7,259 research outputs found
Flash of photons from the early stage of heavy-ion collisions
The dynamics of partonic cascades may be an important aspect for particle
production in relativistic collisions of nuclei at CERN SPS and BNL RHIC
energies. Within the Parton-Cascade Model, we estimate the production of single
photons from such cascades due to scattering of quarks and gluons q g -> q
gamma, quark-antiquark annihilation q qbar -> g gamma, or gamma gamma, and from
electromagnetic brems-strahlung of quarks q -> q gamma. We find that the latter
QED branching process plays the dominant role for photon production, similarly
as the QCD branchings q -> q g and g -> g g play a crucial role for parton
multiplication. We conclude therefore that photons accompanying the parton
cascade evolution during the early stage of heavy-ion collisions shed light on
the formation of a partonic plasma.Comment: 4 pages including 3 postscript figure
Low Dirac Eigenmodes and the Topological and Chiral Structure of the QCD Vacuum
Several lattice calculations which probe the chiral and topological structure
of QCD are discussed. The results focus attention on the low-lying eigenmodes
of the Dirac operator in typical gauge field configurations.Comment: Talk presented at the DPF2000 Conferenc
Sub-gap spectroscopy of thermally excited quasiparticles in a Nb contacted carbon nanotube quantum dot
We present electronic transport measurements of a single wall carbon nanotube
quantum dot coupled to Nb superconducting contacts. For temperatures comparable
to the superconducting gap peculiar transport features are observed inside the
Coulomb blockade and superconducting energy gap regions. The observed
temperature dependence can be explained in terms of sequential tunneling
processes involving thermally excited quasiparticles. In particular, these new
channels give rise to two unusual conductance peaks at zero bias in the
vicinity of the charge degeneracy point and allow to determine the degeneracy
of the ground states involved in transport. The measurements are in good
agreement with model calculations.Comment: 5 pages, 4 figure
ContextVP: Fully Context-Aware Video Prediction
Video prediction models based on convolutional networks, recurrent networks,
and their combinations often result in blurry predictions. We identify an
important contributing factor for imprecise predictions that has not been
studied adequately in the literature: blind spots, i.e., lack of access to all
relevant past information for accurately predicting the future. To address this
issue, we introduce a fully context-aware architecture that captures the entire
available past context for each pixel using Parallel Multi-Dimensional LSTM
units and aggregates it using blending units. Our model outperforms a strong
baseline network of 20 recurrent convolutional layers and yields
state-of-the-art performance for next step prediction on three challenging
real-world video datasets: Human 3.6M, Caltech Pedestrian, and UCF-101.
Moreover, it does so with fewer parameters than several recently proposed
models, and does not rely on deep convolutional networks, multi-scale
architectures, separation of background and foreground modeling, motion flow
learning, or adversarial training. These results highlight that full awareness
of past context is of crucial importance for video prediction.Comment: 19 pages. ECCV 2018 oral presentation. Project webpage is at
https://wonmin-byeon.github.io/publication/2018-ecc
Transport in Floquet-Bloch bands
We report Floquet band engineering of long-range transport and direct imaging
of Floquet-Bloch bands in an amplitude-modulated optical lattice. In one
variety of Floquet-Bloch band we observe tunable rapid long-range high-fidelity
transport of a Bose condensate across thousands of lattice sites. Quenching
into an opposite-parity Floquet-hybridized band allows Wannier-Stark
localization to be controllably turned on and off using modulation. A central
result of this work is the use of transport dynamics to demonstrate direct
imaging of a Floquet-Bloch band structure. These results demonstrate that
transport in dynamical Floquet-Bloch bands can be mapped to transport in
quasi-static effective bands, opening a path to cold atom quantum emulation of
ultrafast multi-band electronic dynamics.Comment: 5 pages, 4 figure
Adding Salt to an Aqueous Solution of t-Butanol: Is Hydrophobic Association Enhanced or Reduced?
Recent neutron scattering experiments on aqueous salt solutions of
amphiphilic t-butanol by Bowron and Finney [Phys. Rev. Lett. {\bf 89}, 215508
(2002); J. Chem. Phys. {\bf 118}, 8357 (2003)] suggest the formation of
t-butanol pairs, bridged by a chloride ion via
hydrogen-bonds, and leading to a reduced number of intermolecular hydrophobic
butanol-butanol contacts. Here we present a joint experimental/theoretical
study on the same system, using a combination of molecular dynamics simulations
and nuclear magnetic relaxation measurements. Both theory and experiment
clearly support the more intuitive scenario of an enhanced number of
hydrophobic contacts in the presence of the salt, as it would be expected for
purely hydrophobic solutes [J. Phys. Chem. B {\bf 107}, 612 (2003)]. Although
our conclusions arrive at a structurally completely distinct scenario, the
molecular dynamics simulation results are within the experimental errorbars of
the Bowron and Finney work.Comment: 15 pages twocolumn revtex, 11 figure
Inclusive Particle Spectra at RHIC
A simulation is performed of the recently reported data from PHOBOS at
energies of 56 and 130 A GeV using the relativistic heavy ion cascade LUCIFER
which had previously given a good description of the NA49 inclusive spectra at
E=17.2 A GeV. The results compare well with these early measurements at RHIC.Comment: 4 pages, 2 figure
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