3,220 research outputs found
Experimental verification of democratic particle motions by direct imaging of glassy colloidal systems
We analyze data from confocal microscopy experiments of a colloidal
suspension to validate predictions of rapid sporadic events responsible for
structural relaxation in a glassy sample. The trajectories of several thousand
colloidal particles are analyzed, confirming the existence of rapid sporadic
events responsible for the structural relaxation of significant regions of the
sample, and complementing prior observations of dynamical heterogeneity. The
emergence of relatively compact clusters of mobility allows the dynamics to
transition between the large periods of local confinement within its potential
energy surface, in good agreement with the picture envisioned long ago by Adam
and Gibbs and Goldstein.Comment: 4 pages, 5 figure
Possible Signatures Of Dissipation From Time-Series Analysis Techniques Using A Turbulent Laboratory Magnetohydrodynamic Plasma
The frequency spectrum of magnetic fluctuations as measured on the Swarthmore Spheromak Experiment is broadband and exhibits a nearly Kolmogorov 5/3 scaling. It features a steepening region which is indicative of dissipation of magnetic fluctuation energy similar to that observed in fluid and magnetohydrodynamic turbulence systems. Two non-spectrum based time-series analysis techniques are implemented on this data set in order to seek other possible signatures of turbulent dissipation beyond just the steepening of fluctuation spectra. Presented here are results for the flatness, permutation entropy, and statistical complexity, each of which exhibits a particular character at spectral steepening scales which can then be compared to the behavior of the frequency spectrum
Bragg spectroscopy for measuring Casimir-Polder interactions with Bose-Einstein condensates above corrugated surfaces
We propose a method to probe dispersive atom-surface interactions by measuring via two-photon Bragg spectroscopy the dynamic structure factor of a Bose-Einstein condensate above corrugated surfaces. This method takes advantage of the condensate coherence to reveal the spatial Fourier components of the lateral Casimir-Polder interaction energy.Fil: Moreno, Gustavo Ariel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Ciudad Universitaria. Instituto de FĂsica de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de FĂsica de Buenos Aires; ArgentinaFil: Dalvit, Diego A. R.. Los Alamos National High Magnetic Field Laboratory; Estados UnidosFil: Calzetta, Esteban Adolfo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Ciudad Universitaria. Instituto de FĂsica de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de FĂsica de Buenos Aires; Argentin
Anomalous Axion Interactions and Topological Currents in Dense Matter
Recently an effective Lagrangian for the interactions of photons,
Nambu-Goldstone bosons and superfluid phonons in dense quark matter has been
derived using anomaly matching arguments. In this paper we illuminate the
nature of certain anomalous terms in this Lagrangian by an explicit microscopic
calculation. We also generalize the corresponding construction to introduce the
axion field. We derive an anomalous axion effective Lagrangian describing the
interactions of axions with photons and superfluid phonons in the dense matter
background. This effective Lagrangian, among other things, implies that an
axion current will be induced in the presence of magnetic field. We speculate
that this current may be responsible for the explanation of neutron star kicks.Comment: 10 page
Floquet topological transitions in extended Kane-Mele models with disorder
In this work we use Floquet theory to theoretically study the influence of
circularly polarized light on disordered two-dimensional models exhibiting
topological transitions. We find circularly polarized light can induce a
topological transition in extended Kane-Mele models that include additional
hopping terms and on-site disorder. The topological transitions are understood
from the Floquet-Bloch band structure of the clean system at high symmetry
points in the first Brillouin zone. The light modifies the equilibrium band
structure of the clean system in such a way that the smallest gap in the
Brillouin zone can be shifted from the points to the points, the
point, or even other lower symmetry points. The movement of the
minimal gap point through the Brillouin zone as a function of laser parameters
is explained in the high frequency regime through the Magnus expansion. In the
disordered model, we compute the Bott index to reveal topological phases and
transitions. The disorder can induce transitions from topologically non-trivial
states to trivial states or vice versa, both examples of Floquet topological
Anderson transitions. As a result of the movement of the minimal gap point
through the Brillouin zone as a function of laser parameters, the nature of the
topological phases and transitions is laser-parameter dependent--a contrasting
behavior to the Kane-Mele model.Comment: 10 pages, 7 figure
The Electrosphere of Macroscopic "Quark Nuclei": A Source for Diffuse MeV Emissions from Dark Matter
Using a Thomas-Fermi model, we calculate the structure of the electrosphere
of the quark antimatter nuggets postulated to comprise much of the dark matter.
This provides a single self-consistent density profile from ultrarelativistic
densities to the nonrelativistic Boltzmann regime that use to present
microscopically justified calculations of several properties of the nuggets,
including their net charge, and the ratio of MeV to 511 keV emissions from
electron annihilation. We find that the calculated parameters agree with
previous phenomenological estimates based on the observational supposition that
the nuggets are a source of several unexplained diffuse emissions from the
Galaxy. As no phenomenological parameters are required to describe these
observations, the calculation provides another nontrivial verification of the
dark-matter proposal. The structure of the electrosphere is quite general and
will also be valid at the surface of strange-quark stars, should they exist.Comment: 20 Pages, REVTeX4.
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