3,210 research outputs found
Nuclear halo and its scaling laws
We have proposed a procedure to extract the probability for valence particle
being out of the binding potential from the measured nuclear asymptotic
normalization coefficients. With this procedure, available data regarding the
nuclear halo candidates are systematically analyzed and a number of halo nuclei
are confirmed. Based on these results we have got a much relaxed condition for
nuclear halo occurrence. Furthermore, we have presented the scaling laws for
the dimensionless quantity of nuclear halo in terms of the
analytical expressions of the expectation value for the operator in a
finite square-well potential.Comment: 14 pages, 3 figure
Quantum Pieri rules for isotropic Grassmannians
We study the three point genus zero Gromov-Witten invariants on the
Grassmannians which parametrize non-maximal isotropic subspaces in a vector
space equipped with a nondegenerate symmetric or skew-symmetric form. We
establish Pieri rules for the classical cohomology and the small quantum
cohomology ring of these varieties, which give a combinatorial formula for the
product of any Schubert class with certain special Schubert classes. We also
give presentations of these rings, with integer coefficients, in terms of
special Schubert class generators and relations.Comment: 59 pages, LaTeX, 6 figure
New supersymmetric solutions of N=2, D=5 gauged supergravity with hyperscalars
We construct new supersymmetric solutions, including AdS bubbles, in an N=2
truncation of five-dimensional N=8 gauged supergravity. This particular
truncation is given by N=2 gauged supergravity coupled to two vector multiples
and three incomplete hypermultiplets, and was originally investigated in the
context of obtaining regular AdS bubble geometries with multiple active
R-charges. We focus on cohomogeneity-one solutions corresponding to objects
with two equal angular momenta and up to three independent R-charges.
Curiously, we find a new set of zero and negative mass solitons asymptotic to
AdS_5/Z_k, for k \ge 3, which are everywhere regular without closed timelike
curves.Comment: Latex 3 times, 42 page
A 2-Component Generalization of the Camassa-Holm Equation and Its Solutions
An explicit reciprocal transformation between a 2-component generalization of
the Camassa-Holm equation, called the 2-CH system, and the first negative flow
of the AKNS hierarchy is established, this transformation enables one to obtain
solutions of the 2-CH system from those of the first negative flow of the AKNS
hierarchy. Interesting examples of peakon and multi-kink solutions of the 2-CH
system are presented.Comment: 15 pages, 16 figures, some typos correcte
Path integrals approach to resisitivity anomalies in anharmonic systems
Different classes of physical systems with sizeable electron-phonon coupling
and lattice distortions present anomalous resistivity behaviors versus
temperature. We study a molecular lattice Hamiltonian in which polaronic charge
carriers interact with non linear potentials provided by local atomic
fluctuations between two equilibrium sites. We study a molecular lattice
Hamiltonian in which polaronic charge carriers interact with non linear
potentials provided by local atomic fluctuations between two equilibrium sites.
A path integral model is developed to select the class of atomic oscillations
which mainly contributes to the partition function and the electrical
resistivity is computed in a number of representative cases. We argue that the
common origin of the observed resistivity anomalies lies in the time retarded
nature of the polaronic interactions in the local structural instabilities.Comment: 4 figures, to appear in Phys.Rev.B, May 1st (2001
Comparisons of Statistical Multifragmentation and Evaporation Models for Heavy Ion Collisions
The results from ten statistical multifragmentation models have been compared
with each other using selected experimental observables. Even though details in
any single observable may differ, the general trends among models are similar.
Thus these models and similar ones are very good in providing important physics
insights especially for general properties of the primary fragments and the
multifragmentation process. Mean values and ratios of observables are also less
sensitive to individual differences in the models. In addition to
multifragmentation models, we have compared results from five commonly used
evaporation codes. The fluctuations in isotope yield ratios are found to be a
good indicator to evaluate the sequential decay implementation in the code. The
systems and the observables studied here can be used as benchmarks for the
development of statistical multifragmentation models and evaporation codes.Comment: To appear on Euorpean Physics Journal A as part of the Topical Volume
"Dynamics and Thermodynamics with Nuclear Degrees of Freedo
Fragment Isospin as a Probe of Heavy-Ion Collisions
Isotope ratios of fragments produced at mid-rapidity in peripheral and
central collisions of 114Cd ions with 92Mo and 98Mo target nuclei at E/A = 50
MeV are compared. Neutron-rich isotopes are preferentially produced in central
collisions as compared to peripheral collisions. The influence of the size (A),
density, N/Z, E*/A, and Eflow/A of the emitting source on the measured isotope
ratios was explored by comparison with a statistical model (SMM). The
mid-rapidity region associated with peripheral collisions does not appear to be
neutron-enriched relative to central collisions.Comment: 12 pages including figure
Coulomb blockade of strongly coupled quantum dots studied via bosonization of a channel with a finite barrier
A pair of quantum dots, coupled through a point contact, can exhibit Coulomb
blockade effects that reflect an oscillatory term in the dots' total energy
whose value depends on whether the total number of electrons on the dots is
even or odd. The effective energy associated with this even-odd alternation is
reduced, relative to the bare Coulomb blockade energy for uncoupled dots, by a
factor (1-f) that decreases as the interdot coupling is increased. When the
transmission coefficient for interdot electronic motion is independent of
energy and the same for all channels within the point contact (which are
assumed uncoupled), the factor (1-f) takes on a universal value determined
solely by the number of channels and the dimensionless conductance g of each
individual channel.
This paper studies corrections to the universal value of (1-f) that result
when the transmission coefficent varies over energy scales of the size of the
bare Coulomb blockade energy. We consider a model in which the point contact is
described by a single orbital channel containing a parabolic barrier potential,
and we calculate the leading correction to (1-f) for one-channel (spin-split)
and two-channel (spin-degenerate) point contacts in the limit where the single
orbital channel is almost completely open. By generalizing a previously used
bosonization technique, we find that, for a given value of the dimensionless
conductance g, the value of (1-f) is increased relative to its value for a
zero-thickness barrier, but the absolute value of the increase is small in the
region where our calculations apply.Comment: 13 pages, 3 Postscript figure
Leading Order Textures for Lepton Mass Matrices
In theories with three light neutrinos, certain simplicity assumptions allow
the construction of a complete list of leading order lepton mass matrices.
These matrices are consistent with m_{tau} \neq 0, Delta m^2_{12} \ll Delta
m^2_{23}, theta_{23} approx 1, and theta_{13} = 0, as suggested by measurements
of atmospheric and solar neutrino fluxes. The list contains twelve generic
cases: two have three degenerate neutrinos, eight have two neutrinos forming a
Dirac state, and in only two cases is one neutrino much heavier than the other
two. For each of these twelve generic cases the possible forms for the
perturbations which yield m_{mu} are given. Ten special textures are also
found.Comment: 17 pages, added reference
Submanifolds in five-dimensional pseudo-Euclidean spaces and four-dimensional FRW universes
Equations for submanifolds, which correspond to embeddings of the
four-dimensional FRW universes in five-dimensional pseudo-Euclidean spaces, are
presented in convenient form in general case. Several specific examples are
considered.Comment: 7 pages, LaTeX, the mathematical part of this paper is based on the
withdrawn preprint arXiv:1012.0320 [gr-qc
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