67,861 research outputs found
Handedness of direct photons
The azimuthal asymmetry of direct photons originating from primary hard
scatterings between partons is calculated. This can be accounted for by the
inclusion of the color dipole orientation, which is sensitive to the rapid
variation of the nuclear profile. To this end we introduce the dipole
orientation within the saturation model of Golec-Biernat and W\"usthoff, while
preserving all its features at the cross-section level. We show that the direct
photon elliptic anisotropy v2 coming from this mechanism changes sign and
becomes negative for peripheral collisions, albeit it is quite small for
nuclear collisions at the RHIC energy.Comment: 6 pages, 6 figures, Based on talk given by A.H.R. at II LAWHEP, Sao
Miguel das Missoes, Brazil, December 3-7, 200
Finite-Element Simulations of Light Propagation through Circular Subwavelength Apertures
Light transmission through circular subwavelength apertures in metallic films
with surrounding nanostructures is investigated numerically. Numerical results
are obtained with a frequency-domain finite-element method. Convergence of the
obtained observables to very low levels of numerical error is demonstrated.
Very good agreement to experimental results from the literature is reached, and
the utility of the method is demonstrated in the investigation of the influence
of geometrical parameters on enhanced transmission through the apertures
Incomplete and Asymmetric Surplus Information in Labor Relations
Numerous laboratory experiments show that workers reciprocate to high wages with high effort, when there is perfect information on the surplus created. Recent field experiments, however, suggest that trust and reciprocity may be lower or absent when the information is incomplete.We report a laboratory experiment with symmetric and asymmetric incomplete surplus information in a bilateral gift exchange setting.We find that trust and reciprocity have a significant positive effect on wages, effort and efficiency.But, all three are substantially lower under incomplete than under complete information.The negative impact on wages and efficiency is even greater with information asymmetry.incomplete information;industrial relations;trusts;efficiency
Alas, the dark matter structures were not that trivial
The radial density profile of dark matter structures has been observed to
have an almost universal behaviour in numerical simulations, however, the
physical reason for this behaviour remains unclear. It has previously been
shown that if the pseudo phase-space density, rho/sigma_d^epsilon, is a
beautifully simple power-law in radius, with the "golden values" epsilon=3 and
d=r (i.e., the phase-space density is only dependent on the radial component of
the velocity dispersion), then one can analytically derive the radial variation
of the mass profile, dispersion profile etc. That would imply, if correct, that
we just have to explain why rho/sigma^3_r ~r^{-alpha}, and then we would
understand everything about equilibrated DM structures. Here we use a set of
simulated galaxies and clusters of galaxies to demonstrate that there are no
such golden values, but that each structure instead has its own set of values.
Considering the same structure at different redshifts shows no evolution of the
phase-space parameters towards fixed points. There is also no clear connection
between the halo virialized mass and these parameters. This implies that we
still do not understand the origin of the profiles of dark matter structures.Comment: 4 pages, 3 figures, accepted for publication in ApJ
Unifying Magnons and Triplons in Stripe-Ordered Cuprate Superconductors
Based on a two-dimensional model of coupled two-leg spin ladders, we derive a
unified picture of recent neutron scattering data of stripe-ordered
La_(15/8)Ba_(1/8)CuO_4, namely of the low-energy magnons around the
superstructure satellites and of the triplon excitations at higher energies.
The resonance peak at the antiferromagnetic wave vector Q_AF in the
stripe-ordered phase corresponds to a saddle point in the dispersion of the
magnetic excitations. Quantitative agreement with the neutron data is obtained
for J= 130-160 meV and J_cyc/J = 0.2-0.25.Comment: 4 pages, 4 figures included updated version taking new data into
account; factor in spectral weight corrected; Figs. 2 and 4 change
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