6,013 research outputs found
Amortized Bayesian Inference for Supernovae in the Era of the Vera Rubin Observatory Using Normalizing Flows
The Vera Rubin Observatory, set to begin observations in mid-2024, will
increase our discovery rate of supernovae to well over one million annually.
There has been a significant push to develop new methodologies to identify,
classify and ultimately understand the millions of supernovae discovered with
the Rubin Observatory. Here, we present the first simulation-based inference
method using normalizing flows, trained to rapidly infer the parameters of toy
supernovae model in multivariate, Rubin-like datastreams. We find that our
method is well-calibrated compared to traditional inference methodologies
(specifically MCMC), requiring only one-ten-thousandth of the CPU hours during
test time.Comment: 5 pages, accepted in the Neurips Machine Learning and the Physical
Sciences conferenc
Unconventional antiferromagnetic correlations of the doped Haldane gap system YBaNiZnO
We make a new proposal to describe the very low temperature susceptibility of
the doped Haldane gap compound YBaNiZnO. We propose a new
mean field model relevant for this compound. The ground state of this mean
field model is unconventional because antiferromagnetism coexists with random
dimers. We present new susceptibility experiments at very low temperature. We
obtain a Curie-Weiss susceptibility as expected
for antiferromagnetic correlations but we do not obtain a direct signature of
antiferromagnetic long range order. We explain how to obtain the ``impurity''
susceptibility by subtracting the Haldane gap contribution to
the total susceptibility. In the temperature range [1 K, 300 K] the
experimental data are well fitted by . In the temperature range [100 mK, 1 K] the experimental data are
well fitted by , where increases with
. This fit suggests the existence of a finite N\'eel temperature which is
however too small to be probed directly in our experiments. We also obtain a
maximum in the temperature dependence of the ac-susceptibility which
suggests the existence of antiferromagnetic correlations at very low
temperature.Comment: 19 pages, 17 figures, revised version (minor modifications
Transition to Chaotic Phase Synchronization through Random Phase Jumps
Phase synchronization is shown to occur between opposite cells of a ring
consisting of chaotic Lorenz oscillators coupled unidirectionally through
driving. As the coupling strength is diminished, full phase synchronization
cannot be achieved due to random generation of phase jumps. The brownian
dynamics underlying this process is studied in terms of a stochastic diffusion
model of a particle in a one-dimensional medium.Comment: Accepted for publication in IJBC, 10 pages, 5 jpg figure
The effects of nuclear spins on the quantum relaxation of the magnetization for the molecular nanomagnet Fe_8
The strong influence of nuclear spins on resonant quantum tunneling in the
molecular cluster Fe_8 is demonstrated for the first time by comparing the
relaxation rate of the standard Fe_8 sample with two isotopic modified samples:
(i) 56_Fe is replaced by 57_Fe, and (ii) a fraction of 1_H is replaced by 2_H.
By using a recently developed "hole digging" method, we measured an intrinsic
broadening which is driven by the hyperfine fields. Our measurements are in
good agreement with numerical hyperfine calculations. For T > 1.5 K, the
influence of nuclear spins on the relaxation rate is less important, suggesting
that spin-phonon coupling dominates the relaxation rate at higher temperature.Comment: 4 pages, 5 figure
Dephasing in matter-wave interferometry
We review different attempts to show the decoherence process in
double-slit-like experiments both for charged particles (electrons) and neutral
particles with permanent dipole moments. Interference is studied when electrons
or atomic systems are coupled to classical or quantum electromagnetic fields.
The interaction between the particles and time-dependent fields induces a
time-varying Aharonov phase. Averaging over the phase generates a suppression
of fringe visibility in the interference pattern. We show that, for suitable
experimental conditions, the loss of contrast for dipoles can be almost as
large as the corresponding one for coherent electrons and therefore, be
observed. We analyze different trajectories in order to show the dependence of
the decoherence factor with the velocity of the particles.Comment: 9 pages, 1 eps-figure. To appear in J. Phys. A: Math. Ge
Decoherence induced by a fluctuating Aharonov-Casher phase
Dipoles interference is studied when atomic systems are coupled to classical
electromagnetic fields. The interaction between the dipoles and the classical
fields induces a time-varying Aharonov-Casher phase. Averaging over the phase
generates a suppression of fringe visibility in the interference pattern. We
show that, for suitable experimental conditions, the loss of contrast for
dipoles can be observable and almost as large as the corresponding one for
coherent electrons. We analyze different trajectories in order to show the
dependence of the decoherence factor with the velocity of the particles.Comment: 13 pages, 3 figures. To appear in Phys. Rev.
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