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Generalised T-Duality and Non-Geometric Backgrounds

High Energy Physics - Theory · Submitted 1 Dec 2005 · 30 references

Pith's verdict: The paper that opened the Q/R flux story; the derivations are clean, but the general both-twist backgrounds are proposed, not constructed, and the authors say so.

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arXiv IDhep-th/0512005 (version 2)
Pith IDSYS2PAOQ, Pith's permanent record of this paper and its review
CitationAtish Dabholkar, Chris Hull. "Generalised T-Duality and Non-Geometric Backgrounds." arXiv:hep-th/0512005 (2005). https://pith.science/paper/SYS2PAOQ
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Referee report
The paper

The paper claims

T-duality is extended to backgrounds where no circle is an isometry, producing spaces that depend on winding coordinates.

The reading

String theory's T-duality is normally a set of rules that only applies when the direction you dualise is a symmetry of the background. This paper asks what happens when it is not, and answers that T-duality still acts, but the result is not a conventional space at all: it depends on the coordinate conjugate to string winding number, so it has no local spacetime description even patch by patch. The authors argue that such backgrounds are forced on us, because T-dualising a three-torus with constant $H$-flux three times must land somewhere, and the third step has no isometry to work with. They give the construction a home in string field theory and in a doubled geometry with coordinates for both momentum and winding, and they show that at special points in moduli space the same objects reduce to asymmetric orbifolds that are already known to be consistent string backgrounds.

What carries the argument

The load-bearing device is the doubled geometry: a torus $T^d$ is promoted to a doubled torus with coordinates $y^i$ and dual coordinates $x_i$, and the T-duality group $O(d,d;Z)$ acts geometrically on the doubled torus even when it acts non-geometrically on $y$ alone. A duality-twisted reduction with monodromy $M$ becomes a bundle over a doubled base, and T-duality is a change of which coordinate is called spacetime. The second device is the scalar potential $W(K) = (1/12) K^{ad} K^{be} K^{cf} f_{abc} f_{def} - (1/4) K^{ad} L^{be} L^{cf} f_{abc} f_{def}$, fixed by matching the Scherk-Schwarz result of Kaloper and Myers and then extended by $O(d,d)$ covariance to arbitrary gaugings; its cubic term in the WZW case gives the determinant form of the Higgs field and the correct flat direction.

Extended reading notes

Core claim

The central claim is that there is a class of non-geometric string backgrounds with genuine dependence on the dual coordinates conjugate to winding number, sitting alongside ordinary flux compactifications and T-folds. T-folds are locally ordinary spacetimes glued by T-duality transition functions; the new backgrounds are stranger, since even locally they are not manifolds. The authors argue that a generalised T-duality acts on this wider class, taking a twisted-torus flux compactification or a T-fold to one of the new backgrounds, and that this is the missing third T-duality of $T^3$ with constant $H$-flux, where the base circle is not an isometry. The mechanism is a change of polarisation in a doubled formalism: the conformal field theory carries both momentum and winding labels, one chooses which coordinate to call spacetime, and the physics is claimed to be independent of that choice. They further construct the bosonic sector of the corresponding gauged supergravities in any dimension, with a universal scalar potential quadratic in the embedding tensor, and check it against the $SO(3)$ WZW model, where the potential reproduces the expected symmetry breaking to $SO(2)$ times $SO(2)$ with a single flat direction.

Load-bearing premise

The construction is classical throughout, and the claim that these dual-coordinate-dependent backgrounds are genuine string backgrounds rests on assuming that the doubled-formalism solutions lift to modular-invariant quantum theories away from the special moduli points where they reduce to known asymmetric orbifolds.

Editorial extensions

If this is right

  • Mirror symmetry for Calabi-Yau manifolds with $T^3$ fibration and $H$-flux would have a concrete non-geometric mirror, obtained by T-dualising all fibre directions, as the Strominger-Yau-Zaslow picture suggests when flux is included.
  • Gauged supergravities whose non-abelian gauge fields come from the antisymmetric tensor, rather than from isometries of the internal metric, acquire classical string liftings, removing an apparent obstruction to lifting a wide class of effective theories.
  • The universal potential gives a complete nonlinear description of a class of WZW-model deformations, including the leading $1/k$ correction to the central charge, which is otherwise an $\alpha'$ effect invisible to supergravity.
  • Every background reached by these generalised dualities inherits the quantum consistency of the background it came from, so T-duals of consistent T-folds are consistent even when no sigma-model metric can be written.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If dual-coordinate dependence is real, momentum modes and winding modes probe different effective geometries of the same background, which suggests that any operational definition of the spacetime in these models must specify the probe, a point the paper raises but does not resolve.
  • The construction predicts that the localised NS5-brane on a circle and the Kaluza-Klein monopole are related by a duality that produces dual-coordinate dependence in the monopole, matching the world-sheet instanton computations cited from Gregory-Harvey-Moore and Tong; a direct check of the full nonlinear map would be a sharp test.
  • Because the doubled torus is a genuine manifold with an $SL(2d;Z)$ action, one could ask whether the doubled description admits a variational principle and a well-defined path integral of its own, which would make the polarisation-independence claim into a theorem rather than a bookkeeping device.
  • Extending the same logic to U-duality would replace winding by brane wrapping, so the analogous exotic backgrounds would depend on coordinates conjugate to membrane and fivebrane charges; the paper flags this as future work, and it is where the classical treatment is most likely to fail first.
Original abstract

We undertake a systematic analysis of non-geometric backgrounds in string theory by seeking stringy liftings of a class of gauged supergravity theories. In addition to conventional flux compactifications and non-geometric T-folds with T-duality transition functions, we find a new class of non-geometric backgrounds with non-trivial dependence on the dual coordinates that are conjugate to the string winding number. We argue that T-duality acts in our class of theories, including those cases without isometries in which the conventional Buscher rules cannot be applied, and that these generalised T-dualities can take T-folds or flux compactifications on twisted tori to examples of the new non-geometric backgrounds. We show that the new class of non-geometric backgrounds and the generalised T-dualities arise naturally in string field theory, and are readily formulated in terms of a doubled geometry, related to generalised geometry. At special points in moduli space, some of the non-geometric constructions become equivalent to asymmetric orbifolds which are known to provide consistent string backgrounds. We construct the bosonic sector of the corresponding gauged supergravity theories and show that they have a universal form in any dimension, and in particular construct the scalar potential. We apply this to the supersymmetric WZW model, giving the complete non-linear structure for a class of WZW-model deformations.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 5,850 input tokens, $0.0002 reported.

What the abstract itself states, as probabilities: claims first 0.07 · states limitation 0.19 · human participants 0.01 · controlled comparison 0.02 · randomized assignment 0.01 · states quantitative result 0.04 · compares with prior results 0.69 · mentions code or data availability 0.01.

The abstract, sentence by sentence

arXiv listing abstract v2. Results and the main claim are underlined; .

We undertake a systematic analysis of non-geometric backgrounds in string theory by seeking stringy liftings of a class of gauged supergravity theories. In addition to conventional flux compactifications and non-geometric T-folds with T-duality transition functions, we find a new class of non-geometric backgrounds with non-trivial dependence on the dual coordinates that are conjugate to the string winding number. We argue that T-duality acts in our class of theories, including those cases without isometries in which the conventional Buscher rules cannot be applied, and that these generalised T-dualities can take T-folds or flux compactifications on twisted tori to examples of the new non-geometric backgrounds. We show that the new class of non-geometric backgrounds and the generalised T-dualities arise naturally in string field theory, and are readily formulated in terms of a doubled geometry, related to generalised geometry. At special points in moduli space, some of the non-geometric constructions become equivalent to asymmetric orbifolds which are known to provide consistent string backgrounds. We construct the bosonic sector of the corresponding gauged supergravity theories and show that they have a universal form in any dimension, and in particular construct the scalar potential. We apply this to the supersymmetric WZW model, giving the complete non-linear structure for a class of WZW-model deformations.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 We undertake a systematic analysis of non-geometric backgrounds in string theory by seeking stringy liftings of a class of gauged supergravity theories. contribution 0.94 0.95 0.08 asserted 0.89
s1 In addition to conventional flux compactifications and non-geometric T-folds with T-duality transition functions, we find a new class of non-geometric backgrounds with non-trivial dependence on the dual coordinates that are conjugate to the string winding number. result 0.89 0.95 0.23 asserted 1.00
s2 We argue that T-duality acts in our class of theories, including those cases without isometries in which the conventional Buscher rules cannot be applied, and that these generalised T-dualities can take T-folds or flux compactifications on twisted tori to examples of the new non-geometric backgrounds. result 0.44 0.84 0.39 asserted 0.74
s3 We show that the new class of non-geometric backgrounds and the generalised T-dualities arise naturally in string field theory, and are readily formulated in terms of a doubled geometry, related to generalised geometry. result 0.64 0.92 0.17 asserted 1.00
s4 At special points in moduli space, some of the non-geometric constructions become equivalent to asymmetric orbifolds which are known to provide consistent string backgrounds. result 0.95 0.68 0.07 asserted 0.76
s5 We construct the bosonic sector of the corresponding gauged supergravity theories and show that they have a universal form in any dimension, and in particular construct the scalar potential. contribution 0.66 0.97 0.09 asserted 1.00
s6 We apply this to the supersymmetric WZW model, giving the complete non-linear structure for a class of WZW-model deformations. contribution 0.79 0.95 0.07 asserted 1.00

What kind of paper the classifier reports this is: theoretical result 0.99 · evidence from proof or derivation 0.99.

What was examined, and what was not

sources read
  • arXiv listing abstract v2
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

References
How later papers used it

78 later papers cite it

Evidence: some. 74 of the citing papers share no author with it, and 3 of those carry a confident label from Pith's citation classifier.

Pith read 21 of the 151 citing sentences, choosing only those whose citation markers point at this paper alone, and wrote the paraphrases from them. The summary, the counts, the evidence level, the links and the quotes come from code; the summary counts the papers listed below. A later paper is listed under a label when Pith's citation classifier gives one of its sentences that label at probability 0.8 or more (0.95 for support), Pith's reading finds that the citing paper itself did it, and a second check confirms the paraphrase against the sentence. This section lists uses only. It does not list criticism or disagreement, so their absence here says nothing about how the paper has been received. Papers that share an author with this one are listed apart, under "By the same authors". A quote is the citing authors' own sentence, shown when their paper's licence is CC BY, CC BY-SA or CC0. JSON

Builds on it 2 of 3 papers with this label · 1 by the same authors
  • Extended this paper's results and showed that all fluxes appearing in M-theory compactifications on manifolds with SU(3) structure that gauge isometries in the vector multiplet sector have a correspondent in heterotic compactifications with duality twists.

    Heterotic type IIA duality with fluxes - towards the complete story (2010) · 0.91 · paraphrased: the licence does not allow quoting

By the same authors

  • Extended the Buscher transformation to the case with dependence on both x and x, providing a generalisation of T-duality of the kind proposed in this paper.

    Double Field Theory (2009) (same authors) · 0.84 · paraphrased: the licence does not allow quoting

Uses its method or tool 1 of 2 papers with this label · 1 by the same authors

By the same authors

How the literature uses it

72 arXiv papers cite this in 144 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 99 sentences without a confident label

Builds on it 3 papers
  • In section [ref] we extended the results in [ref] and showed that all the fluxes which appear in M-theory compactifications on manifolds with $SU(3)$ structure and which gauge isometries in the vector multiplet sector have a correspondent in heterotic compactifications with duality twists as discussed in [ref] .

    Heterotic type IIA duality with fluxes - towards the complete story · Conclusions · 0.91

  • This example with $R$-flux arose from the replacement ([ref]) of $x$ with $x$ in the T-fold generalised metric ([ref]), so that it may be viewed as a $T^2$ fibration over the dual coordinate $x̃∼𝕏^1$ [ref] .

    Non-geometric backgrounds, doubled geometry and generalised T-duality · R-Flux · 0.81

  • The Buscher transformation of $$ was extended to the case with dependence on both $x$ and $x$, providing a generalisation of T-duality of the kind proposed in [ref] .

    Double Field Theory · Spaces large and small · 0.84

Uses its method or tool 2 papers
  • For such cases, we use a generalised T-duality [ref] which takes a background with dependence on $x$ to an essentially doubled background in which the fields depend on the coordinate $$ of the T-dual circle and so are problematic to interpret in conventional terms.

    Noncommutative gauge theories on D-branes in non-geometric backgrounds · D-branes and doubled twisted torus geometry · 0.98

  • For the three-dimensional backgrounds considered here there is no isometry, even locally, in the $x$-direction, so we cannot use the Buscher rules, even on a cover of the space; however, in section three we shall perform a non-isometric or `generalised duality' along the lines of that of [ref] and suggest another dual description of this background.

    Flux compactifications, twisted tori and doubled geometry · T-duality and T-folds · 0.81

Compares with it 1 paper
Cites it as support 3 papers
Cites it as background 30 papers

Discussion

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