417 research outputs found
On the Riemann Tensor in Double Field Theory
Double field theory provides T-duality covariant generalized tensors that are
natural extensions of the scalar and Ricci curvatures of Riemannian geometry.
We search for a similar extension of the Riemann curvature tensor by developing
a geometry based on the generalized metric and the dilaton. We find a duality
covariant Riemann tensor whose contractions give the Ricci and scalar
curvatures, but that is not fully determined in terms of the physical fields.
This suggests that \alpha' corrections to the effective action require \alpha'
corrections to T-duality transformations and/or generalized diffeomorphisms.
Further evidence to this effect is found by an additional computation that
shows that there is no T-duality invariant four-derivative object built from
the generalized metric and the dilaton that reduces to the square of the
Riemann tensor.Comment: 36 pages, v2: minor changes, ref. added, v3: appendix on frame
formalism added, version to appear in JHE
Massive Type II in Double Field Theory
We provide an extension of the recently constructed double field theory
formulation of the low-energy limits of type II strings, in which the RR fields
can depend simultaneously on the 10-dimensional space-time coordinates and
linearly on the dual winding coordinates. For the special case that only the RR
one-form of type IIA carries such a dependence, we obtain the massive
deformation of type IIA supergravity due to Romans. For T-dual configurations
we obtain a `massive' but non-covariant formulation of type IIB, in which the
10-dimensional diffeomorphism symmetry is deformed by the mass parameter.Comment: 21 page
Double Field Theory Formulation of Heterotic Strings
We extend the recently constructed double field theory formulation of the
low-energy theory of the closed bosonic string to the heterotic string. The
action can be written in terms of a generalized metric that is a covariant
tensor under O(D,D+n), where n denotes the number of gauge vectors, and n
additional coordinates are introduced together with a covariant constraint that
locally removes these new coordinates. For the abelian subsector, the action
takes the same structural form as for the bosonic string, but based on the
enlarged generalized metric, thereby featuring a global O(D,D+n) symmetry.
After turning on non-abelian gauge couplings, this global symmetry is broken,
but the action can still be written in a fully O(D,D+n) covariant fashion, in
analogy to similar constructions in gauged supergravities.Comment: 28 pages, v2: minor changes, version published in JHE
On factorizations in perturbative quantum gravity
Some features of Einstein gravity are most easily understood from string
theory but are not manifest at the level of the usual Lagrangian formulation.
One example is the factorization of gravity amplitudes into gauge theory
amplitudes. Based on the recently constructed `double field theory' and a
geometrical frame-like formalism developed by Siegel, we provide a framework of
perturbative Einstein gravity coupled to a 2-form and a dilaton in which, as a
consequence of T-duality, the Feynman rules factorize to all orders in
perturbation theory. We thereby establish the precise relation between the
field variables in different formulations and discuss the Lagrangian that, when
written in terms of these variables, makes a left-right factorization manifest.Comment: 18 pages, v2: reference added, to appear in JHE
Invariances and Equations of Motion in Double Field Theory
We investigate the full set of equations of motion in double field theory and
discuss their O(D,D) symmetry and gauge transformation properties. We obtain a
Ricci-like tensor, its associated Bianchi identities, and relate our results to
those with a generalized metric formulation.Comment: 24 page
The local symmetries of M-theory and their formulation in generalised geometry
In the doubled field theory approach to string theory, the T-duality group is
promoted to a manifest symmetry at the expense of replacing ordinary Riemannian
geometry with generalised geometry on a doubled space. The local symmetries are
then given by a generalised Lie derivative and its associated algebra. This
paper constructs an analogous structure for M-theory. A crucial by-product of
this is the derivation of the physical section condition for M-theory
formulated in an extended space.Comment: 20 pages, v2: Author Name corrected, v3: typos correcte
Ramond-Ramond Cohomology and O(D,D) T-duality
In the name of supersymmetric double field theory, superstring effective
actions can be reformulated into simple forms. They feature a pair of vielbeins
corresponding to the same spacetime metric, and hence enjoy double local
Lorentz symmetries. In a manifestly covariant manner --with regard to O(D,D)
T-duality, diffeomorphism, B-field gauge symmetry and the pair of local Lorentz
symmetries-- we incorporate R-R potentials into double field theory. We take
them as a single object which is in a bi-fundamental spinorial representation
of the double Lorentz groups. We identify cohomological structure relevant to
the field strength. A priori, the R-R sector as well as all the fermions are
O(D,D) singlet. Yet, gauge fixing the two vielbeins equal to each other
modifies the O(D,D) transformation rule to call for a compensating local
Lorentz rotation, such that the R-R potential may turn into an O(D,D) spinor
and T-duality can flip the chirality exchanging type IIA and IIB
supergravities.Comment: 1+37 pages, no figure; Structure reorganized, References added, To
appear in JHEP. cf. Gong Show of Strings 2012
(http://wwwth.mpp.mpg.de/members/strings/strings2012/strings_files/program/Talks/Thursday/Gongshow/Lee.pdf
N=1 Supersymmetric Double Field Theory
We construct the N=1 supersymmetric extension of double field theory for
D=10, including the coupling to an arbitrary number n of abelian vector
multiplets. This theory features a local O(1,9+n) x O(1,9) tangent space
symmetry under which the fermions transform. It is shown that the supersymmetry
transformations close into the generalized diffeomorphisms of double field
theory.Comment: 22 pages, v2: minor corrections, ref. added, to appear in JHE
A Double Sigma Model for Double Field Theory
We define a sigma model with doubled target space and calculate its
background field equations. These coincide with generalised metric equation of
motion of double field theory, thus the double field theory is the effective
field theory for the sigma model.Comment: 26 pages, v1: 37 pages, v2: references added, v3: updated to match
published version - background and detail of calculations substantially
condensed, motivation expanded, refs added, results unchange
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