2,478 research outputs found
Work fluctuations of self-propelled particles in the phase separated state
We study the large deviations of the distribution P(W_\tau) of the work
associated with the propulsion of individual active brownian particles in a
time interval \tau, in the region of the phase diagram where macroscopic phase
separation takes place. P(W_\tau) is characterised by two peaks, associated to
particles in the gaseous and in the clusterised phases, and two separate
non-convex branches. Accordingly, the generating function of W_\tau cumulants
displays a double singularity. We discuss the origin of such non-convex
branches in terms of the peculiar dynamics of the system phases, and the
relation between the observation time \tau and the typical persistence times of
the particles in the two phases.Comment: 7 pages, 5 figure
Glassy transition and metastability in four-spin Ising model
Using Monte Carlo simulations we show that the three-dimensional Ising model
with four-spin (plaquette) interactions has some characteristic glassy
features. The model dynamically generates diverging energy barriers, which give
rise to slow dynamics at low temperature. Moreover, in a certain temperature
range the model possesses a metastable (supercooled liquid) phase, which is
presumably supported by certain entropy barriers. Although extremely strong,
metastability in our model is only a finite-size effect and sufficiently large
droplets of stable phase divert evolution of the system toward the stable
phase. Thus, the glassy transitions in this model is a dynamic transition,
preceded by a pronounced peak in the specific heat.Comment: extensively revised, with further simulations of metastability
properties, response to referees tactfully remove
Effects of an external drive on the fluctuation-dissipation relation of phase-ordering systems
The relation between the autocorrelation and the integrated linear
response function is studied in the context of the large-N model
for phase-ordering systems subjected to a shear flow. In the high temperature
phase a non-equilibrium stationary state is entered which is
characterized by a non-trivial fluctuation-dissipation relation . For quenches below the splitting of the
order parameter field into two statistically independent components,
responsible for the stationary and aging part
of the autocorrelation function, can be explicitly exhibited in close analogy
with the undriven case. In the regime the same relation is found between the response and
, as for . The aging part of is
negligible for , as without drive, resulting in a flat in the aging regime .Comment: 8 pages, 2 figure
Barattiere: An italian local variety of Cucumis melo L. with quality traits between melon and cucumber
Barattiere, belonging to the Cucumis melo L. species, is a local variety of Puglia (Southern Italy), which is consumed as a vegetable at the immature stage, like cucumber. In this study, three Barattiere populations (‘Monopoli’, ‘Carovigno’ and ‘Fasano’) were evaluated for the main quality traits. All genotypes showed a very light green-yellow colour of flesh, without any difference regarding chlorophyll and carotenoid contents. Carovigno’s Barattiere showed the highest values of dry weight (6.8 g 100 g−1 fresh weight-FW), sugars (45 g kg−1 FW), and sweetness index (7.3), while Monopoli’s Barattiere showed the lowest total phenols content (21 mg kg−1 FW). Fasano’s Barattiere showed the highest content of Zn and Cu (2.3 and 0.3 mg kg−1 FW, respectively), while ‘Monopoli’ showed the highest Ba content (0.3 mg kg−1 FW) and the lowest Mg content (94 mg kg−1 FW). No differences between populations were found concerning the content of Ca, K, Na, B, Mn, and Fe. In conclusion, the quality profile of Barattiere makes this local genotype interesting for its traits, and also suggests its consumption by people with specific dietary requirements
Folding transitions of the triangular lattice with defects
A recently introduced model describing the folding of the triangular lattice
is generalized allowing for defects in the lattice and written as an Ising
model with nearest-neighbor and plaquette interactions on the honeycomb
lattice. Its phase diagram is determined in the hexagon approximation of the
cluster variation method and the crossover from the pure Ising to the pure
folding model is investigated, obtaining a quite rich structure with several
multicritical points. Our results are in very good agreement with the available
exact ones and extend a previous transfer matrix study.Comment: 16 pages, latex, 5 postscript figure
Spinodal decomposition of off-critical quenches with a viscous phase using dissipative particle dynamics in two and three spatial dimensions
We investigate the domain growth and phase separation of
hydrodynamically-correct binary immiscible fluids of differing viscosity as a
function of minority phase concentration in both two and three spatial
dimensions using dissipative particle dynamics. We also examine the behavior of
equal-viscosity fluids and compare our results to similar lattice-gas
simulations in two dimensions.Comment: 34 pages (11 figures); accepted for publication in Phys. Rev.
Lattice Boltzmann simulations of lamellar and droplet phases
Lattice Boltzmann simulations are used to investigate spinodal decomposition
in a two-dimensional binary fluid with equilibrium lamellar and droplet phases.
We emphasise the importance of hydrodynamic flow to the phase separation
kinetics. For mixtures slightly asymmetric in composition the fluid phase
separates into bulk and lamellar phases with the lamellae forming distinctive
spiral structures to minimise their elastic energy.Comment: 19 pages, 5 figure
Thermocurrents and their Role in high Q Cavity Performance
Over the past years it became evident that the quality factor of a
superconducting cavity is not only determined by its surface preparation
procedure, but is also influenced by the way the cavity is cooled down.
Moreover, different data sets exists, some of them indicate that a slow
cool-down through the critical temperature is favourable while other data
states the exact opposite. Even so there where speculations and some models
about the role of thermo-currents and flux-pinning, the difference in behaviour
remained a mystery. In this paper we will for the first time present a
consistent theoretical model which we confirmed by data that describes the role
of thermo-currents, driven by temperature gradients and material transitions.
We will clearly show how they impact the quality factor of a cavity, discuss
our findings, relate it to findings at other labs and develop mitigation
strategies which especially addresses the issue of achieving high quality
factors of so-called nitrogen doped cavities in horizontal test
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