# String and Beyond the Standard Model Phenomenology

# Sample PhD Projects

### General Interests

Collider phenomenology, string phenomenology, Euclidean supersymmetry; Brane intersections; phenomenological and cosmological implications, quantum mechanics.

### Professor Alon Faraggi

**1. Perturbative string model building and phenomenological implications**

Systematic classification of heterotic string vacua in the free fermionic formulation. Analysis of string vacua at finite temperature and cosmological scenarios.

**2. Phenomenology and cosmology of physics beyond the Standard Model**

Extracting phenomenological signatures from string models and how they will be seen in contemporary collider and astrophysics experiments. Examples include novel Z' scenarios and dark matter candidates.

**3. Perturbative and non-perturbative dualities in string theory**

At present the main focus is spinor-vector duality in heterotic string compactifications, and understanding the geometrical realisation and implications of this duality.

**4. Foundations of quantum gravity**

Application of the equivalence postulate approach to quantum mechanics for the formulation of quantum gravity and exploration of its phenomenological consequences.

### Dr Ed Hardy

Projects are available in the following areas:

**1. Dark Matter: Axions and Glueballs**

**2. Finite temperature QFT and astrophysical constraints on new light particles**

**3. New Approaches to the hierarchy problem**

**4. Heterotic String theory and its phenomenology**

### Dr Thomas Mohaupt

**1. Exact Solutions of Supergravity Theory and their Embedding into String Theory**

The goal of this project is the construction and study of exact solutions of N=2 supergravity with matter multiplets. Possible directions to explore include: Construction of solutions using special geometry, in particular its real version based on the Hesse potential, and dimensional reduction. Exploration of integrable structures, in particular Riemann-Hilbert problems. Stringy symmetries and dualities. Study of geometrical and thermodynamical properties. Event horizons and laws of black hole mechanics. Black hole attractor mechanism and its generalization. Cosmological solutions with late time acceleration. Relation to AdS/CFT correpondence, information-theoretic concepts such as entanglement entropy, and swampland conjectures.

**2. Geometrical Structures in Supergravity and String Theory**

The goal of this project is to explore the geometrical structures manifesting themselves in supergravity and string theory, starting from the so-called special geometry of vector and hypermultipletes coupled to N=2 supergravity.

Possible directions to explore include: the formulation of theories for space-times of arbitrary signature (Euclidean and multiple time), their relation to string dualities such as time-like T-duality and to string/M-theory with exotic space-time signatures (type-II-star, M-star and M-prime). Inclusion of higher curvature terms (Weyl multiplet), generalizations of special geometry, and relation to the topological string. Para-complex geometry and its relation to generalized/doubled geometry and field theory. Hidden structures of supergravity and string theory. Global geometric formulation of supergravity theories, global structure of moduli spaces arising in supergravity, in particular completeness and quantum corrections.

### Dr Radu Tatar

**1. F-theory compactification and phenomenology implication**

In this project, we consider F-theory as a non-perturbative formulation of string theory and look at various compactifications to 4 dimensions which offer avenues to explore interesting phenomenolgy results like Yukawa couplings, supersymmetry breakings. The study of compactification manifolds implies detailed exploration of interesting topics in algebraic and differential geometry.

**2. Brane Configurations and dualities in field theories**

In this projects we discuss various electric-magnetic dualities in field theories and their relation to relevant brane configuration. This leads to getting interesting data about both field theories and string theories. The study also involves the T-dual transition to a pure geometrical picture where the field theory dualities become geometrical transitions.

**3. Application of AdS/CFT duality**

In this projects we consider application of the AdS/CFT duality which relates field theory results and string theory computations. The geometrical and gravitational perturbations are mapped into deformation of the field theory away from conformal regions and into area of interest of condensed matter physics like the non-Fermi liquids.

### Dr Susha Parameswaran

**1. String theory models of early Universe cosmic inflation and late time dark energy**

An epoch of accelerated expansion in the early Universe solves several cosmological problems and provides the seeds for the large scale structure of the Universe. This inflationary dynamics is extremely sensitive to contributions from quantum gravity, and thus presents both a challenge and opportunity to connect quantum gravity to cosmological observations. We will study the implications of stringy physics on inflation, with a particular focus on how the generic predictions of string theory -- including light moduli, axions and features in the scalar potential driving inflation -- may leave imprints on cosmological observations. This will involve techniques ranging from formal mathematical aspects of string compactifications to numerical studies of cosmological perturbations. Quintessence models of late time dark energy are similarly sensitive to quantum gravity effects, and we will study stringy candidates such as string axions.

**2. Supersymmetry breaking, moduli stabilisation and vacuum energy in string compactifications**

Supersymmetry is extremely well motivated both from string theory and low energy physics, such as the gauge hierarchy problem and unification of gauge couplings. However, if it is an underlying symmetry of Nature, it must be broken, at energy scales anywhere between TeV and the Planck scale. In string compactifications, supersymmetry breaking is usually connected to moduli stabilisation and the vacuum energy. We will develop low energy effective field theory descriptions of string compactifications with spontaneously broken symmetry, and explore their implications for particle physics and cosmology.

**3. The post-inflationary epoch**

At the end of inflation, energy should be transferred to the standard model degrees of freedom and dark matter through a process known as (p)re-heating. (P)reres-heating requires a complete theory of all the degrees of freedom at the given energy scale, which string theory can -- in principle -- provide. We will develop string models that work towards this objective and also study stringy aspects of the reheating phase and dark matter production, and how these constrain string compactifications.