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The complex Liouville string: the worldsheet
by Scott Collier, Lorenz Eberhardt, Beatrix Mühlmann, Victor A. Rodriguez
This Submission thread is now published as
Submission summary
Authors (as registered SciPost users): | Scott Collier · Lorenz Eberhardt · Beatrix Mühlmann · Victor Rodriguez |
Submission information | |
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Preprint Link: | scipost_202506_00053v1 (pdf) |
Date accepted: | July 8, 2025 |
Date submitted: | June 27, 2025, 9:25 p.m. |
Submitted by: | Rodriguez, Victor |
Submitted to: | SciPost Physics |
Ontological classification | |
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Academic field: | Physics |
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Approach: | Theoretical |
Abstract
We introduce a new two-dimensional string theory defined by coupling two copies of Liouville CFT with complex central charge $c=13\pm i \lambda$ on the worldsheet. This string theory defines a novel, consistent and controllable model of two-dimensional quantum gravity. We use the exact solution of the worldsheet theory to derive stringent constraints on the analytic structure of the string amplitudes as a function of the vertex operator momenta. Together with other worldsheet constraints, this allows us to completely pin down the string amplitudes without explicitly computing the moduli space integrals. We focus on the case of the sphere four-point amplitude and torus one-point amplitude as worked examples. This is the first in a series of papers on the complex Liouville string: three subsequent papers will elucidate the holographic duality with a two-matrix integral, discuss worldsheet boundaries and non-perturbative effects, and connect the theory to de Sitter quantum gravity.
Author indications on fulfilling journal expectations
- Provide a novel and synergetic link between different research areas.
- Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
- Detail a groundbreaking theoretical/experimental/computational discovery
- Present a breakthrough on a previously-identified and long-standing research stumbling block
Author comments upon resubmission
General comments.
We are grateful to the referee for their careful reading and thoughtful comments.
Regarding the comment about implementing the bootstrap procedure in the Virasoro minimal string (VMS): precisely because the string amplitudes in VMS are simply polynomials, they have no interesting analytic structure that we can leverage in implementing our analytic bootstrap procedure. It would be interesting to actually prove this polynomiality of the volumes directly from the worldsheet, without having to appeal to the 3d gravity presentation.
We certainly agree that a better understanding of the relation between minimal Liouville gravity, the VMS, and the $\mathbb{C}$LS, perhaps stemming from the limits that relate their underlying worldsheet CFTs, is an interesting future line of research. At present, we do not know if such limits uplift to the full string theory and their string amplitudes.
Regarding the comment about footnote 13, we have narrowed the scope of the footnote to emphasize the fact that correlation functions of degenerate representations in timelike Liouville CFT are not obtained from those of generic representations by analytic continuation, without foreclosing the possibility of a ground ring in the Virasoro minimal string.
Suggestions for improvement.
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We referenced appendix B in the paragraph right before section 6.2.
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We appreciate the referee's careful reading of our manuscript and their suggestions regarding the use of footnotes. While we understand the concern, we believe that the footnotes serve to keep the main text focused while still providing relevant context and clarifications.
That said, we have carefully reviewed our use of footnotes and have made adjustments where appropriate to improve readability. In particular we have removed footnote 2 and included the quantum volumes in the main text. -
Since in the matrix integral paper we present the quantum volumes alongside the combination of $\sin$'s associated to the different vertices we would rather include the quantum volumes in the sum. We do not feel that it detracts from the readability of the equations.
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Addressed.
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We thank the referee for their comment. While the table of contents provides an overview, we believe that a brief outline in the introduction helps guide the reader by highlighting the key ideas and logical flow of the paper.
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Thank you for the comment. We have modified the statement appropriately.
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We have added a clarifying sentence.
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We have removed the word convention, but this is meant to refer to a choice of normalization for the Liouville vertex operators $V_p$, together with the integration measure in the OPE between two such operators, expressed as an integral over intermediate states.
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Done.
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The ghost contributions have been taken into account in those equations. In the case of the torus one-point amplitude, it is the ghost correlator that gives rise to the Dedekind eta factor.
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We clarified the sentence.
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Thank you for pointing out this typo. We have reincorporated the word "second."
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Using a tilde for right-moving quantities is not really unconventional. For example, Polchinski's volumes on String Theory follow this notation. We deliberately adopted this notation in order to avoid the possible confusion that a bar for right-moving quantities does not imply a complex conjugation. We have added a footnote on page 10 explaining this convention. To make the point, consider the conformal block decomposition in Liouville CFT at complex central charge. While the right-moving conformal block involves the cross-ratio $\bar{z}$, it does not involve complex-conjugated external weights, or momenta $p_j^*$.
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We added the word nontrivial.
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Yes. Fixed.
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We believe the statement is readable as is.
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We agree. We would love to be able to prove this property directly from the worldsheet but have not succeeded in doing so.
Published as SciPost Phys. 19, 033 (2025)
Reports on this Submission
Report #1 by Sylvain Ribault (Referee 1) on 2025-6-30 (Invited Report)
Report
The authors have made significant clarifications and corrections to their text, which was already well-written. I have no further suggestions.
As a matter of principle I do not make recommendations on whether to publish articles or not. Editorial decisions belong to editors. Since the computer system makes it necessary to have a recommendation, I picked the first one in the list.
Recommendation
Publish (surpasses expectations and criteria for this Journal; among top 10%)