2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/51907We summarize how to describe D-branes in a matrix theory based on unstable D-instantons, which we call K-matrix theory, and explicity show that D-branes can be constructed as bound states of infinitly many unstable D-instantons. We examine the fluctuations around Dp-brane solutions in the matrix theory and show that they correctly reproduce fields on the Dp-brane world-volume. Plugging them into the action of the matrix theory, we precisely obtain the Dp-brane action as the effective action of the fluctuations.19 pages, Talk given by S.S. at the 17th Nishinomiya-Yukawa Memorial Symposium, Nishinomiya, November, 2003High Energy Physics - Theorytext