334 research outputs found
Development and structure of karstification of the Dong Van Karst Plateau UNESCO Global Geopark, North Vietnam based on cave survey data
This paper presents a quantitative study of the relationship between the cave system and the tectonic and karst evolution of the Dong Van Karst Plateau based on analysis and statistics of geometric parameters and orientation of cave passages. The region is located in northern Vietnam and belongs to the extended part of the South China karst belt (Yunnan karst plateau), which is composed mainly of carbonate rocks. Cave classification based on cave conduits geometric parameters shows that caves developed mainly in the vadose zone (27 vadose branchwork caves, 10 mixed caves developed under the control of fault systems, and 12 water-table caves). The degree of correlation between cave levels and planation surfaces suggests that the development of horizontal cave passages is related to two levels of planation surfaces, including one at 1250–1450 masl (equivalent to cave level at 1350–1450 masl), and at 1000–1250 masl (corresponding to cave level at 1200–1250 masl). Additionally, cave passage orientation shows that the cave system formed and developed under the influence of tectonic activities in the Cenozoic. The dominant orientation trend is roughly in the East–West direction and occurred in the early phase (Eocene–Miocene). Next is a trend roughly North–South that occurred in the late phase (Pliocene–Quaternary). The last orientation trend follows the NW–SE direction due to the reactivation of paleo-fault systems in the same direction. Although there are limitations due to accessibility and the level of cave exploration, this research suggests that analysis and statistics of the geometric parameters and orientation of cave passages based on cave survey data can be one of the effective approaches used to identify the development and structure of karstification in the karst region
A new insight into the observation of spectroscopic strength reduction in atomic nuclei: implication for the physical meaning of spectroscopic factors
Experimental studies of one nucleon knockout from magic nuclei suggest that
their nucleon orbits are not fully occupied. This conflicts a commonly accepted
view of the shell closure associated with such nuclei. The conflict can be
reconciled if the overlap between initial and final nuclear states in a
knockout reaction are calculated by a non-standard method. The method employs
an inhomogeneous equation based on correlation-dependent effective
nucleon-nucleon (NN) interactions and allows the simplest wave functions, in
which all nucleons occupy only the lowest nuclear orbits, to be used. The
method also reproduces the recently established relation between reduction of
spectroscopic strength, observed in knockout reactions on other nuclei, and
nucleon binding energies. The implication of the inhomogeneous equation method
for the physical meaning of spectroscopic factors is discussed.Comment: 4 pages, accepted by Phys. Rev. Let
Merging of single-particle levels in finite Fermi systems
Properties of the distribution of single-particle levels adjacent to the
Fermi surface in finite Fermi systems are studied, focusing on the case in
which these levels are degenerate. The interaction of the quasiparticles
occupying these levels lifts the degeneracy and affects the distance between
the closest levels on opposite sides of the Fermi surface, as the number of
particles in the system is varied. In addition to the familiar scenario of
level crossing, a new phenomenon is uncovered, in which the merging of
single-particle levels results in the disappearance of well-defined
single-particle excitations. Implications of this finding are discussed for
nuclear, solid-state, and atomic systems.Comment: 4 pages, 2 figure
Coulomb Blockade with Dispersive Interfaces
What quantity controls the Coulomb blockade oscillations if the dot--lead
conductance is essentially frequency--dependent ? We argue that it is the ac
dissipative conductance at the frequency given by the effective charging
energy. The latter may be very different from the bare charging energy due to
the interface--induced capacitance (or inductance). These observations are
supported by a number of examples, considered from the weak and strong coupling
(perturbation theory vs. instanton calculus) perspectives.Comment: 4 page
SU(3) symmetry breaking in lower fp-shell nuclei
Results of shell-model calculations for lower fp-shell nuclei show that SU(3)
symmetry breaking in this region is driven by the single-particle spin-orbit
splitting. However, even though states of the yrast band exhibit SU(3) symmetry
breaking, the results also show that the yrast band B(E2) values are
insensitive to this fragmentation of the SU(3) symmetry; specifically, the
quadrupole collectivity as measured by B(E2) transition strengths between low
lying members of the yrast band remain high even though SU(3) appears to be
broken. Results for and using the Kuo-Brown-3
two-body interaction are given to illustrate these observations.Comment: Updated to the published versio
Intensity of Coulomb Interaction between quasiparticles in diffusive metallic wires
The energy dependence and intensity of Coulomb interaction between
quasiparticles in metallic wires is obtained from two different methods:
determination of the temperature dependence of the phase coherence time from
the magnetoresistance, and measurements of the energy distribution function in
out-of-equilibrium situations. In both types of experiment, the energy
dependence of the Coulomb interaction is found to be in excellent agreement
with theoretical predictions. In contrast, the intensity of the interaction
agrees closely with theory only with the first method, whereas an important
discrepancy is found using the second one. Different explanations are proposed,
and results of a test experiment are presented.Comment: Submitted to Solid States Communication
Inelastic electron transport in granular arrays
Transport properties of granular systems are governed by Coulomb blockade
effects caused by the discreteness of the electron charge. We show that, in the
limit of vanishing mean level spacing on the grains, the low-temperature
behavior of 1d and 2d arrays is insulating at any inter-grain coupling
(characterized by a dimensionless conductance g.) In 2d and g>>1, there is a
sharp Berezinskii-Kosterlitz-Thouless crossover to the conducting phase at a
certain temperature, T_{BKT}. These results are obtained by applying an
instanton analysis to map the conventional `phase' description of granular
arrays onto the dual `charge' representation.Comment: 24 pages, 8 figure
QED Calculation of E1M1 and E1E2 Transition Probabilities in One-Electron Ions with Arbitrary Nuclear Charge
The quantum electrodynamical theory of the two-photon transitions in
hydrogenlike ions is presented. The emission probability for 2s1/2 -> 2E1+1s1/2
transitions is calculated and compared to the results of the previous
calculations. The emission probabilities 2p12 -> E1E2+1s1/2 and 2p1/2 ->
E1M1+1s1/2 are also calculated for the nuclear charge Z values 1-100. This is
the first calculation of the two latter probabilities. The results are given in
two different gauges.Comment: 14 pages, 4 tables, 1 figur
Constraints on Lorentz violation from clock-comparison experiments
Constraints from clock-comparison experiments on violations of Lorentz and
CPT symmetry are investigated in the context of a general Lorentz-violating
extension of the standard model. The experimental signals are shown to depend
on the atomic and ionic species used as clocks. Certain experiments usually
regarded as establishing comparable bounds are in this context sensitive to
different types of Lorentz violation. Some considerations relevant to possible
future measurements are presented. All these experiments are potentially
sensitive to Lorentz-violating physics at the Planck scale.Comment: accepted for publication in Physical Review D; scheduled for issue of
December 1, 199
Shell structure of superheavy nuclei in self-consistent mean-field models
We study the extrapolation of nuclear shell structure to the region of
superheavy nuclei in self-consistent mean-field models -- the
Skyrme-Hartree-Fock approach and the relativistic mean-field model -- using a
large number of parameterizations. Results obtained with the Folded-Yukawa
potential are shown for comparison. We focus on differences in the isospin
dependence of the spin-orbit interaction and the effective mass between the
models and their influence on single-particle spectra. While all relativistic
models give a reasonable description of spin-orbit splittings, all
non-relativistic models show a wrong trend with mass number. The spin-orbit
splitting of heavy nuclei might be overestimated by 40%-80%. Spherical
doubly-magic superheavy nuclei are found at (Z=114,N=184), (Z=120,N=172) or
(Z=126,N=184) depending on the parameterization. The Z=114 proton shell
closure, which is related to a large spin-orbit splitting of proton 2f states,
is predicted only by forces which by far overestimate the proton spin-orbit
splitting in Pb208. The Z=120 and N=172 shell closures predicted by the
relativistic models and some Skyrme interactions are found to be related to a
central depression of the nuclear density distribution. This effect cannot
appear in macroscopic-microscopic models which have a limited freedom for the
density distribution only. In summary, our findings give a strong argument for
(Z=120,N=172) to be the next spherical doubly-magic superheavy nucleus.Comment: 22 pages REVTeX, 16 eps figures, accepted for publication in Phys.
Rev.
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