We show, through local estimates and simulation, that if one constrains simple graphs by their densities $\varepsilon$ of edges and $\tau$ of triangles, then asymptotically (in the number of vertices) for over $95\%$ of the possible range of those densities there is a well-defined typical graph, and it has a very simple structure: the vertices are decomposed into two subsets $V_1$ and $V_2$ of fixed relative size $c$ and $1-c$, and there are well-defined probabilities of edges, $g_{ jk}$, between $v_j\in V_j$, and $v_k\in V_k$. Furthermore the four parameters $c, g_{ 11}, g_{ 22}$ and $g_{ 12}$ are smooth functions of $(\varepsilon,\tau)$ except at two smooth `phase transition' curves.
Categories: math.CO cs.SI math-ph math.MP