MPHQ Events

List of past and future MPHQ events

Speaker: Dr. Lucas Hackl

Geometry of variational methods

  • Date: May 24, 2019
  • Time: 11:00 - 11:25
  • Speaker: Dr. Lucas Hackl
  • MPHQ Postdoctoral Fellow
This talk was held by Dr. Lucas Hackl at the MPHQ Spring Scientific Meeting in Harvard. A key challenge in the theoretical study of quantum many body systems is to overcome the exponential growth of the Hilbert space with the system size. Many successful approaches are variational, i.e., they are based on choosing suitable families of states that capture key properties of the system. [more]

Geometric tangent plane methods and the Bose-Hubbard model

  • Date: Feb 21, 2019
  • Time: 12:00 - 14:00
  • Speaker: Dr. Lucas Hackl
  • MPHQ Postdoctoral Fellow
The paradigmatic Bose-Hubbard model describes interacting bosons which can be experimentally realized with ultracold atoms in optical lattices. In this talk, I will focus on the superfluid phase and introduce geometric methods to find approximate ground states and quasi particle excitations. For the variational class of Gaussian states, we can systematically extend Bogoliubov theory and compute quasi particle excitations, life times and spectral functions. To our surprise, we find a bound state below the continuum. Depending on the interaction strength, the dispersion relation of the bound state enters the continuum for large momentum. I will conclude with discussing observable effects and how we can test if this finding is physical. [more]
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