Completeness of the spectrum of charged branes in a quantum theory of gravity naturally motivates the question of whether consistency of what lives on the branes can be used to explain some of the Swampland conditions. In this paper we focus on consistency of what lives on string probes, to show some of the theories with N=(1,0) supersymmetry in 10d and 6d, which are otherwise consistent...

In its mildest version, the Weak Gravity Conjecture postulates the existence of superextremal particles of any charge Q. This is not really a constraint on the low-energy EFT, since this charge could a priori be arbitrarily large, resulting in a very massive WGC particle. This applies to (quasi-)sublattice versions of the conjecture too, where the role of Q is played by the index of the WGC...

Compactifications of Heterotic theories on Calabi-Yau manifolds have a Chern-Simons like contribution to their four dimensional superpotential. In this talk I will discuss some aspects of computations and general theory behind understanding this often ignored contribution to the effective theory of such constructions.

Gravitational waves can be a powerful probe of cosmology, both for what concerns the late-time and the very early universe. I will present the main reasons why and provide some examples, in particular in the context of the space-based interferometer LISA.

I will discuss recent attempts to describe dark energy, including quintessence, using string theory.

I will critically analyze the de Sitter construction of KKLT using ten-dimensional supergravity.

The R-parity violating decays of Wino Chargino and Bino Neutralino LSPs are analyzed within the context of the B-L MSSM. These LSPs correspond to statistically determined soft supersymmetry breaking parameters which, when renormalization group evolved to lower energy, lead to an effective theory satisfying all phenomenological requirements. The explicit RPV decay channels of these LSPs to...

I present some recent progress in formulating new swampland criteria.

While string theory was believed to have a landscape of de Sitter vacua, the recent swampland conjectures postulate that metastable de Sitter vacua are in the swampland. In this talk I will focus on what seems to be the most solid and generic construction of de Sitter vacua in string theory, that of KKLT, and show the multiple reasons why it might be in the swampland.

Three different issues will be discussed and explicitly exemplified that are related to the dS swampland conjecture and are motivated by the questions: Does it hold away from the perturbative regime? What are the logical consequences if it is true? Can one broaden the perspective to circumvent the dS no-go consequences?

I will argue that D-branes provide an interesting ingredient for constructing and understanding non-supersymmetric string theory compactifications. D-branes break supersymmetry spontaneously. This can lead to setups with non-linearly realized supersymmetry. This non-linear symmetry is still constraining the action, can be sufficient to derive renormalization theorems and therefore gives...

The problem of moduli stabilisation and inflation are discussed in type IIB/F-theory. Considering a configuration of three intersecting D7 branes with fluxes, it is shown that higher loop effects induce logarithmic corrections to the Kaehler potential which can stabilise the Kaehler moduli. When a new Fayet-Iliopoulos term is included, it is also possible to generate the required number of...

In this talk, we present whether the new ekpyrotic scenario can be embedded into ten-dimensional supergravity. We use that the scalar potential obtained from flux compactifications of type II supergravity with sources has a universal scaling with respect to the dilaton and the volume mode. Similar to the investigation of inflationary models, we find very strong constraints ruling out ekpyrosis...

In this talk we will investigate the Swampland Distance Conjecture in type IIB string theory compactified on K3 x T2. As conjectured one indeed finds a tower of exponentially light states using the Hodge-Deligne splitting of the middle homology in the degeneration limit. This tower, however, consists of quarter-BPS states, which can potentially decay into a pair of half-BPS states at walls of...

We discuss imposing physical constraints on the recently generated Kreuzer-Skarke Axiverse, namely the application of mass limits coming from black hole superradiance. We briefly touch on how our approach can also be applied to other physical limits on axion masses and decay constants to rule out previously viable string backgrounds.

We show how in a matrix inflationary model, in which there is a non-minimal coupling between the matrix inflatons and gravity and we call non-$\mathbb{M}$-flation for brevity, some of the disadvantages of the minimal model, $ \mathbb{M}$-flation, can be avoided. In particular, the number of D3 branes can be reduced to $\leq \mathcal{O}(10^2)$ which can alleviate the ``potential'' backreaction...

The Swampland Distance Conjecture (SDC) states that an infinite tower of modes becomes exponentially light when approaching a point at infinite distance in moduli space. At the large volume singularities of the Kähler moduli spaces of Calabi-Yau threefold compactifications, we use the monodromy matrices to explicitly construct the towers of states satisfying the SDC, which consist of charge...

We study Noether symmetries in two-field cosmological alpha-attractors, investigating the case when the scalar manifold is an elementary hyperbolic surface. This encompasses and generalizes the case of the Poincare disk. We solve the conditions for the existence of a `separated' Noether symmetry and find the form of the scalar potential compatible with such, for any elementary hyperbolic...

We investigate the possibility of Moduli mediators between the visible and hidden sector in the context of the LVS.

String theory suggests a unique and unambiguous augmentation of General Relativity, in which the entire closed-string massless NS-NS sector is promoted to stringy graviton fields. O(D,D) T-duality then uniquely fixes the coupling of this 'Stringy Gravity' to other matter, leading to a generalization of Einstein's equations with an enhanced energy-momentum tensor. In this talk I will explore...

I will discuss axionic holographic RG flow solutions in the context of general Einstein-Axion-Dilaton theories, where a non-trivial axion profile is dual to the (non-perturbative) running of the theta-term for the corresponding instanton density operator. I will show that a non-trivial axion solution is incompatible with a non-trivial (holographic) IR conformal fixed point. Imposing a suitable...

I will talk about a new scenario for generating a relic density of non-relativistic dark matter in the framework of heterotic string theory with spontaneously broken supersymmetry and at finite temperature. In this scenario, contrary to the standard thermal freeze-out process, dark-matter particles are produced while they are still relativistic and then decouple from the thermal bath because...

The Swampland Distance Conjecture states that at infinite distance in the scalar moduli space an infinite tower of particles becomes exponentially massless. In the context of 4d Calabi-Yau compactifications we find that not only towers of particles, but also towers of strings and domain walls generally become tensionless at different infinite distance points. For $\mathcal{N}=1$ Calabi-Yau...

Recent swampland conjectures highlight again the importance of finding viable scenarios for inflation that are not strictly single-field. In particular, one may wonder whether there are multi-field inflationary scenarios that have a similar phenomenology to single field inflation. We present a family of exact models of inflation - dubbed Orbital Inflation - in which the multi-field effects are...

We investigate the swampland distance conjecture (SDC) in the complex moduli space of type II compactifications on one-parameter Calabi-Yau threefolds. This class of manifolds contains hundreds of examples and, in particular, a subset of 14 geometries with hypergeometric differential Picard-Fuchs operators. Of the four principal types of singularities that can occur — specified by their...

We show that warped throats of the Klebanov-Strassler kind describe fully backreacted solutions of transplanckian axion monodromy. We show that the asymptotic Klebanov-Tseytlin solution features a 5d axion physically rolling through its dependence on an spatial coordinate, and traversing arbitrarily large geodesic distances in field space. We establish the description of the system in terms of...

Demanding unitarity of correlators can put severe constraints on the allowed spectra of SCFTs. We discuss such constraints in the context of half-BPS operators in six dimensions using the conformal bootstrap and possible lower bounds on central charges one gets for theories with flavour. In particular we relate these bounds with results from F-theory and the size of its swampland.

Axionic objects such as axion miniclusters and axion clouds around spinning black holes induce parametric resonances of electromagnetic waves through the axion-photon interaction. Here we discuss various difference gravitational sources from such objects through similar mechanisms.

We consider a cosmological inflation scenario based on a no-scale supergravity sector with U(1)R symmetry. It is shown that a tree level U(1)R symmetric superpotential alone does not lead to a slowly rolling scalar potential. A deformation of this tree level superpotential by including an explicit R symmetry breaking term beyond the renormalizable level is proposed. The resulting potential is...

Holography allows a mechanism for the self-tuning of the cosmological constant by considering a universe brane embedded in a bulk dual to a holographic QFT. This mechanism was shown recently to work bypassing earlier problems with bad bulk singularities. By including also a bulk axion (dual to an instanton density of the holographic QFT), we consider the interplay of the self-tuning mechanism...

I will discuss the the production of gravitational waves which are sourced by the tensor perturbation of SU(2) gauge fields coupled to a spectator axion field. Even though string theory constructions provide a variety of potentials, they can be categorized based on the number of non-stationary inflection points. I will present the resulting GW templates arising from each potential type. I will...

We will consider the construction of 5d superconformal field theories by studying M-theory compactified on a non-compact Calabi--Yau threefold, which is related to the elliptically fibered Calabi--Yau threefold that, in F-theory, constructs the 6d SCFT that circle reduces to said 5d SCFT. We explain how many interesting features of 5d SCFTs, like flavour symmetry enhancement, arise from the...

An anti-D3-brane plays a crucial role in the construction of semi-realistic cosmological models in string theory. Part of its action provides an uplift term that has been used to lift AdS solutions to phenomenological viable dS vacua in the KKLT and LVS setups. This uplift breaks supersymmetry spontaneously and it can be described in the 4d N=1 supergravity language by using non-linear...

We formulate a six dimensional U(1) gauge theory compactified on a (two dimensional) sphere S^2 with flux and localized brane sources. Profiles of the lowest Kaluza-Klein (KK) wavefunctions and their masses are derived analytically. In contrast to ordinary sphere compactifications, the above setup can lead to the degeneracy of and the sharp localizations of the linearly independent lowest KK...

The IKKT model is proposed as a non-perturbative formulation of superstring theory. I consider the magnetized toroidal compactifications of the IKKT model. I find that the chirality and the generation structure are almost same with the magnetized toroidal compactifications of the super Yang-Mills theory. In addition, I compute the Yukawa couplings including a noncommutative parameter. In...

I will discuss the results in hep.th/1810.07673. A local version of the no non-SUSY-AdS conjecture is proposed for warped throats. This essentially bans warped throats with a gravitational dual that locally looks AdS. Several examples are given.

I will argue that global 4d F-theory models generically exhibit holomorphic Yukawa matrices of higher rank. In a toy model, where one can explicitly compute all contributions to one type of couplings, the eigenvalues are shown to develop large hierarchies for generic complex structure moduli.

In this talk, we show that in orbifold GUT models discrete symmetries can be understood as remnants of gauge symmetries that are broken by orbifold boundary conditions. We present a systematic way to determine the discrete symmetries that survive the orbifolding. In particular, we derive universal conditions that need to be fulfilled in order to preserve any discrete symmetry. Finally, some...

We present a systematic study of F-theory on smooth elliptic quotient threefolds. We show that general anomaly cancellation in the 6d SUGRA theory is satisfied upon the addition of additional discrete charged superconformal matter. The quotient generically also breaks the gauge symmetry to a discrete one. We use this method to study an order 6 example explicitly constructed via a quotient of a...

A typical feature of 4D string models is the presence, at tree-level, of a plethora of massless fields called moduli. Some of them are axion-like fields which become massive only via tiny non-perturbative effects which tend to make them naturally very light. When these fields live on a curved manifold a geometrical destabilisation of the inflationary trajectory can be induced since the growth...

We analyse type IIA Calabi-Yau orientifolds with background fluxes and D6-branes. Rewriting the F-term scalar potential as a bilinear in flux-axion polynomials yields a more efficient description of the Landscape of flux vacua, allowing for a systematic search of vacua. We classify families of N= 0 Minkowski, N = 1 AdS and N = 0 AdS flux vacua, extending previous findings in the literature to...

I will briefly describe the classification approach within the free fermionic formalism, then discuss techniques beyond the random generation classification. In particular, explorations of 'fertile regions' within left-right symmetric models that are pre-selected at the SO(10) level for phenomenological favourability. Finally, we will discuss the application of machine learning techniques...

We consider compactifications of M-theory on 7-dimensional manifolds with G2 holonomy and focus on gauge theory sectors that are built as 3-manifolds of ADE singularities. We build novel gauge theory configurations that involve non-commuting normal deformations as well as gauge theory magnetic fluxes and provide methods to detect the presence of localised zero modes that can descend to chiral...

I will discuss relations between the Swampland distance

conjecture, and its generalisations, and potentials in string theory.

I will discuss instances in which discrete identifications in field space (discrete symmetries, dualities and monodromies) interplay with the swampland conjectures.

We discuss how tools from information theory combined with machine learning a direct map from the microscopic parameters of a string inflation mechanism to the CMB observables allows us to systematically estimate the observable footprint of the theory uncertainty. We demonstrate this using the example mechanism of single-field axion monodromy inflation. We find that inflation acts as an...

After a brief summary of some recent work on flat axionic potentials in the regime of subplanckian decay constants, I will turn to the controversial topic of a 10d description of the KKLT scenario. In particular, I will outline a proposal for completing the coupling of D7-brane gauginos to bulk fields. Building on this, I will then argue that the analysis of 10d Einstein equations appears to...

I review ideas related to the landscape of string vacua and restrictions it suggests on the existence of consistent quantum gravitational theories known as swampland conditions. Some implications for particle physics and cosmology are discussed.

We study three topics concerning the role of scalars and the distance conjecture in the Swampland program. First we discuss a Scalar Weak Gravity Conjecture (SSWGC). Solutions for the corresponding extremal equation are compatible with towers of winding and momenta states becoming massless for large fields. We show that this SSWGC implies the refined dS conjecture under certain particular...

There has been progress in recent years on how to include backreacted O-planes in flux compactifications. After a quick review of such solutions in AdS, I will discuss the current situation for de Sitter.

Whether string theory admits a multiverse of de Sitter solutions that look approximately like our universe is a hotly debated current topic. I will overview the basics of landscape constructions and explain my view on this question. I will also outline a possible construction of de Sitter solutions.

An artificial intelligence agent known as an asynchronous advantage actor-critic is utilized to explore type IIA compactifications with intersecting D6-branes. By reinforcement learning, the agent's performance in satisfying string consistency conditions, and finding Standard Model like configurations, is significantly improved. In one case, we demonstrate that the agent learns a human-derived...

Dualities play a key role in our understanding of dynamical systems appearing in effective field theories from string theory and in general in fundamental physics. Dualities in field theory and string theory are a tool to obtain models describing data at a precision beyond a level standard effective field theory techniques allow. At this stage these techniques are not used explicitly in...

We analyze infrared consistency conditions of 3D and 4D effective field theories with massive scalars or fermions charged under multiple U(1) gauge fields. At low energies, one can integrate out the massive particles and thus obtain a one-loop effective action for the gauge fields. In the regime where charge-independent contributions to higher-derivative terms in the action are sufficiently...

We propose quantum states for Little String Theories arising from M5 branes probing A- and D-type singularities. This extends Witten's picture of M5 brane partition functions as theta functions to this more general setup. Compactifying the world-volume of the five-branes on a two-torus, we find that the corresponding theta functions are sections of line bundles over complex 4-tori. This...

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. This conifold destabilization mechanism...

Non-perturbative effects were long ago proposed to be useful for supersymmetric moduli stabilization in Type II string theory compactifications. Their use has been widely studied from the 4D perspective but from the 10D perspective this mechanism is not completely understood. By performing a 10D analysis I will show some features of the mechanism, confirming some old 4D results as well as...

The proposal for a new Swampland conjecture forbidding stable non-supersymmetric "locally AdS" warped throats, which generalizes the Swampland criterion forbidding stable non-supersymmetric AdS vacua, is discussed. The conjecture is motivated by the properties of systems of fractional D3-branes at singularities, and can be used to rule out large classes of warped throats with supersymmetry...

The spaces of zero-energy configurations (moduli spaces of vacua) of supersymmetric QFTs are richly geometrically structured. Realizing quiver gauge theories as the IR descriptions of brane configurations has allowed the recent development of numerous techniques to examine this geometry. I will discuss some of these techniques and how they can be used to investigate the local geometry of...

Gaugino condensation plays a prominent role in many approaches to constructing dS vacua in string theory. While its analysis is generally performed in the low energy 4d EFT, a 10d perspective can be useful to understand possible constraints on dS uplifts. I will discuss aspects of gaugino interactions localized to D7 branes in type IIB theories, and some insights these provide for KKLT constructions.

The KKLT scenario in a warped throat, if consistent, provides a concrete counterexample to both the AdS scale separation and the dS swampland conjectures. In this talk I will analyze the relevant effective field theory for the conifold modulus and the overall Kahler modulus that both have exponentially small masses. In particular, I will focus on KK modes that have masses below the mass scale...

This talk will be divided into two parts. In the first part, I focus on the attempt to construct effective axions with parametrically large decay constants in type IIB string models summarising work with A. Hebecker and D. Junghans (arXiv: 1812.05626). I argue that such axions can be realised as long winding trajectories in complex-structure moduli space by an appropriate flux choice. The...

We argue that ten-dimensional consistency requirements in the form of a certain tadpole cancellation condition can be satisfied by KKLT type vacua of type IIB string theory. The stress caused by the restoring force that the stabilization mechanism exerts on the volume modulus once supersymmetry gets broken can be seen to ensure this dynamically. However, we also explain that it is surprisingly...

The recent swampland conjectures have ruled out some of the simplest models of single-field inflation. Inspired by the distance conjecture and the high-slope conjecture, I will present two families of multi-field inflationary potentials compatible with the conjectures along the trajectory. One family is a helix-type potential that satisfies the conjectures only locally. This family inflates...

The axion Weak Gravity Conjecture implies that when parametrically increasing axion decay constants, instantons corrections become increasingly important. In this talk I will discuss evidence for this statement, obtained by studying the couplings of axions that arise in Type IIA Calabi-Yau compactifications. To be more precise, I will discuss the asymptotic behavior of these couplings as one...

I discuss the properties of massive type IIA flux compactifications. In particular, I will talk about in which cases one can obtain dS vacua at large volume and small coupling. The scaling symmetries will also be discussed in a concrete example. The conclusion of the talk will be that the large volume and weak coupling limit requires a large number of O6-planes. Since these are bound for any...

One of the main contributors to the vastness of the string landscape is the immense number of Calabi-Yau (CY) manifolds on which the theory can be compactified. Currently, one of the largest sets of CYs is obtained from hypersurfaces in toric varieties, which result from fine, regular, star triangulations (FRSTs) of reflexive polytopes. In this talk I will present new developments in the study...

I will present a four-dimensional consistent truncation of type IIA supergravity in the presence of fermionic condensates generated by gravitational instantons. The condensates are controlled by the ratio of the characteristic length of the internal Calabi-Yau to the string length, and can be fine-tuned to be dominant in a region of large volume and small string coupling. The consistent...

We consider geodesics of infinite length in the (classical) hypermultiplet moduli spaceof type II Calabi-Yau compactifications. When approaching such infinite distance points, a large amount of D-instantons develop an exponentially suppressed action ,substantially modifying the moduli space metric. In the corrected metric the path length becomes finite, although the metric at its endpoint...

I will discuss the relations between swampland conjectures and observational constraints on both inflation and dark energy. Using the fact that the constant c appearing in the de Sitter conjecture is a universal constant whose value can be determined from inflation, there may be no observable distinction between constant and non-constant models of dark energy. However, the latest modification...

Hitchin systems and Higgs bundles have recently been used to understand local aspects of M-theory compactifications on G2 manifolds. I will consider a similar approach from the heterotic point of view, using the heterotic/M-theory duality. Specifically, I will study alpha' corrections to the reduced heterotic system using the Hull-Strominger system. I will present some explicit solutions and...

The de Sitter swampland conjecture would be falsified if classical fluxed Type IIA orientifold vacua with a single non-BPS D7-brane were indeed part of the string theory landscape. In other words, the dS swampland conjecture implies the cancellation of K-theory charges on a compact space.

In this talk, we discuss the significance for inflation of the Swampland Distance Conjecture, a proposal for a quantum gravity constraint acting at infinite distances.

It was shown that the majority of Weierstrass models in the 6D/4D F-theory landscape are non-minimal. Physically, these 6D/4D supergravity models are coupled to strongly coupled matter sectors, such as 6D (1,0) SCFTs and their compactifications. In this talk, I will focus on the particle spectrum of these sectors and their physical consequence.

We argue that a new type of extremely light axion is generically present in the type IIB part of the string theory landscape. Its mass is suppressed by the third power of the warp factor of a strongly warped region (Klebanov-Strassler throat), suggesting the name thraxion. Our observation is based on the generic presence of several throats sharing the same 2-cycle. This cycle shrinks to zero...

My talk is a brief account of the increasing body of evidence that line bundle cohomology can be computed in terms of analytic formulae. Our experimental results include spaces such as complete intersections in products of projective spaces (in particular Calabi-Yau threefolds), toric varieties, hypersurfaces in toric varieties and del Pezzo surfaces. Machine learning plays an important role...

Non-perturbatively generated effective potentials play an extremely useful, often critical, role in string and inflationary model building. These potentials are typically computed by Euclidean methods (i.e. instantons) which assume the system is in equilibrium. For systems out of equilibrium---for instance, an inflaton rolling down its potential---we expect there are corrections to the...

Consistent string theory frameworks of quantum gravity often predict the existence of a plethora of ultralight pseudoscalar degrees of freedom forming the phenomenological landscape of the string axiverse. The complexity of the extra-dimensional compactification manifold and vacua in these models indicate these fields may well possess parameters spanning many decades, covering cosmologically...

I will describe a large scale study of Calabi-Yau hypersurfaces in toric varieties. We construct large ensembles of O(10^7) Calabi Yau hypersurfaces and study key topological properties such as intersection numbers, cones of effective curves and divisors, and fibration structures. I will describe how the properties of a generic hypersurface scale with the Hodge numbers and discuss some of the...

I will discuss four-dimensional N=1 supergravity models including 3-form potentials and membranes. These provide a general framework to describe the EFTs of string/M-theory compactifications to four dimensions, in which (part of) the internal flux quanta arise as expectation values of the 4-form field-strengths and large portions of the landscape can be explored within a single EFT. The...

Anomalies are a powerful probe of the dynamics of field theories. In this talk I will discuss how to connect different anomalies in various dimensions, and describe some applications of these ideas in string model building.

We present key steps in explicit construction of a globally consistent F-theory compactifications with the exact chiral spectrum of the Standard Model with gauge coupling

unification. All global consistency conditions can be reduced to a single geometric criterion on the base of the underlying elliptically fibered Calabi Yau fourfolds. For toric bases, this criterion only depends on an...

I argue that the ten dimensional non--supersymmetric tachyonic superstrings may serve as good starting points for the construction of viable phenomenological vacua. Thus, enlarging the space of possible solutions that may address some of the outstanding problems in string phenomenology. A tachyon free six generation Standard--like Model is presented, which can be regarded as an orbifold of the...

In this talk I discuss various aspects of higher spin theories in the context of the swampland.

We investigate string models with broken supersymmetry from the viewpoint of swampland conjectures.

We develop a new method to determine flavor symmetries within compactified string theory. A picture emerges where traditional (discrete) flavor symmetries, CP-like symmetries and modular symmetries combine to a unified flavor group. We observe the phenomenon of "local" flavor symmetries (with non-universality for various sectors of the theory) that opens up a new arena for flavor model building.