Intersecting M-branes and bound states

In this paper, we construct multi-scalar, multi-center $p$-brane solutions in toroidally compactified M-theory. We use these solutions to show that all supersymmetric $p$-branes can be viewed as bound states of certain basic building blocks, namely $p$-branes that preserve $1/2$ of the supersymmetry. We also explore the M-theory interpretation of $p$-branes in lower dimensions. We show that all the supersymmetric $p$-branes can be viewed as intersections of M-branes or boosted M-branes in $D=11$.Comment: Latex, 14 pages, no figures. References adde

Small covers and the equivariant bordism classification of 2-torus manifolds

Associated with the Davis-Januszkiewicz theory of small covers, this paper deals with the theory of 2-torus manifolds from the viewpoint of equivariant bordism. We define a differential operator on the "dual" algebra of the unoriented $G_n$-representation algebra introduced by Conner and Floyd, where $G_n=(\Z_2)^n$. With the help of $G_n$-colored graphs (or mod 2 GKM graphs), we may use this differential operator to give a very simple description of tom Dieck-Kosniowski-Stong localization theorem in the setting of 2-torus manifolds. We then apply this to study the $G_n$-equivariant unoriented bordism classification of $n$-dimensional 2-torus manifolds. We show that the $G_n$-equivariant unoriented bordism class of each $n$-dimensional 2-torus manifold contains an $n$-dimensional small cover as its representative, solving the conjecture posed in [19]. In addition, we also obtain that the graded noncommutative ring formed by the equivariant unoriented bordism classes of 2-torus manifolds of all possible dimensions is generated by the classes of all generalized real Bott manifolds (as special small covers over the products of simplices). This gives a strong connection between the computation of $G_n$-equivariant bordism groups or ring and the Davis-Januszkiewicz theory of small covers. As a computational application, with the help of computer, we completely determine the structure of the group formed by equivariant bordism classes of all 4-dimensional 2-torus manifolds. Finally, we give some essential relationships among 2-torus manifolds, coloring polynomials, colored simple convex polytopes, colored graphs.Comment: 32 pages, updated version with the title of paper changed and a large expansio

Vertical versus Diagonal Dimensional Reduction for p-branes

In addition to the double-dimensional reduction procedure that employs world-volume Killing symmetries of $p$-brane supergravity solutions and acts diagonally on a plot of $p$ versus spacetime dimension $D$, there exists a second procedure of ``vertical'' reduction. This reduces the transverse-space dimension via an integral that superposes solutions to the underlying Laplace equation. We show that vertical reduction is also closely related to the recently-introduced notion of intersecting $p$-branes. We illustrate this with examples, and also construct a new $D=11$ solution describing four intersecting membranes, which preserves $1/16$ of the supersymmetry. Given the two reduction schemes plus duality transformations at special points of the scalar modulus space, one may relate most of the $p$-brane solutions of relevance to superstring theory. We argue that the maximum classifying duality symmetry for this purpose is the Weyl group of the corresponding Cremmer-Julia supergravity symmetry $E_{r(+r)}$. We also discuss a separate class of duality-invariant $p$-branes with $p=D-3$.Comment: Latex, 21 pages, no figures. References adde

Maximum principles for Laplacian and fractional Laplacian with critical integrability

In this paper, we study maximum principles for Laplacian and fractional Laplacian with critical integrability. We first consider $-\Delta u(x)+c(x)u(x)\geq 0$ in $B_1$ where $c(x)\in L^{p}(B_1)$, $B_1\subset \mathbf{R}^n$. As is known that $p=\frac{n}{2}$ is the critical case. We show that the maximum principle holds for $p\geq \frac{n}{2}$. On the other hand, the strong maximum principle requires $p>\frac{n}{2}$. In fact, we give a counterexample to illustrate that no matter how small $\|c\|_{L^{p}(B_1)}$ is, the strong maximum principle is false as $p=\frac{n}{2}$. Next, we investigate $-\Delta u(x)+\vec{b}(x)\cdot \nabla u(x)\geq 0$ in $B_1$ where $\vec{b}(x)\in L^p(B_1)$. Here $p=n$ is the critical case. In contrast to the previous case, the maximum principle and strong maximum principle both hold for $p\geq n$. We also extend some of the results above to fractional Laplacian. The non-locality of the fractional Laplacian brings in some new difficulties. Some new methods are needed

Gauged Kaluza-Klein AdS Pseudo-supergravity

We obtain the pseudo-supergravity extension of the D-dimensional Kaluza-Klein theory, which is the circle reduction of pure gravity in D+1 dimensions. The fermionic partners are pseudo-gravitino and pseudo-dilatino. The full Lagrangian is invariant under the pseudo-supersymmetric transformation, up to quadratic order in fermion fields. We find that the theory possesses a U(1) global symmetry that can be gauged so that all the fermions are charged under the Kaluza-Klein vector. The gauging process generates a scalar potential that has a maximum, leading to the AdS vacuum. Whist the highest dimension for gauged AdS supergravity is seven, our gauged AdS pseudo-supergravities can exist in arbitrary dimensions.Comment: Latex, 13 pages, typos corrected, version in PL