de Sitter constructions in String Theory

Amphitheater Claude Bloch (IPhT, CEA/Saclay, France)

Amphitheater Claude Bloch

IPhT, CEA/Saclay, France


de Sitter vacua in String Theory are usually constructed using effective four-dimensional theories that appear to descend from string theory compactifications with fluxes and localized objects. However, in most constructions it is not clear whether the needed ingredients can be combined directly in String Theory without leading to inconsistencies.

A parallel line of inquiry, based on the properties of consistent effective field theories and known as the Swampland Paradigm, conjectures that these constructions will always be inconsistent. 

This workshop aims to bring together experts on top-down and bottom-up de Sitter constructions, discuss progress and controversies in this area and create the framework for new collaborations and developments.

Organizers: Iosif Bena, Mariana Graña, Ander Retolaza


Invited participants:

David Andriot
Johan Blåbäck
Andreas Braun
Giuseppe Dibitetto
Emilian Dudaș
Renata Kallosh
Manki Kim
Elias Kiritsis
Nicolas Kovensky
Severin Lüst
Luca Martucci
Jakob Moritz
Vasilis Niarchos
Francesco Nitti
Susha Parameswaran
Erik Plauschinn
Lisa Randall
Gary Shiu
Pablo Soler 
Radu Tătar
Bret Underwood
Thomas van Riet
Timm Wrase
Ivonne Zavala


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  • Achilleas Passias
  • Alessandro Bombini
  • Ander Retolaza
  • Andreas Braun
  • Brando Bellazzini
  • Bret Underwood
  • Caroline Brembilla
  • Chiara Toldo
  • David Andriot
  • Elias Kiritsis
  • Emilian Dudas
  • Erik Plauschinn
  • Felicity Eperon
  • Flavio Tonioni
  • Francesco Nitti
  • G. Bruno De Luca
  • Gabriele Lo Monaco
  • Gary Shiu
  • Gerben Venken
  • Giuseppe Dibitetto
  • Iosif Bena
  • Ivonne Zavala
  • Jakob Moritz
  • Johan Blåbäck
  • Lilian Chabrol
  • Lisa Randall
  • Luca Martucci
  • Lukas Witkowski
  • Manki Kim
  • Marco Scalisi
  • Mariana Grana
  • Nam Huy Nguyen
  • Niccolò Cribiori
  • Nicolas Kovensky
  • Pablo Soler
  • Paul Marconnet
  • Philippe Brax
  • Radu Tatar
  • Renata Kallosh
  • Ruben Monten
  • Severin Lüst
  • Susha Parameswaran
  • Thomas Van Riet
  • Timm Wrase
  • Vasileios Niarchos
  • Vincent Van Hemelryck
  • Yixuan LI
  • Yuta Hamada
    • 10:00 AM 10:40 AM
      Non-supersymmetric D-branes 40m

      After some general comments about the search for dS vacua in string theory, I will discuss non-supersymmetric D-branes in flux compactifications. In recent years we have obtained an improved understanding of these interesting ingredients in string compactifications. In particular, anti-D-branes play a crucial role in many constructions of dS vacua in string theory and there is the hope that by studying more general non-supersymmetric brane setups we can learn something about a so far unexplored part of the landscape.

      Speaker: Timm Wrase
    • 10:40 AM 11:20 AM
      Mass production of stable de Sitter vacua 40m

      In M-theory/string theory inspired d=4 N=1 supergravityincluding a nilpotent multiplet (representing pseudo-calibrated anti-Dp branes) we found a relatively simple regular procedure to construct stable de Sitter minima in theories with many moduli and many different Kahler potentials and superpotentials associated with M-theory, type IIA and type IIB string theory.

      Speaker: Renata Kallosh
    • 11:20 AM 11:50 AM
      Coffee 30m
    • 11:50 AM 1:00 PM
      Discussion: Top-down vs. bottom-up 1h 10m
      Speakers: Ander Retolaza (IPhT CEA Saclay) , Renata Kallosh, Jakob Moritz (Cornell) , Gary Shiu, Pablo Soler, Ivonne Zavala (Swansea University)
    • 1:00 PM 2:20 PM
      Lunch 1h 20m
    • 2:20 PM 3:00 PM
      Anti-brane do you even lift? 40m

      I will discuss several issues concerning the uplifting procedure of KKLT that have been discussed over the last year. Ranging from the stability with respect to brane-flux decay, to flattening effects when moduli stabilisation is included. I will try to convey the message that we are far from a proper understanding of whether dS uplifting can be achieved.

      Speaker: Thomas Van Riet
    • 3:00 PM 3:40 PM
      Anti-branes in the blackfold approach 40m

      I will give a brief review of the blackfold formalism which provides an approximate analytic method to obtain black hole solutions and their thermodynamic properties in gravity, including supergravity theories relevent to string theory. Subsequently, I will discuss a recent application of the method to analyze anti-D3-branes at the tip of the Klebanov-Strassler throat, which enables to examine how temperature affects the conjectured meta-stable state. Moreover, these results connect in the extremal limit to those of Kachru-Pearson-Verlinde in a regime that was previously inaccesible. The results are remarkably consistent with complementary analysis of backreacted solutions. I will also summarize corresponding results for anti M2-branes in the eleven-dimensional Cvetic-Gibbons-Lu-Pope supergravity background.

      Speaker: Vasilis Niarchos
    • 3:40 PM 4:10 PM
      Coffee 30m
    • 4:10 PM 4:40 PM
      The boundaries of KKLT 30m
      Speaker: Lisa Randall
    • 4:40 PM 5:50 PM
      Discussion: Anti-branes 1h 10m
      Speakers: Iosif Bena (IPhT, CEA-Saclay) , Vasilis Niarchos, Thomas Van Riet, Timm Wrase, Susha Parameswaran
    • 6:00 PM 8:00 PM
      Reception 2h
    • 10:00 AM 10:40 AM
      Kähler moduli stabilization from ten dimensions 40m

      We describe the back-reaction of gaugino condensates in supersymmetric AdS4 Type II String Theory compactifications with fluxes by using generalized complex geometry. We describe the modification of the ten-dimensional supersymmetry equations and show that the cosmological constant prevents the cycle wrapped by the branes with gaugino condensation from shrinking to zero size. Thus, unlike in ordinary geometric transitions in flat space, the volume of this cycle remains finite. For D7 branes with gaugino condensation, this gives a ten-dimensional account of Kähler moduli stabilization. Furthermore, by matching the ten-dimensional supergravity solutions near and far from the cycle wrapped by the D7 branes, we find a relation between the size of this cycle and the cosmological constant. This relation is almost exactly the one found by KKLT using 4d EFT.

      Speaker: Nicolas Kovensky
    • 10:40 AM 11:20 AM
      de Sitter Vacua from Ten Dimensions 40m

      We analyze the de Sitter construction of KKLT using ten-dimensional supergravity, finding exact agreement with the four-dimensional effective theory. Starting from the fermionic couplings in the D7-brane action, we derive the ten-dimensional stress-energy due to gaugino condensation on D7-branes. We demonstrate that upon including this stress-energy, as well as that due to anti-D3-branes, the ten-dimensional equations of motion require the four-dimensional curvature to take precisely the value determined by the four-dimensional effective theory of KKLT.

      Speaker: Manki Kim
    • 11:20 AM 11:50 AM
      Coffee 30m
    • 11:50 AM 1:00 PM
      Discussion: Gaugino condensates 1h 10m
      Speakers: Ander Retolaza (IPhT CEA Saclay) , Luca Martucci, Manki Kim, Nicolas Kovensky, Radu Tatar
    • 1:00 PM 2:20 PM
      Lunch 1h 20m
    • 2:20 PM 3:00 PM
      10d Description of 4d de Sitter Vacua 40m
      Speaker: Gary Shiu
    • 3:00 PM 3:40 PM
      Uplifting Runaways and the Tadpole Problem 40m

      I will discuss a mechanism which can lead to a possible instability of the KKLT construction for de Sitter vacua. The sphere at the tip of a warped deformed conifold throat can be destabilized by antibranes placed in the throat. Consequently, the stabilization of moduli should not be treated independently from the antibrane uplift in KKLT-like scenarios. A similar bound can be found for numerically constructed Klebanov-Strassler black holes.
      This conifold destabilization mechanism can be avoided by turning on a large amount of flux on the sphere, but tadpole cancelation constraints the hierarchy of scales in a type IIB flux compactification. Even though sufficiently large tadpole bounds can be realized in string theory, they always come at the expense of a large number of moduli. The stabilization of these moduli by fluxes contributes to the tadpole condition as well, reducing the maximal flux on the KS-throat. I will discuss this problem for the example of M-theory on K3 x K3.

      Speaker: Severin Lüst
    • 3:40 PM 4:10 PM
      Coffee 30m
    • 4:10 PM 5:20 PM
      Discussion: Tadpole constraints 1h 10m
      Speakers: Mariana Grana (CEA/Saclay) , Andreas Braun, Severin Lüst, Erik Plauschinn, David Andriot
    • 10:00 AM 10:40 AM
      Constraints on dS from Higher Dimensions 40m

      After a review of some existing constraints on obtaining 4-dimensional de Sitter space in models with static extra dimensions, I discuss a new set of constraints, based on the null Raychaudhuri equation. These constraints indicate that dS spacetimes must have (choose at least one): positive internal curvature, or warping sourced by the 4-d cosmological constant, or violate the null energy condition pointwise everywhere in the extra dimensions. I will compare these constraints to previous ones and explore their application to known models of 4-dimensional dS space with extra dimensions, drawing lessons for future model-building along the way.

      Speaker: Bret Underwood
    • 10:40 AM 11:20 AM
      Two routes to de Sitter in holography 40m

      In the context of holographic model building, I will discuss ways to obtain de Sitter space in four dimensions which do not rely on finding a stable semiclassical vacuum solution with an effective positive potential energy. In the field theory dual description, these de Sitter solutions can be thought of as non-vacuum states in a (deformed) CFT and are arise due to either non-trivial sources or non-trivial initial conditions.

      Speaker: Francesco Nitti
    • 11:20 AM 11:50 AM
      Coffee 30m
    • 11:50 AM 1:00 PM
      Discussion: No-go theorems 1h 10m
      Speakers: Mariana Grana (CEA/Saclay) , Johan Blåbäck (CEA-Saclay) , Bret Underwood, Thomas Van Riet, Giuseppe Dibitetto
    • 1:00 PM 2:20 PM
      Lunch 1h 20m
    • 2:20 PM 3:00 PM
      A new landscape of orientifold vacua 40m

      A consistent O3/O7 orientifold of type IIB string theory is the starting point for KKLT constructions of de Sitter vacua. I will present a vast landscape of such orientifolds that descends from the famous set of complete intersection Calabi-Yau's (CICY). I will present distributions of topological data relevant for phenomenology such as the splitting of Hodge numbers, the D3 tadpole, and multiplicities of O3 and O7 planes. Somewhat surprisingly, almost all of these orientifolds have conifold singularities whose deformation branches are projected out by the orientifolding. However, they can be resolved, so most of the orientifolds actually descend from a much larger and possibly new set of CY threefolds that can reached from the CICYs via conifold transitions. Finally, we observe an interesting class of N=1 geometric transitions involving colliding O-planes similar to another class that has previously been described in the literature.

      Speaker: Jakob Moritz (Cornell)
    • 3:00 PM 3:40 PM
      Solving Global Optimisation Problems 40m

      When answers are difficult to come by via analytical means, they still
      may be possible to find by formulating it as an optimisation problem and
      finding numerical solutions. I will talk about evolutionary computing
      algorithms, differential evolution in particular, and demonstrate how it
      can be used to answer questions related to the landscape/swampland. I
      will recommend software and mention design strategies so that anyone can
      start applying these methods themselves.

      Speaker: Johan Blåbäck (CEA-Saclay)
    • 3:40 PM 4:10 PM
      Coffee 30m
    • 4:10 PM 5:20 PM
      Closing discussion 1h 10m
      Speakers: Iosif Bena (IPhT, CEA-Saclay) , Emilian Dudas (Ecole Polytechnique) , Renata Kallosh, Prof. Elias Kiritsis (UoC and APC) , Giuseppe Dibitetto