396 research outputs found

### Macroscopic superstrings as interpolating solitons

It is known that, in string sigma-model metric, the `extreme' fivebrane
solution of D=10 supergravity interpolates between D=10 Minkowski spacetime and
a supersymmetric $S^3$ compactification to a linear dilaton vacuum. We show
here that, in {\it fivebrane} sigma-model metric, the extreme string solution
of D=10 supergravity interpolates between Minkowski spacetime and a hitherto
unknown supersymmetric $S^7$ compactification of d=10 supergravity to a
three-dimensional anti-de Sitter generalization of the linear dilaton vacuum,
which may be invariantly characterized in terms of conformal
Killing vectors. The dilaton field diverges near the string core but this
divergence may be eliminated by re-interpreting the string solution as the
extreme membrane solution of 11-dimensional supergravity. We show that the
latter has an analytic extension through a regular degenerate event horizon to
an interior region containing a curvature singularity. We obtain analogous
results for other extended object solutions of supergravity theories.Comment: 12 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

### 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

### 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

### Complementarity of the Maldacena and Karch-Randall Pictures

We perform a one-loop test of the holographic interpretation of the
Karch-Randall model, whereby a massive graviton appears on an AdS_4 brane in an
AdS_5 bulk. Within the AdS/CFT framework, we examine the quantum corrections to
the graviton propagator on the brane, and demonstrate that they induce a
graviton mass in exact agreement with the Karch-Randall result. Interestingly
enough, at one loop order, the spin 0, spin 1/2 and spin 1 loops contribute to
the dynamically generated (mass)^2 in the same 1: 3: 12 ratio as enters the
Weyl anomaly and the 1/r^3 corrections to the Newtonian gravitational
potential.Comment: 20 pages, Revtex 3, Discussion on the absence of a scalar ghost
clarified; Additional details on the computation give

### 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

### 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

### The World in Eleven Dimensions

A unified theory embracing all physical phenomena is a major goal of theoretical physics. In the early 1980s, many physicists looked to eleven-dimensional supergravity in the hope that it might provide that elusive superunified theory. In 1984 supergravity was knocked off its pedestal by ten-dimensional superstrings, one-dimensional objects whose

### 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

### Evidence for Heterotic/Heterotic Duality

We re-examine the question of heterotic - heterotic string duality in six
dimensions and argue that the $E_8\times E_8$ heterotic string, compactified on
$K3$ with equal instanton numbers in the two $E_8$'s, has a self-duality that
inverts the coupling, dualizes the antisymmetric tensor, acts non-trivially on
the hypermultiplets, and exchanges gauge fields that can be seen in
perturbation theory with gauge fields of a non-perturbative origin. The special
role of the symmetric embedding of the anomaly in the two $E_8$'s can be seen
from field theory considerations or from an eleven-dimensional point of view.
The duality can be deduced by looking in two different ways at
eleven-dimensional $M$-theory compactified on $K3\times {\bf S}^1/\Z_2$.Comment: 36 pages, LaTe

- âŠ