10,740 research outputs found
Quark-Meson Coupling model based upon the Nambu-Jona Lasinio model
The NJL model for the octet baryons, using proper time regularization to
simulate some of the features of confinement, is solved self-consistently in
nuclear matter. This provides an alternative framework to the MIT bag model
which has been used in the quark-meson coupling model. After fitting the
parameters of the model to the saturation properties of symmetric nuclear
matter the model is used to explore the equation of state of pure neutron
matter as well as nuclear matter at densities relevant to heavy ion collisions.
With a view to future studies of high mass neutron stars, the binding of
hyperons is also explored.Comment: 7 pages and 4 figure
R-Band Imaging of Fields Around 1<z<2 Radiogalaxies
We have taken deep -band images of fields around five radiogalaxies:
0956+47, 1217+36, 3C256, 3C324 and 3C294 with . 0956+47 is found to
show a double nucleus. Our data on 1217+36 suggest the revision of its
classification as a radiogalaxy. We found a statistically significant excess of
bright () galaxies on scales of 2 arcmin around the radiogalaxies
(which have ) in our sample. The excess has been determined
empirically to be at level. It is remarkable that this excess
is not present for galaxies within the same area, suggesting that
the excess is not physically associated to the galaxies but due to intervening
groups and then related to gravitational lensing.Comment: 20 pages, uuencoded compressed PostScript including tables. Figures
available upon request. To appear in the March 1995 issue of The Astronomical
Journa
Toponomic Quantum Computation
Holonomic quantum computation makes use of non-abelian geometric phases,
associated to the evolution of a subspace of quantum states, to encode logical
gates. We identify a special class of subspaces, for which a sequence of
rotations results in a non-abelian holonomy of a topological nature, so that it
is invariant under any -perturbation. Making use of a Majorana-like
stellar representation for subspaces, we give explicit examples of
topological-holonomic (or toponomic) NOT and CNOT gates.Comment: 5 pages, 4 figure
The time traveler's guide to the quantization of zero modes
We study the relationship between the quantization of a massless scalar field on the two-dimensional Einstein cylinder and in a spacetime with a time machine. We find that the latter picks out a unique prescription for the state of the zero mode in the Einstein cylinder. We show how this choice arises from the computation of the vacuum Wightman function and the vacuum renormalized stress-energy tensor in the time-machine geometry. Finally, we relate the previously proposed regularization of the zero mode state as a squeezed state with the time-machine warp parameter, thus demonstrating that the quantization in the latter regularizes the quantization in an Einstein cylinder
Current-induced two-level fluctuations in pseudo spin-valves (Co/Cu/Co) nanostructures
Two-level fluctuations of the magnetization state of pseudo spin-valve
pillars Co(10 nm)/Cu(10 nm)/Co(30 nm) embedded in electrodeposited nanowires
(~40 nm in diameter, 6000 nm in length) are triggered by spin-polarized
currents of 10^7 A/cm^2 at room temperature. The statistical properties of the
residence times in the parallel and antiparallel magnetization states reveal
two effects with qualitatively different dependences on current intensity. The
current appears to have the effect of a field determined as the bias field
required to equalize these times. The bias field changes sign when the current
polarity is reversed. At this field, the effect of a current density of 10^7
A/cm^2 is to lower the mean time for switching down to the microsecond range.
This effect is independent of the sign of the current and is interpreted in
terms of an effective temperature for the magnetization.Comment: 4 pages, 5 figures, revised version, to be published in Phys. Rev.
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