35 research outputs found
Chiral Symmetry Restoration and Pion Interaction in Nuclear Matter
This paper is devoted to the interplay between p-wave, s-wave pion-nucleon/
nucleus interaction and in-medium pion-pion interaction with special emphasis
on the role of the nuclear pionic scalar density driving a large amount of
chiral symmetry restoration. In particular we show that the coupling
constant and the Goldberger-Treiman relation are preserved in the nuclear
medium within certain conditions. We also discuss the related problem of the
in-medium pion-pion strength function.Comment: 12 pages, Latex2e, 2 figures included as eps file
Polarized Fermi gases at finite temperature in the BCS-BEC crossover
We consider a polarized Fermi gas in the BCS-BEC crossover region above the
critical temperature within a T matrix formalism. By treating the mean-field
like shift of the quasiparticle energies in a self-consistent manner, we avoid
the known pathological behavior of the standard Nozieres-Schmitt-Rink approach
in the polarized case, i.e., the polarization has the right sign and the spin
polarizability is positive. The momentum distributions of the correlated system
are computed and it is shown that, in the zero-temperature limit, they satisfy
the Luttinger theorem. Results for the phase diagram, the spin susceptibility,
and the compressibility are discussed.Comment: 9 pages; v2: references and comparison with more recent experimental
data added; v3: reference added and minor correction
Role of fourth-order phase-space moments in collective modes of trapped Fermi gases
We study the transition from hydrodynamic to collisionless behavior in
collective modes of ultracold trapped Fermi gases. To that end, we solve the
Boltzmann equation for the trapped Fermi gas via the moments method. We showed
previously that it is necessary to go beyond second-order moments if one wants
to reproduce the results of a numerical solution of the Boltzmann equation.
Here, we will give the detailed description of the method including
fourth-order moments. We apply this method to the case of realistic parameters,
and compare the results for the radial quadrupole and scissors modes at
unitarity to experimental data obtained by the Innsbruck group. It turns out
that the inclusion of fourth-order moments clearly improves the agreement with
the experimental data. In particular, the fourth-order moments reduce the
effect of collisions and therefore partially compensate the effect of the
enhanced in-medium cross section at low temperatures.Comment: 10 pages, 2 figures; published versio
Linear response theory in asymmetric nuclear matter for Skyrme functionals including spin-orbit and tensor terms
The formalism of linear response theory for a Skyrme functional including spin-orbit and tensor terms is generalized to the case of infinite nuclear matter with arbitrary isospin asymmetry. Response functions are obtained by solving an algebraic system of equations, which is explicitly given. Spin-isospin strength functions are analyzed varying the conditions of density, momentum transfer, asymmetry, and temperature. The presence of instabilities, including the spinodal one, is studied by means of the static susceptibility
Linear response of homogeneous nuclear matter with energy density functionals
Response functions of infinite nuclear matter with arbitrary isospin asymmetry are studied in the framework of the random phase approximation. The residual interaction is derived from a general nuclear Skyrme energy density functional. Besides the usual central, spin-orbit and tensor terms it could also include other components as new density-dependent terms or three-body terms. Algebraic expressions for the response functions are obtained from the Bethe-Salpeter equation for the particle-hole propagator. Applications to symmetric nuclear matter, pure neutron matter and asymmetric nuclear matter are presented and discussed. Spin-isospin strength functions are analyzed for varying conditions of density, momentum transfer, isospin asymmetry, and temperature for some representative Skyrme functionals. Particular attention is paid to the discussion of instabilities, either real or unphysical, which could manifest in finite nuclei
Numerical solution of the Boltzmann equation for trapped Fermi gases with in-medium effects
Using the test-particle method, we solve numerically the Boltzmann equation
for an ultra-cold gas of trapped fermions with realistic particle number and
trap geometry in the normal phase. We include a mean-field potential and
in-medium modifications of the cross-section obtained within a T matrix
formalism. After some tests showing the reliability of our procedure, we apply
the method to realistic cases of practical interest, namely the anisotropic
expansion of the cloud and the radial quadrupole mode oscillation. Our results
are in good agreement with experimental data. Although the in-medium effects
significantly increase the collision rate, we find that they have only a
moderate effect on the anisotropic expansion and on frequency and damping rate
of the quadrupole mode.Comment: 11 pages, v2: minor correction
Skyrme N2LO pseudo-potential for calculations of properties of atomic nuclei
We present recent developments obtained in the so-called N2LO extension of the usual Skyrme pseudo-potential. In particular, we discuss the isovector splitting mass in infinite nuclear matter and the pairing gaps of selected semi-magic even-even nuclei
Linear response theory in asymmetric nuclear matter for Skyrme functionals including spin-orbit and tensor terms II: Charge Exchange
We present the formalism of linear response theory both at zero and finite
temperature in the case of asymmetric nuclear matter excited by an isospin flip
probe. The particle-hole interaction is derived from a general Skyrme
functional that includes spin-orbit and tensor terms. Response functions are
obtained by solving a closed algebraic system of equations. Spin strength
functions are analyzed for typical values of density, momentum transfer,
asymmetry and temperature