User mj125 - MathOverflow most recent 30 from http://mathoverflow.net 2013-05-23T04:41:45Z http://mathoverflow.net/feeds/user/22967 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/115573/two-non-degenerate-quadratic-forms-on-gf22r two non-degenerate quadratic forms on $GF(2)^2r$ mj125 2012-12-06T05:22:23Z 2012-12-06T06:44:13Z <p>I know this:</p> <p>There are two non-degenerate quadratic forms on $GF(2)^2r$. The hyperbolic form may be taken to be $Q^+(x)=x_0 x_1 + \cdots +x_{2r-2}x_{2r-1}$ ,</p> <p>and the elliptic form to be</p> <p>$Q^-(x)=x^2_0 +x_0x_1 +x^2_1 +x_2x_3 + \cdots +x_{2r-2}x_{2r-1}$.</p> <p>and my question is:</p> <p>I want to know more about this, do you know any book or article about this?</p> http://mathoverflow.net/questions/115470/2-rank-of-matrix 2-rank of matrix mj125 2012-12-05T05:34:02Z 2012-12-05T05:50:36Z <p>I want to prove this:</p> <p>If A is a symmetric integral matrix with zero diagonal, then 2-rank(A) (i.e. the dimension of $C_A$ ) is even.</p> http://mathoverflow.net/questions/102031/mclaughlin-graph Mclaughlin Graph mj125 2012-07-12T11:08:55Z 2012-07-12T15:35:18Z <p>how can i construct a strongly regular graph with parameter $(275,112,30,56)$(Mclaughlin Graph), (105,32,4,12)?</p> <p>I need adjacency matrix of them?</p> <p>I know they are unique.</p> http://mathoverflow.net/questions/97776/classify-strongly-regular-graph-with-parameter-25-12-5-6 classify strongly regular graph with parameter (25,12,5,6) mj125 2012-05-23T17:25:22Z 2012-05-23T18:16:27Z <p>how can i classify strongly regular graph with parameter $(25,12,5,6)$?</p> <p>just i know we have fifteen $SRG(25,12,5,6)$ that two come from latin square(5)</p> http://mathoverflow.net/questions/96320/strongly-regular-graph-as-two-graph/96562#96562 Answer by mj125 for strongly regular graph as two-graph mj125 2012-05-10T10:50:52Z 2012-05-10T10:50:52Z <p>ok, that's right, if $\Gamma$ is strongly regular graph with parameters $(v,k,\lambda,\mu)$ then it's regular two-graph if and only if $k=2\mu$</p> http://mathoverflow.net/questions/96320/strongly-regular-graph-as-two-graph strongly regular graph as two-graph mj125 2012-05-08T10:26:11Z 2012-05-10T10:50:52Z <p>is any strongly regular graph a regular two-graph?</p> <p>two-graph:a two graph is a collection $B$ of 3-subsets a set $X$ with the property that, for any 4-subset $Y$ of $X$, an even numbers of $B$ belong to $Y$.</p> <p>regular two-graph:a two-graph is regular if it is a 2-design (with parameters $2-(n,3,\lambda)$ for some $\lambda$ )</p> http://mathoverflow.net/questions/94271/transversal-design transversal design mj125 2012-04-17T04:01:01Z 2012-04-17T09:17:00Z <p>Let D denote a $1-(n, κ, m)$ design where two distinct blocks have at most one point in common (i.e. D is a partial linear space). Then the block graph $\Gamma(D)$ has the blocks of D as vertices and two vertices are adjacent whenever the blocks intersect.and if D is a transversal design $TD_1(κ, m)$</p> <p>is $\Gamma(D)$ a strongly regular graph with parameter $(m^2,k*(m-1),k^2-3k+m,k(k-1))$?</p> http://mathoverflow.net/questions/94271/transversal-design Comment by mj125 mj125 2012-04-18T13:00:32Z 2012-04-18T13:00:32Z thank you for your help. I think That's right. http://mathoverflow.net/questions/94271/transversal-design Comment by mj125 mj125 2012-04-17T15:35:36Z 2012-04-17T15:35:36Z Definition: Let $k ≥ 2$ and $n ≥ 1$. A transversal design $TD(k, n)$ is a triple $(X, G, B)$ such that the following properties are satisfied: 1. $X$ is a set of kn elements called points, 2. $G$ is a partition of X into k subsets of size n called groups, 3. $B$ is a set of k-subsets of X called blocks, 4. any group and any block contain exactly one common point, and 5. every pair of points from distinct groups is contained in exactly one block. http://mathoverflow.net/questions/94271/transversal-design Comment by mj125 mj125 2012-04-17T15:28:55Z 2012-04-17T15:28:55Z no, I see it in the a article, but i can't understand why it's right