132 research outputs found
Superfluid to insulator phase transition in a unitary Fermi gas
We study the evolution of the energy gap in a unitary Fermi gas as a function
of temperature. To this end we approximate the Fermi gas by the Hubbard lattice
Hamiltonian and solve using the dynamical mean-field approximation. We have
found that below the critical temperature, Tc, the system is a superfluid and
the energy gap is decreasing monotonously. For temperatures above Tc the system
is an insulator and the corresponding energy gap is monotonously increasing.Comment: 4 pages,4 figure
Dynamical mean-field approximation for unitary Fermi gas
Dynamical mean-field approximation with explicit pairing is utilized to study
the properties of a two-component Fermi gas at unitarity. The problem is
approximated by the lattice Hubbard Hamiltonian, and the continuum limit is
realized by diluting the lattice. We have found that at zero temperature the
predictions of this theory for the energy and the pairing gap agree remarkably
well with the results of full numerical Monte-Carlo simulations. Investigating
the evolution of the system with temperature we identify the existence of a
second order phase transition associated with a jump in the heat capacity and
the collapse of the pairing gap.Comment: 4 pages, 3 figure
A microscopic calculation of neutrino neutral reaction on 4He
An ab-initio calculation of the inelastic neutral reaction of neutrino on 4He
is presented, including realistic nuclear force and full final state
interaction among the four nucleons. The calculation uses the powerful
combintation of the Lorentz integral transform (LIT) method and the
hyperspherical-harmonic effective interaction approach (EIHH). The neutrino -
nucleus interaction is taken in the impulse approximation. With respect to
previous calculations, the current work predicts an increased reaction
cross-section by 10%-30% for neutrino temperature up to 15 MeV.Comment: 3 pages, talk presented at the "19th European Conference on Few-Body
Systems (EFB2004)", Groningen, Netherlands, August 23 - August 27, 200
Low-Energy Inelastic Neutrino Reactions on 4He
The inelastic scattering of neutrino off 4He is calculated microscopically at
energies typical for core collapse supernova environment. The calculation is
carried out with the Argonne V18 nucleon--nucleon potential and the Urbana IX
three nucleon force. Full final state interaction is included via the Lorentz
integral transform (LIT) method. The contribution of axial meson exchange
currents to the cross sections is taken into account from effective field
theory of nucleons and pions to order O(Q^3).Comment: 5 pages, 1 figure, corrected typos and added reference, submitted to
Phys. Rev. Let
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