2,210 research outputs found
A variational approach to approximate particle number projection with effective forces
Kamlah's second order method for approximate particle number projection is
applied for the first time to variational calculations with effective forces.
High spin states of normal and superdeformed nuclei have been calculated with
the finite range density dependent Gogny force for several nuclei. Advantages
and drawbacks of the Kamlah second order method as compared to the
Lipkin-Nogami recipe are thoroughly discussed. We find that the Lipkin-Nogami
prescription occasionally may fail to find the right energy minimum in the
strong pairing regime and that Kamlah's second order approach, though providing
better results than the LN one, may break down in some limiting situations.Comment: 16 pages, 8 figure
Intermittency at critical transitions and aging dynamics at edge of chaos
We recall that, at both the intermittency transitions and at the Feigenbaum
attractor in unimodal maps of non-linearity of order , the dynamics
rigorously obeys the Tsallis statistics. We account for the -indices and the
generalized Lyapunov coefficients that characterize the
universality classes of the pitchfork and tangent bifurcations. We identify the
Mori singularities in the Lyapunov spectrum at the edge of chaos with the
appearance of a special value for the entropic index . The physical area of
the Tsallis statistics is further probed by considering the dynamics near
criticality and glass formation in thermal systems. In both cases a close
connection is made with states in unimodal maps with vanishing Lyapunov
coefficients.Comment: Proceedings of: STATPHYS 2004 - 22nd IUPAP International Conference
on Statistical Physics, National Science Seminar Complex, Indian Institute of
Science, Bangalore, 4-9 July 2004. Pramana, in pres
Properties of the predicted super-deformed band in ^{32}S
Properties like the excitation energy with respect to the ground state,
moments of inertia, B(E2) transition probabilities and stability against
quadrupole fluctuations at low spin of the predicted superdeformed band of
^{32}S are studied with the Gogny force D1S using the angular momentum
projected generator coordinate method for the axially symmetric quadrupole
moment. The Self Consistent Cranking method is also used to describe the
superdeformed rotational band. In addition, properties of some collective
normal deformed states are discussed.Comment: 7 pages, 3 figure
Selfconsistent calculations of fission barriers in the Fm region
The fission barriers of the nuclei 254Fm, 256Fm, 258Fm, 258No and 260Rf are
investigated in a fully microscopic way up to the scission point. The analysis
is based on the constrained Hartree-Fock-Bogoliubov theory and Gogny's D1S
force. The quadrupole, octupole and hexadecapole moments as well as the number
of nucleons in the neck region are used as constraints. Two fission paths,
corresponding to the bimodal fission, are found. The decrease with isotope mass
of the half-life times of heavy Fm isotopes is also explained.Comment: 29 pages in LaTeX including 14 figure
Heterostructure of 2D Materials: HfS2/HfO2/Si
Heterostructures have been utilized in electronic devices for over 50 years with the proposal for the first heterostructure transistor in 1957. With the scaling of devices, it is necessary to create new heterostructures that will comply with Mooreâs Law, as well as make devices faster and consume less power. Novel 2D materials, such as hafnium disulfide, have shown promise as an active channel layer, while hafnium dioxide is already proven to be a replacement of silicon dioxide for the gate insulating layer. However, fabrication techniques for wide-scale integration of these heterostructures have not yet been achieved. Also, the dielectric properties of hafnium dioxide must be realized before it can be used as a replacement of silicon dioxide. Dielectric spectroscopy results indicate that the dielectric constant for the samples was between 15-29, with sample 2 showing the highest dielectric constant of 28.8 and the lowest range of dielectric loss when measured from 200 Hz to 90 kHz. However, the results also indicate that proper contact of the probe with the electrodes is necessary to minimize error. Thus, the erroneous values at some frequencies could be attributed to poor ohmic contact of the probes, or a miscalibration of the system. I have also shown that hafnium disulfide layers can be created by converting some top layers of HfO2 thin films through sulfidation in hydrothermal process, thus demonstrating that creating a HfO2/HfS2 heterostructure is possible. XRD analysis shows a broad peak after sulfidation that relates to hafnium oxysulfide. In addition, the Raman analysis indicates that hafnium disulfide is present after sulfidation of hafnium dioxide
Unveiling the origin of shape coexistence in lead isotopes
The shape coexistence in the nuclei Pb is analyzed within the
Hartree-Fock-Bogoliubov approach with the effective Gogny force. A good
agreement with the experimental energies is found for the coexisting spherical,
oblate and prolate states. Contrary to the established interpretation, it is
found that the low-lying prolate and oblate states observed in this mass
region are predominantly characterized by neutron correlations whereas the
protons behave as spectators rather than playing an active role.Comment: 5 pages, 6 postscript figure
Properties of nuclei in the nobelium region studied within the covariant, Skyrme, and Gogny energy density functionals
We calculate properties of the ground and excited states of nuclei in the
nobelium region for proton and neutron numbers of 92 <= Z <= 104 and 144 <= N
<= 156, respectively. We use three different energy-density-functional (EDF)
approaches, based on covariant, Skyrme, and Gogny functionals, each within two
different parameter sets. A comparative analysis of the results obtained for
odd-even mass staggerings, quasiparticle spectra, and moments of inertia allows
us to identify single-particle and shell effects that are characteristic to
these different models and to illustrate possible systematic uncertainties
related to using the EDF modellingComment: 43 LaTeX pages, 14 figures, accepted in Nuclear Physics A, Special
Issue on Superheavy Element
Shape evolution and shape coexistence in Pt isotopes: comparing interacting boson model configuration mixing and Gogny mean-field energy surfaces
The evolution of the total energy surface and the nuclear shape in the
isotopic chain Pt are studied in the framework of the interacting
boson model, including configuration mixing. The results are compared with a
self-consistent Hartree-Fock-Bogoliubov calculation using the Gogny-D1S
interaction and a good agreement between both approaches shows up. The
evolution of the deformation parameters points towards the presence of two
different coexisting configurations in the region 176 A 186.Comment: Submitted to PR
Opening up the Quantum Three-Box Problem with Undetectable Measurements
One of the most striking features of quantum mechanics is the profound effect
exerted by measurements alone. Sophisticated quantum control is now available
in several experimental systems, exposing discrepancies between quantum and
classical mechanics whenever measurement induces disturbance of the
interrogated system. In practice, such discrepancies may frequently be
explained as the back-action required by quantum mechanics adding quantum noise
to a classical signal. Here we implement the 'three-box' quantum game of
Aharonov and Vaidman in which quantum measurements add no detectable noise to a
classical signal, by utilising state-of-the-art control and measurement of the
nitrogen vacancy centre in diamond.
Quantum and classical mechanics then make contradictory predictions for the
same experimental procedure, however classical observers cannot invoke
measurement-induced disturbance to explain this discrepancy. We quantify the
residual disturbance of our measurements and obtain data that rule out any
classical model by > 7.8 standard deviations, allowing us for the first time to
exclude the property of macroscopic state-definiteness from our system. Our
experiment is then equivalent to a Kochen-Spekker test of quantum
non-contextuality that successfully addresses the measurement detectability
loophole
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