448 research outputs found
Spin Drag and Spin-Charge Separation in Cold Fermi Gases
Low-energy spin and charge excitations of one-dimensional interacting
fermions are completely decoupled and propagate with different velocities.
These modes however can decay due to several possible mechanisms. In this paper
we expose a new facet of spin-charge separation: not only the speeds but also
the damping rates of spin and charge excitations are different. While the
propagation of long-wavelength charge excitations is essentially ballistic,
spin propagation is intrinsically damped and diffusive. We suggest that cold
Fermi gases trapped inside a tight atomic waveguide offer the opportunity to
measure the spin-drag relaxation rate that controls the broadening of a spin
packet.Comment: 4 pages, 4 figures, submitte
A frame for a computer aided inspection planning system
Coordinate Measuring Machine (CMM) inspection planning is an activity performed by well-trained operators, but
different measurement techniques, using the same data analysis algorithms yield in different measurement results. This
is a well-recognized source of uncertainty in coordinate measurement. A CMM, provided with an automatic inspection
planning (CAIP) system, permits to implement more accurate and efficient operating procedures and to fit higher
quality assurance standards and tighter production timings.
In this paper we present a frame of a CAIP system, able to deal with almost all the decisional stages of CMM inspection.
Moreover, original approaches have been developed and presented in inspection feature selection, part set -up, probe
configuration, and path planning
Pseudospin Magnetism in Graphene
We predict that neutral graphene bilayers are pseudospin magnets in which the
charge density-contribution from each valley and spin spontaneously shifts to
one of the two layers. The band structure of this system is characterized by a
momentum-space vortex which is responsible for unusual competition between band
and kinetic energies leading to symmetry breaking in the vortex core. We
discuss the possibility of realizing a pseudospin version of ferromagnetic
metal spintronics in graphene bilayers based on hysteresis associated with this
broken symmetry.Comment: 5 pages, 4 figures; added figure 1, modified introduction and
discussion; updated reference
Robust Design of a Fixture Configuration in the Presence of form Deviations
During machining, the tool path is defined with respect to the workpiece reference frame. The workpiece's boundary surfaces have form deviations, and the geometry and the position of the locators are imperfect. The resulting misalignment produces geometrical errors in the features machined on the workpiece. The main purpose of this work is to investigate how the geometric errors of a machined surface are related to the main sources of the locator errors and to the form deviations of the workpiece. A mathematical framework is presented for an analysis of the relationship among the manufacturing errors, the part form deviations, and the locator errors
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