Potentials for (p,0) and (1,1) supersymmetric sigma models with torsion

Using (1,0) superfield methods, we determine the general scalar potential consistent with off-shell (p,0) supersymmetry and (1,1) supersymmetry in two-dimensional non-linear sigma models with torsion. We also present an extended superfield formulation of the (p,0) models and show how the (1,1) models can be obtained from the (1,1)-superspace formulation of the gauged, but massless, (1,1) sigma model.Comment: 11 page

Non-Abelian Gravity and Antisymmetric Tensor Gauge Theory

A non-abelian generalisation of a theory of gravity coupled to a 2-form gauge field and a dilaton is found, in which the metric and 3-form field strength are Lie algebra-valued. In the abelian limit, the curvature with torsion is self-dual in four dimensions, or has SU(n) holonomy in $2n$ dimensions. The coupling to self-dual Yang-Mills fields in 4 dimensions, or their higher dimensional generalisation, is discussed. The abelian theory is the effective action for (2,1) strings, and the non-abelian generalisation is relevant to the study of coincident branes in the (2,1) string approach to M-theory. The theory is local when expressed in terms of a vector pre-potential.Comment: 14 pages, phyzzx macro. Minor correction

A new maximally supersymmetric background of IIB superstring theory

We present a maximally supersymmetric IIB string background. The geometry is that of a conformally flat lorentzian symmetric space G/K with solvable G, with a homogeneous five-form flux. We give the explicit supergravity solution, compute the isometries, the 32 Killing spinors, and the symmetry superalgebra, and then discuss T-duality and the relation to M-theory.Comment: 17 page

STRINGY EVIDENCE FOR D=11 STRUCTURE IN STRONGLY COUPLED TYPE II-A SUPERSTRING

Witten proposed that the low energy physics of strongly coupled D=10 type-IIA superstring may be described by D=11 supergravity. To explore the stringy aspects of the underlying theory we examine the stringy massive states. We propose a systematic formula for identifying non-perturbative states in D=10 type-IIA superstring theory, such that, together with the elementary excited string states, they form D=11 supersymmetric multiplets multiplets in SO(10) representations. This provides hints for the construction of a weakly coupled D=11 theory that is dual to the strongly coupled D=10 type IIA superstring.Comment: LaTeX, revtex, 2-column, 10 pages

Single-mode tunable erbium:ytterbium fibre Fabry-Perot laser

A compact tunable single-mode fiber laser is developed by using a novel combination of high-gain erbium: ytterbium (Er:Yb) phosphate fiber and fiber Fabry-Perot (FFP) cavity configurations. Experiments demonstrate the shortest Er:Yb phosphate FFP laser ever reported, which has a 100µm cavity length with a continuous wavelength tuning range over 4.52nm, as limited by the sharp fiber gain peak. In addition, an alternative 3-mirror laser design has also demonstrated single-mode lasing operation

Intrinsic Geometry of D-Branes

We obtain forms of Born-Infeld and D-brane actions that are quadratic in derivatives of $X$ and linear in $F_{\mu \nu}$ by introducing an auxiliary `metric' which has both symmetric and anti-symmetric parts, generalising the simplification of the Nambu-Goto action for $p$-branes using a symmetric metric. The abelian gauge field appears as a Lagrange multiplier, and solving the constraint gives the dual form of the $n$ dimensional action with an $n-3$ form gauge field instead of a vector gauge field. We construct the dual action explicitly, including cases which could not be covered previously. The generalisation to supersymmetric D-brane actions with local fermionic symmetry is also discussed.Comment: 10 pages, LaTeX, no figures. Minor correction; version to appear in Physics Letters

String-String Duality in Ten Dimensions

The heterotic string occurs as a soliton of the type I superstring in ten dimensions, supporting the conjecture that these two theories are equivalent. The conjecture that the type IIB string is self-dual, with the strong coupling dynamics described by a dual type IIB theory, is supported by the occurrence of the dual string as a Ramond-Ramond soliton of the weakly-coupled theory.Comment: 14 pages, phyzz

Geometric Actions for D-Branes and M-Branes

New forms of Born-Infeld, D-brane and M theory five-brane actions are found which are quadratic in the abelian field strength. The gauge fields couple both to a background or induced metric and a new auxiliary metric, whose elimination reproduces the non-polynomial Born-Infeld action. This is similar to the introduction of an auxiliary metric to simplify the Nambu-Goto string action. This simplifies the quantisation and dualisation of the gauge fields.Comment: LaTeX, 9 pages, no figures. Minor corrections; version to appear in Physics Letters

General Brane Geometries from Scalar Potentials: Gauged Supergravities and Accelerating Universes

We find broad classes of solutions to the field equations for d-dimensional gravity coupled to an antisymmetric tensor of arbitrary rank and a scalar field with non-vanishing potential. Our construction generates these configurations from the solution of a single nonlinear ordinary differential equation, whose form depends on the scalar potential. For an exponential potential we find solutions corresponding to brane geometries, generalizing the black p-branes and S-branes known for the case of vanishing potential. These geometries are singular at the origin with up to two (regular) horizons. Their asymptotic behaviour depends on the parameters of the model. When the singularity has negative tension or the cosmological constant is positive we find time-dependent configurations describing accelerating universes. Special cases give explicit brane geometries for (compact and non-compact) gauged supergravities in various dimensions, as well as for massive 10D supergravity, and we discuss their interrelation. Some examples lift to give new solutions to 10D supergravity. Limiting cases with a domain wall structure preserve part of the supersymmetries of the vacuum. We also consider more general potentials, including sums of exponentials. Exact solutions are found for these with up to three horizons, having potentially interesting cosmological interpretation. We give several additional examples which illustrate the power of our techniques.Comment: 54 pages, 6 figures. Uses JHEP3. Published versio