### Conveners

#### Formal Field Theory and Strings

- Michele Cicoli (Università di Bologna)

#### Formal Field Theory and Strings

- Michael Ratz (UC Irvine)

We study the global structure of vacua of heterotic strings compactified on orbifolds T^4/Z_N in the presence of heterotic 5-branes. Gauge symmetry breaking associated with orbifold is described by instantons in the field theory. Phase transition between small instantons and heterotic 5-branes provides top-down, stringy account to the spectrum and modular invariance condition. Also it takes us...

In orbifold compactifications of heterotic string theory, the four-dimensional effective theory (like the gauge group and the particle spectrum) is fully determined by the so-called gauge embedding. However, it is difficult to see directly whether a given gauge embedding leads to "good" phenomenological properties of the resulting model (such as containing the Standard Model spectrum). In this...

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 K\"ahler potential which can stabilise the K\"ahler moduli. When a new Fayet-Iliopoulos term is included, it is also possible to generate the required number...

String compactifications with stabilised moduli and flat directions make it possible to

constrain the theory using phenomenological constraints or data. The base geometry

typically has many, analytically intractible, moduli fields and flux quanta that

characterise the kind of physics which could be explained. Numerical moduli stabilisation will facilitate the connection of Calabi-Yau data,...

In the quest of obtaining models with U(1) symmetries singlets with charges higher than 4 there is no systematic prescription from the point of view of F-theory. Following early work, where we worked out Sen's weak coupling limit for a family of F-theory standard models we now are able to systematically construct higher U(1) charge models in type IIB applying matrix factorization techniques,...

I will discuss certain long-standing features of the string landscape: the ubiquity of scalar and pseudoscalar fields, and the statistical bias towards a large SUSY breaking scale. In particular, scalars present the possibility of an early matter dominated era with important implications for dark matter, while the statistical draw towards large F-terms may be relevant for low-energy...

In the last couple of years it was discovered that some 4d N=1 quantum field theories flow in the IR to 4d N=2 superconformal field theories (often of generalized Argyres-Douglas type), therefore showing a phenomenon of Supersymmetry Enhancement at the IR fixed point. The N=2 IR theory is often non-lagrangian while the N=1 UV theory is lagrangian, therefore such flows are extremely useful to...

I will discuss tests of the weak gravity conjecture in the presence of supersymmetry breaking, performed in the framework of type I string theory with supersymmetry broken by compactification (à la Scherk-Schwarz). Such a (perturbative string theory) setting allows for the presence of runaway potentials (here for the compactification radius), which is the only possibility if one accepts the...

We argue that a new type of ultra light axion is generically present in the type IIB part of the string theory landscape. It arises when fluxes stabilize Calabi-Yau manifolds near a conifold transition locus in moduli space. After accounting for ten-dimensional backreaction the scalar potential features a finite axion monodromy with overall scale far smaller than the weak gravity conjecture...