Swampland Seminar Series

09/03/2021 10:30 am - 12:00 pm

During the 2021-22 academic year, the CMSA will be co-hosting a seminar on Swampland, with the Harvard Physics Department, organized by Miguel Montero, Cumrun Vafa, Irene Valenzuela. This seminar is a part of the Swampland Program. This seminar will take place on Mondays at 10:00 am – 11:30 am (Boston time). To learn how to attend, please subscribe here.

Talks will be posted on the Swampland Seminars YouTube channel. The schedule below will be updated as talks are confirmed.

Spring 2022

Date Speaker Title/Abstract
1/31/2022 Rafael Álvarez-García (DESY Hamburg) Title: Membrane Limits in Quantum Gravity
2/7/2022 Du Pei (Harvard CMSA) Title: Holomorphic CFTs and topological modular forms

Abstract: The theory of topological modular forms leads to many interesting constraints and predictions for two-dimensional quantum field theories, and some of them might have interesting implications for the swampland program. In this talk, I will show that a conjecture by Segal, Stolz and Teichner requires the constant term of the partition function of a bosonic holomorphic CFTs to be divisible by specific integers determined by the central charge. We verify this constraint in large classes of physical examples, and rule out the existence of an infinite set of “extremal CFTs”, including those with central charges c = 48, 72, 96 and 120.

2/28/2022  Tom Rudelius (UC, Berkeley) Title: Generalized Global Symmetries and the Weak Gravity Conjecture
3/7/2022 Fernando Marchesano (UAM-CSIC, Madrid)  and Max Wiesner (Harvard CMSA) Title: 4d strings at strong coupling
3/21/2022 Patrick Draper (Univ. of Illinois) and Alvaro Herraez (IPhT Saclay). Open Mic Discussion
Topic: Entropy bounds (species bound, Bekenstein bound, CKN bound, and the like)
3/28/2022 Fernando Quevedo (Cambridge) Title: On renormalisation group induced moduli stabilisation and brane-antibrane inflation

Abstract: A proposal to use the renormalisation group to address moduli stabilisation in IIB string perturbation theory will be described. We revisit brane-antibrane inflation combining this proposal with non-linearly realised supersymmetry.

4/5/2022 Simon Caron-Huot (McGill University) and Julio Parra (Caltech) Title: Causality constraints on corrections to Einstein gravity

Abstract: We study constraints from causality and unitarity on 2→2 graviton scattering in four-dimensional weakly-coupled effective field theories. Together, causality and unitarity imply dispersion relations that connect low-energy observables to high-energy data. Using such dispersion relations, we derive two-sided bounds on gravitational Wilson coefficients in terms of the mass M of new higher-spin states. Our bounds imply that gravitational interactions must shut off uniformly in the limit G→0, and prove the scaling with M expected from dimensional analysis (up to an infrared logarithm). We speculate that causality, together with the non-observation of gravitationally-coupled higher-spin states at colliders, severely restricts modifications to Einstein gravity that could be probed by experiments in the near future.

4/11/2022 Timm Wrase and Eduardo Gonzalo (Lehigh) Title: Type IIB flux compactifications with $h^{1,1}=0$

Abstract: We revisit type IIB flux compactification that are mirror dual to type IIA on rigid Calabi-Yau manifolds. We find a variety of interesting new solutions, like fully stabilized Minkowski vacua and infinite families of AdS$_4$ solutions with arbitrarily large numbers of spacetime filling D3 branes. We discuss how these solutions fit into the web of swampland conjectures.

4/18/2022 José Calderón (IFT Madrid) Open mic Swampland Discussion

Topic: Cobordism

5/9/2022 Georges Obie (Harvard) Title: Inflation and light Dark Matter constraints from the Swampland

Abstract: I will explore the interplay between Swampland conjectures and models of inflation and light Dark Matter. To that end, I will briefly review the weak gravity conjecture (WGC) and the related Festina Lente (FL) bound. These have implications for light darkly and milli-charged particles and can disfavor a large portion of parameter space. The FL bound also implies strong restrictions on the field content of our universe during inflation and presents an opportunity for inflationary model building. At the same time, it rules out some popular models like chromo-natural inflation and gauge-flation. Finally, I will review another Swampland conjecture related to Stückelberg photon masses and discuss its implications for astro-particle physics.

Fall 2021

Date Speaker Title/Abstract
9/13/2021 John Stout (Harvard) Title: Decoding Divergent Distances

Abstract: Motivated by a relationship between the Zamolodchikov and NLSM metrics to the so-called quantum information metric, I will discuss recent work (2106.11313) on understanding infinite distance limits within the context of information theory. I will describe how infinite distance points represent theories that are hyper-distinguishable, in the sense that they can be distinguished from “nearby” theories with certainty in relatively few measurements. I will then discuss necessary and sufficient ingredients for the appearance of these infinite distance points, illustrate these in simple examples, and describe how this perspective can help the swampland program.

9/20/2021 Manki Kim (MIT) Title: Small Cosmological Constants in String Theory

Abstract: We construct supersymmetric AdS4 vacua of type IIB string theory in compactifications on orientifolds of Calabi-Yau threefold hypersurfaces. We first find explicit orientifolds and quantized fluxes for which the superpotential takes the form proposed by Kachru, Kallosh, Linde, and Trivedi. Given very mild assumptions on the numerical values of the Pfaffians, these compactifications admit vacua in which all moduli are stabilized at weak string coupling. By computing high-degree Gopakumar-Vafa invariants we give strong evidence that the α 0 expansion is likewise well-controlled. We find extremely small cosmological constants, with magnitude < 10^{-123} in Planck units. The compactifications are large, but not exponentially so, and hence these vacua manifest hierarchical scale-separation, with the AdS length exceeding the Kaluza-Klein length by a factor of a googol.

9/27/2021 Eran Palti (Ben Gurion) Title: Convexity of Charged Operators in CFTs and the Weak Gravity Conjecture

Abstract: In this talk I will introduce a particular formulation of the Weak Gravity Conjecture in AdS space in terms of the self-binding energy of a particle. The holographic CFT dual of this formulation corresponds to a certain convex-like structure for operators charged under continuous global symmetries. Motivated by this, we propose a conjecture that this convexity is a general property of all CFTs, not just those with weakly-curved gravitational duals. It is possible to test this in simple CFTs, the conjecture passes all the tests performed so far.

10/18/2021 Thomas Van Riet (KU Leuven) Title: The Festina Lente Bound

Abstract: I will explain what the Festina Lente bound means and where it comes from. Then I discuss its possible implications for  phenomenology, both top-down and bottom-up.

10/25/2021 Joe Conlon (Oxford) Title: Exploring the Holographic Swampland

Abstract: I describe our work looking at `traditional’ scenarios of moduli stabilisation from a holographic perspective. This reveals some interesting structure that is not apparent from the top-down perspective. For vacua in the extreme regions of moduli space, such as LVS in type IIB or the DGKT flux vacua in type IIA, the dual moduli conformal dimensions reduce to fixed values – in a certain sense, the low-conformal dimension part of the CFT is unique and independent of the large number of flux choices. For the DGKT flux vacua these conformal dimensions are also integer, for reasons we do not understand.

11/01/2021 Pieter Bomans (Princeton) Title: Bubble instability of mIIA on AdS_4 x S^6

Abstract: Recently, a set of non-supersymmetric AdS_4 vacua of massive type IIA string theory has been constructed. These vacua are perturbatively stable with respect to the full KK spectrum of type mIIA supergravity and furthermore, they are stable against a variety of non-perturbative decay channels. Hence, at this point, they represent a serious challenge to the AdS swampland conjecture. In my talk, I will review in detail the construction of these vacua as well as introduce a new decay channel, ultimately sealing their fate as being unstable.

11/15/2021 Nima Arkani-Hamed (IAS), and Gary Shiu (UW-Madison)  This week’s seminar will be an open mic discussion which will be led by Nima Arkani-Hamed (IAS), and by Gary Shiu (UW-Madison), and the topic will be Swampland constraints, Unitarity and Causality. They will start with a brief introduction sharing their thoughts about the topic and moderate a discussion afterwards.
11/22/2021 Thomas Grimm (Utrecht University) Title: Taming the Landscape

Abstract: In this talk I will introduce a generalized notion of finiteness that provides a structural principle for the set of effective theories that can be consistently coupled to quantum gravity. More concretely, I will propose a ‘tameness conjecture’ that states that all scalar field spaces and coupling functions that appear in such an effective theory must be definable in an o-minimal structure. The fascinating field of tame geometry has seen much recent progress and I will argue that the results can be used to support the above swampland conjecture. The strongest evidence arises from a new finiteness theorem for the flux landscape which is shown using the tameness of the period map.

11/29/2021 Timm Wrase (Lehigh University) Title: Scale separated AdS vacua?

Abstract: In this talk I will review massive type IIA flux compactifications that seem to give rise to infinite families of supersymmetric 4d AdS vacua. These vacua provide an interesting testing ground for the swampland program. After reviewing potential shortcomings of this setup, I will discuss recent progress on overcoming them and getting a better understanding of these solutions.

12/6/2021 Lars Aalsma (University of Wisconsin-Madison) Title: Extremal Black Hole Corrections from Iyer-Wald

Abstract: Extremal black holes play a key role in our understanding of various swampland conjectures and in particular the WGC. The mild form of the WGC states that higher-derivative corrections should decrease the mass of extremal black holes at fixed charge. Whether or not this conjecture is satisfied depends on the sign of the combination of Wilson coefficients that control corrections to extremality. Typically, corrections to extremality need to be computed on a case-by-case basis, but in this talk I will present a universal derivation of extremal black hole corrections using the Iyer-Wald formalism. This leads to a formula that expresses general corrections to the extremality bound in terms of the stress tensor of the perturbations under consideration, clarifying the relation between the WGC and energy conditions. This shows that a necessary condition for the mild form of the WGC to be satisfied is a violation of the Dominant Energy Condition. This talk is based on 2111.04201.