11,335 research outputs found
Shannon Information Entropy in Heavy-ion Collisions
The general idea of information entropy provided by C.E. Shannon "hangs over
everything we do" and can be applied to a great variety of problems once the
connection between a distribution and the quantities of interest is found. The
Shannon information entropy essentially quantify the information of a quantity
with its specific distribution, for which the information entropy based methods
have been deeply developed in many scientific areas including physics. The
dynamical properties of heavy-ion collisions (HICs) process make it difficult
and complex to study the nuclear matter and its evolution, for which Shannon
information entropy theory can provide new methods and observables to
understand the physical phenomena both theoretically and experimentally. To
better understand the processes of HICs, the main characteristics of typical
models, including the quantum molecular dynamics models, thermodynamics models,
and statistical models, etc, are briefly introduced. The typical applications
of Shannon information theory in HICs are collected, which cover the chaotic
behavior in branching process of hadron collisions, the liquid-gas phase
transition in HICs, and the isobaric difference scaling phenomenon for
intermediate mass fragments produced in HICs of neutron-rich systems. Even
though the present applications in heavy-ion collision physics are still
relatively simple, it would shed light on key questions we are seeking for. It
is suggested to further develop the information entropy methods in nuclear
reactions models, as well as to develop new analysis methods to study the
properties of nuclear matters in HICs, especially the evolution of dynamics
system.Comment: 56 pages, 19 figures.Version accepted by Progress in Particle and
Nuclear Physics. To be published in 201
Investigating the quark flavor dependence of the chiral magnetic effect with a multiphase transport model
Because the properties of the QCD phase transition and the chiral magnetic
effect (CME) depend on the number of quark flavors () and quark mass,
relativistic heavy-ion collisions provide a natural environment to investigate
the flavor features if quark deconfinement occurs. We introduce an initial
two-flavor or three-flavor dipole charge separation into a multiphase transport
(AMPT) model to investigate the flavor dependence of the CME. By taking
advantage of the recent ALICE data of charge azimuthal correlations with
identified hadrons, we attempt to disentangle two-flavor and three-flavor CME
scenarios in Pb+Pb collisions at 2.76 TeV. We find that the experimental data
show a certain potential to distinguish the two scenarios, therefore we further
suggest to collect more data to clarify the possible flavor dependence in
future experiments.Comment: 12 pages, 4 figures; final published versio
Cycle lengths and minimum degree of graphs
There has been extensive research on cycle lengths in graphs with large
minimum degree. In this paper, we obtain several new and tight results in this
area. Let be a graph with minimum degree at least . We prove that if
is bipartite, then there are cycles in whose lengths form an
arithmetic progression with common difference two. For general graph , we
show that contains cycles with consecutive even
lengths and cycles whose lengths form an arithmetic progression with
common difference one or two. In addition, if is 2-connected and
non-bipartite, then contains cycles with consecutive
odd lengths.
Thomassen (1983) made two conjectures on cycle lengths modulo a fixed integer
: (1) every graph with minimum degree at least contains cycles of all
even lengths modulo ; (2) every 2-connected non-bipartite graph with minimum
degree at least contains cycles of all lengths modulo . These two
conjectures, if true, are best possible. Our results confirm both conjectures
when is even. And when is odd, we show that minimum degree at least
suffices. This improves all previous results in this direction. Moreover,
our results derive new upper bounds of the chromatic number in terms of the
longest sequence of cycles with consecutive (even or odd) lengths
Pairing-energy coefficients of neutron-rich fragments in spallation reactions
The ratio of pairing-energy coefficient to temperature () of
neutron-rich fragments produced in spallation reactions has been investigated
by adopting an isobaric yield ratio method deduced in the framework of a
modified Fisher model. A series of spallation reactions, 0.5 and 1 GeV
Pb + , 1 GeV U + , 0.5 GeV Xe + ,
0.2, 0.5 and 1 GeV Xe + , and Fe + with incident
energy ranging from 0.3 to 1.5 GeV, has been analysed. An obvious
odd-even staggering is shown in the fragments with small neutron excess
(), and in the relatively small- fragments which have large
. The values of for the fragments, with from 0 to 36, have
been found to be in a range from -4 to 4, and most values of fall in
the range from -1 to 1. It is suggested that a small pairing-energy coefficient
should be considered in predicting the cross sections of fragments in
spallation reactions. It is also concluded that the method proposed in this
article is not good for fragments with 85\% (where is the
mass number of the spallation system).Comment: 8 pages, 6 figures, to appear on Chinese Physics
Coarse-graining Langevin dynamics using reduced-order techniques
This paper considers the reduction of the Langevin equation arising from
bio-molecular models. To facilitate the construction and implementation of the
reduced models, the problem is formulated as a reduced-order modeling problem.
The reduced models can then be directly obtained from a Galerkin projection to
appropriately defined Krylov subspaces. The equivalence to a moment-matching
procedure, previously implemented in , 2), is proved. A particular emphasis is
placed on the reduction of the stochastic noise, which is absent in many
order-reduction problems. In particular, for order less than six we can show
the reduced model obtained from the subspace projection automatically satisfies
the fluctuation-dissipation theorem. Details for the implementations, including
a bi-orthogonalization procedure and the minimization of the number of matrix
multiplications, will be discussed as well
Phase Behavior in Thin Films of Confined Colloid-Polymer Mixtures
Using self-consistent field and density-functional theories, we first
investigate colloidal self-assembling of colloid/polymer films confined between
two soft surfaces grafted by polymers. With the increase of colloidal
concentrations, the film undergoes a series of transitions from disordered
liquid sparse square hexagonal (or mixed square-hexagonal)
dense square cylindric structures in plane, which results from the
competition between the entropic elasticity of polymer brushes and the steric
packing effect of colloidal particles. A phase diagram displays the stable
regions of different in-layer ordering structures as the colloidal
concentration is varied and layering transitions as the polymer-grafted density
is decreased. Our results show a new control mechanism to stabilize the
ordering of structures within the films
From Generalized Langevin Equations to Brownian Dynamics and Embedded Brownian Dynamics
We present the reduction of generalized Langevin equations to a
coordinate-only stochastic model, which in its exact form, involves a forcing
term with memory and a general Gaussian noise. It will be shown that a similar
fluctuation-dissipation theorem still holds at this level. We study the
approximation by the typical Brownian dynamics as a first approximation. Our
numerical test indicates how the intrinsic frequency of the kernel function
influences the accuracy of this approximation. In the case when such an
approximate is inadequate, further approximations can be derived by embedding
the nonlocal model into an extended dynamics without memory. By imposing noises
in the auxiliary variables, we show how the second fluctuation-dissipation
theorem is still exactly satisfied.Comment: 28 pages, 8 figure
Attractor Bifurcation of Three-Dimensional Double-Diffusive Convection
In this article, we present a bifurcation analysis on the double-diffusive
convection. Two pattern selections, rectangles and squares, are investigated.
It is proved that there are two different types of attractor bifurcations
depending on the thermal and salinity Rayleigh numbers for each pattern. The
analysis is based on a newly developed attractor bifurcation theory, together
with eigen-analysis and the center manifold reductions
Improved Thermometer from Intermediate Mass Fragments in Heavy-Ion Collisions with Isobaric Yield Ratio Difference
\item[Background] Temperature is an important parameter in studying many
important questions in heavy-ion collisions. A thermometer based on the
isobaric yield ratio (IYR) has been proposed [Ma \textit{et al.}, Phys. Rev. C
\textbf{86}, 054611 (2012) and Ma \textit{et al.}, \textit{ibid.}, Phys. Rev. C
\textbf{88}, 014609 (2013)]. \item[Purpose] An improved thermometer ()
is proposed based on the difference between IYRs. obtained from
isobars in different reactions will be compared. \item[Methods] The yields of
three isobars are employed in . The residual free energy of the three
isobars are replaced by that of the binding energy. No secondary decay
modification for odd fragment is used in . \item[Results] The
measured fragment yields in the 140 MeV Ca + Be
(Ta) and Ni + Be (Ta), the 1 GeV Xe + Pb, and the Sn + Sn reactions have been
analyzed to obtain from IMFs. from most of the fragments in
the Ca and Ni reactions is in the range of 0.6 MeV 3.5 MeV. from most of the fragments in the Xe and
Sn reactions is in the range of 0.5 MeV 2.5 MeV,
while the range is 0.5 MeV 4 MeV from most of the fragments in
the Xe reaction. In general, for most of the fragments in the
Ca and Ni reactions are very similar (except in the very
neutron-rich fragments), and from IMFs in the Xe and
Sn reactions is also similar. A slightly dependence of on
is found. \item[Conclusions] Using the binding energy of the nucleus,
can be obtained without the knowledge of the free energies of
fragments. In the investigated reactions, from most of the IMFs is
low.Comment: 7 pages, 9 figures. To appear on Physical Review
Bifurcation and Stability of Two-Dimensional Double-Diffusive Convection
In this article, we present a bifurcation and stability analysis on the
double-diffusive convection. The main objective is to study 1) the mechanism of
the saddle-node bifurcation and hysteresis for the problem, 2) the formation,
stability and transitions of the typical convection structures, and 3) the
stability of solutions. It is proved in particular that there are two different
types of transitions: continuous and jump, which are determined explicitly
using some physical relevant nondimensional parameters. It is also proved that
the jump transition always leads to the existence of a saddle-node bifurcation
and hysteresis phenomena
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