Neil Barnaby's Homepage

I'm a theoretical physicist, currently working at the University of Cambridge in the Department of Applied Mathematics and Theoretical Physics (DAMTP).

For more details, see my CV.

Research Interests

I'm interested in cosmology, quantum field theory and high energy particle physics. A key unifying theme in my research is the idea that cosmological observations can provide a rare observational window into fundamental physics at very high energy scales.

The bullets below give a sampling of some of the specific subjects I've worked on recently; my papers are available here.

• Cosmology: early universe physics, inflation, cosmological perturbation theory, nongaussianity and features in the CMB and LSS, gravitational waves, preheating/reheating, modified gravity, cosmic defects, string cosmology, ...
  
  

• Quantum Field Theory: non-equilibrium dynamics, external backgrounds, particle production, instabilities, nonlocal and higher derivative theories, ...
  
  

• String Theory: tachyon condensation, inflationary model building, ...
  
  

• Mathematical Physics: infinite order differential equations, pseudo-differential operators, ...
  
  

• Other: phase transitions, dynamics of bubbles, ...

Movies and Visualization

The movie above demonstrates the production of inhomogeneities during preheating after string theoretic modular inflation. On the left hand side is a 2D slice through the inflaton field configuation. On the right we illustrate the dynamics of the spatially averaged inflaton as a ball rolling along the potential. The rapid oscillations of the condensate about the sharp minimum of the potential lead to a very efficient form of preheating (probably this is the most violent preheating process in the literature). See this paper for the original research.

The movie above illustrates the production cosmological fluctuations in models with particle production during inflation. The left panel is a 2D slice through the inflaton field configuration while the right panel shows the iso-inflaton field. You can see the initial growth of iso-inflaton fluctuations (due to particle production) which is followed by a longer phase of rescattering. The produced iso-inflaton particles undergo multiple rescatterings off the slow roll condensate, leading to a cascading of power into long wavelength inflaton fluctuations (IR cascading). These secondary inflaton fluctuations cross the horizon and "freeze in," leading to observable features and nongaussianity in the CMB. See this paper for the original research.

DAMTP Journal Club

I'm currently organizing the DAMTP journal club, go here for the journal club webpage.