43,969 research outputs found
Cooperation with both synergistic and local interactions can be worse than each alone
Cooperation is ubiquitous ranging from multicellular organisms to human
societies. Population structures indicating individuals' limited interaction
ranges are crucial to understand this issue. But it is still at large to what
extend multiple interactions involving nonlinearity in payoff play a role on
cooperation in structured populations. Here we show a rule, which determines
the emergence and stabilization of cooperation, under multiple discounted,
linear, and synergistic interactions. The rule is validated by simulations in
homogenous and heterogenous structured populations. We find that the more
neighbors there are the harder for cooperation to evolve for multiple
interactions with linearity and discounting. For synergistic scenario, however,
distinct from its pairwise counterpart, moderate number of neighbors can be the
worst, indicating that synergistic interactions work with strangers but not
with neighbors. Our results suggest that the combination of different factors
which promotes cooperation alone can be worse than that with every single
factor.Comment: 32 pages, 4 figure
A WENO Algorithm of the Temperature and Ionization Profiles around a Point Source
We develop a numerical solver for radiative transfer problems based on the
weighted essentially nonoscillatory (WENO) scheme modified with anti-diffusive
flux corrections, in order to solve the temperature and ionization profiles
around a point source of photons in the reionization epoch. Algorithms for such
simulation must be able to handle the following two features: 1. the sharp
profiles of ionization and temperature at the ionizing front (I-front) and the
heating front (T-front), and 2. the fraction of neutral hydrogen within the
ionized sphere is extremely small due to the stiffness of the rate equations of
atom processes. The WENO scheme can properly handle these two features, as it
has been shown to have high order of accuracy and good convergence in capturing
discontinuities and complicated structures in fluid as well as to be
significantly superior over piecewise smooth solutions containing
discontinuities. With this algorithm, we show the time-dependence of the
preheated shell around a UV photon source. In the first stage the I-front and
T-front are coincident, and propagate with almost the speed of light. In later
stage, when the frequency spectrum of UV photons is hardened, the speeds of
propagation of the ionizing and heating fronts are both significantly less than
the speed of light, and the heating front is always beyond the ionizing front.
In the spherical shell between the I- and T-fronts, the IGM is heated, while
atoms keep almost neutral. The time scale of the preheated shell evolution is
dependent on the intensity of the photon source. We also find that the details
of the pre-heated shell and the distribution of neutral hydrogen remained in
the ionized sphere are actually sensitive to the parameters used. The WENO
algorithm can provide stable and robust solutions to study these details.Comment: 24 pages, 7 figures, accepted in New Astronom
Resummation prediction on the jet mass spectrum in one-jet inclusive production at the LHC
We study the factorization and resummation prediction on the jet mass
spectrum in one-jet inclusive production at the LHC based on soft-collinear
effective theory. The soft function with anti- algorithm is calculated at
next-to-leading order and its validity is demonstrated by checking the
agreement between the expanded leading singular terms with the exact
fixed-order result. The large logarithms and the global
logarithms in the process are resummed to all order at
next-to-leading logarithmic and next-to-next-to-leading logarithmic level,
respectively. The cross section is enhanced by about 23% from the
next-to-leading logarithmic level to next-to-next-to-leading logarithmic level.
Comparing our resummation predictions with those from Monte Carlo tool PYTHIA
and ATLAS data at the 7 TeV LHC, we find that the peak positions of the jet
mass spectra agree with those from PYTHIA at parton level, and the predictions
of the jet mass spectra with non-perturbative effects are in coincidence with
the ATLAS data. We also show the predictions at the future 13 TeV LHC.Comment: 43 pages, 10 figure
Resummation prediction on gauge boson pair production with a jet veto
We investigate the resummation effects with a jet veto, for WZ and ZZ
productions at the LHC in soft-collinear effective theory. We present the
invariant mass distributions and the total cross section with different jet
veto and jet radius for these process at Next-to-Next-to-Leading-Logarithmic
level. Our results show that the jet-veto resummation can increase the jet-veto
cross section and decrease the scale uncertainties, especially in the large
center-of-mass energy. We find that for pt_veto>30 GeV and R=0.4, the
resummation results can increase POWHEG+PYTHIA predictions by about 19% for WZ
production and 18% for ZZ production, respectively. Our results agree with the
CMS data for WZ productions within 2 C.L. at 8 TeV, which can explain
the 2 discrepancy between the CMS experimental results and theoretical
predictions based on NLO calculation with parton showers.Comment: 15 pages, 11 figure
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