24,731 research outputs found
Microscopic study of induced fission dynamics of Th with covariant energy density functionals
Static and dynamic aspects of the fission process of Th are analyzed
in a self-consistent framework based on relativistic energy density
functionals. Constrained relativistic mean-field (RMF) calculations in the
collective space of axially symmetric quadrupole and octupole deformations,
based on the energy density functional PC-PK1 and a -force pairing, are
performed to determine the potential energy surface of the fissioning nucleus,
the scission line, the single-nucleon wave functions, energies and occupation
probabilities, as functions of deformation parameters. Induced fission dynamics
is described using the time-dependent generator coordinate method in the
Gaussian overlap approximation. A collective Schr\"odinger equation, determined
entirely by the microscopic single-nucleon degrees of freedom, propagates
adiabatically in time the initial wave packet built by boosting the
ground-state solution of the collective Hamiltonian for Th. The
position of the scission line and the microscopic input for the collective
Hamiltonian are analyzed as functions of the strength of the pairing
interaction. The effect of static pairing correlations on the pre-neutron
emission charge yields and total kinetic energy of fission fragments is
examined in comparison with available data, and the distribution of fission
fragments is analyzed for different values of the initial excitation energy.Comment: 25 pages, 14 figures, accepted for publication in Phys. Rev.
Field-induced structure transformation in electrorheological solids
We have computed the local electric field in a body-centered tetragonal (BCT)
lattice of point dipoles via the Ewald-Kornfeld formulation, in an attempt to
examine the effects of a structure transformation on the local field strength.
For the ground state of an electrorheological solid of hard spheres, we
identified a novel structure transformation from the BCT to the face-centered
cubic (FCC) lattices by changing the uniaxial lattice constant c under the hard
sphere constraint. In contrast to the previous results, the local field
exhibits a non-monotonic transition from BCT to FCC. As c increases from the
BCT ground state, the local field initially decreases rapidly towards the
isotropic value at the body-centered cubic lattice, decreases further, reaching
a minimum value and increases, passing through the isotropic value again at an
intermediate lattice, reaches a maximum value and finally decreases to the FCC
value. An experimental realization of the structure transformation is
suggested. Moreover, the change in the local field can lead to a generalized
Clausius-Mossotti equation for the BCT lattices.Comment: Submitted to Phys. Rev.
Spectroscopy of reflection-asymmetric nuclei with relativistic energy density functionals
Quadrupole and octupole deformation energy surfaces, low-energy excitation
spectra and transition rates in fourteen isotopic chains: Xe, Ba, Ce, Nd, Sm,
Gd, Rn, Ra, Th, U, Pu, Cm, Cf, and Fm, are systematically analyzed using a
theoretical framework based on a quadrupole-octupole collective Hamiltonian
(QOCH), with parameters determined by constrained reflection-asymmetric and
axially-symmetric relativistic mean-field calculations. The microscopic QOCH
model based on the PC-PK1 energy density functional and -interaction
pairing is shown to accurately describe the empirical trend of low-energy
quadrupole and octupole collective states, and predicted spectroscopic
properties are consistent with recent microscopic calculations based on both
relativistic and non-relativistic energy density functionals. Low-energy
negative-parity bands, average octupole deformations, and transition rates show
evidence for octupole collectivity in both mass regions, for which a
microscopic mechanism is discussed in terms of evolution of single-nucleon
orbitals with deformation.Comment: 36 pages, 21 figures, Accepted for Publication in Physical Review
Catastrophic Photo-z Errors and the Dark Energy Parameter Estimates with Cosmic Shear
We study the impact of catastrophic errors occurring in the photometric
redshifts of galaxies on cosmological parameter estimates with cosmic shear
tomography. We consider a fiducial survey with 9-filter set and perform photo-z
measurement simulations. It is found that a fraction of 1% galaxies at
z_{spec}~0.4 is misidentified to be at z_{phot}~3.5. We then employ both chi^2
fitting method and the extension of Fisher matrix formalism to evaluate the
bias on the equation of state parameters of dark energy, w_0 and w_a, induced
by those catastrophic outliers. By comparing the results from both methods, we
verify that the estimation of w_0 and w_a from the fiducial 5-bin tomographic
analyses can be significantly biased. To minimize the impact of this bias, two
strategies can be followed: (A) the cosmic shear analysis is restricted to
0.5<z<2.5 where catastrophic redshift errors are expected to be insignificant;
(B) a spectroscopic survey is conducted for galaxies with 3<z_{phot}<4. We find
that the number of spectroscopic redshifts needed scales as N_{spec} \propto
f_{cata}\times A where f_{cata}=1% is the fraction of catastrophic redshift
errors (assuming a 9-filter photometric survey) and A is the survey area. For
A=1000 {deg}^2, we find that N_{spec}>320 and 860 respectively in order to
reduce the joint bias in (w_0,w_a) to be smaller than 2\sigma and 1\sigma. This
spectroscopic survey (option B) will improve the Figure of Merit of option A by
a factor \times 1.5 thus making such a survey strongly desirable.Comment: 25 pages, 9 figures. Revised version, as accepted for publication in
Ap
How does a protein search for the specific site on DNA: the role of disorder
Proteins can locate their specific targets on DNA up to two orders of
magnitude faster than the Smoluchowski three-dimensional diffusion rate. This
happens due to non-specific adsorption of proteins to DNA and subsequent
one-dimensional sliding along DNA. We call such one-dimensional route towards
the target "antenna". We studied the role of the dispersion of nonspecific
binding energies within the antenna due to quasi random sequence of natural
DNA. Random energy profile for sliding proteins slows the searching rate for
the target. We show that this slowdown is different for the macroscopic and
mesoscopic antennas.Comment: 4 pages, 4 figure
A limited resource model of fault-tolerant capability against cascading failure of complex network
We propose a novel capacity model for complex networks against cascading failure. In this model, vertices with both higher loads and larger degrees should be paid more extra capacities, i.e. the allocation of extra capacity on vertex i will be proportional to ki γ , where ki is the degree of vertex i and γ > 0 is a free parameter. We have applied this model on Barabási-Albert network as well as two real transportation networks, and found that under the same amount of available resource, this model can achieve better network robustness than previous models
Small ball probability, Inverse theorems, and applications
Let be a real random variable with mean zero and variance one and
be a multi-set in . The random sum
where are iid copies of
is of fundamental importance in probability and its applications.
We discuss the small ball problem, the aim of which is to estimate the
maximum probability that belongs to a ball with given small radius,
following the discovery made by Littlewood-Offord and Erdos almost 70 years
ago. We will mainly focus on recent developments that characterize the
structure of those sets where the small ball probability is relatively
large. Applications of these results include full solutions or significant
progresses of many open problems in different areas.Comment: 47 page
Privacy Mining from IoT-based Smart Homes
Recently, a wide range of smart devices are deployed in a variety of
environments to improve the quality of human life. One of the important
IoT-based applications is smart homes for healthcare, especially for elders.
IoT-based smart homes enable elders' health to be properly monitored and taken
care of. However, elders' privacy might be disclosed from smart homes due to
non-fully protected network communication or other reasons. To demonstrate how
serious this issue is, we introduce in this paper a Privacy Mining Approach
(PMA) to mine privacy from smart homes by conducting a series of deductions and
analyses on sensor datasets generated by smart homes. The experimental results
demonstrate that PMA is able to deduce a global sensor topology for a smart
home and disclose elders' privacy in terms of their house layouts.Comment: This paper, which has 11 pages and 7 figures, has been accepted BWCCA
2018 on 13th August 201
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