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R-symmetries and curvature constraints in A-twisted heterotic Landau-Ginzburg models
Abstract
In this paper, we discuss various aspects of a class of A-twisted heterotic Landau-Ginzburg models on a Kähler variety . We provide a classification of the R-symmetries in these models which allow the A-twist to be implemented, focusing on the case in which the gauge bundle is either a deformation of the tangent bundle of or a deformation of a sub-bundle of the tangent bundle of . Some anomaly-free examples are provided. The curvature constraint imposed by supersymmetry in these models when the superpotential is not holomorphic is reviewed. Constraints of this nature have been used to establish properties of analogues of pullbacks of Mathai-Quillen forms which arise in the correlation functions of the corresponding A-twisted or B-twisted heterotic Landau-Ginzburg models. The analogue most relevant to this paper is a deformation of the pullback of a Mathai-Quillen form. We discuss how this deformation may arise in the class of models studied in this paper. We then comment on how analogues of pullbacks of Mathai-Quillen forms not discussed in previous work may be obtained. Standard Mathai-Quillen formalism is reviewed in an appendix. We also include an appendix which discusses the deformation of the pullback of a Mathai-Quillen form.
1 Introduction
A Landau-Ginzburg model is a nonlinear sigma model with a superpotential. For a heterotic Landau-Ginzburg model Witten:Phases ; DistlerKachru:0-2-Landau-Ginzburg ; AdamsBasuSethi:0-2-Duality ; MelnikovSethi:Half-twisted ; GuffinSharpe:A-twistedheterotic ; MelnikovSethiSharpe:Recent-Developments ; GaravusoSharpe:Analogues , the nonlinear sigma model possesses only supersymmetry and the superpotential is a Grassmann-odd function of the superfields which may or may not be holomorphic.
Heterotic Landau-Ginzburg models have field content consisting of bosonic chiral superfields
and fermionic chiral superfields
along with their conjugate antichiral superfields
and
The are local complex coordinates on a Kähler variety . The are local smooth sections of a Hermitian vector bundle over , i.e. . The are nonpropagating auxiliary fields. The fermions couple to bundles as follows:
where and is the canonical bundle on the worldsheet .
In GuffinSharpe:A-twistedheterotic , heterotic Landau-Ginzburg models with superpotential of the form
(1.1) |
where were considered. It was claimed in GaravusoSharpe:Analogues that, when the superpotential (1.1) is not holomorphic, supersymmetry imposes a constraint which relates the nonholomorphic parameters of the superpotential to the Hermitian curvature. The details supporting that claim were worked out in Garavuso:Curvature ; Garavuso:Nonholomorphic for the case . This curvature constraint has been used in GaravusoSharpe:Analogues to establish properties of analogues of pullbacks of Mathai-Quillen forms. These analogues arise in the correlation functions of the corresponding A-twisted or B-twisted heterotic Landau-Ginzburg models.
In this paper, we will study certain aspects of A-twisted heterotic Landau-Ginzburg models with superpotential (1.1) and . Such models yield the A-twisted Landau-Ginzburg models of GuffinSharpe:A-twisted when and , where is the (2,2) superpotential. Although R-symmetries for (2,2) Landau-Ginzburg models have been classified, this has not been done for heterotic Landau-Ginzburg models. Furthermore, for (2,2) Landau-Ginzburg models, a classification has been given only for the case of holomorphic superpotentials KachruWitten:Computing . We will provide a classification of the R-symmetries which allow the A-twist to be implemented, focusing on the case in which is either a deformation of or a deformation of a sub-bundle of . The curvature constraint imposed by supersymmetry in these models when the superpotential is not holomorphic will be reviewed. The corresponding analogue of the pullback of a Mathai-Quillen form is a deformation of the pullback of a Mathai-Quillen form. We will discuss how this deformation may arise in the class of models studied in this paper. We will then comment on how analogues of pullbacks of Mathai-Quillen forms not discussed in previous work may be obtained.
This paper is organized as follows: The A-twist will be discussed in section 2. A classification of the corresponding R-symmetries, along with some anomaly-free examples, will be given in section 3. The curvature constraint imposed by supersymmetry when the superpotential is not holomorphic will be reviewed in section 4. In section 5, we will discuss how an analogue of a pullback of a Mathai-Quillen form may arise in the class of heterotic Landau-Ginzburg models discussed in this paper. In section 6, we will summarize our results and comment on how analogues of pullbacks of Mathai-Quillen forms not discussed in previous work may be obtained. Appendix A will review standard Mathai-Quillen formalism MathaiQuillen:Superconnections ; BerlinGetzlerVergne:Heat ; Kalkman:BRST ; Blau:The-Mathai-Quillen ; Wu:On-the-Mathai-Quillen ; CordesMooreRamgoolam:Lectures ; Wu:Mathai-Quillen . Finally, appendix B will discuss the analogue that is most relevant to this paper, i.e. a deformation of the pullback of a Mathai-Quillen form.
2 A-twist
Let be a Kähler variety with metric , antisymmetric tensor , local real coordinates , and local complex coordinates with complex conjugates . Furthermore, let be a vector bundle over with Hermitian fiber metric . We consider the action GuffinSharpe:A-twistedheterotic of an A-twisted heterotic Landau-Ginzburg model on with gauge bundle :
(2.1) |
Here, is a coupling constant, is a Riemann surface, , , and
The A-twist is defined by choosing the fermions couple to bundles as follows:
where and is the canonical bundle on . Anomaly cancellation requires GuffinSharpe:A-twistedheterotic ; KatzSharpe:Notes ; Sharpe:Notes
(2.2) |
The action (2) is invariant on-shell under the supersymmetry transformations
(2.3) | ||||
up to a total derivative. Since we have integrated out the auxiliary fields , one may use the equation of motion
(2.4) |
to show Garavuso:Curvature that the action (2) can be written
(2.5) |
where
are the BRST transformations (, where is any field),
and
is the integral over the worldsheet of the pullback to of the complexified Kähler form
3 R-symmetries
Let us now discuss the R-symmetries which allow the A-twist described in section 2 to be obtained. A classification of these R-symmetries will be given in section 3.1. Some anomaly-free examples will be given in section 3.2.
3.1 Classification
For , the twisting is achieved by tensoring the fields with
where the fields have charges and , given in table 3.1,
Field | ||
---|---|---|
0 | 0 | |
0 | 0 | |
0 | 1 | |
0 | ||
1 | 0 | |
0 |
under and R-symmetries, respectively. These R-symmetries defined by and are broken when .
Let us consider an of the form
(3.1) |
Here, is quasihomogeneous and meromorphic, i.e.
(3.2) |
where , and are integers, and the deformation is chosen to be
(3.3) |
For an of this form, we can define new charges and , given in table 3.2,
Field | |||||
0 | 0 | ||||
0 | 0 | ||||
0 | 1 | ||||
0 | |||||
1 | 0 | ||||
0 | |||||
0 | 0 | ||||
0 | 0 | ||||
0 | 0 | ||||
0 | 0 | ||||
0 | 0 | ||||
0 | 0 | ||||
0 | 0 | ||||
0 | 0 | ||||
0 | 0 | ||||
0 | 0 |
expressed in terms of the parameters
(3.4) |
which yield a -invariant action. On the (2,2) locus, we have
Off of this locus, although one has a pair of symmetries, only is an R-symmetry. The twisting is achieved by tensoring the fields with
Recall that for a Riemann surface of genus , the degree of the canonical bundle is . It follows that, for the bundles and to be well-defined, must divide , i.e.
(3.5) |
This genus issue is well understood; more details can be found in GuffinSharpe:A-twisted ; Witten:Algebraic ; Witten:The-N-matrix . Table 3.2 gives a classification of the R-symmetries in the models we are discussing in terms of the charges and .
3.2 Examples
Let us consider some examples in which is a deformation of . For such examples, the anomaly cancellation conditions (2.2) are satisfied.
As a first example, consider the case in which is a complex affine space and is a Fermat polynomial:
Example 3.1.
Let , and
Thus,
and
The twist described in this example can be defined on worldsheets of genus given by (3.5).
As a second example, consider the case in which is a complex projective space and is a Fermat polynomial with zero locus defining a hypersurface in :
Example 3.2.
Let , and
Thus,
and
The twist described in this example can be defined on worldsheets of genus given by (3.5).
As a final example, consider the case in which is a weighted complex projective space and the zero locus of is a hypersurface in that space:
Example 3.3.
Let , and
Thus,
and
The twist described in this example can be defined on worldsheets of genus given by (3.5):
4 Curvature constraints
The action (2.5) is invariant on-shell under the supersymmetry transformations (2.3) up to a total derivative. It was claimed in GaravusoSharpe:Analogues that requiring this invariance when the superpotential (1.1) is not holomorphic imposes a constraint which relates the nonholomorphic parameters of the superpotential to the Hermitian curvature. This curvature constraint, along with an additional constraint imposed by supersymmetry, was derived in Garavuso:Curvature ; Garavuso:Nonholomorphic . Let us now briefly review the key steps of this derivation; see Garavuso:Curvature ; Garavuso:Nonholomorphic for more details.
Since , where is any field, the -exact part of (2.5) is -exact and hence -closed. For the non-exact term of (2.5) involving , note that
and satisfies
Thus,
(4.1) |
It remains to consider the non-exact expression of (2.5) involving
First, we compute
(4.2) |
Now, we compute
(4.3) |
where we have used the equation of motion (2.4) in the first step and in the last step. It follows that (4) cancels (4) up to a total derivative, i.e.
(4.4) |
when both the curvature constraint
(4.5) |
and the constraint
(4.6) |
are satisfied.
Curvature constraints have been used in GaravusoSharpe:Analogues to establish properties of analogues of pullbacks of Mathai-Quillen forms. These analogues arise in the correlation functions of the corresponding A-twisted or B-twisted heterotic Landau-Ginzburg models. The analogue most relevant to this paper, i.e. a deformation of the pullback of a Mathai-Quillen form, is discussed in appendix B.
5 Physical realization of deformation of the pullback of a Mathai-Quillen form
Let us now describe how the deformation , given by (B.1), of the pullback , given by (A.5), of a Mathai-Quillen form , given by (A.1), may arise in the class of A-twisted heterotic Landau-Ginzburg models discussed in this paper.
Mathematically, the tangent bundle to , , is defined by the kernel in the short exact sequence
A deformation of the tangent bundle above is defined by
where the define the deformation.
The action of the A-twisted heterotic Landau-Ginzburg model that RG flows to a nonlinear sigma model with tangent bundle deformation above is given by GuffinSharpe:A-twistedheterotic
(5.1) |
with target space
and gauge bundle , where
and
If we restrict to zero modes on a genus zero worldsheet, in the degree zero sector we find the following interactions among zero modes:
If we now complex conjugate so as to relate the heterotic expression above to standard mathematics conventions, we find
6 Summary and outlook
We have studied certain aspects of A-twisted heterotic Landau Ginzburg models on a Kähler variety with gauge bundle , superpotential (1.1)
and . Table 3.2 provides a classification of the R-symmetries which allow the A-twist to be implemented when is either a deformation of or a deformation of a sub-bundle of . Some anomaly-free examples were provided in section 3.2. When the superpotential is not holomorphic, supersymmetry imposes the curvature constraint (4.5)
and the constraint (4.6)
The curvature constraint (4.5) was used in GaravusoSharpe:Analogues to establish properties of the deformation , given by (B.1), of the pullback , given by (A.5), of a Mathai-Quillen form , given by (A.1). In section 5, we described how may arise in the class of heterotic Landau-Ginzburg models studied in this paper.
It would be interesting to consider A-twisted and B-twisted heterotic Landau-Ginzburg models with more general Grassmann-odd superpotentials. For example, one may consider the superpotential GuffinSharpe:A-twisted
If this more general superpotential is not holomorphic, then supersymmetry should impose a curvature constraint analogous to (4.5) and a constraint analogous to (4.6). These new constraints could be derived using arguments similar to those used in Garavuso:Curvature ; Garavuso:Nonholomorphic . Furthermore, using arguments similar to those used in GaravusoSharpe:Analogues , the new curvature constraint could then be used to establish properties of new analogues of pullbacks of Mathai-Quillen forms which arise in the correlation functions of the corresponding A-twisted or B-twisted heterotic Landau-Ginzburg models. We leave a detailed study of this to future work.
Acknowledgements.
The author thanks Mauricio Romo for useful discussions.Appendix A Review of Mathai-Quillen formalism
Consider an oriented vector bundle of real rank , with standard fiber , where is an oriented closed manifold of real dimension . Suppose that has Euclidean metric and compatible connection . Under these circumstances, the Mathai-Quillen formalism MathaiQuillen:Superconnections ; BerlinGetzlerVergne:Heat ; Kalkman:BRST ; Blau:The-Mathai-Quillen ; Wu:On-the-Mathai-Quillen ; CordesMooreRamgoolam:Lectures ; Wu:Mathai-Quillen provides an explicit representative of the Thom class of . Furthermore, the pullback of by any section of is a representative of the Euler class of . Let us review the formalism in more detail.
A.1 Conventions
Our conventions for , , and the dual of are as follows. The exterior derivatives on and are respectively denoted by and . We choose local coordinates on , where . The connection on is then given by . In terms of this connection, the curvature 2-form on is given by . We choose a local oriented orthonormal frame for and let be the dual coframe, where . The section may thus be expressed as . Similarly, we write , where the are anticommuting orthonormal coordinates on . The dual pairing on is denoted by . Finally, the metric on is denoted by .
Now, consider the pullback bundle , i.e. the bundle over whose fiber at is . This bundle has Euclidean metric , compatible connection , curvature 2-form , local oriented orthonormal frame , and tautological section . (The tautological section of is the section which maps a point to .) The dual bundle has coframe and metric . We write , where the are anticommuting orthonormal coordinates on . The dual pairing on is denoted by .
A.2 Mathai-Quillen Thom class representative
Consider the Mathai-Quillen form
(A.1) |
where
(A.2) |
and
(A.3) |
We wish to show that this form satisfies the following definition.
Definition A.1.
A representative of the Thom class of is a -closed differential form such that .
Proposition A.2.
The Mathai-Quillen form satisfies
-
(i)
-
(ii)
-
(iii)
and hence is a representative of the Thom class of .
Proof.
-
(i)
Since
it follows that
However, only the component of in contributes to . Thus, .
-
(ii)
Since is compatible with the metric , it follows that
where . Furthermore,
(A.4) where we have used the Bianchi identity . From these results, we obtain
Here, the third equality holds because contributes nothing to the Grassmann integral.
-
(iii)
Thus, by definition A.1, is a representative of the Thom class of . ∎
A.3 Mathai-Quillen Euler class representative
Now, consider the pullback of the Mathai-Quillen form by any section of . We write this as
(A.5) |
where is given by (A.2) and
(A.6) |
Proposition A.3.
The form satisfies
-
(i)
-
(ii)
Proof.
Proposition A.4.
The -cohomology class of is independent of the section .
Proof.
Let be an affine one-parameter family of sections of and let
Then
It follows that
Thus, for arbitrary sections and of , the -closed forms and differ by a -exact form and hence are cohomologous. ∎
Corollary A.5.
The form is cohomologous to the Euler form
and hence is a representative of the Euler class of .
Proof.
This follows from proposition A.4 upon choosing to be the zero section. ∎
Remark A.6.
The top Chern class of a complex vector bundle is equal to the Euler class of the underlying real vector bundle.
Remark A.7.
If intersects the zero section of transversely, then is Poincaré dual to , i.e.
(A.8) |
where is -closed.
Remark A.8.
When , integrating over yields the Euler number of .
Appendix B Deformation of the pullback of a Mathai-Quillen form
Various analogues of pullbacks of Mathai-Quillen forms were proposed in GaravusoSharpe:Analogues . Let us now discuss the analogue that is most relevant to this paper, i.e. a deformation of the pullback of a Mathai-Quillen form.
The deformation and are special cases of the analogue of proposed in GaravusoSharpe:Analogues . Briefly,
where and are holomorphic vector bundles on and
Here, indexes local coordinates along the fibers of , indexes local coordinates along the fibers of , indexes local coordinates along the fibers of , and indexes local coordinates on . . The map is smooth and surjective. The curvature term is subject to the constraint
which is imposed physically by supersymmetry. Note that this constraint is consistent with the curvature 2-form being -closed by virtue of the Bianchi identity. One may show that
where . It follows that . Let and let be the restriction to of the kernel of the map . Then
where and is a lift of . For this reason, is called in GaravusoSharpe:Analogues the (first) kernel construction. See GaravusoSharpe:Analogues for further details. One recovers and (when ) in the special case that and with the map defined by
(B.4) |
where is a holomorphic section of . This corresponds to being a deformation of , with the deformation determined by . If , then . Note that
Proposition B.1.
The form satisfies
Proof.
For given by (A.6), we have that and hence
(B.5) |
It follows that
(B.6) |
Using this result, we obtain
∎
Proposition B.2.
The -cohomology class of is unchanged by antiholomorphic deformations of .
Proof.
Let be an affine one parameter family of sections of and let
Then
It follows that
which establishes that the -cohomology class of is unchanged by antiholomorphic deformations of . ∎
Remark B.3.
The -cohomology class of does seem to depend on the choice of the , at least naively. Let and Then
It follows that
which is at least not obviously -exact. The physical meaning of this result is commented on in GaravusoSharpe:Analogues .
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