384 research outputs found
Supergravity Solutions for Branes Localized Within Branes
We construct supergravity solutions describing branes (D2-branes or
NS5-branes or waves) localized within D6-branes in the region close to the core
of the D6-branes. Other similar string-theory and M-theory `near-core'
localized solutions can be found by applying U-duality and/or lifting D=10
solutions to D=11. In particular, the D2-branes localized on D6-branes is
T-dual to a special case of the background describing (D)strings localized on
(D)5-branes and thus is also related to a localized intersection of M2-branes
and M5-branes. D6+wave configuration is U-dual to a D0-brane localized on a
Kaluza-Klein 5-brane or to the fundamental string intersecting a D5-brane with
the point of intersection localized on the D5-brane.Comment: 11 pages, version to appear in Phys. Lett.
Supersymmetric D3 brane action in AdS_5 x S^5
We find the space-time supersymmetric and kappa-invariant action for a
D3-brane propagating in the AdS_5 x S^5 background. As in the previous
construction of the fundamental string action in this maximally supersymmetric
string vacuum the starting point is the corresponding superalgebra su(2,2|4).
We comment on the super Yang-Mills interpretation of the gauge-fixed form of
the action.Comment: 12 pages, latex. v2: misprints corrected, useful representation of
the WZ part of the action added in section
Intersecting M-branes as Four-Dimensional Black Holes
We present two 1/8 supersymmetric intersecting p-brane solutions of
11-dimensional supergravity which upon compactification to four dimensions
reduce to extremal dyonic black holes with finite area of horizon. The first
solution is a configuration of three intersecting 5-branes with an extra
momentum flow along the common string. The second describes a system of two
2-branes and two 5-branes. Related (by compactification and T-duality) solution
of type IIB theory corresponds to a completely symmetric configuration of four
intersecting 3-branes. We suggest methods for counting the BPS degeneracy of
three intersecting 5-branes which, in the macroscopic limit, reproduce the
Bekenstein-Hawking entropy.Comment: 15 pages, harvmac; a reference added (the version to appear in
Nulcear Physics B
On field redefinitions and exact solutions in string theory
String backgrounds associated with gauged WZNW models in general depend
non-trivially on . We note, however, that there exists a local
covariant \a'-dependent field redefinition that relates the exact
metric-dilaton background corresponding to the model to its
leading-order form ( black hole). As a consequence, there exists a
`scheme' in which the string effective equations have the latter as an exact
solution. However, the corresponding equation for the tachyon (which, like
other Weyl anomaly coefficients, has scheme-dependent form) still contains
corrections of all orders in . As a result, the `probes' (the
tachyons) still feel the -corrected background. The field
redefinitions we discuss contain the dilaton terms in the metric transformation
law. We comment on exact forms of the duality transformation in different
`schemes'.Comment: 11 pages, harvmac, CERN-TH.6970/93 [ A new section on tachyonic
equation is added: while there exists a scheme where the exact D=2 `black
hole' metric-dilaton background has semiclassical form, the equation for the
tachyon still contains \alpha'-corrections, i.e. the tachyon still feels the
\alpha'-corrected background
String vacuum backgrounds with covariantly constant null Killing vector and 2d quantum gravity
We consider a sigma model with a - dimensional Minkowski signature
target space metric having a covariantly constant null Killing vector. We study
solutions of the conformal invariance conditions in dimensions and find
that generic solutions can be represented in terms of the RG flow in -
dimensional ``transverse space'' theory. The resulting conformal invariant
sigma model is interpreted as a quantum action of the scalar (``dilaton")
quantum gravity model coupled to a (non-conformal) `transverse' sigma model.
The conformal factor of the metric is identified with a light cone
coordinate of the - dimensional sigma model. We also discuss the case
when the transverse theory is conformal (with or without the antisymmetric
tensor background) and reproduce in a systematic way the solutions with flat
transverse space known before.Comment: 26 p., revised (a discussion of tachyon coupling is added at the end
of section 4), DAMTP-92-4
Self-duality of Born-Infeld action and Dirichlet 3-brane of type IIB superstring theory
D-brane actions depend on a world-volume abelian vector field and are
described by Born-Infeld-type actions. We consider the vector field duality
transformations of these actions. Like the usual 2d scalar duality rotations of
isometric string coordinates imply target space T-duality, this vector duality
is intimately connected with SL(2,Z)-symmetry of type IIB superstring theory.
We find that in parallel with generalised 4-dimensional Born-Infeld action, the
action of 3-brane of type IIB theory is SL(2,Z) self-dual. This indicates that
3-brane should play a special role in type IIB theory and also suggests a
possibility of its 12-dimensional reformulation.Comment: 22 pages, harvmac (minor changes
Generalised chiral null models and rotating string backgrounds
We consider an extension of a special class of conformal sigma models
(`chiral null models') which describe extreme supersymmetric string solutions.
The new models contain both `left' and `right' vector couplings and should
correspond to non-BPS backgrounds. In particular, we discuss a conformal
six-dimensional model which is a combination of fundamental string and 5-brane
models with two extra couplings representing rotations in orthogonal planes. If
the two rotational parameters are independent the resulting background is found
to be either singular or not asymptotically flat. The non asymptotically flat
solution has a regular short distance limit described by a `twisted' product of
SL(2,R) and SU(2) WZW theories with two twist parameters mixing the isometric
Euler angles of SU(2) with a null direction of SL(2,R).Comment: 12 pages, late
Effective potential in non-supersymmetric SU(N) x SU(N) gauge theory and interactions of type 0 D3-branes
We study some aspects of short-distance interaction between parallel
D3-branes in type 0 string theory as described by the corresponding
world-volume gauge theory. We compute the one-loop effective potential in the
non-supersymmetric SU(N) x SU(N) gauge theory (which is a Z_2 projection of the
U(2N) n=4 SYM theory) representing dyonic branes composed of N electric and N
magnetic D3-branes. The branes of the same type repel at short distances, but
an electric and a magnetic brane attract, and the forces between self-dual
branes cancel. The self-dual configuration (with the positions of the electric
and the magnetic branes, i.e. the diagonal entries of the adjoint scalar
fields, being the same) is stable against separation of one electric or one
magnetic brane, but is unstable against certain modes of separation of several
same-type branes. This instability should be suppressed in the large N limit,
i.e. should be irrelevant for the large N CFT interpretation of the gauge
theory suggested in hep-th/9901101.Comment: 14 pages, latex, v2: minor corrections, v3: a comment and references
added at the end of section
On singularities of spherically symmetric backgrounds in string theory
We suggest that for singular rotationally invariant closed string backgrounds
which need sources for their support at the origin (in particular, for special
plane waves and fundamental strings) certain `trivial' \a'-corrections (which
are usually ignored since in the absence of sources they can be eliminated by a
field redefinition) may play an important role eliminating the singularities in
the exact solutions. These corrections effectively regularize the source
delta-function at the \a'-scale. We demonstrate that similar smearing of the
singularity of the leading-order point-source solution indeed takes place in
the open string theory.Comment: 12 pages, harvma
On solvable models of type IIB superstring in NS-NS and R-R plane wave backgrounds
We consider type IIB string in the two plane-wave backgrounds which may be
interpreted as special limits of the AdS_3 x S^3 metric supported by either the
NS-NS or R-R 3-form field. The NS-NS plane-wave string model is equivalent to a
direct generalization of the Nappi-Witten model, with its spectrum being
similar to that of strings in constant magnetic field. The R-R model can be
solved in the light-cone gauge, where the Green-Schwarz action describes 4
massive and 4 massless copies of free bosons and fermions. We find the spectra
of the two string models and study the asymptotic density of states. We also
discuss a more general class of exactly solvable plane-wave models with reduced
supersymmetry which is obtained by adding twists in two spatial 2-planes.Comment: 36 pages, harvmac. v2: discussion of equivalence of the supergravity
parts of the spectra of the NS-NS and R-R models added in sect.5.3; v3: added
remark on periodicity of the NS-NS spectrum; v4: minor correction in sect.6.
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