ITAMP Lunch Seminar Speaker: Michal Tomza, (Warsaw University) Date: Thursday, November 16th Time: 12:00-1:00 pm Includes Pizza. Title: Quantum-chemical approach to few-body quantum systems Abstract: In the first part I will present the application of the quantum-chemical coupled-cluster method to study the properties of a balanced two-component Fermi gas in a one-dimensional harmonic trap. For few fermions we recover the results of exact diagonalization, yet with this method we are able to study much larger systems. We compute the energy, the chemical potential, the pairing gap, and the density profile of the trapped clouds, smoothly mapping the crossover between the few-body and many-body limits. The energy is found to converge surprisingly rapidly to the many-body result for every value of the interaction strength. Many more particles are instead needed to give rise to the nonanalytic behavior of the pairing gap, and to smoothen the pronounced even-odd oscillations of the chemical potential induced by the shell structure of the trap In the second part I will present our investigations of two interacting ultracold polar molecules described as distinguishable quantum rigid rotors effectively trapped in a one-dimensional harmonic potential. The molecules interact via a multichannel two-body contact potential incorporating the short-range anisotropy of intermolecular interactions. The impact of external electric and magnetic fields resulting in Stark and Zeeman shifts of molecular rovibrational states is also included. The importance and interplay of the molecular rotational structure, anisotropic interactions, spin-rotation coupling, electric and magnetic fields, and harmonic trapping potential are examined in detail and compared to the system of two harmonically trapped distinguishable atoms. Presented model and results may provide microscopic parameters for molecular many-body Hamiltonians and may be useful for the development of bottom-up molecule-by-molecule assembled molecular quantum simulators. Location: B-106 @ Center for Astrophysics (60 Garden Street) Directions: After entering the lobby of the CfA, turn right to enter the hallway of the B building. In the hallway, turn right again, B-106 will be at the end of the hallway on the left side.