255,279 research outputs found
Single Inclusive Distribution and Two-Particle Correlations Inside One Jet at "Modified Leading Logarithmic Approximation" of Quantum Chromodynamics II : Steepest Descent Evaluation at Small X
The MLLA single inclusive distribution inside one high energy (gluon) jet at
small x is estimated by the steepest descent method. Its analytical expression
is obtained outside the "limiting spectrum". It is then used to evaluate
2-particle correlations at the same level of generality. The dependence of both
observables on the ratio between the infrared cutoff Q\_0 and Lambda\_QCD is
studied. Fong & Webber's results for correlations are recovered at the limits
when this ratio goes to 1 and when one stays close to the peak of the single
inclusive distribution.Comment: LaTeX, 22 pages, 18 .eps figure
Equilibrium of stellar dynamical systems in the context of the Vlasov-Poisson model
This short review is devoted to the problem of the equilibrium of stellar
dynamical systems in the context of the Vlasov-Poisson model. In a first part
we will review some classical problems posed by the application of the
Vlasov-Poisson model to the astrophysical systems like globular clusters or
galaxies. In a second part we will recall some recent numerical results which
may give us some some quantitative hints about the equilibrium state associated
to those systems.Comment: 8 pages, no figures, accepted in Communications in Nonlinear Science
and Numerical Simulatio
The internal structure of jets at colliders: light and heavy quark inclusive hadronic distributions
In this paper, we report our results on charged hadron multiplicities of
heavy quark initiated jets produced in high energy collisions. After
implementing the so-called dead cone effect in QCD evolution equations, we find
that the average multiplicity decreases significantly as compared to the
massless case. Finally, we discuss on the transverse momentum distribution of
light quark initiated jets and emphasize on the comparison between our
predictions and CDF data.Comment: 6 pages, 3 figures-Talk presented by Redamy Perez-Ramos at Jets in
Proton-Proton and Heavy-Ion Collisions, August 12-14, 2010, Prague, Czech
Republi
Boundary terms in the Barrett-Crane spin foam model and consistent gluing
We extend the lattice gauge theory-type derivation of the Barrett-Crane spin
foam model for quantum gravity to other choices of boundary conditions,
resulting in different boundary terms, and re-analyze the gluing of 4-simplices
in this context. This provides a consistency check of the previous derivation.
Moreover we study and discuss some possible alternatives and variations that
can be made to it and the resulting models.Comment: 10 pages, 2 figures, revtex; v2: typos in some formulas corrected,
version appeared in journa
Forward Flight Rotor Performance at Martian Atmospheric Densities and Sensitivity to Low Reynolds Numbers
Much effort has been made to enhance exploration on Mars. In addition to a rover and Mars-orbiting satellites, a Mars Helicopter Technology Demonstrator was proposed by the NASA Jet Propulsion Laboratory (JPL) to augment planetary research for the Mars 2020 Mission. Understanding rotor performance is vital for operations at Martian atmospheric conditions. The work presented is a study investigating rotor performance at Martian atmospheric conditions. Forward flight rotor tests were conducted in the Planetary Aeolian Laboratory (PAL) at NASA Ames Research Center, which has the capability to evacuate the air in the chamber to reach Martian atmospheric densities. A 1-meter-diameter rotor, roughly approximating the Mars Helicopter Technology Demonstrator, was tested at multiple atmospheric densities, including that of Mars. Rotor rotational speed, thrust, torque, power, and airspeed measurements were collected during the test. These results were then correlated with simulated cases using a mid-fidelity computational fluid dynamics software, Rotorcraft CFD (RotCFD). C81Generator (C81Gen) was used to generate airfoil aerodynamic coefficient for the spanwise locations along the rotor. To observe the differences between the C81Gen flow type modes at low Reynolds number, the simulations at Martian atmospheric densities were run under the fully turbulent, and the fully laminar flow type. In addition, Reynolds number effects (within 2x104 to 9x104) on experimental thrust coefficient, power coefficient, and figure of merit were analyzed. Within this chord- based Reynolds number range, CT and FM decreased around 26% and 36%, respectively, while CP remained fairly constant, exhibiting variations of no more than 5.5%. Despite the challenges involved in testing at a large difference of atmospheric ensities between Earth and Mars, repeatable data was obtained in all the measurements at Martian atmospheric conditions
Stabilizing Entangled States with Quasi-Local Quantum Dynamical Semigroups
We provide a solution to the problem of determining whether a target pure
state can be asymptotically prepared using dissipative Markovian dynamics under
fixed locality constraints. Beside recovering existing results for a large
class of physically relevant entangled states, our approach has the advantage
of providing an explicit stabilization test solely based on the input state and
constraints of the problem. Connections with the formalism of frustration-free
parent Hamiltonians are discussed, as well as control implementations in terms
of a switching output-feedback law.Comment: 11 pages, no figure
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Technological roots and structural implications of the double bubble at the turn of the Century
This paper argues that the two boom and bust episodes of the turn of the Century â the Internet mania and crash of 1990s and the easy liquidity boom and bust of 2000sâ are two distinct components of a single structural phenomenon. They are essentially the equivalent of 1929 developed in two stages, one centred on technological innovation, the other on financial innovation. Hence, the frequent references to that crash, to the 1930s and to Bretton Woods, are not simple journalistic metaphors for interpreting the âcredit crunchâ and its solution, but rather the intuitive recognition of a fundamental similarity between those events and the current ones. The paper holds that such major boom and bust episodes are endogenous to the way in which the market economy evolves and assimilates successive technological revolutions. It will discuss why it occurred in two bubbles on this occasion; it examines the differences and continuities between the two episodes and presents an interpretation of their nature and consequences
Finiteness of a spinfoam model for euclidean quantum general relativity
We prove that a certain spinfoam model for euclidean quantum general
relativity, recently defined, is finite: all its all Feynman diagrams converge.
The model is a variant of the Barrett-Crane model, and is defined in terms of a
field theory over SO(4) X SO(4) X SO(4) X SO(4).Comment: 6 pages, 1 figur
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