Babak Miraftab
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 Jan 12 reviewed Approve Second Order Differential Equation inhomogeneous Jan 12 reviewed Approve limits of function without using L'Hopital's Rule $\mathop {\lim }\limits_{x \to 1} \frac{{x - 1 - \ln x}}{{x\ln x+ 1 - x}} = 1$ Jan 12 reviewed Approve How to solve $\lim\limits_{x\to 0} \frac{x - \tan(x)}{x^2}$ Without L'Hospital's Rule? Dec 20 awarded Constituent Dec 14 answered abstract algebra question with p-subgroup Dec 10 awarded Caucus Nov 27 comment Why this graph has automorphism group is isomorphic to the cyclic group of order 4? @HenningMakholm If $\phi$ carries $v_1$ to $v_2$ where $v_i$'s are vertices with degree 5, then $\phi$ should carry $u_1$ to $u_2$ where $u_i$ is nbhd of $v_i$ with degree 2. We can use this fact for determining $\phi$. Is it clear? Nov 27 comment Why this graph has automorphism group is isomorphic to the cyclic group of order 4? each vertex of degree 5 has exactly one nhbd with vertex 2 so if $\phi$ fixes vertices with degree 5, then $\phi$ fixes vertices with degree 2. Now, since each vertex of degree 2 has exactly one nhbd with vertex 3 so if \phi fixes vertices with degree 2, then \phi fixes vertices with degree 3. Thus \phi fixes all vertices. Is it clear? Nov 27 revised Why this graph has automorphism group is isomorphic to the cyclic group of order 4? edited body Nov 27 comment Why this graph has automorphism group is isomorphic to the cyclic group of order 4? @ChrisGodsil, thanks. Nov 27 revised Why this graph has automorphism group is isomorphic to the cyclic group of order 4? deleted 11 characters in body Nov 27 revised Why this graph has automorphism group is isomorphic to the cyclic group of order 4? added 9 characters in body Nov 27 comment Why this graph has automorphism group is isomorphic to the cyclic group of order 4? Note that there are only two groups with order $4$($\mathbb Z_2\times\mathbb Z_2$ and $\mathbb Z_4$). Nov 27 answered Why this graph has automorphism group is isomorphic to the cyclic group of order 4? Nov 25 comment Graph with only the identity as endomorphism For infinite case, see Graphs with given infinite group by Sabidussi.There are infinitely many asymmetric cubic graphs. Nov 24 comment how we can understand from spectrum of laplacian matrix of a graph that this graph is regular or not . No, problem. It is ok. Nov 24 answered prove that we can calculate $\sum^n_{i=1} d^{2}_{i}$ from the spectrum of laplacian matrix of graph. Nov 24 comment how we can understand from spectrum of laplacian matrix of a graph that this graph is regular or not . khahesh mikonam che jaleb man fkr mikardam shoma Romanian hastid. Nov 24 comment how we can understand from spectrum of laplacian matrix of a graph that this graph is regular or not . @kpax your welcome. May be this paper helps you:Which graphs are determined by their spectrum? by Dam and Haemers. Nov 24 answered how we can understand from spectrum of laplacian matrix of a graph that this graph is regular or not .