M-Theory and Hypercharge

We discuss the possibility that the electro-weak and strong interactions arise as the low energy effective description of branes in M-theory. As a step towards constructing such a model we show how one can naturally obtain SU(N_1)\times SU(N_2)\times U(1) gauge theories from branes, including matter in the bi-fundamental representation of SU(N_1)\times SU(N_2) which are fractionally charged under U(1).Comment: 29 pages Phyzzx. Two figure

N=2 Superfields and the M-Fivebrane

In this paper we provide a manifestly N=2 supersymmetric formulation of the M-fivebrane in the presence of threebrane solitons. The superspace form of four-dimensional effective equations for the threebranes are readily obtained and yield the complete Seiberg-Witten equations of motion for N=2 super-Yang-Mills. A particularly simple derivation is given by introducing an N=2 superfield generalisation of the Seiberg-Witten differential.Comment: 14 pages phyzzx. Added paragraph on the existence of a six-dimensional action. To appear in Phys. Lett.

Branes and Calibrated Geometries

The fivebrane worldvolume theory in eleven dimensions is known to contain BPS threebrane solitons which can also be interpreted as a fivebrane whose worldvolume is wrapped around a Riemann surface. By considering configurations of intersecting fivebranes and hence intersecting threebrane solitons, we determine the Bogomol'nyi equations for more general BPS configurations. We obtain differential equations, generalising Cauchy-Riemann equations, which imply that the worldvolume of the fivebrane is wrapped around a calibrated geometry.Comment: Latex, 35 pages. References added, minor change

The Threebrane Soliton of the M-Fivebrane

We discuss the supersymmetry algebra of the M theory fivebrane and obtain a new threebrane soliton preserving half of the six-dimensional supersymmetry. This solution is dimensionally reduced to various D-p-branes.Comment: 10 pages, phyzz

A New Massive Type IIA Supergravity From Compactification

We consider the most general form for eleven dimensional supersymmetry compatible with on-shell superfields. This allows for the introduction of a conformal Spin(1,10) connection. In eleven dimensional Minkowski space this modification is trivial and can be removed by a field redefinition, however, upon compactification on S^1 it is possible to introduce a non-trivial `Wilson line'. The resulting ten dimensional supergravity has massive 1-form and 3-form potentials and a cosmological constant. This theory does not possess a supersymmetric eightbrane soliton but it does admit a supersymmetric non-static cosmological solution.Comment: 13 pages, phyzzx. The introduction is clarifed and a reference adde

A Modified Stern-Gerlach Experiment Using a Quantum Two-State Magnetic Field

The Stern-Gerlach experiment has played an important role in our understanding of quantum behavior. We propose and analyze a modified version of this experiment where the magnetic field of the detector is in a quantum superposition, which may be experimentally realized using a superconducting flux qubit. We show that if incident spin-$1/2$ particles couple with the two-state magnetic field, a discrete target distribution results that resembles the distribution in the classical Stern-Gerlach experiment. As an application of the general result, we compute the distribution for a square waveform of the incident fermion. This experimental setup allows us to establish: (1) the quantization of the intrinsic angular momentum of a spin-$1/2$ particle, and (2) a correlation between EPR pairs leading to nonlocality, without necessarily collapsing the particle's spin wavefunction.Comment: 12 pages, 2 figure