rho_A,\rho_B](\textbf{r}) reported in our previous publication [Phys. Rev. A 106, 042812 (2022)] to produce the energy gap for some model systems and report in this work the promising accuracy of our results through the comparison with the results obtained from one of the most accurate calculations, OEP theory with the KLI local approximation.Comment: 33 pages, 18 figure

    In Pursuit of Sustainable Strategic Long-term Planning Throughout Meta-postmodernism as New Perspective of Stylistic Design

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    During the different period of architectural design, designers attempt to achieve high level of life quality for all users. Architecture and urban planner want to provide a style of design which not only achieves different function for different users with respect to their ethnicity, ability, age, sex, capability, position, and life style but also improve friendly environment throughout responsive legislation based on long-term planning. Although, the styles are considered some indicators, it is ignored the other important characteristics. Therefore, the existing styles never achieve standard level of satisfaction of different people. The goal of the research is to introduce meta-postmodern style as supplement stylistic approach. The style tries to consider all important indicators that create a strategic long-term planning for different generations. Various characteristics of new style can be applied to improve the quality of human life and provide a health, livable and sustainable planning for all users

    On the Signed 22-independence Number of Graphs

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    In this paper, we study the signed 2-independence number in graphs and give new sharp upper and lower bounds on the signed 2-independence number of a graph by a simple uniform approach. In this way, we can improve and generalize some known results in this area
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