16,226 research outputs found
Isovector channel of quark-meson-coupling model and its effect on symmetry energy
The non-relativistic approximation of the quark-meson-coupling model has been
discussed and compared with the Skyrme-Hartree-Fock model which includes spin
exchanges. Calculations show that the spin-exchange interaction has important
effect on the descriptions of finite nuclei and nuclear matter through the Fock
exchange. Also in the quark-meson-coupling model, it is the Fock exchange that
leads to a nonlinear density-dependent isovector channel and changes the
density-dependent behavior of the symmetry energy.Comment: 20 pages, 9 figures and 1 table, accepted for publication in Nuclear
Physics
Divergent Opinions in the Pre-Issue Market and the Pricing of Initial Public Offerings
Investors in an initial public offering (IPO) face a lack-of-information problem: They have to
guess the new stock’s aftermarket price. This problem poses a risk when there is no consensus
in investors’ pre-issue opinions and the risk is greater when the opinions are more divergent.
We model this lack-of-information problem in an IPO, where, to place a certain number of the
shares, the issuer adjusts the offer price to accommodate the difference in demand between the
pre-issue market and the aftermarket. By examining a large sample of IPOs, we obtain
evidence in strong support of the model’s predictions for IPO underpricing and sales.published_or_final_versio
Demand uncertainty, Bayesian update, and IPO pricing
When the market undergoes a learning process about the IPO, it takes time for the demand to reach the equilibrium consistent with the new issue’s intrinsic value. Hence, the temporary short-term demand can deviate substantially from the stabilized long-term demand. This difference requires the underwriter to respond differently to different pre-market conditions that are dictated by the short-term demand: While she must accommodate the overly pessimistic views of investors in a cold IPO (because the shares cannot be sold at a perceived premium), she has the option to respond only partially to investors’ overly optimistic views in a hot IPO. We model this asymmetric response of the underwriter and derive IPO regularities relating underpricing, partial price revision, and long-run underperformance. We provide evidence that supports the model’s predictions.postprin
On the Application of Gluon to Heavy Quarkonium Fragmentation Functions
We analyze the uncertainties induced by different definitions of the momentum
fraction in the application of gluon to heavy quarkonium fragmentation
function. We numerically calculate the initial fragmentation
functions by using the non-covariant definitions of with finite gluon
momentum and find that these fragmentation functions have strong dependence on
the gluon momentum . As , these fragmentation
functions approach to the fragmentation function in the light-cone definition.
Our numerical results show that large uncertainties remains while the
non-covariant definitions of are employed in the application of the
fragmentation functions. We present for the first time the polarized gluon to
fragmentation functions, which are fitted by the scheme exploited in
this work.Comment: 11 pages, 7 figures;added reference for sec.
Modeling Vocal Fold Motion with a New Hydrodynamic Semi-Continuum Model
Vocal fold (VF) motion is a fundamental process in voice production, and is
also a challenging problem for direct numerical computation because the VF
dynamics depend on nonlinear coupling of air flow with the response of elastic
channels (VF), which undergo opening and closing, and induce internal flow
separation. A traditional modeling approach makes use of steady flow
approximation or Bernoulli's law which is known to be invalid during VF
opening. We present a new hydrodynamic semi-continuum system for VF motion. The
airflow is modeled by a quasi-one dimensional continuum aerodynamic system, and
the VF by a classical lumped two mass system. The reduced flow system contains
the Bernoulli's law as a special case, and is derivable from the two
dimensional compressible Navier-Stokes equations. Since we do not make steady
flow approximation, we are able to capture transients and rapid changes of
solutions, e.g. the double pressure peaks at opening and closing stages of VF
motion consistent with experimental data. We demonstrate numerically that our
system is robust, and models in-vivo VF oscillation more physically. It is also
much simpler than a full two-dimensional Navier-Stokes system.Comment: 27 pages,6 figure
Alternate proof of the Rowe-Rosensteel proposition and seniority conservation
For a system with three identical nucleons in a single- shell, the states
can be written as the angular momentum coupling of a nucleon pair and the odd
nucleon. The overlaps between these non-orthonormal states form a matrix which
coincides with the one derived by Rowe and Rosensteel [Phys. Rev. Lett. {\bf
87}, 172501 (2001)]. The propositions they state are related to the eigenvalue
problems of the matrix and dimensions of the associated subspaces. In this
work, the propositions will be proven from the symmetric properties of the
symbols. Algebraic expressions for the dimension of the states, eigenenergies
as well as conditions for conservation of seniority can be derived from the
matrix.Comment: 9 pages, no figur
Calculation of the spectrum of 12Li by using the multistep shell model method in the complex energy plane
The unbound nucleus Li is evaluated by using the multistep shell model
in the complex energy plane assuming that the spectrum is determined by the
motion of three neutrons outside the Li core. It is found that the ground
state of this system consists of an antibound state and that only this
and a and a excited states are physically meaningful
resonances.Comment: 9 pages, 5 tables, 7 figures, printer-friendly versio
Competition of different coupling schemes in atomic nuclei
Shell model calculations reveal that the ground and low-lying yrast states of
the nuclei Pd and Cd are mainly built upon isoscalar
spin-aligned neutron-proton pairs each carrying the maximum angular momentum
J=9 allowed by the shell which is dominant in this nuclear region.
This mode of excitation is unique in nuclei and indicates that the spin-aligned
pair has to be considered as an essential building block in nuclear structure
calculations. In this contribution we will discuss this neutron-proton pair
coupling scheme in detail. In particular, we will explore the competition
between the normal monopole pair coupling and the spin-aligned coupling
schemes. Such a coupling may be useful in elucidating the structure properties
of and neighboring nuclei.Comment: 10 pages, 7 figures, 1 table. Proceedings of the Conference on
Advanced Many-Body and Statistical Methods in Mesoscopic Systems, Constanta,
Romania, June 27th - July 2nd 2011. To appear in Journal of Physics:
Conference Serie
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