arXiv subjects

Yuho Sakatani

Publications and source records attributed to Yuho Sakatani.

At least 37 records · Page 2Linked to original sources

arXiv2020

Exotic branes and mixed-symmetry potentials II: Duality rules and exceptional $p$-form gauge fields

In U-duality-manifest formulations, supergravity fields are packaged into covariant objects such as the generalized metric and $p$-form fields $\mathcal{A}_p^{I_p}$. While a parameterization of the generalized metric in terms of supergravity fields is known for U-duality groups $E_n$ with $n\leq 8$, a parameterization of $\mathcal{A}_p^{I_p}$ has not been fully determined. In this paper, we propose a systematic method to determine the parameterization of $\mathcal{A}_p^{I_p}$, which necessarily involves mixed-symmetry potentials. We also show how to systematically obtain the T- and S-duality transformation rules of the mixed-symmetry potentials entering the multiplet. As the simplest non-trivial application, we find the parameterization and the duality rules associated with the dual graviton. Additionally, we show that the 1-form field $\mathcal{A}_1^{I_1}$ can be regarded as the generalized graviphoton in the exceptional spacetime.

hep-th↗

arXiv2020

Non-Abelian U-duality for membrane

T-duality of string theory can be extended to the Poisson-Lie T-duality when the target space has a generalized isometry group given by a Drinfel'd double. In M-theory, T-duality is understood as a subgroup of U-duality, but the non-Abelian extension of U-duality is still a mystery. In this paper, we study membrane theory on a curved background with a generalized isometry group given by the $\mathcal{E}_n$ algebra. This provides a natural setup to study non-Abelian U-duality because the $\mathcal{E}_n$ algebra has been proposed as a U-duality extension of the Drinfel'd double. We show that the standard treatment of Abelian U-duality can be extended to the non-Abelian setup. However, a famous issue in Abelian U-duality still exists in the non-Abelian extension.

hep-th↗

arXiv2019

Duality rules for more mixed-symmetry potentials

T- and S-duality rules among the gauge potentials in type II supergravities are studied. In particular, by following the approach of arXiv:1909.01335, we determine the T- and S-duality rules for certain mixed-symmetry potentials, which couple to supersymmetric branes with tension $T\propto g_s^{-n}$ ($n\leq 4$). Although the T-duality rules are rather intricate, we find a certain redefinition of potentials which considerably simplifies the duality rules. After the redefinition, potentials are identified with components of the T-duality-covariant potentials, which have been predicted by the $E_{11}$ conjecture. We also discuss the field strengths of the mixed-symmetry potentials.

hep-th↗

arXiv2019

Type II DFT solutions from Poisson-Lie T-duality/plurality

String theory has the T-duality symmetry when the target space has Abelian isometries. A generalization of the T-duality, where the isometry group is non-Abelian, is known as the non-Abelian T-duality, which works well as a solution-generating technique in supergravity. In this paper, we describe the non-Abelian T-duality as a kind of O(D,D) transformation when the isometry group acts without isotropy. We then provide a duality transformation rule for the Ramond-Ramond fields by using the technique of double field theory (DFT). We also study a more general class of solution-generating technique, the Poisson-Lie (PL) T-duality or T-plurality. We describe the PL T-plurality as an O(n,n) transformation and clearly show the covariance of the DFT equations of motion by using the gauged DFT. We further discuss the PL T-plurality with spectator fields, and study an application to the AdS$_5\times$S$^5$ solution. The dilaton puzzle known in the context of the PL T-plurality is resolved with the help of DFT.

hep-th↗

arXiv2019

Weyl invariance of string theories in generalized supergravity backgrounds

We revisit Weyl invariance of string theories in generalized supergravity backgrounds. In the previous work arXiv:1703.09213, a possible counterterm was constructed, but it seems to be a point of controversy in some literatures whether it is non-local or not. To settle down this issue, we show that the counterterm may be local and exactly cancels out the one-loop trace anomaly in generalized supergravity backgrounds.

hep-th↗

arXiv2019

Holographic integration of $T \bar{T}$ and $J \bar{T}$ via $O(d,d)$

Prompted by the recent developments in integrable single trace $T \bar{T}$ and $J \bar{T}$ deformations of 2d CFTs, we analyse such deformations in the context of $AdS_3/CFT_2$ from the dual string worldsheet CFT viewpoint. We observe that the finite form of these deformations can be recast as $O(d,d)$ transformations, which are an integrated form of the corresponding Exactly Marginal Deformations (EMD) in the worldsheet Wess-Zumino-Witten (WZW) model, thereby generalising the Yang-Baxter class that includes TsT. Furthermore, the equivalence between $O(d,d)$ transformations and marginal deformations of WZW models, proposed by Hassan and Sen for Abelian chiral currents, can be extended to non-Abelian chiral currents to recover a well-known constraint on EMD in the worldsheet CFT. We also argue that such EMD are also solvable from the worldsheet theory viewpoint.

hep-th↗

arXiv2018

Weaving the Exotic Web

String and M-theory contain a family of branes forming U-duality multiplets. In particular, standard branes with codimension higher than or equal to two, can be explicitly found as supergravity solutions. However, whether domain-wall branes and space-filling branes can be found as supergravity solutions is still unclear. In this paper, we firstly provide a full list of exotic branes in type II string theory or M-theory compactified to three or higher dimensions. We show how to systematically obtain backgrounds of exotic domain-wall branes and space-filling branes as solutions of the double field theory or the exceptional field theory. Such solutions explicitly depend on the winding coordinates and cannot be given as solutions of the conventional supergravity theories. However, as the domain-wall solutions depend linearly on the winding coordinates, we describe them as solutions of deformed supergravities such as the Romans massive IIA supergravity or lower-dimensional gauged supergravities. We establish explicit relations among the domain-wall branes, the mixed-symmetry potentials, the locally non-geometric fluxes, and deformed supergravities.

hep-th↗

arXiv2018

Local $β$-deformations and Yang-Baxter sigma model

Homogeneous Yang-Baxter (YB) deformation of AdS$_5\times$S$^5$ superstring is revisited. We calculate the YB sigma model action up to quadratic order in fermions and show that homogeneous YB deformations are equivalent to $β$-deformations of the AdS$_5\times$S$^5$ background when the classical $r$-matrices consist of bosonic generators. In order to make our discussion clearer, we discuss YB deformations in terms of the double-vielbein formalism of double field theory. We further provide an O(10,10)-invariant string action that reproduces the Green-Schwarz type II superstring action up to quadratic order in fermions. When an AdS background contains a non-vanishing $H$-flux, it is not straightforward to perform homogeneous YB deformations. In order to get any hint for such YB deformations, we study $β$-deformations of $H$-fluxed AdS backgrounds and obtain various solutions of (generalized) type II supergravity.

hep-th↗

arXiv2018

Exceptional M-brane sigma models and $η$-symbols

We develop the M-brane actions proposed in arXiv:1607.04265 by using $η$-symbols determined in arXiv:1708.06342. Introducing $η$-forms that are defined with the $η$-symbols, we present U-duality-covariant M-brane actions which describe the known brane worldvolume theories for M$p$-branes with $p=0,2,5$. We show that the self-duality relation known in the double sigma model is naturally generalized to M-branes. In particular, for an M5-brane, the self-duality relation is nontrivially realized, where the Hodge star operator is defined with the familiar M5-brane metric while the $η$-form contains the self-dual 3-form field strength. The action for a Kaluza-Klein monopole is also partially reproduced. Moreover, we explain how to treat type IIB branes in our general formalism. As a demonstration, we reproduce the known action for a $(p,q)$-string.

hep-th↗

arXiv2018

$η$-symbols in exceptional field theory

We present the universal form of $η$-symbols that can be applied to an arbitrary $E_{d(d)}$ exceptional field theory (EFT) up to $d=7$. We then express the $Y$-tensor, which governs the gauge algebra of EFT, as a quadratic form of the $η$-symbols. The usual definition of the $Y$-tensor strongly depends on the dimension of the compactification torus while it is not the case for our $Y$-tensor. Furthermore, using the $η$-symbols, we propose a universal form of the linear section equation. In particular, in the SL(5) EFT, we explicitly show the equivalence to the known linear section equation.

hep-th↗

arXiv2017

$T$-folds from Yang-Baxter deformations

Yang-Baxter (YB) deformations of type IIB string theory have been well studied from the viewpoint of classical integrability. Most of the works, however, are focused upon the local structure of the deformed geometries and the global structure still remains unclear. In this work, we reveal a non-geometric aspect of YB-deformed backgrounds as $T$-fold by explicitly showing the associated $\mathrm{O}(D,D;\mathbb{Z})$ $T$-duality monodromy. In particular, the appearance of an extra vector field in the generalized supergravity equations (GSE) leads to the non-geometric $Q$-flux. In addition, we study a particular solution of GSE that is obtained by a non-Abelian $T$-duality but cannot be expressed as a homogeneous YB deformation, and show that it can also be regarded as a $T$-fold. This result indicates that solutions of GSE should be non-geometric quite in general beyond the YB deformation.

hep-th↗

arXiv2017

Effective Action for Non-Geometric Fluxes from Duality Covariant Actions

The (heterotic) double field theories and the exceptional field theories are recently developed for manifestly duality covariant formulation of various supergravity theories, describing low-energy limit of various (heterotic) superstring and M-theory compactifications. These field theories are known to be reduced to the standard descriptions by introducing appropriately parameterized generalized metric and by applying suitably chosen section conditions. We generalize this development to non-geometric backgrounds by utilizing dual fields pertinent to non-geometric fluxes. We introduce different parameterizations for the generalized metric, in terms of the conventional supergravity fields or the dual fields. Under certain simplifying assumptions, we construct new effective action for non-geometric backgrounds. We then obtain the non-geometric backgrounds sourced by exotic branes. From them, we construct their $U$-duality monodromy matrices. The charge of exotic branes obtained from these monodromy matrices agrees perfectly with the charge obtained from the non-geometric flux integral.

hep-th↗

arXiv2017

Homogeneous Yang-Baxter deformations as generalized diffeomorphisms

Yang-Baxter (YB) deformations of string sigma model provide deformed target spaces. We propose that homogeneous YB deformations always lead to a certain class of $β$-twisted backgrounds and represent the bosonic part of the supergravity fields in terms of the classical r-matrix associated with the YB deformation. We then show that various $β$-twisted backgrounds can be realized by considering generalized diffeomorphisms in the undeformed background. Our result extends the notable relation between the YB deformations and (non-commuting) TsT transformations. We also discuss more general deformations beyond the YB deformations.

hep-th↗

arXiv2017

Weyl invariance for generalized supergravity backgrounds from the doubled formalism

It has recently been shown that a set of the generalized type IIB supergravity equations follows from the requirement of kappa symmetry of the type IIB Green-Schwarz superstring theory defined on an arbitrary background. In this paper, we show that the whole bosonic part of the generalized type II supergravity equations can be reproduced from the T-duality covariant equations of motion of the double field theory by choosing a non-standard solution of the strong constraint. Then, by using the doubled formalism, we show the Weyl invariance of the bosonic string sigma model on a generalized gravity background. According to the dual-coordinate dependence of the dilaton, the Fradkin-Tseytlin term nicely removes the Weyl anomaly. This result seems likely to support that string theories can be consistently defined on arbitrary generalized supergravity backgrounds.

hep-th↗

arXiv2017

Generalized gravity from modified DFT

Recently, generalized equations of type IIB supergravity have been derived from the requirement of classical kappa-symmetry of type IIB superstring theory in the Green-Schwarz formulation. These equations are covariant under generalized T-duality transformations and hence one may expect a formulation similar to double field theory (DFT). In this paper, we consider a modification of the DFT equations of motion by relaxing a condition for the generalized covariant derivative with an extra generalized vector. In this modified double field theory (mDFT), we show that the flatness condition of the modified generalized Ricci tensor leads to the NS-NS part of the generalized equations of type IIB supergravity. In particular, the extra vector fields appearing in the generalized equations correspond to the extra generalized vector in mDFT. We also discuss duality symmetries and a modification of the string charge in mDFT.

hep-th↗

arXiv2017

Connecting M-theory and type IIB parameterizations in Exceptional Field Theory

In the exceptional field theory, there are two natural parameterizations for the generalized metric; in terms of bosonic fields in the eleven-dimensional supergravity (M-theory parameterization) and the type IIB supergravity (type IIB parameterization). In order to translate various results known in the M-theory to the type IIB theory or vice versa, an explicit map between the two parameterizations will be useful. In this note, we present such a linear map. Comparing the two parameterizations under the linear map, we reproduce the known T-duality transformation rules for the supergravity fields. We also obtain the T-duality rules for non-geometric $β$-/$γ$-fields appearing in the type II theory on a torus.

hep-th↗

arXiv2016

Branes in Extended Spacetime: Brane Worldvolume Theory Based on Duality Symmetry

We propose a novel approach to the brane worldvolume theory based on the geometry of extended field theories: double field theory and exceptional field theory. We demonstrate the effectiveness of this approach by showing that one can reproduce the conventional bosonic string and membrane actions, and the M5-brane action in the weak-field approximation. At a glance, the proposed 5-brane action without approximation looks different from the known M5-brane actions, but it is consistent with the known nonlinear self-duality relation, and it may provide a new formulation of a single M5-brane action. Actions for exotic branes are also discussed.

hep-th↗

arXiv2016

Finite Transformations in Doubled and Exceptional Space

In the double field theory, gauge symmetries are realized as generalized diffeomorphisms in the doubled spacetime. By consistency of the theory, dependence of tensor fields on the doubled coordinates is strongly constrained. This causes finite transformation law highly complicated, both technically and conceptually. In this paper, we propose a new, physically intuitive approach to finite gauge transformations by utilizing untwisted form of vector fields. In our approach, finite gauge transformation law is expressed in terms of diffeomorphisms on a maximal null subspace on which dynamical degrees of freedom live and of a local rotation of this null subspace embedded inside the doubled space. We show that our finite transformation automatically satisfies the composition law. We also show that ours is free from the so-called Papadopoulos problem, so can describe background with nontrivial three-form flux $H_3$. Added advantage of our approach is straightforward applicability to general extended field theories. We demonstrate this by explicitly obtaining finite transformation law in the SL(5) exceptional field theory.

hep-th↗