String and Fivebrane Solitons: Singular or Non-singular?

We ask whether the recently discovered superstring and superfivebrane solutions of D=10 supergravity admit the interpretation of non-singular solitons even though, in the absence of Yang-Mills fields, they exhibit curvature singularities at the origin. We answer the question using a test probe/source approach, and find that the nature of the singularity is probe-dependent. If the test probe and source are both superstrings or both superfivebranes, one falls into the other in a finite proper time and the singularity is real, whereas if one is a superstring and the other a superfivebrane it takes an infinite proper time (the force is repulsive!) and the singularity is harmless. Black strings and fivebranes, on the other hand, always display real singularities.Comment: 15 page

Hodge Duality on the Brane

It has been claimed that whereas scalars can be bound to a Randall-Sundrum brane, higher p-form potentials cannot, in contradiction with the Hodge duality between 0-form and 3-form potentials in the five-dimensional bulk. Here we show that a 3-form in the bulk correctly yields a 2-form on the brane, in complete agreement with both bulk and brane duality. We also emphasize that the phenomenon of photon screening in the Randall-Sundrum geometry is ruled out by the bulk Einstein equation.Comment: 6 pages, Latex. We emphasize that the phenomenon of photon screening in the Randall-Sundrum geometry is ruled out by the bulk Einstein equatio

On the determination of the dilaton-antisymmetric tensor couplings in supergravity theories

A new approach is provided to determine the dilaton--antisymmetric tensor coupling in a supergravity theory by considering the static supersymmetric field configuration around a super extended object, which is consistently formulated in a curved superspace. By this, the corresponding SUSY transformation rules can also be determined for vanishing fermionic fields as well as bosonic fields other than those in the determined coupling. Therefore, we can, in turn, use this determined part of the supergravity theory to study all the related vacuum-like solutions. We have determined the dilaton--antisymmetric tensor couplings, in which each of the antisymmetric tensors is a singlet of the automorphism group of the corresponding superalgebra, for every supergravity multiplet. This actually happens only for $N \leq 2$ supergravity theories, which agrees completely with the spin-content analysis and the classified $N \leq 2$ super $p$-branes, therefore giving more support to the existence of the fundamental Type II $p$-branes. A prediction is made of the $D = 9, N = 2$ supergravity which has not yet been written down so far.Comment: 23 pages, harvmac, CERN-TH.6691/9

g=1 for Dirichlet 0-branes

Dirichlet 0-branes, considered as extreme Type IIA black holes with spin carried by fermionic hair, are shown to have the anomalous gyromagnetic ratio g=1, consistent with their interpretation as Kaluza-Klein modes.Comment: 13 pages, Late

The Coupling of Yang-Mills to Extended Objects

The coupling of Yang-Mills fields to the heterotic string in bosonic formulation is generalized to extended objects of higher dimension (p-branes). For odd p, the Bianchi identities obeyed by the field strengths of the (p+1)-forms receive Chern-Simons corrections which, in the case of the 5-brane, are consistent with an earlier conjecture based on string/5-brane duality.Comment: 14 Page

p-brane Solitons in Maximal Supergravities

In this paper, we give a construction of $p$-brane solitons in all maximal supergravity theories in $4\le D \le 11$ dimensions that are obtainable from $D=11$ supergravity by dimensional reduction. We first obtain the full bosonic Lagrangians for all these theories in a formalism adapted to the $p$-brane soliton construction. The solutions that we consider involve one dilaton field and one antisymmetric tensor field strength, which are in general linear combinations of the basic fields of the supergravity theories. We also study the supersymmetry properties of the solutions by calculating the eigenvalues of the Bogomol'nyi matrices, which are derived from the commutators of the supercharges. We give an exhaustive list of the supersymmetric $p$-brane solutions using field strengths of all degrees $n=4,3,2,1$, and the non-supersymmetric solutions for $n=4,3,2$. As well as studying elementary and solitonic solutions, we also discuss dyonic solutions in $D=6$ and $D=4$. In particular, we find that the Bogomol'nyi matrices for the supersymmetric massless dyonic solutions have indefinite signature.Comment: 31 pages, Latex, no figure

Anti-de Sitter Black Holes in Gauged N=8 Supergravity

We present new anti-de Sitter black hole solutions of gauged N=8, SO(8) supergravity, which is the massless sector of the AdS_4\times S^7 vacuum of M-theory. By focusing on the U(1)^4 Cartan subgroup, we find non-extremal 1, 2, 3 and 4 charge solutions. In the extremal limit, they may preserve up to 1/2, 1/4, 1/8 and 1/8 of the supersymmetry, respectively. In the limit of vanishing SO(8) coupling constant, the solutions reduce to the familiar black holes of the M_4\times T^7 vacuum, but have very different interpretation since there are no winding states on S^7 and no U-duality. In contrast to the T^7 compactification, moreover, we find no static multi-center solutions. Also in contrast, the S^7 fields appear "already dualized" so that the 4 charges may be all electric or all magnetic rather than 2 electric and 2 magnetic. Curiously, however, the magnetic solutions preserve no supersymmetries. We conjecture that a subset of the extreme electric black holes preserving 1/2 the supersymmetry may be identified with the S^7 Kaluza-Klein spectrum, with the non-abelian SO(8) quantum numbers provided by the fermionic zero modes.Comment: 18 pages, Latex, minor notation improvements and references adde

The Octonionic Membrane

We generalize the supermembrane solution of D=11 supergravity by permitting the 4-form $G$ to be either self-dual or anti-self-dual in the eight dimensions transverse to the membrane. After analyzing the supergravity field equations directly, and also discussing necessary conditions for unbroken supersymmetry, we focus on two specific, related solutions. The self-dual solution is not asymptotically flat. The anti-self-dual solution is asymptotically flat, has finite mass per unit area and saturates the same mass=charge Bogomolnyi bound as the usual supermembrane. Nevertheless, neither solution preserves any supersymmetry. Both solutions involve the octonionic structure constants but, perhaps surprisingly, they are unrelated to the octonionic instanton 2-form $F$, for which $TrF \wedge F$ is neither self-dual nor anti-self-dual.Comment: 17 pages, Latex; enhanced discussion on supersymmetry, some references adde

Strings from Membranes and Fivebranes

Under the six-dimensional heterotic/type $IIA$ duality map, a solitonic membrane solution of heterotic string theory transforms into a singular solution of type $IIA$ theory, and should therefore be interpreted as a fundamental membrane in the latter theory. This finding pointed to a gap in the formulation of string theory that was subsequently filled by the discovery of the role of $D$-branes as the carriers of Ramond-Ramond charge in type $II$ string theory. The roles of compactified eleven-dimensional membranes and fivebranes in five-dimensional string theory are also discussed.Comment: 12 pages, harvma

Metric and coupling reversal in string theory

Invariance under reversing the sign of the metric G_{MN}(x) and/or the sign of the string coupling field H(x), where = g_s, leads to four possible Universes denoted 1,I,J,K according as (G,H) goes to (G,H), (-G,H), (-G,-H), (G,-H), respectively. Universe 1 is described by conventional string/M theory and contains all M, D, F and NS branes. Universe I contains only D(-1), D3 and D7. Universe J contains only D1, D5, D9 and Type I. Universe K contains only F1 and NS5 of IIB and Heterotic SO(32).Comment: LaTeX, 27 pages; v2: New results on Green-Schwarz corrections; transformation rules for axions; corrected F-theory treatment; other minor additions and correction