Imtak Jeon

Stringy differential geometry, beyond Riemann

While the fundamental object in Riemannian geometry is a metric, closed string theories call for us to put a two-form gauge field and a scalar dilaton on an equal footing with the metric. Here we propose a novel differential geometry that treats the three objects in a unified manner, manifests not only diffeomorphism and one-form gauge symmetry but also

Differential geometry with a projection: application to double field theory

\mathbf{O}(D,D)

Incorporation of fermions into double field theory

T-duality, and enables us to rewrite the known low energy effective action of them as a single term. Further, we develop a corresponding vielbein formalism and gauge the internal symmetry that is given by a direct product of two local Lorentz groups,

Ramond-Ramond cohomology and O(D, D) T-duality

\mathbf{S}\mathbf{O}(1,D\ensuremath{-}1)\ifmmode\times\else\texttimes\fi{}\overline{\mathbf{S}\mathbf{O}}(1,D\ensuremath{-}1)

Double field formulation of Yang–Mills theory

. We comment that the notion of cosmological constant naturally changes.

M-brane bound states and the supersymmetry of BPS solutions in the Bagger-Lambert theory

In recent development of double field theory, as for the description of the massless sector of closed strings, the spacetime dimension is formally doubled, i.e. from D to D+D, and the T-duality is realized manifestly as a global O(D, D) rotation. In this paper, we conceive a differential geometry characterized by a O(D, D) symmetric projection, as the underlying mathematical structure of double field theory. We introduce a differential operator compatible with the projection, which, contracted with the projection, can be covariantized and may replace the ordinary derivatives in the generalized Lie derivative that generates the gauge symmetry of double field theory. We construct various gauge covariant tensors which include a scalar and a tensor carrying two O(D, D) vector indices.

Periodic Arrays of M2-Branes

A bstractBased on the stringy differential geometry we proposed earlier, we incorporate fermions such as gravitino and dilatino into double field theory in a manifestly covariant manner with regard to O(D, D) T-duality, diffeomorphism, one-form gauge symmetry for B-field and a pair of local Lorentz symmetries. We note that there are two kinds of fermions in double field theory: O(D, D) singlet and non-singlet which may be identified, respectively as the common and the non-common fermionic sectors in type IIA and IIB suergravities. For each kind, we construct corresponding covariant Dirac operators. Further, we derive a simple criterion for an O(D, D) rotation to flip the chirality of the O(D, D) non-singlet chiral fermions, which implies the exchange of type IIA and IIB supergravities.

Isobar of an ideal Bose gas within the grand canonical ensemble

A bstractIn 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.

Supersymmetric Double Field Theory: Stringy Reformulation of Supergravity

Abstract Based on our previous work on the differential geometry for the closed string double field theory, we construct a Yang–Mills action which is covariant under O ( D , D ) T-duality rotation and invariant under three-types of gauge transformations: non-Abelian Yang–Mills, diffeomorphism and one-form gauge symmetries. In double field formulation, in a manifestly covariant manner our action couples a single O ( D , D ) vector potential to the closed string double field theory. In terms of undoubled component fields, it couples a usual Yang–Mills gauge field to an additional one-form field and also to the closed string background fields which consist of a dilaton, graviton and a two-form gauge field. Our resulting action resembles a twisted Yang–Mills action.

Erratum: Supersymmetric double field theory: A stringy reformulation of supergravity [Phys. Rev. D85, 081501(R) (2012)]

We continue our study of BPS equations and supersymmetric configurations in the Bagger–Lambert (BL) theory. The superalgebra allows three different types of central extensions which correspond to compounds of various M-theory objects: M2-branes, M5-branes, gravity waves and Kaluza–Klein monopoles which intersect or have overlaps with the M2-branes whose dynamics is given by the BL action. As elementary objects they are all 1/2-BPS, and multiple intersections of n-branes generically break the supersymmetry into 1/2n, as it is well known. But a particular composite of M-branes can preserve from 1/16 up to 3/4 of the original supersymmetries as previously discovered. In this paper we provide the M-theory interpretation for various BPS equations, and also present explicit solutions to some 1/2-BPS equations.