13,236 research outputs found
Evolution of cooperation in multilevel public goods games with community structures
In a community-structured population, public goods games (PGG) occur both
within and between communities. Such type of PGG is referred as multilevel
public goods games (MPGG). We propose a minimalist evolutionary model of the
MPGG and analytically study the evolution of cooperation. We demonstrate that
in the case of sufficiently large community size and community number, if the
imitation strength within community is weak, i.e., an individual imitates
another one in the same community almost randomly, cooperation as well as
punishment are more abundant than defection in the long run; if the imitation
strength between communities is strong, i.e., the more successful strategy in
two individuals from distinct communities is always imitated, cooperation and
punishment are also more abundant. However, when both of the two imitation
intensities are strong, defection becomes the most abundant strategy in the
population. Our model provides insight into the investigation of the
large-scale cooperation in public social dilemma among contemporary
communities.Comment: 6 pages, 4 figures, Accepted by EP
Electromagnetic manipulation for anti-Zeno effect in an engineered quantum tunneling process
We investigate the quantum Zeno and anti-Zeno effects for the irreversible
quantum tunneling from a quantum dot to a ring array of quantum dots. By
modeling the total system with the Anderson-Fano-Lee model, it is found that
the transition from the quantum Zeno effect to quantum anti-Zeno effect can
happen as the magnetic flux and the gate voltage were adjusted.Comment: 6 pages, 5 figure
Effects of Chinese Herbal Recipes on Immunity in Immunosuppressive Mice
The Chinese herbal formula consisting of Astragalus membranaceus, Epimedium brevicornum, Paeoniae Alba Radix and Radix Ophiopogonis in proper proportions were adopted in order to investigate the immunoenhancing properties of the herbal formula. Fifty ICR mice were randomly divided into 5 groups (NS,NS+Hy,L+Hy,M+Hy,H+Hy). The mice in hydrocortisone (Hy) groups were injected with hydrocortisone i.p. to induce the immunosuppressive condition. The mice in group NS were administered with normal saline as controls. The mice in groups NS+Hy, L+Hy, M+Hy, H+Hy were administered with normal saline, low, moderate and high dose of the herbal prescription respectively by gavage for 6 days. The level of serum hemolysin, the function of antibody function cell(AFC)and CD4+/CD8+ T cell ratio were measured at the end of experiments. The results showed that the level of serum hemolysin, the function of AFC and CD4+/CD8+ T cell ratio in L+Hy,M+Hy,H+Hy groups increased significantly compared with those in NS or NS+Hy groups. These results indicate that Chinese herbal medicine prescription can enhance humoral immunity and cellular immune function of the immunosuppressivemouse
Dirac Quasinormal modes of Schwarzschild black hole
The quasinormal modes (QNMs) associated with the decay of Dirac field
perturbation around a Schwarzschild black hole is investigated by using
continued fraction and Hill-determinant approaches. It is shown that the
fundamental quasinormal frequencies become evenly spaced for large angular
quantum number and the spacing is given by . The angular quantum number has the
surprising effect of increasing real part of the quasinormal frequencies, but
it almost does not affect imaginary part, especially for low overtones. In
addition, the quasinormal frequencies also become evenly spaced for large
overtone number and the spacing for imaginary part is
which is same as that of the
scalar, electromagnetic, and gravitational perturbations.Comment: 14 pages, 5 figure
Gap solitons of a super-Tonks-Girardeau gas in a one-dimensional periodic potential
We study the stability of gap solitons of the super-Tonks-Girardeau bosonic
gas in one-dimensional periodic potential. The linear stability analysis
indicates that increasing the amplitude of periodic potential or decreasing the
nonlinear interactions, the unstable gap solitons can become stable. In
particular, the theoretical analysis and numerical calculations show that,
comparing to the lower-family of gap solitons, the higher-family of gap
solitons are easy to form near the bottoms of the linear Bloch band gaps. The
numerical results also verify that the composition relations between various
gap solitons and nonlinear Bloch waves are general and can exist in the
super-Tonks-Girardeau phase.Comment: 7 pages,6 figure
Formation time distribution of dark matter haloes: theories versus N-body simulations
This paper uses numerical simulations to test the formation time distribution
of dark matter haloes predicted by the analytic excursion set approaches. The
formation time distribution is closely linked to the conditional mass function
and this test is therefore an indirect probe of this distribution. The
excursion set models tested are the extended Press-Schechter (EPS) model, the
ellipsoidal collapse (EC) model, and the non-spherical collapse boundary (NCB)
model. Three sets of simulations (6 realizations) have been used to investigate
the halo formation time distribution for halo masses ranging from dwarf-galaxy
like haloes (, where is the characteristic non-linear mass
scale) to massive haloes of . None of the models can match the
simulation results at both high and low redshift. In particular, dark matter
haloes formed generally earlier in our simulations than predicted by the EPS
model. This discrepancy might help explain why semi-analytic models of galaxy
formation, based on EPS merger trees, under-predict the number of high redshift
galaxies compared with recent observations.Comment: 7 pages, 5 figures, accepted for publication in MNRA
Semiquantum key distribution using entangled states
Recently, Boyer et al. presented a novel semiquantum key distribution
protocol [M. Boyer, D. Kenigsberg, and T. Mor, Phys. Rev. Lett. 99, 140501
(2007)], by using four quantum states, each of which is randomly prepared by Z
basis or X basis. Here we present a semiquantum key distribution protocol by
using entangled states in which quantum Alice shares a secret key with
classical Bob. We also show the protocol is secure against eavesdropping.Comment: 6 page
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