40,936 research outputs found
A Symmetric Free Energy Based Multi-Component Lattice Boltzmann Method
We present a lattice Boltzmann algorithm based on an underlying free energy
that allows the simulation of the dynamics of a multicomponent system with an
arbitrary number of components. The thermodynamic properties, such as the
chemical potential of each component and the pressure of the overall system,
are incorporated in the model. We derived a symmetrical convection diffusion
equation for each component as well as the Navier Stokes equation and
continuity equation for the overall system. The algorithm was verified through
simulations of binary and ternary systems. The equilibrium concentrations of
components of binary and ternary systems simulated with our algorithm agree
well with theoretical expectations.Comment: 7 pager, 4 figure
Corrections to di-Higgs boson production with light stops and modified Higgs couplings
The Higgs pair production in gluon fusion is a sensitive probe of
beyond-Standard Model (BSM) phenomena and its detection is a major goal for the
LHC and higher energy hadron collider experiments. In this work we reanalyze
the possible modifications of the Higgs pair production cross section within
low energy supersymmetry models. We show that the supersymmetric contributions
to the Higgs pair production cross section are strongly correlated with the
ones of the single Higgs production in the gluon fusion channel. Motivated by
the analysis of ATLAS and CMS Higgs production data, we show that the scalar
superpartners' contributions may lead to significant modification of the
di-Higgs production rate and invariant mass distribution with respect to the SM
predictions. We also analyze the combined effects on the di-Higgs production
rate of a modification of the Higgs trilinear and top-quark Yukawa couplings in
the presence of light stops. In particular, we show that due to the destructive
interference of the triangle and box amplitude contributions to the di-Higgs
production cross section, even a small modification of the top-quark Yukawa
coupling can lead to a significant increase of the di-Higgs production rate.Comment: 33 pages, 13 figures v2: minor improvements, PRD versio
Probing the Electroweak Phase Transition at the LHC
We study the correlation between the value of the triple Higgs coupling and
the nature of the electroweak phase transition. We use an effective potential
approach, including higher order, non-renormalizable terms coming from
integrating out new physics. We show that if only the dimension six operators
are considered, large positive deviations of the triple Higgs coupling from its
Standard Model (SM) value are predicted in the regions of parameter space
consistent with a strong first order electroweak phase transition (SFOEPT). We
also show that at higher orders sizable and negative deviations of the triple
Higgs coupling may be obtained, and the sign of the corrections tends to be
correlated with the order of the phase transition. We also consider a singlet
extension of the SM, which allows us to establish the connection with the
effective field theory (EFT) approach and analyze the limits of its validity.
Furthermore, we study how to probe the triple Higgs coupling from the double
Higgs production at the LHC. We show that selective cuts in the invariant mass
of the two Higgs bosons should be used, to maximize the sensitivity for values
of the triple Higgs coupling significantly different from the Standard Model
one.Comment: 43 pages, 4 figure
Are complex systems hard to evolve?
Evolutionary complexity is here measured by the number of trials/evaluations
needed for evolving a logical gate in a non-linear medium. Behavioural
complexity of the gates evolved is characterised in terms of cellular automata
behaviour. We speculate that hierarchies of behavioural and evolutionary
complexities are isomorphic up to some degree, subject to substrate specificity
of evolution and the spectrum of evolution parameters
Impact of a non-uniform charge distribution on virus assembly
Many spherical viruses encapsulate their genome in protein shells with
icosahedral symmetry. This process is spontaneous and driven by electrostatic
interactions between positive domains on the virus coat proteins and the
negative genome. We model the effect of the icosahedral charge distribution
from the protein shell instead of uniform using a mean-field theory. We find
that the non-uniform charge distribution strongly affects the optimal genome
length, and that it can explain the experimentally observed phenomenon of
overcharging of virus and virus-like particles
Role of inertia in two-dimensional deformation and breakup of a droplet
We investigate by Lattice Boltzmann methods the effect of inertia on the
deformation and break-up of a two-dimensional fluid droplet surrounded by fluid
of equal viscosity (in a confined geometry) whose shear rate is increased very
slowly. We give evidence that in two dimensions inertia is {\em necessary} for
break-up, so that at zero Reynolds number the droplet deforms indefinitely
without breaking. We identify two different routes to breakup via two-lobed and
three-lobed structures respectively, and give evidence for a sharp transition
between these routes as parameters are varied.Comment: 4 pages, 4 figure
Exploring the assortativity-clustering space of a network's degree sequence
Nowadays there is a multitude of measures designed to capture different
aspects of network structure. To be able to say if the structure of certain
network is expected or not, one needs a reference model (null model). One
frequently used null model is the ensemble of graphs with the same set of
degrees as the original network. In this paper we argue that this ensemble can
be more than just a null model -- it also carries information about the
original network and factors that affect its evolution. By mapping out this
ensemble in the space of some low-level network structure -- in our case those
measured by the assortativity and clustering coefficients -- one can for
example study how close to the valid region of the parameter space the observed
networks are. Such analysis suggests which quantities are actively optimized
during the evolution of the network. We use four very different biological
networks to exemplify our method. Among other things, we find that high
clustering might be a force in the evolution of protein interaction networks.
We also find that all four networks are conspicuously robust to both random
errors and targeted attacks
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