454 research outputs found
The longitudinal and transverse responses in the inclusive electron scattering: a functional approach
The splitting between the charge-longitudinal and spin-transverse responses
is explained in a model whose inputs are the effective interactions in the
particle-hole channels in the frame of the first order boson loop expansion. It
is shown that the interplay between -meson exchange and box diagrams
(two-meson exchange with simultaneous excitation of one or two nucleons to
's) mainly rules the longitudinal response, while in the transverse one
the direct excitations almost cancel the one-loop correction and the
response is mainly governed by the -meson rescattering inside the
nucleus. It is also shown that a small variation in the nuclear densities may
explain the observed discrepancies between different nuclei.Comment: LaTex2e file with 53 .ps figures; submitted to Nucl. Phys
Quantum Interference of Force
We show that a quantum particle subjected to a positive force in one path of
a Mach-Zehnder interferometer and a null force in the other path may receive a
negative average momentum transfer when it leaves the interferometer by a
particular exit. In this scenario, an ensemble of particles may receive an
average momentum in the opposite direction of the applied force due to quantum
interference, a behavior with no classical analogue. We discuss some
experimental schemes that could verify the effect with current technology, with
electrons or neutrons in Mach-Zehnder interferometers in free space and with
atoms from a Bose-Einstein condensate.Comment: 5 figures. Accepted in Quantum on 2018-12-0
Spin and rotational symmetries in unrestricted Hartree Fock states of quantum dots
Ground state energies are obtained using the unrestricted Hartree Fock method
for up to four interacting electrons parabolically confined in a quantum dot
subject to a magnetic field. Restoring spin and rotational symmetries we
recover Hund first rule. With increasing magnetic field, crossovers between
ground states with different quantum numbers are found for fixed electron
number that are not reproduced by the unrestricted Hartree Fock approximation.
These are consistent with the ones obtained with more refined techniques. We
confirm the presence of a spin blockade due to a spin mismatch in the ground
states of three and four electrons.Comment: 16 Pages, 2 figures, accepted for publication on New Journal of
Physic
INFESTATION RATE OF BRANCHIOBDELLIDS IN AUSTROPOTAMOBIUS PALLIPES ITALICUS FROM A STREAM OF CENTRAL ITALY: PRELIMINARY RESULTS
Species identity, infestation rate and distribution over the host body of branchiobdellids (Annelida, Clitellata) have been analysed in an Austropotamobius pallipes italicus population from the National Park of the Foreste Casentinesi, Monte Falterona and Campigna (central Italy). Branchiobdella italica - the nearly unique species present in our samples - did not differ in its occurrence among the size classes of its host, while female crayfish showed a significantly higher infestation rate than the other sex. Branchiobdellids were mostly found on gill chambers and cephalothorax base, and only in the case of larger crayfish and males did they occupy other body areas
Functional approach to the electromagnetic response function: the Longitudinal Channel
In this paper we address the (charge) longitudinal electromagnetic response
for a homogeneous system of nucleons interacting via meson exchanges in the
functional framework. This approach warrants consistency if the calculation is
carried on order-by-order in the mesonic loop expansion with RPA-dressed
mesonic propagators. At the 1-loop order and considering pion, rho and omega
exchanges we obtain a quenching of the response, in line with the experimental
results.Comment: RevTeX, 18 figures available upon request - to be published in
Physical Review
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