217,036 research outputs found
Local molecular field theory for effective attractions between like charged objects in systems with strong Coulomb interactions
Strong short ranged positional correlations involving counterions can induce
a net attractive force between negatively charged strands of DNA, and lead to
the formation of ion pairs in dilute ionic solutions. But the long range of the
Coulomb interactions impedes the development of a simple local picture. We
address this general problem by mapping the properties of a nonuniform system
with Coulomb interactions onto those of a simpler system with short ranged
intermolecular interactions in an effective external field that accounts for
the averaged effects of appropriately chosen long ranged and slowly varying
components of the Coulomb interactions. The remaining short ranged components
combine with the other molecular core interactions and strongly affect pair
correlations in dense or strongly coupled systems. We show that pair
correlation functions in the effective short ranged system closely resemble
those in the uniform primitive model of ionic solutions, and illustrate the
formation of ion pairs and clusters at low densities. The theory accurately
describes detailed features of the effective attraction between two equally
charged walls at strong coupling and intermediate separations of the walls. New
analytical results for the minimal coupling strength needed to get any
attraction and for the separation where the attractive force is a maximum are
presented.Comment: 8 pages, 5 figures. To be published in PNA
Early Time Dynamics of Gluon Fields in High Energy Nuclear Collisions
Nuclei colliding at very high energy create a strong, quasi-classical gluon
field during the initial phase of their interaction. We present an analytic
calculation of the initial space-time evolution of this field in the limit of
very high energies using a formal recursive solution of the Yang-Mills
equations. We provide analytic expressions for the initial chromo-electric and
chromo-magnetic fields and for their energy-momentum tensor. In particular, we
discuss event-averaged results for energy density and energy flow as well as
for longitudinal and transverse pressure of this system. For example, we find
that the ratio of longitudinal to transverse pressure very early in the system
behaves as where
is the longitudinal proper time, is related to the saturation scales
of the two nuclei, and with a scale to
be defined later. Our results are generally applicable if .
As already discussed in a previous paper, the transverse energy flow of
the gluon field exhibits hydrodynamic-like contributions that follow transverse
gradients of the energy density . In addition, a
rapidity-odd energy flow also emerges from the non-abelian analog of Gauss' Law
and generates non-vanishing angular momentum of the field. We will discuss the
space-time picture that emerges from our analysis and its implications for
observables in heavy ion collisions.Comment: 26 pages, 9 figure
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