373 research outputs found
Neutron-Proton Mass Difference in Nuclear Matter and in Finite Nuclei and the Nolen-Schiffer Anomaly
The neutron-proton mass difference in (isospin asymmetric) nuclear matter and
finite nuclei is studied in the framework of a medium-modified Skyrme model.
The proposed effective Lagrangian incorporates both the medium influence of the
surrounding nuclear environment on the single nucleon properties and an
explicit isospin-breaking effect in the mesonic sector. Energy-dependent
charged and neutral pion optical potentials in the s- and p-wave channels are
included as well. The present approach predicts that the neutron-proton mass
difference is mainly dictated by its strong part and that it markedly decreases
in neutron matter. Furthermore, the possible interplay between the effective
nucleon mass in finite nuclei and the Nolen-Schiffer anomaly is discussed. In
particular, we find that a correct description of the properties of mirror
nuclei leads to a stringent restriction of possible modifications of the
nucleon's effective mass in nuclei.Comment: 10 pages, 8 figures, presentation at the 19th Int. IUPAP Conf. on
Few-Body Problems in Physics (Aug.31-Sep.5, 2009, Univ.of Bonn, Germany
Wave packet dynamics and valley filter in strained graphene
The time evolution of a wavepacket in strained graphene is studied within the
tight-binding model and continuum model. The effect of an external magnetic
field, as well as a strain-induced pseudo-magnetic field, on the wave packet
trajectories and zitterbewegung are analyzed. Combining the effects of strain
with those of an external magnetic field produces an effective magnetic field
which is large in one of the Dirac cones, but can be practically zero in the
other. We construct an efficient valley filter, where for a propagating
incoming wave packet consisting of momenta around the K and K' Dirac points,
the outgoing wave packet exhibits momenta in only one of these Dirac points,
while the components of the packet that belong to the other Dirac point are
reflected due to the Lorentz force. We also found that the zitterbewegung is
permanent in time in the presence of either external or strain-induced magnetic
fields, but when both the external and strain-induced magnetic fields are
present, the zitterbewegung is transient in one of the Dirac cones, whereas in
the other cone the wave packet exhibits permanent spatial oscillations.Comment: 13 pages, 10 figure
The description of dendriform algebra structures on two-dimensional complex space
In this paper, we classify all dendriform algebra structures on two-dimensional complex space. We distinguish twelve isomorphism classes (one parametric family and eleven concrete) of two-dimensional complex dendriform algebras, and show that they exhaust all possible cases
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