1,473 research outputs found
Generalized hydrodynamics of classical integrable field theory: the sinh-Gordon model
Using generalized hydrodynamics (GHD), we develop the Euler hydrodynamics of
classical integrable field theory. Classical field GHD is based on a known
formalism for Gibbs ensembles of classical fields, that resembles the
thermodynamic Bethe ansatz of quantum models, which we extend to generalized
Gibbs ensembles (GGEs). In general, GHD must take into account both solitonic
and radiative modes of classical fields. We observe that the quasi-particle
formulation of GHD remains valid for radiative modes, even though these do not
display particle-like properties in their precise dynamics. We point out that
because of a UV catastrophe similar to that of black body radiation, radiative
modes suffer from divergences that restrict the set of finite-average
observables; this set is larger for GGEs with higher conserved charges. We
concentrate on the sinh-Gordon model, which only has radiative modes, and study
transport in the domain-wall initial problem as well as Euler-scale
correlations in GGEs. We confirm a variety of exact GHD predictions, including
those coming from hydrodynamic projection theory, by comparing with Metropolis
numerical evaluations.Comment: 41 pages, 9 figure
Preferred sizes and ordering in surface nanobubble populations
Two types of homogeneous surface nanobubble populations, created by different
means, are analyzed statistically on both their sizes and spatial positions. In
the first type (created by droplet-deposition, case A) the bubble size R is
found to be distributed according to a generalized gamma law with a preferred
radius R*=20 nm. The radial distribution function shows a preferred spacing at
~5.5 R*. These characteristics do not show up in comparable Monte-Carlo
simulations of random packings of hard disks with the same size distribution
and the same density, suggesting a structuring effect in the nanobubble
formation process. The nanobubble size distribution of the second population
type (created by ethanol-water exchange, case B) is a mixture of two clearly
separated distributions, hence, with two preferred radii. The local ordering is
less significant, due to the looser packing of the nanobubbles.Comment: 5 pages, 5 figure
Insights from the Outskirts: Chemical and Dynamical Properties in the outer Parts of the Fornax Dwarf Spheroidal Galaxy
We present radial velocities and [Fe/H] abundances for 340 stars in the
Fornax dwarf spheroidal from R~16,000 spectra. The targets have been obtained
in the outer parts of the galaxy, a region which has been poorly studied
before. Our sample shows a wide range in [Fe/H], between -0.5 and -3.0 dex, in
which we detect three subgroups. Removal of stars belonging to the most
metal-rich population produces a truncated metallicity distribution function
that is identical to Sculptor, indicating that these systems have shared a
similar early evolution, only that Fornax experienced a late, intense period of
star formation (SF). The derived age-metallicity relation shows a fast increase
in [Fe/H] at early ages, after which the enrichment flattens significantly for
stars younger than ~8 Gyr. Additionally, the data indicate a strong population
of stars around 4 Gyr, followed by a second rapid enrichment in [Fe/H]. A
leaky-box chemical enrichment model generally matches the observed relation but
does not predict a significant population of young stars nor the strong
enrichment at late times. The young population in Fornax may therefore
originate from an externally triggered SF event. Our dynamical analysis reveals
an increasing velocity dispersion with decreasing [Fe/H] from sigma_sys 7.5
km/s to >14 km/s, indicating an outside-in star formation history in a dark
matter dominated halo. The large velocity dispersion at low metallicities is
possibly the result of a non-Gaussian velocity distribution amongst stars older
than ~8 Gyr. Our sample also includes members from the Fornax GCs H2 and H5. In
agreement with past studies we find [Fe/H]=-2.04+-0.04 and a mean radial
velocity RV=59.36+-0.31 km/s for H2 and [Fe/H]=-2.02+-0.11 and RV=59.39+-0.44
km/s for H5. Overall, we find large complexity in the chemical and dynamical
properties, with signatures that additionally vary with galactocentric
distance.Comment: 21 pages, 18 figures, 4 tables, accepted for publication in A&
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