### Introduction

Currently there are two major mathematical challenges in theoretical physics: understanding the origins of elementary particles, and understanding cosmology. The standard model of particle physics as well as the standard model of cosmology are successful theories that correctly describe a vast amount of data. Within the Mathematical Foundations we are interested in various kinds of theoretical models like, dark energy, dark matter, teleparallel gravity, modified gravity, Einstein-Cartan theory, brane-world models, inflation and loop quantum gravity. We are also working in classical general relativity and cosmology.

**Dark Energy** -- is a way to model the observed accelerated expansion of the universe with scalar fields or other forms of vacuum energy. One of our main interest is how we can learn more about dark energy with observations. We are also a member of the Dark Energy Survey (DES) team.

**Modified Gravity** -- Dark Energy is not the only possibilty to explain the observed accelerated expansion of the Universe. Modifactions to Einstein's general relativity on large scales could be a valid explanation for the observations. We are investigating how to constrain such theories and how to distinguish them from Dark Energy with observations. We are a member of the COSMOS supercomputing consortium and are using this machine to test comsological models.

**Quantum Field Theory** -- The Standard Model of particle physics is based on the quantum field theories QCD, describing the strong force, and the electroweak theory which contains QED. We work on application of QCD to the physics at particle colliders, in particular on the Large Hadron Collider (LHC) recently turned on at CERN, with special emphasis on the theoretical understanding of quark and gluon distributions and implications for collider experiments.

### Links and connections

- Within the UCL Institute for Origins we have close links with the other departments. Last year we have started a String Theory reading group which was organised by Jochen Weller of the Department of Physics & Astronomy and Christian Boehmer of the Department of Mathematics. The reading group attracted many researchers from across the faculty and meets on a weekly basis.
- We have strong links with the Galaxies and Cosmology Group which is part of the Astrophysics Group within the Department of Physics & Astronomy at UCL. We use this opportunity to attend their weekly CosmoLunch to discuss most recent publications within the fields of Cosmology and Theoretical Astrophysics.
- There is active collaboration with our UCL colleagues at the Mullard Space Science Laboratory (MSSL), especially their theory group. With Kinwah Wu and Houri Ziaeepur we meet regularly and are working on joint projects.

### Current projects

- geometrical understanding of the Weyl Lagrangian
- exact solutions in
*f(R)*modified gravity - dark spinors in cosmology and gravitation
- anisotropic inflation models
- the interior of a black hole in loop quantum gravity
- dynamical dark energy models
- brane-world models and classical tests
- dark matter as a Bose-Einstein condensate
- large scale analysis of collider data to verify QCD descriptions and

extract parton distributions - resummations of perturbation theory at high energies
- study of the effects of mass for quark distributions

### Interested?

If you are interested in any of these projects and would like to get involved, please contact either Dmitri Vassiliev or Christian Boehmer of the Department of Mathematics, or Robert Thorne of the High Energy Physics group of the Department of Physics & Astronomy.

### Recent Papers

#### 2009

**Dark energy with dark spinors**

Christian G. Boehmer and James Burnett

0906.1351 [gr-qc]

** Bounds on 2m/r for static objects with a positive cosmological
constant**

Hakan Andreasson and Christian G. Boehmer

Classical and Quantum Gravity 26 (2009) 195007

0904.2497 [gr-qc]

**Stability of the Einstein static universe in modified Gauss-Bonnet
gravity**Christian G. Boehmer and Francisco S. N. Lobo

Physical Review D79 (2009) 067504

0902.2982 [gr-qc]

**Massless Dirac equation as a special case of Cosserat elasticity**

Olga Chervova and
Dmitri Vassiliev

0902.1268 [gr-qc]** **

**Stability analysis of Newtonian polytropes**

Christian G. Boehmer and Tiberiu Harko

0902.1054 [math-ph]

** Weyl's Lagrangian in teleparallel form**

James Burnett and
Dmitri Vassiliev

0901.1070 [gr-qc]

**Einstein static universes are unstable in generic f(R) models**

Sanjeev S. Seahra and
Christian G. Boehmer

Physical Review D79 (2009) 064009

0901.0892 [gr-qc]

#### 2008

**Dirac equation as a special case of Cosserat elasticity**

James Burnett,
Olga Chervova,
Dmitri Vassiliev

0812.3948 [gr-qc]

**Dark spinors with torsion in cosmology**

Christian G. Boehmer and James Burnett

Physical Review D 78 (2008) 104001

0809.0469v3 [gr-qc]

**Stability of the ****Schwarzschild Interior in Loop Quantum Gravity**

Christian G. Boehmer and Kevin Vandersloot

Physical Review D78 (2008) 067501

0807.3042 [gr-qc]

**Dark spinor inflation -- theory primer and dynamics**

Christian G. Boehmer

Physical Review D 77 (2008) 12353

0804.0616 [astro-ph]

**Dynamics of dark energy with a coupling to dark matter**

Christian G. Boehmer, Gabriela Caldera-Cabral, Ruth Lazkoz and Roy Maartens

Physical Review D 78 (2008) 023505

0801.1565 [gr-qc]

**Solar system tests of brane world models**

Christian G. Boehmer, Tiberiu Harko and Francisco S.N. Lobo

Classical and Quantum Gravity 25 (2008) 045015

0801.1375 [gr-qc]

#### 2007

**Dark Energy: back to Newton?**

Lucy Calder and Ofer Lahav

Astronomy & Geophysics journal of the Royal Astronomical Society 49 (2008) 1.13-1.18

0712.2196 [astro-ph]

**CMB Anisotropies and Inflation from Non-Standard Spinors**

Christian G. Boehmer, David F. Mota

Physics Letters B 663 (2008) 168

0710.2003 [astro-ph]

**Loop Quantum Dynamics of the Schwarzschild Interior**

Christian G. Boehmer and Kevin Vandersloot

Physical Review D76 (2007) 104030

0709.2129 [gr-qc]

**Dark matter as a geometric effect in f(R) gravity**

Christian G. Boehmer, Tiberiu Harko, Francisco S. N. Lobo

Astroparticle Physics 29 (2008) 386

0709.0046 [gr-qc]

**Update of Parton Distributions at NNLO**

A. D. Martin, W. J. Stirling, R. S. Thorne and G. Watt

Physics Letters B652 (2007) 292

0706.0459 [hep-ph]

**Can dark matter be a Bose-Einstein condensate?**

Christian G. Boehmer, Tiberiu Harko

JCAP 06 (2007) 025

0705.4158 [astro-ph]

**Nonparametric determination of the redshift evolution index of dark energy**

Haouri Ziaeepour

Modern Physics Letters A22 (2007) 1569

astro-ph/0702519

#### 2006

**A global fit to scattering data with NLL BFKL resummations**

C. D. White and R. S. Thorne

Physical Reviews D75 (2007) 034005

hep-ph/0611204

**Probing Modified Gravity by Combining Supernovae and Galaxy Cluster Surveys** J. Tang, J. Weller and A. Zablocki

astro-ph/0609028

**A teleparallel model for the neutrino**

Dmitri Vassiliev

Physical Review D75 (2007) 025006

gr-qc/0604011

**A variable-flavour number scheme for NNLO**

R. S. Thorne

Physical Review D73 (2006) 054019

hep-ph/0601245

**The Cosmological Parameters 2006**

Ofer Lahav and Andrew R Liddle

Journal of Physics G33 (2006) 1

astro-ph/0601168

This page was last modified 9 February 2009 by Christian Boehmer