241 research outputs found
A turning point analysis of the ergodic dynamics of iterative maps
The dynamics of one dimensional iterative maps in the regime of fully
developed chaos is studied in detail. Motivated by the observation of dynamical
structures around the unstable fixed point we introduce the geometrical concept
of a turning point which represents a local minimum or maximum of the
trajectory. Following we investigate the highly organized and structured
distribution of turning points. The turning point dynamics is discussed and the
corresponding turning point map which possesses an appealing asymptotic scaling
property is investigated. Strong correlations are shown to exist for the
turning point trajectories which contain the information of the fixed points as
well as the stability coefficients of the dynamical system. For the more
specialized case of symmetric maps which possess a symmetric density we derive
universal statistical properties of the corresponding turning point dynamics.
Using the turning point concept we finally develop a method for the analysis of
(one dimensional) time series.Comment: 37 pages, 11 figures, LaTeX, tccite.sty, to be published in the Int.
J. Bif. Chao
A Model for the Color Glass Condensate Versus Jet Quenching
A model for the Color Glass Condensate as opposed to jet quenching is
proposed for the explanation of the presently available RHIC data. Good fits to
these data are presented. A clear way to distinguish between the two possible
explanations is also given.Comment: 3 pages, 1 figur
Pion Fluctuations near the QCD Critical Point
A critical point of second order, belonging to the universality class of the
3d Ising model, has recently been advocated as a strong candidate for the
critical behaviour (at high temperatures) of QCD with non-zero quark masses.
The implications of this conjecture are investigated in the multiparticle
environment of high-energy collisions. A universal intermittency pattern of
pion-density fluctuations is found, at the critical point, and its association
to the critical exponents is discussed. A Monte Carlo simulation of critical
events, in heavy-ion collisions, reveals the detailed structure of these
fluctuations, suggesting a framework of (event-by-event) measurements in which
the critical theory of QCD may become falsifiable.Comment: 8 pages, 3 figures (ps
Partonic transverse momenta in non-relativistic hyper-central quark potential models
We investigate the impact of three-body forces on the transverse-momentum
distribution of partons inside the proton. This is achieved by considering the
three-body problem in a class of hyper-central quark potential models. Solving
the corresponding Schr\"odinger equation, we determine the quark wave function
in the proton and with appropriate transformations and projections we find the
transverse-momentum distribution of a single quark. In each case the parameters
of the quark potentials are adjusted in order to sufficiently describe
observable properties of the proton. Using a factorization ansatz, we
incorporate the obtained transverse-momentum distribution in a perturbative QCD
scheme for the calculation of the cross-section for prompt photon production in
pp collisions. A large set of experimental data is fitted using as a single
free parameter the mean partonic transverse momentum. The dependence of
on the collision characteristics (initial energy and transverse momentum of the
final photon) is much smoother when compared with similar results found in the
literature using a Gaussian distribution for the partonic transverse momenta.
Within the considered class of hyper-central quark potentials the one with the
weaker dependence on the hyper-radius is preferred for the description of the
data since it leads to the smoothest mean partonic transverse-momentum profile.
We have repeated all the calculations using a two-body potential of the same
form as the optimal (within the considered class) hyper-central potential in
order to check if the presence of three-body forces is supported by the
experimental data. Our analysis indicates that three-body forces influence
significantly the form of the parton transverse-momentum distribution and
consequently lead to an improved description of the considered data.Comment: 8 pages, 7 figure
Finite temperature crossover from a crystalline to a cluster phase for a confined finite chain of ions
Employing Monte-Carlo simulation techniques we investigate the statistical
properties of equally charged particles confined in a one-dimensional box trap
and detect a crossover from a crystalline to a cluster phase with increasing
temperature. The corresponding transition temperature depends separately on the
number of particles N and the box size L, implying non-extensivity due to the
long-range character of the interactions. The probability density of the
spacing between the particles exhibits at low temperatures an accumulation of
discrete peaks with an overall asymmetric shape. In the vicinity of the
transition temperature it is of a Gaussian form whereas in the high temperature
regime an exponential decay is observed. The high temperature behaviour shows a
cluster phase with a mean cluster size that first increases with the
temperature and then saturates. The crossover is clearly identifiable also in
the non-linear behaviour of the heat capacity with varying temperature. The
influence of the trapping potential on the observed results as well as possible
experimental realizations are briefly addressed.Comment: 12 pages, 13 figure
Critical Fluctuations at RHIC
On the basis of universal scaling properties, we claim that in Au+Au
collisions at RHIC, the QCD critical point is within reach. The signal turns
out to be an extended plateau of net baryons in rapidity with approximate
height of the net-baryon rapidity density approximately 15 and a strong
intermittency pattern with index s_2=1/6 in rapidity fluctuations. A window
also exists, to reach the critical point at the SPS, especially in Si+Si
collisions at maximal energy.Comment: 8 pages, 3 figure
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