10,793 research outputs found
Fluctuations in ballistic transport from Euler hydrodynamics
We propose a general formalism, within large deviation theory, giving access
to the exact statistics of fluctuations of ballistically transported conserved
quantities in homogeneous, stationary states. The formalism is expected to
apply to any system with an Euler hydrodynamic description, classical or
quantum, integrable or not, in or out of equilibrium. We express the exact
scaled cumulant generating function (or full counting statistics) for any
(quasi-)local conserved quantity in terms of the flux Jacobian. We show that
the "extended fluctuation relations" of Bernard and Doyon follow from the
linearity of the hydrodynamic equations, forming a marker of "freeness" much
like the absence of hydrodynamic diffusion does. We show how an extension of
the formalism gives exact exponential behaviours of spatio-temporal two-point
functions of twist fields, with applications to order-parameter dynamical
correlations in arbitrary homogeneous, stationary state. We explain in what
situations the large deviation principle at the basis of the results fail, and
discuss how this connects with nonlinear fluctuating hydrodynamics. Applying
the formalism to conformal hydrodynamics, we evaluate the exact cumulants of
energy transport in quantum critical systems of arbitrary dimension at low but
nonzero temperatures, observing a phase transition for Lorentz boosts at the
sound velocity.Comment: 27+22 pages, one figur
Harnessing Interpretable and Unsupervised Machine Learning to Address Big Data from Modern X-ray Diffraction
The information content of crystalline materials becomes astronomical when
collective electronic behavior and their fluctuations are taken into account.
In the past decade, improvements in source brightness and detector technology
at modern x-ray facilities have allowed a dramatically increased fraction of
this information to be captured. Now, the primary challenge is to understand
and discover scientific principles from big data sets when a comprehensive
analysis is beyond human reach. We report the development of a novel
unsupervised machine learning approach, XRD Temperature Clustering (X-TEC),
that can automatically extract charge density wave (CDW) order parameters and
detect intra-unit cell (IUC) ordering and its fluctuations from a series of
high-volume X-ray diffraction (XRD) measurements taken at multiple
temperatures. We apply X-TEC to XRD data on a quasi-skutterudite family of
materials, (CaSr)RhSn, where a quantum critical
point arising from charge order is observed as a function of Ca concentration.
We further apply X-TEC to XRD data on the pyrochlore metal, CdReO,
to investigate its two much debated structural phase transitions and uncover
the Goldstone mode accompanying them. We demonstrate how unprecedented atomic
scale knowledge can be gained when human researchers connect the X-TEC results
to physical principles. Specifically, we extract from the X-TEC-revealed
selection rule that the Cd and Re displacements are approximately equal in
amplitude, but out of phase. This discovery reveals a previously unknown
involvement of Re, supporting the idea of an electronic origin to the
structural order. Our approach can radically transform XRD experiments by
allowing in-operando data analysis and enabling researchers to refine
experiments by discovering interesting regions of phase space on-the-fly
The C-flash and the ignition conditions of type Ia supernovae
Thanks to a stellar evolution code able to compute through the
C-flash we link the binary population synthesis of single degenerate
progenitors of type Ia supernovae (SNe Ia) to their physical condition at the
time of ignition. We show that there is a large range of possible ignition
densities and we detail how their probability distribution depends on the
accretion properties. The low density peak of this distribution qualitatively
reminds of the clustering of the luminosities of Branch-normal SNe Ia. We
tighten the possible range of initial physical conditions for explosion models:
they form a one-parameter family, independent of the metallicity. We discuss
how these results may be modified if we were to relax our hypothesis of a
permanent Hachisu wind or if we were to include electron captures.Comment: 10 pages, 14 figures, MNRAS accepte
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