7,671 research outputs found
Final-State Interaction as the Origin of the Cronin Effect
Instead of adhering to the usual explanation of the Cronin effect in terms of
the broadening of the parton transverse momentum in the initial state, we show
that the enhancement of hadron production at moderate in d+Au collisions
is due to the recombination of soft and shower partons in the final state. Such
a mechanism can readily explain the decrease of the Cronin effect with
increasing rapidity. Furthermore, the effect should be larger for protons than
for pions.Comment: 4 RevTeX pages including 3 figures and 1 table; Some notational
changes and a corrected referenc
Fluctuation Analysis of Human Electroencephalogram
The scaling behaviors of the human electroencephalogram (EEG) time series are
studied using detrended fluctuation analysis. Two scaling regions are found in
nearly every channel for all subjects examined. The scatter plot of the scaling
exponents for all channels (up to 129) reveals the complicated structure of a
subject's brain activity. Moment analyses are performed to extract the gross
features of all the scaling exponents, and another universal scaling behavior
is identified. A one-parameter description is found to characterize the
fluctuation properties of the nonlinear behaviors of the brain dynamics.Comment: 4 pages in RevTeX + 6 figures in ep
Critical Fluctuation of Wind Reversals in Convective Turbulence
The irregular reversals of wind direction in convective turbulence are found
to have fluctuating intervals that can be related to critical behavior. It is
shown that the net magnetization of a 2D Ising lattice of finite size
fluctuates in the same way. Detrended fluctuation analysis of the wind reversal
time series results in a scaling behavior that agrees with that of the Ising
problem. The properties found suggest that the wind reversal phenomenon
exhibits signs of self-organized criticality.Comment: 4 RevTeX pages + 3 figures in ep
Cluster Production in Quark-Hadron Phase Transition
The problem of cluster formation and growth in first-order quark-hadron phase
transition in heavy-ion collisions is considered. Behaving as Brownian
particles, the clusters carry out random walks and can encounter one another,
leading to coalescence and breakup. A simulation of the process in cellular
automaton suggests the possibility of a scaling distribution in the cluster
sizes. The experimental determination of the cluster-size distribution is urged
as a means to find a clear signature of phase transition.Comment: 12 pages + 1 figure. Report # OITS-517. To be published in Phys. Rev.
Lett. 71, xxx (1994
Simultaneous observation of high order multiple quantum coherences at ultralow magnetic fields
We present a method for the simultaneous observation of heteronuclear
multi-quantum coherences (up to the 3rd order), which give an additional degree
of freedom for ultralow magnetic field (ULF) MR experiments, where the chemical
shift is negligible. The nonequilibrium spin state is generated by Signal
Amplification By Reversible Exchange (SABRE) and detected at ULF with
SQUID-based NMR. We compare the results obtained by the heteronuclei Correlated
SpectroscopY (COSY) with a Flip Angle FOurier Series (FAFOS) method. COSY
allows a quantitative analysis of homo- and heteronuclei quantum coherences
Void Analysis of Hadronic Density Fluctuations at Phase Transition
The event-to-event fluctuations of hadron multiplicities are studied for a
quark system undergoing second-order phase transition to hadrons. Emphasis is
placed on the search for an observable signature that is realistic for
heavy-ion collisions. It is suggested that in the 2-dimensional y-phi space the
produced particles selected in a very narrow p_T window may exhibit clustering
patterns even when integrated over the entire emission time. Using the Ising
model to simulate the critical phenomenon and taking into account a p_T
distribution that depends on the emission time, we study in the framework of
the void analysis proposed earlier and find scaling behavior. The scaling
exponents turn out to be larger than the ones found before for pure
configurations without mixing. The signature is robust in that it is
insensitive to the precise scheme of simulating time evolution. Thus it should
reveal whether or not the dense matter created in heavy-ion collisions is a
quark-gluon plasma before hadronization.Comment: 11 pages in LaTeX + 6 figures in p
Charm Correlation as a Diagnostic Probe of Quark Matter
The use of correlation between two open-charm mesons is suggested to give
information about the nature of the medium created in heavy-ion collisions.
Insensitivity to the charm production rate is achieved by measuring normalized
cumulant. The acollinearity of the D momenta in the transverse plane is a
measure of the medium effect. Its dependence on nuclear size or E_T provides a
signature for the formation of quark matter.Comment: 12 pages, no figure
The Uniqueness Theorem for Entanglement Measures
We explore and develop the mathematics of the theory of entanglement
measures. After a careful review and analysis of definitions, of preliminary
results, and of connections between conditions on entanglement measures, we
prove a sharpened version of a uniqueness theorem which gives necessary and
sufficient conditions for an entanglement measure to coincide with the reduced
von Neumann entropy on pure states. We also prove several versions of a theorem
on extreme entanglement measures in the case of mixed states. We analyse
properties of the asymptotic regularization of entanglement measures proving,
for example, convexity for the entanglement cost and for the regularized
relative entropy of entanglement.Comment: 22 pages, LaTeX, version accepted by J. Math. Phy
Weak nonlinearities: A new route to optical quantum computation
Quantum information processing (QIP) offers the promise of being able to do
things that we cannot do with conventional technology. Here we present a new
route for distributed optical QIP, based on generalized quantum non-demolition
measurements, providing a unified approach for quantum communication and
computing. Interactions between photons are generated using weak
non-linearities and intense laser fields--the use of such fields provides for
robust distribution of quantum information. Our approach requires only a
practical set of resources, and it uses these very efficiently. Thus it
promises to be extremely useful for the first quantum technologies, based on
scarce resources. Furthermore, in the longer term this approach provides both
options and scalability for efficient many-qubit QIP.Comment: 7 Pages, 4 Figure
Further results on the cross norm criterion for separability
In the present paper the cross norm criterion for separability of density
matrices is studied. In the first part of the paper we determine the value of
the greatest cross norm for Werner states, for isotropic states and for Bell
diagonal states. In the second part we show that the greatest cross norm
criterion induces a novel computable separability criterion for bipartite
systems. This new criterion is a necessary but in general not a sufficient
criterion for separability. It is shown, however, that for all pure states, for
Bell diagonal states, for Werner states in dimension d=2 and for isotropic
states in arbitrary dimensions the new criterion is necessary and sufficient.
Moreover, it is shown that for Werner states in higher dimensions (d greater
than 2), the new criterion is only necessary.Comment: REVTeX, 19 page
- …