246 research outputs found
Localizability of Tachyonic Particles and Neutrinoless Double Beta Decay
The quantum field theory of superluminal (tachyonic) particles is plagued
with a number of problems, which include the Lorentz non-invariance of the
vacuum state, the ambiguous separation of the field operator into creation and
annihilation operators under Lorentz transformations, and the necessity of a
complex reinterpretation principle for quantum processes. Another unsolved
question concerns the treatment of subluminal components of a tachyonic wave
packets in the field-theoretical formalism, and the calculation of the
time-ordered propagator. After a brief discussion on related problems, we
conclude that rather painful choices have to be made in order to incorporate
tachyonic spin-1/2 particles into field theory. We argue that the field theory
needs to be formulated such as to allow for localizable tachyonic particles,
even if that means that a slight unitarity violation is introduced into the S
matrix, and we write down field operators with unrestricted momenta. We find
that once these choices have been made, the propagator for the neutrino field
can be given in a compact form, and the left-handedness of the neutrino as well
as the right-handedness of the antineutrino follow naturally. Consequences for
neutrinoless double beta decay and superluminal propagation of neutrinos are
briefly discussed.Comment: 12 pages, 5 figure
On Exactness Of The Supersymmetric WKB Approximation Scheme
Exactness of the lowest order supersymmetric WKB (SWKB) quantization
condition , for certain
potentials, is examined, using complex integration technique. Comparison of the
above scheme with a similar, but {\it exact} quantization condition, , originating from the quantum Hamilton-Jacobi
formalism reveals that, the locations and the residues of the poles that
contribute to these integrals match identically, for both of these cases. As
these poles completely determine the eigenvalues in these two cases, the
exactness of the SWKB for these potentials is accounted for. Three non-exact
cases are also analysed; the origin of this non-exactness is shown to be due
the presence of additional singularities in , like branch
cuts in the plane.Comment: 11 pages, latex, 1 figure available on reques
Surface Incompressibility from Semiclassical Relativistic Mean Field Calculations
By using the scaling method and the Thomas-Fermi and Extended Thomas-Fermi
approaches to Relativistic Mean Field Theory the surface contribution to the
leptodermous expansion of the finite nuclei incompressibility has been
self-consistently computed. The validity of the simplest expansion, which
contains volume, volume-symmetry, surface and Coulomb terms, is examined by
comparing it with self-consistent results of the finite nuclei
incompressibility for some currently used non-linear sigma-omega parameter
sets. A numerical estimate of higher-order contributions to the leptodermous
expansion, namely the curvature and surface-symmetry terms, is made.Comment: 18 pages, REVTeX, 3 eps figures, changed conten
The structure of superheavy elements newly discovered in the reaction of Kr with Pb
The structure of superheavy elements newly discovered in the
Pb(Kr,n) reaction at Berkeley is systematically studied in the
Relativistic Mean Field (RMF) approach. It is shown that various usually
employed RMF forces, which give fair description of normal stable nuclei, give
quite different predictions for superheavy elements. Among the effective forces
we tested, TM1 is found to be the good candidate to describe superheavy
elements. The binding energies of the 118 nucleus and its
decay daughter nuclei obtained using TM1 agree with those of FRDM
within 2 MeV. Similar conclusion that TM1 is the good interaction is also drawn
from the calculated binding energies for Pb isotopes with the Relativistic
Continuum Hartree Bogoliubov (RCHB) theory. Using the pairing gaps obtained
from RCHB, RMF calculations with pairing and deformation are carried out for
the structure of superheavy elements. The binding energy, shape, single
particle levels, and the Q values of the decay are
discussed, and it is shown that both pairing correlation and deformation are
essential to properly understand the structure of superheavy elements. A good
agreement is obtained with experimental data on . %Especially, the
atomic number %dependence of %seems to match with the experimental
observationComment: 19 pages, 5 figure
Nuclear Ground State Observables and QCD Scaling in a Refined Relativistic Point Coupling Model
We present results obtained in the calculation of nuclear ground state
properties in relativistic Hartree approximation using a Lagrangian whose
QCD-scaled coupling constants are all natural (dimensionless and of order 1).
Our model consists of four-, six-, and eight-fermion point couplings (contact
interactions) together with derivative terms representing, respectively, two-,
three-, and four-body forces and the finite ranges of the corresponding mesonic
interactions. The coupling constants have been determined in a self-consistent
procedure that solves the model equations for representative nuclei
simultaneously in a generalized nonlinear least-squares adjustment algorithm.
The extracted coupling constants allow us to predict ground state properties of
a much larger set of even-even nuclei to good accuracy. The fact that the
extracted coupling constants are all natural leads to the conclusion that QCD
scaling and chiral symmetry apply to finite nuclei.Comment: 44 pages, 13 figures, 9 tables, REVTEX, accepted for publication in
Phys. Rev.
Rheological Chaos in a Scalar Shear-Thickening Model
We study a simple scalar constitutive equation for a shear-thickening
material at zero Reynolds number, in which the shear stress \sigma is driven at
a constant shear rate \dot\gamma and relaxes by two parallel decay processes: a
nonlinear decay at a nonmonotonic rate R(\sigma_1) and a linear decay at rate
\lambda\sigma_2. Here \sigma_{1,2}(t) =
\tau_{1,2}^{-1}\int_0^t\sigma(t')\exp[-(t-t')/\tau_{1,2}] {\rm d}t' are two
retarded stresses. For suitable parameters, the steady state flow curve is
monotonic but unstable; this arises when \tau_2>\tau_1 and
0>R'(\sigma)>-\lambda so that monotonicity is restored only through the
strongly retarded term (which might model a slow evolution of material
structure under stress). Within the unstable region we find a period-doubling
sequence leading to chaos. Instability, but not chaos, persists even for the
case \tau_1\to 0. A similar generic mechanism might also arise in shear
thinning systems and in some banded flows.Comment: Reference added; typos corrected. To appear in PRE Rap. Com
Non-Hermitian quantum mechanics in non-commutative space
We study non Hermitian quantum systems in noncommutative space as well as a
\cal{PT}-symmetric deformation of this space. Specifically, a
\mathcal{PT}-symmetric harmonic oscillator together with iC(x_1+x_2)
interaction is discussed in this space and solutions are obtained. It is shown
that in the \cal{PT} deformed noncommutative space the Hamiltonian may or may
not possess real eigenvalues depending on the choice of the noncommutative
parameters. However, it is shown that in standard noncommutative space, the
iC(x_1+x_2) interaction generates only real eigenvalues despite the fact that
the Hamiltonian is not \mathcal{PT}-symmetric. A complex interacting
anisotropic oscillator system has also been discussed.Comment: 5 pages, revised versio
Shell Corrections of Superheavy Nuclei in Self-Consistent Calculations
Shell corrections to the nuclear binding energy as a measure of shell effects
in superheavy nuclei are studied within the self-consistent Skyrme-Hartree-Fock
and Relativistic Mean-Field theories. Due to the presence of low-lying proton
continuum resulting in a free particle gas, special attention is paid to the
treatment of single-particle level density. To cure the pathological behavior
of shell correction around the particle threshold, the method based on the
Green's function approach has been adopted. It is demonstrated that for the
vast majority of Skyrme interactions commonly employed in nuclear structure
calculations, the strongest shell stabilization appears for Z=124, and 126, and
for N=184. On the other hand, in the relativistic approaches the strongest
spherical shell effect appears systematically for Z=120 and N=172. This
difference has probably its roots in the spin-orbit potential. We have also
shown that, in contrast to shell corrections which are fairly independent on
the force, macroscopic energies extracted from self-consistent calculations
strongly depend on the actual force parametrisation used. That is, the A and Z
dependence of mass surface when extrapolating to unknown superheavy nuclei is
prone to significant theoretical uncertainties.Comment: 14 pages REVTeX, 8 eps figures, submitted to Phys. Rev.
Multispectral thermal imaging
Many remote sensing applications rely on imaging spectrometry. Here the authors use imaging spectrometry for thermal and multispectral signatures measured from a satellite platform enhanced with a combination of accurate calibrations and on-board data for correcting atmospheric distortions. The approach is supported by physics-based end-to-end modeling and analysis, which permits a cost-effective balance between various hardware and software aspects. The goal is to develop and demonstrate advanced technologies and analysis tools toward meeting the needs of the customer; at the same time, the attributes of this system can address other applications in such areas as environmental change, agriculture, and volcanology
Supersymmetric solutions of PT-/non-PT-symmetric and non-Hermitian Screened Coulomb potential via Hamiltonian hierarchy inspired variational method
The supersymmetric solutions of PT-symmetric and Hermitian/non-Hermitian
forms of quantum systems are obtained by solving the Schrodinger equation for
the Exponential-Cosine Screened Coulomb potential. The Hamiltonian hierarchy
inspired variational method is used to obtain the approximate energy
eigenvalues and corresponding wave functions.Comment: 13 page
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