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...
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...
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...
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...
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...
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...
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...
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.
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 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...
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.
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...
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...
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...
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.
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...
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...
