Topological Massive Sigma Models

In this paper we construct topological sigma models which include a potential and are related to twisted massive supersymmetric sigma models. Contrary to a previous construction these models have no central charge and do not require the manifold to admit a Killing vector. We use the topological massive sigma model constructed here to simplify the calculation of the observables. Lastly it is noted that this model can be viewed as interpolating between topological massless sigma models and topological Landau-Ginzburg models.Comment: 20 pages, Phyzzx. Revised version to appear in Nucl. Phys. B. The construction of the model is clarified and there are a few minor change

Solitons and Domain Walls in Odd Dimensions

We discuss the existance of smooth soliton solutions which interpolate between supersymmetric vacua in odd-dimensional theories. In particular we apply this analysis to a wide class of supergravities to argue against the existence of smooth domain walls interpolating between supersymmetric vacua. We find that if the superpotential changes sign then any Goldstino modes will diverge.Comment: 13 pages. Substantially re-written including a more detailed discussion of fermion zero mode

Particle Production in Tachyon Condensation

We study particle production in the tachyon condensation process as described by different effective actions for the tachyon. By making use of invariant operators, we are able to obtain exact results for the density of produced particles, which is shown to depend strongly on the specific action. In particular, the rate of particle production remains finite only for one of the actions considered, hence confirming results previously appeared in the literature.Comment: LaTeX, 6 pages, 3 figure

M-Theory and Two-Dimensional Effective Dynamics

We calculate from M-theory the two-dimensional low energy effective dynamics of various brane configurations. In the first part we study configurations that have a dual description in type IIA string theory as two-dimensional (4,0) Yang-Mills theories with gauge group SU(N_1)xSU(N_2) and chiral fermions in the bi-fundamental representation. In the second part we derive related equations of motion which describe the low energy internal dynamics of a supersymmetric black hole in four-dimensional N=1 supergravity, obtained as an M-fivebrane wrapped on a complex four-cycle.Comment: Two references added. To appear in Nucl. Phys.

Monopole Dynamics from the M-Fivebrane

We study the BPS states of the M-fivebrane which correspond to monopoles of N=2 SU(2) gauge theory. Far away from the centres of the monopoles these states may be viewed as solitons in the Seiberg-Witten effective action. It is argued that these solutions are smooth and some properties of their moduli space are discussed.Comment: 30 pages phyzzx. Paragraph added to the introduction and some minor corrections. To appear in Nucl. Phys.

Quantizing the (0,4) Supersymmetric ADHM Sigma Model

We discuss the quantization of the ADHM sigma model. We show that the only quantum contributions to the effective theory come from the chiral anomalies and compute the first and second order terms. Finally the limit of vanishing instanton size is discussed.Comment: 19 pages phyzzx. Expanded discussion of various point and some minor correction

D-Branes in the Green-Schwarz Formalism

We give a basic account of supersymmetric open strings and D-branes using the Green-Schwarz formalism, obtaining a manifestly spacetime supersymmetric description of their spectrum. In addition we discuss a mechanism whereby some of the D-brane states are projected out and which can lead to chiral quantum field theories on the brane.Comment: 13 pages phyzzx. Reference added, to appear in Phys. Lett.

Gauge Fields and M-Fivebrane Dynamics

In this paper we obtain both the vector and scalar equations of motion of an M-fivebrane in the presence of threebrane solitons. The resulting equations of motion are precisely those obtained from the Seiberg-Witten low energy effective action for N=2 Yang-Mills, including all quantum corrections. This analysis extends the work of a previous paper which derived the scalar equations of motion but not in detail the vector equations. We also discuss some features of an infinite number of higher derivative terms predicted by M theory.Comment: 27 pages, Phyzzx. Minor corrections and a reference added. To appear in NP

Heterotic p-branes from Massive Sigma Models

We explicitly construct massive (0,4) supersymmetric ADHM sigma models which have heterotic p-brane solitons as their conformal fixed points. These yield the familiar gauge 5-brane and a new 1-brane solution which preserve 1/2 and 1/4 of the spacetime supersymmetry respectively. We also discuss an analogous construction for the type II NS-NS p-branes using (4,4) supersymmetric models.Comment: 23 pages Phyzzx. Extended discussion of self-duality of a gauge field in eight dimensions. To appear in Nucl. Phys.

de Sitter space from M-theory?

In this note we study a massive IIA supergravity theory obtained in hep-th/9707139 by compactification of M-theory. We point out that de Sitter space in arbitrary dimensions arises naturally as the vacuum of this theory. This explicitly shows how de Sitter space can be embedded into eleven-dimensional supergravity. In addition we discuss the novel way in which this theory avoids various `no-go theorems' which assert that de Sitter space is not a consistent vacua of eleven-dimensional supergravity theory. We also point out that the eight-branes of this theory, which couple electrically to the ten-form, can sweep out de Sitter world-volumes.Comment: 7 pages LaTeX. We have added some clarifying remarks and also some references. The tone of the paper is slightly less ebullien