7 research outputs found
T-Duality as a Duality of Loop Group Bundles
Representing the data of a string compactified on a circle in the background
of H-flux in terms of the geometric data of a principal loop group bundle, we
show that T-duality in type II string theory can be understood as the
interchange of the momentum and winding homomorphisms of the principal loop
group bundle, thus giving rise to a new interpretation of T-duality.Comment: 8 pages, latex 2e, new reference added, J.Phys.A: Fast Track
Publications (to appear
Duality symmetry and the form fields of M-theory
In previous work we derived the topological terms in the M-theory action in
terms of certain characters that we defined. In this paper, we propose the
extention of these characters to include the dual fields. The unified treatment
of the M-theory four-form field strength and its dual leads to several
observations. In particular we elaborate on the possibility of a twisted
cohomology theory with a twist given by degrees greater than three.Comment: 12 pages, modified material on the differentia
Loop Groups, Kaluza-Klein Reduction and M-Theory
We show that the data of a principal G-bundle over a principal circle bundle
is equivalent to that of a \hat{LG} = U(1) |x LG bundle over the base of the
circle bundle. We apply this to the Kaluza-Klein reduction of M-theory to IIA
and show that certain generalized characteristic classes of the loop group
bundle encode the Bianchi identities of the antisymmetric tensor fields of IIA
supergravity. We further show that the low dimensional characteristic classes
of the central extension of the loop group encode the Bianchi identities of
massive IIA, thereby adding support to the conjectures of hep-th/0203218.Comment: 26 pages, LaTeX, utarticle.cls, v2:clarifications and refs adde
Gerbes, M5-Brane Anomalies and E_8 Gauge Theory
Abelian gerbes and twisted bundles describe the topology of the NS-NS 3-form
gauge field strength H. We review how they have been usefully applied to study
and resolve global anomalies in open string theory. Abelian 2-gerbes and
twisted nonabelian gerbes describe the topology of the 4-form field strength G
of M-theory. We show that twisted nonabelian gerbes are relevant in the study
and resolution of global anomalies of multiple coinciding M5-branes. Global
anomalies for one M5-brane have been studied by Witten and by Diaconescu, Freed
and Moore. The structure and the differential geometry of twisted nonabelian
gerbes (i.e. modules for 2-gerbes) is defined and studied. The nonabelian
2-form gauge potential living on multiple coinciding M5-branes arises as
curving (curvature) of twisted nonabelian gerbes. The nonabelian group is in
general , the central extension of the E_8 loop group. The
twist is in general necessary to cancel global anomalies due to the
nontriviality of the 11-dimensional 4-form G field strength and due to the
possible torsion present in the cycles the M5-branes wrap. Our description of
M5-branes global anomalies leads to the D4-branes one upon compactification of
M-theory to Type IIA theory.Comment: 19 page
Supersymmetric AdS_5 solutions of M-theory
We analyse the most general supersymmetric solutions of D=11 supergravity
consisting of a warped product of five-dimensional anti-de-Sitter space with a
six-dimensional Riemannian space M_6, with four-form flux on M_6. We show that
M_6 is partly specified by a one-parameter family of four-dimensional Kahler
metrics. We find a large family of new explicit regular solutions where M_6 is
a compact, complex manifold which is topologically a two-sphere bundle over a
four-dimensional base, where the latter is either (i) Kahler-Einstein with
positive curvature, or (ii) a product of two constant-curvature Riemann
surfaces. After dimensional reduction and T-duality, some solutions in the
second class are related to a new family of Sasaki-Einstein spaces which
includes T^{1,1}/Z_2. Our general analysis also covers warped products of
five-dimensional Minkowski space with a six-dimensional Riemannian space.Comment: 40 pages. v2: minor changes, eqs. (2.22) and (D.12) correcte