608 research outputs found

### Non-Critical Strings in Robertson-Walker Space Time

I consider a D+1 dimensional nonlinear $\sigma$ model based on a possible
interpretation of the Liouville field as a physical time. The Weyl invariance
of this theory gives us restrictions for the background fields and the
parameters of the theory, e.g.\ for trivial background one obtains the known
regions for the dimension of the space-time ($\leq$1 or $\geq$25). For a
Robertson-Walker space time a special solution of these equations is discussed.Comment: 9 page

### Static N=2 Black Holes For Quadratic Prepotentials

We employ the principle of minimal central charge and study the entropy of
N=2 black holes corresponding to the most general quadratic prepotential. We
also give a static black hole solution for these models in which the scalar
moduli are non constants. Finally, we speculate on the microscopic origin for
our solution.Comment: 8 pages, Latex fil

### Supersymmetric Intersecting D6-Branes and Fluxes in Massive Type IIA String Theory

We study N=1 supersymmetric four-dimensional solutions of massive Type IIA supergravity with intersecting D6-branes in the presence NS-NS three-form fluxes. We derive N=1 supersymmetry conditions for the D6-brane and flux configurations in an internal manifold X6 and derive the intrinsic torsion (or SU(3)-structure) related to the fluxes. In the absence of fluxes, N=1 supersymmetry implies that D6-branes wrap supersymmetric three-cycles of X6 that intersect at angles of SU(3) rotations and the geometry is deformed by SU(3)-structures. The presence of fluxes breaks the SU(3) structures to SU(2) and the D6-branes intersect at angles of SU(2) rotations; non-zero mass parameter corresponds to D8-branes which are orthogonal to the common cycle of all D6-branes. The anomaly inflow indicates that the gauge theory on intersecting (massive) D6-branes is not chiral

### Bent BPS domain walls of D=5 N=2 gauged supergravity coupled to hypermultiplets

Within D=5 N=2 gauged supergravity coupled to hypermultiplets we derive
consistency conditions for BPS domain walls with constant negative curvature on
the wall. For such wall solutions to exist, the covariant derivative of the
projector, governing the constraint on the Killing spinor, has to be non-zero
and proportional to the cosmological constant on the domain walls. We also
prove that in this case solutions of the Killing spinor equations are solutions
of the equations of motion. We present explicit, analytically solved examples
of such domain walls, employing the universal hypermultiplet fields. These
examples involve the running of two scalar fields and the space-time in the
transverse direction that is cut off at a critical distance, governed by the
magnitude of the negative cosmological constant on the wall.Comment: 18 pages, Late

### A Monopole Solution in open String Theory

We investigate a solution of the Weyl invariance conditions in open string
theory in 4 dimensions. In the closed string sector this solution is a
combination of the SU(2) Wess--Zumino--Witten model and a Liouville theory. The
investigation is carried out in the $\sigma$ model approach where we have
coupled all massless modes (especially an abelian gauge field via the boundary)
and tachyon fields. Neglecting all higher derivatives in the field strength we
get an exact result which can be interpreted as a monopole configuration living
in non--trivial space time. The masses of both tachyon fields are quantized by
$c_{wzw}$ and vanish for $c_{wzw} = 1$.Comment: 14 pages, Latex, DESY 93-15

### Fluxes in M-theory on 7-manifolds and G structures

We consider warp compactifications of M-theory on 7-manifolds in the presence
of 4-form fluxes and investigate the constraints imposed by supersymmetry. As
long as the 7-manifold supports only one Killing spinor we infer from the
Killing spinor equations that non-trivial 4-form fluxes will necessarily curve
the external 4-dimensional space. On the other hand, if the 7-manifold has at
least two Killing spinors, there is a non-trivial Killing vector yielding a
reduction of the 7-manifold to a 6-manifold and we confirm that 4-form fluxes
can be incorporated if one includes non-trivial SU(3) structures.Comment: 13 pages, Latex; minor changes & add reference

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